479th ACRS Meeting - February 1, 2001


                Official Transcript of Proceedings


Title:                    Advisory Committee on Reactor Safeguards
                               479th Meeting

Docket Number:  (not applicable)

Location:                 Rockville, Maryland

Date:                     Thursday, February 1, 2001

Work Order No.: NRC-005                               Pages 1-240

                   NEAL R. GROSS AND CO., INC.
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                                 + + + + +
                               479TH MEETING
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                             FEBRUARY 1, 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, at 8:30 a.m., Dr. George
           Apostolakis, Chairman, presiding.
                       GEORGE APOSTOLAKIS, Chairman
                       MARIO V. BONACA, Vice Chairman
                       DR. THOMAS S. KRESS, Member
                       GRAHAM S. LEITCH, Member
                       DR. DANA A. POWERS, Member
                       DR. ROBERT L. SEARLE, Member
                       DR. WILLIAM J. SHACK, Member
                       JOHN D. SIEBER, Member
                       ROBERT E. UHRIG, Member
                       GRAHAM B. WALLIS, Member
                       JOHN T. LARKINS, Executive Director
           ALSO PRESENT:
                       RALPH CARUSO
                       F. CHERRY
                       N. CHOKSHI
                       F. ELTAWILA
                       JOHN FLACH
                       WILLIAM JONES
                       MARK KIRK
                       RALPH LANDRY
                       SHAH MALIK
                       JOCELYN MITCHELL
                       GARETH PARY
                       NATHAN SIU
                       MOHAMMED SHUCIRI
                       ERIC THORNSBURY
                       EDWARD THRON
                       JARED WERMIEL
                       HUGH WOODS.                                A-G-E-N-D-A
                      AGENDA ITEM                          PAGE
           Opening Remarks by Chairman Apostolakis. . . . . . 4
           NRC-RES Presentation: Status of PTS Rule . . . . . 8
                 Screening Criterion Re-Evaluation
           Siemens S-RELAP5 Appendix K Small. . . . . . . . .91
                 Break LOCA Code
           Proposed ANS Standard on Internal Events PRA . . 142
           Reprioritization of Generic Safety
                 Issue 152. . . . . . . . . . . . . . . . . 222
           .                           P-R-O-C-E-E-D-I-N-G-S
                                                    (8:30 a.m.)
                       CHAIRMAN APOSTOLAKIS:  The meeting will
           now come to order.  This is the first day of the 479th
           meeting of the Advisory Committee on Reactor
           Safeguards.  At today's meeting the committee will
           consider the following.
                       Treatment of uncertainties in the elements
           of the PTS technical basis reevaluation project;
           Siemens S-RELAP5, Appendix K Small Break LOCA code;
           proposed ANS standard on external events PRA;
           repriortization, proposed resolution of genetic safety
           issue 152; design basis for valves that might be
           subjected to significant blowdown loads; and proposed
           ACRS reports.
                       The portion of the session associated with
           the Siemens code may be closed to discuss Siemens'
           Power Corporation's proprietary information.  This
           meeting is being conducted in accordance with the
           provisions of the Federal Advisory Committee Act.
                       Dr. John P. Larkins is the designated
           Federal Official for the initial portion of the
                       We have received no written comments or
           requests for time to make oral statements from members
           of the public regarding today's sessions.  A
           transcript of portions of the meeting is being kept,
           and it is requested that the speakers use one of the
           microphones, identify themselves, and speak with
           sufficient clarity and volume so that it can be
           readily heard.
                       While this is my first day as the
           Committee's Chairman, and I think the first thing we
           should do is thank Dr. Powers, who is just joining
           us --
                       CHAIRMAN APOSTOLAKIS:  -- for the superb
           job that he did the last two years leading this
           committee.  Thank you very much, Dana.
                       CHAIRMAN APOSTOLAKIS:  I would also like
           to thank my colleagues for electing me chairman of
           this committee.  I have been a member for about 5-1/2 
           years now, and I have served under three chairmen --
           Professor Searle, Dr. Kress, and Dr. Powers.
                       And although their managerial styles were
           somewhat different, they all had one common objective,
           namely to make sure that this committee provided sound
           technical advice to the commission in a timely manner,
           and I can only promise to try to do the same.
                       Sadly, today, and this week, happens to be
           the last meeting of Professor Searle.  He is
           completing his second term on the committee.  Bob, I'm
           sure I am speaking on behalf of all of the members for
           the committee when I say that we will really miss you
           and your wise advice.
                       And finally also during the 5-1/2 years
           that I have been a member, I must say that I have been
           very impressed by the professionalism of the ACRS
           staff under the able leadership of Dr. Larkins.  I
           believe it should be on the record that this committee
           could not function without the support that we are
           getting from the ACRS staff.
                       DR. SEARLE:  I may have some remarks to
           make, but I imagine that there will be a more
           appropriate time a little later to do that.
                       CHAIRMAN APOSTOLAKIS:  Whenever you want,
           Bob.  Are there any comments or statements that other
           members would like to make?
                       DR. SEARLE:  I would like to make a brief
           statement.  For the benefit of the members of the
           commission staff that are so intimately involved with
           the ACRS, but whom we have interacted with from time
           to time, I would like to express my own personal
           appreciation and admiration for the way in which
           pretty much across the board they have conducted
           themselves and interacted with the committee.
                       I have always received the utmost
           cooperation when I was in a position where I had to
           work with them, and I guess the thing is that I
           believe we have a climate of mutual respect, and so
           that does the process well.
                       We talk about issues and we don't talk
           about personalities, and I am so very pleased to have
           had the opportunity to work with all of them.  And
           since some of them are here, in here anyway right now,
           I just would like to say thank you very much.
                       CHAIRMAN APOSTOLAKIS:  Very good.  Thank
           you, Bob.
                       DR. KRESS:  I think it is a shame that Bob
           is leaving, just when I am hearing how to speak Texan.
                       DR. POWERS:  And need to learn how to
           speak Texas.
                       DR. SEARLE:  Well, I am still working on
                       CHAIRMAN APOSTOLAKIS:  Our first topic
           today is treatment of uncertainties in the elements of
           the PTS technical basis reevaluation project.  Dr.
           Shack, I believe you will lead us through this.
                       DR. SHACK:  Okay.  We had a subcommittee
           meeting on January 18th, where we had a fairly
           detailed discussion of the treatment of uncertainties
           in the PTS project, and as Tom Kress has pointed out
           before, not only is PTS important in its own right,
           but this we think is sort of a prototype example of
           the kind of detailed treatment of uncertainties one
           may need in other situations.
                       What is unique about this is the attempt
           to integrate the treatment of uncertainties in all
           aspects of the problem in the framework that
           uncertainties have been treated typically in PRAs.
           And I think we saw substantial progress at the
           subcommittee meeting in the treatment of how they were
           handling the aleatory and epistemic uncertainties in
           the fracture toughness.
                       We saw some work towards the treatment of
           uncertainties in the thermal  hydraulics, and I
           believe we are going to get an overview of the
           approach to the treatment of uncertainties from
           pressurized thermal shock in the presentation before
           the full committee today.
                       But again this is a work in progress.  We
           are not really expecting to write a letter at the
           moment.  This is a chance to sort of see how they are
           working their way through it, because they are
           breaking new ground here and it is not a conventional
           treatment of uncertainties that we are looking at.
           With that, I will turn it over to Mike Mayfield, I
           guess, to start, and Nathan Siu.
                       MR. MAYFIELD:  Good morning.  We
           appreciate the opportunity to come to the main
           committee again, or the full committee, and talk about
           the progress that we are making on this project.
                       As Dr. Shack pointed out, this is -- we
           are starting to move back some of the frontiers, at
           least in our traditional treatment of probablistic
           fracture mechanics as it relates to the structural
           integrity of major components.
                       I just wanted to set the stage a little
           bit, and then turn it over to Nathan Siu to work
           through the rest of the presentation.  We just wanted
           to remind you first of all that the objective of the
           program is to develop a technical basis for the
           potential revision to the PTS rule.
                       We are not telling you or the public that
           we necessarily will revise the PTS rule.  Our activity
           at this point is to look at the technical basis to see
           if there is a justification for revising the rule, and
           what that might look like, and then to make
           recommendations to the Office of Nuclear Reactor
           Regulation, since the rule making function is their
                       DR. POWERS:  Could you remind me what
           prompted you to undertake this daunting task?
                       DR. SHACK:  Sure.  We have seen some
           improvements -- well, the PTS rule itself is based on
           technologies from the late '70s and early '80s.  We
           have made some major improvements in a number of
                       For instance, in my business in
           particularly, the probablistic fracture mechanics
           area, our understanding of embrittlement and fracture
           toughness, and the flaw distributions that were a
           major source, and in fact the major source of
           uncertainty in the original analyses.
                       So we felt like based on some very limited
           scoping analyses, we felt like there was a strong
           basis to undertake a more rigorous treatment or
           reevaluation of PTS.
                       The notion at that point was that -- and
           I think going back to the Yankee Row evaluation, that
           there was significant conservatism embedded in the PTS
           rule, and the analyses that are in Reg Guide 1.154.
                       So we thought that the technology had
           improved to the point or matured to the point that we
           should take that up and revisit those technical
                       This is the first major application of
           risk informed methodology to what has been
           characterized as an adequate protection rule, and
           while I don't want to get into a debate on what we
           mean by adequate protection, the rule has been
           characterized as such, and it has to do with
           backfitting -- the regulatory piece of it has to do
           with backfitting requirements.
                       It was originally promulgated as an
           adequate protection rule when we revised it in the
           mid-1980s and early '90s, and it was again treated as
           an adequate protection rule.
                       But the fact that we are now taking a look
           at it in a risk informed approach is causing us to
           examine what we really mean and how we go about
           dealing with that.
                       So that will create for us some additional
           dialogue with the committee, I expect, as we go along. 
           We are evaluating four plants in an effort to develop
           a generic approach that will cover the fleet of PWRs.
                       We recognize going in that evaluating only
           four plants and trying to use that as a surrogate for
           some 80ish PWRs brings with it certain stretches of
           faith, and that is something that we are taking on as
           a specific activity somewhat later in the program.
                       But it is an uncertainty in what we are
           doing.  The four plants we are looking at are  Oconee,
           which is a BMW design, Calvert Cliffs, and Palisades
           are CE designs, and Beaver Valley, Unit 1, is a
           Westinghouse design.
                       We do not intend to do plant specific
           evaluations for the entire PWR fleet.  That is well
           beyond our resource capability, and it is not
           something that is credible for us to undertake.
                       We do feel that by looking at this small
           sample that we can at least improve on the basis for
           the rule that is out there today, which is based
           totally on stylized transients, and no plant specific
                       We are looking to use the best available
           tools for the analysis, the tools that exist today. 
           We are making some advances in some of the tools, but
           we are not looking to make major improvements in some
           of the underlying technologies.
                       And that we felt like the improvements
           that have been made since the time the PTS rule was
           originally promulgated that improvements in the
           technologies up to this point provide a sufficient
           justification, and it is not a practical thing for us
           to undertake major revisions to thermal hydraulics
           neutron transport calculations, and that sort of
                       So we are using the state of the
           technology by and large as it exists today.  As Dr.
           Shack pointed out, this is one of the continuing
           series of briefings that we feel have been very useful
           in bringing the committee and keeping the committee up
           to date on what we are doing.
                       And we are soliciting your feedback as we
           go along.  We didn't want to get into this project,
           which is a major resource investment for us, and spend
           a couple of years working on it, and get to the end
           only to have the committee say, well, you have missed
           these key issues.
                       So we wanted to try and solicit your input
           along the way, not so much in an effort to get your
           preendorsement of the program, but to help solicit
           your input, and if you identify something that we are
           missing, then we can get that fixed as we go along, so
           that at the end of the day we have a complete package
           that the committee can review.
                       DR. SHACK:  Just to come back to Dana's
           question a little bit.  If you were convinced that the
           analysis was conservative, what would be the impetus
           for revising the rule?  Only Palisades is going to hit
           the screen criteria, at least under current
           projections, right, for 40 years?
                       MR. MAYFIELD:  Well, that's true.  For
           Palisades, it was a bit over 40, and there are a small
           number of plants that would be approaching the
           screening criterion out to 60.  There is, however, a
           fair bit of uncertainty within the licensees, or at
           least it has been expressed to us, about what else
           would the staff do with new embrittlement
                       As the committee probably knows, very
           small changes in chemical composition for the wells,
           and our understanding of the chemical composition for
           the wells can make very large changes in the estimates
           of embrittlement of the vessel.
                       So that is something that the -- I think
           the licensees would like to see a little more
           stability in what we are doing, and to remove the
           unnecessary conservatism.
                       So we originally took this on with the
           notion that there was a fair bit of unnecessary
           conservatism embedded in the rule, and to try and
           bring it back, and base it on credible technology, as
           opposed to conservative estimates made out of
           ignorance.  So that was motivating it initially, okay?
                       DR. SHACK:  Okay.
                       DR. SEARLE:  Mike, you made the comment
           earlier that this is based on existing technology.
                       MR. MAYFIELD:  Yes.
                       DR. SEARLE:  At the same time, I think it
           is worthwhile to recall that there were places where
           specifically focused activities took place and
           addressed what were at the time to be considered to be
           concerns. Namely, as I understand it, the ENDF(b)(6).
                       MR. MAYFIELD:  Yes, sir.
                       DR. SEARLE:  And the cross-section
           rendering grew out of a concern for the way in which
           iron was -- and some other things in that
           neighborhood, were being treated in the attenuation
                       MR. MAYFIELD:  That's correct.
                       DR. SEARLE:  So there have been some
           rather focused efforts in various areas to address and
           identify issues of that sort?
                       MR. MAYFIELD:  That's exactly right.  The 
           cross-section libraries was one effort.  We have
           published --  and in fact the committee reviewed in
           December a regulatory guide on neutron transport
           calculations and improvements in the way that we go at
           that, and the way that uncertainties are handled in
           those calculations.
                       We have made improvements in the way we do
           the fracture mechanics analyses, and some of the
           underlying models there.  We have got a much better
           handle on embriddlement trends today, and the flaw
           distribution work.
                       So there have been over the last 10 years
           a number of major undertakings to improvement the
           state of the technology.
                       DR. SEARLE:  If there are -- I have become
           aware of a problem.  Some people who are involved with
           the ASTM code group, apparently had questions
           concerning the attenuation calculation and submitted
           a large number of questions, which were apparently not
           addressed, at least not to their satisfaction, in the
           draft or in what is -- well, 1065, or whatever that
           number is.
                       Anyway, the Red Guide that was published
           just recently, and I believe that George received a
           communication on this concern, and I thought it had
           been passed along to other people in the commission.
                       MR. MAYFIELD:  I'm sorry, but you are
           catching me cold today here.
                       CHAIRMAN APOSTOLAKIS:  I'm not sure I
                       DR. SEARLE:  The thing that we talked
           about here last week.  I'm sorry, but --
                       MR. MAYFIELD:  Historically, there has
           been some disagreement over how attenuation is
           handled, and it is an issue that we agree that the
           technical basis needs to be revisited.
                       I think it would be fair to say that the
           basis for arguing for a change is not a lot stronger
           than the basis arguing against the change.
                       DR. SEARLE:  I'm sorry for blindsiding
                       MR. MAYFIELD:  Well, I will be happy to
           talk to you about it, and see where we can go.  The
           key issue that we are here to talk about today, and
           that we met with the subcommittee on a couple of weeks
           ago, is the treatment of uncertainties and treatment
           of uncertainties in the major areas of the analysis.
                       We are also going to, in addition to
           giving you an overview, we are going to try and deal
           with some of the questions and comments that were
           raised during the January 18th meeting.
                       And with that, Mr. Chairman, I would like
           to turn it over to Nathan Siu to do the bulk of the
                       MR. SIU:  Good morning.  I will first give
           you an outline of what I am going to talk about.  You
           have quite a few slides in your packet, and a number
           of those are backup slides.  So don't worry about the
           length of it.  We can obviously tailor the
           presentation to the time that we have got.
                       But what I would like to talk about first
           of all are the objectives and the conceptual approach
           regarding the treatment of uncertainties.  Sometimes
           we are going to get a little -- well, not muddled, but
           we can't avoid the general issue of how is the
           integrated analysis proceeding, because the
           uncertainty analysis is an integral part of the
           overall analysis.
                       And there will be times when we are
           talking about in general how is the overall
           computation and how we will proceed.  But I would
           really like to emphasize the treatment of uncertainty
           is within that computational flow.
                       I will give you an overview of how we are
           proceeding with the analysis, and we will try and
           provide some of the details that were or the
           information that was perhaps lacking in the
           subcommittee presentation, where we provided a high
           level framework, and then some of the bits and pieces,
           and didn't talk to well to how those two link
                       We will talk about the status of the major
           discipline activities in PRA from a hydraulics and
           probablistic fashion mechanics, and time permitting,
           we will get into each of these areas in a little bit
           more detail.
                       And in particular we have developed some
           draft results from the Oconee study.  We have talked
           these results with Duke Energy a week or so ago and
           received comments on that.
                       These are highly draft results, but we
           wanted to give you a sense of how things are
           proceeding.  In the case of the TH analysis, again,
           obviously we have TH results.  Runs have been
           performed, and we have time temperature traces,
           pressure time traces.
                       The approach refers again to the treatment
           of uncertainties, and how we are going to deal with
           uncertainties in those computations, and similarly we
           are going to talk about the approach we are using for 
           fracture mechanics.
                       And some of these things we are getting
           draft results, but that we are not ready to present at
           this point in time.  At the end, I will then have a
           discussion of key issues and summarize where I think
           we are.
                       Okay.  Again, this part of the analysis,
           we are assessing uncertainties in the estimates of PTS
           risks.  That means that we are going to quantify the
           uncertainties, and also of course try to identify the
           driving sources of those uncertainties.
                       And the reason that we are doing this is
           to support the technical basis for a potential rule
           change.  So, for example, we would be looking at
           potentially new screening criteria, and potentially 
           new guidance for how you do a plant specific analysis
           if the screen criteria are not met.
                       This just illustrates a conceptual diagram
           of how the screen criterium might be developed, and
           shows the roles of uncertainties here, where this is
           the RT-PTS, and the RT and DT of the license, and this
           is the through wall crack frequency.
                       You might have estimates of the through
           wall crack frequency for a given plant, and the
           uncertainty bins about that estimate, and somehow we
           need to develop a line that relates the two, and
           develop a screening value for RT-PTS based on some
           notion of what is an acceptable through wall crack
                       That is conceptually how we might approach
           it.  Again, please don't read too much into that
           diagram, because we have not put a lot of work into
           figuring out we are really going to proceed.  But this
           shows how the uncertainties will play into that kind
           of process.
                       DR. POWERS:  Could you explain to me
           better what the significance of the lines on either
           side of the square are?
                       MR. SIU:  The dashed lines?
                       DR. POWERS:  No, the --
                       MR. SIU:  Oh, this would be the through
           wall crack frequency, or let's say the mean estimate,
           and then maybe you would have a 95th percentile, and
           a 5th percentile.  So it indicates the range.
                       DR. POWERS:  How do you decide to use 95
           rather than 99, or 80, or 2, or --
                       MR. SIU:  Well, that's part of my problem. 
           We have not really gone through the work of figuring
           out exactly how we are going to use these estimates.
                       DR. POWERS:  How do people in other
           contexts decide what to use?
                       MR. SIU:  In other contexts?
                       DR. POWERS:  Yes.  I mean, you haven't
           done it here, but do we know -- I mean, some people
           put like standard errors are the length of those bars,
           and they calculate a variance, and they put the square
           root of the variance on either side for a bunch of
                       It escapes me exactly what the probability
           is on that, but maybe it is like 82 percent or
           something like that, and other people would use 95. 
           I mean, how do you decide?  Is that a subjective
           decision entirely, or --
                       MR. SIU:  I imagine that it would be
           because one of the things that we will get to is that
           these error bars are going to include the computed
                       There will be uncertainties that we don't
           think that we can calculate very well given the
           current state of technology, and in particular model
           uncertainties associated with some of the codes that
           we are using.
                       So I think what you are going to get
           realistically is an estimate of the computed
           uncertainty, plus a description of uncertainties
           associated with other issues -- maybe sensitivity
           calculations, but some indication of what the full
           range of uncertainty might be.
                       So to -- I don't see necessarily -- and
           again we have not worked this out, but I don't see
           just coming up with a simple rule that says pick a 99
           and you are done.
                       DR. POWERS:  But I think you have really
           answered my question.
                       CHAIRMAN APOSTOLAKIS:  Have we used
           percentiles in any other situation?  My impression is
           that we are using mean wise -- is that true -- when we
           allocate or when we decide that the contribution from
           this particular accident is such and such, why --
                       MR. SIU:  Excuse me, George, but this is
           a screening criterion.  This is the first step.
                       CHAIRMAN APOSTOLAKIS:  So it is as
           screening guide then?
                       MR. SIU:  Yes.  They are trying to just
           say that if you meet a certain embrittlement level --
           and that is the current rule right now, but if you
           meet a certain level, and if you don't come up to that
           level of embrittlement, you don't have to do anything
                       CHAIRMAN APOSTOLAKIS:  I see.  Okay.
                       MR. LEITCH:  The three data points there
           represent three different vessels, or is that at a
           different time and --
                       MR. SIU:  Yes, as the embrittlement
           increases, RT-PTS would increase.  Again, how we are
           going to match up with the four plants, which can have
           very different results, and how we are going to
           generalize to the larger population, these are big
                       The analysis -- to do the uncertainty
           analysis now, we have to categorize the sources of
           uncertainty, because that is built into notions of
           which kind of matrix we will be using.
                       We have to construct an aleatory model,
           and I believe we briefed the committee about the basic
           notion of aleatory and epistemic uncertainties in the
           PTS analysis.
                       And we then have to propagate epistemic
           uncertainties through the aleatory model, and I will
           try to walk you through that in a fairly high level
                       Conceptually, how we might approach this
           is that we would develop event sequences, using a PRA
           event sequence model to identify what are the
           potential challenges to the vessel, or scenarios that
           could challenge the vessel.
                       And measure certain frequency, and let's
           call that lambda, and there is uncertainty about that
           frequency.  That is the epistemic uncertainty about
           the perimeter lambda, and lambda is the measure of the
           aleatory uncertainty.
                       That result -- and again this is
           conceptually.  We get fed into a thermal hydraulics
           analysis, where for each PRA scenario we identify a
           number of thermal hydraulic subscenarios, a different
           variance on that PRA scenario; and perhaps differences
           in timing of actions.
                       We would have to develop distributions for
           the probabilities of each of these variance, as well
           as distributions about the thermal hydraulic
           characteristic variances that we care about.  For
           example, the pressure and temperature over time, the
           temperature in the down comer.
                       Using that information, we would feed into
           a stress strength analysis, where you look at the
           stress on the vessel, which is a function of these
           perimeters, the temperature and the pressure. 
           Therefore, that of course would be uncertain as well.
                       And you compare that against the strength,
           which has its own uncertainties, and develop a
           distribution for the conditional probability of vessel
           failure given this scenario, and subscenario, and
           integrate the results together, and get a through wall
           crack frequency with probability distribution.
                       And without getting into the details too
           much, there is something obvious here.  This could be
           a common for an explosion here as you develop more
           thermal hydraulic subscenarios to append on to the PR
                       And that would require a lot of thermal 
           hydraulic analyses, and then you would have to feed
           those into the stress strength analysis, which also
           has its own variance.
                       We are not doing it that way for obvious
           reasons.  It's just that we can't do the computations
           to this level.  So let me talk a bit about some of the
           simplifications we are employing.
                       CHAIRMAN APOSTOLAKIS:  How much of this
           was done in the original analysis?
                       MR. SIU:  Not formally.  My understanding
           is that there were sensitivity analyses, but there
           were no -- for example, even PRA uncertainties in the
           event sequence frequencies were not computed.  This
           was back in the early '80s.
                       MR. MAYFIELD:  The original rule had none
           of the things that Nathan just talked about.  They
           took some stylized transients and did what amounted to
           deterministic calculations.
                       Then there were some on the side
           probablistic fracture mechanics calculations done,
           where they tried to include some of the Monte Carlo
           scheme, including variations or distributions on
           flaws, on chemical compositions, some of the more
           obvious variables to include.
                       But it was nothing as elegant as what is
           being talked about here.  There were subsequent
           analyses, called the integrated pressurized thermal
           shock analyses that Oak Ridge performed, and looked at
           three plants.
                       And those analyses looked more like what
           we are doing today.  But the treatment of
           uncertainties was not as rigorous as what we are
           trying to do today.
                       MR. SIU:  And that is an important point. 
           Again, just because there were resource constraints,
           the time that it actually takes to run a thermal
           hydraulic calculation, maybe on the scale of hours,
           but also the pre-and-post processing requirements --
           you get a result and you have to look at it and make
           sure it makes sense before you go forward with it.
                       DR. POWERS:  Why is RELAP5 and not the
           consolidated NRC, the hydraulic code, being used for
           these analyses?
                       MR. ELTAWILA:  This is Farouk Eltawila
           from research.  We actually are doing the analysis
           using both codes, but we have not finished the
           consolidation completely right now.
                       So once we complete the consolidation --
           so we are doing it, but we are relying on the lab
           because it has gone through a lot of assessments, and
           the consolidated code has not gone through this
           rigorous assessment at this time.
                       So eventually once we finish all the
           calculations, we are going to run with the final
           version of the consolidated codes.
                       DR. POWERS:  So at some point in time, we
           will get a comparison between the two?
                       MR. ELTAWILA:  Absolutely.
                       DR. POWERS:  It may not be part of the GS
           effort, but at some time we will get to see how well
           the --
                       MR. ELTAWILA:  Well, actually the analysis
           is done also at this time with the consolidated code,
           but we are focusing for the purpose of the rule making
           change, we are going to rely on the RELAP5
                       DR. POWERS:  I mean, that's fine, but we
           will get to see it sometime?
                       MR. ELTAWILA:  Yes.
                       DR. POWERS:  That's good.  That's good.
                       MR. SIU:  Correct me if I am wrong,
           Farouk, but even with the consolidated code, I imagine
           I can get significant resource requirements for a
           particular run?
                       MR. ELTAWILA:  There is no doubt about it.
                       MR. SIU:  So for that reason, we need to
           obviously use the standard strategy of being similar
           sequences to represent the results of the PRA analysis
           with a very limited set, a relatively limited set of
           thermal hydraulic times.
                       DR. POWERS:  Can you tell me how you
           decide a sequence is similar?
                       MR. SIU:  We have rules for doing that. 
           I wasn't prepared to get into the details of the
           rules, and we can chat about that as we -- a little
           bit later perhaps, or if I haven't answered that by
           the end of the presentation, I will make sure that we
           come back to it.
                       We did present that at the subcommittee,
           and we had provided samples of the rules that we were
           using.  Another issue with how we are approaching
           this, in terms of that conceptual model -- remember I
           showed you bins for the uncertainties about
           temperature and pressure over time.
                       Part of the uncertainties in those bins of
           course comes from model uncertainties in principle. 
           We don't yet have well established techniques for
           dealing model uncertainties.  There are a number of
           proposed  approaches.
                       We have done some initial work in that
           area, and so I think at this point it is fair to say
           that the formal methods are under development, and we
           can chat about that a lot.
                       But again for the purpose of what we are
           trying to do -- and that gets back to Mike's point
           about using available technology.  This is one case
           where we are not trying to push the envelope very
           hard.  We are trying to use what we have got.
                       One of the reasons, of course, is that we
           have limited data now to really apply the methods that
           we have got if you want to use, for example, a basing
           approach to estimate the -- to quantify the model
           uncertainties, we would like to have some data to use
           as part of that quantification process.  And the
           amount of data relevant for these sequences is highly
                       CHAIRMAN APOSTOLAKIS:  So you will come
           back to this?
                       MR. SIU:  I wasn't planning to, but we can
           talk about it now if you would like.  This is just a
           limitation, and so because of this limitation, this is
           how we are approaching the problem.
                       We are certainly going to quantify
           perimeter uncertainties.  We are dealing with boundary
           conditions.  Again, things like -- you can call them
           perimeters and a time when at which an action occurs,
           and variations in that.
                       Submodels to some extent -- for example,
           if you are talking about flow through an opening, we
           can deal with that.  But talking about -- let's say
           RELAP5 is an assemblage of submodels and of course
           uncertainty is associated with that assemblage.
                       There is uncertainties with the nodding,
           and uncertainties with the application.  These ere
           things that we are not addressing in the quantitative
           analysis at this point.
                       We are not planning to, and we are of
           course going to supplement whatever information we
           have with the results of experiments to address issues
           that were raised in the subcommittee, for example,
           about the possibility of a thermal plume.
                       And we are also going to perform selective
           sensitivity studies.  So we are not going to just
           accept things directly as is, and in fact a comparison
           with the consolidated code probably would be another
           case of providing some benchmarking.
                       But again I think this is where we are
           going to have the qualitative discussion of
           uncertainties, as well as the quantitative discussion.
