490th Meeting - March 8, 2002

                Official Transcript of Proceedings


Title:                    Advisory Committee on Reactor Safeguards
                               490th Meeting

Docket Number:  (not applicable)

Location:                 Rockville, Maryland

Date:                     Friday, March 8, 2002

Work Order No.: NRC-272                             Pages 272-371

                   NEAL R. GROSS AND CO., INC.
                 Court Reporters and Transcribers
                  1323 Rhode Island Avenue, N.W.
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                                 + + + + +
                               490TH MEETING
                                 + + + + +
                               MARCH 8, 2002
                                 + + + + +
                            ROCKVILLE, MARYLAND
                                 + + + + +
                       The Committee met in Room T2B3, Two White
           Flint North, 11 Rockville Pike, Rockville, Maryland,
           at 8:30 a.m., George Apostolakis, Chairman, presiding.
                 GEORGE E. APOSTOLAKIS       Chairman
                 MARIO V. BONACA             Vice Chairman
                 F. PETER FORD               Member
                 THOMAS S. KRESS             Member
                 DANA A. POWERS              Member
                 VICTOR RANSOM               Member
                 WILLIAM J. SHACK            Member
                 JOHN D. SIEBER              Member
           .           ACRS STAFF PRESENT:
                 MAGGALEAN W. WESTON
                 PAUL A. BOEHNERT
                 SAM DURAISWAMY
                 SHER BAHADUR
                 CAROL A. HARRIS
                 JOHN T. LARKINS
                 MICHAEL T. MARKLEY
           .                              C-O-N-T-E-N-T-S
           AGENDA ITEM:                                    PAGE
           Phase II, Pre-Application Review of  . . . . . . 275
           the AP1000 Design
           Applicability of Exemptions and DAC. . . . . . . 299
           Applicability of AP600 Testing . . . . . . . . . 307
           Containment Issues . . . . . . . . . . . . . . . 332
           Applicability of Reactor Codes . . . . . . . . . 339
           Response of Westinghouse . . . . . . . . . . . . 344
           .                           P-R-O-C-E-E-D-I-N-G-S
                                                    (8:28 a.m.)
                       CHAIRMAN APOSTOLAKIS:  The meeting will
           now come to order.  This is the second day of the
           490th Meeting of the Advisory Committee on Reactor
           Safeguards.  During today's meeting, the Committee
           will consider the following; Phase II, Pre-Application
           Review of the AP1000 Design, Future ACRS Activities,
           a Report of the Planning and Procedures Subcommittee,
           Reconciliation of ACRS Comments and Recommendations
           and Proposed ACRS Reports.  
                       A portion of the meeting may be closed to
           discuss Westinghouse proprietary information.  This
           meeting is being conducted in accordance with the
           provisions of the Federal Advisory Committee Act.  Mr.
           Sam Duraiswamy is the designated federal official for
           the initial portion of the meeting.  
                       We have received no written 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 they can be
           readily heard.  I will begin by asking Dr. Kress, a
           member in this issue, to lead us through the Phase II
           Pre-application Review.
                       MEMBER KRESS:  Thank you, Mr. Chairman. 
           I remind the members that the application review for
           AP1000 is being done in three phases.  Phase 1 was for
           Westinghouse and the NRC to identify what would be the
           key issues in the certification and Phase II was for
           Westinghouse to ponder those key issues and come to
           some sort of position on them.  There are four of
           these basically and today that's what we're going to
           hear about, the four key issues and the staff's
           position on these.
                       And I think we'll be asked for a letter,
           of course, on our feelings about these issues.  So,
           with that, I'll turn it over to Jim Lyons.
                       MR. LYONS:  Thank you, Dr. Kress.  I'm Jim
           Lyons, Director of the New Reactor Licensing Project
           Office and we're glad to be here this morning to
           discuss the completion of our review of the AP1000
           pre-application review.  We are getting ready to start
           the review of the design certification which
           Westinghouse is proposing to send in either later this
           month or, I guess, next month.  We are looking forward
           to receiving your letter and with that, I'll turn it
           over to Larry Burkhart, who will make the
                       MR. BURKHART:  Good morning, I'm Larry
           Burkhart, the AP1000 Project Manager and as has been
           said already, we're here to discuss the staff's
           assessment of the pre-application review.  Phase II,
           the end of Phase II brings to a conclusion the end of
           the pre-application review.  
                       Briefly, the agenda, obviously,
           introduction, what I am doing now, Mike Corletti from
           Westinghouse will give us an overview of the AP1000
           design, with some highlights on the differences
           between the AP600 and that AP1000.  We will provide
           our assessment of the four issues that were decided to
           be reviewed for the pre-application review.  I'll talk
           about those details in a second.  
                       We have staff from NRR and the Office of
           Research who were involved in that assessment and
           after our assessment, Westinghouse will give their
           presentation and their comments.  
                       Some background; the AP600 was certified
           in December of 1999.  About that time, Westinghouse
           expressed interest in applying for basically a larger
           version of the AP600, the AP1000, based on the AP600
           design.  Early in the year 2000, we discussed a three-
           phase approach that Dr. Kress mentioned.  Pre-
           application review involved Phases 1 and 2.  Phase 1,
           the scoping review, was completed in July of 2000 and
           Phase II is to be completed by the end of March,
           that's what we're talking about right now, and Phase
           III is the actual design certification review, which
           could come in as early as March, late March or early
                       So getting to the point of what we're here
           to talk about today, the scope of the Phase II review
           is limited to four issues; the applicability of the
           AP600 testing program to the AP1000 design
           certification review, the applicability of the AP600
           analysis codes to the AP1000 design, acceptability of
           using the DAC approach in the INC control room and
           piping design areas and that's in lieu of providing
           detailed design, and acceptability of requesting
           certain exemptions that were granted for AP600.  There
           are three exemptions which I'll talk about later.
                       The staff's assessment on these four
           issues will be documented in a SECY to the Commission
           and that would involve discussions of the design
           acceptance criteria, the DAC, and the other three
           issues would be documented in a letter directly to
           Westinghouse and both of these are on tap to be issued
           by the end of this month.
                       One last introductory slide, interaction
           we've had with Westinghouse, as you imagine, have been
           numerous.  We had eight correspondences, which
           involved requests for additional information that
           actually covered 74 different questions.  We issued
           those RAIs between January and October of 2001 and
           Westinghouse completed their answers to those RAIs by
           November of 2001.  We've had several public meetings
           and tele-conferences and our interactions with the
           ACRS included a briefing on Phase 1 in August of the
           year 2000 and a couple weeks ago, three weeks ago, we
           briefed two subcommittees as listed on the slide on
           our assessments.  
                       At that time our assessments were still
           not completely finalized, as you'll see in the
           discussion of design acceptance criteria.  So moving
           on, I would like to turn over the mike to Mike
           Corletti, who will discuss the background of the
           design, philosophy of design for the AP1000.
                       MR. CORLETTI:  Good morning.  It's a
           pleasure to be here in front of you today.  My name is
           Mike Corletti, with AP1000 Project.  I have quite a
           few slides there in that package.  I think I'm just
           going to try to highlight on a few of those, but
           they're there in case you have questions about the
           background of the design.
                       As Larry said, we are designing AP1000 to
           be based extensively on AP600 and to the extent that
           you see here is a comparison of the general
           arrangement of both AP600 and AP1000.  And you will
           see, we are maintaining the design within the space
           constraints, within the general arrangement of the
           nuclear island.  So the system configuration of the
           passive systems is the same as AP600 I'm going to show
           and here, we typically say to people, "Can you tell
           the difference between the two"?  I think you'll see
           that the steam generators are larger but other than
           that from as far as the structural design here,
           there's not really much difference on this view.
                       However, when you go to a 70 percent
           upgrading, there are some changes that you have to
           make.  Here's a good view of the -- a section view of
           the AP600 compared to the AP1000.  The containment has
           been -- the height of the containment is increased
           approximately 25 feet basically to accommodate the
           larger mass and energy releases associated with the
           design basis accidents, and also to allow for steam
           generator removal, if necessary.
                       Here's a comparison of some key selected
           parameters.  You'll see the power output, electric
           power output essentially 1117, which is more than
           1,000 megawatts and we'd like to say that the 1,000
           doesn't necessarily stand for 1,000 megawatt.  That's
           $1,000.00 a kilowatt which is basically what we're
           designing the installed cost of AP1000 to be. 
                       MEMBER POWERS:  What is W 3XL?
                       MR. CORLETTI:  The 3XL is the Dole and
           Tihange plants in Belgium.  They are 14-foot core
           plants, 157 fuel assemblies.  Pretty much this is the
           core, the reactor vessel that we've started with for
           AP1000 and I have comparison to AP600.  AP600, if you
           remember, was a very low power density core.  We
           essentially had a 1,000 megawatt reactor vessel and a
           1,000 megawatt core and we were running it at 600
                       To improve economic competitiveness, we've
           basically taken the Doel Tihange core and as our basis
           for AP1000 and we have increased its rating to -- a
           comparable power rating to our operating three loop
           plants.  You'll see some of the other key parameters. 
           They both, AP600 and AP1000 uses a 17 by 17 fuel.  As
           I said, we've gone to the 14-foot -- 14-foot active
           fuel length.  One difference of AP600 and AP1000
           compared to most operating Westinghouse PWRs is we use
           gray rods for load follow, so we don't use boron for
           load follow, which minimizes waste production.  
                       CHAIRMAN APOSTOLAKIS:  What did you say
           about the AP1000, what does 1000 means?
                       MR. CORLETTI:  Oh, I'm sorry, that was our
           marketing.  Typically, we started with 1,000 megawatts
           electro-power rating but you see the -- we've actually
           gone to 1117 but the driver for going from AP600 to
           AP1000 was to get a cost competitive product and where
           our U.S. utilities now are -- the target cost that we
           need to deliver on an overnight capital cost is
           essentially $1,000.00 a kilowatt, installed capital
           cost.  This is our major driver for developing --
           taking AP600 and developing it to an AP1000.
                       MEMBER KRESS:  Tell me, what is it -- what
           is the need that drives the pressurizer volume
                       MR. CORLETTI:  The pressurizer volume
           increases there, to handle thermal transients,
           transients that would occur.  
                       MEMBER KRESS:  So it's thermal capacity.
                       MR. CORLETTI:  Yes, and it provides
           basically a much more forgiving plant.  AP600, you'll
           remember, is designed to the utility requirements
           document.  One of those requirements was to eliminate
           the PORV function stemming from the Three-Mile Island
           accident.  So the vendors all -- we've incorporated a
           larger pressurizer to mitigate these transients
           without opening -- without opening the safety valves,
           right, without the need for opening the PORVs.
                       MEMBER KRESS:  So that's what takes the
           volume up.
                       MR. CORLETTI:  That's what drives the
           sizing of the pressurizer and for AP1000 it even got
           larger.  So it really provides a good operational
           benefit for -- to mitigate transients.
                       VICE CHAIRMAN BONACA:  A couple of other
           things; at the surface area, there is a big increase
           over the hedge.
                       MR. CORLETTI:  There's a big increase,
           right.  The steam generator is what we call Delta 125
           and it is similar to the -- it is based on the
           replacement steam generator that we had supplied for
           Arkansas but also essentially a small generator when
           you compare it to the CE type -- you know, the CE,
           System 2 type steam generators, where they fix their
           designs on two loops and with very large steam
           generators.  This generator is within that size.  
                       In the development of AP1000 shortly after
           we started, we had merged with Combustion Engineering
           and we really had the benefit of working with the
           Combustion Engineering steam generator designers and
           the Westinghouse designers in bringing a larger
           generator within their operating -- it had been within
           their design experience.
                       VICE CHAIRMAN BONACA:  The other thing I
           notice there, you have very similar core between the
           Belgium reactors and this but you have much less of
           reactor cool and pump flow.
                       MR. CUMMINS:  Excuse me, this is Ed
           Cummins.  When you compare steam generators and pumps
           to Tihange, you need to consider that there are three
           steam generators and three pumps in Tihange and two in
                       VICE CHAIRMAN BONACA:  Yeah, thank you.
                       MR. CORLETTI:  Yeah, see the vessel flow
           is essentially the same.  
                       VICE CHAIRMAN BONACA:  Yeah, okay, right.
                       MR. CORLETTI:  With AP1000 we have four
           pumps, four reactor coolant pumps.
                       VICE CHAIRMAN BONACA:  The other one has
           three, all right.
                       MR. CORLETTI:  Right.  
                       VICE CHAIRMAN BONACA:  That makes a
                       MR. CORLETTI:  So these are some of the
           key parameters comparing AP600 and AP1000 in the
           reference plan.  
