470TH Advisory Committee on Reactor Safeguards (ACRS) - March 3, 2000
> UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
470TH ADVISORY COMMITTEE ON REACTOR SAFEGUARDS (ACRS)
U.S. Nuclear Regulatory Commission
11545 Rockville Pike
White Flint Building 2
Friday, March 3, 2000
The committee met, pursuant to notice, at 8:30
DANA A. POWERS, ACRS Chairman
GEORGE APOSTOLAKIS, ACRS Vice-Chairman
THOMAS S. KRESS, ACRS Member
MARIO V. BONACA, ACRS Member
JOHN J. BARTON, ACRS Member
ROBERT E. UHRIG, ACRS Member
WILLIAM J. SHACK, ACRS Member
JOHN D. SIEBER, ACRS Member
ROBERT L. SEALE, ACRS Member
GRAHAM B. WALLIS, ACRS Member
P R O C E E D I N G S
CHAIRMAN POWERS: The meeting will now come to
The is the third day of the 470th meeting of the
Advisory Committee on Reactor Safeguards.
During today's meeting the committee will consider
the following: phenomenon identification and ranking table
for the high burnup fuel; proposed resolution of Generic
Safety Issue B-17, criteria for safety-related operator
actions; report of the Planning and Procedures Subcommittee;
future ACRS activities; reconciliation of ACRS comments and
recommendations; proposed ACRS reports.
A portion of today's meeting may be closed to
discuss organizational and personnel matters that relate
solely to the internal personnel rules and practices of this
advisory committee and matters the release of which would
constitute a clearly unwarranted invasion of personal
The meeting is being conducted in accordance with
the provisions of the Federal Advisory Committee Act. Mr.
Sam Duraiswamy is the Designated Federal Official for the
initial portion of the meeting.
We have received no written statement or requests
for time to make oral statements from members of the public
regarding today's session.
A transcript of portions of the meeting is being
kept and it is requested that speakers use one of the
microphones, identify themselves, and speak with sufficient
clarity and volume so that you can be readily heard.
Do any members have opening statements that they
want to make for this session?
I have been informed that Karen Faircloth will be
leaving us for a promotion in the Chief Financial Officers'
Office. Karen, you only got here.
CHAIRMAN POWERS: What, is it something we said?
CHAIRMAN POWERS: Well, congratulations, Karen.
MS. FAIRCLOTH: Thank you very much.
DR. SEALE: It's nice to know someone who works
where they keep all the money.
CHAIRMAN POWERS: Well, in that case we will move
to our first presentation. I will remind members that the
issues of high burnup fuel, the last time we heard about
them I think was about a year ago, wasn't it, Ralph?
This is this very interesting change in phenomena
that occurs as fuel gets up to very high burnup that the
trend in the industry is try to use fuel to ever higher
The Staff has established a limit on how high a
burnup they are willing to go pending additional
information. They did this based on an engineering
judgment, an examination of relevant phenomena, the results
of tests that have been conducted in France and Japan, then
they instituted a confirmatory research program with the
Office of Research.
In the course of discussing that research program
it became obvious to us that the industry has every
intention of trying to push to ever higher burnups, perhaps
going beyond the current limit of 62 gigawatt days per ton
to as high as 75 gigawatt days per ton, and the questions
come up what kind of information do we have to present to
show that using fuel to those very high levels of burnup are
in fact safe, that it would be safe to do so.
At the same time, the Office of Research is
interested in what kinds of investigations it needs to carry
out as part of its confirmatory work and Dr. Meyer has been
busy designing a research program and a process for helping
him direct that research work and so, Ralph, I will turn the
floor over to you at this point.
MR. MEYER: Okay.
CHAIRMAN POWERS: I will interject that this is a
presentation for information to the committee that we are
not anticipating writing anything on this particular
presentation, but pay close attention because this
presentation constitutes background for subsequent
presentations on this subject where there may well be a need
MR. MEYER: This morning I'll just briefly go over
what the PIRT is and why we are doing it, because we had a
lengthy discussion on this a year ago, and then spend a
little time talking about the organization and the status of
the PIRT because there have been some changes along the way
and we are nearly finished with the first PIRT that we are
going to do, the one on the rod ejection accident for the
PWR, so I will give you some results from that and then
comment on our application of the PIRT results.
The application is going to be the key to solving
the problems, and the application itself is not part of the
PIRT process and I think this will unfold as we go through
Just to refresh your memory, you will recall that
the PIRT that we are doing is a structured way to get some
technical information from a bunch of experts and PIRTs by
their nature address a specific scenario and they identify
phenomena that occur during that scenario and then you rank
the importance of those phenomena with regard to some
criteria that you define at the outset of all this.
The scenarios that we have picked are listed
herein the first bullet. The PWR rod ejection accident
DR. WALLIS: I'm sorry, I can't see because you
are standing in front of the screen.
MR. MEYER: I am in the way? Okay. Let me --
CHAIRMAN POWERS: I think if you just moved back
to the screen --
DR. WALLIS: Or to the side or something.
MR. MEYER: If I move back to the screen then I
can't see my notes.
DR. WALLIS: Then you can speak the truth.
MR. MEYER: But I want to say what is in my notes.
MR. MEYER: Okay. This one is a rod ejection
accident in TMI-1. The second one is a BWR event which
involves ATWS related power oscillations in the Lasalle
plant. The loss of coolant accident PIRT will be a
combination of the PWR and the BWR scenarios in the same
PIRT meetings and we haven't yet defined the specific PWR
and BWR scenario that we will be following, but that will be
At a later time, not scheduled in the current
round of PIRTs, we will come back and address the source
Now what I want you to notice here is these three
scenarios that we have picked are scenarios that have
regulatory criteria associated with them, fuel damage limits
in each case. The fuel damage limits are intended to ensure
that core coolability is maintained and that damaging
pressure pulses aren't generated during the event, so these
are the events for which we have speed limits, so to speak,
that keep us from getting into severe accident trouble, and
so these are the design basis accidents which we are
focusing on in the PIRT.
DR. KRESS: Did you have a description of the
scenario from previous work somewhere, you know, like the
progression of the accident in time --
MR. MEYER: Yes.
DR. KRESS: Did you take that out of what, some
MR. MEYER: It's done largely from previous work
and for example the first one that is the most complete,
during the past two years we have been doing a lot of plant
transient calculations on the TMI-1 rod ejection accident.
We had a deck from an international standard
problem and jointly with the French IPSN and the Russian
Kurchatov Institute we have gone through a very extensive
sort of round-robin calculation exercise, and we know a lot
about that particular transient.
DR. KRESS: That makes me feel a lot better. I
was afraid you got it out of the FSAR.
MR. MEYER: No, no, not at all.
Okay, phenomena -- what did I want to say about
phenomena? Nothing in particular.
In the exercise you simply identify the phenomena
and you try to rank them as high, medium or low importance.
We are not trying to find out which is the most important
phenomenon and what is the second and list them in that way.
We just want to know which ones are really important and
which ones don't matter so much, and you do that with regard
to something that you have in mind.
The something that we have in mind is that you
don't go over this cliff and get into a severe accident.
That is characterized by this long-term coolability and
avoiding the pressure pulses that threaten structures, so at
the outset we had this statement that the ranking criteria
were going to be related to fuel integrity, fuel dispersal,
long term coolability, and pressure pulses that threaten
DR. KRESS: Those don't seem to include anything
about the source term.
MR. MEYER: Not yet, no.
DR. KRESS: That is for later? You'll have
another criteria later.
MR. MEYER: That's correct.
DR. APOSTOLAKIS: So let me understand --
MR. MEYER: These events, these four events,
really don't invoke challenges, big challenges to offsite
doses. That is not really the thrust of analyzing these
DR. KRESS: You are assuming ECCS works in these?
MR. MEYER: Yes, right. The source term itself
will be considered as a separate issue, because even when
the source term is applied to the loss of coolant accident
it is this hybrid analysis where you are analyzing an event
that is successfully terminated and using a source term for
a core melt to test the containment integrity and things
These three or four events, however you want to
count them, we are going to look at them just from the point
of view of the severity of the behavior of the fuel with
regard to its long-term cooling and pressure pulse
DR. APOSTOLAKIS: Now let me understand a little
bit the criteria there. You have a number of phenomena.
MR. MEYER: Yes.
DR. APOSTOLAKIS: Typically what number are we
talking about? I mean it's not a fixed number or is it two
or three --
MR. MEYER: No.
DR. APOSTOLAKIS: No?
MR. MADISON: The number of phenomena that we have
considered is on the order of 100 and I can see where you
are going with this question and I am going there.
DR. APOSTOLAKIS: I don't know where I am going
MR. MEYER: Well, then I think you are going to go
DR. APOSTOLAKIS: Okay.
MR. MEYER: And if you can bear with me a
DR. APOSTOLAKIS: Sure.
MR. MEYER: -- I believe I am going to come back
in more detail to this area that you want to discuss.
DR. APOSTOLAKIS: Okay.
DR. WALLIS: The only thing that is different now
is that the fuel has been in there a long time.
MR. MEYER: Correct.
DR. WALLIS: All the other phenomena are the same
as when the fuel is young.
MR. MEYER: They are not all the same.