                       CHAIRMAN APOSTOLAKIS:  But when you say
           submodel, I remember in one of the earlier
           presentations there was a diagram that said here we
           are using the correlation and we are not so sure.  You
           are going to have an uncertainty about the correlation
                       MR. SIU:  Yes, at that level, because we
           can translate that relatively simply into a boundary
           condition kind of representation, and I think that
           there is enough information on that particular
           submodel that this issue is perhaps of less interest,
           the issue of limited data.
                       CHAIRMAN APOSTOLAKIS:  But we have never
           really heard how you are going to do that, right?  I
           mean, you never presented that, right?
                       MR. SIU:  This is still frankly under
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. SIU:  Given those simplifications,
           this is a variance on a diagram that can be seen
           before.  I have tried to put -- there is a lot of
           information here that we don't have to get into at
           this point, but again it shows the PRA event sequence
           analysis, the thermal  hydraulic analysis, and the
           probablistic fracture mechanics analysis.
                       The key point here is just simply the
           banding idea, that we are taking sequences, and we are
           banding them into a small number of thermal  hydraulic
           bins, and then possibly reexpanding those bins to
           account for a variance in the -- let's say the
           boundary conditions just as a simple example.
                       There are uncertainties in all of the
           perimeters and that's why I have the little pi there
           to represent the epistemic uncertainties.  These are
           being propagated through the analysis, and that gets
           fed into a stress strength analysis, where the stress
           now is a function of the deterministic temperature and
           pressure traces here.
                       CHAIRMAN APOSTOLAKIS:  And this is a
           generic pi, right?
                       MR. SIU:  This is a generic pi, yes.  It
           is not the same pi.
                       CHAIRMAN APOSTOLAKIS:  It is not the same
           pi?  Okay.
                       MR. SIU:  But again the point is that for
           each of these thermal  hydraulic subscenarios, we have
           a defined trace here.  We don't have the bands
           anymore, and we try to accommodate the bands through
           the definition of these subscenarios, but this is a
           limitation in the approach that we are taken.
                       CHAIRMAN APOSTOLAKIS:  I'm sorry, but I
           didn't follow that.  What is it --
                       MR. SIU:  In the conceptual model, we have
           the uncertainty bands, and let's say about
                       CHAIRMAN APOSTOLAKIS:  Right.
                       MR. SIU:  What you have here instead is a
           single trace that is dependent on your definition of
           the scenario.  Let's say that instead of 10 minutes
           for the operator to throttle HPI, it is 9 minutes.  It
           won't be to that fine level of detail, but that is the
           kind of idea.
                       Conceptually, you could have, of course,
           different bands, and we are trying to accommodate
           those variance through a discreet number of
           subscenarios.  And a consequence of that is that we
           get basically a stress calculation for the
           deterministic pressure, temperature, and of course the
           heat transfer coefficient, and --
                       CHAIRMAN APOSTOLAKIS:  And so for the same
           thing --
                       MR. SIU:  Let's say P-1.
                       CHAIRMAN APOSTOLAKIS:  -- where you take
           scenarios 1 and 3, and that's one bin?
                       MR. SIU:  This is one bin, that's right.
                       CHAIRMAN APOSTOLAKIS:  According to the
           previous conceptual model, you would run the thermal 
           hydraulic analysis, right?
                       MR. SIU:  In the conceptual model --
                       CHAIRMAN APOSTOLAKIS:  And you would have
           an uncertainly around P and D.  Now, instead of doing
           that, you are running three cases, right; is that what
           this means?
                       MR. SIU:  Yes.  Don't take the three
           literally, but it is a small number.
                       CHAIRMAN APOSTOLAKIS:  And what is
           different from the first to the second?
                       MR. SIU:  Well, the first one just simply
           said in general I could run separate -- I could do
           this expansion if you will for one, two, three, four,
           however many.  So we have to bin down, and the binning
           is a major modeling step.
                       CHAIRMAN APOSTOLAKIS:  Right.  But in the
           thermal  hydraulic analysis, how do you decide to have
           a number of -- what is different between these three
           runs in the same bin?
                       MR. SIU:  Consider perhaps that this was
           the action at 8 minutes, and this is 10 minutes, and
           this is 12 minutes.  It could be.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. SIU:  Now, we have a method for
           identifying what are the important variables to look
           at, and we are trying out methods to identify the
                       CHAIRMAN APOSTOLAKIS:  So what you said
           earlier was that, yes, this uncertainty and the
           boundary conditions would be handled, but the
           uncertainty in the T/H analysis itself, at this point
           at least you are not handling it?
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       DR. POWERS:  So in other words, if I'm
           agitated over the quality of some heat transfer
           correlation, that it is embedded in RELAP?
                       CHAIRMAN APOSTOLAKIS:  You will remain
                       DR. POWERS:  Does that mean that that will
           affect the security of the free world, the security of
           the free world remains in threat?
                       MR. SIU:  We are, of course, not doing
           this entirely arbitrarily.  We have reasons, and that
           is explained in a fairly lengthy report why we are
           concentrating on certain issues and not on others.
                       And in the case of the PTS analysis, part
           of the point is that the time constance associated
           with the reactor pressure vessel, the wall, the
           thermal  response to a transient, is relatively long.
                       And that means that some of the details
           that you might worry about for other situations may or
           may not have a great effect on the through wall crack
                       CHAIRMAN APOSTOLAKIS:  And I don't think
           it is part of your charge to protect the free world is
                       MR. SIU:  That wasn't my stated objective.
                       DR. POWERS:  I guess maybe you need to
           point to me the heart in this lengthy document where
           that is stated, because it seems to me that taking a
           thermal  response time of the wall to decide whether
           I work with heat transfer correlations or not is
           precisely the wrong thing to do.
                       MR. SIU:  Okay.
                       DR. KRESS:  If you are concluding that
           this heat transfer coefficient that Dana might be
           agitated about was very important to your final
           answer, you would include it in these variations, in
           that middle box, perhaps?  That might be the thing
           that you are changing?
                       MR. SIU:  You certainly could.  You could. 
           You know, at this point, I guess we -- and this is
           part of where we are getting feedback from the
           committee, of course.
                       We have identified certain things that we
           think are important and that we do need to address,
           and if the committee gives us a feedback that we have
           not considered some important things, that would be
           important for us to know.
                       CHAIRMAN APOSTOLAKIS:  Yes, because a
           number of calculations will multiply tremendously if
           you are not careful here.  So instead of the three
           subscenarios, you compare an extra 10 to describe
           these uncertainties.
                       DR. POWERS:  George, let me ask you this
           question.  If I set out and do some sort of a Monte
           Carlo approach on this thing, which -- and in which
           some respects they may be doing here, how many samples
           do I have to take in order to get an understanding of
           what the uncertainty is?
                       CHAIRMAN APOSTOLAKIS:  If you do a
           traditional -- you know, a straight sampling, I think
           it would be into the thousands.  But they would
           probably do some latin hypercube sampling to determine
           the number of runs.
                       DR. POWERS:  Well, even if I go to such a
           stretch of the imagination as using limited latin
           hypercube sampling --
                       CHAIRMAN APOSTOLAKIS:  I think in the
           waste business where they have monster codes, the
           number of runs as I recall is not very high, maybe 70
           or 80.
                       DR. KRESS:  Yes, that is what I recall.
                       CHAIRMAN APOSTOLAKIS:  Which is not really
           too large when considering the goals that you are
                       DR. KRESS:  I think you can get by with
           that few.  I think Dana's point is going to be how can
           we trust this particular uncertainty, which looks like
           maybe 5 or 6 cases, when you really need about 70 to
           do it right.
                       MR. SIU:  Well, actually, again, we were
           expanding on one particular thermal  hydraulic bin. 
           There are many thermal  hydraulic bins.  And the
           actual number of runs -- take a wild guess -- in the
           end they might be on the order of a hundred.
                       DR. KRESS:  So you may be covering enough
           there to --
                       DR. POWERS:  Excuse me, but if I just drew
           a circle around this and said that everything that
           goes in here is basically a Monte Carlo analysis --
           and it's not, but let's say that it is.  And I say I
           would like to know this uncertainty.
                       I would like to know that I sampled 95
           percent of the possible range of outcomes with a 95
           percent confidence.  That is not an unplausible kind
           of expectation, and I think you are up around 90
                       And the fact is that I could do that
           calculation.  Can I come back after you are all over
           and answer that question?  Let's see.  At what
           confidence level did you sample what fraction of the
           possible response base here.
                       MR. SIU:  I guess we haven't been thinking
           along those lines, partly because we weren't sure how
           to deal with again this issue of the integrated model
                       And to work the -- to overwork perhaps,
           and maybe that is an unfair term, but to work the
           perimeters side too hard given that you have got this
           other part that you haven't quantified -- I guess we
           just simply weren't thinking in those terms.
                       DR. POWERS:  Well, I think that is a
           question that I would expect this committee to come
           back and ask you, is okay, you have a response base so
                       How much of it did you sample, and at what
           confidence level?  Tom will ask you about the
           confidence level, and Bill will ask you about the
           fraction of the space issues.
                       MR. MAYFIELD:  If I could, because we have
           had -- as we were first getting into this project,
           actually several years ago, some discussions about
           what is the level of rigor, and is it practical to put
           RELAP, or the consolidated code into a Monte Carlo
                       What level of resource are we going to
           invest in it.  That question started being outweighed
           by plant to plant variability.  We are doing four.  So
           I think the qualitative opinion of those others that
           we are talking about is at some point -- that at some
           point the level of rigor in any individual transient
           analysis, or any individual plant analysis, is going
           to be swamped, or that the level of uncertainty in
           those analyses is going to be swamped by the plant-to-
           plant variability.
                       And we were starting to struggle with
           counting angels on heads of pins for one plant, and
           then losing that sense --
                       DR. POWERS:  You came to that conclusion
           for some reason, and I guess it really surprised me,
           because it is not the intuition that I would come to. 
           Can you explain?
                       Maybe not here, but at some point can you
           explain why you would think that the plant-to-plant
           variability would be so large compared to the
           phenomenological uncertainties?
                       MR. MAYFIELD:  We can, and today is
           probably not the best time, but in general, if you
           just look back at the old IPTS studies, Oconee is
           probably not a good example, because that is the first
           one that they did, and there were a lot of assumptions
                       But if you just look at the difference in
           the calculated probability of failure between Robinson
           and Calvert, and that's a CE versus a Westinghouse
           design.  They are about two orders of magnitude apart
           if I remember my numbers correctly, and yet for
           similar levels of embrittlement.
                       So we were struggling with why, what is
           the big deal between them, and it got down to specific
           sequences and what drives it.  In the BMW plants, you
           find that steam generator tube failures is the
           dominating sequence, or I'm sorry, the main steam line
           breaks the dominating sequence.
                       Westinghouse tends to be small break LOCA. 
           I think that is the dominating sequence for CE also. 
           So it is that kind of stuff we felt like was going to
           swamp uncertainties in the specific calculations.  But
           this was a judgment, as opposed to based on hard
                       CHAIRMAN APOSTOLAKIS:  But I am not sure
           that you should be trying to develop a methodology for
           plant-to-plant uncertainty.  I mean, you are
           developing it for a particular type.
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  And then if you do
           it for several plants.  So the uncertainty from plant-
           to-plant really shouldn't play much of a role here.
                       MR. MAYFIELD:  Well, until we go back to
           Nathan's first chart, where we were trying to
           establish --
                       CHAIRMAN APOSTOLAKIS:  Yes, for the
           criteria, but not here.
                       MR. MAYFIELD:  So the notion was -- yes,
           not here.  The notion was what is the level of cut-off
           in rigor for a specific plant analysis.
                       CHAIRMAN APOSTOLAKIS:  That's correct.  I
           understand that.
                       MR. MAYFIELD:  And so it was a judgment
           call as to what level we had to go to.
                       CHAIRMAN APOSTOLAKIS:  But what I am
           getting out of all of this discussion -- and I realize
           that this is still a work in progress, but eventually
           it would be useful to try to see whether you can use
           a limited latin hypercube sampling scheme to
           demonstrate that you have picked the whole range of
                       That's essentially what it does.  And also
           it limits significantly the number of runs that you
           have to make.
                       DR. POWERS:  I will argue that the way
           that George did this -- the number of runs with a
           straightforward Monte Carlo is not larger.
                       CHAIRMAN APOSTOLAKIS:  Well, all of the
           studies have seem to show that there is in orders of
           magnitude --
                       DR. POWERS:  Well, having lived right down
           the hall from them, from them who developed the
           limited latin hypercube sampling for a lot of the
           reactor accident codes, I am fairly confident in my
                       MR. MAYFIELD:  I think Ali Mosleh might
           have a few comments.
                       MR. MOSLEH:  We started with that as an
           approach to take, where it would remove some of the
           uncertainties that would inevitably be encountered in
           the process of reduction, and in the process that
           Nathan showed earlier, we have to go through binning,
           districtizing the continuous universe, and that
           introduces uncertainty.
                       We looked at as a potential problem with
           reducing the problem into smaller pieces, but at the
           same time the complexity of running a full Monte
           Carlo, even with latin hypercube, in a fully
           integrated model, going from the PRA oriented model
           and all the way to the PFM, was just in terms of size
           and resources, and capabilities, was just too much to
           handle in the scope of the analysis that we were
                       CHAIRMAN APOSTOLAKIS:  Well, I would bring
           again the work that has been done in the performance
           assessment of high level waste depositories, which
           cannot be simpler than what you guys are doing now. 
           It is really huge.
                       So maybe what you can do is pick up some
           of their reports and see how they handle that, because
           they certainly have had the same problem.
                       MR. SIU:  We will take a look at that, I
                       CHAIRMAN APOSTOLAKIS:  That's all.
                       MR. SIU:  What I am showing here on this
           diagram, just drilling down one lower level of detail
           than that three box diagram that you had on the
           previous figure, just to show you again the different
           analysis tracks; basically the PRA analysis track, and
           the thermal  hydraulics analysis track, and
           probablistic fracture mechanics analysis track.
                       Part of the point of this diagram is to
           point out that as the way the project is really being
           done, as opposed to how you might conceptualize it,
           these are indeed being done in parallel.
                       Some of the thermal  hydraulics analysis
           is done before we really had significant interactions
           with the event sequence analysis.  So there are some
           runs, for example, that we are using in our analysis,
           and some others are just indications of what might be
           interesting, but aren't really folded into the final
                       And similarly there are currently in the
           results that you are going to be seeing, there isn't
           full feedback yet from thermal  hydraulics into, for
           example, the PRA success criteria that we have used.
                       We have made some assumptions based on our
           understanding of the progression of the accident, and
           that understanding will be improved after we explore
           the detailed results of the thermal  hydraulic
                       So there is a lot of interactions here
           that are taking place.  Of course, the results of the
           PRA analysis will be eventually the frequencies of the
           various bins identified, and that gets fed into the
           probablistic fracture mechanics analysis when we
           quantify through wall crack frequency.
                       Similar to thermal  hydraulics analysis,
           it develops the subscenario histories that get fed
           into the wall crack frequency.  One of the other
           things that I wanted to point out, some of the
           discussion that we had at the subcommittee meeting was
           really on this issue here, what are the potentially
           uncertainty important scenarios.
                       How do we justify narrowing down the
           problem to a limited set of issues, and so that was
           the point of that discussion.  Okay.  Where are we
                       DR. SHACK:  And just coming back to that,
           I mean, that is where you sort of addressed Dana's
           question of how important for example a heat transfer
           coefficient might be.
                       MR. SIU:  We really did look at that
           particular one.  Now, that was the specific issue of
           the heat transfer coefficient in the downcomer, and
           explored if you will through a sensitivity fashion, t
           he variance and the results is not very great compared
           to the variance that you would get from other sorts of
                       Now, whether there are other concerns that
           were not addressed, we obviously did not do an
           exhaustive list, and it was based on the high level
           model of what is important and what isn't important,
           and again we would welcome feedback on that.
                       Where are we now.  We have developed an
           aleatory model and that's what you saw.  That is the
           event sequence model, the T/H subscenarios for
           different bins; and then there is a aleatory treatment
           of the K1C term in this probablistic fracture
           mechanics analysis for fracture toughness.
                       So at least conceptually we have the
           pieces, and we know how they are going to fit
           together.  We have categorized the different model
           perimeters both in the white paper that the committee
           saw several months ago, we categorized -- at least in
           the preliminary fashion -- the probablistic fracture
           mechanics analysis perimeters.
                       And that has been revised a little bit,
           and Mark Kirk talked about that at the subcommittee,
           but we have also categorized the thermal  hydraulic
           perimeters, and as was pointed out at the subcommittee
           meeting, the PRA analysis is conventional.
                       We are treating the uncertainties in the
           perimeters as being epistemic, and that is no big
                       In the PRA event sequence analysis, we do
           have draft distributions for Oconee.  Again, we have
           received a lot of comments on them.  We have our own
           comments as we reviewed the results in detail, but we
           will -- and we expect to revise those distributions as
           part of the iteration process.
                       Nevertheless, we thought it would be
           useful to bring it in front of the committee to give
           you an indication of what are the things that seemed
           to be important, and what sorts of uncertainties do we
           have in the results of the calculations to date.
                       We have in the thermal  hydraulic
           analysis, as I indicated in a previous slide, we have
           identified classes of scenarios where the boundary
           condition uncertainties appear to dominate the model
                       And I am talking about the model as an
           assemblage, rather than individual submodels, because
           the submodels, where they affect the boundary
           conditions, we are treating through the boundary
                       CHAIRMAN APOSTOLAKIS:  A boundary
           condition means at the time of operator action?
                       MR. SIU:  For example, the size of a hole,
           discharged through the hole, and that sort of thing. 
           Things are basically --
                       CHAIRMAN APOSTOLAKIS:  And these would be
           handled as epistemic variances?
                       MR. SIU:  Actually, these are aleatory. 
           Again, you think of the variation in the operator
           actions.  This is a level below which we are modeling. 
           So you are saying that -- you see, the PRA defines
           success and failure in very global terms.
                       Let's say that success is throttling
           before 10 minutes.  Well, there are variance on
           success, but there are also variance on failure.  If
           I don't throttle in 10 minutes, or if I throttle in 15
           minutes, what is the difference.
                       CHAIRMAN APOSTOLAKIS:  And how about the
           size of the hole?
                       MR. SIU:  The size of the hole also is --
           I mean, we have got a big category that is called
           small LOCA , and that accommodate a wide variety of
           break sizes and locations.  So again there is a
           variation there that is all lumped into that category.
                       CHAIRMAN APOSTOLAKIS:  So you think that
           is an aleatory issue?
                       MR. SIU:  That is an aleatory issue.  It
           is different than saying if I have a particular sized
           hole, would I know about it.  Then we have identified
           the potentially important perimeters, and that was a
           table which we will clean up, and which the
           subcommittee has seen in the report.
                       And we need to clarify a few things there,
           but again we feel comfortable, and at least as a first
           shot, we know which perimeters we need to focus on,
           and we are developing a process for quantifying those
           subscenario probabilities.
                       And that question came up in the
           subcommittee as well.  Clearly, we are not taking 5th
           percentiles of variables and combining them and saying
           that is a 5th percentile of the outcome.
                       So basically we are looking at a DPD or
           dispute probability distribution kind of approach to
           identifying subscenarios.  So it would be a
           discretized approach.
                       CHAIRMAN APOSTOLAKIS:  And that is what
           those guys did on the performance assessment and it
           may be useful to you.
                       MR. SIU:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And to see what
           they did.
                       MR. SIU:  Okay.
                       DR. KRESS:  The important perimeters
           identification, was that a PIRT process?
                       MR. SIU:  Marilyn, who did the work,
           started with PIRT, and looked at the approach, but
           basically had to extend it.  And frankly through the
           use of modeling arguments, physical modeling
           arguments, concluded that a very limited set of issues
           was important.
                       Again, a review of the committee would be
           helpful to say whether those arguments are convincing. 
           We will demonstrate this process as part of the Oconee
           analysis, and obviously we intend to use this for the
           other plants as well.
                       The probablistic fracture mechanics.  We
           do have distributions for most of the model
           perimeters.  For example, we have distributions for
           the flaw characteristics, and I think the committee
           was presented with that material, or was it the
           subcommittee.  I don't remember.
                       We have distributions for fluence, for
           chemistry, the copper content and nickel content, and
           phosphorous.  The current work is focusing on treating
           uncertainties and fracture toughness, and that is the
           K1C, and then the RT/NDT, or actually the radiation --
                       DR. POWERS:  I have examined a document
           that I cannot recall exactly, discussing the need for
           continued research in the enburtelment of reactor
           vessels that has the phrase in it that the
           correlations that have been developed are only -- I
           say I believe, but it goes something like this.
                       Semi-empirical in nature and only include
           the effects of copper, nickel, product form, and
           fluence.  It does not go on and tell me what else
           ought to be in there.  But it looks like a lot to me.
                       I mean, nickel, copper, product form, and
           fluence, and it was a little hard for me to come up
           with what else there ought to be.  But I am not an
           expert in that fashion.
                       My point is that that seemed to suggest
           that this was an inadequate understanding here, that
           there was something missing, something better ought to
           be available.
                       Does that mean that we have something here
           through the implausible unknown that just bars
           progress here or something?
                       MR. MAYFIELD:  The model that is going to
           be used in these calculations is the latest thing that
           we have put together, and that I think we have briefed
           the committee on, but I am not sure.
                       It is based on a statistical analysis of
           the existing embrittlement date, and coupled with a
           fair bit of work from Professor Odette, and some of
           the other radiation damage mechanists that have been
           looking at this.
                       The work does go beyond just sort of the
           traditional product form, copper, nickel, composition. 
           It has looked at factors that pop up, such as long
           term thermal embrittlement.  So there is a time at
           temperature factor that gets rolled in.
                       We have been looking at what factors show
           up in the statistical analysis, and do they have a
           physical basis.  Conversely, is there something from
           the physical metallurgy that should be in the data,
           and we have gone looking for that.
                       And in some cases there has been some
           extensive dialogue between the mechanists and the
           statisticians.  We think that the model that we have
           today embraces the physical understanding of
           embrittlement, down at a fairly basic level.
                       And it embraces that, as well as
           statistical trends in the data, and so that's as good
           as I get, I guess is the point.
                       DR. POWERS:  As good as you can get now,
           or as good as can ever be gotten?
                       MR. MAYFIELD:  Well, that's why we
           continue to work on this.  We are not convinced that
           we have the answer.  However, today, and at the level 
           of fluence that the vessels are expected to see
           through 60 years, we think we have a model that
           captures those trends.
                       DR. POWERS:  The phrase that I am
           imperfectly reproducing here has this only term in
           there, as though there was some heat factor, a very
           important factor, missing.  It didn't say what it was
           unfortunately.  It just said we only have this stuff.
                       Now, you have suggested as one the time
           and temperature factor there, but is there some great
           imponderable that just constitutes a barrier that we
           have to put in some fudge factor here to say, well, it
           can be no bigger effect than this?
                       MR. MAYFIELD:  I don't think so, but Mark
           Kirk has come up and perhaps he has --
                       MR. KIRK:  I think, of course, that future
           knowledge is never perfect, but I think the answer is
           that we have beaten that one pretty well.  We have
           looked at a lot of model -- at radiation experiments
           on model materials that are designed to bring out
           certain forms of radiation damage.
                       And those data have been considered in the
           development of the model, and I think that helps to
           screen out some of the imponderables that one might
           otherwise be worried about.
                       But as Mike said, the form of the
           correlation that we are now using, much of it has a
           very firm physical basis, and we feel that it is
           important to combine both the physical and the
           statistical understandings.
                       And not so much for fitting the data,
           because of course you can do that without any physical
           understanding whatsoever, but to provide -- and I
           don't think this is a word in Websters.  Well, I won't
           use it then.  But the ability to extrapolate, which is
           of course what we are always doing here.
                       But we could certainly go into this in
           more detail like Mike said.  I think or I know that we
           have briefed at least the materials subcommittee on
           the embrittlement correlation.
                       That is something that we could do in the
           future.  Certainly this is an area, along with what
           was brought up earlier about through all attenuation,
           in which there has been a lot of interest, both within
           the NRC, and the industry, and the international
           nuclear community, and continues to be -- and in fact
           at the ASTM E-1002 meeting last week on radiation
           damage mechanisms, there was discussion of this issue
           yet again.
                       And I spoke earlier this week with Stan
           Rosinski, who is a program manager at EPRI, and he
           indicated that he was going to initiate a small
           project under their materials reliability project,
           using funding from their materials reliability project
           to do in the short term a review of what technical
           basis there exists through all attenuation functions
           to provide the NRC some assistance in that regard.
                       So that information will be coming in, and
           if it comes in during an appropriate time frame, and
           I think it will, it would be considered.  And just to
           also mention so that there is not the perception that
           the NRC is working in a vacuum on this.
                       We are currently in the process of
           developing a technical basis document for the
           embrittlement correlation.  We have got a deadline on
           that later this year to have a draft new reg.
                       Equally again, EPRI is also working on a
           tech basis document concerning embrittlement
           correlations, and that is due out in February, and
           EPRI has agreed to provide that to the NRC so we can
           have the value of that information as well.
                       DR. POWERS:  So I get the impression that
           what you are telling me is that I should not worry
           about this only.  That you have put in here enough
           description of this embrittlement process for the
           regulatory decisions that you are looking to make
                       MR. MAYFIELD:  I believe that is a true
                       MR. SIU:  And from the standpoint of the
           uncertainty analysis again, those things that are not
           specifically in the models are treated as contributing
           towards aleatory uncertainties.  This was basically
           the reason why we decided that the K1C term needed to
           be treated as an aleatory issue.
                       DR. SEARLE:  Don't worry any more.  Just
           get nervous.
                       DR. POWERS:  Well, I will quit the
           subterfuge here.  It shows me that for both research
           programs on vessel embrittlement are no longer needed
           for making regulatory decisions.
                       MR. SIU:  I will show you -- these are
           pretty hot off the press -- draft PRA results overview
           for Oconee-1, and what is new about this is not only
           the scenario frequencies, which se came up with a few
           weeks ago, and again had some review with Duke Energy
           to talk about specifics relative to how we
           characterize the plant and operations.
                       But also the characterization of
           importance with respect to probablistic fracture
           mechanics.  We have been conducting a scoping study
           for Oconee just to get an idea of where the numbers
           are coming out.
                       So we have a current version of the FAVOR
           code that is being used to propagate the thermal 
           hydraulics traces, the PRAs events frequencies,
           through to the end to develop some notion of small
           crack frequency.
                       We are not confident yet enough about the 
           probablistic fracture mechanics material to give you
           a conditional probability of through wall crack given
           a scenario, because again this is really new stuff.
                       But at least I think we can indicate that
           these were the kinds of scenarios that were turning
           out to contribute to the results, and I am going to
           give you a caveat about these descriptions here in a
                       So, please, again don't take down
           literally as their are described.  But we have
           basically -- if you focus in on these numbers here,
           these refer to specific thermal  hydraulic runs, and
           certain assumptions are made, and the analysis is
                       Frequencies are assigned to these runs,
           and they are run through the probablistic fracture
           mechanics.  These are the kinds of scenarios that
           turned out to be relatively important, and the one
           that I put in gray right now appears to be the most
           important one.
                       Again, all of these things are subject to
           change as we dig into these results and identify what
           is really driving them, and whether we have got it
           right or not.
                       CHAIRMAN APOSTOLAKIS:  If you go to the
           conceptual model, can you tell us at which point these
           frequencies are calculated?
                       MR. SIU:  Sure.  This is the output of the
           event tree analysis basically.  I'm sorry.  Let me go
           to the framework, as I think that would be better.
                       CHAIRMAN APOSTOLAKIS:  Yes, whichever.
                       MR. SIU:  What you are seeing is that we
           have binned the scenarios into about 40 thermal
           hydraulic runs.  We didn't use all 40 as it turned
           out, but that was the universe which we were
                       CHAIRMAN APOSTOLAKIS:  For one scenario?
                       MR. SIU:  No, no.  All the possible PTS
           thermal hydraulic scenarios.  We ran 40 cases of
           RELAP, and we are binning the thousands of sequences
           that we got into one of those 40 cases.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. SIU:  So when you see a specific
           number, like Run Number 3, that is a specific one run
           out of the set of, let's say, 40 roughly.  And we have
           got the probability distributions about those
                       We have not done this part here.  The
           fractionation into subscenarios, which we talked
           about, we haven't approached, but we have not applied
           it yet to Oconee.
                       So we are taking a particular if you will,
           and all of these are collapsed into one.  There is
           only one trace associated with that bin, and that
           trace gets fed into the fracture mechanics analysis
           with this distribution, obviously the convolution of
           the --
                       CHAIRMAN APOSTOLAKIS:  So the frequencies
           on slide 11 are between the first two boxes?
                       MR. SIU:  That's correct.  After you have
           been --
                       CHAIRMAN APOSTOLAKIS:  Over there?
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  But what you show
           as description is one of the scenarios that goes into
                       MR. SIU:  That is the scenario that
           characterized that particular bin.