                       Just quickly here, we see the reactor
           coolant system.  As you'll notice, it is two loops but
           four reactor coolant pumps which is a different
           configuration than the previous Westinghouse plants.
           As I said, the reactor vessel is based on the 3XL. 
           It's the same outside diameter as AP600 but is a
           longer vessel.  The Delta 125 steam generators, the
           use of canned motor pumps which is based on our naval
           applications, a very high, reliable canned motor
           pumps, eliminate seals, no seal injection, no need for
           seal support.  
                       Simplified main loop piping, eliminate the
           cross-over line.  This elimination of the cross-over
           line improves a small break LOCA performance is one of
           the inherent features of the AP600 and the AP1000.
                       VICE CHAIRMAN BONACA:  How do you deal
           with the coast down?
                       MR. CORLETTI:  For the reactor coolant
           pump, for the Navy applications, they have a very --
           do not worry about coast down.  For AP600 we designed
           a high integrity fly wheel, we built it and tested it
           and we've incorporated that in this design.
                       VICE CHAIRMAN BONACA:  Okay, a fly wheel.
                       A VOICE:  It's depleted uranium, right?
                       MR. CORLETTI:  The -- it is constructed of
           depleted uranium.  It is totally sealed.  
                       MEMBER POWERS:  Why a 60-year design
           lifetime and not 80?
                       MR. CORLETTI:  Well, the regulations only
           allow us 40 at this point in time.  We've designed it
           for 60 --
                       MEMBER POWERS:  And you're going to go for
                       MR. CORLETTI:  Perhaps 70 years from now
           we'll be talking about plant life extension.
                       MEMBER KRESS:  And big steam generators
           let you go to a power upgrade.
                       MR. CORLETTI:  Right.  You go into high
           burn-up fuel, I'll tell you that.  
                       What you see here is the passive decay
           heat removal heat exchanger.  This is one of the key
           features of the passive safety systems.  It is used to
           mitigate transients.  It replaces essentially the
           safety grade emergency feed water and ox (phonetic)
           feedwater.  So it's designed for events like a loss of
           normal feed.  The passive heat exchanger is located in
           the refueling water storage tank, inside containment. 
           It's located above the core on a low steam generator
           water level.  Valves are actuated and by natural
           circulation, the heat exchanger provides core decay
           heat to mitigate any of the transients that were
           designed for.
                       MEMBER KRESS:  Does the water boil there
           in the transient?
                       MR. CORLETTI:  Yes, the IRWST, the heat
           capacity is such that after about an hour and a half
           of continued operation, the tank would begin to boil,
           but with the passive containment cooling, where
           condensate then is condensed on the steel shell and
           returned to the IRWST, the passive decay heat removal
           can provide core cooling essentially indefinitely.
                       MEMBER KRESS:  Is there a pump that takes
           that back or is it gravity?
                       MR. CORLETTI:  No, it's by gravity.  The
           -- it's got an arrangement on the containment shell
           that returns the condensate back to the refueling
           water storage thing.
                       MEMBER KRESS:  That's just like the AP600.
                       MR. CORLETTI:  Exactly like the AP600. 
           Now, the heat exchanger has been increased in surface
           area roughly 20 percent.  How we've -- we've kept the
           capacity though in relation to the core power and
           we've achieved that by making the inlet and outlet
           piping a larger diameter so that reduces the
           resistance to the natural circulation driving head and
           we've been able to maintain a capacity about the same
           factor as the core power.  Because this is designed to
           remove core decay heat, we had to maintain that sort
           of a --
                       MEMBER KRESS:  These two valves --
                       MR. CORLETTI:  Those are fail open air
           operated valves, yes, and they receive a signal on low
           steam generator water level.  Again, with AP600 and
           AP1000 with defense in depth, we typically have non-
           safety active systems which is the first line of
           defense.  You would have a loss of normal feedwater. 
           The start-up feedwater pumps would be actuated to
           supply feed water to the generators.  
                       If they would then fail, then the passive
           decay removal heat exchanger is actuated.
                       MEMBER KRESS:  Now, you indicate that the
           four-stage ADS comes out of that vertical line.  I
           thought it came out of the hot leg.
                       MR. CORLETTI:  It shares a connection. 
           The ADS 4 on that loop is actually -- is t'd off of
           this inlet line.
                       MEMBER KRESS:  T'd off of this line.
                       MR. CORLETTI:  Yes.  So it is connected to
           the hot leg, it's very close coupled to the hot leg.
                       MEMBER RANSOM:  At one time there was a
           concern about the ability to model the heat exchange
           and the vertical heat exchanger tubes.  Were any
           experiments done to verify the --
                       MR. CORLETTI:  Yes, as part of AP600, we
           did a full height, full pressure, full temperature
           tests of vertical tubes to develop a heat transfer
           correlation which we then validated our analysis codes
           to that heat transfer correlation and also
           demonstrated it with blind tests at the Rosa facility
           which is one of the test facilities that was conducted
           by the NRC and we had very good predictions of heat
           transfer using that correlation.
                       MEMBER KRESS:  Now, what's the issue then
           with thermal plume there?
                       MR. CORLETTI:  There is a -- the staff had
           asked questions in regards to are you able to have
           steam blanketing on the outside of the tubes.  We
           essentially showed that for the tests that we ran and
           for the tests at Rosa that really that our heat
           transfer correlation which is based on a modified
           Rosenal (phonetic) correlation, was sufficient to
           predict overall heat transfer.
                       I think the concern they had was could it
           degrade the heat transfer of the heat exchanger?  And
           I think that we showed that through our tests and
           through -- we did several sensitivity studies where 
           we --
                       MEMBER KRESS:  Well, I recall in one of
           the presentations or something that I read that if the
           velocity exceeded a certain level, you had a problem
           with that.
                       MR. CORLETTI:  Okay, that is a -- that
           question is specific to the no trump code (phonetic),
           the LOCA Code.  There was an issue there that for the
           correlation that we use in the NOTRUMP code, if the
           velocity was too high, it could be non-conservative. 
           For AP600 the velocity was not in the non-conservative
           region but there is an issue, with AP1000 with the
           higher flow rates, will your correlation --
                       MEMBER KRESS:  Will you get into that?
                       MR. CORLETTI:  Right, and what we're going
           to have to do there as part of -- as part of design
           certification is provide -- is take -- essentially
           adjust that heat correlation so it is not -- so it is
           no longer non-conservative with respect to our test
                       And I think what the staff is requiring us
           to do is provide a justification for that modification
           to that correlation.  So we will plan on doing that as
           part of the --
                       MEMBER KRESS:  The correlation is HA times
           a delta T.  My understanding was you're going to
           adjust the A.
                       MR. CORLETTI:  Right.
                       MEMBER KRESS:  But since it's a product of
           HA, it doesn't --
                       MR. CORLETTI:  Right, that's right and
           this is only for the NOTRUMP code.
                       MEMBER KRESS:  And under certain --
                       MR. CORLETTI:  For the loss of coolant
           accident which really the passive chart is not a big
           -- you know, it's not dominate in the loss of coolant
           accidents.  For the transients, there we've used the
           modified Rosenal correlation that we based on our test
           data.  That's not a concern there.
                       MEMBER KRESS:  It's okay, there.
                       MR. CORLETTI:  Yes.
                       MEMBER KRESS:  And that's in -- what code
           is that?
                       MR. CORLETTI:  That's in the LOFTRAN code.
                       MEMBER KRESS:  The LOFTRAN, okay.  
                       MR. CORLETTI:  Here you see the passive
           safety injection system for the AP600.  I think this
           is probably familiar to most of you, but the features
           of passive safety injection, the accumulators, we have
           two accumulators that are exactly the same for both
           600 and 1000 and they're really sized to mitigate the
           large break loss of coolant accident.  Their size is
           consistent with our operating plants today.  
                       You have the core makeup tanks which are
           aligned at very high pressure in case of a leak from
           the reactor coolant system and they're able to provide
           high pressure injection.  They replace the high head
           safety injection function in today's plants.  They
           also provide boration capability to mitigate steam
           line breaks.  
                       We also have the refueling water storage
           tank which is there and we're going to be talking a
           little bit more later to provide long-term safety
           injection.  As the pressure is reduced following the
           loss of coolant accident, as the core makeup tanks
           would drain, automatic depressurization valves
           connected to the pressurizer designed to reduce the
           system pressure to allow gravity injection from the
           refueling water storage tank.
                       The final stage of depressurization is
           achieved with the four-stage valves which are
           connected to the hot leg and how we've differed the
           design from the AP600, essentially the same
           configuration has been maintained.  We've maintained
           the same elevations.  The core makeup tanks are
           increased approximately 25 percent and the line
           resistance has been reduced to increase their flow
           rates about 25 percent.  
                       The low pressure portion, low pressure
           injection portions of the system, including the ADS
           stage 4, and the IRWST injection lines and the sump
           injection lines have all been increased to -- in
           relationship to core power to accommodate the higher
           core power associated with those. 
                       MEMBER KRESS:  What does FAI stand for on
                       MR. CORLETTI:  That's a fail as is valve.
                       MEMBER KRESS:  Fail as is.
                       MR. CORLETTI:  That's what that means,
           yes.  Those are -- those four-stage valves are Squib
           valves.  They're explosively operated valves that
           operate one time type operation.  When the core --
           following the loss of coolant accident, after the core
           makeup tank has essentially been emptied.  So you've
           had a very large loss of coolant accident.
                       MEMBER KRESS:  What causes the signal?
                       MR. CORLETTI:  On a core makeup tank?
                       MEMBER KRESS:  There's a level signal?
                       MR. CORLETTI:  Yes, there's a 25 percent
           level signal, 25 percent level in the core makeup
                       MEMBER KRESS:  And it's explosive Squib
           valve that once it goes, it's opened.
                       MR. CORLETTI:  Yes, it opens, it opens.
                       MEMBER KRESS:  And the steam just goes
           into the containment there.
                       MR. CORLETTI:  Right, I think my next
           slide, for all accidents, we use passive containment
           cooling, so for an accident like a steam line break or
           a loss of coolant accident where steam is released
           into containment.  Water tanks at the top of
           containment there we have a line that opens.  We pour
           water on the steel containment shell.  There enters
           these baffles that you see on the shield building and
           down and pass over the containment shell and by
           evaporative cooling, provide containment cooling to
           mitigate all design basis accidents.
                       MEMBER KRESS:  That feed line from the
           water tank, it has a valve in it that's not shown
                       MR. CORLETTI:  Yes, in fact, for AP1000 we
           actually have added a third -- there's actually three
           lines, so as part of our PRA studies, we've added a
           third diverse line for passive containment cooling.
                       MEMBER KRESS:  Wide open so --
                       MR. CORLETTI:  Those valves open on high
           containment pressure or high containment temperature.
                       MEMBER KRESS:  Okay, that makes sense.
                       MR. CORLETTI:  The tanks on --
                       MEMBER KRESS:  And where are those
           measurements made?
                       MR. CORLETTI:  Those are made from
           instrumentation inside containment.
                       MEMBER KRESS:  You mean, you have a bunch
           of them redundant?
                       MR. CORLETTI:  Yes, redundant, redundant,
           at least, I believe we have four, four containment
           pressure measurements.
                       The tank is sized for three days of
           containment cooling flow.  After three days we would
           have water tanks and the dedicated pump to provide
           water to replenish the tanks to provide core cooling
           but even after -- on AP600 after three days, our
           studies showed that air cooling was sufficient.  Air
           cooling is also sufficient to keep containment
           pressure below the service level cease limits for the
                       MEMBER KRESS:  Now, these are based on
           your separate effects test with the large containment
                       MR. CORLETTI:  Well, yes, we performed a
           slew of separate effects tests as far as basically to
           get heat transfer correlations to apply for the
           passive containment coolant, heat transfer
           correlations for heat transfer across the containment
           shell.  Essentially, we've used them in a steady state
           heat transfer correlations.  
                       MEMBER KRESS:  Right.
                       MEMBER POWERS:  Where are those
                       MEMBER KRESS:  There was a test basis
           document that --
                       MR. CORLETTI:  Right, for AP1000 we
           submitted a test applicability -- I mean, our
           applicability document that went through all of the
           test programs for AP600 and showed how they were still
           applicable for 1000.  For AP600, we had -- there's
           several different tests, either test reports or the
           final validation report for Gothic which the Gothic
           report showed the validations of the tests.
                       MEMBER KRESS:  We got all those when we
           reviewed AP600.
                       MR. CORLETTI:  Right.
                       MEMBER KRESS:  I don't know if we still
           have them or not.  I've got --
                       MR. CORLETTI:  You know, there were
           several reports.
                       MEMBER KRESS:  They might have just been
           sent to the Thermal Hydraulics Section.