DR. WALLIS: They are not all the same. But they
haven't changed much, have they? It's really the fuel
MR. MEYER: That is really the nub of the issue, I
guess. Some of them have changed sufficiently that, for
example, in the rod ejection accident we found rather early
on -- early being in 1994 and -95 -- that the mechanism of
failure is quite different from the one that we studied with
fresh fuel. It is a brittle, cracking pellet cladding
mechanical pushing interaction mechanism rather than a high
temperature heatup oxidation.
DR. WALLIS: It is the fuel that is different, but
the actual sort of pressure temperature history and
everything is still the same?
MR. MEYER: Yes, yes.
This is a list of the kinds of questions that we
want to address with the PIRT. You are going to see as I go
through here that the PIRT itself is not going to answer
these questions directly but we believe that going through
the exercise will put us in a lot better position to answer
For example, we have now several different
cladding alloys that are being used. We used to use only
zircalloy, which is alloy principally of zirconium and tin,
with some tin in it. Now Zirlo and M5 have niobium in them.
M5 doesn't have any tin, so the question is do the criteria
which were originally developed from experimental work done
on zircalloy still apply to these other alloys. That is a
Can we perform expensive tests with one type of
cladding and extrapolate the results to the other type with
perhaps some information from less expensive tests?
Some more detail questions that come up along the
way -- pulse width, is it a critical parameter or not? We
have seen some evidence of that, and what do we do for the
BWR power oscillations. This is an event that we know very
little about in terms of the fuel response at this point.
I just want to emphasize as you look at these
questions the fact that we view PIRT as just a tool. It is
not going to answer them directly.
CHAIRMAN POWERS: It seems to me when I look at
this list of questions that there must be some background
assumptions of things that don't need to be looked at. What
I am thinking of, for example, there do not seem to be
questions that relate to the propagation or damage from
assembly to assembly or rod to rod?
MR. MEYER: Well, those questions just aren't on
CHAIRMAN POWERS: Okay.a
MR. MEYER: But I can assure you that those
questions are discussed in PIRT panel.
CHAIRMAN POWERS: And recriticality?
MR. MEYER: Recriticality -- I can't recall that
that has come up yet.
Okay, let me go on now and talk about the
organization and status of the PIRT and begin with a list of
We have literally two dozen of the world's best
experts in fuel behavior.
DR. KRESS: Give or take one or two.
MR. MEYER: Give or take one or two. You will
recognize some of the names on the list, like Carl
Alexander, who -- I have given him an extra A in his name;
I'm sorry, Carl.
But I want to talk just a minute about some of
these. I have put in bold letters, four of them. These
four resulted from the ACRS quadripartite interaction.
So you had the Japanese, German, and French
partners in your quadripartite group, and with your
encouragement, we worked through those, and these are the
people that we got back from Japan, Germany, and France.
Now, I think most of you know by now that Franz
Schmitz, who really was the dean of the group, and was
responsible for a lot of progress in this area, passed away
And so, he has been replaced by Joell Papin from
the same laboratory in Caderache, so she is working with us
DR. APOSTOLAKIS: These people are in one room and
are doing this?
MR. MEYER: Yes, yes.
DR. APOSTOLAKIS: Wow.
MR. MEYER: In fact, I will tell you that we do
occasionally use two rooms.
DR. APOSTOLAKIS: Scheduling those meetings must
be a nightmare.
MR. MEYER: Okay, we have done a little dedication
of the report to Schmitz and put an inside-the-cover page to
him, which I think was appropriate. Everybody was happy
with that arrangement.
Okay, a few more comments about the list. Half of
the names on the list came from EPRI suggestions. So we
have three names that came from NRC, ACRS-related; half of
them that came from industry suggestions, and the rest of
them, we also made arrangements for.
Now, almost everyone on this list who
participates, pays their own way; the companies pay their
own way. There are a few exceptions, a couple of college
professors and a retired guy, and we've got contracts to
support those. But by and large, the industry people who
come pay their own ways.
There are no NRC contractors on this list. That
was intentional. We thought there could be some appearance
of conflict if we put NRC contractors on this list. I'm not
sure how that thinks through clearly, but --
DR. WALLIS: Well, I know Hochreiter has a
contract. I hate to -- that doesn't seem to be a true
MR. MEYER: Hochreiter? He does --
DR. WALLIS: He has a large project, yes.
MR. MEYER: He doesn't have a contract from the
high-burnup fuels project.
DR. WALLIS: No, but he's still an NRC contractor.
MR. MEYER: Okay. We tried to avoid putting the
people that we worked directly with on this, but we used
them -- we do use them as resource people.
DR. KRESS: Did you try to get Dick Hobbins on
this at all?
MR. MEYER: no.
DR. KRESS: Is he retired?
MR. MEYER: Yes.
DR. KRESS: Okay.
MR. MEYER: And resource people, we've reached out
to our own contractors plus some others. Typically, the way
we use a resource person is, at the beginning of the
activity, they will come in and make a large presentation
about the scenario that we're talking about.
So there's rod ejection accident, David Diamond
from Brookhaven came in and made a big presentation about
the analysis that had been done in the past couple of years.
Phil McDonald from INEL came in and made a
presentation and stayed with us through one of the sessions.
Phil McDonald was the principal investigator on the PBF work
and some of the SPIRT work in the other days. So he's the
principal author on the classic paper on this subject in the
And more recently, when we switched to the BWR
subject and had our first meeting on the BWR subject, we
invited a fellow named Martin Zimmerman from the Paul
Scherer Institute who had done some work on the BWR power
oscillations, to come over.
So, we've reached out everywhere that we thought
we could benefit, and asked people to come in and provide
information to this group. And that's worked out well for
DR. POWERS: I think the Committee should really
be excited about what they've done here, because this was
our recommendation in this area, that they should reach out
broadly. It just looks to me like they've gone a mile
farther than we even anticipated they would, to reach out to
get the breadth of opinion.
MR. MEYER: Yes, it's hard to imagine reaching any
further. I mean, we've got all the U.S. fuel manufacturers
represented, universities, laboratories, foreign
DR. SHACK: Don't challenge us, Ralph.
DR. POWERS: Come on, the astronomers are
discovering these new planets all the time. You just really
have a narrow focus here.
MR. MEYER: Okay, leave it alone.
DR. SEALE: And you have a fertile imagination.
MR. MEYER: I think when we talked to you last
Spring, we were committed to this, and we were beginning to
make our plans, but we hadn't scheduled meetings, and
certainly hadn't held any meetings.
The first meeting was held at the end of August.
And then two more meetings on the PWR were held in the Fall
of the year, in October and December.
We have a number of people who travel from
overseas, and so we're trying real hard to schedule some of
these meetings close to other events that they'll be
traveling for anyway.
And we've also reduced the number of meets per
PIRT to two in our ambition to try and reduce the amount of
travel. So the work activity is pretty intense, and you'll
see that this is a four-day meeting. So they prefer to work
hard for four days, rather than have to come back at another
Now, that is a large group, and we found that it
was difficult to work with everybody in the room at the same
You're going to see in the organization of the
work in just a minute, that we broke it into two types of
technical activities, the experimental work and the
So we, in fact, have divided it into two groups
that meet in parallel. This just kind of happened
spontaneously in the PIRT effort.
And the two group leaders, who, again, arose
spontaneously, are Arthur Motta from Penn State in the
Experimental Group, and Lee Peddicord from Texas A&M, in the
So now this is kind of a semipermanent, unofficial
arrangement, that we break into these breakout groups and
these guys take over and lead the group through its paces.
Now, we have mentioned the fact that we have a
website and there is the address for the website. On the
website are several documents.
The concept of the website originally was to hold
the transcripts from the meetings. Because we had a large
group, and we thought it would be difficult for the PIRT
facilitator to keep detailed notes, we hired these court
reporters to come in and keep a verbal transcript of the
So they do that and we get them electronically and
put them up on the Web. We also have background
information, general background, the kind of thing that was
on my one of my first slides, the list of participants, the
agendas, and the schedules are put up there as soon as we
have that information.
And then we've also found a need to provide some
more specific background information, almost guidance for
the PIRT participants, prior to the meetings in the various
areas. So there have been two of these background
information papers put on the Web, one pertaining to the rod
ejection accident and one for the BWR.
DR. POWERS: Ralph, the concept of PIRT is heavily
exercised in the thermal hydraulics field, and probably
pretty well known by thermal hydraulics types.
MR. MEYER: Yes.
DR. POWERS: But you're really taking this in a
very creative move and applying it to fuel behavior and
perhaps even the source term issue. People are not so
familiar with the ideas behind PIRT.
Do you find that transition difficult?
MR. MEYER: Yes.
DR. POWERS: Are there lessons that you've learned
out of that process?
MR. MEYER: Yes. Let me just go ahead to the very
next slide which addresses that, because it was difficult.
It cost us one session.
The August/September meeting, the three-day
meeting that we had, I would describe as wandering in the
desert. We were trying to work with these high-level
criteria, and trying to list the phenomena that would occur.
And we couldn't quite put it all together. How
were we going to get anywhere with this monster?
And we had to make some practical adjustments,
which probably, for PIRT purists, makes some substantial
changes to a PIRT activity.
One of the first things that we had to do was to
change the definition of phenomena, to broaden it. You
could almost just put in the word, "stuff," and it would
work. But we have phenomena processes, processes,
conditions, properties, anything that's related to the
subject that we're going to discuss, becomes a phenomenon
for the purpose of the PIRT.
