Thermal-Hydraulic Phenomena - July 18, 2001


                Official Transcript of Proceedings


Title:                    Advisory Committee on Reactor Safeguards
                               Thermal Hydraulic Phenomena Subcommittee

Docket Number:  (not applicable)

Location:                 Corvallis, Oregon

Date:                     Wednesday, July 18, 2001

Work Order No.: NRC-325                             Pages 323-556

                   NEAL R. GROSS AND CO., INC.
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                           PTS RULE REEVALUATION
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                               JULY 18, 2001
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                             CORVALLIS, OREGON
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                 The ACRS Thermal Hydraulic Phenomena
           Subcommittee met at Oregon State University,
           Richardson Hall, Room 313, Corvallis, Oregon, at 8:15 
           a.m., Dr. Graham B. Wallis, chairman presiding.
                 GRAHAM B. WALLIS, Chairman
                 THOMAS S. KRESS, Member
                 WILLIAM J. SHACK, Member
                 PAUL A. BOEHNERT, ACRS Engineer
                 JACK ROSENTHAL, U.S. NRC, RES, SMSAB
                 DAVID BESSETTE, RES/SMSAB
                 VIRGIL SCHROCK, ACRS Consultant
                 ROY WOODS, NRC RES/DRAA/PRN3
                 JAMES T. HAN, RES/DSARE/SMSAB
                       Agenda Item                         Page
           Loop Stagnation and Fluid Mixing in the
                 Reactor Vessel Downcomer Mechanics
                 for Primary Loop Stagnation. . . . . . . . 326
           Cold Leg Thermal Stratification and
                 Plume Formation in APEX-CE . . . . . . . . 366
           Downcomer Thermal Stratification in APEX-CE. . . 426
           REMIX Calculations of APEX-CE Tests. . . . . .   436
           3-D CFD Model of the APEX-CE Test Facility . . . 490
           Summary and Reporting Schedule . . . . . . . . . 540
                                                    (8:15 a.m.)
                       CHAIRMAN WALLIS:  This is the meeting of
           the Thermal Hydraulic Subcommittee of the ACRS.  We're
           looking forward to hearing from Professor Jose Reyes
           and his folks.
                       MR. REYES:  Thank you.
                             VESSEL DOWNCOMER
                       MR. REYES:  Yesterday we started by
           discussing a little bit about the overall program and
           we got into some of the integral test data.
                       Today we're going to focus more on the
           separate effects or the local behavior in the
           downcomer. So the presentations you'll see today all
           deal with plume mixing and our predictions of plume
           mixing or plume behavior in the downcomer.
                       And we'll also talk a little bit about the
           -- this is kind of the bridge presentation here -- the
           primary loop stagnation.
                       What we found was that some of the
           behavior in the cold leg, as affected by HPI
           injection, affects overall loop properties, in
           particular, loop stagnation.
                       So we've identified the different
           mechanisms for loop stagnation.  So I will talk about
           -- one of our tests is an inventory-reduction test. 
           And this is like being able to take snapshots of a
           small break LOCA in progress.  And it's similar to
           some of the tests that performed the Semiscale.  And
           I actually compared some Semiscale data to our
           facility just to give you a feel for where we lie in
           comparison for that.
                       But that gives an idea of as we void the
           plant and the steam generator tubes drain, at what
           inventory would stagnation occur.  And it coincides
           with reflux condensation.  So we'll look a little bit
           more at tube voiding then.
                       Also in terms of one of our tests and what
           we saw there, how tube draining would result in loop
           stagnation for us.
                       And then steam generator reverse heat
           transfer and then loop seal cooling.  And I'll talk a
           little bit about some of the downcomer behavior we
           observed and how that affected the integral system.
                       The reason there's been so much focus on
           stagnation in the past is that it was identified that
           under stagnant loop conditions with HPSI injection,
           that that would most likely be the most severe case
           for producing cold plumes in a downcomer.
                       And I think today what you'll see is that
           we've come to a slightly different opinion for this
           particular plant, and we'll show you why.
                       So first the stepped inventory reduction
           test.  This test was performed basically by holding
           the power constant.  We had a constant steam generator
           pressure, and we opened up a small break on the
           reactor pressure vessel and we would drain some of the
           inventory.  We would stop the drain, and then we would
           let the system go through natural circulation.  And
           we've measured the flow rates in each of the cold
           legs.  And we --
                       CHAIRMAN WALLIS:  Do you have a break in
           the vessel?
                       MR. REYES:  Remarkable.  It's just a small
           little drain valve.
                       CHAIRMAN WALLIS:  It doesn't sound like
           one of those standard accidents, does it?
                       MR. REYES:  No.  It's not a -- this is not
           a standard accident.  This is a drain valve that we
           use for setting up the plant.
                       So we would continue in step-wise fashion,
           drain the plant.  We stopped the drain.  We let it
           reach steady-state natural circulation conditions.  We
           go single phase and then we transition to two-phase
           natural circulation.  And then eventually we pass a
           maximum and then to zero conditions.
                       And the same tests were performed in
           Semiscale back in the 19- -- late '70s, early '80s
           maybe -- a while ago.
                       MR. SCHROCK:  So it's a series of
           steady-state tests that reduced inventory; is that
           basically it?
                       MR. REYES:  That's correct.
                       So we start -- in this corner here, we're
           starting with a system completely filled or including
           a pressurizer, and we let it go to natural circulation
           conditions.  And so these are the flow rates, the
           cold-leg flow rates that you'd see.
                       This is the sum of all the cold-leg flow
           rates is the core flow rate.  And you see for this
           region here it's fairly flat.  And what we're seeing
           is just single-phase natural circulation.
                       We transition then.  As we drain our
           inventory on the bottom, on our x axis here, this is
           a percent of overall reactor coolant, the primary-loop
                       As we drain, we reach a knee here, an
           inflection point, and now we're starting to go
           two-phase.  And we see an increase in our core flow
           rates.  And this is measured by the flow in the cold
                       And so what we found in this test is that
           loop seals play a nice role of separating -- of
           keeping the cold legs single-phase.
                       As we continued reducing our inventory, we
           reach a maximum.  And presumably the maximum coincides
           with the point where you've essentially got two-phase
           going up the tubes and essentially all-condensed
           liquid coming down, or something very close to that. 
           So that would give you your maximum flow through the
                       As we continue draining, then we start
           seeing a decrease in the flow.  These dark triangles
           are steady-state points and the diamonds are actually
           the transient data.
                       And we come down further and further as we
           reduce -- somewhere around 60 percent of our overall
           primary mass we reach a point where essentially we're
           in reflux condensation.
                       And the measured flows then in the cold
           leg are essentially zero.  So injection during this
           point would produce conditions similar to what's been
           tested in the past:  Cold injection with stagnant
           conditions in the primary loop.
                       So our system was about 60 percent of the
           overall inventory.  We want to compare that to what
           was done in the past with Semiscale.  You can see that
           the trends are very, very similar.  We're just a
           little bit offset to them.  This has been normalized
           to the same maximum there.
                       We -- somewhere they both around 65 to 70
           percent -- my battery's charged -- somewhere around 60
           to 65 percent of the mass -- of the total inventory --
           now this excludes the pressurizer liquid mass.  That's
           why the number's different here.
                       Semiscale performed the test with the --
           starting with their pressurizer essentially empty.  So
           they -- all their numbers were based on the percentage
           of primary mass without the pressurizer inventory.  So
           that's what's been done here.  So we have very similar
           results for this design.
                       Okay.  Well, that gives us an idea that if
           our inventory during a small break LOCA drops to
           about, in this case, 65 to 70 percent of the plant
           inventory, of our initial inventory, we would expect
           it to be in stagnant conditions.
                       MR. SCHROCK:  There's an implicit
           assumption that the inventory distribution is the same
           in a steady-state reduced inventory situation as in a
           transient.  What transient, I guess, is the question
           that comes to mind.
                       MR. REYES:  That's right.
                       MR. SCHROCK:  You have on the previous
           graph a lot of data points designated as transient
           data.  What is the transient, just --
                       MR. REYES:  Good.  The --
                       Would you turn to the previous slide for
           me, please?  One more.
                       MR. SCHROCK:  The one before that.
                       MR. REYES:  Yeah, that's it.  Thanks.
                       So what we're designating here is -- what
           we were doing with these steady-state points, we were
           holding at one position and just repeating the
           measurement and coming up with an average condition. 
           And that's how the tests were performed at Semiscale.
                       When we looked at our actual measurements
           throughout the test, as we were -- as we were
           draining, we saw that our drain was slow enough to
           where we actually could use the -- and I'm calling
           this the transient data, because it includes the time
           periods when we were actually draining the facility,
           so the triangles represent the step changes.
                       We found that the transient data in
           between the step changes, because the drain was slow
           enough, seemed to match the steady-state data rather
                       CHAIRMAN WALLIS:  So this isn't some kind
           of a standard transient.  This is a transient that you
           -- you -- you did --
                       MR. REYES:  That's --
                       CHAIRMAN WALLIS:  -- and you did it slow
           enough so that it was quasi-steady state?
                       MR. REYES:  That's right.  So this is --
           that's exactly right.  So this is --
                       MR. SCHROCK:  A small break line on the
                       MR. REYES:  Correct.  So we're draining
           from a low region in the plant.
                       And the idea was just to see what kind of
           inventory behavior.  So you're absolutely right. 
           Depending on the break location, we would see
           different -- different behavior, different voiding of
           the steam generator tubes.  The void distribution is
                       This is just a snapshot of a very
           particular controlled test or controlled small break
                       MR. SCHROCK:  So your transient in this
           case is -- appears to be always quasi-steady?
                       MR. REYES:  That's right.  That's right.
                       And originally we were just going to use
           the steady-state data itself to compare with Semiscale
           because that's how they performed their test.  But as
           we looked at the overall data we realized that --
           actually the test was performed slow enough to where
           we could use the transient data.
                       Okay.  So that gave us -- at least that
           gave us some idea of how the loop seals were
           performing, and they were preventing bubbles from
           getting into the cold leg, and at what conditions we
           might expect to see some stagnation occurring.
                       So loop-stagnation phenomena.  When we
           talk about loop-stagnation phenomena what we're saying
           is that the flow in the cold -- the flow through the
           loop seals and up through the cold leg is essentially
           zero.  The flow rates are essentially zero.
                       You can have HPSI injection, which
           produces some flow.  And that will produce a cold
           layer on the bottom of the pipe.  And that concern, of
           course, is that the cold layer spills into the
           downcomer and it produces some plumes.  And so you
           might see it like this.
                       CHAIRMAN WALLIS:  Now again in some of the
           reactors the HPSI velocity is so great that the
           momentum will carry it to the right.
                       MR. REYES:  Correct.  Yeah.  So for
           example for the side-injection B&W plant they have a
           very high injection flow rate.  It's a small injection
           nozzle.  And you'll actually jet across the pipe and
           impinge the other side.
                       CHAIRMAN WALLIS:  And it swells up on the
                       MR. REYES:  That's right.  So you get a
           tremendous mixing.
                       This plant, for the Palisades plant, what
           we found was that it was the opposite.  They have a
           very large pipe at fairly low injection flow rates. 
           So on a scale -- for their plant the maximum flow rate
           was about 300 gallons per minute per cold leg of HPI
           flow.  So total injection flow was about 1200 gallons
           per minute at the maximum.
                       CHAIRMAN WALLIS:  So it makes a big
           difference whether the stagnation is really zero flow,
           or a little bit one way, or a little bit the other
           way.  I think that would make quite a difference since
           your HPI flow is so low.
                       MR. REYES:  That's right.  Yeah, our HPI
           flow is quite low.  Yeah.
                       And there's a few things that we've
           noticed that, again, we start to couple the separate
           effects with the integral.  And I'll show you what
           happens with that.
                       CHAIRMAN WALLIS:  I presume with this
           Froude number criterion about whether any of it flows
           back, and things like that.
                       MR. REYES:  Right.  Right.  So the
           criteria --
                       CHAIRMAN WALLIS:  There must be some
           condition where all the HPI goes into the vessel. 
           There must be enough.  When there's enough flow rate
           in the cold leg, then all the HPI flow will go to the
           vessel itself.  You've shown it sort of half and half,
           or something like that.
                       MR. REYES:  Right.  This shows spilling
           over this weird -- this little reactor coolant pipe
           lip.  And for certain conditions below a certain flow
           rate all the flow will go towards the downcomer.
                       CHAIRMAN WALLIS:  Does it then fill up the
           loop seal and --
                       MR. REYES:  About -- for higher flow
           rates, you spill over and then you --
                       CHAIRMAN WALLIS:  But then it eventually
           fills up the loop seal with cold fluid, and then it
           all comes back again, doesn't it?
                       MR. REYES:  That's where -- that's where
           I was surprised.
                       CHAIRMAN WALLIS:  Hmm?
                       MR. REYES:  This is where the data
           produced a surprise for us, so I'll show you.
                       CHAIRMAN WALLIS:  Okay.  So we haven't
           seen the -- this is just --
                       MR. REYES:  Yeah, you haven't --
                       CHAIRMAN WALLIS:  -- act 1, scene 1 so
                       MR. REYES:  That's right.  The plot
                       MR. SCHROCK:  It looks like the plume
           narrowed, though.
                       MR. REYES:  The plume narrowed, but the
           plot thickened.
                       These are the integral system tests that
           we performed.  And we wanted to understand a little
           bit about the stagnation.  One stagnation would occur
           for these different types of integral system tests.
                       And so we had the -- numbers 7, 8, and 9,
           these were essentially small break LOCAs -- well, they
           are small break LOCAs.  For 10 -- 11 and 12 are main
           steam line breaks.  And then number 10, which sits
           right in the middle there, that was a combination,
           stuck-open ADV, which would be like a main steam line
           break, in combination with the stuck-open pressurizer
           safety release valve.  So it's a primary side break. 
           So it's a combination case.  We wanted to see what
           would happen with regard to stagnation.
                       What we observed in those tests is that
           for the very small break LOCA, cold legs 1, 2, and 3
           stagnated.  And it stagnated because of the presence
           of this cold loop plug in the loop seals, so it's kind
           of interesting.
                       For Test Number 8 we saw a combination of
           things happening as a larger break/small break.  In
           the previous test there was no tube voiding.  In this
           test there was tube draining.
                       So in the small break, the very small
           break, what we found was that the HPI could keep up
           with the break flow.  As a result we saw the tubes in
           the steam generator remaining full.
                       In the two-inch break we saw draining, so
           we saw a combination of effects there.  Cold leg 1 and
           2 stagnated because of steam generator tube voiding.
                       And cold leg 3 and 4 stagnated a little
           bit before each of the respective partners because of
           this cold liquid plug forming in the loop seals.
                       For the main steam line breaks down below,
           11 and 12, we saw 2 and 4 stagnating due to a loss of
           steam generator heat sink, reverse heat transfer from
           the steam generator.  But we also saw some interesting
           behavior here with regard to the downcomer.
                       The same thing with number 12 where we had
           the break on the other side of the plant.  Cold legs
           1 and 3 stagnated due to the loss of the heat sink.
                       The combination, stuck-open ADV and
           pressurizer safety relief valve, we saw 2 and 4
           stagnate due to the -- because of reverse heat
           transfer in steam generator 2.
                       So we observed different mechanisms for
           stagnation for these different tests, which was very
           nice because that allows us to characterize the
           downcomer under different situations and plume
                       MR. ROSENTHAL:  I'm sorry.
                       MR. REYES:  Sure.
                       MR. ROSENTHAL:  If you would just go back
           one slide.
                       MR. REYES:  Yes.
                       MR. ROSENTHAL:  In all these cases the
           steam generators are full?
                       MR. REYES:  No.
                       MR. ROSENTHAL:  Except for 10?
                       MR. REYES:  In all -- so Test Number 8,
           which was a two-inch break, in that case we did see --
                       MR. ROSENTHAL:  I'm sorry.
                       MR. REYES:  -- the steam generator tubes
           drain.  In the other test --
                       MR. ROSENTHAL:  I meant the secondary side
           of the steam generators.
                       MR. REYES:  I'm sorry?  The primary --
                       MR. ROSENTHAL:  The secondary side.
                       MR. REYES:  Oh, for the main steam line
           breaks the secondary sides, of course, drain for the
           -- for the broken steam generator.  We let them drain
           all the way out.
                       Now we --
                       MR. ROSENTHAL:  Well, I mean the feed
           water would keep up with the stuck-up in ADV, so these
           are just postulated scenarios.
                       MR. REYES:  Correct.  Correct.  That's
           right.  That's a very important point.
                       So some of the assumptions for the main
           steam line breaks we assumed that the operator
           continued to feed the broken steam generator for 10
           minutes.  And then we would adjust -- at which point
           they would diagnose the situation and close the --
           close the feed water to the broken steam generator. 
           And then they would work with the intact steam
           generator to restore the heat transfer to the system.
                       For most of the cases, because we had such
           a -- with such a -- in the main steam line break, for
           most of those cases because we had such a rapid
           cooldown, the feed-water flow and the steam flow on
           the intact steam generator was essentially isolated,
           because we just produced a very cold temperature in
           the core.
                       CHAIRMAN WALLIS:  Yeah.  One steam
           generator is quite enough to cool it down.
                       MR. REYES:  That's -- that's right.
                       CHAIRMAN WALLIS:  It's no problem at all.
                       MR. REYES:  Absolutely.
                       Okay.  So I wanted to just illustrate a
           little bit of what we saw.  I picked the two-inch
           break because that had the draining of the steam
           generator tubes, so I wanted to show that one.
                       It also had the -- the case of the loop
           seal cooling, which resulted in stagnation.  So I
           picked this one.  It's a little bit more complicated
           to demonstrate, but I think it's reasonably clear,
                       CHAIRMAN WALLIS:  What you mean -- you
           don't mean heat transfer from the loops.  You mean the
           cold fluid going into the loops?
                       MR. REYES:  That's right.  That's right up
           where I mean.
                       CHAIRMAN WALLIS:  Because I was really
           puzzled when you had this had a loop seal coolant.  It
           means that it's got cold water in it.
                       MR. REYES:  Right.  It's -- right.  It's
           cold water mixing in the loop seal.  Thanks.
                       So this is the behavior inside the steam
           generator tubes for the two-inch break case.  And what
           we see is that this is -- we have a set of level
           measurements, they're just DP cells in -- attached to
           the long tubes, another set attached to the shorter
           tubes.  So we have the maximum and the minimum
           basically for those and, as far as we can observe, the
           draining in both of those, in both cases.
                       What we do see, and this is an area of
           interest to us with regards to RELAP, is that the
           tubes, first of all, they drain at different rates, at
           different times.  And that's what you'd expect.
                       What it does -- what it does mean, though,
           is that if you're modeling in RELAP with a single
           tube, the question comes up, well, which tube are you
           modeling.  Is it some average tube, or how does that
                       So that's kind of interest to us because
           as long as these short tubes are filled, you still see
           flow in your primary loop.  So there's a range here
           from about 1500 seconds all the way out to, oh, maybe
           about 3,000 seconds that you still see some flow --
                       CHAIRMAN WALLIS:  Excuse me.  Long tubes,
           short tubes?  There's some long tubes out here and
           some short tubes in here, or something.
                       MR. REYES:  That's correct.  Yes.  Long
           tubes go all the way to the top of the steam generator
           tube bundle and short tubes are the inner circle, the
           inner tubes.
                       CHAIRMAN WALLIS:  And you're scaling the
           way a typical steam generator is in terms of the ratio
           of the lengths, are you, or is it exaggerated in your
                       MR. REYES:  So our facility, it's about --
           the length ratio is constant.  It's about 1 to 3.5. 
           So all of our lengths about 1 to 3.5 in the steam
                       So we're actually a little long compared
           to -- compared to Palisades -- compared to our normal
           one-fourth scale.
                       So that's what we see there.  We see this
           draining really begins somewhere around 1500 seconds
           or a little bit earlier on the long tubes.  But we
           still see flow in the primary loop.  And then we
           continue to see flow until the shorter tubes start to
                       MR. BESSETTE:  You see the same sort of
           thing in ROSA at full height.  Roughly, basically the
                       CHAIRMAN WALLIS:  It means that in RELAP
           they might be useful to bundle the tubes.
                       MR. BESSETTE:  In RELAP typically the
           generators model a single tube.
                       CHAIRMAN WALLIS:  Yeah, but that's --
                       MR. BESSETTE:  We have done sensi- --
                       CHAIRMAN WALLIS:  We miss that effect
                       MR. REYES:  Yeah.  We have done
           sensitivity studies where we model three tubes, or
                       MR. BAJOREK:  It depends on the sequence.
                       MR. REYES:  So here's a look at the
           cold-leg flow rates.  And looking at cold leg number
           2 and cold leg number 4 as a function of time for this
                       And here I've identified when steam
           generator tubes and the long tubes begin to drain, at
           the very onset of draining the tubes.  And then -- so
           these are the two different flow rates.  The one on
           the bottom here, which comes along and -- they match
           pretty well for this initial portion of the transient. 
           And then we see they kind of split off here.  The cold
           leg number 4, that goes to zero.
                       Cold leg number 2 experiences a small
           increase and then continues to decrease down.
                       What's happening --
                       CHAIRMAN WALLIS:  Where exactly are you
           measuring this flow rate?
                       MR. REYES:  These are being measured in
           the cold legs.
                       CHAIRMAN WALLIS:  Yeah, but where?
                       MR. REYES:  Oh, so these are just after
           the injection location.
                       Is that right, John?
                       MR. GROOME:  Yeah.  They're right after
           the high-pressure injection --
                       CHAIRMAN WALLIS:  You mean they're
                       MR. GROOME:  -- before the reactor vessel.
                       CHAIRMAN WALLIS:  Oh, they're on the side
           of the vessel.
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  So --
                       MR. GROOME:  They're on the downstream
           side of the loop seal.
                       CHAIRMAN WALLIS:  Yeah, but which side of
           the injection point are they?
                       MR. REYES:  So they sit --
                       MR. BESSETTE:  The vessel side.
                       CHAIRMAN WALLIS:  They're between the
           injection and the vessel.
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  So you could have zero
           flow in the cold leg, and then you would just pick up
           the injected flow --
                       MR. REYES:  We would pick up some injected
                       CHAIRMAN WALLIS:  -- which would be about
           one gpm somewhere.
                       MR. REYES:  Right.  And then we have a
           separate flow meter measuring our injection flow rate
           also.  So we know at all times how to --
                       CHAIRMAN WALLIS:  When you say this goes
           to zero, if you actually had injection --
                       MR. REYES:  Injection flow.
                       CHAIRMAN WALLIS:  -- it could be zero in
           the cold -- in loop seal and then it would be the
           injection flow where you're measuring it.
                       MR. REYES:  That's right.  That's right. 
           Yeah, we haven't subtracted those out.
                       CHAIRMAN WALLIS:  Is that why it bottoms
           out at one instead of zero?
                       MR. REYES:  At one, yeah.  That's right. 
           That's right.
                       So what we saw happening here, we were
           interested in how this flow was splitting.  We
           expected that as the tubes drained, the flow in the
           primary loop would just continue to drop.
                       Because we're draining 133 tubes, it just
           kind of goes in a fairly well-behaved manner towards
           zero.  But we saw the split here, and we were curious
           about how -- what was happening there.
                       And so what we observed was that this Weir
           wall, there was spillover over the weir wall, this
           reactor coolant pump lip.  And the cold water would
           create a plume basically and fall into the loop seal.
                       And now you're producing a very cold loop
           seal.  So the next figure here shows that, illustrates
           that.  So here both loop seals are warm, both for
           number 4 and number 2.
                       When we get to this -- that point, that
           transition point there, the 1500 seconds or so, and we
           see that -- for the cold leg 4 we see some of the
           plume spilling over into the loop seal and starting to
           cool that off.  And that corresponds exactly with the
           time that we see that split.
                       So the loop seal forms -- it's basically
           a cold-liquid plug which resists -- that gravity head
           there resists the fairly low flow of the loop.  And
           the flow is diverted then to the other cold leg.
                       Through the common lower plenum of the
           steam generator, the flow is diverted to cold leg
           number 2.  And so we see an increase in the flow rate
           there and a zero flow in cold leg 4.
                       CHAIRMAN WALLIS:  Did you get any kind of
           loop seal blowout with these cold plugs being blown
           out at some stage?
                       MR. REYES:  We'll have to look at some of
           the other tests to see.
                       CHAIRMAN WALLIS:  That might not be too
           good for the reactor vessel, blew out a plug of cold
                       MR. REYES:  If it put out some cold water.
                       MR. BESSETTE:  You need larger breaks to
           get a loop seal clearing basically in this.
                       CHAIRMAN WALLIS:  You need a larger break
           for that to happen?
                       MR. BESSETTE:  Yeah, to create loop seals.
                       MR. ROSENTHAL:  I'm not sure that the
           vessel, given its mass, would even notice a slug.
                       MR. BESSETTE:  Plus you've got to put the
           break into the cold.
                       CHAIRMAN WALLIS:  Well, it's a question of
           local cooling, isn't it, and --
                       MR. BESSETTE:  You've also got to put the
           break in the cold leg.  This was a hot leg break.
                       MR. REYES:  Yeah, the thought was if --
                       CHAIRMAN WALLIS:  It was just a thought,
           I mean.  While we're thinking about it, it's sort of
           like the boron-dilution problem where you've got a
           slug of something that comes in.
                       MR. SCHROCK:  In the previous diagram you
           have certain events highlighted, number 2, long tubes
           begin to drain.
                       MR. REYES:  Yeah.
                       MR. SCHROCK:  Is that something that you
           see from these traces, or that's just pointing out
           that this is observed from other evidence at those
                       MR. REYES:  This was what was observed
           from other evidence.
                       CHAIRMAN WALLIS:  What's the big hiccup at
           about 1100 seconds?
                       MR. REYES:  We know that the initial steam
           generator tube draining does result in an increase in
           flow, so we're draining those tubes and they're
           draining into the cold-leg side and to the hot-leg
           side.  And we expect to see some increase in flow
           rate.  I would suspect that's related to that.
                       CHAIRMAN WALLIS:  Yeah.  But how do you --
                       MR. REYES:  And we don't see it in the
           other one, so --
                       CHAIRMAN WALLIS:  You need to blow-up the
           scale to see for how long it stayed at zero at around
           1100 seconds, if it did.  You know you can't see it in
           here.  Eleven hundred seconds is a big hiccup.
                       MR. REYES:  Oh, this -- this spike right
           here you see.  Yeah.
                       CHAIRMAN WALLIS:  Yeah, it goes down to
           zero, is the point.
                       MR. REYES:  Right.  Now the -- these
           magnetic flow meters, they're very sensitive to
           voiding.  If you have a bubble through the line and it
           goes past the instrument terminals, you might see a
           spike like that.
                       However, I tend to think this might be a
           real -- we'll look at that a little bit closer.  This
           might be a real...
                       So what we see is the creation of this
           cold-liquid plug in the loop seals and the flow being
           preferentially diverted to the -- through the steam
           generator lower plenum to the other flowing leg with
           the warm loop seal.
                       Later today we're going to show you how
           this works.  We'll take -- when we go to the lab we're
           going to run this experiment for you.  Here we have
           the -- this Weir wall.
                       Imagine in the plant that this whole elbow
           here would be the pump and this would be the outlet of
           the pump.  And you can see that it acts effectively as
           a dam which keeps the cold water on the reactor vessel
                       Eventually you will spill over, and you
           will go into this loop seal, and you'll cool it off. 
           We'll show you that phenomena.
                       CHAIRMAN WALLIS:  Now RELAP has great
           trouble trying to predict that, doesn't it?
                       MR. REYES:  Excuse me?
                       CHAIRMAN WALLIS:  Doesn't RELAP have great
           trouble trying to predict that, that sort of
                       MR. REYES:  I would say that there's no
                       CHAIRMAN WALLIS:  But you can still run
                       MR. REYES:  That's right.  And I think
           what we saw in this test with the RELAP calculation is
           that it did predict reasonably well the steam
           generator tube voiding on some average basis.
                       And so it was in the ballpark.  But as far
           as the sequence of -- the timing and the exact
           sequence, probably would miss.  It can't --
                       CHAIRMAN WALLIS:  It just mixes --
                       MR. REYES:  -- it can't calculate this.
                       CHAIRMAN WALLIS:  It just mixes
           everything, doesn't it?
                       MR. REYES:  Yeah.
                       We're looking at that, though, to see what
           RELAP is predicting as a loop seal temperature during
           the trading and comparing it to what we saw.
                       So you'll see that test a little bit
           later.  Chris Linrud and Ian Davis are here to do that
           for us.
                       Okay.  So we saw steam generator tube
           voiding as a stagnation mechanism.  We saw this cold
           loop seal plug as another stagnation mechanism.
                       The third one that we observed was this
           reverse heat transfer.  And that's when the steam
           generator and the main steam line break, we blow that
           steam generator down on one side.  The other intact
           steam generator is bottled up and becomes a heat
           source eventually.
