483rd Meeting - June 11, 2001
UNITED STATES OF AMERICA
NUCLEAR REGULATORY COMMISSION
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ADVISORY COMMITTEE ON REACTOR SAFEGUARDS
(ACRS)
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WEDNESDAY,
JUNE 11, 2001
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ROCKVILLE, MARYLAND
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The Advisory Committee met at the Nuclear Regulatory
Commission, Two White Flint North, Room T2B3, 11545 Rockville Pike,
Rockville, Maryland, at 8:30 a.m., George Apostolakis, Chairman, presiding.
COMMITTEE MEMBERS PRESENT:
GEORGE APOSTOLAKIS, Chairman
MARIO V. BONACA, Vice Chairman
F. PETER FORD, Member
THOMAS S. KRESS, Member
GRAHAM M. LEITCH, Member
DANA A. POWERS, Member
STEPHEN ROSEN, Member
WILLIAM. J. SHACK, Member
COMMITTEE MEMBERS PRESENT (Continued):
JOHN D. SIEBER, Member
ROBERT E. UHRIG, Member
GRAHAM B. WALLIS, Member
C O N T E N T S
PAGE
Opening Remarks, Chairman Apostolakis . . . . . . 4
Proposed Risk-Informed Revisions to 10 CFR
50.46 and Proposed Revisions to the Framework for Risk-Informing the
Technical Requirements of 10
CFR, Part 50 . . . . . . . . . . . . . . . . . . . 5
Presentation by Louis Ward . . . . . . . . . . . .84
Policy Issues Related to Safeguards, Insurance,
and Emergency Preparedness Regulations at
Decommissioning Nuclear Power Plants Storing Fuel
in Spent Fuel Pools . . . . . . . . . . . . . . .98
NEI Presentation . . . . . . . . . . . . . . . . 161
Need to Revise 10 CFR, Part 54, Requirements
for Renewal of Operating Licenses for Nuclear
Power Plants . . . . . . . . . . . . . . . . . . 196
NEI Presentation . . . . . . . . . . . . . . . . 206
Control Rod Drive Mechanism Cracking . . . . . . 212
NEI Presentation . . . . . . . . . . . . . . . . 280
. P R O C E E D I N G S
(8:32 a.m.)
CHAIRMAN APOSTOLAKIS: -- and he's being replaced by
Sher Bahadur, who is joining us as Associate Director for Technical Support.
Also, Mr. Steve Rosen now is a member of the Committee
officially. Welcome, Steve.
DR. SHACK: We don't have to quit being nice to him?
CHAIRMAN APOSTOLAKIS: Not anymore. You can be ask
nasty as you want.
And finally, you have this pink thing, "Items of Interest." There
are four speeches by the Commissioners, three by the Chairmen, and one by
Commissioner Merrifield. The second one, the evolution of safety goals and
their connection to safety culture, is of particular interest, I think, to the members
or should be, but the others are very interesting, too.
And so members have any issues they would like to raise?
(No response.)
CHAIRMAN APOSTOLAKIS: Okay. We can begin then with
the first subject: proposed risk-informed revisions to 10 CFR 50.46 and
proposed revisions to the framework for risk-informing the technical
requirements of 10 CFR, Part 50.
Dr. Shack, would you lead us through this?
DR. SHACK: We discussed this as a subcommittee meeting
on Monday. So this is deja vu all over again.
CHAIRMAN APOSTOLAKIS: Today being Wednesday.
DR. SHACK: And I think Mary will be leading us through this.
Why don't you just go ahead and start?
MS. DROUIN: My name is Mary Drouin with Office of
Research. Also at the table with me is Alan Kuritzky.
We did meet on Wednesday --
CHAIRMAN APOSTOLAKIS: No, Monday.
MS. DROUIN: Monday. Sorry.
We were trying to go through the presentation, and we did a
little reordering of it based on how the discussion went so that we would go
through it a little bit more smoothly.
Again, just quickly the points that we want to try to get to
today; again, the purpose of what we're seeking out of the meeting; a quick
background on Option 3 to emphasize some of the points; what our tentative
recommendations and schedules are; and then based on that, to get into the
detail then for each of our proposed recommendations; and then, again, wrap
up with what your current status and schedule is.
Just briefly, again, here we're to report on where we are on
50.46, in particular. I want to remind the committee that the paper that they
have currently is still pre-decisional. It's still at the EDO's office, and has not
been signed off.
Hopefully, you know, within a week it will get up to the
Commission and become public, but right now it still is pre-decisional.
We did have in the paper noting that we have requested a
letter from the ACRS, and that hopefully it would follow shortly after the July
meeting. But based on that, you know, we would particularly appreciate, you
know, comments on our options, any comments on implementation issues,
whether we've noted them all, if there's something missing, and then looking at
the feasibility, the things that we think are feasible in the short term and things
that we think are perhaps feasible, but are longer term efforts, and we will get
into each of those.
Again, on the background, this is just a reminder and a
refresher that in looking at Option 3, there are two phases to Option 3. The first
phase is what we call the feasibility study, and at the end point of the Phase 1
is where we have our recommendations to the Commission.
In going through the Phase 1, we identified, you know, what
are the candidate requirements, which are those that are amenable to being risk
informed. We prioritized them. The prioritization does look at not only the
resources and costs, but the desirability of doing it, which of course feeds in the
resources and costs, and you know, how much safety benefit would come out
of it.
And then the third part once we have done the prioritization
is to take and look at the feasibility and provide recommendations. But I want
to emphasize again it's a feasibility study. The Phase 2 is getting into the
detailed technical work to support the rulemaking.
It could turn out that when we get into Phase 2 something that
we thought was feasible isn't feasible, but we do go into it with a lot of
confidence that it is doable.
Based on that, we'll get right into 50.46. We wanted to quickly
give an overview of what we're talking about. We use the term "50.46," and
when we talk about 50.46, we always mean in that context Appendix K in GDC
35. All three of these entities go hand in hand.
And when you look at it, we're going to be going through what
we call these four topical areas here: the ECC reliability; the acceptance
criteria; the evaluation model; and the LOCA size definition.
When you look at the requirements that are stated in the
50.46, Appendix K, and 35, they divide up into these four topical areas or four
categories, classes, whatever word you want to use. But, in essence, they
establish the reliability and what your acceptance criteria is and what evaluation
model you need to be using in analyzing your ECCS, and then looking at the
LOCA sizes.
So when we look at those four topical areas and looking at
information that we have that we've learned over the years and our knowledge,
and looking at the top three, we do feel that it's feasible right now in the short
term to do things to the requirements that are associated with the reliability, with
the acceptance criteria, and with the evaluation model.
When we look at the fourth one, we haven't completely
established the feasibility. We feel we need to do a lot more work in that area,
and that's a longer term effort.
I don't know if you want to add some stuff to this, Alan.
MR. KURITZKY: Just mainly for this last one, I think the
important thing is that we need to improve our state of knowledge of LOCA
frequencies. I mean, right now our current estimates of large break LOCA
frequencies, we know or we feel that right now they're not low enough that we
could rule out a large break LOCA as a classroom design basis.
As we go and look into more and improve our state of
knowledge of LOCA frequencies, we may decide that there are further
relaxations that we can afford large break LOCAs. That's just something that
will have to be determined as we continue the feasibility study.
DR. POWERS: Let me just understand that a little bit better.
You're defining large break LOCA in this case as something like a six inch break
size.
MR. KURITZKY: Yeah. In this example, using the PRA
definition, which for PWR would be greater than six inches.
DR. POWERS: Do you think that you could rule out some
larger size break? Would you feel comfortable that, you know, you can argue
that that frequency is low enough at this point?
MR. KURITZKY: Well, the point is that right now what we
don't have is data for LOCA frequencies versus pipe size. The current data, the
best data we have right now is for the group in the PRA, which is six inches and
above.
DR. POWERS: You're not likely to get data on breaks, you
know, of larger pipes.
MR. KURITZKY: Well, right, right, right. Well, not data, but
you can do analyses, and you're going to have some consideration of service
data to help fashion your end -- the frequency you come up with.
But the bottom line is that we recognize that a double ended
guillotine break of the large pipe in the RCS is a very low frequency event, but
if we're going to eliminate that one from the design basis, we have to set a new
point of where we're going to -- the maximum that can be considered.
And right now we don't feel that we have enough information
to be able to confidently say what that point should be. So what we will be
doing in the next few years as part of this effort will be to try and improve our
state of knowledge of LOCA frequencies; maybe to come up with some kind of
curve of LOCA frequency versus pipe size; and at that point, we may feel that
at a certain point we can either say these LOCAs -- and it doesn't have to be at
the six inch point, but at any point -- that LOCAs above this size don't need to
be considered at all in the design basis; LOCAs in this interval need to be
considered, but not to the full extent they are right now. You know, there could
be some graded approach.
But all of that hinges on our improvement of the state of
knowledge of LOCA frequencies, which is fairly rudimentary right now.
DR. KRESS: Does that assume that the frequency is only a
function of pipe size? It seems like there's some other variables in there.
MR. KURITZKY: Yeah. In fact --
DR. KRESS: You would hide those in the uncertainty
distribution some way maybe?
MR. KURITZKY: Well, if you had the metallurgical people
here, they could give you a whole bunch of other things, the locations, and I
don't know whether it would be -- I don't want to speak in those areas because
Dr. Shack can do a lot better job at this than I could, but whether it be like
number of wells and, you know, the --
DR. KRESS: In any given plant, there's not a continuum of
pipe sizes? There's a set of discrete sizes?
MR. KURITZKY: For the most part, yeah.
DR. KRESS: So you go from six inches to what? The next
size up is?
CHAIRMAN APOSTOLAKIS: If you had a guillotine break of
the largest pipe, what is the equivalent diameter?
DR. SHACK: Twenty-four to 36.
MS. DROUIN: Yeah, on that order.
MR. ROSEN: I would make a simple point that we are getting
data on large break LOCA frequency every day. Every day that we don't have
one is another day that we add to the database.
DR. KRESS: It's going to take a long time.
MR. KURITZKY: Right.
CHAIRMAN APOSTOLAKIS: I guess you are proposing that
the first three boxes of the previous slide -- maybe you can put it back -- the
reliability, acceptance criteria, and evaluation model for the ECCS. We can do
something about these in the short term, right? Whereas the size will have to
wait for later.
I wonder what the dependence of the first three boxes is on
the fourth one.
MR. KURITZKY: It's a good point. Specifically the first box --
the second and third, not as much, but there could be some dependence
especially on the third, but the first one very much so could be dependent on the
same thing.
CHAIRMAN APOSTOLAKIS: Well, I mean, the third, too. I
mean --
MR. KURITZKY: The third to some extent also.
CHAIRMAN APOSTOLAKIS: Realistic assessment of
uncertainties, doesn't that depend on what kind of size of break you have?
MR. KURITZKY: Right, and you could adjust that. The
current model is looking at all of them. So it's not as important.
CHAIRMAN APOSTOLAKIS: Right.
MR. KURITZKY: If you want to try to scale back what your
requirements would be for that model for different sizes, which is something
we're also looking for in the long term.
In the graded approach I was referring to, you may have
something where certain size LOCAs, it doesn't mean you take them out of the
design basis, but you may lessen the degree of conservatism as defined in the
modeling for those, in the performance calculations.
But particularly in the first one, too, I mean, the frequency of
LOCAs would be very -- you know, improved state of knowledge on LOCA
frequency would be very useful to that first one. What we were trying to do in
the short term, just to kind of rehash what we discussed on Monday, is we're
coming up with two options under there, and I don't want to jump the gun too
much, but one of them would be more prescriptive where the NRC would set
what boundary conditions you would have to consider for your ECCS
performance calculations, and we would do that based on our current
knowledge of large break LOCAs.
We would also have an option where a licensee could do plan
specific calculations to further fine tune what needs to be considered in those
calculations.
One of the areas where they could help them fine tune --
MS. DROUIN: I think we're getting way ahead of our
presentation here.
CHAIRMAN APOSTOLAKIS: I understand that.
MS. DROUIN: We've got slides on all of this.
CHAIRMAN APOSTOLAKIS: But the point is that ideally the
size of the LOCA should be critical to the evaluation of all boxes, right?
MR. KURITZKY: Un-huh.
CHAIRMAN APOSTOLAKIS: The reliability of response and
so on. The reason why perhaps -- I'm trying to understand now -- the reason
why the first three boxes are easier to handle in the short term is because they
are deterministic. You are really looking at the availability of on-site power and
this and that, and you say, "Gee, I can do something about it, even though I
don't know the exact size of what a large LOCA is."
MS. DROUIN: That is correct.
CHAIRMAN APOSTOLAKIS: Right? But if I were to do a
detailed reliability calculation in the sense of PRA, I would have to know, but the
criteria are deterministic due to tradition. So you say, "No, no, no. I can do
something about it because what I can do is independent of the size."
MR. KURITZKY: Right, though we try to assume --
CHAIRMAN APOSTOLAKIS: Okay. So that's a correct
understanding then.
MR. KURITZKY: We still have to assume a LOCA frequency
of the --
CHAIRMAN APOSTOLAKIS: Sure, but whether it's six inches
equivalent in diameter --
MR. KURITZKY: Right, exactly.
CHAIRMAN APOSTOLAKIS: -- or ten, it doesn't affect the
first three boxes.
MR. KURITZKY: Exactly.
CHAIRMAN APOSTOLAKIS: Does it? I mean, because if it
does, we need to know.
DR. SHACK: The first box, the proposal is going to certainly
depend on their ability to discriminate from break sizes, but that's getting ahead.
MR. KURITZKY: I understand. There's something we can do
now.
CHAIRMAN APOSTOLAKIS: Which is independent of size.
MR. KURITZKY: Right, and then more could be done with --
CHAIRMAN APOSTOLAKIS: Okay.
DR. SHACK: Size matters.
MS. DROUIN: We're going to come back and revisit this as
we get into it, go into the presentation. But just quickly, you know, when we just
talk about that, the first three boxes are in the short term, the fourth box in the
longer term.
What do we mean by that? And you heard on Monday that
in the short term we have this A and this B. Well, the A is looking at making
changes to the current 50.46, and that's looking at changes that would be made
to the acceptance criteria in the evaluation model, and this is stuff that is not so
much risk informed as clean-up, and we're going to get into each one of these
in more detail.
The only thing I want to point out is that we have two things
that we're doing in the short term, and that's changes to the current 50.46 and
also developing here a voluntary risk informed alternative.
DR. POWERS: This I don't understand, why you're making
these changes.
MS. DROUIN: Excuse me?
DR. POWERS: Why are you making these changes?
MS. DROUIN: If you will hold off, we're going to get into what
the changes are and why we're --
DR. POWERS: Why don't you tell me now?
MS. DROUIN: Can I -- can we skip to that slide, then?
I guess I don't understand the why.
DR. POWERS: So you're making changes to the tech.
requirements of the current 50.46 related to the acceptance criteria in the
evaluation model. I just wanted to know why.
MS. DROUIN: I guess we have --
DR. POWERS: If you don't like them --
MS. DROUIN: We have better knowledge. We're trying to
address the conservatisms that we think are unnecessary.
MR. KURITZKY: I think that is the previous slide is where you
want to go.
MS. DROUIN: Make it more up to date.
MR. KURITZKY: Option 3 is directing us to look at regulations
that we can make changes to technical requirements, to reduce unnecessary
burden, to enhance safety.
DR. POWERS: So you've got some measures of burden?
MR. KURITZKY: Yes, we do.
MS. DROUIN: Yes.
MR. KURITZKY: That have been supplied by industry.
DR. POWERS: And you're going to tell me about those?
MS. DROUIN: Yes. I'm sorry. I wasn't -- I just didn't
understand what your why -- where you were coming from on that question.
DR. POWERS: Yeah, I just want to understand why you're
making these changes.
DR. SHACK: It says for improved safety and to reduce
unnecessary burden kind of a question.
MS. DROUIN: Yes.
DR. SHACK: But A is primarily an unnecessary burden
question.
MS. DROUIN: Absolutely.
DR. SHACK: And B, we could argue --
CHAIRMAN APOSTOLAKIS: And improved knowledge of,
and improved knowledge.
MS. DROUIN: I also want to point out that in both the short-
term and the long-term considerations that we're trying to do, is that we are
following the guidelines of our framework.
And on the last one, in following the guidelines of the
framework, again, to reinforce that this is not risk based. It is risk informed. So
if we go back to the framework, we had those six principles of defense in depth,
and those always have to be met.
Just schedule-wise, in looking at the proposals that we have
under consideration, the short-term one we're looking at in terms of develop the
proposed rule that the 12 months after the issuance of the SRM or two months
after the completion of the technical work.
Then when you look at the technical work, if you're looking at
changes to the current 50.46, we're going to continue. We aren't going to stop
right now. We're going to continue doing the technical work. We feel we can
have the first one done by July of 2002, and then in terms of the risk informed
alternative option, that's in April of 2002.
DR. POWERS: Proposing in this is work to be done in July
2002? Is that why you're proposing changing Baker-Just to Cathcart-Pawel?
MS. DROUIN: Yes.
DR. POWERS: Can you explain to me the rationale behind
that change? In particular, what I'd like to understand exactly is Cathcart-Pawel
kinetics are based on plant sheds exposed to steam, and how do you apply flat
surface data to curved surface fuel clad?
And the issue of spallation at high oxidation extents.
MS. DROUIN: Okay. We're going to ask Norm, who's the
expert.
MR. LAUBEN: I don't want to represent myself as the expert
in this. I think Ralph Meyers, our fuels expert, but the idea of changing -- the
idea of the change here is to get a more realistic heat generation rate. When
it comes to cladding embrittlement and that sort of thing, that's being handled
in the criteria part, not the change to Cathcart-Pawel.
Well, there are two things. First of all, as far as embrittlement
is concerned, the current rule addresses zircaloy and ZIRLO fuels, and the idea
of the change there is to look at embrittlement for all zirconium based claddings.
But the purpose of this is the known fact that the parabolic
rate laws that govern all of these things are probably pretty conservative, well,
is known to be quite conservative by using Baker-Just at the higher
temperatures.
So to use another rate equation for heat generation is
certainly justified by the data, and the data is taken from cylindrical cladding.
At least it is for Cathcart-Pawel, and Baker-Just is the one that's based on
dropping pieces of metal in water and things like that.
So I think that --
DR. POWERS: What I'm really asking is how do you handle
the deviation from parabolic kinetics due to spallation of the oxide.
MR. LAUBEN: Okay. That's going to be -- there is no
deviation. All of the rate equations now are parabolic, Cathcart-Pawel, Baker-
Just and all of them.
DR. POWERS: -- all of them parabolic.
MR. LAUBEN: Right.
DR. POWERS: The question is how the metal behaves.
MR. LAUBEN: Right, and there is ongoing work that's being
done by industry and our group of people who's at Argonne and so forth, who
are looking at other information on oxidation, including the long-term pre-
oxidation prior to the accident and so forth.
Is that kind of what you were asking about? There's a lot of
pre-oxidation that might be affected during the accident and so forth?
DR. POWERS: There's a lot of deformation in the material --
MR. LAUBEN: Okay.
DR. POWERS: -- that takes place prior to accident.
MR. LAUBEN: Yes, right.
DR. POWERS: And so what you're going to look at is kind of
optimal material that Cathcart and Pawel used, and then you're going to say
that applies to something that is beaten, folded, and manipulated before it's
oxidizing.
You also bring up the pre-oxidation. That clearly occurs, too,
and I'm wondering how do you justify this. The one thing we knew when we
used Baker-Just is we were definitely bounding things.
MR. LAUBEN: Well, it doesn't take into account any of these
other factors either that you're talking -- excuse me?
DR. POWERS: We knew that it was giving us an upper
bound on things.
MR. LAUBEN: Okay. Well, you know, beyond the fact that
all indications are that it's very upper bounding when it comes to heat
generation rate, this is the only reason we were going to change this.
DR. POWERS: Now are you going with something that is
more realistic, or is it a lower bound?
MR. LAUBEN: Oh, no.
DR. POWERS: Cathcart and Pawel takes this nice, pristine
material, hasn't been zapped by a single neutron. It hasn't been deformed,
hasn't been cold worked, and oxidizes it.
Okay. Is that going to give you correct kind of reaction
kinetics, remembering, recalling that there is nothing about zirconium oxidation
that predisposes it to be exactly parabolic. It's just what we do to fit the
equations, and sooner or later, it's going to fracture.
MR. LAUBEN: Yes, but the idea is that in the criteria itself,
which are embrittlement criteria, the idea is that you -- well, let me put it this way
then. Maybe this will help. In terms of embrittlement, for instance, Baker-Just
would still be used. You can always carry along two equations in your code,
one to calculate oxygen update, equivalent oxygen or ECR as they call it,
equivalent clad reacted, which is related to the embrittlement criteria. You can
carry along Baker-Just for that and still use Cathcart-Pawel to calculate the heat
generation rate due to the oxide -- due to a parabolic oxide thickness equation.
So that's my feeling at this point, but that goes into a lot of
detail that we haven't really studied a lot, but I've discussed it with our fuels
people, and this is what we think that we would do at this point.
So Baker-Just would still be there to calculate embrittlement.
Cathcart-Pawel would be there to calculate oxidation rate or -- excuse me --
heat generation rate due to an oxide thickness diffusion.
DR. SHACK: I thought you had a rather good discussion in
the framework document of this problem of you're trying to introduce some
conservatism somewhere that are covering uncertainties and non-
conservatisms in other elements, and that you have to be careful when you're
reducing known conservatisms that you're not leaving yourself vulnerable to the
things that you were non-conservative about and uncertain about elsewhere.
MR. LAUBEN: But that's also a somewhat dangerous thing
to do because that says that you can use one conservative phenomenology to
offset another non-conservative phenomenology, and that's sort of subtracting
apples and oranges, and I'm not sure that that's a very effective way to do it.
DR. SHACK: Well, it seems to me dangerous to just go
around reducing conservatisms on one element without looking --
MR. LAUBEN: Absolutely.
DR. SHACK: -- at what those conservatisms were covering
elsewhere.
MR. LAUBEN: Absolutely.
DR. SHACK: But I thought this is, again, a feasibility
argument.
MR. LAUBEN: Yes.
DR. SHACK: What we were talking about here is your current
judgment is this can be done, but you will be doing the detailed technical work
to support that.
MR. LAUBEN: Yes, and also I think that that are things in
50.46 that we are not changing that say that errors and changes need to be
assessed and reported, and so forth. So I think that that provides a basis to
assure yourself that acknowledged non-conservatisms are not now going to
become dominant in a way that you would not like.
And, therefore, I think the regulatory guide could take care of
a lot of this to make sure that you don't allow that to happen.
DR. SHACK: Now, when you say you're going to do this
proposed rulemaking, that would have the accompanying reg. guide as part of
that when the package is ready?
MS. DROUIN: Yes, that goes with it.
DR. KRESS: This whole discussion seems to me to scream
out for a real good uncertainty analysis to be accompanying the Appendix K
type things. I just thought I throw in --
MS. DROUIN: I agree.
DR. KRESS: -- my favorite subject here.
MS. DROUIN: I agree.
DR. POWERS: I guess the question that comes to my mind,
Tom, is why would you call out a kinetic expression at all if your objective is to
get wider utility of cladding without exemptions. Why not just say, "Look. I want
you to calculate in a reasonable fashion the amount of heat generation of the
chemical reaction, and I want you to estimate the loss of ductility"?
DR. KRESS: Oh, definitely. In fact, I thought actually that
was the direction they were going in in rewriting the rule. Yeah, I think you're
absolutely right. That's the way to express it.
DR. POWERS: They write out Cathcart-Pawel. You've got
a problem. First of all, there's not a specific --
DR. KRESS: Yeah, yeah. I think that's --
DR. POWERS: So the generality is now suddenly suspect.
Plus they're hanging onto the concept of old parabolic reactions, a material that
inherently doesn't want to be parabolic and geometries that don't inherently
want to be stable.
DR. KRESS: Yeah. I think it's the old problem of what do you
put in a rule and what do you put in a reg. guide. I certainly wouldn't put it in the
rule, but in the reg. guide I would allow a lot more flexibility, but you know, the
tendency is to say this is one way that's acceptable to us, and I don't know if
they want to make that judgment or not.
See, that's a judgment that --
DR. POWERS: It seems to me that following your tact, that
they have to scrutinize the reg. guide very closely because if they're enamored
with parabolic kinetics, which are nice and simple, on a material that itself is not
nice and simple --
DR. KRESS: And you know, they're trying to loosen it up to
allow other types of clad, and I don't think we know what those other -- those
other types of clad may very well depart more from parabolic. So I would have
written it more generally also.
DR. POWERS: I mean, we're looking at what they're fixing
to do, and they seem to have a strategy that inherently has a difficulty in it in
that it's simply replacing one set of determinisms with another set of
determinisms and saying, "Ah, but these are risk informed."
They're no more risk informed now than they were, or no less,
than the original ones were.
DR. KRESS: Yeah. I think that's almost a good description
of the nature of everything they're doing under A, and that's why we're more
interested in what they're going to do under B, I think.
MS. DROUIN: I agree with your statement, and one of the
points that we did make on Monday is that when you look at the A and the
changes that we're considering to the current 50.46, that we wouldn't call this
risk informed. We were looking at this more as just a clean-up in terms of we've
got newer information, and that's why we were in terms of this one modifying the
current --
DR. WALLIS: This isn't a clean-up. This is a change in
philosophy. I mean it's moved away from prescriptive to performance based.
That is a change in approach, and I think we supported that idea, I mean, when
you were here a couple of days ago.
MS. DROUIN: Yes. That is correct.DR. WALLIS: And that's
the thrust of the previous discussion we just had, is that don't be prescriptive.
Don't replace one prescription with another, but replace it with a really well
thought out performance based requirement.
Now, we talked a bit about whether or not these requirements
were worded in a suitable way, I remember, and we have to be very careful
about how we define the requirements that the cladding must satisfy.
I don't see this as a clean-up. I see it actually as a change in
approach.
MS. DROUIN: For this part of it, that would be true.
MR. KURITZKY: Yes.
MS. DROUIN: But this is the first part of A. There were two
parts to A, and I just --
DR. WALLIS: I think we were supportive generally of this
approach on Monday.
MS. DROUIN: Yes, you did. Yes, you did.
MR. KURITZKY: Okay. Actually so let me go right here.
Under A, as Mary said, there are two sets of changes we're looking at on A and
B, for lack of a better discrimination, but the A is the changes to the current
regulations and whether you consider it to be clean-up or more performance
based; really the purpose of this first part to make it more performance based
is to make it more flexible, allow it to apply to more than just the zircaloy and
ZIRLO cladding.
So we have A, which is the changes to the current
requirements, and B is the more risk informed piece. So first to discuss the
changes to the current requirements, there are two pieces to that really also.
The first is this one that Dr. Wallis was just mentioning about the performance
based requirement for the acceptance criteria, and the second one is going to
be changed to the Appendix K required features, which Dr. Powers was
bringing up some questions on.
So first we'll touch base with the acceptance criteria. What
we're considering doing is replacing the current five prescriptive acceptance
criteria which are in Paragraph B of 50.46 over the performance based
requirement, and just as a quick rehash, those current five acceptance criteria
are the peak cladding temperature limit of 2,200 degrees F. and the 70 percent
total oxidation, and those two are really surrogates for embrittlement, for an
embrittlement criterion.
And then there's a limit on hydrogen generation. The fourth
one is to maintain core geometry which deals with the ballooning and
swallowing of the fuel to make sure that you have adequate core fold area
(phonetic).
And the last one is the need to maintain long-term cooling,
and what we were proposing here, we would have a performance based
requirement to demonstrate adequate post quench cladding ductility and
adequate core flow area to insure that the core remains amenable to cooling,
and what that would do is that would really cover us for the first two, like one,
two, and four of the original five criteria, the two embrittlement criteria, and the
one to make sure that the core geometry remains amenable to cooling.
But in the second part of our performance based
requirements after the duration of the accident, we maintain calculated core
temperature at an acceptably low value, and we move to K heat, and that's
essentially just copying the fifth one, the long-term cooling one from the current
criteria.
DR. WALLIS: On Monday we discussed these, and I think we
encouraged you to think again about how you define these because adequate
cladding ductility is a pretty vague expression.
MR. KURITZKY: Right.
DR. WALLIS: And then you can always cool things, but then
the question is what are the consequences of the way you cool. So you have
to be very careful about how you define these performance based
requirements, and I think we felt that that particular one you've written there
needed some work.
MR. KURITZKY: Right, and in fact, I have noted that there
were comments on what we talked about as far as remaining amenable to
cooling and also, you know, maintaining the temperature and acceptably
evaluate. We did note those comments.
MR. LEITCH: Would you then leave unchanged the hydrogen
generation specification?
MR. KURITZKY: No, actually as was mentioned, the
hydrogen one was actually being dropped from the performance based
requirement because it's not found to be controlling, and the hydrogen
generation is covered by the 50.44, the hydrogen rule.
MR. LEITCH: Okay.
MR. KURITZKY: The combustible gas rule. So it would have
the hydrogen piece left in the ECCS rule.
MR. LEITCH: So this would be silent then on --
MR. KURITZKY: On the hydrogen generation, yes.
DR. POWERS: If your objective is to have a coolable
geometry, why do you bring up cladding ductility and flow areas? Why not just
say be able to cool this core?
MR. KURITZKY: Well, again, this is not my expertise, and if
Ralph Meyer, had he been here probably could fill you in better, but I think you
try to start at the highest level possible. Obviously, what you just mentioned
would be the highest level, and so there could be some argument of why we
would want to maintain it there, but I guess you want to also go down to a level
you feel you can have some metric or some way of measuring your
performance, and so it's at that level, it's my understanding, that that's where
we're comfortable and where we can measure something.
DR. WALLIS: Well, I think we said you could cool a rubble
bed, too. I mean you've got to be more specific than just you can cool it.
MR. KURITZKY: Right, right, and demonstrating adequate
post quench ductility kind of maintained -- is telling you that you're going to keep
the basic structure of the core. So you're not --
DR. WALLIS: Why don't you say something about release of
fission products? I guess we said this on Monday. That seems to be what
you're trying to prevent.
MR. KURITZKY: Right, right, and that kind of goes, I think,
along with what Dr. Powers said, but I think the same reason was it was hard
to specify a limit if we looked at that high level, and this was the next level down
where it felt comfortable, and it could become established criteria or measurable
criteria.
DR. POWERS: Well, you way it's hard to establish a limit on
fission product release. Actually it's easy to establish a limit. You can pick one.
What you're saying is it's hard to pick one that easy to justify.
MR. KURITZKY: Exactly.
DR. POWERS: Now, doesn't risk have a role in trying to
make that justification?
MR. KURITZKY: Risk may have a role. We actually had
considered some risk informed changes here. We didn't feel that at this time
that we were in a position to make recommendations along those lines. So we
were sticking with just the so-called clean-up aspects of these requirements.
I mean as part of the long-term work when we're looking at a
greater approach, there may be some other changes we would consider.
DR. WALLIS: I'm not sure risk helps you at all because you
talk about core damage frequency. A different number of kinds of core damage
doesn't tell you how much is tolerable, and LERF just says your large release
doesn't tell you. It asks about the frequency. It doesn't talk about how much.
So I'm not sure those measures help you. You need some other kind of
measure.
DR. KRESS: Yeah, you need an FC acceptance curve.
MR. KURITZKY: So anyway, in the short term --
DR. POWERS: He never gives up. He never gives up.
MR. KURITZKY: In the short-term, just to recap, for this part
of the changes to the current requirements, we're just looking at making --
replacing the existing criteria with the performance based criteria, which gives
you a little bit more flexibility.
The main point is right there in that last bullet. This is really
just to allow use of cladding materials besides zircaloy and ZIRLO, without
requiring the licensees to submit an exemption request, which is what currently
would be the case or is the case.
DR. POWERS: I guess, I mean, that's the one I just want to
ground on. Every time I see the words "Cathcart-Pawel" and then I see this
line, why? Why call out the kinetic expression?
MR. KURITZKY: Well, are you discussing the changes to
Appendix K now, the Cathcart-Pawel replacement? Because that's going to be
the next piece we're going to talk about.
This line here applies to only these changes which apply to
the acceptance criteria, not to the evaluation models, is where we're going to
discuss Cathcart-Pawel.
DR. POWERS: Okay, but I can't separate those two.
MR. KURITZKY: Well, I think, and again, it's not my area, but
as Norm had mentioned, really in the modeling my understanding is that you
can actually separate those two or you can use Cathcart-Pawel just for the heat
--
DR. POWERS: It applies to a particular material. It happens
to be a zircaloy. It doesn't apply to ZIRLO. It doesn't apply to M-5. Why call it
out? Why not say you've got to evaluate this stuff, whatever kinetic expression
you use?
MR. KURITZKY: Unfortunately I can't respond to that
because that's no my area.
DR. POWERS: Well, I mean, it seems remarkable that you've
got a strategy here in which each is an isolated fiefdom and there's no contact
between the two.
MR. CUNNINGHAM: If I might, this is Mark Cunningham from
the staff.
I think it's important to go back to a point, I believe, that Dr.
Shack made a little while ago, is that the context of what we're talking about
here in these changes is that this is the results of a feasibility study, and there's
more work to be done to develop the technical basis for a rule change and to
develop the language in the rule or the rule changes.
And we've got a year's worth of work in front of us in order to
do that. In the paper, I think we tried to be very explicit that possible changes
to the current 50.46 could involve a number of things, including the changes
from Baker-Just to Cathcart-Pawel. It doesn't mean it's done, but we think it's
something that makes -- based on a feasibility study, it makes sense to do.