                       MEMBER POWERS:  None of this is very
           hopeful because there's a mountain of information
           here.  Could somebody point me toward where all this
           stuff is?
                       MR. CORLETTI:  Sure.
                       MEMBER KRESS:  Well, we'll get -- these
           are sort of just for our information now because we'll
           get a chance to go over all this again when we talk
           about the recertification.  This is just to orient us
           more or less.  I don't think there's any decisions
           that have to be made regarding these things at this
                       MR. CORLETTI:  Yes, right.  I think during
           the review the crux of the review from this issue was
           that were the tests that we performed for AP600, was
           AP1000 still within the range of those tests that were
                       MEMBER KRESS:  Yeah, that's the issue,
           that's the issue.
                       MR. CORLETTI:  And I think the staff's
           going to report on their findings on that.  
                       Just a couple slides just showing some of
           the performance of the passive systems.  You'll see,
           here's a comparison for a large break LOCA showing the
           large margins that the passive plants provide for
           mitigation of a large break.  
                       For AP600, peak clad temperature was less
           than 1640 degrees fahrenheit.  For AP1000 it will be
           higher but we will be well within the regulatory
           limits for it.  Essentially, here the dominate
           phenomena is not the passive systems, it's really the
           accumulators and the core-stored energy.  
                       This slide here shows a comparison for
           small breaks, for small break LOCA margin.  One of the
           key features of the passive safety systems was that
           the improved performance for small break where we
           would not have core uncovery for these events, for our
           current PWRs, for two-inch, three-inch sized breaks
           where they're limited on safety injection flow
           typically you would have a fairly decent, fairly
           significant heat-up, still under the regulatory
                       Here you see for the passive plants
           essentially you have no core uncovery for the range of
           small breaks.  A couple others I just will real
           quickly go; this just shows a comparison of our PRA. 
           This is another one of the benefits of the passive
           systems, you see very low risk margins for AP600.  We
           expect AP1000 to have similar results.  
                       MEMBER POWERS:  I'm unfamiliar with the
           requirement for -- NRC requirements.  What are you
           referring to there?
                       PARTICIPANT:  The one times tenth to the
           minus four core damage frequency for initiating
                       MEMBER KRESS:  It don't think it's a
                       MR. CORLETTI:  Probably it's a guideline,
           I think.  It's probably not a requirement.
                       MEMBER KRESS:  Yeah, a guideline is a
           better word.
                       MR. CORLETTI:  Yes, I think that's fair. 
           And this last slide really shows you a comparison of
           the size of the 600 compared to an evolution style
           plant, I'm sorry, AP1000, compared to an evolutionary
           plant.  This is Sizewell.  And you see with the
           passive systems, that we've been able to achieve a
           much simpler design and a much smaller plant footprint
           because due to the modular construction the plant, the
           whole plant is designed in modules and very much
           smaller footprint than those in the past, such as the
                       MEMBER KRESS:  What's the power of
                       MR. CORLETTI:  Sizewell, yeah, we are
           cheating a little bit there, about 3800 megawatts
           thermal, we're 3400 megawatts thermal.
                       MEMBER KRESS:  Not that much difference.
                       MR. CORLETTI:  Yeah.   I think Larry
           talked about the scope of Phase II of this pre-
           certification review that we've just finished and I
           think the four major questions that we were looking to
           answer in regards to the applicability of our test
           program that we completed for AP600, as we said, we
           completed a very thorough test program that was
           extensively reviewed by ACRS and the staff.  We're
           looking to see the applicability of that test program
           to AP1000.  
                       And also then the AP set of analysis codes
           that were validated against those tests, we plan on
           using those codes too, in the design certification for
           AP1000.  And then the other two issues, the one is on
           the issue of the use of piping design acceptance
           criteria and the issue of the exemptions approved for
                       That's all I have.  I think I'm going to
           turn it over to the staff now.
                       MR. BURKHART:  Dueling slides.  You've
           seen this slide before.  It's not a new one.  It
           reflects what Mike just stated as the scope of review
           and here we'll start the staff's assessment.  I will
           discuss the applicability of the exemptions and the
           DAC approach and Steve Bajorek from the Office of
           Research, will discuss the applicability of the AP600
           testing program and Ed Throm and Walt Jensen from NRR
           will discuss the analysis codes. 
                       PARTICIPANT:  Do you have copies of these
           slides, sir?
                       MR. BURKHART:  Yeah, this was a previous
           slide I had in my introduction.  Okay, exemptions, the
           applicability of the exemptions; the three exemptions
           that Westinghouse plans to request for the AP1000,
           this is a rundown of what the requirements are. 
           Section 50.34 (f)(2)(iv) additional TMI related
           requirements regarding technical information contained
           in application requires the safety parameter display
           console, 50.62, requirements of the reduction of the
           risk from ATWS requires diverse and automatic
           initiation of auxiliary feed water, emergency feed
           water and the third GDC 17 which requires two
           physically independent offsite power sources.  
                       A little more information added on this
           slide, based on the design, the passive design of the
           AP600, mostly, these exemptions, the request for
           exemptions were granted for the AP600 and based on
           meeting the special circumstance, that application of
           the regulation is not necessary to achieve the
           underlying purpose of the rule.  And based on our
           review, we believe that due to the similarity in
           design between the AP600 and AP1000, that it's
           appropriate to ask for these exemptions and expect
           that they will be justifiable and the exemptions are
           basically applicable.  We will do the complete
           detailed review during Phase III, the design
           certification review.  
                       Design acceptance criteria; I'd just like
           to go over the requirements and how we've used the
           design acceptance criteria approach in the past in
           design certification reviews.  The requirement in Part
           52 is as stated; "An application must contain a level
           of design information sufficient to enable the
           Commission to judge the Applicant's proposed means of
           assuring that construction conforms to the design and
           to reach a final conclusion on all safety questions
           associated with the design before the certification is
                       Not a prescriptive requirement, but pretty
           clear on the intent.  And after Part 52 was issued,
           there were issues that came up on the level of detail
           that was being provided in the ABWR and the System
           80+.  And where we start to get some clear direction
           and guidance on the use of the DAC approach was in
           SECY-92-053 and this is again during the review of the
           System 80+ ABWR.  The staff observed that applicants
           weren't providing the level of information that we
           thought we would get and this is where the DAC
           approach first was discussed.  
                       And the DAC, Design Acceptance Criteria,
           are defined as, "A set of prescribed limits,
           parameters, procedures, and attributes upon which the
           NRC realized in a limited number of technical areas
           that making a final safety determination to support a
           design certification".  And it was conceived that, you
           know, this concept would enable the staff to make a
           final safety determination as required by Part 52,
           subject only to satisfactory design implementation,
           verification by the combined licensee for appropriate
           use of inspections, tests, analysis and acceptance
                       And the staff concluded that you should
           restrict the use of DAC to two cases where a design
           area is characterized by rapidly changing technology
           and thus, if you finalize a design at the design
           certification phase, it may be obsolete by the time a
           plant is actually built or design areas for which as-
           built or as-procured information was not available.
                       And how we use it in design
           certifications, for the ABWR the System 80+, we
           approved the DAC approach for the I & C and control
           room or human factors engineering areas due to the
           rapidly changing technology aspects.  We also, for
           both of these design certifications, approved the DAC
           approach for the piping and radiation protection areas
           based on the lack of as-built or as-procured
           information being available.
                       MEMBER KRESS:  So you were able to approve
           the piping DAC for ABWR and System 80+ without it
           being a safety issue apparently.
                       MR. BURKHART:  Correct, we were able to
           come to a conclusion on all safety questions, right,
           as required by Part 52.
                       MEMBER KRESS:  And you feel like you can't
           do that with AP1000?
                       MR. BURKHART:  We're getting to that.
                       MEMBER KRESS:  Okay.
                       MR. BURKHART:  Our conclusions may be a
           little bit different than what we discussed back in
                       MEMBER KRESS:  Okay.
                       MR. BURKHART:  Okay, so chronologically
           moving on to the AP600 design certification review, we
           allowed the use of DAC in the I & C and control room
           areas just as we did for the ABWR and System 80+, same
           reason.  However, piping back was not requested and it
           wasn't used.  And even though the as-built or as-
           procured information wasn't available, Westinghouse
           completed the piping design and they basically assumed
           that information.  
                       The DAC approach as proposed for the
           AP1000, a little history here; originally,
           Westinghouse proposed or it was discussed that DAC,
           the DAC approach would be used in the I & C, the
           control room, the piping, the structural and the
           seismic areas for hard rock and non-hard rock sites. 
           And that was definitely expanding the use of DAC as
           compared to what we had done before.  And we had some
           discussions with Westinghouse on our ability to come
           to conclusion on all safety questions due to coupling
           all of these together, especially the piping
           structural and seismic areas. 
                       We had some conversations and some public
           meetings and voicing our concerns, and basically on
           February 13th, Westinghouse revised their proposal for
           the use of DAC to limit DAC in the I & C, control room
           and piping areas.  They would basically provide
           sufficient information to preclude the use -- the need
           to use DAC in the seismic and structural areas and in
           that same letter, they provided more information
           supporting why they should be able to use DAC in the
           piping area.
                       So our assessment, we think the DAC
           approach is acceptable for the I & C and control room
           design areas, the same reason as we approved it for
           the previous three design certifications, rapidly
           changing technology.  In the piping area, we do
           recognize that Westinghouse completed the piping
           design in the AP600 and due to the similarity, we
           think there will -- we will realize the benefits of
           standardization that they'll carry over from the AP600
           to the AP1000 due to the similarity.  
                       Westinghouse noted in their February 13th
           letter that it gained very little regulatory benefit
           by performing a detailed piping design because they
           were still subject to pretty much the same ITAAC as
           the ABWR and System 80+.  And due to the similarities
           in design, we find that the completed AP600 piping
           layout and design provides a sufficient level of
           detail to assure that the benefits of standardization
           will be achieved for the AP1000 piping.  
                       MEMBER RANSOM:  I have one question on the
           instrumentation and control, are these hard wired
           plants, or have they gone to fiber optic pipe systems?
                       MR. BURKHART:  Mike, do you know the
           answer to that?
                       MR. CORLETTI:  Yes, we do use a digital I
           & C.  We are hard-wired from the sense of to the data
           highway but we have gone to the digital.
                       MEMBER RANSOM:  So you have two
           independent systems then?
                       MR. CORLETTI:  We have three actually.  We
           have a safety related protection monitoring system. 
           We have the plant control system and we have a diverse
           actuation system which is digital also but is diverse
           to the protection system and it provides certain
           protection type functions.
                       MEMBER RANSOM:  Thank you.
                       MR. BURKHART:  So based on the arguments
           on the previous slide, we find that the piping DAC
           approach is acceptable for the AP1000.  However, just
           as with any DAC, it's contingent upon being able to
           agree with Westinghouse on adequate DAC.  Again,
           that's for any design acceptance criteria used.  There
           will be changes in piping size and we will have to
           identify areas of concern.  We think we can -- we can
           be able to make -- come to a conclusion on all safety
           questions but there are some areas where some changes
           may cause us to focus, again, areas for Phase III,
           design certification review and some of those areas
           are listed here.
                       Now, the impacts of using design
           acceptance criteria; it has a potential to increase
           the likelihood of post-construction hearing petitions,
           and to expand the scope of a hearing.  Compliance with
           a DAC can be subject of a hearing just prior to
           operation, including those DAC that were intended to
           be verified early in the construction process.  
                       MEMBER KRESS:  In other words, you're
           moving towards what you used to do when you had to
           have a construction permit and an operating permit.  
                       MR. BURKHART:  A little and I do want to
           say that we're -- with allowing pipe DAC for
           Westinghouse, we're not expanding the use of DAC
           compared to what's been used before.
                       MEMBER KRESS:  Because you did it before.
                       MR. BURKHART:  Because we did it before. 
           In fact, Westinghouse -- well, ABWR and System 80+
           used it for radiation protection. They're not using it
           in this case.  So the reason for approving the piping
           DAC is a bit different than the reason we use for
           approving the DAC approach for the ABWR and System
           80+. That was, again, for as-built or as-procured
           information not being available.  We think because of
           all the work that's been done on the AP600 and the
           similarity of the design between the 600 and the 1000,
           which the exact extent of that similarity will be
           determined in the Phase III review, but because of the
           work that's been done and the degree of
           standardization we'll probably get from the AP600
           design, that's why we're finding it acceptable for the
                       Well, that concludes the assessment of the
           exemptions and the design acceptance criteria.  Now,
           Steve Bajorek from the Office of Research, to discuss
           the staff's assessment of the applicability of the
           AP600 testing.
                       MR. BAJOREK:  Okay, thank you, Larry. 
