Thermal-Hydraulic Phenomena - August 23, 2001
Official Transcript of Proceedings
NUCLEAR REGULATORY COMMISSION
Title: Advisory Committee on Reactor Safeguards
Thermal Hydraulic Phenomena Subcommittee
Docket Number: (not applicable)
Location: Rockville, Maryland
Date: Thursday, August 23, 2001
Work Order No.: NRC-389 Pages 200-223/392-404
NEAL R. GROSS AND CO., INC.
Court Reporters and Transcribers
1323 Rhode Island Avenue, N.W.
Washington, D.C. 20005
(202) 234-4433 UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
+ + + + +
MEETING
ADVISORY COMMITTEE ON NUCLEAR REACTOR SAFEGUARDS
(ACRS)
THERMAL-HYDRAULIC PHENOMENA SUBCOMMITTEE
+ + + + +
OPEN SESSION
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THURSDAY,
AUGUST 23, 2001
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The Subcommittee met at the Nuclear
Regulatory Commission, Two White Flint North, Room
T2B3, 11545 Rockville Pike, at 8:30 a.m., Dr. Thomas
S. Kress, Acting Chairman, presiding.
PRESENT:
THOMAS S. KRESS Acting Chairman
F. PETER FORD Member
VIRGIL SCHROCK Consultant
JOHN D. SIEBER Member
ACRS STAFF PRESENT:
PAUL A. BOEHNERT
MEDHAT EL-ZEFTAWY C-O-N-T-E-N-T-S
AGENDA ITEM PAGE
Reconvene/Opening Remarks. . . . . . . . . . . . 202
NRC/Industry Resolution. . . . . . . . . . . . . 204
Revised EPRI Report. . . . . . . . . . . . . . . 211
NRC Review of EPRI Report Results and. . . . . . 392
Concluding Remarks
P-R-O-C-E-E-D-I-N-G-S
(8:30 a.m.)
CHAIRMAN KRESS: The meeting will now come
to order. This is a continuation of the meeting of
the ACRS Subcommittee on Thermal-Hydraulic Phenomena.
I'm Tom Kress. I'm acting chairman of the
subcommittee since the real chairman is out of the
country for the moment. ACRS members in attendance
are Peter Ford and Jack Sieber. Also in attendance is
ACRS consultant Virgil Schrock.
The purpose of today's session is to
review the resolution of issues associated with the
Electric Power Research Institute Report TR-113594,
"Resolution of Generic Letter 96-06 Waterhammer
Issues". The Subcommittee will gather information,
analyze relevant issues and facts, and formulate
proposed positions and actions, as appropriate for
deliberation by the full committee.
Mr. Paul Boehnert is the Designated
Federal Official for this meeting. The rules for
participation in today's meeting have been announced
as part of the notices of this meeting previously
published in the Federal Register on July 30th and
August 15th, 2001.
Portions of today's meeting session will
be closed to the public to discuss EPRI proprietary
information. A transcript of the meeting is being
kept and the open portions will be made available as
stated in the Federal Register Notice. It is
requested the speakers first identify themselves and
speak with sufficient clarity and volume so that they
can be readily heard. We have received no written
comments or request for time to make oral statements
from members of the public regarding today's meeting.
If you recall we had a meeting on this
subject previously, I forgot the date, in January was
it? For the benefit of those of you who might not
have been here, we had some problems with the
resolution of the waterhammer issue that had to do
with the test apparatus that -- to measure the
quantity of air that got released and became an air
cushion. We thought the results would be apparatus
dependent.
In addition, I think we had some problems
with the product of the heat transfer coefficient and
area for the condensation to steam on the liquid
surfaces. So today I think we're going to hear how
EPRI intends to deal with those two issues. Who do I
call on, Mr. Tatum to start the meeting?
First, I'll ask, do the members have any
comments before we start? Virgil? No? Okay, with
that, we'll turn it over to you.
MR. TATUM: Good morning. I just have a
few introductory slides I want to present here
primarily to -- it's been awhile since we met on this
subject. I just wanted to in the way of introduction
revisit what the issue is briefly and provide, I guess
a perspective as far as where the staff is in terms of
our review and whatnot. So let me go ahead here again
with this first slide.
First of all, let me see, that's not the
first slide, this is the first slide. There we go.