DR. POWERS: And I think what I'm telling you is that's not
the right way to go at this.
MR. CUNNINGHAM: Okay, and that's fair.
DR. POWERS: The way to go is to say, "Look. We want to
include chemical reaction, heat, into these calculations. When you do it,
recognize the following things," and don't call out parabolic kinetics. Any
kinetics you want to that you can justify, but recognize that the surface is not
going to be flat. It's not even going to have constant radius curvature anymore,
and address these questions.
There's the technical feasibility to do this. The French have
done some very nice things looking at the stability of the oxide coating as a
function of the oxide thickness and deformations of the surface. So you're not
asking people to invent new technologies here.
MR. CUNNINGHAM: Okay. That's fair. thank you.
DR. WALLIS: When you get down the road a bit, you've got
to think about how you actually administer. Probably the NRR folks are going
to decide when they've got an application and somebody comes in with some
new way of trying to show that the core remains cooled; without using the old
criteria, how someone is going to decide whether this is an acceptable
application.
You've got to think it through all the way to how is the person
who's actually got to make the decision going to be helped by the new rule. If
it's not specific enough, it's going to be difficult. Everything is going to be
debatable to the nth degree.
MS. DROUIN: If I'm understanding -- maybe I'm still a little bit
confused by Dr. Powers' statement -- but is your objection that we're taking
specific criteria in Appendix K and replacing it with other specific criteria, or that
we should take what's specific and replace it with more performance?
So if I look at the example here, the Baker-Just, don't take the
Baker-Just and replace it with something else prescriptive --
DR. POWERS: Replace it with what you're trying to achieve,
yeah.
MS. DROUIN: But take the Baker-Just, for example, and
replace it more with a performance criteria.
DR. POWERS: Well, tell the people what you --
MS. DROUIN: Not prescribe another -- another --
DR. POWERS: What you want to achieve is you want to take
into account, for instance, in connection with your Cathcart-Pawel, as I
understand now that's strictly a heat generation. You want them to calculate for
chemical reaction heat generation. Okay. That's a reasonable thing to do.
There's a lot of heat here.
Okay. As soon as you say use this this kinetic expression,
you're taking a whole set of physics and you're saying this is not important.
You're saying that it's parabolic at the beginning. It's parabolic at the end.
Nothing ever happens. Nothing ever spoils, no new information, no radiation
effects on this oxidation process that are important to the calculation of heat.
That may or may not be true for every kind of clad that you get
in. So you're far better off to say -- to give them something that says what your
objective is and let them figure out how they're going to do it, and put in your
reg. guide all of the things that you're going to take into account.
DR. WALLIS: Even so, you still haven't got to a performance
criterion. I mean, the real performance criterion has to do with the integrity of
the clad and the nonrelease of fission products and all of that, which is affected
--
DR. SHACK: But this is an evaluation part here.
DR. WALLIS: -- which is affected by temperature and the
temperature is affected by anything that raises or lowers the temperature,
including chemical reactions and so on. So the chemical reactions are a means
to an end. They're not a performance based criteria.
It's just that in order to properly achieve that performance, you
have to consider all of the things that affect it.
MS. DROUIN: Absolutely.
DR. WALLIS: So you think about briefly what are the
performance goals and how you define them clearly, and you've got to consider
all of the physics and chemistry and everything else that goes into evaluating
that performance. That's what you need to do.
MS. DROUIN: I guess, you know, just to reiterate what Mark
said, you know, we're just in the feasibility, and I will admit that in terms of the
evaluation model and prescriptive requirements in Appendix K associated with
it, we had not looked at that in terms of taking those, as you can see, very
prescriptive requirements and replacing them like we did on the acceptance
criteria with more performance based. That's not something we had thought
about.
I think, you know, it is a good comment and something we
should pursue and look at in more detail. It's just a very good comment. We
just hadn't gone down that road.
So why don't we get over to --
MR. KURITZKY: I guess since you flipped on the second
side, this is just basically the changes that we had looked at as far as Appendix
K. We discussed them on Monday. We would certainly take into account the
comments today about looking at something more, specifying a performance
goal or working along a performance goal as opposed to just replacing one
prescriptive criterion with another one, and that can be looked at under our
Phase 2 work.
And again, just to reiterate, the last bullet there which goes to
the issue that was actually discussed a little bit already this morning, but that
when we go about --
DR. WALLIS: Now, those performance items -- excuse me --
those performance goals, if you really wanted to be risk informed, should be risk
informed in some way.
MR. KURITZKY: Right.
DR. WALLIS: Use the risk information to determine the goals,
and then you say you've got to use whatever physics, chemistry, and so on is
justifiable to achieve those goals. Isn't that where the risk informed comes in?
MR. KURITZKY: Yes.
DR. WALLIS: That doesn't come in at the level of Cathcart-
Pawel.
MR. KURITZKY: These were not supposed to be risk
informed changes, but you're right. To do that risk --
DR. WALLIS: Yeah, but how do you know what your
performance goals are until you actually look at the consequences of the
accident and do some evaluation of risk? Isn't that where the risk informed
comes in?
Otherwise you're just picking something.
MR. CUNNINGHAM: Yeah, this is Mark Cunningham.
I think we agree, Dr. Wallis, that in effect what we're saying
is we can make these changes and have confidence from a risk assessment
standpoint that we're not changing the risk to the public by making these
changes.
So it comes in as a metric at that level as opposed to saying
whether or not it's Cathcart-Pawel versus Baker-Just.
DR. WALLIS: But I think you don't know. You see, you're
asking for some requirement on cladding ductility. Unless you make the link
between cladding ductility and public safety, you don't know what sort of
cladding ductility to require.
MR. CUNNINGHAM: But I think we have some confidence
at the end where you could make these changes and know that it's not going
to change your risk assessment results.
DR. WALLIS: Well, that's a kind of litany though. You've got
to make the analysis to show that's the case.
MR. CUNNINGHAM: Yeah, yeah. But that's the underlying
presumption here, and I think we can justify that.
DR. WALLIS: I think we're trying to be helpful. We seem to
be slowing down your enthusiasm, but we don't want to do that.
MS. DROUIN: No, no.
DR. WALLIS: I don't want to do that.
MS. DROUIN: It's not that. You've just raised a good point
we hadn't thought about, and you caught us off guard.
DR. WALLIS: I'm a little bit disturbed because on Monday you
seemed to be so full of enthusiasm, and we seem to have slowed you down.
I don't want to do that.
MS. DROUIN: I don't think that's occurred.
DR. WALLIS: Okay, good.
MR. KURITZKY: You've just given us more things to look at
under our Phase 2.
MS. DROUIN: Shall we go to B?
MR. LEITCH: Just before you move to B, in your discussion
of A, I see a lot of discussion about acceptance criteria and evaluation model,
but I thought that A was also going to address ECCS reliability.
MS. DROUIN: No, that's B.
MR. LEITCH: That's B?
MS. DROUIN: That's B. So why don't we go ahead and get
to B?
MR. LEITCH: Okay.
MS. DROUIN: A was the changes to the current 50.46, and
that was just strictly changes to the acceptance criteria, and the evaluation
model.
MR. LEITCH: Okay.
MS. DROUIN: Changes to the ECCS reliability, which Alan
will get into, that is developing risk informed. Now we're really starting to bring
in risk information.
MR. KURITZKY: In fact, it's so different than the last one that
we actually call it 50.466 so that there's no confusion with 46.
(Laughter.)
MR. KURITZKY: The B changes, the risk informed changes
that we're looking at apply to the ECCS reliability requirements. If you
remember the figure that Mary put up in the beginning, we subdivide the
requirement into four categories, and the one that we're looking specifically at
risk informed are those that deal with the reliability of the ECCS system, and we
wanted to make those reliability requirements commensurate with the frequency
of challenge to the system.
And we have come up with two options to accommodate --
DR. POWERS: Why do you choose frequency of the
challenge to the system and not the consequences of system not being
mitigated?
MR. KURITZKY: Well, I guess you would probably get -- you
see, actually the two options that we have, what we're going to come up with
there is going to be based on a metric -- in our case, we're currently using core
damage frequency, but you are looking at the consequence of what happens
with system failure.
It's just that in looking at -- I think it was like an equation that
we had things multiplied by each other, and so you want to make A times B
equal something. You know, you're going to want to make them consistent.
If A is much lower, you can let B be higher, you know, and
vice versa. So that's what we mean when we say commensurate with the
frequency of challenge. If you multiply them together, you get the consequence,
but in looking at what we're going to allow, where we can allow flexibility, you
know, if you have two variables, if one goes higher, if you fix the one point, then
you can let A get higher and B gets lower, et cetera.
DR. POWERS: That's too abstract for my brain this morning.
MR. KURITZKY: All right. Well, let me go through --
DR. POWERS: It seems to me that an accident that results
in lots of consequences, even if it has a fuller frequency than one that results
in zip consequences is what am I going to focus on. So I would look at
consequences and not on frequencies.
MR. KURITZKY: Let me see if I understand your question.
Instead of focusing on, let's say, core damage frequencies are metric, you're
saying we should actually look at release.
DR. POWERS: Sure.
MR. KURITZKY: That's something that could be considered.
In fact, we had to make a determination at least according to how we feel we're
going to approach it, whether we're going to try to tie it to core damage
frequency; if it would just be on the frequency of the accident or LERF, which
would be on the frequency of obviously release from, you know, containment,
or you could go all the way as you suggest, Dr. Powers, and look at essentially
a Level 3 and have numbers.
But I think the reason -- and Mary or Mark will correct me if I'm
wrong -- but I think the reason why we kind of were thinking of sticking with core
damage frequency as I mentioned was just because that was one that had the
best understanding and had the best, you know, peer raised (phonetic) in
existence, the level on peer raised, and there are a lot more, and there's a little
more accomplished, and the results from the Level 1 that we have and some of
the Level 2 and Level 3 peer raised. So it was kind of a --
DR. POWERS: You've done a lot in looking at some of these
consequences. So you have information that could use at least in your design
of the regulation studies.
MR. KURITZKY: Yes, there is information there, and it's
something that we can consider whether or not we should make the metric CDF
LERF or actual release.
MS. DROUIN: You would not do this in absence without
considering your consequences. The primary measure that we are thinking
about is CDF, but that wouldn't mean that we would not give any consideration.
That violates the basic premise of our framework where we said you will be
balanced between your prevention and mitigation. So --
DR. KRESS: The problem with the framework partially, Mary,
is that the column on conditional containment failure probability has .1 in it, as
best I remember.
MS. DROUIN: At the lower level. There's levels to the
guidelines.
DR. KRESS: Yeah, but we're writing a set of voluntary rules
for existing plants, and not all of those plants have .1 conditional containment
failure probability.
MS. DROUIN: That's correct.
DR. KRESS: In fact, some of them have .5, and I'm not sure
how -- if one of those plants wants to voluntarily use this new rule, do they have
to improve their containment down to .1 or are they just excluded from being
able to make use of this rule?
MS. DROUIN: No, that wouldn't be the case.
DR. KRESS: Well, how --
MS. DROUIN: Because that's where you could back up to
your CDF.
DR. KRESS: So you are saying focus on maybe a LERF, and
they could back down on their CDF.
MS. DROUIN: Yes.
DR. KRESS: But then your guidelines and your framework
document are not hard and fixed. You're saying that they could -- as long as --
MS. DROUIN: The primary guideline of the quantitative
guidelines and the framework starts with a LERF.
DR. KRESS: See, what I'm getting at is what George brought
up in the subcommittee meeting, that why not just say in words that the LERF
will not exceed a certain level, and you must also have a CDF that doesn't
exceed a certain level. Why not word it like that rather than put those numbers
in the framework boxes that you have?
MS. DROUIN: I guess I don't see the difference. To me the
framework, in essence, does say that because it starts out with the LERF and
then the next consideration that we have there is the CDF.
DR. KRESS: But I don't think it gives much guidance for
those plants that have a conditional containment failure probability that's .5 or
.8. I mean, what do those people do? I don't think it gives any guidance there
and doesn't seem to say, "All right. If you've got" --
MS. DROUIN: But let's remember the framework is not for the
licensees. The framework is for us in formulating the regulation and how we
want to do it. This is an internal document.
The framework is not something that licensees have to meet.
That is, those are guidelines for us.
DR. KRESS: But you're going to use it to write the rule, and
they'll have to meet the rule now.
MS. DROUIN: Yes.
DR. KRESS: So there's a nexus between them.
MR. CUNNINGHAM: This is Mark Cunningham.
If you look at Item 2 here, ECCS functional reliability
requirement, we talk about it in terms of a CDF, but in effect, it's a CDF and a
LERF that would have to come into play here, and a plant that has a high
conditional containment failure probability, given core damage, is not going to
get as much benefit out -- wouldn't get as much benefit out of Item 2 than a
plant that would have a very low conditional containment failure probability
because they'd be constrained more by LERF than by CDF.
MS. DROUIN: Right.
MR. CUNNINGHAM: And that's going to have to come into
play as we develop the details associated with one and two there.
MS. DROUIN: Correct.
MR. KURITZKY: In fact, this original option had LERF in there
instead of CDF, which we changed later, and so Mark's point that LERF is some
aspect to be considered also.
DR. WALLIS: We talked on Monday about what you mean
by reliability. It seems to me there are two areas here. One is that you've got
an ECCS system. The requirements like the 2,200 degrees are really based on
the idea that you've designed the system so that there's no core damage
frequency if it works. And then you can talk about reliability.
Do you have one train or two trains and all of that? That's in
the PRA space, but there are almost two worlds, and I don't quite know how to
bring risk information into the first world, about how to define the criteria for
whether it works or not, the 2,200, the technical criteria for it's supposed to work
if all of these things happen.
You, I think, claim that reliability covered both the question of
whether there's one train or another, and also there's the technical questions.
If it works as designed, then there will be no core damage. Is that also in the
area of reliability or is that something else?
MR. KURITZKY: Like I said on Monday, when I think of
something as being reliable, it only has to, you know, turn on or run, but it also
has to meet the safety --
DR. WALLIS: Yeah, but if you think deeper than the 2,200,
well, what's the reliability or the rationale that we went through in our thermal
hydraulic analysis to pick 2,200? You know, that's also reliability in a sense.
MR. KURITZKY: I guess the 2,200 was more a safety margin
type of thing, but again, the point being when we talk about being reliable, those
performance calculations have to show that what one pump or two pumps or X
pumps, you're going to be able to keep your --
DR. WALLIS: That's PRS/PRA space and you aren't allowed
to do that.
MR. KURITZKY: Well, I was trying to show you that it's below
2,200. Then the PRA space says, okay, given that that calculation showed I
needed one or two or three pumps, now how reliable -- or I need some set of
pumps -- how reliable do I have to make that set of pumps be?
DR. WALLIS: Yeah, but then there's model uncertainty that
we talked about, and we don't know how to put that into the PRA space.
MR. KURITZKY: Right, and it kind of almost has to be
addressed in the hydraulic space. But I guess, again, I don't want to dive into
a whole discourse on uncertainty. I'm not expert on that. Everybody here
knows a lot more about it than I do, but it does have to model uncertainty. You
know, data uncertainty, I think we have a fairly good way of handling. Model
uncertainties are obviously a trickier beast to deal with, but it's obviously
something that has to be considered.
I mean, that's true, and that's going to be part of our brain
scratching for that second phase.
DR. WALLIS: That's what we talked about under A, I think.
MS. DROUIN: Right. I mean, when you get into your model
uncertainty, that's where you're getting into your acceptance criteria and your
evaluation, and that would be taking care of that part. You have designed that
ECCS system, and that's where you're also getting into, as Alan said, the
thermal hydraulics.
Whether or not you're going to be providing enough coolant
and the uncertainties of that would be taken care of under your acceptance
criteria and the performance you have to meet.
DR. WALLIS: Well, then you have to bring some sort of risk
criteria into the performance criteria, and we discussed how difficult that might
be.
MS. DROUIN: Yeah. I don't mean to allude that it's going to
be easy.
MR. KURITZKY: Yeah, I think Dr. Wallis' point is well taken.
That is, that's just one of the areas that we have to -- that interconnection or
connection, whatever you want to call it, you know, that passover, that's
something that has to really be thought out to make that seamless connection.
DR. KRESS: Does that bullet under two imply that you may
have different CDF thresholds for different plants?
MR. KURITZKY: No, actually that is supposed to -- that the
NRC would prescribe a CDF threshold, and then --
DR. KRESS: For all plants?
MR. KURITZKY: -- has to be required to meet that.
They could use plant specific information on LOCA
frequencies or ECS reliability to --
DR. KRESS: To arrive at it.
MR. KURITZKY: -- to arrive at it.
DR. KRESS: But the threshold itself will be --
MR. KURITZKY: Right. It is one across the board, and
essentially it's going to be -- you know, it's only specified in a reg. guide or
whatever for the licensees to use in Option 2. Under Option 1 the NRC is going
to give prescriptive requirements. We're still going to be using that same --
whatever we arrive at, that same threshold will be used in our thinking to come
up with what we're going to prescribe.
And again, as Mary said in the beginning, you know, right now
we've done Phase I work, the feasibility study. There's a lot more technical
work to be done under Phase 2, which would be to support the rulemaking.
Specifically for the risk informed, the voluntary risk informed
alternative, there's a number of things up there. We've been discussing a lot of
them in the list. I don't know if the list is necessarily growing, but we have some
more ideas under these bullets that we have to consider that we're going to put
emphasis on.
But coming up with acceptable methods and assumptions for
performing these CDF or LERF analyses or system reliability analyses and also
coming up with the appropriate thresholds, making -- you know, giving due
consideration of uncertainties and both coming up with the thresholds and how
the calculations are done to meet those thresholds, something Mary's staff has
put a lot of work into.
Also we have to identify features or conditions at the plant that
would tend to decrease the conditional probability of losing off-site power, given
a LOCA, and determine acceptable methods and assumptions for estimating on
a plant specific basis what that probability would be.
And I think that third bullet really goes to the first option on the
previous slide, which is the prescriptive one, where we would say, yes, you
don't need to consider loss of off-site power for this set of LOCAs if your plant
has this feature or that feature, for instance, the ability of the plant to
communicate with their transmission system operator, which would tend to
decrease the probability of loss of off-site power after a LOCA.
So there would be a certain feature that maybe a plant would
have to meet in order to be able to qualify, to not consider the fountain pen as
loop (phonetic).
In the second case, the fourth bullet really applies to the
second option from the previous slide where the plant would be doing plant
specific calculations, and licensee would be doing plant specific calculations,
and so therefore, they would need to consider in their analysis of the reliability
of the ECCS -- they'd have to consider the probability of losing off-site power
after the LOCA. And so they'd have to do some kind of plant specific calculation
in that regard.
That's what's going to keep us busy through April 2002.
MS. DROUIN: July.
MR. KURITZKY: July. No, this is the April one. This is the
April one.
DR. WALLIS: I'm still sort of thinking. Suppose that you in
the prescriptive world were to say or were to consider the possibility of raising
its reliable temperature to 2,300 from 2,200. Could you calculate the change
in CDF resulting from that?
MR. KURITZKY: If there would be a change in that peak clad
temperature?
DR. WALLIS: Right. Is there a mechanism? Does PRA
enable you to bring in that sort of information and calculate a change in CDF?
Undoubtedly there is a change in CEDF if you do that.
MS. DROUIN: Yes, it does. That's for your success criteria.
DR. WALLIS: It does enable you to do that?
MS. DROUIN: Yes, because that goes to your definition of
your core damage.
DR. WALLIS: So you assume that if you get over 2,300 you
get core damage? That's the definition of core damage?
MS. DROUIN: Well, I mean, when you go to the PRAs, you
know, the definition of core damage will change. I mean, for example,
somebody might define it as top of the active fuel uncovered, the bottom of the
active fuel. Some people define it as the peak cladding temperature, but my
point is that that gives directly to the definition, and as you change the definition,
then you change your success criteria.
DR. WALLIS: So you can change the CDF by changing your
definition of core damage?
MS. DROUIN: Absolutely.
DR. WALLIS: Just by words?
MR. KURITZKY: Well, not --
MS. DROUIN: It's not by words. I mean, then you have to go
and you do your calculations to see which systems. If, for example, I look at
a boiler, and if I define my core damage as top of active fuel versus a little bit of
uncover versus GP above the bottom of the active fuel versus my peak cladding
temperature --
DR. WALLIS: How do you make those choices?
MS. DROUIN: You do a lot of calculations to see, you know,
where you're going to start getting your releases.
DR. WALLIS: Oh, so you get back to releases, yes.
MS. DROUIN: You always go back to releases.
DR. WALLIS: Thank you. Good, good.
MS. DROUIN: But you will get different systems available.
MR. KURITZKY: Or the number of trains required.
MR. LEITCH: The third bullet there concerning loss of off-site
power following a LOCA, you used as an example there the ability of the plant
to communicate with the system operator. I'm just having trouble figuring out
how --
MR. KURITZKY: That would help?
MR. LEITCH: Well, first of all, who wouldn't have the ability
to do that? And how would it help?
In other words, what I'm picturing is some kind of a seismic
event that causes a LOCA and brings down the transmission line
simultaneously. So how does talking to the system operator help that?
Maybe I'm not following exactly what your thought is there.
MR. KURITZKY: Well, I think you bring up a couple of good
points. The issue of the seismic event that would bring down the grid at the
same time that it, you know, tripped the large break LOCA is definitely in that
case talking and isn't really doing you any good. I mean that's got its own
problems, and that's one piece that goes into the calculation.
That would be a case where the conditional loss of power is
one for that event. I mean, there's nothing you can do about that.
However, in other types of situations -- and I'm not the
electrical engineering expert, and I don't see the gentleman that we've been
working with on that -- but the idea being that if you have -- in a lot of cases you
have the grid tends to -- the area grid will have bolted sags and may have a
degrade of voltage there, which would increase your chance of causing a
separation to grid when you have the plant trip and the ECCS pump start.
Communication with the transmission system operator would
allow you in certain situations, I think, to allow the operator to readjust the flow
of current in the grid to may be beef up, you know, voltage to the plant so that
you're not as susceptible to having that going to the trip point, going to the
under voltage relay set points trying to separate you from the grid.
So you're getting the area grid managed where the
transmission system operator in communication with you, you know, in sync
with you to help you ride out, you know, that electrical transient, can help reduce
your transient having a separation from the grid.
And my understanding is that far from all plants actually, you
know, have procedures in place to routinely, you know, contact the transmission
system operator under such conditions. Some plants do, but some plants don't.
MR. LEITCH: I would just think they all would. I'm surprised
at that.
MR. KURITZKY: I guess, they all have the capability
obviously. I guess it's more of whether it's proceduralized, I guess, is maybe
the issue.
MR. LEITCH: Yeah.
MR. ROSEN: There are INPO requirements that have been
in place for several years to have good communications with the grid operators,
and I think I would be very surprised of any plant has not already complied.
MR. KURITZKY: Then that would help for all plants to take
advantage of if that's the case.
DR. SHACK: But, again, just coming back to that, I mean, you
would work out a sort of statistical analysis of the likelihood of loss of off-site
power, and then you'd modify that in some way by features. Is that the kind of
thing that's envisioned?
MR. KURITZKY: Yes, that' the type of thing we're looking at.
We'll build out some of the work that was done for generic Issue 171 and try to
identify, and some of the work that has been done since then and try to see if
we can identify features that can have some measurable impact on that
conditional loss of off-site power probability.
MR. LEITCH: Coming into that, again, is this issue that we
always have a lot of trouble with, and that is assessing how well the operator
would perform under those circumstances. In other words, he's just has a
LOCA. Although he has procedures to contact the system operator, you know,
is he going to do the right thing? Is he going to --
MR. KURITZKY: And that's the error of probability, right.
DR. BONACA: And I had the same thought, but my
understanding will be that from more credible break sizes you would still
preserve LOOP and single failure requirements.
MR. KURITZKY: Yes.
DR. BONACA: You would relax those for break sizes which
right now seem to be so unlikely, like the double ended guillotine break. You
don't have the basis to eliminate that from the rule right now, but you have the
basis for utilizing that inside till it lacks something like the LOOP or -- okay. So
that's the context of that.
MS. DROUIN: What you've heard to date is the proposed
considerations for the short term, and now looking at what we're considering for
long term, our long-term effort.
MR. KURITZKY: Okay. That goes to the fourth box. That
was in the figure Mary put up before, the definition of large break LOCA sizes.
Additional changes to 50.46 may also have some merit, including possibly
change in the definition to inspection of breaks and locations.
The extent of the potential changes to 50.46 is dependent on
our state of knowledge of LOCA frequencies as we discussed before, and
here's an example of how we might use that information.
If we could feel confidence, considering uncertainties, that we
have a collecting infrequency of occurrence below let's say ten to the minus four
a year for a set of LOCAs, then we may believe that some regulatory relief is
appropriate for those, that set of LOCAs, which is pretty much what we're doing
right now with the changes we discussed under Item B.
If, for instance, we could also or in addition we could feel
confident that the LOCAs were at frequencies below ten to the minus five, we
may feel that we could go even further and possibly remove these from the
design base, but as long as there was maintained some plant mitigated
capability to address those accidents.
And further, if we could feel confident that we could -- that
there was a set of LOCAs whose collective frequencies were below ten to the
minus six per year, we may say that's so low we can take them out of the
design basis completely and they don't have to be addressed at all.
So that's kind of how as we improve our state of knowledge
of LOCA frequencies we could, you know, further change what would be the
regulatory requirements associated with those set of LOCAs.
DR. POWERS: You'll never get somebody to come in and
say probability of LOCA is definitely absolutely less than ten to the minus fifth
per year. I just know how people are. They'll say, "Well, I'm not too certain
about this, but it's the mean value maybe is less than ten to the minus fifth," or
some confidence level or something.
What kind of confidence level are you looking for?
MR. KURITZKY: Okay. That will have to be decided as we
go through. This is long-term work, and so that's something that will have to be
considered, but you're right. You consider uncertainty analysis. You have to
consider, you know, would it be something that we want the 95th percentile to
be below that level? Would it be the mean? You know, do we feel the mean
would be sufficient?
If you used the mean, you would probably want to have a
more -- maybe a little more strict on what the professional guy would be. If you
used the 95th percentile, then you may be a little more or less concerned
exactly what that threshold is.
But all of that has to be figured out as part of that as long
term.
DR. POWERS: Yeah, I guess I'm wondering how you do that.
I mean, you said if you use the mean you'd be a little more restricted. You're
doing something when you say that, doing some mental integration there. Can
you tell me what that mental integration is?
MR. KURITZKY: Well, again, I guess you're tying it to release
or, you know, core damage frequency or LERF or actual fission product release,
but you're going to have some metric that you're going to run up against, and
then you're going to back out, you know, frequency that you're going to --
MS. DROUIN: We're in the very early stages here on this.
I mean, we know we're going to have to deal with the uncertainties. That's a
given. How we're going to incorporate that into this, it's a blank sheet of paper
almost at this point. We just know it's an issue we've got to address, and when
you look at the time frame that we talked about where this is up to three years,
this is one of the factors that comes in there because it's not a trivial issue.
So there's a lot of work that's going to have to be done here,
particularly when it comes to the uncertainties.
DR. WALLIS: Well, thinking about long term, there's a certain
CDF allowed by the present rule due to LOCAs and LOCAs contribute a certain
amount to CDF, right? We know that. We know that LOCAs contribute.
It may be plant specific, but you can evaluate the contribution
of LOCAs to CDF now, and presumably that's tolerable because we license
reactors.
Now, we talked on Monday about optimizing the ECCS
system. Why don't you in the long term think about allowing the licensee to
simply optimize the ECCS system in any way, response to break sizes,
reliability of this? I mean whatever it is as long as some CDF value criterion is
met. Then it's up to the licensee. I mean, you don't specify all of this stuff. You
simply say, "Evaluate all of your LOCAs, and the total CDF contribution is not
to be more than a certain amount."
MR. KURITZKY: I mean that's --
DR. WALLIS: Isn't that really risk informing the whole thing
in the long term?
DR. BONACA: Well, I must comment that people can be very
creative in telling you that single failures can happen, and yet you know, TMI
had many failures happening, you know. They happen, I mean, and I agree that
as a general principle I think -- but you've got to be very careful.
DR. WALLIS: This is long term.
DR. BONACA: Yeah.
MR. KURITZKY: The risk-informed in that respect --
DR. WALLIS: Well, that's a little bit of a --
MR. KURITZKY: We don't want to put all of our eggs in the
CDF basket.
DR. WALLIS: You can always quibble about it. Whenever
you want to do something really logical say, "Oh, don't do that because it's risk
based," you know.
DR. BONACA: With this, you know, I had a question
regarding it a little bit. Are we going to have at some point in the future a menu
driven LOCA requirement such that this plant will have this criterion and this
plant will have relaxed large break LOCA based on -- you know, simply that
won't relax it, but simply that it assumes still double ended guillotine break, but
only one train above a certain size break, and others will come in and in the
future use -- I'm trying to understand what's going to be. I mean, you know,
these plants are so different from each other already. I mean one of the issues
have always been lack of standardization.
Are we going to have a future where we're going to even less
standardization?
MR. KURITZKY: Well, I think if you just even look at the
changes under B, that first option with the NRC would specify. Everybody
would either pick that or something else.
But the second option under B, even there plants would -- you
know, that's the change we're considering if it should go to implementation. You
would have plants that could -- if they wanted to go through the analysis, they
could demonstrate that they could adjust their --
DR. BONACA: Okay.
MR. KURITZKY: -- that different plants would, in fact, have
different requirements for LOCA. I mean, you're right. It flies against
standardization, but it allows for more use of risk information.
DR. BONACA: Okay. Plant specific relaxation, yeah, right.
MR. KURITZKY: Okay. Again, as part of this long-term work,
one of the main things that we're really trying to strive at is to improve our state
of knowledge of LOCA frequencies. In that vein, the staff is continuing to meet
with representatives of the nuclear industry in public meetings to try and
address a set of technical issues.
For example, the initial fall distributions, degradation
mechanisms, uncertainty analysis, et cetera, that would go into those
calculations of LOCA frequencies. As has been --
DR. POWERS: That seems to address the regulatory guide
aspects of this. Those meetings don't seem to address, discussing earlier, your
ten to the minus four, ten to the minus fifth business.
MR. KURITZKY: Yes. I was just going to point out that the
next set of means that we have set up with the industry are to address this
particular topic, but in order to actually carry through these changes to their
implementation, there are many issues as were discussed here at these
meetings today as well as other issues that would all have to be considered.
We currently have plans to meet with industry because this
is one hurdle that has to be dealt with to move forward, but it is certainly not the
only hurdle that has to be jumped over.
DR. POWERS: This seems to address the question of
whether LOCAs occur at all.
MR. KURITZKY: Well, or whatever frequency they occur at.
DR. POWERS: Maybe it addresses what happens when you
see that they reflect knowledgeables (phonetic) and things like that.
MR. KURITZKY: In other words, all of those issues need to
be -- that all falls into those metallurgical concerns.
And just to sum up, if something -- if large break LOCA
redefinition, the size redefinition is found to be feasible, the staff would
recommend, you know, additional changes potentially involving additional
rulemaking to change the wording in Part 50 to allow the licensees to select an
alternate pipe size as their pipe size for the design basis subject to some level
of NRC approval. So that's a potential carrot out there if this can be done.
MS. DROUIN: So far what we've covered is what our plans
are in both the short term, what we're considering in both the short term and the
long term for 50.46. In terms of just the global look at Option 3 activities and
some things that are on the plate, we had talked about, you know, the ECCS
reliability. That gives directly to GDC 35 that talks about the single failure
criteria.
Right now what is proposed in the short term is just fixing that
as it pertains to the ECCS, but as you look at Appendix A, there are a lot of
other GDCs that also address the single failure criterion.
So one of the things that we are considering that do think that
it is a generic change to the single failure criterion to take it beyond just as it
applies to ECCS.
Another Option 3 activity also that we had started was looking
at the special treatment, at the technical requirements of the special treatment.
Now, when we mentioned this, we mentioned this in terms of Option 3. Option
2 is moving forward, and that is looking at the scope of your components, your
structure systems and components that are under the special treatment.
But if you look at the actual requirement, for example, your
QA requirements, are those the correct requirements when you start bringing
in risk information?
So changing the actual technical requirements is an Option
3, but in both of these in terms of looking generically at the single failure
criterion, looking at the special treatment, both of those efforts for right now
have been deferred because we want to take our resources and focus them in
getting 50.44 and 50.46 through the system first.
So for the next couple of years, that's where our focus is
going to be.
DR. POWERS: If I change the reliability of the ECCS systems
and risk assessment, is the CDF linearally related to that change?
MS. DROUIN: It is certainly related. Is it linear related?
MR. KURITZKY: Yeah, I would be hard pressed -- that one
I'm trying every --
MS. DROUIN: I would be hard pressed to say that.
MR. KURITZKY: -- every core damage sequence in the PRA
has ECCS failure in it, and there could be things at risk that may be not --
DR. POWERS: I don't think so. They would just treat those --
all those other things would be constant contribution maybe, nd so all you'd do
is just increase the contribution due to LOCAs.
DR. SHACK: But you have a reliability that depends on the
frequency, right? Doesn't that make it non-linear? They're proposing that the
reliability essentially be a function of frequency.
DR. POWERS: Maybe that's what they are proposing. I was
asking a simpler question. What's the situation now?
MS. DROUIN: I would not say that it's a linear relationship
personally.
MR. KURITZKY: Because, first of all, the reliability of the ECS
now is different. I mean it's different for a small break LOCA versus a large
break LOCA. You have different success criteria. So you already have some
disconnect there that, you know, wouldn't tend to lend itself to being linear.