           Good morning, my name is Steve Bajorek.  I'm from the
           Office of Research.  What I'm going to talk about
           hopefully over the next 20, 25 minutes or so is the
           research evaluation of the test programs that
           Westinghouse is using for the AP1000 and that were
           done primarily in support of the AP600.  As Larry and
           Mike Corletti mentioned, as part of the AP1000
           application, Westinghouse has proposed to use the test
           programs that were used for the AP600 in support of
           all of the data needs for the AP1000.  
                       Their contention is that the data from the
           AP600 programs is adequate.  It's sufficient and it
           covers the range of conditions that one would expect
           for accident scenarios in the AP1000.  The research
           role was asked to come in and for those tests that
           effected the primary system, evaluate those tests,
           perform an independent evaluation and come up with our
           own opinion on whether that data is truly acceptable.
                       What we did is we broke our evaluation up
           into what I would consider three overall segments. 
           One, which I'll refer to as a top down scaling
           approach which takes a look at the major interactions
           of the system between other subsystems, how it
           interacts with safety systems and how the system
           behaves as a whole.  We supplemented that with
           simplified calculations.  You might think of a first
           principles thermodynamic evaluation looking at the
           RCS, the flows into and out of the system in order to
           get a better handle on the transient behavior as the
           AP600 or AP1000 transitions from its high pressure
           performance as the ADS 1/2/3 are on all the way
           through to the IRWST injection phase.  
                       Finally, we did another evaluation that
           has been referred to as a bottom up scaling approach
           that looks at those individual two-phased processes
           that you really can't address very well, either with
           simplified numerical calculations or in the top-down
           scaling approach which really homogenizes everything
           that goes on in the system.  
                       You could spend a couple of days just
           going over different top-down scaling methodologies
           and what they entail.  Essentially, what is done in a
           top down scaling approach is to look at the mass
           momentum and energy equations for a particular flow
           circuit in a system and non-dimensionalize those and
           then you look at those non-dimensional terms which
           appear in front of each one of the major components of
           that mass momentum or energy equation.  This gives you
           a set of dimensionalist groups, what we would refer to
           as pi groups that you can compare from one facility to
           the next and make a decision if the important
           processes in the AP600 or the AP1000 are those same
           things that occurred in the major integral test
                       MEMBER KRESS:  Let me ask you a question
           about that.  When you take these pi groups, you ratio
           the -- say from 1000 to the test or to 600 and you say
           that if that ratio for any one of these umpteen pi
           groups falls in a range of .5 to 2, then that's an
           acceptable range so that the phenomena you would
           expect to be the same.  My question is, how did you
           arrive at that range and why is it -- why is it the
           same range for every pi group ratio?
                       MR. BAJOREK:  It necessarily isn't the
           same range for every pi group.  Let me just briefly
           describe the overall approach.
                       MEMBER KRESS:  Okay.
                       MR. BAJOREK:  It's to take a look at these
           dimensionless groups and if you -- the ratio of those
           is between .5 and 2.  Essentially, if everything is
           within an order of magnitude it was deemed acceptable. 
           Now, in answer to your question on where I got that,
           I got that from the AP600 review, used that as an
           acceptability criteria.  It was the tighter of the
           acceptability criteria that was used.  In some cases
           it was between .3 and 3.  Now, we didn't just base our
           conclusion on all pi groups falling within that range.
                       Indeed, if you take a look at the test,
           some of them fall without that, outside of that range. 
           We independently evaluate each one of those groups to
           come up with a determination; one, is it really
           important to the problem.  In the INEL methodology
           that we applied, one of the nice features is that the
           pi groups are such that ones with very large values
           are indicators, these are important.  Ones with very
           small values are effectively unimportant.  
                       So when we looked at those --
                       MEMBER KRESS:  That's like saying it's a
           coefficient multiplying something that determines the
           influence of that something in the equation.  And you
           know, I think it's both the size of the coefficient
           and the something that determines.  I mean, you have
           to have -- you can't look at the coefficient by
                       MR. BAJOREK:  Okay.  I guess, you know,
           the best I can say is we tried to follow what was done
           in the AP600.  We stayed on the tighter side of that
           criteria.  And when we did this we looked at things. 
           If they were outside of the range and distorted, we
           tried to come up with a rationale, did it really
           matter?  And if it didn't matter, or if they were such
           that the process in the AP1000 was going to be more
           benevolent, have more mass in the system, behave
           better than the tests, then you would assume that that
           distortion was a conservative one and it would be
                       A real concern are those things that we
           could identify as being very important to how the
           AP1000 behaves and were not represented well in the
           experiments.  And usually, I think we would fine in
           these scale groups they were fairly close to 1, 1.2,
                       MEMBER KRESS:  And those things came out
           of the PIRT?
                       MR. BAJOREK:  Yes, yes, or they fell
           outside of that range.  If we changed that range a
           little bit, we would come up with essentially the same
           conclusions.  So I think that, yes, we did look at the
           sensitivity to that and things that we will identify
           as being important we think would fall outside of an
           acceptability criteria even if you made it much
                       Okay, with respect to the top-down
           scaling, the news is basically good here, in the use
           of the AP600 integral tests.  We looked at two
           different scenarios, a one-inch cold leg break, a
           double-ended guillotine of a DVI line, which tends to
           be perhaps the most important of the transients,
           looking at small break processes and we found that for
           five -- four of the five major periods of the small
           break and a long term cooling transient, tests that
           were done in support of AP600 cover what we would
           expect for the AP1000.  
                       I show here on these bullets the five
           different periods.  Early in time, we see that the
           AP1000 scales very well with SPES.  In fact, AP1000
           scales better with SPES than the AP600 did based on
           the changes that were made to the system.  If you go
           further out in time, there weren't a tremendous amount
           of changes that were made effecting the IRWST.  The
           sizes were larger but elevations which effected
           driving heads didn't change that much, so again we
           reached the conclusion that AP1000 scales fairly well
           with APEX, the facility at OSU for the late phases.
                       Now, we do have what I might call a
           difference of opinion with Westinghouse on the one
           phase that transitions from high pressure to low
           pressure.  I refer to this as the ADS-4 blowdown. 
           Westinghouse claimed in their submittals that APEX,
           the OSU facility, was valid and that data was good
           throughout that period.  When we do our scaling
           evaluation we find that APEX starts to fall just
           outside of that acceptability range but SPES remains
           within that range.  
                       So with regards to the test programs, we
           would conclude, yes, the tests are available.  During
           this period we think SPES is probably the better one
           to base your conclusions on code accuracy as opposed
           to APEX but once you get down to lower pressure, APEX,
           again, becomes the facility that you should base your
           decisions on.
                       MEMBER KRESS:  Is this one of your
           bottoms- up scaling?
                       MR. BAJOREK:  No, this is a top down.
                       MEMBER KRESS:  This is top down.
                       MR. BAJOREK:  This is top down.  
                       MEMBER KRESS:  So you're dealing with the
           momentum and energy equations.
                       MR. BAJOREK:  Yes, yes.
                       MEMBER KRESS:  And what pi groups come out
           of that?  Are they -- 
                       MR. BAJOREK:  Essentially --
                       MEMBER KRESS:  Froude number?
                       MR. BAJOREK:  Well, in this one it is a --
           well, there's actually about 65 to 70 scaling groups.
                       MEMBER KRESS:  Total, yeah, so they don't
           all apply to APEX.
                       MR. BAJOREK:  Total.  They don't all show
           up in each one of the periods.  They change as you go
           throughout.  The Froude number and things like that,
           that's for bottom up and we'll get to that in just a
                       Now, one thing that we do note with the
           ADS-4 blow-down and this is perhaps more of a critique
           on the methodology itself, is it does make some
           assumptions on what goes on in the tests and in the
           AP1000 and one of those is that you have a certain
           exit quality leaving the ADS.  We stayed consistent
           with the methodology.  We didn't want to invent
           anything new at this point but we did note that during
           this period, those assumptions and the scaling groups
           are relatively sensitive to your assumption in what is
           that flow quality?  How much liquid is leaving during
           this period.  And we thought, well, this is something
           that means we should look at it in a little bit more
                       We continued with the bottom up --
                       MR. CORLETTI:  Steve, could I just make
           one comment?  This is Mike Corletti, Westinghouse.  In
           regards to our code validation, we did validate our
           codes to both APEX and SPES and typically we wanted to
           have at least one of the facilities be well-scaled in
           all of the regimes, so we did actually have acceptable
           validation for one well-scaled facility for AP1000,
                       MR. BURKHART:  That's right and that's
           basically what my conclusions say.  Based on top-down,
           you don't need any more data.  It may be how we look
           at what validation you did that's the determining
           factor in how good the code is doing.  But we went on
           and we still want to look at the bottom up processes. 
           As part of that we set up a simplified model.  It
           looked that the RCS essentially is one node, takes the
           mass equation, the energy equation and sets up
           essentially a thermodynamics problem to look at the
           shrink and swell of the phases, the flows into and out
           of the system.  
                       The conclusion that we get out of those
           calculations is that regardless of what we assumed for
           exit quality out of the ADS, the pressurization of the
           system didn't change all that much.  Now, that's
           important because it says the delay time between when
           you have CMT flow and that essentially stops and
           you're waiting for the IRWST to come into the system,
           that period of time stays about the same.  But what
           the sensitivity also showed us that we would very
           drastically reduce the mass in the vessel, in the
           AP1000 relative to the AP600 or the experimental
           facilities at a rate at which suggested maybe we're
           going to see some core uncovery because of this
           uncertainty in the exit quality through the ADS.  
                       That starts to point at things in a bottom
           up evaluation.  It says, well what would contribute to
           a high amount of flow leaving the system, things like
           entrainment in the vessel and in the hot leg.  So this
           starts to support some of our conclusions in the
           bottom up scaling where we look at precisely those
           phenomena that get missed in a top-down scaling.  
                       And these are things in two-phase flow
           which tend to act as cliffs, flow regime transitions. 
           Are you homogenous or are you stratified or annular? 
           Are you flooding in the surge line or are you not
           flooding in the surge line?  Entrainment is another
           process by which you have a gas flow, there's no
           entrainment.  Higher gas flow, no entrainment. 
           Suddenly you reach a critical point and you have a
           great deal of entrainment.  So we looked at the bottom
           up processes for flooding, flow regime transition and
           again, I think the message should be that the news is
           really quite good here because when we looked at
           regime transition, flooding, core level swell and void
           fractions again, they're not too far off from the
           ranges that we saw in the AP600 tests.  
                       The exceptions, the things that start to
           stand up as important items to look at in Phase III
           are two-fold.  Both are related to entrainment; one in
           the hot leg.  The other I'll refer to as a pool type
           entrainment.  And this is entrainment that occurs at
           the top of the core, between the top of the core and
           the upper plenum.
                       MEMBER KRESS:  Now, did any of the tests
           have a way to determine what that particular
           entrainment was?
                       MR. BAJOREK:  Yes.
                       MEMBER KRESS:  You were able to get that
           out of some --
                       MR. BAJOREK:  Yes, I'll jump ahead a
           couple of overheads, but after the AP600 tests were
           completed, the NRC ran what they called no reserve
           tests.  Now, these were tests in which you had mass in
           the upper plenum, they turned on the power, evaporated
           and swept out that liquid.  It showed from the test
           results that there was an unexpectedly high amount of
           entrainment from the upper plenum pool.
                       MEMBER KRESS:  You could compare the level
           change with the amount of energy going in and if it
           wasn't going out as steam --
                       MR. BAJOREK:  It was going out as liquid
           and they used the separator tanks also to catch that.
                       MEMBER KRESS:  I was going to ask you, you
           could catch it.
                       MR. BAJOREK:  Yes.
                       MEMBER KRESS:  Okay.
                       MR. BAJOREK:  Now it wasn't a primary
           focus in the APEX tests that were run integrally for
           looking at one-inch cold leg breaks and you can't
           really get it out of those.  There's too many things
           going on.  But in these no reserve tests, they noted,
           yes, this is a process that was going on and what
           became bothersome is that RELAP calculations,
           simulations of those events under-predicted the
           entrainment, where when they ran the tests they got a
           lot of entrainment, actually got the level into the
           core.  RELAP couldn't predict that.  It was getting
           too high a level.
                       Now, those tests are not a good indicator
           of whether you will have core uncovery or not.  But
           they are indicative of the fact that for flows similar
           to AP600, AP1000, you will have a lot of entrainment. 
           One thing I want to point out, there's two different
           entrainment processes.  We talked about this at the
           combined subcommittee meeting a couple of weeks ago
           and I want to make sure that we're clear on the
                       One is entrainment in the hot leg and
           we're looking over at this region of the figure where
           gas that leaves the core goes into the hot leg.  The
           principal view that people have is that there's a
           stratified level in the hot leg.  The high gas
           velocities entrained droplets from this stratified
           layer and it gets swept into the ADS.  Where we did
           have some discussion and what I think a better view is
           called for is, where we really expect the most
           entrainment is when the levels are fairly high in the
           hot leg. 