DR. WALLIS: It's very interesting, the analysis
not as a phenomenon.
MR. MEYER: What?
DR. WALLIS: Analysis may be a phenomenon. That
puts it in a new category.
MR. MEYER: Well, then in the category area, we
had to break this down into some practical elements. We
were struggling with these four areas, with the plant
transient analysis, integral testing in big machines that
cost a lot of money.
Transient fuel rod codes were being used in this.
Also, we're trying to measure mechanical properties to
facilitate the use of transient codes to allow us to
understand the experimental results to see how these fit
with the plant transient.
So at that point, after the first meeting, we
regrouped, we decided that we would list this generalized
definition of phenomena in these four categories, and we
made one other major change. That was, we backed down a
notch on our criteria.
After discussing -- trying to discuss coolability
and pressure pulse generation, we realized that we really
didn't have a database, and didn't want to get into those
areas with design basis accidents.
So nobody wants to try and talk about debris
coolability or the efficiency of a fuel/coolant interaction
in a design basis accident. So we decided, as a practical
matter, that we would roll this back to the fuel dispersal
and flow blockage, where flow blockage here, in our minds,
is like in a loca, ballooning and reduction of the flow
So, these became the criteria. Now you look at
the plant transient analysis and the experiments, and you
rank the phenomena with regard to the outcome of the
analysis or the experiment in relation to dispersing fuel or
ballooning fuel rods.
DR. KRESS: I think that was a good move, Ralph.
That probably focused a whole lot of attention on that.
DR. POWERS: I think the whole enterprise of
taking this technology that's been so useful in one field
and applying it in another is, Ralph deserves all the credit
in the world for making that, and he also deserves credit
for recognizing that a direct transfer is just never going
to be possible. You have to make some accommodations to the
vicissitudes of the field.
So I'm not surprised at all, and I think you made
some good changes.
MR. MEYER: It became very apparent after the
first meeting. The first meeting was uncomfortable. I
mean, you're trying for three days to get somewhere, and
you're frustrated, and you wander off into these deep areas
that you can't handle.
So, we made these adjustments, we wrote the first
background paper prior to the second meeting. We put it out
on the Web, we communicated with e-mail and we came back and
engaged the group in this revised way of treating a, quote,
DR. WALLIS: Are you going to cover all
eventualities about the fuel result without blocking and
still be awkward to deal with, without necessarily
MR. MEYER: Could you say that again? I just
didn't hear it.
DR. WALLIS: Well, if it distorts efficiency, it
may be hard to handle, or it may prevent some mechanical
motion of self or rods or whatever. But it won't
necessarily disperse or block flow; it just changes its
geometry sufficiently so that it would be awkward to deal
MR. MEYER: That's considered, swelling, in
particular, but also bending, getting in the way of control
DR. WALLIS: That's included.
MR. MEYER: Yes. Now, let me give you just a few
sample results. I don't want to go into a lot of detail on
this. In the plant transient analysis category, there were
probably 25 phenomenon that were ranked.
I just looked through the table and picked out a
half dozen that had really, you know, like -- we voted. Let
me digress here a second:
With a smaller group, you might come to a
consensus rather quickly on high, medium, or low. But in a
huge group like this, we decided that we would vote and
record the tally of votes on high, medium, and low.
And we asked the PIRT members only to vote if they
felt that they really had some knowledge and opinion on this
subject, so that we expected that the plant transient
analysis experts might not vote when you came to a question
about the experimental measurement of a mechanical property.
And so you don't have total votes that total up to
24. And, in fact, after doing this for awhile, it became
clear that half of the room would vote on the analysis
activities, and half of the room would vote on the
experimental activities, and so we just got another room for
them and did the work in parallel.
But what I did then was to look through the table
with the final vote tally, and pick out the lopsided votes
for high-ranked phenomena. And here are six of them that I
have on the screen here.
They're not too surprising, in themselves, but you
try and get from this, as much as you can. These last
three, fuel temperature feedback; delayed neutron fraction;
and heat capacities of the fuel and cladding, are basic
You can't do much about those, except get them
right in your codes. But the first three, the control rod
worth, the fuel cycle design, and the pin-peaking factors,
you can actually change those in the core design.
So I think of these three together as core design.
Now, this has some practical implications. Now I'm
wandering into the application part of this.
So after this is done, we're sitting back and
we're looking at this and saying, if you get some limiting
value that is a little difficult to live with, you can alter
the control rod worths and bring the deposited energy down.
Or, conversely, if you have some target fuel
enthalpy that you want to stay below, we began to see in the
presentations, that you couldn't get up to that value if the
control rod worth was not greater than such a value.
It then suggested that somehow we can use control
rod worth in combination with some other factors about the
core design, and perhaps make some equivalence to the peak
fuel enthalpy and thereby avoid doing a 3-D plant
calculation for each and every core, and simply look at the
core design and the control rod worths that you're going to
have, and reach some judgment about whether or not this is
going to exceed the fuel design criteria.
DR. UHRIG: So your fuel cycle design is -- you're
talking about 24 months, 18 months, or are you talking about
the leakage configuration, of all of the above?
MR. MEYER: All of the above. So, here is an
idea, a new idea that has come out of these discussions,
which we haven't completely ironed out yet. And this is one
of the reasons that we're not quite ready to present the
But this is one result of this PIRT activity that
I think is going to be valuable.
DR. POWERS: It looks like it's crucial, because
this is the kind of information that line organizations
would want to have when somebody proposed to go to high
MR. MEYER: Yes. And I also want to mention that
the insights that we're going to get from the PIRT activity
are not all going to come from just looking at the ranking
scores. But you've got two dozen people engaging in
discussions for three-day periods, and during those
discussions, a lot happens, and you sit there and you get
So, the activity itself is part of the equation.
DR. KRESS: Ralph, the delayed neutron fraction,
it strikes me as a strange one to be in here, because I
would have thought, number one, it has a one-to-one
relationship with burnup. And it seems to me, like there is
very little uncertainty in what you know about it.
So that even thought it may have a real impact on
what you do with the transient, how the transient goes, it
seems like you know enough about it, and it's only related
to burnup itself, that I don't know where I'm going, but I
was surprised to see it ranked as high.
I guess --
MR. MEYER: Which one was that?
DR. KRESS: The delayed neutron fraction.
MR. MEYER: Oh, the delayed neutron fraction, yes.
DR. WALLIS: I'm really surprised that cooling of
the cladding doesn't come into it.
DR. KRESS: Well, I think that fuel temperature
feedback implies something about how you calculate the
temperature, too. But these things go so fast, that --
DR. WALLIS: But it's still pretty rapid cooling
DR. KRESS: I know, but I think these things are
almost adiabatic, aren't they?
MR. MEYER: It is nearly adiabatic. The transient
is -- the pulse has a half width of about 30-50
milliseconds. And the fuel has a time constant of three to
five seconds. So, you don't get a lot of heat transfer but
you do get some.
DR. WALLIS: If you heat up the cladding, then you
probably heat up some water as well.
MR. MEYER: Yes.
DR. POWERS: I think that on the delayed neutron
fraction, I think you're right that if you ask me about a
specific piece of fuel, that I probably can calculate the
delayed neutron fraction with a fair degree of accuracy.
When I use these codes, I don't use that number; I
use a fudge factor to give me an average. And at least one
of the NRC contractors has written on this subject, saying
that we need to look at it.
And my recollection is that Dave Diamond was doing
some uncertainty analyses on that aspect of the calculation.
MR. MEYER: Yes. I think it was his presentation
that led to this ranking.
There are also some interesting things that don't
make the high list, and one of them was rate of reactivity
I think a lot of us who weren't specialists in
that area thought at the outset that rate of reactivity
insertion was going to be a big actor. And it wasn't.
As long as you can get the reactivity inserted in
about a couple hundred milliseconds, it doesn't matter.
DR. POWERS: I recall lots of questions in this
room, exactly about transients in the experiments being too
short. And people complained that the experiment were
I think what you're saying is that as long as
they're about right, it doesn't make a lot of difference.
MR. MEYER: Yes. Now, the next group of phenomena
are the integral experiments. These are the experiments
like at Cabris or at NSRR.
And, you know, at first, these don't look very
surprising, but burnup of the test rod, there was a lot of
discussion about burnup of the test rod. After you
understand a little bit about the failure mechanism for
these high burnup rods, and realize that the hydrogen
embrittlement of the cladding is a major factor, you can
begin thinking that, well, the actual burnup of the test rod
may not be so important, as long as I've got the right
amount of hydrogen in the test rod.
And you might get that in -- you know there may
not be a one-to-one coupling between burnup and oxidation,
which leads to the hydrogen, because the oxidation is also
affected by how high the temperature is in the plant, and
the water chemistry.
But n further probings the group realized that the
burnup itself is going to lead to fission gas distributions
on the grain boundaries in the pellet, and these are going
to perhaps have a big effect on the implied loading on the
DR. KRESS: I was going to ask you about that
particular thing. Now that you are on it, I will. I would
have thought somewhere in there you might have been -- the
amount of time the fuel sits around after burnup, before you
put it in, would be an important consideration just because
you change that distribution of fission gases on the grain
boundaries and you age the grains themselves and change that
grain structure a little bit. Was that one of the
considerations? Usually you don't just have the fuel right
there after burnup -- it sits around.