Now, first of all, Generic Letter 96-06 the topic that
we're talking about here has to do with waterhammer
and the proposed or at least the accepted methodology
in the Generic Letter was that that was part of
NUREG/CR-5220 which is very conservative. I think
everyone recognizes that to be the case.
And EPRI about two years after the Generic
Letter was issued established a working group to try
to come up with a methodology that would be less
conservative but adequate for addressing the issue and
it's involved a lot of testing, research, analysis and
data and whatnot to try to come up with this
methodology and EPRI and the working group have met
with the ACRS Subcommittee now on two previous
occasions.
Issues have been raised. The working
group has gone and done additional research and
testing and here they're back today for the third
meeting to try to address the remaining significant
issues so we can get on with our SE and resolution for
the participating industry group, industry utilities
anyway.
Just in the way of introduction, I'm Jim
Tatum from Plant Systems Branch, one of the technical
reviewers for the topic. We also have Gary Hammer,
Walt Jensen, who are also involved with the review.
Beth Wetzel is the Project Manager and the responsible
SCS manager is John Hannon, Plant Systems Branch and
George Hubbard is the supervisor.
Just to revisit the specific issue that
we're dealing with here I've borrowed a couple of
figures from the EPRI submittal. Basically, I think
this is Figure 2-1, I think from Volume 2 of the
report.
Essentially, what we're looking at, the
issue boils down to if you have a LOCA or a main steam
line break event in containment, what you have is the
containment fan cooling units stop operating if you
have a loss of power that is concurrent with that and
the heat from the containment or from the accident,
then is transferred to a stagnant cooling water system
because if you lose power, of course, until the
diesels are loaded, you don't have flow through the
system.
And so the concern essentially boils down
to whether or not during that period of time you have
steam formation, and if you do have steam formation,
whether or not there's a significant waterhammer
concern as a result of that. Now, if you look at the
typical fan cooler for a plant, and this is very
representative, I think of most plants but you have a
number of -- a series of heat exchangers basically
that a fan or multiple fans will force the air through
the heat exchangers.
You have a tube fin type arrangement and
it tends to be very efficient in the way of heat
transfer. So the concern is that as the fans coast
down during the event, the heat from containment, from
the containment atmosphere is effectively transferred
into the fan cooler unit and the water in the tubes is
contained in the tubes that has become stagnant will
heat up and boil and in many cases you will get steam
formation.
Now, there is some variance among the
plants as to whether it's a closed loop system,
whether you have a static head on the system, and
those are plant specific details where the utility
determines whether or not or to what extent they
actually have boiling. However, the EPRI member
utilities that are involved with this effort
obviously, experience boiling or there wouldn't be a
need for them really to participate in this group, per
se, and they're trying to establish a way to
effectively conclude that they don't have a problem or
at least minimize any modifications that they would
have to make to address the problem.
And they have found that by using the
analytical approach, that's proposed in NUREG/CR-5220,
that significant modifications could be required and
by using what they've established as an alternate
approach but apparently conservative, they would have
to do much less and demonstrate that they would not
have a problem in dealing with the event, should it
occur.
Now, from the last meeting there were a
number of issues that were raised. I've tried to
characterize those here on this slide. Basically, I've
broken them down into those that were raised by the
Thermal-Hydraulic Subcommittee last time around and
those have been already mentioned I think for the most
part. As far as the NRRL staff, you know, based on
our review, we had a number of open items that we
wanted to pursue further with the working group and we
have done that and had additional discussion.
Also the EPRI group has made a couple of
submittals; one, to address the HRS Thermal-Hydraulic
Subcommittee issues and that was -- the submittal I
think was July 10th that we all received. Then there
was a subsequent submittal after that to address the
NRC staff concerns. It was a separate letter that we
received and we've had some opportunity to review that
and have additional discussion with the working group
about resolution of those items. But this was kind of
the position --
MEMBER SCHROCK: Excuse me. Could you
comment just a little more in depth on which part of
the problem you've thought about this "h" for
condensing heat transfer? Specifically, does it deal
with the heat transfer by condensation during
compression of the air/steam mixture in the column
closure case. Is that the one that you're addressing?
MR. TATUM: Yes.
MEMBER SCHROCK: That is.
MR. TATUM: Yes, uh-huh. That was the ha
-- it was the "h" from the "hA" term for the
condensing heat transfer.
MEMBER SCHROCK: Yeah.
MR. TATUM: Yeah.