                       It's not quite entrainment from a
           stratified layer but what we've seen or I should say
           some of us have seen in -- of some flow visualizations
           that have been done at OSU is that you get entrainment
           there but you also get most of your entrainment from
           plugs intermittent flows that occur in the hot leg. 
           Now, trying to predict that, trying to scale that
           leaves us at a loss.  When we take the best
           correlation that we can find, best we can say at this
           point is we'd expect a lot more entrainment in AP1000
           than what we would expect in the tests or in the
           AP600, but we can't put a good number on that. 
                       MEMBER KRESS:  In other words, it's kind
           of self-limiting as the level gets down --
                       MR. BAJOREK:  It may well be.  I think my
           point on this is this is something that we cannot say
           at this point has been well scaled in the tests but
           keep in mind, when it occurs, there's a lot of water
           in the system.  This is up close to the top of the hot
                       MEMBER KRESS:  Yes, so one asks the
           question, does it really --
                       MR. BAJOREK:  It is --
                       MEMBER KRESS:  -- from the standpoint of
                       MR. BAJOREK:  My point here is, is the
           data acceptable to evaluate these models in the code? 
           That's one question.  Well, even if they aren't, then
           those models are not doing a great job, the other
           question that needs to be answered, I think, in Phase
           III is how safety significant is that?   The answer
           that's still open, okay, and we have our opinions on
           that at this point is, well, is this really going to
           be important to the safety of the plant and uncovery
           of the core if you aren't predicting this properly.  
                       My opinion is probably not, but we've got
           to get --
                       MEMBER KRESS:  It's kind of a race. 
           You've got the decay heat driving stuff off and if you
           -- and it's going down and if you've thrown out too
           much already, you're starting from lower level, it
           means you're going to dip farther into the core
           depending on how much that was.  
                       MR. BAJOREK:  Right, right.  Now, this
           process goes away when you start to get down into the
           core and --
                       MEMBER KRESS:  Does this -- does the fact
           that you now have a 14-foot core instead of a 12-foot
           one impact on this at all?
                       MR. BAJOREK:  Not this because the upper
           plenum hardware has remained the same.
                       MEMBER KRESS:  Oh, the same.
                       MR. BAJOREK:  Unless I've missed it, Mike. 
           Upper plenum elevations and that hardware is identical
           to the AP600.  
                       MEMBER SIEBER:  What's the distance from
           the top of the core to the bottom of the hot leg?
                       MR. BAJOREK:  I estimate it as 1.82 meters
           based on some numbers that I had, six feet or so.
                       MEMBER SIEBER:  Six feet.
                       MR. BAJOREK:  Yeah, and that's to the top
           of the active part of the core.  The core plate is a
           few inches off of that.   
                       Now, I think what you were referring to,
           Dr. Kress, was the other entrainment process that
           starts to become dominant if you have scenarios that
           lead to a two-phase level that drops below the top of
           -- the bottom of the hot leg.
                       MEMBER KRESS:  Yeah, that's what I was
           concerned about.
                       MR. BAJOREK:  Now, this gets away from the
           slugging and stratified entrainment in the hot leg but
           it's a different physical process by which you have
           gas bubbling through a pot, in this case liquid
           trapped in the upper plenum, entrains these droplets
           and if that gas velocity is high enough, it sweeps
           those out through the ADS.  
                       Now, where this starts to get our
           attention is in the double-ended guillotine break of
           the DVI line, where calculations done by both the
           staff and Westinghouse suggest that that level will
           drop and reach a minimum, I think it's about a foot
           above the core, more or less.  Our question now is, if
           you do not predict that adequately, are you looking at
           a level that remained in the upper plenum or
           potentially drops into and uncovers the top part of
           the core?  
                       So we focused more of our attention on
           scaling this process from a bottom up viewpoint.  And
           on page 8, I put a little bit of that -- those numbers
           and some of the scaling criteria that we used to take
           a look at this process.  First, this is something that
           does show up being highly ranked in the PIRT.  Okay,
           this is Westinghouse's and what we also believe to be
           correct it this is a truly important process,
           especially for this double-ended guillotine break of
           the DVI line.  
                       And as I mentioned just a few minutes ago,
           tests that were done after the AP600 program, did show
           what when you had the two-phase level below the bottom
           of the hot leg, I did have significant amounts of
           entrainment and that we had a very difficult time
           trying to determine how much should be entrained in a
           calculation using RELAP.  Now, there's a flock of
           correlations that have been proposed to take a look at
           this.  The chemical industry very interested in
           separations processes, so we see an amount of work.  
                       Principally, what happens is it depends on
           one, what's the gas velocity as you bubble through
           this pool and secondly, how far to you have to entrain
           a droplet before it goes up and out of your system. 
           So it's basically two parameters which are dominant in
           these correlations.
                       MEMBER KRESS:  E is defined as the ratio
           of the mass of liquid to the mass of vapor?
                       MR. BAJOREK:  Right.  It's a mass of the
           liquid -- it's the liquid flux over the gas flux. 
           Okay, and it's a dimensionalist way of representing
           the entrainment.  Looking at the correlations that we
           find to be closest to the AP1000 in the test and we
           did find those to be in the same range, okay, we find
           that this relative entrainment scales to Jg the gas
           velocity to the third, maybe the fourth power.
                       MEMBER KRESS:  That's looking at these
           correlations you say exist.
                       MR. BAJOREK:  Yes.
                       MEMBER KRESS:  I mean, it doesn't come out
           of this.  It just --
                       MR. BAJOREK:  These are correlations that
           were done.  There was some work done in Russia to take
           a look at this.  Ishii had done some work at Argonne.
           There had been some other work.  They all basically
           suggest that E scales with Jg to the third, fourth or
           higher power.  
                       So I defined a scaling ratio based on
           those correlations and if you assume, as I think we've
           just heard, AP600 has the same upper plenum hardware,
           same geometry but you increase the power by 75, 76
           percent, you can very quickly estimate that the AP1000
           should have at least five times the amount of
           entrainment that occurred in the AP600.  
                       MEMBER KRESS:  Now, this is decay heat
           driving this.
                       MR. BAJOREK:  This is decay heat driving
           the --
                       MEMBER KRESS:  So you wouldn't quite
           expect the same ratio of decay heat as due to the
           power, would you?
                       MR. BAJOREK:  Well, no, we did take that
           into account.  Yes.
                       MEMBER KRESS:  Oh, the 75 is --
                       MR. BAJOREK:  Yeah, the decay heat goes up
           by 75 percent.
                       MEMBER KRESS:  Okay.
                       MR. BAJOREK:  So the power -- depending on
           when you look in the transient, that's scaled power
           still goes up by 75 percent.  Now, there are some
           differences in pressure and in what that scale power
           was in the facility and we sharpened our pencil and we
           looked at those and we found that SPES or AP1000 would
           have over 100 times the amount of entrainment as the
           SPES facility, roughly 20 times what you saw in ROSA
                       APEX, only about six, somewhere between --
           well, I estimated 6.3. APEX is a lot closer.  It still
           is a bit of a concern because the way APEX got closer
           was not because of the gas velocity being correct for
           the entrainment but the fact that it was a one-quarter
           facility.  So we're looking at it in -- from the
           viewpoint that APEX is closest at this point.  It's
           distorted in a non-conservative direction but the one-
           quarter height may actually save some of those test
           results so that eventually they may be able to be
           applied to the AP1000.  
                       But our conclusion to date is looking at
           this process, which was ranked high by Westinghouse,
           using the best information we have, we find that none
           of these test facilities were appropriately scaled to
           capture this phenomena which we think is going to be
           important in determining whether we have uncovery or
           not in the AP1000.  So by conclusion --
                       MEMBER KRESS:  So your concern, though, is
           only on this upper plenum entrainment --
                       MR. BAJOREK:  That's basically --
                       MEMBER KRESS:  -- and not at the ADS-4.
                       MR. BAJOREK:  We think we still need to
           take a look at entrainment in the hot leg.  The
           question is, well, how does this effect other parts of
           the transient and you may want to use those results to
           make other decisions, not just on whether you have
           core uncovery or not.
                       MEMBER KRESS:  So there's two areas of
           entrainment, the ADS-4 and then the other one is --
                       MR. BAJOREK:  The other is the hot leg. In
           one case, I think it's a lot easier to make the
           argument it may not be safety significant.  And I
           think that's the distinction.  So by conclusion, we
           should lost sight of the fact that by and large those
           tests for AP600 are still valuable.  They cover --
           they answer an awful lot of questions for the AP1000. 
                       We feel there are a couple of issues, a
           couple of problems that stand out as exceptions to
           that.  Both involve entrainment.   As we looked at the
           RAIs, information that was submitted to Westinghouse
           and results of our own independent investigation, at
           this point we conclude that Westinghouse has not
           demonstrated that the test data is adequate for
           validation for these processes and we suggest that
           they and we need to come up with either alternative
           data, a different criteria for scaling or some new
           test results in order to close out these issues and we
           think this is going to be something that we need to
           look at in Phase III.
                       MEMBER SIEBER:  Has that decision been
           made yet, which of the three approaches?
                       MR. BAJOREK:  No, we've -- in the SECY, I
           believe the language is such we're leaving this open
           for discussion.  We're not saying you've got to go out
           and run tests because there may be other entrainment
           tests that can be used.  They may not just be what was
           done in the original AP600 test.
                       MEMBER SIEBER:  But of all the phases,
           this is the most important because it results in the
           loss of inventory.
                       MR. BAJOREK:  Yes, this one is going to
           basically show us do you have core uncovery and some
           clad heat-up or not in the AP1000.  Now, again, I
           think there's -- you can do some other work looking at
           how quickly you should lose liquid from the upper
           plenum.  Again, you may be able to demonstrate that
           the uncovery that you expect is not going to be
           significant or that it's going to take so long to get
           that last bit of liquid out of the upper plenum,
           again, your concern may not be justified.
                       But at this point, the data doesn't bound
           the types of things that we expect in the AP1000.
                       MEMBER KRESS:  If more data were needed,
           can APEX be used to produce that data?
                       MR. BAJOREK:  I think so.  In fact, I
           think that a series of tests could be run in the APEX
           you should do something to the no reserve but you do
           it under steady state.  Okay, they still had
           complications in the no reserve because they started
           from a high pressure and flashed a lot of liquid.  Run
           some steady state tests to get the effluent and the
           exhaust flow rate and bench mark these correlations
           which we still have questions about.  I mean, these --
                       MEMBER KRESS:  What would you do about the
           H difference?
                       MR. BAJOREK:  The H difference, I think,
           can be addressed, although I would not do that in the
           APEX facility itself.  There is a sister facility out
           at OSU called ATLAS.  It has the same diameter vessel.
                       MEMBER KRESS:  ATLAS.  That's the one we
                       MR. BAJOREK:  That's the one we saw but
           they didn't have anything in their upper plenum, okay,
           or above the core.  But they do have some nice
           visualizations and working with plexiglass and lower
           pressure is a lot easier than messing around with
           APEX, where you have all the instrumentation.  I think
           it would be very feasible to put in upper core plate,
           simulated upper internals, a couple of DP cells and
           try to get at some of these same things.  There you
           could, I think, fairly easily change your upper plenum
           geometry, okay.  
                       You could put in what I'd call a donut in
           the upper plenum to restrict some of the flow and
           change your gas velocities or change the height of the
           core plate and get at some of those things.  So an
           answer, yeah, I think APEX would help.  I think maybe
           that sister facility may be a better place of
           exercising some of these parameters that apparently
           effect the correlations.
                       MEMBER SIEBER:  Just stepping back and get
           the big pictures.  ADS operates to get the pressure
           down enough so that you can inject from the
           accumulators.  Roughly, what is that period of time
           from the time that ADS-4 begins to operate until the
           accumulators inject and I'm sure it's a function of
           break size.
                       MR. BAJOREK:  Yeah, it's -- I believe that
           what happens in like a double headed guillotine
           transient is that the accumulators come in while
           you're still depressurizing.  The length of time then
           between ADS -- or excuse me, accumulator injection and
           the time you actually get the IRWST is on the order of
           several hundred seconds.  Mike, do you remember that?
                       MR. CORLETTI:  Yeah, the core makeup takes
           time to drain in about 20 minutes and then after that,
           the ADS-4 is actuated and IRWST injection can occur
           immediately to some time there's a delay a hundred,
           couple hundred seconds.  It ranges, as I said, based
           on the break size.  But it's not a long duration and
           essentially once you get the IRWST injection, we're
           flooding in the vessel in the hot leg and so we're up
           to, you know, a lot of water, a lot of water in the
                       MEMBER SIEBER:  Now, once ADS-4 operates,
           it's there forever, right?   It's open.