MR. MEYER: I don't think we talked about the time
that it would sit around at room temperature, but we talked
about the preconditioning that might take place in the test
reactor when you are warming up and getting ready for the
DR. KRESS: Yes.
MR. MEYER: There the discussion focused more on
what you might do to the distribution and orientation of
hydrides in the cladding rather than on the fission
products, but nevertheless the fission product issue
promoted the burnup of the test rod to a high ranking and
what this means in a practical way in our interpretation is
that if you are going to go from 62 to 75 gigawatt days per
ton burnup that you need to test rods with burnups up to 75
gigawatt days per ton and not just stop with rods that have
62 gigawatt days per ton but a lot of oxide on them, which
we have in our test programs.
DR. KRESS: I think that is a real good insight
MR. MEYER: The coolant heat transfer conditions
during the tests obviously have implications with regard to
whether you can be satisfied with tests in a sodium loop or
whether you need to test in a water environment. That one
is pretty transparent. Pulse width during the test was also
discussed a lot and thought to be important.
There are, however, two aspects of the pulse that
were not high ranked. They were only medium ranked and
maybe one of them was low. I have forgotten, but there have
been two concerns expressed about the pulse and the power
One was about the shape of the pulse. In Cabri we
had one test with a big double humped pulse. They were
trying to get a broad pulse and it is very difficult to
operate the valves in the Helium 3 system fast, and they
didn't get a good operation of the valves and they got two
pulses sort of merged together with a clear dip in the
middle. I thought that that was bad news, but I was
probably the only one who thought that was bad news.
Everybody who discussed it thought no, it doesn't matter so
much as long as you get the enthalpy in the fuel, right, is
the integral of that thing more than the shape of it that
The other related parameter that was discussed was
the power history during burnup accumulation in the power
plant before the rod is tested.
DR. KRESS: I would have thought on the pulse
width that you were right. If it is broad pulse width or
humped like that you have a problem, but I would have
thought that as you come down in the pulse width you will
reach a place, a width, beyond which it doesn't matter
anymore, and that would have been -- so as long as you stay
within the given pulse width that you'll be all right. Did
that come out?
MR. MEYER: Well, there is a feeling that for the
very narrow pulses that there is some -- I don't know if I
am going to get this right -- coherency in the expansion of
the gas on the grain boundaries and pushing out fragments,
grain size fragments of the pellet, into the cladding, which
might if given a little more time to spread out not
contribute so significantly to the mechanical --
DR. KRESS: That's why I thought it would be
maximum pulse width beyond which you wouldn't want to go,
but if you are within that narrow range, it doesn't matter.
MR. MEYER: Well, but the thinking is the other
way around. If you get too small you get an extra kick from
the fission gas and as long as you get above a certain
amount you don't get that kick and then it's just the
thermal expansion of the pellet which is related to the
enthalpy that you get into the U02.
DR. WALLIS: Well, if it is rapid enough, you have
to worry about sort of wave-like transient propagation of
things. It's more like an explosion than the swelling --
very short transients.
MR. SIEBER: I presume that when you are talking
about agglomerates in the test run you are talking about
plutonium particle size?
MR. MEYER: Yes.
MR. SIEBER: Did you go to the extent to figure
the effect of the particle being hot enough to burst through
the cladding during the pulse?
MR. MEYER: What we had presented to us was some
metallagraphic examination from the Cabri test with mixed
oxide fuel. Now these have the minus MOX fabrication route,
which does result in plutonium-rich agglomerates. I think
it's 50 percent UPU mixed oxide in those agglomerates. It's
not pure PUO2, and from those results they did not see
melting or gross microstructure change in the vicinity of
the particles so there was the feeling that the extreme high
temperature wasn't the main actor in the MOX effect which
was seen prominently in these Cabri tests but rather that
the MOX effect was related to a high burnup rim around each
Sort of like the rim that we talk about around the
outside of a UO2 fuel pellet at high burnup, you have these
ultrahigh burnup islands with their own rim around them, so
this is the current thinking on this, and it is not the high
temperature part, so I think the melt-through of the
cladding would not be thought to be an important process at
the moment based on what they have seen.
MR. SIEBER: There were a number of experiments in
a test program called the Plutonium Utilization Program in
MR. MEYER: Yes.
MR. SIEBER: Done by the Battelle at Hanford. Are
you familiar with that?
MR. MEYER: Yes.
MR. SIEBER: Okay. They did get clad perforation
on those tests.
MR. MEYER: Yes. Well, when we looked at the
transient fuel rod codes, and for us the transient fuel rod
code is FRAPTRAN, you find some conclusions, some high
ranked phenomena that seem pretty obvious, but they may have
some not so obvious implications.
For example, the gap size is obviously going to be
a high ranked thing because you have the pellet expanding
and pushing on the cladding to generate the stress that
leads to the fracture. If there is a gap between the pellet
and the cladding, the pellet has some free movement before
it starts applying the stress, so getting the gap size is
obviously going to be important.
It strikes me from just sitting and listening to
the discussions and putting two and two together that in our
code the gap size is based largely on temperature validation
of the code rather than the mechanical part. Now we do have
some, because we do look at axial elongation of the
cladding, which is a result of gap closure and lockup, so we
have some indirect ways of measuring the interaction between
the pellet and the cladding which then gives you information
about the gap closure, but I would want to look back at our
code and to see if there is any need to tune up the gap size
modeling such that it not only hits the temperatures right
but it also hits the mechanical interactions right.
Now I am not sure that it doesn't do that, but I
am just saying when you go through this you get these kinds
of implications that cause you to go back and look at some
of your models.
DR. KRESS: Did you say your code was FRAPTRAN?
MR. MEYER: FRAPTRAN is the new incarnation of
DR. KRESS: FRAP-T, okay. I hadn't heard of
FRAPTRAN. Are we going to see that code sometime?
MR. MEYER: Yes. FRAPTRAN is going through its
validation assessment now, and we are planning a peer review
this summer and so we will have the assessment and the
documentation, the peer review, then revisions and then the
publication of the documentation. That is taking place this
DR. WALLIS: Does this code assume things like
cylindrical symmetry to make things simple but maybe miss
some real phenomena that way?
MR. MEYER: Yes. It does.
One other thing -- here is one that was not ranked
high and that was the mechanical properties of the pellet,
because in the equations you have got a pellet that can give
and the cladding that can give, and you have got the model
on both. Well, pellets are a lot stiffer than the cladding
is and so getting the pellet model accurately is not as
important as getting the cladding model accurately.
We currently have a rigid pellet model in our code
and we are not sure yet that that is not sufficient.
DR. WALLIS: As long as it is intact.
MR. MEYER: As long as what?
DR. WALLIS: As long as it is intact.
MR. MEYER: Yes.
And then finally we looked at things important in
making mechanical property measurements. There is really
not a whole lot that jumps out here that would be of
interest to talk about.
We were looking at such things as the way you
select specimens and design specimens, and it was clear to
everyone that the detailed shape of these ring tensile
specimens, for example, is extremely important.
And we have been working on this for a couple of
years now, and this work has spread around to other
laboratories. We've been working with cooperating with
So it's really not a surprise when you reach out
and get the experts, and you've been working with them
already on this subject, that you find out that you're on
the right track and you really need to do those things.
DR. WALLIS: The thing that concerns me about
PIRTs is when there is a lot of extrapolation of experience.
It seems to me that the actual base of knowledge for really
high burnups is very skimpy.
MR. MEYER: Yes.
DR. WALLIS: So all of these experts are
extrapolating their experience.
MR. MEYER: Yes.
DR. WALLIS: And it becomes more and more
guesswork, the further out they get.
MR. MEYER: Yes. But we don't have an empty
slate. We do have a lot of data for the reactivity
transient, but much of that was obtained under conditions
that weren't ideal.
But you still learn from those things. And also
in the loca transient, there is preliminary information in
France, and we're on the verge of getting these data
ourselves now in our program at Argonne.
So the one where we really have the least to go on
is the BWR transient.
DR. POWERS: I noticed that on your previous
slide, you had a MOX callout on that. How much is MOX
figuring into these PIRT activities?
MR. MEYER: Not a lot, but let me tell you the way
that we do this, and you can see exactly how it's done.
We look at the specific sequence, and it's
specific right down to the fuel type. So, in the case of
TMI-1, it's a 15 x 15; it's zircalloy four; it's UO2
pellets. And it's got a certain enrichment and oxide
thickness, and everything is assumed.
And then we go through the exercise. At the end
of the exercise, we ask ourselves several extra questions.
And we go back through each phenomenon, and the question is,
would the ranking, high, medium and low, change if you now
went from a UO2 fuel to a mixed oxide fuel?
And you can go through large lists of phenomena
and say, no change; and then you find one that would change.
And we do the same -- if you change the cladding type from
zircalloy to zirlo or M-5, would the high, medium, and low
Was there another one that we did, Harold?
MR. SCOTT: Burnup.
MR. MEYER: Yes, burnup. We did this for 62
gigawatt days per ton, because 62 gigawatt days per ton is
the burnup limit for which the NRC has said we will provide
the confirmatory work. Going from 62 to 75 is the
So we did the basic exercise at 62, and then we
asked the question, if you went from 62 to 75, would the
ranking change. And you go through each and every one of
them. And those are tabulated in the report.