                       And so you see in this schematic here,
           this is for Test Number 12, a main steam line break at
           full power.  We have steam generator temperature and
           the hot-leg temperature.  We see initially the hot-leg
           temperature is greater than the steam generator
                       As we go through the blowdown, of course,
           we drop that hot-leg temperature well below the steam
           generator temperature.  And we see stagnation of cold
           legs 1 and 3 occurring within this band right here. 
           So it doesn't occur immediately.  There's a band that
           -- there's a delay time and then a band.  And we were
           curious about that.
                       Now later on what we see is the -- as the
           primary plant reheats and repressurizes, our
           temperature goes up above the steam generator
           temperature.  And we see a resumption in the cold leg
           1 and 3 flow.  So it works as expected.  And again we
           see that occurs relatively close to when we cross that
           -- when we made that transition.
                       We were -- and that's to be expected. 
           What we were curious about was this little delay here
           and what might be causing that.  Here's looking at
           the, again, cold-leg flow rates for 1 and 3.  And you
           can see that we start off with our pumps on, come way
           down.  We go to zero, essentially zero flow for the
           flow meter.
                       Come -- and we resume our -- this steam
           generator is a heat source.  And here the steam
           generator is a heat sink again.  And we come back to
           our flow intake.
                       CHAIRMAN WALLIS:  What does negative flow
           in the cold leg flow area mean?
                       MR. REYES:  Negative flow, I don't think
           we're seeing negative flow in this.  It's just the --
                       CHAIRMAN WALLIS:  Isn't that what it says?
                       MR. REYES:  It certainly does, but I think
           we're just zeroed.  We're a little bit off in our
                       This flow meter is -- I'll ask John Groome
           to tell me the range for that flow meter on the test.
                       Do you remember this one?
                       We've been struggling with memory lately,
                       MR. GROOME:  Yeah, I'm sure my memory's
           not any longer than yours though, Jose, so I don't
           know if I'll be able to answer the question, but my
           name's John Groome.
                       And these flow meters are ranged positive
           to negative 100 gallons per minute.  And, you know,
           there's some interpretation that you have to do with
           all data.
                       And I'm of the same opinion as Jose,
           that's just a zero shift there on that second meter. 
           And that could be not just due to the meter.  It could
           be due to the actual estimate loop that carries the
           signal back to the data acquisition, so...
                       CHAIRMAN WALLIS:  You really need a more
           sensitive flow meter because you're talking about low
           flows in the order of one gallon per minute.
                       MR. GROOME:  Yeah.  And, you know, these
           flow meters are actually quite phenomenal.  When we
           first worked with Westinghouse back in the early '90s
           we couldn't measure flow in our cold legs.  And so
           part of the problem was our temperature and pressure.
                       And so we actually worked with them to
           develop a new flow meter to -- that we put a flow
           meter in to test, at about $4,000 a test we'd break a
           flow meter.  And so these flow meters have been in for
           about going on three and a half years, and they've
           worked for three and a half years successfully.
                       And, you know, this is a meter that's
           capable of flow ranges up to about 700 to 800 gallons
           a minute.  So when you're down here looking at zero
           and you're nitpicking about a gallon-per-minute flow,
           I think you ought to be happy you have any data.
                       CHAIRMAN WALLIS:  Well, how does a flow
           meter work when you have, say, a stratified
           countercurrent flow?  Does it --
                       MR. GROOME:  Well, it's a void average. 
           Unfortunately, it measures in gallons per minute.  But
           it's a void average flow, a volume-average flow.
                       CHAIRMAN WALLIS:  So it has -- does a --
           is it slices, or something, or --
                       MR. GROOME:  No.  It actually has just
           two, and I can show you some flow meters today if
           you'd like, but it just has two contact points in the
           middle.  So it assumes that the velocity profile
           through the -- through this bore of the flow meter is
                       CHAIRMAN WALLIS:  Well, that's very
           difficult if you've got a countercurrent flow, with
           cold water going one way and hot the other, --
                       MR. GROOME:  Sure.
                       CHAIRMAN WALLIS:  -- it must get very
                       MR. GROOME:  Sure.  And that could be
           what's happening.
                       CHAIRMAN WALLIS:  So it might well give
           you a faulty reading.
                       MR. GROOME:  Right.  Right.
                       MR. REYES:  Sure.  Sure.  Yeah.
                       Thanks, John.
                       CHAIRMAN WALLIS:  So it just measures at
           one point essentially?
                       MR. GROOME:  Correct.
                       CHAIRMAN WALLIS:  And then assumes a
           velocity profile?
                       MR. GROOME:  Correct.
                       CHAIRMAN WALLIS:  Oh.
                       MR. REYES:  So reduce the stagnation
           occurring and then resumption.
                       CHAIRMAN WALLIS:  So what it's measuring
           is the velocity at the point where it measures what it
           calls flow.  That's what it's really doing.
                       John, it's --
                       MR. GROOME:  Excuse me?
                       CHAIRMAN WALLIS:  It's really just
           measuring the velocity at the point where it measures.
                       MR. GROOME:  Correct.
                       CHAIRMAN WALLIS:  And then from that it
           tries to predict the flow.
                       MR. GROOME:  Right.  In those -- in those
           areas --
                       CHAIRMAN WALLIS:  And if it has an S-shape
           velocity profile, it's going to go --
                       MR. GROOME:  It doesn't -- it doesn't know
           how to calculate that, right.
                       CHAIRMAN WALLIS:  But it still knows to
           calculate the local velocity.  That's what you --
                       MR. GROOME:  Right.  So it measures
           essentially a velocity and it knows the area.
                       CHAIRMAN WALLIS:  So you might actually
           try looking at that velocity and recasting it in terms
           of what's actually happening in the pipe and getting
           a better sen- --
                       MR. REYES:  And try to get the better,
           yeah.  Yeah.
                       MR. SCHROCK:  Is it in the proximity of
           the bend?  Most everything is.
                       CHAIRMAN WALLIS:  Everything is,  yeah.
                       MR. REYES:  How many -- how many l over
           ds, John, from -- did we require for the --
                       MR. GROOME:  It's -- l over ds, yeah, it's
           right there on the bend.  It's maybe like 2 d. 
           Actually I have a slide if you'd want to go back and
           pull it up and we could actually look at a plan view
           of it.  But it's maybe like one and a half d from the
                       But that's fortunate for magnetic flow
           meters to have the, you know, the least-required l
           over d for flow measurement, or typically anywhere
           from 1 to 5 d.
                       MR. REYES:  Okay.  So what we saw then was
           loop stagnation due to the steam generator, one of the
           steam generators becoming a heat source instead of
           heat sink.  But there was a delay, and we were curious
           about that.  So we investigated a little bit further.
                       And what we realized was that we're
           injecting cold water to downcomer.  And so we're
           cooling off the downcomer.  Of course, we have core
           heat.  And so we are creating a density difference in
           the driving head.  So the downcomer driving head,
           because the system is completely liquid filled, is
           still driving the flow.
                       And so what's happening is that the
           reverse-heat transfer from the steam generator is
           acting like a break.  It's resisting the positive
           flow, but it's not able to stop the flow.  And so
           that's why we see a continued natural circulation for
           that period of time.
                       Eventually we get to a large enough delta
           T on the steam generator where it is able to overcome
           the driving head produced by the downcomer injection. 
           So you do have a downcomer recirculation.
                       That was -- that plays an important part
           when you're working -- when you're looking at an
           integral system injection.  Because what that means is
           even when you have "stagnant conditions," as soon as
           you begin injecting, if you have any core heat, you
           will create some natural circulation flow.  And so you
           -- by virtue of injecting you're producing a natural
           circulation flow.  So it's kind of --
                       CHAIRMAN WALLIS:  As long as the injection
           goes the right way.
                       MR. REYES:  That's right, into the
           downcomer.  That's right.
                       Okay.  So we observed those phenomena.
                       Steam generator tube voiding.  That should
           be the loop -- the cold-liquid plug --
                       CHAIRMAN WALLIS:  If the steam generator
           wins over the downcomer, then presumably the flow goes
           the other way, if that's possible.
                       MR. REYES:  The resistance is pretty large
           in the other direction.
                       CHAIRMAN WALLIS:  I was thinking of the
           buoyancy.  You're saying the buoyancy in the steam
           generator counteracts the buoyancy in the downcomer.
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  Presumably there's a
           situation where the steam generator could win and the
           flow could go the other way.  Don't pull that cold
           stuff into the loop seal, --
                       MR. REYES:  Well, I think --
                       CHAIRMAN WALLIS:  -- ready to come back
                       MR. REYES:  I think what -- of course, the
           top of the plant will just get real hot and stay hot
           and the cold water will stay on the bottom, so...
                       Okay.  So we identified three modes of
           loop stagnation, which we were interested in
           understanding for integral tests.
                       One of them, the loop seal, the cold plug
           in the loop seal actually is tied to a local
           phenomenon, which I thought was one of the key
           findings as far as relating our separate effects test
           to the integral system test.
                       The other thing was the presence of this
           RCP Weir wall.  That really does delay the loop seal,
           the formation of a cold-liquid plug in the loop seal. 
           And hence it delays stagnation in the loops.
                       So if we didn't have that Weir wall we
           would have expected possibly to have stagnated a bit
           earlier, because we would have formed cold plugs in
           the loop seals.  So that's kind of an interesting
           result.  So having them actually delays stagnation.
                       MR. SCHROCK:  Isn't that Weir an attempt
           at simulating the real plant?
                       MR. REYES:  That's right, yeah.
                       MR. SCHROCK:  And so how do you judge the
           quality of that simulation?
                       MR. REYES:  Right.  Now at this point all
           we can do is use our, in this case, CFD Codes to see
           if we can, first of all, benchmark the CFD Code
           against our test.
                       And then have a little bit of confidence
           then that we can go forward and try to do a more
           accurate model of the real plant.
                       Now in talking to the folks at Palisades,
           they do indicate to us -- I mean they gave us the
           dimension of this lip.  And they have indicated to us
           that, in fact, when they are draining, trying to drain
           the cold legs they can't drain it completely because
           of this lip.  So we know it's an effect.
                       The other thing that it does cause -- that
           we do observe is that the presence of that Weir wall
           also, with side injection, we're going to see a lot of
                       The plume doesn't come in from the top of
           the pipe and then mix on the way down.  So typically
           the flow is going to be in the positive direction,
           because it's not mixing on the way down, and you've
           got this wall, this dam on the other side which, in
           essence, is driving all the flow towards the downcomer
           up to a certain point.
                       We said that reverse-heat transfer can
           either -- it can reduce or stop the primary loop
           natural circulation, depending on the available
           downcomer fluid driving head.
                       Okay.  So that's what we saw in the area
           of loop stagnation.
                       CHAIRMAN WALLIS:  What are your scaling
           laws now?  I would think that you have some scaling

           laws for your loop.
                       MR. REYES:  Correct.
                       CHAIRMAN WALLIS:  And then I would think
           that some sort of Froude numbers scale these, whether
           it goes over the Weir and the stratification.
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  Is that consistent with
           your scaling of other things like velocities and
                       MR. REYES:  Yes.
                       CHAIRMAN WALLIS:  It is?
                       MR. REYES:  Yes.  And so what we're doing
           now is -- we have run a preliminary series.  And we're
           going to run several just to be sure.  We're going to
           identify the conditions for the onset of the loop seal
           spillover, which is a very nice project for any
           volunteering students.
                       It's a very straightforward effort.  And
           we know basically what the dimension of those groups
           should be.  And I think we can do a good job on that
           one.  So we're gathering that data right now.
                       MR. BAJOREK:  Jose, your pump is down at
           the bottom --
                       MR. REYES:  Our pump is at the bottom of
           the --
                       MR. BAJOREK:  -- of the loop seal as
           opposed to up at the top.
                       MR. REYES:  Correct.
                       MR. BAJOREK:  Are there any additional
           restrictions in a regular PWR pump lower than the Weir
           that a positive steam flow through the loop would
           prevent some of that liquid coming back over the Weir
           and delaying the cooling?
                       MR. REYES:  Now we're talking steam flow?
                       MR. BAJOREK:  Yes.
                       MR. REYES:  There was a schematic that
           John had showed us yesterday, and it's a fairly short
           -- what it is it's kind of a relatively flat --
                       MR. BAJOREK:  Impeller.
                       MR. REYES:  -- impeller with -- in a
           volute.  Okay.  I was looking for the right word, a
           volute.  So if that comes -- your cold leg comes out
           at this angle, and then you've got this -- a short
           drop and then to the loop seal.
                       So I don't think there's anything other
           than the impeller itself that would hinder the steam
           from getting up there and going out.  Is that -- I'm
           not sure if I understand.
                       So you're going to have -- you're going to
           have -- the steam will come in, and if there's water
           on the bottom of the cold leg, it's basically just a
           stagnant pool almost, except for right at the surface.
                       Okay.  Now we'll talk a little bit about
           -- if there's no other questions on stagnation. 
           Again, the reason we looked at stagnation so heavily
           was because in previous studies the thought was, well,
           if the primary -- if the cold legs are stagnant, then
           injection under those conditions would essentially be
           the worst plume conditions.  Okay.  As we continued
           with our study we saw that we came to a different
                        PLUME FORMATION IN APEX-CE
                       MR. REYES:  So I'll talk a little bit
           about cold leg thermal stratification first, and then
           we'll talk about the plume behavior in the downcomer.
                       Okay.  We did these flow visualization
           tests, which were really very helpful.  We started by
           just doing a series of tests in APEX at pressure and
           temperature.  And we were measuring our -- we had our
           thermocouple rake in there.
                       We were seeing constantly that we had cold
           temperatures at the bottom for most of the flow rates
           that we generated, the cold-leg flow rates.  And we
           were curious then what was going on.  So we built this
           very simple flow visualization test that allows us to
           take a look at the similar Froude number conditions,
           what might be going on in the pipe.  And we --
                       CHAIRMAN WALLIS:  This is green salty
           water; is that what it is?
                       MR. REYES:  That's green salty water.  So
           we're injecting -- we're using sodium fluorescein to
           actually give us that green color.  And if you hit it
           with ultraviolet light you get a very bright image
           with that.
                       So we've put sodium fluorescein in our
           salty water.  And we're using that to represent our
           cold injection.
                       The pipe is initially filled with fresh
           water.  And that whole tank actually is filled with
           fresh water initially.
                       So we begin our injection, and this is the
           type of behavior that we see.
                       CHAIRMAN WALLIS:  Where is the injection
                       MR. REYES:  I lost my mouse.  Oh, here it
           is.  Thank you.  So --
                       CHAIRMAN WALLIS:  It's the pipe that we
           can't see, which is there?
                       MR. REYES:  Yeah, that's right.  It's a
           side injection.  And so from a top view the injection
           line would be behind the pipe.
                       CHAIRMAN WALLIS:  That's why we can't see
                       MR. REYES:  That's right.  That's right. 
           So...  Thank you.
                       CHAIRMAN WALLIS:  So is this fog flowing
           down the Columbia Gorge.
                       MR. REYES:  It's the fog coming down the
           Columbia and out towards the ocean here, I guess.
                       Here's the Weir wall.  So for this
           injection flow rate and for this combination of
           cold-leg flow rate, we're not getting it -- well,
           maybe we are spilling over a little bit here.  Here's
           a side view.  So we're not, okay.  So for this --
                       CHAIRMAN WALLIS:  It doesn't look like a
           very flat layer, does it?
                       MR. REYES:  Say again.
                       CHAIRMAN WALLIS:  It doesn't look like a
           very flat interface between the green and the blank.
                       MR. REYES:  It's not very flat.  For this
           flow rate it's not very flat.  That's right.  So what
           we're looking at then is a -- we're at about the 12-
           gallons per minute in the cold leg.  And we're
           injecting probably somewhere around a gallon per
           minute here through the -- so you see the side
                       The plume comes in.  It travels both
           directions, and back towards the vessel and towards
           the loop seal.  But this acts as an effective wall to
           prevent the flow.
                       CHAIRMAN WALLIS:  I guess the drag from
           the other flow keeps the -- it's what causes it to
           flow in this arrangement.
                       MR. REYES:  So here's a closer look at it,
           and I'll show you the Weir wall.
                       But here we're injecting again.  This is
           -- you can see this --
                       CHAIRMAN WALLIS:  Well, that shows how
           stratification inhibits the mixing.
                       MR. REYES:  Right.  Here's a close-up of
           the -- of that --
                       CHAIRMAN WALLIS:  You can't just use the
           normal CFD in a stratified flow like that.  K-epsilon
           doesn't work in their stratified interface.
                       MR. REYES:  That's one of the -- this is
           where -- this is -- Ian's nodding his head yeah.
                       Working with CFD Codes, and we'll talk
           about that a little bit later, but that's some of the
           challenges that we face with using these types of
           codes.  And so we're going to be looking for some
           advice from experts.
                       CHAIRMAN WALLIS:  The turbulence is really
           suppressed at the interface.
                       MR. REYES:  Yeah.  So this is at the Weir
           wall, and we see that basically the cold fluid from
           the cold leg -- I mean the cold-leg fluid is sweeping
           all that fluid back.
                       Okay, another look here.  We have a little
           bit of spillover in this case.  We've got the flow
           rate.  And then this is looking again at the spillover
           into the loop seal.  So we'll perform some of those
           visualizations for you when we go over there after
                       Okay.  So let's talk a little bit about
           what we saw with regards to the stratification in the
           cold legs, some of the measurements from APEX-CE.
                       So we did --
                       CHAIRMAN WALLIS:  Now are you going to
           tell us about analysis of this in terms of some math
           and some predictions?
                       MR. REYES:  Yes.
                       CHAIRMAN WALLIS:  Somebody -- somebody is.
                       MR. REYES:  When we talk about the plumes.
                       CHAIRMAN WALLIS:  Somebody is.  Well, what
           about the cold-leg behavior and the stratification and
           all that?
                       MR. REYES:  We have some predictions to
           show you later on if you -- we can chart --
                       CHAIRMAN WALLIS:  Any comparisons with
                       MR. REYES:  We have lots of data.
                       CHAIRMAN WALLIS:  Do you have -- well,
           come on.
                       MR. REYES:  We'll give you some.  You'd
           like some theoretical...
                       Well, we have looked at the plumes in the
           downcomer, and I'll present some equations there.
                       In the stratified region, we're still
           looking at developing what's going on in that section.
                       We have a -- there was a -- I think I know
           what you're referring to.  Early on in the development
           of this project we were real curious about the onset
           of thermal stratification and came up with pretty good
           criteria that was used -- that you could use to
           predict when you have essentially well-mixed
           conditions in the cold leg.
                       Now the presence of this Weir wall has
           changed that somewhat.  So we're looking -- that's why
           we're changing the theory some, to examine that Weir
           wall more closely and understand how that's affecting
           the flow and what that really means in terms of a
           stratification criteria.
                       CHAIRMAN WALLIS:  It looks like a real
           candidate for the Kelvin-Helmholtz instability type of
                       MR. REYES:  That's right.  That's right. 
           So now you've got -- I mean that's exactly right.  So
           that's what we're looking at right now.
                       So what this tells me then is that the
           stratification criteria that we use that P. F. Foss
           had developed, and then the modified version which I
           had developed, which was based on the Froude number of
           the cold-leg stream squared plus the Froude number of
           the hot leg squared equal to one.
                       With the presence of that Weir wall we
           need to look at that and say, okay, now we've got a
           slightly different situation.
                       CHAIRMAN WALLIS:  What is 10 gpm in terms
           of Froude number, using the density difference.
                       MR. REYES:  Oh, 10, that -- with using
           that combination, I think it's like .04.  That's that
           modified Froude number.  That --
                       CHAIRMAN WALLIS:  You're using the density
           difference between the fluids?
                       MR. REYES:  Density difference between the
           fluids.  And using --
                       CHAIRMAN WALLIS:  That's the only Froude
           number.  It's not modified.  That is the Froude
                       MR. REYES:  Well, this -- they're modified
           in terms of -- it uses the HPI injection.
                       CHAIRMAN WALLIS:  Density.
                       MR. REYES:  Density --
                       CHAIRMAN WALLIS:  Minus --
                       MR. REYES:  -- with the cold leg --
                       CHAIRMAN WALLIS:  Minus the density of the
                       MR. REYES:  Oh, okay, I'm sorry.  The
           Froude for the cold leg.  Yeah, I'll have to look that
           one up.  I was giving you the injection, injection
           Froude.  Yeah, I can look that up for you.
                       CHAIRMAN WALLIS:  You can tell us after
           the break.
                       MR. REYES:  You bet.  We've got lots of
                       So what we found, though, is that the
           presence of the Weir wall results in some
           stratification for the full range of conditions that
           we studied.
                       So this test 003, what we were doing was
           we were putting -- we were parametrically varying the
           cold-leg flow rate and the injection flow rate for 16
           different cases.  We wanted to see what we would
           observe as far as stratification in the cold leg.
                       So what we saw was that at the presence of
           the Weir wall there was always some stratification for
           the flow conditions that we looked at.  And we were
           looking at essentially from one and a half percent to
           K to four percent to K powers over a range of about
           30- to 100-percent HPSI injection flow rates.
                       The spillover was not observed in any of
           these tests, which meant that our -- above 30-percent
           HPSI for us, what we saw was that we had enough flow. 
           It was greater than 10 gallons per minute in the --
           excuse me -- for one-and-a-half percent to K power,
           our flow in the cold legs was greater than 10 gallons
           per minute.
                       So we always kept flowing in the direction
           of the reactor vessel.  And there was no spillover for
           any of these tests.  So this is the range of
           conditions we cited.
                       We would vary the K power.  That would
           change our natural circulation of flow rate in the
           loop.  And in between each test we would turn our
           pumps for a while and get everything back to uniform
           temperature and then do another parametric study.
                       So here's that --
                       CHAIRMAN WALLIS:  What's the basis of
           these HPSI flow rates?  What's the basis for choosing
           these values?
                       MR. REYES:  Oh, that's -- that basically
           was the limits of what we could do.  Yeah.  So 30
           percent, when you drop below 30 percent on our
           injection, we have difficulty controlling our -- well,
           for -- for the cases that we looked at, I guess we can
           get down to --
                       CHAIRMAN WALLIS:  Presumably it's a scaled
           HPSI from reactor conditions.
                       MR. REYES:  Right.  Right.  So point --
           the lowest we did was .35 gallons per minute, which
           corresponds to about 30 percent of one injection flow. 
           So that was what --
                       CHAIRMAN WALLIS:  So this is a throttled
           HPSI of --
                       MR. REYES:  Right.
                       This shows the range of tests that we did. 
           And in between each test, again, we operated our
           reactor coolant pumps.
                       Once we put in several hundred gallons per
           minute through the loops.  Of course, everything warms
           up pretty uniformly.  All our thermocouples matched
                       This is looking at the top of the cold leg
           number 3 and this is the bottom of cold leg number 3,
           so we're going -- we're looking at the temperature
           stratification in the cold legs.
                       And this shows that for the different
           conditions we saw we always saw some stratification. 
           Even at our minimum being .35 gallons per minute, we
           saw some stratification in cold leg number 3.
                       Again, this being the bottom of the cold
           leg here and all the way up at the top would be the
           top, so they actually went in order.  So we saw that
           stratification for our tests.
                       Here we are at -- for cold leg number 4,
           the same test, we were running -- we ran two different
           injection flow rates for that --
                       CHAIRMAN WALLIS:  What is your temperature
           of your HPSI?
                       MR. REYES:  HPSI temperature is about 65
           degrees Fahrenheit.
                       CHAIRMAN WALLIS:  So this is a lot hotter
           than the HPSI itself.
                       MR. REYES:  Oh, much, much hotter, right. 
           Yeah.  So what we're seeing is by the time we get to
           this -- the typical rates, we are seeing some -- quite
           a bit of mixing.
                       And the total -- well, I mean this is 150
           degree delta T from the bottom of the pipe to the top
           of the pipe, so it's a pretty big stratification.
                       This case and this case, we also used to
           model with STAR-CD.  So these two cases we modeled
           with STAR-CD.  And later on you'll see the results of
           those comparisons.
                       CHAIRMAN WALLIS:  So maybe if you had
           bottom injection you might actually have those minima
           going down to something like the HPSI temperature. 
           Because presumably it's bottom injection; it doesn't
           mix with anything.
                       MR. REYES:  That's right.
                       Now I'm not sure if there are any plants
           that do bottom --
                       CHAIRMAN WALLIS:  I don't think there are,
           but just for comparison sake.
                       MR. REYES:  -- with the big --
                       CHAIRMAN WALLIS:  I mean you said with top
           injection there's more mixing and side injection you
           get more of this.
                       MR. REYES:  Right.  So the bottom might be
                       CHAIRMAN WALLIS:  Presumably there's one
           limit where you just ooze the cold water in and it
           flows along without mixing with anything.
                       MR. WACHS:  You get conducted heating from
           the metal in the cold leg.
                       MR. REYES:  Dan.
                       MR. WACHS:  I said you'll still get
           conducted heating from the metal in the cold leg, so
           there will still be some warming.  You won't -- you're
           unlikely to --
                       CHAIRMAN WALLIS:  Yes.  Yes.
                       MR. WACHS:  -- get that small.
                       CHAIRMAN WALLIS:  Yeah, I guess you need
           to estimate that, too.
                       MR. REYES:  Okay.  So the upshot of it for
           us for these series of tests was that for all the
           natural circulation cases that we examined, we always
           saw some stratification.
                       And this case here being the maximum
           stratification we observed, which was not the -- not
           the lowest flow rate, but it was -- it was essentially
           close to the highest flow rate, but not the -- not
           necessarily the lowest.  Well, like big yeah, the
           trend is getting bigger as we go to lower -- lower
           cold-leg flows.
                       Okay.  So we always see some
           stratification, which was different than what we've
           seen in the past.  If we kept the criteria, the
           stratification criteria the way it was, it would
           predict good mixing for some of these tests.
                       So we see that the Weir wall has no -- has
           an effect.  And we need to change that theoretical
                       Okay.  Now we'll talk a little bit what's
           going on in the downcomer as far as plumes.
                       I'll start off with kind of a typical
           analysis and what's been done in the past.  The
           classic analysis is you have a single planar plume
           falling into a stagnant, uniform ambient fluid.
                       Okay.  That would be the classic analysis. 
           And it's been done -- it's been done for a long time. 
           Bachelor did a study on it and Morton and Rouse and --
                       CHAIRMAN WALLIS:  You say, "planar."  You
           mean it's 2 d?
                       MR. REYES:  Correct.  Yeah, they're 2 d.
                       CHAIRMAN WALLIS:  They're also
           cylindrically symmetrical.  The simple ones are --
                       MR. REYES:  Right.  The --
                       CHAIRMAN WALLIS:  -- planar or --
                       MR. REYES:  Right, the axisymmetric --
                       CHAIRMAN WALLIS:  -- axisymmetric.
                       MR. REYES:  Right, axisymmetric case.  You
           just change the coordinates and unwrap it and get a
           planar.  Yeah, so the 2 d case.
                       And these involve some very classic
           assumptions, some very -- which work very well for the
           single planar plumes and also for the axisymmetric
                       CHAIRMAN WALLIS:  Oh, review that for me. 
           If I have, say, a faucet, the plume actually
           accelerates instead of -- because the density
           difference is so enormous.
                       MR. REYES:  Right.  Yeah.
                       CHAIRMAN WALLIS:  And then if I have a
           very low-density difference, presumably the buoyancy
           is not so big and the plume spreads a lot.  What sort
           of range are you in in terms of the density
           difference, in terms of, you know, whether the plume
           spreads a lot or --
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  -- doesn't because of
           the gravity accelerating it?
                       MR. REYES:  Right.  For these tests, our
           delta rho over rho was like .18.  So I'd have to go
           back and see what just a delta rho is.  But -- so it's
           comparable to what you would see in the plant, not --
           not as large, but it's within 10 percent.
                       CHAIRMAN WALLIS:  But it's something like
           the plume from a cigarette, or something, in terms of
           what you --
                       MR. REYES:  Oh, no.
                       CHAIRMAN WALLIS:  -- imagine in terms of
           things you know about?
                       MR. REYES:  Okay.  So smoke and air, maybe
           -- maybe like --
                       CHAIRMAN WALLIS:  Smoke from a chimney,
           from -- on a clear day.  Something like that.
                       MR. REYES:  Yeah.  I'm thinking of my
                       CHAIRMAN WALLIS:  Yes, something like
                       MR. REYES:  I'm looking at the stack way
           out there.
                       CHAIRMAN WALLIS:  But, you see, if you
           have a hot enough fire --
                       MR. REYES:  I'm looking at the stack way
           down there.
                       CHAIRMAN WALLIS:  -- your plume actually
                       MR. REYES:  Yeah, it would be similar --
                       CHAIRMAN WALLIS:  -- can go up and
                       MR. REYES:  Right.  So --
                       CHAIRMAN WALLIS:  Before it spreads.
                       MR. REYES:  -- you'll see a lot of
           examples of the reverse.  You'll see a hot plume --
                       CHAIRMAN WALLIS:  Right.
                       MR. REYES:  -- going up in air.
                       CHAIRMAN WALLIS:  Depends on how hot it
                       MR. REYES:  So it -- from the shape of it,
           I'd say --
                       CHAIRMAN WALLIS:  So I'm trying to get a
           feel for which kind of a plume is it.  I think it's a
           spreading plume.