                       MR. CORLETTI:  It's open, yes.
                       MEMBER SIEBER:  Open to the containment
           forever.  All right, okay.
                       MR. CUMMINS:  This is Ed Cummins.  There
           is actually a black valve that you could close but
           that's not the intention.  The intention is that the
           steady state safety case remains open.
                       MEMBER SIEBER:  Right.
                       MEMBER KRESS:  But even then, steam
           condenses on the walls and goes back to the IRWST.
                       MEMBER SIEBER:  Yeah, there's a reciro
           path that -- yeah.
                       MR. BAJOREK:  Okay, well, thank you and I
           think the next presentation is by Ed Throm and he's
           going to talk about the containment issues.
                       MR. BURKHART:  This is Larry Burkhart just
           to be clear, our assessment on the codes testing and
           exemptions issues we documented in a letter to
           Westinghouse, not in a SECY.
                       MR. THROM:  Good morning, my name is
           Edward Throm and I'm with the Plant Systems Branch and
           I'll be going over the WGOTHIC computer program review
           that was done for the AP1000 Phase II evaluation. 
           WGOTHIC is the computer program that Westinghouse uses
           to evaluate the design basis accident response of the
           containment to double-ended guillotine primary LOCAs
           and main steam line breaks.  
                       The code is described in WCAP 14.407 and
           basically WGOTHIC is an extension of the numerical
           applications incorporated GOTHIC 4.0 computer program
           and what Westinghouse did was included a model in the
           code called a Clime which represents the heat transfer
           modeling to look at the condensation on the inside
           surface, through the wall and the evaporation of the
           PCS water flowing down the outside of the vessel.
                       The staff's evaluation was presented in
           NUREG-1512. It covered the scaling studies, the part
           studies, the testing program, a description of those
           parts of GOTHIC that we reviewed, our review of the
           Clime model and our overall conclusions on the
           acceptability of what we came to call an evaluation
           model for doing these types of analysis.  
                       The evaluation model basically consists of
           the use of the lumped parameter modalization process
           in the WGOTHIC program.  We believe that the lumped
           parameter approach is applicable based on looking at
           the buoyancy of the jets Froude number scaling, also
           in looking at international test programs such as the
           Patel model containment and the HDR which showed that
           you would get a fairly well-mixed environment for all
           parts of the transient. 
                       One issue that we had to deal with was the
           large scale test facility.  It was not really scaled
           for transient applications, so there were a lot of
           questions on the circulation, stratification and
           mixing of the steam environment within the
                       Westinghouse has addressed these in
           conservative manners.  Two address circulation, for
           example, after the blow-down period, they don't take
           any credit for steam that might get into the dead-
           ended compartments below the deck.  So they're not
           trying to take any credit for any mixing that the code
           might be calculating because of the uncertainties. 
           Stratification is also a concern with potentially
           creating an air blanket on the operating deck which
           will be a relatively large heat structure, so they
           don't take any credit for the operating deck as a heat
           structure in the analysis.  
                       Also for horizontal surfaces that may get
           condensing pools on them, they also don't count those
           as heat structures.  The other things that are done in
           the evaluation model, is the PCS flow and mass and
           heat transfer models are conservatively used.  They
           use minimum PCS flows in the massive heat transfer
           models.  They apply multipliers onto essentially bound
           the uncertainty in all the data that went into
           developing these models.  
                       The AP1000 is a little bit different than
           the AP600 as been noted before.  The power level is
           quite a bit higher, about 75 percent.  The vessel
           itself is about 25 feet higher.  It's a slightly
           larger volume.  In looking at the PIRT and looking at
           the fact that the AP1000 is using the same mechanism
           for heat removal, we didn't see any changes in the
           PIRT rankings of the important phenomena.  There were
           a couple of issues that we were concerned with in
           going up to the AP1000.
                       One of them was whether or not the shell
           temperature would get above 212 degrees Fahrenheit
           before the PCS water came on.  If that were to occur,
           then we would have a problem with the model for the
           film.  We'd have to consider boiling of the film and
           potentially breakup of the film.  Westinghouse did
           calculations that showed that at the time the PCS
           water would be credited in the calculation.  The shell
           is only going to be about 180 degrees, so we don't
           have to be concerned with that particular problem.
                       The other one was in looking at the
           increased power and basically size of the AP1000 and
           the stored energy and mass is somewhat larger than the
           AP600.  So the question was, are the massive heat
           transfer correlations still being used within their
           applicable range.  And that was pretty much the focus
           of the review was to go out and look at the mass and
           energy, the heat fluxes that had to be addressed in
           the correlations.  
                       Okay, then in summary, no new phenomena
           were identified in the process and the PIRT rankings
           remained unchanged.  The heat transfer models and
           correlations are being used within their applicable
           range.  This is based on scoping studies that
           Westinghouse performed provided to the staff in
           December of last year in which they looked at most of
           the dimensionalist groups and found that the expected
           performance of the AP1000 wold fall within the
           applicable ranges of all the data upon which these
           correlations were based.  
                       So we basically feel that WGOTHIC when
           used with the evaluation model, is applicable to the
           AP1000.  The lumped parameter, mixing, we expect it to
           be a well-mixed environment.  They're still using the
           same conservative approaches in addressing circulation
           stratification and heat transfer. In Phase III there
           are some things that we need to go back and look at
           because the scoping analysis were not done completely
           in accordance with the evaluation model but they're
           very close. 
                       They have not applied what they call their
           evaporated flow model.  And this is just a model that
           adjusts the PCS flow to only take credit for the
           amount of water that you could evaporate.  The
           standard review plan has mechanisms or guidelines for
           calculating the mass and energies from both LOCA and
           steam line releases.  The LOCA analysis that was in
           the scoping analysis is not quite in conformance with
           what we expect to see in the design certification
           analysis but we don't believe that that's a problem. 
           Also in the scoping analysis that Westinghouse did,
           they looked at the ADS-4, IRWST and sump flows based
           on the AP600.  There's going to be some changes to
           those in the long term and defining the mass and
           energies that you have to account for in the process.
                       So during Phase III we will go back and
           look at those evaluations again and we will --
           Westinghouse, I believe, is committed to providing us
           with similar evaluations to demonstrate that the codes
           are still being applied within the applicable ranges.
                       I don't see any particular problem with
           the expected changes in those but we reserve the right
           to assure ourselves that we haven't gone outside the
           applicability of the code.  We have done Contain 2.0
           audit calculations for the scoping analysis.  We got
           a very good comparison for the steam line break where
           the passive containment cooling system is not really
           a contributor to the peak pressure calculation. 
                       We did do the large break LOCA
           calculation.  We did not do it for a licensing case
           but we did it for the one of the reference cases that
           Westinghouse provided us back in December 2000 we
           calculated a peak pressure of about 54 psia compared
           to that calculation which would have calculated about
           60 psia.  The contained two code is designed to be a
           best estimate code for all practical purposes.  
                       We did to a sensitivity study that tried
           to mimic the penalties or multipliers that
           Westinghouse applies to the heat transfer correlations
           and we got about a two psi increase which we would
           expect.  We've not yet attempted to model or remove
           any of the other heat structures from the contained
           code to see if we could actually predict all of the
           conservative features that are in the evaluation model
           that Westinghouse uses with WGOTHIC.  We do plan to
           perform audit calculations as part of the Phase III
           review once the mass and energies are finalized and
           Westinghouse provides us with the detailed information
           to make sure we've got all the volumes and heat
           structures that we do apply in the code properly
                       So we believe that the WGOTHIC code is
           applicable to the AP1000.  That it will be used within
           its range of applicability in terms of the mass and
           heat transfer models that Westinghouse developed for
           the PCS.  That's all I really wanted to say this
                       MR. BURKHART:  Great.  Now, we'll turn it
           over to Walt Jensen to discuss the applicability of
           the reactor codes.
                       MR. THROM:  Thank you.
                       CHAIRMAN APOSTOLAKIS:  No, if he wants to
           stand, he can stand.  Do you want the mobile
                       MR. JENSEN:  I'm Walt Jensen of the
           Reactor Systems Branch of NRR and I was responsible
           for the review of the LOFTRAN, NOTRUMP codes that will
           be used by Westinghouse for analysis of AP1000.  The
           LOFTRAN code is used by Westinghouse for non-LOCA
           transients, including steam generator tube rupture and
           it's used with other codes to assess the maximum
           reactor system pressure, fuel temperature and the DNBR
           that might be obtained.  
                       The NOTRUMP code is used for small break
           LOCA but in the time between a break occurs and stable
           flow is established from the IRWST. After that the
           WCOBRA track code is used for long term cooling
           evaluation.  And the staff did detailed reviews of
           both these codes for operating plants in the mid-
           1980's and again for AP600 and wrote an SER in 1998.
                       The review process that we took just these
           codes that have already been reviewed in some detail
           in the past.  We looked at the differences that might
           effect the analysis between the AP600 and the AP1000
           plants.  In particular the PRHR heat exchanger carries
           a greater heat exchanger carries a greater heat load. 
           Steam generators are larger and the ADS-4 is larger
           and carries more flow and has a greater role in small
           break LOCA mitigation than it did for AP600.
                       We looked at the scaling, which you've
           just heard about, of the tests that were used to
           qualify the codes for AP600 to see if they would still
           be qualified for AP1000.  We obtained the Westinghouse
           standards for generating input to the codes and this
           is important because both codes are very versatile and
           allow many  user options.  And Westinghouse has
           established the set of options that should be used to
           analyze the passive plants and we reviewed those.  
                       And then we performed independent audit
           calculations using RELAP5.  We looked at a main steam
           line break, small break LOCA.  We got similar results
           as Westinghouse for small break LOCA, but we did get
           a very minimal amount of core uncovery for the double-
           ended DVI injection line break.  We took a look at the
           limits in NOTRUMP and analyzing the PRHR heat
           exchanger and we looked at the hot leg velocity and
           how it might effect the entrainment going out of ADS-
                       First, conclusions with LOFTRAN, we found
           LOFTRAN was capable of analyzing the anticipated
           transients and accidents, non-LOCA, for AP1000. 
           However, the steam line break is still open. 
           Westinghouse has not performed the steam line break
           for AP1000 and we are concerned that the voiding in
           the reactor system might extend beyond the capability
           of the LOFTRAN code, though they have done one
           preliminary calculation of steam line break that shows
           there to be very low voiding.
                       The NOTRUMP code, we also found that to be
           acceptable with the following exceptions that are
           still open, and number one is the liquid entrainment
           out of the -- which began in the core into the upper
           plenum and out of ADS-4.  Westinghouse has proposed to
           bench mark the NOTRUMP code which has a very
           rudimentary entrainment model against the WCOBRA tract
           that they've modified with correlations to predict
           entrainment and then they will bench mark that WCOBRA
           tract code against experimental data which is still
           under discussion with the staff.
                       Perhaps we will do some sensitivity
           studies with RELAP to see the effect of entrainment on
           the core.  The conservatism of the PRHR heat exchanger
           model is still under review.  There's a limitation in
           NOTRUMP to limit the code to flow rates in the primary
           side of the PRHR heat exchangers to less than 1.5 feet
           per second and this is based on a limit in the heat
           flux comparisons with the experimental data by the
           time correlations that's used in NOTRUMP that was
           found to be non-conservative in comparison to the
           experimental data for high heat flows.  
                       So we'll be looking at that but
           preliminary studies here show that the PRHR heat
           exchanger flow has a very small effect on the course
           of a small LOCA.  And finally, we only looked at a few
           breaks with either RELAP or NOTRUMP and the
           entrainment issue is still open and this will effect
           the results.  So if core uncovery is calculated, we
           will have to take up the review of the core uncovery
           models in NOTRUMP and in the SBLOCTA code that's used
           to evaluate the final core temperature when the core
           is uncovered.  
                       So that's where we stand at the end of
           Phase II and we will be continuing the review in Phase
           III.  Thank you.
                       MR. BURKHART:  Thanks, Walt.  Just a quick
           summary, again, the scope of Phase II was limited to
           four issues.   You've seen this slide before, this was
           from my introductory slides.  As you've heard in
           general, the AP600 testing program and analysis codes
           are applicable to the AP1000 design.  We've noted some
           exceptions and where we will focus our efforts on the
           review during the design certification review.  
                       We've also shared that the staff finds the
           DAC approach in the I & C, human factors, control room
           design and piping areas acceptable and also that the
           three exemptions that are proposed for AP1000 are
           applicable.  And that concludes our presentation of
           the staff's assessment.  I'll turn it over to Mike for
           Westinghouse's presentation.  