This is what the report looks like in paper. The
report is on the website in its entirety, and it's kept up
to date. We use it as a working draft, and it's in a
near-final condition, but there will be some more changes on
this one, even though we've moved on now to the ATWS PIRT.
DR. POWERS: So by the time you're done with this
particular item, you'll have a pretty good idea? I mean,
somebody could look at this and have a pretty good idea that
it says if I want to go to 75 gigawatt days per ton, the
kind of information I need to have available for the NRC
with respect to rod ejection accidents is here. I mean,
it's listed down for you.
I would really like to just say, yes, to your
question, but I think there is an interpretive step in
DR. POWERS: Okay.
MR. MEYER: I can't tell you for sure that our
conclusions and our applications of the PIRT will match up
with what the industry does with it. I hope so, but --
DR. POWERS: I wouldn't presume to say that the
industry would follow it blindly, but with the purposes -- a
hypothetical industry guy comes in and asks, what do I need
to bring, that you're happy with my arguments on 75 and has
something to point to.
MR. MEYER: Yes, yes.
DR. POWERS: What he actually brings may be up to
MR. MEYER: Yes. Okay, this is my last slide and
there's not much on it. It just say that we're now working
on an application for the PWR rod ejection case. I think we
cannot only see light at the end of the tunnel; I think we
can see the tunnel clearly enough that we can get out
without bruising ourselves too much.
There will be some additional work required, in my
opinion, to get there, but it's not endless; it's finite.
And we have a draft document with this written down. It
simply hasn't been reviewed. It will be changed and
adjusted, and that's the document that I would have really
liked to have discussed with the Committee, but it was
clearly not ready for discussion.
But I do want to leave the impression that we
think we know what to do with this, with regard to the first
event type, the PWR rod ejection accident. And when we work
out the details of our plan for resolution, then we'll be
able to discuss that with you.
MR. SIEBER: When do you think the report will be
ready in paper form as a final, not necessarily approved?
MR. MEYER: Well, we're probably not going to make
a large paper distribution of this report. The whole agency
is moving towards a paperless existence.
DR. SEALE: Well, will it be on the Web?
MR. MEYER: It's no the Web right now; it's there
MR. SIEBER: Reading a couple hundred pages off
the screen is tough.
MR. MEYER: Well, you need to get Matt to print it
for you. He's got a good printer.
DR. POWERS: We've got at least a draft of the
MR. EL-ZEFTAWY: Yes, I'll print it from the Web
and distribute it to all the members.
MR. MEYER: We have made one decision relevant to
this question, though, and that is, we're not going to
finalize the first PIRT report until we finish all of them.
DR. POWERS: All right.
MR. MEYER: As we move into the subject of the BWR
ATWS, we remember, oh, we forgot something on the PWR. And
we have to go back and make that adjustment.
They're all sitting on the Web. They're available
to anyone. I don't expect the changes to be major, but
we're not going to issue them with publication dates until
we're finished with the last one.
DR. POWERS: Okay.
MR. MEYER: That's all.
DR. KRESS: Ralph, what I heard so far and see so
far just validates my original impression that this was a
stroke of genius to go this route for this particular issue.
I think you're on the right track, and it looks very
MR. SIEBER: Yes, it is.
MR. MEYER: I really have to give credit for
Farouk Eltawila for the idea of pushing us into the PIRT
DR. KRESS: It certainly is an application that
has a lot of excitement.
DR. POWERS: I think it makes us seriously think
about lessons learned.
DR. KRESS: Yes. I agree, that that might be a
really good addition to this, lessons learned from applying
a PIRT to this particular application. It might be a real
good little thing to put out, some sort of document on that.
DR. POWERS: For your brethren who are going to
have similar problems of reaching out. When the Committee
has written before that we think especially in these areas
where you're going into something new, it's useful to reach
out and try to find out what the world knows about these
But it would stun and appall me if we could take
what the thermal hydraulicists have said is and use it
MR. MEYER: Yes.
DR. POWERS: I think what you found is, no, you
can't do that.
MR. MEYER: It's just very different. I mean,
with a thermal hydraulic code, you're modeling the
phenomenon, so you go down the phenomena one-by-one, but
here we're trying to resolve a regulatory issue.
And it involves more than just a code with
DR. BONACA: I have a question regarding the
scenario where you discuss the PWR for the ejection
accident. You're looking at a classic reactivity insertion
resulting from the ejection.
MR. MEYER: Yes.
DR. BONACA: And are looking at how likely the
event is going to happen. I mean, one issue that was
debated for a long time was, typically what you postulated
is the extreme event, which is rod ejection at zero power
with all the rods inserted, et cetera.
MR. MEYER: Yes.
DR. BONACA: It's an extremely unlikely event
because of what you have to assume, I mean, including the
rupture of a nozzle and the ejection. And then you have, of
course, hardware up there that will prevent the ejection.
MR. MEYER: Right.
DR. BONACA: So you're not looking at all to the
MR. MEYER: No. I would say, to the contrary. We
did, and you have to go back two years to the time when we
were developing the agency's high burnup program plan.
At that time, we did an explicit, albeit very
simple, risk assessment of each of the issues in the program
And there was no question that all of the design
basis accidents have low frequencies of occurrence. But
when you're talking risk, you obviously have to have
consequence, so you can't just hone in on a higher
probability even that can't lead to a consequence.
And consequence means essentially melting fuel and
getting big fission product releases. So, the PWR rod
ejection accident that had been the traditional design basis
accident, stayed on the plate after that little examination.
But the corresponding rod-drop accident for the
boiling water reactor didn't, because what we found is that
there is this other reactivity-related event, the power
oscillations related to an ATWS, that are higher probability
and probably -- although we're unable to do a real risk
analysis, we can see that the type of damage to the fuel
could be serious enough to lead you into consequences.
And so our conclusion was that the power
oscillation for the BWR was a higher risk event than the
rod-drop for the BWR, and so we have turned our attention to
DR. BONACA: Okay.
DR. KRESS: There is in the plans, you said, some
time to repeat this exercise for the source term?
MR. MEYER: Yes. We don't have it schedule.
DR. KRESS: That's down the road some time?
MR. MEYER: The reactivity-related events and the
loss of coolant accidents will be finished up this year.
And I would expect that we would try and schedule the source
term one in 2001, but it is not scheduled at this time.
DR. KRESS: It will probably concentrate on locas
MR. MEYER: I would think you would have to take
several severe accident sequences.
DR. KRESS: Okay, you may want to take some.
MR. MEYER: For the source term, you're probably
going to have to take three or four sequences.
DR. KRESS: It's probably sufficient to just take
a low-pressure accident these days.
MR. MEYER: Okay, it might be.
DR. KRESS: You can look into it.
DR. POWERS: Well, good. Do members have any
DR. POWERS: Dr. Meyer, that was just an excellent
background briefing. That was very helpful to the
DR. SEALE: Yes, super.
DR. POWERS: And we look forward to a presentation
on final interpretations and whatnot. Just keep us informed
on your progress.
MR. MEYER: Okay.
DR. POWERS: Thank you a lot. I am going to
recess till 10:30.
CHAIRMAN POWERS: Okay, let's come back into
session. We turn now to the topic of the proposed
resolution of Generic Safety Issue B-17, criteria for
safely-related operator actions. I think this is a subject
that has been before this committee a couple times in the
Professor Seale, I think you will lead us on this
DR. SEALE: Okay. As you all know, we have been
trying to encourage our way through the resolution,
disposition of all the -- as many of the generic issues as
possible. We have two of them here, closely related --
B-17, which is old enough to drink --
DR. SEALE: -- and B-27, which is old enough to
DR. SEALE: And hopefully we will hear from the
Staff to dispose of these.
Now there is a record of prior committee
consideration of these two issues. Back in November of '95
we had a proposal from the Staff to close this issue out on
the basis of the endorsement of an proposed ANSI ANS
Standard 58-8, 1994, time response design criteria for
safety-related operator actions.
The committee reviewed this proposal and took
sharp exception to it on the basis primarily that the times
that were identified for operator action in the standard
were based on information which was not readily available to
either the -- well, to the public -- and that there were
proprietary restrictions on the availability of that data
that made it inappropriate for a standard of this type.
So as a result of that, why that proposal was
withdrawn and now the Staff is coming forward with an
alternative approach to this, a different tack. We also
understand that there is a possibility of reconsideration
action on the standard, and basically what we want to do
today is to, first of all, look at the proposal from the
Staff as to how they propose to resolve these issues, and
then secondly to hear a little bit about any plans they have
for this standard to see whether or not there is going to be
any effort to address the concerns we had earlier when we
looked at that.
Jay Persensky is going to be giving us our
presentation and you have a couple of your colleagues, Rossi
MR. ROSSI: I am Ernie Rossi. I am the Director
of the Division of Systems Analysis and Regulatory
Effectiveness and we have Jack Rosenthal, who is the Branch
Chief of the Regulatory Effectiveness and Human Factors
Branch here with us, and we have Harold Vandermolen, who is
the person who is basically in charging of closing out and
prioritizing and all the other actions associated with
generic safety issues in the Office of Research, but Jay
Persensky is going to be the person who gives the
presentation today and --
DR. SEALE: -- the guy in the barrel.
MR. ROSSI: -- and Harold Vandermolen will pull
him out of the barrel if necessary, and I'll watch, okay?
DR. SEALE: Very good.
MR. ROSSI: Thank you.