                       CHAIRMAN APOSTOLAKIS:  But that bin may
           include other scenarios as well.
                       MR. SIU:  Exactly.
                       CHAIRMAN APOSTOLAKIS:  And the one you
           showed here is what, is a representative, or just one
           of them?
                       MR. SIU:  The one I showed on this chart
                       CHAIRMAN APOSTOLAKIS:  On 11.
                       MR. SIU:  Okay.  Let me get back to Slide
           11, because this is worth talking about.
                       CHAIRMAN APOSTOLAKIS:  So when you say the
           one that you have shaded there, the large MSLB is
                       MR. SIU:  Yes, lots and lots of scenarios
           feed into this bin.  The total number of sequences was
           around 14,500 I believe.
                       CHAIRMAN APOSTOLAKIS:  So lots of them are
           going into 25?
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  And why are you
           showing the large main stream line break?
                       MR. SIU:  This is the description of this
           particular run.  So this is the -- to run RELAP, of
           course, you have to provide the initial conditions,
           the boundary conditions, and certain things that occur
           over time.
                       This is a description in very loose terms
           of what that run did, the T/H run.
                       CHAIRMAN APOSTOLAKIS:  But there are other
           scenarios that lead into --
                       MR. SIU:  That's right.  We have been many
           scenarios into this, which some of them may not follow
           this description very closely.
                       CHAIRMAN APOSTOLAKIS:  Okay.  So the
           reason why you have not is because it is kind of
           representative of that?
                       MR. SIU:  In a sense.  I mean, if I gave
           you a number, it wouldn't mean anything either.  So I
           have to give some idea of what kind of scenario this
           run represents.
                       But, yes, there are lots and lots of
           scenarios feeding into these, and we are examining --
           now that we have got some sense of priorities here, to
           see if this is really right.
                       Are we feeding the right stuff into this
           bin, and do we need actually another run because the
           contributions from this are so large, but they are not
           really well represented by that run.  That is the
           question that we have to raise after we get a chance
           to get some results.
                       CHAIRMAN APOSTOLAKIS:  So this includes
           now aleatory stuff and everything?
                       MR. SIU:  Again, we do not have the
           subscenario fractionation.
                       CHAIRMAN APOSTOLAKIS:  We don't have it?
                       MR. SIU:  We do not.  This is simply the
           PRA results.
                       CHAIRMAN APOSTOLAKIS:  So does the
           operator intervene here anywhere?
                       MR. SIU:  Well, he fails to.  For example,
           he fails to throttle the HPI.
                       CHAIRMAN APOSTOLAKIS:  So you are just
           using a representative time for that?
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  Which later on
           would be refined.
                       MR. SIU:  Which has to be refined based on
           now a more careful look at that particular scenario.
                       CHAIRMAN APOSTOLAKIS:  So up until this
           point, you really don't have any model uncertainty do
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  So this is a
           traditional PRA.
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  But the new thing
           is that you have these bins that you are showing?
                       MR. SIU:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Okay.  Fine.
                       MR. SIU:  And now to say what is new or
           not, but simply this is how we are progressing through
           the analysis.
                       CHAIRMAN APOSTOLAKIS:  So this will go
           into 25, but 25 has not been run yet?
                       MR. SIU:  No, 25 has been run.  That's why
           -- look, 25 -- I can show you.  In your viewgraph, on
           the back of the viewgraphs, this is Run 25, the
           thermal  hydraulic trace.  This -- and I don't know if
           it is smoothed out or not, but it gets fed into FAVOR,
           with a frequency and uncertainty about that frequency.
                       And based on the combined results of all
           of those things, including the PRA frequencies, we
           have some sense of priority, and this is what you are
                       DR. POWERS:  Now, when you formulate the
           RELAP model for this number 25 calculation, which of
           the myriad of conditions do you tell it about?  Do you
           tell it about the mean condition or the 95th
           percentile condition, or the 5th percentile condition?
                       MR. SIU:  I will give you a high level
           description, but I think Dave -- well, Dave is here. 
           Can you answer to that?
                       MR. BASETTE:  Let me see if I caught the
           question correctly.  This is David Basette.  Of
           course, RELAP gives you a median or a nominal best
           estimate calculation for a given, or however you fix
           the initial boundary conditions, it gives you a best
           estimate calculation.
                       DR. POWERS:  He has described this grade
           line as main steam line break, with full high pressure
           injection.  He has told us, however, that there are 
           scenarios within that bin that can deviate to some
                       He has provided a synoptic description of
           a distribution for that bin that includes a mean, a
           95th, and a 5th percentile.  Now, you have to
           formulate a run with RELAP.
                       You cannot put those distributions in. 
           You have to say it is this plant, and at this time
           this operator does this successfully or
           unsuccessfully.  Which one of those did you tell RELAP
                       MR. SIU:  Let me respond to that, as I
           think I can take that.  This is a somewhat more
           careful description of that particular scenario.  So,
           for example, you see high pressure injection 21
           seconds into the transient based on the control logic
           for HPI.
                       Now, there are variance on this.  You
           could say the operator doesn't throttle in 5 minutes. 
           The operator doesn't throttle in 10 minutes.  The
           operator doesn't throttle in 15 minutes.  That's not
                       This is literally what they have.  So the
           PRA at this point was not telling the thermal 
           hydraulics this is the variant that you need to look
                       When we talk about subscenarios, which
           again we have not applied the Oconee yet.  We have to
           start investigating those variance, and say what are
           the possible variance that we want to model, and then
           identify are there RELAP runs that will represent
           those variance reasonably well, or do we need new
           runs.  We have not done that yet.
                       DR. POWERS:  For this particular case, is
           the scenario you told about RELAP indicative of a
           frequency equal to mean, the 95th, the 5th, or some
           other one?  Yes is not a suitable answer.
                       MR. SIU:  No, there is no frequency
                       DR. POWERS:  There is a frequency
           associated with whatever calculation you told RELAP
                       MR. SIU:  We have not -- let me give you
           an example.  Let's talk main steam line break.  This 
           is a large break, and we have defined large to be
           greater than 8 inches here, because the size, I
           believe, of the TBBs.
                       We have not said that we have a frequency
           for breaks in the range of 8 to 9 inches, from 9 to 10
           inches, 10 to 11.  Yeah, you could -- we would have to
           give you -- and I don't know this off the top of my
           head -- what was the size of the particular hole, and
           what was the shape of the hole, and what discharge
           coefficients are associated with that.
                       So I don't have that information there. 
           You could come up with, if you will, density functions
           for these characteristics like the break size.  We
           haven't done that.
                       So I guess you could say, well, what is
           the frequency that you have of a break between or
           larger than 8 inches.  Yes, we do have that.  That is
           the PRA frequency that we have used, and that is the
           .0 -- well, I shouldn't give you a number off the top
           of my head.
                       We do have that based on an empirical
           dataset.  I mean, we had one failure in 600 odd
           reactor years.
                       MR. MAYFIELD:  I think the answer is that
           it doesn't necessary represent any of the frequencies
           here.  It is a descripter of a class of transients
           that fits in the bin, and at this stage, I don't think
           we can tell you that they have gone back to the PRA,
           and we have taken up a bunch of things through some
           rules that have been developed, and have taken a bunch
           of transients that fit that set of rules, and put them
           in this bin.
                       And he is telling you about the
           distribution of frequency on those transients, and I
           don't think we can tell you today that the particular
           RELAP run that was made, called Number 25, where that
           fits in this frequency, and it is my guess that it is
           probably closer to the mean than any.  But I don't
           think we can pin that down.
                       DR. POWERS:  I think that would be an
           inadequate answer for me, to say, well, it is roughly
           the mean, or maybe the appropriate answer is it is
           none of these particular ones, but its going to be
           kind of representative in a sense that it will be
           carefully explained.
                       MR. SIU:  Yes.  I think as we define
           really what those subscenarios are -- I mean, right
           now you have a cartoon.  It says we will develop
           subscenarios, but you have to develop those
           subscenarios based on the underlying principles.
                       And the principles would be, for example,
           what are the key variables, and what variations are
           you going to consider, and what probability are you
           going to assign to each of these variations.
                       And then I think at that point, I think we
           can give you a more meaningful answer, because now by
           definition when you have these discreet scenarios, you
           have binned things.  It is either in this bin, that
           bin, or that bin.  We haven't done that yet.
                       MR. MAYFIELD:  Does that answer your
                       DR. POWERS:  Well, the underlying question
           is we are going to have a bunch of thermal 
           hydraulics, and they believe they have got these huge
           uncertainties in their codes that need to be resolved.
                       And they are going to come in and say, oh,
           this is giving me an unfair answer, and that the
           thermal hydraulics don't make any difference, because
           had you done this thing out here at either 95th or 5th
           percentile, and I am not sure which one.
                       You would have seen it, and it would have
           made all the difference in the world, this strange
           coefficient in an equally strange empirical
           correlation that does not include anything in it,
           except maybe copper, nickel, or fluence.
                       And that is what I have to listen to on
           why this is an unfair characterization of the
           uncertainly of the thermal  hydraulics.
                       MR. ELTAWILA:  I have tried to resist
           getting into this, but when it comes to thermal 
           hydraulic uncertainly, I think you raised that issue
           several times.  When we are dealing with single faced
           flow, which is the case for this particular
           application, the uncertainty in the heat transfer
           coefficient -- and we are going to give you a paper.
                       We have done specific studies which shows
           that is not important.  The main important perimeter
           would be the pressure and the temperature, and have
           confidence that the code can calculate these very
           accurately or reasonably accurately.
                       I think your question has the right issue,
           that the particular thermal hydraulic calculation that
           we presented, it is a representative of one particular
           scenario, which will give you a mean answer for that
           particular scenario.
                       We have not gone back now to look at all
           the other scenarios and redefining process.  Is there
           much variation if I change the break size, or I change
           operator action.  What will be the effect on the
           pressure and the temperature, and that's when we will
           be able to at that point to give you the 95 percent
           and 5 percent uncertainty.
                       But the model uncertainty itself is not
           going to be the driver in this case.  In this case, it
           is going to be the boundary condition as everybody
           said here.
                       DR. SEARLE:  I must express some curiosity
           about the difference between runs 3 and 4 on page 11. 
           There is a factor of 2 in the flow area, and a factor
           of two orders of magnitude in the mean probability.
                       MR. SIU:  I was afraid that you were going
           to ask that.
                       DR. SEARLE:  Clearly, there has got to be
           a snake in the grass somewhere.
                       MR. SIU:  There is a reason for that, and
           now it actually gets back to George's question, and
           that's why I wanted to characterize these as not
           literally what the PRA sequences are, but what the
           thermal hydraulic run is.
                       Again, there was a binning choice to say
           out of the myriad of sequences that we have, we have
           some of them going to this one, and some of them going
           to this one, and so on and so forth.
                       What you are seeing here in the PRA space,
           we don't have a fine distinction between 2 inch LOCAs
           and 2.8 inch LOCAs, and 1.4 inch LOCAs.  We have
           LOCAs, small LOCAs with a certain frequency.
                       What you are seeing here in this
           particular scenario, and what this particular scenario
           is really representing LOCAs where, even though the
           HPI is on, the pressurization is sufficient that you
           are going down to a lower pressure.
                       So again I don't want to take these labels
           literally.  This is the RELAP run that was done, and
           we binned a bunch of stuff into that.  Again, we are
           going to reexamine that as we go further.
                       DR. SEARLE:  My only comment is that the
           way in which you differentiate between the runs is
           probably woefully inadequate at this point if you are
           going to really examine the differences in the
                       MR. SIU:  We know, of course, exactly what
           the input decks are, and we know what scenarios feed
           into those.  That's correct.
                       CHAIRMAN APOSTOLAKIS:  So you said earlier
           that the size of the break within the class of small
           breaks is aleatory.
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  So can you
           elaborate a little bit on that?  I mean, what kind of
           distribution did you assume here, and so what fraction
           of --
                       MR. SIU:  Again, this is part of the
           problem with flashing results at a summary level.  The
           scenarios that got fed into this particular bin are
           LOCAs, with either the HPI throttled or the break was
           large enough that the system depressurized quickly. 
           Most of the contributing ones I think were just small
           break LOCAs, where HPI was throttled.
                       That doesn't match exactly the description
           you have here.  In the physical world, when you have
           a break that is large enough, you do depressurize the
                       CHAIRMAN APOSTOLAKIS:  But then it is not
           a small break anymore is it?
                       MR. SIU:  Well, remember now that the
           small break refers to the diameter for which we have
           event statistics.
                       CHAIRMAN APOSTOLAKIS:  Right.
                       MR. SIU:  And small, actually believe
           extends beyond 2.8.
                       CHAIRMAN APOSTOLAKIS:  Well, how do you
           decide?  I mean, what is the aleatory probability that
           I would have a 2 inch small break, or a 2.8?
                       MR. SIU:  That has not been addressed. 
           This is the PRA sequences within which, and we still
           have to fractionate, and when we fractionate, we will
           actually find that maybe there is some bifurcation at
           some critical value, and we can argue if we know that
           critical value very well.
                       But the pressure is going to go along one
           path, and the other one is going to drop rapidly.
                       CHAIRMAN APOSTOLAKIS:  I don't understand
           that.  I mean, the frequencies you show there on the
           table include the frequency of the initiating event.
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  So the initiating
           event in one case is a 2 inch break, and --
                       MR. SIU:  No.
                       CHAIRMAN APOSTOLAKIS:  It's not?
                       MR. SIU:  No.  The initiating event is a
           small break LOCA, which includes a whole range of
           sizes.  So that's why this is so anonymous.  You say,
           oh, my goodness.  How do I know really that a 2.8 inch
           break is two orders of magnitude less likely than the
           2 inch break, because everything else looks the same.
                       It is the binning that we assign the
           sequences to this particular thermal hydrologic
                       CHAIRMAN APOSTOLAKIS:  So for this
           calculation, the frequency of the 2 inch and the 2.8
           inch break is the same?
                       MR. SIU:  Exactly.  It is a small LOCA.
                       CHAIRMAN APOSTOLAKIS:  It's a small LOCA.
                       MR. SIU:  And this one we don't throttle,
           and this one we do.
                       DR. SHACK:  So what we are looking at is
           the difference between pressurized and depressurized?
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  But later on you
           will have some fraction?
                       MR. SIU:  Oh, yes.  Again, that is one of
           the important perimeters obviously as you go through
           this, because you have qualitatively different
                       CHAIRMAN APOSTOLAKIS:  And that's why it 
           is --
                       MR. SIU:  That's right.  We have 15
                       CHAIRMAN APOSTOLAKIS:  We have 15 minutes,
           yes.  Now, at some point, at some subcommittee meeting
           -- and I don't know if you did it last night, but I
           really would like to follow one sequence from
           beginning to end.
                       CHAIRMAN APOSTOLAKIS:  Right.  With all
           the uncertainties, have you discretized how you did
           it?  Did it happen with some epistemic uncertainty
           with you, Mike?
                       MR. MAYFIELD:  Well, it is our intent --
           and we were talking about it before the session
           started, that probably in the May-June time frame, we
           will be far enough along with our calculations that we
           can come to -- I don't like coming in -- we felt like
           we needed to do something.
                       CHAIRMAN APOSTOLAKIS:  No, I am not
                       MR. MAYFIELD:  What we would like to do is
           have gotten far enough through this so that we are not
           giving you real time results; that we have had a
           chance to look at it and make sure that it is holding
           together.  So it is probably in the May-June time
                       CHAIRMAN APOSTOLAKIS:  But we will take
           one sequence and beat it to death all the way?
                       MR. MAYFIELD:  We will take one sequence
           and walk you right through it.  That's the intent.
                       MR. SIU:  That's right.
                       CHAIRMAN APOSTOLAKIS:  One question I had,
           since I am beginning to understand this, but as you go
           to your Slide Number 12, before you do that, could you
           put up your --
                       MR. SIU:  This is the backup slide --
                       CHAIRMAN APOSTOLAKIS:  Which is the same
           as this?
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  So that is the
           scenario that you are calling Number 25?
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  And the Number 27
           would be the one where you succeed --
                       MR. SIU:  Well, whatever scenario.  There
           is a mapping of it.
                       CHAIRMAN APOSTOLAKIS:  But you are listing
           those two, 25 and 27, and runs as you call them.
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  And those two are
           the ones in red, and the one --
                       MR. SIU:  This would feed into 27,
                       CHAIRMAN APOSTOLAKIS:  What happens with
           all the other scenarios now?  You are throwing them
           out into different bins?
                       MR. SIU:  We are throwing them in
           different bins.
                       CHAIRMAN APOSTOLAKIS:  And some of them
           may not be steam line break bin?
                       MR. SIU:  That's correct.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. SIU:  And some that feed into the
           steam line break bin may not be steam line breaks.
                       VICE CHAIRMAN BONACA:  So you are looking
           at the pressure temperature behavior, and the fluid
           behavior, and --
                       MR. SIU:  That's right.  That's the
           binning and the mapping between scenarios, and that's
           where we discussed with the subcommittee some of the
           subjective judgment is right now in going from all
           these sequences to a somewhat more detailed
           description, which we feel pretty comfortable with.
                       But then jumping from that to the limited
           set of thermal hydraulic bins that we do have.
                       MR. MAYFIELD:  And part of the work, yes,
           is subjective, but to try and bring in a rule based
           scheme, where it is not just tossing coins, but there
           is actually some technical basis for the judgment.
                       VICE CHAIRMAN BONACA:  So it is very plan
                       MR. SIU:  Yes.
                       VICE CHAIRMAN BONACA:  And so I understand
           much more than I did before.
                       CHAIRMAN APOSTOLAKIS:  Okay.  So what else
           would you like to tell us?
                       MR. SIU:  Okay.  Let me just talk in
           summary about the draft PRA results.  We do obviously
           have issues and we have talked about these.  The
           binning of the sequences, and the time frame for the
           operator actions, which we now have the thermal
           hydraulic runs to get a better sense of that.
                       And dependencies.  This particular
           scenario involves three operator actions or failures. 
           Failure to isolate the break, and failure to isolate
           the flow, and failure to throttle HPI flow.
                       We need to make sure that we are handling
           the dependencies not only for the dominant scenarios,
           but obviously the scenarios that might have dropped
           off the map because we didn't address those in detail.
                       CHAIRMAN APOSTOLAKIS:  Where do the
           operator --
                       MR. SIU:  This is the Atheana Team.  This
           is a subjective assessment process based on a
           description of context.  At the Duke Energy meeting,
           we actually got very positive responses on our
           descriptions of the context, and actually there was
           some discussion about the numbers that were assigned.
                       But we didn't seem to be way off is my
           notion of that.  Again, these are things that we will
           continue to refine.  We had put intentionally
           conservative numbers in many places just to make sure 
           that we didn't lose anything as part of this process,
           and now we are reexamining what we have got.
                       Thermal hydraulics analysis.  I think we
           have talked about this already.  This just illustrates
           more of a process rather than results, because we
           don't have results at this point on the uncertainty
           part of the analysis.
                       We have identified the key sources of
           uncertainty, and we talked about boundary conditions
           on models, and of classified scenarios regarding in a
           simplistic fashion whether they involve single-faced
           flow, or two-faced flow.
                       And for single-faced flows, we are going
           to follow the approach that we have basically
           described already.  We are going to look at
           representative boundary condition variations to define
           subscenarios, and we are going to develop
           distributions for the subscenario probabilities.
                       And then either identify an existing T/H
           run to map to, or perform an additional run, and
           that's just the approach that we envision at this
                       CHAIRMAN APOSTOLAKIS:  Are you going to
           identify -- and not necessarily only here in the
           thermal hydraulic analysis, but the overall analysis,
           the important perimeters or models that seem to drive
           the risk?
                       MR. SIU:  That's right.  That's part of
           the assessment process.  It's not only what is the
           number, but what is driving that number.
                       CHAIRMAN APOSTOLAKIS:  And how are you
           going to do that?  I mean, you have perimeters all
           over the place.
                       MR. SIU:  Yes.  I imagine that there will
           be some sense of decomposing the results, because of
           course one of the results of a risk assessment is that
           the dominant scenarios also typically dominate the
                       That's just the way that the math works
           out.  You can have a very unlikely scenario that is
           very uncertain, but it doesn't really contribute then
           to the final result.  So I think we will be able to
           concentrate on a few scenarios, and that's the hope.
                       CHAIRMAN APOSTOLAKIS:  But then you are
           going to the P/H analysis and FAVOR, and --
                       MR. SIU:  But again the point of what
           Professor Almenas showed was that there is a rationale
           for identifying what are the important perimeters, and
           so that would at least be our starting point for
           talking about what seems to be driving this.
                       CHAIRMAN APOSTOLAKIS:  My understanding is
           that in the waste area that they have been struggling
           with this issue now for 2 or 3 years, and I have seen
           a paper or two where they have proposed something to 
           Hizenberg, who used to be a member of the staff.
                       I am not saying that is the way to do it,
           but since those guys have attempted, it would be
           worthwhile looking.
                       MR. SIU:  Thank you, yes.
                       CHAIRMAN APOSTOLAKIS:  Actually, your
           problem has a lot of similarities with that problem,
           because it involves complex computer programs and
           uncertainty propagation, and so on, and so you can
           benefit a lot from what those guys have done.
                       MR. SIU:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Of course, they
           cannot use the traditional importance measures that we
           use in level one and PRAs.
                       MR. SIU:  Right.
                       CHAIRMAN APOSTOLAKIS:  Because you have
           computer programs with physical phenomena.  That's why
           it may be worthwhile to look at what they have.
                       MR. SIU:  This is a Mark Kirk slide
           obviously.  It is 21st Century stuff.  I am way
           behind.  But this is just an indication of --
                       MR. KIRK:  What is wrong with this?
                       MR. SIU:  Nothing is wrong.  This is
           great.  Let's walk through it.
                       DR. POWERS:  The thing that jumps out
           immediately is that the embrittlement model only has
           fluence, copper, nickel, and product form on it.  All
           this other stuff that you told me that yo were going
           to put into it apparently doesn't make this viewgraph
                       MR. SIU:  Well, my understanding of what
           are the important perimeters, yes, are here.  And the
           point is to show that these are the major uncertain
           elements feeding into the shift model, which I
           understand work is still ongoing as to the shift model
                       It has a blue band around it, and I don't
           know if that is an indicator, but this is one place
           where work is going on, and that's one of the issues
           that I indicate, and where we are still doing things.
                       But the point is to show that there are
           perimeters feeding in, and there are epistemic
           uncertainties associated with these perimeters, and
           they get fed into the process, to the resistance side
           if you will of the stress strength equation.
                       And on this side, on the driving force,
           you have uncertainties in the flaw density and flaw
           size.  Again, we have characterized these
           distributions already.
                       Of course, you have the thermal hydraulic
           input, pressure and temperature, and you have the
           vessel dimensions that get fed into the stress
           intensity factor calculation, and determine if the
           applied stress is greater than the strength.
                       And this box here shows again the
           recognition that because of the things that are not in
           this model explicitly, you have chosen a model at a
           certain level, and the strength is an aleatory issue,
           and that gets fed into eventually an aleatory
           description of the vessel response to the thermal
           hydraulic scenario, which is the applied stress.
                       In the interest of time, I think I will
           move on.  There is a similar diagram for arrest
           toughness.  Okay.  Only two slides to go.  Key issues. 
           These issues again become apparent as we dig into the
           results.  We finally have a prioritization of results
           that tells us which things to focus on.
                       The success criteria, and how much time is
           available for the operators to perform their actions
           is something that we need to look at very carefully. 
           And more generally how do we quantify the human error
           probabilities, which is -- obviously a consideration
           of uncertainties is an important part of that
           quantification process.
                       And in the thermal hydraulics analysis,
           there is the question of how we are going to deal with
           model uncertainties, especially for the two-phase
           scenarios, and we still have to develop just as a
           mechanical matter the perimeter of distributions, and
           what are the uncertainties for the boundary
                       Probablistic fracture mechanics analysis. 
           We have uncertainties in the fracture toughness and
           the radiation shift.  Again, that is that
           embrittlement model that I talked about, and there are
           significant uncertainties in crack arrest and how you
           model that, that still need to be addressed.
                       I separated the integrated analysis out
           from these three because in some fashion we have been
           focusing so much on the three boxes, and we have not
           talked enough about the integration of those boxes,
           and I am talking about our project, as well as this
                       And this binning is obviously really,
           really important.  It drives a lot of the results.  We
           have to look at that very carefully.  This is one
           where again I suspect we wouldn't be quantifying the
           uncertainties in our binning process, but we would
           have to recognize it is a source of uncertainty.
                       We believe that we are consistently
           treating uncertainties across the different
           disciplines, and we are trying very hard to be 
                       We think we are quantifying most of the
           potentially important source of uncertainties, and
           again we have a rationale for saying that.  So the
           model perimeters, boundary conditions, and submodels. 
           We are addressing those explicitly.
                       Model structure uncertainties associated
           with the system codes, for example.  And as was
           pointed out, maybe these are not important for many of
           the scenarios that we care about, but they are likely
           to be important for some of the scenarios.
                       And I believe at this point that we can
           only treat them qualitatively, but we will see.  We
           recognize that we may need to refine our models,
           depending on the results of experiment sensitivity 
           and perhaps the integrated code word.
                       We will document the approach and we will
           update to the white paper the committee saw earlier. 
           And this was mentioned already, but work is in
           progress, and we are iterating on the initial results.
                       So later when spring comes by, hopefully
           we will have something.  But we indeed can walk
           through a scenario, and what we tried to do today, of
           course, was give you some sense of at least the
           beginning parts of that scenario.
                       We think that the approach for treating
           uncertainties may be useful, and another risk informed
           applications, and certainly it is a model that we are
           going to try out as we start approaching other issues. 
           And with that --
                       MR. LEITCH:  Might this work lead to
           relaxation of some conservatism that is in the
           pressure temperature curves that are in the tech specs
                       MR. MAYFIELD:  That's another possible
           application of this.  We have backed off quite a ways
           there, but that is another possible application of
           this, as well as using this kind of scheme to look at
           relief for the boilers.
                       As the embrittlement trends tend to go up,
           the boilers are being pinched more and more on their
           hydro test temperatures, and the time that it takes
           them to get to those temperatures.  So we think this
           structure may be a good way to look at the
           underpinnings for those pressure temperature and hydro
           test temperature requirements.
                       MR. LEITCH:  I think that some licensees
           have already applied for some relaxation in those
           curves to give them greater operating flexibility.  Is
           the basis for that some of this work?
                       MR. MAYFIELD:  No, it is simply a change
           in the fracture toughness curve.
                       MR. LEITCH:  Okay.
                       MR. MAYFIELD:  We went way from the very
           conservative reference fracture toughness curve, and
           are permitting them to use the initiation fracture
           toughness curve, and that's the big change that was
           made in the ASME code.
                       MR. LEITCH:  Okay.  Thank you.
                       MR. MAYFIELD:  Mr. Chairman, there are two
           points that I would like to make as we close.  We have
           named four plants here, and I would like to emphasize
           with the committee and on the record that we are using
           them because they have kindly volunteered to support
           this effort, and not because we are concerned about
           their integrity from a pressurized thermal shock
                       So they have stepped forward and
           volunteered to help us in this activity.  And finally
           I would note that we welcome the opportunity to come
           before the committee and discuss the pressure vessel
           embrittlement research, and the need for it, and to
           explain to you why Dr. Powers is so completely wrong
           in his assessment.
                       MR. MAYFIELD:  And unless there are any
           other questions, we thank you.
                       DR. POWERS:  I would hope that Dr. Powers
           would get a chance to rebut.
                       CHAIRMAN APOSTOLAKIS:  Dr. Shack, are we
           done with this?
                       DR. SHACK:  We are done with this.
                       CHAIRMAN APOSTOLAKIS:  Well, we finished
           a minute-and-a-half early, which pleases me to no end. 
           Thank you very much, Nathan and Mike.  We will recess
           until 10:35.
                       (Whereupon, a recess was taken at 10:14
           a.m., and the Committee meeting was resumed at 10:34
                       CHAIRMAN APOSTOLAKIS:  We are back in
           session.  The next topic is the Siemens S-RELAP5
           Appendix Case, Small Break LOCA Code.  Dr. Wallace as
           I understand it could not get here on time, but Dr.
           Kress has kindly agreed to lead us through this.  Dr.
                       DR. KRESS:  Thank you.  Dr. Wallace is
           having airplane delay problems, and that's why he is
           not here.  I am sure that he would have wanted to be
                       The purpose of this meeting today is for
           the full committee to review the NRC staff safety
           evaluation report on the Siemens Power Corporation S-
           RELAP5, which is a thermal hydraulic code.
                       The application for its use is for
           Appendix K Small Break LOCA analysis only.  You want
           to keep that in mind, because our review should focus
           on the Appendix K requirements, and not best estimate,
           or those things.
                       We will get a chance later when we come
           back to us for application to have this code be used
           for best estimate for large break LOCA, but that's not
           part of today's meeting.