MEMBER SCHROCK: Well, I missed that
meeting in January and as I read this new material it
occurred to me that there ought to have been
discussion and maybe there was and I simply didn't
catch it in what I read, about the issue of using a
constant value of h.
MR. TATUM: Uh-huh.
MEMBER SCHROCK: Is that going to get
addressed here today?
MR. TATUM: I believe that's something
that Altran is going to discuss. That was actually
discussed to some extent I know with the staff and I
think it was also discussed to some extent at the
meeting, if I recall correctly. But I'll defer
further discussion. I think we need to hear from
Altran on that particular topic. It's one of the
issues that's on the table.
MEMBER SCHROCK: Okay.
MR. TATUM: If that's okay with you. I'm
not really -- you know, I'm interested as well in some
of this final discussion on these issues.
As far as the current status of the
technical review, this hasn't changed, this review
comments. They remain the same as they were last
time. We still believe that the effort that's been
put forth by industry to establish the analytical
methodology is a very good effort. They've done, I
think, a good amount of testing, correlation of data
and tried to make sense of the work that they've done
and through the PIRT process have tried to establish
where they need to focus their attention and
resources. And I think for the most part, they've
done a very good job and the staff is pretty pleased
with the work that has been done to this point.
Also, we recognize that the level of
expertise that has been involved in their selection of
the expert panel members, I think was very good and it
helped essentially to address many of the issues that
have come up. So I want to go ahead and acknowledge
that here at the beginning here. And having looked
over the latest submittals and whatnot, you know,
there still remains at least in our mind, we -- and I
characterize these as areas of continuing review. We
really haven't reached a conclusion. We probably need
to think a little bit more in these areas.
And some of these areas are topics for
discussion here today. They were recognized during
the previous meeting and we still need to understand
for example, I think in our mind the two major issues
that we need to understand better are the air release
fraction and the scaling of heat transfer surface are.
But in addition to those, we have several other issues
that we're still thinking about, still evaluating and
still discussing with the working group and I've
identified those here just so you know where the staff
is with respect to our evaluation of the submittal and
whatnot. These are the issues that remain open for
us.
And having said that, I think we're ready
to move onto the EPRI presentation and hear what they
have to say about resolution of the remaining items
that were raised at the last Thermal-Hydraulic
Subcommittee meeting. So I guess, Vaughn, Vaughn
Wagoner will be making the introductions and initial
presentation.
MR. WAGONER: Thank you, good morning.
I'm Vaughn Wagoner, Chair of the Utility Advisory
Group for this issue that we are working with
resolution of the Generic Letter. We're all set
there? Okay, I guess by way of introduction just for
the record, we have here with us today Dr. Peter
Griffith and Dr. Fred Moody and Dr. Tom Esselman with
parts of our expert panel as well as our consultant
we're using on this, Greg Zysk, who's worked
extensively on the analysis work itself.
Not here with us today is Dr. Ben Wylie.
I think he's out somewhere in the wilds and was unable
to join us today and also Dr. Avtar Singh from EPRI,
who had worked with us from the EPRI perspective. So
we're here today hopefully to address the remaining
questions that have been raised relative to what we've
been doing, present to you some of the results of
additional testing, et cetera, that we've done.
Just by way if introduction, very brief,
I just want to run back through a couple of things.
How do I make slide changes? Okay, thanks. When we
started into this after the Generic Letter came out
and the concern was raised, several of us recognized
that there were lots of information around on high
pressure waterhammer phenomena, but there wasn't a lot
around on low pressure stuff and there wasn't very
much at all around on low pressure waterhammer where
there was a potential for air release and cushioning
and those kinds of things.
So recognizing what we had were events
that were occurring at atmospheric or sub-atmospheric
or slightly above atmospheric pressures, we recognized
that we needed to do some additional work to try to
understand that phenomena that could potentially occur
in the power plants. So we set about trying to do
that, understand the phenomena and ultimately to
understand how it relates to piping support loads
because that's the analysis and that's the
qualification process when it's all said and done.
And quite frankly, when we looked at it
from just a pure waterhammer perspective, you take
peak waterhammer loads, input them as static loads and
then build pipe supports and frankly, that appeared to
be the wrong thing to do. I don't have a PhD but my
experience in a power plant has been is when we have
waterhammers, the more you tighten up the system and
the more rigid you make it, the more things you tear
out of the wall. So it looked like the wrong thing to
do, to go in and just start putting more steel in to
address these peak Joukowsky type loads from these
waterhammers.