So, yeah, I would have to tend to -- without having actually
looked at it, you know, I would guess that it probably wouldn't be unless you
somehow couch your definition to account for the differences in success criteria
for different cases.
DR. SHACK: Just coming back to a slightly different question,
you know, we always make the assessment of the risk impact of these things
based on the existing PRA, and if we change this rule, somebody is going to
make changes, and that presumably could impact the PRA in ways that you
don't -- but when you make this rule, somebody is going to have to make a --
you know, if he wants to change his tech. spec., you will then come back and
be able to assess all of the risk implications of changing that tech. spec.
So you really have a second chance to look at all of the risk
implications that you're introducing by changing the rules.
MR. KURITZKY: Yeah, I think that's the way to do it because
you can't a priori identify every single possible change a plant could make and
come up with what would be the impact to risk because it's different for different
plants. So I think you need to have some -- the rule change can be made, but
then when it goes -- a plant can choose to take advantage of that or a licensee
can choose to take advantage of that, but when they want to actually make a
change in their plant, then because of that you need to have some, you know,
reg. --
DR. BONACA: Oh, so you would require something like that?
MR. KURITZKY: I don't know. We haven't thought that all of
the way through, but I mean --
DR. SHACK: But he doesn't have to come back in in 1.174
space. He comes back in now in, you know, I'm following the regulations.
MS. DROUIN: That's right. In 1.174, he doesn't have to meet
1.174. He chooses the alternative rule.
DR. SHACK: But you presumably now -- it comes back again
to this threshold of when you can come back and ask him for risk information.
MS. DROUIN: That would be dependent on how we write this
and how the reg. guide -- I mean it might not necessarily be --
DR. BONACA: Well, sine it is a plant specific change --
MS. DROUIN: -- that way.
DR. BONACA: -- and since there is plant specific options,
wouldn't you want to have an analysis like that?
MS. DROUIN: I'm sorry. I couldn't hear you.
DR. BONACA: It seems -- I mean, this I raised earlier, that
plant specific changes and they're based on some risk informed consideration.
Wouldn't you want to know that? The point that --
MR. KURITZKY: The total risk impact at that plant.
DR. BONACA: Yes.
DR. SHACK: I would. The question is whether the
regulations --
DR. BONACA: That's right.
MR. KURITZKY: And I think it goes back to it depends on
how much -- when we look at it ourselves and start to assess what we think the
changes would be and what would be the risk impact, it depends if we feel
confident that all other possible changes for the different plants all fall within
some band, and that band is acceptable, maybe we're not as concerned. If we
can't get that comfortable feeling, you know, then I guess the reg. guide or
whatever would have to be worded in such a way that you'd have some kind of
way of assessing that.
MR. ROSEN: I think any competent utility PRA practitioner
group which was intending to take advantage of the provisions of new rule as
a very first step would run a "what if" calculation through their PRA based on the
changes that they would make in their modeling and see what the impact is and
see in which sequences it's important and make a judgment based on that, very
first level judgment.
Do they want to proceed with it? And that would reveal a lot
of things to the utility, and I'm sure they'd share them with the staff.
MR. KURITZKY: But the question is if they would be required
to share with us. I think that's what Dr. Shack and Dr. Bonaca are getting at.
DR. BONACA: Well, yeah. The reason I was asking is you
had on this slide a number of bullets regarding, for example, single failure
criteria, and I agree that it may be over burdening in some cases.
It has served well the industry in other cases. I mean,
anybody who lives close to a plant knows there are a lot of valving problems at
time. Systems are left out by accidents. I mean, there are errors taking place
out there.
The fact that you had single failure capabilities oftentimes
save the day because you have --
CHAIRMAN APOSTOLAKIS: Well, they are not eliminating
them.
DR. BONACA: I understand. I'm only saying that we are
asking these questions for that very reason, that you may try to put together a
rule in place -- let me finish --
CHAIRMAN APOSTOLAKIS: Yeah, sure.
MS. DROUIN: Okay.
DR. BONACA: -- and then -- and then -- okay.
MS. DROUIN: I'm sorry. I thought you were --
DR. BONACA: I just was trying to complete the statement.
I think the message got there.
MS. DROUIN: Thank you.
Just to wrap up again, to go over our schedule, again, the
paper is pre-decisional. We do hope that it will get up to the Commission within
the next week. We are requesting a letter from the ACRS.
In looking at our short-term changes that we have proposed,
development of the proposed rule in the short term, 12 months from the
issuance of the SRM or two months after the technical work is complete,
whichever is later. A very important point there.
In terms of performing the technical work, we will not wait for
the SRM. We're going to continue proceeding forward. In terms of modifying
the current 50.46, we feel we can have that done by July 2002.
In terms of looking at the ECCS reliability requirements, which
is the alternative to 50.46, to have that complete by April of 2002.
Looking at the feasibility to complete the feasibility of
redefining the large break LOCA, we feel that could take up to three years. A
lot of issues involved in that one.
MR. LEITCH: It seems to me that a lot of the benefits that
industry could see from this program may be in the longer term options, and I
guess I wonder if in the short term options, particularly in the part that you've
called A, are there any -- do you think there would be sufficient benefit that there
would be any takers? In other words, is there a danger that we are spending
a lot of money here to throw a party and nobody will come?
MS. DROUIN: I can't speak for industry, but we do feel there
is some benefit there. Otherwise we would not be pursuing it.
MR. KURITZKY: Yeah, I think to keep the reduction at the K
level --
MR. LEITCH: I'm talking about for the current generation of
plants. I mean --
MR. KURITZKY: Yes.
MS. DROUIN: Yes.
MR. KURITZKY: Under A where we have -- the part on
acceptance criteria is not meant to provide unnecessary burden reduction. I
mean it may, but that's not what is intended. It's intended to allow other types
of cladding materials to be used without having to --
DR. SHACK: You're also not intending to give them a choice.
MR. KURITZKY: Right.
MS. DROUIN: No, no, no, no, that's not true. They will be
allowed to stay with what they have.
MR. KURITZKY: But the decay heat one particularly, our
understanding is that there could be a fair amount of benefit for some plants
under that second part of A.
DR. SHACK: Under the second?
MR. KURITZKY: Yeah, the reduction of the decay heat level.
DR. SHACK: That certainly seemed to get some enthusiasm
on Monday.
MR. KURITZKY: Yeah, particular BWR. We heard from the
BWR owners group.
MS. DROUIN: But the answer is, yes, we do think there's
benefit to be had. And that concludes our presentation unless there are
anymore questions.
DR. SHACK: We have a representative of the Westinghouse
Owners Group if he'd like to make some comments.
MR. WARD: Come up here or --
DR. KRESS: It would be better if you'd come up.
MR. WARD: Good morning. I'm Lewis Ward. I'm the
Chairman of the Westinghouse Owners Group, large break LOCA redefinition
project. I work with Southern Nuclear Operating Company with the Vogtle
Plant.
I missed the Monday meeting, but I did get several reports
from the occurrence from here from the people who were here Monday.
We did meet yesterday and last night with NEI and some
WOG (phonetic) representatives, and we believe that the priority that we just
saw is reversed from what we would really like to see.
The large break LOCA redefinition for us has by far the most
benefit down the road with plant changes and core changes and analysis
changes that we can get some benefit out of fairly immediately and some of
them much longer term.
So that's what we want to focus on within the Westinghouse
Owners Group. I know that the BWR owners are fishing for the loss of off-site
power option with this, and I don't want to take away from that at all, but within
the Westinghouse Owners Group, the only thing that I remember are interested
in and have put a significant amount of money on the table to support is the
LOCA redefinition.
The other two owners groups, B&W and CE, are very
interested in that, and we've had presentations here with them also.
So I think it's safe to say where our money is right now if you
want to judge from that is on large break LOCA redefinition.
There is a meeting in progress right now down at NEI to lay
out the risk informed task force, you know, what they want to present as a
strategy, and I'm not there obviously. So I may be speaking a little bit out of
turn. They could come back with some different conclusions, but I kind of doubt
it.
Presuming this recommendation goes forward and gets
Commission approval, our tendency right now is to petition for rulemaking for
the redefinition, and we have started that effort already. We have started a draft
of a rule with statements of considerations, and our time frame would be to
submit that possibly in about six months.
The one technical issue that was presented this morning that
we do want to focus some more on is the pipe break frequency. We get some
indications that there may need to be more rigorous work done to support a
frequency curve, depending on how you want to use that curve, and I think that
is pure science.
A pipe break curve ought to be good. If it's a sound curve, it
ought to be good for however you're going to use it, and so we want to meet
with the staff, and we're trying to set up a meeting with the staff hopefully early
next month to go over some of those issues and see if we can get them at least
on the table so that we can get our technical people, Warren Bamford and the
other experts in the reactor mechanics group in Westinghouse working on that.
They are already addressing the issues that we know of, and
you know, we plan to put together a paper probably in the form of a WCAP
(phonetic) that will be part of the technical support behind the petition.
Some of the other issues that came up this morning, just very
briefly --
DR. POWERS: Well, could we pursue just a little bit this
LOCA redefinition?
MR. WARD: Certainly.
DR. POWERS: I take it what you're coming in -- they had a
slide there, ten to the minus fourth, ten to the minus fifth, ten to the minus sixth.
You're saying that the frequency of these large break LOCAs is small enough
that we don't need to include them in the design basis.
MR. WARD: Yes. Yes, sir, and I think we need to come to
a very, very good consensus, understanding of where the break-off of that curve
is.
One of the questions earlier, our pipe sizes are incremental.
At least in the Westinghouse fleet, they go from six to eight to ten, up to 14 in
two inch increments, and then the next largest size is the RCS. So, you know,
it's not a continuous spectrum of pipes in there.
The calculated frequency of the large LOOP breaking double
ended guillotine is on the order of ten to the minus ninth or ten to the minus
11th. So if you integrate that curve down, which is not a continuous curve, and
you throw in a 14, the total combined frequency of those is more, ten to the
minus eight.
DR. POWERS: How do you know these frequencies?
MR. WARD: How do I know that?
DR. POWERS: I mean, I'd like to see this database that gets
these frequencies.
MR. WARD: And I'm not a mechanics expert at all. So I --
DR. POWERS: That means there can't be any data at all,
right? I mean, if it's ten to the minus 11th, that's a little longer than the age of
the universe --
MR. WARD: Right.
DR. POWERS: -- by a factor of ten years or by a factor of ten.
MR. WARD: Right.
DR. POWERS: So what makes you think that this is -- I
mean, this must be the products of calculations.
MR. WARD: Yes, that's right.
DR. POWERS: I mean, is this like F equals MA? I mean,
these calculations, there's no question about them? They're known absolutely?
MR. WARD: There are questions in there, and I think that's
what needs to be agreed to, that all of the known uncertainties and
conservatisms --
DR. POWERS: Has there never been in the history of the
universe a large pipe break?
MR. WARD: Yes, there have been large pipe breaks.
DR. POWERS: Oh, well, so the frequency is ipso facto
wrong.
MR. WARD: There has never been a large pipe break on the
type of material in a nuclear reactor of the grade and type and pedigrees that
are in nuclear reactors.
DR. WALLIS: There have been through wall cracks.
MR. WARD: Yes. But, for example, one of the things we're
wrestling with is not only just the pipe size, but possibly a flow criteria instead
of a pipe size criteria. For example, at full pressure, the six inch break is
equivalent to about 30 to 40,000 GPM flow. That's a huge crack that would
produce that amount of flow, and whether it's a severance of a small pipe or a
smaller split in a weld of a larger pipe, you know, it would encompass all of that.
But you know, it may turn out that this curve that we're talking
about is a flow based curve instead of a pipe size break, but that to me is one
of the key technical pieces that we really need to get nailed down, and we're
working with the staff, and we would like to have a meeting fairly soon to at least
get on the table all of the issues that we need to address.
And a fair part of our money is allotted to addressing a
technical issue in coming up with a common standard.
I guess the next piece is how do you use that. You know, say
we did get a rule change, and what we're going to propose in the guide is that
we have or in the statements of considerations is basically to put some bounds
on how we would like to use the rule and how we would propose that it not be
used.
For example, we don't want to degrade containment
requirements in any form. We do not want to allow ourselves to even work on
throwing out imported ECCS equipment, like the charging safety injection or
RHR pumps or accumulators, but there may be some relaxation in the
requirements on some of those, in particular accumulators.
Some of the other ECCS equipment, particular room coolers
that are there just peripherally for the long-term operation of the ECCS
equipment, we may see some relaxation in those, and that's where we get
some benefit.
But what we would like to do in this, what we're going to draft
is to try to put some bounds on maintaining some mitigation capability, but try
to put a bound on what is off limits for future changes.
So I heard your question earlier about are we going to have
to come in and ask for a license change on every change or do we have the
liberty to run off and do anything we want to, and I don't think you're going to let
us do that, for number one.
But I'd like to have some boundaries on what we can do and
what we cannot do under 50.59.
DR. POWERS: It seems like a lot of things that you've
mentioned specifically, you've said requirements on accumulators,
requirements on room coolers, a couple of other things like that, that those can
be addressed in risk based without getting into arguments over the pipe break
frequency.
MR. WARD: They can be, but they cannot be done across
the board.
DR. POWERS: Well, I'd like to just see one of them dealt
with. I mean, I'm listening to a performance on risk informing 50.46, and I
haven't seen a risk number yet.
Has anybody tried to do these things, to look at how you can
adjust success criteria and stuff like that around and see what impact it has on
CDF or LERF or some more reasonable FC curve?
You can react, but it seems like that would be a good context
to look at these thing because I'll bet you can.
MR. WARD: We probably can. It requires each example that
you come up with to go do a detailed analysis to justify that change and then
justify a change to your design basis, you know, one piece of equipment at a
time, and that does not at all lead to any uniformity within a unit, for example.
We just cut out a cooler, a room cooler, at Vogtle temporarily
for a cycle. We based it on deterministic calculations as well as PRA, but in
order to keep our design basis consistent between two trains and both units,
we're going to go replace a cooler. It's minor, $100,000, but if I had this rule
change, that cooler is really inconsequential and doesn't need to be there, and
I could go remove all four of them from my design basis and be done with it.
DR. POWERS: Suppose you said you did the risk analysis
and said, "Okay. The cooler means nothing." And I could show that based on
risk. Couldn't you do it under 1.174?
MR. WARD: I could justify it. I would probably -- I may need
to do a 50.92 license change to get it permanently removed from the design
basis anyway.
CHAIRMAN APOSTOLAKIS: Bill, when do you think we're
going to roughly stop? We're 20 minutes --
DR. SHACK: We're just about finished.
MR. WARD: Yes.
CHAIRMAN APOSTOLAKIS: There's a lot to do this
afternoon.
MR. ROSEN: Could I ask one quick question, George?
I'm surprised, Lou, not to hear you express any interest in the
replacement of the 1971 ANS decay heat curve with a more updated version.
That seems like a simple thing.
MR. WARD: There is interest in that. I believe NEI is
planning to -- and I can't speak for NEI again -- but I believe they're planning to
petition for a rule just on that part, to go from 71 to 94 fairly soon, a couple of
months.
MR. ROSEN: So your silence on that matter doesn't imply
that you're not interested in it. You're just letting that be handled by NEI.
MR. WARD: Yes. Now, the LOOP part of it, I've got some
serious questions about that, but I'm not going to sit up here and try to
undermine interests for other people, you know, with the issues going on in the
utility today on the grids and newspaper articles every day on power blackouts
in California. The PR end of that bothers me as much as anything, but that will
have to be addressed, and I guess the staff has got a plan on how to deal with
that.
CHAIRMAN APOSTOLAKIS: Now, you said that you think
that the staff's approach places priorities the wrong way.
MR. WARD: Yes, sir.
CHAIRMAN APOSTOLAKIS: But they didn't really say, as far
as I recall, that they think Plan A is more important than B. They just created
A and B on the basis of what can be achieved real quick and what can wait a
little later.
So it's not a matter of they are thinking that A is more
important than B. It's just that they feel that in 12 months they can do certain
things, clean up the regulation and so on, and so you disagree with that?
MR. WARD: I don't disagree with that, and I think if the staff
wants to work on that, that's fine. I think we would like to not wait for three
years or however long the long-term program is to get to the last element.
CHAIRMAN APOSTOLAKIS: They believe it will take that
long because there will be issues to be address, is a different issue now. Do
you believe that the issues are not such significance or they will not be so time
consuming so it can be done in a year and a half?
I mean, that's a different kind of disagreement. It has nothing
to do with priorities now.
MR. WARD: Right.
CHAIRMAN APOSTOLAKIS: It's a matter of assessing what
it will take to do it.
MR. WARD: I believe the issues on the redefinition should be
able to be addressed in the next year if we work on it.
CHAIRMAN APOSTOLAKIS: Mark?
MR. CUNNINGHAM: Just to clarify one point, the staff is not
suggesting in the paper that it will take three years to do that. It could take up
to three years.
CHAIRMAN APOSTOLAKIS: Up to three years. I was aware
of that.
MR. CUNNINGHAM: And the discussions that Mr. Ward
alluded to earlier about between us and the staff will have a strong element in
defining whether it's one year or two years or three years. So we're not a priori
saying that it's going to be three years.
CHAIRMAN APOSTOLAKIS: But it's not really a matter of
priorities though. It's a matter of, you know, what can we do immediately and
what can we do a little later.
MR. CUNNINGHAM: And the way we think of it is that these
are three parallel activities.
CHAIRMAN APOSTOLAKIS: Yeah, that paragraph.
MR. CUNNINGHAM: The work on the large break LOCA
redefinition is not being slowed down, if you will, because of a lack of resources,
a reallocation of resources to the other parts. I think it's intended to go on, and
you couldn't tell it from the presentation, but in the paper, I think it makes clear
that the staff is committing substantial resources to the third part of this.
CHAIRMAN APOSTOLAKIS: Very good.
Bill, where are we?
DR. SHACK: We're through at this point unless there are any
--
CHAIRMAN APOSTOLAKIS: Thank you.
DR. SHACK: -- further comments or questions.
CHAIRMAN APOSTOLAKIS: Well, I'd like to thank the
presenters, and we are 20 minutes behind. I want to remind the committee that
we have a large number of letters we have to complete this month. So I'm very
sensitive to the timing here.
So we'll break until 10:40, and we'll come back. We're
recessed.
(Whereupon, the foregoing matter went off the record at
10:24 a.m. and went back on the record at 10:40 a.m.)
CHAIRMAN APOSTOLAKIS: Our next topic is policy issues
related to safeguards, insurance and emergency preparedness regulations at
decommissioning nuclear power plants, storing fuel in spent fuel pools. Dr.
Kress is the cognizant member.
DR. KRESS: Thank you, Mr. Chairman.
Just to remind you, the staff was considering some generic
rulemaking related to decommissioning plants, particularly with respect to the
possible requirements for insurance and emergency preparedness and other
things, and in order to guide their thinking on this rulemaking, they developed
a technical study which we reviewed and wrote a letter on, had some opinions
on.
They used this technical study then to identify some policy
issues associated with possible rulemaking and rule changes, and it's these
policy issues that we're going to hear about today, and the options they've
identified to deal with policy issues and what their preferred options are.
We do expect to have a letter on this because I suspect the
Commission will want to know what our opinion is on the policy issues
themselves.
So with that, I guess I'll turn it over to Bill Huffman of NRR.
MR. HUFFMAN: Thank you very much.
I am Bill Huffman. I'm a project manager at NRR, and I
helped push this paper through, and I'm going to present a series of slides
basically that overviews the paper and hopefully give you an opportunity to ask
and probe as we go through the presentation.
The very last issue I'm going to turn over to a colleague of
mine on the EP area.
Dr. Kress summarized this, and so I don't know if we need to
go over it again, but the three areas -- there are certainly a lot of areas that we
want to improve in the decommissioning regulations, but the three that have
significant burden to the industry that looks amenable to reduction and also
directly tied to the zirconium fire issue are insurance, security, and emergency
planning.
And there's a long history in trying to fix these, and it's failed
several times, and we're going to try again.
We're starting from a technical study that was recently issued,
NUREG 1738. It was a technical study. There were findings in the study, but
in reality it just reports the risk, but it doesn't make any specific
recommendations.
And as the project manager dealing with that study and trying
to develop rulemaking, we felt that we needed some further clarification and
direction from the Commission because some of these areas are new and
unique in rulemaking, especially an application of risk informing.
And so we have the technical study. The risk is very low. It
meets the quantitative health objectives and safety goals. If you agree that the
safety goals are applicable to decommissioning plants with fuel stored in a
spent fuel pool, then it develops a methodology that you can apply, use reg.
guide 1.174.
And it also concludes that taking a thermal hydraulic approach
to eliminating or precluding the possibility of a zirc fire is difficult to do, and
therefore, we do have to look and see if maybe the risk argument is the best
approach.
MR. LEITCH: Is the operative way there generic? If you went
plant by plant, could you define a time?
MR. HUFFMAN: The study says generic, but if there's
someone who wants to take a gander at that, I don't believe a plant specific
thermal hydraulic analysis would be any easier because the problem is the
configuration after these dominant events, like a seismic event or some other
event that might rupture a spent fuel pool or drain it rapidly. You just don't know
what it's going to be in.
So even on a plant specific basis, in the past when we
approved exemptions in these areas, we assumed a normal design basis
configuration for the fuel. We assumed that air flow was unobstructed. In some
analyses, I think we assumed building ventilation existed.
It's not likely in a seismic event that those conditions are going
to exist. So don't know that you could even do it on a plant specific basis.
DR. FORD: Excuse me. I'm new to this group. So I don't
know anything at all about background. Can you just tell me very briefly in one
sentence or paragraph what physical instances go into the first bullet, what
physical processes? What happens there, a leak in the pool or what?
MR. HUFFMAN: Well, we have this report that looks at
various accident scenarios, looks at slow drain-downs, evaporations.
DR. FORD: Okay.
MR. HUFFMAN: Those take hundreds of hours. There really
has to be a breakdown in the safety culture of the plant to have those kind of
things occur without mitigation.
What you're looking at is a very, very low frequency event,
such as a -- in fact, the dominant event that the report concludes would cause
this rapid drain-down of the pool would be a very large, low frequency, seismic
event.
DR. FORD: So it would be seismic events primarily?
MR. HUFFMAN: Yeah. The second dominant event,
although there's some industry disagreement with that, might be a cask drop,
a 100 ton cask drop moving spent fuel.
DR. FORD: Okay.
MR. HUFFMAN: It might punch a hole.
DR. FORD: Okay. Thank you.
DR. WALLIS: And your assumption is that if this happens, a
fire happens.
MR. HUFFMAN: That's the assumption.
DR. WALLIS: -- is one
MR. HUFFMAN: There is no conditional -- yeah, your answer
is correct. It's one. There's reason to believe that there can be mitigated
actions taken, that it probably wouldn't be one, but the assumption was that if
the pool is drained, the fire occurs.
MR. ROSEN: Now, when you say spent fuel pool accident
risk is low, do you have a number on that?
MR. HUFFMAN: We have a bounding number, again, pretty
much dominated by the seismic frequencies of the plant locations, but it's on the
order of two to three times ten to the minus sixth, is the upper limit. It's less
than that.
DR. POWERS: There have been a number of instances
within the zirconium production industry of zirconium fires, spontaneous fires.
Have you looked at those at all?
MR. HUFFMAN: The technical group did look at that.
George, do you want to answer that?
MR. HUBBARD: George Hubbard from the Plant Systems
Branch.
The individual who looked at the thermal hydraulics in NRR
and also in research, they did look at the information available regarding fuel
fines for the zirconium fines, and I believe, you know, that is addressed in there.
I know we did take a look at it in the 1738.
MR. HUFFMAN: Okay. I'm going to proceed on. One
clarification -- oh here.
MR. GILLESPIE: Frank Gillespie from NRR.
In the report there were really two conditions to get to the
zirconium fire which were listed. One was a drain-down of the pool, but then
you had to violate what you already said, and that's our previous assumption of
the design basis configuration.
So, one, the pool has to be drained down, and, two, the fuel
has to somehow be reconfigured to allow the heat build-up that you need to
start the zirconium fire.
MR. HUFFMAN: It's not necessarily reconfiguration. For
instance, if the roof of the spent fuel pool fell and capped the top of the spent
fuel pool and prevented air flow circulation.
MR. GILLESPIE: Going out in the longer term, the report
assumed an adiabatic situation.
Tim.
PARTICIPANT: Well, we did both.
MR. GILLESPIE: Okay. Because a simple drain-down is not
going to lead to one for one to a fire. That's all I'm saying.
PARTICIPANT: Right. We looked at a situation where there
was 80 there to heat up, and we also looked at a situation where there was full
air cooling, and even with full air cooling for short decay times, you can have a
fire situation. It depends on the amount of decay heat that was still present.
So there are situations. Even with the normal channels
available for air flow, if it's soon enough after the last off-load, you could get to
a fire temperature.
DR. WALLIS: So I think you're wrong, Frank.
MR. GILLESPIE: Well, when I think of five to ten years after
fuel load --
DR. WALLIS: Oh, yes. Maybe that's the case.
MR. GILLESPIE: And that's what I mean. We're in
decommissioning space, and the question implied that you could have a fire
going out to infinity, and that's really the problem we're trying to deal with, is this
finding that we cannot preclude the fire ever.
DR. WALLIS: But no one is smart enough to tell where the
time is, where the scenario just described stops.
MR. GILLESPIE: Yeah, right. But it becomes more
complicated as it goes out.
CHAIRMAN APOSTOLAKIS: Would you go back to Slide 2?
Would you explain a little bit the third bullet?
MR. HUFFMAN: All right. In the report -- and then I might let
Bob Palla (phonetic) speak a little bit more detail on this, but in the report they
applied the principles of the methodologies in reg. guide 1.174 to EP. They
looked at what would happen if you removed or significantly reduced off-site EP
shortly after a reactor permanently shut down. They chose 60 days as the
threshold where you don't have to worry about decay gap release of iodine.
So they did a study with EP in effect, without EP, early
evacuation, late evacuation, and they showed that there is a small increase in
risk in terms of early fatalities, but it meets the criteria of reg. guide 1.174.
DR. WALLIS: Does normally 174 refer to fatalities or does it
refer to LERF?
MR. HUFFMAN: It doesn't, but they quantified it by the -- I
may be digging myself in a hole. They turned it into a probabilistic
quantification.
CHAIRMAN APOSTOLAKIS: You converted the delta CDF.
DR. KRESS: They have a fraction of LERF that's permissible,
and so they say, "Well, we'll have a fraction of change in early deaths," which
is basically equivalent application of it.
MR. HUFFMAN: Okay. The first policy issue is a pretty
simple one, but we had to ask it because we're relying in the report, the
technical study, saying that it complies with the safety goals, but the safety goal
policy statement doesn't address a decommissioning reactor. It talks only about
operating reactors and core damage.
So simply we wanted to clarify with the Commission that, you
know, we can use the safety goal policy statements and the quantifications for
this application.
DR. WALLIS: These are the safety goals that one strives for,
but never hopes to achieve or are these the safe goals one actually enforces?
MR. HUFFMAN: I'm not sure I understand what you mean.
DR. WALLIS: Well, I keep being told that safety goals are
things that we should strive for, but not go beyond, and if we don't quite get
there, it's because we're trying to get there eventually. There's no kind of
assumption that you ought to get there.
And so I'm just asking the question again that I always ask.
Are they things you try to get? Are these the safety goals you actually use to
say you've got to get there or are they something which is out there as an ideal?
MR. HUFFMAN: Well, again, the safety goals are qualitative
statements on cancers and on early fatalities. At a decommissioning plant
especially, if you get there, you've got some serious problem, but --
DR. WALLIS: So you're saying you must not step over these
goals.
MR. HUFFMAN: Well, you would hope that the only accident
we're talking about here is a zirc fire. You would hope that you would never
even come close to challenging it, but for making risk informed decision making,
again, going back to reg. guide 1.174, which is an implementation of this long
train of logic, you know, ultimately its roots lie in the safety goals.
So we just wanted to get a blessing from the Commission that
it was okay to use those safety goals, but we visualize that there will be other
regulatory areas just besides these where we may want to apply reg. guide
1.174 in making our decisions.
DR. WALLIS: Well, what you're really meaning is it should be
used on 174.
DR. KRESS: Well, it's hard to use 1.174 since it deals with
CDF and LERF.
MR. HUFFMAN: Yes.
DR. WALLIS: Just explain how you --
CHAIRMAN APOSTOLAKIS: Well, we just derive delta risk
though.
DR. KRESS: Yeah. So they use the concepts in 1.174. Plus
1.174 calls for other things like defense in depth and margins and compliance
with other rules and things of that nature, and I think you tried to apply that
thinking also.
MR. HUFFMAN: Yes.
CHAIRMAN APOSTOLAKIS: You would have a problem with
the monitoring, particularly with emergency planning, how you monitor.
So your recommendation is one?
MR. HUFFMAN: Yes, do it.
DR. KRESS: Before you leave that slide, your rationale for
saying, yeah, go out and use the safety goals is because the consequences
from a zirconium fire could be just as bad as --
MR. HUFFMAN: the consequences are similar to a core
damage accident with a large release or can be worse if you're talking about
multiple cores.
DR. KRESS: Okay.
MR. ROSEN: It seems to me you're asking the wrong
question about this. Is there any evidence that the Commission didn't intend
safety goals and the safety goal policy statement to apply to the whole life
cycle?
MR. HUFFMAN: Yes. It says specifically, and I thought we
stated so in the paper, that it doesn't apply to anything other than -- we've
quoted things out with the safety goal policy statement. It's clear it doesn't apply
to fuel cycle areas. Just operating reactors.
MR. ROSEN: it applies to operating reactors only.
MR. HUFFMAN: Yes.
MR. ROSEN: And it says that very clearly.
MR. HUFFMAN: Yes.
MR. ROSEN: It doesn't apply to decommissioned reactors.
MR. HUFFMAN: Yeah, it doesn't mention decommissioned
reactors, and in reality most people would probably say a decommissioned
reactor, if it weren't for the zirc fire issue, is more of a material site rather than
a reactor.
DR. WALLIS: So these goals could be applied to a pool
which is connected to an operating reactor, but as soon as you shut down the
reactor and decommission it, it becomes something else?
MR. HUFFMAN: The goals are applied to the entity of the
reactor operating. It's my interpretation. I didn't look at it before I got involved
in this paper. I'm not an expert here, but it's my interpretation based on reading
it that it was pretty clearly applying the core damage of an operating reactor.
I don't think -- again, this is speculation, but no one visualized
that fuel would be kept in these reactors for eternity. They'd be moved off site
to Yucca Mountain by now.
DR. KRESS: And the safety goals also explicitly excludes
issues of safeguards.
MR. HUFFMAN: Yes, it does. It does explicitly exclude
safeguards considerations. That's a good point.
Speaking of safeguards considerations, when SRM from the
Commission asked us to try to resolve this zirc fire issue a couple of years ago,
you know, using a risk informed approach, one of the things that probably
wasn't thought out real thoroughly at the time was safeguards, and it really turns
out that it's difficult, if not -- it's just not within the state of the art right now to
characterize the probability of an adversarial attack on a site, the probability of
radiological sabotage.
There are limited, I guess, methods used once you assume
the attack takes place that might be able to characterize the probability of
success, probability of interdiction, but the initiating event we just don't have a
handle on, and therefore, a lot of --
DR. KRESS: Is it so much that the methods don't exist or the
database?
MR. HUFFMAN: Does someone from NMSS want to take a
shot at that?
MS. WARREN: There are many databases available to us,
including ones that we have available to us here in the Commission that involve
the intelligence community. However, it's the methodology that at this time does
not exist.
You know, we have looked into that area very thoroughly, and
the state of the art is that we don't use this type of method in determining
probability for these type of events.
DR. WALLIS: Well, the problem is that it's not based on
science. It's based on human behavior, and I can think of historical events and
changes in society which would make the likelihood of sabotage either minute
or much larger than today.
MS. WARREN: Well, we certainly have all of this type of
activity under continuous evaluation.
I'm Roberta Warren. I'm the team leader for our threat
assessment team, and I think we've spoken before to your group about, you
know, the program that we have in place for threat assessment.
MR. HUFFMAN: So what motivated us to ask this policy
question is, well, we can try again. It's going to be a deep hole, throwing a lot
of resources and money and effort into, and there's no guarantee to success.
That's option one.
We can just give the Commission an update, a kind of a paper
as to where the state of the art is now without actually committing to try to do it,
or we can continue our current practice and with an open mind as, you know,
the PRA methodology is developed. If something comes up, we'll revisit this,
but our recommendation is Option 3.
DR. KRESS: Well, what then is your judgment about the
associated risk?
MR. HUFFMAN: Well, I was trying to articulate that in the
paper, and our judgment is the risk is kept low. Hopefully it's not greater than
the risk of these other dominant events, but the risk is kept low by a rigorous,
deterministic program for safeguards.
DR. KRESS: Is that an assumption or do you have some way
of validating that?
MR. HUFFMAN: Well, we do have things like OSRES, but I
don't want to get any further than that. I, again, would like somebody from our
safeguards group or NMSS if they want to. You know, OSRES tests the
capability of plants and able to defend against DBTs, other inspections,
assessments.
MR. TRACEY: Bill, Glenn Tracey.
OSRES are at operating reactors, however, not
decommissioning sites.
MR. HUFFMAN: Right.
MR. TRACEY: And we don't conduct OSRES at those sites,
and essentially you have safeguards in place at decommissioning facilities. Of
course, the next policy question is what level of protection and what level of
safeguards should be maintained, and Bill will get to that in a second.