                       MR. REYES:  It's a spreading plume.
                       CHAIRMAN WALLIS:  Yeah.  You have the
           fire, the density difference is two to one or
           something.  So it's...
                       MR. SCHROCK:  These theories pertain to,
           as you've said, a large field.  You've got the
           downcomer walls that are confining the plume.  Are you
           going to address that?
                       MR. REYES:  I'll cite the difficulties
           with those things, right.  Yeah.
                       We'll go on, and I'll show you some of the
           problems we're facing --
                       CHAIRMAN WALLIS:  There's a good --
           there's a good book on this by some German whose name
           I forget, who studied all kinds of plumes and all the
                       MR. REYES:  I've got it in my bag.
                       CHAIRMAN WALLIS:  Okay.
                       MR. REYES:  It's Rodi and Chatney.
                       CHAIRMAN WALLIS:  Rodi, that's right. 
                       MR. REYES:  They did a ton of work in --
           you're welcome to look at the book.  Yeah.
                       CHAIRMAN WALLIS:  It's pretty
                       MR. REYES:  It is.  It was a very nice --
           one of the few that covered a wide range of
           axisymmetric and -- but I'll show you another paper
           today, which is fairly new, which is closer to our
                       CHAIRMAN WALLIS:  It's got too many ns.
                       MR. REYES:  So we're familiar with the
           classic assumptions for the planar plumes.  The idea
           that there's a linear spread of plume radius with
           axial position, because you have a constant
           entrainment rate.  And that assumption works
           reasonably well for the planar plumes in stagnant
                       You've used the similarity of velocity and
           buoyancy profiles.  And you can come up with some
           universal curves that way.  And in REMIX they kind of
           use that technique of producing these universal
           curves.  And then at different locations it says,
           okay, for this set of dimension groups you kind of
           convert it back into what you should be reading there,
           so that works well.
                       And, of course, they always -- you
           typically assume the Gaussian-shaped profile for this
           stagnant media.  I'll show you a couple of pictures.
                       Back in 1934, we've got some data which
           shows the same situation.  Here you have the velocity
           measurements inside the plume.  The scale's missing
           here.  That should be centimeters per second on the y
                       The velocity measurements for the plumes
           at different axial locations.  And if you -- you can
           actually scale it with a mean velocity of plume and
           come up with a single shape, a single universal
           Gaussian curve.  So we know that that theory works
           very well.
                       So the thought was, well, we can apply to
           some of the similar concepts to our test --
                       CHAIRMAN WALLIS:  Well, I'm trying to
           think, though.  When you pour -- pull this stuff over
           the lip of a pipe, --
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  -- you don't have the
           sort of starting condition of a uniform velocity.  It
           has to sort of accelerate out of the pipe.  So it's
           accelerating for a little while before it does this
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  Isn't it?
                       MR. REYES:  So -- yeah, I was --
                       CHAIRMAN WALLIS:  I don't quite know how
           you modeled the starting condition for coming out of
           the pipe and going over the lip and into the
           downcomer.  How do you start your plume for an
           analysis like this?
                       MR. REYES:  For an analysis like this what
           we think is actually happening is that the plume is
           jumping the gap.  Eventually it's --
                       CHAIRMAN WALLIS:  It hits the other wall.
                       MR. REYES:  -- it hits the core barrel
           wall.  Now you've got another, another problem.  So
           that's what we believe happened.
                       CHAIRMAN WALLIS:  This is like the
           experiments that we did with the injection of water
           into a steam down- -- filled downcomer.  It jumps to
           the wall and goes down the other side.
                       MR. REYES:  Which test was that?
                       CHAIRMAN WALLIS:  When was that done?
                       MR. REYES:  Yeah.
                       CHAIRMAN WALLIS:  7-70, or something like
           that.  1970 maybe.
                       MR. REYES:  Yeah.  For our test number 13
           we're thinking of something similar, so I'll ask you
           a little bit more about that.
                       The -- so that's right.  There's some type
           of flow establishment region.  If you have a forced
           flow, you have a momentum dominated, then some kind of
           a transition.  And then you eventually gets to this
           buoyancy-dominated region for the plume.
                       So this region actually could be fairly
           short.  And where you'd like to be is kind of in this
           region as far as analysis.  So you've got this
           spreading plume.  But again that's for a stagnant
                       If you have -- if you have any
           complications to it, you really have to -- I mean it
           complicates the analysis quite a bit.  If you're
           impinging onto a core barrel wall, well, how do you
           analyze that.
                       So we very quickly got -- as we started
           looking at the different complications, that's where
           we said, well, we need to use to some of the CFD and
           see if we could understand that a little bit better.
                       CHAIRMAN WALLIS:  Now let's look at Mr.
           Foerthamnn's experiment.
                       MR. REYES:  Sure.  Can you go back?
                       CHAIRMAN WALLIS:  Now it seems as if the
           width of the plume is about four centimeters, or
           something, but the velocity in the middle hasn't died
           to half the initial one until it's gone 75
           centimeters.  So this is a plume that's very
           persistent.  It's gone an awful long way before its
           velocity in the middle has gone down by a half.
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  So your plumes aren't
           anything like that.  Yours --
                       MR. REYES:  No.
                       CHAIRMAN WALLIS:  -- spread much more
           rapidly, don't they?
                       MR. REYES:  Correct.  Correct.
                       CHAIRMAN WALLIS:  Why is that?  There's
           something different about some dimensionless number in
           your experiment than in this one?
                       MR. REYES:  Right.  Now for this
           experiment --
                       CHAIRMAN WALLIS:  There must be something.
                       MR. REYES:  I think -- yeah.  There -- I'm
           not exactly familiar with the delta rho over rho in
           this test or the density difference in this test and
           what was going on as far as the buoyancy.
                       CHAIRMAN WALLIS:  I think this is actually
           spreading less than the jet would in just -- the
           shrifting-type jet with no buoyancy at all.  This one
           is actually buoyant, so it's spreading less than a
           jet.  And --
                       MR. REYES:  Than the actual.
                       CHAIRMAN WALLIS:  -- that's why it's so
           surprising that your plumes spread so rapidly.
                       MR. REYES:  Well, there's other -- so
           there's other -- right.  So there has to be other
           mechanisms that are --
                       CHAIRMAN WALLIS:  You think about the
           plume from the stack from the incinerator next to your
           -- do you have an incinerator next to your building?
                       MR. REYES:  It's a -- well, I can see it
           from --
                       CHAIRMAN WALLIS:  That probably goes quite
           a long way on a clear day before it spreads much.
                       MR. REYES:  That's right.
                       So what we -- we started looking at our
           plumes and realized that there's something -- it's
           significantly more complicated, especially for the
           conditions that we were looking at, because we had
           multiple asymmetric plume interactions.  We actually
           had some cases where we had cold flow.
                       So now instead of a stagnant downcomer,
           what you actually have is hot-leg flow.  You're
           putting hot water -- the way this was stratified,
           you're -- basically the cold water is pouring --
           pouring out the bottom of the pipe.
                       You still had positive hot-water flow on
           the top of the cold leg going into the downcomer.  And
           you were forcing this flow through the downcomer co-
           current with the plume.  So now you've got a
           could-current situation.
                       CHAIRMAN WALLIS:  That could be worse.
                       MR. REYES:  Yeah.  So now I'm starting
           thinking relevant velocity between the plume and your
           medium.  If you have a stagnant case, your plume comes
           in and the relative velocity for that case is going to
           be larger than if the media traveling with the plume
           is at nearly the same velocity.  So now the relative
           velocity between the plume -- and that's a well
           documented -- that's this plume behavior in cold flow.
                       And so we searched the literature for
           that, and we found a paper that was fairly recent that
           tried to address that, by Wood.
                       So potentially with some cold flow you can
           actually have less -- you'll preserve the plume
           further under certain conditions, okay.
                       There are other compounding conditions, of
           course.  We -- and our tests, of course, as opposed to
           some of the studies done previously, we have a core
           with a core barrel.  And that's dumping heat into the
           downcomer.  So there are other things which are
           heating up this plume and causing it to dissipate a
           bit earlier.
                       So you have these -- all these different
           factors, some trying to preserve the plume and some
           trying to destroy the plume.  Okay.
                       So we very quickly came to realize that if
           we wanted to do a realistic or something realistic,
           that maybe we can bound the problem asymptotically and
           look at some of the ranges of the plume spreading.
                       But, in fact, the thought then came, we
           need to do some type of CFD work.  And that, of
           course, brought with it its own set of problems, how
           to understand CFD and who would volunteer to do the
                       And so we'll present that later on.  And
           we're wide open to suggestions on that.  But you'll
           see some of the comparisons, and you can be the judge
           of what the problems might be or what went right.
                       Okay.  So, in essence, there is a test
           facility in Finland, Imatran Voima Oy, which in the
           good old days they did these flow visualizations.  And
           I guess they had an artist watching the stuff, because
           this is an artist sketching.  He must have been very
                       CHAIRMAN WALLIS:  Well, Leonardo did it
           all 500 and some odd years ago.
                       MR. REYES:  That's right.  I think this
           may be a da Vinci.
                       CHAIRMAN WALLIS:  But Creare did something
           like this, too, didn't he?
                       MR. REYES:  Yeah.  So Creare had that --
           well, they only had the single.
                       CHAIRMAN WALLIS:  It was red or blue, that
           stuff that they used, but it was -- they had pictures
           like this, I think.
                       MR. REYES:  They did?  I don't think -- I
           think they had a single injection, a single --
                       CHAIRMAN WALLIS:  Unwrapped?
                       MR. REYES:  -- cold leg.
                       CHAIRMAN WALLIS:  I thought they had an
           unwrapped --
                       MR. REYES:  Well, maybe they did have two.
                       CHAIRMAN WALLIS:  Maybe -- well, go back
           and find out.
                       MR. REYES:  I don't know if they ever --
           I never saw they had for two.  Yeah, I saw two tests
           that they did.
                       But they had -- they were using that red
           dye and they were injecting into each of the cold legs
           and sometimes they flow, but they were getting some --
           they were getting plume merging.  And so, of course,
           that -- you know, what's the strength of the plume
           where they -- when they merge and how does that affect
           heat-transfer coefficient, da-da-da.  It goes on and
                       So in terms of simple analyses, they very
           quickly -- it became obvious that it was beyond what
           you can do on the back of an envelope --
                       CHAIRMAN WALLIS:  That plume seems to be
           going a lot more than 4 ds.  You were talking about
           mixing by 5 ds.  Or the beltline is at 5 ds from the
           pipe, or something?
                       MR. REYES:  Right.  For Palisades it's
           somewhere up there --
                       CHAIRMAN WALLIS:  And this one seems to be
           going down a lot more than that --
                       MR. REYES:  This -- this -- yeah, this
           looks like it's going down for -- now the flow rates
           for the -- for what they were doing were very, very
           high in these tests.  So that's a big part of it.
                       And I think we have a picture later on
           that we'll show you that kind of goes back to this
           test.  And, of course, we saw similar behavior as far
           as merging, but we didn't see the plumes, you know,
           getting --
                       MR. BESSETTE:  You have to remember also
           this is an artist's rendition.
                       MR. REYES:  So da Vinci --
                       MR. BESSETTE:  Done by -- Actually it was
           done by Tuemisto himself.
                       MR. REYES:  Tuemisto, okay.
                       MR. BESSETTE:  Yeah.
                       MR. REYES:  Tuemisto da Vinci.
                       CHAIRMAN WALLIS:  They didn't have
           photography in those days.
                       MR. REYES:  We have some --
                       MR. BESSETTE:  Not -- well, I don't know. 
           Like I say, he'd interpreted what he saw, and he did
           it by drawing.
                       MR. REYES:  So when we started looking at
           the plumes we were having difficulty interpreting what
           was going on in the downcomer.  So Kent Abel, one of
           our graduate students, came up with this idea of
           putting together this, an unwrapped map.
                       And so each -- this shows all four of the
           cold legs.  On top of it, it gives you the flow rate
           through the cold leg, and then the HPSI flow rate for
           each of the cold legs.  So those are listed up on top. 
           And then along side here he's got a color code for the
           different temperatures.
                       And then here in the cold leg you can see
           if the cold leg is stratified or not, so again by
           temperature.  So we can observe stratification.  When
           this light is green, it means that the HPSI is flowing
           for that particular transit.
                       You can pull up any one of the tests that
           we've performed into this format, and it'll just play
           the downcomer for you, which I love it.  I can -- I
           sit there and watch the lights.
                       CHAIRMAN WALLIS:  Do you have music?
                       MR. REYES:  HPSI, HPSI.  You get
           hypnotized kind of by it.
                       But this is just an example.  If we have
           time I think we can run one of these or two to show
           you a couple of different scenarios and what we see.
                       It's useful because we break it up into a
           gradient, a delta T that your eye can actually catch
           instead of a continuous type of a thing.
                       And what we see in this particular
           snapshot, we see this plume, we see cold temperature
           over here and cold temperature over here, so we're in
           the dark, this dark blue region over here.
                       CHAIRMAN WALLIS:  It's not very obvious.
                       MR. REYES:  It's not real obvious, but it
           does interact --
                       CHAIRMAN WALLIS:  Can't you get more
                       MR. REYES:  Right.  In some of the other
           -- I think in some of the others we'll see more
                       CHAIRMAN WALLIS:  Yeah.
                       MR. REYES:  But the thing is that the
           temperature difference is not -- you're within --
           they're typically within 10 degrees or so, 10 or 15
           degrees.  And so we could do some more contrast.
                       So what we see is a kind of interaction
           here, and then we do see colder here and some cold
           down here.  So we kind of see a merging plume over
           here.  But then again the ambient is relatively cold
                       So in terms of a delta rho, we're not
           looking at a very large delta rho.  However, we are
           seeing this merging and then getting down blow here. 
           So you can imagine that if we had a couple thousand
           more thermocouples, that would have been ideal.
                       So that's one example.
                       Now you can see it a little bit better as
           we run -- is that the next -- yeah.  We'll run this
           for you, and then you can see a little bit better the
           temperature changes.  And this was for the -- this was
           for the main steam line break case, so you'll see
           eventually everything will turn blue because the --
                       CHAIRMAN WALLIS:  Yeah.  I think if it's
           dynamic it will be easier to see.
                       MR. REYES:  Right.  And I think that's
           what we'll do.
                       Okay.  So it's running right now.  We're
           getting -- the time on the upper left-hand corner is
           the time to start the test.  And so it's jumping. 
           We're jumping about -- every step is about eight
           seconds or so.
                       And this is the main steam line break.  So
           we've opened up the break, and so you see all the
           temperatures are uniform.  Now the break's open. 
           We're starting to see cooling, but that's not cooling
           to the HPSI.
                       Now the green -- the HPSI's on now at this
           point, and so you'll start seeing colder temperatures
           underneath the cold legs.  So there you go.  So you
           see some of the yellow and the green, so it's getting
           colder underneath there.
                       CHAIRMAN WALLIS:  Can you -- uh-huh, okay.
                       MR. REYES:  And we can step through it if
           you want to go slower.  So you see --
                       CHAIRMAN WALLIS:  So this is typically the
           whole downcomer, so the beltline is sort of where in
           this, in the middle --
                       MR. REYES:  The beltline is between the 4
           d and the 8 d.
                       CHAIRMAN WALLIS:  Somewhere in the middle
           of the page.
                       MR. REYES:  Yeah.  And we -- and that's
           actually where our beltline is.  We have a big flange
           sitting there so we couldn't get thermocouples in it.
                       And so you can see at this point the cold
           leg number 3 there is still so much stratified.  Cold
           leg number 4 is completely cold, but then that was
           where the broken steam generator was.  So you're
           seeing some cold flows there.
                       So now that the whole downcomer is
           overwhelmed basically by the transient itself, the
           steam line break.  Looking --
                       MR. BOEHNERT:  So that was every eight
           seconds, was it?
                       MR. REYES:  Correct.  Correct.  Yeah, I
           think we're -- were we jumping eight seconds there,
           Ken?  Yeah.
                       CHAIRMAN WALLIS:  If you go back to about
           one or two seconds after it began to turn yellow, --
                       MR. REYES:  Okay.
                       CHAIRMAN WALLIS:  -- you've got some --
           some spludges pretty low down of the -- a really
           different color from the surroundings.  I got the
           impression that there was some plume activity down to
           maybe 10 d or something.  Not insignificant.
                       MR. REYES:  Right.  Well, -- yeah.  In
           fact, we'll talk about what happens when you have that
           cold-leg flow and you're trying to preserve the plume. 
           We see it -- the behavior is somewhat different.  I
           won't steal -- I won't steal their thunder.
                       But, yeah, we do see a different behavior
           for cases where your cold legs are flowing and -- for
           this plant.
                 (Discussion held away from the microphone and
           simultaneous talking.)
                       MR. HAN:  One of the things to keep in
           mind --
                       MR. REYES:  It was one of our
           thermocouples --
                       MR. HAN:  -- in terms of the vessel is
           that transient --
                 (Discussion held away from the microphone.)
                       MR. HAN:  -- behavior is not important
           because of the time constant of the vessel wall --
                       MR. REYES:  This is James Han.
                       MR. HAN:  -- things that happened over the
           time of, say, one minute, for example, don't matter
           because you don't build up a stress.  So you can have
           these plumes.  Let's say, if they're moving and
           whatever, that the transient behavior doesn't matter. 
           It's the longer-term behavior that's important, things
           that happen over the course of 15 minutes to 45
                       CHAIRMAN WALLIS:  It's a question of the
           balance between the surface h and what you think of
           sort of internal heat transfer distance of the wall.
                       MR. BESSETTE:  And it's conduction -- it's
           conduction --
                       CHAIRMAN WALLIS:  It's certainly not an
           infinite h on the surface.
                       MR. BESSETTE:  No, but if it does -- the
           h doesn't matter.  It's because it's so conduction
                       CHAIRMAN WALLIS:  Yeah.  So it's like an
           infinite h?
                       MR. BESSETTE:  It's like an infinite h. 
           If you had an infinite h or not an infinite h, it
           doesn't really matter too much.
                       CHAIRMAN WALLIS:  So you're immediately
           chilling the surface to the temperature of the water?
                       MR. BESSETTE:  Essentially your boundary
           layer doesn't matter that much.  It's the ambient --
                       CHAIRMAN WALLIS:  But you had to know h
           because if you assumed h is infinite it's not very
                       MR. BESSETTE:  Well, --
                       CHAIRMAN WALLIS:  You have to know h.
                       MR. BESSETTE:  -- if H is infinite -- if
           h is infinite, it means you have no boundary layer. 
           It means your ambient temperature is the temperature
           of the surface of the wall.
                       CHAIRMAN WALLIS:  I don't think you want
                       MR. BESSETTE:  It doesn't matter that
                       CHAIRMAN WALLIS:  It stresses the wall. 
           That temperature difference is what stresses the wall,
           the difference from surface from the average, is it?
                       MR. REYES:  There is a thermal penetration
           of time that --
                       MR. BESSETTE:  The difference between the
           ambient fluid temperature and the wall surface
           temperature is never large, no matter what h is.
                       CHAIRMAN WALLIS:  Then you might as well
           assume h is infinite for your -- and forget about
           everything else as long as you know what the
           temperature is.
                       MR. BESSETTE:  That's right.  You can do
                       CHAIRMAN WALLIS:  I don't think that's
           very good for -- well, maybe we -- that's a different
           discussion somewhere else.
                       I thought it was pretty critical what h
                       MR. BESSETTE:  No.  In fact, we've done
           those sensitivity studies already --
                       CHAIRMAN WALLIS:  Okay.  So we'll go back
           to that some time.
                       MR. BESSETTE:  -- to show that h is not
                       MR. SHACK:  I mean that's good news.
                       MR. BESSETTE:  Yeah.
                       MR. HAN:  That's good news, yeah.
                       CHAIRMAN WALLIS:  So we just forget about
           thermal hydraulics.
                       MR. SHACK:  No, no.  You had to set the
                       MR. KRESS:  No, you need the temperature.
                       CHAIRMAN WALLIS:  Okay.
                       MR. BESSETTE:  We've been trying to tell
           you that.
                       MR. SHACK:  But it's still your
           penetration depth that you're interested in, isn't --
                       CHAIRMAN WALLIS:  See, there's a white --
           there's a light-colored one way down there, right? 
           Presumably that -- what's happening there?  It looks
           very strange to me.  You've got colder stuff down
           there than you've got --
                       MR. KRESS:  At the middle it curled over.
                       CHAIRMAN WALLIS:  Yeah.  But it's just
           going to warm again at the top, isn't it?  Or, no,
           maybe I've -- yeah, it's going to warm again at the
           top.  There's a plug, sort of a lump of cold fluid in
           there not even connected to the pipe.
                       MR. REYES:  Yeah.  And sometimes what you
           see is -- well, our thermocouples -- that's a good --
           that's a good point.
                       Our thermocouples are closer to the vessel
           wall because that's where we wanted to measure, what
           was impacting the wall.
                       CHAIRMAN WALLIS:  Oh, so if it jumps away
           to the inside, --
                       MR. REYES:  If it jumps --
                       CHAIRMAN WALLIS:  -- you won't see it?
                       MR. REYES:  Yeah.  So quite often --
           that's right.  So quite often what we see is when
           we're injecting -- it'll jump that first thermocouple. 
           And that one will read hot.  And all the thermocouples
           below will read cold.  And so it's impacting the
           barrel wall, mixing up, and then it's --
                       CHAIRMAN WALLIS:  But here we have -- do
           those yellow things -- are they those things -- they
           look -- that doesn't look like a plume.  It just looks
           like a -- sort of a odd-shaped lump of fluid.
                       MR. REYES:  It's not like the -- well,
           again we don't have -- we don't have a lot of
           thermocouples to get a good fine detail of this thing.
                       But you're right, the shapes are not going
           to be nicely-spreading plumes.  There are going to be
           some meandering --
                       MR. SHACK:  Will we see this in the CFD
           calculation, something like this?
                       MR. REYES:  Well, yeah, I think you'll see
           that the CFD calculation does more of the meandering
           and the curling-type behavior, so...
                       Okay.  I'll let them get us back to the
                       Okay.  So one of the things that we've
           observed is that at least as far as -- in terms of an
           asymptotic solution or trying to imagine a little bit
           of what's going on, there was a paper recently by
           Wood.  It was called, "Asymptotic Solutions and the
           Behavior of Outfall Plumes."
                       And it was very nice -- nicely done
           because you don't -- it was the only one I found that
           was fairly recent that talked about the spreading of
           the plume under some unusual conditions, either
           crossflow or co-flow.
                       So what is done basically is the b
           represents the half width of the plume.  Okay, and z
           is the axial position of the plume as it comes down.
                       And so this basically describes the
           spreading of the plume.  So for a stagnant case, u
           subinfinite here, that's a stream velocity.  Up is the
           plume centerline velocity.  And ks is the spread
                       And so for a stagnant media where you're
           injecting these plumes, k is a constant.  I mean this
           goes to zero.  The ups cancel in case.  So he was able
           to kind of unify that behavior.
                       Whenever you have a flow, this is the
           angle between the trajectory of the plume versus your
           flow.  So if it's co-flow, that would be -- the
           cosine's zero is one.  So you'd have up over up plus
           u infinite.
                       So what this is telling us then is it's a
           factor that makes this constant smaller and as a
           result you get a plume width which is smaller, tighter
           as you go down in your axial position.
                       So this confirmed an idea that, well, for
           co-flow you would expect to see tighter plumes.  They
           might be preserved a little bit longer than you'd
           expect to see in a stagnant media.
                       So this suggests that for certain -- so
           now a scenario comes to mind.  You have stagnant
           conditions in your -- in your downcomer.  You inject
           the plume.
                       You'll get very good mixing because the
           relative velocity between the plume and the ambient is
           going to be higher than the case when you have co-flow
           at low-flow rates.  When you've got a co-flowing
           plume, so you'd expect the plume to be preserved a
           little longer.  And we'll talk about the phenomena
           that we see in co-flow versus stagnant because we did
           both cases.
                       Of course, if your stream-flow rate
           continues to increase, eventually something's going to
           -- this model wouldn't apply.  So there's got to be a
           limit to this.  And so that would be on the asymptotic
           end of this study.
                       So if you'd get enough crossflow or enough
           downflow, you'd expect the plume to break up because
           of it.  So again it's probably -- you've got a
           relative velocity criteria and -- if I come up with
           something that works reasonably well.
                       So again this just explains what I just
           said, that the spreading for the stagnant condition,
           you expect it to be greater than spreading for a co-
                       Now this is -- again this is a nice
           uniform co-flow, so we have some other behavior which
           could complicate this -- this -- what we see in our
                       Okay.  So what we did see, we did see
           downcomer thermal stratification under the flowing
           case.  And we had a presentation on that which
           describes what we saw when we were injecting these
           plumes for the co-flow case and why that data looks
           different, the downcomer profile looks different than
           what we saw for --
                       CHAIRMAN WALLIS:  Actually going db/dz
           when you have these very irregular plumes must be a
           little bit awkward.  It's not as if you just have a
                       MR. REYES:  Yeah.  We --
                       CHAIRMAN WALLIS:  You measure the db/dz,
           this thing is swirling around.
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  So you had to -- do you
           actually measure db/dz some --
                       MR. REYES:  No, not with --
                       CHAIRMAN WALLIS:  So this statement here
           is inference from the theory.
                       MR. REYES:  Inferred -- is inferred from
           theory.  It's inferred from theory.
                       CHAIRMAN WALLIS:  Okay.  I thought you
           meant you had measured it.
                       MR. REYES:  Yeah.  That would -- that's my
                       If we could set up a -- this would be
           simple enough to set up with a flow visualization.  I
           think it's something that --
                       CHAIRMAN WALLIS:  With one plume?
                       MR. REYES:  Just one plume, yeah.  We
           wouldn't see --
                       CHAIRMAN WALLIS:  Once you start --
                       MR. REYES:  Then grow to two plumes --
                       CHAIRMAN WALLIS:  Once you start setting
           up swirlies in the downcomer, all the plumes are going
           to start wandering around.
                       MR. REYES:  "Swirlies," I like that.
                       Okay.  There's an appendix I have added to
           this which deals with a little more details of what we
           were seeing as far as the plume stratification or cold
           leg -- excuse me -- cold-leg influ- --
                       CHAIRMAN WALLIS:  Well, let's see.  So far
           it's kind of qualitative, isn't it?  I mean I didn't
           get anything I can grasp which is something I can use
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  But you're going to give
           us something which is more quantitative.
                       MR. REYES:  Right.  Now we're getting into
           some more of the measured -- what we're seeing for the
           different scenarios, the flow case and the stagnant
                       So this is a stagnant loop case.  We did
           Tests Numbers 4, 5, and 6.  We had the system
           essentially stagnant.  And we're injecting cold water. 
           There was no core heat.  The system was hot initially. 
           We had all of our structure.  Everything was hot in
           that pressure.  And we just started injecting cold
           water into the cold leg and watch it spill into the
                       What this represents are all the
           temperatures, and that's this part.  Okay.  These are
           all the temperatures that lie underneath cold leg 1. 
           So directly beneath it and to the sides of it,
           everything that's underneath cold leg number 1, all
           the way down to the 8 d mark.
                       And on the -- of course, we're looking at
           a decay situation.  And so at first glance it looks
           like everything is fairly tight.  And this is kind of
           what you'd expect to see.  But at the very beginning
           what happens is that your density difference, of
           course, is the greatest.  Okay.  So you inject this
           cold plume into the stagnant media.
                       And what happens, of course, is as time
           goes on you're cooling off the whole system.  And so
           your delta rho is getting smaller and smaller as time
           goes on.  So you expect that difference to narrow.  I
           mean the plumes are, in essence, -- it's as if the
           plumes are getting weaker, because the ambient is
           getting colder.
                       So we see the largest temperature
           differences initially, and this could persist for a
           while, but some of the thermocouples we'll read.  So
           here we are at that 275 or so.  We're looking at only
           about a 25-degree-Fahrenheit difference from the
           coldest point in the plume -- or the coldest location
           in the downcomer, which is the 1.3 d for a lot of
           these tests, and then down to about 4 d -- well, this
           actually goes only 8 d.
                       So we're not seeing a very large -- except
           maybe at the beginning, we see 50 degrees or so.
                       So when you first come in and the system's
           hot, you really see a large temperature difference. 
           So you'd expect --
                       CHAIRMAN WALLIS:  You've got so many
           colors it's very hard to figure out anything.
                       MR. REYES:  Oh, yeah.  Yeah, this -- yeah,
           that's a good point.
                       What I'd like to -- what I'd just want to
           point out is the shape of this thing.  Okay.  How well
           it's -- how tight it is, okay.
                       So what you see is kind of the --
           throughout the test, these --
                       CHAIRMAN WALLIS:  Which are the worst
           spikes?  Which ones are they?
                       MR. REYES:  These bottom -- so what you
           see are these bottom --
                       CHAIRMAN WALLIS:  Which are the worst
           spikes in terms of where they are, the location?  Are
           they at 2, or 3, or 4, or 8?