So we started to look at it and say, "What
makes sense"? So we went through and did the work.
We've done modeling. We've done plant specific models
and generic models to understand the phenomena from
the time the pumps shut down and the fans coast down,
till the pumps come back on with the power sequencers,
et cetera. And we've looked at single coolers. We've
looked at multiple coolers. We've tracked steam
bubbles throughout the system and looked at how they
interact. So we done that phenomenalogical study.
Did I pronounce that right, and we're into the
process.
And we've went through the -- we've looked
at how then we can -- what the magnitude of those
loads are and then how they translate through modeling
into loads, into the structure that we can understand.
And let's see, I'm sorry, we should be on the next
slide. That's where we are. And so we went through
that process and developed a user's manual that
provides guidance for how a utility takes what we've
learned and applies it to the plant.
It's not a cookbook, a 100 percent
cookbook. It gives you a process and within that
process there are places where you can use the
information that's in the user's manual. It's backed
up by the Technical Basis Report or there are places
where you have to supply plant specific information
because the process, it doesn't encompass every detail
of plant specific. So there are some things that
you've got to dig out.
But we've identified that based on
comments from both technical and user friendly
comments from review by staff and review by ACRS
members and we have incorporated that and we've built
a process flow chart. And if you'll look at the flow
chart, we provide places where, "Do this step out of
the user's manual. Here's one that's plant specific.
If you get into this region, you've got to go pull the
plant specific".
For example, model basic system
hydraulics, that's a plant specific thing that you
have to do. That's an input to get into the process.
So anyway we've set the user's manual. Now, these
have been outlawed in schools because kids point them
at each other's eyes. My wife's a teacher.
But having -- like I say, we've set it up
so that it delineates where you use the process and
where there are plant specific inputs. So we
appreciated that kind of comment. We've had it
reviewed by utility folks. The utility folks can use
it, can understand it. So I guess what I'm trying to
say is we think we've built a process that, in fact,
can be used by the utilities.
And that Technical Basis Report has got a
number of topics in it. We've been through these with
you and with the staff at various stages. We're going
to come back and hit on two or three of the basic
areas that we're talking about. Air release is one of
them. Built within here in the scaling of "h" and "A"
and looking at the -- how our test apparatus and our
testing in general that's been done is applicable to
larger pipe sizes and we're going to talk about those
area.
One of the things I wanted to do before we
get into that is just take a look at it from a
perspective that as utility members we look at things
a lot in a risk informed world and in an engineering
applications world, what makes sense and I wanted to
share with you where, frankly, I think we are in a
what makes sense perspective. The first thing is,
we're dealing with an event much less than 10-6 and
frankly, when we looked at -- when we looked at the
plants that are participating, even to get it up to
10-6 we had to assume the simultaneous occurrence of
the LOOP and the LOCA over a 24-hour period.
Now, design basis is simultaneous. So to
get a 10-6 in 24 hours, you take it down to the 30 to
60 seconds that this phenomena is occurring in we're
up to 10-9. So first off we're dealing with a
probability of event in the first place that's much
smaller than 10-6. We're into the 10-9, some plants up
to the 10-13 range. Of course, that's why separating
or getting rid of simultaneous LOOP/LOCA there's other
efforts going on within the industry and the
regulation to throw that out as a design basis event,
period, and that's why, because we're dealing with
such a low probability.
But that's the starting thing. There's
already margin in the capacity of the pipes, as you
know. There's ASME Code margins and things like that.
We're dealing with pressure impulses that we're
calculating in 600 psi range with a burst test
capability of tubes and piping of over 3,000 psi. So
there's a huge margin even if the phenomena does occur
to bursting. And then what's really got to happen is,
we've either got to burst something or we've got to
shake it so badly that it deforms and bursts.
And frankly, folks, there just ain't
enough energy in these low pressure events to make it
happen. We just don't seem to be able to get there
from here. Inadvertently, these systems have been
banged a lot during start-up. And you have a shut-
down system, you do LOOP testing, the service water
pumps shut down. The system drains down. You fire
them back up. We don't have auto flow controls that
we'd like to have and we bang these things and they
get banged a lot.