MR. HUFFMAN: Well, I think the gist to your question was,
well, if there's so much uncertainty, you know, how do we know that the
frequency of these events and the risk isn't greater than the others, and I don't
think I can say.
DR. KRESS: Well, I guess my question is if you want to try
to decide on what level of safeguards is necessary and even what level of
emergency preparedness is necessary, it would be predicated on what level of
risk you're trying to protect against.
And my question was what do we know about that risk and do
we know enough to make judgments on those things.
MR. HUFFMAN: You know, that exists in all PRAs. I guess
most PRAs, the expert judgment would be that the risk of sabotage is in the
grass compared to the other dominant events.
MR. GILLESPIE: Bill, let me help you out here.
MR. HUFFMAN: Yeah.
MR. GILLESPIE: Twice a year Bobby's staff actually
prepares a briefing, and Mike Webber I saw here earlier, prepares a briefing for
the Commission which addresses the design basis threat and what they feel the
credible threat is. And that goes in every six months, the deterministic view of
what it is is revisited by the Commission.
So her staff does do that, and I don't want to get into any
more detail because all of a sudden I'll creep into something that's classified.
DR. KRESS: I have the same problem. You know, we have
a set of design basis accidents for operating reactors, and then when I ask
myself, well, what does that -- being able to meet those design basis accidents
by the design and operation, what does that mean in terms of the risk status of
the plant?
And nobody can ever answer that unless they go and say,
"Well, we'll do a PRA then."
And then you do the PRA, and it tells you the risk status, and
it tells you something about the correlation between those design basis events
and the risk status, but here all we have is the design basis event. We don't
have a PRA.
So I don't know how to make that correlation. How do I know
that the design basis threat and being able to meet it results in an acceptable
safeguards risk status with respect to decommissioning plants?
I don't know how to make that jump, and I was wondering how
you guys are making it. That's the nature of my question.
MR. ROSEN: And the other side of that is how do we know
that the resources we're committing both at the staff and at the utilities is in any
way commensurate with the risk.
DR. KRESS: Yeah. I don't know.
MR. ROSEN: It may be way too much.
DR. KRESS: It may be too much. It may very well be too
much.
MR. ROSEN: Not too little.
CHAIRMAN APOSTOLAKIS: At the same time though the
problem here is not of the same nature as risk due to accidents. I'm not even
sure that the policy issue is phrased the appropriate way. Using probabilistic
risk assessments for quantifying the likelihood of sabotage, I mean, here you
have somebody who's intentionally trying to damage, and PRA doesn't deal with
that. PRA deals with accidental failures.
There are other ways of attacking this. So I'm not even sure
that the whole question is meaningful, although I do agree with you guys that
some sense of what are the numbers we're talking about is needed.
Also, I'm bothered by the loose use of language like
assessing likelihood in a qualitative manner. I really don't know what that
means, although I understand what you're trying to say, but I mean the
language is not the right one.
So, I mean, you will never attempt to develop PRA methods
to estimate the likelihood of sabotage because it's a different thing, a different
question. You know, you are playing games now.
DR. KRESS: That's like an initiating event frequency. You
don't use the PRA.
CHAIRMAN APOSTOLAKIS: It's not initiating. I mean here
the guy is some smart fellow who's trying to do damage.
DR. KRESS: That's an initiating event.
CHAIRMAN APOSTOLAKIS: Yeah, but it's not like pipe
break.
DR. KRESS: Well, it's not stochastic.
DR. POWERS: It could be exactly a pipe break.
MR. HUFFMAN: I guess what we were trying to get at was
that there may be vulnerabilities that could cause -- you know, responding to
Mr. Ford's question, you know, how do you rapidly drain down the pool? That's
one of the ways to do it. And that's an incompleteness in the study.
DR. WALLIS: Or how you change the geometry that you were
talking about.
MR. HUFFMAN: That would do it.
CHAIRMAN APOSTOLAKIS: I think you still have the
problem of how likely is it that somebody would try to do it.
MR. HUFFMAN: That's the answer we can't --
CHAIRMAN APOSTOLAKIS: Maybe we can separate that.
MR. HUFFMAN: That's a question we can't answer.
DR. WALLIS: Well, obviously if you took the fuel away, which
is the sensible thing to do, the problem would disappear.
(Laughter.)
MR. HUFFMAN: That's one way to solve the problem, is to
put it in the dry cask storage.
MR. ROSEN: I think you're formulating the problem in a
manner that makes it too hard to solve. You're talking about trying to use PRA
to assess the likelihood of an initiating event, and I don't think that's something
we could touch.
But, on the other hand, you could assess the likelihood of the
mitigation of an event with the systems that remain in operation, successful
mitigation of a radiological sabotage event with the systems that remain in
operation in decommissioning plants, and PRA would be a tool that could
potentially be used for --
DR. KRESS: As a function of the level of the threat.
CHAIRMAN APOSTOLAKIS: But you would not be
addressing the question of quantification of the likelihood of sabotage.
MR. ROSEN: Of successful sabotage because you wouldn't
have a number for the initiating event. You'd only have a number for the
mitigation potential.
CHAIRMAN APOSTOLAKIS: But is Option 3 using this kind
of input from PRA right now?
MR. HUFFMAN: No. Option 3 is not. Option 3 is the status
quo.
CHAIRMAN APOSTOLAKIS: Why nothing? I mean, it makes
sense to me.
MR. ROSEN: Well, it makes perfect sense to me. I mean if
we were willing to talk about conditional containment probability, conditional
core damage probability given an initiating event yesterday at some of the
subcommittee meetings and we argue about whether it should be one or some
number less than one, it seems to me you could apply exactly the same logic
here.
Forget about the initiating event. We know so little about it.
It's not under our control anyway, and how robust is the existing
decommissioning plant and its systems and facilities and its people and its
management against an initiating event?
CHAIRMAN APOSTOLAKIS: And then perhaps a third
observation there, that it would take substantial resources to develop these
methods, would not be applicable, right?
That's 34 PRA, isn't it?
MR. ROSEN: I think it is.
CHAIRMAN APOSTOLAKIS: In a much simpler system.
MR. ROSEN: Yeah, and applied to a very simple system
compared to what we now apply PRAs to, which are much more complex than
this.
DR. KRESS: Well, it's more comparable to the Level II, where
you don't have the phenomenological things to go into your model.
MR. ROSEN: Well, you have a spent fuel pool, and you have
fuel in it. Now, that's what you're trying to protect, and you have cooling to it,
and with air conditioning, and so you look at all of those kinds of systems and
see how robust.
DR. BONACA: What's the complexity involved in developing
a PRA methodology? I don't understand the methodology word. The
methodology is there. It's more like --
CHAIRMAN APOSTOLAKIS: I think it's more like two.
Evaluate.
DR. BONACA: Yeah.
CHAIRMAN APOSTOLAKIS: The methodology you have
now to identify its uses in the sabotage question, which is, I think, what Steve
and Tom just told us. There are places where you can use it. So two would
seem to be a reasonable option.
MR. ROSEN: It won't give you the whole answer, George, but
it will give you some of the answer, and that's better than nothing.
CHAIRMAN APOSTOLAKIS: Not after a complete answer
ever.
MR. GILLESPIE: George, the staff has actually been
grappling with this for several years, and we're kind of doing what you're saying.
Let me just go to operating reactors and your OSRE program, and one of the
major questions we had when we ran exercise is if you run four scenarios and
you fail one out of four, does that mean you fail security? If you fail two out of
four?
So conceptually in the OSRE program already, in fact, in the
significancy determination process for evaluating drills is the concept of we're
not striving for perfection; we're striving for reasonable protection, and there is
a consideration that if you fail one out of three scenarios, did you fail it because
of a programmatic failure that could be repetitive.
And those kinds of questions are built into the current
significancy determination process so that the risk concepts that you're talking
about are there in the security area, but they're not articulated in mathematical
terms.
CHAIRMAN APOSTOLAKIS: But I repeat. I think the
language in this slide is not the right one, and I think what you just said supports
that.
MR. GILLESPIE: Yeah, the potential, the probability of
success is, in fact, right now a qualitative consideration in what's being done in
security, and in fact, DOE has computer programs that actually do that
mathematically for them when they run similar exercises.
CHAIRMAN APOSTOLAKIS: But even in the significance
determination process, when you decide it's a green, I mean there is some sort
of quantitative evaluation, although you're not saying it's 1.2, ten to the minus
four or five or whatever.
MR. GILLESPIE: Oh, yeah.
CHAIRMAN APOSTOLAKIS: And there is some element --
MR. GILLESPIE: For operating reactors it's a little easier.
CHAIRMAN APOSTOLAKIS: It's a qualitative assessment of
a likelihood, right?
MR. GILLESPIE: Yeah, that's what it really is, and in the
second paper, which unfortunately we haven't gotten to you, which is the
safeguards addendum kind of to this paper, it does talk about the consideration
in safeguards terms of systems and walls and how much reinforcement bar is
in and what's the likelihood of the design basis threat doing something to the
systems that are inherently there already and how you might go about looking
at that.
CHAIRMAN APOSTOLAKIS: But what's wrong with
proposing, recommending Option 2? I mean, it seems to me from the whole
discussion that this is really -- and some of the evaluation has already been
done because you're already using the methodologies, right?
MR. GILLESPIE: I think what you're doing, you've switched.
This was written really, and you got it in a different -- the context of this was in
the return frequency of the event, in the likelihood of what armament that event
would pertain to. So you have to understand these words and the idea of how
they were written, and they were really written in the context of return frequency
of a particular threat, and what is the size of that threat.
So it wasn't written in the idea of coming up with the
probability of success on a conditional level, which we're kind of doing already.
CHAIRMAN APOSTOLAKIS: But the way it's written now, if
I take it literally, it says for assessing sabotage, and that probably is out of the
question. But if you say, "Evaluate current state of the RPRA methodologies,"
or "evaluate the role that current state of the art RPRA methodologies can play
in this issue of sabotage," then it's a different story, isn't it? Because then the
role is clear, what is conditional on the threat.
MR. GILLESPIE: Yeah, and that is --
CHAIRMAN APOSTOLAKIS: And you're doing some of it
anyway.
MR. GILLESPIE: We're kind of doing it qualitatively right now,
and DOE does it in a very -- they have handbooks that say if a soldier runs X
number of yards carrying a weapon loaded so much, the likelihood of his shot
being successful is this percent. They have it down -- yeah, they have
handbooks down to that level of detail.
I don't know that we want to get there.
CHAIRMAN APOSTOLAKIS: That's not what I had in mind.
MR. GILLESPIE: No, I didn't have that in mind.
MR. ROSEN: I have the feeling I'm not being understood.
What I'm talking about is using PRA in almost a traditional way to talk about how
robust are the mitigating systems if someone were to take and break a pipe
somehow. We're not talking about whether it's a soldier or with explosives or
whatever. Forget about all of that. Just assume the pipe is broken and how
robust is this system. Is it two trains, three trains? How big a pipe do you need
to break?
CHAIRMAN APOSTOLAKIS: I understand that.
MR. ROSEN: It's like use the PRA methodologies we now
use to assess the capability of the decommissioning plant to mitigate potential
sabotage, and forget about -- forget completely about the probability of --
DR. KRESS: They actually did that in the technical study.
MR. HUFFMAN: I guess this goes a little bit beyond that
though, and I don't want to get into any safeguards information, but just say
theoretically that you could put a very large hole in the bottom of a spent fuel
pool. There are no mitigating systems for that.
DR. KRESS: It's going to go.
MR. HUFFMAN: There's no mitigating system.
MR. ROSEN: That's one of the events that you say is going
to go --
DR. BONACA: But I think that's the issue.
MR. HUFFMAN: Yeah.
DR. BONACA: If I understand it, on the mitigation side there
isn't every much.
MR. HUFFMAN: We're not talking about pool cooling here.
DR. BONACA: On the initiation side it's a very complex issue,
the different sequences you have, potential initiator of sabotage that is difficult
to estimate, and that's really probably what the complexity is.
MR. HUFFMAN: Absolutely.
DR. BONACA: That's what it is, and there isn't much you can
describe as a mitigation.
CHAIRMAN APOSTOLAKIS: But still you would not be
developing PRA methods for estimating the likelihood of sabotage. You would
be doing something else because this is not accidental anymore.
MR. HUFFMAN: No.
CHAIRMAN APOSTOLAKIS: A different story.
MR. HUFFMAN: Okay. So you agree that number one would
be a waste of time.
CHAIRMAN APOSTOLAKIS: Number one would be a waste.
Wait a minute.
(Laughter.)
CHAIRMAN APOSTOLAKIS: "Commit resources."
DR. WALLIS: Are you saying this is something like aircraft
sabotage?
CHAIRMAN APOSTOLAKIS: I think it's not phrased well.
DR. WALLIS: I mean it doesn't make sense to do a PRA to
study what happens to the aircraft if the bomb explodes in it.
MR. HUFFMAN: I would agree. That would be a similar
analogy.
CHAIRMAN APOSTOLAKIS: I guess what you're saying,
Steve, would apply more to the reactor.
MR. ROSEN: No, I don't agree. I don't agree to that. It
seems to me that number two, if you constrain it and phrase it properly,
constrain it properly, then you can get some sense of the relative robustness of
the barriers to eventual successful radiological sabotage, absent discussion of
the initiating event.
Now, I recognize, and I think I agree with Bill Shack, that you
can envision an initiating event which no existing mitigating systems can do
anything with, but that's true in the reactor, too.
DR. BONACA: Well, I think what we were saying is that whole
PRA here would be driven by a number of initiating events which dominate the
risk
MR. ROSEN: Right.
DR. BONACA: And the mitigation portion is probably not a
very complex thing because there isn't much that you can do, even initiate it to
deal with it, but are limited so that you are still missing most of the insights that
you expect from the PRA, which are coming from in this particular case from
initiators that you can't quantify.
MR. ROSEN: If you don't do the work and you don't put some
people who know how to do PRA to work on this thinking about it, you'll never
get the insights that would allow you to assess the capability and perhaps
enhance the capability of the mitigating systems. You're simply foregoing any
of that.
So my feeling is a properly structured Option 2 would be of
some value.
DR. KRESS: Looking for vulnerabilities maybe.
CHAIRMAN APOSTOLAKIS: I agree.
DR. KRESS: That you can detect.
CHAIRMAN APOSTOLAKIS: I think Option 2 is rephrased.
MR. ROSEN: Yes.
DR. WALLIS: So design changes could make a difference.
I mean you could probably require, if it were desirable, that the fuel should be
stacked in a way so that if the pool drains it cannot catch fire.
MR. ROSEN: Well, that's one possibility.
DR. WALLIS: That's one possibility as an extreme measure.
CHAIRMAN APOSTOLAKIS: No, but I think Steve is right.
Unless you look --
DR. WALLIS: There are physical things you can do to make
a big difference to the probability of a major accident.
DR. BONACA: I understand from Mr. Gillespie that, hey, look.
CHAIRMAN APOSTOLAKIS: That isn't what the --
DR. BONACA: Yeah, I understand. I understand.
CHAIRMAN APOSTOLAKIS: I think we -- policy issue three.
MR. HUFFMAN: Thank you.
All right. That question goes well beyond decommissioning.
We just decided to tackle it because we are trying to address the more specific
issue of how do we address what safeguards requirements are appropriate for
the spent fuel pool.
And we have three options. The slides are on this. The third
opinion is on the next page, but Option 1 would be essentially the requirements
that now really exist at a decommissioning plant because it is still a Part 50
licensee, which should be the operating reactor requirements, you know, with
the full response force, you know, being able to interdict the DBT.
It seems excessive. Certainly if it's good enough for an
operating plant, there can be little argument that it's good enough for a
decommissioning spent fuel pool, but that's one of the options.
Option 2 is something that you may or may not be familiar with
since it went in parallel with this paper, is staff's proposed rule changes to 73.55
to make it less prescriptive, more performance based, and in addition, put a
performance standard associated with it.
This is basically look at where the DBT can do damage and
see what you have to do to prevent that damage from occurring, you know,
such that you don't exceed radiation doses at controlled area boundaries that
exceed five rem. In a spent fuel pool situation, the only situation that's going to
get you to that radiation level is a zirc fire.
So if, for instance, licensees were given Option 2, you know,
depending on the plant specific configuration in the fuel pool, say it's a seven
foot thick pool, high seismic area, a lot of rebar buried in the ground. It's
probably not too difficult for them to demonstrate that you can't poke a hole in
it to drain it. And they may have to do a very minimal amount to be able to
demonstrate that they can meet that criteria.
DR. KRESS: Would the design basis threat be the same one
you use --
MR. HUFFMAN: Yes.
DR. KRESS: -- in operating the reactor?
MR. HUFFMAN: Yes, the same design basis threat, a slightly
different approach, and you don't have to interdict it. You don't have to stop
them at the fence. You don't have to worry about defending something
unimportant.
DR. WALLIS: Aren't you coming around to Steve's argument?
There are a lot of things you can do with design to change the problem.
MR. HUFFMAN: Absolutely. But, again, we're going to use
judgment, engineering, and perhaps PRA can play a role here, but this is a
broad based recommendation right now. You know, the details, reg. guides,
how we figure that out in regulatory space is not what we intended to do.
DR. WALLIS: Proposing to redesign fuel pools in some way
or modify existing fuel pools in some way then?
MR. HUFFMAN: That would not be our recommendation, but
that would be an option. If they wanted to build a cage around the pool, and
believe me, this is not what we're recommending, but pursuing your thought, it
might make it impossible to put an explosive charge close to the wall, and that's
cheaper than maintaining additional guards 24 hours a day, 365 days a year.
DR. WALLIS: This is the option you're --
MR. HUFFMAN: That would be an option to take.
DR. WALLIS: -- recommending.
MR. HUFFMAN: Yes.
DR. WALLIS: Is to make the thing impregnable or whatever
you want to call it or robust, robust.
MR. GILLESPIE: Graham, what we're offering is a
performance criteria that leaves to the licensee the method.
MR. HUFFMAN: The licensees would make that decision,
right.
MR. GILLESPIE: So if they want to trade off design features
for manpower costs, that should be their economic decision, not ours. So this
is a rule that would set a limit at the site boundary, and the licensee figures out
how to do it.
And this also brings into harmony with Part 72.
DR. WALLIS: Are there licensees who think this is feasible?
MR. HUFFMAN: We'll find out within a --
DR. WALLIS: Well, I mean, it doesn't seem to make much
sense to suggest an option that if it's not feasible.
MR. HUFFMAN: I agree. We would not want to propose a
rule if nobody was going to be able to utilize it to reduce burden, if it made no
sense.
DR. KRESS: As time went on in decommissioning,
presumably the probability of a zirconium fire gets less, although you know
there's some question about that. Would the level of protection then be variable
with time rather than a fixed something?
MR. HUFFMAN: Does Glenn Tracey -- would you allow me
to speculate on this?
MR. TRACEY: Yes, speculate.
MR. HUFFMAN: Okay. Again, since this is a performance
based rule, mitigation time is certainly a consideration in the argument a
licensee may make. If you're Humboldt Bay and you've been shut down for 30
years and it would take even in an adiabatic thermos, you know, weeks to get
there, you could certainly argue; a licensee, I think, could make a pretty darn
valid argument that they could do something ad hoc to mitigate the results of the
sabotage.
DR. WALLIS: Enclose it in a block of ice 100 foot thick and
it slowly melts away.
MR. HUFFMAN: Or in Humboldt Bay's case, the water will
probably leak in anyway.
(Laughter.)
MR. HUFFMAN: So maybe that was a bad choice. Anyway,
I think that's what we're getting at.
DR. WALLIS: Well, seriously, is this something that's going
to find some takers?
MR. HUFFMAN: I can't answer you right now.
MR. TRACEY: It's very consistent with current Part 72, which
NMSS has pools and also has dry casks. So since it's consistent with what the
industry is practicing from the materials side, I would think it will have takers.
MR. HUFFMAN: There is the third option, and the third option
is to apply what we currently apply at dry cask storage storage facilities.
DR. SHACK: How is it different? My criteria seems to be the
same.
MR. HUFFMAN: Dry cask storage, the facilities aren't
required to meet the DBT. So it's significantly different. That's why it's a policy
decision.
DR. POWERS: It seems to me that that's not an exactly
equivalent option, is it?
MR. HUFFMAN: Well, I don't think that a dry cask is
equivalent to a spent fuel pool. So, right, I don't, and I hate to confuse the
issue, but there is one wet storage facility out there, G.E. Morris, and the same
regulations apply there.
DR. POWERS: So all you're saying is we may have made a
mistake.
MR. HUFFMAN: May have, but that's a policy decision that
the Commission has to make.
DR. POWERS: Well, it seems to me that in thinking about
Option 3, you need to be very clear that dry casks, a little bit of the fuel per
cask; spent fuel pools are a whole bunches.
MR. HUFFMAN: I agree that they're apples and oranges.
MR. GILLESPIE: Also, Dana, it's not quite as clear cut as
even it was just made to sound. Within Part 72, if you have a dry cask storage
under a general license at a reactor, the design basis threat does apply, but if
you have a specific license, it doesn't. So there's even an inconsistency there
within the same rule.
So there's some clean-up here that needs to take place.
DR. WALLIS: Well, I'm concerned about this really
performance. Some design that assures no fuel damage that exceeds off-site
dose limits? No idea what it might be?
MR. HUFFMAN: The design -- I hope we're not being thrown
off by the word "design," because that includes security plans, and it's not just
a physical design. It's the security system.
DR. WALLIS: You're going to trade off. You said you're going
to trade off sort of people versus physical things. How do you do that if you
can't assess the sort of risk associated with people performance? I don't know
how you do the tradeoff in a logical way.
MR. HUFFMAN: Anybody out there want to answer that
question?
MR. GILLESPIE: You've got a design basis threat. You could
make certain decisions. For example, if putting a hole in the pool drains the
pool, but you decide to put -- I don't know -- a spray system of some kind in to
put a fog spray over this thing, you could --
DR. WALLIS: For a long time.
MR. GILLESPIE: -- that could become a consideration.
I don't know what the tradeoffs could be. The idea of having
a performance criteria was to allow licensees to make that decision and not
have the regulator making it for them.
So the system, the design of the system, it's the pool; it's the
security system; it's the number of guards; it's how close the LLEA is to come.
If the LLEA can be there in 15 minutes versus 30 minutes,
that could make a significant difference, particularly if you have older fuel, which
is the point I was making earlier on having to reconfigure the fuel if it's older fuel
potentially.
DR. WALLIS: It's amazing. Maybe we should have the same
rule for reactors.
MR. HUFFMAN: Well, that's what we're proposing. That rule
is for reactors right now proposed, and we're suggesting that --
DR. WALLIS: No fuel damage?
MR. HUFFMAN: No. That's --
MR. GILLESPIE: No core damage.
MR. HUFFMAN: -- no core damage.
MR. TRACEY: No spent fuel sabotage which would exceed
five rem, 100 meters. So the 72106 standard.
DR. WALLIS: No damage?
MR. TRACEY: That would exceed.
DR. WALLIS: You're going to get probabilities in there.
MR. HUFFMAN: No damage that exceeds five rem. If you
threw acid in the pool, that definitely would damage the fuel, but that's not what
we're talking about.
DR. WALLIS: You'd have to talk about probabilities. You
can't go with no damage. You're going to have to do a PRA for this new design,
whatever it is. You're going to have to do something like a PRA.
MR. HUFFMAN: You would have to have some kind of a
justification that demonstrates that it doesn't exceed the performance criteria of
five rem at the controlled area boundary.
DR. WALLIS: You can never do nothing. You've got to have
a probabilistic measure. You cannot say you'll never have.
MR. GILLESPIE: I think we have to agree. The thought is
that it will likely not exceed. We have to have reasonable assurance it won't
exceed because the right words may be yet to be selected, but we're looking for
reasonable assurance, which gives a sense of we're not dealing in absolutes.
We're not looking for the absolute assurance. We agree.
DR. KRESS: I think we need to move on to the next policy
issue.
MR. HUFFMAN: Okay. Policy Issue 4 is what do you do
about insurance. There's two types of insurance in the facility, and our
recommendation would probably be applicable to both, but we're primarily
concerned about Price-Anderson, and when do you reduce Price-Anderson
insurance coverage from limits and allow these decommissioning facilities out
of the secondary retrospective premium?
We looked at it, had a lot of debates, and this is probably the
closest you're going to get to a risk based recommendation, number four,
because it doesn't directly impact public health and safety, and frequencies are
very low, and our recommendation is to allow them out of the insurance limits
for operating reactors very shortly after they permanently shut down and off-
load.
MR. ROSEN: This is Price-Anderson?
MR. HUFFMAN: Yes, Price-Anderson.
MR. ROSEN: Not 50.54(w)?
MR. HUFFMAN: We would also recommend changes to
50.54(w). We would recommend in the details of this -- again, this is the broad
scope for the Commission -- to say, "Okay. We agree that you can use a
frequency based argument on this one."
But the details were proposed back to the Commission in '93,
SECY 93-127, where we would let them out of the secondary retrospective
premium. We would lower the primary limits on Price-Anderson to 100 million,
and probably reduce 50.54(w) to around 50 to 25 million.
MR. ROSEN: From its current --
MR. HUFFMAN: From it's current, yeah, exactly.
DR. KRESS: Now, how did you arrive at those particular
numbers?
MR. HUFFMAN: We endorsed the same -- there are other
things that can cause, you know, exercising of insurance. Even if, you know,
somebody thought that there might be an accident and suffered mental anguish,
they can sue for insurance.
You could have a tank with radioactive liquids spill and there
would be off-site liability associated there. Ninety-three, one, twenty-seven
went into detail what those appropriate limits might be in those situations, and
we see nothing in 93-127 that's been superseded, and so we thought those
limits were still appropriate.
DR. KRESS: That's where they came from.
MR. HUFFMAN: Yeah.
DR. KRESS: Okay.
MR. ROSEN: Fifty, fifty-four (w) covers property insurance,
minimum requirements of property insurance. What you'd be covering is the
radiological to clean-up on site, not off site; on site.
MR. HUFFMAN: Right, on site.
MR. ROSEN: Clean-up of a --
MR. HUFFMAN: With a tank spill.
MR. ROSEN: -- tank spill.
MR. HUFFMAN: Right.
MR. ROSEN: Or some other accident that resulted in some
radioactive contamination of the fuel handling facility.
MR. HUFFMAN: Yeah, right.
MR. ROSEN: And that would be in the range of 25 to 50
million.
MR. HUFFMAN: Twenty-five to 50 million, yeah.
MR. ROSEN: That seems consistent.
MR. HUFFMAN: Yeah. That concludes my part. Randy
Sullivan from the EP Branch is going to come up here and finish it off.
MR. SULLIVAN: Hi. Thanks. Randy Sullivan from NRR.
I wanted to talk about emergency preparedness, and as it
relates to this SECY.
Option Number 5 is to determine policy of what level of
emergency preparedness would be appropriate, and the options are fairly
simple. It's just a logical step through.
Do little. Do most everything we're doing now, or do
something in between. We suggested that the something in between is
appropriate. That's Option Number 3.
DR. KRESS: The policy issue stated with the qualifier on it
is given the low likelihood of a radiological release large enough to exceed
protective action guidelines. That's based on, since it's a likelihood -- is that
based just upon the earthquake PRA that they did in a technical study or does
that include safeguards?
MR. SULLIVAN: We feel that it envelopes the safeguards
issue. Actually in emergency preparedness space, we feel that that issue is
enveloped by the emergency planning that this would propose. So it doesn't
matter what the initiator is.
DR. KRESS: You're making a judgment that the safeguards
--
MR. SULLIVAN: Yes, we are.
DR. KRESS: -- risk is low enough --
MR. SULLIVAN: Yes, we are.
DR. KRESS: -- that it probably is the same order of
magnitude of the earthquake.
MR. SULLIVAN: Well, you know, I'm glad you brought that
up actually. It's a little more -- I want to address that in a little more depth. In
emergency preparedness, we're not working simply against risk. Our obligation
is against defense in depth, you know, as stated in the '86 Commission policy
on the safety goals. It reiterates a couple of times that emergency
preparedness is an element of defense in depth.
So while we want to risk inform this process, you know, as is
appropriate and in accordance with Commission guidance, what we're
attempting to do here is maintain the appropriate level of defense in depth.
Now, --
DR. KRESS: So you'd have to answer a question, and that
is: what is the appropriate level of defense in depth?
MR. SULLIVAN: Exactly, and we think we can do that in the
rulemaking process; that there be a level of emergency preparedness we
believe is appropriate, and we have technical arguments for that.
Now, what we would base these decisions on are not only
risk, but the four bullets in the middle of the page. There's the physics of the
situation. You know, you cannot get a rapidly evolving accident with the spent
fuel pool. There is --
DR. KRESS: Even if you rapidly drain the pool.
MR. SULLIVAN: Right.
DR. KRESS: It still takes a long time.
MR. SULLIVAN: Well, even with fairly new fuel, it takes a
couple of hours. You know, in a reactor, our emergency plans are poised for
immediate action. I mean within 31 minutes.
DR. POWERS: It seems to me that when you make these
arguments about it taking a long time, you're presuming that the decay heat is
going to be responsible for raising the temperature to the point that you get
some rapid reaction. It's not evident to me that that's necessarily true as we
move to high burn-up fuels where we have zirconium hydrides inclusions
distributed in the clad.
MR. SULLIVAN: Well, we're basing our path forward on
1738. So I'm using the technical analysis.
DR. POWERS: Well, I would hope that we include in that
looking at the issues of ignition by spontaneous combustion of zirconium
hydrides.
MR. SULLIVAN: As part of the emergency preparedness
rulemaking process or as part of the technical --
DR. POWERS: In general.
MR. SULLIVAN: Okay. Certainly.
DR. KRESS: I think there's a significant of zirconium hydrides
even without high burn-up fuel in the spent fuel pool fuel.
DR. POWERS: I think most of those, Tom, though -- until you
get to high burn-up, those hydrides are distributed. It's only when you start
getting inclusions where you have real microscopic quantities that you need to
worry about them as ignition source it seems to me.
DR. KRESS: Because they concentrate near the surface of
the --
DR. POWERS: They concentrate near various points that are
a little lower in temperature, and it's incrementally lower, but they concentrate
as nodules, big, and so if you get just a casual fracturing, they get exposed to
air.
But what I don't know, and we've not had any discussion from
the staff on this, is the pyrophoricity (phonetic). Is the pyrophoricity on these
things equivalent to uranium hydride, in which case they'll ignite things, or are
they more like magnesium hydride, in which case maybe they won't?
MR. SULLIVAN: Well, that's clearly an issue that's going to
have to be dealt with, but we're basing it on the accident as described in 1738,
and we're assuming that we've got, even at the very shortest time that we're
talking about, you know, less than a year, a number of hours before this
accident can begin.
That would allow certain -- that would change the focus of
emergency preparedness from the way it is at operating plans in some
fundamental ways.
There are some other angles. Potassium iodide wouldn't be
relevant, you know, because you don't have iodine. So there is a series of our
regulations that --
DR. POWERS: It just wouldn't be radioactive.
MR. SULLIVAN: Right. So there's a series of our emergency
preparedness regulations that are obvious that would no longer be applicable.
DR. POWERS: That would be a health benefit to the
population?
(Laughter.)
DR. WALLIS: This ten hours doesn't make any sense to me,
and suppose that an event happens, and then ten hours later you know there's
going to be a fire, and there's going to be a large release of radioactivity, a very
large release of radioactivity. Ten hours? What can you do in ten hours that's
going to make much difference?
You can get people out of there. You may get them to hunker
down or something, but --
MR. SULLIVAN: I don't want to confuse you with what we're
proposing here. We're proposing that emergency preparedness in Option 3,
what we're proposing to the Commission, is that emergency preparedness be
maintained as is at the operating plant for some period of time. That period of
time is less than a year, but it will be determined in rulemaking. All right? We
don't know what the exact time is.
Then there will be a decrease in requirements commensurate
with the physics of the situation, these four bullets in the middle here, the
physics of the accident, the ease of mitigation, the ease of protective actions,
and the low risk.
MR. ROSEN: And paying attention to Dana's point about
hydrides.
MR. SULLIVAN: Yeah, well, apparently, yes.
Now, at some time in the future when the fuel is sufficiently
decayed such that the physics of the situation dictates under worst case
conditions, minus what you mentioned, at least ten hours, but probably no more
than 24 hours to take action we would propose making the EP regulations
similar to that for a spent fuel storage facility.
DR. WALLIS: So you're assuming that someone is going to
prevent the fire occurring in that ten hours?
MR. SULLIVAN: No, and the basis of this is that we've looked
at a study of evacuations in the United States, and in fact, there's an -- this is
1980s data, I'm afraid to tell you, but it was the best data that I could find --
there's an evacuation about every two weeks. They are largely successful, and
they are largely ad hoc, and yet, indeed, there are cases where 12,000 people
are moved in six hours without a nuclear grade emergency plan to do it.
There are cases when 6,000 people are out and back in in 11
hours. Now, we are using that historical evidence to base --
DR. WALLIS: But now you've eliminated the EP after this
situation. So what's going to get them out when the fire is waiting to happen for
ten hours? What's going to happen to them then? Are they just going to sit
there and wait for the fire?
MR. SULLIVAN: No, not at all. The emergency plan would
always require off-site notifications, that there be an on-site emergency
capability. The issue really is the level of off-site emergency.
So we're expecting notifications to be made, and we're
expecting there to be off-site agencies that are capable of acting on those
notifications, and there's a good reason to assume that. You know, there's a
good, historical record that these evacuations take place. They're done
effectively, et cetera.
DR. KRESS: So the technical issue is how long do you have
to decay before you reach some ignition temperature that's currently ill defined
for ten hours. So that's the technical issue that has to be determined.
