464th Meeting - July 14, 1999

UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
***
464TH ADVISORY COMMITTEE ON REACTOR
SAFEGUARDS (ACRS)

U.S. Nuclear Regulatory Commission
Two White Flint North
Conference Room 2B3
11545 Rockville Pike
Rockville, Maryland
Wednesday, July 14, 1999
The committee met, pursuant to notice, 8:30 a.m.
MEMBERS PRESENT:
DANA POWERS, Chairman, ACRS
ROBERT SEALE, Member, ACRS
GEORGE APOSTOLAKIS, Member, ACRS
MARIO BONACA, Member, ACRS
JOHN BARTON, Member, ACRS
GRAHAM WALLIS, Member, ACRS
ROBERT UHRIG, Member, ACRS
THOMAS KRESS, Member, ACRS
WILLIAM SHACK, Member, ACRS
JACK SIEBER, Member, ACRS
P R O C E E D I N G S
[8:30 a.m.]
DR. POWERS: Let's bring the meeting to order. This the
first day of the 464th meeting of the Advisory Committee on Reactor
Safeguards. Today is Bastille Day. I can think of no more appropriate
day to attack the Ancien Regime, and we are certainly going to do that
with our first discussion of RETRAN-3D and thermal-hydraulic transient
analysis code.
We are also going to be looking at proposed revision to
Appendix K of 10 CFR Part 50, Options for Crediting Existing Programs
for License Renewal. This is a particularly important discussion since
it relates to the ACRS's statutory mandate to look at the requests for
license renewal.
We will also look at proposed revision to Regulatory Guide
1.160, Assessing and Managing Risk Before Maintenance Activities at
Nuclear Power Plants. This is the continuation of our discussion of the
Maintenance Rule.
A proposed approach for revising 10 CFR 50.61, Fracture Test
Requirements for Protection Against Pressurized Thermal Shock Events.
PTS comes back as it does on a regular basis.
And we will be preparing reports from the committee, I think
we have five reports at this hour to prepare at this meeting.
The meeting is being conducted in accordance with provisions
of the Federal Advisory Committee Act. Dr. John T. Larkins is the
designated federal official for the initial portion of the meeting. We
have received written comment and a request for time to make oral
statements from a representative of Caldon Corporation regarding
proposed revision to Appendix K for 10 CFR Part 50.
A transcript of portions of the meeting is being kept and it
is requested that speakers use one of the microphones to identify
themselves and speak with sufficient clarity and volume so they can be
readily heard.
I think members are now aware we have a new member. Jack
Sieber is now full-fledged and bona fide and allowed to vote.
MR. BARTON: That means he is allowed to accept work then,
too, right?
DR. POWERS: And he has a full status of work and we will
conduct the initiation ceremonies at the close of business today. For
the rest of the week, but then there are the hard things.
I think members are also aware that Greta Joy Dicus is now
the Chairman of the Commission and functioning as same. I call members'
attention to a reactor leak that has taken place at the Tsurga reactor
in Japan. It dumped about a third of their coolant inventory.
Apparently they have isolated the leak. We will probably hear more
about that as the day goes on.
We have some new faces around the committee. I would like
to introduce some people that you will have a chance to work with
beginning with Juan Peralta, who is here on rotational assignment. He
will be working as one of our staff engineers. Juan comes to us with a
tremendous background, some 14 years of experience in QA, and he has
already picked up responsibilities for the PTS work and some accident
management work, so he has hit the ground running.
Juan, welcome aboard. We are looking forward to have a
chance to work with you on this side of the table. We are really nice
guys. You may not know that.
[Laughter.]
DR. SEALE: Rumors to the contrary.
DR. POWERS: I would introduce Karen Faircloth. I think
most of the members have gotten e-mail messages from Karen testing out
her machine and whatnot.
Karen, welcome aboard. And you may not think we are such
nice guys, but you have the right to keep us in line.
Cheryl Hawkins is our freshly-minted chemical engineer out
of the University of Maryland.
Cheryl, I think you are working with our sister group, the
ACNW. Cheryl, you may want to stay around for this opening meeting. I
understand that the first speaker is going to delve heavily into Bird,
Stewart & Lightfoot and explain to us some on thermal-hydraulics and you
can try to keep honest on this stuff.
MR. BARTON: It sounds like a rock group.
[Laughter.]
DR. POWERS: There are a lot of us that carried around Bird,
Stewart & Lightfoot for a while and thought it was a rock, all right.
With that, I will ask if there are any comments that the
members want to make at the opening session?
[No response.]
DR. POWERS: Seeing none, I will turn the floor to Professor
Wallis and a discussion of RETRAN.
I am sure that members will want to call attention to the
gross violation of our rules on how viewgraphs should be formulated,
numbered and with names and phone numbers on the corner of these.
DR. WALLIS: Well, good morning. My phone number --
[Laughter.]
DR. WALLIS: My phone number is 1789, this is the day of the
Bastille storming. That is a true statement. The reason for storming
the Bastille was to release prisoners, I believe, who had been
imprisoned for their point of view, and one might say that in the
present context, there may have been some prisoners who had doubts about
the origin of the RETRAN equations who have not been heard.
DR. SEALE: There is a lot of truth to that.
DR. WALLIS: I am going to talk about RETRAN. I am not
going to say what I was going to say a month ago. My ideas about RETRAN
have been evolving, they are evolving a little bit, but they seem to
have hardened. I don't think they are going to evolve much more.
The sources of my review are two. One is the manual, this
is Volume 1 of a manual which was submitted to the NRC for review by the
authors of RETRAN. And my second source of information is a RETRAN
report. This is a report on RETRAN written for EPRI, NP-1415, about 20
years earlier. This was kindly supplied to by Lance Agee. And the
words in the report are very similar to the words in the manual, but the
figures I will use are taken from both of these sources.
This is a mature code, been around for 20 years or more and
I just wanted to point out to you, it is obvious that a code goes
through various stages of development. Engineers model is and then
supervisors approve it. It is approved by the company, it is approved
by EPRI. It is reviewed by NRC. It is used by the utility. At least
RETRAN-2 was reviewed by the NRC. RETRAN-3D is being reviewed by the
NRC. And I should point out RETRAN-3D is not a 3D code, it is a 1D
code, one dimensional code.
DR. KRESS: After all that, it has to be right, right?
DR. WALLIS: And utilities have used RETRAN-2. And this has
been going on for not quite half of my life.
DR. SEALE: Graham, is there any hint as to why it is called
3D?
DR. WALLIS: I don't think it matters. There is nothing
much in the name.
DR. SEALE: Well, no, except that certainly using the term
raises one's expectations.
DR. WALLIS: It raised my expectations, but I realized it
was not a 3D code. It is 3D nucleonics, but it is 1D
thermal-hydraulics.
DR. SEALE: Ah, okay. Okay.
DR. WALLIS: Of course it could mean it is RETRAN Version 3,
A, B, C, D.
DR. SEALE: Yeah, I appreciate that.
DR. WALLIS: I don't know what the source is. So what is
the purpose of a code? The purpose is to analyze reactor transients.
You have seen figures like this before. I will just point out there are
lots of elements here, inter-connected, and although these are drawn as
boxes, there are a very few parts of this circuit which are straight
long pipes. They have bends and joins and all sorts of things, they are
not just straight, long pipes. That is about all I want to say about
that figure.
And this figure is a -- all these figures are taken from the
RETRAN reports. This is nodalization of reactor vessel. The point I
would like to draw your attention to here is that not only aren't they
straight pipes, but this node down here has flow coming in one way,
going out another way. It may even have a cross-flow here. So there
are flows are different directions. The same thing with downcomer up
ahead and so on. So these things are anything but straight pipes.
The approach would seem to be very straightforward. Choose
the properties that you are going to use to define what is going on in
each volume, write down some equations, usually based on conservation
laws, mass momentum and energy and so on. Use them to derive
expressions for the rate of change of the properties you are using to
describe what happens, d by dt of something, and step forward in time to
the next time and go ahead, and you then will predict the course of a
transient.
The method used in RETRAN, the choices made about the
variables, to use the flow rates, the enthalpy of the thermal-dynamic
properties, density enthalpy, flow rate areas and so on, and to use a
staggered grid so that these dashed things labeled i minus 1i, these
control volumes are for mass, so mass goes in here and goes out here.
Mass accumulates in the dashed volume. But for momentum, there is a
staggered grid where the momentum self-starts in the middle of the mass
cell and goes to the next mass cell, and then the flow rate across here,
W, has to be interpolated in some way. If you know the mass flow here
and here, you somehow have stepped it up here, you have to interpolate
somehow to get the flow across the boundary.
DR. KRESS: Why do they use two different grids for those?
DR. WALLIS: If you ask me questions like why did that, you
have to ask them.
DR. KRESS: Oh, okay.
DR. WALLIS: A staggered grid is fairly standard in
combination flow dynamics. A staggered grid, there is interest
surprising about a staggered grid, but you do realize that you do have
to do some interpolations because you are calculating properties and you
have to interpolate to get some of the properties.
So that is not -- the geometry, well, this is a short,
straight pipe, this doesn't tell you much about geometry. We are
interested, this is also from the RETRAN report, presumably, in applying
the laws of motion and so on to a control volume which looks much more
complicated than the short pipe which I just showed you.
Now, I am going to confine my attention entirely to the
momentum equation and this is a momentum equation which is established
for a control volume and is probably -- about which there is no debate,
I would say. This is the rate of change of momentum of the fluid inside
a control volume. This is the mass flow coming into control, going
through some port or some surface where fluid can enter, and this the
momentum it carries with it.
I will say -- draw your attention to the fact that is of the
nature rho vj daj. It is a dot vector product between the velocity and
the area. And this part here is a different vector, vi, and the
momentum -- the direction of the momentum is determined by this velocity
or by this vi, not by the vj. In the case where i is parallel to j,
then this becomes a j, you get rho vj squared daj, and, indeed, the area
gives the direction of the momentum transform.
But there are cross-momentum terms of the vi vj nature where
these vi and vj are in two different directions, perpendicular, and that
is what, in the RETRAN documentation, is called the cross-momentum flux.
Flow comes in this way, but it carried momentum going that way, right
angles to it.
The pressure action on an area provide a force, this is f
equals ma, if you like, the pressure for it. And I have removed the
shear stress for the force acting on the fluid because this is
conventional to do so and Bird, Stewart & Lightfoot and others have
excuses for why you can throw away the shear stress in calculating the
force acting on the fluid coming in through surfaces.
This term here is the force on walls, and this is a
gravitational force.
Now, we want to do our analysis in terms of a more lumped or
global picture, the way we do with flow rates, so all of this is treated
as one flow rate instead of integrating over a surface, flow rate across
a junction, and it carries this momentum with it. And this -- some sort
of averaging is implied here. These are the pressure forces of the
junctions multiplied by the area of the junctions. This is the force on
the walls. This is a momentum change inside the junction, the mass
inside them, the average velocity of the stuff inside.
So some problems must be faced upfront by the engineer
trying to use these equations. One is this is a vector equation. If
you are going to turn it into a scalar equation you have to result in
some direction. And since these forces and flows can be in any
direction, this velocity can be in any direction, so some choice has to
be made about how to resolve this vector, which can be in any direction,
and to pick some direction to resolve it in if you are going to just
write down one equation instead of three.
The mass flow rate is a scalar quantity, and if you are
going to use the rate of change of a vector velocity to calculate dW/dt,
which is what is needed for the numerical scheme, there has to be some
way of getting a scalar flow rate from a vector velocity.
This may be a surmountable problem, but this equation in
almost all textbooks is used to calculate the force. The force on the
bend is calculated from momentum balance. So F is usually unknown,
which you solve the equation for. If you're going to solve the equation
for the left-hand side, then you have to know F. I think it will turn
out that in RETRAN, there is no way of calculating F that makes any
sense.
All right. I was not going to show you equations, but I am,
because now this is important. This is the first time that, in these
reports, you find reference to a generalized RETRAN equation, so this
better be important. We are now going to develop some generalized
equations. And there are some words which are equivocal in the report
about, well, the flow should be perpendicular to the area. So flow is
coming down this pipe, this red surface is perpendicular to the flow.
So the natural control volume to use for momentum is the red one I've
shown here.
The one which it appears that EPRI wants to use is the green
one where a momentum cell is defined, which is perpendicular to some
direction which has to be chosen, and these walls here are
perpendicular, and they can't cut the wall as drawn here, they've to be
something like the one I've drawn here, green inside, because they bound
the fluid.
So this may be a good development because they define the
momentum cell, which is not perpendicular to the flow, but maybe is
convenient because the surfaces are perpendicular to the direction in
which I'm going to evaluate my momentum. So maybe there's some real
physical insight here.
Okay. So here is an equation that's going to be used to the
momentum -- applied to the momentum cell, this one here which is
labelled 2.3-5, and then I hope whoever reads the transcript can figure
out what I'm saying. I'm not going to be reading into the record
everything necessary for the poor reader of the transcript, but I will
try to make reference to a few things.
This is the equation 2.3-5 from the fat EPRI documentation
here. Now, this equation gives the direction of the momentum as the
direction of the area. The vector symbol is put on top of the area.
This equation only applies when the flow is perpendicular to the area,
so it applies to the red cell here. Isolate a purple cell up on the
screen, so I don't know what's happened. This is a red cell.
The green cell is the one that EPRI says it applies to, so
at the outset, this equation does not apply to the cell that it's stated
it applies to, this one here; it applies to something else like the red
cell.
Then this equation is derived from this. Now, Vk psi is the
symbol for the velocity in the direction of this direction that they've
set up for the green cell, so this Vk psi, as I understand it, is the
velocity in this direction perpendicular to this direction here.
As written, this equation contains that velocity multiplied
by Ak. Now, Ak is the area of the pipe, the purple surface, not the Ak
prime, which is the green surface. So this equation is also incorrect;
these should be prime values here. If these are prime values, this
equation is correct, although it takes a little bit of work to show that
it is. In both of these equations, we have forces from the walls. It's
not clear what the difference between these two forces is. It doesn't
really matter; there's some unknown force from the wall.
The reason that the flow comes out of here going up in that
direction when it came in in this direction is because it lands on the
wall in order to turn. The wall pushed it, the pressures didn't push
it, the wall pushed it. So to get the momentum balance right, you've
got to get these forces from the wall right.
Now, we'll come back to that several times.
Now, this equation is derived from that. The equation in
II.3-10 in EPRI documentation is derived from II.3-7 by dividing by the
area Ak. Well, that is not correct. This should be an Ak prime. You
cannot just divide this by a -- I came to the conclusion -- you can do
this for homework -- that this shouldn't be a Ak squared here; it should
be an Ak, Ak prime, this should be an Ak, Ak plus 1 prime, this should
be -- Pk should be Pk times Ak prime divided by Ak. So this is simply
derived from this by dividing by Ak where Ak is the same for the
incoming pipe and the outgoing pipe. So Ak equals Ak plus 1. But Ak
prime doesn't equal Ak plus 1 prime because the angles may be different.
So the areas are not the same for the green volume; they are for the
red.
So the outset for this very, very simple control volume, we
have obviously some confusion in my mind or in the mind of the authors
of this documentation about which area they're talking about, which
direction they're talking about and how you can divide things by other
things and cancel things out.
So one is driven to reflect about why this is done at all.
This is just a kink in a pipe; it's nothing to do with a reactor circuit
or some of the complex systems we're going to deal with. I came to the
conclusion that it's done because the reader wants to convince -- the
author wants to convince the reader that a term like this, which is W
over rho A-squared, W-squared over rho A-squared is really a rho
V-squared term. W over rho A is V, so this is rho V squared. And this
is P without any area. So the author wants to convince the reader that
what started out as rho V-squared times an area, which had to be
resolved, and the areas are not all the same, degenerates to simply rho
V-squared, rho V-squared, and P without any areas at all. That's the
purpose of, it seems to me, the author, is to convince the reader by
arguments which probably have holes in them that what emerges is
pressure stark naked, not multiplied by anything, and these rho
V-squared terms.
This force has not gone away, this force is still here and
has to be determined. I don't know the difference between these forces.
And there's another peculiarity here. It's in the
documentation, this W is referred to as a mass flow rate resolved in the
direction of psi. Now, mass flow rate, as I said before, is a scalar.
Mass flow rate does not get resolved in any direction. Mass flow rate
resolved in a direction is not a meaningful concept. But because the
collision procedure uses mass flow rate, which mass flow rate appears in
this equation, because that's what we want to solve for and use as a
variable, so velocity is turned into mass flow rate, vector is turned
into a scalar in some way which we will come back to.
Now, in that figure over there, it seemed to me that the
author is trying to convince me to use a green volume where all the
surfaces are perpendicular to my chosen direction for evaluating
momentum.
Okay. So here I've got this complicated control. Here is
my chosen direction for evaluating momentum here. This is what it says.
I guess it also is the direction for momentum.
Does that mean that I'm going to draw my control volume for
all these parts perpendicular to side like this and this and connect it
around like this for my control volume? And here, where is it going to
go? It's going to go way down this pipe. And then if I do that,
there's going to be all sorts of forces from these walls put in my
momentum balance. Heaven knows, with this pipe, gets lost. I don't
believe that's what is really done. I have great difficulty stretching
my mind to say that that's what's actually done, although I tried very
hard.
Now, let's move on. This is a slightly more interesting
situation than the one on the picture I just showed you. This is the
geometry for RETRAN momentum equation with a variable area. It is a
straight pipe going into another straight pipe with a change of area.
What one would look for here perhaps would be a momentum
equation for what I have drawn here as the green volume, which encloses
the cell, the momentum cell, the fluid in the momentum cell.
What is actually done is to say, we'll divide this into two,
we'll do the straight pipe and we'll do this straight pipe. The reason
we do straight -- excuse me -- straight pipes is because all we know how
to do is straight pipes. So we will divide this into two straight pipes
in we'll write a momentum equation for each.
When we do that, we're faced with what pressures and
velocities we put in as a boundary condition here. With the green
volume, what we're faced with is what forces we put on this disk-like
surface because we've got to get a force from the surface. Now, we
don't want to address that, so we'll divide -- we'll say that there's a
pressure jump of this.
Now, the normal assumption for an orifice like this, as you
may well be aware, is that the pressure of the fluid coming out of the
hole is the same as the pressure on this flat surface across here.
What's done here is to say, oh, no, we won't do that, we
will use an energy loss equation from Bird, Steward and Lightfoot to
calculate this P plus minus P minus, or P minus minus P plus depending
on which side of the equation it is at this junction. So we'll use some
kind of energy dissipation argument to get the pressure jump, although
there is no pressure jump in reality. And then we will write the
equations for these two red pipes, momentum equations, which being one
dimension are okay, we'll divide by the areas to get rho V-squared for
each one of these, we'll do some elimination and we'll end up with this
equation, which looks like the one we had for that one on the other
figure, the kink in the pipe.
Just remind you, we've got rho V-squared here and pressure,
and we've got some force which now is only the frictional force along
these walls because we've taken care of the disk by this pressure jump,
and this part here in the momentum equation accounts for this Pi plus
minus Pi minus from this energy dissipation.
If the flow is incompressible, the net effect is that this
was a rho V-squared term, this is a minus rho V-squared term, this has
an opposite sign from that, this has an opposite sign from that. So the
net effect is you get rho V-squared over 2, so the net effect is you get
P plus rho V-squared over 2 for K minus P -- the difference in the
Bernoulli head is pushing the flow and creating this momentum, momentum
change.
So there's a mix here between energy like terms in the
right-hand side and momentum like terms in the left-hand side. This may
be appropriate to some extent; however, I'll draw your attention to the
fact that when Bird, Stewart and Lightfoot calculate this EI star, this
energy dissipation at the junction, the way they do it is to do a
momentum balance for the green volume assuming that the pressure jump
across here is zero. So you start from a momentum balance assuming the
pressure is here and derive an energy equation which says they're
different. And you might get away with that if this pipe were very long
compared with the mixing region and this I-plus were really down here
somewhere and the pipe were long.
But it is, some think, logically inconsistent, starting from
a momentum balance which says A equals B and using it to derive A minus
B or something, not zero. But that is maybe. This is all
preliminaries. This is just to see if you fall asleep or not.
What we want to do is write equations of something real that
might occur in a reactor system, a more general control volume, and so
I've got here the equations in the figure that appear in the appendix of
the original document. And this is, as he said, the conservation of
momentum equation. Conservation of mass is easy. Conservation of
momentum -- well, we should spend some time on this equation, VIII.1-9
from the EPRI report.
It appears in the appendix with this figure. You will spend
many sleepless nights and tear your hair out if you try to find any
connection between this figure and that equation. What you have to do
is go back to a picture like this somewhere in the text.
I'll remind you, we're using a staggered grid, so this is a
volume for which you're going to use mass bounds, this is the volume for
other mass bounds. Momentum cell like the green cell and the kink in
the pipe goes from the middle of this mass cell to the middle of that
cell somehow like that, this flow in here, and there may be a connecting
port like that. So that is more the geometry to which this ought to
apply.
Well, this plainly is not a momentum balance because this
should be rho V-squared times an area, and this is actually just rho
V-squared by itself. So something has happened here, but at least this
looks like W over rho A because this is -- this is -- this is something
like and it originally came from the momentum flux across his surface
here, this surface here into this momentum cell. So that makes some
sort of sense, and the momentum out of here is the L term there, and
that makes sense, too.
What's the momentum change? Well, the momentum change is
for all the fluid inside here presumably, inside the cell. And that is
somehow -- there's a change -- there's a change from I to J, which it
simply said let's change I to J in the text, so WJ is really this flow
through here.
So the idea is physically that something pushes on here,
something pushes on here, and it changes the momentum in the cell and
the momentum is characterized by the flow through the hole, although
obviously something has to be done to relate that flow to a real
momentum in the volume.
There are some problems with that. Well, let's say what are
some of the problems. Here's one of the problems. This cell doesn't
have a clever shape like that; the cell could be like this. The
boundary could be the green curve I've drawn here.
Now the flow between the cells is going down like this.
This pressure is pushing up that way, this pressure pushing up that way.
It's actually in the opposite direction of this momentum, so the sign is
wrong in the term if you simply say the force is in the direction the
momentum changed.
Although it is true physically that this pressure pushes the
stuff through, how can it be if pressure in one direction pushes stuff
through in another direction and accelerate it? Well, of course, it
leans on the wall up here. It goes up and bends around and comes down
again. The force on that wall does not appear in any of the equations.
So -- then there's another problem, and if you look at the
control volume -- again, this is now figure II.3.5 from the RETRAN 3
documentation. There is a port shown here and a port shown here. Well,
it's conceivable that the flow comes in here and goes out -- the flow
comes in here and goes around like that. So for characterizing the
momentum as all being in this direction here is a little bit of a leap.
What I conclude was done and I can't find anything else in
the rationale, is someone said, well, the only thing we know how to
solve is the two pipe problem, so we will treat everything as two pipes.
That looks like something like two pipes so we'll draw this black thing.
One pipe is this one, that pipe is the other one. Flow is coming here
and it's going out there, and we'll just use willy-nilly the same
equation we derived for two pipes for this more complicated control
volume. That's all the justification there is.
Okay. So these, then, became divided by an area because of
the manipulation of the equations for the two pipes. This is not a
momentum equation for any control volume; this is a two-pipe equation
manipulated in the way I described applied to anything.
This term here is said to be the momentum flux change due to
area change as if that was a standard thing. In fact, what it is is the
difference in Bernoulli head from here to here, assuming the fluid comes
in here and goes out reversibly. It's the pressure recovery you would
have if the flow flowed reversibly. It has nothing to do with momentum
flux due to area change. So this is a complete misnomer. And that
combined with all this stuff here is really the PI-plus minus PI-minus
that you saw for the pipe problem, which was a sort of -- an engineer's
attempt to simplify the problem into something he could solve. It
simply carried over from the two-pipe problem with no justification
whatsoever.
These pressures don't multiply areas. That's a sure
indication it's not a momentum bounds. But they blend away because of
what was done with the two pipes.
This term here is interesting. This is said to be the cross
momentum. You remember I talked about a cross-momentum flux? A
cross-momentum flux -- flow comes in across the surface but it carries
momentum in a different direction from the direction of the surface. I
cannot -- I cannot figure out any connection between this term and this
figure and anything else.
Aj and rho-j and Wj -- the j's refer to the junction. So
that has something to do with the flow going through this hole between
this strangely shaped -- and this one, this hole, this one here, which
is called Vj.
This is a sum of things, so this must be a sum over I for
this volume. It must have something to do with flows in and out because
the only W's which are different from J's are flows in and out. So that
presumably has something to do with these guys coming in here and coming
in here, which, I don't know, they must go somewhere into that
mysterious straight pipe as well.
But there's absolutely no reason one should take a flow rate
of one junction multiplied by a flow rate -- that cannot be right. No
way that you can have flow rate in one junction multiplied for another
junction. And I have dug into the origin of this. I cannot for the
life of me understand what is going on, and these pressures, as I said
before, have lost their areas because everything is being treated as two
pipes.
Well, I should say that by now, I feel something like Alice
in Wonderland, but maybe -- maybe it will all come clear when we look at
some examples and some other information supplied.
I even hate to put this up -- what is the meaning of that?
Another one of your homework assignments is to figure out what is the
meaning of sundial? It doesn't show any structure, it doesn't show any
flows really, it just doesn't show any junctions, and I don't understand
the message, but it's supposed to explain what was done.
So at this point, we have got some problems, or I have some
problems, and what has happened is that there's been an attempt to make
a 3-D problem a solvable 1-D problem using what I find are confusing
definitions and inconsistent equations. I doubt if any of the equations
written are consistent with any interpretation of momentum balances.
The two-pipe area change problem appears to have been
generalized without any argument, doing any geometry, and the momentum
equations simply look the same, and I don't understand how this is
logically justifiable.
The forces from solid surfaces are simply absorbed into a
Pi-plus minus Pi-minus type energy balance, energy dissipating approach,
and I don't see any place to draw my Pi-plus, Pi-minus a generalized
control volume, so I don't know what is going on here. I also note that
mass flow rate along the line got treated as a vector when it's a
scalar.
Well, maybe it will all become clear when we look at simple
examples, because unless the professor who gives you all these I's and
J's and sums over this thing can solve a simple problem, you begin to
wonder if he understands what he's doing. So let's look at a simple
problem -- flow around the bend. And again, I don't quite know where to
start in my critique here.
Here's flow around the bend. It looks as if there's a cell
here and there's a cell here, and there's three cells outlined in black.
Those must be the mass ones, and the flow rate between them are these
W-1, W-2, W-3. And this looks as if it's a momentum equation, doesn't
have a D by DT, but it would be another term for D by DT in momentum in
general. It looks as if it's an equation between 2 -- now, remember,
Stigard grid -- between 2 and 3, which is here.
Now, I don't quite know what to do. If I draw the green
one, which the rule says is perpendicular to -- this must be for the X
duration because X is here, and by inference, since this is X, this must
be X. I can't draw a control volume coming down right here. It doesn't
bound any sensible control volume. So using that rule doesn't make any
sense. I've got to fall back on something I think I understand, which
would be a control volume like this. So it looks as if I ought to be
getting a momentum equation with something like this.
Okay. Well, I've got P2, and it should really be multiplied
by the area of the pipe, but this has obviously been divided by the area
of the pipe. How about P3? P3 acts on this area. If I'm doing an X
balance, I would have to multiply by one over root 2 if I'm going to
divide by area of the pipe. So somehow, the resolution will have the
pressure vanished from here.
This is a rho V-squared term. It's divided by the area of
the pipe for here. That makes some sense. What about this one? This
is W3 X squared. W3 X. Okay. That's a flow rate result in the X
direction, although it's a scalar, all right?
So what is it? Okay. I'll tell you what it is. It's half
the flow rate. If this were an incompressible flow, the same flow rate
would be going through this pipe everywhere. It's half the flow rate.
So the argument seems to be half the flow is going in the X direction
and half the flow is going in the Y direction. Add them up and you get
the total flow rate.
Is that true? The flow rate across any control surface
crossing this pipe is exactly the same. This, if it means anything at
all, is a sort of liberal arts or grade school interpretation -- I'm
sorry, I've got to be careful what I say -- of flow rate. It doesn't
make any sense. That's simply said. It doesn't make any sense.
If you substitute that into here, what you get is something
like a quarter W-squared over rho A-squared. You get a quarter or rho
V-squared for this term. If one did a momentum balance here, what one
should do is say there's W this way and the velocity associated with it
is W over rho A and result in this direction is one over square root of
two. So you multiply that. You get one over the square root of two
instead of a factor of four.
But anyway, I don't know what is going on, but this is my
interpretation of what must have gone through the mind of anyone who is
claiming this was a momentum balance for a control volume.
This Pi-plus minus Pi-minus is simply borrowed from another
problem which has nothing to do with this geometry and written down. I
could probably say more about this problem, but let's going on because
our time is limited.
This is the problem of flow in the bend, transient flow in
the bend. The flow comes around like this. You want to evaluate the
change of the flow rate. If you write an X direction momentum equation
for a bend like this, you get the pressure on the end here times the
area, you get the momentum flux coming in here at the inlet one, and
there's a force from the bend on the fluid, and that's what turns the
fluid and makes it come out here. There's no exiting momentum or force
in the X direction here, and that -- so this is the force and that's the
rate of change of momentum inside the control volume.
You cannot solve this. Obviously it's useless physically
because it doesn't include the pressure here, which is, the -- you know,
P1 minus P2 is what's making things happen. An equation which doesn't
include what's making things happen cannot make any sense or be useful,
cannot be useful. And the force from the bend here isn't known, so
there's no way you can solve for what you want by using this approach.
So this problem cannot be solved using an overall global momentum
balance. It cannot be solved using an overall global momentum balance.
So any equation that purports to represent that based on an
overall global momentum balance has some fundamental difficulty.
The problem can be solved by using mechanical energy
conservation between points 1 and 2. Bird, Stewart and Lightfoot -- I
don't know why we have to evoke the names of the saints, but --
[Laughter.]
DR. WALLIS: This gives it more authority. When Bird,
Stewart and Lightfoot are confronted with a problem like this, they use
mechanical energy conservation. This is how they solved the manometer
oscillations problem, for example, if you study their book, and this is
how they solve other system problems. They very carefully stay away
from difficult problems like this, although they can be solved, this
problem can be solved using mechanical energy conservation, that will be
on the homework.
Well, if this conclusion applies to a bend, I think one can
justifiably say that similar conclusions apply to nuclear subsystems
except for straight pipes.
Well, let's look for more enlightenment. Let's look for
other examples. Examples are very useful for understanding
generalities. So here is a tee. It's the bottom figure on my left.
This figure on my right I will talk about. To start with, you have to
figure out what's meant by X and Y direction as well. I will tell you
just what they are. You have to figure out, okay, does the W-1-1 flow
going here, W-1-2 flow crossing here, W-1-3 -- so these are flows
crossing boundaries, so we want to control on this for momentum balance.
Here's the pressure acting on the bottom of this cylinder.
Here's the pressure acting on the top. Obviously the areas have been
divided out. This is a momentum flux coming out of here. I don't have
much difficulty with that one. What is this? This term -- I'm looking
now at equation II.3-36a from the EPRI documentation supporting RETRAN
3-D, and there's a term which has W bar-squared 1, 2, Y. This is a mass
flux crossing 1, 2 here, result in the Y direction, is that way, up.
Well, it can't resolve mass fluxes in any direction. So this must have
something to do with velocity in the Y direction, so this is a rho
V-squared term in the Y direction for this surface 1, 2. But when you
do that, you have to say, here's W coming across here, it transports
with it VY and VX. The X momentum being transported across here is W
times VX; the Y momentum is W times VY. Or if you want to be more
sophisticated, VY, rho, VX, AX for W.
So you've got to take the mass flux and multiply by
momentum. There is problem because of the curvature of the stream
lines, there probably is some Y direction momentum crossing this
boundary. The point is, it's of the cross momentum type, which we saw
earlier on, and this is of the -- well, this isn't anything really.
This is a rho V-squared term, though, but it's based on a velocity in
the Y direction, which doesn't relate to flows across the boundary at
all. So this term here, one could say, is an Alice in Wonderland term,
and this part here is simply Pi-plus minus Pi-minus term borrowed from
the two pipes together. I can't draw anything in here which has
anything -- where I can identify a plus and a minus surface.
Moreover, there is momentum coming in here which is not
accounted so, and there is momentum going out there which is not
accounted for.
So -- oh, I haven't finished. Sorry.
And this velocity in the Y direction of the flow coming in
here is said to be a half -- I'm sorry -- the flow rate, the flow rate
in the Y direction, the non-existent thing which might have something to
do with velocity is half the flow rate going out there. I see
absolutely no basis for saying that the resolve flow rate, if there was
such a thing in the Y direction across up here, is half the flow rate up
there or going up there, because some of what comes in here goes out
there. This has no relationship to a mass balance, this has no
relationship to a momentum balance, and this isn't the momentum balance
anyway.
All right. Let's press on, as if we haven't had enough.
Let's go on to the Tee, time for Tee.
Here is a side branch in a Tee. Flow those coming along
here and going out. It's also going out. So this is one of the key
problems that research is now researching for what happens in Tees.
Because the modelers only know how to model straight pipes,
this is modelled as a straight cylinder connected to another straight
cylinder with a change of area, which doesn't look too bad for the
picture shown here, but if you, for your homework, make theta large for
the pipe is sticking up at a much bigger theta, this dimension here gets
very big compared with that, and it looks as if the side pipe is
connected to a very big pipe at the bottom, which isn't there.
All right. This is -- now let's think about the momentum
balance for this control volume. Well, I will not show you all the
equations, but I will tell you some features of what's tabulated as
terms in the momentum balance.
One is a momentum term due to this rapid change of area
which doesn't exist in reality. The rapid change of area doesn't exist
in reality and the term itself is itself questionable even if there were
a change of area.
The mass flux at surface L is resolved in the -- it is
claimed that the new feature of the new -- new method developed in this
report is better than the old method in the old RETRAN, which was not a
vector RETRAN, because it deals with vectors better.
So what's done is to say the flow rate crossing this dashed
line is very much the same as the flow rate in the pipe. The flow rate
coming in here goes out there, so the flow rate crossing there is the
same as the flow rate in the pipe.
It is then resolved in the theta direction by multiplying by
cosine theta. So what crosses this surface is not what it should be,
which is the total flow in this pipe, but the flow rate times the cosine
theta. And then when this is turned into a rho V-squared, we get two
cosine thetas, so we get cosine theta squared in the momentum term for
the momentum crossing this surface in the X direction, X being in this
case this way.
Well, what should be done is to take the total flow rate
across here without resolving these in any way whatsoever. If you want
to resolve, it turns out that the velocity in the area is resolved. One
has a cosine as a numerator, on the denominator, so that the cosine
disappear. If you simply take the velocity, the W, the total W without
resolving it at all and divide by this area, you get the right -- there
shouldn't be any cosine thetas at all there.
So this whole idea of resolving mass flux shows up what we
can say as a conceptual problem of whoever wrote the document in terms
of how you evaluate mass fluxes and their relationship to momentum
balances.
All right. Now, this is also an illuminating document,
because a cross-momentum term is put in for this surface. Now, what's
happening at that surface is there's flow across it. Well, there's
actually flow across it, it's a W, it's a scalar.
Now, you can evaluate it if you would like as the velocity
in this direction times this area or the velocity in that direction
times that area. It's the same thing.
But anyway, there's a W there times a Vx when its direction
plus a Vy. These are vector directions. And so the momentum in the X
direction is the mass flux crossing it times Vx in that direction, which
is what the direction of the momentum balance is. The mass flux times
Vy is Y direction momentum carried across this surface. It's the
momentum balance in this direction that would have that term in it, but
that's perpendicular to the momentum balance direction which is being
written.
So this cross-momentum is simply put in the equation because
it appeared in the original vector equation; it shouldn't be there, it's
in the wrong direction. So there's a conceptual problem revealed in
this example in understanding what is meant by cross-momentum terms.
There is no account taken whatsoever of the momentum leaving
surface two. Stuff comes in here, some of it goes out the bend, the
Tee, some of it carries on straight down the pipe. There is no account
at all because all we know how to solve is straight pipes connected
together, and, of course, flow doesn't go through the wall of a straight
pipe. Maybe. I don't know. But anyway, that term is missing, and
there's no real -- although P-plus, P-minus method is used, I don't see
any way to draw control volume. If you're going to draw control volume,
you should be consistent and you should say where your P-pluses and
P-minuses are, and then if you're going in the formula for them, that's
okay.
Well, I don't know where to draw P-plus, P-minus, and simply
adding terms from another context for with problem doesn't make sense to
me, and there are some other typos, I presume, in the answer because
there are some quarters where there should be halves and so on. I found
something like seven terms to question out of maybe eight momentum terms
or something in this example.
These are not complicated problems.
So what's the conclusion? I think the NRC and the ACRS has
to reach its own conclusions about this kind of thing. Here are some
conclusions for you to think about. One is that, from what I've showed
you, I doubt very much if the method of saying we're using a global
momentum equation to solve the rate of change of flow rate which we then
turn into a rate of change of mass flux can be used for any control
volume other than a straight pipe. So at some very fundamental level, a
method is being used which does not apply.
All system components -- I cannot see how you can simply
decree that all system components are straight pipes. In this example
-- I'm now looking at the Tee example -- the momentum term -- the rate
of change of momentum term here, these are two equation lengths of
straight pipes. Now, in L-2-3, I can sort of understand; it goes from
here to here. But what's L-1-3? What's the straight pipe that
represents this stuff when flow is coming in this way and going out that
way and so on? I don't understand that.
I'm sorry I went back to that one, but this conclusions
reminded me of something else I could say.
The rationale for reducing the 3-D momentum balance to a 1-D
formula contains statements that appear inconsistent, maybe not to you,
but I had trouble with them. And it's probably the result of trying to
do the impossible, trying to make the terms in the momentum balance look
like the terms in Bernoulli's equation.
If you're going to use a momentum balance, you must include
forces from the wall. They cannot be modelled simply by saying they're
energy dissipation.
When we do look at examples supplied in the documentation of
very simple geometries -- the kink in the pipe, the bend, the Tee and
the Y -- all of them appear to contain major conceptual errors of the
type that I would grade as wrong in undergraduate homework.
Flow rate is a scalar; it cannot be resolved. It is like a
vector. It is not a resolvable quantity. And flow rate in a volume is
not a meaningful concept. If you're going to use the idea of flow rate
in a volume, you have to be very careful about your definitions. One
can talk about the value average mean velocity, which is a vector. Flow
rate is something crossing an area. You have to say what area you're
talking about. And flow rate in a volume is not a meaningful quantity.
Throughout this documentation, you see references which
sound good. This is why I say it's like Alice in Wonderland. You read
things which look good when you read the English, but then you think,
you say, something is being written about which really isn't quite the
way it's described, unless I'm wrong, and I spent quite a lot of time on
this by now, far too much.
Okay. So let me go a bit further. This is a scalar code.