Those are close to Joukowski-type loads
because that's just water hitting water, no steaming,
no bubbling, no air release, no anything that goes on
in there. And the systems have withstand it and have
for years and years and years. And, frankly, the more
flexible the system, the better they stand it because
the energy is dissipated by the pipes dancing around.
We've watched them, we've video taped them. And the
pipes dance around a little bit and you go on about
your business.
So the bottom line is, we think between
the structural margins that are inherent in the
design, we've got the low energy that's available and
this really 10-9 probability event that we're looking
at, there's no way that we'll ever compromise a safety
function. The bottom line is we've got to deliver
cooling for -- post-accident cooling, we've got to
deliver the cooling through the containment and we've
got to maintain the integrity of the containment
because these pipes are part of containment boundary
and we just don't see any way that we're going to
violate this.
Now, we can argue a little bit about is
the air really 52 percent or 48 percent or stuff like
that, but frankly, we think that we're at a big enough
picture where we banged them close to Joukowski type
stuff, nothing happens. The thing is going to boil,
there's going to be some amount of cushioning. We can
argue about exactly how much, but frankly, we think
we're there. We think we understand the phenomena,
that we're not going to violate a safety function.
And with that, I guess I'll turn it over
to --
CHAIRMAN KRESS: In those events you say
were pretty much the Joukowski banging water against
water, why didn't those have air in them?
MR. WAGONER: Well, what happens, there's
no LOCA, so there's no heat.
CHAIRMAN KRESS: Okay.
MR. WAGONER: No boiling. It's just you
know, the containment is sitting there 80 or 90
degrees, 95 degrees maybe.
CHAIRMAN KRESS: Okay, you didn't boil off
first.
MR. WAGONER: That's right, that's right.
CHAIRMAN KRESS: Okay, appreciate that.
MEMBER FORD: Vaughn, forgive me, I'm
learning here. In your remark you said early on in
operations you got a lot of this banging and bucking
around, and therefore, that is where you came up with
the 10-9 originally or a 10-6 frequency. How would
your argument change if you made the same -- made the
same argument 30 years down from licensing when you
might have environmental degradation in your piping,
I mean, fatigue, a crack of some sort or vibration
induced fatigue crack, would you then be so sure that
you wouldn't have a problem?
MR. WAGONER: Well, two responses. One is
the frequency was not determined by the early testing.
That frequency actually has nothing to do with this
testing. It's just a frequency looking at the
combined probabilities of a small, medium or large
break LOCA and a LOOP event the loss of offsite power.
MEMBER FORD: Okay.
MR. WAGONER: So that frequency came from
looking at that phenomena, I mean from those events.
Secondly, in several cases because -- and frankly,
because of the Generic Letter, we looked at the -- I
know of several plants that looked at -- because the
piping moves around, we did fatigue analysis. We
actually measured displacements at critical areas and
looked at fatigue and usage factors over the rest of
the life of the plant. It's not a concern.
And then the systems like this, depending
on plant specifics, may be monitored for things like
erosion and stuff like that. So they would always be
in a position to have maintained at least their design
basis through the life of the plant. So my
engineering response would be, not an issue.
MEMBER SCHROCK: I'm not clear on your
response to Tom concerning Joukowski type events that
occur routinely. How does this occur? Do you have
vacuum voids in the system occasionally? What -- how
does that happen?
MR. WAGONER: What happens is particularly
at coolers that are above sea level, whatever sea
level at the plant above the water level, and we do
loss of offsite power testing, so when you do loss of
offsite power testing, the plant goes black and for 20
or 30 or 40 seconds, however long it takes the diesels
to fire up and in the load sequence to tie your pumps
back on. And so during that black time, then God
makes the water drain to seek, you know, the gravity
level.
So during that time, you can get voids
that form in the system and then when the --
MEMBER SCHROCK: You're imagining these
voids to be pure vacuum.
MR. WAGONER: Yeah, or close to it, yes,
otherwise there would be leaks in the system.
MEMBER SCHROCK: That's what I wonder
about.
MR. WAGONER: Well, if you had leaks in
the system, we'd have water in primary containment,
because that's where the concern about leaks would be.
And we don't have leaks in the primary containment the
service water.
MEMBER SCHROCK: But you have gas in the
water.
MR. WAGONER: Okay. So it would be some
release but it wouldn't be any release from boiling
because the stuff typically would not boil at the
temperatures that it would be at.