                       MR. REYES:  They're all above the 4 d.
                       CHAIRMAN WALLIS:  They're at 3 maybe?
                       MR. REYES:  No, 2.
                       CHAIRMAN WALLIS:  At 2?
                       MR. REYES:  At 2 and 1.
                       CHAIRMAN WALLIS:  2 and 1?
                       MR. REYES:  And that 1.3, it jumps and
           sometimes it mixes back up.  So you see -- you'll see
           it come on and off basically.  So we're still looking
           for the --
                       MR. KRESS:  And like David said, those
           spikes don't matter.  You can just ignore them.
                       MR. BESSETTE:  I think, you know, to me
           this one plot says that we have no plume problem.
                       MR. REYES:  Yeah.  It says it's relatively
           tight all the way through.  And you'd expect it to get
           tighter --
                       CHAIRMAN WALLIS:  Well, see if you had
           bottom injection in that of ACC or -- you might have
           a problem.  The temperature differences would be much
                       MR. REYES:  Yeah.  If the concern is
           duration of temperature.
                       CHAIRMAN WALLIS:  Yes.
                       MR. REYES:  And when we look at the
           flowing case --
                       CHAIRMAN WALLIS:  And also magnitude.  I
           mean you're actual driv- -- your different temperature
           differences in the cold leg aren't that big, anyway.
                       MR. REYES:  That's right.  Right.  When we
           look at the stratification.
                       So the rest of the plots, I'm going to
           just skim through, but you see similar results.
                       CHAIRMAN WALLIS:  Yeah.  There are one or
           two that look worse.
                       MR. REYES:  Okay.  That one was a little
           bit more severe, but...
                       Again these are -- typically it's early on
           in the transient, so we can just go through.  So let's
           jump over to the flowing case.  So we'll jump over to
           the natural circulation case.
                       So those tests represent essentially --
           I'll say essentially stagnant plume.  Again, what we
           saw when we -- as soon as we injected it generated
           initial loop flow which gradually stopped, so it was
           hard to get -- for the tests that we did, because we
           had system full, we saw a little bit of flow in the
           cold legs initially, and that tapered off.
                       Okay.  Now to the circulation case.  This
           was a series of parametric tests that we performed. 
           And what we had going on there is we used the core
           power to generate a natural circulation flow rate
           through the loops.
                       And then we varied our HPI in a stepped
           fashion.  And we produced 16 different cases, 8 cases
           under cold leg 3 and 8 different cases for cold leg 4. 
           Okay.  So they're on opposite ends of the plant under
           different steam generators.  So we were trying -- we
           were watching both of these for the two situations.
                       And the idea is that we would hold it for
           a small period of time and we would observe what type
           of downcomer behavior, what type of plumes we would
                       So what you can see here is for one of the
           more severe cases here about 200 kilowatts of core
           power, which corresponds to about two-percent decay
           heat for us and about half a gpm, which is about
           50-percent HPI flow for that one leg.
                       We get about 300 -- about a 30-degree
           temperature difference.  And these top lines here,
           again it's hard to see with this, but the bottom ones
           are typically the 1.3 right at the outlet.  And the
           tops, it's kind of a merger of the -- between 4 and 8.
                       So we're seeing that the plumes have
           essentially dissipated by the time you get to 4.  And
           I can show you individual plots with just -- which
           would be a little bit easier to see, but this shows
           all the data.
                       So that was -- the most severe case was
           under 4, I think.  Let's see -- no, so 3 was the more
           severe case.
                       So we're seeing here only about 20 degrees
           of temperature difference --
                       CHAIRMAN WALLIS:  So 8, I can't see where
           8 is because of where the color is.
                       MR. REYES:  Oh, okay.  Yeah, 8 merges all
           the way up on top here.  Yeah, 8's up on top.
                       And I can certainly -- we can pick any one
           of these and blow it up.
                       CHAIRMAN WALLIS:  And those are much less
           than the stratification in the cold leg which you
           showed us on another figure.
                       MR. REYES:  Correct.
                       CHAIRMAN WALLIS:  Much less.
                       MR. REYES:  So the same test.  First we
           looked at the cold leg and then we looked at the
                       CHAIRMAN WALLIS:  At most 30 percent or
                       MR. REYES:  Right.  So we are seeing --
           now the difference in this, in terms of a scenario --
           okay.  So if you have a reactor plant and you're
           concerned about cooling at a -- for duration, well,
           potentially in this situation you can have natural
           circulation through a core.  The core's producing hot
           water.  And so you're continually feeding hot water to
           the cold leg.
                       So the difference between this and the
           stagnant case is that in the stagnant case the plumes
           will decay over time because the whole system is
           cooling down.  In this one you're using the hot water
           from the cold leg to essentially keep your downcomer
           warm.  And so you can make these plumes persist a lot
           longer.  I think that's just an important point.  But
           we're seeing that temperature difference is not very
                       Okay.  And so if you get to even much
           higher flow rates or -- with pumps on, it's not going
           to be a big effect.  But the difference is that you
           can make these persist a lot longer because you've got
           flow.  You're replenishing your downcomers with hot
           water.  So that's the big difference there in terms of
           an integral system.
                       CHAIRMAN WALLIS:  Well, how big a
           temperature difference do we need to see for Dave
           Bessette to get worried?
                       MR. ROSENTHAL:  Well, yeah, if I can
           interject, it's not a question of Dave Bessette
           getting worried but Nilesh Chokshi getting worried. 
           And we're talking -- what were you saying, 25 c, some
           numbers like that.
                       CHAIRMAN WALLIS:  So 25 c is bad?
                       MR. ROSENTHAL:  Well, I mean --
                       MR. BESSETTE:  Noticeable.
                       MR. ROSENTHAL:  That's where it's starting
           -- it will show up in their probabilistic fracture
           mechanics case.
                       CHAIRMAN WALLIS:  So these are less --
           these are all less than 15 and maybe more.
                       MR. ROSENTHAL:  Half.
                       CHAIRMAN WALLIS:  In fact, the way you
           worry about it is more like 2 or 3 c, isn't it?
                       MR. ROSENTHAL:  Well, this is all good
           news, but let me --
                       MR. REYES:  Now --
                       MR. ROSENTHAL:  -- let me back up a little
           bit if I might just for a moment because I'm worried. 
           You know, if we go read this transcript two years from
           now, the --
                       CHAIRMAN WALLIS:  We should, yes.
                       MR. ROSENTHAL:  -- we ought to put it into
           a little bit of perspective.
                       We're talking about pressurized thermal
           shocks.  We're talking about low temperatures at some
           higher pressure.  We're talking about cases that would
           have to persist for some period of time.
                       Roy Woods' probabilistic work will tell us
           the probability of sequences.  But here we're focused
           on a small break LOCA sequence where the break is big
           enough that you don't refill it and depressurize, but
           not so big that you depressurize the system, so it
           would be a case again.  So it's sort of a
           perverse-size break.
                       And then the issue comes up:  Okay, we
           know that under force-flow conditions we think that we
           can predict things rather well.  Under conditions
           where you don't have force flow are you going to have
           a problem with plumes and stagnant conditions and
                       CHAIRMAN WALLIS:  Like you said, this was
           an -- it's an artificial kind of break, but isn't it
                       MR. ROSENTHAL:  No.  It's just a purp- --
                       CHAIRMAN WALLIS:  -- artificially made to
           be a pretty bad break from the point of view of --
                       MR. ROSENTHAL:  Of PTS.
                       CHAIRMAN WALLIS:  -- of PTS.
                       MR. ROSENTHAL:  Right.  Right.  But it's
                       CHAIRMAN WALLIS:  And, of course, the risk
           -- the risk-informed people will probably say it's
           never going to happen anyway, so...
                       MR. ROSENTHAL:  Well, he's going to give
           us the probability of this thing some day.  And then
           when you throttle HPSI flow, then there's some
           associated HRA numbers associated with that.
                       But from a thermal hydraulic standpoint,
           it's still very interesting, so -- okay.
                       CHAIRMAN WALLIS:  But you're trying to
           look at the worst case, or something close to the
           worst case in that?
                       MR. ROSENTHAL:  Well, in this.  I mean we
                       MR. REYES:  Right.
                       MR. ROSENTHAL:  Because I think that we
           have confidence that in force-flow situations that the
           codes will do a better job predicting --
                       CHAIRMAN WALLIS:  So it is only if we
           could say that this is something like the worst case
           or very close to the worst case, and the temperature
           differences here are so small that they don't
           challenge in any way the vessel, then --
                       MR. ROSENTHAL:  Okay.  But stagnant --
                       CHAIRMAN WALLIS:  -- we don't need any
           PRA.  We can forget it.
                       MR. ROSENTHAL:  Well, fine.  Okay.  But --
                       CHAIRMAN WALLIS:  And then we're really
           happy then.
                       MR. ROSENTHAL:  But the -- yeah.  But the
           stagnant thing was something of true concern, --
                       CHAIRMAN WALLIS:  Yes.
                       MR. ROSENTHAL:  -- so I'm glad that we --
                       CHAIRMAN WALLIS:  Yes.  Oh, yes.
                       MR. ROSENTHAL:  -- had the experiments.
                       CHAIRMAN WALLIS:  Yes, indeed.  Indeed.
                       MR. ROSENTHAL:  And --
                       CHAIRMAN WALLIS:  Otherwise, you could
           argue about it forever.
                       MR. BESSETTE:  Yeah.  And it's worth
           noting, we didn't do these experiments by accident.
                       CHAIRMAN WALLIS:  Well, I hope you don't
           do many experiments by accident.
                       MR. ROSENTHAL:  David keeps whispering
           little insights in my ear about the timing, et cetera. 
           I mean --
                       CHAIRMAN WALLIS:  Someday --
                       MR. SHACK:  Again this is all for
           Palisades.  You know, you're going to have to somehow
           do the calculations to convince us that it's this good
           for everybody.
                       MR. ROSENTHAL:  Okay.  But this is where
           -- and we'll do lots of calcs, but I mean this is
           really very good benchmark stuff.  And even if you
           take the broader perspective, we have relatively
           little data on steam line break experiments.  So the
           fact that we're generating these have a broader
           applications in terms of --
                       MR. SHACK:  Well, that, I guess, was
           another question --
                       MR. ROSENTHAL:  -- code validation.
                       MR. SHACK:  -- is I assume you're getting
           all this in a nice optical disk somewhere so someday
           in the future if somebody wants to benchmark
           calculations, this won't disappear.
                       MR. BESSETTE:  It's all going on our
           databank, yes.
                       MR. ROSENTHAL:  Oh, so you can get it
           right off the web.
                       MR. SHACK:  Yeah, I could.  From the NRC
           website.  Good luck.  Or you're going to put it in
                       MR. REYES:  There is one qualifier that --
           I just want to remind you, that this is -- we are a
           reduced-pressure facility.  And so as a result our
           delta rhos over rho are somewhat less.  What you'd
           expect to see in Palisades is something on the order
           of 10 percent or more.
                       CHAIRMAN WALLIS:  That's when we get into
           the question of when you get a big enough delta rho do
           things change significantly, or is it still the same?
                       MR. REYES:  Is there a transition
           somewhere.  So that's just a -- just as a qualifier.
                       We're fairly close.  I mean .18 is
           relatively typical.  But I think for Palisades plant
           we're going to see they start up at a higher
           temperature, 570 and -- or hot leg 570, the cold leg
           530.  So they're 530, we're at 420.  So there is some
                       CHAIRMAN WALLIS:  But it's not as if
           you're way off.
                       MR. REYES:  Right.  That's right.  Okay.
                       CHAIRMAN WALLIS:  And if you have a good
           theory, then maybe extrapolating it that far isn't too
                       MR. REYES:  That's not so bad, no.
                       Okay.  So concluding with this one, what
           we saw was that the downcomer plumes were -- we saw it
           both for the stagnant case and natural circulation
           flow conditions.
                       For the range of natural circulation flows
           we examined from one and a half percent to four
           percent decay power in this test number 3 and about 30
           to 100 percent HPSI flow.
                       The plumes were, for all those cases, they
           were well mixed by about four cold-leg diameters, is
           what we saw.  Okay.  Everything was relatively back to
           the ambient temperature.
                       CHAIRMAN WALLIS:  How does that compare
           with what we started out with?  You know, we started
           out with a theoretical plot for the infinite plume. 
           You said Rodi or someone has all these different
                       Does yours fit in in any way with the
           classical experiments with isolated plumes?
                       MR. REYES:  With the -- we haven't --
           right.  We haven't done that comparison yet.
                       CHAIRMAN WALLIS:  But this seems to be a
           very rapid mixing.
                       MR. REYES:  It's a very rapid mixing.  We
           haven't -- my first thought was to use the co-flow
           work and the isotonic models to compare, just to see
           if that makes a difference.  But I haven't done that
                       But we have done calculations with REMIX
           and with STAR-CD, our CFD codes, to try and see if we
           can predict some of the meandering behavior in some of
           the --
                       CHAIRMAN WALLIS:  This is funny, because
           jets are sort of well mixed by 10 diameters, aren't
           they?  And you'd expect plumes to go further because
           the buoyancy is driving them.  So it's kind of
           surprising that four diameters are enough to --
                       MR. REYES:  To mix this --
                       CHAIRMAN WALLIS:  -- to wear out these
                       MR. REYES:  These are -- again, this is
           for the flow rates that we're looking at.  And, again,
           for the CE Plant that they're a very low injection
           flow compared to what we see in other plants, so...
                       Dave suggested that --
                       CHAIRMAN WALLIS:  Well, it may well be --
           excuse me -- but the actual plume, when it starts out,
           is much smaller than --
                       MR. REYES:  I know, just --
                       CHAIRMAN WALLIS:  -- the whole cold-leg
                       MR. REYES:  Right.  That's right.
                       CHAIRMAN WALLIS:  For instance, this
           spills out --
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  -- and maybe you should
           take -- if you took a quarter of a cold leg diameter,
           this would look like 16 diameters.
                       MR. BESSETTE:  That's right, yeah.
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  Maybe that makes more
                       MR. BESSETTE:  It's not evident that the
           cold-leg diameter has any particular significance.
                       MR. REYES:  Okay.  Today --
                       CHAIRMAN WALLIS:  Well, it's a way of
           scaling things, isn't it?  It's just...
                       MR. REYES:  You're right.  It's a good
                       Today when we run the test I'll need
           someone take a look in the tank and I think, you know,
           we'll be able to see as it pours into the sides of the
           -- I think you're right.  It doesn't fill the pipe.
                       CHAIRMAN WALLIS:  We'll see a plume?
                       MR. REYES:  You'll see a plume.  Well, one
           person will.
                       CHAIRMAN WALLIS:  Only one person, no
           independent check on that?
                       MR. REYES:  That's right.
                       CHAIRMAN WALLIS:  One person goes in the
           tank and looks through the wall?
                       MR. REYES:  One in the tank.
                       CHAIRMAN WALLIS:  Do you need a volunteer?
                       MR. REYES:  Well, we've got two.
                       Okay.  Are any other questions on what
           I've presented?
                       (No audible response.)
                       MR. REYES:  If not, then we'll move to the
           next presentation.
                       Brandon is going to talk, Brandon Haugh
           will be talking a little bit about what we saw for
           these force flows or natural circulation flows, what
           we saw happening in the downcomer that was a bit
           different than when you had the stagnant flow.
                       MR. HAUGH:  Just give me one second here.
                       MR. HAUGH:  Good morning, everybody.  My
           name is Brandon Haugh.  I'm a graduate student in the
           Department of Nuclear Engineering.  I'll be giving you
           a presentation on downcomer thermal stratification we
           observed in our CE Tests in the APEX facility.
                       I am going to talk about a description of
           what downcomer thermal stratification is.  I have a
           diagram and some tests from the IVO facility in
           Finland, observations of what we saw in our test
           facility.  And we're also going to run another one of
           those transient temperature maps that we saw in a
           previous presentation, and it will help to easily
           demonstrate what thermal stratification is.  And then
           I'll come to a few conclusions.
                       The figure here is rather dramatic.  It
           doesn't actually look that stratified.  This is just
           for an appearance of -- it looks good in black and
           white, so we'll leave it at that.
                       And the plume isn't this concentrated.  It
           obviously spreads and dissipates some.  But you'll see
           that there's co-flow of velocity in the downcomer and
           velocity in the plume when we see a stratified layer
           in the lower portion of the downcomer.
                       We observed in our tests that this
           occurred in the presence of natural circulation flow. 
           It didn't happen in any of the stagnant cases.  And it
           seems the co-flow of the downcomer fluid stream in the
           plume reduces the mixing and seems to permit the onset
           of downcomer thermal stratification.
                       It seems to help confine the plume, and it
           seems to just go to the bottom and start cooling the
           bottom and working its way up.
                       These figures here are taken from the IVO
           facility.  I would say the full name, but I would
           probably butcher it.
                       This is from Test Number 102.  In some of
           the tests they used photography so it was just not all
           artist rendition.  But for this test they had one
           injection in one cold leg and then cold-leg flow in a
           different cold leg.  But it was a rather high flow
           rate, so you can see it's pretty dramatic, the
           stratification they see --
                       CHAIRMAN WALLIS:  Well, that plume isn't
           mixing much at all, is it, unless I'm mistaken.
                       MR. HAUGH:  Yeah, exactly.  There's a 66
           gallons per minute cold-leg flow and 6.6 gallons per
           minute HPI flow.  So this is much larger than we see
           in our facility.
                       CHAIRMAN WALLIS:  What we see on the left
           is --
                       MR. HAUGH:  Yeah.  You'll see the plume
           almost penetrates fully to the bottom.
                       CHAIRMAN WALLIS:  The plume doesn't seem
           to spread at all.
                       MR. HAUGH:  Yeah, exactly.  And that's
           kind of the argument of the co-flow case.  It seems to
           help confine the plume.
                       And you'll see the stratification.  I mean
           it's rather dramatic because of the dye.  You can't
           really tell kind of how much it mixed at the bottom.
                       CHAIRMAN WALLIS:  Then you say,
           "Temperature gradient observed in the downcomer" are
                       MR. HAUGH:  Yeah, we see similar in our
           facility, but it's not quite as dramatic.
                       CHAIRMAN WALLIS:  What's this?  I would
           think that you'd actually get cold temperatures lower
           down with that, a plume like that.
                       MR. HAUGH:  Yeah, that's what we see.  You
           know, in the transient temperature map you'll see that
           we don't seem to catch the plumes due to maybe our
           thermocouple spacing or it jumping and may be sticking
           to the core barrel side.  But we definitely see the
           stratification.  Okay.
                       For the test that we ran, an integral
           systems test, and some of the separate effects test,
           this is just kind of a map of what we did and what we
           saw related to downcomer thermal stratification.
                       The first three, 4, 5, and 6, were the
           stagnant cases with no cold-leg flow.  And we observed
           basically no downcomer thermal stratification.
                       In tests 7, 8, and 9, those were the small
           break LOCAs, where we had natural circulation flow in
           at least some of the cold legs, we did observe some
           downcomer thermal stratification.
                       CHAIRMAN WALLIS:  And by "thermal
           stratification," you mean temperature as a function of
           z, or as a function of Froude?  So the pool --
                       MR. HAUGH:  Yeah, in an axial measurement. 
           So from the bottom of the lowest point --
                       CHAIRMAN WALLIS:  -- a pool of cold s- --
                       MR. HAUGH:  -- in the downcomer to the
                       CHAIRMAN WALLIS:  Why doesn't that wash
           out when you have circulation?
                       MR. HAUGH:  That's -- we don't quite -- I
           don't quite understand that.  I think Dr. Reyes might
           be able to field that.
                       MR. REYES:  What we've got is a relatively
           low natural circulation flow.  And that's introducing
           the hot water into the top of the downcomer.  And that
           water is -- at the bottom you do see some of that,
           that mixing occurring.  And so it's constantly
           replenishing that mixing region which is a little bit
           lower in the downcomer.
                       CHAIRMAN WALLIS:  So the hot water is
           getting out by mixing with the cold, presumably. 
           Otherwise --
                       MR. REYES:  Right.  That's right.
                       CHAIRMAN WALLIS:  -- it would --
                       MR. HAUGH:  You'll notice that the
           stratification we observed isn't very significant in
           terms of the delta T, from 8 diameters to 1.3
           diameters; in tests 7, 8, and 9 it was between 35 and
           40 degrees Fahrenheit.
                       In Test Number 10 -- that was a
           combination test of a safety relief valve in the
           pressurizer and an atmospheric dump valve on the steam
           generator side -- we saw a little, of a slightly less
           stratification, but it was observed.
                       In the hot zero power main steam line
           break due to the -- we have no core power basically. 
           Well, it was very low, like 45 kilowatts, we weren't
           replenishing the hot water in the top of the
           downcomer.  So we didn't observe the thermal
           stratification.  It appeared to be relatively well
                       In Test Number 12 in the main steam line
           break from full power while the steam generator was
           blowing down, the downcomer was relatively well mixed
           because the cold legs feeding in were relatively cold
           from the broken side.
                       But after the steam generator finished
           flowing down and we started reheating the plant after
           we repressurized, we saw the onset of thermal
           stratification because we started feeding hot water
           into the top of the downcomer.  But it was very minor
           and not significant delta T from the top to the
                       This is a snapshot of one of the transient
           temperature maps from Test Number 9, which was a
           stuck-open safety relief valve on the pressurizer. 
           This is the initial conditions.  We can see it's
           relatively all the same temperature.  I'll move
           quickly to the next slide.
                       This is 3500 seconds into the test, and
           it's pretty obvious to see.  You can see the
           stratification in the downcomer.  It's easy to note
           that it's, you know, only 30 degrees Fahrenheit, but
           it is there.
                       Later on in the test we can see that the
           bottom is cooling up, but we're still replenishing hot
           water due to the core power to the top, so it's
           stratified.  But the stratification layer is getting
           much closer to the cold legs at this point.
                       CHAIRMAN WALLIS:  With the stratification
           that high it really kills the plume, doesn't it?  The
           plume goes right into the --
                       MR. HAUGH:  Yeah, we --
                       CHAIRMAN WALLIS:  -- stratified thing, and
           then --
                       MR. HAUGH:  In the facility and in some of
           the plots that we don't have.  But when we play the
           transient temperature map, you can -- you won't even
           notice that there's a plume there.  It just seems that
           you just see the stratification, and that's about all.
                       And then for Test Number 6, which was one
           of the stagnant cases where we didn't observe thermal
           stratification, this is about 800 seconds into the
           test, you can see that it's all relatively well mixed.
                       And at this point the delta rho over rho
           is a -- well, the delta rho between the downcomer
           fluid and the plume is relatively low, so you don't
           really see much plume activity, either.
                       And now we'll play the transient
           temperature map from Test Number 9.  And I'm starting
           about 2,000 seconds into the test, because that's when
           it's easiest to see this onset of the stratification. 
           And you can see that the bottom is slightly colder
           than the top.  And it'll build as it runs.
                       You can also notice the stratification in
           the cold legs from the injection.  And it seems to be
           pretty much -- above the Weir wall height it's
           relatively constant temperature fluid.  But due to the
           side injection below the Weir wall height it's
                       And when you've seen enough, just let me
                       CHAIRMAN WALLIS:  If you gave each one of
           those dots a note you could play music.
                       MR. HAUGH:  Next time.
                       And as you can see, it's starting to cool
           as we go up.  That's probably...  I mean would you
           like to see more?  It's entertaining.
                       That's probably enough, Kent.
                       Just click on "Resume Slide Show" up
           above.  There you go.  Okay.
                       Now that we've seen that, I hope it was
                       So the conclusions about downcomer thermal
           stratification, DTS, we observed it in the APEX
           facility in tests where we had natural circulation. 
           And we noticed it did not occur in the stagnant loop
           cases or when we had a very high cool-down rate, such
           as in a main steam line break.
                       But after the blowdown ceased in Test
           Number 12, when we started reheating, we saw the onset
           of thermal stratification.
                       We have come to the conclusion that a
           probable mechanism for downcomer thermal
           stratification is the co-flow of the downcomer fluid
           stream and the plume, which tends to preserve the
           plume and helps it get to the bottom.
                       And also we have the replenishment of the
           hot fluid from the core power heating up the top of
           the downcomer.
                       CHAIRMAN WALLIS:  There's more to it than
           at that time, though, isn't there?  I mean it somehow
           has to go through almost a shock wave.  The plume
           comes down and then it all mixes up in this colder
           thing at the bottom.
                       MR. HAUGH:  Yeah, there's a mixing -- with
           a thermal stratify decay there's like a mixing --
           there's probably some penetration.
                       CHAIRMAN WALLIS:  I would think you'd have
           to explain that.  It's not just a fact that the plume
           is helped by the co-flow.  Why does it stop?  Why does
           this mixing occur at that level?
                       MR. HAUGH:  That's a good question.
                       This was just a preliminary conclusion. 
           There's obviously more mechanisms present that --
           there's the plume interaction with the thermal
           stratified layer also hitting the core barrel. 
           There's several other things that will probably need
           to be examined to further define this phenomena.
                       That concludes my presentation.  Is there
           any more questions I can field?
                       (No audible response.)
                       MR. HAUGH:  Okay.
                       CHAIRMAN WALLIS:  Well, we're looking
           forward to a really good theoretical model.
                       MR. HAUGH:  And the work is in progress.
                       (Aside comments off the record.)
                       CHAIRMAN WALLIS:  I think we have one more
           presentation before the break.
                       MR. BOEHNERT:  That's correct.
                       MR. YOUNG:  My name is Eric Young.  I'm a
           graduate student here, a graduate student of Dr.
           Reyes.  I'd like to take this opportunity to thank Dr.
           Reyes for giving me this opportunity for presenting in
           front of the council -- or the Committee.
                       I'll be presenting on the REMIX
           calculations or predictions on the STAR- -- or on the
           APEX-CE facility.  The presentation will progress in
           the following manner.
                       I'd like to describe the objectives of the
           study; go through a description of the REMIX model; a
           description of the APEX-CE stagnation tests that we
           did a comparison with, these being Tests 4, 5, and 6;
           some insight into the effects of the core barrel heat
           transfer and effective thickness; and the recommended
           summary -- or summary and conclusions.
                       The objectives of the study was to
           benchmark STAR-CD against the integral test facility,
           this being the APEX-CE facility here at Oregon State
           University; identify any of the code limitations in
           predicting downcomer and well-mixed temperatures at an
           integral test facility; --
                       CHAIRMAN WALLIS:  You said STAR-CD, did
           you, or REMIX?
                       MR. YOUNG:  Did I?
                       MR. REYES:  Yeah, REMIX.
                       MR. YOUNG:  REMIX.  Sorry.  I worked on
           both things.  I might put the two together sometimes.
                       ...benchmark REMIX against the APEX-CE
           facility; and assess the applicability of the code for
           integral system geometries.
                       The REMIX Computer Code is used for
           calculating well-mixed core inlet temperatures along
           with downcomer temperatures in any specified locations
           below the cold-leg injection into the downcomer.
                       It's based on the regional mixing model
           originally designed by Dr. Theophanus and is described
           in the following figure.
                       CHAIRMAN WALLIS:  Dr. who?
                       MR. ROSENTHAL:  Theophanus.
                       CHAIRMAN WALLIS:  Theophanus?
                       MR. YOUNG:  And it's described in the
           following figure.  This is out of the REMIX Manual.
                       It assumes that the cold stream originates
           at the high-pressure safety injection site, forming a
           cold stream along the bottom of the cold leg, which
           then flows towards the downcomer and the loop seal
           portions of the primary system.
                       At these two jump locations it generates
           a buoyant plume, which decay into the loop seal and
           into the downcomer.  Most of the mixing -- or the
           mixing is most intense at certain mixing regions, and
           these are the regions that REMIX calculates mix and
           entrainment, which it uses to then determine the cold
           stream temperature that enters into the downcomer, and
           it also does a global system calculation for the
           well-mixed temperature inlet to the core.
                       CHAIRMAN WALLIS:  Is there some kind of
           coefficients which describe the mixing --
                       MR. YOUNG:  Yes.  Yes, sir.  This is --
                       CHAIRMAN WALLIS:  -- which are different
           in the different regions and determined in some
           empirical way?
                       MR. YOUNG:  I'm sorry?
                       CHAIRMAN WALLIS:  Are they determined
           empirically, these mixing coefficients?
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  So the data are made to
           fit these experiments, or...?
                       MR. YOUNG:  It was pitted against --
                       CHAIRMAN WALLIS:  Some similar...?
                       MR. YOUNG:  It was originally validated
           against the Creare one-fifth, I think, scale test, and
           it was again modified using some mixing experiments at
           Perdue University, I believe.
                       MR. SCHROCK:  Could you go back and
           explain this pump?  What is this description of the
           pump all about?  I don't understand it.
                       MR. YOUNG:  Okay.  In REMIX you're able to
           specify a certain pump volume in the pump heat
           transfer area to take into account any contribution
           that the pump material or structure would have in
           contributing to the temperature of the system, of the
           coolant inside the system.
                       It's an option allowed in REMIX.