It uses scalar variables and yet it tries to make a momentum balance,
which is essentially a vector thing. Probably there is a fundamental
difficulty with trying to make any laws that apply to vectors collapse
into laws that apply scalars. There's a fundamental difficulty which
cannot be the resolved.
So I searched for a scalar which might describe things like
how much something is in a volume and how much has it changed with time
and so on, and a candidate for that is not momentum, but mechanical
energy, kinetic energy, rho V-squared average to a volume, not V as a
vector average to a volume.
This is what Bird, Stewart and Lightfoot would do whenever
they're faced with this kind of a problem. They use mechanical energy
conservation.
RETRAN's momentum balances, because they are converted in
ways which you may or may not like from rho V times V.A, a vector type
thing, because they're converted by various manipulations into rho
V-squared like terms, and because the energy conservation term bring in
a rho V-squared over 2 term, which when you take it away from the rho
V-squared term goes back to a rho V-squared over 2 term, the momentum
equations which claim to be a momentum equation begin to look like
energy conservation equations. They look something like energy
conservation equations. But because of the way the mass flux is
resolved, they're not really quite that because they still purport to be
resolved momentum equations. So they have components of mass flux when
they should perhaps have the whole mass flux. If that were a meaningful
mass flux, it could go into mass flux.
So probably something that looks something like the RETRAN
equations could be put together in a logically consistent way by using
mechanical energy conservation, but I don't think it's my job to do it.
However, there also remain other modeling problems which will occur to
you from what I've said.
So let's go back to my first transparency. Let's take a big
view of things.
This is my giving you the kind of talk I gave you today.
Engineers employed in this industry are presumably well educated,
intelligent people and know what they're doing. And the probability
that they're writing the kind of stuff that I saw here is I would hope
less than 1 percent, so I put down 2 percent. And they may write it
down, but on reflection they'll say it doesn't make sense, I better do
better than that. So let's say the probability of engineers coming from
a respectable university, even one where football is the main
preoccupation, would have a probability of about 2 percent of writing
this kind of stuff.
Their supervisors are presumably more sophisticated. Some
may even be retired professors, professors who have left the university
for industry or someone like that. They ought to be able to pick up
things. But I'm assuming that supervisors don't have quite as much time
to think about the problem, so I would give them a 20-percent chance of
catching errors.
But the internal company QA is an important thing, and that
should involve real professors from real universities and people who can
look carefully at this and say do I believe it or not, should you be
doing this? Because that protects the company from then going further
down the line and issuing something which eventually gets to the ACRS in
the form that this came. So I'll give that a 5 percent chance of
allowing errors through.
Then EPRI paid for this, they're going to put their name on
it, they better do a pretty good QA, so I've given them a 5 percent
chance of letting through the kind of things that I talked about.
Now, NRC. Well, I don't know what the basis of NRC review
is. NRC did review RETRAN-2, but NRC does seem to be preoccupied with
regulating and not with technical matters. And so let's say that NRC
review under the pressure of various things might only catch -- 20
percent probability of catching errors. You can put your own numbers on
this table.
And then utilities use this thing which has been through all
these reviews, and I don't think it should be up to the utility, even if
they have qualms about what they see, to go back and say we don't quite
believe what we read, so I give them a 50-percent chance of saying there
are errors in this, send it back.
So I add up in the traditional way, and since this Committee
likes to see numbers of the order 10 to the minus something, I say the
probability a priori of these types of things surviving that I've talked
about today should be 1 in 10 to the minus 6.
DR. POWERS: A critique of Professor Wallis' treatment of
probabilities as independent will be held at the break.
DR. WALLIS: No, these are conditional. This is the
conditional probability of that. This happens unless a condition --
these are all conditional probabilities. They're not independent,
they're conditional. So they do multiply, I think.
Anyway, we're used to that. So you can show indisputably,
or you can make your own estimates, the probability of this happening is
so small it cannot happen. Therefore, I must be wrong. Or the value of
the information I'm giving you in the information theory sense, when you
change your probability in the light of new information, if you change
it from a very low value to a very high value, that's a hell of a lot of
information in that new information. That's what the base theorum tells
you.
So either I'm completely wrong and have been dreaming or
there's a lot of information, I think, in what I've been telling you
this morning. And you have to think about it, and the NRC and everyone
else along the line has to do I think a great deal of soul-searching.
Thank you very much.
DR. POWERS: Do Members have any questions they'd like to
pose to Professor Wallis unconnected with his treatment of
probabilities?
Thank you, Professor Wallis.
Since you're in charge of this session, I think we --
DR. WALLIS: I don't think it would be fair for me to be in
charge. If I can, I'll pass the gavel to Professor Kress, who is my --
do you want -- or leave it with you.
DR. POWERS: I think I have the schedule here, Tom, so I'll
just go ahead.
DR. KRESS: Just go ahead.
DR. POWERS: I think we are now scheduled to have a
presentation by Mr. Agee from EPRI.
MR. AGEE: Mark will give the statement.
DR. POWERS: Okay.
MR. PAULSEN: My name is Mark Paulsen. I'm with CSA, an
EPRI contractor currently doing RETRAN development, and I'd like to make
a few comments.
First of all, after the May 26 ACRS subcommittee meeting on
thermal hydraulics, some information in the transcript indicated that
there was a serious error in the momentum equation. At that time EPRI
requested some additional information regarding the status of that
error, and I think we've been informed a little bit more where Dr.
Wallis was coming from today in his discussion.
At that time we were provided with some draft information
regarding the momentum equation. It was work in progress, comments, and
no real specific questions. At this time I believe the NRC and the
staff are in the process of formulating questions in the form of a
request for additional information, which we will be responding to.
Since in the ACRS subcommittee meeting there was an
indication of a potential flaw in the momentum equation, basically a
fundamental flow, we took that as a serious potential problem. And so
it has been reviewed. And at this point our feeling is that there has
been some misunderstanding even after today's discussion on how the
momentum equation formulation is used.
I don't believe we have time to treat that adequately today,
and we'll be doing that in the future. But basically the
misunderstanding has to do with how the momentum is handled at the
boundaries of the momentum cell which Dr. Wallis had on one of his
slides. And basically what we do is resolve the velocity components at
the boundary at the inlet of a momentum cell and an exit of a momentum
cell in the angle of the junction orientation. And that is where the
vector information is applied.
DR. POWERS: But Professor Wallis in his presentation called
attention to the fact that in some cases he couldn't even tell how the
boundary would be drawn.
MR. PAULSEN: There are some difficulties, and that gets
back to modeling practices when you're trying to use a 1D representation
of a momentum equation to do a complex three-dimensional plant, and much
of that information is handled in how the engineer inputs geometric
information for a particular junction.
DR. POWERS: Well, I mean, it sounds very challenging to the
engineer.
MR. PAULSEN: It is, but we must not forget that we have had
somewhere in the vicinity of 30 years of experience using the momentum
equation that's formulated, as is the one in RETRAN. It was based on
work originally done for the NRC on the RELAP-4 code series, and there
have been improvements made. So this formulation of the momentum
equation goes back starting in the early seventies with additional
development done in the early eighties.
DR. WALLIS: Can I ask you then about that? If I were to
study RELAP, would I find the same kind of things that I found in this
document?
MR. PAULSEN: If you were to look at RELAP-4, you would find
no information on the vector nature, because it basically solved the
scalar equation. And because of that, there were serious problems at
times when you were handling components like t's and y's where the
full -- let me say the complete upstream flow was being considered in
the momentum at a 90-degree angle. And that was one of the reasons that
some of the work was done.
DR. WALLIS: RELAP is used, I understand it, by the NRC and
by many, many people.
MR. PAULSEN: This is RELAP-4 that I'm referring to.
DR. WALLIS: But I'm just concerned that -- all I looked at
here was RETRAN. I'm concerned that if there's a generic difficulty
with momentum equations, we may have to deal with that too.
MR. PAULSEN: Well, I think if you look at the RELAP-5
equation, you're going to find that it degenerates basically to
something very similar to what we have for RETRAN.
DR. POWERS: Well, that doesn't change the question, I
think. I guess I'm a little confused. Can you explain what the
misunderstanding is here?
MR. PAULSEN: Well, I think it's probably going to take more
time than we've been allotted, and Mr. Agee has something that he would
like to comment on. But basically I think the confusion is related to
the definition of that W psi term that is in effect the velocity vector
at the surface of the momentum cell. And I think it's going to take
more than the time we have allotted here to resolve that.
Basically, though, as a result of this discussion about the
momentum equation, we at CSA, the EPRI staff, and some additional EPRI
contractors have reviewed the momentum equation, and it is still our
feeling that the momentum equation is being handled adequately and that
there really is no safety implications right now because of the
formulation of that momentum equation.
DR. WALLIS: No, no. I am sorry, I am going to have to talk
to you here. You know, this has been an ongoing dialogue now for a
couple of months, and I think you folks have to listen carefully to what
I said, and simply saying everything is all right makes it worse.
MR. PAULSEN: I think we are basing our justification -- our
statement on the fact that we think we can mathematically justify what
has been done in the momentum equation, and even more than that, I think
we can demonstrate from a number of plant analyses, there are hundreds
of plant analyses where RETRAN has been compared against plant data,
where we have flow calculations that compare against plant data. We
have separate effects tests where we have --
DR. POWERS: I can't imagine how a plant analysis would
persuade me that the equations were proper in a code.
MR. PAULSEN: We can do separate effects tests also.
DR. POWERS: Well, even that strikes me as somewhat
challenging, to show me that my comparison of in to out and the
predictions of same show me that all the equation inside of some
geometry are correct. I can't imagine how you would go about doing
that.
MR. PAULSEN: Okay. What we can demonstrate is that we can
match experimental flow rates and pressure drops. We can --
DR. POWERS: I bet I can write a code now, at this table,
with -- on one sheet of paper, that, for any experiment you would care
to describe to me, would be capable of matching the experimental result.
DR. KRESS: If you had an adjustable.
DR. POWERS: If I had one -- one or two adjustable
parameters.
MR. PAULSEN: If they are loss coefficients, that's right.
DR. POWERS: Yeah, a few loss coefficients, a few friction
fractures and I will get it.
MR. PAULSEN: And that is the standard engineering practice
is to use loss coefficients in these complex geometries so that you can
match the pressure balance.
DR. WALLIS: No, no, no. Please, please. I know -- I know
what I am going to hear. I am going to hear things like standard
engineering practice and engineering judgment and so on. That is not
the right way to handle this, because that just -- that just makes one
wonder what kind of judgment this is. It is actually bringing engineers
into disrepute by saying this is the kind of judgment -- you have got to
be very careful when you are faced with a very fundamental problem like
this, which I think is real, of saying, oh, it is okay, because it is
just engineering, or it is just government work, or it is just nuclear
reactor safety or something. That isn't -- that makes it worse.
MR. PAULSEN: I don't think we are taking that cavalier
attitude. And I guess there is going to have to be some more discussion
on this, but, basically, I wanted to point out that we have reviewed it
and at this point we don't feel that there is a serious safety
consideration.
And at this time I would like to turn the time to Mr. Agee.
MR. AGEE: Thank you, Mark. Thank you, gentlemen, for
offering us the time to talk a little bit in response to Dr. Wallis'
statement.
I would like to back the conversation up a few minutes and
point out what the fundamental reason for RETRAN is. Why did we develop
the code? And that was basically to predict the overall behavior of the
plant accurately enough to make operational decisions and safety
evaluations. Clearly, the detail behavior at the micro-structure is not
of interest and intentionally is averaged out of these equations.
We use and depend heavily on the known plant condition prior
to an event as part of the calculations. In fact, RETRAN is set up to
take advantage of the known information. It doesn't do any good to have
a computer program that is set, that uses information that is not
available to the people doing the modeling and to the engineers making
the calculations.
As has been repeated a number of times, RETRAN has been
successfully used over a 20 year period for many plant analyses, and
very successful for this. Statements that may imply that momentum
cannot be used in the codes ignore this proven history and discredit the
standard engineering practices for large facilities.
Clearly, any code can be improved. We acknowledge that at
EPRI. We have worked very hard in terms of developing fundamental
theories and expanding the state of the art. This work will continue.
However, to focus on unimportant events into a particular analysis
capability is counter-productive.
I would like to back up and show just a couple of
viewgraphs, given the time. This is the recommendation that the
subcommittee made to the AIF Policy Committee following the Three Mile
accident. Existing safety and licensing analysis practice tend to
concentrate on limiting worst case events, with particular emphasis on
hypothetical accidents to the neglect of the higher frequency and lower
consequence events. The principle recommendations are close the loop
between the plant safety and performance analysis, and actual operating
experience using more realistic analysis. Use systematic engineering
tools to extend present areas analysis and scope, duration and event
consistent to provide a broader, more realistic basis for operating
procedure and reliability of systems.
This is the specific focus of RETRAN, gentlemen. That is
what we are doing.
DR. POWERS: I guess I am at a loss to understand that this
has to do --
MR. AGEE: And as we are doing that, I think it is important
to look at the type of things that we are trying to solve. We are not
trying to solve something from a fundamental point of view, in terms of
knowing nothing about it other than the basic geometry and fundamental
physics.
If you would look at most operational transients, and there
are hundreds of them, you have primarily a mild thermal-hydraulic event,
there is some type of action, generally, control operator action, which
ends up with an equipment response, some type of SCRAM, valve motion, et
cetera.
There are some very important modeling features that
generally are not considered specifically in large break LOCA type of
analysis and other events. That is, one must properly describe all
applicable systems. The hydraulic network is part of this, so I am not
taking and trying to say it isn't. The control system, the component
characteristics, the feedback parameters, all of this type has to be
described the best you can. Again, this is engineering. You have to
use what is available to you at this point, you can't generate something
that is not there.
The way that we do this in RETRAN, again, is to use the best
information from the plant, the pressures, the flows, the temperatures,
and then you back out the so-called loss coefficients in all of the
areas where there is question in terms of the momentum equation. We
grant that this is an approximation, there is no other word for it. If
you don't make that class of an approximation, you can't start, so you
do that. You use realistic boundary conditions.
What is the response to this?
I mean, this goes back to our 20 years of experience with
the code. I found one interesting comment in the transcript from the
May 25 ACRS meeting. And here the Committee was discussing the code
developers should actually go out and model a few plants and learn
something.
I'd like to point out that that's exactly what we have done.
The work that EPRI does, our contractors, we work with utilities and all
the analysis, we looked at all the issues involved. We've been there.
We've done that.
It's not that we're perfect. We're not saying that. But
we're trying to use what is available to get the right results. That's
why when I talk about this type of thing, I'm talking from experience,
not in terms of the theoretical basis, but what is the fundamental
behavior of the plants.
DR. POWERS: I guess --
MR. AGEE: I think that the case in point was lost that the
cumulative effort -- this is not just EPRI, this is hundreds of utility
engineers. It's the people that are working on the plant. The plant
experience is what goes into the knowledge base on this type of thing.
DR. POWERS: I guess I'm confused. We've had a question
posed about the treatment of the momentum equation. Are you telling me
that we have all these hundreds of engineers working at plants that have
looked at this momentum equation and they say it's okay? I mean, I'm
just perplexed at where we're going with this discussion.
MR. AGEE: I think you're missing the point. If you look at
the standard text, Bird, Stewart, and Lightfoot, this is precisely the
treatment that is given in these books. This is what these engineers
have been trained out at the university in how to use this information
to be able to handle and model real systems. You don't have full
information. You use what you have.
DR. APOSTOLAKIS: Is there going to be a detailed response
from EPRI and its contractors to Professor Wallis' points? Because at
some point we will have to form an opinion in this committee, and it
seems to me that Professor Wallis was very detailed in his comments, and
you are very general. To say that it's standard engineering practice
doesn't mean anything to me. He told us explicitly where he thinks
equations are wrong, and I think it would behoove you to come back and
say he is wrong there and be as specific as he was.
MR. AGEE: We specifically requested a meeting with Dr.
Wallis to go over that type of issue --
DR. APOSTOLAKIS: Okay.
MR. AGEE: Two weeks ago before this meeting. Dr. Wallis
was unavailable to attend that meeting. And that to me is the only way
we're going to get this type of thing resolved is to sit down and go
over that.
DR. APOSTOLAKIS: Okay. Fine. Thank you.
MR. AGEE: However, I guess I would also make a statement
we're not going to meet with complete closure. These software codes
have complexities, and this is what I'm trying to point at, is that real
systems don't lend themselves to simplicity at the level that one would
like. What one has to fall back on is the assessment. And this is what
I keep pointing at, is that this is what I keep coming back to here.
Within the document we gave the NRC, we have 18 separate
effects, 10 system effects. We have comparisons that tie the two codes
together. We have within that document 20 cases of real plant data.
Within other places we have over 80 different cases of actual
demonstrated capability versus plan. Now this gets back to what is
safety? What are we talking about here in this room?
DR. POWERS: Well, I think it gets back to the question of I
guarantee you, I guarantee positively that I could take every one of
your cases, I could sit here at this table and in half an hour write a
model that would match those.
MR. AGEE: I am missing your comment.
DR. POWERS: Having a bunch of cases, complex cases, and
saying I matched input and output with the computer code, therefore the
equations must all be correct in them, is not very persuasive to me,
because I can do that. I can always do that if you give me enough
adjustable parameters.
MR. AGEE: Let me put it this way. No computer program --
and I've made that statement earlier -- is perfect. There are
approximations in there. In terms of errors, what do you refer to as an
error? What you have to do is to make an engineering decision based on
the information you have in front of you.
DR. APOSTOLAKIS: As I recall --
MR. AGEE: The state of the art that we have right now --
DR. APOSTOLAKIS: As I recall, Professor Wallis' comments in
his presentation he did not use the word "approximation." He used the
word "wrong."
MR. AGEE: And I disagree with that statement.
DR. APOSTOLAKIS: Okay. So you should address his comments,
it seems to me --
MR. AGEE: We feel that some of Dr. Wallis' statements are
very simply confusing the momentum and the nodal balances of the
equation. These equations are straight out of Slattery and Bird,
Stewart and Lightfoot. It's not simply EPRI's --
DR. WALLIS: Can I comment on that, please?
I have taught from Bird, Stewart and Lightfoot for about
half my life, and I cannot find anything in Bird, Stewart and Lightfoot
which is correctly being interpreted in the literature you gave me.
MR. AGEE: This is fundamental --
DR. WALLIS: It's been misunderstood and misused, and it is
wrong -- excuse me -- it is inappropriate to invoke Bird, Stewart, and
Lightfoot as an authority for what was done.
DR. APOSTOLAKIS: Can't invoke the saints.
It seems to me, though, that -- I agree with you that a
subcommittee meeting is the appropriate form to address --
DR. WALLIS: Exceptionally appalling, exceptionally
appalling. You talk about hundreds of engineers misusing a basic text.
I find it absolutely incredible.
DR. APOSTOLAKIS: All I'm saying is that when I form an
opinion, I would like to have detailed responses to Professor Wallis'
criticism, because he was very detailed when he criticized the work, and
to come back with statements as to what safety is, it seems to me that
that doesn't get you very far with this Committee. And I can assure you
this Committee is very pragmatic. We do live with approximations all
the time. So this will not be the first time that we will be faced with
something like this. This is not an academic committee. So that's all
I want to say. And it seems to me the proper form for addressing the
questions is a subcommittee meeting.
DR. WALLIS: Well, I don't know, because --
DR. APOSTOLAKIS: Or a detailed document, written document.
DR. WALLIS: I mean, I have spent a lot of time on this, and
I am not going to accept any more than I would accept from a student.
I've explained to a student, you know, why this homework is wrong. I'm
not going to accept a protestation that it's right. It's got to be very
clearly explained, and I think you're going to have a very rough time if
you want to claim that these equations have an intellectual authority.
Now if what is encoded fits the data is good enough for NRC,
that's another question entirely.
DR. POWERS: Well, that's a question --
DR. WALLIS: It's not what I was addressing this morning.
DR. POWERS: It's a question for the NRC to answer for
themselves. It's clear that the ACRS has to make an independent
judgment, and it's clear to me, to echo Professor Apostolakis, we've had
a detailed critique. It has not been a critique on whether or not the
code was able to match some experiments or not. It's a critique on its
intellectual foundations. And at the very minimum it's a critique on
the adequacy of the documentation. It may in fact go farther than that
by a substantial margin.
And pending some edification on that, I think we'll draw
that critique.
DR. WALLIS: I'd like to say I'm very sorry that this
happened to EPRI. I think what was revealed here is something that is
not just peculiar to this particular story. That there are other places
in the history of this Agency where for some reason I just cannot fathom
people have been prepared to write down anything which seemed to get
them to step 1 and then spend all their life worrying about fitting
reactor data and making arguments about safety. That really you've got
to worry I would think about step 1, because your integrity is at stake.
It's very difficult to say all the other steps are fine if there's
something in the past which is going to be unearthed.
This isn't -- I don't think it's -- I'm very sorry that EPRI
is the example of this. I think if we look at some other work, we're
going to find the same kinds of thing. So this Committee and this
Agency have to examine essentially -- make a moral decision I would say,
is intellectual integrity of any value in evaluating -- making
regulatory judgments.
MR. AGEE: Well, let me put it this way, I have 20 years in
the area and understanding of the codes, not only at EPRI, those
generated by NRC and the vendors, and the approximations and the
summations that are used in RETRAN if anything are more precise than
those in the other codes. So, gentlemen, what you're looking at here is
a question of the foundation basis of the entire industry.
It's not RETRAN that you're talking about here. It's the
way one has to get from the current state of the art to analyzing real
plants. If you take and look at the geometry of any reactor, I agree
with Dr. Wallis fully, you can't look at it as a series of little pieces
of straight pipe. It's a very complicated machine. The components in
the steam generator, the pumps, et cetera. They do not lend themselves
normally to one-dimension analysis. I can be perfectly precise.
DR. WALLIS: One could simply say I hypothesize that this
equation works and I will use it for reactors, and if it seems to work,
that's okay. But when you give it intellectual foundation, then that
intellectual foundation has to be examined carefully.
MR. AGEE: And the intellectual foundation I think you're
looking at is the first time that the documentation has ever made an
attempt to tie in all of the pieces. What you're looking at in RETRAN
is probably an extremely thorough job of documenting the miniature
details that one has to make, the engineering decisions that have to be
made in this. Other software has to do the same thing.
However, the lack of the documentation is I think what is
missing. In terms of going into a code like RETRAN clearly we're using
a one-dimensional tool, and we're using it extended beyond the range
that the logic would normally say it can be used. That, gentlemen, is
really the reason that we have to go back to the what does the plant
say? Can we do this? Who do we show the results?
DR. WALLIS: Could I ask, suppose that everything I said
this morning was correct. Does that make any difference?
MR. AGEE: If everything you said is correct?
DR. WALLIS: Everything I said this morning was correct. It
doesn't make any difference to most of your arguments. Should it make
any difference to how RETRAN is viewed?
MR. AGEE: I think that what we tried to do -- let me answer
the question slightly different. What we tried to do was to spell out
where -- let me say the bones are buried so that the engineers applying
the code could make the best decisions possible. Now we intentionally
showed the weak spots along with the strongest points.
I do not believe that if everything you said today was
brought in and evaluated you'd see any difference in plant analysis.
There's just at the current level that you're talking about modeling the
systems you're talking about making nominally a hundred -- in the range
of 100 nodes in a system. Now there's no way that one can get into the
complex detail of a full three-dimensional model. Now I would like to
point out again though that getting into the complexity does not buy you
anything. This is the reason I keep coming back to the safety point.
DR. WALLIS: Well, Lance, let me tell you my problem. You
don't seem to have a problem. I have a problem of this type, that if a
student working on thermal hydraulics uses this as an authoritative
document, and as part of his thesis wants to use equation so-and-so, and
brings it in in his thesis, I look it, I say I can't accept that in your
thesis. He says but it's in RETRAN, therefore it must be okay. I have
a problem with that. You may not have a problem with it. But at a
university we have real problems with that kind of thing.
MR. AGEE: But what you're looking at is the state of the
art 20 years ago has been taken one small step forward. We have tried
to correct some of the more glaring deficits which I think you're here
pointing out some of them -- you have missed a number of them,
incidentally -- in terms of the foundation of the software. We've tried
to point out where that is, and we've tried to make first-order
corrections to it. These first-order corrections have been very
beneficial.
Whether it is apparent or not to the Committee, the changes
that we have brought into RETRAN have made it considerably better in
terms of reproducing and reliability than they were before this. This
is part of the point that I'm trying to make, gentlemen, you've got to
take and evaluate what you have in terms of what currently is available
and what you can do, not in terms of what you would like in a perfect
world. And that's why I keep going back to what is the purpose of the
tool, and that has to be used in terms of asking for it.
Now why are we documenting the code, and I told you that, is
to demonstrate where these assumptions are made, what are our closure
assumptions. In this particular case I would like to make a distinction
between the momentum equation as it's fundamentally written and the
assumptions that we're making to close the equation. If I heard
anything this morning, it was questioning those assumptions and closure,
not necessarily in our concept of what the momentum equation has done,
how do you go from a complicated system, close it with the proper number
of unknowns, and solve something? And what degree of accuracy do you
get when you solve it?
Now, okay, so again this gets back to what I was starting to
make the point on safety. What we're trying to do is understand how to
safely operate the plants and how to set limits on them. What you're
looking at in particular is that the plant operator at this point does
not have control over the design. Most of these plants have been
designed. They're now operating them. So they have considerations on
the operation of them.
What is implied here is that the safe operation means
understanding how the plant will perform and being able to keep away
from those situations that are considered -- let me use the word
"dangerous." I'd like to note at this point that this does not
necessitate precision. You don't necessarily have to know how deep the
rut is to avoid it. The specific here is anticipating the plant
response. And this is time-sequencing of events.
This is why you can take and use the momentum equation as we
have, normalize it to the conditions that you're starting with, put in
coefficients that come from the plant data, the best estimate of what
that is, force them into the form that resembles the one-dimensional
momentum equation, and then use them to extend and predict outward.
It's simply engineering practice. That's how it is. And this has
clearly made an outstanding contribution to the safety of the plants.
Although it does not seem to be acknowledged by the Committee, this part
of understanding how the plant will perform and being able to see that
when you do this and the plant responds that way, that you can now make
and interpret engineering questions and go forward with decisions on
that.
DR. SHACK: Well, as Dr. Powers said, at the very least we
all know that from the momentum equations and the energy equations you
can't get closure to this problem. You have to make additional
approximations, closure statements. What's been clear is that we have a
thermal-hydraulics expert who can't see how you've made those closure
arguments, and, you know, you clearly have to clarify that.
You know, I'm willing to believe that you understand the
momentum equation and the energy equation. It's what you did after that
that comes into question, and you need to clarify. You clearly can't
have been too successful. Those utility engineers aren't going to be
able to understand approximations any better than Professor Wallis has.
MR. AGEE: That's clear. Again, all I can say is that we
came back to Washington two weeks ago to sit down and go over it with
this stuff in detail and try to explain the closure. I do not believe
that Dr. Wallis will fully agree with all the assumptions made. In
fact, I told him that in terms of the notes that we had sent back and
forth. I thought there were many assumptions that we've made for
closure that are questionable.
DR. WALLIS: Well, Lance, I don't think I had any questions
about assumptions. Maybe I had one or two.
MR. AGEE: Let me simply say that --
DR. WALLIS: My remarks were of an entirely different nature
than about assumptions.
MR. AGEE: Let me simply say in the discussion this morning
that I heard, I think that a number of the places the questions that you
were pointing to really get down to what assumptions are used for
closure of the systems, Dr. Wallis. I'm not trying to be argumentative
in this point. I think if we get into the staggered-grid concept and
start working through, an approximation you have to make something at
some place.
Many of the cases that you were questioning were simply a
zero added to a number because these were the two points. We knew the
numbers should be zero at one point, and we had a value of it somewhere
else. We have to make a closure assumption because the component did
not exist. It wasn't the ignorance in the form that I think you were
thinking that the equations were in your discussion this morning. We
were working in the other direction, and we were working from a zero
boundary point to get to something.
So each one of the issues that you were bringing up goes
back to how does one go through this. And it's very complicated. This
is again where I'm stating that I think this is the first time that all
of the details of going through this have been spelled out in great
detail. I think you'll find that every other one of the software
packages has these or more, and so without belaboring the point --
DR. POWERS: I'm running into a time problem, so could you
conclude your statement, please?
MR. AGEE: Excuse me?
DR. POWERS: I'm running into a time problem, and if you
would conclude, please.
MR. AGEE: We did not anticipate to be able to close this
today. That's why we were hoping to discuss it earlier before while we
had time.
I guess the only thing that I can say is that the use of
this type of tool, even with its flaws, is a very important safety
component in the utility area out there, and this has made decisions
consistent with what the operator is seeing. And before people were
using the tools like RETRAN, the operators were anticipating that an
event be an overpressurization event when it was underpressure. These
were because the only tools they had were far more conservative and were
giving the wrong implications.
This is where I consider the benefit of being able to
extrapolate from the known conditions. Whether it's perfect or not I
think is another question. Whether it can be used and can be
demonstrated to be used successfully, I think that is the primary
question.
DR. POWERS: Okay. Thank you.
MR. AGEE: Thank you for your time, gentlemen.
DR. POWERS: I think we're scheduled now to hear a response
from the staff. Mr. Landry.
MR. LANDRY: Okay. My name is Ralph Landry, I am with the
Reactor Systems Branch in NRR, and involved with the RETRAN-3D review.
And what I would like to do this morning is just give you a brief update
on the status, explain where we are in the review and where we see
ourselves going at this point.
RETRAN-3D was submitted to the staff for review in September
of 1998. We issued an acceptance for the review. We decided to change
the way we do code reviews. The code reviews are being done in-house
now instead of using contractor support. And we decided that, based on
the experience we had with recent code reviews, that -- and the
criticisms of the documentation which we have been seeing, that before
we accepted the code for review, we were going to look at the
documentation and try to make a determination that the documentation was
sufficient to permit us to do the review.
We issued an acceptance for the review of RETRAN-3D in
December of 1998, and since that point we have met three times with the
Thermal-Hydraulics Subcommittee. The meetings with the
Thermal-Hydraulics Subcommittee are in themselves a part of the way we
have revamped the way we do code reviews.
Part of that code review revamping involves getting the code
in-house, not just the documentation, but an electronic form of the
code, put the code up on our computers and run the code. We have had a
lot of experience now with RETRAN-3D. We have learned a lot from doing
the review in this manner, and a number of the requests for additional
information we have issued were based on things that we learned in
running the code itself.
And, again, as I said, part of this revamping is to work
more closely with the Thermal-Hydraulics Subcommittee than we have in
the past. In the past when we did a code review, we would go to the
subcommittee and then to the full committee once we had completed the
review and we had our SER prepared. At this point we have been
interacting with the subcommittee all along the way with the review,
informing them of our concerns and hearing their concerns also.
The first round of the requests for additional information
were issued. We have received the responses to those requests. We are
reviewing those responses. We have come up with additional concerns.
Dr. Wallis' concerns, we have been informed of along the way, and we
have formulated those concerns in the form of a set of questions. And
we wanted to wait and see what the discussion -- how the discussion went
this morning before we issue those requests for additional information
to the applicant.
We have now taken on a member of the RES staff to assist us
with this review. The review has been done in NRR by four people. We
have the assistance from a member of RES staff who has also come up with
another series of concerns, and we are waiting to hear from him formally
what his concerns are because we issue those to the applicant.
We have performed an extensive assessment of the 3D kinetics
in the code. As you heard Dr. Wallis say this morning, RETRAN-3D, in
his opinion, was a misnomer because it is a 1D thermal-hydraulics code.
Well, the 3D does come from the neutronics part of the code, that it is
a 3D neutronics package.
We have performed extensive calculations. We looked at some
suggestions which Professor Shrock has made that we look at the SPERT
tests that were performed back in the late 1960s and determine if a code
of this nature can indeed calculate the response of a core to such
things as super-practicality. And based on the work that Tony Ulses has
gone with the NESTLE code in calculating this SPERT-Ecore test, yes,
they can. Tony has gotten some excellent results with NESTLE, which is
a three-dimensional nodal diffusion code calculating the hot standby and
full power tests in the NESTLE facility.
Now, we are going to request that formally, that EPRI do
those calculations with the RETRAN-3D code. We asked them to do that
when we met with them in May and now we are going to formally ask them
in writing to calculate those tests with RETRAN.
We have a number of plant decks which we have received from
the applicant. We have asked for additional decks which we want to
further test the code.
As we have discussed with the Thermal-Hydraulics
Subcommittee, this code has a great many options to it, which makes the
code probably the most user-influenceable code we have ever seen.
Because of that, we feel that the training of the code users is
essential. It has to be high quality, it has to be very well done.
There is going to be a training course in August in Idaho for code
users. We are sending two staff members to that course to audit the
training. We are going to make the training that is given to the code
users a part of our review and a part of our discussion on the SER.
There are code modifications which have been made since we
began the review. We are reviewing the documentation on those
modifications, and as soon as the code with those modifications
installed is available, we will be working with that version of the code
also.
So where do we stand? We plan on having the requests for
additional information to projects this month, before the end of July.
We are planning to audit the RETRAN-3D training course in August, and we
are looking forward to completing an SER, hopefully, this calendar year.
We are quite concerned about Dr. Wallis' concerns. We are
reviewing the information which he has presented. We are discussing
in-house with members of the research staff and with members of NRR
staff, and looking at the way in which the -- looking at what Dr. Wallis
has said and trying to make some determinations internally about this.
Now, I would just say that part of the way we revamped this
review was we would only look at the delta in the code, the change in
the code from when we reviewed the RETRAN-02 version. In doing so, from
what Dr. Wallis has seen, we feel that by looking at only the new
material, we did not go back and look at the old material, then perhaps
something may have slipped through. But we don't know at this point and
we want to continue our review of Dr. Wallis' concerns.
DR. POWERS: Do any of the members have questions to pose at
this point?
[No response.]
DR. POWERS: I notice that your schedule says sometime in
the calendar year. It seems to me that that is an extension of what I
have seen previously. Is that the case?
MR. LANDRY: We have been saying our schedule was by the end
of October, to have the SER. Based on some of the concerns that have
been coming up, and some of the concerns that we have been discussing
with research and with Dr. Wallis, and with the additional requests for
additional information we are going to be issuing, I think October would
be rather optimistic.
DR. POWERS: I think the committee was concerned about the
tight schedule when we went over schedules in the past. It is not a
criticism, I think you need to take time on this and whatever time it
takes, it is better to do a good job than to do a quick job in this
case.
MR. LANDRY: That is our feeling also, that we are not -- we
are not officially changing our schedule at this point, but we don't
want to be driven by schedule. We want to make sure that when we do
this review, because we are doing this review in a different manner than
we have in the past, we want to be sure that we do a good job.
DR. POWERS: You are doing a pilot here.
Do members have any other questions they would like to pose?
[No response.]
DR. POWERS: Well, thank you, and thank all the speakers.
Thank you, Professor Wallis for your tutorial.
I will declare a recess until 10:35.
[Recess.]
DR. POWERS: Let's come back into session. We are now going
to go from the theoretical to some of the more practical aspects of
thermal-hydraulics in the nuclear industry, and I will call upon the
Chairman of the Thermal-Hydraulics to introduce this subject and get us
on the pathway.
But before I do that, Professor Uhrig, do you have a piece
of essential information for us?
DR. UHRIG: Yes. I think the committee and the audience
needs to know that I am a project manager on a DOE supported project on,
among other things, developing an inferential method of feedwater flow
measurement in nuclear power plants. And because this is a potential
competitor to one of the methods being discussed here this morning, I
will limit my participation to the regulatory aspects.
DR. POWERS: Thank you, Professor Uhrig.
Professor Wallis.
DR. WALLIS: This is a very interesting subject. It has to
do with margins of safety and, specifically, when margins exist because
of uncertainties, in order to be sure you don't step over some bound
because you are uncertain of your calculations, you back off a bit from
that bound. That is just called a margin. And this is why the
licensees are required to assume a 102 percent power, 102 percent of the
power that they actually think they have in their reactor, because of
uncertainties in measurement, they might actually have some more.
And the real issue here before the committee is this
principle of if -- if you get better information and your uncertainties,
therefore, are reduced, and the uncertainties in the calculations, what
you do with this information are also reduced such that you feel that
you can get away with a smaller margin. Is this then grounds for
changing the regulations?
And this is really what I think we should be focusing on
today. This is just an example of this greater principle. Whether or
not there is a flow meter which can reach this sort of level of
certainty or reduce this level of uncertainty is I think a secondary
question and I don't think we need to get into much detail about flow
meters might qualify.
And I think the staff does need to think about the
requirements they are going to impose on licensees in order to show that
the uncertainty has been suitably reduced, and how they are going to
process that in a way which convinces them that margins be reduced in
some appropriate way, because the connection between uncertainty and
margin has not really been spelled out too well by this agency. Maybe
this issue will force them to do that.
So I would like to hear then from Joe Donoghue.
MR. DONOGHUE: Good morning. Thank you.
DR. POWERS: Good morning.
MR. DONOGHUE: As you know, my name is Joe Donoghue, I work
in Reactor Systems in NRR, and some of the committee may be familiar
with the briefings I gave on the steam generator rule, the non-rule, and
you will be relieved to know I have nothing to say about that any more
today.
MR. BARTON: That is probably a smart move.
MR. DONOGHUE: I came here to talk about our proposed
revision to Appendix K in Part 50. The objective that we have is to
take the opportunity to reduce regulatory burden. This is based on some
licensee-industry initiative that I will talk about in a second. But we
see the opportunity to reduce the burden and this will permit a
reduction, as you have just heard, in the assumed reactor power for LOCA
analysis.
This is an opportunity for some licensees to pursue small
uprates in power or some other benefits that they could see being cost
beneficial.
From our point of view, from the staff's point of view, the
agency's point of view, we see it as a way to avoid what we expect to be
a large number of -- a potentially large number of exemption requests
based on the potential to reduce the uncertainty and pursue the smaller
-- reduced regulatory burden.
There is one example that I will mention in a second. Oh,
it is right on this page. I want to jump down to the fourth point here,
where Comanche Peak has obtained an exemption, the staff has granted the
exemption, yet they cannot implement that until the power uprate, the 1
percent power uprate is approved. That is still being reviewed.
As I mentioned, the rulemaking has been initiated by the
proposed use of improved methods to measure feedwater flow, hence,
reactor power. The case was made to the staff in the exemption request,
anyway, the case was made that indeed a smaller uncertainty due to this
instrument could justify a reduced margin that was imposed by the rule.
Before the staff even started reviewing the instrument that
Comanche Peak wants to use, which is incidentally made by Caldon, the
licensees, the industry in general, voiced a lot of support for an
effort to review the instrument, and I think in the vicinity of 20 or so
licensees expressed interest in the letters to the NRC.