                       We did have a couple of subcommittee
           meetings, one back in August, and the latest one on
           January 16th and 17th.  We had a real turnout of
           committee members to that.  I think the people there
           were me and Graham Wallis.
                       So what you hear today is -- and we did
           have our consultants there, too, our usual suspects. 
           But what you will hear today is a very abbreviated
           summary of what went on in the subcommittee meeting.
                       So with that -- and we are expected to
           have a letter on this.
                       CHAIRMAN APOSTOLAKIS:  In fact, we have a
                       DR. KRESS:  I think there is a draft.
                       CHAIRMAN APOSTOLAKIS:  There is a draft in
                       DR. KRESS:  So with that, I will turn the
           floor over to Ralph Landry.
                       MR. LANDRY:  Thank you, Dr. Kress.  As Dr.
           Kress said, my name is Ralph Landry.  I was the lead
           on the review of the Siemens S-RELAP5 code, and what
           we would like to do today is present to you the
           results of our review of S-RELAP5.
                       And as Dr. Kress said, S-RELAP5 has been
           submitted by Siemens Power Corporation for application
           to small break LOCA in PWRs, specifically Westinghouse
           and Combustion Engineering Design PWRs, under the
           guidelines of 10 CFR, Part 50, Appendix K.
                       So that a lot of what we did in the review
           is supposed to be along the guidelines of Appendix K
           and the requirements that came out  post-TMI-2
           accident.  But we looked at a lot of depth in this
           code,, a lot more depth than has typically been done
           in small break LOCA analyses code reviews, because we
           knew that the code was coming in again for a large
           break LOCA for a best estimate application.
                       So while we were looking at the code, we
           looked at a lot of depth in it to make sure that we
           understand this thoroughly before we even start the
           next phase of the review.
                       What I would like to do today is cover
           some of the milestones in the application which we
           received and talk about very briefly some of the code
           modifications that have been made.
                       This code is a combination of a group of
           codes that have been approved individually, some
           additional modifications.  This combines the A&F RELAP
           code, which was submitted and approved for small break
           LOCA under Appendix K, which combines that with the
           TOODEE2 HROD model code; the RODEX2 fuel model code,
           and the ICECON containment model code.
                       So that the code that is now running under
           the name of S-RELAP5 is a combination of the codes to
           run as an integrated unit, rather than individual
           codes from which data must be taken and put into the
           next code, that code run, and you can iterate back and
                       But now the codes can talk to each other
           and transfer information at specific time intervals 
           without having to manually take data from one code to
                       I would also like to spend a little time
           talking about t he assessment which is done for this
           code.  The assessment has been done more extensively
           than is required under the guidelines of Appendix K
           and the requirements of NUREG 0737.
                       We would like to talk about some of the
           regulatory requirements and how the regulatory
           requirements for a small break LOCA have been
           satisfied in the code, and the conclusions of the
                       We received the code just a little over a
           year ago.  Now, when the application came in,  Siemens
           understood that the manner in which we conduct code
           reviews today is that we have to have not only the
           documentation for the application, documentation for
           the code, but the code itself.
                       The applicant submitted to us the code in
           a source code form and in a bindery form so that we
           could install both on the computer.  We could build
           the code ourselves and make sure that the code builds
           the same as the code that is being used by the
                       We have test cases that we can run on the
           code, and we have of course all documentation for the
           code.  We requested or sent out a request for
           additional information in December, and we have now
           received the formal response to those requests for
           additional information.
                       That sounds like there is not much time in
           which to review the REIs.  In reality, the way we have
           been conducting code reviews has been to communicate
           to the applicant as we perform the review the concerns
           and issues that we have in our examination of the
                       So that we have communicated our REIs to 
           the applicant throughout the past year.  Then when we
           had all the REIs together, we then sent the REIs
           through the normal signature process, and formally
           asked them in December.
                       We have received draft copies of their
           responses along the way from the applicant, and now
           the applicant has formalized and gone through their QA
           procedure, and is sending their formal response to the
                       So it sounds like there is a big time  lag
           before the REIs, and then suddenly everything comes at
           the end.  In reality, it is not a big time lag,
           because we ask the questions and get answers as we go
           through the review.
                       And we have found in conducting these
           reviews that this is a very efficient way for us to
           conduct a review.  We have prepared a draft safety
           evaluation report that was submitted to the Thermal
           Hydraulic Subcommittee for their review.
                       We have discussed that with the Thermal
           Hydraulic Subcommittee as Dr. Kress pointed out.  We
           have had meetings with the subcommittee, and we talked
           very briefly with them back in March in the context of
           other code reviews.
                       That, yes, we had received the code, and
           yes, we were accepting it for review.  There seemed to
           be sufficient material to allow us to do a formal
                       We met with them in August to go through
           the review plans, and to talk in detail about the
           contents of the code, and then we met with the
           subcommittee again in January, at which point we
           reviewed with them the safety evaluation report, which
           the staff had prepared.
                       And we are meeting today with the full
           committee, and we plan on finalizing the SER after
           this meeting.
                       We will go through and make sure that we
           have covered every concern that we have raised, and
           that we have covered every concern that the
           subcommittee has raised, and the concerns that you may
           raise today.  So that when we issue a final SER, we
           can have all the issues properly closed.
                       Very briefly, some of the modifications
           that have been made to the code.  The code started at
           A&F RELAP, which is a version of RELAP5 MOD2.  You are
           probably all aware that the version that research has
           is RELAP5 MOD3.
                       Siemens started with a MOD2 code, and made
           some changes, such as making the code
           multidimensional, TOODEE2 capable, in the hydraulic 
                       This is used primarily in the areas such
           as the downcomer, where we have been seeing that 1D
           modeling does not seem to be the best way.  That there
           are TOODEE hydraulic effects, and so the applicant has
           modified the code to make it 2D hydraulic capable,
           especially in those areas where 2D effects become
                       There have been changes made in the 
           energy equations.  They have been reformulated to get
           rid of some of the problems that we have seen with
           RELAP5 in the past.
                       One of the problems that we had several
           years ago was a misapplication of the code for
           containment analysis, and that came back to us, and we
           looked at what was being done.
                       And we said, wait a minute, you can't do
           this with RELAP5 because if you go from a very high
           pressure node to a very low pressure node, with a very
           large change in area and volume, the code doesn't
           conserve energy properly, and this is not the intent
           of the code.
                       Well, changes have been made in the way
           the energy equation is formulated in the code so that
           some of those problems are alleviated in this version
           of S-RELAP5.
                       We looked a lot at the numerical solution
           scheme that has been installed in the code.  The
           numerical solution has been changed, and the approach
           to the S-RELAP5 code over the other RELAP5 codes to
           correct some of the numerical problems that create
           numerical instabilities, numerical diffusion, and
           other problems.
                       Those have long been a problem with the
           code.  Sometimes they are created because the code
           developer's intent is to make the code fast running. 
           Well, they make it fast running, but they make the use
           of the code a real art form because if you don't use
           the code exactly right, you can create numerical
                       Some of that has been taken out to make
           the code more robust, and with the recognition that
           you can still have a fast running code today without
           having to use the numerical schemes that make it
                       DR. POWERS:  Instability tends to be a
           self-revealing thing.
                       MR. LANDRY:  Right.
                       DR. POWERS:  I mean, you get a bunch of
           spikes with RELAP.
                       MR. LANDRY:  Right.
                       DR. POWERS:  The other issue of numerical
           diffusion is a little more subtle isn't it?
                       MR. LANDRY:  Yes.
                       DR. POWERS:  Is it possible to tell just
           by routine examination of the results if you are
           getting a numerical diffusion?
                       MR. LANDRY:  A knowledgeable user can.
                       DR. POWERS:  All right.
                       MR. LANDRY:  What Siemens has done is
           improved the numerics and the solution techniques, so
           that it reduces the amount of numerical diffusion, and
           it makes it less of an art so that the user, while
           they still are using knowledgeable users, it becomes
           less of an art, and less sensitive to the user.
                       They have improved the aspect of numerical
                       DR. POWERS:  What I am struggling with is
           when people talk about uncertainty analysis -- and I
           am dealing with an issue somewhat tangential to this
           particular SER -- they sometimes raise the issue of
           the numerical solution itself being a source of
                       And I am wondering is that a major
           uncertainty here?
                       MR. LANDRY:  We don't think it is.  So we
           are going to get into that more when we look at the
           code for the large break application, because that is
           based on an uncertainty analysis.
                       But in the discussions which we have had
           with Siemens' personnel at this stage, it appears to
           us that they have done a lot to take that numerical
           uncertainty out of, or reduce it, in the code.
                       DR. POWERS:  Now, are there things that
           one should worry about other than the numerical
           diffusion and instabilities in these codes as far as
           the solution algorithm itself goes?
                       MR. LANDRY:  There could be if the code is
           used by an unknowledgeable user, because you have to
           make sure that you are not making all the standard
           mistakes that a user would make, violating courant
           limits, and things of that nature.
                       DR. POWERS:  This code lets you know about
           violating courant limits?
                       MR. LANDRY:  Well, codes don't always come
           right out and tell you that.  You have to be
           knowledgeable enough to recognize what the code is
                       DR. SEARLE:  That is where some of the
           instabilities come in.
                       MR. LANDRY:  That is where some of the
           instabilities come in, but a lot of this is in the
           hands of the user also to recognize when the code is
           not behaving --
                       DR. POWERS:  Noding schemes area also a
                       MR. LANDRY:  -- numerically correct, and
           when the result that the code is giving is wrong for
           numerical reasons, and not because of a
           phenomenological reasons.
                       Let's see.  One of the points that we
           looked at was with the heat transfer model.  While the
           vast majority of the correlations that are used in the
           code are directly out of the RELAP5 set of codes, a
           change has been made to incorporate, instead of
           Dittus-Boeter for field boiling and for gas heat
           transfer, another correlation, the Shiralkar-Rouse
           correlation, which has a better representation of
                       It is a newer correlation, and represents
           data that has been checked against
           FLECHT SEASET data, and appears to be a better
           correlation to use.  A very close correlation to
           Dittus-Boeter, but the uncertainty in the data seems
           to be much better.
                       So we feel like that is the kind of
           attitude that we want to see in an applicant that they
           will not just use a correlation because it has been
           used for 35 years, but look at it and say there is a
           better correlation today.
                       And let's try it out, and if it works
           right, and it gives very good answers, and it is
           stable, and it represents data better, let's go to a
           better correlation.
                       DR. SHACK:  Just for my information, where
           does the virtual mass term arise from in here?  Why do
           I get a virtual mass term in the momentum equation?
                       MR. LANDRY:  Gee, I wish Graham Wallace
           was here so he could go into that one.  Let me ask Joe
           Kelly from Siemens if he could respond to that.
                       MR. KELLY:  Joe Kelly from Siemens Power. 
           It comes out in the toofuwood (phonetic) model, and so
           if you have an equation for the relative velocity, it
           comes in the time rate of change and in the relative
           velocity in the phases.
                       So it is the idea of like if you have a
           ball of liquid, or excuse me, a bubble trying to be
           accelerated in a liquid, it has to also accelerate
           some of the liquid around it.
                       MR. LANDRY:  Thanks, Joe.  Joe has been
           dealing a great deal in this discussion with the
           concerns that Dr. Wallace has raised on momentum, and
           so I appreciate his response.
                       Some of the models that have been changed
           to be consistent with the requirements of Appendix K
           include adding the Moody choke flow model.  Power
           current flow limit has been upgraded.
                       DR. KRESS:  We had some discussion about
           that in the subcommittee.  Why do you have a code that
           is configured in such a way that it is basically
           incompatible with something like a Moody model, in the
           sense that the code itself calculates the things that
           create the critical flow as things progress down the
           pipe to the hole?
                       But the Moody model takes boundary
           conditions and calculates the same thing in a
           different way.  Do you recall how that discussion
           turned out?
                       MR. LANDRY:  That discussion came out that
           if all of the conditions were being calculated and fed
           directly into the Moody model, there could be a
           problem.  But the code calculates fluid conditions,
           which then become the boundary conditions for a hard
           line Moody model.
                       And once those conditions are input into
           the Moody model, the Moody model will calculate
           correctly as it is supposed to calculate.
                       DR. KRESS:  So you just calculate the
           boundary conditions?
                       MR. LANDRY:  Right.
                       DR. KRESS:  And where do you stop the
           calculation to decide where the boundary is?
                       MR. LANDRY:  That is in the nodalizing of
           the pipe or --
                       DR. KRESS:  It is the hole in it, the
           nodes of the pipe with the hole in it, you stop there?
                       MR. LANDRY:  Yes, but that has to be in
           the user guideline specifications; that part of the
           sensitivity studies are where to come with the final
           mode before you nodalize for the break itself to see
           that you are getting the right conditions into the
           node for the break.
                       Okay.  They have added to the code EPRA 
           pump data.  They have added, as I said earlier, the
           ICECON code, RODEX2, TOODEE2, and they have changed
           the code architecture, so that even though it is based
           on the RELAP5 MOD2 code, the architecture now matches
           the RELAP5 MOD3 series of codes, the more modern
           architecture, and it is based on FORTRAN 77.
           So they are upgrading into a more modern structure.
                       DR. SEARLE:  I have a couple of questions. 
           Well, one basically.  Is there somewhere in all of
           this that tells us what the limits are on the
           application of this code?
                       MR. LANDRY:  In the submittal, yes.  Th is
           application is for a small break LOCA.
                       DR. SEARLE:  No, no, I am talking about in
           terms of the models that are being used to define
           specific physical phenomena, are there any cautions
           about trying to apply this code in cases where clearly
           you don't have that situation?
                       DR. KRESS:  Are you thinking maybe about
           upgrades?  Is there something --
                       DR. SEARLE:  Well, for example, we know
           that there are a bunch of people running now talking
           about increasing the burn up on fuels.  I think there
           are probably problems with Baker-Just when you go
           above  40K maybe.
                       DR. KRESS:  Yes, I think you're right.
                       DR. SEARLE:  And is there anything that
           cautions you that you may be walking the plank if you
           try to use this in the wrong region?
                       MR. LANDRY:  Well, the documentation
           provides the perimeter range over which the different
           models are reviewed, assessed, and acceptable.  We
           have to rely on user guidelines that they will not use
           the code outside those ranges.
                       And then we do have the option or we have
           the requirement when a calculation comes in to review
           the application of the code to see that it was applied
           and used within the proper range of perimeters for
           each model.
                       DR. SEARLE:  You mentioned user
                       MR. LANDRY:  Yes.
                       DR. SEARLE:  Have you looked at the user
           guidelines to convince yourself that a reasonably
           sensitized user would be able to pick up on any
           problems by looking at those guidelines and thinking
           about what it is that he is trying to apply to them?
                       MR. LANDRY:  Well, the manuals that we
           have seen, we would in our judgment say, yes, the
           reasonable user would understand where the code is to
           be used and where it's not.
                       This code -- I think what you may be
           referring to is other codes which are given out, or
           sold, or distributed throughout the world, and
           throughout the industry, and you don't have the
           control over the user.
                       This code is used solely within the
           corporate structure of Siemens Power.  So that they do
           have through their quality assurance program have the
           control to ensure that the code is used properly, and
           it is not used outside acceptable ranges or applicable
           areas for even things like Baker-Just equation.
                       DR. KRESS:  And we had a concern in the
           subcommittee about default values built in, and they 
           might not properly be used.  But Ralph's answer was
           what set our mind to ease on that, that it is within
           the corporation, and when they get specific
           applications, that is one of the things that they look
                       MR. LANDRY:  Right.  It is not a pure
           black box where the code is used, and just an answer
           is given to us.  We have the responsibility to review
           the way it has been applied also.
                       MR. LEITCH:  I seem to recall some earlier
           versions of RELAP5, when you put in various sizes of
           small break LOCAs, a prediction of peak fuel
           temperatures had some fairly significant
           discontinuities in it, and gave rise to questions
           about the validity of the code.  Does this have that
           same problem?
                       MR. LANDRY:  This I don't believe does,
           because the RODEX2 model has been incorporated in the
                       MR. LEITCH:  Say again?  RODEX2?
                       MR. LANDRY:  Which is the fuel model. The
           fuel model, which Siemens is using in this code, is a
           fuel model which we have reviewed and approved for use
           in the Siemens fuel design work.  We have reviewed
           that pretty heavily, and that is not using the RELAP5
           fuel model now.
                       MR. LEITCH:  Okay.
                       MR. LANDRY:  In talking briefly about the
           code assessment that has been done, the small break
           LOCA assessment cases are pretty well defined   for
           applications.  Post-TMI, the requirement came out in
           NUREG 0737, Section II.K.3.30, of what was required
           for assessment of a small break LOCA code.
                       And there the position of the staff is
           very short, and says that appropriate LOFT and semi-
           scale tests are to be used for assessment of small
           break LOCA.
                       If you go down in the text, it then
           suggests two specific tests; a specific LOFT test, and
           a specific semi-scale test, should be used for the
           assessment purposes.
                       DR. KRESS:  That wa a subject discussed
           also at the subcommittee.
                       MR. LANDRY:  Right.
                       DR. KRESS:  And I remember the flavor of
           the discussion was why is it that we believe that just
           two tests provide sufficient validation for a code for
           Appendix K purposes.  And I don't recall what the
           answer to that was.
                       MR. LANDRY:  Well, those two tests looked
           at two specific problems that came out from the
           calculations that were done for the TMI-2 accident.
                       DR. KRESS:  As I remember, one of them, I
           believe, was the LOFT test.  Basically you could match
           it with just some energy balance, which almost any
           company could do.
                       MR. LANDRY:  Right.  But in assessing the
           S-RELAP5 code, Siemens has gone beyond those two 
           tests that were required.  In fact, they looked at all
           the test data that were available and said these two
           tests are superseded by other tests at a later time.
                       DR. KRESS:  That was the answer.  I
           remember it now.
                       MR. LANDRY:  And would be better tests,
           and tests that would give a more thorough examination
           of the capability of the code.  In fact, the
           assessment was done against a different semi-scale
           test, and a different LOFT test, against the --
                       DR. KRESS:  And that leads me to another
           question.  Do we have a bad rule when we specify just
           those two tests are sufficient to validate a code?
                       You know, it has nothing to do with this 
           Siemens application.  But is this a bad rule that we
                       MR. LANDRY:  Well, I would rather say that
           at the time, and with the data that were available, we
           felt that this was --
                       DR. KRESS:  Well, at the time, that may be
           just about all it was.
                       MR. LANDRY:  -- the best information we
           had for assessing the phenomena that we saw occurring
           in CMI, and that the codes had to predict in
           particular -- well, there are other tests or other
           assessments that have to be done.
                       DR. KRESS:  Does the rule read -- well, it
           may not be in the rules.  It is in the NUREG.
                       MR. LANDRY:  The NUREG says --
                       DR. KRESS:  Does it suggest at least these
                       MR. LANDRY:  Well, I quoted the position
           of the staff in the SER verbatim, and the position
           simply says or concludes with that they have to assess
           against appropriate LOFT and semi-scale tests.
                       In the descriptive material that follows
           that position, it suggests that these two tests  are
           the tests that must be used, L3-1, and S-07-10B.
                       DR. KRESS:  So Siemens could have stopped
           with just those two?
                       MR. LANDRY:  According to those
           requirements, they could have, but they didn't.
                       MR. BOEHUERT:  But it's really up to you
           guys though, isn't it, Ralph?
                       MR. LANDRY:  Yeah.  But they didn't stop
           there.  They went into two different LOFT and semi-
           scale tests, plus 2D flow tests, and UPTF tests, and
           a very recent BETHSY test.
                       But then in looking at the assessment that
           was done, Siemens put together what they called an
           informal PIRT, because Appendix K doesn't require a
                       But they put together an informal PIRT
           that looked at different locations in the reactor
           cooling system, and different phenomena that would
           occur, and how they rank those phenomena, and then
           what test data, what test facilities, what test data
           would best represent the phenomena that they are
           trying to examine.
                       That was then used and the total
           assessment was based on that informal PERT.  So the
           assessment that was performed was not just based on
           the one semi-scale and LOFT test, but it was based on
           these tests, plus all the tests that were done in
           response to their informal PERT.
                       So our conclusion was that they examined
           significant perimeters throughout the range that could
           occur in different components of the system, and
           throughout the different aspects of the small break
                       They have substituted newer tests, which
           are supposedly and should have better data, better
           qualified data, for the older tests.  So they have
           used good tests, better qualified data, and a more
           expanded assessment that is required.
                       DR. POWERS:  A NUREG is not a rule.  It is
           a recommendation.
                       MR. LANDRY:  That is correct.  The only
           caveat that we make is that following the issuance of
           the NUREG and the bulletins and orders, some plants
           may have had put into their licensing basis the
           requirement that they have to analyze these two tests.
                       So that when we get the applications and
           using this code that we would have to make sure that
           if it is in the licensing basis of a particular plant
           that they use S-07-10B and L3-1.
                       That those cases would be analyzed or 
           there would be a change made to their licensing basis
           to use these assessment cases instead.
                       DR. POWERS:  An interesting point.
                       MR. LANDRY:  Now, we have already touched
           on some of the regulatory requirements in a previous
           discussion.  In looking at the application which we
           have received, the modeling requirements of 10 CFR,
           Part 50, Appendix K, which such is Moody critical
           flow, have been incorporated in the code.
                       We believe that the assessment not only
           meets the intent of II.K.3.30, but goes beyond the
           requirements  of II.K.3.30.  A full assessment has
           been done, a very good assessment.
                       Instead of calling it an informal PERT,
           this is a step beyond the requirements of Appendix K.
                       Many sensitivity studies have been put
           into the application, and these are required of all
           licensing basis LOCA codes.  They have looked at a
           range of break size once they determine the worst
                       Then they vary the effect of time step,
           loop seal model, and pump model, radial flow foreign
           coefficient, nodalization, and what they found in all
           of these sensitivity studies after they determined the
           worst break size is that each of these effects is less
           than five degrees on peak clad temperature.
                       So that then comes to the conclusion that,
           yes, they have a converged solution, and the code is
           functioning properly.
                       DR. KRESS:  It also says that peak clad
           temperature is not very sensitive to those things.
                       DR. POWERS:  Why does it show that they
           have got a converged solution?
                       MR. LANDRY:  I'm sorry?
                       DR. POWERS:  Why does it show that they
           have got a converged solution?
                       MR. LANDRY:  Well, in addition to looking
           at the numeric response, it shows that there isn't a
           big variation for any of these perimeters. 
           Altogether, it is not just those perimeter variations.
                       DR. POWERS:  You can't tell from the fact
           that it is only 5 degrees.  You can only tell how the
           iteration approaches that 5 degrees.
                       MR. LANDRY:  Correct.  Correct.  It's not
           just that.  It is everything combined that indicates
           that they are converging
                       DR. POWERS:  All right.
                       MR. LANDRY:  Conclusions that the staff
           has arrived at is that the ANF RELAP code which was
           approved, the RODEX2, TOODEE2, ICECON codes, all of
           which were approved individually by the staff, have
           been combined into an integrated code, an integrated
           package that can perform the entire calculation
           without transferring data manually from code to code.
                       We believe that the code documentation
           supports the modifications made to the ANF RELAP code. 
           We accept the modifications.
                       DR. KRESS:  Let me ask you a question
           about that.  I think in our subcommittee meeting, we
           put it this way.  We expressed some disappointment in
           the status of documentation, in the sense that the
           equations and models that we were presented were
           different than the ones that are in the documentation
           we had.
                       And that some errors in the previous
           equations were still in the documentation.  Is that
           going to be fixed over some time period, or is the
           situation going to be different when they submit for
           the best estimate application, or maybe I should be
           asking this to the Siemens people.  I don't know.
                       MR. LANDRY:  Well, I think Jerry Holm from
           Siemens will address -- would you rather address that
           now or later, Jerry?
                       MR. HOLM:  I can address it right now. 
           There were a number of what were characterized in the
           subcommittee meetings as typos identified in two of
           the documents that we submitted, the models and
           correlations document in the programmer's manual.
                       And in conjunction with supplying the
           response to the request for additional information, we
           went through and tried to identify all the typos in
           those two documents, and we have provided revised
           documents, along with the RAI responses.
                       DR. KRESS:  And those will be the
           documents, plus any MODs that you make, and that you
           will submit for the best estimate analysis?
                       MR. HOLM:  They will be the starting point
           for the best estimate.  There have been some small
           number of additional model changes made for the best
           estimate program, and we will describe those and
           modify those documents.
                       DR. KRESS:  You will get rid of the Moody
           model, for example?
                       MR. HOLM:  It won't be used for the large
           break LOCA, but it will still be in there, because we
           have to use it for small breaks.
                       DR. KRESS:  So it would be an option, I
                       MR. HOLM:  Yes.
                       MR. LANDRY:  Okay.  As was just discussed,
           we point out errors in the course of the review and in
           documentation.  One thing that we would like to
           emphasize is that this has been a very fast review.
                       If you look at the history of reviewing
           computer codes, one year is a fairly quick turnaround
           on a review, and we feel that is primarily because
           Siemens Power Corporation has been very responsive and
           very cooperative during the conduct of this review.
                       When we asked questions, they were very
           quick to work together with us to arrive at an
           acceptable answer.  We feel that their cooperation and
           their willingness to work through any problems that we
           discovered in this review was instrumental in being
           able to conduct a review in such a relatively short
           period of time.
                       DR. KRESS:  I would like to second that
           comment, Ralph.  We found in the subcommittee meeting
           that their ability to answer our questions, and their
           candidness with their responses was actually
           refreshing.  So I agree with you.
                       DR. SEARLE:  Are we going to see some
           actual run results later?
                       DR. KRESS:  Probably not.  Did you plan on
           presenting some results still?
                       MR. LANDRY:  Yes.  In my presentation I
           will show one data  --
                       DR. SEARLE:  Very good.  Thank you.
                       MR. LANDRY:  So the conclusion of the
           staff's review is that we find the S-RELAP5 code
           acceptable for use in satisfying the requirements for
           analysis of the small break LOCA under the
           requirements of 10 CFR, Part 50, Appendix K.
                       DR. KRESS:  That is the major finding
           right there.
                       MR. LANDRY:  That is the import that you
           have to get to.
                       DR. KRESS:  You have to get there, 
           otherwise --
                       MR. LANDRY:  Otherwise, we go back and
           start over.
                       DR. KRESS:  -- you go back and start over,
           yes.  Okay.  I guess now we turn the thing over to
           Jerry Holm, of Siemens.
                       DR. SEARLE:  Jerry, I've got to say this
           logo you have on here with a PWR bird cage, and a BWR
           box, gives me the cold shivers.
                       MR. HOLM:  The topic today will be the
           Siemens PWR Appendix K small break LOCA analysis, and
           this is going to be based on the code S-RELAP5, and my
           name is Jerry Holm, and I am the manager of product
           licensing for Siemens.
                       And I will give a short introduction, and
           then Joe Kelly will give some more detailed
           information about the code and the methodology.  But
           of course we have to keep it to something of an
           overview since we have only got about 45 minutes or
                       Again, I am just going to give about three
           slides for an introduction, and then Joe Kelly will
           talk about the S-RELAP5 code, and the first thing he
           will show is the relationship to the RELAP5 family of
           codes, since RELAP5 itself is extensively used in the
                       We will give a summary of Siemens'
           enhancements, and only a selected few of those that
           Ralph Landry talked about, the ones that we thought
           were most important.  We will give a summary of the
           methodology for the Appendix K LOCA, analysis, and
           then a summary of validation.
                       And we have chosen one of the benchmark
           cases to show some plots from so you can see the
           technical comparisons.  Then I will get up at the end
           and just make a quick conclusion.
                       Okay.  Ralph Landry alluded to the fact
           that we are going to be presenting or submitting to
           the staff a large break LOCA methodology, and what we
           call our realistic large break LOCA methodology using
           S-RELAP5, and that submittal will be later this year.
                       Right now what we have submitted to the
           NRC is the use of S-RELAP5 for small break LOCA, and
           we have also submitted it for non-LOCA methodology. 
           Our future plans are to extend this code to BWR LOCA
           analysis, and long LOCA analysis.
                       And in fact the R&D program for the
           conversion to a BWR LOCA will start later this year
           after we submit the realistic LOCA methodology and 
           the development staff free up to do that work.
                       Our motivation for this is primarily that
           the cost of benchmarking and doing maintenance on
           codes is increasing, and our desire is to choose one
           code to try to maximize the results of our
           benchmarking work, and also to maximize the expertise
           of our staff.
                       It is a lot cheaper for us to do work and
           become experts in one code, rather than six, and that
           is the main purpose.  We have been working on S-RELAP5
           for realistic LOCA methodology for close to 15 years
           now, and it is that extensive effort that led us to
           choose this as the base code.
                       We provided, we think, an extensive amount
           of information to support the staff's review, and we
           have a topical report which describes the methodology
           in the benchmarking.
                       And then in addition to that, we provided
           a significant amount of supporting documentation; our
           models and correlation manual, a programmers guide, an
           input requirements manual.  We provided on a CD-ROM
           the code source and an executable version, and sample
           cases so that the staff could actually run the code.