DR. SEALE: All right, well, Jay, why don't you go
MR. PERSENSKY: Good morning. Actually Bob stole
a lot of the first couple of slides here by going over a
very detailed history of where we were a while ago. As
indicated, I will be making the bulk of the presentation.
Harold is here particularly to answer any questions on the
cost benefit issue, and Paul Lewis is also here, who helped
to develop this approach and gather the information for it.
We did send a memo on February 17th with our
approach described in that, which would close out both
Generic Issue B-17 and GI-27 with no new or revised
As Bob indicated, there is a long history -- B-17
was first identified, the best we can make out, in about
1978, which is pre-TMI, which is an important element in our
approach to closing this out.
B-17 basically says that in some cases plants
required operator action and that in fact operators may not
be able to take the appropriate action in time, therefore
they have to do a study and determine whether or not it
should be automated. That was the basic intent -- should we
automate something or should we leave it as an operator
action, and they have to take credit in their FSAR for that.
GI-27 is very similar. It came up later on, but I
will get into that in a minute. The proposed solution was
set up some time in the mid-'80s and we are not even sure
who came up with the issue or the idea of closing it out
using 58.8. It just seemed because of the title and
everything else that it would be an appropriate way of
closing out this issue, since it was to set up criteria for
We monitored the development of that standard. We
had either contractors whom we were involved with actually
in the development of that standard through about 1994, when
it was published. In 1995 the Staff proposed to endorse it
with Reg Guide 1.164 and at that point we felt that we could
close out the issue. ACRS did not support the endorsement
and they had very strong words and very strong opinions with
regard to the use of the information in 58.8. I won't go
into that again.
So we were sent back to the drawing boards and it
probably was a good thing.
DR. WALLIS: I'd like to ask that the emphasis
seems to be here on time rather than the operator's taking
the wrong action.
MR. PERSENSKY: The emphasis was that it could be
done correctly in the amount of time available. That was
assumed and that was the basis of a lot of the data
DR. WALLIS: After TMI was there a concern with
MR. PERSENSKY: There was concern with
inappropriate action all the way along as far as I know. I
mean that was always there was time to do it correctly.
CHAIRMAN POWERS: I think it is fair to say that
the standard in the Staff thinking was a pretty disciplined
examination of the kinds of things that you take into
account on operator action -- does the operator diagnose the
problem, does it accurately diagnose it --
MR. PERSENSKY: Yes, and there were, if you go
back to 58.8 there was essentially a timeline formula that
would get into questions of diagnosis action time. The
action time was important. There was the whole series of
things within that and it was based on collection of
In any event, after your clear statements, we went
back and took off our blinders. We said we have been
following this one path for a long time but we took off our
blinders and said, okay, what other ways can we look at
this? How can we look at this differently?
Again, remember this was written pre-TMI, the GI.
After TMI there were a lot of things that
happened, particularly with regard to operators. There was
improved training. Simulators were now -- well, every plant
has its own simulator now a site-specific simulator. EOPs
were changed. In fact, that was part of the problem with
the original data for ANS 58.8 was that there was a change
in procedures during that time, so there were a lot of other
activities that were going on that we feel now actually meet
the intent of B-17 and that is why we think we don't need
anything else to do the same thing that is already been
We feel it can be closed with no new or revised
MR. ROSSI: Let me just follow up with what he
just said about closing it with no new or revised regulatory
activities. I think as we go through this we need to keep
in mind that the major purpose of the effort on this Generic
Safety Issue is to make a decision on whether we need to
impose new actions on the part of licensees as a result of
this issue and in order to close it out.
In order to impose new requirements on licensees
we have to have a disciplined and good reason for doing
that, and so we have to keep that in mind as we are doing
it. That is the real question. Do we have a basis and need
for imposing new criteria on licensees or do we have a need
to ask the Staff to do additional things in this area to
ensure that where manual actions are required by the
operators that there is a reasonable assurance that they
will perform them within the time limits allowed and they
are available and that they will do it accurately, so I just
want to have you keep that in mind.
MR. PERSENSKY: Okay. As I said, B-17 was based
on the fact that plants did require certain actions. In
some cases they could be done manually. If they could not
be done accurately in the time, then the plant was to make a
decision to automate that action.
In 0933, which the Generic Issue Management
System, there was some work done -- again this would have
been in the mid-'80s -- indicating that it would include
requiring plants to perform task analysis, simulator
studies, analysis and evaluation of operational data, and it
was the approach that proposed and because 58.8 has some of
that already built into it, that was one of the reasons they
suggested at that time to move in that direction.
Around 1993 Issue 27 came up, and that was just
titled manual versus automated actions. It was based on the
fact that they had been doing some reviews of plant design
and emergency procedure reviews and said maybe we should
look at this again. In that issue, though, it was said to
be subsumed under B-17 -- if we dealt with B-17, we dealt
then with Generic Issue 27 as well.
I think formerly if it is stated to be subsumed,
it's already closed or listed on the closed list, but we put
it in here just so you are clear that we are addressing it
DR. WALLIS: But it's not closed until B-17 is
MR. PERSENSKY: Right -- well, no. It is listed
on our list of things as closed. Once it is subsumed under
something else we count it in terms of our bean count, but
the scope is still covered. The intent of it is not covered
until B-17 is closed.
The justification that we are proposing for the
closeout again is really a series of other regulatory
actions that have taken place since B-17 was identified and
primarily those things that happened after TMI.
There are a number of requirements, training,
simulators, operator licensing, EOPs, increased staff that
are all basically thing things that have changed. As you
might remember, I just mentioned that they talked about task
analysis, simulator studies, review of operational
If you look at the training rule which is in 10
CFR 51.20 and for the operators in Part 55 they both
indicate that training programs are supposed to be based on
systems approach to training.
Well, a systems approach to training specifically
talks about doing task analyses to identify what are
learning objectives and performance objectives. From those
then developing tests to make sure that people have
accommodated through the training to be able to do the tasks
that are called for in task analysis. So here is part of it
that has already been identified through that process and if
they can't perform the objectives then there is a problem.
If they can't perform it because there just isn't
enough time, then the plant would have already made the
decision to go ahead and automate --
DR. APOSTOLAKIS: Yes. I had a question on this,
as I looked at the slide. This, if I just read the slide
without listening to you, it looks like the emphasis is on
how to make sure the operators will actually be able to
perform a function within a given amount of time -- training
and so on -- but this amount of time comes from physics,
thermal hydraulic calculations and so on. I mean this is
the timed window you have, right --
MR. PERSENSKY: Correct.
DR. APOSTOLAKIS: -- on the system. So my
question was, and I guess you answered it partly, is there
may be some situations where it is nearly impossible for the
operators to actually or with reasonable assurance to
perform that function because the time is simply too short.
I mean you can't train people to do the impossible, but you
just said that if that's the case we take care of it
MR. PERSENSKY: Yes -- well, it would have to be
taken -- if they cannot meet the performance objectives, and
this is also true if we take the issue of operator
licensing, that is where we really get into the picture,
because with operator action operator licensing we have them
using plant-specific simulators that have all those physics
in them and thermal hydraulics in them. If they can't pass
their operator licensing examination, so they can't perform
the operations necessary to pass a licensing examination,
then there is evidence there that something has to be fixed
and it can't be trained in, it can't proceduralized in, then
we have a reasonable assurance that they can do it, that the
plant would have done something else in order for us to
license their operators.
It's sort of an indirect approach to it, but
nonetheless it's what we consider a performance based
approach, because we are looking at it in terms of the
performance of the operators -- can they perform the tasks
within the time required based on the simulator examinations
and that builds in those thermal hydraulics and physics.
DR. APOSTOLAKIS: There is a mechanism, formal
mechanism, for handling these things, these situations?
MR. PERSENSKY: Yes.
DR. WALLIS: Now if I applied defense-in-depth, I
would say, well, I have to look at the contingency that the
operator doesn't do the right thing and therefore I put in
some other thing to back up in case the operator screws up.
MR. PERSENSKY: Correct.
DR. WALLIS: And you are saying we don't need
anything like that?
MR. PERSENSKY: That is part of the analysis that
they have to do in their FSAR in terms of do they have
defense-in-depth. That is all part of building up --
DR. WALLIS: Yes, but this wonderful
defense-in-depth that we invoke is there because you are
uncertain whether something will really happen the way you
thought it would.
DR. APOSTOLAKIS: Well, if you are a
structuralist, you don't need any analysis.
DR. WALLIS: I am not an anything. I am just an
independent thinker on defense-in-depth. I have been told
it's a good thing to think about.
DR. BONACA: Many of these transients are --
DR. WALLIS: So you are going to tell us that you
have enough assurance that the operators will do the right
thing, you don't need a backup system of any sort?
MR. PERSENSKY: No. This is not addressing a
backup system. This is addressing the system that would
replace operator action.
DR. WALLIS: Well, you could have a backup --
MR. PERSENSKY: And in the backup systems --
DR. WALLIS: -- if they haven't done it by a
certain time it happens by itself, sort of.
MR. ROSSI: Let me just try something here and see
if this helps. The nuclear power plant is designed and in
the design they automate some things and they make some
things require operator action when they do the initial
design, so the design is done and then they have to do a
series of analyses of that design to show what happens
during various transients and accidents.