                       MR. SCHROCK:  I don't understand what this
           diagram is intending to convey with a stratification
           situation.  It looks like it's spilling over in a
           reverse flow and then an arrow showing something else
           moving forward.
                       MR. YOUNG:  Okay.  In the calculation of
           the amount of mixing entrainment from the cold stream,
           there needs to be a countercurrent hot stream flow
           from the downcomer and the loop seal portion.
                       The countercurrent flow from the loop seal
           portion is generated from the inventory that's in the
           loop seal during the injection and is then mixed with
           a cold stream.
                       The cold stream was injected from the
           high-pressure safety injection location and flows
           towards both ends of the cold leg.
                       The hot stream that finds the mix and
           entrainment region flows from the upper downcomer --
           the upper plenum in the downcomer into the top of the
           cold leg.  And that finds the mix and entrainment at
           the falling plume location, which is the high-pressure
           safety injection location.
                       CHAIRMAN WALLIS:  So these MR 1, 3, and 4
           are the areas which have some kind of a coefficient to
           describe mixing, which is different for each region?
                       MR. YOUNG:  Yes, sir.  These are regions
           that are assumed to be determinant in how much mixing
           occurs between the cold stream and hot stream.  Any
           mixing at other locations of the system are
                       It's assumed that there is a stationary
           interface between the cold and hot streams on -- in
           any locations, other than these mixing regions.
                       MR. SCHROCK:  MR5 is insignificant or
                       MR. YOUNG:  MR5 is calculated in REMIX,
           and the only insignificant mixing region is MR2.  It
           isn't shown in this map, but it's between the high-
           pressure safety injection and the vessel in that
           length of cold leg.
                       Okay.  Some of the limitations of the --
                       MR. SCHROCK:  The code chops this up into
           elements and calculates something?  It's kind of a
           sketchy description of what the code is.
                       CHAIRMAN WALLIS:  I presume it has nodes
           and --
                       MR. BESSETTE:  Volumes.
                       CHAIRMAN WALLIS:  -- cold volumes.
                       MR. YOUNG:  Yeah.  In the -- in order for
           REMIX to calculate the temperature transients at the
           downcomer locations and the well-mixed temperature
           transient at the core inlet, it is required that you
           specify certain volume, the total volume,
           participating volume, of the system; the total mixing
           volume of the system, which is considered to be in
           well-mixed conditions.
                       Any material structures that are masses
           indirectly specified by their wall thickness and their
           material properties, which is the conductivity and the
           diffusivity of the material structures, which allows
           any conduction calculation to be calculated along with
           the transient temperature of that material.
                       MR. SCHROCK:  Okay.  I'm exhausted.
                       MR. YOUNG:  Is that sufficient?
                       CHAIRMAN WALLIS:  I presume there's a
           document somewhere that describes REMIX.
                       MR. YOUNG:  Yes, there is, sir.  I have
           two REMIX Manuals, if you'd like to look at them.
                       MR. BOEHNERT:  We can get that for you as
           soon as you get back to the office.
                       CHAIRMAN WALLIS:  Yet another code to
                       MR. SCHROCK:  I'm not sure I'd like to
           review it, but I'd like to be reminded of something
           that I did look at more than 10 years ago.  I'm not
           getting very much from this.
                       MR. BOEHNERT:  I'll get you a copy.
                       MR. BESSETTE:  You might say that each of
           those mixing regions that are labeled, you might say,
           are distinct calculations that REMIX does.
                       MR. YOUNG:  It predicts -- a plume is
           assumed to be developed within two diameters down from
           the cold-leg injection.  This temperature is
           calculated and many other specified locations in the
           downcomer which are desired are then calculated from
           this location.
                       And then a lumped parameter calculation is
           made to determine the well-mixed core inlet
           temperature, which is simply an exponential decay to
           a stable temperature.
                       Some of the limitations of the code in the
           version that we're using.  The version that we used
           for the comparison is the code -- is the 1986 version. 
           And some of the limitations in this code is that it
           was not designed to predict the effects of multiple
           plume interactions.
                       It's not designed to predict temperatures
           or calculate temperatures in the presence of cold-leg
           flow.  The only output that's available from this
           REMIX is the cold centerline temperatures and the core
           inlet well-mixed temperature.
                       You can't specify locations that are any
           different as a myth of location, so -- in between two
           of the cold-leg injections; it's only along the
                       And it doesn't predict plume velocities or
           any other flow characteristics.  It uses a fixed-heat
           transfer coefficient, which we'll see later to be
           negligible or really not that important in the
                       And it does a 1-D conduction heat-transfer
           analysis in the metal structures.
                       The three tests that we compared with
           REMIX were tests OSU-CE-004, 5, and 6.  The
           superficial Froude number for these tests range
           anywhere from .019 to .0402.
                       The temperature difference between the
           high-pressure safety injection and the primary
           inventory gave delta rho over rho values of .18.
                       Between the three tests, the first test,
           004, only had one injection location, where Tests 5
           and 6 used all four high-pressure safety injection
                       CHAIRMAN WALLIS:  Qhpsi is per injection?
                       MR. YOUNG:  I'm sorry, sir?
                       CHAIRMAN WALLIS:  Qhpsi is the flow rate

           per site, so we have --
                       MR. YOUNG:  It's per site.
                       CHAIRMAN WALLIS:  Okay.
                       MR. YOUNG:  And in the case of four
           high-pressure safety nozzles being operated it's an
           average flow rate between the four, because there is
           some variance between them.
                       The input data to describe the APEX-CE
           facility model in REMIX was created by specifying the
           volumes for the -- in the one high-pressure safety
           injection case the entire downcomer and lower plenum
           was considered as a portion of the total volume.
                       In the four high-pressure safety injection
           case, the lower plenum and downcomer region was
           partitioned into four equal volumes.
                       The material properties for the
           structures, which I mentioned before were the
           conductivity and diffusivity, were specified:  The
           HPSI flow rates and relative flow temperatures or
           fluid temperatures; initial system temperature; heat
           transfer areas in each of the regions along with their
           respectful heat transfer coefficients.
                       CHAIRMAN WALLIS:  You input those; they're
           not calculated in some way?  You just put some number
                       MR. YOUNG:  These are variables that you
           have to put in to describe the facility to REMIX.  So
           you have to specify a certain amount of volume that
           you consider to participate in this calculation.  And
           a well-mixed volume, which I mentioned, is considered
           to be well mixed during --
                       CHAIRMAN WALLIS:  Well, how do you figure
           heat-transfer coefficient?
                       MR. YOUNG:  The heat-transfer coefficients
           that I calculated were calculated using analytic plume
           velocity in the downcomer region.  And in the cold leg
           I used the flow rate over the area of the cold stream
           for that velocity.
                       CHAIRMAN WALLIS:  These are just at the
           wall; they're not between streams, aren't they?  Just
           at the wall?
                       MR. YOUNG:  This is not between the
                       MR. SCHROCK:  I thought David told us
           that's essentially infinite heat-transfer coefficient.
                       MR. YOUNG:  That is -- we did a heat-
           transfer coefficient sensitivity, which I'll show you
           towards the end of this presentation, and it's fairly
           insensitive to any changes in heat transfer.
                       In calculating -- or in properly
           describing the REMIX facility or the APEX-CE facility
           with REMIX, we considered the core region to be
           participating in the heating of the downcomer fluid.
                       As you can see in the figure in front of
           you that there is a ceramic annulus, which is of
           nonuniform thickness, around the core.  It's directly
           in contact with the core barrel and supplies energy to
           the core barrel for heat transfer to the downcomer.
                       In order to maintain a correct description
           of the heat conductance in our -- during our test, we
           used an equivalent material which would include the
           downcomer stainless steel and the ceramic of the
                       We considered these to be homogeneously
           mixed.  And we calculated an effective thermal
           conductivity for this material to specify in REMIX. 
           And then we increased the core barrel thickness to
           include the thickness of both of the materials.
                       This is to account for any energy stored
           in the reflector that is available for heat transfer
           to the downcomer fluid.
                       Now I'd like to show you some of the
           comparisons between these four -- three tests.
                       CHAIRMAN WALLIS:  So even in the transient
           you can use just conduction here to the core barrel
                       MR. YOUNG:  Yes, sir.  We gave -- we
           specified an effective diffusivity so that REMIX would
           be able to calculate the temperature transient of the
           material and from that the heat transfer to the
           downcomer fluid.
                       And the heat-transfer coefficient was
           again the calculated heat-transfer coefficients used
           in the plume velocities.
                       In the first graph, this is the core inlet
           well-mixed temperature for Test 4.  This is with one
           HPSI being operated.
                       As you can see, REMIX underpredicts the
           temperatures at all the locations within 40 degrees of
           the actual well-mixed core inlet temperature.
                       CHAIRMAN WALLIS:  Well, the well-mixed
           temperature is simply mixing the fluid and having some
           heat transfer from the wall to change it?
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  And so the only variable
           really is the heat transfer from the wall.  The mixing
           is this first law conservation of energy.
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  So what, so the
           difference is presumably in getting the heat-transfer
           coefficient right.
                       MR. YOUNG:  It is in correctly modeling
           the amount of heat transfer that the --
                       CHAIRMAN WALLIS:  Right.
                       MR. YOUNG:  -- core region contributes to
           the downcomer.
                       In REMIX calculations and in the Manual
           it's recommended that a core barrel thickness be
           specified.  This is specified in any previous
           literature with validation.  Only the thickness of the
           core barrel itself was described.
                       It's seen in some of these plots that a
           portion of the core region and energy stored in the
           material and possibly even some of the primary
           inventory in the core region is contributing to heat
           transfer through the downcomer region.
                       This next plot is a temperature comparison
           between 1.3 cold-leg diameters below the cold leg
           injection into the downcomer for the case of one
           high-pressure safety injection being operated.
                       Again, REMIX initially underpredicts the
           temperature of the plume at the location and
           throughout the entire test.  It's within 60 degrees of
           the actual calculations.
                       CHAIRMAN WALLIS:  But REMIX is predicting
           far bigger temperature differences than you actually
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  So it seems to be way
           off, rather.
                       MR. YOUNG:  Well, it's much more accurate
           in predicting a four high-pressure safety injection
           case than it is a single high-pressure safety
           injection case.
                       I think this is due to -- maybe I'm not
           completely understanding the mixing volumes that are
           participating in the one case.
                       This is for four cold-leg diameters below
           the cold-leg injection into the downcomer.  And again
           REMIX underpredicts the temperatures within 40
                       The same calculations were carried out
           previous to increasing the core barrel thickness to
           include the mass.
                       CHAIRMAN WALLIS:  Excuse me.
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  I think that Professor
           Reyes showed us that this 4-D temperature is very
           close to the mixed temperature.
                       MR. YOUNG:  In the facility?
                       CHAIRMAN WALLIS:  Yeah, right.  So that,
           in fact, REMIX is getting the mixed temperature wrong. 
           It's really giving it a tremendous difference.  It
           very well matters really.  So the difference between
           the 4-D temperature and the mixed temperature, is what
           you're worried about, which we know to be very small. 
           So REMIX --
                       MR. YOUNG:  After approximate- -- yes,
                       CHAIRMAN WALLIS:  -- on that basis is way
           off, isn't it?
                       MR. YOUNG:  Yes, sir.
                       MR. BESSETTE:  And you'll notice the
           offset seems to occur from time, from your initial
                       MR. YOUNG:  We noticed in the stagnation
           cases that after approximately 500 seconds into the
           test the plume had seemed to have been completely
                       So at that point REMIX doesn't calculate
           any other flow configurations which would enable it to
           determine whether or not the plume existed.
                       The next --
                       MR. ROSENTHAL:  Yeah, if you'd just flip
           back one slide.  So this is the centerline, roughly? 
           This is along the centerline?
                       CHAIRMAN WALLIS:  It probably gets too
           cold, the plume just coming out of the pipe.
                       MR. BESSETTE:  That's right.  I think
           that's what the problem is.  If you -- I -- you know,
           what REMIX does for this, if you go back to Viewgraph
           Number 4, what REMIX does for mixing Region 3 is
           arbitrary.  And I think it's getting that --
                       CHAIRMAN WALLIS:  It doesn't mix enough.
                       MR. BESSETTE:  Yeah.
                       MR. ROSENTHAL:  Okay.  But, you know, last
           week and the week before we're running RELAP and REMIX
           calculations.  And if you look at 4,000 seconds you
           see about a 50F difference on that graph.  And so
           that's now something that we would start to see in the
           fracture mechanics stuff.
                       So the offset is important to us.  And we
           had, you know, RELAP Code and REMIX Code.  And we're
           scratching our heads whether we should believe any of
                       So now we've got some REMIX versus some
           experimental data, which will allow us to come to some
           conclusions about what we should do with the REMIX.
                       CHAIRMAN WALLIS:  So your strategy might
           be --
                       MR. ROSENTHAL:  So I'm just pointing out
           that, you know, where this fits in the grander scheme.
                       CHAIRMAN WALLIS:  So your strategy might
           be to try to fix up REMIX to represent these
                       MR. ROSENTHAL:  Or shuck it and go to
           CFD's stuff --
                       CHAIRMAN WALLIS:  Or go to something else,
                       MR. ROSENTHAL:  -- that you couldn't have
           done in the mid-'80s.
                       CHAIRMAN WALLIS:  All right.
                       MR. YOUNG:  If you're able to --
                       CHAIRMAN WALLIS:  If no one else wants to
           speak, is it your objective to just run REMIX and see
           how it does, or is it to fix up REMIX to be more
                       MR. YOUNG:  Well, it was originally to use
           the recommended REMIX or the -- what REMIX recommended
           for the volumes and structural materials to see how
           accurately it could determine integral test facility
           with either a heated core region --
                       CHAIRMAN WALLIS:  So then an assessment of
           REMIX, yeah.
                       MR. YOUNG:  -- or mix.
                       An assessment.  And in doing this,
           describe any limitations and fix these limitations
           that REMIX might have.  And this was -- in my first
           attempt -- was to increase the core-barrel thickness
           to include any of the mass.
                       CHAIRMAN WALLIS:  Right, right.  So you
           are fixing it up, as well?
                       MR. YOUNG:  I'm trying to -- I'm trying to
           find if REMIX is applicable to an integral test
           facility, since there are only basically two different
           conditions that can change the fluid temperatures. 
           And that's the mixing and the thermal conduction from
           the wall.
                       CHAIRMAN WALLIS:  Right.
                       MR. REYES:  Now there appears to be
           limitations to what we're seeing in the experiment
           compared to what REMIX can predict.
                       You know plume interactions and things
           like that REMIX cannot do, so Eric's been working, of
           course, with STAR-CD.  And you'll hear another talk on
           that, trying to see if we can come up with some better
           -- better tools to predict the behavior, because we
           think there are some limitations to what the code was
           designed to do.
                       It was really for a stagnant condition, a
           single plume.  And he'll show you some more plots
           looking at one plume versus four plumes.  But we see
           big differences in the behaviors -- in the calculation
           versus the behavior.
                       MR. YOUNG:  As we've seen in a lot of the
           CFD calculations or we will see later on today, the
           ability for REMIX to predict the location of the
           coldest transient is almost impossible with REMIX,
           because it predicts only centerline temperatures.
                       We're finding our coldest downcomer or our
           coldest vessel-wall temperatures to be located between
           two interactive plumes after they have merged.  So
           it's not really applicable to the case where there's
           more than one injection.
                       CHAIRMAN WALLIS:  Now you're going to show
           us all the graphs.  They all look very similar.
                       MR. YOUNG:  I'll just show you a couple
           more, and I'll go on to the --
                       CHAIRMAN WALLIS:  Right.  Then go on to --
                       MR. YOUNG:  -- transfer system.
                       CHAIRMAN WALLIS:  -- improvements, such as
           bringing in the core barrel, or whatever.
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  Thank you.
                       MR. YOUNG:  I'll just flip through these
           quickly then to show you that REMIX does underpredict
           because it is, indeed, calculating that there is a
           plume there.  That's inherent in the code.
                       Pick one of the well-mixed temperatures
           here.  Here's a case where four injection -- HPSI
           injections were being operated.  You can see that it
           predicts the well-mixed temperature or the coolant
           temperature much more accurately.
                       CHAIRMAN WALLIS:  If it starts right it
           seems to do better.
                       MR. YOUNG:  Yes.
                       CHAIRMAN WALLIS:  It has to start right at
           the top.
                       MR. YOUNG:  Yes.
                       Yet it still underpredicts the downcomer
           locations.  These are more accurate.  They're still
           under by 25 to 30 degrees.
                       One of the things that we found very
           important in these REMIX calculations was the effects
           of the core barrel or the core region or any materials
           in the core region that had stored energy that could
           be supplied to the downcomer.
                       We did a heat-transfer coefficient
           sensitivity study along with downcomer thickness,
           wall-thickness sensitivity.
                       In this first slide we varied the heat-
           transfer coefficient from 100 watts from u squared
           degree Kelvin up to 6,000 watts from u squared degrees
                       You notice that the difference in
           temperatures calculated for the core inlet temperature
           are very negligible.  They're only within a couple
           degrees, maybe 5, 10 degrees.
                       This, indeed, is the case because, as
           David Bessette had mentioned, that we are
           conduction-limited and there are the skin effects of
           the heat transfer, removing the energy from the skin
           of the materials.
                       Yet when we vary the thickness of the core
           barrel to include the mass of the reflector, we see
           that we calculate temperature differences up to 35 to
           40 degrees Fahrenheit.  So the material or the energy
           stored in the core region is, indeed, important in
           these calculations.
                       MR. KRESS:  So did you vary the mixing
           rate in the downcomer?
                       MR. YOUNG:  That's not available in the
           code that I'm aware of, sir.  I think it's hard-coded
           in it.  They have I think a linear segregation of the
           plume from the injection location down to two
                       MR. KRESS:  That would -- that would
           certainly be a way to bring the codes -- the cores
                       MR. YOUNG:  If we were able --
                       MR. KRESS:  Yeah.
                       MR. YOUNG:  -- to understand a little bit
           more of how the mixing occurred and to introduce that
           into the code.
                       CHAIRMAN WALLIS:  Now there's Mixing
           Regions 1 and 3 you need to do right.  You have the
           starting condition right.
                       MR. KRESS:  Well, he also gets -- needs to
           do it in the plume, because --
                       CHAIRMAN WALLIS:  Yeah.
                       MR. KRESS:  -- because that's why it cools
           -- cools off faster than --
                       CHAIRMAN WALLIS:  But by now he's probably
           got four tuning coefficients.  He should be able to do
           very well.
                       MR. KRESS:  Yeah.  You ought to be able to
           match it exactly.
                       MR. KRESS:  He's only got one for the
                       MR. YOUNG:  So, in summary, the REMIX
           model was developed and applied for three of the
           stagnant loop conditions.  In the comparisons for the
           one high-pressure safety injection operation, REMIX
           underpredicted both the core inlet and the downcomer
                       For the cases of tests 5 and 6 where four
           high-pressure safety injections were operated, the
           predicted -- or calculated temperatures were much more
           accurate, yet REMIX still underpredicted all of them.
                       One of the reasonings behind the
           underprediction of the 1.3 location is again that we
           believe the cold stream entering into the downcomer
           jumps over this location, so the temperature or
           thermocouple in the APEX facility isn't reading the
           cold stream temperature.  It's rather reading the wall
           -- near-the-wall temperature.  And --
                       CHAIRMAN WALLIS:  So you're saying in
           reality the plume jumps and REMIX doesn't consider
                       MR. YOUNG:  No, it doesn't, sir.
                       And REMIX generally underpredicted all the
           fluid downcomer temperatures.  One of the reasons may
           be that these locations -- the temperatures of the
           centerline of the plume isn't located below the
           downcomer injection but rather between two of the cold
                       That about wraps up what --
                       CHAIRMAN WALLIS:  So the question is what
           happens now.  Are you going to keep working with
                       MR. YOUNG:  No, sir.  I don't believe --
           I don't --
                       CHAIRMAN WALLIS:  You --
                       MR. YOUNG:  I don't believe that REMIX is
           going to be able to consider all the physics involved
           in determining the downcomer temperature transients.
                       CHAIRMAN WALLIS:  So your conclusion is
           that we should replace REMIX with something better?
                       MR. YOUNG:  Yes, sir.
                       CHAIRMAN WALLIS:  Okay.
                       MR. SHACK:  Well, I mean if the -- if the
           temperature differences are always as small as they
           seem to be as in these experiments, I mean RELAP does
           just as well, doesn't it?
                       MR. ROSENTHAL:  I think the point is that
           RELAP doesn't model the mixing.  See, you wanted to
           explore this aspect.  And we back on the East Coast
           tried REMIX also and we got offsets very, very similar
           to their showing, and they were enough to be important
           in the wrong direction.
                       We would have to have incorporated it into
           the uncertainty analysis that we passed on to the
           fracture mechanics.
                       And you do it -- you know, we did it
           because it's cheap and fast, and whatnot.  But I think
           we'll have to make a decision with what we do REMIX
                       And the point was that you couldn't -- I
           mean Theo put it together to solve a problem in the
           mid-'80s.  He just -- you didn't have the options you
           have today.
                       MR. YOUNG:  We'll see in comparison to the
           CFD Codes that the calculated temperatures are not in
           the same accuracy of the CFD Codes.
                       Thank you.
                       CHAIRMAN WALLIS:  Well, we have one more
                       Anyone have anything more to say?  NRC
           want to say anything more?
                       MR. BESSETTE:  Well, I guess, you know, --
                       CHAIRMAN WALLIS:  One minute.
                       MR. SHACK:  Forty seconds.
                       MR. BESSETTE:  You know, of course we
           wanted to run REMIX because this was a code we
           developed for PTS -- for the purpose of PTS analysis.
                       So, if nothing else, somebody along the
           line would have said, well, why don't you run REMIX. 
           So we wanted to run REMIX against actual data and just
           to see how it does.
                       But like we said, you know, when we
           developed REMIX in 1985 we couldn't do CFD analysis,
           but now we can.
                       MR. KRESS:  And was -- REMIX was fitted to
           real data back in '85.  What this is telling me is
           this data gives different results than the '85 data,
           presuming the REMIX --
                       MR. SHACK:  The Creare one-fifth test,
                       MR. BESSETTE:  Well, yeah.  But, see,
           REMIX was always run against the fluid-mixing
           experiments, which were designed to look kind of like
           REMIX.  They incorporated only that part of the system
           that REMIX models, so the cold leg and downcomer.
                       So that the experiments, the configuration
           of the experiments matched the part of the system that
           REMIX models.  So maybe that helped REMIX to model
           those experiments.
                       And this system is more of a -- you have
           more of an integral system even when we're running
           these sort of separate effects kind of tests where
           we're just looking at the -- trying to focus on the
           HPI injection and the plumes.
                       MR. YOUNG:  And I'd like to mention is --
                       MR. REYES:  Get to a mic here, Eric.
                       MR. YOUNG:  Oh, I'm sorry.  This is Eric
           Young.  I'd like to mention that the facilities that
           REMIX was validated against didn't include any core
           region and were simplified plume geometries, a planar
           plume, and a rectangular duct, and didn't include any
           of the endless geometry or heat from the core region
           that we're seeing here.  So it's not able to do that.
                       CHAIRMAN WALLIS:  So I will declare a
           break and we will remix here at quarter to 11:00.
                       (Recess taken from 10:30 a.m. to 10:45
                       MR. HAUGH:  I'll dim the lights just
           slightly so you can better see the animations and
           everything in the presentation.
                       I'm doing a presentation on STAR-CD and
           the Creare half-scale PTS test facility benchmark
           calculations.  My name is Brandon Haugh.  I was here
                       The objectives of this presentation are to
           introduce the STAR-CD CFD Code and basically just a
           preliminary of what it is; a description of the test
           facility that was compared; a description of the tests
           that I ran and calculated; a description of the model,
           the computational maps that I generated; and a
           comparison of the results from calculation with actual
           data from the test facility.
                       And I will make some conclusions about how
           it compared.
                       CHAIRMAN WALLIS:  Do you remember when the
           Creare tests were run?
                       MR. HAUGH:  These half-scale tests were
           run, I believe, in 1987.
                       CHAIRMAN WALLIS:  '87?
                       MR. HAUGH:  Yeah.
                       Okay.  Well, the objectives here are to
           benchmark STAR-CD; provide insights into the CFD Code
           operation to help with the APEX-CE simulations; and
           also to establish a learning curve for the STAR-CD
                       CFD Codes are tricky to run, and so
           there's a lot of things that you learn along the way.
                       The STAR-CD CFD Code is from a
           computational fluid dynamics code.  The acronym "STAR"
           stands for simulation of turbulent flow in arbitrary
                       The code consists of three major
           components:  A preprocessor/postprocessor called
           Prostar, which is where you build a mesh and it sets
           up the problem.
                       CHAIRMAN WALLIS:  Does it have automatic
           grid generation also to stuff that makes it easy?
                       MR. HAUGH:  It does, yeah.  It makes it
           easier.  It's never easy, the CFE, but there's a
           package called ISM CFD, which will allow you to take
           a 3D like ProE-generated models and insert them and it
           will generate the mesh automatically.
                       For the purpose of this study we're kind
           of -- for the entire learning curve, I was using the
           built-in mesh generating tools and built it by hand.
                       There's the analysis package called STAR
           which is a Fortran Base Code that runs the problem and
           does the calculations.
                       And there's also a parallel computing
           interface called Pro-HPC, which is important in CFD
           because you need a lot of computational horsepower.
                       CHAIRMAN WALLIS:  Is this one that
           converges on the answer; it does all kinds of
                       MR. HAUGH:  Yes, it does a lot of internal
           sweeps --
                       CHAIRMAN WALLIS:  And tells you what the
           residuals are or --
                       MR. HAUGH:  -- for every iteration.  Like
           it does sweeps --
                       CHAIRMAN WALLIS:  Sometimes in these
           problems it doesn't converge.  I mean if the plumes
           are wandering around all over the place, it won't
           converge on any answer at all.
                       MR. HAUGH:  Yeah.  And it will let you
           know if it diverges.  It produces an error file, and
           it will let you determine -- it will help you
           determine what parameters you might have set up
           incorrectly, or if your timed step was off, things of
           that nature, yes.
                       The code has the capability of handling
           many types of fluid flow, dispersed flow, and chemical
           reactions, compressible flow, moving meshes, all kinds
           of things.
                       The Creare half-scale test facility, which
           ran their tests in 1987, was built to not model any
           particular PWR but to be flexible with interchangeable
           cold legs and injections, to be able to do different
                       The configuration used in the MAY-105 and
           -106 tests is displayed here to the right.  On the
           next slide I will give you some characteristic
           dimensions since they didn't show up too well.  But
           you can kind of see it's a planar downcomer, a cold
           leg that's horizontal, top injection with a loop seal
           and a pump simulator.
                       CHAIRMAN WALLIS:  Because it's a downcomer
           with walls on the side, that's what restricts the
           plume, doesn't it?
                       MR. HAUGH:  Exactly.  Yeah.  So it will
           make a difference.  It's different than an integral
           facility or a full-scale plant.
                       Some of the characteristic dimensions from
           the test facility, the cold leg inside diameter was
           14.3 inches.  HPI inside diameter, 4.5 inches. 
           Downcomer width, 63.7 inches.  The gap 5.4.  Thermal
           shield thickness, one and a half inches.  There was a
           thermal shield in place, which also had a height of
           100 -- let's see -- I forgot to put in -- of 95
           inches.  And vessel wall thickness for the core side
           and the vessel side of 2.75 inches, and that was
           carbon steel.
                       Now the MAY-105 test --
                       CHAIRMAN WALLIS:  I think that was scaled
           so that it was big enough so that it was thermally
           thick and it didn't have to be any thicker.
                       MR. HAUGH:  Exactly.  Yeah.  So you still
           had -- you had a conduction-limited period and 8 d
           back -- 8 d back period.
                       The test that was ran for the MAY-105 was
           a stagnant loop, 462 k or 189 c.  That's 372 degrees
                       It had a constant HPI injection flow of
           5.17 ten to the minus third meters cubed per second,
           which is about 1.37 gallons per minute; at 14.2
           degrees C, which is about around 70 degrees F.
                       The test duration was --
                       CHAIRMAN WALLIS:  That's pretty low
                       MR. HAUGH:  Yeah.  It was still pretty low
           velocity.  It was actually kind of comparable to the
           APEX test.  The velocity for the injection ended up
           being about half a meter per second or about 1.6 feet
           per second.  So not terribly high, but actually I
           think it will help compare to the APEX facility.
                       And test duration was a little over 2,000
                       For the STAR-CD model a computational grid
           was generated using the built-in tools in STAR-CD. 
           The resulting grid consisted of a little over 200,000
           fluid cells and 60,000 solid cells representing the
                       I'll show here, this is what the
           computational grid looks like, the red representing
           the fluid cells and then the yellow representing the
           steel.  Sorry you can't see the refinement better. 
           It's kind of hard to get it on a PowerPoint slide, but
           you can see that the downcomer -- actually you
           probably can -- is far more refined than the loop seal
           or the cold leg, because I wanted to try to capture
           the plume behavior very well.
                       You can see the thermal shield in place. 
           And I only inserted steel on the core side and vessel
           side of the downcomer since that was comprised of most
           of the volume.