There is a competitor to the Caldon instrument that we will
talk about a little bit, ABB-CE has a system known as cross-flow. There
may be others out there that haven't talked to the NRC. We have had
meetings with ABB-CE on their instrument and I am aware of at least one
licensee that will be pursuing using an instrument, possibly submitting
an exemption request this year.
A little bit of background. At the end of last year we
started the idea of pursuing a rule change. Early in the year we
submitted a SECY paper which was a rulemaking plan and the Commission
told us to go forth and, as a matter of fact, rapidly go forth and put
together a proposed rule.
CRGR was briefed early in the year and they will want to
hear from us again, but, basically, they had positive things to say
about what we were doing. At this point the proposed rule has completed
most of the concurrences. Right now it is in the Office of NRR, but it
is very shortly going to go to the EDO.
And so the package you have, I think that you -- that the
ACRS staff received about two weeks ago was somewhat revised based on
some OGC comments but the technical content in there is the same. The
things, the kind of things that you will see change are in the Federal
Register Notice. I will get into that here a little bit where the
history of the Appendix K rule, the original Appendix K rulemaking was
laid out in more detail.
As you know, 50.46 requires that evaluations be done either
on a best estimate or an Appendix K basis. The 102 percent requirement
is one of many conservatisms in Appendix K. It is interesting, but
there is no other regulations that specify a power level to be assumed
for analysis. Although there are regulatory guides and SRP sections
which do, either through reference to Appendix K, or directly state that
some, usually 102 percent, power level be used.
I will add here that in many of the SRP sections that do
mention the specific power level, it is always connected directly to
instrumentation uncertainties. The rule language in the existing
Appendix K is a little bit ambiguous, it has the phrase "such as
instrument uncertainties" in there, and that is an issue that we have
deal with in the concurrence process on this proposed rule.
Okay. I will bore you with a little bit of Appendix K
history. What we have learned by going through the actual ECCS hearing
transcripts and exhibit material was that it wasn't a detailed basis
written down. Maybe people thought about it and talked about it, but it
wasn't written down anywhere, a detailed itemization, you might say, of
the 2 percent. Why was 2 percent chosen and put in the rule? What was
the technical basis for that is not clear. It was mentioned in
connection with power measurement uncertainty, that kind of language, as
you just mentioned, went into the rule itself. But we were hoping to
find a little bit more detailed background on why the 2 percent was
chosen to see how -- first of all, whether, and then how it could be
reduced. It wasn't there.
We also saw in several places -- I mention here the standard
considerations for the original ECCS rulemaking, as well as some later
work where the staff considered the best estimate LOCA methods and
changing, making that change to 50.46, where the staff acknowledged
there were significant conservatisms in the Appendix K requirements.
As a matter of fact, the Commission said in the statement of
considerations for the ECCS rule, that it expected future relaxations
based on increased knowledge. One step was the work done to get best
estimate analyses permitted in the rules. We see this as a very small
step in relaxation, but it is significant to the licensees. They see it
as important to their well-being.
DR. WALLIS: Can I ask you something now?
MR. DONOGHUE: Yes, sir.
DR. WALLIS: If you don't have a detailed basis for 102
percent, are you going to supply it for 101 percent? Are we going to
simply say that because uncertainty has been reduced by a factor of 2,
we will reduce the margin by a factor of 2, though we don't know why the
initial -- original amount is in existence in the first place?
MR. DONOGHUE: Right now we are not trying to establish a
minimum. As I will show --
DR. WALLIS: Well, it seems to me you need something more
than saying it was 102 for reasons we don't know, now we have got better
measurements, so we can reduce it to 101. You really have to, I think,
give a basis for the 101, because the 102 may have just been somebody's
guess and in the modern climate not acceptable as a rationale.
MR. DONOGHUE: Agreed. Agreed. I think we are going to
leave it to the review of the particular amendment requests or whatever
the uncertainty analysis is going to be at the licensees or vendors.
DR. WALLIS: Do you have the wherewithal to do that?
MR. DONOGHUE: Well, we have done it. We have gone through
the process so far with Comanche Peak.
DR. WALLIS: Well, review -- I mean do you have the
wherewithal to make your own calculations, whether it should be 101 or
102 percent? Not to review someone else's which you then buy into or do
not. That is the problem with the whole NRC review process. Someone
looks at it, I don't see any element it would take to apply it.
You want to have some intellectual basis for you own
decisions.
MR. DONOGHUE: Yes.
DR. BONACA: I see this as just looking at LOCA, but isn't
it true that all the accident analysis done, for example, for the
Westinghouse plant assumed 2 percent error, you know, from bystables,
for the string value for the measurement of power, and also 2 degrees F,
and also 50 power supplies. I mean there was something tied to the
instrumentation that led to those values assumed by the vendors and then
the NRC grabbed it and put them in the regulation.
MR. DONOGHUE: Well, that's --
DR. BONACA: Well, that is history, I mean.
MR. DONOGHUE: Well, that is what we tried to ferret out of
the rulemaking.
DR. BONACA: I understand that. But I am saying if you are
only focusing on LOCA when there is, you know, a pattern of application
that goes in through the whole accident analysis.
MR. DONOGHUE: We are focusing on the rule change that we
are making.
DR. BONACA: Yes.
MR. DONOGHUE: A power uprate amendment, and that is what we
are doing right now with Comanche Peak. When a power uprate amendment
is submitted to the staff, we have to look at all the accident analyses.
DR. BONACA: Yes.
MR. DONOGHUE: And, indeed, the majority of them for this
plant were done at 102 or sometimes higher power levels.
DR. BONACA: The point I am trying to make is that the
answer that you are looking for may not be in the LOCA rule, it may come
from all the other applications in the accident analysis and how it was
treated, and particularly in the treatment of uncertainty for the
reactor protection system. It has a clear description of why 2 percent
was used.
MR. DONOGHUE: As far as the set point methodologies, I
guess, right.
DR. BONACA: Oh, yeah, in the LOCA analysis. All the other
analysis and how it was treated.
MR. DONOGHUE: What we have looked at so far for Comanche
Peak, that is the one example I am most familiar with right now, the set
point methodology uses a 2 percent number and from what I understand, it
was used for -- it doesn't spell out in the set point methodology WCAP
exactly why that was used for power measurement, for feedwater flow
input to power measurement. And right now we think that for our
purposes, for just effect on the LOCA analysis, there is not a problem
with reducing that uncertainty based on what they have submitted for the
Caldon instrument.
But for power uprate we have to look at all the other
accident analyses to make some sense.
DR. WALLIS: Reducing the uncertainty is one thing.
Reducing uncertainty in measurement is one thing. But then going from
that, making -- to reducing margin implies that you somehow have a
rationale for knowing why there's a 2-percent margin today, rather than
it was grabbed from somewhere and put into the regulations, as I think
my colleagues have described, from some vendor calculations.
I'm not sure that you have the wherewithal to know really
what your bound is and what the margin is and what the probabilistic
chance of going over the bound is, all that kind of thing, the
analytical tools to figure out what the margin is and what it should be
if you get better information. I'm not sure you've really crossed that
bridge yet.
MR. DONOGHUE: I can't disagree with you. I mean right
now -- for example, if a licensee challenged us to reduce the margin
to -- to reduce the analysis margin to zero, to do all the analysis 100
percent --
DR. WALLIS: Well, even 1 percent. You've still got to have
a rationale. I mean, you're going to say he's reduced -- he's measuring
instead of 2 percent inaccuracy by 1 percent inaccuracy, so we'll let
him have 2 percent on this margin rather than the 1 percent. That seems
sort of plausible. But there's no direct connection between the two
logically.
DR. BONACA: Realize, I really wasn't making a comment
regarding the adequacy of removing the margin. I was only -- from the
presentation it sounds that it was extremely obscure where the 2 percent
came from, and I do believe if you go back to the specific topicals on
set point calculation and the measurement errors and how they were
derived adding together string errors by stable error and so on, you'll
find that's where you've got 2 percent. And that's where the vendors
put it in. Now the LOCA rule was the only one where it was grabbed in
and made part of the regulation. And all he's saying that -- I don't
think it was obscure as it seems from the presentation.
DR. WALLIS: Okay.
DR. POWERS: If we attempt to go back into the history and
search for the origin of the 2-percent conservatism and we fail to find,
you know, exactly why they picked 2 percent or what it was intended to
do or a rationale, do we have to go back and look at the intent of the
rule and all the conservatisms that are in there to see if maybe that
putting 2 percent on the power is a trivial conservatism compared to all
the additional ones that are put in?
MR. DONOGHUE: One thing I was going to mention was -- and
the answer I think was yes, to some extent. We did go back and look at
the work that was done to justify the best-estimate analysis, and the
NUREG number escapes me, but the ECCS compendium contained a lot of work
where people tried to compare the levels of conservatism of the
different requirements and assumptions, and you saw a relatively
small -- in terms of calculated peak centerline temperature a relatively
small effect of the power being changed. You know, compared to things
like decay heat, which is a huge assumption and some other things.
DR. POWERS: Yes, if you put 20 percent on the decay heat,
what in the world does 2 percent on the power do to you? People are
contemplating changing the decay heat as well.
DR. WALLIS: Decay heat comes from the power.
DR. KRESS: Yes, but --
DR. POWERS: 1.02 times the curve that they're using times
1.2 -- that 1.02 kind of falls out somewhere there. There are people
contemplating changing that 1.2 as well.
MR. DONOGHUE: Yes, I was going to mention that in a minute
or two. We're dealing with one relatively small conservative assumption
in Appendix K.
One of the comments that's been made during the clearance
process and will I'm sure be made during the public comment period will
be why aren't we addressing all the conservatisms? Why aren't we
comparing in some detailed manner the conservatisms on the 1.02 to the
other items in Appendix K? And I'll jump ahead and say right now that
we for one thing practically want to make this change relatively
quickly. But also there's another effort afoot in the -- as I'm sure
you know.
That is SECY-98-300, a risk-informed Part 50 effort, which
is going to prioritize -- this is my understanding -- it was going to
prioritize all the things that we want to consider to change in Part 50,
and this should be among them, and if the staff decides at some point
that changing Appendix K in total is appropriate, that will be
addressed. And we didn't see this change as short-circuiting that
effort, nor did we see a reason to stop this effort in order to wait for
that to be done.
DR. WALLIS: Well, let me ask you, it's a LOCA analysis, 1,
2% of licensed power rate. Why have 2 percent more power than I think I
have? This means some things are hotter than I think they are? Also
affects the decay heat to some -- but not by a direct 2 percent. If I
go up by 20 percent in power, I don't go up by 20 percent decay heat, or
do I?
DR. KRESS: No.
MR. DONOGHUE: No, the same information I think that was
generated for the ECCI compendium mentioned that.
DR. WALLIS: But do they -- are they related linearly or
some other way?
MR. DONOGHUE: From my understanding it's not linear.
DR. WALLIS: No, it's not.
MR. DONOGHUE: And --
DR. WALLIS: So the effect on the LOCA analysis of not being
sure about your power level is not a straightforward thing. You can't
say well just take everything proportional. It's 2 percent here, it's 2
percent there, 2 percent -- it may be 2 percent flows up to 10 percent
when you analyze it, or it goes down to 1 percent all the way through
the analysis. And its effect on peak clad temperature may be .01
percent. I don't know.
MR. DONOGHUE: Well, the compendium was pretty clear in
saying that they had a thumb rule in there that several percent, I think
it was 5-percent change of power level correlated with something like
60-degree change in peak centerline temperature. So, I mean -- to peak
clad temperature. So we -- it may not be linear, that that really may
not be linear, but we didn't see it as being a major -- 1 percent change
in power being major, because the rule in 50.46 it itself says --
DR. WALLIS: I'm not sure if you have to do all this or not.
I'm just probing to see how complicated your decision process is going
to have to be. Maybe you can reach some argument about 102 percent
being a margin which is being going through all the calculations. So
all we have to do is make sure it doesn't go over 102 percent of what it
is today, so we're allowing it to be 101 percent, 101 nominal power plus
or minus 1 percent is okay. Are you going to make that sort of
argument, or are you going to follow it through all the LOCA things to
affect on peak clad temperature and --
MR. DONOGHUE: We're not planning on doing that, no.
DR. WALLIS: Why not?
MR. DONOGHUE: At this point. Well, right now we -- maybe
the expert on the instrumentation itself can answer this better I did --
DR. WALLIS: That's not a problem. The instrumentation is
irrelevant. If you get better information about flow rate, how does
that influence the way in which you regulate?
MR. DONOGHUE: Okay.
DR. WALLIS: I think you have to do some hard work so that
you have an intellectual basis for your decisions, not just hand-waving
about percentages.
I'm not trying to be critical. I'm just trying to be
helpful. We've got a real important issue here. As you learn more,
your analysis, your knowledge gets better. It seems you ought to be
able to reduce safety margin. Now if you're going to do that, you've
got to be pretty clear what you mean by a safety margin.
I think this Agency is incredibly vague about what it really
means by safety margin. It just gets thrown around as a word. I'm
suggesting you need to get hard-nosed about what you really mean by
margin if you're going to talk about this and invoke it and use it as a
reason for doing things.
DR. KRESS: I think in this case Professor Wallis you would
repeat the Appendix K calculations of peak clad temperature using the
different power and see if you still stay below the acceptance value for
peak clad temperature. So basically if you stay below it your
margins --
DR. WALLIS: But what did this 2 percent have to do with
that? I don't think the 2 percent came from any kind of peak clad
temperature calculation, it came from something about --
DR. KRESS: Well, it came from the fact that when you're
controlling your reactor, you want to hold it to the power that you're
limited to in the tech specs. And the problem is when you're
controlling it you have to measure it, and the measurement of that power
could be off. So in order to assure that you don't exceed this peak
clad temperature, they make you calculate it at a little higher power
level that's based on the accuracy of your instrument.
Now if that instrument's better, then they ought to be
allowed to use a better power input into the calculation of peak clad
temperature.
DR. WALLIS: I agree entirely.
DR. KRESS: And the margin is built into that --
DR. WALLIS: I agree entirely, but the question is how
far --
DR. POWERS: Excuse me.
DR. WALLIS: I was going to say how complicated is this
connection. The connection may be very simple.
DR. KRESS: It's a thermal-hydraulic code.
DR. WALLIS: No, it may be simply saying we've already
calculated 102 percent. That's simple. We don't need to recalculate it
as long as our new --
DR. KRESS: It's not quite that way, because it may change
the flow rate instead of the power.
DR. BONACA: That's right.
DR. KRESS: It may change other things. And it's a
thermal-hydraulic calculation.
DR. WALLIS: So you have to go through all the
thermal-hydraulic calculations all over again?
DR. KRESS: yes.
DR. BONACA: In not only for the LOCA, I guess also for the
other accidents if they want to take credit.
DR. KRESS: You have to do it for the various design-basis
accidents.
DR. BONACA: A lot of work that you have to do.
You know, one point I would like make about the margin, and
that's really a philosophical point, is that there are margins which are
not specifically assigned to certain -- coming from certain specific
reasons I believe we have to be very concerned about eliminating or
reducing in any way or fashion, because they're built in, the whole
framework of analysis and design.
There are specific margins which are really coming directly
from specific, for example, uncertainty on measuring a parameter that
are specified that way in the regulation, and I really see them
differently from the previous one, because essentially what we did in
the regulation, we assigned -- we took and attributed that margin
specifically for that purpose, an allowable in tech spec, for example.
If you can have a better way of measuring that such that you can reduce
that number, okay, you are not really reducing the margin of safety in
the plant, what you are doing, you are simply saying I know better now,
okay, where are the uncertainties in the parameters, so I know with less
uncertainty if I am at 100 percent power. And by that amount, I can ask
for some credit. That is the way I view, I mean a difference between
the general treatment of margin and the specific one to do with the
measurement of a parameter.
DR. WALLIS: See, probabilistically, you would say that
everything you know is subject to uncertainties, and uncertainties you
propagate through you LOCA calculation, and you get some conclusion. As
you would use some certainty, that propagates through the LOCA
calculation and changes your equation. We don't know how to do that
yet. I don't think we have that kind of thing built into LOCA
calculations. You have a lot of work ahead of you.
DR. POWERS: It seems to me that if you think about how you
would have done this in the past, you would say, yeah, there are a lot
of things I am uncertain about. I may not measure this flow property
right, but I look in the steam tables and, gee, the properties of water
are a little bit uncertain, too. And I can sit here and I can do a
fairly simple calculation, I don't need a thermal-hydraulics code to
effect -- to understand how an uncertainty in my flow measurement, and
an uncertainty that I impute from the steam tables combine together to
give me at the same confidence level under uncertainty in my
understanding of heat removal from the system. Okay.
Now, suppose one element of that becomes absolutely known to
15 different figures. I don't think the uncertainty margin changed very
much, in fact, I think it changed by roughly the square root of 2.
Okay. I mean it is a more complicated thing, but it didn't mean that my
certainty and knowledge in one of the uncertainties, potential
uncertainties, changed the allowable margin.
And I think that is what Joe was wrestling with here is he
didn't know what that tablet, that engineer's tablet all had on it.
DR. KRESS: You have got uncertainties in the Dittus-Boelter
equation they probably used.
DR. POWERS: I am willing to bet on the steam tables.
DR. KRESS: The steam stables have uncertainties in them.
DR. POWERS: Just from the era that they came in.
DR. KRESS: But if you did the best estimate approach
correctly, you would do just what Dr. Wallis said, because you want to
have 99 percent -- or 95 percent confidence in your numbers, so you
would have to do an uncertainty analysis. You would have to propagate
these things through. But this is in Appendix K, which is just -- it
submerges all that into margins.
DR. WALLIS: It a logical misfit, though, because --
DR. KRESS: Yeah, it is a misfit.
DR. WALLIS: Logically, you can't introduce margin and
probability into a deterministic appendix.
DR. KRESS: That's right.
DR. WALLIS: That is one of the things we have wrestled with
many times.
DR. KRESS: That's right. And then superimposed on that is
the fact that what you are interested here is -- your final product is a
peak clad temperature. What that has to do with safety is another
question, and how it really affects safety and how it assures safety is
another question also.
DR. WALLIS: I think there is a way to make the argument
much simpler, but I hope you can find it.
DR. BONACA: It will come.
DR. WALLIS: But if it does come that simple, then it should
be sound.
DR. POWERS: The other point to be made or plot to think
about is that you have a lot of conservatisms in Appendix K. This one
is a small one. And I wanted to do something quickly, because I am
going to have all these things to handle, I want to do the right thing.
On the other hand, do I want to invest multiple FTEs in handling what I
know to be a small conservatism, it contributes a small amount to the
safety margin, or not? And does it decrease my level of comfort that
much if I am completely wrong about this? And I think that is what Joe
is wrestling with.
DR. KRESS: Especially when they get ready to apply this,
for whatever reason. You know, it doesn't necessarily mean a power
uprate. That is the most likely thing. But when they get ready to
apply it, they will relook at that and say, well, is this really okay to
let us have this power rate? And they will look at it from a different
viewpoint.
DR. WALLIS: Yes.
DR. KRESS: So, you know, it is -- go ahead, I am through.
DR. WALLIS: I was going to say Dana's arguments would apply
to changing the 102 percent to 101 percent or whatever, without any new
information about flow. You would simply say this has a very, very,
very small impact on peak clad temperature. It is a silly requirement,
let's make it 100 percent, without improving the flow measurement at
all.
DR. POWERS: Yeah, it definitely could. I mean this part of
Appendix K is, to my mind, always a peculiarity. It reads much more
like a regulatory guide than it does an actual rule. It has always been
a peculiarity.
MR. DONOGHUE: I have a slide coming up I think that
addresses the point about the powers. And I will just add that one
thing that we realized from the beginning is that we didn't want to
create so much work that we never got done, but also we didn't want to
impose requirements or guidance in order to allow licensees to use this
that were akin to performing a best estimate calculation, because people
just -- have already decided whether or not they going to do that.
All right. Let's jump ahead to the proposed rule language
almost as proposed to appear. There's two things I wanted to point out
that we have done here, in addition to some plain language type of
changes that we were made to do. We have changed the clause in here to
attribute the current requirement, which is staying in the rule, to just
instrumentation error, power measurement instrumentation error, based on
the historical research that we did, we have talked about for a little
while.
Then a big change is this added sentence where we will allow
-- as an option, we will allow licensees to use a lower power level in
their analysis provided they can adequately justify that. There are
some additional words that don't appear on this slide that during the
OGC concurrence we did add. OGC doesn't want anybody to use a power
level lower than 100 percent. We have put some words in there to make
sure people don't do that, but --
[Laughter.]
MR. DONOGHUE: But it is making it through concurrence, so
we did it. But this has been demonstrated, language is what we are
going to be concentrating on in these reviews. And the requirements or
criteria that we are going to use are things that we are going to have
to develop as we review the different applications, when people want to
either increase their power level or get some other kind of relaxation
to the ECCS tech specs, et cetera.
DR. WALLIS: See, you have still got to use a criterion for
this demonstrated to account for uncertainties, if 1.02 is sort of a 95
percentile or something. I don't think it has a basis, and you use that
criterion for the new one. You don't have any basis for 1.02. I don't
know what criterion you use to do this sort of demonstrated to account
for uncertainties. Has it got to be within, what, 0001 percent sort of
likelihood of going over a margin, or what is it, 99.9 percent
uncertainty or what? We don't know, so you have got to, in a Reg. Guide
or something, be more specific about what you mean and why.
MR. CARUSO: Dr. Wallis.
DR. WALLIS: Yes.
MR. CARUSO: This is Ralph Caruso from Reactor Systems
Branch. As Mr. Donoghue said earlier, we have unfortunately not been
able to identify a particular basis, a specific basis for this 1.02
number and it is unfortunate. We just -- we don't know where it came
from. And one of the things we are hoping from this comment period is
if somebody out there does have some history and know where it came
from, they will tell us and let us know. But right now we just don't
know where it comes from and we are saying that if a licensee wants to
use a smaller value than that, they should justify it and explain it to
us.
And I understand your concern that we should have acceptance
criteria for it, and we will develop a Reg. Guide to be able to all us
to evaluate values less than 1.02. But right now we don't have an
anchor point for that Reg. Guide in the sense that we have a basis for
where the 1.02 number came from. It is almost like a received number.
DR. WALLIS: It is almost better off. Almost better off.
DR. POWERS: Suppose that you went through the comment
period and nobody came forward and said, ah, I remember where it was, I
have got it on my engineering notebook number 203. Nobody has said
anything and you come to write and your Reg. Guide, are you going to
have any major difficulty in just saying, well, my God, 102 is a 95
percent confidence level, and so 95 percent applies to anything we want
to use here.
MR. CARUSO: We don't have any reason to say that the 1.02
number is a 95 percent confidence level. We don't know where it came
from.
DR. POWERS: I understand, you don't have any basis for
saying that now.
MR. CARUSO: We wouldn't say it because we don't --
DR. POWERS: Yeah, but you would have heartache just
speaking from the cathedral if that is a 95 percentile.
MR. CARUSO: We could only say it came down on a table, that
is all.
DR. WALLIS: But that is no good because then you would have
to send the new application up for a new tablet.
MR. CARUSO: Well, part of the reason why we decided to do
this this way is because we didn't want to -- one of the options that we
considered was not specifying the number and making everybody justify
the numbers that they used. And we thought this would be an
unreasonable burden on existing licensees who decided that they didn't
want to change their analysis methods. It would be a backfit on those
licensees.
Right now they all use the 1.02 number and some of them may
be very content to use that. If we change the regulation to say
everybody has to justify the exact number that they used, then a lot of
people would have to do a lot of work to justify that value.
Right now this is an unusual number, it is the only
uncertainty number in the regulations that is actually specified. There
are lots of other values that are used in LOCA analyses for which
licensees have methodologies to calculate the uncertainties, to
calculate the value that is actually used in the analyses.
Dr. Bonaca explained there are uncertainties on the SCRAM
times, there are uncertainties on the ECCS flow values that are used.
And licensees have methods of accounting for them and coming up with the
actual value that they use.
DR. BONACA: Yes.
MR. CARUSO: One number for which there is a number on a
tablet is this number, and it is unusual, and we can't explain it.
DR. WALLIS: Ralph, you have a wonderful opportunity now.
DR. KRESS: Get rid of it.
MR. CARUSO: Yeah, but we didn't, as I said --
DR. WALLIS: It is an opportunity to say we will say we now
provide a rationale for the new number.
DR. BONACA: See, but the point is that the rationale wasn't
developed by the regulators. Okay. The rationale really came from
Westinghouse. Okay. It was Westinghouse that 30 years ago, in response
to NRC concerns with the treatment in analysis, used 2 percent power,
because that was a typical uncertainty of the bystables and string, 50
power supplies, that was like a standard number that seems to bound, and
2 degrees Fahrenheit, in whichever direction appeared to be
conservative.
Now, that was propagated into the accident analysis. Now,
when Appendix K came then regulation took it and said 2 percent and made
it part of the rule. Okay. I think there is a clear history there if
you go back and ask questions, at least the old-timers there, there are
some of them still alive. But --
MR. BARTON: You can always go on TV, "Unsolved Mysteries."
DR. BONACA: That's right. But all I am saying is that
there is a foundation there for where it came from and I surprised that
-- you know, clearly, in LOCA, there was no basis for it except it was
the only place where it was grabbed from experience and used application
from other accidents and put into the LOCA. And, you know, I think it
shouldn't be that difficult to identify where it came from. And, again,
it doesn't have that kind of sound basis for it except it seemed to
bound calculational uncertainty.
And that was a target of every vendor from that point on to
develop hardware. Like, for example, bystables, they would deliver a
string value in delay times or in errors, okay, that would be within
these values. That became a target for the CE plants because it was
part of the accepted way of addressing the uncertainty in the analysis.
Now, it is so clear it went from Westinghouse and on BWRs,
GE took a totally different approach, took the position that
uncertainties don't have to be treated expressly because they are
conservatisms in the analysis that take care of them. And, in fact,
every BWR does not assume any errors in temperature, in pressure and so
on.
So there is a history there which is, however, not in the
regulatory area, it is in the industry that developed these things
originally. So, just I am offering it because I think my memory still
serves me reasonably well.
DR. WALLIS: Well, I think we need to go on, but I think,
Ralph, you do have two options. You are not going to get a tablet, so
either you have to find the rationale for the old one and say, that is
right, we are going to use this rationale for the new version, or you
are going to have to develop your own rationale because there isn't one.
You cannot wave some hands and say we will accept something based on
some criteria which is not explicit, simply based on someone's guess at
the time. But you don't have a tablet. Tablets, I don't think are
acceptable. There has to be some rationale. Either you use the old
rationale when you find it or you develop your own.
MR. CARUSO: Well, what we want to do is we want to allow
people to continue to use the existing 1.02 number, just from a point of
regulatory stability. Or if they want to use a different number, they
can use it but they have to justify it.
And we do this commonly for when people want to change some
part of the plant design. In a lot of cases we have standards for
judging whether a change is acceptable, but in a lot of cases, it up to
the licensee to make the case, as we say, that a change is acceptable.
Cases where the staff hasn't come to a position, a licensee builds the
case and makes the argument, provides the experimental basis, technical
justification, and the staff, after consulting with such august bodies
as the ACRS, decides, yes, that is a good argument.
DR. BONACA: One question I have, however, is you are making
this unique change in just this specific rule. As I pointed out before,
if you take accident analysis, Chapter 15, every accident there
initiates at 102 percent power. It is not specified in the law, but
that it is what it is. To some degree, through 50.59, you will have
also to accept changes in those accident analysis because the licensee
cannot recognize that they have a 2 percent error everywhere in the
accident analysis on power measurement, and then not to have it in the
LOCA analysis, irrespective of what the rule says. The 2 percent has to
come from somewhere again, and it has some logic there has to be
reviewed.
It seems to me that these changes, in response to a licensee
request, in isolation, give a lot of concern regarding the bigger issue
of how you treat the whole regulation, the fabric of it, and margin in
terms of what Dr. Wallis is pointing out. I don't understand this
specific request and this response to address such a narrow assumption
without looking at what -- or how that changes the whole approach
regarding accident analysis, because no licensee would be able to take
away 2 percent without addressing the other accidents.
MR. DONOGHUE: Well, what we did look for in other parts of
the regulation, I mentioned that we also looked in the SRP guide -- in
the Reg. Guides themselves to see where we either specify 102 percent
for it references Appendix K directly, or allows people to use an option
that they can justify. Those are the kind of words that we found. And
it was related to instrumentation error.
DR. BONACA: Yes. But again, yeah. But accidents -- but
don't look at the regulation, look at the FSARs, Chapter 15, they are
all starting at 102 percent power.
MR. DONOGHUE: Following the SRP and Reg. Guides.
DR. BONACA: Just like the LOCA analysis. There has to be
-- there is consistency there. If you just change it, the regulation of
LOCA, and you have no regulation specifying to present to the other
accidents, still the licensees have got 102 percent in their FSAR.
MR. DONOGHUE: Okay.
DR. BONACA: So they have to do something under 50.59 to
modify all those assumptions.
MR. DONOGHUE: They will have to address those changes if
they are looking for relaxation to part of their license. Right now the
rules allow -- 50.46 allows a change to the ECCS analysis without a
review, provided the change is a small enough change of the PCT, it is
just an annual report.
MR. BARTON: They are going to stumble across that when they
try to do a safety evaluation for the change, they are going to stumble
across that, I tell you.
DR. BONACA: My point, John, is that it seems to me that
there is consistency between 102 percent being used in every accident
analysis and the LOCA. Okay. And I told you what I think the history
is. But, anyway, there is consistency there. Now, you are removing the
requirement on LOCA as if it was totally in a vacuum.
Without looking at the fact that every other accident is
assumed 102 percent and is controlled under 50.59, right? So, yes,
there are vehicles to address that. But I think it is -- to me I have a
problem in this piecemeal approach.
MR. BARTON: You're saying why isn't that addressed up front
here.
DR. BONACA: Yes. It has to be done in a comprehensive
fashion to resolve the issue of why they are only 102 percent. Not only
the LOCA. Okay? And if it is in fact related to the instrumentation,
let's deal with the instrumentation issue and adequacy of measurement
and apportionment of 2 percent to the specific bystables used to measure
power, rather, you know, the point that Dr. Wallis made, rather than
just simply saying well, we don't know where it comes from, let's
eliminate this, but there is consequences by doing that in isolation.
DR. WALLIS: I think we should move on. I think those are
very good points you have to consider, how broad your scope is going to
be in terms of rationale for this proposed change, what its consequences
are across the board.
MR. DONOGHUE: Okay. I don't think there's any more
questions on the proposed rule language.
We've talked about some of the implications so far, and the
only other things I'll point out here are that -- there's a financial
benefit; that's obvious. But the last bullet here, we don't see a
direct -- and the considerations that are brought up now may change our
opinion. But we don't see a direct problem with other uprate programs
that are ongoing such as the BWR extended power uprates. We consider
this to be kind of a separate effort to change the LOCA requirement.
I did mention that licensees can adopt the instrumentation
change without a review. Right now there are plants out there with
ultrasonic flow meters installed and are using them, but not as a direct
input to power measurement. And the enforcement regulatory angle on
this is that when the change to the ECCS analysis is made, the staff
review begins when the relaxation is requested in technical
specifications in the license or when the staff sees a significant
change in the ECCS analysis that it thinks may affect the analysis
method.
DR. WALLIS: In your bullet 3, is it really true, I thought
102 percent was written into the law. They can't change that.
MR. DONOGHUE: Correct. No, in general I'm saying -- right.
DR. WALLIS: So they can't, 102 at the moment. The problem
is that it's not written into the law as a result of uncertainty, so
that when you change the uncertainty -- it's specified as 102 percent
without any rationale at all. I don't see how they can change that part
of the LOCA analysis.
MR. DONOGHUE: If we institute the revised rule.
DR. WALLIS: Well, after -- this is after. Okay.
MR. DONOGHUE: The licensee -- yes, I'm sorry. The
licensee --
DR. WALLIS: Then they can simply say without license
amendment we have better instrumentation, we can use -- you're going to
use 100.5 percent or something.
MR. CARUSO: Actually no, because to use a new instrument
like this, they would have to incorporate a topical report or
description of the instrument in their methodology, which requires a
tech spec change.
DR. WALLIS: There is a license amendment.
MR. DONOGHUE: Let me be real clear on that. The majority
of tech specs include a listing of the methodologies. That is not a
universal requirement of tech specs, however. There's a handful of
plants out there, and this has to do with following -- making
commitments to a generic letter that was issued to upgrade tech specs.
There's a handful of plants out there that could indeed take 102 --
number less than 102 percent, revise their ECCS analysis, and we would
not necessarily know until their annual ECCS report under 50.56 would
show up. Okay? At that point the staff -- and this is the way the rule
was set up in 50.46 -- would look at the methods used for the change.
As I said before, we don't expect the change to be
significant, below 50 degrees Fahrenheit PCT change. So that's why it
would be an annual report, not an immediate report or 30-day report.
But it would have us look at the methods used for the change, and if it
was a method, for example, the flow meter may have been reviewed in the
past and accepted by the staff, there may not be any further action. If
it was a new methodology, a new instrument that we've never seen or
heard of before, the staff would then have to start asking questions.
DR. KRESS: How do you determine the significance of
something like 50-degree change?
MR. DONOGHUE: I'm sorry, I'm getting simple-minded about
it. The rule -- 50.46 was written that way. I think part of the
risk-informing Part 50 effort, when we get to that, would start to
answer those kinds of questions. We haven't even attempted to try to
answer that question here.
DR. WALLIS: The real question would seem to be if you do
all this stuff, what's the effect on likely people-rem from an accident.
MR. DONOGHUE: Well, that's the ultimate answer.
DR. WALLIS: But it's a long connection to make.
MR. DONOGHUE: And we may not ever answer it to that extent.
DR. WALLIS: Unless you do that by the time you sort of eat
away all these margins by this kind of procedure. Those questions need
to be answered. You are changing the --
MR. DONOGHUE: We're going beyond the level 2 PRA.
DR. WALLIS: Safety status of the plant in some way.
Anyway, I think we need to finish up.
MR. DONOGHUE: Yes. Okay.
I think I'll end with this, as a matter of fact. I won't
discuss backfits, because we discussed that already. It won't be a
backfit. But the risk considerations I want to touch on.
We wanted to make sure we could have some understanding of
any risk impacts, and we had some recent experience dealing with the BWR
extended power uprate question. There was a letter to the ACRS last
year where the staff explicitly said that you don't expect -- we don't
expect adverse risk impact from marginal 1-percent was used in the
letter -- for power uprate. So we use that right now as the basis for
saying for this kind of a change where a licensee would use the amended
rule to pursue a small power uprate, we don't see a risk -- significant
risk impact. And we talked about the risk-informed Part 50 effort.
There's a -- the last slide in your handout talks about the
schedule. I'll just say right now it looks like we're adhering to that
schedule, and we'll be going to public comments at the end of the year.
Finishing up the public comment period by the end of the year is what we
expect to do.
Thank you for your attention.
DR. WALLIS: Thank you very much.
Just to summarize for the Committee, I think that the
subcommittee likes the idea that as you get better information, you can
reduce margins. And in this case it may well be that some rather simple
arguments can be made to say that for LOCA purposes this is a good idea,
although you have to be specific about -- much more specific about how
you're going to evaluate applications.
I think you do have to think about Dr. Bonaca's point that
102 percent appears elsewhere. What are the sort of broader
implications of changing that at some point. And maybe you don't have
to base the broader question of how should -- what should be the
intellectual methods, logically consistent rationale and so on, for
using better information about uncertainty to reduce margin.
This is very broad question, and I don't think you're going
to come up with a road map for how to do that generically. But sometime
this Agency's got to face that. It may not have to -- if you do have to
face it, that's a big task.
MR. DONOGHUE: I agree.
DR. WALLIS: Anyone have any other --
MR. BARTON: Are there any open issues with the instrument
on this?
DR. WALLIS: Well, after getting -- the subcommittee's
feeling was that the rule -- we should concentrate on the rule. If the
rule sounds sensible, we should comment on that. Whether or not a
flowmeter can or cannot measure more accurately is not really the point
of this discussion.
Down the road, of course, people want to know whether or not
it can be done, but if it could be done, would one allow backing off on
the regulations. That's the real issue before this Committee at this
time. We will have a quick presentation by Caldon claiming that
uncertainties have indeed been reduced and yes, there is some real
substance to this request.
MR. DONOGHUE: Okay.
DR. WALLIS: Am I in charge of this session?
Can we take about ten minutes, please? We've really enjoyed
your presentation, Mr. Estrada, at the subcommittee meeting.
MR. ESTRADA: I'll be very brief. About five minutes.
That's all.
MR. BOEHNERT: Well, go up front, Herb. If you use the
microphone, I'd appreciate it.
MR. ESTRADA: Yes. Thank you. I'm Herb Estrada, chief
engineer at Caldon. We make precision flow-measurement systems and
leak-detection systems. And we've been providing flow-measurement
systems to the nuclear industry for six years. Westinghouse developed
the technology which we own, provided those same kinds of instruments
for about 20 years before that.
And it's an advanced version of our flow-measurement system
which is being installed at Comanche Peak and which is the basis for the
exemption to Appendix K that the utility has requested.
My purpose in being here today is to suggest to the ACRS and
to the staff that with this revision there is need for specific guidance
in the treatment of uncertainties.
In the determination of thermal power. That guidance might be applied
in regulatory guides or perhaps in ASME or other kinds of supporting
documentation.
I say this because when we began developing 30 years ago
ultrasonic instrumentation for the nuclear power business, we were
fortunate both at Westinghouse and in the power business at that time in
finding engineers who were skeptical and scientific, and they forced us
into a rigorous treatment of the uncertainties in our instrumentation
which perhaps without such oversight we might not have done. And as a
consequence, I don't think we have overpromised in the performance of
our instrumentation.
But we were lucky. And, frankly, in recent years we have
not found in electrical utilities large numbers of engineers who are
skilled in the science of measurements and in the treatment of
uncertainties. And I think perhaps it's not reasonable to expect that
they should be. That's not a skill which is used every day in the
operation of powerplants. One could argue perhaps that the generation
of power is something that requires careful measurement, but in fact the
fact of the matter is that while we have found some engineers who are
very good at it, we've not found that universally.
And so for this reason we've submitted to the Chairman and
to the staff some guidelines that we've applied to ourself in the
development of our instrumentation.
I don't want to talk about them all. I just want to mention
two which we think are essential in such an endeavor as increasing
thermal power.
One, most important, the measurement of the variables from
which the thermal power is calculated must rest on bona fide physical
principles. Without such resting, the mathematical relationships on
which such principles apply, without those one cannot make a
mathematical model to assess numerically the uncertainties in this
measurement.
How then can one make any definitive statement about the
modeling uncertainties in the measurement of thermal power? And without
mathematical models, how can anyone state with confidence that his
analysis of the uncertainties in the power measurement is complete?
The second principle which I wanted to mention is that the
accuracy of key variables in the power determination process should be
verifiable on line. That means mass flow of feedwater. That means the
temperature of the feedwater. That means the pressure of the steam.