                       And we have made a presentation to the
           NRC in March of last year, and two presentations to
           the ACRS Thermal-Hydraulic Subcommittee.  And then we
           provided a formal response to the RAIs which we sent
           last Friday.
                       And the main point is that we have tried
           to provide sufficient information to support the use
           of the code for small break LOCA.  With that, I will
           turn it over to Joe Kelly.
                       MR. KELLY:  Okay.  This is the same
           outline slide that you saw just a minute ago with
           Jerry, and I am going to give a very brief overview of
           the history of S-RELAP5 thermal hydraulics code, and
           then talk about the Appendix K methodology for small
           break LOCA.
                       And show one example of the validation,
           and that is the BETHSY test, and it is the
           International Standard Problem Number 27.  Actually,
           Ralph Landry covered this, but I had it in pictorial
           form, and it is the relationship of the S-RELAP5 code
           to the other flavors of RELAP, and also the other
           codes that we have incorporated in it.
                       We started with MOD-2 of the RELAP5 code
           which was developed at the IENL, and we made changes
           to it to perform non-LOCA transients, main stream line
           break, and small break LOCA Appendix K analysis.
                       And this resulted in the ANF-RELAP code
           which had been submitted and approved in several
           different topicals between the years of 1983 and '89. 
           And so this is the code that we have been currently
           been using in our licensing applications.
                       Since that time, RELAP5 Mod 3 was
           developed, and from that we have primarily taken
           upgrades to the code architecture to make it more
           portable.  Again, as Ralph said.
                       Also, there are three stand alone codes;
           RODEX2, which is fuel rod performance, TOODEE2, which
           is a hot rod model accounting for diversion flow due
           to flow blockage; and ICECON, which is a containment
           analysis code.
                       Again, these are stand alone, and they had
           all been submitted and approved individually, and they
           were used in concert with ANF RELAP, and that required
           manual transfer of data from one code to the other.
                       You know, the output of one is input to
           the other, and sometimes it would require an iterative
           process in those two.  So what we have done now is
           build these three codes into what is now history lot
           5, and so the data transfers happen automatically so
           you don't have a staff intervention there.
                       And also so that if it is something like
           the effect of containment pressure on a large break
           LOCA, that is an integral part of the analysis, and
           not something that has to be done off-line, iterating
           between the results of two codes.
                       DR. KRESS:  This may be a little off the
           subject, but how do you validate a hot rod model like
           TOODEE2?  Don't you have to have a full bundle test,
           with an actual and a radial power distribution?  How
           is something like that actually validated?
                       MR. KELLY:  Well, unfortunately, you have
           the wrong person up here to answer that, because my
           experience is more in realistic, and this is more
           Appendix K, and from what little I know of it, what it
           does is that it implements NUREG 0630, and the
           regulations to do with that.
                       DR. KRESS:  Okay.  I understand that. 
           Okay.  But you may need something more when you get to
           the realistic.
                       MR. KELLY:  If on realistic we were going
           to try and take credit for the enhancement in heat
           transfer that you see when you have blockages is a
           drop with shattering, et cetera.
                       And that would be a much longer assessment
           program to validate that, using something like the
           FLECHT-SEASET 163 rod test, but we are not planning to
           try and take credit for that.
                       And then finally there are a number of
           enhancements that Siemens developed, which I will
           briefly show in the next slide.  There are a number of
           enhancements, but they mainly fall into four different
                       They are mass conservation, energy
           conservation, momentum conservation, and the
           constitutive models.
                       In mass conservation, the numerics have
           been improved to minimize mass error during long term
           transients, and I will show something on that in the
           next slide.
                       Energy conservation, again, Ralph
           mentioned this.  We reformulated the energy equation
           to eliminate the problem that would occur when you
           have a flow going across a large pressure drop.
                       It is not important for small break, but
           it is important for large break, having to do with
           energy deposition into the containment.
                       For  momentum conservation, traditional
           RELAP5 uses cross-flow junctions, and in a way to try
           to emulate multi-dimensional, or multi-regional flows
           might be a better way of saying it.
                       What we did instead was implement a 2-D
           component, and is primarily used in either the core or
           the downcomer.  And what had been seen in the past
           with cross-flow junctions was anomalous flow
           recirculations.  The 2-D component eliminates those.
                       Of course, there are hundreds of
           constitutive models in the codes, and a number of
           those have been upgraded, primarily to increase
           accuracy in the large break LOCA application.
                       But there are also modifications to what
           is called a vertical stratification model, which helps
           improve the loop seal clearing prediction.
                       And in talking about long term mass
           conservation, when system thermal hydraulic codes,
           such as TRAC and RELAP5 were first applied to small
           break LOCA back shortly after the TMI, one of the
           primary challenges was long term mass conservation.
                       When you start running these transients
           out to a million time steps, what would happen is that
           the errors in solving the mass equation would
           accumulate over time, such that in effect the code
           would be either creating or destroying mass.
                       And if that fraction became appreciable
           relative to the inventory in the vessel, then there is
           no validity in the calculation whatsoever.  So this is
           an area that Siemens paid some attention to.
                       And so what I am going to show is from
           results from integral assessments and the small break
           LOCA sample problem, which were part of the submittal
           in the topical report.
                       So the three integral tests and the PWR
           sample problem, the transient time for each of the
           tests, the number of time steps, and the mass error,
           and again, this is the error in conserving mass for
           the entire system, normalized with the initial mass
           and expressed in percent.
                       So, for example, if you go to the BETHSY
           test, there were over a million time steps, and the
           cumulative mass error is less that 2/1000ths of 1
           percent.  So that is very good.  So we do not have a
           problem anymore with long term mass conservation.
                       And that is all that I am going to say
           about the code, unless I get questions, and we are
           going to switch to an overview of the methodology.
                       And the first thing to realize is that we
           define a methodology as basically two things.  It is
           the codes that we use, but it is also how we use those
                       And once a topical report has been
           approved that methodology is then encapsulated into an
           analysis guideline.  And then that analysis guideline,
           together with the quality assurance procedure --
           because as Ralph said, all our users are in-house, and
           they are subject to the analysis guideline and a QA
                       So consequently you have the plant model
           nodelization specified, and you ensure that the
           Appendix K conservatisms are correctly applied.  Also,
           there are sometimes additional conservatisms that
           Siemens prescribes.
                       For example, the way that we do loop seal
           modeling for the small break LOCA; and also things
           like the delays in diesel start times.  And these are
           all specified as exactly what you are going to do in
           the analysis guideline.
                       And then because of the QA procedure, the
           analysts are constrained to adhere to those
           guidelines.  So that gets rid of things like the user
           effects that you hear about a lot these days.
                       When you looking at performing small break
           LOCA analysis, you can do a PERT and come up with
           many, many phenomena that appear to be important.  But
           there are really four major factors.
                       The first is, if you will, the transient
           that you are running, for determining the limiting
           single failure; and for most of our plants, this is 
           usually a loss of one diesel generator set.
                       So consequently we are going under the
           assumption of only one high head safety injection
           system being available.  That's what makes the small
           break LOCA something interesting.
                       The next is where you are in the fuel
           cycle, and the limiting condition is normally the end
           of cycle, and the reason for that is that gives you a
           top-skew power profile, so that your high power part
           of the core is in the part of the core that will
           become uncovered.
                       The next is break size, and so we perform
           a break spectrum to determine the limiting condition,
           and that is really looking for a window.  And what the
           window is bounded by are very small breaks, where the
           break flow would be smaller than the capability of the
           safety injection system to  make it up.  So those
           cases don't even uncover.
                       It is bounded on the other side by breaks
           that start getting large enough so that you get a
           fairly rapid depressurization to the accumulator set
           point, which then recovers the core.
                       So what you need is a break that is small
           enough that the flow is -- excuse me, large enough so
           that the flow is greater than the safety injection
           makeup, but small enough that you get a gradual
           depressurization rate so that you have a prolonged
           transient with significant core uncover.
                       And then finally there is how you treat
           loop seal clearing.  The peak clad temperature is
           affected by both which loop is clear and the number of
                       So we have come up with a proposal and a
           methodology for this in order to remove the
           variability that you see between calculations.  I did
           bring backup slides on both the break spectrum and the
           loop seal clearing.  So if there are questions about
           that, I can provide more details.
                       Now, looking at the validation matrix. 
           Actually, there is four of them.  The first is called
           the general matrix, and it is a set of separate
           effects and integral effects tests, and those are
           performed and documented for every code version.
                       Then there is the small break LOCA matrix,
           and again it is both integral and separate effects
           tests, which is what Ralph showed.  And that was part
           of the small break LOCA submittal.
                       Similarly, there is a non-LOCA assessment
           matrix, and those are a set of integral tests which
           were part of the non-LOCA submittal, and for the
           realistic large break LOCA, there is a PIRT based
           matrix that is much more extensive.  You know, in the
           order of more than a hundred tests.
                       And so when we come in with the realistic,
           you will be seeing that, and what that does is that it
           shows not only code applicability of the transient,
           but also how we determine the uncertainties in the
           models so that it can then get propagated through the
           uncertainty analysis.
                       And the small break validation matrix you
           have already seen.  It is one BETHSY test,
           International Standard Problem 27, two-inch LOCA
           break, and this one goes through pretty much all of
           the expected phenomena that you want to see.
                       You know, the natural circulation phrase,
           loop seal clearing, core boil-off, and also recovery.
                       Semi-scale S-UT-8 has core uncover before
           loop seal clearing.  So it is a different kind of
           test.  LOFT LP-SB-03 is basically a core boil-off and
                       UPTF loop seal clearing, this is a
           proprietary test that was run at KWU, and so it is a
           full-scale model of the loop seal.  And so there is a
           separate effects test to examine the clearing process.
                       And then 2-D flow test, and the purpose of
           those was to provide some assessment for our 2-D
                       I am going to show the results of one, and
           this is the BETHSY ISP-27, and it is probably being
           shown for two reasons.  One of those is that it is the
           most comprehensive test, in the sense of going through
           all of the phenomena.  The other one is that it is
           also the best data comparison.
                       BETHSY is a full-height, 1/100 square
           model of a 3-loop RWR.  So as test facilities go, it
           is pretty big.  For example, it is 17 times larger
           than semi-scale.
                       Test 9.1b is a 2 inch break with no high
           head safety injection.  It results in deep core
           uncover and rod heat-up.
                       In the S-RELAP5 assessment, the input 
           model follows our small break LOCA modeling
           guidelines, with a few small changes.  Obviously if
           you are doing an experiment and you want a realistic
           prediction, you don't use ANS, plus 20 percent, for
           the power.
                       You use the actual power that was used in
           the test.  Also, we note from the test results that
           one of the intact loops, and so loop number 2 clears.
                       And so what we have done is apply our loop
           seal modeling methodology, where we bias the broken
           loop and one intact loop to plug.  So then in our
           calculation, we clear loop number 2 just as it was
           done in the test.
                       And that loop seal clearing is something
           that we can talk more about if you would like.  It is
           something that in reality is more statistical, and you
           can't really do it deterministically.
                       And so what we have done is put in a
           biasing methodology to limit the variability and
           ensure a conservative result.  Also, for the critical
           flow model, getting the break flow correctly in a
           small break test, if you want to do a prediction of
           the test, it is very important.
                       And so you can't use Moody here.  So we
           use the more realistic critical flaw model in the
           code.  Similarly, even though I said BETHSY is pretty
           large, it is only about 420 rods, and so it is just
           slightly larger than one 17-by-17 assembly.
                       So using a 2-D component for the core
           didn't make a lot of sense, and we used a 1-D core
           model.  And as I said, we get an excellent comparison
           of both the core collapsed liquid level, and the
           maximum rod temperature.  And that's what I am going
           to show.
                       So this is the core collapsed liquid level
           comparison.  The black line is the data, and the red
           line is the S-RELAP5 prediction.  It says core
           collapsed level in meters.  It is actually core, plus
           a good chunk of the lower plenum, okay?
                       And it's versus time, and the data is done
           by delta-P cell, and so what you are really seeing is
           a delta-P measurement.  And that is what we have
           plotted also for S-RELAP5.
                       This is not a sum of wood fractions, but
           rather it is a pressure difference between replacing
           the lower plenum and the top of the core.  So what you
           are seeing here in the initial part is  the front
           coast down, and that is the frictional pressure drop
           having to do with the flow coasting down.
                       Once you get to this point, the two-phase
           mixture level is in the upper plenum, and the core,
           although two-phase, is completely covered.  That's why
           the collapsed liquid level just sits here constant for
           a while.
                       The little blips in both the data and the
           calculation is the depression and recovery of the core
           level did a loop seal clearing.  Immediately after
           that, the liquid level in the upper plenum has receded
           into the core, and you begin the boil off part of the
                       It is at this point that you have reached
           a pressure, such that the accumulators begin to
           inject.  You recover the core inventory, and the PCT
           location would occur about this point in time.
                       And for the maximum clad temperature, it
           is temperature versus time, and again the black curve
           is the data, and the red curve is S-RELAP5, and as you
           can see, there is a very good prediction of the dryout
           time, and also the peak temperature and the recovery.
                       And there is about a 20 to 25 degree K
           overprediction in the S-RELAP5 calculation, but this
           is considered to be an excellent comparison.
                       DR. KRESS:  Could I see your previous
           curse a minute?  Although it doesn't matter to the
           temperature, what causes the bouncing around to 4,000
                       MR. HOLM:  Well, that is a good question. 
           At this point, the core is two-phase.  It is a liquid
           solid at about this point.  So you have a two-phase
           level in the core, and remember I said that there are
           delta-P measurements, and not just measurements, but
           it is the delta-P in the core.
                       So you are not seeing void fraction
           changes, because this looks like a two meter change in
           level, which would be catastrophic.  But actually it
           is an instantaneous delta-P difference between two
           computational volumes.
                       And what you are seeing is a liquid level
           crossing a cell boundary, and the thing that we
           discussed in the subcommittee about having to
           accelerate the liquid, and it gives you a little bump
           in the momentum equation.
                       And so there is an instantaneous pressure
           spike associated with the level crossing.  So what you
           are probably seeing, because you see so many of them,
           is the level doing this, going back and forth across
           the cell boundary.
                       But the indication of the collapsed level
           is artificial, in the sense that we are not taking two
           meters of water in and out.  So, in summary, the
           proposed Siemens SBLOCA methodology replaces the
           combination of ANF-RELAP and the TOODEE2 code with S-
           RELAP5, thereby streamlining  the analysis.
                       And that is good for us from the
           standpoint of being able to concentrate more
           effectively, but it also makes the reviews easier. 
           And also we have done some work to improve the loop
           seal clearing behavior, and that is the biasing
                       And now I did not show this, but Ralph
           alluded to it as well, and it is in the topical
           report, but the results from the PWR sample problem
           and the sensitivity calculations show that this
           methodology is both convergent and robust.
                       The assessment shows that S-RELAP5 is 
           capable of capturing the important phenomena for
           SDLOCA, specifically loop seal clearing, core boil-
           off, and recovery, with an acceptable level of
                       And therefore the proposed methodology, or
           the proposed use of S-RELAP5 for an Appendix K SDLOCA
           is suitable for licensing.  And then I will give the
           floor back to Jerry Holm.
                       MR. HOLM:  Since I only have one slide, I
           will use this mike if that is okay.  The bottom line
           from our perspective is that the SER provides Siemens
           with the ability to reference the topical report in
           future licensing submittals without further NRC
           review, and that's why we submit topical reports.
                       And the draft SER to be seen has no
           additional conditions or restrictions over and above
           what we have put on the methodology ourselves inside
           the topical report.  So we consider that a very
           successful review from our perspective.
                       Our goal in this meeting is to hopefully
           come out of here with concurrence from the committee
           that the NRC can issue this SER by the end of
           February, and that is our presentation, unless you
           have questions.
                       DR. KRESS:  Do the members have any
           burning questions that they want to ask?  I remind the
           committee that there is under Tab 3 that there is a
           report on the subcommittee meeting, and provided by
           the cognizant engineer.
                       And we also have one of our consultant's
           reports under PINK3, and then we have a draft letter
           that we can look at.
                       DR. SEARLE:  Is the consolidation of these
           cases the aspirations of doing BWR with the same codes
           as you do PWRs with?  Does this suggest that these
           predictions are going to become once again the realm
           of the physics, rather than the realm of the
                       DR. KRESS:  I am not sure I know what you
                       DR. SEARLE:  I am being facetious.  I am
           very happy to see that it does appear that physics is
           being to reemerge in the storm tossed waters of this
           whole process.
                       CHAIRMAN APOSTOLAKIS:  Are we done?
                       DR. KRESS:  Yes, I can refer it back to
                       CHAIRMAN APOSTOLAKIS:  Well, it seems that
           we are doing great today, right?  We are 20 minutes
           ahead of time.
                       DR. KRESS:  We have a skillful chairman.
                       CHAIRMAN APOSTOLAKIS:  Wow, I'm impressed. 
           Yes, sir?
                       DR. POWERS:  Let me point out that I had
           passed out to members a section of the research report
           which involves a pretty categorical disagreement
           between two members in assessing three research
                       And one of those members is being
           vigorously and heavily lobbied, but has not wavered
           one iota in his position.  We will need to have an
           ACRS position.
                       We need to look at that and be prepared at
           least to interrogate the two people on their
           positions, or to establish a run.
                       CHAIRMAN APOSTOLAKIS:  Okay.  By the way,
           are we going to receive the full research report?
                       DR. POWERS:  Undoubtedly at some time. 
           Like since I don't have at least three of the inputs,
           and I am struggling with at least three others.
                       CHAIRMAN APOSTOLAKIS:  But sometime during
           this meeting you mean?
                       DR. POWERS:  I didn't say that.
                       CHAIRMAN APOSTOLAKIS:  That's why I asked
           you.  If you had said it, I would not have asked.
                       CHAIRMAN APOSTOLAKIS:  Okay.  So we will
           recess and reconvene at one o'clock.
                       (Whereupon, the committee recessed at
           11:40 a.m.)
           .                     A-F-T-E-R-N-O-O-N  S-E-S-S-I-O-N
                                                    (1:01 p.m.)
                       CHAIRMAN APOSTOLAKIS:  Okay.  This
           afternoon the first subject is the proposed American
           Nuclear Society Standard on Eternal Events PRA, and we
           have three members of the group that developed the
           standard here, Bob Budnitz, Ravi Ravindra, and  Nilesh
           Chokshi, right?
                       Ravi Ravindra is with EQE, and Dr. Budnitz
           is with Dr. Budnitz.  We all have the draft, and I
           understand that it is not out for public comment yet
           is it?
                       And there will be no transparencies, but
           we will have a short introduction by Dr. Budnitz, and
           then perhaps we can discuss the standard.  So, Bob.
                       MR. BUDNITZ:  I am going to spend what I
           think is less than 10 minutes with an introduction,
           and what I am going to do, because I think it is the
           right thing to do, is to outline for you a half-a-
           dozen technical issues that we face, and some only a
           minute or so about them, so that you will know what we
           think are the important issues that confronted us.
                       And there was some stuff that we did that
           wasn't or we don't think was controversial, although
           you might, and that's fine.  But we are going to at
           least outline to you what we think is the central
           technical challenge that we faced going in and how we
           resolved it.
                       And then you can ask questions, and we
           will be happy to discuss with you whatever.  And just
           to be sure that you understand, there was a five
           member writing group, and the others were Tori Ye from
           Southern California Edison, and Bill Henries from M-
                       But in fact the writers are in front of
           you.  The three of us wrote everything that you see. 
           Those others didn't write anything, although they were
           very important in review.  Nilesh had principal
           responsibility for the seismic hazard part, and Ravi
           Ravindra wrote the seismic peculiars part, the part on
           seismic margins, the part on wind.
                       I wrote all the rest -- the flooding. 
           Ravi and I together wrote the part on how you screen
           other events, and Nilesh was in there working on all
           that stuff, too.  So it was a three-person effort.
                       CHAIRMAN APOSTOLAKIS:  Does ANS have a
           procedure in which --
                       MR. BUDNITZ:  Yes, I am going to say that
           next.  The procedure is as follows. The American
           Nuclear Society has a committee, a risk committee, a
           Risk Informs Standards Consensus Committee, and Paul
           Miko chairs it.
                       It has 24 members on it, and it has been
           in existence a couple of years, and that committee in
           the ANS is the balloting committee.  That committee
           appointed us, and we report to them.
                       The ANS committee recently balloted to
           release this standard for public comment.  There is
           two ballots.  There is a ballot to release public
           comment, and then a few months from now, or a few
           centuries from now, depending on how it goes, they
           will ballot to accept the standard, and then it goes
                       So it was released for public comment on
           January 26th, which was just the other day, 60 days,
           and anybody can get it.  We sent it to you in advance. 
           It was publicly available about the first of the year,
           and we sent it out to a lot of people in the first
           year, but the comment period started on the 26th.
                       And that process will run its course as we
           get public comments and we respond to them.  We
           started this process in the summer of '99.  It was
           about a year-and-a-half, but all of the serious
           writing was done between about the 1st of January a
           year ago and August.
                       We pretty much had this thing wrapped up
           in that 7 or 8 month period, and from August until we
           released it, we held it up for 4 or 5 months because
           we were waiting to watch what happened to the ASME
           standard which were coordinated, and I will say
           something about that next.
                       As I hope you know, the ASME, American
           Society of Mechanical Engineers, outfit has a
           committee on which I serve, which I spent three years
           trying to put together a standard for PRA methodology
           for internal events, accidents that initiate from
           transients and LOCAs, and that's what we mean by
           internal events.
                       And that process after 3 years isn't quite
           done, although it is converging very rapidly now.  I
           am on that committee, and we hope that in another
           couple of months we will have that done, because we
           are now responding to public comments from the draft
           that was issued for public comment in August.
                       We think in another couple of months that
           will be done, and we were waiting to release this for
           that period because the ASME standard had  not settled
                       There were some very important questions
           that were being discussed, which we will come to in a
           minute, which we were hostage to, in the sense that we
           rely on, and we waited.
                       It turned out that that came out in a way
           that didn't effect very much of anything that we had
           written, and so then we released it for public
                       So I am just going to make it real quick
           and short so that we have time for discussion.  I am
           going to talk about the scope.  The scope of our thing
           is earthquakes, wind, flooding.
                       And then a section that I am going to call
           other external events.  They are external to the plan. 
           Fires is not part of this, unless it is a forest fire. 
           But aircraft crash, industrial facilities, and so on.
                       Earthquakes have a separate chapter, and
           winds, and flooding, they have separate chapters.  And
           we have another one on other.  Now, the other has two
           sections.  One is screening, so you can screen
           something like hail storms if you are in Arizona.
                       But if you can't screen it, there is also
           a section on how you analyze it if you can't screen
           it.  And then we also have a separate chapter on
           seismic margins, separate from seismic PRA, and I will
           describe that in a minute.  So that is the scope.
                       Now, a crucial piece of this is that  the
           scope also includes important sections that are this
           long, just a few lines, because we referenced the ASME
           standard by reference.  We say do ASME, and I will
           just describe what they are.
                       For example, the whole system's analysis
           part of PRA, we reference ASME directly.  I mean, we
           weren't going to rewrite how you do a Bayesian update
           of generic data.  ASME does that.  Although we have
           some places where we supplement ASME because we need
                       Like, for example, in HRA, human
           reliability analysis, if you have to do something a
           little different for seismic, we tell them that, but
           the rest of it we reference directly.
                       We reference directly the peer review
           requirements of the ASME, and how you put together a
           peer review team, but we have supplementary guidance
           in there, some requirements about peer review.  For
           example, emphasizing lockdowns, because that is
           something important for us that was not quite so
           emphasized in ASME.
                       We reference the documentation section in
           ASME directly, but we have supplemental requirements
           and documentation, and how you document seismic
           margins, or when, or whatever.
                       And we also reference the application
           section, the crucial section on applications in ASME
           which tells you how you go about doing application
           once you have got a PRA.
                       We also in order to make it seamless with
           ASME, we use the same format.  The ASME has high level
           requirements in a broad area, and then what we call
           sporting requirements, which are the ones that you
           have really got to meet, that are below that and we
           did the same thing.
                       The idea was so that a person who is using
           it together would see the same sort of thing.  But
           crucially we don't have three columns of capability,
           and I will come to that in a minute.
                       We don't have that.  We have one, which
           was intended to be what ASME's column 2 was in the
           first round before they got to three, which is what we
           will call a good quality, state-of-the-art PRA today,
           and that's what we have.  I will talk about that in a
                       And also crucially, for almost every
           requirement, you will see that we wrote a commentary. 
           Sometimes short, and sometimes long.  Sometimes longer
           than the requirement.  ASME doesn't have any of that. 
           We think that is a valuable addition, and you can quiz
           us about that if you want.
                       I mentioned already peer review, and I
           will come back to the three columns in a minute.  We
           wrote a special set of requirements on peer review,
           and Ravi actually wrote them, emphasizing the need for
           walk-downs to make sure that for external events that
           you captured the plant, because plant specificity is
           crucial for these events which damage things in the
                       PSHA.  As you have observed, I'm sure, we
           exclusively endorse the Livermore and EPRI hazard
           studies of the late '80s by saying that if you did one
           of those, you met the standard for probablistic
           seismic hazard analysis.
                       But what we mean by she made the standard
           for 1988, you still have to do an update to make sure
           that no earthquake information has come along since
           then that would invalidate what they did.
                       But we explicitly endorse that, but we
           also have a whole lot of requirements, which if you
           are doing it over, or if you didn't do that or
           whatever, that you have to meet.
                       And those requirements are pretty much
           tailored to the well-known -- and I will say this
           because I was an author, as was our chairman, George
           Apostolakis, of the well-known SSHAC process, the
           senior seismic hazard analysis committee that I served
           on and George did.  I chaired it a few years ago.
                       And which has a process for seismic hazard
           analysis, and we explicitly have based our thing on
           that.  If you are doing it over, or if you hadn't done
           it in IPEEE.  I am just going on with issues, and then
           you can talk later.
                       Fragilities.  Ravi wrote this piece.  The
           seismic fragilities for PRA are the well-known
           standard methods that have been used for some years
           with the fragility curves.
                       But for seismic margins, we explicitly
           reference -- and if you do it, your okay, the CDFM,
           and if it was used in seismic margins, and if you do
           that, that's the acceptable method.
                       Uncertainties.  This is a crucial point. 
           We explicitly incorporate treatment of uncertainties
           in the standard, in the requirements, in the things
           that you have to do.  You can't meet this standard if
           you have not considered uncertainties.
                       The reason that I am saying that is
           because if you don't know, I will tell you, but the
           word uncertainty appears almost nowhere in the ASME
           standard for internal events.
                       I am on that committee, and have been for
           3 years, and I am unhappy with that, but that's the
           way it is.  I am a minority there.  We have done that. 
           We don't see how you can do an external events PRA
           without that.
                       One last topic, and then I will turn it
           over to you, and you can ask questions, or if my
           colleagues want to add something that I went by in
           this introduction, they will tell me.
                       Seismic margins.  As you know, more or
           less half of the nuclear plants in the United States
           did a seismic margin review than a seismic PRA when
           they were satisfying the IPEEE around 6 or 8, or 10
           years ago.
                       And if they did a seismic margin review
           well, they ought to be able to meet the standard that
           we wrote for seismic margin.  And the reason that we
           did that is because if you have done that rather than
           the other, and you meet it, we want to give them the
           benefit of that.
                       Because there are some applications for
           which seismic margin is very well tuned, and they
           ought to be able to say we met it and we can do those
                       By the way, there are many applications
           where seismic margins is not well tuned, and I can
           mention those if you want, or I can them here, or you
           can ask me, and for those, those limitations you can't
           do it.
                       But at least if you did that, then you
           ought to get the benefit of that.  So we have written
           a whole separate section of the standard outlining the
           method of seismic margins, and these are IPEEE
                       And it is well know that those that did
           it, mostly we think did quite well there, and they
           ought to be able to meet the standard, and then there
           are some applications that they can do.  The crucial
           limitations of seismic margins are as follows.
                       Well, I will just say what it is good for,
           for sure.  If I have got some SSC that is very, very
           stout against earthquakes, and the seismic margin
           review has revealed that through the analysis, why
           that information is just as valid as if you did a
           seismic review.
                       And it turns out that there are a lot of
           applications like that, and that is very valuable, and
           they can do that.  On the other hand, if in your
           application you have got some accident sequence in
           which a seismic failure combines with a human error,
           or with some non-seismic unavailability or something,
           seismic margins doesn't do that very well at all.
                       It doesn't capture it well, and the
           analysis isn't structured to do that, and it wasn't
           intended to.  And certainly seismic margins can't
           produce for you a core damage frequency, at least not
           as structured.
                       So those sorts of applications are
           unavailable to some plant that has only a seismic
           margin review.  However, it is our opinion, and when
           we issued this now just for comment, it is our opinion
           that nevertheless those that have a good one that can
           meet it ought to be able to get the benefits of what
           they can do, and that is our motivation.