MR. SULLIVAN: We came to consensus with FEMA on 24
hours being an absolute maximum.
DR. KRESS: Well, whatever the time is, you still have to
decide what the ignition temperature is, and you'll have a pretty good handle on
the decay heat..
MR. SULLIVAN: Yeah.
DR. KRESS: I guess you'll let it be adiabatic just to not have
to deal with the --
MR. SULLIVAN: We're proposing using the graphs in 1738
and not doing a site specific analysis. So if it's a BWR, it's X number of hours
and X number of years and off you go.
DR. KRESS: For a fixed ignition temperature.
MR. SULLIVAN: Yes.
DR. KRESS: That somebody has specified.
MR. SULLIVAN: That's right.
DR. KRESS: But that has to be put on a pretty good technical
basis in view of, say, Dana's hydride.
MR. SULLIVAN: This determination is based on 1738. If
1738 needs to be informed by Dr. Powers' question, then so be it.
DR. WALLIS: Well, Bill Huffman said you cannot predict
when the zirconium fire is not physically possible, and now you're going to
predict how long it takes to occur when it is possible.
MR. SULLIVAN: Yes, 1738 does exactly that.
DR. WALLIS: Well, it just seems to me there's some
inconsistency here.
MR. SULLIVAN: It's assuming there --
DR. WALLIS: You can't predict when it's possible, and yet
you can predict how long it takes to occur. Well, you've got to first know if it's
possible.
MR. SULLIVAN: No, you can't predict when it's not possible.
DR. WALLIS: Well, then you can't predict when it is possible.
That's the logics.
MR. SULLIVAN: No, I think 1738 would say that it is possible.
DR. WALLIS: If you can't predict when it's not possible, you
can't predict when it is possible. It's sort of if A, then B, and if not A, not B.
MR. SULLIVAN: Well, why don't we let somebody who
helped write 1738 address that rather than me?
MR. HUFFMAN: I'm not the one who did the thermal
hydraulic analysis, and I'm not an expert in that area, but I guess 1738 on the
most conservative approach, the adiabatic approach, it is a fairly simple thermal
hydraulic calculation of how long it will take if there's no energy leaving the
system to reach the assumed zirconium ignition temperature. Okay? That's not
a complicated equation calculation, and that's the number that Randy is talking
about.
On the other hand, it's very difficult to prove that you won't
reach that zirconium ignition temperature when you don't know what the
configuration is and what the cooling and heat removal from the system is.
That's the difference.
DR. KRESS: And the problem there is deciding what that
ignition temperature ought to be, and they fixed a number, you say, in this other
one, and that's the one that I think we're saying may be in some doubt.
MR. SULLIVAN: Well, yeah. When 1738 was presented to
the Commission, it was presented as a bounding. In a sense, you could
interpret the way it was presented was that it was an adequate bounding
analysis, and that if we worked off this, you know, reasonable assurance that
public health and safety could be insured. So that's --
DR. KRESS: Do you recall what the ignition temperature
was? Was it about 1,500 degrees C. or something like that?
MR. SULLIVAN: I think it was 900.
DR. KRESS: Nine hundred.
MR. SULLIVAN: Is there a thermal hydraulicist?
MR. TINKLER: When we evaluated the criteria that we
consider to be appropriate for ignition, we considered a range of different
possible thermal hydraulic boundary conditions, and we specified ignition
temperatures for a long-term operation as low as 600 C. up to about 900 C.,
depending on the age of the fuel, whether or not we thought there was a
significant ruthenium inventory remaining the fuel.
And as I recall, the lower temperatures of 600 degrees C., we
did address the issue of hydride reactions and considered that they would not
be limiting at such low ignition temperatures.
Now, the concentration of hydrides and inclusions in the fuel,
the extent to which we have data on whether or not that would lower an
effective ignition temperature, I don't recall exactly, but the general conclusion
was that those temperatures as low as 600 would cover the effects of hydriding.
Now, I wanted to also just say briefly, too, that was when we
were considering things like the break-away oxidation and the range of different
temperatures and the low temperature.
No matter what ignition temperature was selected, we
recommended that the calculation had to be done to show that you could
maintain an equilibrium condition, you know, regardless, and whether or not a
particular calculation is conservative, that judgment can't be reached unless you
are considering the effects of reactions, the chemical energy. It may be slow,
but now you're competing against a decay heat level, which is low.
So reaching a judgment as to whether or not oxidation energy
is important or unimportant can only be made relative to the magnitude of decay
heat and the heat losses. So we recommended that a calculation be done
actually addressing heat generation and losses.
DR. WALLIS: Well, I go back to my point. You're going to
predict here when it reaches a temperature for at least ten hours and maybe it's
24 hours, and then you can also predict reaching a temperature for 100 hours,
but predicting when it can reach an ignition temperature for any number of
hours is just a thing which we were told you couldn't do.
So something just doesn't seem consistent.
MR. SULLIVAN: Well, from an emergency preparedness
point of view, we think that somewhere we'll come down with our stakeholders'
FEMA states and decide what's a reasonable number.
DR. WALLIS: So you're going to negotiate by words rather
than by technical analysis.
MR. SULLIVAN: Well, the technical analysis will give us some
indication of when this ignition temperature is possible between the ten and 24
hours time frame, and that's in the report.
The infinite time frame is not in the report. The 100 hours is
not in the report. I suppose it could be.
DR. WALLIS: You've got equations. Presumably you can run
them for any number of hours.
MR. SULLIVAN: Yeah, the equations could be run, but --
DR. WALLIS: We're told you can't do that.
MR. SULLIVAN: Not by the EP guys. The EP guys are
simply telling us 24 hours would be more than adequate to take protective
measures off site, and so if you'll give me chart that will go up to 24 hours, I can
write an emergency preparedness regulation that will assure public health and
safety reasonably. That's kind of what we're saying here.
MR. LEITCH: Can I probe a little bit as far as what you mean
by emergency preparedness? Full scope, I assume, you know, initially after
shutdown, full scope is full scope, including sirens, emergency response
organizations, ELF, Technical Support Center, all of that, Media Center, all of
that kind of thing.
MR. SULLIVAN: All of that stuff.
MR. LEITCH: And in the last category, the eventually
eliminate EP, I guess what I'm picturing is once you get down to that situation
where you have ten hours before you reach ignition temperature, what you have
at that point is no sirens, no requirements for sirens at any rate, no off site
facilities. What you really need at that point is one guy who's still standing who
can call the local --
(Laughter.)
MR. LEITCH: -- and his instructions are if for any reason that
water goes down, call the local law enforcement agencies and tell them they've
got ten hours to evacuate.
Is that it?
MR. SULLIVAN: Somewhere more than one guy is still
standing, I think.
No, I hope i Haven't confused you. We're really talking about
off-site EP requirements. The on-site program would look a lot like an ISFS on-
site program. There's training; there's drills; there's people; there's pagers;
there's call-outs. You know, there's a --
MR. LEITCH: Even an eventually?
MR. SULLIVAN: Yeah, yeah. If you have spent fuel under
ISFS regulations, 72.32, there's a whole program. It just doesn't involve off-site
folks much. The off-site folks are invited to training. They're invited to
participate in drills. They're invited to an annual meeting, but that's about it.
There's no sirens. There's no funded EOC. There's no mandatory off-site drill.
But on site there's a fairly, you know, reasonable level of
emergency preparedness. It's not inconsequential.
MR. LEITCH: So when we say eliminate EP, you're talking
about eliminating off site.
MR. SULLIVAN: It should have said eliminate off-site EP.
MR. LEITCH: Okay. So --
MR. SULLIVAN: And really it's not totally eliminated, but that
the requirements are very much reduced.
MR. LEITCH: And on site would be similar to the ISFS
requirements.
MR. SULLIVAN: Yes.
MR. LEITCH: Okay.
MR. SULLIVAN: Which doesn't have a TSC and an EOF and
all the stuff you're used to at power plants, but it's not inconsequential either.
It's a fairly robust program.
DR. KRESS: Okay. At this time I think we'd like to hear from
NEI. I think Lynette Hendricks and Bob Henry are here.
MR. SULLIVAN: Thank you very much.
DR. KRESS: Thank you.
PARTICIPANT: Do we know how long? Till 12:30?
DR. KRESS: This will probably last another 20 minutes or so
or half an hour. Half an hour.
MS. HENDRICKS: Good morning. It's a pleasure to be here
again, and thank you for the opportunity.
This is an overview, upside down overview, of what we'd like
to cover today. I'd like to talk -- I guess we're showing our hand here, is that
we're going to return a little bit to our premise that we had the last time we were
here, that the study is in large part an excellent compilation of outstanding work,
but we think in a few critical area it isn't complete, and that the benefits, cost-
benefit of the completion is definitely there and definitely worthwhile.
I'm going to begin briefly to talk about some of the impacts
that we see if the study is not completed, and I'm going to turn it over to Dr.
Henry to go over a summation of what he believes would be necessary to
complete the study, and then I'm going to briefly cover our views, industry
views, on the options that are presented.
DR. POWERS: And I know you'll include zirconium hydride
ignition in your things that need to be completed.
MS. HENDRICKS: That's right.
DR. POWERS: Bob will cover that one, right?
MS. HENDRICKS: Let's see. Where am I here?
Here's some of the impacts that we view for failure to
complete the study, and again, to sort of revisit where we are on that, and Bob
will go into detail, but we think best estimate is possible with existing data for
percent of ruthenium release, and we question whether the cask drop has the
energy necessary to catastrophically fail the pool. That's sort of where we're
coming from here.
Failure to address these deficiencies in our view -- and I'll get
into the discussion specifically when I talk about the options, but it definitely
impacts the options shown and associated value impact and cost benefit of
those options.
Also, going forward, these things once on the shelf, this issue,
zirconium fires, is going to essentially be with us forever, and without completing
the study and getting a sort of best estimate with a quantification of the
uncertainties, you end up with a less than number, that the risk of the zirconium
fires much less than 3E to the minus six, it's not going to be feasible to deal with
a less than number in the context of PRAs, and yet we're already seeing that
the number is -- you know, we are taking actions. The example was for
safeguards for operating plants based on this zirconium fire.
DR. WALLIS: Excuse me. I'm sorry. I'm lost here. Are you
talking about NUREG 1738?
MS. HENDRICKS: Correct.
DR. WALLIS: Well, we were told it is complete, and you're
saying it should be completed. What's the truth here?
MS. HENDRICKS: Well, we're suggesting that it be recalled,
if you will, and completed subject to peer review.
DR. WALLIS: Oh, you're saying it's a bad study and it should
be revised.
MS. HENDRICKS: It's a very good study to a point, and we
think --
DR. WALLIS: Yeah, I know. That's what we always say when
we want to criticize someone's work.
(Laughter.)
DR. POWERS: I think that in my understanding, and correct
me if I'm wrong, is that in doing this study there were several points that they
reached a conclusion that said they were happy with that conclusion, but now
they're taking things that would be logically follow-ons to that and using that in
formulating their strategy here.
In addition to that, we have this question which Dr. Henry
addressed to us last time about whether one of the initiating events was, in fact,
a feasible initiating event or not.
I mean, I think the staff would admit to you that they cut off
work at various points when they thought they had reached their risk
assessment conclusions, but we already saw today, as you so deftly pointed
out, that trying to draw conclusions about what the follow-on work would have
shown to design their other strategy.
So it's not completed. There needs to be a follow-on to get
the technical data they need to draw these conclusions. That's my
understanding of it.
MS. HENDRICKS: Yeah, and I agree with you completely, Dr.
Powers, and to say that definitely I think the staff has stated that this less than
three to the minus six number is well within the safety goal. So good enough.
And maybe, well, I'd like to suggest as we look at the options
later that maybe it's not good enough, and you have the question of how does
it then relate in PRA space to relative risk of core damage. How accurate are
your value impact assessments going to be when you need to look at the delta
in risk for cost spent if you are dealing with, again, a less than number, and it's
going to be difficult, I think, to accurately quantify benefits.
One final issue is that when studies like this sit on the shelf,
they are going to be used for other applications. We had some indications
talking to the staff, for example, that the cask drop results were going to be
pulled directly into a PRA that's being done from the dry cask standpoint.
We cautioned them about that, and I'm sure they're going to
look carefully at it, but I think the point is that pieces of this study will be used
outside the context that it's, you know, as a very bounding number less than the
safety goal.
With that I'd like to turn it to Dr. Henry.
DR. HENRY: Thank you, Lynette.
I'd just like to touch on a couple of points. As Graham just
said, this is not a complete study so the second word up here can't possibly be
correct in terms of a draft study, but we do believe it provides a good summary
of the much needed information related to this, and it is a good foundation for
evaluating the probability of losing cooling to the pool.
I think our biggest difficulties arise when we then get to using
this for risk informed type of decisions as is discussed in the issue and options
paper. We believe that when you do this, it certainly would be very helpful to
people when assessing issues and options to have a best estimate evaluation
for the different types of initiators that are considered.
As Lynette said, the last time we had the pleasure of
discussing with you, talking with you, we presented a technical database related
to whether or not the cask drop could actually be something that would cause
catastrophic leakage from the pool, and we surely don't find that to be the case,
and we think that that should be put into the study in a very mechanistic way so
that people truly understand what this risk is or is not.
The same thing is related to the issues that Dana has been
talking about earlier with respect to oxidation, ruthenium release, et cetera.
There is a technical basis out there. We suggest that that technical basis be
formulated in a way that we could make use of it through the current evaluation.
In particular, if we look at the screen criteria, which I think are
very well founded, the two that got my attention is would a risk informed
approach help to effectively communicate a regulatory decision or situation, and
of course, here you want to have the best technical foundation that you can
have, and that, of course, trips to the success criteria number five or screening
criteria -- excuse me -- that says if you have information or analytical models
that exist or are of sufficient quality or could be made of sufficient quality to
really support that kind of decision.
Certainly in the term of the cask drop, I think that's clearly
there. In the term of zirc oxidation and the release of ruthenium, I believe that
it's there. That's my opinion, but I think that it should be put in the form where
it's a sound technical basis, and it's made use of instead of we just can't use
hand waving in this type of assessment. It's too important.
In particular, I won't use all of these in the interest of time
because I know you're running a little bit behind time, but a couple of things
here that I find of particular importance is once the study is done, it's amazing
how many different ways these things get used.
I think it is certainly as it says here, difficult to provide the
necessary foundation for risk informed decision making without having
something, without having an analysis, which is a best estimate. I mean, what
is it you're really talking about?
The best estimate also needs to represent the uncertainties
involved, and without using the technical basis in something in a quantitative
manner, then you're really not sure what it is you're coping with.
DR. WALLIS: Why don't we have the only CRS?
(Laughter.)
DR. KRESS: Sounds like something we've said before.
DR. WALLIS: We've been saying that for years.
DR. HENRY: Well, I already travel enough.
After a study is completed, the results are likely to be used for
other tangentially related studies, and if you don't have a sound description, you
know, well informed basis that you've drawn from that people are forced to then
live by when they use those studies, you have no control over how those
numbers get used.
DR. WALLIS: I guess you're saying all of this with the
implication being that these guidelines have not been followed in some way by
the NRC?
DR. HENRY: Well, I think particularly with the cask drop. I
think that's one that should be very clearly -- the technical basis should be put
out there. I think it relates to issues of EP that we were just talking about
because that is the issue unless you're talking huge seismic events. We're not
talking about EP related items here.
So we want to make sure that we're communicating what's
really known in a technical community.
One of the places where I had a small part of how the number
got generated, I remember why it got generated. I also saw how it got misused,
and I just put this example down, is in the Swedish reactor safety study, which
the people that did that had their own bent on what they wanted to accomplish
in that study, but it was paid for by the Swedish government.
And they say in the study that they are using WASH-1400
methodology. One of the places where I thought they grossly misrepresented
what was done was in the area of steam explosions. WASH-1400 used a
number of ten to the minus two because at that level, that issue was no longer
risk significant, and we didn't have to go through all of the weeping and
gnashing of teeth from then on. So it was a compromise, and it's all the further
the number had to be taken.
They turned this number around and said, "Well, it's ten to the
minus two. Those are the experts. We're not the experts, but they gave us the
number, and we have three places instead of one where it applies. So we'll
make it three times ten to the minus two."
And just forced it into something which now was risk
significant because they wanted it to be that way, and then when they showed
the consequences of all over northern Europe, that was one of the first grains
of sand in the oyster that brought down Barseback, and so there was no control
of how it got used.
And I think we have to be concerned about that because we
didn't really say at the time we're just going to make this number the way it is
because from here on it's not risk significant, and below that number maybe
people disagree, but the disagreements don't matter.
This next table is just abstracted from that Swedish reactor
safety study, and you can see this is the WASH-1400 number, and they merely
said, "We're going to use something three times that because we have three
different places in the RCS and the containment where this could happen."
The next you've already seen before, but this is just things
that we believe are strong parts of the technical basis, things that are well
known that should be included in the study, and in the interest of time, I know
Lynette has a few other things to say, too. I won't take you through that
because we talked about it the last time, but the real issue is we strongly
recommend that the technical basis be formulated and used to the best ability
that we can use it now.
So in conclusion for this part, we believe that a best estimate
evaluation is essential to communicate what we really know about the subject
here, the cask drop being the one that we think there's a very clear basis on,
and even thought it's a completed study now, I think a peer review of that would
still be most helpful, and it certainly would be very helpful in the public arena,
which these types of studies get reviewed and used.
Lynette.
MS. HENDRICKS: I'd like to go now to our analysis on the
specific options. For the safeguards option, the way we read the -- and I'll
always be referring to the option that the staff indicated a preference for, and I'll
characterize it and then give some insight on what I think issues are with the
option as proposed.
For safeguards, the way I read the option, and I think it's still
correct after listening to the discussion earlier, is that you will start out having
to protect against the design basis threat analogous to what is existing for
reactor operations with the difference that you'll have a specific five rem at the
site boundary standard that you're working against.
A number that the staff put in the options paper that I think is
very important is that they equate that to a need for five armed guards, and the
point I'm going to try to be conveying throughout these options is when you're
decommissioning cost is people. Cost is the number of staff that you have to
carry forward is a good way to think of it, and for these five armed guards for the
first part of the option, it's not really five because you have to go around the
clock. It may be 15 to 20, and when you do that, you're talking about an amount
of, let's say, a low estimate would be $2 million a year.
So just to kind of put a bound around the costs, that's what
we're talking about.
The "or" I think is the option that the staff indicated that you
could demonstrate through plant specific analyses if the fire is, in fact,
precluded, and so your standard then doesn't become one of defend against
the frontal assault by these adversaries in the design basis threat. You've
precluded it, and then you're in more of a standard that's a little more equivalent
to this, but not quite the same. It's more lost of control, call the local law
enforcement. So that's the difference.
The specific indication that they gave on how you could
demonstrate that the fire was precluded, we talked earlier about design
features, heat up analysis. They also referred to mitigating actions, including
response by law enforcement before the fire commences, and this makes a real
important point that I wanted to emphasize.
The timing is very different for this event compared to a
reactor, and even in the worst case situation, the two or thee hours, the thing
with the safeguards option is you regain control of the facility essentially
immediately. So your opportunity to mitigate is there.
It's not like the seismic event where you can still claim some
mitigation capability, but it can be questioned on the basis that the magnitude
of the seismic event may render some of your mitigation uncertain.
And I'd also like to point out that one of the industry
commitments that's referenced in the study is we do have a commitment for
capability for remote access such that if the pool was drained without undue
concern for the radiation hazard, you could have a mechanism to try to reflood.
I think it was pointed out this morning it's not so important to reflood as much as
it is to spray the core in the pool such that steam cooling will remove the heat
as it's generated and prevent you from getting to the critical temperature for the
zirconium exothermic reaction.
DR. POWERS: Have we ever done that?
MS. HENDRICKS: Pardon?
DR. POWERS: Have we ever done that experimentally, take
a bunch of fuel rods, let them get warm, and then spray some fog or something
like that over that and see if that, in fact, keeps -- the steam cooling actually
works?
MS. HENDRICKS: No, I guess I'd have to say I haven't.
DR. WALLIS: But it's predictable.
DR. POWERS: Well, you know, I wonder how predictable it
is because the things I'm familiar with, it's steam and steam, but now we have
steam and air, and I don't know what happens in steam and air. I don't know
what happens with irradiated clad.
DR. WALLIS: Yeah, the cooling isn't so bad. It's the
chemistry, I think.
DR. POWERS: Yeah, I'd like to know what kind of chemical
reactions actually do occur.
DR. HENRY: I can't remember the exact references now, but
there are references out there, Dana, which are steam and air sprayed in their
overheated surfaces. Condensation is obviously much more susceptible to
small air concentrations than evaporation is. Evaporation just depends upon
local contact.
But as Graham says, the chemistry obviously is a little more
complicated with steam and air.
DR. POWERS: I just don't know what it would be because,
well, irradiated clad, especially high burn-up irradiated clad, and quite frankly,
that's the ones you're worried about, is the more recent off-loads, which are
going to be more highly burned than the things in the pool right now, and I have
no idea what exactly happens in those kinds of circumstances.
DR. HENRY: Obviously if you're going to have to spray
anything, you'd like to spray at the lowest temperature possible.
Thermomechanically it's much better, but there are data taken with sprays on
surfaces in air that effectively remove heat. That's not an issue. The chemistry
is, again, more complicated.
DR. WALLIS: You're also getting the droplets into the interior
of a bundle. That's not a trivial matter. You're going to spray somewhere.
DR. HENRY: You want to spray somewhere, and the best
thing you could have is to begin to at least accumulate some films that drain
down on the surfaces.
DR. POWERS: I had another question on your previous
viewgraph. You began that with a discussion of the cost, and until we have
provided adequate protection to the public health and safety, we really can't
consider costs. So you must have some idea in your mind in bringing up costs
what adequate protection to the public health and safety is.
Can you kind of equate that?
MS. HENDRICKS: Well, I don't think it's an absolute number,
but I think when you do a cost-benefit, you look at the delta. If you're going to
spend $2 million, can you demonstrate that there will be some increase in
protection of the public as you take it all the way out through, you know,
eventual exposure to the public?
DR. POWERS: Okay. So you would come back in saying
you really do need this probability of sabotage.
MS. HENDRICKS: I don't know whether it's wise to go there.
Probably not, but here I go. Whoever said I was wise?
DR. POWERS: I was definitely leading you to a trap.
MS. HENDRICKS: I think actually that the issue earlier about
whether you can apply probability to the probability of the event happening, I've
never understood really why not. I mean, you have crime statistics. You have
a certain number of these events of any type that have happened, let alone
have they happened to facilities that are hardened targets where the probability
of these people going for those targets is admittedly low.
So I can't help but think even if you didn't have a perfect value
and perfect methods, that you could do an awfully law in that area in addition
to the mitigation potential and some of the other things that were talked about.
But in terms of sort of giving an absolute indication of our
industry views on the options, I think it's difficult to do so because we haven't
had any opportunity to comment on the safeguards analyses paper that's being
prepared which will give us, I think, a sense of how feasible it will be to get to
the "or preclude" part of the options such that you could potentially reduce your
staff significantly, which is where the savings would be; get rid of some number
of the armed guards, and that's where the cost savings would be.
And then some of these other things are sort of the comment
that any change to the adversary could invalidate the entire program. That's
sort of just a constant whenever you talk about safeguards, but I think it's
always important to reinforce that. We're always on sort of a tightrope when
you come to the safeguards area from that perspective.
And then just to note that the standard does say preclude a
zirconium fire, and you know, there's no such thing as zero, but I would like to
see when we talk to the EP option of getting a little more acknowledgement of
that approach, that we do have -- you know, the word "preclude" is used, and
it doesn't seem to be reflected in the EP analysis when you start talking about
difference in depth.
The insurance option, I think it was covered pretty clearly. We
may question the $100 million, and we did when the SECY was originally put
out, that even 25 million is probably excessive. It's more than has ever been
spent on clean-ups that would involve a truck spill or some other local
contamination.
But it doesn't get to really in the end matter that much from
what I've gleaned from talking to folks because your premiums aren't
necessarily going to go down that much ironically if your coverage goes down
from 100 million to 25 or 50 million.
DR. WALLIS: What is the premium for 100 million?
MS. HENDRICKS: It's difficult to quote a number. I think if
you're a single unit facility in decommissioning, it's a couple million dollars. A
good part of that -- if you're a multi-unit facility, it's an increment, and it's --
DR. WALLIS: So they're charging you two million for 100
million coverage?
MS. HENDRICKS: No, no. That's what you'd be going down
from. You'd get a significant reduction, plus you wouldn't have to have the
liability of potentially participating in the secondary pool.
DR. WALLIS: So we don't know how much the premium
would be.
MR. ROSEN: The premium is not going to be two million
year for primary coverage if that's what you meant. I don't think you did, but --
MS. HENDRICKS: No, I'm saying as an operating plant,
when you had --
MR. ROSEN: Yes, as an operating plant, it could be that
much, but for a shutdown --
DR. WALLIS: In other words, there's no quotes yet for
premium.
MS. HENDRICKS: It would go down significantly.
MR. ROSEN: Well, we're talking for property coverage, two
million a year. Primary coverage at an operating plant is much less than that.
I think the coverage we're talking about here, your first bullet, this is Price-
Anderson primary coverage you're talking about, right? Would be in the order
of tens of thousands of dollars per year, not millions. Very inexpensive because
it's so unlikely that would be called upon.
MS. HENDRICKS: It's obviously very different than the
number I was quoted, but I certainly accept your first-hand experience.
But anyway, the bottom line for insurance is we don't have
any issues with the option the staff is proposing. It seems very rational and risk
informed.
The EP option, as Randy, I think, deftly explained, you get
some reduction in the first year, and the vision is complete elimination of off-site
EP at five years. Again, this is a bit like safeguards analyses. It's difficult to
quantify the benefits.
EP is very analogous to safeguards cost, as the number of
people. So until you get into the specifics, as they had indicated through the
regulatory guide of exactly what you would be exempted from in the reduced
period, and ultimately it's hard to put a benefit in terms of cost savings on what
they're talking about here.
In terms of, you know, EP space, you're obviously not in the
position of feeling comfortable going completely on a risk basis, and so you
acknowledge up front that you are in defense in depth space, but I think having
said that, even though defense in depth is a great concept, I think it's incumbent
upon the agency to demonstrate that you really have defense in depth, that you
have something quantifiable that you can point to for the cost of maintaining the
off-site EP in limited form until the five-year period.
The reason I question whether you can actually quantify
defense in depth is it may be nonexistent if ad hoc EP is just as effective shortly
after shutdown. That was discussed at, I think, great length in the technical
report.
And finally the technical report also acknowledges that it's
optimally of limited effectiveness and causes delays if you're talking about an
earthquake of .6 G, and it goes on to say if it's in excess of .6 G, evacuation is
virtually -- I think they come down and say it's virtually not going to happen.
You get no credit for it at all.
When we were here last time, we had a graph that tried to
break out the percent of the risk of pool failure by seismic magnitude, and what
the graph showed was in excess of 90 percent of the risk is attributed to
earthquakes in excess of 1 G, and that's really not hard to come to intuitively
because of the robustness of the pool.
The HCLPF based on very conservative analyses that the
staff did is .5 G. So it's logical that the biggest contribution of the risk is going
to come from enormous earthquakes, and when you have then the
acknowledgement that you are going to get basically zero benefit, zero
evacuation is going to be possible, again, I bring the question back to defense
in depth is a good concept to explore, but can you actually point to it and say,
"We have. We can provide defense in depth"?
Otherwise you may be misleading the public to talk about a
concept when, in reality, it's not going to really materialize.
Another thing that I guess leads us to that question is the fact
that, again, to reiterate, we don't believe the cask drop is a realistic event, which
leaves essentially seismic and sabotage as the issues that you're talking about,
and sabotage, again, you're using the standard of preclude and potentially --
and again, unlike the seismic event, you have recontrolled the facility in very
short order, and unlike the seismic event, your mitigation capability should
remain intact.
So I guess to summarize, we would recommend that the risk
study be completed and peer reviewed, and that efforts be made to derive a
best estimate using existing data on ruthenium release and also cask drops,
with an effort, of course, to quantify the uncertainties.
I've mentioned under EP and also insurance that in order to
get these benefits, you have to meet the industry commitments as well as the
staff assumptions. One of these staff assumptions is that you will fulfill the
requirements of the seismic checklist, which because of the -- it wasn't based
on a large number of plant fragilities, is acknowledged to be rather conservative.
The net effect of that is that our experts indicate that to comply with the checklist
you're getting into sort of an engineering evaluation of the seismic
considerations around the pool, and we estimate that's going to cost about 50
to $100,000.
And then certainly if you failed the checklist and get into any
kind of a situation where you're going to go back and ironically maybe do any
engineering to improve the situation when you're going to, you know, a few
years down the road tear it apart anyway, but it certainly gets into real money
very quickly if you have to go back and do much structural work to comply with
the checklist.
And finally, the recommendation that the EP reductions be
commensurate with risk and some quantifiable assessment of the defense in
depth that you actually get with EP.
DR. WALLIS: If we could quantify defense in depth, that
would be a wonderful thing.
MS. HENDRICKS: Well, I think in this case you can quantify
it.
CHAIRMAN APOSTOLAKIS: Isn't that what PRA does? It
quantifies defense indefinitely. Am I missing something?
DR. POWERS: That's what it misses a great deal.
CHAIRMAN APOSTOLAKIS: Huh?
DR. POWERS: It misses it a great deal. Your PRA does not
address the sabotage issue at all.
CHAIRMAN APOSTOLAKIS: No, no, no, no, no.
DR. POWERS: Defense in depth does.
CHAIRMAN APOSTOLAKIS: It says quantifiable defense in
depth. If you want to quantify defense in depth, that means you want to do a
PRA.
DR. POWERS: No.
CHAIRMAN APOSTOLAKIS: How else would you quantify
it?
DR. POWERS: Well, certainly not with PRA because you --
CHAIRMAN APOSTOLAKIS: How else would you quantify?
DR. POWERS: We're going to ask her how to do that here
in a second. I think that's what Graham just asked, as a matter of fact.
MS. HENDRICKS: I think it's a very fair question. I think you
can do it qualitatively or quantitatively. Qualitatively you can ask --
DR. WALLIS: But you can't qualitatively quantify. Now, wait
a minute.
MS. HENDRICKS: Well --
CHAIRMAN APOSTOLAKIS: Yeah, because I mean that's
exactly what PRA does. It quantifies the level of defense you have. So if you
want quantification, that's what you are calling for.
Now, that doesn't mean you're going to do a small LOCA. I
don't mean PRA the way we do it for -- I mean the philosophical approach.
That's exactly what it does.
Now, whether it's incomplete, that's a different story. Whether
you don't believe it.
MS. HENDRICKS: The example is if you acknowledge that
you're looking at the primary risk from an enormous seismic event and you can't
evacuate people, then you can quantify that defense in depth from fancy
evacuation procedures aren't going to do you much good.
DR. POWERS: I think what you really said there, to avoid
provoking the Committee, you would have said quantify the benefit --
MS. HENDRICKS: Thank you.
DR. POWERS: -- derived from these measures, which I think
you've made the point. We ought to look and see if there's some benefit there.
MS. HENDRICKS: Thank you, Dana.
DR. POWERS: Because otherwise defense in depth is a
difficult thing to do for quantification, and that's why I was trying to put it in the
context of fire. You know, we're certainly going to try to prevent the events from
occurring. That's the first step in fire protection. We're going to suppress the
effects of a pool drain-down or something like that. That's why you've got fog
nozzles and things like that.
And then we're going to protect the vulnerable components,
which in this case is the public, from the effects of fires that we failed to
suppress, and what you're saying is you may not be able to do very much there.
And you ought to know how much you're going to do before you spend a lot of
money on it.
That seems fair.
MS. HENDRICKS: Exactly.
DR. POWERS: It seems fair.
MS. HENDRICKS: Thank you for your mentoring. That's a
wonderful skill, to learn how to not provoke the committee. I will learn.
DR. POWERS: We spend a lot of time discussing defense
in depth here.
MR. BAGCHI: Mr. Chairman, can I quickly share a
perspective on cask drop?
CHAIRMAN APOSTOLAKIS: Can you identify yourself to us?
MR. BAGCHI: Yes, sir. My name is Goutan Bagchi. I'm the
Senior Advisor in the Division of Engineering.
I understood from previous discussions that there were some
comparisons back 20 years ago based on every (unintelligible) missile studies,
which in the report itself concluded that the analytical predictions were way too
conservative.
The basis for the conclusions that were presented in the NEI
slide today and the previous time was perhaps this, that the (unintelligible)
comparisons were too conservative and, therefore, the implication is that the
cask drop is now going to lead to some kind of a failure of the pool slab.
There are clearly some kinds of pools where the pool slab is
supported by the soil medium where the failure is not very likely, but there are
other cases where the slab is way up in the air, as in some or most of the BWR
spent fuel pools. A 100 ton cask falling through maybe 30 feet depth is going
to produce a significant amount of impact force that is, in my opinion, going to
lead to a failure, and I'm going to tell you why.
Because, you know, the 20 year analytical capability, 20 year
old analytical capability has now been substantially improved, and our
colleagues in NMSS have undertaken a study where drops were made and then
comparisons were made by using more recent techniques, and they have
plotted various deceleration diagrams based on those studies, actual studies
and comparisons with analytical tools.
And based on that I got a deceleration force and applied that
to the full slab, not supported by soil or anything, but the slab by itself, and there
is no way that kind of a deceleration force will be withstood by a pool slab,
which is, you know, not supported by anything else.