Those variables must be verifiable on line.
Lots of measurement systems start their operational careers
meeting very rigorous and very narrow accuracy requirements, but the
probabilistic arguments on which any uprate must ultimately rest require
that those design bases be met not just initially but continually in the
operation of the plant. And for that reason we believe that it's very,
very important that variables that are important to the determination be
verifiable on line.
That's my statement. Thank you very much.
DR. WALLIS: Thank you. Do we have any questions for --
DR. POWERS: Well, I'd just like to thank Mr. Estrada for
sending me copious amounts of information. I am not skilled in
instrumentation. I have to say that I learned a lot about some of the
difficulties in your world from your documentation.
DR. WALLIS: Anything further?
It's all yours, Mr. Chairman.
DR. POWERS: And I will recess the session until 20 minutes
of one.
[Whereupon, at 11:40 a.m., the meeting was recessed, to
reconvene at 12:40 p.m., this same day.]. A F T E R N O O N S E S S I O N
[12:40 p.m.]
DR. POWERS: The first topic this afternoon has to do with
the license renewal program, and it's the options available to the staff
for crediting existing programs for aging management at plants that are
receiving license extension. And, Professor Seale, I guess you have
been elected as the cognizant member on this issue?
DR. SEALE: Yes.
DR. POWERS: And so I'll turn the meeting to you, but I will
remind the members this is an issue that relates very directly to the
statutory responsibilities of the committee, so it's not just a question
of NRC work practices and rules, it's a question of what kind of
information we need about existing programs in order to assess these
applications for license renewal.
Professor Seale?
DR. SEALE: The particular topic this afternoon is on credit
for existing programs for license renewals. This is an issue which
pervades the whole license renewal spectrum. There have already been
two treatments of the problem by the two currently -- well, the two
license -- or the two applicants who are under consideration. Quite
rightly, I think the intent is to come up with a position which will
apply to the general process so that we have a template that will allow
evenhandedness and appropriate consideration of this problem.
We have a presentation from both the staff and from the NEI.
There are currently three potential positions on how existing programs
will be treated. We are expected to provide a letter at the end of this
meeting for the commissioners on this issue. It's my understanding that
the Commission has already gotten the -- a report from the staff, and so
we're putting our recommendation in for their consideration.
Without going into a great deal more detail, because I think
our presenters are going to give us that, then I think we should get
started. Again, we'll be asked to write a letter, and we're going to
need to make some decisions on which of the three potential positions we
will wish to endorse; or, if we wish to fabricate or come up with an
alternative, that's always possible.
I guess I should add also that we've already -- the
subcommittee has already received presentations from the staff and from
NEI. Both have been very helpful in delineating the issues for our
subcommittee. And I guess what I'm going to do is ask Chris Grimes to
go ahead and get us started.
MR. GRIMES: Thank you, Dr. Seale.
My name is Chris Grimes. I'm the chief of the License
Renewal and Standardization Branch. As Dr. Steel (sic) mentioned, this
is a policy issue that really gets to the heart of what is the mission
the Commission wants us to pursue in terms of identifying an appropriate
scope of review for license renewal application.
We presented this issue, as it's described, in Sec. E 99-148
yesterday morning to the Commission, along with presentations by NEI and
the NEI Working Group on License Renewal; and a presentation by UCS on
their views concerning their staff's review for license renewal.
And we're essentially -- we're going to go through about the
same presentation that we went through for the subcommittee, as it has
evolved for the Commission and now for the full committee. And Dr. Sam
Lee, who's a senior engineer in our branch, is going to make the
presentation. Sam.
DR. LEE: I think this is the issue that we're trying to
address; this is to what extent should the staff review existing
program, relied on by the License Renewal applicant to manage aging.
By manage aging, this is a shortcut for manage the effects
of aging on functionality of structures and component in the period of
extended operation.
NEI sent in letters in March and in May to describe the
issue, and the NRC License Renewal Steering Committee, and my view NEI.
And NEI indicates that existing programs are subject to the regulatory
oversight and NRC inspections and are not required to be reviewed by the
staff to any extent for license renewal purposes; and that the staff
develop the Sec. E. paper 99-148 to describe options and make
recommendation to the Commission.
And what we heard here yesterday from the -- from NEI at the
Commission briefing was that they have another concern, which is
regulatory creep. This is ratcheting. They say they're comfortable
with the first two applications, but when the 10, for the 20th
application comes in, is the regulatory requirement going to increase.
And that's -- is a now concern, and that is a management discipline
issue. Okay.
MR. GRIMES: Yeah, I'd like to add -- Sam mentioned that the
concern could be expressed in terms of the -- does the NRC staff need to
review existing programs to any extent. And, in fairness, there is a
question about which programs exist with a sufficient regulatory
footprint on them that the staff could accept that regulatory control as
a basis for concluding that it's adequate for the period of extended
operation.
And that's where the staff and NEI started to depart
philosophically in terms of trying to identify that line, and Sam's
going to explain a practical implication of that. But it's not that the
license -- that NEI or the industry feels that the staff shouldn't
review anything. It's a question of why are we bothering to review
things that we should be able to take advantage of the regulatory
process for.
DR. LEE: In 1991, the Commission issued the Licence Renewal
Rule, and they also based on a report called the New Act 1412, which
says the regulatory process is adequate, okay. But then in 1991, the
Commission said the process is adequate, and then the draw for license
renewal is to manage aging that's unique to license renewal; that is,
new and different aging that occurs after year 40. And they started
trying to implement that 1991 rule, and we found that the staff and
industry found that there is no such unique aging. Aging is a
continuous process. So, in 1995, the Commission amended the License
Renewal Rule. And this is the two principles behind the 1995 Rule
Amendment. Okay, this is taken from the statements of consideration of
the rule, and it still says that the process, the regulatory process, is
adequate, and the print specific licensing bases must be maintained.
DR. WALLACE: Excuse me.
DR. LEE: Yes.
DR. WALLACE: This is a principle?
DR. LEE: Yes, that is the --
DR. WALLACE: The regulatory process is adequate as a matter
of principle or as matter of having been evaluated or what?
DR. LEE: See. Okay. The staff actually evaluated that in
the 1991 rule, and that is documented in 1412. And that they go by
examples of things to happen and the process picks that up. So the
Commission was comfortable that the process is adequate.
DR. WALLACE: Okay, so this is really -- this is really as a
result of a review. Okay. It's not some -- just declared that it's
adequate.
DR. LEE: No, that was not.
DR. WALLACE: It's a result of --
DR. LEE: No, that was actually the basis for the 1991 rule
making. Okay, in the rule making the and new record for public comments
we had gone for the whole process.
DR. WALLACE: Okay.
DR. LEE: But in 1991, the before this goes on -- unique
aging -- new and different aging effects. And since -- and in 1995,
this part is still maintained, but the rule had changed, and that's the
underlying portion. Okay. And now the focus, or the exception, is on
the managed aging, okay, not the new and different aging. Okay. So
that's what we are doing for license renewal, is to look at aging
management. Okay.
MR. GRIMES: I think the interesting point that I want to
emphasize here is when the staff reads the exception of the detrimental
aging effects on certain system structures and components, we read
certain to mean any passive, long-lived system structure component that
performs an intended function as defined by the rule. When NEI reads
certain system structures and components, they read that in the context
of for which the regulatory process does not adequately manage aging.
And that's why we developed this in terms of a policy issue to present
to the Commission. Did they intend? Does this Commission intend that
we should review all aging management programs for passive long-lived
system structures and components or only those -- those aging management
programs for which there is not some regulatory process that manages
aging.
DR. WALLACE: I think what I understand from this is that
you're saying the present regulatory process is adequate to ensure the
licensing basis in the future after renewal will provide an acceptable
level of safety.
MR. GRIMES: That's correct.
DR. WALLACE: I see what you're saying because one has to
sort of fill in a little bit to figure out what is meant by the
statement.
MR. GRIMES: That's correct. You're -- you're -- we and NEI
both have tried to take certain statements out of context and build our
case around those statements, and when they're taken out of context,
that is relatively dangerous.
DR. LEE: So the principle, like Chris indicates, talks
about certain aging management of certain structures and components.
And if you follow the rule, the discussion -- okay, in the 1995 rule
making process, the Commission decided existing programs would
adequately manage active and short-lived structures and components. And
they score them from the scope of license renewal review. However, the
-- when the Commission looked at the passive long-lived, they believed
that the effects of aging on this equipment is less obvious, less
apparent, and also there's less monitoring experience. So the rule is
focused on the aging management of passive long-lived. Okay, that is
the shortened structures and components like which, you know, we
described earlier.
DR. WALLACE: What is a short-lived structure?
DR. LEE: Something that's replaced, periodically.
DR. WALLACE: Well, everything is eventually replaced, so --
but there is some definition that makes sense; someone isn't going to
quibble about, well, this is -- this really is a short-lived structure,
therefore, it falls in this category rather than another one.
DR. LEE: Yeah, the way the world defines it is short-lived
is based on a time period. So if you have a component that's replaced
every 10 years, every 20 years --
DR. WALLACE: Regularly replaced.
DR. LEE: Regularly. Okay, so the process will catch up
with that --
DR. WALLACE: The reactor vessel is not a short-lived
structure?
DR. LEE: Or the steam generator is not a short-lived.
DR. KRESS: Hopefully, not short lived.
DR. LEE: Okay. Yeah. So -- if you replace a component
based on performance, like steam generator, at some point --
DR. WALLACE: I guess if it lives through more than one
cycle of license renewal, it's along the --
MR. GRIMES: We've developed a position to clarify
short-lived that speaks to things that are replaced many once an outage
or once every 10 years. There are some valves that are -- that have
degradeable materials in them, and so they just replace the whole valve
-- Squib valves.
DR. WALLACE: But really short-lived structure itself
response to aging management. If it has aged so much that it has to be
replaced, that's also aging management.
MR. GRIMES: Yes.
DR. LEE: The replacement is aging management program.
DR. WALLACE: Right.
MR. GRIMES: We have an interesting open item in accounting
on whether or not a roof is a -- is a routinely replaced element of the
structure. Tar and ship is something that's done a fairly frequent
cycle relative to a 40-year plant life, and so we're trying to sort that
out in terms of how aging management affects the roofs of certain
structures that have tar and ship covers.
DR. LEE: Okay, based on the rules, the staff sees its job
is to review the applicant's demonstration of aging management for
long-lived passive structures and components.
And in doing that, the staff reviewed all programs relied on
by the applicant to manage aging, including existing programs. Because
the staff revealed existing programs, NEI indicates that we are -- we
are verifying following the current licensing basis.
DR. WALLACE: But you need more than just manage them -- you
could say something about adequately managed, because one can manage
anything by simply saying one has done it.
DR. LEE: That's correct. Yes.
DR. WALLACE: It has to be some -- I'm sure you have some
standard so it's acceptable management.
DR. LEE: Yeah --
DR. POWERS: All the rules in the world --
DR. LEE: They then said --
DR. POWERS: Of course, the rule do include adequately
managed.
DR. LEE: We don't -- we try not to put too many words in
the slide. But the way, we actually do our review is that in the
standard review prime, we have 10 attributes of a program that we look
for, when they manage aging. Like was the acceptance criteria, what is
frequency, what kinds of inspection do they perform, and what kind of
documentation and administrative control--corrective action. So there
is that attributes that we look for to come to that adequacy
determination.
MR. GRIMES: Actually, we've specifically took the adequacy
out because when we used the term adequate, then we're accused of --
that's how we got into this issue about whether or not the staff was
reverifying the current licensing basis; and that the phrase that we've
used with the Commission is that the standard that's set forth in 54-21
is whether or not aging management is demonstrably effective.
DR. LEE: Okay. So in the existing program, we are not
challenging the program in terms of meeting the current licensing basis
requirements. We are looking at the existing program to determine
whether they are effective in managing aging.
Also, this kind of review will result in a situation where
there -- where we identify additional aging management activities
required up to year 40 that's not required in the first 40. And like we
said earlier, aging is a continuous process. There's nothing unique or
new and different up to 40, so the way we handle this situation is that
we -- we take these additional activity that we decide are needed after
year 40, and we take it through the backfit process to see if they are
also warranted for the first 40 years.
DR. WALLACE: Every member of the ACRS is open.
DR. SEALE: Can I ask a couple of questions here? You do
have some aging management programs that apply to active components?
DR. LEE: That's correct.
DR. SEALE: Whenever you have a program in place and a
system, whether it be an active or passive, under though some kind of
stress, either a mechanical problem or perhaps a chemical corrosion
exposure of an unusual nature, or even perhaps a temperature problem, I
assume that there is in the already existing aging management program
process mechanisms for doing appropriate special inspections to make
sure that those kinds of insults did not result in an immediate adverse
effect on the components, is that a fair assumption?
DR. LEE: I think that's fair because when we look at the --
I guess -- the last time we know review what we find is that we do not
find big gaps in terms of, gee, that's a big chunk of the plan that
there's not aging management on. Okay, because, like you said, there's
aging going on, and there are existing programs to deal with that.
DR. SEALE: But particularly if you have an event that --
DR. LEE: Yes.
DR. SEALE: That perhaps stresses a component in some way or
a system, then you don't have to wait to look to see whether or not
there's a requirement for an inspection sometime soon -- you do it right
away if it's indicated.
DR. LEE: Yes.
DR. SEALE: Okay.
MR. GRIMES: Dr. Seale, you are quite right. That was the
fundamental reason to start ASPP. The Accident Sequence Precursor
Program wanted to look at how close did we come when there were failures
resulting from whatever insults or whatever design problems had been
revealed through plan operation and events, and we see a combination of
an assessment of the immediate corrective action; and then also a
reflection through the normal quality assurance process that says what
do we need to do in order to try and prevent this from the future. That
kind of experience led us to the maintenance rule.
DR. SEALE: Yeah.
MR. GRIMES: For active components.
DR. SEALE: And the intent now is that notwithstanding
whatever may be in the aging management extension rule, if I may, or
finding that after the 40-year time, in the 40- to 60-year gap, if you
had any of those kinds of events, you'd treat them just like you would
now.
DR. LEE: That's correct.
MR. GRIMES: That's correct.
DR. SEALE: So there's -- we're talking strictly an overlay
--
DR. LEE: That's correct.
DR. SEALE: On a process that's already in place?
DR. LEE: Yes.
DR. SEALE: I just wanted to make sure that was clearly
understood by everybody.
DR. LEE: This slide shows some numbers of the Aging
Management Program for license renewal, identified by the initial
applicants. The pie chart on the left, this is Calvert Cliffs, and here
it shows about 70 percent of the license renewal programs are existing
programs without modification. The other 30 percent are modified
existing programs or new programs.
For Oconee, it's nice -- about 60 percent are existing
programs without modification and about 40 percent are modified existing
programs, new programs, for license renewal.
DR. WALLACE: Why such a huge difference between the total
numbers for the --
DR. LEE: Okay. These numbers are actual count of programs'
activities. They -- the reason why Calvert Cliffs is -- has so much a
higher number than Oconee is Calvert Cliffs tend to count at a lower
procedural level. They count procedures.
DR. WALLACE: They count more of the details?
DR. LEE: More of the details, like what activity that you
do, and Oconee target a higher program level, which groups a bunch of
procedures or activities.
DR. APOSTOLAKIS: Also, Calvert Cliffs I guess manages to go
about 100 percent, don't they?
DR. LEE: That's just a roundoff, I guess. When we put the
-- I guess --
MR. GRIMES: That's a Y2K problem. That's the way the
software generates the percentages.
DR. APOSTOLAKIS: Y 99 problem.
DR. POWERS: I am stunned that somebody that works in PRA
worries about discrepancies of less than one percent.
[Laughter.]
DR. LEE: Okay, there is another observation is that your
local say Oconee has more new programs than Calvert Cliffs, and this is
also a difference in the approach. For Calvert Cliffs, if they found
certain additional activities they could be done for license renewal,
they tend to modify an existing program. While Oconee tend to create a
new program for those additional activities.
But the overall observation, okay, is that most of the
programs for license renewal are existing programs.
Another observation is that about 30 percent of license
renewal programs are modified existing programs, new programs. Okay, to
us that is the contribution of the license renewal effort.
DR. WALLACE: When you look at the actual programs, but in
the two cases, are they sort of similar? I mean, you can say that
there's an aging program for this piece of equipment in both of them,
and they're both doing it?
DR. LEE: That's correct. They are pretty similar except
for some planned differences.
DR. WALLACE: Just the way they subdivide things?
DR. LEE: Yeah.
DR. WALLACE: They're doing the same things essentially?
DR. LEE: That's right. Yeah. Well, this is how the plan
actually -- you know, to maintain the plan -- I mean, they have
different procedures on how they track it. And there are some
differences, like Oconee has a dam, and Calvert Cliffs does not. So we
got some differences.
And when we review these applications, they stop and
identify open item and confirmatory item in all areas -- and, for
example, in existing program area, we identified places where they need
some additional inspections.
DR. POWERS: Sam, before you move on, I want to make sure
that the Committee clearly understands: this is the way that the
applications were presented to us. The results of the staff's review
identified open and confirmatory items that touched on all three
areas--existing, modified, and new. And also, where -- not all programs
or activities are equal. One of the existing programs may be something
that's done once a week. And one of the new programs may be something
that's going to be done once in the whole life of the plant. So they're
not all equal in terms of their importance or their impact on the
utility.
DR. LEE: Here are some of the examples of the acceptable
program that the staff found out within the initial applications.
Environmental qualification. This is the example which helped drive
this policy issue. The staff had extensive interaction with the initial
applicants on how the 50.49 EQ program will manage aging, okay. And
then we asked more questions, and we get a lot of, you know, RAI
responses from the applicants. And in the end, the staff determined
that the existing EQ program is acceptable to manage aging without any
modification.
And here are some examples of existing programs require
modification. For the modified program, they can range significantly to
some simple enhancement of administrative control or adding another
component in the big program, to some more technical examples. And I'll
show some examples I guess in the next couple of slides in the examples
of new program.
For the in-service inspection, the USME code does not
specify inspection of small-bore piping to detect internal cracking.
And there is ongoing industry initiative to address the inspection of
small-bore piping, in particular the hyper injection line. However,
they started to determine how this aging is being managed for license
renewal. And the staff has accepted a one-time inspection of small-bore
piping for one plant, and is resolving open items for the other the
applicant.
DR. KRESS: Well, it may be that the most dangerous loki is
actually from a small pipe.
DR. LEE: Understand.
DR. KRESS: So would the rationale for not looking at small
pipes was what, too many of them or something?
DR. LEE: Well, I guess what the industry was saying was
that the ASME code addresses small-bore piping. They looked for
leakage. That kind of activity, and then you detect spent leakage
limits. So the industry was saying if you package that, that would be
sufficient to manage small-bore piping. Okay. We are looking more
towards an inspection activity, and that's the open item.
Also, in in-service inspection, ASME does not specific
inspection of -- be authorized internals for cracks. And there's
ongoing activities of the Owners Group to address internals, and in
particular the BWI Owners Group has a very active program. So based on
that, Owners Group activity, they started to determine that an enhanced
visual inspection is an acceptable method to manage cracking of the
internals, and we are resolving open items with the two applicants.
DR. WALLACE: What does visual inspection of internals
involve?
DR. LEE: It involve (sic) being able to detect small cracks
that are --
DR. WALLACE: What does visual inspection mean? Is there
some sort of a television camera?
DR. LEE: Yeah, probably camera. Yeah, probably some
slides.
MR. SIEBER: Ultrasonics of some sub-components?
DR. LEE: It would probably just be a camera. You'll
probably put a camera on a probe.
DR. SEALE: These are the things you do during a refueling?
DR. LEE: Yes. On pressurizers, one plan has crafted the
pressurizer clearly, and based on that the staff is asking the
applicants to manage potential cracking of cladding. And Section 11
does not address the under in-service inspection, so the applicants have
proposed these one-time inspections to look for cracking.
MR. BARTON: What do you do for vessels. You got to look a
cladding cracks in the vessels, too, or just pressurized?
DR. LEE: This is just for a pressurizer, because the
pressurizer sees more of a cyclical loading. Okay, and based -- you got
the heaters. You got the fluctuating water level so that area is
probably more severe in terms of creating cracks. And also reactor
vessel is looked at when you take out the internals and look at that
anyway, you'll see that.
Okay, this is the reactor vessel surveillance program.
Appendix H requires the monitoring of neutron brittle on the reactor
vessel, and it reference (sic) a national standard. However, that
national standard is designed for 40-year plant operation, so it
specifies how many capsules, how many specimens you put into the vessel
to DA and then was it time sequenced to take out the samples. But
that's all predicated on 40 years. So the staff question is how would
applicants get data that goes out to 60 years of operation. And the
applicants had notified their insurance program to deal with that.
MR. SIEBER: How were those programs modified?
DR. LEE: Okay.
MR. SIEBER: You only have a certain number of --
DR. LEE: One plan added additional capsules. Okay. And
then for -- that's for Calvert Cliffs. For Oconee, they joined the
other activity which was they originally included additional capsules,
and then they extended it to high fluence level to cover 60 years.
DR. POWERS: When you add capsules, except for additional
data, do you specify irradiation of those capsules to get them up to
speed or are you melting them into a curve?
DR. LEE: You cannot put them in an area where they get
accelerated radiation and then cause melting to occur?
MR. BARTON: Yeah, but how do you age them?
DR. POWERS: I think he's -- what he's saying --
DR. LEE: Yeah, you just put them closed.
DR. POWERS: You put for a while in a new region of
accelerated --
MR. BARTON: Well, okay.
DR. POWERS: And then you move back to the wall.
MR. BARTON: Okay.
DR. POWERS: After they've pick up the requisite amount of
-- that's fine as long as you don't have a flex effect. If it's
strictly a effluents effect, then that's fine. Now, there's some
question about formal versus fast neutron nicks in those places, but I
think that's a small effect.
DR. LEE: This is an example of a new program. There is the
place of the plant before the buried those pipes they're coded and they
are wrapped in protective tape, but they might still be susceptible to
corrosion. So the staff accepted a new program to inspect a sample of
the buried pipe, and they should be solving open item with another
applicant.
DR. WALLACE: What this involves is digging down and looking
at the pipe?
DR. LEE: For one plan, they actually dug up some of the --
a sample of buried pipe, and inspected the external surface.
MR. BARTON: That's pretty expensive -- once you pre-cut
some buried pipe leaks in service water. Each time we had a leak, and
we had to go down with a million -- a million dollar hole each time. So
I think to fix it now, just to dig down there and inspect is not going
to be --
DR. KRESS: At least you pipe was still there.
MR. BARTON: Fine, yeah. You can find a leak by bubbling to
the surface. It's not as scary, but --
DR. SEALE: There is particular the problem where you've got
seawater -- problems.
MR. BARTON: Yeah, that's the trouble -- that's the trouble
with that plant.
DR. LEE: Okay. As we saw earlier, most of the license
renewal programs are existing programs so we can improve the license
renewal process efficiency, if we can credit existing program. And we
described three options in Sec. E. paper 99-48, and this is option one.
Okay, this is not to review the existing program. This is the staff's
approximation of what NEI's proposal is. And NEI believes that these
options can be implemented and for real change; however, the staff feels
that this needs a real change.
DR. POWERS: And why does the staff believe that?
DR. LEE: Say that?
DR. POWERS: Why does the staff believe that?
DR. LEE: Okay. The staff believe that we need a real
changes because that we do not have a basis for the conclusion about
aging being adequately managed before looking at the program.
MR. MATTHEWS: Plus there's wording in the rule that
involves the concept of demonstration. This is David Matthews, Director
of the Division of Regulatory and Public Programs. And the presence of
that wording, backed up by the statement of consideration that supported
the implementation of that wording, that supports our view that if you
were to do this you would have to have a rule change to effect that
change.
DR. POWERS: Your interpretation of the statement's
consideration, then, is that the word demonstration is consciously
included in the rules and that it was the engineers' interpretation of
the word demonstration and not some legalistic interpretation. That is,
I think all engineers understand what the role demonstrate means. It is
-- it's not set it on the table and show me who gets the right answer --
show me who gets the right answer for the right reasons.
MR. MATTHEWS: But it's -- in this instance, it's a
combination of both our engineering view that we do safety evaluations
based on demonstrations of program descriptions given to us by an
applicant, and we have the General Counsel's view that they have a
certain expectation about what a demonstrated effectiveness of what
aging management would consist of. And so, even if we could find a
technical way to try and argue for a process description of the credit
for existing programs, your general counsel still thought that -- how we
would be explicit by changing the language in the rule. So, we're
holding hearings on this one.
DR. POWERS: You're still stuck in this -- the
interpretation of the word demonstrate -- you're still demonstration on
paper, because there is no conceivable way to say, yes, I have done an
experimented which has shown that this type of program will, in fact,
take care of aging for 20 years of extended life of the plant?
MR. MATTHEWS: Yes.
DR. POWERS: It's still a paperwork demonstration?
MR. MATTHEWS: Yes. It's still predictive.
DR. POWERS: Predictive. That's right.
MR. MATTHEWS: Yes.
DR. LEE: Okay. Under this option, the staff would rely on
the current process. We will use that fit to address any potential
questions with existing programs. We address it in current operating
terms, zero to 40, and then carry that into license renewal. And in
this case, then, we would not have a jump in agency management
activities in year 40, okay, under this approach.
DR. POWERS: What you're saying is that if the staff, for
some reason, came to the conclusion there was something wrong with an
existing program, presumably generically or plant specifically, that
they would have to go through a regulatory analysis and see that it
passed the backfit rule. They couldn't do it by on a compliance basis?
DR. LEE: It could be compliance.
DR. POWERS: Or maybe it could be.
DR. LEE: Backfit probably is compliance. But then you'll
basically backfit it to current operating term, and that becomes as part
of his current licensing basis and that carries forward into licensing
renewal. I mean, the application, okay, the -- under this approach, the
applicant would describe here's a component; here's aging effects, and
then map it to an existing program.
Okay, but then the staff is not going to challenge that
claim, okay, under this approach. And the staff is not recommending
this approach because we've seen before they are 30 percent of programs
that may need to be notified.
MR. GRIMES: Sam, before you leave this point. In fairness,
I think, we should have pointed out that the advantage to option one,
the advantage to declaring this -- the credit for existing programs
explicitly in the rule -- would mean that we're essentially are not
going to have any discontinuity. If an applicant says that they're --
that they rely on the existing process and the CLB and use of the
existing programs, then we're -- we end up only changing the CLB to
capture things that are purely aging management for the scope of license
renewal. And so there's a clear definition about what the delta is
being under CLB and why it's there. And, as Sam just pointed out, we
don't favor this approach because we found 30 to 40 percent of this
stuff cross cut the existing programs. And so we're not sure we have a
clear picture about what that delta is, whether or not we've captured
the right delta.
DR. POWERS: When you found things in the so-called existing
programs that you felt like needed some modification, some refinement,
was this major things or minor things, or what kind of things were?
MR. GRIMES: As Sam pointed out before, because we have this
reliance on the existing process, we didn't expect to find, you know,
like whole systems that aren't being inspected. These are relatively
small things like, for example, adding to the -- to a system walkdown on
the checklist, pointing out that the walkdown should also look at
potential corrosion on fasteners, despite the -- you know, in spite of
the fact that we had a bulletin on fastener corrosion and fastener
problems, just adding fasteners to the checklist for a system walkdown
provides confidence that they're going to -- they're going to catch it
during the routine, during the process. That was a modified program.
MR. SIEBER: To what extent would you use performance
indicators or performance history as a demonstration of the adequacy of
programs for aging?
MR. GRIMES: We typically refer to reliance on conditioned
monitoring as a basis for managing aging effects, and conditioned
monitoring can be a part of it; but it's simply -- it's a feature of an
inspection activity, typically, in terms of identifying when it's --
when it's the right time to take an action. Where we usually get stuck
on conditioning monitoring is whether or not condition monitoring
provides a wholesale basis for saying that something is replaced on a
routine basis.
DR. SEALE: There's nothing in this option if you adopted it
that would restrict your ability to have new programs?
MR. GRIMES: That's correct.
DR. SEALE: Okay. And since you also have no a priori limit
on the number or extent of new programs, if you -- you could take this
approach and then have some new programs applying to already covered
systems which had that increment in a "new program" although that would
be a bookkeeping monstrosity and --
MR. GRIMES: We would not think that the staff would be
acting in good faith if we were to pursue that kind of a approach.
DR. SEALE: I understand.
MR. GRIMES: We intended that this would clearly specify
that the applicant would identify existing programs. And then we would
go back to work with NEI on the form and content of the application so
that there would be some consistency expected in the way that applicants
would refer to existing programs. But we still think that this is a
feasible approach in order to more clearly focus the scope of a license
renewal review.
DR. SEALE: Well, it's certainly -- it's certainly desirable
for you to not get in a position where you're trying to throw curve
balls at each other, and I applaud that.
DR. LEE: Okay. Even though this option would significantly
reduce the start-up applicant burden, okay, we do not believe that this
will provide or identify the 30 percent that we discussed earlier.
And the second option, describing in the Sec. E. paper is
alleged to amend the rule to actually specific which are existing
programs and which structures and components are subject to these
programs, and, therefore outside the scope of the rule. Okay, so this
is a clean way to just basically excluded all the programs -- all the
structures and components subject to existing programs.
Option three. This is the staff recommended approach -- is
to focus the standard review plan. This is a continuation of what we
are doing. This is an improvement of the standard review plan, and we
are involved the public in terms of developing this document. We heard
a lot yesterday at the Commission briefing about being transparent,
being open to the public, and that's what we intend to do under this
option.
A significant piece of this option is the -- what we call
the generic aging lessons learned, the GALL effort. We have initiated
this effort to evaluate existing program. GALL actually has a lot of
history behind it. It's based on extensive work by the Office of
Research, and they had nuclear plant aging research program, which had
gone on for many years. They produced over 150 reports. And also
NUMARC or NEI had prepared the industry report to manage it to address
aging of 10 major components or structures in the plant. So, that forms
the basis for GALL, and then we have been updating it identified -- we
identified component, aging effects, and want our programs to manage
these aging effects. And what we are now doing is generically assessing
the adequacy of this program to manage aging; okay, using the -- looking
at the program attributes -- the 10, like frequency inspection,
acceptance criteria. And then we identify programs and put them in the
70 percent bin if they are adequate for modification, or we putting in
the 30 percent bin, where they might need to be modified in some
fashion.
And GALL will document the basis why. And then the Standard
Review Plan will reference GALL, and hopefully the Standard Review Plan
will then focus on the 30 percent. And by doing this way, safety is
maintained because we are looking at all the programs, okay, at least
generically, and then we focus on the 30 percent where we will get most
of the safety gain.
MR. GRIMES: Sam, I want to point out two specific things at
this point. The first is last fall when we came to the Committee and
talked here about process, we pointed out that we had a feedback loop
built into -- in our office for the 805 that would capture generic
lessons learned and address the 106 -- I think at that time -- it's now
109 -- generic renewal issues. We had intended all along that we were
going to fix the details in the Standard Review Plan, address the NEI
comments on the Standard Review Plan, and also provide improved guidance
to the staff on how to conduct a license renewal review.
This represents a substantial expansion and more aggressive
approach towards that by simply going out and collecting everything that
we know about existing programs based on the first two applicants and
getting expertise to help us try and fill in the blanks on what
particular attributes go with particular programs. So this is an
acceleration of the feedback loop that we described to you last fall.
And also I want to point out we're confident that this
approach would work because we had very little debate about what are
applicable aging effects for particular components based on all the work
that -- from the industry reports and the research activities that led
to what we call GALL I, which is the catalog of which aging effects
apply to which components.
So, we have some experience that suggests that this approach
could -- would be very successful.
DR. POWERS: When I look at your three candidate options you
put in, the paper you assembled for the Commission, I was struck by the
kind of all or nothing type of approach. I mean, there is -- one option
was, okay, we won't inspect anything and the other one option if I
characterize is we'll do what we've been doing -- or what we planned to
do all along.
And there is -- there was not -- they really didn't strike
me as options that were milder than those are nothing kinds of options
whose -- is that -- was there -- is there any thinking behind that?
MR. GRIMES: Yes, there was a lot of -- a lot of thinking
behind that. I think we started off with maybe five options, but
variations on this theme, but what it boiled down to was that there was
-- that this was a fundamental policy, black and white problem. The
staff was going down a road where we were going to sort out details and
essentially accept a discontinuity at year 40, and say there's a CLB for
license renewal, and there's a CLB today, and the difference is
effective aging management. And NEI was going in a different direction
that said, no, it's that your mission was to go fix the regulatory
process relative to aging management; and all you're supposed to look at
it is what has changed beyond the regulatory process.
DR. POWERS: I characterize in my own mind the differences.
You saw a first order phase transition, and they saw a second order of
phase transition. You saw a discontinuity. They saw change in slope.
And --
MR. GRIMES: And so, it ended up that we -- we basically had
an all or nothing proposition where well, let's go fix the rule to make
it clear or let's go deal with this in a more systematic and pointed way
in the expectations for aging management programs.
DR. POWERS: And you were confident that the policy makers
could, if they saw fit, make an interpolation between the bounds?
MR. GRIMES: That's correct.
DR. POWERS: I kind of suspected that that was the thinking
behind it because I was struck by -- you really didn't give any middle
ground in your options.
DR. SEALE: No.
MR. GRIMES: Option Two was simply -- that's Option One in a
different packaging.
DR. LEE: To continue on Option 3, is that it deals with the
unnecessary burden, because then it is focused on 40 percent, and then
-- indicates that we will still have the discontinuity at year 40 under
Option 3. So that's why this is really a policy question. Do you want
this continued to year 40 or you don't.
Our recommendation is that we should review the existing
programs, and we think this process works. We looked at the two initial
applications, and they are maintaining safety because we identify like
40 percent of programs. And we recommend Option 3, which is use the
standard review plan, and we'll improve the efficiency of the process,
and we'll do it gradually as we learn.
Right now, we're only at a B&W plant and a CE plant, Calvert
Cliffs and Oconee, and we haven't seen a BWR yet, so we'll do a couple
more applications, and then based on that, we will have an opportunity
to further improve the efficiency, but right now, we're looking for
gradually homing in on the final standard review plan.
MR. GRIMES: And at this point, I would like to conclude the
staff's presentation by pointing out that we want to emphasize that we
view the purpose of license renewal not as a challenge to the adequacy
of existing programs or to reverify the current licensing basis, but as
an assessment of the effectiveness of existing, modified and new
programs to manage aging effects for the passive long-live systems,
structures and components within the scope of license renewal.
We believe the industry's fundamentally concerned about the
justification for any staff requirements beyond those proposed by an
applicant for the enlargement of the renewal reviews as the staff
becomes smarter in asking questions about how effective programs are.
We believe that that's a management issue that relates to providing
better guidance in the standard review plan and holding managers
accountable for an appropriate decision-making process, and we believe
it's more appropriate to address the industry's concern there rather
than in a selective reading of what Part 54 intended.
MR. MATTHEWS: Okay. The only other thing I would like to
add is just to be fair to the discussion yesterday in front of the
Commission, that UCS presented a view that would have had a continuation
of our existing review process. They would have recommended us to go
very slow with regard to treating anything generically. And I think
that was based on their concern that -- what Sam mentioned, the limited
sampling that we've had so far with regard to the range of vendors with
regard to the plants.
They also recommended and I think there was a sympathetic
response both on the part of the staff and the Commission, that the
process that we have been engaged in to resolve some of these generic
license renewal issues, which the 109 you've heard about on more than
one occasion, where we identify a possible generic resolution, we
forward it to NEI, we get an NEI response, industry-wide comment on it,
and then it heads back towards us to be incorporated into the next
update of the standard review plan, that process along with the review
of the different evolutions of the GALL report would be something that
be much more transparent and provide opportunities for wider comment by
interested parties.
Although we have made such interactions publicly available,
it wasn't with the intent of soliciting per se additional input or
comment, and that's a facet to the program that we're going to expand.
DR. POWERS: It sounds like you're suggesting to the
committee that we review the transcript on that, your meeting with the
Commission in order to get a good understanding of the UCS view.
MR. MATTHEWS: I wasn't suggesting that, but I think that
transcript will be available very shortly and I think it would inform
your decision.
DR. POWERS: Thank you.
DR. SEALE: Okay. If there's nothing else from the staff,
--
MR. GRIMES: That complete the staff's presentation.
DR. SEALE: All right. We also have Mr. Walters from the
NEI to tell us what their position on this issue is.
How badly hurting am I on time, Mr. Chairman?
DR. POWERS: You're doing fine.
DR. SEALE: Okay. Thank you. I think this is an important
issue.
DR. POWERS: Yes. I think we can take the time that this
issue takes. Nominally, according to the schedule, you've got 20
minutes, but I would be more interested in getting the point of view --
DR. SEALE: Good.
DR. POWERS: -- on the table than adhering strongly to a
schedule.
DR. SEALE: Thank you.
MR. WALTERS: Good afternoon. My name is Doug Walters. I
am with the Nuclear Energy Institute. I have had responsibility for
license renewal since about 1992, and before I begin my formal remarks,
I'd just like to sort of frame our position this way:
Existing programs and taking credit for those is not a new
issue. This has been an issue since probably 1994, maybe 1995. And we
reached an impasse at that point with the staff because we hadn't seen
an application and we talked a lot of philosophy about how credit ought
to be given for existing programs, but we really had no real objective
evidence, if you will, to go on to advance that issue.
So we agreed with the staff that what we would do is wait
until we had an opportunity to see a review of a real application and
then revisit the issue, and so that's where we are today.
So what I would like to share with you is first of all give
you a sense of what licensees do when they prepare an application and
how they look at existing programs; share with you what we think the
issue is; give you a few observations on the SECY. I'm not going to go
through each option and comment, but we do have some observations we
would like to provide to you. And then recommendations. Now, these are
the recommendations we provided to the Commission yesterday, and then
some concluding thoughts.
DR. POWERS: When I think about this, this issue, and during
our discussions in the previous presentation, a lot, in my mind, hinges
on the interpretation of the word demonstrate.
MR. WALTERS: Right.
DR. POWERS: And will you, in the course of making this
presentation --
MR. WALTERS: Yes.
DR. POWERS: -- give us some understanding of how you view
the word demonstrate?
MR. WALTERS: Yes, I will.
DR. POWERS: Thank you.
MR. WALTERS: This is a simple flow diagram that describes
typically the process that a licensee will go through to prepare a
renewal application. We start with the plant system, structures and
components, and we throw that into a hopper, and we apply the scoping
and screening criteria that are delineated in the regulation. And out
of the bottom of that, you will get your long-lived passive structures
and components.
DR. POWERS: Does there tend to be disagreement on that
screening?
MR. WALTERS: I don't think there's disagreement. There may
be some uniqueness, if you will, to certain definitions that a licensee
has on perhaps what --
DR. POWERS: But this is a pretty easy chore?
MR. WALTERS: Yeah. I think that's pretty deterministic.