                       I just have one other thing to say about
           that, and then I am done.  For at least a decade, the
           community of people that play around in this sandbox,
           of which the three of us are among them, have
           struggled with what we could do to provide additional
           guidance, so that if someone with a seismic margin
           review could get more out of it.
                       And the proposal has been around for a
           long time, including a very thoughtful proposal that
           Ravindra came up with with Bob Murray about 10 years
                       Your own staffer, Rich Cherry, ACRS staff,
           five years ago wrote a very useful paper about that. 
           A couple of years ago, Bob Kennedy wrote another one,
           and we finally decided that it was time to do
           something to explore how to do better.
                       And this is relevant to this directly, but
           about a year ago Ravi and I went to the NRC and ANS --
           and Nilesh has got a conflict with this hat on, but
           NRC gave a grant to ANS to fund Ravi and me to do that
                       And Ravi and I have just within the last
           few weeks completed a study and published it, and I
           have it in front of me -- but you don't have it yet,
           although I will send it to you -- whose scope is the
                       We have explored how you could take a good
           quality seismic margin review, and extract more from
           it than you would think.  For example, more risk type
           information, or more CDF type information, by doing in
           some cases directly, or by doing some additional work.
                       And we have written a paper that explores
           the things that you can do with it, and what the
           limitations are.  And that has been published, and
           although it was reviewed by a few people, we are going
           to send it around the community of people, people like
           you, but also the seismic margin side of the community
           and get some feedback from them.
                       Because if what we propose makes sense to
           them, then sometime in the next 6, 8, or 12 months, we
           are going to propose an amendment to this standard, a
           supplement, and in which requirements for that will be
           in there.
                       So that if you can do that, then you can
           use the seismic margin review that you have to get
           more out of it than you now can.  And in order to push
           that along, our final report, which I have in front of
           me, actually has in it proposed draft standard
           language, just like in the requirements that you see.
                       And it is Ravi's and my cut as to what the
           requirements would be, and that if you did them, then
           you could get more out of it, but there are some
                       And I will just end with that, and ask my
           colleagues, Chokshi and Ravindra, whether they want to
           add something that perhaps I went over too quickly,
           and then you get to ask us.  Anything that I didn't
                       Oh, wait, I have left something out.  Very
           important.  When we had what we thought was a
           satisfactory draft, about six months ago, we sent it
           around to 6 or 8 of our peers; peers meaning they
           could have been people like us and been on the
           committee, but the committee was just small.
                       And we got review comments back from most
           of them, which were very helpful for us, in terms that
           we made some changes.  But this was an informal
                       And because mostly what we got back was,
           yeah, you are on the right track, we have a lot of
           confidence that what we are doing here is congruent
           with the larger community.
                       Crucially, we got comments back from Bob
           Kenney, from Leon Reiter, from Alan Cornell, from Bob
           Murray.  EPRI actually funded Greg Hardy to do some
           work, and Bob Kassawara participated in that.
                       So we have before the final, we have those
           comments and feelings, and so we have a feeling like
           I said that that's okay, and then also crucially, John
           Stevenson, another important member of this community,
           was originally going to be a member of the writing
                       And then just as we were starting, he
           dropped off, but has remained sort of an associate
           member right along.  We have sent him everything, and
           he has made comments.  His stuff is here, too.  Okay. 
           I just wanted to be sure that I put that in.
                       And then finally, this work was partially
           supported by the Nuclear Regulatory Commission, who,
           besides that special project that Ravi and I did, the
           NRC gave a grant to ANS to support this, and the
           support by the way paid for staff and so on.
                       But it also paid for things like our
           travel and some administrative expenses.  So I want to
           recognize that Nuclear Regulatory Commission support
           for this effort.
                       CHAIRMAN APOSTOLAKIS:  Thank you, Bob.
                       MR. LEITCH:  My first question I think
           relates to exactly the issue that you were talking
           about, and perhaps it is my lack of understanding
           concerning exactly what a seismic margin assessment
                       I am referring to page 5, the third
           paragraph.  I guess these are all paginated the same
                       MR. BUDNITZ:  I hope so.
                       CHAIRMAN APOSTOLAKIS:  Maybe you can use
           the page numbers at the top.
                       MR. LEITCH:  Yes, that is page 5.
                       MR. BUDNITZ:  By the way, if you could
           also point to the section, like 1.3.2, it will help
                       CHAIRMAN APOSTOLAKIS:  Page 5.
                       MR. LEITCH:  It is the paragraph that
           immediately precedes 1.3.3, and it says throughout the
           standard the phrase, PRA, is used in a generic sense.
                       And then the intent is to include SMA
           methods, as well as PRA methods within the scope of
           the phrase, PRA.  So when we see PRA in this document
           then, as I understand it, it may mean either what we
           normally understand by PRA, or it may mean SMA.
                       And I'm just not sure that I understand
           the distinction between those two.  Could you held me
           with that a little?
                       MR. BUDNITZ:  Sure.  Well, what I meant by
           that paragraph, which I wrote or I suppose I'll say
           we, is that, for example, it says 1.4 to 1.10, and
           when you are talking about peer review or that sort of
           stuff, and we just didn't say PRA or SMA everywhere.
                       But the sections that are explicitly SMA,
           differ.  You pretty much have to sort it out.  Are you
           unclear about what an SMA is and what it does?
                       MR. LEITCH:  Yes.
                       MR. BUDNITZ:  There was an expert panel
           that I chaired in 1984, '85, and '86, although these
           fellows were involved, which invented that method. 
           The purpose of a seismic margin review is to evaluate
           the plant, and ascertain its seismic capacity, defined
           in terms of the way we define fragilities; the
           fragility curve or fragilities.
                       But if you have, say, four components,
           then you have to combine them in the right way, for
           example, and they might even have various other
                       So the purpose of a seismic margin review
           is that you go to your plant and you evaluate its
           capacity.  You don't pay any attention to the hazard. 
           Now, the way it was structured was a little different
           than that.
                       You pick what we call a review level
           earthquake.  In the east, we suggested it, and almost
           everybody picked .3G.  The idea was that it has to be
           higher by a factor than your design basis, which is
           3.1 or .15.
                       But by the way, if you are in Arizona, in
           Palo Verde, with a .25G design, you pick .5 as your
           review in other words.  And you review the plant to
           the review level earthquake, and it has guidance in
           there that tells you how you can screen out using the
           guidance a whole lot of SSCs that clearly are stronger
           than that, and then you have to evaluate the ones that
                       So, for example, you might end up in
           typical power station with only 2 or 3 dozen
           components, SSCs, for which you have to actually do an
                       And for those, it goes further.  You don't
           work out in the seismic margin method that everybody
           uses.  You don't work out the full seismic fragility
           curve.  You develop what we invented and called the
           HCLPFC capacity, the high confidence low property
           failure capacity, which is the capacity which
           literally on a full fragility curve is the capacity in
           which there is a 95 percent confidence that you have
           less than a 5 percent probable of failure.
                       But really it was intended to be the
           capacity at which -- we have a very high confidence
           that this thing wouldn't fail, because you don't
           really believe the tales of these log normals all that
                       And the notion was -- and there is a
           method called the CDFM method, the conservative
           deterministic failure margin method, or else you can
           get it from your fragility curves, for working out the
           HCLPFC capacity of a pump, or a valve, or a wall, or
           a large tank.
                       And what the seismic review margin was or
           did was that it worked out the HCLPFC capacities of
           every one of those SSCs that wasn't screened out, and
           then it combined them to work out the HCLPFC capacity
           of the station by choosing two success paths -- they
           are supposed to be different if they can be -- that
           the operators would use.
                       Say you need this component, and you need
           this component, and you need this component, and you
           need that system, and you need this thing.
           And then we will imagine that they are called success
           paths A and B.
                       And you would work out the HCLPFC capacity
           of the success path A, and the HCLPFC  capacity of
           success path B.  And then the stronger of those was
           the HCLPFC capacity of the plant, because if you used
           that success path, you had high confidence that with
           that HCLPFC capacity that you could shut down, and
           that's how it is done.
                       That is a real tour.  There is a little
           more to it, but that's a quick tour.
                       DR. KRESS:  Somehow on page 18, your
           discussion on the definition of seismic margin doesn't
           reflect very much of what you just said, but still it
           is not a very satisfactory definition.
                       MR. BUDNITZ:  That's fair.
                       DR. SHACK:  There is nothing about margin
           in it.
                       MR. BUDNITZ:  Probably what we should have
           done was just said go to the SMA literature.
                       DR. KRESS:  Or something maybe.
                       MR. RAVINDRA:  Initially, we were thinking
           of writing an appendix, like what we have for the
           seismic PRA, and we were thinking of writing an
           appendix that describes the salient features of the
           SMA method.
                       And we were kind of debating whether such
           an appendix would help the user or not.
                       DR. KRESS:  Well, would that show up in
           your proposed addendum to the thing?
                       MR. BUDNITZ:  No, but we could do that. 
           There is a lot out there that we could probably pull
           together.  We ended up not doing it.  There are 5 or
           6 reports, which taken together, tell you everything
           you want to know about it.
                       CHAIRMAN APOSTOLAKIS:  There is a danger
           here of jumping back and forth.  Why don't we start
           with questions on Chapter 1, called the introduction. 
           Do the members have any questions, which is the first
           10 pages.  Which numbering scheme are we following?
                       Let's go with the printed numbers at the--
                       MR. BUDNITZ:  Well, we can do it by
           section.  If you go to Section 1.9 --
                       CHAIRMAN APOSTOLAKIS:  Well, let's do it
           by chapter, the first 10 pages.  Any questions?  Well,
           I have some.  On page 5 and 6, Section 1.3.3, there is
           a very interesting discussion of LRF, and maybe it is
           just an opportunity to comment on it.
                       You state that some accident sequences
           that are externally seismic initiated, which do not
           contribute to LRF in the internal event analysis, in
           fact now contribute to LRF because you assume there is
           no evacuation, right?
                       MR. BUDNITZ:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And the evacuation
           was the criterion for whether something is early or
                       MR. BUDNITZ:  Or it is impaired or
                       CHAIRMAN APOSTOLAKIS:  And you assume
           there is no evacuation at all?
                       MR. BUDNITZ:  No, we told the analyst to
           figure out what they assume.
                       CHAIRMAN APOSTOLAKIS:  To do what?
                       MR. BUDNITZ:  To work it out.  If
           evacuation is impaired, then you do count for that. 
           We don't say assume no evacuation.
                       CHAIRMAN APOSTOLAKIS:  But that is a
           judgment call isn't it?
                       MR. BUDNITZ:  Absolutely, but that is the
           analyst's job.
                       CHAIRMAN APOSTOLAKIS:  They are not going
           to do any analysis for that and see what buildings
           collapse, and bridges fall down.  They will just make
           a judgment, that the evacuation is really not
           effective against LRF, right?
                       DR. POWERS:  George, I think you could
           -- you know, your consequence code, typically you
           could have quite a range of inputs to the code.
                       CHAIRMAN APOSTOLAKIS:  But they don't do
           that though I don't think.  It is just a judgment on
           the part of the analyst.  You don't run any codes to
           see the impact of evacuation, right?  It is just a
           judgment on your part.
                       MR. BUDNITZ:  Well, just to describe what
           we said.  If this isn't clear, we have to clarify it.
                       CHAIRMAN APOSTOLAKIS:  No, it is clear. 
           I just wanted to --
                       MR. BUDNITZ:  To meet the standard, the
           analyst is not to take the LRF from the internal
           events and swallow it whole.  He may observe that in
           fact protective actions are impeded, and perhaps not
           as effective, or whatever, for a big tornado, let's
                       And the analyst is explicitly told that
           the analyst shall account for that before he
           categorizes alert sequence for LRF or not, depending
           on the event.  Nothing more, but nothing less.
                       CHAIRMAN APOSTOLAKIS:  Very good.
                       MR. RAVINDRA:  I think that after the core
           damage, if the containment systems don't function,
           then you have a question of release; am I right?
                       MR. BUDNITZ:  Sometimes.
                       MR. RAVINDRA:  So because of that, in the
           seismic event, the containment systems are not any
           stronger than the actual core itself.  Therefore, the
           assumption that the containment systems would remain
           after the core damage has occurred may be not really
           true for seismic events.
                       MR. BUDNITZ:  So that is the reason that
           you have to look at that.
                       MR. RAVINDRA:  Yes, that you have to look
           at that.
                       MR. BUDNITZ:  Sure.
                       DR. KRESS:  That is accounted for in the
                       VICE CHAIRMAN BONACA:  Yes, the PRA
           accounts for that.
                       CHAIRMAN APOSTOLAKIS:  That is just a
           definition of LRF.  Look, there was no question.  It's
           just that I like it.
                       DR. KRESS:  We are glad that you pointed
           that out actually.
                       CHAIRMAN APOSTOLAKIS:  On page 7, you
           state what you also told us, that this category was
           consistent during the spirit of category 2 of ASME
           standard.  And I am wondering why the forces that
           forced ASME to have a category one did not apply to
                       MR. RAVINDRA:  Currently, they are at
                       CHAIRMAN APOSTOLAKIS:  They are at work
                       MR. BUDNITZ:  Yes.
                       DR. KRESS:  They are working on it.
                       CHAIRMAN APOSTOLAKIS:  Are they doing any
                       DR. SHACK:  You have a seismic margins
           analysis, which to a certain extent is a category one.
                       MR. BUDNITZ:  There is actually a
           technical thing here.  We don't believe, the three of
           us, that we know how to write a capability category
           three just to start for seismic, or for tornados, or
           for the external hazards.
                       And the reason is because there are
           certain technical things that you have to do that we
           don't do, and we don't know how to do.  A category
           three --
                       CHAIRMAN APOSTOLAKIS:  One is the
           question, not three.
                       MR. BUDNITZ:  How about three?  So we
           don't know how to write three, okay?  We don't know,
           for example, how to capture in a way that you would
           actually like to capture the correlations.  We don't
           know how to do HRA well for post-seismic or post-
           tornado human actions.
                       Those are major things that are pointed
           out there.  There are a whole lot of things.  We don't
           know how to do three.  If somebody came in and said
           they put down a category and claimed it was a category
           three, I would have real trouble trying to agree with
           that unless we had done something that no one has ever
                       And by the way the notion of category
           three in ASME was somebody at least had to have done
           it sometime so we would have an example.  It can't be
           something that is a dream.
                       Now, category one is different, capability
           category one.  The idea of capability category one is
           that you have compromised your peer rate compared to
           the middle column, which is the --  by one of several
                       For example, you might use generic rather
           than plant specific things.  You might be conservative
           rather than realistic.  I don't mean conservative for
           screening, but actually conservative in your analysis. 
           Or you might not have much level of detail.
                       VICE CHAIRMAN BONACA:  But you are
           allowing this in the standard, too.
                       MR. BUDNITZ:  Right.  So we could have
           candidly written another category for that, but
           instead we have allowed it here.  If you do less, why
           is there some stuff that you can't do.  But we didn't
           write a whole column for it.  We could have, but we
                       VICE CHAIRMAN BONACA:  I would just like
           to express a personal opinion.  I was very impressed
           by this standard, for the simple reason that it looked
           like a standard, and the ASME standard, I don't feel
           like it looks like one.
                       And yet you are allowing the kind of
           latitude in the approach in the context of the
           standard, which should be there.  But I felt that it
           was well developed, and by the way, the commentary
           that you have is a key issue, because it allows you to
           pull out all the discussion that I saw in the ASME
           rev. 10, which I think was the one impeding somewhat
           the document.
                       And here it is separated that way, but I
           think that one of the great strengths of this thing is
           that you don't have category one, two, or three.
                       DR. KRESS:  With respect to your one
           category, in your Chapter 6, you strictly endorse the
           ASME, which is Chapter 3 in the ASME.
                       MR. BUDNITZ:  We don't endorse it.  We
           incorporate it by reference.
                       DR. KRESS:  Incorporate it by reference. 
           I'm sorry.
                       MR. BUDNITZ:  But that is an important way
           to say it.
                       DR. KRESS:  That is.  But my question is
           that chapter in the ASME document is cast in terms of
           the three categories.  Is there any conflict between
           yours and that, or can one just assume that you are
           looking at the category two parts?
                       MR. BUDNITZ:  I'm glad you asked that.
                       DR. KRESS:  Okay.
                       MR. BUDNITZ:  I am sure that after the
           ASME process has run its course, but before we
           finalize this finally, because that is probably a few
           months away, we are going to have to rewrite some of
           this to clarify that.
                       But the problem is that the ASME process
           -- I'm part of it and I'm on the committee -- is still
           in the works, and so we are trying to get this thing
           out and gone, and go through the process and get the
           technical stuff right.
                       And later on we are going to have to
           clarify exactly what by reference means, because the
           thing that we referred to when we wrote this -- that
           Chapter 3 is different.  It changed last week, and we
           have another meeting in two weeks and it is going to
           change again.  And sometimes the change is
                       DR. KRESS:  I had that problem trying to
           relate the two, because I don't have the latest one
                       MR. BUDNITZ:  If you think about the
           middle category as a good quality pairing, that's --
                       CHAIRMAN APOSTOLAKIS:  But maybe what Dr.
           Shack said is really the reason why you don't have
           pressure.  You have a screening, you have the SMA,
           which the main idea behind category one was to use a
           quick calculation to rank systems, structures, and
           components, and to do certain things very quickly for
           which those people felt that you didn't need a
           detailed uncertainty analysis.
                       MR. BUDNITZ:  Actually, I don't agree with
           you.  That is only one of the motivations behind the
           capability of one in ASME.  Unfortunately -- and I say
           this now as a member of that team -- some people think
           they can do more with it than that, and that is
           partially true.
                       But I don't think there is an awful lot
           more -- some people think there is a lot more that
           they can do than I can think of.
                       CHAIRMAN APOSTOLAKIS:  Well, that is the
           essence of it.  The idea was to be able to screen
           quickly and identify contributors --
                       MR. BUDNITZ:  Well, some people think the
           idea of it was more than that.  Some people think that
           you can do everything you can do in PRA with that
                       CHAIRMAN APOSTOLAKIS:  No, no, no.  That's
           not reality.
                       MR. BUDNITZ:  I am just exaggerating. 
           Nobody really thinks that.
                       CHAIRMAN APOSTOLAKIS:  Ravi.
                       MR. RAVINDRA:  Now, the chapter on the
           external event screening, if the analyst wants to use
           it, he can treat that as any other external event, and
           decide based on the frequency of the break itself, he
           can screen it out, and based on some bounding
           calculations, he can screen it out.
                       Or he can use the seismic margin approach
           to go a little further to screen out initial
           components and systems.  So this is a continuous
           screening process.  So the method is already there. 
           Now just to reformat it into category one or category
                       We were also waiting for the ASME to
           complete his work, and for the dust to settle down,
           and only then can we do it.
                       CHAIRMAN APOSTOLAKIS:  Okay.  On page 7,
           you say that the ASME, the bottom paragraph -- well,
           first of all, you say that a well executed SMA
           represents a good fit to many of the applications
           contemplated for ASME category one.
                       MR. BUDNITZ:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And then you go on
           and say especially insofar as an SMA generally is well
           suited to the categorization of SSCs according to
           their size and capacity, and to the screening of SSCs
           according to their safety significance.
                       This refers to what you said earlier, Bob,
           with the two parts and so on?
                       MR. BUDNITZ:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. BUDNITZ:  But there are limitations.
                       CHAIRMAN APOSTOLAKIS:  But the
           categorization, you see, that word means something
           about internal event PRA.  You don't mean
           categorization according to some importance measure
           and so on do you?
                       MR. BUDNITZ:  I think it says
           categorization of SSCs according to their capacity.
                       CHAIRMAN APOSTOLAKIS:  And what does that
                       MR. BUDNITZ:  HCLPF above .3G.
                       CHAIRMAN APOSTOLAKIS:  Okay.  That kind of
                       MR. BUDNITZ:  The sort of things that SMA
           does for you.
                       DR. SHACK:  Just coming back in my
           absolutely simple-minded view of these things, as I
           don't know anything about it, it seemed to me that in
           a seismic margin analysis, you have a simple amount of
           -- I mean, you have identified two of the ways that
           you can succeed.  So you have sort of set a bound on
                       MR. BUDNITZ:  Correct.
                       DR. SHACK:  And so to that extent, you
           actually have some PRA like information, but what you
           don't have is a complete set of event trees.  But you
           have picked your two success paths, and so to that
           extent you do have some bounding information.
                       MR. BUDNITZ:  Correct.
                       DR. SHACK:  For example, suppose you
           stupidly forgot about the strongest success path,
           where you had a whole bunch of SSCs  that were
           extremely stout earthquakes, but had no human
           intervention, and it was all automatic, and you knew
           it and so on.
                       You might completely misunderstand your
           seismic capacity.  You might think it is smaller, when
           it is really very strong.
                       MR. BUDNITZ:  Correct.
                       CHAIRMAN APOSTOLAKIS:  Anything else on
           chapter one?
                       (No audible response.)
                       CHAIRMAN APOSTOLAKIS:  Okay.  Chapter 2 is
           definitions.  Any comments?
                       MR. WALLIS:  Well, the seismic margin one
           didn't help me, and then when I looked at Chapter 3.5,
           you launch into methodology without saying what it is
           that you are doing.
                       In seismic fragility, there is a very nice
           definition of Seismic fragility.
                       MR. BUDNITZ:  Point taken.
                       MR. WALLIS:  It is not there for seismic
                       MR. BUDNITZ:  Perhaps Ravi and Nilesh, we
           have to go back and rewrite that appendix on seismic
           margin that we wrote for --
                       VICE CHAIRMAN BONACA:  On the positive
           side, I didn't see any glaring error or mistake.
                       CHAIRMAN APOSTOLAKIS:  Oh, you mean on
           chapter two?
                       VICE CHAIRMAN BONACA:  Yes.
                       CHAIRMAN APOSTOLAKIS:  I have a couple of
           comments on chapter two.  Anybody else wants to go
           ahead of me?  The definitions?
                       DR. KRESS:  The definition of core damage.
                       MR. BUDNITZ:  Oh, wait.  We took that
           straight from ASME.  All the systems stuff, and just
           so you understand, but we were constrained and so we
           decided to make it seamless with the ASME standard
           that we are going to use, and if their definition is
           changing, and it has changed a little bit, we are
           going to incorporate it.
                       Perhaps I need to say that up front.  The
           idea was --
                       DR. KRESS:  That might be helpful.
                       MR. BUDNITZ:  We are doing a low power
           shutdown standard by the way, too.  If all the
           definitions aren't the same, you sure won't be able to
           use them together for applications.  Let me make a
           point to be sure to say that.
                       CHAIRMAN APOSTOLAKIS:  On the same page,
           page 13, the discussion of epistemic uncertainty
           focuses on model uncertainty, but part of epistemic is
           perimeter uncertainty as well.
                       And maybe if you can make that a little
           bit clearer, because the definition seems to focus
           almost exclusively on the modeling assumptions.
                       MR. BUDNITZ:  I don't see that.
                       CHAIRMAN APOSTOLAKIS:  I see it.
                       MR. BUDNITZ:  Okay.  Thank you.
                       CHAIRMAN APOSTOLAKIS:  Anything from the
           members on definitions?  That's it.  Now, Chapter 3 is
           very big.  So maybe we can break it up.  Maybe go and
           include 3.1 and 3.2, and 3.3, first; is that
           reasonable?  Technical requirements, general.  Now,
           which pages are these?
                       It starts from page 20.  Does anybody have
           any comments on that?
                       (No audible response.)
                       CHAIRMAN APOSTOLAKIS:  No?  Okay.  3.4,
           technical requirements.  Yes, let's do the whole 3.4.
                       MR. BUDNITZ:  Oh, by the way, I want to
           make a comment about context here that I think will
           help you.  Having just spent 3 years with the ASME
           team, one of the complexities that the ASME team faced
           and faces in writing its standard is that there are a
           hundred plants out there that have had a PRA, and
           because of twins, there are 60 or 70 PRAs.
                       For many of the sections of internal PSHA,
           the plants use different methods, very different HRA
           methods, very different methods for success criteria,
           and very different methods for this and that.
                       And to try and write a standard that
           captures and enables those with good quality to still
           meet it turned out to be a difficult trick.  And it
           was a big struggle.
                       It is important for you to understand that
           it is our opinion here as writers of this that there
           is far less variability in the way the size of PRAs
           that were done were done and were accomplished.
                       They are mostly similar; the fragilities
           part, the hazard part.  So it was simpler for us.  We
           didn't have to struggle in very many places.  We are
           trying to write a requirement and that we know someone
           had done quality work different ways.  That was good
           luck for us.
                       CHAIRMAN APOSTOLAKIS:  Let's go to page
           24.  I mean, it may be an unfair question, but I think
           we have to see if we can resolve it.  The seismic
           hazard analysis high level requirement, (a), says that
           the frequency of earthquakes shall be based on a site
           specific PSHA that reflects the composite distribution
           of the informed technical community.
                       Now I know where that comes from, but
           somebody who takes this and is innocent in the ways of
           life, how does he make sure that this is a composite
           distribution of the informed technical community?  I
           mean, are you imposing an impossible requirement?
                       MR. CHOKSHI:  I think if you go, in terms
           of how you meet the requirement, it basically says the
           SSHAC approach is one --
                       CHAIRMAN APOSTOLAKIS:  But the whole thing
           rests on experts you choose, right?
                       MR. CHOKSHI:  Yes.
                       CHAIRMAN APOSTOLAKIS:  And how you define
           the community.
                       MR. CHOKSHI:  Yes, but the chart lays out
           the selection of experts, and the process of how you
           go about doing that.
                       CHAIRMAN APOSTOLAKIS:  So that is really
           the intent?
                       MR. CHOKSHI:  Yes.
                       MR. BUDNITZ:  And in fact if you turn to
           the detail a few pages later, it goes to that
                       CHAIRMAN APOSTOLAKIS:  And the same thing
           on the same page, page  24, there are words like
           credible and I wonder.  I mean, that becomes clearer
                       DR. SHACK:  The big difference here is
           their commentary gets a lot of that in, and the high
           level requirements become very concrete --
                       CHAIRMAN APOSTOLAKIS:  When you go to
           their comments.
                       DR. SHACK:  Yes, and their commentary is
           a very strong suggestion, like do it.
                       MR. CHOKSHI:  We were struggling how to
           get some of these ideas across and the commentary was
           a good vehicle to do it.
                       VICE CHAIRMAN BONACA:  It is a good
           commentary, and I agree, but it gives you the written
           path, which is the standard way to do it.
                       DR. SHACK:  It gave you guidance.
                       VICE CHAIRMAN BONACA:  It doesn't say you
           can't do it otherwise.
                       CHAIRMAN APOSTOLAKIS:  I am a little
           confused though.  If you go to page 26, where the
           commentary says existing LNEL and EPRI hazard studies
           and many hazard studies conducted for plant PSHAs also
           meet this overall requirement.
                       Now, are these two studies, studies that
           differ by a factor of 10?
                       MR. BUDNITZ:  It is Livermore '93.
                       CHAIRMAN APOSTOLAKIS:  So it is the
           updated Livermore?
                       MR. BUDNITZ:  Yes.
                       CHAIRMAN APOSTOLAKIS:  So they don't
           differ that much anymore.
                       MR. BUDNITZ:  Except for details.
                       CHAIRMAN APOSTOLAKIS:  All right.  On page
           31, the last note at the bottom of the page, HA-D3,
           somewhere in the middle it says that the
           characterization of ground motion includes an
           epistemic uncertainty in the ground motion model.
                       Have people done that?  Have people
           developed an epistemic uncertainly in the ground
           motion model?
                       MR. RAVINDRA:  For each ground motion --
           well, there are many ground motion models, and so the
           collection of that represents the distribution.
                       CHAIRMAN APOSTOLAKIS:  But who developed
           the distribution?  I mean, I can have five models with
           uncertainties, and as you know, people have been
           arguing about a particular model from Southern
           California and so on.
                       But if I pick one, how do I develop the
           epistemic uncertainty in the model itself given that
           I have the other six models floating around?  Is there
           a methodology that tells me how to do that, or do I
           have to --
                       MR. BUDNITZ:  I understand your point,
           George.  Suppose the word said, "an epistemic
           uncertainty amongst the several ground motion models." 
           Suppose it said that.
                       CHAIRMAN APOSTOLAKIS:  Yes, we need a
           better word.  I am not sure that is the best, because
           that is related to another question that I have
           regarding sensitivity studies.
                       MR. BUDNITZ:  But that is not a small
           point.  In fact --
                       CHAIRMAN APOSTOLAKIS:  It is not a small
           point, no.
                       MR. BUDNITZ:  In fact, if you go with --
           let's say you go with Dave Boore's model.
                       CHAIRMAN APOSTOLAKIS:  Yes, good fellow.
                       MR. BUDNITZ:  Then if you are ignorant
           that Abramson has done a different model, then you may
           not capture this model epistemic uncertainty.
                       CHAIRMAN APOSTOLAKIS:  Exactly.  But if I
           am aware though that Abramson has another model, I
           still don't know how to meet the standard.  You know,
           how do I develop my epistemic uncertainly now, and I
           think that is something that needs elaboration,
           because I don't think we should ask the user of the
           standard to do research.