MEMBER SCHROCK: I guess my reaction to
your explanation is it's a little too broad brush to
believe that it's truly Joukowski level pressures.
MR. WAGONER: And I wouldn't argue with
you on that but there has been some measurements of --
some pulse measurements and --
MEMBER SCHROCK: Okay.
MR. WAGONER: Okay? Any other questions?
With that, I'll quit and -- I guess I would say at
this point, that handout was the non-propriety
portion.
MR. BOEHNERT: All right, we're going into
closed session now.
MR. WAGONER: Yes.
MR. BOEHNERT: All right, go to a closed
session transcript.
(Whereupon, the Subcommittee went into
closed session.)
(12:52 p.m.)
CHAIRMAN KRESS: I guess one of the main
things we need to do now is decide what to present
during out one hour and 40 minutes to the full
committee so that you can convince them as well as us
things are okay. So is there -- I do think you need
to answer the three questions; the R evolved during
the various conditions, the "h" and along with the "h"
the scale-up question. So is there -- the question is
how to condense that down to an hour and 40 minutes,
including the time that is going to get eaten up by
the questions of the full committee members.
And keep in mind, we'll have Graham Wallis
back and we'll have George and Dana here, so like 50
percent of the time at least.
MR. BOEHNERT: Let me stop you a second.
The staff, did they have any concluding comments or
any concluding presentations comments.
CHAIRMAN KRESS: Yeah, that might be well
worthwhile before we totally decide on what we can.
MR. HUBBARD: This is George Hubbard.
John Hannon had to leave but the -- you know, from the
staff's standpoint and, you know, taking a management
perspective in looking at the risk versus the burden
of this issue, I think the question that comes up is
has EPRI provided a methodology in which is either
conservative or reasonably is reasonable assurance
that a utility can take the information, do their
calculations and then apply the various what is the
gas or air that's released, what is the steam volume,
and go through and make a reasonable assessment of
what are the loads on the pipe and do they need to
make a change or add steel as Vaughn says.
The thing that I think we're seeing is
that we see that the -- there is a methodology there.
There may be a few questions there as Jim Tatum
mentioned earlier. You know, we've got a few things.
We're still going through to make sure we've got it
straight in our mind but I think our view is there is
a proposed methodology that in the most part, we think
provides a justified way to determine whether you need
to add steel and if there are some things in there
that aren't real straightforward, when we write our
safety evaluation, we'll put some restrictions on how
you apply this TBR.
But the question being is, is this
methodology that the plant's going to use. Is it, you
know, reasonable or conservative? Yes, I know from
listening to all the discussions we can always do more
to get a better test data, make the test a little more
conclusive, but we're looking at it is, the -- with an
event that is low, the LOCA or main streamline break
with a loss of offsite power, the -- you know, how far
do we have to go? And I think we're seeing that for
the most part it probably is. You could take the
methodology with maybe some caveats and apply it.
MEMBER SCHROCK: In the risk question,
don't you have to ask also what is the consequence?
MR. HUBBARD: Yes.
MEMBER SCHROCK: So the risk is very low
but the consequence is very high; isn't that true?
MR. TATUM: This is Jim Tatum.
MEMBER SCHROCK: If you lose the fan
cooler, you jeopardize containment.
MR. TATUM: No, this is Jim Tatum. There
have been plenty of tests done I think to show the
robustness of containment. So the containment fan
coolers really it's not a foregone conclusion that
because you lose the cooling medium, you have a break
in the piping system, that you've really significantly
impacted safety. You may --
MEMBER SCHROCK: Why was the issue brought
forward to begin with?
MR. TATUM: That was one of the
considerations. The other consideration that we were
concerned with was by-pass of containment through the
piping system itself. That was a possibility. And if
you look at, you know, containment by-pass, that would
be another plant specific analysis but in fact, dose
assessments, I think, you would find not to be a
significant or overwhelming compromise to public
health and safety.