                       CHAIRMAN WALLIS:  Now your nozzle here,
           now their nozzle was more characteristic of a PWR, it
           wasn't just a pipe stuck in with a sharp corner?
                       MR. HAUGH:  Exactly.  Yeah, it has the
           gradient of a typical nozzle.
                       It's still a sharp edge.  I didn't
           incorporate a smooth edge, so there's some difference
                       MR. SCHROCK:  And you put your boundary
           condition for the injection back up in the pipe there
                       MR. HAUGH:  Yeah.
                       MR. SCHROCK:  Is that what that shows?
                       MR. HAUGH:  Yeah.  Right at the top of the
           pipe here is where the boundary condition for the
           injection of the HPI was.
                       There was also a boundary condition here,
           but the velocity was specified as zero, so it did the
           correct pressure, back-flow stuff.
                       Now the outlet is different.  You'll
           notice the lower plenum isn't the same as the test 
           facilities.  Theirs kind of came out here and was more
           -- it was triangular.
                       Due to the built-in mesh-entering tools in
           STAR-CD, that wasn't really a possible geometry to
           replicate.  So I tried to preserve volumes as best as
           possible.  And along with the curvature right here to
           promote the mixing.
                       MR. SCHROCK:  And this grid is cylindrical
           in the downcomer?
                       MR. HAUGH:  It's -- no, it's planar.
                       MR. SCHROCK:  Planar.
                       MR. HAUGH:  Yeah, which is what the test
           facility was, too.
                       MR. SCHROCK:  Oh, yeah.  That was an
           unwrapped in it, yeah.
                       MR. HAUGH:  Yeah.  And so the outlet is
           actually right here.  You can't see it.  It's actually
           more characteristic.  It's right here.  It consists of
           six cell faces which comprise within three percent the
           same area as the outlet of the standpipe on the Creare
                       CHAIRMAN WALLIS:  It's a constant pressure
           with a hydrostatic term or something there?
                       MR. HAUGH:  Yeah.  It's just -- it's
           treated as an outlet so it won't let it drain.  Just
           kind of -- it's the same pressure as what the fluid is
           in the lo- --
                       CHAIRMAN WALLIS:  And there's no --
           there's no problem with reverse flow.  The problem
           with outlets is if you can reverse flow it everything
           gets confused.
                       MR. HAUGH:  The code will get confused if
           you have that, which I initially had, but I adjusted
           some parameters and no longer see that in my runs. 
           But, yeah, there will be some problems with that.
                       Here's the volume comparison.  I'm pretty
           close in most things except for the pump simulator,
           and that was user error.  This was the first time I
           was running CFD and the first mesh I had ever
           generated.  And so I was concentrating on the cold
           legs and the downcomer and basically the lower plenum
           and loop seal.  And for some reason I lost my mind on
           the pump simulator, and that's a large part of the
           mixing volume there.
                       So you will be able to see the slight
           discrepancies in the comparisons I'll show later, but
                       CHAIRMAN WALLIS:  So you're going to fix
                       MR. HAUGH:  Yeah, I will.  I was in the
           process of it.  But due to the geometry and how the
           grid was, it became more time-consuming, so I couldn't
           get it done in time, but I will have better results
           for you.
                       The STAR-CD model inputs, you get to
           establish some parameters for the model to be able to
           run the problem, such as a turbulence model.
                       I chose to use a high Reynold's number,
           k-epsilon model but, as Dr. Wallis pointed out
           earlier, I didn't have a lot of experience in
           turbulence modeling, so it might not predict the
           correct interface in the stratified cold leg, so there
           might be some errors associated with that.
                       There are several different turbulence
           models that can be applied and any input that you can
           provide would be very valuable.
                       The density was treated just as a function
           of temperature, not pressure.  It's basically a
           constant pressure system so it's isobaric, just
           function of the thermal expansion coefficient.
                       I used a time step of a quarter second. 
           I ran 4,280 iterations for about half of the tests. 
           Basically at that point in the test the facility was
           almost all the way cooled down and so we capture most
           of the important transient I think in this first part. 
           I can run the rest of it, I was just under a time
           crunch --
                       CHAIRMAN WALLIS:  My experience of CFD is
           it's pretty grid dependent.
                       MR. HAUGH:  Yeah.  Yeah, exactly.  Your
           time step is related to your mesh size.  And so this
           produced sufficient convergence for me that I felt the
           accuracy was okay.
                       I also used only an upwards difference
           numerical discreditization scheme.  And so it's just
           a single-step first-order accurate method.
                       CHAIRMAN WALLIS:  You're supposed to try
           sort of good refinement in various areas --
                       MR. HAUGH:  Exactly.
                       CHAIRMAN WALLIS:  -- and also to see if it
           makes any difference.
                       MR. HAUGH:  Yeah.  There's some gradients
           around the thermal shield that probably need to be
           refined, but as the first time in CFD, this is kind of
           my best effort at this point.
                       MR. SHACK:  What were your run times like?
                       MR. BOEHNERT:  The next page.
                       MR. SHACK:  Oh, never mind.
                       MR. HAUGH:  Yeah, I'm getting there.
                       It ran for 7.7 days on -- I ran it in
           parallel, so two processors.  It's a Sun Blade 1000
           work station, 750-megahertz processors, and one gig of
           RAM.  It's a UNIX terminal.
                       The results I'm going to present here are
           some of the cold-leg stratification predictions, some
           downcomer temperatures.  I have some animations
           showing the plume activity on both sides of the
           downcom- -- over both sides of the thermal shield, so
           the core side and the vessel side.  It's pretty
                       And just a couple of snapshots of some of
           the convection circulation patterns around the base of
           the thermal shield.
                       For my cold-leg stratification comparison,
           there is a cold-leg raking in the Creare test facility
           9.1 inches after injection towards the vessel.  The
           rake is centerlined, the spacing being about 1.43
           inches between thermocouples.  And they're labeled 1
           through 10 starting at the bottom.
                       This is the greater representation at that
           same location in STAR-CD, so you can see that my grid
           isn't quite encapsulating every thermocouple location. 
           Sometimes two thermocouples will fall in one cell.
                       And also that I didn't have cells right on
           the centerline, so in my comparisons I used both
           cells.  Since they were pretty close in temperature
           they'll both be on the box.
                       And I'll show you, I compared position 1,
           position 10, and position 4, which is right here,
           which is this set of cells.
                       For position 1, the bottom of the cold
           leg, I seemed to predict that pretty well in STAR-CD. 
           It looks like it may be slightly under the average of
           -- read by the Creare facility, but the mesh was also
           pretty course, so I feel that it did a fairly good job
           representing that.
                       The next location of position 4, which is
           slightly below centerline, I still did pretty well. 
           I even captured the step phenomenon that they captured
           in their data for the mixing --
                       CHAIRMAN WALLIS:  The wiggles are the
           data, aren't they?  The wiggly curve is the data.
                       MR. HAUGH:  Yeah.  The wiggly curve is the
           data, due to the splashing in the interface and stuff. 
           And in my model, probably do the turbulence model, I
           don't see that kind of --
                       CHAIRMAN WALLIS:  Now you didn't fudge
           anything?  I mean you didn't change dials on the
           model, or anything?  This is just straightforward
           using whatever's in the code?
                       MR. HAUGH:  Yeah.  I just specified a
           mixing length --
                       CHAIRMAN WALLIS:  You didn't have to tune
           anything or --
                       MR. HAUGH:  -- and a turbulent energy and
           that was all.
                       There's lots of knobs you can turn, but it
           kind of -- I think the kind of idea was, well, let's
           see just straight out of the box what kind of -- well,
           how good will it do.  And it seems to do okay here,

           but you notice the next plot, this is the top of the
           cold leg, I seemed to not predict this very well.
                       Initially I do, but later I dip down
           pretty good.  It's as much as almost 50 degrees
           Fahrenheit, so it's probably due to the mixing in my
           turbulence model in the cold leg.
                       And possibly the cell on the top of my
           pipe is quite large, and I didn't include steel on my
           cold leg.  So there might be some conduction there
           affecting that.  But I don't think it would bring it
           up quite so much.  So there's a little bit of
           investigation that needs to be done into why I was so
           far off, considering the other two locations seemed to
           be pretty good.  I just kind of still in the process
           of figuring it out.
                       For the downcomer temperatures I created
           an animation of the model to visualize the plume
           activity, which is a nice thing about CFD is it will
           give you some visualization which a lot of other types
           of codes can't.
                       The first animation is via the vessel
           side, which is the side that's important for
           pressurized thermal shock and the second is the core
                       CHAIRMAN WALLIS:  Is there any other
           option in this k-epsilon model you might use?
                       MR. HAUGH:  Well, I can specify different
           turbulent energies and mixing lengths.  And I can also
                       CHAIRMAN WALLIS:  But you can't account
           for stratification, though, can you?
                       MR. HAUGH:  There's different turbulence
           model I might be able to use.
                       CHAIRMAN WALLIS:  Does it have effective
           thermal stratification on the turbulence itself?  I
           don't think --
                       MR. HAUGH:  No, it doesn't incorporate
                       CHAIRMAN WALLIS:  It probably doesn't.
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  That's well known to be
           a problem.
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  All the CFD people will
           tell you it's a problem, --
                       MR. HAUGH:  Yeah, but the --
                       CHAIRMAN WALLIS:  -- but they won't give
           you much of a solution to it.
                       MR. HAUGH:  Yeah.  They're good at that. 
           They say, oh, it can do anything, but maybe it won't
           do that, but they won't tell you why.
                       So -- yeah, so there's probably some work. 
           The company that distributes this in the United States
           has been pretty good at working with us for support
           and stuff.  And they're always interested in other
           things they could add to their code.
                       CHAIRMAN WALLIS:  Do you mind if I show
           this to Creare?
                       MR. HAUGH:  No, I don't mind at all. 
           Yeah, that would be fine.
                       So I'll start the animation here.  I
           recorded data every five seconds.  And so to play the
           whole test it's playing rather quickly.  But you can
           see that the plume activity on that vessel side isn't
           terribly significant in terms of the gradient on the
           side here.  I mean really as the test goes on and it
           cools down, it's maybe 10 to 15 degrees Kelvin in the
                       You can kind of see -- you can also see
           that the loop seal riser and the top of the downcomer
           don't participate in the mixing volume, which is
                       CHAIRMAN WALLIS:  A real illustration of
           sort of thermal waves are clearly different from the
           fluid flow direction.
                       MR. HAUGH:  Yeah, exactly.  It's --
                       CHAIRMAN WALLIS:  And nothing's moving up
           in the downcomer.
                       MR. HAUGH:  Yeah, so it's kind of neat.
                       CHAIRMAN WALLIS:  This is distorted.  Have
           you made the downcomer extra fat in order to show
           what's happening there?
                       MR. HAUGH:  Well, I twisted it.
                       CHAIRMAN WALLIS:  You twisted it?  Ah,
                       MR. HAUGH:  Yeah.  So it's --
                       CHAIRMAN WALLIS:  So we're looking at
           different --
                       MR. HAUGH:  -- a slightly angled so you
           can see the --
                       CHAIRMAN WALLIS:  Okay.
                       MR. HAUGH:  -- the cold leg and the
                       Yeah.  And these lines here represent the
           top and bottom of the thermal shield.
                       What was interesting to see is in the next
           animation that the thermal shield actually plays a big
           role.  It seems that the plume comes out of the cold
           leg and hits basically right in the middle of the top
           of the thermal shield and kind of splits and washes
           back and forth.  But it also has enough momentum that
           it seems to -- you'll see right here -- it impinged
           definitely more on the core side as the plume -- much
           more significant --
                       CHAIRMAN WALLIS:  Oh, yeah, it goes a long
           way down there.  Doesn't it?
                       MR. HAUGH:  Yeah.  But this is on the
           core-barrel side, where in the PTS phenomena we don't
           really care, so --
                       CHAIRMAN WALLIS:  Hey, it looks like some
           sort of a dancer there.
                       MR. HAUGH:  Yeah, but it is.  It's still
           only like 20, 30 degrees Fahrenheit -- I mean Kelvin. 
           But it is.
                       CHAIRMAN WALLIS:  But that -- look at
           that, I mean that looks like a plume that's getting
           narrow at the bottom.
                       MR. HAUGH:  Yeah.  It is.  It's not --
                       CHAIRMAN WALLIS:  Accelerate.
                       MR. HAUGH:  -- what you'd conventionally
           think of the rising.  So it could be the CFD model and
           the turbulence or --
                       MR. WACHS:  So it's a temperature probe --
           that's just the peak temperature in the center is
           getting narrower.
                       MR. HAUGH:  Yeah.
                       MR. WACHS:  It's actually just sporadic --
                       CHAIRMAN WALLIS:  Right.  That's right. 
           We're just looking at temperature.
                       MR. HAUGH:  Yeah.  When you come over this
           afternoon, I have much more information available. 
           Like I can show you velocity distribution of the
           plume.  And it's actually -- it does widen.
                       CHAIRMAN WALLIS:  I think Walt Disney
           could really put that to music.
                       MR. HAUGH:  We could make millions.  Yeah,
           so it's pretty interesting.
                       Now for a comparison in the plots of the
           actual data, this is a map of some of the
           thermocouples in the Creare downcomer.  They did have
           more in this row, but these are just the ones I chose
           for comparison, to not overdo you with too many plots.
                       I'm going to be comparing rows 5 and 9
           just for -- to keep it brief.
                       In this plot I've included both -- there's
           thermocouples on both sides of the thermal shield in
           the center of the downcomer gap in that region.  So
           I've presented both the vessel and the core side.
                       I think -- probably in black and white
           it's not very easy to see on the paper.  It's a little
           easier in color here.  The Creare is the blue and the
           pink.  This is the row 5, column 7.  So this is
           centerline below the cold leg.  And then the STAR-CD
           data is the black and the red.
                       But you can see for the core side that
           STAR-CD seems to do pretty well.  It even predicts
           some of the plume behavior.  And due to the fact that
           I recorded data every five seconds, it's not going to
           get all the plume behavior, so just keep that in mind.
                       But it seems to do a reasonably well job. 
           At the bottom here I'm slightly below, and that could
           be due to my mixing volume being slightly off.  But on
           the vessel side I seem to be underpredicting what
           Creare does.  I get the plume that he did pretty well,
           but as the test goes on, you'll see I'm below what the
           actual data presents.  But I mean it's really not too
           bad.  It's maybe --
                       CHAIRMAN WALLIS:  Which would -- which
           would indicate there's really more mixing than you're
                       MR. HAUGH:  That's kind of what I'm kind
           of leaning towards.  Or it could be the mixing volume,
           and so my cool -- cool-down rate is a little bit
           faster than what it was in the real facility.
                       I'm working on producing these in a
           nondimensional format with the mixing volume or the
           mixing time on the bottom.  And so I'm hoping that
           will clash the data a little tighter, but we'll have
           to wait and see.
                       This is pretty much the bottom of the
           downcomer, or really close, centerline as well.  And
           you'll see that on the core side I'm pretty much right
           on until the end.  And of course that comes back up,
           but I kind of stay down.
                       And on the vessel side I'm pretty much
           below the whole time.
                       The order of magnitude is not too bad. 
           It's maybe 20 degrees Fahrenheit.
                       CHAIRMAN WALLIS:  This is really quite
           good for CFD and the new problem --
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  -- without any kind of
           tuning or --
                       MR. HAUGH:  Yeah, without turning the
           knobs or anything.
                       CHAIRMAN WALLIS:  -- tweaking.
                       MR. HAUGH:  I mean relatively it's pretty
                       I mean in terms of the overall like a
           power plant operation, this is a much simplified
           model, with the planar geometry, stagnant loop, and
           just the injection.  So --
                       CHAIRMAN WALLIS:  And you've still got
           that piece that you modeled wrong, too?
                       MR. HAUGH:  Exactly.  So when I correct
           that I'm hoping the data will be much more agreeable,
           I mean given the fact that it's so good now, hopefully
           it should get better.
                       And here's the well-mixed temperature for
           the inlet of the core, which is -- which would be the
           standpipe temperature in the Creare facility, which is
           just the outlet of my model.
                       CHAIRMAN WALLIS:  This is just a heat
           balance, isn't it?
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  So you think you should
           get that pretty --
                       MR. HAUGH:  Well, if my volumes are off,
                       CHAIRMAN WALLIS:  Yeah.
                       MR. HAUGH:  -- you can see it right there. 
           So I think when I nondimensionalize it and fix my
           models, I think it should be just about right on.  So
           it seems to be meeting that pretty well.
                       Okay.  Now for the velocities on the
           thermal shield, this is just kind of interesting to
           note.  I'll kind of explain it a little more.
                       Now this is the opposite side of the plume
           entry.  So the plum, the cold leg was not in the
           center of their planar section downcomer, it was more
           to one side.  So on the opposite side of that at the
           bottom of the thermal shield, you noticed we have a
           convection pattern so we have upflow.  So there's a
           cell that built inside of the downcomer.
                       Now if you'll look at the other side where
           the plume is we see the downflow, but there's still a
           slight -- a swirl on the core side right here.  But I
           just thought it was interesting to point out.  And the
           velocity magnitudes are given here.  So it has decayed
           and slowed down a little bit because of the density
                       This is also at 60 seconds into that
           transfer --
                       CHAIRMAN WALLIS:  That could be a bit
           awkward because somewhere in that -- that swirl, on
           the edges of it, you've got stagnation points, --
                       MR. HAUGH:  Yeah.  Well, actually I --
                       CHAIRMAN WALLIS:  -- and most-heat
           transfer correlations would --
                       MR. HAUGH:  -- this is more looking this
           way.  And I can show you later that these velocities
           are actually impinging the wall.
                       CHAIRMAN WALLIS:  They are?
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  They can't go through
           it.  So somewhat there you've got a stagnation point
                       MR. HAUGH:  Yeah.
                       CHAIRMAN WALLIS:  -- because you know it
           devised.  And so I think your heat transfer and your
           CFD would probably predict there's no heat transfer
           there or very, very low H.
                       MR. HAUGH:  Yeah, it probably will.  I do
           have heat-flux data that I didn't present here because
           it's very new, but I can show you later if you want to
                       Just to mention it, my heat fluxes that
           the CFD predicted were pretty -- on order of two in
           some locations greater than what the Creare reported. 
           But their measurement was kind of, well, here's the
           thermocouple in the middle of the fluid.  Here's the
           thermocouple at the wall, and they guessed the heat
                       CHAIRMAN WALLIS:  Now this is an
           instantaneous picture.  If you did it 20 seconds later
           it would probably look quite a lot different.
                       MR. HAUGH:  Yeah, it would look completely
           different given the transient case.  I can show you an
           animation back in the lab if you'd like to see what it
           looks like.  It's pretty interesting.
                       Some preliminary conclusions I made is
           STAR-CD is a benchmark against the Creare data for a
           first-case, rudimentary analysis.
                       The well-mixed temperatures were slightly
           underpredicted, but that's most likely due to my
           model's mixing volume being 6.7 percent less than the
           Creare facility.  So I apologize for that.  That's my
                       Predictions of plume temperatures in the
           downcomer compared reasonably well with the data. 
           Considering that I didn't do much adjustments or
           anything, I felt it was reasonably good.
                       CHAIRMAN WALLIS:  How long did it take you
           to get to the point where you actually could --
                       MR. HAUGH:  I started doing this last
           summer, and so about a year.  And I'm getting
           reasonable results.
                       CHAIRMAN WALLIS:  And you ran it last week
           or --
                       MR. HAUGH:  I ran it and finished a month
                       CHAIRMAN WALLIS:  A month ago, okay.
                       MR. HAUGH:  Yeah.  And I've been running
           jobs throughout and just -- just kind of -- initially
           I had my turbulence wrong because I was learning.  And
           so as you learn, you go, oh, well, that wasn't very
           smart, and so you rerun it.  And then it takes some
           time --
                       CHAIRMAN WALLIS:  Did you learn on this or
           did you learn by running a lot of other problems
                       MR. HAUGH:  Well, I kind of learned on
           this just seeing, well, that doesn't look right.  And
           then with information from Adapco and Dan Wachs
           helping with the input, people with more experience
           than myself helped me do a better job at establishing
           the correct parameters for the model.
                       And it's probably a good thing to point
           out the CFD is largely an experience based kind of
           usage of the code.  The more you learn about -- I mean
           because you need to know about a good background in
           turbulence and things like that to be able to apply
           phenomena in models to correct circumstances.  So --
           so I learned how to use STAR-CD using parallel
           processing, which was kind of interesting on its own.
                       Parallel computing is kind of relatively
           complicated.  I'd like to acknowledge the computer
           support staff at the College of Engineering helping
           out with that.  They did a great job.
                       But it was obviously -- the parallel
           computing helped me speed up the problem quite a bit.
                       And the benchmark calculations aided in
           the selection of turbulence models, the selection of
           the fusion links, and turbulent intensities for
           preliminary runs.  You can see that things weren't
           quite as they were supposed to be.
                       And that's the end of my presentation.
                       CHAIRMAN WALLIS:  If you look at various
           weather patterns you can see how stratification kills
           the mixing and you get distinct layers and they go a
           long way.
                       MR. HAUGH:  Yeah.  And something
           interesting that I was thinking might be able to help,
           this was kind of after the fact, is the Oceanography
           Department here does extensive meteorological research
           on vast supercomputers.  And they might be able to
           give better insight into what models they use to
           represent stratification.
                       CHAIRMAN WALLIS:  Yes.  yes.
                       MR. HAUGH:  Yeah.  Well, thank you.
                       CHAIRMAN WALLIS:  Thank you very much.
                       MR. WACHS:  Okay.  I guess I get to finish
           up here.  We're going to talk about the 3-D CFD model
           we used for the APEX-CE facility.  And on this work I
           worked with both Eric Young and Brandon.  And we got
           quite a bit of help from the Adapco folks for the U.S.
           distributors for computational fluid dynamics.
                       I'm a grad from Oregon State.  I'm now at
           Argonne, so I have to do a little shift in gears from
           sodium pool fast reactors back to water reactors.  I
           think I can make the switch.
                       First off, I'll talk a little bit about
           what our goals were with this model.
                       We wanted to explore the potential of CFD
           modeling, to treat some of these individual phenomena
           that we were seeing in the reactor out there that we
           didn't think codes like RELAP and REMIX were going to
           be able to capture.
                       And to do that we chose one particular
           test, we chose the OSU-CE-3 test to try to model and
           see what we could come up with.  After I talk about
           that a little bit I'll talk about our particular model
           and the components we included in the model and things
           we did with that.
                       I will look at a couple of the phenomena
           that we were able to observe in both the model and the
           APEX facility, including stratification of the cold
           legs, comparison of the core inlet temperature, the
           downcomer temperature profiles.  And then we'll try to
           extrapolate to some -- some data that they used in the
           Creare facility with some models they used to look at
           plume velocities and heat-transfer coefficients.  I
           will summarize that.
                       And then after that we'll speak just a
           little bit about some of the lessons we learned on
                       On this particular test the objective was
           to look at cold-leg stratification and the downcomer
           profiles.  And that's why it was a good one for us to
           attack with CFD.  In the particular test the reactor
           coolant pumps were turned off and natural circulation
           was driven entirely by -- by core decay heat.
                       We did a couple of different tests, and
           this is the one Dr. Reyes showed where he had five or
           six different stratification plots.
                       We chose to go with the 200-kilowatt case
           because that gave us the greatest amount of
           stratification experimentally, and we wanted to see if
           we could capture that.
                       Describing the model, it's -- the
           objective of the model is to capture all this thermal
           hydraulic behavior in just the cold legs and the
           downcomer. But in order to do that we had to include
           some of the peripheral pieces of the facility for
           either reasons of convenient boundary conditions or we
           thought that it might be participating in behavior to
           a certain extent.
                       In particular, for inlet conditions we
           needed to include the loop seal and the HPSI.  We
           couldn't inject directly into the cold leg; you
           weren't going to get a real good profile.
                       And we had to assume adiabatic walls
           outside of the model.
                       CHAIRMAN WALLIS:  You had to assume that?
                       MR. WACHS:  Well, you don't have to, but
           you can -- you can specify heat fluxes on the walls. 
           But you're not necessarily going to know those
                       CHAIRMAN WALLIS:  Unless you model them. 
           Didn't we learn from some of the earlier presentations
           that the heat transfer from the wall matters?
                       MR. WACHS:  Oh, yeah.  Oh, yeah, we have
           the wall included and we have the outer vessel wall
           included.  But on the outer vessel wall.
                       CHAIRMAN WALLIS:  Oh, the outer of the
           outer vessel wall altogether.
                       MR. WACHS:  So convecting off to the
           environment.  Right.  So it's insulated, but there's
           still a certain amount of convective loss.
                       CHAIRMAN WALLIS:  Oh, I see.  I thought
           you meant --
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  -- the inside, too.  So,
           no.  No, your -- where it matters you actually modeled
           the heat transfer.
                       MR. WACHS:  Yeah -- well, yes and no,
           because we included the outer wall but not the inner
           wall, and that shows up as a problem later on.  That's
           something that would certainly be added in the future.
                       The boundary conditions we treated in this
           particular test.  I think that's a typo on the initial
           temperature.  I think it was closer to 400 Fahrenheit. 
           But the loop-flow rates, in cold leg 3 we had 14
           gallons per minute in the HPS -- or through the loop,
           and 12 in the other cold leg.  The HPSI lines were
           about a half gallon per minute and a gallon per
                       And these were extracted directly from the
           test facility.  So we ran a test, got our boundary
           condition and applied it to this -- to this model.
                       Now here's a picture of the model.  You
           can see the two cold legs on each side.  We have a
           loop seal attached to each.  The HPSI lines are coming
           in at an angle on the horizontal plane.
                       We have the downcomer.  We have the full
           region of the downcomer.  And in the center we had to
           include pieces of -- well, we had to include the core
           region in order to keep away from numerical problems
           with changing directions and backflow, which Dr.
           Wallis mentioned earlier.
                       And we also have a half of the core vessel
           overlayed on top of that as solid cells.
                       One thing that's important to note,
           though.  Since we were initially just treating the
           internal core region as a stop gap for numerical
           problems, it's adiabatic, those cells are not
           connected.  Okay, so there's no communication
           temperature-wise between those two regions.
                       Now here's a closer look at what we used
           and where we assigned boundary conditions.  Here's the
           cold leg, and we assigned a boundary condition right
           at the edge of the HPSI line directly from our
           facility.  The HPSI line is long enough so we can get
           a pretty full developed flow and get a good idea of
           what the mixing may be like.  And the steam generator
           inlet boundary condition was the loop-flow rate.
                       One thing you might note is that we did
           try to maintain as much of the geometry as we could
           reasonably include, so the injection nozzle does have
           the tapered approach.  There are sharp angles on the
           inside, though.  You start rounding them, the cells
           get to be really difficult to draw and maintain.
                       One thing you might notice that right at
           the HPSI injection, it's really hard to see the mesh
           density in here.  We doubled -- well, actually we
           quadrupled the density of the mesh at HPSI injection. 
           And I think that that was a good first step, but in
           the end I don't think it was enough.  We should have
           done some more.  The injection region was larger than
                       CHAIRMAN WALLIS:  Maybe you need to get a
           smaller mesh just where -- where the jets coming in
           and then --
                       MR. WACHS:  Right.  Right, and that's what
           we tried to accomplish there, but the jet I think ends
           up being a little bit longer.
                       CHAIRMAN WALLIS:  Does this STAR-CD enable
           you to refine the jet in places where you say have big

           velocity gradients, or something?
                       MR. WACHS:  Yeah, you can do adapted
                       CHAIRMAN WALLIS:  Automatically, yeah.
                       MR. WACHS:  And one of the problems -- and
           you had mentioned this problem earlier in that one of
           the things you always want to do with the CFD is you
           want to prove that it's mesh independent and just keep
           increasing the density of the mesh till you see it
           doesn't change.
                       CHAIRMAN WALLIS:  So the answer doesn't
           change, right.
                       MR. WACHS:  But in this case it took 10
           days to run.  And when we --
                       CHAIRMAN WALLIS:  So you'd either run out
           of money or the answer doesn't change.
                       MR. WACHS:  Yeah, that's right.
                       CHAIRMAN WALLIS:  Or time, right.
                       MR. WACHS:  And --
                       MR. ROSENTHAL:  Ten days to run on your
                       MR. WACHS:  No, on -- on a four processor
           Sun.  So it's -- we have substantially machinery we're
           running it on.
                       MR. YOUNG:  A four-parallel processor.
                       MR. WACHS:  Yeah, right.
                       So -- but absolutely, that's something
           that needs to be done.  And I think that we need to
           address our computational ability in order to be able
           to do those things.  Until we can do that it's hard to
           really say we have the right answer.  But we're
           working on pieces of that.  I think that's coming
                       So in this case we wanted to extract some
           of this data from the model after it had been run this
           transient over -- I think we went between 3- and 400
           seconds.  I can't remember, it was like 600 time
                       (Brief discussion held beyond the range of
           the microphone.)