Obviously, there are some questions. The staff has an obligation to
make sure this is complete. But I don't think there's an disagreement
on the criteria that are used to get to that set.
We also identify the aging effects and the functions
associated with those long-live passive components.
DR. POWERS: I get the impression that there is a -- there
has been a fair continuity of mind on the aging mechanisms that take
place here, that that too is not a very controversial process.
MR. WALTERS: No, I don't think so. I think, as Chris said,
the set of aging effects is pretty well defined and we have, I think, a
pretty good understanding of what those are.
We then do what we're terming as mapping, and I think this
is a piece that's not well understood, but we actually take these
long-lived passive components and structures and we've got the aging
effect identified, and let me just digress for a minute.
When we revised the rule in 1995, the staff is correct that
the active components were excluded because of the maintenance rule and
the fact that aging was readily observable, I think were the words that
were used. The Commission could not conclude generically that all
licensees had programs that managed the aging on long-lived passive
structures and components.
The industry's view on that, as documented in our comments
on the '95 rule, is we thought that most if not all long-lived passive
structures and components were in fact managed, but that the obligation
that the licensee had was to go back and do a review and give themselves
reasonably assurance, draw their own conclusion that there is reasonable
assurance that the program is managing the aging.
I think the results that were presented show that, in fact,
we are managing the long-lived passive structures and components. But
we felt we had an obligation to go back and assure ourselves that the
programs were doing what we thought they were doing and, you know,
certainly there are instances where we found new programs were needed.
But we do do this mapping. It's a conscious look at the programs and
activities.
And I would also point out that the adoption of Option 1
does not mean this goes away. We will do this regardless. The
Commission could say all existing programs are adequate; we'll still do
this. We feel we have that obligation. We have an obligation to go
back and make sure that the program is mapped to the aging effect.
When you do this mapping, one of three results is likely.
You're either going to find that you have an existing program or
activity without change, and Sam went through these, but you'll find
that you may have an existing program that needs modification. I'm
going to talk about these in a little more detail in a minute. Or you
may need a new program. That's the process that I think typically BG&E
and Duke use.
The other important point of this is, it's through this
process right here and the licensees identified those 30 to 40 percent.
The licensee identified those. This process produces that -- or those
pieces of the pie, if you will, and that's not going to go away.
DR. POWERS: Have there been instances in the pilots where
the staff has come in and said, no, Applicant, you completely left out
one entire area and we need a big program here?
MR. WALTERS: No. As I mentioned before, the staff's review
results were on the same scale as the way the proposed program changes
were presented to us. We didn't identify anything that constituted a
real significant difference.
We did identify some areas where they had an aging
management program that they didn't credit. Typically they didn't take
credit for ISI in a lot of cases where we felt that that was an
appropriate thing to do, and they did identify an aging effect and they
argued that they didn't need to manage it, and we kept saying, no, you
are managing it. So there were some differences like that.
DR. POWERS: Understand, the fact that you haven't
identified big programs is not a criticism; I'm just understanding how
well this process the speaker is discussing is working.
MR. WALTERS: The staff agrees, we think that the process
works well. As a matter of fact, we -- and we rely heavily on the
process as it's described in the rule. It says that there will be an
integrated plan assessment. A process drives capturing all of the
systems, structures, components, commodities. We rely on that to make
sure that everything that needs to be managed is being managed, but then
we review it at a program level, and now the question is, but how much
does the program need to be reviewed, how deep does the staff need to go
in terms of challenging its ability to manage the aging effects.
You've already seen this pie. I would only make one point
in response to -- I'm not sure which member asked the question, in the
charts that the staff showed, for BG&E, this number was about 329, I
believe, this was 101, I believe. That's 430. I happen to have a slide
that BG&E used, and I just wanted to mention that within this piece, the
question was asked, why is that number so big versus what Duke had. 309
PM programs. So that's the level they work. Duke rolled those up into
more of a generic program.
Again, this is just to demonstrate that -- no pun intended
-- that these are the typical results, and our position on this is that
these pieces of the pie which are existing programs really fall into two
categories. There are some programs in both pieces of the pie that are
current licensing basis programs, and there are some that are
non-current licensing basis programs in both pieces, even though they're
existing. There are some CLB programs and some non-CLB programs. And
our position is that if it's a CLB program, the technical adequacy, the
ability of that program to manage the aging -- let me strike that.
If it's a CLB program that manages aging today, and we've
got a lot of examples, that manages aging today, we believe the rule
found that it's technically adequate to manage that same aging in the
period of extended operation. And I'll give you an example that -- in
the example that was provided on small bore piping, I don't know if it
occurred to you, but it occurred to me that there was no reason given
why that cracking from the inside out is different for renewal. Why is
that only a concern for license renewal? And we ought to know why,
because I would think if I were the plant manager and somebody said,
hey, you've got cracking from the inside out of that pipe, I would like
to take care of it today.
DR. POWERS: Good point.
MR. WALTERS: What was the standard that it met that said,
no, no, we've got to deal with it only in the renewal period?
So our view is that if it manages the aging today, like
Section 11 does, it's adequate for the period of extended operation, CLB
program. If it's not a CLB program but it's existing -- and let me just
reiterate the point that on all those programs, CLB and non, we're going
to do this mapping. Then on a non-CLB program that's existing, we
clearly have to provide some technical discussion in the application.
DR. POWERS: Now, the previous speaker indicated that when
they had gone through the first two of these applications, that they had
found what they called adjustments, modifications and omissions across
the board, all through your colors on your pie chart there, including --
MR. WALTERS: That's right.
DR. POWERS: -- those in the purple region.
MR. WALTERS: Right.
DR. POWERS: In those in the purple region, did they find
modifications that were necessary and that everybody agreed were
necessary for CLB programs?
MR. WALTERS: Yes. There were some adjustments to CLB
programs. I would -- I don't want to misspeak, and so I can't tell you
that I've looked at all those, but I will tell you, the ones that I'm
aware of were probably done for expediency.
DR. SEALE: Isn't it true that that pie chart we saw was an
application product and not a staff product?
MR. WALTERS: That is correct.
DR. SEALE: Are you telling us, then, that when you go
through and do the hopper, culling, sorting, whatever --
MR. WALTERS: Yes.
DR. SEALE: -- you want to call it, and you find that a
program, due to your enhanced state of enlightenment compared to the
time at which you first put the program in place, whether it is a CLB
program or not, in fact, requires additional elements that you would,
under those circumstances, with Option 1, essentially call that a new
program and --
MR. WALTERS: Yes.
DR. SEALE: -- designate it as such and carry forward --
MR. WALTERS: Yes.
DR. SEALE: -- from there?
MR. WALTERS: Yes. Some of this is semantics. We may not
be saying modified in -- let me -- the answer to your question is yes.
Let me make clear that when we're talking about modified programs, I
think what we first two applications would tell you is that a modified
program was still an existing program, and the substance of the program,
what the program required you to do, what action it required you to take
did not change.
I'll maybe modify that a little bit, but in essence, that --
the program itself stayed the same. A modified program was designated
as such because perhaps additional scope was added. Maybe you needed to
manage the aging on this valve and, boy, that fit nice in this program
because I'm doing valves just like that, and so we'll add the scope. Or
it was a documentation enhancement. The inspector from the plant, not
the NRC inspector, but the inspector from the plant goes into an area
and the procedure says observe for signs of degradation. Well, in that
area, there may be a pipe run, and that specifically is in the scope of
renewal. The procedure would be updated to say look specifically at
that pipe for signs of erosion on the external surface or something.
Those are what we mean by modified programs.
DR. SEALE: That's interesting because I would prefer to
think that maybe you didn't know it all the first time you did it and
you've learned something since then. And so I would not be -- that
doesn't bother me that you might feel that you had to augment and
existing program.
MR. WALTERS: Right.
DR. SEALE: But you call that a new program?
MR. WALTERS: Yeah. I mean, if we -- if in our mapping we
found an aging effect that was not managed today but clearly it was
there, that's a new program and, boy, we've got to define what we're
going to do, how we're going to do it, et cetera.
But if we do the mapping and we say, well, gee whiz, we've
been looking for, you know, wall thinning on this pipe from the first
day of operation under this same procedure, and the date of the
procedure is 1965 and there's a couple of revision bars, I think we have
pretty good assurance that we're managing that aging and the
continuation of that program will manage that same aging in the renewal
period.
So that's what we think we need to do. Now, of course, we
have the yellow piece, which is where most of the attention is focused
right now, but even on that piece of the pie, I think the applications,
the first two, would certainly tell you those are a lot of one-time
inspections and engineering analyses. And it's curious that somehow
one-time inspections now equate to the same significance as ISI or
something like that.
The issue that we're here to deal with, we don't disagree
with the staff. This is exactly the way -- well, we copied, actually,
what they -- the way they characterize it.
A couple of observations on the SECY. We heard a lot about
Option 1. It doesn't really, we don't believe, convey our position.
Just to be -- I don't know if I have a copy of the SECY with me, but I
think it says -- the first Option says do not review existing programs.
That's not our view. We've never maintained a position that existing
programs shouldn't be reviewed. As we'll talk a little bit later, we
just don't think they should be reviewed under Part 54. And let's be
frank. Under Part 54, there's no backfit protection. If I have a
particular interest about fatigue or EQ, and I can't pass the backfit
test under Part 50, oh, but you've got a renewal application in there --
I'm going to look at that program and I'm going to say I think we need
to do something different because it's necessary for license renewal.
You don't have to go through that safety hurdle of the backfit rule.
That's a concern. I don't have any objective evidence at
this point that that's been the case, but we are concerned about that.
I think we also, in the same context of do not review, I
think the first two applications in the process show that we do a fairly
rigorous review. I'm not going to try to define rigorously for you. I
won't tell you it's the same for every program, but the point is we do a
review of the programs and we use engineering judgment to conclude that
there's reasonable assurance that that program is going to manage
whatever aging effect --
DR. POWERS: When you say we, what's the antecedent?
MR. WALTERS: I'm sorry?
DR. POWERS: What's the antecedent of we when you say we do
review these programs?
MR. WALTERS: Our process.
DR. POWERS: Your process.
MR. WALTERS: The process that is --
DR. POWERS: The application goes through.
MR. WALTERS: Yes. And I would point out that -- let me
just again put this up -- this really, I think, is a flow diagram of the
process you would see in our guidance document, NEI 95-10, and that's
typically where -- well, certainly that's where the first two
applications started in terms of developing their own plant-specific
program and others are doing the same. So when I say we, I mean --
DR. POWERS: Yes. I understand.
DR. WALLIS: Are we talking about the same issue, though? I
thought the review was reviewed by the staff rather than an internal
review by the license.
MR. WALTERS: Right.
DR. WALLIS: You're talking about what the licensee does; I
thought they were talking about how much they needed --
MR. WALTERS: Right.
DR. WALLIS: So there are two different we's here. Are you
saying that the NRC doesn't need to review it or --
MR. WALTERS: Well, no. We're saying they can review it.
We're saying all programs are subject to review, can be subject to
review. The issue is, for license renewal, if it's an existing CLB
program, to what extent should the staff review that program, and we're
saying that they don't need to, that as long as we've done the mapping
program --
DR. WALLIS: This is a "trust us" type of statement.
MR. WALTERS: Well, no, it's more than "trust us." NUREG
1412, 1991, adequacy of the current licensing basis, supplement to the
statements of consideration for the 1991 rule, basis for the two
principles that the staff showed you on a previous -- in their previous
presentation.
DR. BONACA: But on some occasions, the applicant finds that
the current program still needs to be modified.
MR. WALTERS: Perhaps. Sure.
DR. BONACA: Okay.
MR. WALTERS: That's always a possibility, sure.
DR. BONACA: And then in some cases, it's not applicable,
you have to have a new program.
MR. WALTERS: Right.
DR. BONACA: And you have recognized that in the pie chart.
MR. WALTERS: Right.
DR. BONACA: And the question I have is, but you really
don't want to have the NRC reviewing that statement of adequacy? I
mean, what you're saying is that when we have made a determination that
the current program applies, okay, then don't look at it. I mean,
that's --
MR. WALTERS: No. And I will get to you very point --
DR. BONACA: Okay.
MR. WALTERS: -- in two more slides if you'll indulge me.
What we're saying is in terms of Option 1, and it's not
don't review existing programs, we're saying that the whole history of
the rule, the principles of the rule, this NUREG, all provided and were
intended to show that the current licensing basis is adequate. And in
fact, if you look at NUREG 1412, there is a specific analysis of EQ, and
so you might ask, well, why would we need to say anything or do anything
more in terms of presenting the how do we implement EQ in a license
renewal application? It's a regulation. This NUREG evaluated, it said,
well, it will continue to protect public health and safety, and we just
think we should get credit for that.
DR. POWERS: I guess I'm still a little puzzled by the
second bullet.
MR. WALTERS: Okay.
DR. POWERS: And it may be interpretation here. Your
contention is, and I think you're accurate, is that the applicant goes
through his existing programs and looks at them very carefully and says,
let me make sure this these things are good for an additional 20 years
of operation, that I haven't got something buried in them that says quit
doing this because there's only ten years of life left in this
component, and the aging mechanism is such that it takes twelve years
for it to fall apart.
MR. WALTERS: Yes.
DR. POWERS: So don't worry about it. They make sure that
sort of thing doesn't exist, and I'm sure he does. Everything I have
seen says yeah, they do a pretty good job on that. Nevertheless, when
the staff has come through and looked at those programs, they've come up
and said, gee, you needed to modify this program or add this thing in,
and some of them are minor things by their admission here just minutes
ago. They said that these are relatively minor things. But they still
find things in there.
So though it's reviewed strenuously and even rigorously,
that doesn't mean that other people operating from different
perspectives won't find things that got omitted. Am I wrong there?
MR. WALTERS: No, I don't think that's wrong, but I might
argue that -- well, let me go back. The modified and new programs have
all been identified by the applicant, and I might argue, but certainly
maybe the staff's the better party to ask here, but I might argue that
the enhancements that have been suggested or imposed by the staff really
challenge the current licensing basis.
I mean, this gets back to what was the basis for asking for
the enhancement. What is the deficiency in what I'm doing today that
requires me to do something different only for license renewal? And
small bore piping is an example of that, I think.
DR. BONACA: Well, this to me seems that -- yes, I
understand the specifics, but it seems to me that the applicant reviews
existing programs for applicability and makes a determination, either
accepts or augments.
MR. WALTERS: Yes.
DR. BONACA: As a process.
MR. WALTERS: As a process. That's right.
DR. BONACA: Shouldn't the NRC review the adequacy of this
process? Not specifically looking at --
MR. WALTERS: Yes.
DR. BONACA: -- individual existing licensing commitment,
but the adequacy --
MR. WALTERS: Right.
DR. BONACA: -- of the process. And the only way you can do
that is to read what each issue was and how existing programs address it
or --
MR. WALTERS: Yeah.
DR. BONACA: -- how they were --
MR. WALTERS: And I don't want to leave you with the
impression that in an application for an existing CLB program, there's
no discussion. There is some discussion needed. It's minimal. And
they can look at the adequacy. And our argument is if you want to look
at the adequacy of that CLB program, look at it under Part 50.
DR. BONACA: Yes, I'm not questioning the CLB; I'll talking
about the process by which the applicant is going to the determination
that 28 ends up in this pile, --
MR. WALTERS: Yes.
DR. BONACA: -- 11 in this pile, and --
MR. WALTERS: The answer to your question is yes.
DR. BONACA: Because I think that's really the --I mean --
MR. WALTERS: Right. They clearly have that obligation.
DR. BONACA: Okay.
MR. WALTERS: They clearly have that obligation. I think
it's how -- perhaps what we're discussing here is how can they make that
finding, if you will, of adequacy, and we think that there is enough
language in the rule, that the principles of the rule, this NUREG, a
number of other things, give them that foundation to say it's adequate.
MR. PIERCE: I'm Chuck Pierce with Southern Nuclear.
The NRC, under the industry process, would review the
mapping.
MR. WALTERS: Yes.
MR. PIERCE: And the mapping is what identifies, in our
mind, many of the inadequacies of these programs that we're talking
about here today, this 30 percent. The mapping is 70 --
MR. WALTERS: Let me clarify that point. In our -- I don't
know where that slide was -- but in the flow diagram where we have the
mapping, we have to put information in the application that shows we did
this and how we did it and what the results are. I mean, this is
information that clearly has to be presented in the application, and the
staff has to agree with that. I'm going to talk about that in just one
more slide.
We heard a little bit about the option that's been
recommended for adoption. We have several concerns with this generic
aging license -- lessons learned, excuse me, approach. We think it
undermines the conclusions that are in this NUREG that talks about the
adequacy of the CLB. It focuses on more of the programmatic aspects of
the current licensing basis programs.
In NEI 9510, we've identified ten criteria that we think
would typically make up an aging management program, and the intent of
the GALL approach is to take those ten criteria and now, in some
regards, turn those into requirements and evaluate all existing programs
against those attributes. We already know that there's a number of
programs that aren't going to have all ten attributes.
I think our biggest concern is this bullet here. There's no
obvious process that controls the imposition of new activities, and this
gets back to no backfit protection, no standard that says, here's why
you need to do with for license renewal.
I think there's another example we've already seen with this
on IWE, IWL. I won't go into a lot of detail, but there is a rulemaking
in 1996 which is significant because it's after the '95 Part 54 license
renewal rule as amended that says implementation of 5055-A, IWE, IWL,
containment inspection will be adequate for license renewal, and we have
already seen that for inaccessible areas, the staff does not agree with
that, and there is a separate NUREG now that says here's what you need
to do for renewal. That's the kind of concern we have with the GALL
report.
This gets to the demonstration issue, and our view on
demonstration is that it's undefined. We've done actually a review of
10 CFR and you would be amazed at how many times demonstrate occurs in
the regulations. It's in the ATWS rule, for example.
But we didn't have to go through this kind of, you know --
well, I'll say we didn't have to provide the kind of information and the
level of detail of information that we're now saying is necessary for
renewal because of the demonstration.
So it's an undefined term, and I think that, you know, you
can apply a definition that suits your objective, but to us, we think
the demonstration is made for existing CLB programs in the principles of
the rule.
DR. POWERS: And don't you think it's undefined because,
like most of the words, nearly all of the words in the 10 CFR series,
those that there's a reasonable expectation that knowledgeable
individuals will understand the meaning of the word, it isn't defined.
And here particularly in connection with this rule, in looking at the
statement of consideration for the 10 CFR 54 rule, it -- my reading of
it says very clearly that the authors of those documents were using the
word demonstrate in its engineering sense, that it was more than simply
saying identification, or enumeration or assertion, that there was more
to it than that in their minds.
MR. WALTERS: Right.
DR. POWERS: And that it is, as I said earlier, not just
telling me the answer, but showing me how you got to that answer was the
idea behind it, recognizing it's still a paperwork exercise --
MR. WALTERS: Right. Right.
DR. POWERS: -- that you're forced by circumstances to be in
a -- what was called I think a predictive situation because there are no
experimental data.
MR. WALTERS: Right.
DR. POWERS: And so I guess I don't understand why you think
it's undefined. I mean, there's a lot of language associated with it.
MR. WALTERS: There is. And again, I think it depends on
your interpretation of the language. I wouldn't disagree with your
assessment necessarily, but that might go to, you know, to this issue,
this is what we recommended to the Commission. And you saw the first
principle of the rule. The staff explained that this means certain
plant systems, means long-lived passive. Why didn't the Commission just
say, with the exception of detrimental effects of aging on long-lived
passive structures and components? I mean, if it's that clear, it seems
to me -- and they had already made the decision that the active stuff
was out. Why didn't they just say detrimental effects on long-lived
passive?
I think we could go to numerous parts of the SOC that might
argue that this means something else, and our view is that the certain
means the long-lived passive structures and components where the CLB is
not current managing the aging, and on that interpretation, then I would
agree that's where the demonstration is and the demonstration is exactly
the way you characterized it.
DR. POWERS: Yes. And I agree with --
MR. WALTERS: And so that's our interpretation, and we
suggested -- recommended to the Commission that they clarify that.
We also recommended that the Commission affirm that the
adequacy of what we do today be addressed under Part 50. There are some
provisions in the rule that get to this point, 5430.
Then lastly, we recommended that we should work with the
staff and stakeholders to expeditiously finalize the standard review
plan to reflect the following, and this will get to some of your
comments. This is the way we see it.
You have CLB programs and activities, you have modified CLB
programs and activities, you have non-CLB programs and activities and
modified, excuse me, non-CLB programs and activities, all which exist
today. So you have four classes, if you will, of programs and
activities.
In terms of what needs to be done and what goes in the
application, if it's an existing CLB program or activity, as our process
showed, we need to map that activity to the aging effect or effects and
the scope of the program. And what we -- and we ought to provide
information in the application that explains that, and what the staff
ought to do is verify that mapping. We think that that's all that needs
to be done if it's an existing program that manages aging today.
If it's a modified -- let me go back. An example of that we
would say is EQ. Why did you have me implement the EQ? Why do I have
an EQ rule? If I don't have it to manage aging, why do I have it? And
are you telling me that you only promulgated Part 54 -- excuse me --
50.49 for 40 years for his plant and his plant and his plant? I don't
think so. If we did, we wouldn't need regulatory oversight; we'd just
operate for 40 years without any.
So it's an existing CLB program, it manages the aging today,
I'm going to map it, the staff should verify my mapping.
If I modify an existing CLB program, same thing. Now, might
be a little more information in the application in terms of what the
modification is, but again, these are program enhancements -- I'm sorry
-- documentation enhancements perhaps or additional scope.
If it's an existing non-CLB program or activity, we've got
to do a little more. Makes sense. We've got to provide a description
in the application that demonstrates that the aging is managed, and I
would say that the demonstration is as Dr. Powers suggested.
Staff ought to verify the mapping, and they ought to
evaluate the adequacy of the program. If it's a modified existing
non-CLB program, same thing.
New programs, lots of detail, lots of information, lots of
justification, but most of these are one-time inspections, verification
inspections.
DR. BONACA: Could you put it back?
MR. WALTERS: Sure.
DR. BONACA: I guess the question on the second category
that have, modified CLB program activities.
MR. WALTERS: Uh-huh.
DR. BONACA: Assume that the modification is that you find
that the program is adequate except you want to make one-time inspection
40 years. That would be a new one. I'm talking about the modified.
MR. WALTERS: Right. Well, I was -- I'm sorry. I was
reacting -- you said a one-time inspection.
DR. BONACA: Yes.
MR. WALTERS: I would say that's a new --
DR. BONACA: Okay.
MR. WALTERS: This again would be -- and maybe the staff has
better examples -- our understanding based on the first two applications
is modified is we need better documentation. We're not changing the
substance of the program. I think Appendix H, the vessel surveillance
program, where you need to modify your schedule so you can cover the 60
years, you haven't changed the substance of the program, you just
changed the schedule of withdrawal of the samples. That's probably a
modified CLB program.
Modified, at least as we're using it here, does not mean
we're modifying the substance of the program and what the program
requires us to do. If we did that, it's probably down here.
DR. BONACA: I would like to hear from the staff now. On
category 1 and 2, do you find any examples where by following this
guidance of just mapping, you have inadequate review?
MR. GRIMES: In the course of the review of the first two
plants, we found examples where the applicant referred to an existing
program for which it wasn't clear whether it was CLB or not. They made
proposals to modify that program and we had open items related to the
nature of the modification and its extent.
And the example that I gave before was they have an existing
program to perform system walkdowns. It's not clear how the system
walkdowns are captured by the current licensing basis, but they are
clearly an existing program. They fall within Appendix B.
They proposed to modify their walkdowns to inspect for
certain aging effects related to certain systems. We ended up with open
items related to inspecting other things, like fasteners, for other
aging effects.
So that's the difficulty we have in trying to understand how
we would implement this concept in terms of if they come in and propose
it as a modified CLB program, I've got -- I can go after it with Part
54, no backfit protection. But if they declare it is a CLB program and
they're complying with Appendix B and I want them to change the walkdown
procedure, I'm in 5109 space.
DR. BONACA: Thank you.
DR. SEALE: Okay.
MR. WALTERS: In conclusion, we think we can say with
certainty that the first two reviews clearly demonstrates -- no pun
intended again -- that we are managing very aging on long-lived
structures and components. We need the staff reviews to be focused.
Just to digress for a moment, we're going to have an
application at the end of this year, we're going to have another
application in probably January of 2000, we're going to have a third
application at the end of 2000, we're going to have, we think, if there
is an exemption request granted, we'll have probably eight -- I think
eight units -- strike that -- probably five or six units in 2001. We've
got a lot of people lined to for renewal.
We always have to ensure, of course, that --
DR. POWERS: Our own planning is a steady state rate after
2000 of seven plants a year.
MR. WALTERS: About, yes.
We need to be focused, and we shouldn't be spending a lot of
time reverifying what we're doing today on the licensing basis that we
have today, which, by the way, you know the current licensing basis is
defined in Part 54, so --
DR. WALLIS: Maybe they need to be focused on the future?
MR. WALTERS: No. They need to be focused on the pieces of
the pie that are new and modified, or --
DR. WALLIS: Well, they will eventually get to that anyway.
You're saying they would be more efficient if they did that.
MR. WALTERS: Right.
DR. WALLIS: Put more effort into that rather than the other
--
MR. WALTERS: Well, the GALL report is going to tend to move
towards this by looking at every existing program to see if it has ten
attributes, and we're saying that's already been done.
DR. WALLIS: But if they do that and find nothing, then it's
just a waste of their time. We're just concerned for how they're
spending their time and spending public money.
MR. WALTERS: Well --
DR. POWERS: Well, let me just say that it probably does
hurt him as an embodiment of the industry as a whole --
MR. WALTERS: Thank you, because I don't have a plant --
DR. POWERS: -- in the sense that the staff has a finite
number of warm bodies to look at these things and if they're looking at
things that are a waste of their time, that means that somebody else in
the queue of seven plants gets to wait a little for the duration of that
wasted time. So it does hurt in some sense.
Now --
DR. WALLIS: So it's the time you're worried about.
DR. POWERS: Now, whether -- I mean --
MR. WALTERS: Well it's time --
DR. POWERS: Whether that's our concern or not as a
committee, I think it is not because that's the management of the agency
as a whole, but not -- our concern more is what does it take to have
confidence that these plants are adequately safe for 20 years of
continued operation.
MR. GRIMES: And I feel compelled to point out, since I'm
the guy who signs the piece of paper that tells the guy sitting next to
me that the million dollars that we're going to spend to go out and do
this mapping in order to identify how the staff's review can be focused,
we don't think it's a waste of money because we had the first two
applicants point out to us that where there are gaps in the existing
programs, one applicant did one thing and the other applicant did a
different thing.
So I feel that safety is being enhanced by going out and
figuring out where these gaps are and then trying to derive generic
solutions for what is the optimum plant walkdown, just like we did with
the effort to develop the catalog of applicable aging effects, which was
GALL I, which we did not consider to be a waste of time or a waste of
money because we had very few arguments about what were applicable aging
effects, maybe less than a half of 1 percent of the declared applicable
aging effects, or as the other applicant calls it, plausible aging
effects, since the language consistency still hasn't been achieved.
There were very few disputes about what are applicable aging effects.
There are quite a few differences in terms of what are
needed program enhancements or augmentation, and when the applicant
comes in and tells us, well, I need to change the program to enhance it
to manage aging effects, but if we ask a question, we're reverifying the
current licensing basis, I have a logic discontinuity problem.
MR. WALTERS: I would just answer the gentleman's question
that it's also this issue. It's long-term stability.
DR. WALLIS: I guess the reason I just asked the question
was I got the impression from the staff's presentation that they were
doing a pretty good job of focusing on what mattered, and so I wondered
why you had to say that it needed to be focused.
MR. WALTERS: Okay.
DR. WALLIS: I wanted some more specifics about that.
MR. WALTERS: Environmental qualification required by
regulation talks specifically about aging, gives specific actions you
can take. You can requalify the equipment, you can use condition
monitoring, you can replace it. It's an existing program subject to
inspection then enforcement.
Now, if the staff says, well, we haven't inspected it for
ten years, I think that's a bigger issue than license renewal. If you
look at the application that was submitted by BG&E, it was on the order
of 100 pages of discussion on EQ.
Now, you saw in the staff's presentation that that was a
program that didn't require modification, but it shouldn't take 100
pages to get to that point and then to say, well, we resolved the EQ
issue. And then I think there was a supplemental submittal that was
probably on the order of 25. But the point is that we don't believe
that serves any benefit. There's no basis for that. And that's why
we're saying they ought to be focused. We ought to be focused on the
things that the applicant says need to be modified or the new things
that need to be, because all of this is for long-term stability, because
as I said, we've got a number of applicants -- excuse me -- licensees
lined up.
And also, let me not, you know, leave this with we're
dissatisfied, those guys sitting over there are bad guys. It's not that
way. There is no question that the first two reviews are going
extremely well and probably better than we thought they would, and that
is a, you know, it's a compliment to the Commission and the staff. But
there has been a number of factors that have helped that.
DR. POWERS: It's a compliment to the applicants as well.
DR. SEALE: Yes. True.
MR. WALTERS: And compliment the applicants as well. We've
had Congressional oversight, we have had Commission involvement. It's a
high priority issue. But there is no question that the reviews are
going well, and so this is a policy issue that came up, you know, back
in 1994 and 1995. We're trying to get resolution of it because we're
concerned about the next 20 applicants that are coming in, and once the
Commission decides on this, we'll move on and we'll have more, you know,
more issue to deal with, I'm sure, as we go through this.
But that concludes my remarks, and I thank you for the
opportunity to present them.
DR. POWERS: Thank you.
DR. SEALE: Thank you.
Does the staff wish to make any other comments?
MR. GRIMES: No.
DR. SEALE: Okay. Brevity is the soul of discretion.
Well, Mr. Chairman, I assume we'll have some time to discuss
this after our next presentation.
DR. POWERS: No, we have two more presentations before we
have --
DR. SEALE: Oh, two more presentations.
DR. POWERS: We have adequate time this evening to discuss
this.
DR. SEALE: Okay. Fine. I would just remind everyone that
we have a nail to hit on the head here, and we've got to make a decision
as to which one it is. And so -- and we do need your -- we do need the
Committee's guidance in order to finish the preparation of the letter.
So with that, I'll hand it back to you, Mr. Chairman.
DR. POWERS: Fine. I'm going to go right on to the next
presentation, which addresses the regulatory guidance that's being
developed for the maintenance rule, and Mr. Barton, I believe you're the
cognizant member in charge of that presentation.
MR. BARTON: Yes, I'm the guilty victim of this one.
DR. POWERS: You're the lucky manager of our investigations
of maintenance rule?
MR. BARTON: Yes, sir.
The purpose of the session today is to hear presentations
from and hold discussion with representatives of the staff and Nuclear
Energy Institute regarding proposed Revision 3 to Reg Guide 1.160,
assessing and managing risk before maintenance activities at nuclear
power plants, and the draft revision to Section 11 to NUMARC 9301, which
is the industry guidelines for monitoring the effectiveness of
maintenance at nuclear power plants.
The Committee has reviewed the maintenance rule and on June
18th, the Commission approved the final rule, amending 10 CFR 50.65 to
require the power reactor licensees before performing maintenance assess
and manage the increase in risk that may result from the maintenance
activities. The Commission agreed with the staff at that time that the
final rule should not become effective until the final regulatory guide
is in place for 120 days.
During a May ACRS meeting, the staff briefed the committee
regarding the proposed revision to the regulatory guide. There have
been some changes in the proposed regulatory guide since the ACRS
briefing in May, and NEI has also been working on Section 11 to NUMARC
9301 and we expect to hear from the industry at this meeting also.
The expected action from the ACRS is to provide a report.
We're being requested to review and endorse the current version of the
draft regulatory guide which was developed to supplement Reg Guide 1.160
and that guide describes an acceptable method for performing
pre-maintenance risk assessments required by the new paragraph A4 of 10
CFR 50.65, the maintenance rule.
At this time, I'll turn it over to Rich Correia of the staff
to bring us up to date on the revisions to the Reg Guides since our
briefing in May.
MR. CORREIA: Thank you and good afternoon. Actually you've
discussed already a lot of the background information that I was going
to start with.
As you said, the Commission approved the rule on June 18 of
this year, and now they have directed us to prepare a regulatory guide
for public consideration and finalization.
In their SRM 99-133 the Commission referred to their May 5
SRM which discussed the draft regulatory guide, and in that SRM they
directed us among other things to seek review by ACRS and provide the
draft reg guide to the Commission for information. That's one of the
reasons we're here.
Since our last meeting --
DR. POWERS: But you just love coming in to talk to us. I
mean, you would have come here whether they had an SRM or not.
MR. CORREIA: That's true. That's true.
DR. POWERS: I knew that.
MR. CORREIA: Since our last meeting, we have made some
changes to the regulatory guide reflecting comments from the Committee
and the stakeholders and the Commission, largely in the area of the
scope of structures, systems, and components subject to the A4
assessments, and the risk-significant configuration criteria. I've
asked Dr. See-Meng Wong to address those changes, and then I'll finish
up with the status of where we are and where we plan to go.
DR. WONG: Hello. Does this work?
DR. POWERS: Hopefully.
DR. WONG: Okay. Good afternoon. I am See-Meng Wong of the
PRA branch, NRR, and in our April briefing to this Committee, we
presented an initial draft of the proposed reg guide for the maintenance
rule A4 assessments. In that presentation we discussed the
considerations for the scope of the SSC's that need to be addressed for
maintenance rule A-4 assessments, which was an issue that was brought
forth by NEI and industry representatives with the concern that the
scope may not be manageable.
As I recall, in that presentation we stated that the scope
of the -- the focus of the assessment should be on systems at the train
functional level. As Rich has stated, as a result of the comments at
the May 5 Commission briefing and also comments from your Committee and
other committees and public meetings, we revised this draft reg guide
document to provide an approach to define a scope that's consistent with
or to reflect the last sentence of the rule language.
We stated that the scope may be limited to SSC's that the
risk-informed evaluation process has shown to be significant to public
health and safety. So our revision in this reg guide is actually to
state that all SSC's modeled in the PSA need to be considered, as well
as SSC's that are considered to be high-safety-significant by the
licensee's expert panel.
In addition to that, we had one area of concern that we
think the licensee should be considering is the low-safety-significant
SSC's, which we have discussed, that in some combinations it would have
an impact on the planned risk. And in trying to identify the
low-safety-significant SSC's that would have an impact, we think that
the licensee should be looking at support systems and systems with
interdependencies.
DR. APOSTOLAKIS: So what you're saying is that there are
situations where these are no longer low-safety-significant SSC's.
DR. WONG: Yes.
DR. APOSTOLAKIS: So why are you calling them
low-safety-significant?
DR. WONG: Okay.
DR. APOSTOLAKIS: Because at power they turned out to be
low-safety-significant.
DR. WONG: Okay. These are low-safety-significant SSC's
that when we look at the maintenance rule scoping matrix of a couple of
plants, zero identified low-safety-significant SSC's.
DR. APOSTOLAKIS: Using what criteria?
MR. CORREIA: Power.
DR. APOSTOLAKIS: Power.
DR. WONG: At power; yes.
MR. CORREIA: And looking at individual SSC's, one at a
time.
DR. WONG: One at a time.
MR. CORREIA: It's a risk-ranking process that the NEI
guidance document describes.
DR. APOSTOLAKIS: But it seems to me that we are
perpetuating the problem here by taking a terminology that is relative,
implies relative worth, and then giving it an absolute meaning that
low-safety-significant really as specified by an analysis of PRA for
power operations.
MR. CORREIA: That's correct.
DR. WONG: That's correct.
DR. APOSTOLAKIS: And I think that really creates a hell of
a problem.
DR. SEALE: A heck of a problem.
DR. BONACA: In addition to the synergistic effects that you
have when you take multiple components out of service.
DR. APOSTOLAKIS: What's that? Do you want to elaborate?
I really think the terminology in this new application is
very important language, and I think we went out of our way last time to
point out in our letter that safety significance is something that is --
MR. BARTON: Depending on plant configuration.
DR. APOSTOLAKIS: Plant configuration, mode of operation, so
on. So I suggest that you take back that terminology and maybe have
yourselves a paragraph there explaining that this is something that is
variable.
DR. BONACA: Excellent. That's an excellent recommendation.
DR. SEALE: Yes.
DR. WALLIS: This concerned me too about the expert panel.
It's not the SSC by itself which is safety-significant, it's in a given
context is or is not safety-significant. And the expert panel needs to
be given the context, and may not even be able to assess without given
an analysis of the situation which is put in this context.
DR. BONACA: I would like to also point out one thing from
experience. There are 450 days in a cycle; that's a lowball. And, you
know, one thing I learned is that you really can do a lot of online
maintenance by taking just one component out of service at a time. And
that's really the rule that we ultimately chose. And the reason is that
anytime you go with two or three, you have some complications. You just
increase the risk.
All I'm trying to say here is that the rule we are proposing
talks about three components or more. That's a lot of components in 450
days minimum that you take daily out of service. You're talking about
thousands. And why do you have to do it that way without proper
control? So I'm saying -- I'm trying to understand also the logic for
talking about more than three components and so on and so forth
associated with again a ranking that is based on taking one component
out of service at a time.
MR. CORREIA: We don't disagree. It's just as a matter of
convenience for our inspectors and the industry to use this terminology
so they understand at least initially what SSC we're talking about.
DR. APOSTOLAKIS: I believe it would be a good idea in this
guide to have a separate section -- your sections are relatively small,
I know, short -- up front explaining the terminology, the concept, that
this is relative, depends on the configuration of the plant, and then
maybe say low-safety-significant for power or low-safety-significant,
you know, for something else.
DR. POWERS: Well, the crucial thing is
low-safety-significant and high-safety-significant based on a ranking
that takes one component out at a time.
DR. APOSTOLAKIS: That's also important. Explain the
whole --
DR. SEALE: The only excuse I can think of that would
justify keeping the definition the way it is is that if you do that,
then you have a very, very good way to assess the quality of the job the
utility is getting from its expert panel, because if they don't pick up
those systems that are important as you take systems out one at a time,
then that's not the kind of expert panel review you want. But the point
is that's not what we're about here. You know, we're not about a metric
to rate the expert panel, we're trying to assess the safety. So let's
don't have that ambiguity in there.
DR. WONG: Okay. We understand that.
DR. APOSTOLAKIS: We are in violent agreement.
DR. WONG: Okay. Well, in the next slide, again it responds
to a question of what are the conditions that you want upon this scope
when you're looking at the low-safety-significant SSC's that are support
systems or interdependent. And we identified four conditions that would
put the SSC's to be in the scope for the assessment when you take
multiple SSC's out of service.
The first condition is that if the SSC support system for
high-safety-significant SSC's, and have provided here some examples
which we have looked again in the maintenance rule scoping matrices of a
couple of sites that we have inspected and found that these examples
were identified as not modeled in the PRA when they were taken out one
at a time. Okay?