                       MR. CORLETTI:  We'll have Bill Brown, will
           be our next presenter, will be presenting some of the
           issues in regards to the applicability of the tests in
           response to Steve Bajorek's presentation.
                       MR. BROWN:  Okay.  PIRT scaling and
           entrainments assessment; Steve's already covered a lot
           of this which we pretty much agree on most points, and
           that is that there is no new phenomena expected for
           AP1000 and we've already submitted our scaling
           analysis to demonstrate that our 5600 test facilities
           are applicable to AP1000.  We previously presented
           this work to both the NRC and the ACRS subcommittee.
                       Obviously, there were some issues
           discussed here with respect to entrainment, especially
           in the upper plenum and because of that, we went back
           and did some additional evaluation and some scaling
           which I'll present here in a moment.  Before I do
           that, though, I thought it was maybe a little bit
           helpful in that I tried to come up with a -- sort of
           an integral effect type of a slide to put this
           entrainment a little bit in a system level
           perspective.  I know we kind of have focused on this
           a lot from a very separate effect level and it
           certainly is something that is considered to be high
           ranked or important during the ADS to IRWST transition
           phase of the transient but I think we need to keep in
           mind a couple of things that are going out during this
           time frame as well as not only do we have stuff going
           out but we've also got potentially a lot of stuff
           going in.
                       And one of the biggest things to always
           keep in mind is that we've got roughly a 600,000
           gallon tank sitting up here after the core make-up
           tank, which is continuing to drain through the ADS-4
           as well, that is certainly willing to sit there and
           feed whatever entrainment that might be going along,
           but based on our testing and a lot of the analysis
           that we had done on the AP600, what we would expect to
           see here which we had seen in AP600, is more of a
           situation where you might start off in a phase where
           you've got the ADS-4 is on and been actuated and is in
           here venting steam to reduce the RCS pressure. 
                       We've got injection from a core makeup
           tank and then later here with a significant amount of
           water from the IRWST potentially available here to
           inject.  We've got liquid perhaps in a first phase
           being entrained from the upper plenum due to the high
           steam flow associated with the AP1000.  We would
           expect some amount of phase separation in the hot
                       Some of the de-entrained liquid here would
           initially start to accumulate somewhat in the hot leg. 
           We would expect that this process would continue.  As
           Steve mentioned earlier, we probably wouldn't
           initially get a significant amount of entrainment
           through the ADS-4 at this point until we reach a
           critical inception level within the tanks so that the
           velocity is high enough and to draw it, sort of a
           Bernoulli effect, sort of sucking the water out of the
           hot leg, so that we continue replenishment here in the
                       The ADS-4 would still be venting and
           eventually we hit this point where we begin to hit an
           inception point we now begin to entrain the liquid up
           into the vents.  At that point, then, as we would draw
           the liquid up into the vents at this point, now you've
           got the vents now that were predominately venting
           steam out probably got to clear this liquid out, so at
           that rate we'd probably see a bit of a reduction in
           the amount of injection but on the other hand, now you
           don't have a nice path for the steam to go out any
           more, so now you've temporarily got a lower velocity
           of steam and so you've got an entrainments reducing.
                       So the system is kind of correcting itself
           here a bit and it's clearing itself purging the liquid
           out.  So eventually you clear out, so again you get
           the pressure back down, you've vented the steam here,
           so now you can resume to inject more water and entrain
           more liquid out here and the process would then repeat
           and we would see this going on through the long-term
           cooling phase.
                       So that just sort of sets up a little bit
           of the, I think, more of a system level effect to put
           the local entrainment into context for you.
                       MEMBER SIEBER:  If I look at the slide 9
           and compare it to your drawing, it looks like ADS-4
           comes off the line at the next ER of EST to the hot
           leg, instead of as you show it there where it comes
                       MR. BROWN:  The ADS-4 here?
                       MEMBER SIEBER:  Yeah.
                       MR. BROWN:  The ADS-4 comes off the top of
           the hot leg.
                       MEMBER SIEBER:  Now, the IRWST line comes
           in the same place, right?
                       MR. CUMMINS:  This is Ed Cummins.  I think
           the thing that you're looking at is the PRHR heat
                       MEMBER SIEBER:  Okay.
                       MR. CUMMINS:  The PRHR heat exchanger is
           a tank within the IRWST.  It is connected to one of
           those two ADS four lines.  
                       MR. BROWN:  Off the top of this line right
           here, you would have a connection from PRHR off of one
           of these ADS-4s that continues up and then that comes
           up into here which is the exchanger sitting in the
           tank here.
                       MEMBER SIEBER:  All right.
                       MR. CUMMINS:  If you look at slide 10, in
           your presentation, all the injection from the core
           makeup tanks to the accumulators and the IRWST for
           make up to the reactor vessel, is through two direct
           vessel injection lines which are basically independent
           of other lines.
                       MEMBER SIEBER:  Okay, I see that.  Thank
                       MR. BROWN:  In fact, we finally see in the
           tests that the PRHR actually helps to provide
           fissional depressurization because it does condense
           more steam.
                       MEMBER POWERS:  Can you give me a feeling
           for during this period where you have entrainment what
           the superficial gas velocity through the core region
                       MR. BROWN:  Through the core region
           itself?  Well, obviously not as -- I think really the
           highest velocity you could get is through the upper
           core plate.  That's really the highest velocity that
           you get.  It's pretty substantial.  I'm trying to
           remember what that was off-hand.  Steve, do you
           remember?  Is it 100 feet a second or something like
           that?  I think it's pretty high.  And it's moving up
           through there, yeah, yeah, to the core plate and then
           you would expand into the upper plenum where you -- 
                       MR. BAJOREK:  This is Steve Bajorek for
           Research.  I don't exactly remember the velocity at
           the core plate.  However, in the AP1000 your
           superficial velocity through the upper plenum, the
           free part was about two and a half meters per second. 
           So given that there was a restriction down at the core
           plate, three to four maybe.
                       MR. BROWN:  It's probably somewhere
           between those to if you want to try to bound that,
           yeah.  It's definitely higher than AP600.  
                       Well, I just wanted to start with that
           one, just to sort of put it in sort of a system level
           context, so Steve's gone over some of this before. 
           We've looked at the -- first of all in the upper
           plenum entrainment.  Some of the work by Katoaka-Ishii
           looked at full entrainment in vessels and identified
           a near surface region and a momentum controlled
                       The near surface region, very, very close
           to the water surface, was found to correlate simply on
           a density ratio.  The momentum controlled region,
           where you would move further away from the surface of
           the liquid, was found to be a function of density
           ratio, hydraulic diameter, viscosity number, but
           primarily most strongly upon superficial gas velocity
           divided by a dimensionless height.  So it's really a
           combination of the two of the Jg star and an H star
           which are really the dominant terms in the momentum
           controlled regime.
                       And to help you a little bit we're trying
           to put this again, in context in terms of what type of
           events might this be of interest to us or what type of
           events would we be looking at things where we have,
           for example, a level in the hot leg, we would be more
           interested in what is the near surface type of
           entrainment where we essentially have water already in
           the hot leg, we're not having to lift it up from the
           vessel into the hot leg, it's already there, versus
           events where we would get into a momentum controlled
           regime where we've got to actually lift the water
           droplet up into the hot leg.
                       If you think of some of the two slides
           that Steve just presented, you can see a good -- he 
           had a better picture of that than I do.  These would
           give you an idea of the type of events that we've seen
           not just from analysis but also from looking back at
           the OSU tests for example, and all the test programs. 
           Typically, the half inch, the one inch, the two inch
           cold leg breaks, the hot leg break, two inch DVI and
           the doubled ended core make-up balance line break, all
           typically have a level within the hot leg already.  So
           for those events we've got a level in the hot leg. 
           We're in this near surface entrainment regime and
           looking at the scaling.  This indicates that we're
           simply a function of a density ratio and since we
           essentially have pressure scale facilities, the
           scaling is good.  
                       So the one in which we have a momentum
           controlled regime where we don't have a level in the
           hot leg, really is the DE DVI line break.  So this is
           really the focus of all this.  So we even talk about
           entrainment, you know, trying to put it in a system
           level context and now in terms of events, which ones
           are we focused in on.  So we really, if you look at
           all these tests, we're well scaled as far as
           entrainment is concerned.
                       In the hot leg, for example, we've got
           mixture levels in there and it's really only the DE
           DVI line break that we really need to focus in on.  So
           based upon looking at this type of pool entrainment,
           similar to the work of Kataoka-Ishii, we would say
           that the entrainment is well scaled in the test
           facilities for small break LOCAs where we've got a
           mixture level in the hot leg, which was most of the
           small break LOCA events I just listed, where pressure
           is preserved and therefore, density.
                       It's in this momentum entrainment,
           momentum controlled regime in which we're dependent
           upon the superficial gas velocity divided by height in
           which we have a potential distortion in the AP600 test
           facilities due to the fact that we do have a higher
           superficial gas velocity in the AP1000 core.  
                       MEMBER RANSOM:  Excuse me, what is the
           dimensionless height?  Is that just a height through
           the outlook flow?
                       MR. BROWN:  Yes, it's basically, if you
           did a measurement, yeah, it's basically how far do you
           have to lift up a droplet in order to carry it away,
                       MEMBER KRESS:  How do you non-
           dimensionalize it?
                       MR. BROWN:  It's non-dimensionalized, I
           think, it's got a square root of density difference,
           gravity and surface tension.  I think that's how it's
           -- so essentially, again, if you have a pressure scale
           facility, you're just looking at just dimensional H
           really and the velocity.  And we are at this time in
           the transient, we've essentially depressurized in the
           facilities.  We're to the point where you're really
           looking at just Jg divided by H, dimensional.
                       It gives you a little better idea, I guess
           on the next page here.  I tried to put this together
           a little bit in another way to digest this
           correlation.  Some of the details are down below, but
           essentially if you were to start off with the
           correlation here that Steve presented earlier, that
           you've got the Jg divided by H star cubed and the
           viscosity number and the hydraulic diameter number,
           you can eventually -- you can relate this for pressure
           similitude and for saturated conditions in the vessel. 
           You can come up with an expression for Jg and come up
           with a simple expression like this where you've got
           core power, area, height, and the hydraulic diameter
           ratio here as far as looking at entrainment in a pool
           type situation.  So this is really the basis for which
           to look at.
                       And the key is, is obviously, this term
           right here is really the -- obviously, the dominant
           term, the core power and the height and the area. 
           When you try to take this scaling ratio and put some
           numbers into it, similar to the question you asked Dr.
           Powers about the velocity and so on, if you sort of
           range the velocity through the upper core plate up
           into the upper plenum, you would come up with a number
           in this range of roughly a quarter to a half, which,
           you know, based on our criteria, the half were here,
           based on the criteria that was used previously by
           Brookhaven for AP600, at roughly a third, it kind of
           looks like we're -- you know, we're kind of close.
                       So you know, we find that we're certainly
           in the range at which I think Westinghouse would say
           that, well, there may be a possible distortion, we're
           certainly on the non-conservative side, as Steve says,
           but we don't think that this distortion is very far
           off that we can't use this data for code validation
           purposes for AP1000.
                       The next step, I sort of tried to ask
           myself a little bit presented before to the
           subcommittee was, well, what does this -- what might
           this correlation look like?  If I were to come up with
           a little simple model of an upper plenum mode where I
           had really no water in the hot leg and I was just
           worried about I've got some mixture level sitting up
           above the core in the upper plenum at the bottom of
           the hot leg and what if I put in this pool entrainment
           correlation and essentially assume that the core decay
           heat was driving it off.  I had just enough liquid
           here or mass flow to make up and match decay heat at
           that time.  Well, what might happen and how long might
           it take for this entrained liquid to effect the upper
           plenum level?
                       So I come up with sort of a simple little
           model here in which I had a transient conservation of
           mass here for the upper plenum and I just started with
           the upper core plate to the bottom of the hot leg as
           this initial two-phase region.  And I used a simple
           void fraction correlation using the YEH correlation
           here to determine void fraction in this area right
           here.  And then I used the upper -- for the upper
           plenum entrainment, then I used the pool entrainment
           correlation form from Kataoka-Ishii here to try to
           determine what was the mass flux of the liquid that
           was entrained out of this mass and then from a
           conservation of mass on the core, and I just for
           conservatism I decided not to even account for any of
           the sub-cooling which might help me here and said,
           well, even if I just simply have saturated conditions
           in the core here, what might my steam generation rate,
           steam velocity be?  