                       MR. WACHS:  Okay.  So we wanted to extract
           some of the data from the model and compare it to what
           we saw with the APEX test facility in the thermocouple
           rakes.  And this next plot -- and these are the -- and
           these are the cells that would coincide with those
           particular temperature thermocouples.
                       All you could see are the red lines are
           our model.  And the black lines are from the APEX
           facility.  You could see that the -- well, we are
           getting thermal stratification.  It doesn't match up
           as well as we'd like, unfortunately.  And I think
           that's driven by the fact that we didn't include
           enough cells in the region to really show a fully
           developed mixing region.  Maybe the size of the cells
           were smaller than the -- or larger than the scale of
           the mixing phenomena, or something.
                       Anyway, that's an area where increasing
           the grid density may be an effect.  In fact, Eric did
           some tests --
                       MR. SHACK:  And you're at k-epsilon again?
                       MR. WACHS:  I'm sorry.  Go ahead.
                       MR. SHACK:  You're at k-epsilon
                       MR. WACHS:  Yeah, we used k-epsilon in
           this case.  You know like we said before, we started
           with a default, the ones that generally worked the
           best, to see what would happen.
                       And it would be nice to do a parametric
           study on several other of the models they have
           available and see how it works.  And I think it's been
           shown time and time again that changing the turbulence
           model changes your results, and you want to find the
           one that works best for your case.
                       CHAIRMAN WALLIS:  There seem to be more of
           these calculations or six of them, then there are five
           of the APEX data.  So is something missing in the APEX
           data there?
                       MR. WACHS:  I think some of the upper ones
           may be overlaying on top of each other.
                       CHAIRMAN WALLIS:  That close?  They do
           have wiggles.  It would be unusual for the wiggles to
           overlay.  It looks as if there are five APEX groups
           here and six -- is there one reason the -- it looks as
           if there's an APEX missing in the middle or there's an
           extra CD where there isn't an APEX measurement or
                       MR. WACHS:  I had to change -- I changed
           the colors on them.  I may have grabbed the one and
           changed it incorrectly to a wrong color and just had
           it disappear.  I can -- I can replot that for you this
           afternoon if you'd like.
                       MR. YOUNG:  One thing is -- this is Eric
           Young.  One of the things we'd like to mention is we
           did do a refinement on the cold leg with the loop seal
           geometry and everything and reran it for a stagnant-
           loop condition and achieved very accurate results in
           this cold-leg stratification or the temperature
           grading across the cold leg for the same geometry.
                       MR. WACHS:  Right.  And by just looking at
           the cold leg we were able to get the cell small enough
           that you could run the test relatively quickly, in the
           course of a day easily.
                       MR. YOUNG:  Two days to make that right.
                       MR. WACHS:  Two days?  Yeah.  So that
           lends to that effect, but I -- yeah.
                       CHAIRMAN WALLIS:  So it stratifies more in
           reality than you predict?
                       MR. WACHS:  Yeah.  We saw a greater degree
           of stratification.  I think the model showed more
           mixing than there really was.
                       CHAIRMAN WALLIS:  And that's what you'd
                       MR. WACHS:  Yeah, right.
                       I go onto the next one.  Looking at the
           core inlet temperatures, the APEX facility shows
           warmer inlet temperatures than we saw in the STAR-CD
           model.  And one of the reasons that we're postulating
           for that is that we didn't include communication with
           the downcomer or the core barrel, okay.
                       And had we included thermal communication
           between those two -- two pieces, we would expect the
           temperature for the STAR-CD model to shift up.  And
           whether it would reach and match, we don't know, but
           I think it was partially to move it in the right
                       CHAIRMAN WALLIS:  You should get this
           fairly well.  This is an energy balancing --
                       MR. WACHS:  Yeah, I think so too.  I think
           so too -- well, --
                       CHAIRMAN WALLIS:  It's not so sensitive --
                       MR. WACHS:  Yeah, at that point --
                       CHAIRMAN WALLIS:  -- to the plumes and all
           that stuff.
                       MR. WACHS:  -- it's all well mixed, that's
                       CHAIRMAN WALLIS:  It's all mixed up, isn't
           it, by now?
                       MR. WACHS:  Yeah.  I would think that
           that's a fair estimate.
                       MR. YOUNG:  One thing that needs to be
           mentioned about the core inlet temperature is that the
           location that you choose to actually compare this, the
           -- you can just choose one node or cell at the core
           region.  Now if you went and chose a cell at a
           different location and with the plume interaction and
           hitting it, you're going to get different
                       CHAIRMAN WALLIS:  Well, the plume doesn't
           go that far.
                       MR. WACHS:  So there's still some mixing
           behavior going on in the lower plenum.
                       MR. YOUNG:  Yeah.  So there is some mixing
           behavior going on in the lower plenum.  So the choice
           of the cell location with the temperature --
                       CHAIRMAN WALLIS:  I thought it was well
           mixed long before that.
                       MR. YOUNG:  There's -- it's well mixed,
           yes, sir.  It is well mixed.  But have certain stunts
           of plume and interaction where it will fold down into
           the region.  And large recirculation zones will occur
           and you will get kind of a stunt of water go down.
                       The temperatures between those stunts
           aren't that much, but it will change the accuracy
                       MR. WACHS:  Yeah.  If you look at the
           temperature distribution it's only 10-degrees
           difference.  It doesn't change a whole lot.  So if you
           get just a mild recirculation where maybe this half of
           the downcomer is cool and it's falling in, it's still
           going to be displacing some hot fluid that's sitting
           in there, so it's a dynamic behavior.
                       CHAIRMAN WALLIS:  Well, then you'd expect
           more wiggles perhaps in the data, wouldn't you?
                       MR. WACHS:  Yeah.  Well, the facility, I
           don't think it's got some of these -- I think we're
           overpredicting some of the convective behavior --
                       CHAIRMAN WALLIS:  Something is wrong about
           the heat input or something here, because you're off
           by a large amount in the temperature change at the
           end, by almost a factor of 2.  So it looks as if some
           source of heat or something's missing in the model.
                       MR. WACHS:  Oh, yeah, absolutely.  That's
           -- I agree.  That's where the --
                       CHAIRMAN WALLIS:  That's what you said at
           the beginning, I think.
                       MR. WACHS:  The core barrel effect is I
           think important then.
                       CHAIRMAN WALLIS:  You could estimate that,
           couldn't you?
                       MR. WACHS:  What's that?
                       CHAIRMAN WALLIS:  Can't you estimate that? 
           Do some --
                       MR. WACHS:  Off the top of my head, no.
                       CHAIRMAN WALLIS:  Some quick -- yeah, back
           of the envelope, transient heat transfer.
                       MR. WACHS:  I don't know what the total
           mass is of that, so --
                       CHAIRMAN WALLIS:  But you can find that
           out if you --
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  Someone will tell you
           its shape and size, and you can just do a calculation.
                       MR. WACHS:  Oh, yeah, sure.  If you know
           what the injection flow rates in the initial -- yeah,
           I agree.
                       Looking at the downcomer temperatures, if
           you look at 1.3 cold-leg diameters below and we tried
           to compare the flows, the STAR-CD calculation is -- is
           a bit lower than what we're --
                       CHAIRMAN WALLIS:  It seems to suddenly go
           wrong at one point and never recover.
                       MR. WACHS:  This one does?
                       CHAIRMAN WALLIS:  Yeah.  It seems to go
           wrong at about 80 seconds and then it never comes back
           to --
                       MR. WACHS:  To lift back up to that --
                       CHAIRMAN WALLIS:  Something happened at 80
           seconds to get it wrong.
                       MR. WACHS:  Well, that's where injection
           begins, where you start to see the cold fluid falling
                       CHAIRMAN WALLIS:  Oh, okay.
                       MR. WACHS:  And I think that this is
           clearly the worst agreement between the downcomer
           ones, this one right below.  And I think we see some
           dipping behavior in the --
                       CHAIRMAN WALLIS:  Well, isn't this the
           business of it hitting -- going across and hitting the
           inner wall?
                       MR. WACHS:  The thermocouple, yeah.  So
           that's kind of the problem with these -- with
           comparing these analyses.  You'd have to grab a single
           point out of the facility and hope that your phenomena
           you're looking for crosses it.  And it may or may not. 
           Because realistically we can't expect with this kind
           of behavior STAR-CD to exactly match what -- what's
           happening at the facility because it's somewhat
           unstable behavior.
                       CHAIRMAN WALLIS:  So you don't have many
           nodes across the downcomer, do you?
                       MR. WACHS:  Radially or axially?
                       CHAIRMAN WALLIS:  Radially?
                       MR. WACHS:  Or azimuthally?  Not very
                       CHAIRMAN WALLIS:  No.  So --
                       MR. WACHS:  But you saw with Kent Abel's
           work, when he had the plot in Excel with the single
           data points, those were our points.  And you could see
           the plume moving from place to place.
                       MR. YOUNG:  Dr. Wallis, the number of
           nodal locations crossed down by the gap is 8.
                       MR. WACHS:  Oh, okay.
                       CHAIRMAN WALLIS:  Oh, so you should be
           able to pick up the difference between the inside and
           the outside?
                       MR. WACHS:  Oh, yeah.  Oh, yeah. 
           Definitely.  And I have -- I'll talk about that a
           little later.
                       CHAIRMAN WALLIS:  You're actually -- this
           is STAR-CD predicted at the location on the outside --
                       MR. WACHS:  Yes.
                       CHAIRMAN WALLIS:  -- where the
           thermocouple is.  Oh, so that's not the explanation
                       MR. WACHS:  On the next slide you're
           looking at two diameters below.  It seems to do a
           little bit better.  Kind of crosses through the middle
           of all the wiggles.
                       And at three diameters it's still pretty
                       MR. SCHROCK:  Your calculation seems to
           smear out some oscillations in the actual --
                       MR. WACHS:  Yeah.  I -- that's definitely
           true.  I don't think that it's -- well, again we're
           looking at the effect of turbulence and some of these
           eddies and whether the code will be able to capture
           that, I don't know whether it will or not.  Apparently
           it looks like it doesn't catch it as well as reality,
           but we still get -- the mean behavior is similar.
                       So at four diameters it looks pretty
           similar also.  We're in the right ballpark at the very
                       This is a vector plot of the plume
           velocity at a cross section in the downcomer.  So
           we're in the middle of a downcomer.  We've peeled off
           the layers.  And you can see where these plumes are
           going.  They're obviously merging together and
           interacting into a single plume.  And we actually see
           a convection cell around --
                       CHAIRMAN WALLIS:  And those colors are
           what?  They're velocities?
                       MR. WACHS:  It didn't come across very
           good.  The darker -- or the redder colors are faster
           velocities in the Z direction.
                       CHAIRMAN WALLIS:  So it gets faster as it
           goes down?
                       MR. WACHS:  Well, that's kind of -- one of
           the problems with this is that we have several layers
           to choose from.  And by choosing this middle layer it
           seems to be fastest at the bottom, where if you choose
           the layer -- chose a layer closer to the inside of the
           core barrel it would be higher up.
                       CHAIRMAN WALLIS:  Well, that's very funny
           because we were told that the plumes dissipate after
           about 4Ds and here they are going faster at the
                       MR. WACHS:  Well, you have to consider the
                       CHAIRMAN WALLIS:  I'm not sure any --
           there's any excuse for it, is there?  It just seems to
           be different altogether.
                       MR. WACHS:  Yeah.  Well, we actually see
           some temperature -- well, this is just a model, too. 
           And we haven't really had an opportunity to compare
           velocities from the model to that of the facility.
                       CHAIRMAN WALLIS:  Yeah, but the STAR-CD
           did so well in the more detailed analysis we just saw.
                       MR. WACHS:  In the Creare facility?
                       CHAIRMAN WALLIS:  Yeah.
                       MR. WACHS:  Yeah.  And that's a smaller
           facility, too.  And I think that the geometry --
                       CHAIRMAN WALLIS:  Well, this is kind of
           surprising.  You're saying that you get these big
           velocities at the bottom of the downcomer?
                       MR. WACHS:  Well, in this particular
           slice, --
                       CHAIRMAN WALLIS:  And someone else --
                       MR. WACHS:  -- that's where the peak
           velocities are.
                       CHAIRMAN WALLIS:  -- is telling us that
           the plumes die --
                       MR. WACHS:  I'm sorry.  Go ahead.
                       CHAIRMAN WALLIS:  -- four ds below the
           injection point.
                       MR. WACHS:  Say it again.  I'm sorry, I
           didn't get it.
                       CHAIRMAN WALLIS:  I'm just trying to
           reconcile it.  We were told earlier that the plumes
           essentially die and everything is well mixed up to
           about 4 ds.
                       MR. WOODS:  Well, there's --
                       CHAIRMAN WALLIS:  And here we've got to
           these plunging plumes which are more intense at the
           bottom than the top.
                       MR. WACHS:  Yeah.  I guess I'm not really
           willing to say that that's the most intense region.
                       CHAIRMAN WALLIS:  Well, that's what that
           red flash showed us.
                       MR. WACHS:  Right, in this particular
           slice.  I think if we took a slice in a different
           location, it would change that -- that look.
                       CHAIRMAN WALLIS:  Could you back up and
           show us that again, that red --
                       MR. WACHS:  Yeah, I can show you that.
                       MR. REYES:  I think the other thing is
           that this test we had a plume with cold flow.
                       CHAIRMAN WALLIS:  Yes.
                       MR. REYES:  So you have downcomer flow due
           to the cold-leg flow.  And I think we're seeing kind
           of a mixing due to that.
                       CHAIRMAN WALLIS:  Yes.  But still you've
           got these intense velocities.
                       Could you go back?  And if you could tell
           us what the red magnitude is compared with the red
           there, the background?
                       MR. WACHS:  Okay, it's a radial.
                       CHAIRMAN WALLIS:  We saw a red thing in
           the middle there, then.  That velocity is very much --
           well, that yellow patch, how -- what's that.
                       MR. HAUGH:  That's about a point -- looks
           like .21.
                       MR. WACHS:  Yeah, that's about right.
                       CHAIRMAN WALLIS:  What's the average
                       MR. HAUGH:  The average velocity looks to
           be about .1 --
                       MR. KRESS:  Two, big red.
                       MR. HAUGH:  -- .1 --
                       CHAIRMAN WALLIS:  Go back to that red one,
           there.  Go back to that big red smudge there.  Another
           one, there's another one.  Well, it happened twice.
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  So it's not -- it's not
           just erratic.
                       MR. WACHS:  Yeah.  It's about two-tenths
           of a meter per second.
                       CHAIRMAN WALLIS:  Compared with an average
           of --
                       MR. HAUGH:  Of .15, it looks like.
                       MR. WACHS:  Right, I think that's about
                       CHAIRMAN WALLIS:  So it's another big
                       MR. WACHS:  Yeah.  So it's -- yeah, I
           would agree.  I think that's a strange behavior from
           a model.
                       But, again, this is -- before we were
           talking about some stagnant cases.  And it's possible
           that -- I don't know -- maybe we're missing the plume
           with the 8 d thermocouples.  I think it will be a
           little clearer when we get to later on we'll see --
                       CHAIRMAN WALLIS:  Well, I thought that
           some of the conclusion we seemed to be coming to from
           the previous presentation was that we should replace
           REMIX with CFD, because CFD does better and models
           more things, catch they data better.
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  And this seems to be
           showing that CFD can also predict things which may be
                       MR. WACHS:  Oh, absolutely.  There's no
           question about that.
                       CHAIRMAN WALLIS:  -- we could lose faith
           in its ability.
                       MR. WACHS:  Yeah.  Well, we should.  You
           should -- yeah, I am sure you guys know that CFD is
           not a black box.  These codes are not black-box codes.
                       CHAIRMAN WALLIS:  Well, I think we have to
           make an assessment of the probability of CFD giving
           good enough answers.
                       MR. WACHS:  Right.  I think what -- it
           just hits me.  In my personal opinion I think what we
           would need to do is if we were ever going to
           incorporate the CFD Code is we would have to develop
           a mature code that worked well for a particular set of
                       And we would want to understand that code
           and feel comfortable with the results it gave us
           before we actually went out and applied it to a
           general case, or to another case.  I don't really
           think we're at a mature stage on this code yet.  I
           think that it still lies on the young state of this
           particular model.
                       CHAIRMAN WALLIS:  Well, the remarkable
           thing was Brandon did something which was as immature
           as possible.  In fact, he hadn't tuned anything.
                       MR. WACHS:  Right.
                       CHAIRMAN WALLIS:  He just took something
           out of the box and raised it.  And it seemed to work
           very nicely.
                       MR. WACHS:  Oh, yeah, right.  I agree. 
           It's hit and miss.
                       CHAIRMAN WALLIS:  And it's the same code
           that you are running here.
                       MR. WACHS:  It's the same code, but it's
           a different model, so --
                       CHAIRMAN WALLIS:  Different person.
                       MR. WACHS:  Well, I would -- well, I don't
                       CHAIRMAN WALLIS:  So it's used as a
                       MR. WACHS:  He helped.
                       Yeah, -- no, it is used to depend, that's
           definitely true.  And does the model you apply capture
           the behavior you're looking for?  So on this case we
           have loop flow.  In Brandon's case we didn't have loop
                       CHAIRMAN WALLIS:  I know what is.  It's
           that he's a student.  You're working for ANL.  Isn't
                       MR. WACHS:  I'm a student, too, still.
                       CHAIRMAN WALLIS:  Oh, okay.  I thought you
           were --
                       MR. WACHS:  I just transferred to a new
                       CHAIRMAN WALLIS:  It's an ANL effect, is
                       MR. WACHS:  Yes.  So -- but, yeah, I
           definitely think that -- you know, we talked about the
           size of Brandon's model.  He used about 2,000 nodes,
           and we're about 750,000 nodes.  And that may have some
           impact as well.
                       MR. REYES:  This is a more complicated
           case, though.
                       MR. WACHS:  Yeah.  There's --
                       MR. REYES:  The other case was a stagnant
           injection -- injection into a stagnant region.  And
           this is a flowing case, but not only flowing, but some
           asymmetric injection --
                       CHAIRMAN WALLIS:  In a sense none of these
           are explanations as to excuses --
                       MR. REYES:  Right.
                       CHAIRMAN WALLIS:  -- or possible
           hypotheses and --
                       MR. REYES:  Hypotheses as to why we don't.
                       CHAIRMAN WALLIS:  So it would be
           interesting to resolve this.
                       MR. REYES:  Absolutely.
                       MR. WACHS:  Sure.  Because we came in, we
           even stated a couple of times that it's an exploratory
           issue.  We're trying to see how well it will do.  And
           I think it's important to note that it worked really
           well in one case and it's not working so well in the
           other case.  So there's a certain level of confidence
           that you should try to extract from that.
                       The next thing I tried to --
                       CHAIRMAN WALLIS:  You're not seeing --
           you're not seeing this stratification effect that we
           heard about before, are you?
                       MR. WACHS:  In the downcomer?
                       CHAIRMAN WALLIS:  You are, you're getting
           more of it than was predicted.  I thought earlier you
           were predicting -- your red code showed more
                       MR. WACHS:  That's only in the cold leg. 
           That was the cold-leg behavior.
                       CHAIRMAN WALLIS:  Oh, that was in the cold
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  But not in the
                       MR. WACHS:  Not in the downcomer. 
           Actually, the downcomer, it seemed to work pretty
           well.  Other than that first node right below, it --
           no -- was so-so.  But the other node seemed to work
           pretty well.
                       Then from these velocity profiles we went
           in and tried to extract the peak velocity for the
           plume in order to compare to some of the work that
           they did at the Creare facility in modeling with what
           they saw experimentally.  So we took off this peak
           velocity and got a Reynold's number for the flow.
                       And that what they do at Creare, they use
           these Reynold's numbers.  Well, they picked out their
           peak velocity and tried to compare it to -- they tried
           to calculate a peak velocity and compare it to their
           actual facility.  And we tried to do that same thing
                       In our case, we -- looking at each
           individual cold leg as an independent plume generator,
           and using this model that the Creare people used to
           come up with a maximum plume velocity, you know, in
           one case we would have two plumes.  We got the lower
           of the two curves here.  So we got two independent
           plumes of moderate velocity.
                       When you combine those two plumes and you
           see they have the same strength, they have the QHPI, it
           goes together, you get a larger plume as you'd expect. 
           And this larger plume, the model predicted, seems to
           match better with what we saw in the model, whatever
           that's worth.
                       CHAIRMAN WALLIS:  I'm not quite sure what
           I'm looking at here, these points way down the
           left-hand side there.
                       MR. WACHS:  Yeah.  I'll get it for you.
                       Yeah.  Now what do I have to do to roll. 
           These points down here, these are from the model.  And
           what this is showing is it's showing the --
                       CHAIRMAN WALLIS:  Model's warming up, or
                       MR. WACHS:  Yeah.  It's getting started.
           The plume is forming.  So the velocities are low as
           it's forming, initially.  In terms of the model that
           they, the Creare people, which we are trying to apply,
           it doesn't treat that.  It just said the plume was
           there and it's performing in a certain way.
                       CHAIRMAN WALLIS:  Well, once it gets going
           this isn't all that bad, then?
                       MR. WACHS:  No.  Yeah, right.  And it
           developed, you know, a pseudo-developed plume.  It
           seemed to match okay.  Now that's just a check to see
           a guess what they got.  And it's kind of interesting
           that you have to combine the plumes in order to get
           that similar behavior.
                       CHAIRMAN WALLIS:  Where do you recall this
           maximum plume velocity?
                       MR. WACHS:  Well, as you saw in the --
                       CHAIRMAN WALLIS:  Is it that red flash, is
           the maximum plume?
                       MR. WACHS:  Yeah, basically that's what
           you have to do, because the plume is always moving
           around.  You look for the hot spot, and you say, "Oh,
           that's the peak velocity at this particular point in
                       And so you have a group of cells which you
           grab, and you say the velocity is something like that. 
           And that's one of the real challenges with comparing
           this type of model data to real data.  It's...
                       Now this is a look at the downcomer fluid
           temperature.  In this case, I superimposed to the mesh
           over the top.  And they look better out in the sun
           than they did on the presentation.  Again, this is a
           mid-plane temperature in the middle of the downcomer.
                       CHAIRMAN WALLIS:  So  here we've got a
           plume which is going way down.
                       MR. WACHS:  Well, the temperature
           gradients here, it's like 475 to 468.
                       CHAIRMAN WALLIS:  Can we freeze it?  Let's
           see -- no, go back.  Go back one or two.
                       MR. WACHS:  See, I don't know if we have
           to let it finish before we can --
                       CHAIRMAN WALLIS:  Go back -- you have to
           go through?
                       MR. HAUGH:  Yeah, and it will finish,
                       MR. WACHS:  I think we do.  It's a movie
           file in place.
                       CHAIRMAN WALLIS:  You have to start again,
           or something?
                       MR. HAUGH:  Yes.
                       CHAIRMAN WALLIS:  Because there was a time
           there where you had a plume which seemed to bring --
           again, it's difficult to see the colors, but there's
           a yellow plume that seemed to go all the way down.
                       MR. HAUGH:  Yes, exactly.
                       MR. WACHS:  Um-hum.
                       MR. SHACK:  Yeah, but the whole
           temperature range is what, 468 to 474?
                       MR. WACHS:  Yeah, it's not a very big
           temperature range, right.
                       CHAIRMAN WALLIS:  So it's very little.
                       MR. WACHS:  So, you know, if you see it
           cooling you're going to see profiles.  It's not a very
           strong plume.
                       CHAIRMAN WALLIS:  So what's the
           temperature of the fluid coming out of the cold leg?
                       MR. WACHS:  Yeah, like I said, this is a
           mid-plane, so it's jumping over the plane that we are
           looking at.
                       CHAIRMAN WALLIS:  But what's it coming in
                       MR. WACHS:  What's it coming in at; the
           temperature rise of the plume?
                       CHAIRMAN WALLIS:  Yeah, what's the
           temperature when it comes out of the cold leg?
                       MR. WACHS:  I would assume it was coming
           in at about what the thermal -- or the cold leg, cold
           stream, the same.
                       CHAIRMAN WALLIS:  Is that the 468, or
           something, whatever is at the bottom there?
                       MR. WACHS:  I would say that it would be
           a little bit cooler than that.  I think there's
           certain amount of mixing that has gone on before it
           gets back to this plane.
                       It's coming in through these holes here
           (indicating).  These are a couple of cells that were
           part of a different part of the model.
                       CHAIRMAN WALLIS:  It may be there is
           something which is just distorted here.  It may be
           that there's a big temperature change at the top,
           which you're not really seeing.
                       MR. WACHS:  Right.
                       CHAIRMAN WALLIS:  And then there is a
           survival of a plume at the bottom, because there is
           some mixing, even though it's stratified.  And we are
           just focusing on that because that's all we can see.
                       MR. WACHS:  Yeah, I agree.
                       CHAIRMAN WALLIS:  I don't know.
                       MR. WACHS:  That's probably true.
                       CHAIRMAN WALLIS:  Hard to tell.
                       MR. WACHS:  I think that, yeah, a majority
           of the mixing is going to go on in this initial
           falling area where it's impinging on the far wall.
                       CHAIRMAN WALLIS:  It doesn't mean to say
           that there's no mixing velocities below that.  There
           seem to be a lot of mixing velocities below that.  Bi
           because it's all about the same temperature it doesn't
                       MR. WACHS:  Right.
                       CHAIRMAN WALLIS:  So it seems to be that
           you have to really separate out your idea about what
           the velocities are doing from what the temperatures
           are doing.
                       MR. WACHS:  Right.  Yes.  It's the post-
           processing.  There's a lot of data to sift through and
           choose which ones you want.
                       Did you want to see that again?
                       MR. SHACK:  Was it possible to refine the
           mesh right up in that region, right at the nozzle?
                       MR. WACHS:  Oh yeah, absolutely.
                       MR. SHACK:  I mean it --
                       MR. WACHS:  That's a thing you can do.
                       MR. SHACK:  And that seems to be where the
           action is.
                       MR. WACHS:  Yeah, that's one of the things
           that you'll want to beforehand.  We'll talk of little
           bit about that when we get to some of the summary, how
           we would do that.
                       Now this is a movie of the vessel wall
           temperature.  So the temperature differences here are
           on the order of four degrees from top to bottom on the
           range.  You can see they seem to mimic the temperature
           profiles in the fluid pretty well.  But the gradients
           are really small, what it's expecting to see.
                       CHAIRMAN WALLIS:  Again, this is
           emphasizing what maybe a rather small changes at the
           bottom of the annulus.
                       MR. WACHS:  Yes.
                       CHAIRMAN WALLIS:  And not really showing
           you that the mixing is occurring at the top.
                       MR. WACHS:  Yeah.  Well, this is actually
           the steel, the first node of steel.  So showing the
           overall cooldown of that body.
                       CHAIRMAN WALLIS:  Because it's surprising
           the steel is changing temperatures so rapidly.
                       MR. WACHS:  Well, it's not changing much.
                       CHAIRMAN WALLIS:  It's not?
                       MR. WACHS:  No.  This is the -- the full-
           scale from red to black is less than four degrees.
                       CHAIRMAN WALLIS:  Okay.  That's part of
           it.  You've magnified it.
                       MR. WACHS:  Yeah.  That's essentially what
           it does.
                       MR. SHACK:  If you look at it close
           enough, there's always big differences.
                       MR. WACHS:  Yeah.  And, you know, if I
           hadn't done that it would be red.  You know, you don't
           really see any of the behavior.
                       CHAIRMAN WALLIS:  If you go long enough,
           he's going to write OSU in the annulus.
                       MR. WACHS:  Yeah.  I'll have to play that
           on the scoreboard at the football game.
                       The next step that we wanted to try to
           accomplish there was to try to extract some heat
           transfer coefficients and see what we could look at. 
           In order to do that --
                       CHAIRMAN WALLIS:  Now who is this guy
           Newton?  Is that a reputed reference?
                       MR. WACHS:  Yeah, that's by name-dropping.
                       So we want to extract it.  In order to
           come up with this we have to extract a heat flux from
           the problem, and we have to find some way to
           demonstrate the delta t.  And heat flux isn't too bad. 
           You just take a delta t over the reactor vessel wall. 
           And we know the thermal conductivity of that
           particular material so we can extract the heat flux.
                       And again you'll want to do that at the --
           or I did that at the area of the peak velocity, a
           plume velocity we chose.
                       Then you just plug it in and choose an
           ambience temperature.  I chose the temperature at the
           mid-plane, just to have something to work with.  And
           you can translate that into a Nusselt number.
                       In the Creare work they compared their
           Nusselt numbers that they calculated and measured to
           -- so they Spelter equation.  They didn't get good
           agreement, either.  And we tend to not see -- be off
           by about -- well, we're around a hundred and they were
           around two hundred.
                       MR. SCHROCK:  Well, that's kind of a
           casual determination of the representative fluid
                       MR. WACHS:  Yeah, it is.
                       MR. SCHROCK:  You need something more
           definitive than that.
                       MR. WACHS:  Absolutely, I agree.  And one
           of the hard things with doing that is you get a
           nonuniform temperature profile.  Ideally you would
           like to choose a mixed mean temperature of the plume. 
           And how to do that is not trivial.