The second condition was that the SSC would have
interdependencies with another low-safety-significant SSC. And the
qualifier here is that the other SSC may have been ranked by the PRA
importance measures as being low.
The third condition is that SSC failure could increase the
likelihood of initiating events and also SSCs that are in low frequency
cut sets that could increase the CDF or LERF significantly when multiple
SSCs are out of service.
So these are four conditions that we have tried to identify
as a way or as an approach to identify this.
DR. APOSTOLAKIS: So the reason why you need this slide --
DR. WONG: Yes.
DR. APOSTOLAKIS: -- is because LSS up there means produced
in a certain way for a certain rule, correct?
DR. WONG: Right. Right.
DR. APOSTOLAKIS: Otherwise, you would not need this line.
DR. WONG: That's right.
DR. APOSTOLAKIS: Okay. So in the new version --
MR. BARTON: This could be an example in the new version of
what you are talking about.
MR. CORREIA: This just amplifies your point.
DR. APOSTOLAKIS: Yes.
DR. WONG: Right.
DR. APOSTOLAKIS: You can use the same examples here, but to
argue why it is important to re-rank SSCs in a different --
DR. WONG: SSCs.
DR. APOSTOLAKIS: Okay. Fine.
DR. WONG: Yes. Thank you.
DR. APOSTOLAKIS: Fine.
DR. WONG: Okay. Then on the next slide we look at examples
of low safety significant SSCs that are not modeled in the PSA that we
think might be excluded from the scope of the assessments. Examples we
have provided are like emergency DC lighting, communication systems,
post-accident sampling system, hydrogen concentrated monitoring,
post-accident sampling system, water level indication, enunciators,
post-accident hydrogen system and gaseous waste processing systems.
These are just examples to be found to test this out.
DR. POWERS: I have to admit, when I looked forward in your
slides and I saw emergency DC lighting up there, I was struck. Is that
fairly important for responding to a fire accident? Isn't that
absolutely crucial if you have to evacuate the control room?
MR. CORREIA: Again, this doesn't eliminate it from the
scope of the rule. It is just I think, relatively speaking, for
accident mitigating systems, it is less important. But I agree with
you. And we struggled with this.
MR. BARTON: I think you will find these rules under a list
of low safety significant. They will be in the Maintenance Rule utility
under a low safety significant category. They will be in there, they
are not excluded from the rule.
DR. POWERS: And I have no doubt that they would put it in
there because they do not have the capability to include fire in their
PRAs
DR. BONACA: Now, let me ask a question now. You put some
examples for help. Okay. So now something happens out there in the
plant which is tied to an assumption based on an example, and this is an
event that is not desirable. Who is responsible for it? I mean have
you delegated -- have you taken responsibility away from the person who
does the actual online maintenance by providing examples that exclude?
I am just concerned about, you know, the degree to which you are putting
examples also provides some relief of the person who used the example to
make a determination. Do you see what I am trying to say?
MR. CORREIA: Yeah, I understand. It is kind of a
liability.
DR. BONACA: I am not suggesting they shouldn't have
examples, I am only saying that -- and I am always going back to the
issue that you are taking out a component of the service, you are
responsible for performing an evaluation. And so I like the examples,
but, also, --
DR. WONG: We have to be careful about them.
DR. BONACA: Yes. Do they provide --
DR. APOSTOLAKIS: I am a little confused by the second
bullet. So if all your telephones die and there is no way for people to
communicate, we don't care? I mean what --
MR. CORREIA: No. Behind this is the understanding that
there are multiple ways of implementing these functions.
MR. SIEBER: Radios.
DR. APOSTOLAKIS: Oh, that is why these are -- but it is
says systems. I would say all of these are communication systems.
MR. CORREIA: We had talked about radios, gatetronic
systems, telephones, there are several. I can't imagine a plant
intentionally taking all of them out.
DR. POWERS: I think we have instances on the record in
which plants have taken out the normal communication and found that the
radio systems were not functional. Then when they tried to rely on them
as a compensative method, it didn't work, and they had nothing else.
They resorted to having runners running around. I mean I think that is
an LAR that has occurred in the last ten years. Not to change your
point.
MR. CORREIA: I understand.
MR. BARTON: Turkey Point during Andrew is a good example.
DR. POWERS: No, I think a plant took its intercom system
out for maintenance and said, okay, we have got the radios, handed out
the radios, everybody had them. When they went to use them, they found
out they were all on like different frequencies or all the crystals had
been taken out of them or something, and they didn't work.
DR. SEALE: Preventive maintenance.
DR. POWERS: And they were in a position of no return, you
know, the system was out for maintenance and they couldn't get it back
together again.
DR. WONG: These examples of these systems, they are all in
the scope in the big Maintenance Rule scope. And what we are trying to
say is that if you are trying to look at multiple SSCs that are out of
service, would this have a significant impact? And what you are saying
is that in certain contexts or certain conditions, it may have. And it
is, you know, -- and like I said, one needs to be very careful, but
these are just, you know, what we think are examples they are issuing to
come to a manageable scope of trying to do the assessments. That is
what we are trying to show.
MR. CORREIA: Perhaps, I would imagine a licensee would,
through the normal work practices of planning and scheduling maintenance
activities, no matter what they were working on would have to consider
it somehow, maybe not as formally as an A-4 or as rigorous as an A-4
assessment, but I would give them some credit for that, I would hope.
Maybe that is something we could add to the Reg. Guide.
DR. POWERS: I think there is a danger in formulating this
Reg. Guide, that you focus a lot of attention on things that nobody in
their right mind would ever. And I come back to Mario's point, the
easiest way in the world to do is to take systems out one at a time.
You have got 450 days, you can do -- one at a time, you can do an awful
lot. And I think that if we focus a lot of attention in trying to
handle it just right, taking out multiple systems all the time, in the
most pristine fashion, and don't pay attention to making it very
convenient to dot the one at a time type of approach, that we will end
up with a Reg. Guide we are not happy with.
DR. WONG: Should we go on to the next?
DR. POWERS: Please continue.
DR. WONG: Okay. The other revision was in the section in
which we are trying to define criteria for risk configurations.
Essentially, we just included a paragraph to say that the criteria for
risk configuration should be based on an increase in core damage
probability or a large early release probability. And we referenced the
Reg. Guide 1.177, Section 2.4, where they provided a number of 5e minus
7 as a numerical number. And we had discussions with the industry and
they are somewhat in a protesting mode to say we should not be, you
know, using numbers. This is what we have added to a revision.
DR. POWERS: It is interesting because we were just
discussing, for another reason, exactly that section and exactly that
number, and debating its origins and whatnot. Do you happen to remember
what the origin of the 5 times 10 to the minus 7th number was?
DR. WONG: Okay. All I know is that the basis of the 5e
minus 7 is based on a five hour duration of some equipment that is taken
out of service that would increase from a baseline of 1e minus 4 -- 1e
minus 3, and I think the 1e minus 3 is in the NRC's strategic plan that
you will not allow an event of that probability.
DR. POWERS: I think it has -- actually, there is a more
horrific -- horrific is the wrong word -- a more ancient origin for that
number. But, nevertheless, it is a number that has a pedigree to it
that is very attractive.
DR. WONG: Okay. I have looked at also the PSA guidelines
of the number that they used. I have difficulty finding what is the
basis. They have come up with a 1e minus 6 number and so we are still
having discussions here with the NEI representatives. I think they may
talk more about it.
But these are essentially the two major revisions to the
Reg. Guide. It is still a draft, okay, so what I am saying is that we
would still try to refine it in the areas based on your comments and
based on the comments of this committee, and also the CRGR which we have
been told by the Commission to also present this Reg. Guide for review.
DR. APOSTOLAKIS: Your next slide is not technical so I have
three comments on the Regulatory Guide and maybe this is the time to
raise them.
DR. WONG: Okay.
DR. APOSTOLAKIS: The way I understand this process, there
are two ways of doing this. One is traditional, deterministic kind of
engineering analysis, and you say somewhere that this probably can be
done for a single item, single SSCs. If you go to two or more, you
probably have to go to PRA.
DR. WONG: Yes.
MR. BARTON: That is in there, right?
DR. APOSTOLAKIS: Yes. So you can do this traditional
analysis for single or maybe even double sometimes SSCs.
DR. WONG: Double. Yeah, two.
DR. APOSTOLAKIS: But that is about it, I mean you don't go
beyond that. Then there is a whole discussion on quality and
sophistication of safety assessments, which is really PSA, and you go
back to 1.174 and you talk about state of knowledge uncertainty, without
using the modern name. You talk about model uncertainty. You talk
about things that people have to do to account for those and so on.
And for the other side, though, for the guys who are
deterministic, you give no guidance, and you just say a risk significant
configuration is one that would significantly affect the performance of
safety functions. And somewhere else on page 5, you say -- you refer to
the informed judgment of a trained license operator that is sufficient
to evaluate the safety impact of the maintenance activity on the simple
SSC or SSC train.
MR. BARTON: Because they are trained to do that.
DR. APOSTOLAKIS: They are trained to take into account
parameter uncertainty and model uncertainty and do the sensitivity
studies that the PRA guy is supposed to do?
DR. WONG: No.
MR. BARTON: And you are not asking them to do that.
DR. APOSTOLAKIS: And why aren't you asking them to do that?
Because it is obvious what the answer is?
DR. WONG: Okay. In response to your question is that issue
came up when we presented this to the CRGR and they asked me the
question. I said, would you address inherent uncertainties of the PRA
estimates of configuration risks? And so there was an attempt, or I
made an attempt to go back to Reg. Guide 1.174 and looked at what was
presented, and how, you know, the uncertainties for parametric
uncertainty, model uncertainty and configuration uncertainty is being
treated.
DR. APOSTOLAKIS: I know. I know.
DR. WONG: Okay.
DR. APOSTOLAKIS: I suspect what we have here is a situation
that is similar to the guy who lost his keys and he was looking under a
lamp post, even though he was not sure he had lost them there, but there
was light there.
DR. WONG: Okay.
DR. APOSTOLAKIS: So just because people have been beating
on PRA and talking about model parameter uncertainty and 1.174 has a
whole section, then you take that and put it in here. In the
traditional approaches, we don't do that, therefore, there is nothing
there. So the guy who is not doing a PRA is in fact doing -- expending
less effort in doing this analysis.
Now, I admit that the PRA evaluations, if you have more than
two SSCs out, are probably more sophisticated. But it just strikes me
that, you know, if I choose to use a less sophisticated approach, I am
asked to do less.
MR. BARTON: That is because it has been looked at and you
have got a matrix which shows those systems and combinations of systems
components in a simple maintenance format that are safe and that you can
do without increasing risk. And I think when you look at that
deterministic approach, George, you are talking about the operator
making informed judgments. It is really simple maintenance, when he has
the matrix and he has the guidance there, he is able to make those kinds
of judgments.
DR. APOSTOLAKIS: I understand.
DR. BONACA: And oftentimes those tables are generated with
PRA by a third party, an external company, for example, and then they
sit there. They are used now from that point on, so you have that
evaluation, that probably is PRA based, but it is static, okay. It
doesn't -- you know. So it prescribes what kind of two systems you can
take out of service. Okay.
DR. POWERS: I think what they are saying is that the
sophistication in analysis has taken place in the one time assessment.
DR. BONACA: One time assessment.
DR. POWERS: And it is no less, it is just that now you have
got a little chart and the guy that does it doesn't have to redo that,
it is already built into the chart.
DR. BONACA: Right.
MR. CORREIA: With the idea that is all they are going to
work on, one or two, no more than that, of those pre-analyzed
configurations. Anything more than that, the sophistication of the
analysis has to be commensurate with the complexity.
DR. APOSTOLAKIS: Maybe I am too sensitive.
DR. POWERS: Right. We hadn't noticed it, George.
DR. APOSTOLAKIS: You are discouraging the use of PRA by
doing this all the time. The only thing that saves it is that you are
talking about relatively simple configurations.
DR. WONG: Yes.
MR. BARTON: And that is the way they have been doing
maintenance since the plant started up really.
DR. APOSTOLAKIS: Okay. So I can rely then on the informed
judgment of people in that situation. My second point --
MR. CORREIA: During our baseline inspections, one of the --
DR. APOSTOLAKIS: My second point, if you go to page 8 of
the guide, 15 for the members, the handwritten 15, there is a sentence
there that I am not sure I like. You see the long paragraph at the
bottom. It starts --
MR. BARTON: Yes. It starts with "Any PRA calculation."
DR. APOSTOLAKIS: Yeah. Okay. If you go down to the middle
somewhere, after it talks about state of knowledge uncertainty, it says,
"It is believed that setting the threshold for risk significance
demarcation of plant maintenance configuration sufficiently low enough
compensates for this impact." The uncertainty, in other words. Which
now tells me something new that I hadn't seen anywhere else.
It tells me that you are assuming that the PRA has not done
an uncertainty analysis and that all you're getting is a point estimate.
And I'm not sure that that assumption is a good assumption. There are
many PRA's, IPE's even, who have done an uncertainty analysis, so they
may be working their mean value. So are you penalizing then those
people by setting the threshold very low to accommodate people who don't
bother to do an uncertainty analysis, but then you are penalizing the
guys who are willing to do an uncertainty analysis?
Are you going to have two thresholds if I have done my
uncertainty analysis or not? It seems to me that's an important point.
We cannot go out of our way always to accommodate people who don't want
to do an uncertainty analysis and then penalize the other guys. So this
sentence is very suspicious to me. I don't know what you can do about
it. It really bothers me. We are catering to the guy who's doing a
sloppy job.
DR. WONG: Well, we can delete it, but --
DR. APOSTOLAKIS: You don't have to answer now.
DR. WONG: Okay.
DR. APOSTOLAKIS: You will get that comment again.
DR. WONG: Yes.
DR. APOSTOLAKIS: Oh, you want to answer. Okay.
DR. WONG: Well, what I was trying to attempt here to say,
okay, is what -- okay, from the point of practicality, I looked at say
the risk-monitoring software codes and looked at, you know, do people do
uncertainty analysis when they calculate, you know, the point estimates
for the configurations that they are going into.
DR. APOSTOLAKIS: If you are using a PRA that has done an
uncertainty analysis, all your rankings are done using mean values --
DR. WONG: Yes.
DR. APOSTOLAKIS: So the uncertainty is built in, except for
the model uncertainty.
DR. WONG: Right. So I looked at it and see practically can
people do it or not, okay? And I've not seen it built into the programs
yet.
So what I'm trying to say here is that if people want to do
the uncertainty analysis, good, you know. I favor that. But for those
who do not want to do it, I'm in a dilemma. Is there a requirement that
we ask them to do uncertainty analysis?
DR. APOSTOLAKIS: No. But what you can do is instead of
putting it here --
DR. WONG: Okay.
DR. APOSTOLAKIS: You put it as part of your advice to the
expert panel.
DR. WONG: Okay.
DR. APOSTOLAKIS: And you're telling them look, in case a
PRA has done uncertainty calculations, don't worry about parameter
uncertainty anymore. That's built into their mean values.
DR. WONG: Okay.
DR. APOSTOLAKIS: Worry about model uncertainty, play
sensitivity games and all that, a la 1174.
If, on the other hand, you are getting point estimates
alone, these are suspicious, and you should be much more careful when
you evaluate the rankings. See, this is the proper way of doing it, and
giving credit where credit is due. So I would take this paragraph,
rearrange it along the lines I just said, and make it part of the advice
to the expert panel. Because these are the final arbiters.
DR. WONG: Okay.
DR. APOSTOLAKIS: And that again -- see, I'm going out of my
way to save you work, too.
DR. WONG: Good. Thank you.
DR. APOSTOLAKIS: And then the third one is related to what
Professor Wallis in a different context said this morning.
MR. BARTON: Do you have a page reference, George?
DR. APOSTOLAKIS: It's the very last page. It doesn't have
a typed -- it's 31 for us; it's a mystery to them. It's NUMARC 93-01
R-2 Appendix B. It's the very last page of what I have.
MR. BARTON: Definitions? Yes.
DR. APOSTOLAKIS: Don't you have that?
MR. BARTON: Yes.
MR. CORREIA: The NEI guidance.
MR. BARTON: Yes, this is the last page of the NEI. It's
Appendix B of the NUMARC document.
DR. APOSTOLAKIS: Is the NEI guidance appended to the
regulatory guide? I mean, why is it here?
MR. CORREIA: Not this version.
DR. WONG: Not this version.
DR. POWERS: That's for your information.
DR. APOSTOLAKIS: Just for my information. It will not be
in an NRC document.
DR. WONG: No, I don't think so.
MR. BARTON: No, we're trying to endorse the NUMARC -- the
NEI document -- the reg guide.
DR. APOSTOLAKIS: Okay.
MR. BARTON: So they're going to be tied.
DR. APOSTOLAKIS: This page.
DR. WONG: Okay, there has been a lot of discussions about
the definition.
DR. APOSTOLAKIS: Yes, because it's completely wrong.
DR. WONG: Yes. I agree with you.
DR. WALLIS: Is that the part that I said this morning
DR. APOSTOLAKIS: Yes, intellectually you're undermining the
credibility of everything we're doing by taking the simplest definition
in reliability and managing to screw it up.
DR. WONG: Yes. Yes. I think I've explained --
DR. APOSTOLAKIS: It's awful.
DR. POWERS: We will be having discussions with the
representative of NEI today, and you can excoriate him.
DR. APOSTOLAKIS: Yes, but I can --
MR. BARTON: You can bring that up with Tony.
DR. WONG: Yes. We have told them so, and I think there are
efforts to try to come up with a definition --
DR. APOSTOLAKIS: Efforts?
DR. WONG: Yes. He will talk about --
DR. APOSTOLAKIS: Five seconds is an effort?
MR. CORREIA: As a matter of fact, this issue of
unavailability has become so important to industry that next week at
INPO is an all-week meeting --
DR. APOSTOLAKIS: To define?
MR. CORREIA: Among other things discuss the definition of
"unavailability" as it applies to different applications, because there
is a lot of confusion out there.
DR. APOSTOLAKIS: There are four definitions of
"unavailability" that have been published in the literature. What you
have here is not one of the four. People have studied those things for
years. I mean, they are there, and the one we are using in the business
is the average unavailability, okay? From the four definitions. And I
can send them to you if you want. It's something that's out there. I
mean --
DR. WONG: Yes.
DR. APOSTOLAKIS: From the old days. So I don't know that
there is confusion about these things. Maybe there is confusion in some
quarters.
DR. POWERS: Apparently there is confusion in some quarters.
MR. BARTON: Thank you, George.
Any other comments Committee Members have got of the staff
on the proposed reg guide?
DR. BONACA: Just, you know, a general observation on the
management portion, managing --
MR. BARTON: Do you have a page reference here?
DR. BONACA: Yes, when you talk about page 9, section 6.
There are a lot of good words about what should be done or not done, two
things that are striking me again. There is no word anywhere that
discourages removing multiple components simultaneously. I mean, I'm
not saying that there should be a prohibition. I'm only saying that it
would be possible that that's not a good practice. And that's a
judgment, but, you know, it comes from experience, and I've seen it for
many years. It's not a good practice.
And, second, especially where you have multiple components
out of service and you have risk monitored, that gives you some
competitive data. And you have references from tech spec examples of
what is acceptable and unacceptable based on past experience.
For example, how much risk do you have by removing a diesel
and so on and so forth. I understand we have no quantitative basis here
to, but there should be an encouragement to use some reference values as
acceptable or not acceptable. I understand there are utilities out
there that do in fact look at risk changes, but they have no specific
rule, it's self-imposed on what it is about, there is a limit. So if
you increase your core damage probability by a factor of 20, well, they
say well, it's a factor of 20, and they just go into it. I'm trying to
understand --
DR. APOSTOLAKIS: Do you mean the bound they have of 5 10 to
the minus 7 is not sufficient?
That imposes a bound.
DR. BONACA: It does?
DR. APOSTOLAKIS: Yes.
MR. BARTON: And that was just added since the last time we
saw this manual. You'll find that on page 8, I think, page 7 and 8.
DR. BONACA: I'll take the comment back in that case.
DR. APOSTOLAKIS: It's 10 to the minus 3 for five hours.
It's 2 10 to the minus 3 for 2-1/2 hours. It's 4 for 1 hour 25.
DR. BONACA: I'll take my comment back.
DR. APOSTOLAKIS: Dividing the time, increasing the
frequency. Where do you draw the line and say the frequency now is
high? If you leave for a 10 to the minus 2 frequency of core damage for
25 minutes?
MR. CORREIA: I'll swallow very hard and say perhaps.
DR. POWERS: Please say no.
MR. CORREIA: Definitely no.
DR. APOSTOLAKIS: Think about it. It's really the
frequency. It's not the probability of the event itself. So let's
not -- I think we're used to working with frequencies as if, you know,
if the frequency is one, boy, the thing is going to happen tomorrow.
This is the frequency. So to calculate the probability, you have to
take into account the fact it's only 25 minutes.
MR. CORREIA: Yes.
DR. APOSTOLAKIS: So I would have a difficult time saying
no. But then if you make it 3 or 4 minutes, I don't know whether I --
DR. SHACK: I think the answer we always get is that there
are other rules that get you -- you're never going to get there for
other reasons.
DR. APOSTOLAKIS: Well, if it's for 20 minutes, you might.
DR. POWERS: You know, when we discussed this exact issue in
relation to 1.174, we were assured by the esteemed Mr. --
DR. SHACK: Holahan.
DR. POWERS: Holahan that he was quite confident some other
rule would get you before you got above 10 to the minus 2.
DR. APOSTOLAKIS: It depends on how short the time is, but
Mr. Holahan is esteemed.
DR. POWERS: I had him down to a minute and a half, I think.
MR. BARTON: I think the rule is when you get that close the
plant manager has to sign, and he's going to go to jail if --
[Laughter.]
DR. POWERS: That's the one.
DR. BONACA: So, just going back to complete, off the
record, and I'll take back the statement, because clearly I missed that
change. And second, however, I would like to see somewhere some
reference to encouraging or discouraging from the number of components
being taken out of service.
DR. APOSTOLAKIS: Is it just a number that bothers you,
Mario, or --
DR. BONACA: No, I'm only saying that --
DR. APOSTOLAKIS: Let me clarify it in my own mind. The
number itself cannot really be the only criterion. You are really
talking about a number of components that are performing some -- are
affecting the same safety function, perhaps.
DR. BONACA: Well, I'm talking about the fact that -- I
think it's a philosophy, okay, that the utility has of being careful how
many components you pull out, versus -- the rule doesn't say here, the
reg guide doesn't say -- says if you take out one component, okay, you
perform a basic evaluation. If you get two, you perform an even more
thorough evaluation. For three or more --
DR. APOSTOLAKIS: Go to PRA.
DR. BONACA: To PRA. Three or more, what does it mean? I
mean, as you increase the number of components, I feel more conflict
about that. And there should be some message that says there should be
some understanding in this managing risk also that at some point -- I
mean, there should be some discouragement of taking too many systems out
of service.
DR. APOSTOLAKIS: I don't understand why.
MR. BARTON: Isn't that in here someplace where, as you keep
increasing risk and taking systems out, you need to get increasing
levels of approval to do that.
MR. CORREIA: That is the idea behind this.
MR. BARTON: So you just can't arbitrarily go do that at a
maintenance level.
MR. CORREIA: No, but if there is an emergent situation.
DR. BONACA: Because you are taking configurations further
and further away from the basic configuration of the plant.
MR. BARTON: Right.
DR. APOSTOLAKIS: No, but they are supposed to do an
evaluation. If they plan to take six components out, --
DR. BONACA: I understand that.
DR. APOSTOLAKIS: -- then they will do an evaluation.
DR. POWERS: But, George, I think you operating on the basis
of saying this model I have got is as confidently applied with five
systems out as it was with zero systems out. And I think Mario is
saying he is concerned about the unfamiliarity, the lack of experience
with it. It starts going up pretty dramatically as he crosses the 3
line and starts moving toward 4 and 5 and 6.
DR. BONACA: It is a just a general philosophy.
DR. POWERS: He is saying -- whereas, he is not saying, no,
don't do that, --
DR. BONACA: Don't do that. I am only saying that the
farther you depart from your normal configuration for the plant, design
configuration, okay, and you perform evaluations with what typically it
is a limited PRA, because it is not a full blown PRA, typically, you
have a like a CAFTA model that has only 100,000 components in it rather
than being --
DR. POWERS: Only.
DR. BONACA: Well, I mean, but still, I mean you are really
looking at a more and more diverse configuration from the one that is
licensed, that is defined, that is applied and studied. So, I am not
saying that you should make a prohibition, but I think there should be
an encouragement to limit at some point the number of components or be
self-policing yourself as you do that.
DR. APOSTOLAKIS: How about if you put a statement to the
effect that they will receive increased management attention as a part
of the standard. That way you are discouraging it implicitly, but you
are not really discouraging it.
MR. BARTON: Well, doesn't management --
DR. APOSTOLAKIS: In other words, we are going to pay more
attention if you do that.
MR. BARTON: Doesn't Section 6 do that? Section 6 does it.
Maybe you don't like the way they have --
DR. APOSTOLAKIS: I didn't raise the issue.
MR. BARTON: What?
DR. APOSTOLAKIS: I did not raise the issue.
DR. BONACA: No, I did.
MR. BARTON: Take a look at Section 6. If that doesn't do
it for you, give me some words to put in the letter.
DR. BONACA: Okay.
MR. BARTON: If there are no other questions of the staff at
this time, we will hear from NEI.
MR. CORREIA: I just have one just quickly.
DR. APOSTOLAKIS: I have some.
MR. BARTON: Oh, you have something else.
MR. CORREIA: For your information, again, you are aware
that NEI has brought forward a revision to Section 11 of 93-01 for our
consideration. We have interacted with them in two public meetings,
gave them comments back, and they are committed to providing feedback to
us by the end of the month.
Schedule-wise, the Commission has laid out a very nice
schedule for us, including meeting with the committee again. We are
doing everything we can to accommodate them, given schedules and our
interaction with NEI.
One item that the committee recommended, I think at the
April meeting, was a workshop. There is a planned workshop scheduled
for September 13th and 14th, that NEI is sponsoring, that we are
participating in. And we are going to encourage as many NRC inspectors
and reviewers to attend, again, to hear it all at the same time. One of
the items we will be talking about, obviously, is the change to the rule
and the Reg. Guide.
DR. POWERS: Where is that located?
MR. CORREIA: It is in Miami, 13th and 14th. We will get
you the details once they become available, and it is a public workshop.
MR. BARTON: In order to boondoggle, you have to have some
pain, George. Miami in August is pain.
DR. APOSTOLAKIS: I would have said Boston in August.
DR. WONG: September.
MR. BARTON: September is worse than August in South
Florida, believe me, I lived there.
Is that it?
DR. WONG: Thank you.
MR. CORREIA: Thank you again.
MR. PIETRANGELO: Good afternoon. I believe you were
provided with the July 1st draft of Section 11 of NEI 93-01.
DR. APOSTOLAKIS: This one.
DR. POWERS: That is what you are reading from.
MR. PIETRANGELO: Right. That draft was the subject of a
public meeting last week with the staff. It is currently under revision
to incorporate some of the comments we received from the staff, as well
as a task force we have in place to help us with this effort.
Rich mentioned the schedule. Right now we are trying to get
a draft back to the staff by the end of next week, and I think we will
be able to meet that for a broader agency review, as well as a 30 day
industry-wide review on the next draft.
So I didn't prepare any slides because I think they dovetail
pretty well with what he staff presented to you. I will go through a
couple of topics, and if you have any questions on the draft, I would be
happy to try to answer them.
DR. POWERS: Apparently there is one about a definition.
MR. PIETRANGELO: Yeah, I am not sure I am going to be as
happy to answer that one as some of the other ones. Well, let me just
go through the staff's thing and then tell you how we are dealing with
it in here.
But I think for the most part -- let me ask a question
first. Has the committee been briefed on the new reactor oversight
process, in particular, the significance determination process for
inspection findings? Good. So you are all well aware of that.
DR. UHRIG: Right.
MR. PIETRANGELO: One of the questions the staff gets quite
often with any of the newer activities, either PRA-related,
reform-related, is -- how does it fit into that new scheme for
regulatory oversight? And, clearly, here is one revision to the
maintenance rules that is going to have to be well integrated with that.
As you know, the maintenance rule is also going to be on the first
regulations looked at in terms of risk-informing Part 50, and part of
the change that the Commission made before this rule was finalized was
to try to risk-inform the scope that applies to the A-4 provision.
And, remember, I came back and the staff did, the day after
the Commission briefing, and we had a discussion about that. And I
think the committee was on the other side of that issue, quite frankly.
And today I wanted to address a little bit about scope and how this new
oversight process interacts with this process, and how we have to make
sure that they are consistent and integrated, and, really, how it
matters in determining the scope of what you look at in the A-4
assessment.
There is really two, I think, competing interests that are
going to ultimately determine what the scope of this assessment is. I
mean the staff went through in their slides, you know, what is in the
Level I -- what is modeled in the Level I PRA? What was determined as
high safety significant by the expert panel before? As well as some of
these things that potentially, in combination, could be significant.
And we don't disagree with that.
The other factor, though, is that as part of that new
significance determination process, when you are crediting equipment to
say it will take care of that function that is needed in that event, for
the licensee to be able to take credit for that particular SSC, it has
to be within the scope of the maintenance rule, in particular, the A-4
assessment.
So, and some of you are former licensees. You know the
sensitivity out there to the inspection and enforcement process, and a
licensee wants to have a lot of margin when it comes to inspection and
assessment and enforcement. And I think that new significance
determination process, first of all, we think it is quite amenable to
the assessment that one has to do for removing equipment from service.
And it is also a very good tool to blend PSA insights, as well as
deterministic insights, and really, truly be risk-informed.
One of the concerns we have about sticking a number in the
Reg. Guide like 5e to the minus 7th is that you are really using the
weakest part of the PSA as a deciding line, as a bright line. And,
George, your subcommittee went through so many deliberations about how
it is not a bright line, how it is different for different plants and
how that is the weakest part of the PRA, and here is why.
So we are very hesitant to try to stick a number in the
guide and say that ought to be your action level across the industry.
Rather, we think this significance determination process, it looks at
all the events of interest, the frequency of those events, okay, the
level or defense-in-depth of equipment for dealing with those events, as
well as the timeframe for how long a particular piece of equipment is
going to be out of service. That is really all the elements that make
up part of this new assessment that is required under the maintenance
rule.
Now, in the same token -- so you want to have a lot of
equipment to draw on, to use in your little matrix. Every licensee is
going to do this without being directed to or told. I mean that is just
the nature of the beast in the industry. If we know that our
enforcement is going to be based on what is in this chart, we are going
to make sure we comply with that chart. It is just a given.
On the other side of the coin is that you don't want to put
a lot of very low safety significant items in the scope of this A-4
assessment because then you are burdening the process by having to do
this assessment on stuff that is not going to matter, and I think the
staff gave some good examples of some of what those might be.
So, ultimately, when you put what was modeled in the PSA and
what the expert panel determined before, what you want to take credit
for in that significance determination process -- remember, that has to
be under the scope of A-4, as well as your consideration of not
overburdening yourself, you add those all up. We think people are going
to get -- right size the scope of this assessment through that process.
I think it will address the concerns that were raised here
before about potentially low combinations in a way that -- in the
discussions we have had with the staff on this, the real need is to have
a common understanding of when you are going too far with removing
equipment from service, and I think that is what Dr. Bonaca was speaking
to also. You need to have a common understanding of what is too much.
All right.
We believe that that significance determination process that
has been developed helps provide that when you have gone too far, and it
does so in way that blends the deterministic and probabilistic insights.
The other thing I want to mention about that is that next
time you get Mr. Holahan here, he has put together a chart, that he has
pinned up in his office, that takes all the risk metrics from various
documents that have been developed, both by industry, some of the Reg.
Guides, what the new significance determination process says. There is
about a half dozen, six or seven of these things. Some deal with
permanent changes, some deal with temporary conditions. But they all
tend to, you know, the significance line, you look at all those
different documents that have been developed, they all seem to converge
on the same point as what is significant and what is not significant.
What is going to matter in the regulatory process is that
significance determination process. So if a licensee, and many of them
already do, have established action levels, and we talk about it in our
guideline, for if you have a relative increase of 10 percent or an
absolute value that is higher than a speed limit type approach, or a
cumulative type approach of how much risk you are accruing over time,
those are all good ways to manage risk. And depending on what your
plant type is, you know, you need to set a number that you are
comfortable with.
But, ultimately, that significance determination process is
going to be used to calibrate that number. We have one calibration and
that is that SDP. That is the one that is going to be used. And we
talked about this at the last meeting with the staff, you can fold up
all those other columns and just look at the one, and then make sure any
other metric you use ought to be consistent with that. That is how you
ask -- answer the Commission's question about how you integrate what you
are going to do with these other activities with the new reactor
oversight process.
And so we think about it in terms of action levels, like
when would I establish a compensatory action or a contingency plan when
I've removed this equipment from service.
And if you look at the green and white bands on that chart,
the green band is, you know, you still have full margin, and the white
band is really a minimal reduction in safety margin. And I would think
most licensees would want to stay in the white or the green.
The yellow is kind of a, you know, you've had a clear
reduction in margin. You might say, I might develop a compensatory
action or a contingency plan such that had I found I went to yellow when
I removed that equipment from service, I've got to find something else
to credit to get me back in the white or the green. And it's very clear
to both the regulator and the licensee what those lines of demarcation
are.
And that's what really that whole oversight process is about
is trying to be very objective and clear about what the expectations are
and what the levels are. And we want to leverage that, what's been done
in that area, and use that to help not only the scope determination in
A4, but also to determine levels at which you manage the risk to. And
you're going to see that a lot more in the next version of this
document.
We started kind of -- we didn't have enough time to really
fully describe it in this version, but I think the next version -- and
we'll make sure you get a copy -- this is the one that's going to go out
for industry comment as well as agencywide review -- you're going to see
almost a verbatim description of what's in that oversight significance
determination process.
Some of the other areas I wanted to talk about. Somebody
had a question about the quality of the PSA that's used and all that
kind of stuff. And there's a reference in our -- this draft that you
have to the industry's peer review guidelines, okay? We don't --
remember I used to use a slide for many years don't let -- PSA is not an
end in itself, it's a tool, it's a means to an end. You know, we don't
want this maintenance rule exercise to be, you know, let's go attack the
tool. All right? But you want the tool to be right for the job.
And what we want to try to do, and you'll see in an appendix
to this draft, is try to lift out what we're already using in the
industry as peer review to determine the quality of your PRA and where
it needs to be upgraded and things. We're going to put some of that
guidance in here, either reference it outright or put some of those
guidelines in here. So again, there's not guessing about was my PSA
good enough for this application. You'll know it up front when you
apply those guidelines.
DR. APOSTOLAKIS: The certification process?
MR. PIETRANGELO: Yes. Yes, we kind of changed the name to
peer review process from certification. So again we're trying to
leverage what happened in another activity and use it here. And what's
interesting about this is that -- and, George, you probably know this
better than any -- we spent a lot of time with infrastructure, okay?
All those reg guides that the staff developed, the 174 through 179. We
had the applications guide. Then we developed the SERP process. And
now we're starting to be able to use some of these things, this
infrastructure, and apply it to regulations. And that's why we think
this whole risk-informing Part 50 will be -- should be better.
We're in a lot better shape to do that than we were three or
four years ago, because we've got the tools and the structure and the
framework and the guidance, and this oversight process is kind of that
ultimate framework to fit all the stuff in. And it's a top-down
approach. So we should be able to stay consistent between, you know,
the maintenance rule and other things. And, again, we're going to try
to leverage all of that structure that's been done, all the work that's
been done, and make sure we're not, you know, reinventing the wheel
through this exercise.
DR. POWERS: Let me just interrupt --
MR. PIETRANGELO: Sure.
DR. POWERS: And say -- make sure I understand what I've got
here. This is bureaucratic stuff. I've got a draft of a document here
from you.
MR. PIETRANGELO: Um-hum.
DR. POWERS: And then you're going to send that out for --
MR. PIETRANGELO: Yes, this is already dated --
MR. BARTON: Not this one. This is already -- this is
outdated.
MR. BOEHNERT: Out of date.
MR. BARTON: Right.
MR. PIETRANGELO: Right.
DR. POWERS: And when do we get one that we should be
looking at really closely?
MR. PIETRANGELO: Well, probably in the fall. We'd be more
than happy to take your comments on the draft that's about to go out.
DR. POWERS: I understand. But --
MR. PIETRANGELO: But we're going to come back to you, and
hopefully -- we have to come back to you, and it'll be at a point where
the staff's comfortable enough to recommend endorsement of our guideline
in the reg guide, and then you'll, you know --
DR. POWERS: And that will be sometime in the fall.
MR. PIETRANGELO: Yes. I forget the exact date we talked to
Rich about, but it's in the fall.
DR. POWERS: It's not tomorrow -- it's not September.
MR. PIETRANGELO: Well, it's not that far -- yes, it's
September. Yes, it's not this Friday.
DR. POWERS: Okay.
MR. PIETRANGELO: That's about all I had. I mean, this is
in progress.
DR. POWERS: You can't get away from the definition.
MR. PIETRANGELO: Oh, yes. Yes.
Let me -- I need to set this up a little bit.
DR. SEALE: It's not Appendix B.
MR. PIETRANGELO: No. Let me set this up and put it in
context, and then I'll entertain your questions.
DR. APOSTOLAKIS: In context?
MR. PIETRANGELO: This definition --
DR. APOSTOLAKIS: I don't want to hear it.
MR. PIETRANGELO: You don't want to hear it? All right.
Then I'm off the hook.
DR. APOSTOLAKIS: I don't want to fight with you, Tony.
MR. PIETRANGELO: No, we're not going to fight. I was going
to make sure we don't fight.
MR. BARTON: In other words, we'll just ignore what you've
got here and look for the next version.
DR. APOSTOLAKIS: I'm going to send to Jit four definitions,
and I'll tell him that number 4 is the one that has been used by the
industry for years. If you want to get a copy of that, we'll be happy
to send it.
MR. BARTON: But then the week they spend with INPO they'll
probably come up with a different one.
MR. PIETRANGELO: The problem -- let me just --
DR. APOSTOLAKIS: It's no different.
DR. POWERS: Let him talk.
DR. WALLIS: But, George, besides saying it's been used by
industry for years, you've got to say if it's right.
DR. APOSTOLAKIS: It's right. Yes, it's correct.
MR. PIETRANGELO: The issue with unavailability is that
there are several definitions out there. There's been one that's been
in NUMARC 93-01, the maintenance rule guidance. There's another one
that's developed for the performance indicators in the new oversight
process. There's the WANO indicators that are different from that that
uses another definition of unavailability. And I'm forgetting -- SSPI
had a different one. And we've been hearing from our members that hey,
you know, we really need to get down to one definition that serves all
the end users, because this is really a pain to have to really collect
essentially the same data four different ways in different rules. This
is just inefficient.