So, you know, when we consider this and of
course, our thinking has evolved over time as well but
in looking at the current picture, I think, when you
recognize what is the risk associated with the LOCA
main steam line break and you combine that with loss
of offsite power, and then you look at, well, okay, if
that did happen, what would be the consequences? Is
it likely that you would or could fail containment, is
it likely that service water, if that's a system
that's providing cooling and you have a failure in the
system and it's going into containment, is it likely
that you lose the cooling function of that system or
do you have means of isolating that break in
containment which typically plants do have plenty of
capability available to them to isolate them so that
you don't lose the service water function and then
when you put together the robustness of containment
design as we have seen over other considerations,
other issues that we have gotten into with
containment, and the by-pass leakage sought, I mean,
overall I don't see a terrible -- terribly large
threat to public health and safety when you put all
this together and that's why I think George Hubbard in
his assessment is looking at trying to balance here
what the industry is proposing, looking at these other
factors and asking ourselves the question when is
enough enough for this, you know, recognizing that it
could be a substantial expenditure to the industry as
we've, I guess we've had meetings, I guess it was with
Calvert Cliffs, wasn't it, that explained that if they
take credit for air, it's quite a reduction in the
cost to them in addressing the problem.
And so there can be a substantial cost to
industry. Obviously, additional testing would involve
not only cost to industry but also more time and the
question in our minds is, well, given all these other
factors, is all that really warranted. And that's
really a management decision but I think we're
thinking that given what the industry has done, we're
pretty pleased at least with the methodology and
justification that's been put together. As I
mentioned earlier, we do have some open items that we
want to have further discussion on, make sure we have
a clear understanding and if we feel that any of these
raise what we would call significant concerns in our
minds, I think our view would be to address that
somehow in the safety evaluation to have restrictions
on how this methodology would be applied or some
criteria for when it would be applied, approach it in
that manner.
CHAIRMAN KRESS: In making a safety
evaluation, one could see the standard Chapter 15 like
safety evaluation or one could -- using the
methodology to get the pressures and so on or one
could see the risk analysis to compliment that, where
what I think I hear you saying is that if one did a
risk analysis that the risk importance worth of the
fan cooler is probably pretty small and really it's
not doing much for you in the first place from a risk
standpoint.
MR. TATUM: Right, I think --
CHAIRMAN KRESS: And would that be, you
think, considered in the safety analysis that --
MR. TATUM: Well, I think we can't avoid
having some discussion.
CHAIRMAN KRESS: It's not an easy analysis
to make because you've got all the different plants
and you're talking about a Generic Rule, how to deal
with a Generic Rule in a generic sense and you're
mixing risk space into the terministic space.
MR. HUBBARD: I think the thing is -- and
I'm not the risk expert, as I understand risk, you
know, this Generic Letter was issued because we saw it
as a compliance issue.
CHAIRMAN KRESS: It was a compliance
issue.
MR. HUBBARD: Right.
CHAIRMAN KRESS: And that's --
MR. HUBBARD: Now, when you start
factoring in the risk aspect --
CHAIRMAN KRESS: You're mixing apples and
oranges a little bit.
MR. HUBBARD: Right, then you've got to
look at, okay, if you have this waterhammer, are you
really going to fail that pipe? And you get into the
codes where you get into the faulted condition as
opposed to the design condition and then when you
start, is the pipe going to fail, the -- that's when
you start getting into the risk and probably not. You
know, you're going to get shocked. It's going to be
moved around but are you going to get the containment
back. I guess my feeling is the pipe is probably
going to stay intact.
You know, you could argue, no, it isn't
but that all goes into the risk factor, you know, in
determining, okay, of it fails what are the
consequences and, you know, put the risk number with
it. This was -- you know, they're looking -- they've
got a design to consider this load in here and, you
know, that's designed. Then you go to risk, and, you
know, it's a little different.
CHAIRMAN KRESS: Well, do you guys have
enough guidance to figure out how to condense this
into a presentation? I don't know what to tell you
other than I'm sure they'll want to hear about the new
test results and why we should believe the percentages
of air and they'll want to hear that "hA" argument.
So you'll have to figure out how to really condense
those down.
DR. ESSELMAN: The discussion today, I
think, is helpful both in figuring out how to condense
it but also I think the detail that we need to have
that we can augment this with before then and augment
it before the final report.
CHAIRMAN KRESS: I wouldn't leave out the
low frequency risk argument because that goes a long
way in my mind to -- as to how I view the importance
of the problem and so I wouldn't leave that out but I
wouldn't -- you know, you're going to get a lot of
questions like, how do you know what the frequencies
actually are and -- the argument of the initiating
frequency of LOOP and LOCA is good enough, I think,
you don't even have to factor in break probability.
It's probably low enough there to say that this is
really -- not really significant in risk base and I
wouldn't leave that argument out because that's
convincing to a lot of the members.