                       So then I did this, and I put this into
           MathCAD.  This is the result I got which showed that
           very, very quickly, extremely quickly, I approached
           sort of a quasi-steady state level above the top of
           the core plate here and within seconds, I reached an
           equilibrium level.  So, very, very quickly this very
           strong function of entrainment, this Jg really dropped
           me very rapidly but then, of course, remember that
           it's Jg over H and so H very quickly restores you into
           sort of a self-limiting type process and so at some
           point you very rapidly settle out at a steady state
                       So it kind of gives you a feeling of what
           the -- how the correlation and the behavior should be
           for this type of entrainment.  So what I concluded
           from this was that are entrainment was sufficiently
           scaled in the upper plenum for all possible events
           with the exception of maybe the DE DVI line break in
           which we didn't have a hot leg -- a level up in the
           hot leg for very long there during this phase.  And
           that the entrainment scaling was really of concern
           during this transition phase of the DE DVI vent where
           we were subject potentially to this momentum
           controlled regime.  That this distortion in OSU does
           not appear to be so large that would render our codes
           unusable and that the momentum controlled regime, the
           entrainment in the upper plenum here seems to be
           somewhat of a self-limiting process because we've got
           the Jg relative to H and because of this, we don't
           expect to really see that there's going to be a
           serious safety issue here with AP1000.
                       We also looked at hot leg entrainment as
           well, and we expect to see a stratified type pattern,
           although certainly Steve says we may see some slugs in
           there and that's possible.  I don't expect to see
           cliescent (phonetic) stratified flow but we certainly
           expect to see something that's stratified.  
                       There's a Froude number type correlation
           with a length to diameter of up-take type of
           correlation which is responsible for predicting the
           onset of entrainment from the flow into the hot leg,
           into the ADS-4 and this was used to scale this.
                       The results of the scaling indicated that
           our Froude number seemed to be acceptably scaled to
           AP600 and AP1000.  The real difference was in the
           dimensionalist ratio of liquid level in the hot leg
           relative to the ADS-4 pipe, which would indicate,
           which I would agree with Steve, we would expect to see
           -- we would expect to see entrainment begin at a lower
           level in the hot leg in AP1000 relative to AP600 and
                       However, I guess I'd say on the other
           hand, the fact that we've got a level in the hot leg
           and we're looking at those type of events, it's not
           something I think that's quite as much of a concern. 
           We probably would accumulate less water in the hot
           legs, however, usually having the hot water -- having
           the level in the hot leg would tend to indicate we've
           got core coverage.  So we're certainly not as
           concerned about that event than we would where we're
           going to go below the hot leg potentially in events
           such as a DE DVI event.
                       So some of our plans for trying to address
           this situation in Phase III, we're going to
           demonstrate through calculation and analysis that the
           entrainment phenomenon in the upper plenum and hot leg
           during this limiting small break LOCA does not
           challenge the safety and see it as sort of using a
           term of extreme entrainment here would be addressed on
           one of several ways; assessing margins relative to the
           regulatory limits, adjusting upper plenum/hot leg
           correlations to increase entrainment, assessing upper
           plenum de-entrainment due to the reactor vessel
           internals, also potentially increasing pressure drop
           in the ADS vents such as whenever the liquid is being
           discharged through there and we plan to submit a
           topical report to address this later this year in
                       The overall conclusions that I have from
           the testing and scaling, again, no new phenomena in
           AP1000.  The separate effects and integral effects
           tests are acceptably scaled.  Upper plenum
           entrainment, there's a local effect that appears to be
           self-limiting.  We don't think additional testing is
                       MEMBER POWERS:  Can I ask a question?
                       MR. BROWN:  Yes.
                       MEMBER POWERS:  Which you showed was a
           simple calculation --
                       MR. BROWN:  Yes.
                       MEMBER POWERS:  -- in which you had an
           entrainment and then you had water feed.
                       MR. BROWN:  Uh-huh.
                       MEMBER POWERS:  And you said, gee, it
           starts at one level and it comes to another level.
                       MR. BROWN:  Right.  
                       MEMBER POWERS:  It seems to me that that's
           an unremarkable conclusion for a first order
           differential equation with a source and a think term
           to come to another level.  That has nothing to do with
           the entrainment correlation.  It has to do with the
           fact that you've got a loss term and a gain term. 
           They balance each other if you go out long enough in
                       MR. BROWN:  That's true, but I think I'm
           just trying to demonstrate the fact that I think
           sometimes when the entrainment is presented, people
           tend to forget about the fact that there is -- that in
           looking at certainly the relative order, that there
           certainly is a restoring term in there for H as far as
           how far that level is.
                       MEMBER POWERS:  But that calculation
           doesn't show that.  I mean, the calculation only tells
           me a loss term and a gain term and the relative
           magnitudes of those two will determine where that
           balance is.
                       MR. BROWN:  Yeah, and well, we're not
           trying to make -- at this point, not trying to make
           any claims about the absolute value of where that
           steady state level is.  I'm not trying to make any
           claim about that at all.  I mean, certainly this is a
           very simple calculation.
                       MEMBER POWERS:  I thought what you were
           claiming that this was self-limiting because as that
           H got bigger and bigger it reduced that J over H term
           to --
                       MR. BROWN:  Right.
                       MEMBER POWERS:  -- the point that -- and
           that's just not obvious to me that that's the case at
                       MR. CUMMINS:  Hello, this is Ed Cummins. 
           I think what Bill did in his calculation just for
           simplicity, he set the in-flow equal to the out-flow 
           so that the mass was -- the core was covered and what
           he was trying to assess was the effect of -- the
           separate effect of entrainment, which is the same
           thing that Steve was trying to assess.  It's not the
           whole integral effect.
                       So if you assess the separate effect of
           entrainment, what is the effect of H and Jg working
           together for the entrainment phenomenon and I think
           those things suggest that at some level Jg dominates
           and then after awhile H corrects it.
                       MR. BROWN:  The point is to try to find
           out at what H do we come to some kind of a steady
           state.  I mean, I agree that it's a steady state
           calculation.  I mean, eventually we're getting to that
           point, but there is an H associated with that Jg in
           which you balance and the question I have the interest
           is, is well is it something that looks like it's, you
           know, a foot or two away or is it 20 feet deep or how
           far into this thing does it look like it goes and so
           that was of some use.
                       MEMBER POWERS:  I can make that carried
           out, just by changing your inlet term.
                       MR. BROWN:  Well, it was driven by the
           decay heat in this case.  I mean, the decay heat was
           driving the mass flow which was representative at this
           point in the transient.  So yes, if I picked a
           different decay heat, sure I would get a different
           value and this certainly should decrease over time.
                       MR. CUMMINS:  If you deal with -- Ed
           Cummins again.  If you deal with the entire system
           performance, then the top down scaling is appropriate
           and whether you get in-flow and out-flow depends
           mostly on the relative pressure drop between the
           forced states and the pressure available from the
           IRWST.  But as we, I think pretty much agree with the
           staff, the top down scaling for the AP1000 is
           acceptable and we happen to be now looking at a bottom
           up scaling for a particular phenomena which is pool
           entrainment from the upper head pool and what we were
           trying to show that performance with some simple
           calculation to give you a feel for what the
           characteristics were.
                       MR. BROWN:  I mean, it's very similar to
           some of the things we had done in AP600, looking in
           the containment.  I mean, we all felt eventually that
           we would, for example, remove the energy through the
           containment shell.  What the question is, is at what
           temperature would the inlet -- the flow through there
           balance and that's simply what I was trying to get at
           was, okay, given that this entrainment occurs, what
           would be the height at which I would reduce to given
           the core power which would, again, influence the
           velocity, at what height at which I would be able to
           balance the entrainment relative to the flow that was
           coming in?  That's all I was trying to get at.
                       MEMBER POWERS:  And again, let me control
           the source term and I can make that height anything
           you want.
                       MR. BROWN:  Again, I would agree that if
           we put a different flow rate in there, we'll come to
           a new value.  It's just that I was using typical
           values that we got from our safety analysis code at
           the time in which ADS-4 went off to represent to you
           what might that look like at the time when ADS goes
           off.  And so we went into the code and said, okay,
           what's the decay heat during that period and said,
           okay, this is how many BTUs per second we're putting
           into this point, this is the energy that's driving
           this.  What does that -- what might that steady state
           height come out to be?  
                       Any other questions?
                       MR. CUMMINS:  Yeah, I think it's important
           that we have not completed the calculation in the
           topical report we plan to submit.  When you use the
           appropriate decay heat for the point of -- the point
           of time for the transient, I think, you're right, you
           could put any heat level in you want and drive any
           answer, but when you put the appropriate decay heat
           level, we'll have -- essentially we'll see a delta on
           what the level could be.
                       MR. BROWN:  Yeah, and we were curious
           about that ourselves, so we decided to try it and see
           what it looked like.  
                       MEMBER KRESS:  Do you have this model
           built into your code?
                       MR. BROWN:  Not this specific one like
           this, no, but again, this was again, sort of a --
                       MEMBER KRESS:  I mean, the entrainment.
                       MR. BROWN:  -- yeah, what would this look
           like if we were --
                       MR. CUMMINS:  Ed Cummins again.  I think
           when we deal with both injection and venting, we go
           back to the system level performance and we get away
           from the local effects.  And if you remember I think
           both the staff and Westinghouse feel that on a system-
           wide basis, the AP1000 scaled well to the test and on
           a system-wide basis we would expect that the level
           predicted would be scaled.
                       MR. BROWN:  Anyway we do intend to do a
           topical in which we would actually to certainly some
           more rigorous calculations here and so on.  This was
           just in the time frame that we could get to present
           was to get some sort of an order of magnitude of what
           we were looking at relative to the best information we
           had as far as decay heat and so on at the time, the
           best estimate of a velocity we could get there.  
                       Yes, Steve.
                       MR. BAJOREK:   This is Steve Bajorek from
           Research.  I guess I just want to kind of add to it. 
           Our concern is a couple fold on this.  As we look at
           things from a top down system-wide level, okay, we
           would agree that most things are okay.  However, when
           we have to look at these bottom up processes, we have
           to limit ourselves to the steady state behavior and on
           that basis we are restricted because the correlations
           that are developed, we have questions on whether they
           apply strictly to the geometry that we're now trying
           to extend those two. 
                       Secondly, when it goes back to the system-
           wide effects, we have to add flashing terms back into
           this.  And when we look at both of those occurring
           simultaneously, this leads to our concern and question
           that even on a system-wide basis, should we be
           concerned with additional liquid being flushed out of
           this upper plenum.  
                       So I think at this point we would still
           disagree with the statement that APEX is well-scaled
           for this particular process.
                       MEMBER KRESS:  Okay, we have what --
                       MR. BROWN:  Michael just has a --
                       MR. CORLETTI:  Yeah, and I could probably
           summarize right from here.  I think Bill's pretty much
           summarized our conclusions.  Our conclusions with the
           tests in regard to the applicability of the tests
           remembering the four issues we were asking the staff
           to approve here was the applicability of our AP600
           test to AP1000.  We believe we've shown that by and
           large these tests are applicable and we believe are
           sufficient for certification for AP1000.
                       The one issue that does remain is this
           effect of entrainment.  We believe we'll be able to
           demonstrate that when you take it in context with the
           large margins we have, and not only margin to core
           uncovery but also margin to regular limits as far as
           peak clad temperature are essentially -- for instance
           for one of the loss of core accidents for AP600 where
           we did have core uncovery that's for the 10-inch
           break, we had a core heat up of 400 degrees PCT
           because it was a very short duration.  
                       We had -- essentially, this plant is not
           a small break LOCA limited plant and we will be able
           to show a very large margin to regulatory limits in
           that regard.  So I think in that context, this is why
           we believe we'll be able to demonstrate that in our
           topical report with that sort of a bounding
                       With regards to our analysis codes, we are
           -- our conclusions were that they are largely
           applicable to -- they are applicable to AP1000 and
           then will be able to be used for design certification. 
           There are certain conditions that the staff has pretty
           much made clear.  They've spelled them out here and
           our plan is to follow those conditions as far as
           design certification.  
                       In regards to the other issues on the
           piping DAC and I think we are in agreement with the
           staff's position on that.
                       MEMBER KRESS:  Okay, thank you very much. 
           I think that brings us to the end of this session. 
           We're running a little late.  At this time I'm going
           to declare a break until 11:00 o'clock and some of us
           will not come back, including our chairman. 
                       MEMBER POWERS:  And I won't be back here
                       MEMBER KRESS:  So we won't have a quorum. 
           so I guess we're recessing now till 1:00 o'clock.
                       MEMBER POWERS:  And I don't think you need
           the Reporter any more, do you?
                       MEMBER KRESS:  And I think this is the end
           of the need for a Reporter.  We'll recess until 1:00
                       (Whereupon, at 10:44 a.m. the above-
           entitled matter was concluded.)

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