And now that it's also part of the oversight process, and
we've raised this issue to the management in the Agency, you need to
have one definition too. Besides the maintenance rule, you've got the
oversight process and such. I don't think it's going to be as hard
maybe as -- this definition -- you almost have to put it in categories.
There are certain issues associated with each definition of
"unavailability." What conditions are you looking at? Are you looking
at design basis conditions? Are you looking at more realistic
conditions like those in the PSA success criteria?
How do you treat fault time? You know, what's your treatment of
operator actions or compensatory actions?
And these different definitions treated these different
ways. We actually had a matrix that had here's all these issues
associated with the definition, and across the top was the different
documents that had definitions, and, you know, you'd fill in the box on
how that particular document treated that issue. And it's all over the
place.
DR. APOSTOLAKIS: Now, you gave me an idea now. In the
maintenance rule, when I keep track of the unavailability of a standby
component, then I really look at it at periodic intervals. I mean, I am
not monitoring all the time, because it's standby. So once a month I
try --
MR. BARTON: Whatever the frequency is; yes.
DR. APOSTOLAKIS: It's typically once a month, isn't it?
Anyway -- surveillance. So once a month I go there, the first Monday of
the month, and try to start it, and it doesn't start every now and then.
I'm not sure -- and then I take the number of tries and divide, you
know, the number of failures and get an unavailability.
MR. PIETRANGELO: That's reliability.
DR. APOSTOLAKIS: Unavailability -- well, you see, that's
the thing. That's not reliability. That's unavailability.
MR. PIETRANGELO: You're in the PRA world.
DR. APOSTOLAKIS: Well, that's where these concepts came
from.
MR. SIEBER: Unavailable half the time.
DR. APOSTOLAKIS: Reliable means a period of time,
successful operation, a period of time. So --
MR. PIETRANGELO: I know how it's treated in PSA, and I'm
not disagreeing with --
DR. APOSTOLAKIS: Yes, but even in PSA, that's not what we
calculate. We calculate the average unavailability, which is the
average time between the intervals it was down divided by the interval.
MR. PIETRANGELO: That's the fault time exposure.
DR. APOSTOLAKIS: Well, there we have a serious problem.
MR. PIETRANGELO: Yes.
DR. APOSTOLAKIS: We really have a serious problem.
MR. PIETRANGELO: We understand that. That's why there's
this kind of --
DR. APOSTOLAKIS: And I suggest that you follow the
traditional definition --
[Laughter.]
From reliability period. You can't use something that was
developed just for the nuclear people at nuclear plants.
MR. PIETRANGELO: Well, here's one thing that we have to
keep in mind, and this is the other feedback we've gotten from our
members. Somebody's got to go out there and collect data, and it's got
to be simple rules.
DR. APOSTOLAKIS: Simple. Very simple.
MR. PIETRANGELO: It can't be all this, you know, if it was
this and if that caveat was true and if it was in this condition, then
it was either, you know, available or -- it can't be complex, okay?
DR. APOSTOLAKIS: But also remember --
MR. PIETRANGELO: Go ahead.
DR. APOSTOLAKIS: We are as an agency supposed to use
standards that societies have developed. If the ASME has a standard for
something and it fits our needs, we're supposed to use it. That's what
the Federal rules say. Now if I extrapolate, I think it behooves the
industry to use terminology that has been used by communities like
operations, research reliability people --
DR. POWERS: I think it said reputable communities.
[Laughter.]
MR. PIETRANGELO: I am not ready to say it behooves us or
not, because it depends on how much it costs sometimes too, George.
DR. APOSTOLAKIS: Yes, but I don't think that, for example,
fault exposure time -- I don't think that that's universally accepted by
the industry. Maybe some within the industry use that. We don't
even -- I mean, other terms that are more widely used are not used.
MR. PIETRANGELO: Right. The real issue here, at least let
me try this a different way, the real issue here is I think surveillance
testing, I don't think there's too much disagreement when you've tagged
out the system, okay, for either a PM or a corrective maintenance, that
it's unavailable. And a lot of people have electronic tagging systems.
It's very easy to compute the unavailability time from the time you slap
the tag on to the time you take the tag off. All right? Very simple,
very easy.
It's when surveillance testing, if I'm testing a diesel, am
I unavailable when, you know, within -- I'm already running. Can I
realign the thing with an operator action within the time frame that the
thing is going to be needed? That's where it starts to get tricky is
when you're surveilling -- it's really not unavailable. You're testing
the reliability of the machine.
DR. APOSTOLAKIS: But what you're saying is that the
function is not unavailable, but the component is. That's how I
would --
MR. PIETRANGELO: Yes.
DR. APOSTOLAKIS: What you're saying is the function really
is not unavailable, even though the component is --
MR. PIETRANGELO: Yes.
DR. APOSTOLAKIS: Because I can do this. See?
Mathematicians are not stupid, you know.
DR. POWERS: I think maybe we've gone astray from the focus
of our discussion here.
MR. PIETRANGELO: Eventually there should probably be a
single ACRS agenda item on unavailability.
DR. APOSTOLAKIS: I'd love to see your new definitions and
comment free of charge.
MR. PIETRANGELO: Could you send me the --
DR. APOSTOLAKIS: I'll send you that -- can I communicate
with him without going to jail?
MR. SINGH: No, send it to me.
DR. APOSTOLAKIS: See, Tony, they know.
[Laughter.]
DR. APOSTOLAKIS: This was very good, by the way.
MR. BARTON: Graham, you have a question?
DR. WALLIS: No, I was just --
MR. BARTON: Okay. I thought you were formulating a
question in your mind.
DR. WALLIS: No, I was just hypothesizing we might be
through.
MR. BARTON: Okay. I think we might also.
DR. APOSTOLAKIS: It's always exciting to talk to Tony
Pietrangelo.
MR. PIETRANGELO: I told you we weren't going to fight.
MR. BARTON: Thank you, Tony.
MR. PIETRANGELO: Thank you.
MR. BARTON: I'll turn it back to you, Mr. Chairman.
DR. POWERS: And I will recess the session until four
o'clock.
[Recess.]
DR. POWERS: I think we are ready to come back into session.
And we come to one of our perennial favorites, the general topic of
pressurized thermal shock. Maybe this is one of the vampires of reactor
safety, it keeps rising up again. And we have had various promises that
a stake will be driven through its heart one of these days.
DR. KRESS: Vampires, is that a bloodsucker?
DR. POWERS: I have no such perjoratives against a benighted
minority in this country.
I think, Dr. Shack, you were the cognizant member on this
area, so I will ask you to introduce this topic and tell us what we
ought to think about this.
DR. SHACK: Okay. Mike Mayfield will be making the
presentation along with Farouk and Mark. This is an update of a plan to
reevaluate the pressurized thermal shock screening criteria, to
incorporate a great deal of the understanding that has been developed
over the years since the initial pressurized thermal shock criterion was
set. And this is an information only one.
We have had much of this presented through a Materials and
Metallurgy Subcommittee meeting, and, again, it is a topic that can be a
killer for plants, so we thought it was worthwhile to bring it to the
committee, just to let everybody know where they were going with this
and to offer what input we might have on their plans to move forward
with the revised criteria.
DR. POWERS: I mean PTS has this really interesting
integration between materials phenomena and thermal-hydraulics heat
transfer and the like, and probabilistics as well. So I mean you have
got the right panel of people up here. Are we getting these
technologies all up to a uniform level of sophistication or do we still
have greater sophistication in the materials than the thermal-hydraulics
or vice versa?
MR. MAYFIELD: I am not sure I would say greater
sophistication. To some -- well, the materials analysis part is I think
a much easier problem that the thermal-hydraulics analysis. When we get
off into some of the questions about embrittlement and what really --
what material do we have, those get to be thornier questions. But in
terms of the analysis, I think our job is easier than Farouk's job. So
what we are trying to do is to bring in consistent levels of technology
and try, to the extent that it is feasible, bring the state of the art
to the table at the same time. So, hopefully, that is some of what you
will see this afternoon.
I am Mike Mayfield from the Division of Engineering
Technology. I am joined by Farouk Eltawila from the Division of Systems
Analysis and Regulatory Effectiveness in Research and Mark Cunningham
from the Division of Risk Analysis and Application. And we are here to
talk about our PTS reevaluation project.
We will start by talking about a little bit of background
behind PTS, how we got to where we are, what the issues are, what our
goal for this overall project really is, explain to you a little bit
about why we think there is a success path.
Dr. Powers, you talked about PTS being one of these issues
that you kept hearing promises we would drive a stake through its heart,
we think we have got the hammer in our hand and the stake placed over
its heart, and it remains to be seen whether we get the stake driven.
But we do believe there is a success path.
We will talk a little bit about our approach to this
reevaluation. In fact, we will talk more than a little bit. And then
we will talk about the milestones of the schedule.
I should emphasize for you we do not today have results to
talk about. This was an information brief to tell you about our plan
and the approach we are using to this, to solicit any feedback from the
committee, if you have got observations to give us at this time about
the plan, and our notion is we will periodically bring the subcommittee
or full committee, if it is requested, as we go through this program.
DR. SHACK: Mike, just one large question. How does this --
you have an action plan and the industry apparently has an action plan.
MR. MAYFIELD: I will talk about that, but this is a
cooperative program with the industry. We have -- there are action
plans on both sides and what we are doing at this stage is meeting
fairly regularly. We have met monthly so far to share information,
share ideas and try and reach some common understanding about the
technical inputs. At the end of the day, the responsibility for the
analysis rests with the staff. The industry guys may or may not choose
to go on and do a completely parallel activity. But what we were
wanting to do is reach a common understanding on the input variables
upfront -- we may not agree, but at least to understand the technical
basis that each side wants to bring to the program. So there is very
much a parallel activity and right now they are very much integrated.
I will talk a little bit about some of the background for
this activity. In 1985 the NRC promulgated the PTS rule, it is 10 CFR
50.61. It established embrittlement screening criteria applied to all
pressurized water reactors. The guts of the rule say that if the
pressure vessel -- if the level of embrittlement in the pressure vessel
is projected to exceed these generic screening criteria, the first thing
a plant is supposed to do is implement a flux reduction program to try
and stay below the screening criteria.
If they are still projected to exceed the screening criteria
by the end of the operating period, whether it is an initial 40 year
period, or a license renewal period, they would have to do an analysis
to demonstrate the continued safety of the pressure value and that
analysis would be submitted to the staff three years in advance of
exceeding the screening criteria.
During the early to mid-1980s, we conducted what we are
characterizing as a full scale analysis of three plants, the Oconee
plant, Calvert Cliffs and H.B. Robinson, to look at pressurized thermal
shock threats to those three plants. Not that they were particularly
perceived as a threat, it is just those three plants agreed to
participate in the activity and to make their information about their
plants, and a fair bit of work on their part, available to the staff to
evaluate this.
These are known as the Integrated Pressurized Thermal Shock
or the IPTS studies. The results from those studies were used as the
technical basis for the Regulatory Guide that lays out the format and
content for analyses a plant would perform if they are projected to
exceed the PTS screening criteria.
Coming out of those studies, what we discovered is that
there are some characteristic types of transients that lead to
pressurized thermal shock events. Generally, you see small break LOCAs
as contributors, steam line breaks, steam generator overfeed and reactor
trip with stuck open secondary. So you see some consistent types of
events that lead to these pressurized thermal shock events.
It was found that -- this is going to get distracting. It
was found that the dominant PTS transients had repressurization during
the latter portion of the transient. It is important to remember that
-- the important thing about pressurized thermal shock is it is the
initial thermal shock loading that gets you a high thermal stress across
-- through the vessel wall, and a high positive stress, tensile stress,
at the inner surface. That gets crack initiation in the most highly
embrittled material, with the assumption, of course, that there is a
crack in that material.
Thermal shock alone generally will not cause a crack to
drive through the pressure vessel wall. You need some pressure stress
to cause the crack to go ahead and penetrate the wall. This late
repressurization phase of these transients provides the driving force
you need to cause the cracks to go ahead and penetrate the wall and then
run the length of the pressure vessel. So that was a common feature we
saw in these transients that caused the failures.
Sensitivity analyses in the IPTS studies gave us some
insights to some of the more critical variables. First, we find that
the crack-related variables, the orientation, the location of the cracks
and how they are distributed through the thickness of the vessel, -- in
our case, they are all located on the inner surface of the vessel --
that had a significant effect. In fact, it had the most significant
effect of any of the variables in the analysis.
The level of conservatism in these flaw-related variables
was significant. The approach that we used at that stage was a flaw
size distribution that came out of the Marshall study in the U.K. We
put all of the laws on the inner surface, we made them all
surface-breaking and oriented in the worst possible direction. So that
turns out to have a huge impact and it is one of the areas where we have
made a lot of progress and that lead us to believe there is a success
path.
There were other factors that were found to be important.
DR. POWERS: I mean this whole business of the flaw
distribution and the conservatism and the Marshall distribution -- the
Marshall distribution is kind of expert elicitation kind of
distribution.
MR. MAYFIELD: That is a charitable characterization.
DR. POWERS: Okay. I mean the situation is that in any
vessel anywhere, you really don't know what he flaw distribution is.
MR. MAYFIELD: That is correct.
DR. POWERS: And so it is always kind of an expert
elicitation of some sort.
MR. MAYFIELD: Yes.
DR. POWERS: And are we going to, at the end of this thing,
effort that you are talking about, going to be able to say, this is the
flaw distribution that we assume to be present and the uncertainty
bounds on this flaw distribution at some confidence level are this?
MR. MAYFIELD: Yes. That is our goal.
DR. POWERS: And the reason we think this is because we have
looked at enough experimental data to substantiate that?
MR. MAYFIELD: Yes. And we will talk a little bit more
about that, and if you want to explore it some more, we can as we go
through the presentation.
DR. POWERS: I mean I think that is --
MR. MAYFIELD: But that is the guts of why we think there is
a success path. We have made marginal improvements in a number of the
areas, but the thing that made us really take this on was work that we
have done in ultrasonic inspection of pressure vessels and segments of
pressure vessels that we have acquired. That is something that Marshall
really didn't have. We have also done destructive analysis of the welds
and looked at very limited amounts of plate material.
DR. POWERS: So we are not going to have to come in here and
say, okay, we have got this distribution that we found in some way and
we are going to put these all up to the surface, and orient it in some
way? We are going to have some --
MR. MAYFIELD: Well, we are jumping ahead a bit, but let's
go ahead and do it. We have got this --
DR. POWERS: But this is a crucial element.
MR. MAYFIELD: It is a crucial element and the gist of it is
that we have got experimental data we will now have from a CE --
actually, I guess it is two CE fabricated vessels. We have got pieces
from -- I am sorry, my mind has gone blank -- Midland, which was a B&W
fabricated vessel, the CE fabricated vessel that you will see
characterized as PVRUF, which was the Pressure Vessel Research User
Facility at Oak Ridge. We got pieces from Shoreham. We got pieces from
River Bend. What am I forgetting?
DR. POWERS: Hope Creek.
MR. MAYFIELD: Hope Creek has a boiler. So we have gotten
from five, pieces of pressure vessel from five different canceled
plants.
DR. POWERS: No TMI?
MR. MAYFIELD: No TMI. No Yankee Rowe.
DR. POWERS: No Yankee Rowe.
MR. MAYFIELD: So we have got those and for Midland and
PVRUF, we have done the detailed UT exams with some limited destructive
examination of both of the weld ones to follow it up. And this is not
the classic UT that you would find used in the field, this is a fairly
advanced state of the art technique, it is called the Saft UT method.
It is an enhanced three-dimensional --
DR. POWERS: How far down do we get to go?
MR. MAYFIELD: Sir?
DR. POWERS: How far down in flaw size do we get to go with
this device?
MR. MAYFIELD: A couple of millimeters. I mean the
technique, you start to get down to the noise level, but it is in the 1
to 2 millimeter range. Then we follow that up with destructive
examination to provide ourselves some confidence that we really do know
what we are doing.
DR. POWERS: But it seems to me that there are two parts to
the distribution, and the tails.
MR. MAYFIELD: Yes.
DR. POWERS: The big tail and the little tail. The little
tail has always been limited by resolution of the device.
MR. MAYFIELD: Right.
DR. POWERS: Okay. And you are saying, well, I am down to 2
millimeters and I don't care about anything smaller than that. Okay.
The big one, the problem is how many specimens you look at, because they
are rare.
MR. MAYFIELD: Yes.
DR. POWERS: And have we got enough specimens to have any
statistics up there at all?
MR. MAYFIELD: And the answer to that is no. So, the other
piece of this is to -- and it is one the pieces that Mark will talk a
little bit about this afternoon, is to use an expert elicitation, -- at
least I think he is going to talk a little bit about it this afternoon
-- is to use an expert elicitation, a formal process that I think the
committee is familiar with from the NUREG-1150 days, is to use that
process, coupled with the experimental data that we have, as well as all
the other data that have been made available, to come up with those
distributions of size, location, orientation and distribution through
thickness, as well as the uncertainty bounds, to the extent that an
expert elicitation is able to do that.
DR. POWERS: And the probabilities are presumably not
independent.
MR. MAYFIELD: They are not independent.
DR. POWERS: There is some correlation among them. We will
get the correlation?
MR. MAYFIELD: That is the goal. How far down that path we
get, we will see. But that is the goal.
DR. POWERS: Mark is in charge, so I have no doubt that we
will get it all.
MR. MAYFIELD: Thank you, Mark.
MR. CUNNINGHAM: No problem.
MR. MAYFIELD: So that is where we are going.
Going back to the slide, we did find some other factors to
also be important, the embrittlement variables, the shifts due to
irradiation damage, the fracture toughness value, which is --
DR. POWERS: You are going to have to help me a little bit.
I forget these nil ductility labels that you use there. You have got
the shift in the nil ductility temperature.
MR. MAYFIELD: That is the delta RTNDT. Then the RTNDT-0 is
the initial unirradiated value. You use the sum of RTNDT-0 and the
delta to come up with an index temperature that is used to deduce
fracture toughness, so that is the status of these things.
We also found that the thermal-hydraulics transient data
were important and the uncertainties in those.
DR. POWERS: The K1A is not important?
MR. MAYFIELD: K1A turns out to be a second order effect.
We spent a lot of money in the late '80s looking at some wide plate
tests to get very high values of arrest toughness, and we demonstrated
that, indeed, you get very high values. It is possible to get very high
values of arrest toughness.
When we asked the "So what?" question -- okay, fine, you got
those, what difference does that make in the analysis? -- we found that
we spent a whole lot of money to prove something that doesn't make a big
difference in the analysis. The reason is the dominant transients are
the repressurization transients and, while you may get some intermediate
arrest -- it don't matter. It is the pressure that drives these things
through the wall. So arrest is, in that sense, a second order.
DR. POWERS: Do cladding interfaces and things like that
make any difference in this?
MR. MAYFIELD: They become areas that we are looking at
through sensitivity studies, but thickness, cladding thickness, the
stress free temperature that you get through the vessel fabrication
process, those get to be important variables, not as important as, if
you will, they are second order compared to the flaw distribution.
We can refine these to levels of precision that are far and
away better than anything we would get from the flaws, and even if we
knew them precisely, it wouldn't make any difference, compared to the
flaws.
DR. WALLIS: Can I ask you about the last bullet, or are you
going to explain it?
MR. MAYFIELD: Farouk is going to talk at some length about
the last bullet. What we find is that, as we rank the significance of
the, if you will, the uncertainty in these things, because of the large
uncertainty in the flaw-related variables, these other factors have a
relatively lower importance. However, as we improve our understanding
of the flaw-related variables, these will come back up and we do have a
significant piece of the program that will address the
thermal-hydraulics.
DR. WALLIS: Because it seems to me at this point it is not
just the data, it is actually how you make predictions about what is
going to happen in a real reactor.
MR. MAYFIELD: That is correct. That is correct. The
overall goal for this activity is to promulgate a risk-informed revision
to 10 CFR 50.61. As I am sure this committee knows, the Office of
Research no longer manages rulemaking, that is handled out of NRR. We
have, however, met with the office level management at NRR, briefed them
on this initiative, and they have agreed to participate and agreed that
this is something that they would very much be interested in seeing the
technical basis for a rule change. Therefore, we believe the overall
goal is an appropriate goal.
The specific goals for our research project is to develop
the technical basis for this revision, and it will be a risk-informed
revision to 10 CFR 50.61.
Jack Strosnider from NRR makes the point that, and it's kind
of an interesting one, the PTS rule is probably the first risk-informed,
performance-based regulation we had.
Now it certainly isn't going to stand up to the scrutiny
that this Committee or the staff would apply to a risk-informed
performance-based rule today. But the fact is the screening criterion
is a performance-based approach, and the way the screening criteria were
developed was risk-informed. And the details certainly wouldn't stand
up to scrutiny today, but the concept was there.
And we intend to pursue that just trying to use the
techniques that are accepted today. We intend to approach this project
and have initiated it as a full participatory project with the public
and with technical experts from the industry, academia, whoever is
interested in participating. We have met three or four times now, there
are three separate groups that have been formed, one to look at the
probabilistic fracture mechanics, the second group looking at the
thermal-hydraulics activities, and a third group looking at the
risk-related information.
Our goal then is to achieve a common understanding among the
various stakeholders that the proposed revisions are practical, that
they're technically credible, that they're cost-effective, and that
they're scrutable. One of the big criticisms of the existing PTS rule
is where did that come from? Well, the good old boys in the
smoke-filled room, but it wasn't written down anywhere. It's our
intention to have this fully documented and able to be understood by
everyone hopefully.
DR. WALLIS: I hope among the stakeholders you will include
the intelligent student or research fellow who reads the documentation
five years from now?
MR. MAYFIELD: Hopefully.
DR. WALLIS: Not just people who have some stake in the
answer today.
MR. MAYFIELD: Our intent is to have this be the last time
we work on the PTS rule. That the intent. Now again we'll come back in
a couple of years and you can tell us whether or not you agree that we
achieved that goal, but our intent --
MR. ELTAWILA: That's our intent.
MR. MAYFIELD: Pardon me? Our intent is to have this be the
last time we fool with this rule.
Why do we think that there's a success path here? Well,
recent work that we've done shows that you can pick up about an order of
magnitude in the calculated probability of vessel failure, probability
of through-wall cracking, given that the transients occur, mostly due to
the treatment of the flaws.
DR. APOSTOLAKIS: So (E) --
MR. MAYFIELD: So E is the event. The probability of
failure given the PTS transient.
DR. APOSTOLAKIS: Given the PTS.
MR. MAYFIELD: Yes, sir. The --
DR. WALLIS: The treatment of flaws. Does that mean
physical treatment or --
MR. MAYFIELD: No, it's the mathematical treatment. The
mathematical treatment. And it's specifically the distribution of size,
whether they're all placed on the surface or distributed through
thickness, and the number, just the number density of flaws in the
region.
DR. WALLIS: So this is another example of how better
information allows you to quantify a conservatism and therefore --
MR. MAYFIELD: Yes.
DR. WALLIS: Make a hopefully better decision.
MR. MAYFIELD: Yes. This has been --
DR. POWERS: I just keep coming back and saying yes, I fully
believe that if you treat these things, the distribution, the
orientation, and the placement is independent, that you can get an order
of magnitude. That should be easy to do.
MR. MAYFIELD: Yes.
DR. POWERS: I am unpersuaded that they are independent
distributions.
MR. MAYFIELD: Well, when you say we treated them
independently, we developed distributions based on data that we measured
from these pressure vessels, specifically from the PB Ruff vessel. So
in that sense I'm not sure that I would agree they are independent
distributions.
DR. POWERS: What you did in the analysis in the past they
were completely dependent distributions, and that you took the Marshall
distribution and said they were all on the surface --
MR. MAYFIELD: Yes.
DR. POWERS: And they're all oriented in the worst possible
way. So --
MR. MAYFIELD: Yes.
DR. POWERS: So they were totally correlated distributions.
I fully believe that if you treated them as uncorrelated that you'd get
an order of magnitude automatically. I mean, just by making them
uncorrelated distributions.
MR. MAYFIELD: Well, it turns out it's not very hard to get
an order of magnitude out of this analysis when you start fooling with
the flaw distributions. Maybe we can take that tack.
DR. WALLIS: Is this a one-shot problem where once in the
lifetime of a vessel you pour cold water down a hot wall, or is it
something that happens several times?
MR. MAYFIELD: It's something that potentially could happen
several times. Anytime you get a safety objection event --
DR. WALLIS: So if -- falls once and something happens and
then you do it again, doesn't that have some kind of cumulative effect?
MR. MAYFIELD: Well, what -- nominally you -- well, anytime
you have a cyclic or a periodic loading on the vessel, you could do some
fatigue damage. However, the number of times those events occur is very
small. It's not necessarily one, but it is a small number. And the
stress cycles are just not large enough to do appreciable fatigue
damage. It's not that it's zero, but it's not substantive.
So in this case what we're really talking about is the set
of conditions where you pour cold water down a hot vessel wall, you've
reached a level of embrittlement where a preexisting cracklike defect
could extend under that particular set of circumstances.
The notion that, well, the fact that we've gone through
several of these cycles before for whatever reasons might have lowered
the fracture toughness or lowered the ability of the material to resist
crack extension, that's been looked at in a number of settings, and the
answer is no, not unless you're really getting very large plastic
deformation in the steel. And that's not the situation we're seeing
here.
We are looking at other areas of conservatism that we know
need to be included -- or excluded from the analysis. We need to do a
better job of course on the flaw density and size distribution in the
plate materials. There were some fairly crude assumptions made, how you
take the distribution information from welds and extrapolate that to
plates. We need to do a better job of plates, since it amounts for 90
percent of the volume of the vessel. We need to do something better
about the flaw density in welds. That's something that's still
evolving.
And we need to impose up-to-date fluence maps. Right now they've taken
the peak fluence and applied it at the worst possible location and said
oh, geez, look what happens. By the time we include a fluence map and
the variation of fluence around the vessel, we know we get an
appreciable change in the level of embrittlement.
DR. SHACK: What does an order of magnitude buy me in the
embrittlement?
MR. MAYFIELD: I'll show you. It's a couple of slides away.
The other thing we need to do is incorporate accurate
chemistry data, looking at its impact on not just the shift but also the
material processing and the initial values.
There is reason to believe that the screening criteria can
be increased significantly by reducing the excessive conservatism in the
rule. We believe and we think we've demonstrated that there is
significant excess conservatism, and we think we have a basis for
reducing that.
Bill, this goes to your question if I reduce -- let's see if
this mouse is going to work -- if you go to 40 effective or 32 effective
full-power years, we've done four different analyses here, and really
the point of comparison is from the top one. You can see the 5 times 10
to the minus 6 line. That's the current criterion in the regulatory
guide, and you contrast that to the lower curve. And so you can see
that at this lower curve we're going to go a long time in life of the
vessel or EFPY before we would ever come near the 5 times 10 to the
minus 6 line.
So we believe that there can be -- on that basis there can
be a significant change in the screening criteria. Now it's not that
this plot is the final answer. This is one of the pieces of information
that led us to suggest to the management that this is a project that's
worth investing resources on.
DR. POWERS: You have all these factors, the chemistry
factor, the unirradiated mill ductility temperature, and things like
that. A lot of those I think have to do with not only the chemistry of
the material, but the way it was actually fabricated. Do we have
sufficient information about all the vessels in the country to make use
of that kind of an analysis?
MR. MAYFIELD: With less on the specific processing history,
although that information is available. But that's -- if chemistry and
thermal-hydraulics data are second order, the processing history is at a
third or fourth order.
In terms of the chemistry, NRR has spent a fair effort along
with the industry under Generic Letter 9201 in deducing appropriate
chemistry values, and frankly some ranges in those values, for all of
the plants in this country. So we have a pretty good handle on the
materials and the fabrication processes in making the fleet of pressure
vessels in this country. So that's certainly a much better picture than
we had when we looked at the Yankee Rowe vessel.
What's our approach to the reevaluation? It's a two-track
approach. I think that's all of them. The bulk of the work will be in
determining the appropriate screening criteria, and we've got a flow
chart to lay some of this out. There are numerous aspects of the
existing rule that also need to be evaluated, the embrittlement
correlations, and there's been a lot of work ongoing and continuing
looking at that. The margins that are included in those correlations
and that are subsequently used in this analysis. The credibility
criteria for surveillance data, whether those really make sense, should
they be applied when you're evaluating PTS screening criteria and so on.
There are a number of these that go beyond just the strict reevaluation
of the screening criteria. Those aspects also need to be looked at as
we're reevaluating the rule.
Again, we anticipate this to be a fully participative
process, and I should say we've had very strong support from the
industry in this undertaking. We have commitments, and it's more than
commitment, we've had input and participation from the three original
plants, Oconee, Calvert, and Robinson. And the Palisades plant has made
the commitment and has been involved in this activity, and they will
fully support the activity. So we've had a lot of strong support from
the industry. They've been bringing staff as well as consultants to the
table, and have been making contributions and are fully engaged.
Our notion is to periodically brief at least the
subcommittee and the full committee as it's appropriate. As you're
going to see here on this slide, there are pieces of this that we think
might intrigue the Committee. They seem to intrigue the Subcommittee.
This lays out the overall approach, the fully participative process,
meet with the public and the industry to lay out the program, and what
we're undertaking and then as we go down through here, there are three
major parts of this program, and this is where Mark and Farouk will --
I'm sorry, I can't read the computer screen from here, so I have to
resort to something I can see.
On the right-hand box we have the probabilistic fracture
mechanics analysis. That's where we'll look at the flaw distribution as
well as the other material-related issues. We have the
thermal-hydraulics portion of the program, and then the identify and bin
events. Those are just the three major pieces of traditional
probabilistic analysis.
DR. WALLIS: Do you say use public meetings?
MR. MAYFIELD: I'm sorry?
DR. WALLIS: Maybe you have a different idea of a public
meeting than I do.
MR. MAYFIELD: I'm sorry, which box are you looking at?
DR. WALLIS: Well, a public meeting in the sense that I
understand it -- you're looking at the right-hand box. The box you're
talking about. It says use the public meeting.
MR. MAYFIELD: I'm sorry, you're up at the top.
Okay. We're using public meetings and --
DR. WALLIS: Same thing? Isn't that where you were, in that
box?
MR. MAYFIELD: Oh, I'm sorry, I had come down several lines.
But that's all right. Let's talk about the use of public meetings.
DR. WALLIS: Maybe I'm -- it just seemed to me incongruous.
A public meeting is where you try and put into simple words that the
public can understand what you're doing. And I can't really imagine --
MR. MAYFIELD: That is one type of public meeting --
DR. WALLIS: Thermal-hydraulics.
MR. MAYFIELD: The other type of public meeting that we have
is where they are open to all participants from the public as well as
from the regulated industry.
DR. WALLIS: This might be a type of a seminar in a
university?
MR. MAYFIELD: Not so much a seminar at a university --
DR. WALLIS: University of Tennessee and say we're going
to --
MR. MAYFIELD: Well, no, we --
DR. WALLIS: On the spot. He's going to give a seminar on
the thermal-hydraulics of this issue, and you guys can shoot him down if
you can?
MR. MAYFIELD: That could be one type of public meeting that
Farouk and his colleagues might choose to use.
DR. WALLIS: Not a bad one. Not a bad test.
MR. MAYFIELD: It's -- I would probably pay to go watch that
meeting.
[Laughter.]
Just to throw that in.
DR. WALLIS: Maybe we should put him in the football
stadium, like the Coliseum.
MR. MAYFIELD: We might be able to support this whole
activity. The notion here is to make available to any interested party
the opportunity to come and participate in these meetings where we talk
about the specifics of the various activities. The meetings that we've
had with the public and the industry on the probabilistic fracture
mechanics analysis are not either of the types of meetings you've talked
about. They are rather detailed, technical discussions.
DR. WALLIS: I guess what concerns me is what you call
public meetings or what get called stakeholder meetings, tend to be
meetings where various people with various political motivations try to
get their point of view accepted. They are not ways to review technical
issues at all.
MR. MAYFIELD: Again, what we have seen historically, coming
out of the Yankee Rowe experience, as we have opened these meetings and
have gone to some length to invite the public to come and participate,
we don't find in this particular arena that objective surfacing.
Rather, they are people with technical backgrounds or a technical
interest in the subject that come and offer very good information, ask
challenging questions, and that's the type of public meeting that we're
really talking about here.
DR. WALLIS: Thank you.
MR. MAYFIELD: Okay. If we come down in the center of the
chart, one of the points, so working back to the center to collect
information, do specific analyses, to resolve the open questions, that's
work that's ongoing now. One of the things that we have done is to
involve the probabilistic risk assessment folks. Nathan Siu has been
active in our meetings on the probabilistic fracture mechanics. And to
do that up front rather than wait till the end of the analysis and try
and involve people and let them try and justify what we've done, rather
than do that we've involved them early.
DR. APOSTOLAKIS: Which box are you at?
MR. MAYFIELD: This is --
DR. APOSTOLAKIS: Which one?
MR. MAYFIELD: That box.
DR. SHACK: That box.
MR. MAYFIELD: Involve PRA statisticians.
DR. APOSTOLAKIS: PRAicians.
MR. MAYFIELD: PRAicians. Yes.
DR. POWERS: I guess the thing that kind of distresses,
you've got this fantastically detailed technical analysis that you're
going to do on the flaw distribution, and then it says use expert panel
and limited thermal-hydraulics analyses to estimate the effect of
improved thermal-hydraulics. It seems that there is an incongruity in
the level of technical analysis here.
MR. MAYFIELD: Farouk is going to start holding forth here
shortly. If I could ask you to defer your question until he's had an
opportunity to present what he's really talking about doing. I hope you
will be persuaded that it's more rigorous than this flow chart would
suggest to you.
If we look to the right-hand box over here, one of the
fundamental questions that keeps coming to the table is why 5 times 10
to the minus 6? Is that the right number? What's the basis for that
number? How did it come about? Was it really that Members of this
Committee suggested you needed an additional factor of 2? That's why
the number went from 10 to the minus 5 to 5 times 10 to the minus 6. I
think if you looked at transcripts you'll find that's what happened, but
why is that the right number? Is it the right number? And if it isn't,
what should it be?
And what is the basis for selecting that target?
DR. POWERS: I hand it to you. Thank God, somebody is going
to go back and look at it again, because I know how it came about.
MR. MAYFIELD: Yes.
DR. POWERS: And I don't have any fault with the way it was
done in the past, because somebody had to come up with a number and they
did, and they it with the guru of the field, and he probably knows more
on the back of his head than the rest of the world knew collectively on
this subject. Okay. But it is time to put that on some sort of
credible basis.
MR. MAYFIELD: It is time to put it on a credible basis.
DR. POWERS: And to get that question answered, whether
people are satisfied with it or not, at least not wave your hands
anymore.
DR. APOSTOLAKIS: So this will be the mean frequency upper
bound for all events that involve PTS?
MR. MAYFIELD: It is the -- Mark, why don't you?
MR. CUNNINGHAM: Mean frequency of a through-wall crack,
given the set of events that could cause such --
DR. APOSTOLAKIS: So this is a conditional probability?
MR. CUNNINGHAM: No, it is a frequency of --
DR. APOSTOLAKIS: You said given, that is why I am confused.
MR. CUNNINGHAM: I'm sorry. Okay.
DR. APOSTOLAKIS: It is a frequency of the sequences?
MR. CUNNINGHAM: The frequency of the sequences can lead to
through-wall cracks, yes.
DR. APOSTOLAKIS: So all sequences can lead to failure of
the vessel.
MR. CUNNINGHAM: All sequences. Yes.
DR. APOSTOLAKIS: Through --
MR. CUNNINGHAM: Through the pressurized thermal shock
mechanism.
DR. APOSTOLAKIS: Yes. Yes.
MR. CUNNINGHAM: Yes.
DR. APOSTOLAKIS: So all sequences.
DR. WALLIS: Could I go over a bit on what you just said
about putting this magic number on a sounder basis? Now, what magical
process would you appeal to, what criteria, what high order of numbers
which have not been dropped from the sky would you appeal to in order to
refer to some sounder basis?
MR. MAYFIELD: I will defer to my colleague here.
MR. CUNNINGHAM: There is a slide about this later, but --
DR. WALLIS: There is.
MR. CUNNINGHAM: Yes. But the short answer is when this was
put together, when the 5 times 10 to the minus 6 was arrived at, there
was a lot of work that we now have that didn't exist. For example, the
safety goal policy statement did not exist. A lot of the PRA work that
the agency now uses in risk-informed regulation did not exist. So it
was a precursor to a lot of the deliberations we have had on coming up
with frequencies, acceptable frequencies of events.
DR. WALLIS: So you would use something like the PRA and the
safety goals? You would make a bridge between real effects on public
safety and this -- whatever you choose this number to be?
MR. CUNNINGHAM: Yes.
DR. KRESS: That number automatically becomes a core melt
frequency.
MR. MAYFIELD: Yes, for the purposes of the PTS analysis, it
is equivalent to a core melt frequency, that's right.
DR. KRESS: So here, you are allocating the distribution of
core melt frequencies. You are allocating that much to pressurized
thermal shock.
MR. MAYFIELD: Yes.
DR. KRESS: And it is an allocation issue.
MR. MAYFIELD: That's right. Yes, that's right.
DR. APOSTOLAKIS: So it is really a policy issue.
MR. MAYFIELD: Yes.
DR. WALLIS: If the vessel -- this is the core melt?
MR. MAYFIELD: It is assumed in these types of analyses that
a through-wall crack of the magnitude we are talking about here will --
DR. WALLIS: So it is a catastrophic vessel failure, it is
not just a crack?
MR. MAYFIELD: Yes. No, it is a --
DR. KRESS: That is a bit of a assumption.
MR. MAYFIELD: Yes, but it is not much of an assumption.
DR. WALLIS: It is just cracks and leaks, then --
MR. MAYFIELD: But we are not -- that is not the way these
-- for the problem we are addressing, that is not the way the vessel is
going to fail.
DR. POWERS: Mark, you are going to try to tie this to the
safety goal? Are you going to tie it to a CDF then? Isn't it with the
baggage, I mean if you try to go to a safety goal, and I am going to
say, okay, you have done this fantastic analysis on the fracture
mechanics, you have done this unbelievably good analysis on the
thermal-hydraulics, you have got your probabilistics down fine, your
source term is the worst thing that I ever saw in my life. It has no
technical basis and whatnot. Your analysis of transport into the
environment, your evacuation model are no good at all. I mean you are
adding layer after layer after layer onto the problem.
MR. CUNNINGHAM: That's right.
DR. POWERS: I think it would be wonderful if you could tie
it to the safety goal, but you are biting off a big chunk.
MR. CUNNINGHAM: I think it won't be tied directly to the
two quantitative health objectives. I think we are going to have to
work with some of the other subsidiary objectives that we have come up
with over the years to make this practical, if you will. One of the
questions we will get is to is, to what degree is a pressurized thermal
shock a challenge to the containment? So how much flexibility do we
have between a core damage frequency and LERF?
DR. POWERS: You are going to get the rocket scenarios and
things like that.