I think you have to go over the tests and
how they're run and what the results mean but I would
certainly try to focus and the "hA" argument was, in
my mind, a little shaky. I think you did go a long
way in convincing me on the conservatism in the air
release part. But I'm still not convinced on the "hA"
part. I'm not sure it matters what much but I would
-- I don't know how time you have but I would pursue
this jet argument and the question of how much
entrainment you actually get because I think this is
an entrainment heat transfer question.
And if the entrainment is effected by the
velocity and the pipe size and scale-up, then I think
the -- I think you could certainly add to your
argument if you had arguments along those lines that
would help convince me. I don't know what you can do
between now and the full meeting along that line. Are
there other comments from the --
MEMBER FORD: I just got a brief one.
I've given it low sensitivity of your Delta P to the
gas contact and "h" and all this, maybe these
questions about modeling become more of an academic
issue. However, I have big concern. No one seems to
be talking about integrity of the welded carbon steel
piping that's been exposed to oxygenated water for 20
years and you will have a large delta P not to be
cushioned that much due to waterhammer.
So whether this degraded piping, it will
be degraded to a certain extent, can stand it.
MR. BROWN: This is Tim Brown from Duke
Energy. We have -- service water system is in our ISI
program. It's also in our raw water inspection
programs. So we go to great pains to look at that
system and I think everybody is having raw water
piping problems and in fact, we're thinking about
replacing some of ours. So that's something we do
look strongly at.
MEMBER SIEBER: Probably the weakest point
is the expansion joints --
MR. BROWN: Yes, at the --
MEMBER SIEBER: -- between the headers and
the components that it connects to because where the
failures occur, they usually fail there.
MEMBER SCHROCK: Is that where you'll see
the pressure spike?
MEMBER SIEBER: The pressure spike goes
throughout the system. Another weak -- you don't have
it in the fan cooler but anything with a tube sheet
there is usually a lot of force on a tube sheet in a
waterhammer. You know, they start these systems up
and even though they're partially throttled when they
start them up. It's quite similar to the kind of
situation that you're talking about during a LOCA.
You actually don't run the fan. You know, the motors
will burn out on the fans because the containment
pressure is too high. And so the only thing -- the
only reason this issue exists is because the service
water system goes down, all these valves are open and
you start that pump again and everything rushes
through and when it hits the resistance, that's when
it collapses.
DR. ESSELMAN: Today we can't focus, I
think only on these three issues. I think we need to
step back and consider the big picture because they
haven't had the benefit --
MR. BOEHNERT: Well, I was going to
suggest that maybe we'll have the staff give an
opening to set the stage and talk about that and then
we can go into the specific issues on the table.
CHAIRMAN KRESS: See if -- possibly we
won't have time for this issue on the agenda.
MR. BOEHNERT: What, like two hours?
CHAIRMAN KRESS: Yeah, I think it would be
better if we had two hours.
MR. BOEHNERT: Okay, I'll try to do that.
CHAIRMAN KRESS: I think there was
something potentially dropped off of the September
agenda I heard.
MR. BOEHNERT: Well, we've pretty much
been through that.
CHAIRMAN KRESS: Oh, we've already done
that.
MR. BOEHNERT: Yeah, we've been there --
CHAIRMAN KRESS: Oh, we've already taken
that step.
MR. BOEHNERT: But there still may be time
because I think one of the issues is a little shaky
and they may not take all their time, in fact, the one
just before us. So we may be in good shape here.
CHAIRMAN KRESS: I think we can --
MR. BOEHNERT: I think we have the time
available, so it shouldn't be a problem.
CHAIRMAN KRESS: Okay.
MR. BOEHNERT: The agenda is kind of
light.
CHAIRMAN KRESS: See if we can get a
little more time.
MR. BOEHNERT: Sure.
CHAIRMAN KRESS: I think it's going to
take -- and you know, we want this to be the last
meeting here.
MR. BOEHNERT: Yeah.
MR. WAGONER: That we all agree on.
CHAIRMAN KRESS: With that I'm --
MR. BOEHNERT: You're going to adjourn the
meeting?
CHAIRMAN KRESS: Yeah, unless -- I don't
hear any opposition. I declare this subcommittee
meeting adjourned.
(Whereupon, at 1:09 p.m. the subcommittee
meeting concluded.)
Page Last Reviewed/Updated Tuesday, August 16, 2016