So when you say that the cask drop is way too conservative,
please take a look at more recent data, more facts that have been substantiated
by even NRC initiated studies.
DR. HENRY: My response to that, I think the last time that we
had the opportunity to talk to the committee we did look at at least the most
recent data, and we asked if there was anything that we didn't have, we would
sure like to know about it because the data that we had -- give me a second
here. Let me find the right one -- included the studies that BNFL did here up
through 1993, and they were with full size casks dropped from heights at least
up to five feet, and those just barely made a dent in the concrete.
We're not here to argue which is right or wrong. What we
really would like to do is make sure that the technical basis is clearly spelled out
in the report and where the conclusions come from because I didn't even see
any of these tests referenced in the report.
Now, if there were calculations behind the report that we didn't
know about, we'd be more than happy to hear about them, but all we're really
here to plead for is let's have the technical basis clearly defined, especially the
experimental basis.
MR. BAGCHI: Those studies, those study reports came from
the NUREG CR that was developed, and comparisons were made.
Deceleration forces were given. You can take that and apply to the slab.
I don't know that you have had any of your structural experts
look at that. I am a structural expert as a professional engineer, and I looked
at that. My conclusion has been that pool slabs that are not supported by any
soil are not going to withstand that kind of a drop.
DR. HENRY: I'm not here to impugn your capabilities, you
know. All I'm saying is if you've done those analyses, I didn't see those
referenced in the report and anything I could really point to.
I mean, this is a very important part of the study.
MR. BAGCHI: I'm confused about what you're implying here
by this slide.
DR. HENRY: Give me a second then. I mean this is the test
that was done.
DR. WALLIS: Which is what you talked about last time.
DR. HENRY: The last time, and this is the damage that was
seen.
MR. BAGCHI: That's not my point. These are not one-to-one
comparisons to what I was referring to, a slab purely unsupported by anything
else.
My point was whether or not those references were included
in our report. The answer is, no, we didn't because we had a very specific study
done on a pool, Vermont Yankee pool, and the results are available in the
NUREGs here.
DR. HENRY: They are?
MR. BAGCHI: Yes. There was a finite element study, and I
think your implication was that that study used rather conservative assumptions.
DR. HENRY: But where were those in the report? The
conclusions may have been there.
MR. BAGCHI: It was a reference in our report, 1738.
DR. HENRY: It may have been referenced, but I mean, that's
all that was there.
MR. BAGCHI: It is based on that finite element analysis in
that report.
DR. HENRY: I'll be more than happy to -- if you can send me
that, I'd be more than happy to look at it because I'm most interested in it, but
the other aspect is did you conclude from that that it's a catastrophic leakage
of the pool?
MR. BAGCHI: If there is a drop of 100 ton cask on a pool that
is high up in the air and not supported by soil, my personal conclusion is that,
yes, it's going to fail catastrophically.
DR. HENRY: And in that analysis, did you include the water
and the other fuel that's already there as any kind of shock absorber
mechanism, regardless of what its configuration?
MR. BAGCHI: It was -- in that analysis it was assumed to fall
freely.
DR. HENRY: But since this is an initiating event, there would
be fuel there. There would be water there also because your whole basis was
on rates of deceleration. So the more you slow it down in advance of hitting the
concrete, the more you spread out the load, right?
MR. BAGCHI: If in the path to fall to the floor there is no
intervening fuel, then you cannot assume any resistance from that.
DR. HENRY: Or the water.
DR. WALLIS: It seems we have a technical debate going on
with the results somewhere else.
DR. KRESS: This seems like something you guys could
debate --
MR. BAGCHI: I just wanted to say that there was a study that
updated the analytical methods and compared that against the drops, and
deceleration values are clearly relevant.
DR. POWERS: I thought the exchange was helpful, by the
way, because it puts context on two different analyses that we've seen.
DR. KRESS: Yeah.
DR. POWERS: And it's a fairly -- I mean it's a non-trivial issue
to resolve as whether this is an initiating event or not.
DR. KRESS: Are there any other questions or comments
from the committee?
(No response.)
DR. KRESS: Well, thank you very much.
MS. HENDRICKS: Thank you.
DR. KRESS: We appreciate the input, and we'll turn it over
back to George.
CHAIRMAN APOSTOLAKIS: Thank you, Tom.
Yeah, I'd like to thank also the presenters today, the staff, and
NEI.
How about if we have a 45 minute lunch break?
DR. KRESS: Yeah.
CHAIRMAN APOSTOLAKIS: So 1:30, 1:30.
(Whereupon, at 12:40 p.m., the meeting was recessed for
lunch, to reconvene at 1:30 p.m., the same day.). AFTERNOON SESSION
(1:30 p.m.)
CHAIRMAN APOSTOLAKIS: Our next topic is the need to
revise 10 CFR, Part 54, requirements for renewal of operating licenses for
nuclear power plants. Dr. Mario Bonaca is the leader.
DR. BONACA: All right. Good afternoon after lunch.
All right. On August 1999, the Commission requested the
staff to provide internal analysis and recommendation to the Commission on
whether it would be appropriate to resolve generic technical issues raised by
the industry in many cases through rulemaking, and we are at the point where
the staff has concluded its own evaluation, and we're going to hear from them
today.
So I'll turn over the meeting to Mr. Grimes.
MR. GRIMES: Thank you, DR. Bonaca.
My name is Chris Grimes. I'm the Chief of the License
Renewal and Standardization Branch.
And rather than repeat the purpose of the meeting too many
times because the staff presentation is going to make the purpose of the
meeting clear and our message, hopefully, will be clear to you, and we request
that the committee support our view at the conclusion of this presentation, that
there's no need to revise the license renewal rule at this time.
And with that I will turn over the presentation to Dr. Sam Lee.
Sam was the team leader who headed up the development of the regulatory
guidance and standard review plan for license renewal, and he's going to
explain the extent to which we've explored the possibility of rulemaking.
Sam.
DR. LEE: Yeah, my name is Sam Lee. I'm from the License
Renewal and Standardization Branch, NRR. And with me here today I have
Greg Galletti, Brian Thomas, and Steve Koenick coming up here from the NRR
staff so that they will be here in case your questions they can answer.
About two years ago in response to SECY 99-148, the
Commission directed the staff to prepare the improved license renewal
guidance document that used the generic lessons learned, the core report, the
standard review plan, and the reg. guide for license renewal.
In the same SRM, the Commission also directed the staff to
prepare a recommendation on whether the license renewal rules should be
revised. And we have held a public meeting to get comments on whether
there's a need to review the rule, and we plan on providing our recommendation
to the Commission by the end of August.
The ACRS has previously provided their comment in a letter
responding to the improved generic guidance documents, and the ACRS
indicated that the staff should encourage applicants to provide scoping process
results in the application, and that would have the review process and to make
the information more transparent.
The staff agrees with this committee. The initial license for
new applicants have provided this information for staff review, and also the
standard review plan and industry guidance NEI 95-10 indicate that such
information should be provided. The staff recommendation is that we will
continue to work with industry to clarify the guidance document that address
these comment.
MR. GRIMES: Excuse me, Sam.
I would like to point out that we're making a distinction here
between acting on a recommendation to provide the information in a voluntary
way as opposed to codifying a requirement for the results of the scoping
process in more detail as a requirement in the rule.
So all of these comments relate to possible changes to the
rule.
DR. LEE: Okay. The Union of Concerned Scientists originally
planned to attend the public meeting. However, they were not able to. So they
provided comment and a letter, and they have three comments.
The first comment, and the Union of Concerned Scientists,
UCS, indicated that the license renewal rules should be revised to add the rad
waste system into the scope of license renewal because the failure of such
systems can cause excessive release of radioactivity into the environment.
The UCS had previously provided this as a rulemaking
petition to establish regulating this separately under the petition process.
The second comment is that the UCS cited cases where the
equipment had failed because of aging and caused plant shutdown since last
year. Since the beginning of last year they cited about eight cases. So their
comment is that we should define the minimum standards for an effective aging
management program.
We have looked at the eight cases that were cited by UCS.
Only one case that relates to the Indian Point 2 steam generator degradation,
related to passive component, and that's already been addressed in the Gall
report.
The other cases relate to active components, such as
transformers, sonar (phonetic) valves and breakers. Active components are
addressed by the current regulatory process, and they are not subject to the
additional requirements of license renewal.
And regarding the effective aging management programs, the
guidance documents, the improved guidance documents evaluates programs
using ten program elements, such as the scope of the program, the problem
with this monitor acceptance criteria, corrective action, operating experience.
The staff recommendation is that we'll clarify the guidance
document to address this problem, and in particular, relate to the element of
operating experience.
The last comment is that the staff is accepting applicant
commitments to perform one time inspections many years from now, to confirm
that either aging is not occurring or it's occurring at such a slow rate that you do
not need an aging management program.
UCS comment is that should the one time inspection be real
aging degradation, the licensee at that time of renewal license would cite back
the protection if the program need to be changed.
The staff believes that if aging degradation is detected by one
time inspections, the plant's QA program would identify the appropriate
corrective action, and should the staff consider changing previously approved
aging management programs, back-fit is the appropriate regulatory process to
evaluate the needed changes.
And again, we will consider clarifying the guidance document
to address the one time inspection comment.
Okay. The industry through NEI provided the comment and
letter, and NEI indicated that rulemaking is not necessary at this time, similar to
what Chris had indicated earlier, and NEI is going to make a separate
presentation after the staff.
Our conclusion, the staff recommendation. Based on the
experience of renewing license renewal applications and developing the
improved license renewal guidance document, the staff believes that
rulemaking is not necessary at this time.
The improved license renewal guidance documents are living
documents, and we plan on clarifying and updating them to address these
comments and also additional experience from future license renewal reviews
and the ongoing NEI demonstration project in which industry is using these
documents to prepare sample application sections.
And the staff will continue to monitor the license renewal
process and experience and other rulemaking activities done by license
renewal.
That concludes our presentation.
DR. BONACA: On slide number four under the first comment
by UCS, your recommendation was to address rad waste systems under
rulemaking petition process. Could you expand on that?
MR. KOENICK: Yes. What we do is in accordance with some
interim guidance that NRR issued in February, we have a petition for rulemaking
process. As part of this process, this is also consistent with NUREG ER-53,
which is NRC regulations handbook, and what we do is we have a working
group with disciplines represented, and we come up with a recommendation
that goes through a Petition Review Board, and then we document our
resolution, and then follow up with the necessary actions.
DR. BONACA: This is not inconsistent then with your
recommendation of not changing the rule right now?
MR. KOENICK: Well, the petition is pre-dispositional now.
MR. GRIMES: This is Chris Grimes.
I'd like to point out that if the petition review process should
conclude that the rule should be reviewed to address rad waste systems, and
that would go to the Commission then for approval of the rulemaking plan, and
if that should occur as Dr. Lee pointed out, that would be an opportunity to
change the rule and perhaps do some of these other things that we've
recommended clarifying in the guidance.
But right now we are not taking on that, the decision for the
petition. That's going through NRR's process.
DR. BONACA: Okay. Thank you.
DR. UHRIG: I have a question. Could you comment on how
monitoring rulemaking activities will provide opportunities to improve the license
renewal process? This is the last statement on page 6.
DR. LEE: I guess some of the rulemaking activities, for
example, okay, like ongoing there's a proposed rulemaking on POP 2
(phonetic), on the formal hearing process, to quote the informal hearing
process, and if that would happen, we'll make the conforming changes in POP
4 (phonetic) to go into an informal hearing process.
And also there are other rulemaking activities, such as 55(a)
on in-service inspection. That's the referencing ASME code. If the ASME code
decides to take up certain aging activities and goes through 55(a), then we'll
probably make the conforming changes in POP 54 (phonetic).
DR. UHRIG: Thank you.
DR. BONACA: Any other comments for Dr. Lee?
MR. GRIMES: Dr. Bonaca, this is Chris Grimes.
I would like to sort of add as a postscript that when the
Commission issued the staff requirements memo, I think at that time there was
some -- we had mentioned some possibility of trying to incorporate generic
aging lessons learned into Part 54 in much the same way that the generic
environmental impact statement for license renewal is incorporated in Part 51.
We also discussed that at the public meeting, and we
concluded that the need to maintain GALL is a living document and continue to
fold back experience and expand and clarify GALL as a tool does not lend itself
to rulemaking.
And so implicit in this recommendation was a specific
consideration of whether or not to codify GALL in Part 54, and we similarly
concluded that that would not be appropriate at this time. We may want to
consider that later if GALL matures to the point where we think it's sufficiently
stable to codify it in rule, but we don't believe that it's right for that opportunity
today.
DR. POWERS: I wonder, Sam, if you can explain a little bit.
The Commission asked you to do this what they called a detailed analysis and
report back to them. We really haven't done a license renewal study completely
through for BWR. Why don't you just ask them for a little more time on this
one?
DR. LEE: For PWR?
DR. POWERS: BWR.
DR. LEE: Oh, BWR.
MR. GRIMES: I'll tackle that.
DR. POWERS: Sure.
MR. GRIMES: We think we're sufficiently far along with the
Hatch review that we haven't seen anything that makes the system distinctions
any different from what we've learned in GALL as treatment of aging effects.
DR. POWERS: Do you think you're in a position now you can
go ahead and answer the Commission's question?
MR. GRIMES: That's correct. I don't think that we're going
to learn so much more in the back end of the Hatch review or even the start of
the Peach Bottom review that would change our view about the immediate
question of whether or not rulemaking is going to substantially improve the
process.
DR. BONACA: Okay. Any other comments from members?
(No response.)
DR. BONACA: If not, thank you for the presentation.
I understand we have a brief presentation from the industry.
MR. NELSON: I don't even know if I need to sit down.
(Laughter.)
MR. NELSON: My name is Alan Nelson. I'm a senior project
manager with NEI.
When they asked me if I'd like to give some brief remarks, that
was before I knew that they were going to say they agreed with the industry and
no rule was needed, but just the same, we'd like to go on the record today.
Basically you're aware we had sent some correspondence
into Mr. Grimes on June the 4th. Industry met with the Commission on June
14th, Mike Huffman, and we met with the staff on June 28th, all expressing our
interest in seeing that the no rule be forthwith in the near future.
Actually, we've watched three approved re-licenses, six units.
We have some experience under our belt. We feel that the process is stable.
It's reasonable, and it's predictable.
As was stated by Dr. Lee, we're in the process of evaluating
a demonstration project which would -- four applications which would determine,
you know, the most efficient and effective way to provide applications looking
at the year 2002 and beyond.
We don't believe even through that demonstration process
that there would be a need for a rulemaking change, and essentially we agree
with the presentation that was made previously.
So I appreciate the time you've given me, and it's less than
a tenth.
(Laughter.)
MR. NELSON: You're not going to let me off the hook that
easy?
DR. POWERS: Maybe not quite that easy. I wonder if you
care to address the comments that have been made by the Union of Concerned
Scientists.
MR. NELSON: As I stated, I've only been on this project
about 30 days.
DR. POWERS: Oh, okay. It might be a little difficult.
MR. NELSON: Yes, I'm not in a position to address that, and
we certainly addressed it in -- I think we may have made comments on it before,
but I'm not sure what they are.
MR. GRIMES: This is Chris Grimes.
Just to make sure that the record is clear, first, Mr. Nelson
said that no rule is necessary. I want to make sure that it's understood there is
a rule, and we're not proposing to change it, but in terms of the UCS petition to
include rad waste systems was sent out for public comment, and I believe that
NEI commented on behalf of the industry, and I think that we received
comments from the industry related to clarifying the staff's expectations for
aging management programs, for which NEI and UCS both, I think, have
encouraged us to more clearly articulate the standards of acceptability for
effective aging management programs.
So I think that the industry's comments would direct us
towards pursuing that improvement in the guidance.
DR. BONACA: And we have noted, too, you know. We made
some remarks in the last letter we wrote regarding, for example, small bore
piping and lessons learned from Arkansas, whether that would justify changes
to GALL. We received a response that essentially GALL is, in fact, a document
which is not completed in a certain way. I mean, it is going to be updated to
reflect this kind of experience and insights.
And I think it's appropriate not to have it codified. That's just
a personal judgment.
DR. UHRIG: Chris, I noticed in the document handed out this
morning that the comment period on the Turkey Point license extension
application had been extended. Is there a reason for this that's unique to
Turkey point or is it something that's going to be done on all?
MR. GRIMES: That was a direction that applies to all license
renewals. We had suggested that we were going to shorten the public
comment period on the draft environmental impact statement from 75 days to
45 days, which is what the law requires or what the regulations require, and we
were doing so for reasons of process improvement efficiencies.
But the Commission felt that shortening the public comment
period would damage public credibility of the process, and so they directed us
to revert to the 75 days.
DR. UHRIG: Okay. Thank you.
DR. BONACA: Any other questions? If not, I thank you for
your comments.
MR. GRIMES: Thank you.
DR. BONACA: Amazing to see such an agreement between
the staff and industry. It's good.
DR. POWERS: There must clearly be something wrong,
right?
DR. BONACA: No, but I think that considering the amount of
technical work that took place and so many issues that were debated, it's
encouraging to see that there has been a real process of resolution.
And with that I wonder if any of the members have additional
comments to provide. We are going to write a letter, a report to give our
perspective, too.
And with that I give it back to you. I note that --
CHAIRMAN APOSTOLAKIS: Excellent job, Dr. Bonaca.
DR. BONACA: -- the meeting in --
CHAIRMAN APOSTOLAKIS: Excellent job. You run us back
to schedule.
PARTICIPANT: Perhaps he should run the rest of them there.
CHAIRMAN APOSTOLAKIS: Oh, oh, oh.
(Laughter.)
CHAIRMAN APOSTOLAKIS: What a mistake to welcome you
this morning.
Well, the next presentation is scheduled for 2:15 on control
rod drive mechanisms, and I think we should not start before the scheduled
time.
DR. SHACK: Especially since no one is here.
CHAIRMAN APOSTOLAKIS: Yeah, that might make it a little
difficult. So we shall recess until 2:15.
(Whereupon, the foregoing matter went off the record at 1:52
p.m. and went back on the record at 2:14 p.m.)
CHAIRMAN APOSTOLAKIS: Okay. We're back in session.
We have lost Dr. Shack.
The next item on the agenda is control rod drive mechanism
cracking. Dr. Ford, please lead us through this.
DR. FORD: We had a joint meeting of the Plant Operations
Subcommittee yesterday, the 10th of July, and a brief by NRR and the industry
on CRDM housing cracking at Units 1, 2, and 3 and ANO. This is the first time
we've had such a briefing.
As you probably know, there have been many similar
incidences of large diameter penetrations due through pressurized water at the
heads in the last ten years abroad. It was the first time in this country.
The objective of the meeting was to be briefed by the NRR
and research and industry on these incidences with the specific request that we
issue a letter giving our comments on the timeliness of issuing a bulletin on this,
on these incidences, and also about the timeliness and appropriateness of the
actions that are going to be taken.
And Jack Strosnider is going to lead the presentations.
DR. POWERS: Let me understand a little better, Peter.
DR. FORD: Yeah.
DR. POWERS: It seems to me several years ago the French
had some cracks in the --
DR. FORD: That's what I was referring to.
DR. POWERS: And it seems to me that at that time, the NRC
reacted to that finding and went through and looked at all of -- asked the
licensees to look and gave them all a clean bill of health.
DR. FORD: They started at Bujay 3 (phonetic) in 1991 in
France, Framatome. I'll let Jack respond to the question about the NRC's
response to those particular instances.
MR. STROSNIDER: Good afternoon. Is the microphone
working?
My name is Jack Strosnider. I'm Director of the Division of
Engineering.
I appreciate the opportunity to talk to the committee this
afternoon.
The industry went first yesterday. So I guess the staff will go
first today, but hopefully you'll keep me from going into their time.
Anyway, but do you want me to start off to respond to some
of the history there?
DR. FORD: Yes.
MR. STROSNIDER: Just briefly, if you go back to the
discovery of cracking at Bujay and then additional operating experience leading
into the mid-'90s, we staff did interact with the industry, and the industry
provided an assessment of that issue, and we issued a generic letter in '97, 97-
01.
The thrust of that generic letter basically was -- the response
from the industry was what I'll characterize as an integrated industry program
to monitor this situation, and they came up with a susceptibility ranking, and
they indicated that the more highly susceptible plants would do examinations
of the CRDM penetrations. And they have been conducting those since that
time.
And the idea was that the more susceptible plants could serve
as leading indicators for what was going on with the fleet. So that's why those
inspections, actual eddy current examinations, have been going on.
In addition, licensees were committed under some prior
bulletins back in the late '80s to do boric acid walk-downs and look for that on
the head.
One of the things that was addressed in the safety evaluations
supporting that activity was that axial cracks, you know, did not constitute a
significant safety concern. It was partially a matter of leakage, and it would be
something that could be detected. That was the expectation at that time. It
could be dealt with.
However, it was acknowledged that a circumferential cracking
or cracking that could lead to a failure of a penetration were it to occur, that that
would be a different situation. That was addressed in the safety evaluations,
and there was an expectation that the industry would inform the NRC if that sort
of thing occurred, which is what has now happened.
So that's a little bit of the background. Does that answer your
question with regard to that?
DR. POWERS: Yes.
MR. STROSNIDER: Good. I wanted to talk about actually
five different things today. I guess first of all, I just wanted to give a very general
summary, a safety perspective on this.
Then yesterday we had some discussion. The subcommittee
focused on some specific technical issues that we were asked to address at
today's briefing. So I'm going to talk about those technical issues.
I also want to take a little bit of time to contrast the difference
between what the industry has proposed to do and what the NRC, what the
bulletin, in fact, is proposing, and that's something we didn't talk about
yesterday, but I felt at the end of yesterday's discussion that it would be
important to provide that perspective.
I want to talk a little bit then about some of the risk
perspectives, and then about additional work that's planned either ongoing or
planned.
And finally, I'd like to talk about how this issue fits into the
agency's four performance goals.
So just to start off with a summary, and I'll talk in a little more
detail in a later slide about the risk aspects of this, but just to give a general
safety perspective, the failure of one of these nozzles, the circumferential crack
leading to failure of the CRDM penetration and ejection from the vessel head
would constitute a loss of coolant accident and also a control rod ejection
accident, and like I said, I'll talk a little bit more about what that means from a
risk perspective in a later slide, but --
DR. POWERS: What does it mean from a neutronic --
MR. STROSNIDER: -- just to say at this point in time that
when we look at the existing PRAs without doing a lot of additional work to try
to tailor them to this specific issue, but just taking what's readily available, it tells
us that there's a level of risk associated with this event that requires increased
attention.
Having said that, I think we should note that the worst crack
found to date at one of the more highly susceptible plants in accordance with
the industry plant ranking, the remaining ligament had a factor of safety of
approximately six to failure. So it's about 165 degrees around the
circumference.
The bad think about inconel (phonetic) is that it cracks in
these sorts of environments. The good thing about it is that it's very flaw
tolerant. All right?
This assessment does not address the issue of continued
crack growth rate. We'll talk about that in the next slide.
DR. POWERS: Well, I mean, that's a non-trivial point, isn't it?
MR. STROSNIDER: It's a very important point.
DR. POWERS: I mean you've got a factor of six to failure
right now, but if that goes to a factor of zip in two months, that's not a very
comforting thing.
MR. STROSNIDER: Right, and I'm going to talk a little bit
more about the crack growth rate in the next slide.
I want to make the point that there's no reason to conclude
that cracking won't occur in other units and in other nozzle housing. The
expectation is that it will. You know, the environment stresses, the material, it's
all the wrong combination to support this sort of thing. It's a matter of time then.
With regard to the bulletin, we believe that timely and
effective, and I'll talk a little bit more about what we mean by effective in terms
of qualification, inspections should provide additional information on the extent
of the problem and provide confidence that safety is maintained and regulatory
requirements are satisfied.
We'll talk a little bit more about the bulletin. You know, we're
asking if people are not performing inspections by certain dates to provide
additional justification for that, which would get into some of these other
technical issues.
I think also it's important to note, and we added this bullet
since yesterday. There was not a whole lot of discussion on this yesterday,
although I think Dr. Kress brought it up. If you look at this size loss of coolant
accident in terms of the existing risk assessments, it's not expected to provide
a challenge to containment integrity.
So from an overall risk perspective, if you look at risk to public
health and safety in terms of Part 100 dose consequences, we wouldn't expect
a significant challenge there based on the existing calculations.
MR. ROSEN: Jack, on your fourth bullet you say there's no
reason to conclude that cracking won't affect additional units. Would you also
be able to say that there's no reason to conclude that cracking won't affect
additional housings at the plants that have experienced this cracking?
MR. STROSNIDER: Yeah, there's no reason to conclude that
additional housings would not experience cracking.
Now, if the people had additional information with regard to
the heats of those materials and the fabrication and their susceptibility, you
might be able to make some arguments about the timing and that sort of thing
or susceptibility, but that sort of information isn't available, and we can't
conclude that it's not going to occur.
DR. POWERS: I'm trying to understand a little better on your
last point. You're saying that CRDM nozzle failure, not expected to challenge
containment integrity given no additional failures.
MR. STROSNIDER: Yes. Well, no, what I'm saying is if you
look at the existing PRAs, if you go to the IPEs as an example and you look at
the size breaks that we're talking about, they do not provide a significant
challenge to containment integrity.
Now, I'll talk later. Okay? When we talk some of the
discussion yesterday with regard to risk insights about collateral issues and
other damage that might occur that haven't been specifically considered in this
sort of evaluation at this point.
DR. POWERS: Well, I guess I'm still missing something
because a large break LOCA clearly can challenge containment.
MR. STROSNIDER: It clearly can't?
DR. POWERS: Can challenge containment. An unmitigated
large break LOCA accident will definitely challenge containment.
DR. ELTAWILA: Dr. Powers, this is Farouk Eltawila from
Division of Engineering, NRR.
You're correct. Yeah, small break LOCA can lead into a core
damage if you have a multiple failure.
DR. POWERS: That's right.
DR. ELTAWILA: I think Jack is going to get into that. So I'm
trying to not steal his thunder, but for that particular scenario, if you look at small
LOCA, it occurs at the top of the vessel. So really if you would -- management
of the inventory, the operator would be able to extend, prolong the injection
phase and does not switch to the collision phase, and that's when most of the
core damage happens in that situation.
DR. POWERS: So he has to have an additional failure.
DR. ELTAWILA: Absolutely.
DR. POWERS: Okay. So it's a conditional statement. Given
no additional failures. Okay.
And also on your control rod ejection, can you explain what
the neutronic effects are?
MR. STROSNIDER: Well, only -- and I was going to get into
this later, and I've got a slide on some of the risk considerations.
DR. POWERS: Okay. Whenever.
MR. STROSNIDER: Okay. We'll see if we can address that
then.
As I said yesterday, following yesterday's discussions, the
subcommittee actually toward the end of the meeting provided a list of technical
issues that they asked us to talk about today.
Susceptibility model uncertainties, effectiveness of visual
inspections, evaluation of crack growth rate. Some risk assessment issues
were also on that list, and like I said, I'm going to address those on a separate
slide.
I think the industry did a good job yesterday of explaining the
operating experience and explaining what we know from a technical point of
view that would help us to assess this issue, and also explaining what we don't
know. And I think the subcommittee did a good job in zeroing in on some of
those issues and they are listed here.
So when we were asked to address this today, the one thing
I've got to tell you up front is we don't have the answers. We don't know, for
example, what crack growth rates are because there's uncertainty about the
chemistry or crack initiation rates because we don't know what the annulus
chemistry looks like, and so there's some questions there.
And that's one of the reasons that we're going out with the
bulletin, is the request for information, and what I wanted to focus on is how we
consider these technical issues in crafting the bulletin and our expectations with
regard to the information we're going to get.
We recognize that the susceptibility model certainly has
uncertainties in it. We have a lot of experience with trying to put these kind of
susceptibility models together, and they're not perfect.
However, we do think that it's a reasonable basis for the
graded approach that we've laid out in the bulletin, and if you've looked at that,
what you see is that we're recommending different information requests and
justifications based on the level of susceptibility.
We've broken the plants into four different categories. For
example, the plants that have actually identified leakage and cracking, they
need to do -- need to provide justification why they wouldn't do additional
volumetric examinations. Plants that are in the first four effective full power
years away from being equivalent to a CONY (phonetic), we'd need to provide
justification for not doing examinations by the end of this calendar year.
So we think that this is a reasonable model for laying out that
sort of graded approach, recognizing that the intent here is to collect additional
information to determine what additional actions may be necessary or
appropriate.
DR. POWERS: I guess I'm trying to understand why you use
the word "reasonable" associated with this, and maybe I almost need to see
something quantitative from your model because if you've got a very uncertain
-- that's fine. Things can be very uncertain, and you've broken it up into a
bunch of blocks in there, but I don't have a feeling for how relative to the size of
those blocks -- how big your uncertainties are.
If you say four effective power years away from a CONY, it
could be four or as small as six months?
MR. STROSNIDER: Yeah, and unfortunately, we don't have
the information to quantify that uncertainty. When you look at what drives the
susceptibility here and you look at the variables that are important, you start off
with time and temperature, and those are the two variables that were used in
this susceptibility model, and they clearly are the dominant factors.
DR. POWERS: Okay.
MR. STROSNIDER: Then you get into issues like the
microstructure of the material, you know, carbide distribution of the grain
boundaries, that sort of thing. That information is not available.
Fabrication history, you know. What did it take to get this
particular penetration inserted? Did it have to be straightened? What sort of
chemicals might have been used in cleaning, et cetera?
And that sort of information just isn't available in some cases
or in other cases, you know, it just hasn't been pulled together yet to be put into
the sort of quantitative assessment that you're looking for.
So we know there's uncertainties in it. We have experience
from the earlier susceptibility ranking, which, in fact, was off by several years,
okay, ten years or more in the case of predicting some of the cracking. All
right?
So we know that uncertainty is there, but the ability to quantify
it doesn't exist, and what we're proposing in the bulletin is that we've just looked
at the data in terms of some natural breaks with regard to how the plants are
grouped and said, "Here's some higher and medium ranked plants," and you
know, tailored the information request based on that.
The idea is to get additional information which will help us
then to better understand what those uncertainties are, but right now there's not
a quantitative model that I can tell you that you've got this sort of standard
deviation or something like that.
DR. POWERS: I mean, I guess what I'm fishing for is why
you call this a reasonable basis then.
MR. STROSNIDER: Well, we think it's reasonable because
it considers the primary parameters and temperatures.
DR. POWERS: Time and temperatures, things like that.
MR. STROSNIDER: And another way I could say it is it's the
best available we have at this point if you want to look at it that way, but we
definitely need better information to understand how good it is.
DR. POWERS: I guess it would be interesting to understand
why you broke it into four groups instead of just two.
MR. STROSNIDER: Okay, and I can start with the first group
were plants that have actually experienced cracking. All right, and so they have
the disease.
The second grouping basically, and I don't know if we have
the plot available, but this was pretty simple. There's just some judgment
involved here where we looked at the plants and how they stacked up in terms
of time to where they would be equivalent to Oconee, where the cracking was
discovered.
DR. POWERS: Yeah.
MR. STROSNIDER: We looked for a natural break, and we
said for effective full power use, there appears to be a natural break in the
ranking of the plants. Again, it would be based on time and temperature. We
said these plants that are above four effective full power years looks like the
group of most highly susceptible.
Then we went from that break back to another break in the
data which went out to I think it's 40 -- 30 full power years. Okay. So there's
nota whole lot more to -- okay. What you're looking at here, again, these are
effective full power years to where the time and temperature would be
equivalent, and using a Errhenius relation to what Oconee had, and we just
looked at this break and said, "This is the group of more highly susceptible
plants, and we think if we understand what's going on at those plants, you
know, we will have information that will help us to understand more about the
uncertainties in this assessment."
I should say that when you go beyond here out to 30 effective
full power years, we're also asking these people to do examinations. All right?
But it's different. This could be a VT-2 visual sort of examination.
DR. POWERS: Yeah, well, we'll get into that, whether that's
effective or not.
MR. STROSNIDER: Yeah.
DR. POWERS: I'm just trying to understand why you grouped
them as they are, especially since if I had put error bounds on these things,
which you couldn't really do because you can't even quantify your uncertainties,
but presumably they're big, that you would not see any such breaks.
MR. STROSNIDER: Yeah.
DR. WALLIS: We went through that yesterday, and they were
reluctant to put the error bands (phonetic) on, but it's obviously true that if you
put the error bands on, the points move around a lot.
DR. POWERS: It has real implications, it seems to me, on the
bulletin because it says why have four groups. Why not just have two?
DR. WALLIS: I think we felt there would be a big enough
sample or something like that, 25 plants or something by the time you've done
that.
DR. KRESS: One of my points, which I'm not sure I made
very well, Dana, was that these are relative to a CONY. Now, if they could go
to a CONY and look at all of these other parameters that they expect to affect
this susceptibility and somehow identify that the cracked parts of a CONY have
attributes of these parameters that they would expect to be high with respect to
shortening the justification time, if they could somehow make a judgment, then
they can say that the error bounds on all of these other things are -- that you
don't really need this error band because these things are relative to Oconee
and Oconee is already on the high side.
And I don't think I made that point very clear, that you don't
have to do the pool uncertainty. You have to go look at Oconee and see if you
could make a judgment that it's likely to be on the high side of the uncertainties.
DR. WALLIS: But isn't it normally on the high side? They
inspected nine tubes and had no cracks. So it's not all on the high side. It's
only some of Oconee that's on the high side.
DR. KRESS: Well, this is relative to the cracks that were
there at Oconee. So I'm saying look at the attributes of the ones in Oconee that
cracked and see if you can make some judgment about whether or not you
caught the most susceptible ones, and then I think you can make some
judgment that this susceptibility curve is probably a reasonable basis.