MR. CUNNINGHAM: Yes, exactly. That's exactly right.
DR. APOSTOLAKIS: Regulatory Guide 1.174, though, would not
apply here, because you don't have any changes here.
MR. CUNNINGHAM: That's correct. The Reg. Guide 1.174 does
not strictly apply. What we are talking about here is --
DR. APOSTOLAKIS: The spirit.
MR. CUNNINGHAM: -- extending the philosophy, the spirit
that is in 1.174, and the safety goal and the PRA policy statement into
changes in rules. That is why this thing is -- this rule change is a
stalking horse for a lot of the other things that are coming on Part 50.
DR. WALLIS: Do you have analyses for what happens if the
vessel fails?
MR. MAYFIELD: To what extent?
DR. KRESS: It is a very large break LOCA.
DR. WALLIS: It makes a lot of difference. No, it is not so
simple. It depends on how it fails. If it blows the top off, we take
out all the control rods --
MR. MAYFIELD: We have looked at some of that phenomenology,
and losing either head is not going to happen. Those -- well, I
shouldn't say it so definitely. They are very low frequency events.
DR. APOSTOLAKIS: Let me understand the -- I'm sorry. Go
ahead.
MR. MAYFIELD: What we are talking about here are a set of
cracks that will give you, nominally, a large axial split in the side of
the pressure vessel, and it will be sufficiently large that as the crack
propagates, and cracks propagate at the speed of sound in the material,
so this -- we have a very rapidly opening crack. Because of this, you
get flaps, essentially, that open up on the side of the vessel, and you
are going to start exhausting the core basically, the coolant in the
core.
DR. WALLIS: The crack propagates until -- what stops the
propagation of this crack, if it going, say, around the vessel? Like a
can opener going around a vessel.
MR. MAYFIELD: Just because the material at either end
hasn't been so severely embrittled and it remains a very ductile
material, and it will tend to arrest the cracks.
DR. KRESS: It is an axial crack.
MR. MAYFIELD: It is an axial crack. There are a set of
vessels where a circumferential crack --
DR. WALLIS: Up and down, and so it doesn't go
circumferential.
MR. MAYFIELD: In the welds.
DR. WALLIS: A part which still has a core in it, it leaves
something out.
MR. MAYFIELD: Right. So there are a set of vessels where
circumferentially oriented cracks either in the plate, the forgings or
the circumferential weld in the middle of the beltline are of interest.
They tend to be of less interest, but they can't be ignored. So they
will be included.
The failure scenario there, it gets to be very difficult to
actually separate the vessel. But that is one that would have to be
looked at. The issue of more concern is this large, rapidly opening,
axial split in the vessel.
DR. APOSTOLAKIS: Just a clarification. We have been told,
or I have been told time and time again, that the core damage frequency
goal of 10 to the minus 4 is not part of the regulation, so we cannot
really use it, asking the licensees to do things. Now, you are about to
develop a rule that will have a goal for a subset of the sequences that
lead to core damage.
Why can you do that?
MR. CUNNINGHAM: We are not about to do that, it -- the
rule's been on the books since 1985.
DR. APOSTOLAKIS: But you will include this thing now in the
new --
MR. CUNNINGHAM: The 5 times 10 to the minus 6 value has
been there since 1985.
DR. APOSTOLAKIS: So why is it legitimate then to have a
bound or a goal for a subset of the sequences that lead to core damage
and not to have a goal that is being used by the regulations for all the
sequences? I mean, am I missing something? I'm sure I am.
MR. CUNNINGHAM: There is an inconsistency there.
DR. APOSTOLAKIS: I'm sorry. It's the last thing I
expected.
MR. CUNNINGHAM: I'm sure you're shocked, but there's an
inconsistency there.
DR. APOSTOLAKIS: I'm shocked. I'm pressurized shocked.
[Laughter.]
DR. WALLIS: Are you going to split axially or --
[Laughter.]
DR. SEALE: Now that I'll pay for.
MR. MAYFIELD: I think in the interests of time perhaps if
we took a -- stepped on through this and let Farouk and Mark deal with
their pieces of this. The research results have significantly improved
our understanding of the key variables. I'd mentioned that we will use
an expert elicitation in addition to the data that we have from these
pressure vessels to work on a credible set of distributions to use for
the flaw-related variables.
DR. APOSTOLAKIS: Now the expert elicitation will be pure
11.50? Or as amended?
MR. CUNNINGHAM: It will have a lot of similarities to the
11.50 work, but we have learned a few things along the way, too. Since
then we've had major expert elicitations in the area of the seismic
hazard, and in the area of looking at offsite consequence parameters,
and I think we're --
DR. APOSTOLAKIS: The major --
DR. POWERS: The expert elicitation that you've done on the
transport parameters, plume transport, what not, was one that you did in
coordination with -- in cooperation with Europeans who had substantial
expertise in that area. There's another area where -- both
thermal-hydraulics and materials they have a substantial expertise.
Have you solicited their interest in this topic?
MR. CUNNINGHAM: We haven't solicited their interest yet,
but we have talked about it internally, about the benefits of doing it,
and some of the mechanics of how we could do it. Again, from our
experience from the work on offsite consequence analysis.
DR. POWERS: And of course they have strongly held views on
how --
DR. APOSTOLAKIS: Unlike us.
DR. POWERS: Expert opinions should be solicited and the way
you treat distributions.
MR. CUNNINGHAM: Yes.
DR. POWERS: It might be interesting to factor their
thinking in.
DR. APOSTOLAKIS: But I would make one statement here, that
I strongly urge you to rethink the idea of assigning equal weights to
the expert --
DR. POWERS: The Europeans will give them that strongly held
view as well.
MR. CUNNINGHAM: That is one of the --
DR. APOSTOLAKIS: They can't give equal weights, but they
have a strange way of finding the weights. But there are ways of
handling that in the integrated decision making process.
MR. CUNNINGHAM: Yes.
DR. APOSTOLAKIS: But I really don't think we should go back
to stating by fiat, you know, whatever the experts give you, add them up
and divide by n. Everything else I think is just minor improvements,
but this particular item I think is important.
MR. CUNNINGHAM: Okay. As Dr. Powers was alluding to, in
the case of the offsite consequence analysis --
DR. APOSTOLAKIS: Yes.
MR. CUNNINGHAM: This was an issue. In that piece of work
we ended up going back on the nominal case to an equal weighting,
because of some of the problems that we encountered, but --
DR. APOSTOLAKIS: Yes. You can go back -- you can use equal
weights assuming certain conditions are satisfied.
MR. CUNNINGHAM: Yes.
DR. APOSTOLAKIS: Namely you have educated the experts, you
have -- equal. I'm not sure I like the quantitative weighting scheme
that comes from Europe. But then again, you know, I haven't really
studied it that much.
MR. CUNNINGHAM: And we encountered some problems with --
some problems in the mechanics of that as we were trying to do it, and
that's why we ended up not using it in that form.
DR. KRESS: You could get another set of experts to rank the
experts.
DR. APOSTOLAKIS: No. I think you can bound the problem,
but the equal-weights issue really deserves special attention.
DR. KRESS: It does.
DR. APOSTOLAKIS: Are we going to be briefed on this while
you're doing it, or next we see you we'll see the results?
MR. MAYFIELD: We can do it either way. And that's part of
why we wanted to come brief you at this stage, to find out what areas
you were particularly interested in and when you wanted to hear from us.
DR. POWERS: I remind Professor Apostolakis that he has from
the planning procedures committee a request to decide on the amount of
time that he wants to devote to this particular issue that would
translate into the frequency of briefings that he wants on this issue.
So it's in his hands.
DR. APOSTOLAKIS: I don't remember that. I'm supposed to
decide on this?
DR. KRESS: On expert elicitations.
DR. APOSTOLAKIS: On expert elicitations.
DR. POWERS: Now you're supposed to decide on how much time
and effort this Committee wants to devote to this particular topic.
DR. APOSTOLAKIS: Since I'm an expert on PTS.
DR. POWERS: You will be if you proceed along this --
[Laughter.]
DR. WALLIS: I have question on equal weights -- who is the
chair of this session?
DR. POWERS: Dr. Shack is.
DR. WALLIS: I think when you elicit experts, you should not
just say what do you think and give them some weight. I think there
ought to be a dialogue among the experts.
DR. APOSTOLAKIS: Sure.
DR. WALLIS: If there are ten experts and one expert says
wait a minute, something is phony about this thing, you guys better look
at it, then that dialogue should continue until there's some sort of
agreement.
DR. POWERS: If you --
DR. WALLIS: Every expert doesn't have the time to look at
everything.
DR. POWERS: If you look at the rather elaborate process it
at its inception was adopted for NUREG-1150 and subsequently refined in
a pathetic way for seismic, and in a very good way for the consequence
analysis.
[Laughter.]
You'll see that there are all kinds of not only that you
have the dialogue but the way you do it and the subsequent way you do
the elicitation to give you some sort of assurance that you're at once
informing yet not inhibiting experts and things like that. There are a
lot of -- quite a lot of experience, which I think has been fairly
positive across the board.
MR. CUNNINGHAM: Yes.
DR. POWERS: I think you had experts coming out with smiles
on their faces from NUREG-1150. It sounds like you had experts gnashing
their teeth after the consequence analysis, but not because of the
process --
MR. CUNNINGHAM: Process, that's right.
DR. POWERS: Because of the subsequent analysis of the data.
DR. APOSTOLAKIS: I would also bring to your attention the
study on vulcanism that was done by DOE for the Yucca Mountain project.
That is a good application, what the NRC developed, expert elicitation
process for seismic.
MR. CUNNINGHAM: Okay.
MR. MAYFIELD: With that I would like to turn this over to
Farouk to talk about the thermal-hydraulics activities.
DR. APOSTOLAKIS: So this is the minor part of the effort?
MR. ELTAWILA: It's amazing that I assumed that we are in a
very small supportive role until I came here in front of this Committee.
[Laughter.]
And my role is becoming bigger and bigger.
DR. POWERS: We've learned to have such admiration for your
capabilities and what not, we like you to take a bigger role in all of
these programs.
MR. ELTAWILA: Oh, good. Thank you very much, sir.
DR. SEALE: We will sell tickets.
DR. APOSTOLAKIS: With the same resources.
MR. ELTAWILA: The same resources. That's exactly what's
happening.
I think I can answer both Dr. Powers and Professor Wallis.
I think Professor Wallis' question is the answer to Dr. Powers'
question, why we're saying that we have a very limited thermal-hydraulic
analysis. I think the main reason that although that there have been a
lot of improvement in the thermal-hydraulic areas over the past 20
years, our analysis tool is still unable to predict the condition that's
conducive to PTS flow stagnation.
We have a one-dimensional code that cannot calculate
stratification, so that's why we said this is going to be a limited set
of analysis, and we're going to focus more on an approach that
incorporates both expert elicitation, experimental and scaling analysis,
supported by some limited code calculation. And that's the reason for
the limited role of the thermal-hydraulic analysis per se.
MR. ELTAWILA: Yes. I suggest you drop the word limited
from the chart. It gives the wrong impression. It means that you can
do it, but we decide to do it in a limited way, and you just told us
it's the other way, that the methods and tools themselves are limited,
and I'm not sure that word belongs, then, to that chart. It's a matter
of communication.
MR. MAYFIELD: All right. That's how I --
DR. WALLIS: Well, can I ask, you know, why -- there may be
a lot of reasons to make a decision to proceed that way, but Mayfield
has told us, gee, they have gone to heroic lengths to take the
technology they had available to them on the cracks. I think the
probabilistic fracture mechanics was developing independent of you, but
you had to get yourself acquainted with that, and then you're going to
go even a step further and improve your technology for expert
elicitation.
But you find yourself in inhibited capability and you
developed that capability to get up to the status that you wanted to to
attack this problem in what you've called a definitive way.
Why is it that we have the thermal hydraulics over here and
we say we can't -- our code is no good for doing this? Well, change the
code. Get a code that is good for this.
MR. ELTAWILA: We have supplementary tools that I am going
to discuss, and hopefully at the end of the five-minute presentation,
you will be able to be convinced that we will provide them with the
important information that they will need.
But we see ourself in a supporting role in three areas. The
first area will be supporting Mark Cunningham in the screening criteria.
We will start with the full PRA, we will look at all the scenarios. We
are going to develop a very simplified thermal hydraulic model that's
just pressure and temperature and take the fracture mechanic as the
boundary condition and try to screen this scenario to a smaller subset
of scenarios, and so we'll be able to do analysis, hopefully no more
than five scenarios at the most, because, to be honest with you, our
codes are slow right now, still working on improving them, and it takes
a long time to run this calculation and it's very expensive to run these
calculations.
DR. WALLIS: Could you clarify something for me? Is this a
single-phase problem?
MR. ELTAWILA: It is a single-phase problem, yes.
DR. WALLIS: It's very difficult to run a code for a
single-phase fluid?
DR. KRESS: It's stratified, so it's almost like --
DR. WALLIS: Yes, it has variable properties.
MR. ELTAWILA: But the code cannot -- because of the control
volume approach, it makes everything so the condition -- all you're
talking about, a simple different code --
DR. WALLIS: Why run a code that doesn't bottle the physics
you need to represent?
MR. ELTAWILA: Because the plant-specific features have been
proven to play an important role of PTS, and we want a code that will be
able to model all the control systems in the plant and all the different
nuances of how the ECCS is injected in the cold leg and so on. So that
is the reason why, and that -- but once we reach the point that we have
stratified flow, we would like to switch to other tools like CFD code,
like Remix code or something like that, and that's --
DR. POWERS: So the situation is that you have a way in mind
in which you've got kind of a stratified set of code calculations,
you're kind of using a one-parameter control volume code to kind of get
you the boundary conditions, and then you're going to do something much
more sophisticated --
MR. ELTAWILA: That's correct.
DR. POWERS: I can't get my tongue around that three-letter
acronym. But then you'll do something sophisticated, you know, more
locally.
MR. ELTAWILA: More locally to calculate the pressure and
temperature in the region of -- but I --
DR. POWERS: You're overly apologetic about what you've got
planned here. I mean, that doesn't sound like --
MR. ELTAWILA: Well, no, I'm not apologetic about our system
codes, not about the plan itself.
So the second element of the program is -- now the first
element is the screening criteria, and then we will reduce the number of
scenarios to a limited set. The second element of the program is to do
an actual calculation to be able to identify the onset of -- and the
thermal hydraulic prediction in downcomer.
The third element of the program we have not really looked
at --
DR. SEALE: How much detail do you need? I mean, suppose
you make limiting analysis where you simply say the coldest water in the
system comes in at the quickest time in the worst place.
MR. ELTAWILA: But that --
DR. SEALE: Is that what you do now?
MR. ELTAWILA: Well, that eliminates all the benefit that he
gains out of his --
DR. SEALE: That really matters if you assume that it's a
really bad story, you have to do something better, is that --
MR. ELTAWILA: I think we need to do better than that, yes.
DR. SEALE: So the limiting analysis shows things are bad,
so you've got to do better than that?
MR. ELTAWILA: Yes.
MR. MAYFIELD: The problem we ran into in developing the
original PTS rule is that you can always -- and we've kind of known this
-- you can always define a transient that will fail the reactor pressure
vessel. Now, the frequency of occurrence of that transient is
enormously low, but the reason we went to a risk-based or risk-informed
approach was to get away from the issue of defining the worst possible
scenario.
DR. WALLIS: You have to do all those things.
MR. MAYFIELD: Yes.
DR. WALLIS: Because it would be very nice if you dismiss it
on the grounds of something much more global.
MR. ELTAWILA: Well, I think that's the third element of our
program. After we finish all activities that you will hear here, we're
thinking about getting Professor Theophonus at the University of
California, Santa Barbara, use his raw methodology, and try to see if
there is a generic resolution for this problem, you know, that it does
not exist physically, you cannot get into this condition, and we can
dismiss it. But that's long-term effort.
DR. APOSTOLAKIS: The expert elicitation Mark referred to
will be part of ROAM? As I understand, ROAM involves experts, or is
that a separate exercise?
MR. ELTAWILA: It's --
DR. APOSTOLAKIS: A separate exercise.
MR. ELTAWILA: Yes.
DR. APOSTOLAKIS: So you will provide input to ROAM?
MR. ELTAWILA: We will provide input to ROAM, and Professor
Theophonus is going to be a part of that whole process and he will
integrate the whole information at the end through ROAM and see if we
can come up with a generic --
DR. APOSTOLAKIS: So then the very low probability sequences
that you referred to, Theophonus will call them physically unreasonable,
and they acquire a different aura that way.
MR. ELTAWILA: Shall I continue? Okay.
Let's talk about the tools that we are going to use. As I
indicated earlier, we are going to use our existing system code, like
the RELAP 5 and the TRAC code, which they have been validated against
experimental data, and they have the capability to model the
plant-specific feature that's important for PTS.
I'm going to jump to the third bullet, but we know that this
code had deficiency and we will be able to look at other tools that we
have -- for example, the Remix code that was developed by UCSB some time
ago which is based on correlation and has a plume model, so you will be
able to calculate if the plume penetrate into downcomer and you get a
better distribution of the pressure and -- and the temperature in that
region. And if we need to do CFD code, we'll be able to do this
additional calculation.
DR. WALLIS: Isn't this an old problem? People have looked
at downcomer plumes for ten years or something?
MR. ELTAWILA: That's correct, yes.
DR. WALLIS: Didn't they try CFD to predict those downcomer
plumes?
MR. ELTAWILA: Yes.
DR. WALLIS: Did someone cut off the funding or something?
I thought this was going on a few years ago.
MR. ELTAWILA: But I think we have the tools. All that we
have to do is apply them for a plant-specific case.
DR. WALLIS: Did it work?
MR. ELTAWILA: Yes, they work, the plume model and the --
DR. WALLIS: So it has been shown by experiment and use of
CFD that --
MR. ELTAWILA: Well, I honestly cannot --
DR. WALLIS: -- there's a validated method to predict?
MR. ELTAWILA: I can't talk about CFD. I don't know if
that CFD model has been validated. But I know that the Remix model has
been validated against -- it's actually a set of correlation and been
validated by experimental data.
DR. WALLIS: So it's dial twiddling or is it real CFD?
MR. ELTAWILA: No, Remix is not a CFD code at all.
DR. WALLIS: It's correlating things and --
MR. ELTAWILA: Correlating, that's correct, yes.
What is important in this element, that we are really going
to run experimental program at the Oregon State University at the Apex
Facility, and that additional data will be helping us identify the
condition for the PTS.
But in order to discuss the experiment, I would like to make
a distinction between two types of plants: the H.P. Robinson plant,
which you have one cold leg for each hot leg per loop, and the Palisades
plant, which has two cold legs per one hot leg per loop.
And what we notice through our test program at Oregon State
University and at the University of Maryland, which both of them have
two cold legs per hot leg, that although you can get one loop to
stagnate, the other loop does not stagnate. The other loop in the --
the other leg in the same loop continues to circulate. And we want to
look at the effect of the circulation in the other loop on downcomer
mixing.
So we are going to modify the Apex facility. We add a rack
of thermocouple under each cold leg in the downcomer, rack of
thermocouple in each cold leg, and we're going to run a spectrum of
breaks and see if really the condition that -- will start the
stagnation, and if stagnation happens in one loop -- in one leg, what
will happen in the other leg, and if that mix the downcomer.
I think there is a potential that this experiment by itself
with the scaling analysis may be able to solve the problem for the two
plants without having to do any analysis.
DR. WALLIS: Where is the crack? Is the crack right at
where the cold water comes in from the cold leg?
MR. ELTAWILA: That's correct, spilling from the cold leg.
DR. WALLIS: So how it spills is very important.
MR. ELTAWILA: That's correct, yes. That's why it's --
DR. WALLIS: Whether or not there's separation at the lip
and things like that are very important.
Isn't it a local phenomena? Why do you need all this global
study of the downcomer for a local --
MR. MAYFIELD: The cracks can be located anywhere in the
vessel, so it's not just located right under the plume.
DR. WALLIS: There's probably some places where it's most
likely.
MR. ELTAWILA: No, the temperature --
MR. MAYFIELD: The stresses are worse right under the plume.
The potential for cracks to appear --
DR. WALLIS: So you have to model the whole downcomer in
order to --
MR. MAYFIELD: Basically you have to model the whole
downcomer.
DR. SHACK: The problem is really driven by where the
biggest crack is more than the stress.
MR. MAYFIELD: It's not just the biggest, it's where is the
crack that's in the right size range for this particular loading
sequence.
DR. POWERS: That's a very interesting kind of material
embrittlement.
MR. MAYFIELD: Yes.
DR. POWERS: Because you're kind of mapping now, you're not
--
MR. MAYFIELD: Yes.
DR. POWERS: You don't have the worst spread over the entire
vessel.
MR. MAYFIELD: Exactly.
DR. WALLIS: The effluence isn't worst at the place where
the thermohydraulics is the worst and --
MR. MAYFIELD: Right. Life would be somewhat easier for us
if that were true, but it's not the way it works.
MR. ELTAWILA: I think we would be able to start the test at
OSU sometime this calendar year, and based on -- we have done
preliminary analysis for -- scaling analysis for the Palisades, and we
feel that the OSU facility will represent the plan very well, so we are
going to focus our test program for the Palisades and try to come up
with the condition under which flow stagnation occurs, and if we can use
this information to be able to identify a condition, that we can use our
system code to the point that this condition occurs, and then we can
switch from that to the more detailed analysis.
DR. POWERS: Suppose that you did a bunch of experiments at
these facilities and you found, whoa, it's very difficult to get flow
stagnation.
MR. ELTAWILA: We solved the problem.
DR. POWERS: Have you solved the problem? You have these
experimental facilities, they show you something, and you say, gee, I
can adjust my model to predict that for that experimental facility, and
then I take it and I apply it to a real reactor, and sure enough, the
same thing comes through, the code predicts it. Do you have to do
something with the full facility, the actual reactor, to show that in
fact, your extrapolation from the experiment of the full scale reactor
was a valid and useful thing to do before you can say the problem's
solved?
MR. ELTAWILA: Well, I think you're asking a very good
question, but I don't think we're going to -- we don't have to go to the
full plants, but we need to run the same type of experiment in another
scaled facility. I really don't think any utility will volunteer their
plants for us to run a test, but we might consider, for example, going
to the Rosa facility if we really see a condition that it's impossible
to get flow stagnation, and everybody is telling us it's a prerequisite
for PTS to have flow stagnation.
If that condition is impossible to achieve, I think it might
be worth it that we will go to a bigger facility like the Rosa facility,
and based on a scaling rationale, which I think we have come a long way
and we know how to apply it right now, might be able to -- so that you
can extrapolate to the full scale.
DR. POWERS: So what you say is at least I know the trend in
my extrapolation is a valid thing to do.
MR. ELTAWILA: That's correct. Yes.
DR. SEALE: Have you checked the scaling between the OSU
facility and say Robinson?
MR. ELTAWILA: No. We checked it with Palisades. Robinson
is one to one. It has one --
DR. SEALE: Oh, okay.
MR. ELTAWILA: So Palisades is the one very close to the
facility, and we don't have to make any modification except adding the
instrumentation.
Oh, I'm sorry, we make one modification that, as you know,
AP600 does not have a loop seal, so we are going to add a loop seal to
the OSU facility, so we really will have an actual representation of the
facility -- of the plants.
DR. WALLIS: Palisades is a CE plant?
MR. ELTAWILA: That's correct, yes.
DR. WALLIS: Okay.
MR. ELTAWILA: I think, therefore, the -- the last two
viewgraphs is just a summary of what I said and I'll let Mark now
address his part of the presentation.
DR. WALLIS: Well, let's see, I hope that -- the research is
very interesting. The researchers tend to look at things and study them
on the point of view of interest. I hope they come up with methods
which are then usable to the reactor safety analysis in some way,
they're answering the right questions which are being asked, whoever is
doing the safety analysis. Presumably you folks, or somebody else?
MR. MAYFIELD: Research will have -- has the task to put
together the complete package, to develop the technical bassi that would
be presented to NRR to support a rule change. So the three people you
see sitting here are the three managers responsible for the activities
that will put together the complete story.
DR. WALLIS: You can be sure that whatever the result from a
university study, a master's thesis or something, actually answers the
questions in a form which is useful to --
MR. MAYFIELD: Yes.
MR. ELTAWILA: Absolutely.
MR. CUNNINGHAM: In Slide 21, we talked about already a
little bit basically the acceptance criteria that we have to develop.
The five times ten to the minus six that was talked about earlier was
developed in 1985 or before 1985, so it predates much of the work that
we've done in risk-informed regulation.
A real task is now that we -- in the last couple of years,
we've come up with the one -- Reg Guide 1174 guidelines for a different
circumstance, so we need to in a sense bring these two together to say
what -- does it still make sense to use five times ten to the minus six;
is there something else that we should use.
Again, as I mentioned earlier, this 50.62 change is the
first place where we probably would use this revised concept or the new
concept on what's an acceptable value, and we'll see it in other parts
if Part 50 changes down the road, probably.
DR. KRESS: If you change that by an order of magnitude,
five times ten to the minus five, would the PTS problem go away?
MR. CUNNINGHAM: Yes.
MR. MAYFIELD: Yes. If you take it an order of magnitude
the other direction, life is going to get a lot more interesting.
DR. KRESS: Yes. So it's very critical that you get the
right value.
MR. MAYFIELD: Yes.
DR. POWERS: You can't run the plant if you take the other
direction.
DR. KRESS: Yes.
MR. CUNNINGHAM: But I imagine this is something we would
want to come back in particular to talk to the committee about, given
the time some of us has spent on the issues in 1174. I think this is
the next annex, another extension of what we've been doing there into
other arenas.
DR. WALLIS: But if this is probability of a through-wall
crack, what's the probability of small surface crack?
DR. KRESS: They are there.
MR. MAYFIELD: They are there. Now you see surface crack.
DR. WALLIS: So visual inspection already reveals surface
crack, does it?
MR. MAYFIELD: No, they -- by and large -- and these are not
just surface cracks that are of interest. You can also have imbedded
cracks that are just below the clad to base metal interface that will
lead to vessel failure. So it's not just a surface --
DR. WALLIS: I'm very tempted to ask the question what is a
crack? It's not an easy --
MR. MAYFIELD: This is not an easy question. I mean, there
is -- there's the facetious answer where it's a separation between
layers.
DR. WALLIS: We had a candidate who was presenting his
thesis and it was all about cracks, and I asked -- the first question I
asked was what is a crack, and he fell apart because he couldn't answer
it. So I won't even ask you that one.
MR. MAYFIELD: We do appreciate that.
[Laughter.]
DR. POWERS: Well, it's a non-trivial question.
DR. WALLIS: It's not a trivial question.
MR. MAYFIELD: It is not a trivial question. Out of the
in-service inspections, what we get are flaw indications, and then comes
the question, well, how many of those are the kinds of defects, assuming
that they're real, are the kinds of defects that underloading would
actually propagate. If it's a volumetric kind of defect where it
blunted edges, it's not going to do very much. If it has sharp edges,
now it's much more interesting and will behave more like a very sharp
notch.
DR. WALLIS: So to talk about something I have experience
with, if I skate over the ice, I see all sorts of cracks in it. The
things I'm worried about are the booms where the crack starts here and
goes right across the pond --
MR. MAYFIELD: Yes.
DR. WALLIS: -- like a piece of thunder, and suddenly
there's a crack a millimeter wide. Of course, that's the sort of thing
you're worried about.
MR. MAYFIELD: Yes.
DR. WALLIS: A lot of difference between that and all these
little cracks that you see.
MR. MAYFIELD: Yes. All these little benign fissures.
You done? I'm done.
MR. CUNNINGHAM: I'm done.
MR. MAYFIELD: The last slide in the presentation, unless
there are some specific questions, I would simply go to the last one.
DR. APOSTOLAKIS: Where would you put the ACRS in there?
MR. MAYFIELD: And I'm not trying to be flip, it's wherever
you want to appear.
DR. POWERS: I mean, that's the tour. You've got the
planning and procedures meeting --
DR. APOSTOLAKIS: And I am collecting information to let me
answer the P&P's charge that I was not aware of.
MR. MAYFIELD: We would anticipate -- I see we have touched
on a nerve here.
[Laughter.]
MR. MAYFIELD: We would at least anticipate coming and
talking to you when we are proposing the revised screening criteria,
sort of the minimum number of times we would anticipate talking to the
committee.
DR. APOSTOLAKIS: Where is that?
MR. MAYFIELD: Proposed revised screening criteria --
DR. APOSTOLAKIS: Right after September of 2001, or before.
MR. MAYFIELD: Probably before that milestone. Again, this
is sort of the minimum of times that we would see coming to the
committee. And then when we're done, sort of December of 2001, we think
there would be value in talking with the committee and getting your
views on the expert elicitation as we get into that, not just wait until
the end of it, but as we get into it to come and talk to if not the full
committee, at least --
DR. APOSTOLAKIS: But where is that?
MR. MAYFIELD: It would be up in this range. The -- I can
give you a more specific date. We are anticipating initiating that
literally as we speak with the notion that we would be done and flaw
distributions provided to the analysts by June of next year, the
finished product, usable information by March of next year, usable by
the analysts.
So we would anticipate maybe useful dialogue later this
fall, October, November, maybe as late as December. December, we would
be well into the elicitation. We would anticipate having formed the
panel and the first round of meetings in the September time frame,
September, October.
MR. ELTAWILA: I would like to add that we would like to
have the input from the thermohydraulics subcommittee about the approach
that we are taking towards addressing this TH issue. So we will have a
separate meeting.
DR. APOSTOLAKIS: That would be when?
MR. ELTAWILA: I think we have a meeting scheduled for
September. Maybe you can add a date. It's up to Professor Wallis if he
wants to add a day after the subcommittee meeting to discuss the PTS
issue or a separate meeting any time between now and December, we would
be happy to meet with you. I think we need to get your comments early
on in the process before we start making the modification to the
facility and so on.
DR. WALLIS: It seems to me that you see milestones as being
public meetings.
MR. MAYFIELD: We had to choose something off of the chart
and those are the things we chose.
DR. WALLIS: While we're doing it, I would attempt to say
that's a milestone: I'm going to solve the thermohydraulics by; solve
these problems by; --
MR. MAYFIELD: This was --
DR. WALLIS: -- do some work by, not just have a public
meeting by.
MR. MAYFIELD: Well, the notion is that that's --each of
those public meetings represents when we would be discussing the
completion of a significant piece.
DR. WALLIS: You would need materials for those public
meetings.
MR. MAYFIELD: Yes. Yes.
DR. WALLIS: You would need some substantial technical
material, --
MR. MAYFIELD: Yes.
DR. WALLIS: -- which better be ready for the --
MR. MAYFIELD: Yes.
DR. POWERS: Just to tell you something about what this
committee has been doing in anticipation of this presentation, the
planning and procedures committee was asked to think about how much of
our committee resources we wanted to devote to doing what you're talking
about, meeting here interim-wise, and whether it should be something
where Farouk is talking to the thermohydraulics committee and you're
talking to the mechanics and metallurgy and Mark is talking to the PRA
committee, or you have one group of people that you're talking to about
all three subjects, whether we wanted to sit in and observe the expert
elicitations, what goes on in connection with ROAAM, which is kind of an
orthogonal approach toward things, has proved useful to you in the past,
whatnot, you know, how far in-depth, and I don't think we've made any
decisions on those things, but we've kind of anticipated that you would
come forth with this stake through the heart approach to a problem that
has been around a long time and one that is seriously impinging on the
industry right now.
MR. MAYFIELD: Yes.
DR. POWERS: But we haven't made any decisions yet.
DR. APOSTOLAKIS: Now, when you say -- Farouk was very
specific. He said he wants to meet with the thermohydraulics
subcommittee. You guys said ACRS. You mean the full committee?
Subcommittees?
MR. MAYFIELD: Let me back up and try this a little
differently. We would like to have the ACRS as involved in this up
front as you can afford to be, whether that be through the full
committee or through the subcommittees or both. We think it is to our
advantage to have you engaged in providing us your feedback early rather
than wait until we've spent several hundred thousands of dollars and
tied up two years of staff effort, and then have you gentlemen identify
a fatal flaw in the approach. We don't think that's a good use of our
resources. So we would very much like to have you involved as much as
you can afford to be involved in whatever capacity or through whatever
mechanisms you choose to be involved. We don't have specific hard
targets that we're asking you --
DR. WALLIS: How much will we have to review?
MR. MAYFIELD: Sir?
DR. WALLIS: How much paperwork will we have to review?
MR. MAYFIELD: At the end of the day, if we waited until
12:01, it's going to be a substantial volume of paper. If we're
involved along the way, then I would anticipate it's not going to be so
much paper at each stage.
DR. WALLIS: Well, I would hope that when you give us this
paper, that you don't just give us a great stack of paper, that Farouk
says here's all this paper, but these are things I'm really worried
about, I need some help with, please focus on this, this and this. It's
very difficult with a large stack of paper to figure out what to --
MR. MAYFIELD: Yes.
DR. WALLIS: -- I mean where to go in the stack of paper.
MR. MAYFIELD: What may be useful is to get some thoughts
back from the committee about how you would like to be involved, and
then assuming it's through the subcommittee structures, we can engage
with each of the subcommittee chairs in the three key areas and decide
what specific areas we need to engage on and to provide exactly the
feedback that you're talking about.
DR. APOSTOLAKIS: Well, I'm not sure if it's a good idea to
have separate subcommittee meetings. They should be joint subcommittee
meetings.
DR. KRESS: Yes, I think joint ones would be a good idea.
DR. POWERS: I think that's a decision that we have to make
--
DR. WALLIS: Effectively the whole committee --
DR. POWERS: -- at another venue, and it has to be made in
the face of seven other topics, as you recall. But, I mean, this is
intensely interesting and a very well thought out and interesting
program. I think I will have a hard time restraining members from
having an interest here. The other seven projects may take a beating
because this one is so well thought out and well done by respected
members of the community here.
MR. MAYFIELD: Again, we hope we have put together and we
think we've put together a credible program. We've worked around to get
input from interested parties. Principally it's been the regulated
industry, but we have tried to make sure we've got input from the
interested parties.
DR. POWERS: I take this as designating something as being
decided upon in the future on exactly what it looks like. One of the
things that -- every time Research gets reviewed by some outside body
like the National Academy of Sciences, they just beat you bloody about
publishing in the archival literature, reviewing it in front of learned
societies and things like that. Is that a factor at all in the thinking
here?
MR. MAYFIELD: We have already been publishing some of this
work. The one plot that we showed on the change in --
DR. POWERS: Yes, I think --
MR. MAYFIELD: -- the condition, probably -- that's --
that's in a published paper that's coming out in the next few weeks. So
some of that work is already ongoing. We're anticipating that the
dialogue Mark would have in trying to set the criterion, it would be
fodder for some interesting paper and some academic discussion.
DR. POWERS: I think you would not be remiss in contacting
your European colleagues about this program maybe through your severe
accident program or something like -- or --
MR. ELTAWILA: We are participating in the RCAS program.
DR. POWERS: Yes. I think -- I mean, it sounds fun, and it
sounds like they might be interested actually in observing if nothing
else.
MR. MAYFIELD: Well, there has been interest through CNSI;
there's also interest from some of the IAEA links in this. There have
been active programs under CNSI Principal Working Group 3 primarily, but
there is a lot of interest through the other -- some of the other
principal working groups at CSNI in this general subject.
We think as we embark on this program, we're going to see a
lot more interest from them.
DR. POWERS: I know that Farouk has good connections in the
Soviet Union, former Soviet Union and likes to travel there on a regular
basis, and he may well be able to find a full-scale test facility there
that's available for use.
MR. ELTAWILA: You remembered that. We are not going to get
into that trip whatsoever.
[Laughter.]
DR. KRESS: Well, one piece of early input is I think the
most crucial task you have in front of you is this acceptance criteria,
five times ten to the minus six. That drives everything else.
MR. MAYFIELD: Yes.
DR. KRESS: And I would jump on it first. That would -- I
would have something concrete on it before I get into the whole rest of
the thing, because it makes a big difference on what you have to do.
MR. MAYFIELD: Yes.
DR. WALLIS: We think if you can actually change that in the
right direction, the whole problem might go away.
DR. KRESS: It could go away, or it could dictate how good
these tests and things have to be if it goes the other way.
MR. MAYFIELD: Yes.
MR. CUNNINGHAM: When we talked about it internally, we came
up with two that were kind of key items, and that's one, and the other
is, if the fracture mechanics work that has been done over the last four
or five years doesn't make a compelling case, then that's another
show-stopper, if you will.
DR. KRESS: And the problem I have with acceptance criteria
is there quite often isn't a good technical basis that you can pull on.
I mean, it's what people are willing to accept.
MR. MAYFIELD: Yes.
MR. CUNNINGHAM: Yes.
DR. KRESS: And that's a tough thing to deal with in the
regulatory arena.
MR. MAYFIELD: That's right.
DR. APOSTOLAKIS: It's a policy issue.
DR. KRESS: It's a policy issue.
MR. CUNNINGHAM: It's a policy issue.
DR. KRESS: And so, you know, it might be a tough one, a
tough nut to deal with.
MR. MAYFIELD: Yes.
DR. KRESS: It's not something you can sit down and write an
equation for.
MR. CUNNINGHAM: That's right. This is coming from the --
more from the establishment of the history over the last five or ten
years in terms of what we've accepted and what policies we've set up.
DR. SHACK: We're running a half an hour over, but obviously
this was not a discussion we wanted to cut off.
DR. POWERS: A lot of interest in this. But to maintain our
own schedule, I think it's time to say thank you very much.
DR. SHACK: Mike's off to scenic Oregon anyway. We wouldn't
want to hold him up.
MR. MAYFIELD: I had the good sense to reschedule my flight
for 8:00, thank you.
DR. POWERS: It's okay, they probably have thunderstorms
there and you won't get in until midnight.
MR. MAYFIELD: Yes.
[Laughter.]
MR. MAYFIELD: Thanks.
DR. POWERS: Thank you.
Gentlemen, what I want to do now is to walk through those
presentations that we had where we have an obligation to have reports,
and to offer some feedback to the authors on those particular topics so
that we can then take a recess for a while and allow those authors to
prepare drafts of their letters.
For those that don't have letters, I will point out that you
have at your place the reconciliation on our letters from previous
meetings, and so there's plenty to keep you busy. You ought not
hesitate to offer assistance in drafting the reports to the primary
authors if you have contributions to make.
The first of the presentations that deal with reports have
to do with the proposed revision to Appendix
K of 10 CFR Part 50, and so I'll ask you, Graham, if you have some
preliminary thoughts, and then I'll ask the other members to --
DR. KRESS: Are we through with our transcript?
DR. POWERS: Oh. At this point, I think we can close off
the transcript. I'm sorry. Thank you, Tom.
[Whereupon, at 5:31 p.m., the recorded portion of the
meeting was concluded.]

Page Last Reviewed/Updated Tuesday, July 12, 2016