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Thermal-Hydraulic Phenomena - August 23, 2001

 

                
                
                Official Transcript of Proceedings

                  NUCLEAR REGULATORY COMMISSION



Title:                    Advisory Committee on Reactor Safeguards
                               Thermal Hydraulic Phenomena Subcommittee



Docket Number:  (not applicable)



Location:                 Rockville, Maryland



Date:                     Thursday, August 23, 2001







Work Order No.: NRC-389                     Pages 200-223/392-404





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

 
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