MR. STROSNIDER: I understand the desire to see a more
quantitative evaluation and to see these sort of uncertainty bounds.
DR. POWERS: I'm just trying to understand the reasoning.
MR. STROSNIDER: We don't have it, and quite frankly, we
don't have all of the information, couldn't do it if we sat down to do it. You could
make some assumptions on some of the parameters, but some of these
variables we don't have.
DR. KRESS: And you really don't know how the parameters
affect the thing, too. You don't have the model.
MR. STROSNIDER: We don't have the model?
DR. KRESS: Yeah. I don't think you can have a relationship
between the micro structure and --
MR. STROSNIDER: Well, there's that, too. You can go back
and look at the susceptibility ranking that was put together to support 97-01, and
in fact, its initial attempt was that to be a more sophisticated model, it did where
they had information try to include microstructure and some other variables.
I mentioned earlier it was off. If you look at Arkansas where
the cracking was detected early this year, by that original model, that plant was
predicted to be 11 or more years away from a condition where you might expect
to see that.
So interesting though when you take this model, which is a
much more simplified model, just looking at time and temperature. Arkansas
moves up, and it moves into this more highly susceptible categorization.
DR. POWERS: See, now, that's very useful information. I
mean that explains a lot when you tell me that.
MR. STROSNIDER: I'm sorry. I didn't hear.
DR. POWERS: That explains a lot when you tell me that,
okay, you had a model. It was off demonstrably by a lot, its prediction, but now
you're using a model which may well be more simplified, but the impact kicks
it up.
MR. STROSNIDER: But I want to be very careful here
because this is not intended to be a predicted model in terms of how many --
you know, at what point in time you're actually going to see cracking. It's a
relative ranking, and there's uncertainties in there. I mean, there's the
possibility that there could be plants out there that are cracked, you know --
DR. POWERS: Right now.
MR. STROSNIDER: -- like Oconee or worse, yeah.
DR. POWERS: Oh, yeah.
MR. STROSNIDER: The whole point of the bulletin is to go
out and get information, and then when you talk about reasonableness, you
say, "Well, you know, the bins that we've grouped the plants into, does it look
reasonable for getting that sort of information?
DR. KRESS: And, once again, if you could show somehow
that Oconee is somewhat the worse case, then you can make this statement
that this ranking is a pretty doggone good way to do it.
MR. STROSNIDER: If you could, but you need more
information to make that --
DR. KRESS: Yeah, you need some more information about
Oconee, like what is the -- you need some information about those things you
think affect the susceptibility to cracking, and I don't know how you get there,
but I thought perhaps there might be a chance for one plant of getting some of
that.
MR. ROSEN: So what this adds up to, Jack, in my mind is
you're telling us that you would not be greatly surprised if the plants in the four
to 30 year range, some number of them reported cracking.
MR. STROSNIDER: There's a possibility that when they go
out and do leakage monitoring that they're going to find some leakage, yeah.
Based on the last susceptibility model, there's a plant that was 11 or more
years, and it found --
MR. ROSEN: So there could be some in the four to 30 that
end up reporting some leakage and some in the earlier group that don't.
MR. STROSNIDER: That's correct.
MR. SIEBER: Well, I guess when I listened yesterday and
considered all of the uncertainties that appeared to be in the data and the
analysis, it seemed to me that the cutoff point would have been better set at ten
years rather than four years. That's 25 plans. So all of the cold head plants
would be in the latter category.
MR. STROSNIDER: And there's a matter of some judgment
and then the timing that's associated with that.
MR. SIEBER: Right.
MR. STROSNIDER: And in the next viewgraph I'll compare
some of the industry proposal to what the --
DR. BONACA: Well, one thing that at least for some of us
stopped the questioning was that you have approximately 24 plants that are
going to perform inspection between now and next spring in the group. It's a
large number, if I remember.
MR. STROSNIDER: We're getting into the next viewgraph.
DR. BONACA: No, but I'm just saying, however, that that was
the reason why I felt comfortable with what you had because I think we'll gather
a lot of information over the next few months, and then the focus of our attention
then became the effectiveness of the visuals because, you know, hopefully if
they're effective, then we'll learn a lot about what's taking place, much more
than we know right now.
MR. STROSNIDER: Yeah, and I'll talk about some of those
numbers.
DR. WALLIS: Are you going to talk about the visual
inspections?
MR. STROSNIDER: Yeah. If I could talk about effectiveness
of visual inspections, there was a lot of discussion yesterday about
effectiveness. Basically, to put that in regulatory terms, how would you qualify
this sort of examination?
And in the bulletin, and we presented yesterday we have
some specific criteria or issues that need to be considered when the industry
goes to qualify these sorts of examinations.
The first thing is the availability of deposits on the head, and
this gets to the issue of understanding what the interference fit is, the size of the
crevice between the penetration and the reactor vessel head, and what we've
suggested in the bulletin is that for those plants that are highly susceptible, if
they're going to do a visual examination, they need to convince themselves and
then have a basis to say that you're actually going to get leakage up out of the
crevice, and that you're going to have deposits on the head. That's the first
issue.
Now, we know that some plants have actual as built
dimensions on those interference fits, and they can do analyses, you know, to
measure those fits, and there was discussion yesterday about the ability
perhaps to do some calculations and understand the deposits and how that --
DR. WALLIS: But I think the key point was how does the
deposit correlate with the crack you're worried about. If the deposit is due to an
axial crack in the weld which squirts stuff through and eventually it makes it up
to the head, but you don't foresee it. First it creates this aggressive chemical
environment around the highly stressed bottom just above the weld, bottom of
the guide tube, and there's a race between the beginning to form circumferential
cracks there and the emergence of this deposit on the top, and we don't really
have a good basis for deciding how quickly these two processes occur and
whether the deposit is really visible before all the cracks got big enough and all
of that.
That's sort of really --
MR. STROSNIDER: And as you describe it, it really is a race
between getting that deposit on the head and detecting --
DR. WALLIS: I mean, the assumption seems to be that if you
don't see the deposit, there isn't a crack which you worry about, and that's not
necessarily so.
MR. STROSNIDER: Well, a ;couple of observations. One is
that if you look at the experience to date where these deposits have been
identified, we noted Oconee was the worst situation. There are other situations
where there were axial cracks that have led to leakage, and that's been
detected.
So the experience to date would suggest that those deposits
can deposit, but on a plant specific basis, you need to understand whether that
mechanism is really going to work or not. If you have a very tight interference
fit or if you have some different conditions, then it may not happen.
So what we talk about in the bulletin is for each licensee to
provide a basis to say, yes, we think that, in fact, those deposits would
accumulate.
DR. WALLIS: But they have to do this correlation between
the time where you can actually see the deposits and the time where the crack
has grown to the point where you worry about it. They have to do all of that
analysis. Do they have a basis for that?
If you wait long enough, you're going to get deposits because
other things may be happening while you're waiting for the deposit to be visible.
MR. STROSNIDER: Yeah, it's not specifically addressed.
DR. WALLIS: And that seems to be a weakness of relying
only on visual inspection.
MR. STROSNIDER: Well, let me go through the rest of the
logic because there's more there.
Once a plant, one of the higher susceptibility plants, if they
convince themselves that, yes, they will get deposits on the head, then you've
got the issue of being able to discriminate those deposits possibly from
preexisting deposits.
We saw some photos yesterday. There are leaks from other
sources, from flanges and seals that are up above, and depending upon what
the history of the plant is in terms of cleaning those or perhaps what their
photographic documentation is, there's questions about can you discriminate
new deposits from old deposits.
And the other issue that comes up here is the insulation
because there are various types of insulation. At least we heard yesterday that
the B&W units, the insulation is raised off the head. So there is access. For
some units it conforms to the head, but it's lifted off, access, but perhaps more
difficult, and there's other units where it lays and it's, in fact, glued right to the
head, and there's other issues associated with that.
So in order to qualify visual exam, you have to address those
issues, and that's addressed in the bulletin.
So our expectation is that the industry would come up with
methods for doing those sorts of qualifications.
Now, with regard to growth rate and annulus chemistry, all
right, and this is an issue that got a lot of attention yesterday, and as was
pointed out, it is important to understand and what is a factor of safety of six
mean in time. All right?
We don't have data to help us understand that, particularly
because of understanding what the environment and what the chemistry in the
annulus might be and how that could impact us. We've got some work going
on and the industry is doing some work to try to understand that better.
But what we're telling the industry in the bulletin is if you don't
plan on doing inspections by a certain time, either by the end of the year,
depending on your susceptibility or your next outage, you need to provide a
basis, and that basis would have to address this issue.
All right. So we don't have the answer right now. That's the
purpose of the bulletin, is to basically force that sort of evaluation, if that's the
basis.
DR. WALLIS: I guess what I was saying just now is that in
order to assess the effectiveness of visual inspections, you may also have to do
some of that.
MR. STROSNIDER: Well, when I come back to that, you
know, in assessing the effectiveness of the visual exams in this race between
the crack growth and whether you're going to see the deposit, the best thing we
have to point at at this point is like you said the operating experience, where
when you see those deposits and you go in and actually look at the crack sizes,
they have had margin. And that's the best logic I can offer right now.
MR. ROSEN: But you don't know how many other cracks
there are.
MR. STROSNIDER: That's right. Well, you have this whole
question of will, in fact, some of these penetrations leak or not.
MR. ROSEN: I'm just saying that we found a lot of cracking
from looking at boron deposits. It doesn't give me a lot of comfort that there isn't
cracking going on because it's not going to call you up and tell you, "We're
cracking down here." It's just going to keep on cracking until one of two things
happens, one very bad, and the other which is detectable.
MR. STROSNIDER: Which supports the basis for a need for
an assessment, and if you can't provide the data and assessment to support
that you don't have this problem, that you need to do timely inspections. That's
the logic we're trying to build into the bulletin.
MR. ROSEN: You know what they say about absence of
evidence.
MR. STROSNIDER: Excuse me?
MR. ROSEN: You know what they say about absence of
evidence, not evidence of absence.
MR. STROSNIDER: One other comment I wanted to make
on this is, again, if you look at the logic we're laying out in the bulletin, it goes
along the lines of if you're not going to do an inspection by the end of this
calendar year, for example, for high susceptibility plants, and I just point out,
you know, with this uncertainty in the growth rate, we're saying you need to do
a timely inspection, and again, there's some judgment involved here, but we're
saying at the end of the year for high susceptibility plants is reasonable.
But the other point I wanted to make is that the bulletin offers
the opportunity for the licensee to provide a basis for not doing that inspection
by the end of the year and doing it on some other schedule, and they need to
address these and a number of other issues that were raised in requests for
additional information that we provided in response to the industry report on
this.
And the point I wanted to make is that the information that was
provided in that report and in the responses to those requests for additional
information was not sufficient to answer this question. If it had been sufficient,
then we wouldn't be talking about this bulletin.
So there needs to be additional information provided to
provide justification for why these inspections could not be done sooner.
So as I said, there are a lot of good questions. We would like
to understand in a quantitative sense these issues better, and actually there is
work going on to try to do that, but at this point in time when we don't have all
of those answers, the intent is to try to address them through the bulletin.
Now, I wanted to summarize perhaps briefly if I can the
difference between what was proposed by the industry and the logic in the
bulletin, and let me start with the industry approach.
If we talk about the examination method, the recommendation
that the industry made was a visual examination capable of detecting small
amounts of boric acid deposits for plants that are within ten effective full power
years of Oconee 3 and continued boric acid walk-downs for others.
Now, this is basically the extent of the recommendation. In
the generic letter, we've laid out a graded approach, but it talks about the issues
that need to be addressed as part of the qualification, and I talked about some
of that on the last viewgraph. You know, what's the interference of it at your
plant? What's the history of deposits? Can you really discriminate or can't you?
What's the insulation situation? Do you have to remove insulation?
Those are all issues that would have to be addressed in
response to the bulletin.
DR. WALLIS: These are small amounts. Has anyone tried
to quantify this? You have to have a certain amount before you can see it.
MR. STROSNIDER: Well --
DR. WALLIS: Some sort of quantification of how much that
implies by the time you see it it's been going on all that time while it's been
building up and so on, or you just sort of assume that by the time you can see
it, you've got enough information or something?
MR. STROSNIDER: The discussions to date have been a
small amount. The example being given is Oconee, which is our understanding
was less than one cubic inch, and when you look at the photo of the head, you
see a lot of white deposits on there. Some of that is residue from prior cleaning,
et cetera, but what we were informed is that what actually came from the
leaking nozzles was less than a cubic inch.
So it is a very small amount, and in fact, it's a change in mind
set, if you will, I think, for the industry perhaps. When we talk about these boric
acid walk-downs where people have in the past found hundreds of bounds of
boric acid, and now the focus has to be on a much smaller amount because
that's the expectation, the sort of thing we would expect to see addressed in
qualification of these visual exams.
DR. WALLIS: Do you see it because it reflects differently from
the steel? It has a different color from the steel or something? It's something
you detect which is --
MR. STROSNIDER: Different color from the steel. There's
been discussions with the industry about different morphology, if you will, of
what the texture of it looks like, depending upon whether it's bubbling up with
a crevice or running down from someplace else, but I think the point here is that
all of those sorts of things need to be assessed and qualified. You need some
sort of quantitative method for saying that this examiner can actually identify --
DR. WALLIS: Perhaps 180 degrees around the tube, too.
You mustn't just look at it. You've got to look around the back of it and look as
well because it might be building up there.
MR. STROSNIDER: Okay, and when we talk about this
graded approach, again, to come back to the examination method, what we're
asking for in the bulletin is for plants that have identified leakage, unless they
can provide some other basis, a volumetric examination, the point being here
that the intent is to avoid a recurrence of reactor coolant pressure boundary
leakage.
They've actually had this. They've had leakage. They've had
through wall cracks, and we want to see an examination that's capable of
maintaining the sort of criteria that exists in the ASME code, which would say
you're not supposed to have through wall cracks in the reactor coolant pressure
boundary.
In order to do that, you basically need some sort of volumetric
exam.
DR. WALLIS: What does volumetric mean here?
MR. STROSNIDER: It means being able to interrogate not
just the surface, but actually the volume of material.
DR. WALLIS: Look for cracks throughout the whole volume.
MR. STROSNIDER: And I want to be a little careful here, you
know. I guess that could suggest there's the possibility of using surface exams,
like a penetrant exam or something like that. Even the eddy current that was
done is a very shallow exam, and depending upon what a licensee would do if
they find something, an analogy might be steam generator tubes where --
DR. WALLIS: Well, you know what --
MR. STROSNIDER: -- if you find an eddy current indication
and you can't size it, you repair it.
DR. WALLIS: You know what the most susceptible place is
for the centrifugal -- the circumferential crack, right?
MR. STROSNIDER: Yeah.
DR. WALLIS: And you know that's not on the surface. So
you're going to have to look inside quite a way.
MR. STROSNIDER: Plant specific visual examinations for
plants that are within a less than four effective full power years, and that's what
I was talking about, the qualification there, you know, providing a justification
that they will, in fact, see deposits, that the deposits will exist, and that they will
see them.
And it goes on to talk about if you do see a leakage, you
know, what's the follow-up. And you know, without some additional justification,
and if you look at the regulations it would appear to drive you into a volumetric
examination.
A visual examination for these moderate susceptibility plants,
that's what's in the four to 30, and that requires something more than what's
stated here. You still need to be able to discriminate. You've got issues with
regard to insulation, but it might not require quite as much as for high
susceptibility plants.
DR. POWERS: Could you explain a little bit about the
phenomenology of the cracking here? We have a stress corrosion cracking
process going on. So we get some initiated cracks. Did they go through wall
before they propagate farther in distance or can they propagate along before
they go through wall?
MR. STROSNIDER: The possibility exists for multiple
initiation sites.
DR. POWERS: Right.
MR. STROSNIDER: All right? Which could lead to what we
call complex crack geometry.
DR. POWERS: Right.
MR. STROSNIDER: You might get one part growing through
a wall and part through a wall at others. To my knowledge, what was found at
Oconee was more a simple through wall crack. I don't know that they -- you
know, we didn't have reported any other initiation sites, but the possibility is
there, and it's going to be driven, again, by the environment, the residual
stresses, you know, what the residual stresses look like and how they relax as
the crack rose, and that could depend upon different initiation sites.
There's a lot of questions there, more questions than I have
answers.
DR. POWERS: It seems to me that your visual inspection
depends on it going through wall, doesn't it?
MR. STROSNIDER: Well, let me back up a second and make
sure that -- because I'm not sure if you understood this part of it. The residual
stress distribution on the inside of the penetration tends to drive axial cracks.
That's pretty well demonstrated by the analyses and by the operating
experience.
There's also the possibility for cracks to initiate on the outside
of the J groove weld and grow up behind them, but the mechanism appears to
be that you first grow a crack of that type such that you provide a pathway for
coolant to get into the crevice between the tube and the shell, the vessel.
Once that crevice or annulus has an environment in it that will
support stress corrosion cracking, the residual stresses on the outside support
the circumferential crack growth.
So the race that was discussed earlier is from the time that
you get coolant into that annulus, presumably from an axial flaw, all right? And
it works its way up to where you can see a deposit. How much circumferential
crack growth would you expect to see?
So but there is at least the notion that you're going to have
this axial crack through wall that's going to begin leaking. Now, there's
questions about once you get that axial crack does it require an independent
initiation site with a circumferential crack or can the axial crack turn. That
becomes important because initiation times can be significant.
DR. WALLIS: The initial axial crack can be just through weld
and give you deposits. It doesn't have to go through any wall at all. It doesn't
have to affect the wall at al.
MR. STROSNIDER: That's true.
If you look at what's involved in these different categories,
plants that have actually experienced leakage, there's four of those. Other
plants that would be in this high susceptibility ranking, there's another ten, and
there's in the medium susceptibility another 31 plants, which the generic letter
is asking those licensees to tell us if they're not planning inspections to provide
a basis for that, and that's a total -- it's a different type of inspections, but it's a
total of 45 plants compared to the industry proposal which would capture those
plants in the first ten EFPY, which is 25 plants.
DR. POWERS: And the first 14 of yours are totally
encompassed in the first 25 of theirs?
MR. STROSNIDER: Yes.
The other issue that come sup here is with regard to the
timing of the inspections, and again, we're asking for justification for not doing
inspections before the end of this calendar year. Six of those 14 high
susceptibility plants are not scheduled for outages before the end of the year.
Actually I wanted people to understand that, compared to the
industry proposal, which would be at the next refueling outage. So some of
these 25 plants would go out to next spring, and I think a few of them until next
fall, based on the industry proposal.
DR. POWERS: When I think about timing the issues of
quantitative measures of risk, I mean, that's almost my first question. When you
discuss risk, are you going to go into something more quantitative on this?
MR. STROSNIDER: No, not much more. You raised a
question right at the beginning about crack growth rates, and as I said, we really
don't have a good handle on the initiation times and the growth rates.
The point we're making here is that we're looking for what we
consider an appropriate sample of plants to look or just why they're not looking
at what we think is a fairly timely manner, by the end of the year. The question
is: are you willing to go off an additional six months or if you'll look at the
proposal here, are you willing to go off an additional year and a half with this
unknown parameter of growth rate?
DR. POWERS: Well, I'm going to say, "Look. That's a
known." But Farouk just told me that we really don't get into a CDF situation
until I have some additional failure.
Okay. Additional failures I've got some handle on in my risk
assessments. That's where I would start asking the PRA --
MR. STROSNIDER: Well, let's try to -- when we get to that
slide, which I think it might be the next one, let's see if we can't address that.
DR. POWERS: Okay.
MR. STROSNIDER: Sample size is another issue that comes
up here, and talking about 100 percent of the head penetrations. That's similar
to the industry for visual examinations.
When you get into doing volumetric examinations, however,
we're also asking for justification why 100 percent shouldn't be looked at. I think
the industry approach was really silent on this, although you could look at the
ASME code, which indicates that you basically double your sample size, which
at a CONY, for example, found nine leaking penetrations. Then they went and
looked at another nine beyond that.
Our basis for this is when you look, if you try to approach this
from a statistical point of view and you ask yourself, you know, if success is not
having one penetration with an unacceptable crack in it, define that however
you want to define it; you know, the statistics are the sampling, so you basically
need to go look at all of them.
Now, you want to temper that a little bit with engineering
judgment. All right. But if you go look at Oconee and you look at the distribution
of penetrations that experience cracking, there were some on the outer
periphery, which is expected to have higher residual stresses because of the
geometry, but there were some that were just a few rows from the center that
hadn't.
All right. So it's very difficult even to construct an engineering
argument that says look at these first based on the operating experience.
MR. LEITCH: Jacks, just before you leave that one, could you
differentiate under the examination method between Group 2 plants and Group
3 plants? What's different about a plant specific visual qualification between the
two?
MR. STROSNIDER: The major difference that we discuss is
providing an assessment that says that the boric acid deposits will really find
their way up the crevice --
MR. LEITCH: Okay.
MR. STROSNIDER: -- and deposit themselves on the head.
That may not be a trivial thing to do. For plants, we know from
the public meeting we had that at least the B&W units do have some as built
dimensions that they could use to put into an analysis to do that. We don't know
if all the vendors have that sort of information.
Absent being able to demonstrate that, you basically have to
justify why you wouldn't do a volumetric examination.
MR. LEITCH: So absent that data, that means that some of
that family of plants might have to take the head off. The volumetric exam
means take the head of basically.
MR. STROSNIDER: Yes. And again, that reflects the graded
approach where for these moderate susceptible plants as we've characterized
them, and we are not looking for quite as stringent a qualification, but depending
upon what comes out of -- you know, what information we get between now and
the end of the year, we'll have to look at that.
DR. POWERS: Can I ask you about the volumetric
examination and into reliability? It seems to me in the 1997 time frame some
examinations, volumetric examinations, yielded fuzziness that indicated there
might be something and there might not be something. Is that a problem here?
MR. STROSNIDER: Well, there's a significant issue here,
and it's a significant challenge for the industry in that for some portions of this
penetration, for the welds in particular, there aren't any qualified examination
methods right now.
Okay. Now, when we talk about qualified, there's various
levels of qualification. You know, Appendix 8 code talks about a PDI,
performance demonstration initiative type qualification. Frankly, from a practical
point of view, there's not going to be enough mock-ups built in order for them
to do that between now and the end of the year.
There are some examination methods, and we've asked some
of the experts instead of being contracted by research, Steve Docteur in
particular, to tell us what sort of capabilities, you know, might be possible.
So looking at that, but there is a challenge in terms of
qualifying these methods, and I think we're going to have to work with the
industry to understand what they can do.
The volumetric exams are not perfect. In fact, if you go back
and look at the Oconee experience, the volumetric exam did not detect the
circumferential cracking. All right? That was detected actually when they went
in to do the repairs, and they had to do some penetrant examinations as part of
the repair process.
So there needs to be work done in this area. It is a challenge,
and the industry will tell you we don't have a qualified method at this point.
MR. SIEBER: Well, it depends on the plant, too. B&W plants
have cylindrical CRDMs so you can shoot through it with a UT probe and find
the weld, except the geometry is real complex. It's not clear what it is you're
looking at.
MR. STROSNIDER: There's different geometries with
different access. Some plants may have thermal sleeves in here. Some may
not. There's --
MR. SIEBER: Well, the Westinghouse plants have a thermal
sleeve. So there's no way to get the transducer in contact with the cylindrical
portion unless you get one thin enough that you can slide down between the
thermal sleeve and the actual base metal of the CRDM housing, and so under
those circumstances, I don't know how you would do a volumetric exam, but --
MR. STROSNIDER: So I want to make it clear when we talk
about an information request. That may sound somewhat benign, but it really
isn't. There's a significant challenges to justifying why a plant wouldn't do
inspections, and if a plant get into inspections, depending on the time, there's
some challenges being able to --
DR. WALLIS: Well, are you in some cases asking them to do
things beyond the state of the art?
MR. STROSNIDER: Some of the things that they might be
driven into here are going to require additional development between now and
the fall.
Now, I would point out that regardless of what goes out in the
bulletin, there is the potential for people to finally -- with the current
examinations and have to deal with these issues, all right, and if you look at the
Oconee experience and other experience, there should be a real motivation to
develop this technology because the exposures and the costs associated with
these inspections and repairs can be very high.
DR. FORD: Excuse me. Could I just have a sanity check
here? Larry, we're supposed to finish this whole meeting at quarter to four. We
do have the presentation by -- could I ask, Larry, approximately how long would
you need? I notice you've got pretty well the same presentation you had
yesterday.
MR. MATTHEWS: As long as they ask questions --
(Laughter.)
DR. FORD: I just wanted to know. They identify nine leakers
at Oconee, and they understand that nine additional ones were inspected, right,
of the nozzles?
MR. STROSNIDER: Right.
DR. FORD: And typically do an inspection of that type to
verify that there isn't further leakage. I understand the difficulty of inspecting,
but given the number, the number grew from zero to nine. Why didn't we have
100 percent inspection of the other nozzles?
MR. STROSNIDER: I think the licensee's action at the time --
and they'd have to speak to this -- but I'm assuming that they were looking at
ASME code requirements which say, you know, double your sample size, and
they didn't find anything in that additional sample. But I point out in developing
this communication, we went back and did some statistical analyses and said,
"What does that really tell us?"
And statistical evaluation says it doesn't really give you a high
level of confidence that there aren't other cracks out there.
DR. BONACA: Because it's hard to believe that, you know,
there were only nine there, and they evolved over the years until they all came
up at the same time, and now they're all Scott free. I mean, but that's
considerations for the next inspections.
DR. WALLIS: Well, it didn't happen at the same time. I think
Oconee told us that probably they've been occurring over several years. They
happened to be detected at the same time.
DR. BONACA: I understand that, but I'm saying that so why
not affect the other nine the next outage.
DR. FORD: Could I make, again, a sanity check request?
Larry, would it be acceptable to you to cut down your talk and address quite
specifically the areas where you might disagree with what Jack is saying?
None of the background slides that you have --
(Laughter.)
DR. FORD: Would that be okay, Larry?
MR. MATTHEWS: Yeah.
DR. FORD: Good.
MR. STROSNIDER: Let me try to move through the rest of
this a little bit more quickly if I can. A lot of discussion about risk, right insights
yesterday. Some questions have already been raised today.
The failure or ejection of one of these housings, there's two
different issues or events you can look at here. One is a loss of coolant
accident, and the other is a reactivity insertion, loss of the rod.
Let's talk about the LOCA for a second. As I understand this,
if you look at existing risk assessments, okay, they include small or medium --
excuse me -- this would be medium in PRA space, medium break LOCAs as
one of the initiating events, and then you go on from there with additional
failures and you figure out what the probability of the core damage might be.
The point here is that if you just take that break and you look
at the reliability of the mitigating systems, you look at the operator's ability to
configure the system into the recirculation mode, which is an important aspect
that tends to drive some of the risk numbers, but that's pretty well understood
in terms of, you know, there's an existing analysis that tells you how it's going
to work.
Now, those analyses aren't necessarily, in fact, probably
aren't for this specific location. Some people will characterize this as if you're
going to have a medium LOCA, this is one of the better places to have it. All
right?
It's more forgiving. There's a longer depressurization time,
which gives the operator more time to align the system. Okay? So you could
go back and look at this and try to understand better the specific thermal
hydraulics in this event with this break location and understand is there more
time and can you credit operator action as being more reliable. So that's on the
plus side.
All right. Now, I'll get down here and talk about some
collateral issues in a minute. Now, the other issue is the rod ejection which
could cause an insertion, a reactivity insertion event, right? Now, if this occurs
at full power, the rods are out in most plants the way they operate today. So
there's no real activity issue or reactivity issue there.
If you look, however, from the hot zero power condition, all
right, it could be a more significant event. Now, there was some discussion
yesterday about the fact that that event is analyzed as part of the licensing basis
for the plant, and those license basis analyses show that you could have some
fuel damage, as I understand it.
However, we had some discussions yesterday, and we
wanted to point out there's some additional, more recent work that's been done
and is ongoing in the Office of Research using more realistic assumptions,
which might be appropriate from a risk assessment perspective that say that
you would not experience core damage in that event.
So that's just sort of an understanding of, you know, what
exists in the licensing basis evaluations and what you might conclude from
looking at existing risk assessments.
Now, again, if we look at this specific situation, there are some
questions that can come up which we categorize as collateral issues, and
what's the potential for multiple rod ejection? If one rod comes out, can it
damage another to the point where it might fail or where it might render it unable
to insert, in which case you get something that's beyond what's been evaluated
to date?
DR. POWERS: Well, I guess I would ask the question as do
we understand the kinds of loads placed on the other CRDMs when we have
the depressurization associated with one fracturing? And does that lead to
other cracks, cracked housing, having the crack propagate?
MR. STROSNIDER: And the answer is that we've initiated;
we're working right now to get information on what the configuration, the design
looks like, the missile shield, the supports. There's seismic supports up there,
which I think provide mainly lateral support, but we're collecting information to
understand what those structures look like so that we can provide some
assessment of that.
But that's work that has been initiated. We don't have the
answer at this point.
There was a discussion yesterday about pressurization
effects and that sort of thing. The industry is initiating some risk assessment.
We're going to be discussing with them some of these areas.
DR. POWERS: Your statement that core damage is unlikely
based on some of the more modern reactivity analysis for the hot zero power
event, but it seems to me that I recall a test in France where there was a
reactivity insertion on a fuel rod, and they got fuel damage at relatively modern
insertion energies.
MR. STROSNIDER: I'm not the person to answer that
question.
DR. POWERS: Farouk is.
DR. ELTAWILA: Dr. Powers, as you know, the Office of
Research has an extensive fuel program, and what we are trying to utilize here
is a snapshot of the information that we have. We know that research is going
on. So from the neutronic point of view, if you look at the amount of energy, the
U-3D neutronic (phonetic), the amount of energy inserted for the high worth rod,
you will find that the amount of energy in the order of about 15 calorie per gram,
and if you look at the worst situation, can go all the way up to 50 calorie per
grams.
Now, I'm aware of the test in the A-1 debt field (phonetic), and
there is a lot of disagreement about that, and I think there is a consensus that
test might be an anomaly and not representative of what really might happen
in the reactivity insertion accident.
The third point that I would like to make is that if you look at
all the tests in A-1, you found that we never had any dispersal for a pulse with
greater than 20 milliseconds. All of them have a very small pulse width.
If you look at the actor itself, the pulse width is in the order of
.29 to .5 millisecond. So, again, as a snapshot we're utilizing the best
information that we have and say, "Okay. We're continuing the research, but
based on the collective information that we have, we really don't think that it's
an issue that is going to lead into core damage at this time."
MR. STROSNIDER: Thank you, Farouk.
One other point I'd make with regard to this failure under this
particular condition, is that plants are in that condition for a very short period of
time. So you're going to start off with a window of vulnerability that's fairly small,
and it's going to drive down the initiating event frequency.
But, you know, these are areas -- I guess the other point that
was made here, just one thing is recirculation issues. I think you heard
something this week about some blockage issues. That's an issue that's being
developed, that's being looked at now. These are things that would probably
need to be considered in some additional work.
Probabilistic fraction mechanics analysis. The subject came
up yesterday. We talked about everything pretty much that we're talking about
up here is the consequences of an event should it occur, and we had quite a bit
of discussion yesterday about what assumptions do you make on the frequency
of that initiating event.
The answer to that will come up through some probabilistic
fraction mechanics assessments. The industry is working on that now.
I wanted to make a point with this, with regard to this. The
NRC was involved in some of the -- in fact, developed some of the original
computer codes and models that are used to do this, and so we're fairly familiar
with this. The point I want to make here is that like any other computer model,
it's only as good as the information that goes into it. All right?
So there's a real challenge again here because you get back
to some of the same questions we were talking about earlier. What do you
assume for growth rates? What do you assume for the environment? What are
the material properties, et cetera?
People often fall into the trap of saying, "Well, I don't have
enough information to do a deterministic analysis. So I'll do a probabilistic
analysis."
Well, the fact of the matter is you need more information to do
a credible probabilistic assessment than you need to do the deterministic
assessment. All right?
And I make this point just to emphasize that if you're going to
look at numbers that come out of this sort of analysis in a quantitative sense,
you need to have some good confidence on the input parameters.
All right. Now, having said that, these models can also
provide very good sensitivity insights to understand where the most important
parameters, and you know, that can help you to just decide how to manage an
issue.
But we're going to see some calculations like this which are
going to be driving it, trying to establish an initiating frequency, and we're going
to have to look real hard in terms of do we have confidence in the inputs to that
model.
Again, we talked briefly on my first slide with regard to if you
want to take this risk assessment all the way out about, you know, what
challenge there might be to the containment.
MR. ROSEN: About that probabilistic fraction mechanics
analysis, when you get it, it's going to be time dependent. It will be a snapshot
in time for a nozzle at this much time and temperature, with these properties,
but the time and temperature will change, of course, as it continues to operate.
So you'll need as a function of time and temperature.
MR. STROSNIDER: If temperature changes, yes.
MR. ROSEN: Well, time is going to change.
MR. STROSNIDER: You need to modify the model.
In regard to time, these models have the capability of
incorporating crack growth rate, and if you've got the distributions to put in
there. All right? So they --
DR. POWERS: Don't worry, Steve. That will show ten to the
minus 11th, your return frequencies. They always do.
(Laughter.)