We have a deterministic way now which we are going
to change to a risk informed way of doing that, but we go
through the analyses and we take single failures and we
assume various things and we assume that the operator will
do the actions that are required to be done by operators in
the analyses and we show that given all of that the plant is
The next thing that happens is the plant gets
built. They build a simulator that is very, very similar
and there are requirements on how similar and good the
simulator has to be that simulates the actual operation of
the plant, and then we have the operators who are going to
run this plant and they get run through the simulator, they
get run through the testing program. Well, first they get
trained on what they are supposed to do, and then they get
tested on the simulator and they have to pass that test in
order to get their license.
As a matter of fact, I guess we take other actions
if we find that a large number of the operators can't pass
the test during a period of time -- then the utility is on
the spot for looking at their training program, so the point
is that they get tested and then they get retested and
retrained from time to time.
MR. PERSENSKY: It is a continuous process.
MR. ROSSI: Right.
MR. PERSENSKY: The requalification process,
especially for the operators, requires that they go through
certain testing -- training and testing continuously, most
of them on a six week basis, and each one of those includes
some time in the simulator, and at each -- they may not get
tested on every one of the scenarios every time, but there
is a sample of scenarios that they go through so that there
is -- again, what we are looking at is are we confident,
reasonably assured, that the operators can handle the tasks.
That, the plant requires of them. And if they
can't, if none of the operators can, the we're going to shut
down the plant until they can make that happen.
MR. ROSSI: Or even a large percentage or a
moderate percentage. If they are having difficulty getting
MR. PERSENSKY: If they don't have enough people
to staff the plant because they can't accomplish the task.
Let's face it, this happened in 1978, and we have yet to
shut down plants because of that.
DR. WALLIS: I understand all of that. It just
seems to me that one could still realize that human mistakes
are one of the major causes of a screwup at a plant. Do you
have any backup system if they do this?
And that would be the idea of defense-in-depth.
You're saying that they're so well trained, nothing is going
to go wrong.
MR. PERSENSKY: No, there are things, and I'm not
MR. ROSSI: I was going to say one other thing,
and that is that along the road, the emergency operating
procedures have been designed. We've got a philosophy on
how they ought to be designed, and that philosophy is
basically symptom-based emergency operating procedures.
And they have a lot of the things that you're
talking about, built into them. The operators are supposed
to look for the symptoms, and they're supposed to do certain
And those are basically built into the emergency
operating procedures, including, I believe, the use of
backup systems where something doesn't work.
And they get trained on those, again, and they get
tested on them.
MR. SIEBER: I think it's important to think a
little bit about what happens during an accident scenario in
the control room, you know. The plant is designed to
respond automatically to the Chapter 15 design basis
And the operator does very little except verify
that all these functions have taken place. And if they
don't, then they try to restore that function.
And the backup systems, however, come into play in
a PWR, all the way down to the switch from ejection to
recirc, which should -- at times can take an hour or so.
And so the job of the operator is to monitor
what's going on by looking at his control board, analyze and
diagnose the accidents and know which branch he is on,
depending on what his instruments tell us.
So, if everything works in the plant, the
operator's job is little more than reading instruments,
verifying settings, flows, temperatures, pressures, and so
If you try to go beyond that and automate the
backups when a failure occurs, that process becomes very
complex. And somebody would have to be knowledgeable, be
there to intervene in case the actuation of some backup
would interfere with the primary recovery of the plant.
So I don't think that automation to a second,
third, or fourth level is totally advisable, given the kind
of training and the way the plants are automated now.
Perhaps you can comment on that, but that's my experience,
MR. PERSENSKY: Well, generally that's the case,
and that's where we get into some things that are happening
now, though, in a sense, that some automated systems are
being turned off.
MR. SIEBER: Okay.
MR. PERSENSKY: That's just not the purpose of
this generic issue. It's another step.
MR. SIEBER: Okay.
MR. PERSENSKY: But, again, the whole purpose of
this generic issue was for the plant in the design process,
to make a decision as to whether or not something should be
MR. SIEBER: Right.
MR. PERSENSKY: And a basis for it was time, but
it was time to do the work correctly.
MR. SIEBER: Right.
MR. PERSENSKY: And all we're trying to say here
is that we have regulations or regulatory actions in place
that allow us to know whether or not the plant and the
operators are doing that, performing the job properly. It's
really, like I said, a performance-based approach.
DR. WALLIS: And you have a measure of those? All
you've said so far is qualitative, but you have a measure
which is through some PRA technique that the system now in
MR. PERSENSKY: Can I get to that? We're going to
look at that in a minute.
DR. WALLIS: You need some quantitative criteria,
I think, eventually.
MR. PERSENSKY: Well, we have a quantitative
criterion in the sense, as we said, that operators have to
be able to accomplish the tasks that come out of the task
analysis. It's a one or a zero from that standpoint.
And that task analysis is a function-based, based
on the functions of the entire system.
DR. WALLIS: But will they do it? That's the real
MR. PERSENSKY: That's the basis of HRA, you know,
what people will do when they're faced with different
situations. And that may be -- that's a topic, I think, of
some other discussions where you have coming up next month.
DR. BONACA: But I am interested, however, in this
criteria, in part because, although a lot of things have
happened since TMI -- and I totally agree with your point
here -- still at other plants, you have conditions
occasionally where you have a new situation, and you're
evaluating whether or not you can dedicate an operator to go
somewhere, do something in 20 minutes, and would it be
Decisions are being made and criteria being used
for licensing those, so I would be interested in hearing how
you go about doing that.
MR. PERSENSKY: I think we covered a lot of things
already. What I've got on here is operator licensing, the
licensing program, plant-specific simulators. These are all
things that have happened, again, since TMI, since this
thing was initiated.
Before B-17 was initiated, there may have been
four or five simulators in the country, if that. Now, every
plant has its own simulator, people are trained on it,
people are examined on it.
It includes the functions that the operators have
to deal with. And we are involved with that process. If
they don't have enough people to do the exams or to carry
out operations after exams, they may not operate.
Ernie mentioned emergency operating procedures.
Prior to TMI, we did not have the symptom-based emergency
operating procedures; the symptom-based operating procedures
were put into place after TMI.
Back in the late 80s and early 90s, the agency
actually went through and did a detailed inspection of
emergency operating procedures at every plant. I know in
some cases, not all of them, this included -- well, it
always included actions outside the control room, not just
actions inside the control room. So it's not just the
things that are in the simulator.
But we walked-down the procedures with them to
make sure that, again, those actions could be accomplished
in accordance with the procedures. The procedures, again,
are based on task and function analysis.
These are the same kinds of things that we've
talked about before: The function task analysis, operating
experience; these are all things that are built into the
development of those procedures.
And the staffing rule was put into effect in the
early 80s, which, in fact increased the number of people in
the control room so that you have more people to do the
task, so that it increased the minimum requirements of
people, if necessary.
With regard to the PRA aspect of it, the IPE
program, part of the IPE program was to go out and to
identify vulnerabilities through the use of PRA techniques.
Are there vulnerabilities out there that have to be dealt
Licensees did identify and considered the
time-critical safety-related operator actions as part of
that process. If, in that process, they found that there
were problems, again, they were to go out and fix those
problems. And they could fix it with automation or some
other way that would satisfy the Agency.
There's a list of important human actions in NUREG
1560, which is the lessons-learned report, so those are
things that we are particularly concerned with.
The primary scenarios are the switchover, which
was mentioned in B-17; feed and bleed, and depressurization
and cooldown. These are the more important of the human
actions with regard to the PWRs.
DR. POWERS: There is a lot of controversy about
switchover of suction from the flow into the core.
MR. PERSENSKY: Yes.
DR. POWERS: Some of them are automatic and some
of them are --
MR. PERSENSKY: Yes, in fact, I think all the CE
plants are automated. And there's a certain amount of other
plants that are. The issue -- and if we can step on to the
next slide, really -- as you know, the burden is on the
staff to demonstrate that the implementation of the generic
issue meets the requirements of the backfit rule.
We feel that, in fact, through this deterministic
or performance-based process, we already have done that by
saying we've got things in place; we don't need new
regulations to deal with it.
So we did not initially do our own cost/benefit
analysis for B-17, and this was one that was specific to
B-17. But we did find that there was a cost/benefit
analysis done for automatic ECCS switchover to
recirculation, which was Generic Issue 24.
DR. POWERS: ACRS signed off on it.
MR. PERSENSKY: ACRS reviewed and signed of on
that document, and it essentially said that backfitting from
manual to semiautomatic system or fully automatic system is
not justified under cost/benefit basis.
So we're using that, since -- in fact, it's
probably the most risk-significant of the scenarios that we
talked about. Now, Harold is here if you have any questions
on that particular issue.
Finally, on our conclusion slide, we find that
there is both a technical and regulatory basis, because
these are already regulations or requirements in place that
we can close the issue.
Most of these things have taken place since the
promulgation of -- all of them have taken place since the
promulgation of the GIs. Plant-specific vulnerabilities
have been identified in the IPEs, and part of that whole
program was to then, based on those PRAs and IPEs, to
address those vulnerabilities.
I think this is a more performance-based approach
rather than a deterministic approach to closing the issue
and therefore we request a letter from the ACRS supporting
closure of B-17. Questions?
DR. WALLIS: You sounded to me pretty persuasive.
The thing that gives me a little uncertainty is the human
error part of it, of course. Human error has been assessed.