                       CHAIRMAN WALLIS:  Maybe this is one of the
           problems with REMIX.  And REMIX has to do things like
           get an average heat transfer coefficient in this sort
           of way.
                       MR. WACHS:  Right.
                       CHAIRMAN WALLIS:  And this is kind of
           indicating that that is not a very good
                       MR. WACHS:  Right.  It's a constructive
           parameter.  Extracting a heat transfer coefficient is
           not -- you know, this kind of code isn't intended to
           do that kind of thing.
                       CHAIRMAN WALLIS:  Your CFD has to do
           something about predicting the wall heat transfer
                       MR. WACHS:  Not really.  It's just -- it's
           looking at nodes.
                       CHAIRMAN WALLIS:  Yes, it does.  You can't
           just -- you know, but that doesn't give you a
           coefficient of the wall.  There's got to be some model
           that goes from the velocities in the nodes to a heat
           transfer coefficient at the wall.
                       MR. WACHS:  Well, use a strict convection
           of and conduction between the two.
                       CHAIRMAN WALLIS:  It uses some kind of a
           law of the wall.  It uses some kind of a model of
           what's happening in the boundary there.
                       MR. WACHS:  Yeah.  It does use the law of
           the wall.  That's incorporated into there.
                       CHAIRMAN WALLIS:  Right.  It's not clear
           that that applies when these plumes are doing what
           they are doing here.
                       MR. WACHS:  Right.  I agree.
                       CHAIRMAN WALLIS:  So that you've got the
           same problem with CFD, but there's a different level
           than that.
                       MR. SCHROCK:  Dave says just use infinity. 
           Is that universal, then?
                       MR. WACHS:  Between all the codes?
                       I'm sorry, I didn't get that.
                       MR. BESSETTE:  Well, I think what we've
           shown is that if you're within a factor of 2, then
           that's plenty good enough.  If so, if you choose --
           that's why -- like in REMIX, you know, in REMIX you
           input the heat transfer coefficient.
                       So you can just choose something like a
           thousand-watt square meter degree k.  And if you're
           off by a factor of 2, it doesn't matter.  It's 500 or
                       CHAIRMAN WALLIS:  Don't use an infinity of
           it because then you'll find that five different
           calculations will give you infinite changes in the
           step and you'll be in real trouble.
                       MR. KRESS:  I'm surprised that the data is
           below the Dittus-Boelter.
                       MR. WACHS:  But in this next slide we'll
           talk about that a little bit, how that works, and why
           that is.
                       CHAIRMAN WALLIS:  Or a lot.
                       MR. KRESS:  Yeah.  I would have thought it
           would have been above it.
                       MR. WACHS:  Just a little bit on the
           Dittus-Boelter equation.  It's based a fully-developed
           flow, and that's not really the case we are looking
           at.  In our case --
                       MR. KRESS:  Yeah, you've got an interest
                       MR. WACHS:  -- if you look here, one of
           these is --
                       MR. KRESS:  How do you calculate the
           Reynold's number?
                       MR. WACHS:  -- the one on the left --
                       CHAIRMAN WALLIS:  Well, that's the whole
                       MR. KRESS:  I think that's the issue
                       MR. WACHS:  On the left side here we've
           got an axial slice of the temperature profile.  On the
           right, we've got an access slice of the velocity
           profile in the z direction.
                       If you look in the upper-right quadrant
           there you can see where the cold plume is located at. 
           And, you know, that's about five degrees.  And this is
           about mid-plane.  You can see that it's attached to
           the inner wall.  It's clearly not running down the
           center of the vessel -- of the annulus.
                       And you can see on the velocity profile
           that the plume is moving with that cold stream just
           like you would expect.
                       MR. SHACK:  Where am I at in z again?
                       MR. WACHS:  This is right by the mid-plane
           of the downcomer.  So I don't know.  What's the total
           depth of the downcomer?
                       MR. HAUGH:  Total diameter is 86 inches.
                       MR. WACHS:  It's like 71 inches, but I
           don't -- so it's probably around 35 inches.  So that's
           about 10 diameters from the upper-vessel head, not
           from the downcomer, or from of the cold leg injection
                       So we can see that the actual velocity
           next to the outer wall is relatively small.  And thus
           you'd expect the heat transfer coefficients of the
           model was -- would you extrapolate from the model
           would be smaller than what you'd get with a
           fully-developed flow with the cold plume running down
           the middle as opposed to the far side.  So the
           effective diameter for the Reynold's number is
           probably different.
                       CHAIRMAN WALLIS:  These two plots
           correlate pretty well, don't they?
                       MR. WACHS:  Yeah.  Oh, I think so, with
           the velocity and the --
                       CHAIRMAN WALLIS:  Which I think means that
           they're calculating the heat transfer coefficient from
           the velocity.  And that gives you the temperature.  So
           you would expect them to correlate pretty well.
                       MR. WACHS:  With the Dittus-Boelter
                       CHAIRMAN WALLIS:  Well, whatever model
           they have in CFD for the heat transfer coefficient.
                       MR. WACHS:  Oh, oh, I didn't use the --
                       CHAIRMAN WALLIS:  It's probably -- is
           probably --
                       MR. WACHS:  The CFD model didn't extract
           the h coefficient.  I extracted that from the data.
                       CHAIRMAN WALLIS:  Oh, you extracted that?
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  You extracted that.
                       MR. WACHS:  Yeah.  You have to do some
           special things beforehand in order for it to calculate
           an h value.  You have to --
                       CHAIRMAN WALLIS:  I think CFD would make
           h roughly proportional to v.
                       MR. HAUGH:  Yeah.  I did that in my Creare
           model on the last run.  What you have to do is between
           the solid and the fluid cells you insert a wall
           boundary.  And it's just zero resistance.  That's just
           a point for the code to monitor heat flux.  And then
           from the heat flux you can provide a mix mean
           temperature, and it will give you a heat transfer
                       MR. WACHS:  Right.  Yeah, it will
           calculate the y plus value and then try to extract the
           heat transfer coefficient.  But it's something you
           have to do before you run the model really early on in
           the development.
                       Just some of the conclusions we could
           make:  Like we said before the nodalization was a
           little bit coarse in the cold leg, and I think we
           could get better results if we were to densen that up. 
           And as a part of that we need to show great
                       The downcomer temperatures seem to be in
           pretty good agreement.
                       The core inlet temperatures were mildly
           underpredicted.  And, as we postulated before, I think
           that's due to the omission of the core barrel.
                       Now in terms of phenomena base we do see
           plume interactions, which is something that we think
           we've seen in the facility from the data that we have
           available.  And those interactions should be affecting
           the plume velocities.
                       In addition, the plume doesn't necessarily
           run right down the middle of the downcomer.  It moves
           in its radial location from inside to outside,
           primarily down the outside.  Generally that affects
           the agreement with some of the standard convective
           coefficient -- heat transfer coefficient models.
                       We also really need to run some more runs
           and tweak the model a little bit to include some of
           the physics that we want to make it match the data a
           little bit better, or to model the same problem,
           essentially.  Essentially, we are not treating the
           same set of problems.  And we also need to show that
           the cell density is appropriate.
                       MR. SCHROCK:  So your heat transfer --
                       MR. WACHS:  There should be one more on
           lessons learned.
                       Any questions?
                       MR. SCHROCK:  Your Nusselt number
           comparison is even worse when you recognize the
           Dittus-Boelter equation is for the length average in
           a long tube, fully-developed conditions.  And you're
           applying it in developing conditions.
                       MR. WACHS:  Right, I agree.  They don't
           really treat the same problem.  The only reason I put
           that on there is because the Creare people put that on
           there when they looked at their data.  I just wanted
           to compare how well our model was working against how
           well the model they used.
                       This should be another one lessons learned
           that you've got in there.
                       MR. HAUGH:  What's the name?
                       All right, I got it.
                       MR. WACHS:  Also I'll talk a little bit
           about the lessons we learned from this stuff, with
           Brandon -- it took Brandon and Eric and I working on
           it for the last year.  There's some significant things
           to take with us.
                       On the CFD methodology there's some
           distinct steps to that you need to go through in
           creating a model.  And each one of those steps has got
           its own set of problems and difficulties that you can
                       The first step is you really need to
           define your problem well.  You need to know exactly
           what behavior you're looking for.  You need to know
           exactly what your geometry is going to be like, where
           you know inlet conditions and boundary conditions.
                       And so you need to be familiar with the
           system before you come in.  It's going to be really
           difficult to get any reasonable results if you come
           into a system fully blind on the physics.
                       The next step that you have to go through
           is you really need to construct the mesh.  You'd have
           to construct the mesh.  And the way you construct that
           mesh needs to be attached to the way you want to model
           the physics and the physics you want to capture.
                       Finally, you need to set up your problem. 
           So you need to choose your models, what physics do you
           want to include, which turbulence parameters you want
           to -- or turbulence models for you want to run.  And
           then you need to run the problem.  And that goes into
           the computational ability that you have in your
           facility, how you go about doing that and what you can
           do.  And then post-processing presents its own set of
                       So things to consider, but you have to
           understand the physics before you go in.  It's not
           going to be something that you treat as a black box
           and you just take somebody who knows how to run
           software, and you put them on it and try to run the
           problem and expect to get anything that's worth
                       In terms of mesh building, one thing we
           found -- that Brandon found -- was that he found it
           easier to import the geometry from some CAD program
           that was more suited to generating rough geometry.
                       In general, the CD or the STAR -- or the
           CFD codes are not real good at generating initial
           geometries.  They're good at generating meshes, but
           they're not good at initiating initial geometries. 
           You don't have the same amount of tools.  And you can
           be more efficient and more complete in representing a
           geometry when you do that.
                       Now your mesh gradients need to match the
           physical gradients of the phenomena.  It's really
           important to do that.
                       And a lot of times people think of CFD as
           you put more nodes in, and you make time step smaller,
           it's going to work better.  And that's not always
           going to be the case.  You can get too small just as
           well as you can get too large.  So you need to be
           careful about that as well.
                       In terms of running the codes, modeling
           large --
                       CHAIRMAN WALLIS:  So interesting.  You can
           refine the cells in local places but you have to run
           everything at the same time, that you step --
                       MR. WACHS:  Right.  You have to rerun the
           entire problem.  Yeah, because there are all
           communicating with each other.
                       CHAIRMAN WALLIS:  You can't refine the
           time in certain regions?
                       MR. WACHS:  Well, yeah.  I guess -- yeah,
           I guess I'm thinking of time -- transient time scales.
                       CHAIRMAN WALLIS:  I guess you could, but
           I don't think they ever do that.
                       MR. WACHS:  Do what, vary time?
                       CHAIRMAN WALLIS:  Refine the time.
                       MR. WACHS:  Oh, oh, yeah.
                       CHAIRMAN WALLIS:  In certain regions you
           run the very small time set only in this region, --
                       MR. WACHS:  Oh, okay, yeah.
                       CHAIRMAN WALLIS:  -- but the rest you're
           on --
                       MR. WACHS:  Yeah, you're right.  You have
           to vary the time globally.  You can't vary it in time.
                       CHAIRMAN WALLIS:  Globally but not
                       MR. WACHS:  Yeah, you're right.  At least
           not at this time.  I wouldn't be surprised if they
           decided that they could do that, whether they could or
                       The next thing, when you dealing have
           large systems and have large numbers of nodes, you
           need a lot of computing power to be able to treat
           those models.  That's where parallel computing really
           came in useful for us.  Had we not had the parallel
           computing capability we'd still be running models
           probably months ago.  You know, it would be -- our
           particular model with the APEX-CE facility took 10
           days to run on a four processor parallel machine.
                       So you take that onto a single processor
           and you're talking about order of months.  So that's
           a significant advantage.
                       Now another thing we found was that you
           needed to have your computing platforms homogeneous. 
           You couldn't work with an HP and a Sun separately. 
           The code didn't like that.  It wants to stay on the
           same platform all the time.
                       And in terms of post-processing, one of
           the main difficulties in comparing to experimental
           data, even in a very well-instrumented facility like
           ours, we are on the order of hundreds of data nodes,
           okay, with the -- with the CFD we're on the order of
           a hundred thousand locations.
                       So how you take this two-dimensional or
           even three-dimensional behavior and try to benchmark
           it against basically one point in time and really get
           an idea of whether you're seeing the same behavior. 
           And that's difficult.  I think that that's --
                       CHAIRMAN WALLIS:  Which is always a
           problem with code assessment --
                       MR. WACHS:  Yeah.
                       CHAIRMAN WALLIS:  -- with RELAP or
           anything else.  I mean you get a whole lot of data
           points and a whole lot of predicted points and how you
           assess the comparison between them --
                       MR. WACHS:  Right.  It's not trivial.
                       CHAIRMAN WALLIS:  -- in other than some
           sort of superficial way, or you just look at a few
           pictures and say, "All right, it's good enough."
                       MR. WACHS:  Right.
                       Let's see.  Yeah.  So we were talking
           about multi-dimensional behavior.  I think that's it. 
           That's -- because we've add sections.
                       CHAIRMAN WALLIS:  So we are getting very
           close to the end.
                       MR. WACHS:  What's that?
                       CHAIRMAN WALLIS:  We're getting very close
           to the end here.
                       MR. WACHS:  Yeah.  Any questions on that
           at all?
                       CHAIRMAN WALLIS:  Any questions?
                       (No response.)
                       CHAIRMAN WALLIS:  So, Jose, are you ready
           to wind this up for us?
                       MR. REYES:  I'm ready to do that.
                       MR. SCHROCK:  So we have a new NRC
           dilemma.  When is enough CFD enough?  Never.
                       MR. SHACK:  When you run out of money.
                       MR. REYES:  As I went through this I
           realized there's a lot to summarize.  And I'll kind of
           hit on some of the highlights that I think we saw as
           far as observed phenomena and what we've learned in
           the process.
                       In terms of separate-affects-type
           behavior, we've taken a look at using this both
           APEX-CE and the flow visualization group.  We take a
           look at a specific mixing behavior in the cold legs. 
           We looked at thermal stratification.
                       We found that the effect of the Weir wall
           was very important.  So that was something that was --
           originally we didn't think that much about, but as we
           went into the testing and we observed the results,
           especially in the flow visualization group, we
           realized that that was an important part.
                       The separate affects can be integrated now
           with the integral system test, because we see that the
           formation of a cold liquid plug in the loop seal can
           affect integral system behavior.  It affects
           stagnation in the loop.  So that's a very important
           piece of our research, I think.  And so we will
           continue development in that area as far as analytical
                       In terms of the integral system testing
           one of the things we observed there, or some of the
           key points that we observed for the integral system
           test, were for all the small break LOCAs, the main
           streamline breaks, and then the combination breaks,
           what we observed with regards to the mixing in the
           downcomer was that the plume basically within four
           diameters was well mixed.
                       For cases where we had flowing cold legs
           in conjunction with injection we also saw thermal
           stratification.  And that ranged -- the maximum we saw
           was about 40 degrees F from the bottom of the
           downcomer to the cold-leg location.  So we were seeing
           small temperature differences.
                       We recognized the unique design of the
           facility we're scaled here to, the Palisades plant. 
           It does have a lower HPI than some of the other plants
           that are out there today.  And so we recognize that
           aspect of it.  And so we are seeing some of that
                       We generally tend to produce relatively
           weak plumes which mix relatively quickly in the
           downcomer.  That's what we're seeing.
                       With regards to the two situations, the
           stagnant injection in a stagnant media as opposed to
           a cold flow.  For a stagnant media case what happens
           is that initially you see good-sized temperature
           differences between the -- within one or two d, about
           15 degree F difference between the ambient temperature
           and the plume temperature.
                       But as time goes on you're -- in the
           stagnant case you're mixing that volume, and it's
           becoming more and more cold.  And so you're seeing a
           smaller delta t with time and a weakening of the plume
           with time.
                       With regards to the situation we have of
           flow in the cold legs, what we see there is a
           possibility of having a prolonged contact with the
           downcomer vessel, because you are resupplying that hot
           fluid.  And so you're maintaining a larger delta t for
           a prolonged period of time.
                       So as long as you're feeding hot water
           into the downcomer region, you're able to keep this
           plume relatively strong because you're continuing to
                       However, we saw maximum case of about --
           I think we saw between 30 and -- I think 30 to 35
           degrees was the maximum we saw for the situations that
           we were setting.
                       However, it does provide an opportunity
           for a prolonged contact but it's fairly small,
                       With regards to our analytical
           capabilities, we looked at RELAP5 Code, the Gamma
           version.  And for the main streamline breaks, the
           prediction seemed to compare very well.  There were a
           few areas that we still need to look at.
                       In particular, the pressurizer liquid
           level we saw didn't predict exactly as we measured in
           the test.
                       And then there are some issues with
           regards to break flow, for the small break LOCA that
           we wanted check into also as far as comparisons there.
                       So there's still some work in that area
           that needs to be done with regards to the integral
           system modeling.
                       In general, we observed that RELAP
           predicted the stagnations reasonably well as far as
           the stagnation occurring.  The mechanism was typically
           either reverse heat transfer or steam generator tube
                       It could not take into account the effect
           of the cold loop seal plug because of spillover over
           the Weir wall.  So we noticed that.
                       With regards to the separate-effects-type
           modeling, we used to two codes.  We used REMIX Code
           and we used STAR-CD.
                       REMIX is a control volume lump parameter
           type of a regional-mixing mode, which is significantly
           simplified.  It just addresses certain regions within
           the mixing volume of a cold leg loop seal and
                       And we observed, in comparing to our data,
           that it didn't -- it underpredicted basically all of
           the temperature is in the downcomer that we were
           looking at.
                       We also observed that with REMIX you can
           include and you should include a section of the core
           barrel to model the core stored-energy release or the
           barrel stored-energy release into the fluid.  And that
           played an important part.  And that effect was also
           carried over, we saw, into the STAR-CD calculations.
                       For STAR-CD we used a -- we did two
           calculations.  We benchmarked the code first with the
           Creare half-scale data.  And we saw a very good
           comparisons right out of the box with that.
                       And I think if you look at the APEX-CE the
           temperature scaled was fairly tight.  And so I think
           the comparisons are actually better than they appeared
           on the screen.
                       So if you go back to that again, I think
           you'll see you're still within about plus or minus -- 
           within 10 degrees of the actual measured.  So go back
           to that and look at the scale, and you'll see that
           it's a little bit tighter than the picture tends to
                       So we do see a better prediction than I
           think was the image portrayed somewhat.  Would we
           think we are seeing some reasonable predictions with
           the STAR-CD code.
                       There's more to learn with regards to the
           turbulence models and what's being done there.
                       Overall, if you look at the project as a
           whole and what we were trying to accomplish and where
           we are right now, I think we've accomplished quite a
           bit.  And so I'm pleased with that.
                       We will be documenting all of this and
           providing you with the Final Report.  And we'd like to
           make it fairly comprehensive so it's a standalone
           document.  So it will describe the entire project in
           its entirety.
                       There's some additional work that's going
           on right now.  We are still looking at some
           theoretical models for the plume.
                       We're also looking at a theoretical model
           for a prediction of loop seal spillover.
                       We're also looking at some refinements
           that have been done, I guess, already on the cold leg
           to see if we can't -- using STAR-CD to predict better
           comparisons of stratification by refining the cold leg
           a bit more.  So we have those.
                       And we also have one test which right now
           we still need to specify a little bit better, Test
           Number 13.  And we're looking at discussions with NRC
           as to what's the best way to portray that.  That would
           be basically a cold injection of HPI into essentially
           a steam environment where you have a level in the
           downcomer.  So we'd like to take a look at that to
           understand that better.
                       So that's kind of where we're at.
                       With that I'll talk about the reporting
           schedule.  The Scaling Analysis Report is completed. 
           We've submitted it to the NRC.  And it's actually gone
           through the technical review.  And now it's going
           through an editorial review.  So we are waiting for
           comments back from NRC Publications.  Not comments
           from technical but the publications folks to get back
           with us and get us into the right format for the
                       The Final Report, we are planning to --
           we'll probably have several, at least one or two
           drafts before the Final Report, which we'll provide to
           NRC for their review.  We hope to issue that by the
           end of the year.  That will include the following
                       Review of the previous PTS research.  That
           will be a section in there.
                       Description of our test facilities.
                       An overview of Palisades operations, what
           we learned as far as operations of the Palisades
                       The results for all of our tests.  It will
           include the RELAP5 comparisons.  And that includes all
           the comparisons.  We didn't show you all of them.
                       We will include the REMIX and STAR-CD
           final calculations.
                       And then, of course, we'll have a CD with
           all of our data and all of our drawings for the
           facility.  So typically we can bundle that essentially
           on three CDs.  So you'll get a three-CD set.  You can
           pick up your copy at the door.  So that's how we'll
           document this project.
                       So I think it's a fairly comprehensive
           piece of work.  And hopefully you will be able to
           benefit from this.
                       But I would like to express my thanks to
           the Committee for being here.  And it's always a
           pleasure to get a review.  And on behalf of our
           students, who have worked very hard and I think they
           themselves have learned quite a bit from this process,
           I extend the thanks to the Committee and hope we can
           interact with you again in the future.
                       CHAIRMAN WALLIS:  Well, thank you.
                       I think we've enjoyed hearing from you and
           your colleagues and students.  You've given us a lot
           to think about.
                       I think the Agenda calls for a
           Subcommittee caucus.  I think what I'd like to ask is
           what the ACRS role will be in the future.
                       Usually we review things like this in the
           context of our review of RES programs when this
           happens once or twice a year.  This will be very
           useful input, I think, for that purpose.
                       But I don't think the whole ACRS is
           specifically going to focus on this project at any
           particular time, except in the context of PTS or some
           safety issue when we will really get involved.
                       So I see this mostly as contributing to
           our decisions we have to make about PTS, any
           rulemaking, particularly, and any regulatory action
           which the Agency is going to make.
                       MR. BESSETTE:  Well, I think that's right. 
           I think this -- you know, the PTS work here is -- it's
           very issue-oriented as opposed to generic, like -- so
           it's different than when you review the code
           development or something like code consolidation.
                       This feeds into the -- this was intended
           to feed into the work on the thermal hydraulics
           aspects of PTS and it was a key part of it.
                       CHAIRMAN WALLIS:  Now down the road I can
           see -- we've been reviewing vendor codes.  As you
           know, we've got three or four of them we're doing now. 
           And presumably down the road the NRC, or the
           licensees, or somebody may wish to approve in some
           formal fashion the use of CFD in various forms, just
           the way that they approved the use of GE Code, or
           Westinghouse Code, and so on.
                       So I can see down the road we may have to
           face that question.  And these sorts of results will
           presumably be part of a review of that type.  But
           that's probably down the road somewhere.
                       I assume that what we are going to do is
           we're going to go back and at the next full Committee
           meeting we'll make a report as a Subcommittee, which
           will be 15, 20 minutes, half-an-hour, summarizing what
           we heard here, anything that the whole Committee needs
           to know.
                       MR. ROSENTHAL:  Yeah, let me just
           reiterate.  I mean, with respect to PTS, you know,
           we've got a schedule.  We'd like to continue on. 
           We're doing plant-specific RELAP calculations.
                       We're going to do some benchmark against
           this facility, price the calcs we're doing, but based
           on the work that they did with RELAP.  But I would
           expect that that would come out rather well.
                       We had some show-stopper questions in
           terms of plumes and stagnation, which I'm encouraged
           in terms of getting some answers.  So we start PF- --
                       MR. CHOKSHI:  The thermal hydraulics
           condition in September.
                       MR. ROSENTHAL:  In September.  And then we
           are due to come to the ACRS in September, also.
                       MR. CHOKSHI:  In other words, the
           methodological --
                       MR. ROSENTHAL:  And what I think you've
           asked us to do is spread out, you know, a
           beginning-to-end for some sample case.  So it would
           involve three divisions in Research.  And I don't
           think we would belabor the thermal hydraulics very
           much, given what the Subcommittee has heard.
                       MR. SHACK:  Well, it seems to me you've
           gotten lots of visual insights into thermal hydraulics
           and PTS from this room.
                       But what are your next steps now in the
           thermal hydraulics part of the PTS analysis?
                       MR. BESSETTE:  Well, basically we've done
           our analysis of Oconee, which is the B&W design. 
           We've run about 60 transients, call them scenarios, or
           whatever, PTS, potentially PTS-significant transients
           to map out the plant.
                       MR. SCHROCK:  Using RELAP?
                       MR. BESSETTE:  Using RELAP.
                       We've done selected transients as well
           with TRAC.  So we have a TRAC RELAP comparison.  So
           that work is done.
                       We've started our calculations on Beaver
           Valley and Calvert Cliffs.  Beaver Valley is a 
           Westinghouse 3 plan and Calvert Cliffs is a CE.  And
           we hope to be well along in those analyses by, let's
           say, October, which is when the fracture mechanics
           people need the results to run through FAVOR.
                       And so that's where we stand.
                       MR. SCHROCK:  And they need a --
                       MR. SHACK:  But what kind of calculations
           are you going to do assure yourself that the plume
           behavior you see in those other plants is comparable
           to the plume behavior -- I mean, the conclusions here,
           I think, are that, you know, the PFM guys don't have
           to -- you know, they're golden.  And, you know -- but
           can you reach that conclusion generically yet?
                       MR. BESSETTE:  Well, as far as -- you
           know, as far as a downcomer goes, basically, you know,
           you have your initial conditions, which is what enters
           from the cold leg.
                       And we would expect to cover the range of
           conditions that we could expect from -- you know, for
           a B&W plant you've got a high-mixing region when HPI
           comes in.
                       CE and Westinghouse is similar in that you
           get the stratified flow coming into the downcomer.
                       The HPI flows are slightly higher in the
           Westinghouse Plant and CE, but we'll, you know, we'll
           cover that, that range.
                       CHAIRMAN WALLIS:  So are you going to
           accept Westinghouse CFD calculations, something like
           what we saw here, which are actually, you know,
           reflecting the conditions in their plume, which is
           somewhat different than there.
                       Are you going to except those predictions
           for temperature, and so on, as inputs into --
                       MR. BESSETTE:  Well, actually, we aren't
           even getting any submittals from Westinghouse.
                       CHAIRMAN WALLIS:  No, but I mean, what are
           you going to do about the plumes, then?  Is someone
           going to make a calculation of what the plumes are
           doing in a different plant?
                       MR. SHACK:  I mean, Jack mentioned you
           were looking at REMIX, which doesn't look very promi-
           -- very good here, I mean.
                       MR. ROSENTHAL:  Well, you know, I always
           -- first of all, we are not getting -- let me just
           clear.  We're not getting anything, any calcs from
           Westinghouse.  We're doing the Westinghouse calcs.
                       CHAIRMAN WALLIS:  Well, I was just
                       MR. ROSENTHAL:  Yeah.  Now --
                       CHAIRMAN WALLIS:  But somebody is
           responsible for facing the issue of:  Is there a plume
           and how big is it, and what are their temperatures?
                       MR. ROSENTHAL:  Well, I think of the
           three, I am, but I'm going to enlist the two people to
           my right.
                       But I always saw this as a question of we
           would do some RELAP calculations, and we would have to
           associate an uncertainty with those calculations.
                       And I always saw that it wouldn't be a
           constant uncertainty.  Dave has pointed out to me more
           than once that when -- for those sequences in which
           you have pumps running, for example, you have a very
           well-mixed case.  And the uncertainties ought to be
           smaller than in the stagnant cases, et cetera.
                       So I always, at least in my head, thought
           there would be that qualification on which sequences
           and we'll know the associated probabilities of those
                       Now, should it come to pass that we have
           some critical cases, either in terms of extremes of
           pressures or temperatures, with high-enough
           probabilities that you care about, then we're going to
           have to do some more homework.
                       And REMIX we could always run, and it's
           cheap.  And as long as we have sequences in which you
           don't cool down very much, or the pressures aren't
           very high, and they can live with 25 c, or 50 c
           uncertainty, then I don't -- I'm not convinced that we
           should do any more.
                       But as soon as I get less than twen- -- if
           they start telling me that 25 c delta really matters
           in some sequence, then I think we're going to have to
           do some more work.
                       CHAIRMAN WALLIS:  From what you've seen
           here, the work that's being done here, by the time
           that you can extrapolate to the Final Report, you
           think the information in that Final Report is going to
           be just what you need to make these decisions?
                       MR. BESSETTE:  I think so.
                       CHAIRMAN WALLIS:  You think so?
                       MR. BESSETTE:  Yeah.
                       CHAIRMAN WALLIS:  That sounds very good,
           then, as an output from this research work.
                       MR. ROSENTHAL:  Oh, yeah, it's very
                       CHAIRMAN WALLIS:  So, Jose, you heard
           that.  I think that's a very good outcome.  These are
           getting to be more internal NRC-type discussions that
           you're just listening to.
                       Does the Subcommittee have anything else
           to say at this time, or shall I just wind things up by
           complimenting all the speakers.
                       It's been very interesting.  It's very,
           very nice for us to see technical work done from
           theory, and experiment, and asking questions, and
           getting answers.  It's been a good couple of days.
                       Thank you.
                       (Whereupon, the meeting was adjourned at
           12:17 p.m. on July 18, 2001.)

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