MR. STROSNIDER: Okay. Additional work. You know,
we've talked about information that we don't have, we'd like to have to better
quantify some of these issues. The first thing is I want to acknowledge the
support we've had from the Office of Research. They've contracted some
experts in the area of NDE, fracture mechanics, and nondestructive testing, and
they've also been providing support in this risk assessment. We've asked them
to independently look at our assessment of the existing risk analyses, and
they've been helping us out there.
So that work needs to be completed. It will be documented,
and that will be made available.
In addition to that, I want to point out that we have back in
June actually -- the Office of Nuclear Reactor Regulation provided the Office
of Research with a user need to address issues associated with cracking of
inconel. I'm not going to go through this whole list, but you'll see that a lot of
issues we're talking about in terms of NDE growth rate, et cetera, is on this list,
and you know, we've already started to initiate work in that area.
Similarly, and nuclear reactor regulation is working with
research in these areas of understanding risk and systems evaluation.
I want to emphasize the additional work here of continued
review of industries activities. It's industry's responsibility to address these
issues, and we're working with the Office of Research. We're doing our own
evaluations in nuclear reactor regulation to understand it and to be in a position
to do a review, but this is a responsibility of the industry.
The bulletin, I think, is intended to make that point.
DR. POWERS: On this general subject of additional work,
everywhere we seem to use Inconel 600 it seems to crack. Other than job
security, are there other places that we should be looking where Inconel 600 is
used?
MR. STROSNIDER: Well, in fact, we do have piping issues,
and there's another industry initiative underway by the Jules (phonetic)
Reliability Project, and we've been interacting with the industry. VC Summer
had a crack in the pipe last year, and so we are in fact -- this work that I just
described is not limited to control rod drive mechanisms, but -- and our
interactions to the industry is not limited to that either.
So if we're looking to understand where in the system inconel
was used, where it is susceptible, and you know, a lot of the work, however,
when you start talking about some of these different things, it does overlap.
You can apply it, and so -- but we're not restricting this just to control rod drive
mechanisms.
DR. POWERS: I guess I was looking for a little more
specifics, and you certainly mentioned the Summer issue. You probably just
assume I'd never brought up the word "steam generators" again. Now we've
got control rod drive mechanisms.
Are there any other particular locations in the plant that we
should be concerned about?
MR. SIEBER: Don't some plants have inconel pressurizer
heater thimbles?
MR. STROSNIDER: Yeah. Well, in fact, we've asked the
industry, and they're working through their initiative to identify various locations,
various susceptibilities. You can get into issues like were the inconel welds
shop fabricated or field fabricated, which can have some influence, and they're
doing an assessment of that now.
I would point out with regard to the Summer pipe cracking that
in our assessment of that we don't see the risk or the safety significance at this
point in time associated with that that we see with the CRDMs. The crack was
axial. It was limited to the width of the weld.
One of the issues that we're working to understand is the
potential for circumferential cracking, which of course would again change the --
DR. POWERS: Ten to the minus 11th, I know. It's a constant
in these calculations.
MR. STROSNIDER: Then I wanted just briefly to, if I could,
conclude with summarizing this issue in terms of the NRC performance goals.
In terms of maintaining safety, we talked a little bit about the risk perspectives
that we have based on existing analyses, and clearly, you know, there's a
number of issues there that can be -- that need to be worked, but based on
what we understand for this issue and based on existing PRA analyses, you
know, we conclude that this is an issue that required additional attention.
That's reflected in the fact that we're proceeding to issue a
bulletin.
With regard to reducing unnecessary burden, I want to
emphasize the word "unnecessary." All right. There will be burden. The
industry is going to have to spend resources to deal with this issue.
All right. Having said that, we have challenged ourselves and,
in fact, as part of our process in developing this bulletin, we've been challenged
by our various review committees to try to minimize the information requests,
to focus it on the information that we really think is necessary to understand this
issue, and make sure that, in fact, we can maintain safety.
Some of that is reflected in the graded approach, and if you
look at the information that we're requesting.
Improved efficiency and effectiveness. First, to deal with
efficiency, I think it's important to understand in previous issues like that the
industry has chosen to go out and try to develop generic responses to the
extent possible.
Now, the bulletin goes out on a plant specific basis, but there
may be some aspects of this that can be dealt with by those plants referencing
generic evaluations, showing that they're applicable to their plants, and we're
certainly amenable to that process. It tends to be more efficient.
With regard to effectiveness, we have had good
communications with the industry. Those communications need to continue
right through this issue. We need to have good understanding between the
staff and the industry as to these responses and what's acceptable and what
isn't acceptable in terms of addressing the issue.
It's not going to serve anybody well if these responses come
in in early September, in late August or early September time frame, and I think
that the industry has missed the mark. So from an effectiveness point of view,
we need to continue the communications.
DR. WALLIS: What would be an effective ultimate conclusion
of this issue?
MR. STROSNIDER: Well, you have to go back to the logic
in the bulletin. The industry needs to provide additional information --
DR. WALLIS: Are you just going to keep inspecting forever
and gathering information forever?
MR. SIEBER: For a new reactor head.
MR. STROSNIDER: Well, let me first address the short term,
which is the bulletin recognizes a snapshot in time. So the options that are in
there provide additional information, as I noted earlier, beyond what's been
provided to the staff to date, to provide a justification for not doing inspections
on the sort of schedule that we've --
DR. WALLIS: Well, eventually it's not replacing your head.
MR. STROSNIDER: -- that we've suggested.
DR. WALLIS: Eventually it's not replacing the head.
MR. STROSNIDER: Or doing inspection. In the longer term,
okay, and I come back to the comment I had on the first viewgraph, there's no
reason to expect that this cracking is not going to continue to occur and to affect
more plants. So there needs to be a long-term program. They include
inspection, head replacements.
The industry needs -- that's their determination based on the
finances, et cetera.
The ASME code has recognized this issue. They have a
group that's off already looking at augmented inspections, and we want to
encourage that effort. This just gets us through the first -- you know, the near
term here. There needs to be a longer term program to manage the issue.
Finally, with regard to increased public confidence, one of our
main efforts here is to keep the public informed. It's the industry and other
stakeholders. We have a Web site where we're trying to get information on
there as rapidly as we can. So I just want to make sure that everybody
understands that that's available.
We've had some feedback that people find it pretty useful. If
there's any comments on how to improve it, let us know.
DR. FORD: Thank you, Jack.
MR. STROSNIDER: That concludes what I planned on
saying.
DR. FORD: Thank you very much.
Any last minute questions for Jack?
DR. POWERS: I guess what I'm still wrestling with a little bit
is the effectiveness of the inspections you're proposing people to do. Have you
given any thought to the advantages that might accrue to having an improved
inspection method if you gave them more time to develop one perhaps
generically?
Is there any way in the, say, reasonably short term between
now and the end of the next or the following refueling outage to have a better
way of inspecting?
MR. STROSNIDER: My expectation based on experience
with these sort of issues is that the inspection technology would improve with
time. You mention steam generators. You can see the changes in the
technology that existed there.
We understand that there are limitations to what's available
today, and that there's a challenge for the industry, but we have to balance that
against maintaining safety of the plants, and we put that challenge out there that
they need to be able to do effective inspections.
Bolton, you know, puts that responsibility, I think, squarely on
the responsibility of the industry.
DR. POWERS: I'm struggling trying to understand your timing
because I don't have this conditional probabilities for core damage in mind on
these things. I mean, you've told me you're not going to threaten containment
integrity, but I know you can if you have other failures.
What I don't understand right now is what the probability,
conditional probability of having these other failures is.
MR. STROSNIDER: We had a prolonged discussion on that
yesterday. At the risk of repeating it, I'll just tell you that we did present
yesterday -- we asked that question. What's the conditional probability of core
damage, given this event occurs?
And I want to emphasize because it came up yesterday we're
not saying that we think the initiating event has a probability of one, but we're
trying from, as I characterized it yesterday, a decision making under uncertainty.
You know, can we get any insights?
The conditional core probability, damage probabilities that you
get out of looking at existing PRAs, and I think that's basically the IPEs, ranges
from like ten to the minus third to as high as actually a little higher than ten to
the minus second in some cases. It's driven largely by the ability and the
configuration the plant needs to go to to get to the recirculation mode.
But when I said that when we look at this issue from a risk
perspective, based on what we know today, okay, we look at those numbers
and say, "This issue needs additional attention."
All right. Now, we need to take into consideration what the
initiating event frequency is, and we don't have a good estimate of that now, and
that's why we want to go out and get more information.
But those were the numbers that if you look at the range from
the IPEs.
DR. WALLIS: So you would want to get the initiating event
frequency down to ten to the minus three as a result of better understanding
and regulation.
DR. FORD: Jack, thank you. We appreciate it.
I'd like to ask Larry Matthews from the Materials Reliability
Program at NEI to give a presentation.
Larry, do not feel confined by the quarter to four. I've been
told that I'm not supposed to tell you that.
(Laughter.)
DR. FORD: Go as long as you want, but recognize most of
the panel have already heard your presentation of yesterday, apart from Dana.
MR. MATTHEWS: Yes.
DR. FORD: Was I correct in saying that? No? Five minutes?
Four o'clock.
MR. MATTHEWS: Maybe I can get through in time for some
discussion.
DR. FORD: Good.
MR. MATTHEWS: I'll start with Slide 76 if you want to thumb
through there from yesterday's presentation. I didn't realize I needed to bring
a separate package today, so what we passed out yesterday.
Basically the industry feels there's reasonable assurance that
the PWRs don't have circumferential cracking that would exceed the structural
margins based on a few things. Oconee and ANO-1 says here in the highest
grouping these four units are the four highest units in America on time at
temperature.
These leaks that were found at these plants were discovered
by careful visual examination. We recognize, everybody recognizes we're
looking for something different than we probably were looking for a year ago.
Oconee-1, when they found out a very small amount of
leakage, everybody recognizes that that's what we have to be looking for now.
Volumetric exams that were done at Oconee-1 and 3 on a
scope expansion or whatever you want to call it, extent of condition examination
of the other nozzles that were not leaking, and only found minor craze cracking,
which they've been seeing in other nozzles and tracking for years.
These leaks were discovered in time with plenty of structural
margin remaining at the time they were discovered and repaired.
DR. POWERS: Could I ask you what the significance of that
second bullet is or maybe it's the third one? Volumetric examination, minor
craze cracks. Are you saying the volumetric examination is not a reliable --
MR. MATTHEWS: No, that's not what I'm saying. I'm saying
-- I'm not talking about the nozzles that were leaking. I'm talking about the
nozzles that were leaking. I'm talking about other nozzles.
The volumetric examination did not, and we have to admit this
right now, a priori pick up the circumferential flaws, et cetera, that were found
in Oconee. Going back and looking now at the data, you know, NDE's hindsight
is great, but now we have the lessons learned. They call it lesson learned.
Now those things are available to the people as we move into the future.
DR. POWERS: What you're saying is the volumetric
examination for those that crack, the volumetric examination detected nothing,
not even minor craze cracks?
MR. MATTHEWS: No, no, no, no, no. The volumetric exam
could pick up the cracking, and when they go back and look at it, they could find
all sorts of cracks in those nozzles that did crack. The one thing they missed
was the circumferential flaws.
Then when they go back and look at the data after they
discover those circumferential flaws in the process of repairing the nozzle and
look at the data, they say, "Oh, yeah, there was evidence."
And we're working with the industry right now and with the
NDE Center and with the vendors to refine those techniques so that we've got
a better shot at finding those kinds of things when we do volumetric.
DR. POWERS: Well, I guess I'd come back. What's the
significance of only minor craze cracks?
MR. MATTHEWS: Oconee units and several other units have
seen this kind of very, very shallow, multi-initiation sites, axial flaws on the ID
of the nozzle that don't grow, and they've tracked those for years at Oconee.
They call it craze cracking, and they haven't grown, and they've tracked those
for, I think, three examinations, three outages at Oconee, and just there they
are. They don't grow.
The significance is when they look at the other nine nozzles,
they found no significant flaws. That was the significance of that.
DR. POWERS: They looked at the nozzles the first time
around and they found no significant flaws either.
MR. MATTHEWS: Which ones?
DR. POWERS: The ones that were cracked.
MR. MATTHEWS: On Oconee-1 that's true, on Oconee-1.
They were looking -- on Oconee-1, the detection, I mean, the NDE was
different. They used eddy current. Eddy current would not see the OD flaw.
Now that's not what we're talking about on volumetric exams here.
DR. FORD: You're talking about ultrasonic?
MR. MATTHEWS: Ultrasonic and/or I heard someone today
talking about complete with the surface eddy current, which is where you come
down all the way back up the OD of the tube and the weld, do eddy current on
all of that.
And if you've got no initiation sites and no cracks there, you
don't have anything in the annulus, but, yeah, UT also for the volume of the
tube.
PARTICIPANT: You find a lot of stuff that isn't there.
MR. MATTHEWS: Okay. The other point, several other
plants this past spring after they knew about Oconee-1 and Oconee-3, several
other plants and some of those in the highest group went and did top of the
head, under the insulation visual inspections and found no evidence of leakage.
DR. POWERS: So license renewal is the key here. If you get
your license renewed, then you get cracks.
(Laughter.)
MR. MATTHEWS: I hope not. Hatch is up next, but Hatch
cracked a long time ago all over the place.
DR. POWERS: Short parameters come to mind here.
MR. MATTHEWS: I hope Calvert isn't in that list.
The schedule for some of this stuff, we weren't going to get
some revised inspection recommendations by the end of this month, but due to
the pending bulletin, we decided to hold off and see what we could work out.
We have convened an expert panel to look at the crack
growth issue both in annulus and normal, and their first meeting is next month.
DR. POWERS: Since the experts never anticipated this kind
of a cracking to occur, why are they experts?
MR. MATTHEWS: They're the guys from all over the world
who have been doing this lab work on crack growth data and --
DR. POWERS: But in 1997 we have everybody in an uproar
looking at this stuff, and they gave us a clean bill of health, I mean.
MR. MATTHEWS: Well, this is a new -- the OD initiated
clause is new.
We were planning numerous inspections during the fall 2001
outage. The final RPV penetration safety assessment was scheduled for the
end of this year, and reassessment of the inspection results that come out of the
fall outages, we were going to get that in time to give some help to the spring
outages.
We have other activities ongoing. We're working on the risk
assessments. That's going now. We're going to try and get something here
very shortly to work with the staff and make sure we're kind of in agreement on
what the risk of this event is.
We're initiating some probabilistic fraction mechanics as part
of our risk assessments.
NDE demonstration, that's ongoing now or not the actual
demonstrations, but discussions with the vendors about what kind of NDE
capabilities they have, what kind of sabers they can throw up, the
Westinghouse or any of them. That's under technique development.
We're designing a block with OD initiated flaws to get that
thing available so that these vendors -- and it won't be a PDI qualification. It will
be an open demonstration, but at least we can take a look at what the
capabilities are before we throw this under a head.
We're developing an information and training package for
those people who will be doing the visual examinations, will be using lessons
learned from the plants that have already done them, including Oconee and
some of the other plants that did them this spring.
They're working on flaw evaluation guidelines and review and
repair of mitigation strategies would be a longer term approach.
DR. POWERS: In the material that the staff has put together,
they make quite a point about training people to distinguish old boric acid
crystals from new boric acid crystals or something like that. What are you telling
people in this training package?
MR. MATTHEWS: We're going to show them what old looks
like. We're going to show them what new looks like.
DR. POWERS: I'm fascinated. They have different wave --
different vibrational frequencies, different -- I mean, what is different about an
old crystal and a new crystal?
PARTICIPANT: Color.
MR. MATTHEWS: This is what a leak looks like.
DR. POWERS: That's 100 percent of every leak that will
possibly occur, is going to look like that?
MR. MATTHEWS: Everyone we've seen has had something
that's similar. Here's the Oconee-1 one. This was one at Oconee-3. This was
another one at Oconee-3.
DR. POWERS: That tells me about Oconee.
MR. MATTHEWS: Yes. The only other one we've got is
ANO, and it looks pretty similar.
DR. WALLIS: So you look for white stuff appearing around
the --
MR. MATTHEWS: Yeah, white stuff right around, and every
one of them has had downhill -- on the downhill side, if there is a downhill side,
that's where the stuff has accumulated. Basically there's an annulus that's kind
of angled here, but it's flat on the bottom, and this is the low point, and so
anything that liquid got in there would run out down here.
DR. WALLIS: Well, liquid is available because the acid
changes the boiling point so much that you don't boil off all the water. It is a hot
surface.
MR. MATTHEWS: Yeah, it's hot.
DR. WALLIS: You expect the water to disappear.
MR. MATTHEWS: It could be leaking when it's cold, too.
DR. WALLIS: When it's cold it leaks?
MR. MATTHEWS: I don't know. I don't know where this stuff
is coming from.
(Laughter.)
MR. MATTHEWS: It's coming from down there, and it leaks
out.
MR. SIEBER: It's not leaking when it's cold because you can't
pressurize the vessel when it's cold because of brittle fracture.
MR. MATTHEWS: That's true.
DR. POWERS: It seems to me that I would be very
suspicious of using color as an indicator because that says something about
how dirty or not dirty the head was at the time the material came out.
DR. FORD: Radiochemistry -- when we asked this question
yesterday and had your E-mail, we asked this question. There was an answer
to do with radiochemistry. I don't know if they --
DR. POWERS: F centers? F centers and boric acid crystals
or something?
DR. FORD: All I'm doing is just repeating what the answer to
it was.
MR. MATTHEWS: Looking at the activation and the decay,
they can tell to some extent.
DR. FORD: Can tell the age of the --
MR. MATTHEWS: How old the boron deposits are, if they got
irradiated in the vessel, picked up neutrons. They can look at the ratios and
figure out is this new boron or old born.
DR. WALLIS: That means you actually grab the boron and
do tests of it?
MR. MATTHEWS: Yeah. You got up there, and you scrap
some off, and you take it to the county lab.
DR. WALLIS: That's very different from relying on visual
inspections.
MR. MATTHEWS: Yeah.
DR. POWERS: Well, I mean, it sounds like fairly fuzzy --
MR. MATTHEWS: But they didn't do that until they had the
leak and they were trying to figure it out how long it had been leaking.
DR. POWERS: I mean, quite frankly, it sounds preposterous.
The crystal forms only when the boric acid solution gets outside of the vessel,
right?
MR. MATTHEWS: Right.
DR. POWERS: Okay. Is it the irradiation there that does
something to --
MR. MATTHEWS: No, no, no, no, no. It was when it was
whipping through the core over and over.
DR. POWERS: When it was whipping through the core, it
was in solution.
MR. MATTHEWS: Yeah, and then it leaked out and formed
a crystal, but the boron didn't change a lot from the time it was inside the core
until the time it leaked out, but --
DR. POWERS: Yes, it did. It crystallized.
MR. MATTHEWS: Okay. We're looking for the --
DR. POWERS: -- absorbed the neutron or something like that
--
MR. MATTHEWS: It did.
DR. POWERS: -- and changed its --
MR. MATTHEWS: It did.
MR. SIEBER: There's plenty of neutrons on the outside of the
head, I think. So you look at the ratio between boron and whatever it turns into,
lithium, and from that ratio you can get some sort of an estimate sa to how
many neutrons this stuff absorbed.
DR. POWERS: Once it's outside and crystallized.
MR. SIEBER: Once it's outside, yeah.
DR. POWERS: Nothing to do with what it was inside.
MR. SIEBER: Well, the same process goes on, but there's
a different removal process.
DR. POWERS: How do you distinguish the lithium form by
transmutation from the lithium that was formed because they put lithium in the
solution?
MR. SIEBER: Well, at hot zero power, the boron
concentration is 1,800 ppm, and the lithium that's added provided that you have
a plant where you add it is at 2 ppm. So, you know, I would suspect that the
lithium --
DR. POWERS: That's good. Two ppm of lithium represents
how much neutron absorption? A bunch.
MR. SIEBER: Yeah. That's right.
DR. POWERS: Okay. All taking place on the outside of this
head.
MR. SIEBER: Some, and it's not a very good method.
MR. MATTHEWS: Sine we don't know much about the
driving forces here, like Jack said, he did a pretty good job of describing the
model. What we've done is an effective time and temperature model to rank the
plants, the point being not to try and predict that this plant is going to leak in 15
years, but to try and decide where we should concentrate our resources as an
industry to try and learn more about this issue.
And it's an effective time at temperature because these plants
don't all have the same head temperature, and it's very driven by the
temperature. So we normalized everything to 600 degrees and ranked them up
here. The three Oconee units are right at the top of the heap.
One of the things is will it leak. These are the interference fits
of all the leakers, and even nozzles that have interference fits as tight as 1.4
mLs here leaked when they developed the through wall cracks.
This is a cold, as manufactured. We have calculations which
I thought --
DR. WALLIS: You were telling us that they opened up when
they're actually --
MR. MATTHEWS: Yeah, they do tend to open up when you
pressurize the head because the dilation of the head, and I could put that up.
I think I'll skip it.
Several plants did inspections. These are the ones that did
inspections this spring. Robinson-2, Salem-1, Farley-2, Prairie Island-1. Prairie
Island has a configuration not exactly like, but similar to the --
DR. WALLIS: You're talking about this interference fit opening
up, and it opens up essentially an enormous area compared with the size of the
-- it's a huge flow area compared with the little crack area.
MR. MATTHEWS: The flow area.
DR. WALLIS: That's what we need to think about. The area
of the annulus interference is enormous compared with flow area.
MR. MATTHEWS: Well, the PWSCC cracked.
DR. POWERS: -- will crack, which is supplying it.
MR. MATTHEWS: Yeah. Most of these heads on these
plants which are all Westinghouse units except SONGS are reasonably free of
any kind of masking, boric acid deposits. These deposits have a tendency to
be much more evident on the B&W plants because of their flanged CRDM
configuration.
Basically the industry believes that most, if not every single
one of these, penetrations would leak if you -- and show boric acid. This is
something that the staff says we need to prove or at least those high
susceptibility plants need to prove it.
This is just another way of looking at the histogram. These
plants that come out here that show hundreds of years to being equivalent to
a CONY are actually co-head plants. Their heads are running in the 560 range.
Most of these heads are hot or warm head plants. "Warm" might not be a right
term, but it's pretty hot.
DR. POWERS: "Hot head" is probably not the right term
either.
MR. MATTHEWS: Yeah. Well, the Oconee head is pretty
hot, and all of the B&W units. These are the Oconee units. I believe this is the
A&O unit. These histograms were on preliminary information, but this is the first
ten years. This is where we proposed as an industry that all of these plants do
a visual of the top of their head at the next refueling outage.
And what we were showing here is that this plant here and
that one and that one would be the only three that would not have done a visual
inspection by the end of the spring outage season, and they would be into the
fall.
DR. WALLIS: The thing I've been dying to ask is when you've
done all this, is there some sort of idea of how you interpret the data when you
find something, or are you just going to figure that out when you find it?
MR. MATTHEWS: When we find a leak, you know, we start
over.
DR. WALLIS: Anyway, you start thinking again?
MR. MATTHEWS: Pardon me?
DR. WALLIS: You haven't thought about -- you're doing an
experiment here. So you want to think about how you interpret the data when
you get it.
MR. MATTHEWS: Yes.
DR. WALLIS: I haven't seen any of that. It's all just when we
get the data, then we'll think about what it might mean.
MR. MATTHEWS: Well, when we get the data and we find
a leak, we go find out what it is.
DR. WALLIS: It makes a big difference whether it's one on
the left of that curve or one on the right.
MR. MATTHEWS: Yes. If it's one over here, then that brings
--
MR. ROSEN: I didn't see your -- if it's one over?
MR. MATTHEWS: If it's one over here or out there
somewhere, then that's a totally different scenario than if this plant here or that
plant there finds a leak.
And recognize that all of these plants that do have leaks so
far are B&W design units. We don't know if that means anything or not, other
than the fact that they typically run with fairly high --
DR. WALLIS: It's a very interesting drama. When you find
the next leaker, everyone is going to scurry around saying, "What does he
mean? What does he mean? What do we do?"
MR. SIEBER: Well, if you found one that was half way --
MR. MATTHEWS: If we found one here.
MR. SIEBER: -- on the right-hand side of this particular curve,
it would destroy the theorem upon which susceptibility is based.
MR. MATTHEWS: Yeah, if one of those cold head plants
finds a leak and it is a PWSCC leak, et cetera, then you know we've got a lot of
rethinking to do and so does the standard and everybody else.
DR. POWERS: I mean before I would trash the whole theory,
I would say that right now they're operating on the basis of temperature and
time being their two dominate variables and residual stresses which they can't
really estimate as being something that's secondary in the effect. If you found
one off in the other group, you'd probably just find that that other variable was
very important.
MR. MATTHEWS: Yes.
DR. POWERS: And so it's not clear to me that everything is
lost.
MR. MATTHEWS: Stress is a very important factor in
PWSCC also, and you can override a lot of stuff if you put enough stress on it,
but you can't get much beyond yield.
MR. SIEBER: I think the problem is there aren't enough
records, for example, what heat, what solvents, what the fit was, the welding
technique. You can probably find in your lay records welding rod records. You
might have copper intrusion or some other phenomenon.
MR. MATTHEWS: I guess the thing I really wanted to say --
oh, somebody had mentioned about will it leak before or the rates between leak
and a circ crack, and basically we've had 15 nozzles in the U.S. to leak so far,
and three of those have had circ cracks, and 12 of them have had only axial or
through wall cracks in the axial direction and no circ cracks. And one of the circ
cracks was a very shallow on the OD of the tube that had not propagated
anywhere near through wall. It was only an inch or so long.
So the horse race seems to be won by the leakage over the
circumferential crack growth at this point in time based on those 15 leakers that
we've had to date.
MR. SIEBER: Yeah, but you can't detect that leakage until
you do the visual inspection.
MR. MATTHEWS: Exactly, and if it's all going to happen
within two months, you know, we're --
MR. SIEBER: You can't pick it up while the plant's operating.
MR. MATTHEWS: Right.
MR. SIEBER: Leakage instruments just aren't sensitive
enough.
MR. MATTHEWS: I guess the reason I was putting this up
was because I wanted to just address the fact that these are analyzed events.
The rod ejection accident is an analyzed event, but it was selected as the
bounding reactivity insertion event that's possible, and you blow the rod out in
100 milliseconds. The transient is over before the rod gets out of the core. It's
already turned around, and the reactor is subcritical again before the rod is
completely withdrawn in the ejection event.
Another ejection, very unlikely in our opinion. These are very
heavy tubes. This is a very tolerant material. We haven't done the calculations
yet. We're going to have to. It's a four inch diameter tube with a five-eighths
inch wall. It's going to take something else to knock that thing off of there. It's
going to take a lot of force and --
PARTICIPANT: Well, we have to go figure all of that. We
don't know what it is yet.
DR. POWERS: If it's intact.
MR. MATTHEWS: If you've got a bunch of them sitting there
that are already cracked all the way to where they're just barely staying in there,
yeah, we don't think that's very likely either.
DR. POWERS: Well, I mean, you had how many of them
cracked in your 20 plants?
MR. MATTHEWS: We had only two on Oconee-3 that had
circumferential flaws. We had one that was a partial through wall on Oconee-2.
Those are the only three circ flaws that have been discovered. That's the only
thing that threatens an ejection. Axial flaws will not threaten an ejection.
DR. POWERS: So if I -- what you're saying is at Oconee we
could have had two ejections.
MR. MATTHEWS: No. If we'd have buried our head in the
sand for a long time, there was plenty of structural margin there, plenty of
structural margin there, a factor of six to ejection, I think.
DR. POWERS: Yeah, and two much how much of a factor?
MR. MATTHEWS: Well, we think, you know, if you assume
reasonable crack growth rates, I believe they had years, but if you assume that
the crack growth rates just from Alloy 600, the crack growth rates that we've
been using in other arenas, it was four to five years before they had got to the
ASME code margin, which has a factor of three in it, and it was more years than
that before they would have ejected the rod.
DR. POWERS: Yeah, but we have just given it a 20 year
extension of license. We've got lots of time here.
MR. MATTHEWS: Well, the Oconee units have committed
to replace their heads. I'm not saying the rest of the industry is going to do that
by any stretch, but --
DR. FORD: Larry, could you put Slide 18 up?
MR. MATTHEWS: Eighteen? I'm not sure we have 18.
DR. ELTAWILA: Then can I try to answer the issue of
multiple ejection?
This is Farouk Eltawila.
Really all what you need is a period the distance between the
multiple ejection greater than the .5 millisecond. So because they are not
relative, you know, by the time the first policy goes and you decay immediately
in about .5 second, even if the second policy started, they are not going to add
together, and it could be a different deposition.
So you really -- it's not the summation of the individual
policies. It would be -- so all what you need is .5 seconds between policies, and
you can accommodate that.
DR. POWERS: So anything over a half a second --
DR. ELTAWILA: If they are delayed by over half a second,
I really think the first pulse will completely disappear before the second one
takes effect.
DR. POWERS: So it's not coherent in that. Now let me ask
the next question. How many do I have to eject before I have a recriticality
issue?
DR. ELTAWILA: We need to do this analysis. There is no
doubt. I just tried to answer, you know, that even if you have them more than
one, you know, that -- that's to say they are not having in a sense continuously
at the same time.
DR. POWERS: One of the things you worry about is suppose
you eject one. Now you've got coolant blowing out of here, and you propagate.
You cause a crack in the next one, and that one becomes coherent with the
three next to it, for instance, in this map that I'm looking at here. They have a
problem there.
I mean it's a little tricky thing, but what you're saying is the
time constant you're looking for is a half a second less.
DR. ELTAWILA: A half a second.
DR. POWERS: And that's good information. The criticality
would be a good information, too.
MR. MATTHEWS: Well, if you get into multiple ejections,
you're going to have SI going. You're putting high concentration boric acid in
there. So, you know, that's going to help to keep the thing shut down.
All of the cores are designed with between one and two
percent shutdown margin with the strongest rod shut out. I mean out, and that's
at the cold condition. So, you know, if you took the thing from hot to cold and
left the strongest rod out because you blew it out, you've still got one to two
percent shutdown by the time --
DR. POWERS: And I wonder if the safety injection would
have time to have any influence in your time schedules that we're looking at
here.
MR. MATTHEWS: I Understand.
DR. FORD: Well, your risk assessment would be taking into
account, for instance, the groupings of those, all those circle point and housings
there presumably had circumferential cracks. They had boron deposits.
MR. MATTHEWS: Oh, absolutely not. The only ones that
had circ cracks, there were only two.
DR. FORD: Oh, okay.
MR. MATTHEWS: It was 56 and 50. These are the only two
that had circ cracks anywhere, and this is an agglomeration of Oconee-1 and
3. So --
MR. ROSEN: Show me again which ones.
MR. MATTHEWS: Fifty-six and 50. Those are peripheral
penetrations, and those are the only two on Oconee-3 that had circ flaws. I'm
not sure which one -- I don't have Oconee-2. Yeah, the four leakers on
Oconee-2 I don't think I have on here. So I'm not sure which one is leaking.
DR. UHRIG: The fact that that is circumferential is not there
related to the steeper slope?
MR. MATTHEWS: I don't know. You know, that's something
we'll have to figure out. We used to think these are the only ones that are
really, really susceptible before of the stress, the residual stresses, but maybe
it means that because of the residual stresses, they crack first and they've had
longer to grow a circ crack.
DR. FORD: Any last minute questions for Larry?
DR. POWERS: Well, I guess one. The bulletin proposes
some fairly prompt inspections and whatnot, and certainly you have outlined
both in your oral presentation and in looking through your slide package quite
a lot of activities going on. I wonder if you could speak to the issue of how
much better of a job you could do if you had a little relaxation, especially for
those units that are not in your very highest susceptibility category.
MR. MATTHEWS: Well, the ones that aren't in the highest
susceptibility category, what the staff is proposing is the VT-2, qualified VT-2.
That's not a cheap exam. In some plants it could be a million and a half dollars
depending on their inspection -- I mean they insulation packages.
But the improvement on the VT exams is probably not going
to grow tremendously. The volumetric exams, I think we're on the leading edge,
and we are scrambling to develop technology, and the vendors are working to
try and get it in the field and get it demonstrated for those plants that may wind
up doing volumetric in the fall, and that's a scramble. It's a real scramble, and
the demonstration that we're going to pull off, we hope, before the fall for those
vendors is not -- it's not a qualification like we did in the 97-01 response. It's an
open test. Here's the sample; here's what's there. Can you find it?
DR. POWERS: I understand what you're going to do. I'm
trying to understand how much better could you do if you had a little more time.
MR. MATTHEWS: Well, I think we could do better. How
much better I'm not sure. They could refine what ducers to use, what angles to
use. They could be refining, and maybe the eddy current technology, and
especially the delivery technology might be improved significantly over the next
few months as we move toward trying to make this a cheaper, better, faster
exam.
DR. UHRIG: But you would lose the opportunity for those
plants to refuel in the fall if you delayed it.
MR. MATTHEWS: If we delayed the volumetric, yes. But I'm
not sure how many of them are going to do volumetric, and you know, it's been
proposed by the staff for the ones that are leakers or have leakers, those four
units, only one of which is coming down this fall. I suspect the other three are
going to try and put together some alternative, and I'm not sure. You know,
they're going to be working with the staff to figure out what that is.
DR. FORD: Thanks so much, indeed.
MR. MATTHEWS: Thank you very much.
DR. FORD: Sorry we pushed you at the end there.
MR. MATTHEWS: It's okay.
DR. BONACA: Okay. Thank you very much, and we'll take
a break now for half an hour, and I guess we'll get together again at 25 of five.
(Whereupon at, at 4:04 p.m., the Advisory Committee meeting
was adjourned.)
Page Last Reviewed/Updated Monday, August 15, 2016
Page Last Reviewed/Updated Monday, August 15, 2016