I just don't know with what sort of certainty it can really
be assessed in a quantitative way.
DR. UHRIG: But isn't there some evidence that
training has sort of reached a saturation point where the
error rate doesn't go down any further?
MR. PERSENSKY: There is some evidence of that. I
think there is also a question of what to focus on in the
training. I mean we have been looking at that through the
accreditation program with the industry, but there is some
baseline human error probability. What that is --
DR. UHRIG: So you may be getting there with your
MR. PERSENSKY: The contribution of training to
that. There may be other ways of reducing error or reducing
the probability of error that aren't covered, depending on
how effective is the --
DR. UHRIG: That is the question, yes.
MR. PERSENSKY: Yes, how effective are they, but
human error is considered as part of the IPEs. It was
considered in the cost benefit analysis that was done for
Generic Issue 24. There are techniques out there that we
are looking as an agency at improving techniques, coming up
with better techniques -- as well as the industry as a
whole, both internationally and here in the U.S. as to how
to address that kind of problem.
DR. BONACA: I'm sorry, go ahead.
MR. SIEBER: That's specifically why the STA was
put on shift.
MR. PERSENSKY: I forgot to add that one. STA
isn't on there.
MR. SIEBER: The shift supervisor or the SRO in
charge is telling operators what to do following EOPs and
the STA is supposed to be standing back to say is the
diagnosis right, did they fail to do something that they
should have done, or did they do something that they
shouldn't have done, and so that becomes the second view or
the defense-in-depth or the human error portion of the
operating curve and, you know, what else can you do?
DR. BONACA: My question was to do with
irrespective of the GSI and the closure, and I personally
believe that the situation has changed today and you have a
good position there, but there are still circumstances where
people are dealing with having to make a decision on whether
or not an operator action is adequate.
If I can think about it, a recent example
concerned with inadvertent actuation of safety-injection on
PWRs where people have tried to resolve the issue of
bleeding PORVs by isolating block valves, and now the issue
is how do you deal with inadvertent actuation. Do you have
enough time to deal with it should you resolve the issue
that way, and I know some utilities have proposed, in fact,
that you have -- you can keep your block valve closed and
with inadvertent actuation they are trying to demonstrate
they have enough time.
You are talking about maybe eight minutes or five
minutes or whatever, and there is an issue of what
information do the licensees and the Staff use to propose in
fact a solution of that type and to accept on the part of
the Staff a solution of that type.
I would like to know what kind of information and
I will tell you where I am going. In absence of other
information, they are going to still rely on this ANSI
standard irrespective of the GSI closure, okay? I just am
interested in knowing what do they rely on, because they
have to make these tough decisions.
MR. PERSENSKY: There are some NRR Staff here that
may be able to address it more fully than I can at this
point. There is a Generic Letter 97-78 that went out that
talked about just that kind of issue --
MR. GALLETTI: Information Notice.
MR. PERSENSKY: I'm sorry, Information Notice --
the author is here, Greg Galletti -- and in that there were
options, ways of doing it, in terms of describing it and in
that document they in fact refer to ANS 58.8.
What we are doing in addition to that -- this is
the backup slide -- is that since we do have to review
license amendments for this type of issue -- we have the
Information Notice. NRR has also asked RES to develop risk
informed guidance for review of these license amendments.
We have a draft inhouse. It is under review at
this point for that guidance, and it addresses a number of
ways to approach it. It essentially requires a
site-specific as opposed to a generic analysis.
MR. BOEHNERT: Jay, can you move the slide over a
little bit? We can't see the whole thing. Thank you.
MR. PERSENSKY: I'm sorry -- what are the actions,
what is it that has to be done and it goes into various
steps of how you would make a presentation or make a
decision on that and how we would make a decision.
For your information, because I know there's some
concern about 58.8, at this point it cites 58.8 as a source
for checking your plant-specific information, that you have
to go through a process of determining the appropriate
times. The appropriate actions and to test them out on the
simulator -- 58.8 is in this document, only as a way of
looking at it as a sanity check or something like that or
possible check, so that is the current status. Again, this
is still in review. We have not necessarily agreed with
that guidance. When it comes to the point where I think it
is ready for review we would be glad to bring it down to the
ACRS for you review, but that is where we are on it.
CHAIRMAN POWERS: Okay. I think it is unavoidable
to not be interested in this because the history of ANS
58.8, I mean in 1995 the database, the proprietary database
that underlay 58.8 was old then --
DR. SEALE: Yes.
CHAIRMAN POWERS: -- has not gotten younger since.
It was developed with older simulators. It was developed
with older sets -- I wonder how useful it is, though I guess
I agree with you, Jay, it provides a pretty good framework
for looking and saying how I did it and how other people did
it, did I do it -- is there any validity.
MR. PERSENSKY: Well, it's how you do it and as
far as the actual numbers -- I think the important part of
58.8 was the formula or that timeline type of formula they
established in there. Here are the different parts of
CHAIRMAN POWERS: Breaking it down into cognition
and action and things like that.
DR. SEALE: Yes, there is the question of the
specifics of 58.8 and then there is also the question of
what pedigree do we expect of something that has the status
of a standard.
CHAIRMAN POWERS: They are two different things.
DR. SEALE: Yes, they are two different issues and
we are interested in both.
MR. PERSENSKY: And it may be that ANS needs to go
back and look at --
CHAIRMAN POWERS: Yes, ANS definition needs to go
MR. PERSENSKY: -- at anything new that has come
up that we can use and improve the actual criteria that are
in that standard.
DR. SEALE: Well, the thing before us now is even
a third issue, and that is the resolution of B-17.
You have given us your presentation.
CHAIRMAN POWERS: In summary, it seems to me what
they have said is it's taken care of by all the other things
that have gone on and if there is a plant out there that has
some deficiencies in it, it is a plant-specific issue now
and not a generic issue.
DR. SEALE: More than that, I think it is
noteworthy that we have here an example of an issue that is
now resolved on the basis of a legitimately made claim.
That it's a performance-based resolution, and it's
interesting, really, interesting, as opposed to a formula
like AMS 58.8 suggested.
Are there any other questions from any of the
members of the Committee?
DR. POWERS: I guess the question that comes up
immediately mind, though it doesn't have anything to do with
this question, but it does have to do with operator action
times and databases for those: I assume those things still
exist, and the issues still exist and questions and things
like the ATHEANA code and like that.
Are we doing anything to gather data in that area,
or is that still a troublesome point?
MR. PERSENSKY: Well, we don't have a dedicated
program to go out and gather that data. We have been
talking, for instance, with Halden about a lot of the data
that they have from their simulator studies, and that they
will be collecting in the future from their simulator
studies, as to how we can best mine that data.
DR. POWERS: Yes.
MR. PERSENSKY: So that is one place. As we get
submittals for changes, if people are providing simulator
data in those submittals that we can review, that can start
building up further information.
DR. POWERS: I have always wondered, especially on
the identification of a problem, how transferable data are
from one culture to another. The actual physical act of
carrying something out, I bet is very transferable.
But the problem diagnostic process, cognitive part
of the process, it's not obvious to me that information from
Finland is transferable to Japan.
MR. PERSENSKY: I think some of that data is.
Whether it's all or not, we have not done a study in that
With the -- you mentioned bringing up Halden is
the fact that they have been doing everything in the past on
the Finnish simulator with the Finnish operators, but they
now have a PWR that's based on the Fessenheim plant in
France, and they have access to French operators. They will
soon have a BWR simulator that will be based on the -- I
think it's Barsebeck. It's one of the --
DR. UHRIG: Forsmarc.
MR. PERSENSKY: Forsmarc, yes, in Sweden, which is
very similar to a lot of other BWRs in Sweden. They would
have a lot of access then to Swedish operators.
We have been making a concentrated effort to get
more involvement of our U.S. utilities. In that last EPRI
meeting in Charlotte, the Halden people came to make some
presentations, and there was a lot of interest in more
participation from the utilities in that effort.
But that is, again, one source of data. It's one
that we have probably more control over or more access to
than the utility simulators.
DR. UHRIG: There have been some attempts to make
this type of thing independent of cultures. Specifically
there is the EPRI work with the BWR in Formosa.
The essence of what they did was to put in an
expert system. They found that the use of that really
didn't help their best operators very much, but it did take
the new operators and the average operators and bring their
performance up to the best level.
So, I think that type of thing is almost
independent of a culture.
MR. PERSENSKY: The other aspect of it is that
there are certain things that we can look at in other
applications. If we got data from FAA, though it may be a
different situation, that there are still some things in
terms of time to do something, whatever that action might
And we are looking at cooperation with other
agencies in those areas.
DR. POWERS: I would think that issues of
complexity and things like that might have some
MR. PERSENSKY: Yes, and it's interesting.
DR. SEALE: Okay, any other comments or questions?
DR. SEALE: Does staff have anything else they'd
like to ask?
MR. ROSSI: I don't think so, thank you.
DR. SEALE: Well, thank you. I guess we'll have a
draft of a letter here for folks to comment on shortly.
MR. BORCHERT: Jay, I need that last slide for the
record, if you could give me a copy. Thank you.
MR. PERSENSKY: Yes.
DR. SEALE: Mr. Chairman, I give it back to you.
DR. POWERS: We will recess till 11:30, and we can
dispense with the transcript.
[Whereupon, at 11:18, the recorded portion of the
meeting was concluded.]
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