                       By the way, I am focusing on things that
           I thought required discussion.  I think this is a very
           good standard.
                       MR. BUDNITZ:  Well, George, let's go on
           then.  Just keeping reading, because --
                       MR. RAVINDRA:  In terms of the person
           writing the commentary, I think the civil engineering
           professionals are the first one that came up with that
           concept.  Most of the civil engineering standards and
           building codes come with commentary so that the user
           knows the basis, and not just the requirements.
                       CHAIRMAN APOSTOLAKIS:  Wonderful.  It is
           about time we learned something from you guys.
                       MR. BUDNITZ:  George, let's keep going. 
           The next sentence --
                       CHAIRMAN APOSTOLAKIS:  I read the next
                       MR. BUDNITZ:  But it says that SSHAC gives
           guidance on an acceptable process to be used for
           determination of -- and in fact you and I were
           authors, and that guidance isn't really enough.
                       CHAIRMAN APOSTOLAKIS:  It is not.  I think
           you need to soften a little bit what you are saying
           here, and find a way around it.
                       Now, on page 33 -- and this is something
           that is not unique to the standard, but something that
           bothers me in general, but look at the requirement HA-
           F2, which I think is a reasonable thing to say, but I
           will voice my concern.
                       The PSHA shall include the appropriate
           sensitivity studies, and then you have a commentary,
           which is fine.  It says examples of useful sensitivity
           studies include an evaluation of alternate schemes
           used to assign weights to experts, and so on, and so
                       My problem with sensitivity studies is
           that I don't know what to do with them.  What if some
           combination of these things shows a core damage
           frequency that is way out of this world, or it is
           above the goal?  Now what do I do?
                       I did the sensitivity study, and I am
           above the goal, and everything else that I have done
           shows that I am below the goal.  What good is it?  I
           mean, shouldn't we be through Bayesians assign
           probabilities to all of these things, and include
           them?  I mean, Bob, I don't know what to do with that.
                       MR. BUDNITZ:  Read the sentence.
                       CHAIRMAN APOSTOLAKIS:  I read the
                       MR. BUDNITZ:  It tells you why.  The PSHA
           shall include appropriate sensitivity studies and
           intermediate results.  Why?  To identify factors that
           are important to the site hazard, and that make the
           analysis traceable and reviewable.
                       Now, here is the point.  If you do a
           sensitivity study and find out that Factor 44 is not
           important, then you have learned something.  If you do
           a sensitivity study and find out that Factor 44 is
           important and you didn't include it, you have actually
           erred.  So that is how it is used.
                       CHAIRMAN APOSTOLAKIS:  No, that is not the
           way that I read it.  If I assign different weights to
           individual expert models, or an evaluation of the way
           different experts make different assignments, and I
           find a result that is an order of magnitude greater
           than what I believe is a realistic estimate, I don't
           know what to do with it.
                       What do I do?  Do I report it to the
           regulator, for example?  And what is the regulator
           going to do?  Because you give a realistic
           distribution and they say, well, if I do this gain
           here, I am a factor of 10 higher.
                       MR. CHOKSHI:  I think within the
           sensitivity studies you still have to be realistic. 
           You still have to use realistic assumptions and
                       CHAIRMAN APOSTOLAKIS:  I think this is a
           relic of traditional engineering, where they were not
           doing uncertainly analysis, and let's play with the
           variables a little bit to see what happens.
                       When you do a rigorous uncertainty
           analysis the way you guys demand it, I think you have
           to be very careful with what kinds of sensitivity
           studies you are asking.
                       I mean, I can see saying, you know, maybe
           the distribution has a higher this or that, but it has
           to be constrained.  Otherwise, I can see it getting
           out of hand, and that is not the intent for sure.
                       MR. BUDNITZ:  Look at the note. 
           Sensitivity studies in the intermediate results
           provide important information to reviewers.  And by
           the way, you might also say the analysts, of course.
                       CHAIRMAN APOSTOLAKIS:  Yes.
                       MR. BUDNITZ:  About how some of the key
           assumptions affect the final results of this complex
                       CHAIRMAN APOSTOLAKIS:  Right.
                       MR. BUDNITZ:  It is no more, but it is no
                       CHAIRMAN APOSTOLAKIS:  Bob, let's say I do
           find that I have two key assumptions, and then I
           change things.  I assume something else and the thing
           jumps up.  Am I under a requirement here that says,
           no, you are not going to play that game.
                       If you want this factor to become six, you
           also have to tell me what is the probability that it
           will be come six.  That's where I am going. Otherwise,
           I don't know what to do with it.
                       MR. BUDNITZ:  George, this is a deep
           intellectual challenge.  Let me give you an example,
           all right?
                       CHAIRMAN APOSTOLAKIS:  All you have to do
           is say do I look --
                       MR. BUDNITZ:  No, let me just give you an
           example straight from seismic hazard.  Suppose there
           were five of us at the table, and --
                       CHAIRMAN APOSTOLAKIS:  When in fact you
           are only three.  But go ahead.
                       MR. BUDNITZ:  But suppose there were five
           of us at the table who were ground motion experts, and
           who had different ground motion models, and even
           though they are all different, A, B, C, and D, whether
           you used A, B, C, or D models didn't make much
           difference to the results.
                       But you went to E, and you used hers, or
           his -- it doesn't make a difference -- and it made a
           big difference.  Now you know something.  What you
           know is -- first of all, you know what I just said,
           but you also know that there is the possibility that
           the other four might be wrong, and so then you have
           got to go and inquire.
                       So what you do with it depends on what you
           learn, but we don't tell you to incorporate it in the
           analysis.  It is nothing more than important
           information about how some of the assumptions effect
           the result.
                       CHAIRMAN APOSTOLAKIS:  But you know that
           the paralysis that this --
                       MR. BUDNITZ:  Are you suggesting that we
           should not have done that?  Are you suggesting not to
           do sensitivity analysis?  Are you suggesting not to
           publish intermediate results?
                       CHAIRMAN APOSTOLAKIS:  No, I want you to
           define them better, and tell me what to do if I find
           a situation like that.
                       MR. BUDNITZ:  I can't tell you what a
           decision maker would do.
                       DR. KRESS:  If you are requiring a good
           vigorous uncertainty analysis, what do you need with
           a sensitivity analysis?
                       CHAIRMAN APOSTOLAKIS:  Exactly.
                       DR. KRESS:  I think that is the point.
                       CHAIRMAN APOSTOLAKIS:  And you guys do
           require a vigorous uncertainly analysis.
                       MR. CHOKSHI:  Even if you do a vigorous
           uncertainty analysis in something like hazard, you
           will be making some --
                       CHAIRMAN APOSTOLAKIS:  You can say
           identify what is important.
                       MR. CHOKSHI:  Exactly.
                       CHAIRMAN APOSTOLAKIS:  I think it is time
           that we abandon this.
                       MR. BUDNITZ:  George, you and I both
           understand how difficult it is to deal with the inside
           that you got from this assumption that you made that
           you know is wrong.  I mean, sometimes you can assume
           something that is physically incorrect, and couldn't
                       You say, gee, let's suppose the water has
           density, too, or something.
                       CHAIRMAN APOSTOLAKIS:  It's not always
                       MR. BUDNITZ:  And it is not going to make
           any difference, and if it doesn't make any difference,
           it doesn't.
                       CHAIRMAN APOSTOLAKIS:  But this is
           related, Bob, to the issue of assigning equal weights
           to the experts, I think.  All of these things go
                       MR. BUDNITZ:  It is all related.
                       CHAIRMAN APOSTOLAKIS:  We have to finally
           say, look, this is the probability that I am assigning
           to this, okay?  Whatever that is.  You don't disagree
           with that do you?
                       MR. BUDNITZ:  I am not going to argue
           that.  Let me describe.  In the end, George, there is
           an analyst, a person, or perhaps it is a team.
                       CHAIRMAN APOSTOLAKIS:  Yes.
                       MR. BUDNITZ:  And if they sign the thing
           and say I, we, take professional responsibility for
           what we did, and the sensitivity study showed
           something cockeyed, and we don't believe it.
                       CHAIRMAN APOSTOLAKIS:  Oh, they say we
           don't believe it.
                       MR. BUDNITZ:  No, they might say.  Let's
           assume that, or else they might say, gee, maybe we
           should believe it.  In other words, it comes down to
           professional responsibility doesn't it?
                       CHAIRMAN APOSTOLAKIS:  And eventually
           maybe --
                       MR. BUDNITZ:  Well, he assigns the
           probabilities after it.  If he finds out that it
           doesn't make any difference, then he is not going to
           worry a priori about assigning probabilities to these
           things.  I mean, I look at it as a way of narrowing
           down --
                       DR. KRESS:  You can't really do that
           because in order to do a sensitivity analysis, you
           have to put ranges on these things.  And you are not
           going to just arbitrarily choose those.  You are going
           to choose something that is within the range of
                       CHAIRMAN APOSTOLAKIS:  Exactly.
                       DR. KRESS:  So you do assign some sort of
           probability to it.
                       MR. BUDNITZ:  There is assigned
           probabilities, and there is assigned probabilities.
                       CHAIRMAN APOSTOLAKIS:  I would like to see
           a discussion or part of the commentary here that
           reflects what we just said.
                       MR. BUDNITZ:  That is very helpful.
                       CHAIRMAN APOSTOLAKIS:  That's all I am
                       MR. BUDNITZ:  That is very helpful.
                       CHAIRMAN APOSTOLAKIS:  Page 43.  You
           already talked about it, the HRA thing, and you
           recognize that this aspect can represent an important
           source of uncertainty in the numerical results.
                       You are silent regarding references here,
           where I see in other places that you are more than
           willing to provide references.
                       DR. KRESS:  Does George have a lot of
           references on this?
                       CHAIRMAN APOSTOLAKIS:  No, but for
           example, if --
                       MR. BUDNITZ:  Are you looking at SAB2?
                       CHAIRMAN APOSTOLAKIS:  I am looking at
           SAB2, yes, the very last sentence.
                       MR. BUDNITZ:  The point is well taken. It
           seems to me that we could and should provide some
                       CHAIRMAN APOSTOLAKIS:  Especially if there
           some studies that are particularly related.
                       MR. BUDNITZ:  Absolutely.  It is an
                       CHAIRMAN APOSTOLAKIS:  Any other comments
           on 3.1, .2, .3, from my colleagues?
                       MR. LEITCH:  I have a question about 37.
                       CHAIRMAN APOSTOLAKIS:  Page 37?
                       MR. LEITCH:  Page 37, yes.
                       MR. BUDNITZ:  Can you cite the
           requirement, like SM-A1 or something?
                       CHAIRMAN APOSTOLAKIS:  Yes, we can do
                       MR. BUDNITZ:  It is somehow different from
           yours because of the printer.
                       MR. LEITCH:  This is,
                       CHAIRMAN APOSTOLAKIS:  Introduction to the
           seismic PRA technical requirements.
                       MR. LEITCH:  And it speaks about the
           trimming of certain events and the adding of certain
           events.  And it gives some examples of trimming. 
           Could you help me with an example of adding?
                       MR. BUDNITZ:  Of course, and perhaps we
           can add that.  The internal events PRA model basically
           has in their basic events no structures.  Walls don't
           fail.  But there can be a basic event of wall fails,
           and then of course harm is pump, or piping, for
                       That is an example of where one must
           expand the horizon of the SSCs concerned.  There are
           others, but that's an obvious one.
                       MR. LEITCH:  That helps my understanding
           of it.  Thank you.
                       CHAIRMAN APOSTOLAKIS:  Any other comments
           on technical requirements for systems analysis,
           seismic fragility analysis?  I don't have any, except
           that it seems to me that it would require a specialist
           to do this analysis.  It is not like the internal
                       MR. BUDNITZ:  I would argue that you
           require a specialist to do internal events, too.
                       DR. KRESS:  I was kind of shocked to hear
                       CHAIRMAN APOSTOLAKIS:  Well, what I mean
           is that you can have a systems engineer spending some
           time learning what the fault trees and the event tree,
           and he can develop those and do a decent job.
                       I don't think you can take a systems
           engineer, train them a little bit, and have him do
           this.  This is really a specialist's job.  That is
           what I mean.
                       VICE CHAIRMAN BONACA:  The hazard analysis
           has to be done by specialists.
                       CHAIRMAN APOSTOLAKIS:  Yes, because there
           are so many disciplines that have to come today.  Bob,
           you have been with it for too long,  and you think it
           is trivial.
                       MR. BUDNITZ:  Obviously, unless you know
           how buildings respond to ground motion, you can't do
           the response analysis.  That's a specialty.
                       CHAIRMAN APOSTOLAKIS:  Well, even
           understanding the fragility curve.  So, shall we move
           on?  I don't see -- well, Jack?
                       MR. SIEBER:  I think that one of the
           problems here is that because a lot of confluence have
           fragility associated with them that the event trees
           change.  You end up blocking off success paths as you
           go through.  That has to be by a person more
           knowledgeable than system engineers that I know.
                       MR. BUDNITZ:  The appendix on seismatary
           explicitly tells you that this must be done by a team
           of systems fragilities and so on people interacting,
           and short of that, it won't be successful, and it
           tells you that in plain English.
                       CHAIRMAN APOSTOLAKIS:  Okay.  So we will
           move on to -- I'm sorry.
                       MR. LEITCH:  page 45, and it is
           requirement SAE8.  There is a sentence there that
           puzzles me a little bit.  It says that while this
           standard does not require the analyst to assume an
           unrecoverable loss of off-site power after a large A
           earthquake, the general practice in seismic PRAs has
           been to make such an assumption.
                       That seems a little confusing to me.  Why
           doesn't this standard require that?
                       MR. BUDNITZ:  We permit the analyst to
           argue if a basis can be established for the recovery
           of off-site power after the earthquake.  They have to
           have basis.  So I would just say that it does not
           require the analyst to assume that loss of off-site
           power is unrecoverable.
                       MR. WALLIS:  Isn't this where you need one
           of your little notes that peer review will look over
           this assumption real closely?
                       MR. BUDNITZ:  Well, just to give an
           example, there are some exit sequences that run up to
           120 hours and one might successfully argue that at my
           plant I will recover one of those through some --
           well, we just -- we didn't want to require that
           conservatism if there was a basis, and so we
           explicitly permitted it.
                       MR. LEITCH:  Okay.  I understand.
                       MR. BUDNITZ:  And I am quite sure that is
           the right thing.  You don't want to require something
           that they could argue for.
                       MR. RAVINDRA:  Also, it is a function of
           the size of the earthquake.  If it is a small
           earthquake, you make be able to quickly record some
           off-site power.
                       MR. LEITCH:  This specifically says a
           large earthquake.  But I understand.
                       CHAIRMAN APOSTOLAKIS:  All right.  3.5,
           seismic margining assessment.  We already have a
           comment from Dr. Wallis that he hasn't seen a
           beautiful description of what it is.  Can you guys
           provide a beautiful description of what it is?
                       MR. BUDNITZ:  We said we were going to
           write that appendix that we sort of didn't do yet.
                       CHAIRMAN APOSTOLAKIS:  All right.
                       MR. UHRIG:  I am a little bit confused
           here.  3.5.1 has the feed high level requirements.  If
           you go to the definition of success paths, it talks
           about bringing the plant to a stable hot or cold
           shutdown condition, and maintain it in this condition
           for 72 hours.
                       And then seismic requirement B here is the
           minimum of two diverse success paths, and so two of
           those methods, shall be developed consistent with
           structures and equipment that can be used to bring the
           plant to a safe stable shutdown, and maintain this
           condition for a period of 72 hours following an
           earthquake larger than the RLE, which is the review
           level earthquake.
                       Whereas, it doesn't talk about the review
           level earthquake in the definition of the success
                       MR. BUDNITZ:  Correct.  The success path
           -- you are looking at the definition section, back in
           the definition section?
                       MR. UHRIG:  Yes.
                       DR. POWERS:  Page 65.
                       MR. UHRIG:  Well, that's where the
           requirements are.  The definitions are back about 10
                       MR. BUDNITZ:  No, page 18 says a success
           path is a set of components that can be used to bring
           the path to a stable condition in 72 conditions.
                       DR. POWERS:  Right.
                       MR. BUDNITZ:  Now, this says -- oh, you
           are talking about the hot or cold?  Maybe we need to
           add that.
                       MR. UHRIG:  No, no.
                       MR. BUDNITZ:  This says --
                       MR. UHRIG:  You want two sets of
                       MR. BUDNITZ:  -- this requires.  So that
           defines or requires that you shall develop two of them
           that can do it after an earthquake larger than the
           RLE.  So that is more restrictive, except for the --
                       MR. UHRIG:  It really doesn't define the
           level of earthquake.
                       MR. BUDNITZ:  Correct.  It just tells what
           the path is.
                       MR. WALLIS:  And what is this review level
           earthquake?  It seems to have a pretty wishy-washy --
                       MR. UHRIG:  Well, it is about a factor of
           two greater than your safe shutdown isn't it?
                       CHAIRMAN APOSTOLAKIS:  Let's answer this
                       MR. BUDNITZ:  Nilesh, do you want to
           answer that?
                       CHAIRMAN APOSTOLAKIS:  Let's finish this
           question first
                       MR. UHRIG:  No, I think it is pertinent
           here, but the way I interpret this is that roughly a
           factor of two greater than these safe shutdown
           earthquake is what you are defining as the review
           level earthquake.
                       Certainly at least 50 percent greater; .3
           versus .5, and you have a .5 for the review level, and
           the .3 is your SSE.  Or if you have a .5 as a safe
           shutdown, then what would you say, a .8?
                       MR. BUDNITZ:  Well, of course, we don't
           use it up there, but that's right.  It is specifically
           instructed that the margin method doesn't apply for
           places where the design basis of this earthquake would
           be way above high-G.  It just doesn't.  Go ahead.  You
           are looking at requirement SM-A1 is where it tells you
           about that.
                       CHAIRMAN APOSTOLAKIS:  Page what?
                       MR. BUDNITZ:  SM-A1.  It is sort of page
           66 in my version.  The requirement is that it just has
           to be larger, and then the guidance says more.
                       MR. WALLIS:  But how much larger?  Larger
           by a fraction, or by a factor of two?
                       CHAIRMAN APOSTOLAKIS:  The note tells  you
                       MR. CHOKSHI:  I think the background of
           the matter, and based on similar experiences used in
           nuclear power plants, there has been two level
           earthquakes that have been established, 0.3G, and
           0.5G, and basically they look at those two, because
           that provides a very good level for screening.
                       You can screen a number of margins at
           0.3G, and you can screen fewer at .5G.  So primarily
           in the margin matter it is 0.3G or 0.5G are used if
           anyone wants to know what your design basis was.
                       So if you are at 0.2G, you can still use
           0.3G, but if your design basis was much greater than
           0.3G, most likely you will have to use 0.5G.  So the
           practical is 0.3G and 0.5G dealing with earthquakes.
                       MR. WALLIS:  Is your standard saying that
           you shall use 0.3G and 0.5G?
                       CHAIRMAN APOSTOLAKIS:  No.
                       MR. CHOKSHI:  Well, by reference,
           referencing the matters.  You know, if you go to the
           definition, and if you look at page 17, and in the
           note it refers to that point; that the majority of
           plans in the eastern and midwestern United States held
           reviews of 0.3G, because their design basis is 
           generally lower than 0.3G.
                       And then if you go to the seismic margin
           methods, which are referenced here in the EPRI
           reports, they explicitly talk about 0.3G and 0.5G.
                       MR. BUDNITZ:  But the requirement is only
           that the hourly shall be selected greater than the
           SSE.  That is the only thing that is required.
                       Now, if you select a review level
           earthquake that is 20 percent above your SSE, you
           don't get as much information.
                       MR. WALLIS:  So don't you need more
           guidance about how to select?
                       CHAIRMAN APOSTOLAKIS:  There is a whole
                       MR. WALLIS:  So there is a whole NUREG,
           which I don't have the benefit of.
                       CHAIRMAN APOSTOLAKIS:  There is a whole
                       MR. UHRIG:  The other issue that was
           confusing me here on page 66, and this issue is that
           you have a high level requirement E, which says the
           seismic margin calculations shall be performed for
           critical failure modes in structures, systems, and
           components, such as structure failure modes, et
           cetera, and failure modes again.
                       And then down to requirement G, the
           seismic margin shall be reported based on margins
           calculated for the success paths.  And I am confused
           by the shift in emphasis here.
                       MR. BUDNITZ:  Oh, let me -- let's go to
                       MR. UHRIG:  Require E versus Require G.
                       MR. RAVINDRA:  Do you want me to answer
                       MR. BUDNITZ:  Go ahead.
                       MR. RAVINDRA:  For every component that is
           on the success path, we either screen the component
           out because it has a high capacity, or we make a
           calculation as to the seismic capacity of the
                       Now, the success path is a chain of a
           series of components, and so when you calculate the
           success path capacity, generally you take the lowest 
           of the capacities of the components that appear on the
           success path.
                       MR. BUDNITZ:  The weakest of them.
                       MR. RAVINDRA:  The weakest.
                       DR. SHACK:  The ones looking at a
           component margin is looking at the plant seismic
                       MR. BUDNITZ:  So, you see, G says the
           plant seismic margin shall be reported based on the
           margins calculated for the success paths.  I mean, if
           it is four components -- A, B, C, and D -- and let's
           say that three of them have a HCLPF capacity of 0.1G,
           and one of them has a HCLPF capacity of 0.2G, then
           0.2G is the capacity of the success path because that
           is the weakest link.
                       MR. UHRIG:  Yes.
                       MR. BUDNITZ:  I mean, it is a little more
           complicated than that.  If you do and's and or's, you
           have to take the strongest of the or's, and the
           weakest of the and's.  Maybe I said that backwards.
                       MR. UHRIG:  Is there anything magic about
           72 hours?  Is that when all the after shocks have
                       MR. BUDNITZ:  No.
                       MR. UHRIG:  So is that just an arbitrary
                       MR. BUDNITZ:  No.  It is what the systems
           people have always used.  Nothing more than that.  It
           comes straight from the systems, and not from the
           after shocks.
                       MR. SIEBER:  That's right.
                       CHAIRMAN APOSTOLAKIS:  Anything else?
                       (No audible response.)
                       CHAIRMAN APOSTOLAKIS:  Where are we now? 
           Oh, 3.6 and 3.7., other external events.  Comments  on
                       (No audible response.)
                       CHAIRMAN APOSTOLAKIS:  And 3.8, high
                       VICE CHAIRMAN BONACA:  I thought those
           were very good sections.
                       CHAIRMAN APOSTOLAKIS:  I thought so, too.
                       VICE CHAIRMAN BONACA:  And particularly
           the commentary.  It is so helpful because it gives you
           a lot of reference.  It is almost like hands-on, and
           it is succinct enough.  The other thing is that it
           provides a clear understanding of how you are looking
           missiles and how you are looking for targets.  So it
           is well done.
                       CHAIRMAN APOSTOLAKIS:  Have there been any
           PRAs with high winds?
                       MR. RAVINDRA:  The example is Indian
                       CHAIRMAN APOSTOLAKIS:  High winds?
                       MR. RAVINDRA:  For high winds, yes,
           because there were some structures that were not
           designed for the missile and for the loading, and they
           had the potential to fade and collapse on other
                       And so the high wind was considered as an
           important external event for Indian Point.  There was
           a partial look into some systems that are affected by
           the high winds.
                       But the experience is somewhat limited
           compared to the seismic.  And when it comes to the
           external flooding, the experience is much more
                       MR. BUDNITZ:  There are 3 or 4 external
           flooding PRAs that I happen to know about.
                       CHAIRMAN APOSTOLAKIS:  That dominate?
                       MR. BUDNITZ:  That are important enough
           that they actually carried it through.
                       MR. UHRIG:  Quad Cities?
                       CHAIRMAN APOSTOLAKIS:  No, that was
                       MR. BUDNITZ:  The one I know is the
           Westinghouse plant in Kishko, in Slovenia.  But by the
           way, it is a perfectly good Westinghouse plant.  It
           just happens to be on a river that floods every
           hundred years.
                       And although the dike is big enough, they
           had to do the whole analysis because it wasn't all
           that big.
                       VICE CHAIRMAN BONACA:  And winds with the
           early plants, they really had no screening, and so
           they were very vulnerable.  Adam Neck was a perfect
           example.  It had plenty of missiles and plenty of
           targets.  So it was really a dominant contributor.
                       MR. BUDNITZ:  And ANO did a complete
           flooding analysis right down to the end, and then
           found that it wasn't important, and so it didn't
           matter much.  But they actually did this some years
                       MR. UHRIG:  George, can I go back to one
           quick question here.  In 3.5, you talk about generic
           data.  What is the source of this generic data?  Page
           66.  It says that it must be justified if you use it.
                       There is two or three places in here where
           it refers to generic data, and I just wondered.
                       MR. RAVINDRA:  Over the years, there has
           been a collection of data from sources, either the
           qualification test data, which has gone beyond the
           qualification level for components, and --
                       MR. UHRIG:  Is this coming out of the reg
                       MR. RAVINDRA:  No, this is the sanction
           qualification data.  The industry has collected data
           on the seismic qualification of different kinds of
           components, and that part of the database.
                       Then we have also collected the data on
           the earthquake experience, looking at how the nuclear
           plant type equipment were found in the large real
                       And then there have also been some tests
           conducted by Lawrence Livermore Lab and Sandia, and
           Brookhaven, sponsored by NRC, to do the fragility
           testing.  All that information forms a database that
           is generic, and not specific to any particular
           component in the plant.
                       So if someone wants to use generic data,
           he has to certify that it is really applicable to the
           particular component.
                       MR. UHRIG:  So he has to show that the
           numerical values in his plant are comparable to those
           that are being used there?
                       MR. RAVINDRA:  Yes.
                       MR. BUDNITZ:  Which comes around to saying
           that my compact valve is similar enough to those that
           were tested or observed.
                       CHAIRMAN APOSTOLAKIS:  All right.
                       MR. UHRIG:  Thank you.
                       MR. BUDNITZ:  I mean, that's what it comes
           down to in terms of the engineering.
                       CHAIRMAN APOSTOLAKIS:  All right.  3.9,
           external flooding.
                       DR. KRESS:  Just a general question, and
           not on 3.9, but when you incorporate references to
           acceptable methodologies -- for example, in the high
           winds, you have three or four.
                       Now, the NRC, I don't know how they will
           use this standard, but if they say we want you to use
           this standard for the quality of your PRA, are they
           going to have to go in and study all these references,
           and decide whether or not they really think they are
                       What was the criteria for deciding that
           they were acceptable methodologies?  Was it just the
           expert judgment of you three, which I figure it was. 
           That's probably good enough for me, but I don't know
           if it is good enough for NRC or not.
                       MR. BUDNITZ:  We decided that a particular
           methodology or in some cases an application, go there
           and see what they did, would be acceptable.  And what
           we are seeking is a review of our peer community to
           make sure that they also agree.
                       CHAIRMAN APOSTOLAKIS:  But eventually the
           staff will have to decide whether to adopt this,
                       MR. BUDNITZ:  Whether they also agree.
                       CHAIRMAN APOSTOLAKIS:  And that's when
           this question will come up.
                       DR. KRESS:  I would hate to have to go to
           every one of these and review every method on them.
                       CHAIRMAN APOSTOLAKIS:  They have already
           members who know that.  There is some knowledge within
           the staff.  PRA configuration control.  Fine?
                       DR. SEARLE:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Risk assessment
           application process.
                       DR. KRESS:  That's fine.  They didn't
           reference.  They incorporated by reference the --
                       MR. BUDNITZ:  You skipped right over peer
                       CHAIRMAN APOSTOLAKIS:  I skipped what?
                       MR. BUDNITZ:  The peer review.
                       CHAIRMAN APOSTOLAKIS:  Because it is
           unimportant.  Peer review.
                       VICE CHAIRMAN BONACA:  Here I think you
           are making a reference to the ASME description of
           that, and that is somewhat of a contested issue here.
                       You know, what do you mean by -- I mean,
           you seem to impose additional requirements here just
           because I expect the expertise that you need in
           seismicity, and special exception events is somewhat
           different than the one that you use for the level one.
                       MR. BUDNITZ:  Right, but --
                       VICE CHAIRMAN BONACA:  And so maybe that
           is a moot issue here.
                       MR. BUDNITZ:  But the general requirements
           are taken from ASME by reference.  For example, ASME
           has a section that describes how you pick two of your
           that don't have a conflict of interest, or that type
           of requirement.  That requirement, we just are not
           going to do it over.
                       CHAIRMAN APOSTOLAKIS:  So, application
           process and documentation.  I don't know --
                       DR. KRESS:  You skipped over my section
                       CHAIRMAN APOSTOLAKIS:  No, risk assessment
           and application process?
                       DR. KRESS:  I wanted him to reiterate this
           is incorporated by reference to Chapter 3 of the ASME,
           and go back to it to see if there was any
           incapabilities or any inconsistencies.  I don't know
           what Chapter 3 now looks like in the ASME.
                       And the version that I had, there did seem
           to be some inconsistencies, and so I don't know if
           they will stay or not.
                       MR. BUDNITZ:  The only person around this
           table that knows is I, because I am on the team.
                       DR. KRESS:  Yes.
                       MR. BUDNITZ:  But it is not a secret, and
           I can tell you.  It is very important that you should
           understand that there has been a change in the words,
           which may or may not represent a change in the
           philosophy, but let me describe.
                       When the three columns first came out a
           year-and-a-half ago, they were described as
           application categories.
                       DR. KRESS:  Right.
                       MR. BUDNITZ:  Like somebody thought that
           ISI would be in category one, and core damage
           frequency application is in category two.  Over the
           last 18 months, it has become transparent that that is
           not the right way to think about it, and those three
           columns are now capability categories for the PRA, or
           for elements of the PRA.
                       Now, what that means is that you grade
           your PRA once, just once.  You go find out your
           capability one for this, or capability two for that. 
           Or by the way, in our case, you either meet it or you
                       If you don't meet a piece of this, you can
           still the thing if that piece you don't meet doesn't
                       Now, what Section 3 in ASME does is it
           says, okay, you have an application.  You go to the
           application and you decide which pieces of the PRA you
           need for that application.
                       For example, you may not need the HRA
           piece, or maybe it is at the center of your
           application.  So you decide which piece, and then you
           decide whether or not for your application that you
           need capability two or capability one, or capability
           three, although I kind of think it will always be two,
           but let's not argue, except for screening.
                       And then you go to the PRA, and see what
           you have got.  If you need capability two for the
           application that you have got, and everything that
           needs it is two, then you are home.
                       If you need capability two, HRA, and you
           have a capability one, then you can't do it.  You have
           to either upgrade it or do something else.  So that's
           exactly what it is, and this is just the same.
                       DR. KRESS:  Okay.  It sounds like they are
           consistent now.
                       MR. BUDNITZ:  Now, here, what you do is
           that since we don't have three categories, you are
           going to decide whether you need -- for example,
           suppose in the application you don't need the hazard,
           because the only thing you are worrying about is the
           capacity of a large pump.
                       Then if you meet the standard for the
           fragility's part, then you can use it, even if you
           don't meet the standard for the hazard part.  It is
           just as simple as that, and I think it is pretty
                       CHAIRMAN APOSTOLAKIS:  Does the industry
           certification process include external events?
                       MR. BUDNITZ:  No.
                       CHAIRMAN APOSTOLAKIS:  And do they plan to
           use this?
                       MR. BUDNITZ:  No, they have made an
           informal commitment, and it is not in writing, but
           they have said the words; that they will add to the
           certification process review requirements that cover
           this topic, and also low power shutdown when it comes
           along, and also fire when it comes along, so that they
           would have the same scope in the end.
                       CHAIRMAN APOSTOLAKIS:  Okay.
                       MR. WALLIS:  And what about the Section 7
           documentation?  I found the small print part, the
           note, useful, and it deserves bigger print.  And we
           might even borrow some of your remarks, speaking about
           documentation for other purposes, such as thermal
                       CHAIRMAN APOSTOLAKIS:  Are you allowing us
           to do this?
                       MR. BUDNITZ:  I don't run anything, but it
           is my view that if you cite any American National
           Standard, as is in anything else, you can do anything
           that you want with it.  It is a public document, and
           you just have to reference where it came from.
                       MR. WALLIS:  We have a bit of a struggle
           with documentation requirements in other fields, and
           not just in this one, and we find that a surprising
           reluctance on the part of the originators of documents
           to make sure that they are right, and it is
                       DR. SEARLE:  One is moved to wonder
           whether or not the clientele that will use this
           standard is any more competent in reading these words
           than these other people have been decoding similar
                       DR. KRESS:  I don't think this needs much
           decoding.  It is pretty clear.
                       CHAIRMAN APOSTOLAKIS:  Okay.  We have two
           minutes.  Does anyone have a comment that is of great
                       DR. KRESS:  I think they did a good job.
                       MR. WALLIS:  They did a good job.
                       CHAIRMAN APOSTOLAKIS:  It is a good job,
           but that is not of great significance.
                       DR. KRESS:  For this committee, that is.
                       DR. SEARLE:  It is, and actually, George,
           I was surprised.
                       CHAIRMAN APOSTOLAKIS:  Okay.  We don't
           even have two minutes because NEI wants to say a few
           words.  Bob, real quick.
                       MR. BUDNITZ:  I need 10 seconds.  I just
           turned to page 109 as I was turning through.
                       CHAIRMAN APOSTOLAKIS:  And you have a
                       MR. BUDNITZ:  And in the middle of the
           page is two references to Bernard, et al.
                       CHAIRMAN APOSTOLAKIS:  Two references to
                       MR. BUDNITZ:  Bernard, et al, and I want
           to tell you that Don Bernard died a month ago, and I
           miss him, and I just want to say that I miss him.  He
           was a terrific guy, and this field we are in is richer
           for his work, and I just wanted to say that for 10
           seconds, okay?
                       CHAIRMAN APOSTOLAKIS:  Thank you.  Okay. 
           Mr. Heymer.  Do you want to come sit up front, or --
                       MR. HEYMER:  I will just make comments
           here, George, and it will be very quick.  My name is
           Adrian Heymer, and I am project manager at NEI with
           the Reg Reform Group.
                       The reason why I am here and some of the
           other people aren't is because they are out of town. 
           The standard has only been out for a couple of days,
           and we have got some preliminary feedback.  We did
           call some people when it came out.
                       We have had some feedback from EPRI,
           preliminary feedback, and preliminary feedback from a
           couple of the other groups.
                       And that feedback which came in this
           morning by a telephone call -- and as I sat here
           listening to the presentation, I just wondered if we
           were looking at the same documents.
                       And it may be because when you do a quick
           read, you read from the dark side and think the worst,
           and have not had time to digest it.  But the gut feel,
           or at least the initial feel from the industry that
           have looked at it is that for reasons best known to
           themselves, I guess, judging by the discussions that
           have gone on, they feel they are precluded from using
           seismic margins approach.
                       DR. SEARLE:  By this?
                       MR. HEYMER:  Yes.
                       CHAIRMAN APOSTOLAKIS:  Why?
                       MR. HEYMER:  They just -- the comment I
           got back is that we have invested a lot of time and
           effort in seismic margins, and we failed to use this
           in a risk informed approach, and we would have to go
           to a seismic PRA.
                       So that is -- and I think that may be a
           process of the way that they have read it, and how
           they think they might have to apply it.  But I think
           that might need some interaction, and we will provide
           you some comments on that as we will, and there will
           be some interaction on that as we go.
                       CHAIRMAN APOSTOLAKIS:  Thank you.
                       MR. BUDNITZ:  Just to say, about 50 plants
           did a seismic margin review using the EPRI method.  We
           wrote these requirements to track the EPRI method.  It
           is our judgment without knowing in detail that most of
           the plants that use the EPRI method will be able to
           show that they meet the standard.
                       Now, you don't go any further than that.
           If they have a competent margin review, it is our
           opinion that we have written the standards so that
           they will meet it.
                       Now, once they have met the standard, if
           they can't use it, that's not a fault of our having
           written the standard to tell them what they did, and
           to check it right, I think.  In other words, I don't
           quite understand the match here.
                       MR. HEYMER:  Well, you will have to take
           the comment in the sense of people are reading it for
           a couple of days, and they need to think about it, and
           sit down, and produce some comments, and there is
           going to be some industry iteration.
                       Because it was also interesting to note
           that the same people that made that comment said now
           what would really be good in this standard is if we
           had some additional guidance to take the seismic
           margins approach further.
                       And that's what I heard you were going to
           do anyway.  So I encourage you to work on that and
           incorporate in the standard if you can.
                       MR. RAVINDRA:  Can I add one thing to
                       MR. HEYMER:  Yes.
                       MR. RAVINDRA:  This committee has a
           subcommittee that endorsed our earlier draft of the
                       CHAIRMAN APOSTOLAKIS:  I think Adrian made
           the point.  Thank you.
                       MR. HEYMER:  There was a comment on the
           uniform hazards spectra, and there was a feeling that
           you are asking us to reevaluate that, and verify it,
           and there was significant effort and resources
           expended in doing that some time ago.
                       And it wasn't clear to the people who were
           reading it why we have to go back and reassess that.
                       MR. CHOKSHI:  I also got an informal
           feedback on that point, and all it needs is a little
           bit more guidance and explanation.
                       MR. HEYMER:  I think some of the other
           points that have been mentioned here have been good. 
           I think on the plus side, I think the commentary
           section, I think if you expand on that, a lot of
           people found that very useful and a very good
                       And there was a lot of positive comment in
           that regard.  And I guess if we are saying that we are
           going to allow seismic margins, or at least not to
           cover seismic margins in the standard.  And there is
           also going to be a section in there on the seismic
                       Perhaps we need some insights or some
           screening criteria of when one would be appropriate,
           and when you should move to a seismic PRA.  And that's
           about it with regards to the extent of the comments.
                       CHAIRMAN APOSTOLAKIS:  Thank you, Adrian.
                       MR. BUDNITZ:  Thank you.
                       CHAIRMAN APOSTOLAKIS:  Thank you,
           gentlemen, very much.  This has been very enlightening
           and useful, and very friendly.  You did a great job.
                       MR. BUDNITZ:  Can I ask one further
                       CHAIRMAN APOSTOLAKIS:  Yes.
                       MR. BUDNITZ:  I have no idea what to
           expect.  Are you going to consider writing a letter?
                       CHAIRMAN APOSTOLAKIS:  Yes, we will
           consider writing a letter.
                       MR. BUDNITZ:  Thank you.  I just didn't
                       CHAIRMAN APOSTOLAKIS:  We will recess
           until 2:50.
                       (Whereupon, the committee hearing 
           recessed at 2:33 p.m., and was resumed at 2:50 p.m.)
                       CHAIRMAN APOSTOLAKIS:  Okay.  The next
           issue is Reprioritization of Generic Safety Issue 152,
           Design Basis for Valves that Might be Subjected to
           Significant Blowdown Loads.  Mr. Leitch is our leader
           on this.  Graham.
                       MR. LEITCH:  Dr. Apostolakis, the purpose
           of this session is to hear a presentation from the NRC
           staff regarding the proposed resolution of generic
           safety issue 152.
                       And that issue is the design basis for
           valves that might be subjected to significant blowdown
           loads.  It is of particular interest for HPCI and
           RCIC, and reactor water cleanout valves on boiling
           water reactors.
                       And the concern was that while the valves
           might meet the NRC approved design basis, the design
           basis might not address the need for the valves to
           close against the differential pressure resulting from
           a large sized high energy pipe break.
                       So with those words of introduction, I
           will turn it over to Mr. Michael Mayfield, who will
           introduce the staff's presentation on this topic.
                       MR. MAYFIELD:  Thank you.  I am here this
           afternoon, and Ken Karwoski, who has recently joined
           my division, is going to make the presentation.
                       He is supported this afternoon by Sher
           Bhatar, the Chief of the Engineering Research
           Applications Branch, and Tom Scarborough from NRR.
                       So we are here to talk about the closeout,
           and not just  reprioritization of this generic safety
           issue.  So with that, Ken, why don't you go ahead.
                       MR. KARWOSKI:  Good afternoon.  My name is
           Ken Karwoski, and I will be discussing the staff's
           basis for proposing the closeout of generic safety
           issue 152 and seek ACRS endorsement on this proposal.
                       Generic safety issue 152 was raised by the
           ACRS back in the 1989 time frame, and as a result of
           its review of the staff activities related to generic
           safety issue 87, which had to do with the failure of
           the high pressure coolant injection isolation valves
           to close following a postulated pipe break.
                       GSI-87 is closed and it was closed in-part
           as a result of industry activities in response to
           Generic Letter 89-10 and its supplements, and in
           particular Supplement 3 to Generic Letter 89-10.
                       Generic Letter 89-10 focused on the
           ability of valves to function as designed.  What the
           ACRS was concerned about though was the adequacy of
           that design, were those valves capable of closing
           following a postulated high energy line break.
                       In order to understand the staff's basis
           for closing out generic safety issue 152, I would like
           to spend a few minutes on Generic Letter 89-10.  In
           the mid-to-late '80s, the Office of Research did some
           testing on motor operated valves and identified a
           number of valve performance weaknesses.
                       As a result of that, they issued Generic
           Letter 89-10, and once again focusing on the ability
           of the valves to function as designed.
                       However, as part of that, licensees had to
           resurrect what the design basis for these valves were,
           and how to dig out the information to say what are
           these valves, or how are these valves supposed to
           operate, and under what conditions.
                       After the research testing results became
           available, the industry also did some additional
           testings on motor operated valves.  They confirmed a
           lot of the problems that were identified in the
           research sponsored tests, and as a result of that,
           they started to develop working groups and users
                       And there currently is still a joint
           owners group addressing valve issues, not only motor
           operated valves, but air operated valves.  Generic
           Letter 89-10 had seven supplements, and those
           supplements were -- the first one was issued in '89,
           and the last one in 1996.
                       Although Generic Letter 89-10 focused on
           the ability of the valves to operate as designed, the
           capabilities of the valves, that is, the actual design
           basis of the valves, was captured as a result of
           industry activities.
                       And the adequacy of the design was
           confirmed in part based on NRC inspections performed
           in response to  89-10, and confirmed through review 
           of various documents, including the inspection
           reports, FSARs, and other licensee and NRC documents.
                       The NRC inspections did evaluate the
           reasonableness of the design pressures.  If there
           looked like there was an indication where the valves
           were not designed to a full differential pressure,
           some of those issues were flagged to ONRR.
                       One of the examples that we provided in
           our write-up was Big Rock Point, where the valves were
           not designed for a full differential pressure, and
           ONRR subsequently evaluated those exceptions on a
           case-by-case basis and determined that in the case of
           Big Rock Point that even though the valves were not
           designed for that condition, it was acceptable from a
           safety standpoint.
                       Priority focus of many of the early
           inspections in response to Generic Letter 89-10 were
           the more risk significant valves of HPCI, RCIC and
           reactive water cleanup.
                       Although the inspections focused on those,
           the lessons learned from the inspections applied to
           all motor operated valves, and in some cases applied
           to other valve types.
                       The staff briefed the ARCS numerous times
           in the 1990s regarding motor operated valves.  In
           particular, in October of '93, the staff briefed the
           ARCS subcommittee on mechanical components, and at
           that time the chairman of the subcommittee, who
           happened to be the individual that raised the concern,
           indicated that he believed that the issue  had been
           addressed and would recommend closure to that.
                       Subsequent to that, research confirmed
           many of the results and analysis presented to the ACRS
           at that time, and we confirmed basically that the
           actions taken by the licensees and by the industry in
           general, that we believed that there was sufficient
           evidence to close Generic Safety Issue 152.
                       And that concludes my presentation.  If
           there are any questions, I will be glad to try to
           address them.
                       MR. LEITCH:  So the reason for our
           confidence then is that Supplement 3 to Generic Letter
           89-10 basically focused the industry's attention in
           this area.  The industry did get the message, and
           investigated these valves and corrected them, if
                       And that was all backed up by NRC
           inspection activities?
                       MR. KARWOSKI:  Yes.  Basically, although
           89-10 focused on the adequacy or the capability of the
           valves to function as designed, the industry took the
           initiative on their own, and in some cases upgraded
           the design of some of these valves.
                       So we are confident that those valves are
           capable of operating under a postulated pipe break
           event.  And the industry has and continues to take an
           initiative in MOVs.
                       There is a periodic valve verification
           program currently underway.  So they have taken those
           lessons, and they continue to apply them, and as they
           identify weaknesses, they improve their programs.
                       MR. WALLIS:  Can I ask you about the
           distinction between design and performance?  I mean,
           you have used the word design a lot.  And they may
           well be designed to do something.  Do they actually do
                       I mean, if they were tested against the
           full differential pressure several times, did they
           still work?
                       MR. KARWOSKI:  In the early days, I think
           the early testing indicated that, no, they wouldn't
           work under those conditions.  As a result of 89-10 and
           the work done in response to that, that is where the
           licensee said, okay, here is the pressure that I need
           to operate against.  Do they operate.
                       And that's where -- and so that is the
           performance aspect, and that is what the whole purpose
           of the 89-10 program was; is do they function as they
           were designed.
                       MR. SIEBER:  Yeah, but they were relied on
           testable prototypes, as opposed to valves in a plant,
           in order to establish the relationship between design
           and actual performance; is that not correct?
                       For example, there was an industry
           program, and they did it in some steam plant
           someplace, a coal plant, where they tested prototype
           valves of various types in order to see whether the
           valve would lock up under these high DPs and high
           flows, or how much force it took in order to move the
                       And a lot of utilities found that the
           motors were too small, or the gear trains were wrong. 
           And then when they changed the gear train, it was too
           slow to perform the isolation in the time frame called
           for by the safety analysis.
                       Or if they changed the motor and didn't
           change the valve, the motor was so strong that it
           would drive the valve disk through the bottom of the
                       Or you would overheat the wiring to it,
           and so this was not without a lot of problems.  I
           presume that in the inspection process that every BWR
           was evaluated as to whether they did in fact determine
           what the design conditions were, and did it have an
           appropriate prototype test to say that their valve was
           good or not good.
                       And did either leave things as is, or
           change gear trains, motor operators, or the valves
           themselves.  But that's what I gathered from the
           inspection material that I reviewed.  Is that correct?
                       MR. KARWOSKI:  Tom Scarborough may be able
           to add more, but the inspection did look at the
           reasonableness of the design and focused on valve
           factors and whether or not the licensees were
           implementing the latest lessons learned.
                       With respect to the actual testing of the
           valves, I know that there were some concerns expressed
           by licensees regarding the reasonableness to test all
           the motor operated valves under postulated pipe break
                       And so in some cases there may be
           groupings of valves, where they tried to group valves
           in order to limit the amount of testing based on the
           limitations in the plant.  But Tom may be able to add
                       MR. SCARBOROUGH:  Yes.  This is Tom
           Scarborough.  One of the things that you mentioned,
           that earlier program on the prototypes.  Once they got
           89-10, they realized that they needed a better way of
           learning more about blowdown flow conditions.
                       And the Electric Power Research Institute
           established that multi-million dollar program to do a
           number of blowdown tests and develop a first
           principle's model to look for blowdown performance.
                       And they found that there were critical
           perimeters of the sharpness of the edges, internal
           edges, and the clearances, in part in running the
                       And so what happened, especially for the
           HPCI, RCIC, a lot of licensees ended up running the
           EPRI model, and determining if they had any concerns
           regarding performance under blowdown conditions.
                       And then if they did, they would go in and
           adjust the internal clearances, or round off the
           internal edges to the valve.  So that is how they were
           able to address performance, because of the definite
           concerns of trying to run a test on those type valves.
                       And during the inspections which I
           participated in, a large number of them, we did look
           at the difference of pressures that they were
           assuming, and how they came up with the thrust
           requirements for the used valve factors in the EPRI
           model, and then what actions did they take to address
           those.  So those are the types of things that we
           looked at.
                       MR. WALLIS:  So the assurance that they
           will work is based on the fact that they conform with
           an EPRI model?
                       MR. SCARBOROUGH:  That's part of the
           basis.  They would run the model, and we would prepare
           a safety evaluation on the model, and we evaluated it,
           and the licensees would use that as part of their
                       Some licensees --Comanche Peak, for
           example -- actually did run some blowdown tests on
           their unit two when they were starting up to get
           direct information that they could apply to unit one.
                       So there was some actual test data that
           people had, but in a large number of cases it was
           using the EPRI model for the blowdown conditions.
                       MR. SIEBER:  I guess in an operating plant
           you just can't create the conditions necessary to test
           the valves without taking a saw and sawing them off.
                       MR. SCARBOROUGH:  Right.
                       MR. WALLIS:  It is a basic problem, but it
           is very difficult to be sure a valve will work without
           testing.  I mean, you can't just compute, and you're
           not always sure it will always do exactly what you
           thought it would do.
                       MR. SIEBER:  Well, the EPRI models is an
           empirical model, and it is based on tests of prototype
           valves under a variety of conditions.  So it is
           probably the best thing that you can do.
                       DR. POWERS:  If I recall the SDR on that
           model properly, and I may not, my recollection is that
           there were questions about the length of upstream and
           downstream piping around the valve.  Did those get
                       MR. SCARBOROUGH:  Yes.  As part of the 
           evaluation of the model itself, and adjustments to the
           model, this was like a 2 or 3 year process when we
           reviewed it, and we were able to resolve those.
                       There were some changes to the model  
           that were made, and the model, as it turned out, seems
           to be reasonable, and it seems to be tracking pretty
                       DR. POWERS:  And I further recall that
           there were questions about whether the valves being
           tested had experienced the kind of aging and
           degradation that valves in the plants would have
           experienced.  Did that issue get resolved?
                       MR. SCARBOROUGH:  Right.  And in the case
           of the Board Warner valves, we were concerned that
           there wasn't enough, and so EPRI did add an additional
           5 percent margin any time that you are using a Board
           Warner valve with the EPRI model.
                       But we did evaluate and thought there was
           enough preconditioning of those valves as part of
           that, and that was part of our evaluation of what the
           model was predicting, and what the actual thrust
           requirements were.
                       So we went back and looked at all of
           those, and in the final analysis, whether or not we
           accepted the model was based on having enough margin
           to account for any preconditioning that the valves had
           not achieved as part of the test process.
                       DR. POWERS:  I guess the question always
           arises on how you decide how much margin to ascribe
           the phenomena that are of aging and degradation kind
           of nature.
                       MR. SCARBOROUGH:  And that is part of what
           the joint owners group program that Ken mentioned are
           doing.  Right now they are doing testing of valves in
           the plants under flow conditions -- not blowdown, but
           flow conditions -- and looking for changes in the
           thrust requirements.
                       And at the end of October of 2002, their
           five year testing program will be complete, and  they
           will be preparing an updated report to establish a
           long term periodic verification program, with some
           potential need for testing either static or dynamic,
           but with diagnostics to evaluate that.
                       And one of the things that they are
           finding so far is if you open the valve up and do any
           maintenance, internal maintenance on the valve, the
           thrust requirements drop dramatically immediately.
                       But then they rise back up, and so that is
           something that had been found during the EPRI testing,
           and they are confirming it through the JOG program,
           and that will probably be part of their long term
           program when they come in in 2002.
                       DR. KRESS:  Since the subject of your
           report is adequacy of the design basis, I guess your
           basic conclusion is that the design basis was
                       MR. KARWOSKI:  No, the conclusion is that
           the licensees, as a result of 89-10, and the emphasis
           on MOVs during the 1990s, that we confirmed that
           licensees did design the valves, or the valves are
           capable of operating under blowdown conditions.
                       DR. KRESS:  With the improvements?
                       MR. KARWOSKI:  With the improvements.
                       DR. KRESS:  But those improvements didn't
           come about because of the design basis?
                       MR. KARWOSKI:  Well, you see, that is
           where the concern has broken up into two phases; the
           adequacy of the design, which is GSI-152, and then the
           capability of the valves to function as designed,
           which was the focus of 89-10.  It is hard to separate
           the two, but that's the distinction between the two
                       DR. KRESS:  But my conclusion would have
           been that the design basis was inadequate.
                       MR. SIEBER:  In some plants.
                       MR. MAYFIELD:  This is Mike Mayfield. 
           That was the question that was put on the table, and
           as I understand from looking and reading that I have
           done, and in the briefings that I have had, what the
           89-10 determined was that in general things were okay. 
           And where there were some difficulties, the licensees
           had taken action to correct those.
                       DR. KRESS:  But they weren't required to?
                       MR. MAYFIELD:  They weren't required to. 
           And as it turns out, the resolution to this generic
           safety issue doesn't require any subsequent action on
           the part of the staff because the licensees had
           already taken that action.
                       DR. KRESS:  That is what I was going to
           get to; do we need to change the design basis.
                       MR. MAYFIELD:  And I think the answer to
           that is that when you say design basis, as I
           understand it, these were -- did they correctly
           estimate how big the opening would be, and had they
           fully expected the full break, the full opening break,
           downstream in the valve.
                       And in some cases -- and I understand that
           the answer to that was no, and they have gone back and
           fixed that.
                       MR. KARWOSKI:  Or like I mentioned at Big
           Rock Point, where they analyzed and determined that
           even though they weren't designed for that, that it
           was not a safety factor.
                       DR. KRESS:  I guess in another world,
           where we might be getting new reactors every 3 or 4
           months, or something, you would be constrained to go
           back and change the rule, or change the design basis. 
           And under the situation now, you don't have that.
                       MR. MAYFIELD:  I don't think it is so much
           that they -- I don't know that there is anything that
           we would go change other than we would look a lot
           harder perhaps at specifics that were included in the
                       MR. KARWOSKI:  And I think the concern,
           the original concern was for older plants rather than
           the newer, because in the newer plants, they are
           frequently analyzed for pipe breaks.
                       MR. SIEBER:  And the actual requirement
           comes from the ASME code does it not, and which says
           that under certain conditions you classify this as a
           high energy line, and if you need to be able to
           isolate it, as opposed to someplace in a rule or a reg
           guide saying that.
                       So if you endorse the code, and you have
           a code book plant, the requirement is embedded in your
           license, in your FSAR.
                       MR. KARWOSKI:  But also from a practical
           standpoint, if a licensee says they are going to
           operate this system in this fashion, and it calls for
           the valve to close -- and this was part of the 89-10
           review --
                       MR. SIEBER:  Right.
                       MR. KARWOSKI:  -- they have to show that
           the valve is in fact capable of doing that.
                       MR. SIEBER:  Of closing.
                       MR. KARWOSKI:  Because they were supposed
           to review the procedures and determine under what
           conditions the valves were expected to operate.
                       MR. WALLIS:  It is a little tricky,
           because your are asked to demonstrate that a valve
           will do something which it never does, and so you
           never have a realistic test really in the plant.
                       So it must be rather difficult to give
           such conclusive proof when this thing has been sitting
           there all this time, and it is always going to work
           when it is called upon to work when it never does it
                       MR. KARWOSKI:  That's correct, but that's
           the purpose for the testing and the monitoring, to
           provide you added assurance.  And there is in most
           cases redundancy.
                       MR. WALLIS:  But then you don't test
           something that has been sitting in the plant for 10
                       MR. SIEBER:  I think that 89-10 requires
           licensees to commit to periodic testing.
                       MR. WALLIS:  At full pressure.
                       MR. SIEBER:  Well, to test the torque
           requirement and the stem factor, and so on, and that's
           what MOVATS  and MOVs, and all those are required to
                       MR. SCARBOROUGH:  The new Generic Letter
           96-05, which is sort of the follow-on of 89-10, is the
           periodic verification, and that is part of the joint
           owners group program; is that now that they have
           established the design basis capability for these
           valves, how do we monitor them and make sure that we
           don't have degradation.
                       And those programs have in place where
           they use diagnostic testing, and there is a dynamic
           diagnostic testing program going on to look for areas
           of degradation.
                       And then they are going to have an ongoing
           static diagnostic, with possible some dynamic
           diagnostic testing in the future.  So they have a
           program established to look for that type degradation.
                       MR. LEITCH:  Any further questions?
                       MR. WALLIS:  Why do valves stick?
                       MR. SIEBER:  Packing glands dry out and
           operators pull up on the nuts.  They rust.
                       MR. KARWOSKI:  And pressure locking from
           a binding.
                       DR. KRESS:  The perversity of nature.
                       MR. WALLIS:  Maybe small leaks that build
           up oil or something?
                       MR. SIEBER:  No, that's the BWR.
                       MR. WALLIS:  So if you knew why they
           deteriorated, you could specifically look for those
                       MR. KARWOSKI:  That is correct, whether it
           be the grease deteriorating or whatever, correct.
                       MR. UHRIG:  Isn't most of that done with
           signature analysis in the testing?
                       MR. SCARBOROUGH:  Yes.  Now a lot of the
           plants use stem mounted string gages for a direct
           measure of the torque and thrust.  But in the future,
           especially for the low risk valves, they are looking
           for a motor control center improvements in that area
           that have been made in the last 2 or 3 years, which
           are quite dramatic.
                       And which they can actually get a good
           impression of what the thrusts are that are coming out
           of the motor, and so there are a lot of improvements
           in that area that they are looking for as well.
                       MR. LEITCH:  Okay.  Any other comments or
                       (No audible response.)
                       MR. LEITCH:  Thank you.
                       MR. KARWOSKI:  Thank you.
                       MR. LEITCH:  Dr. Apostolakis is away from
           us for a few minutes.  I think the next thing on the
           agenda is writing reports.
                       DR. POWERS:  Fortunately, FACA prevents
           you from starting anything until it's time.
                       MR. LEITCH:  So let's adjourn until four
           o'clock then.
                       (Whereupon, the meeting was concluded at
           3:15 p.m.)


Page Last Reviewed/Updated Thursday, June 04, 2020