ML20151D173

Summary of ACRS Thermal Hydraulic Phenomena Subcommittee Meeting on 880120-21 in Los Alamos,Nm Re Review of Documentation Developed by Lasl to Support Trac PF1 Thermal Hydraulic Code

ML20151D173
Person / Time
Issue date:	02/18/1988
From:	Advisory Committee on Reactor Safeguards
To:	Advisory Committee on Reactor Safeguards
References
ACRS-2547, NUDOCS 8804130438
Download: ML20151D173 (79)

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'DATE' 7 8/2 Advisory Cemnittee on Reactor Safeguards Thermal Hydraulic Phenomena Subconnittee Meeting Minutes January 20-21, 1988 Los Alamos National Laboratory Los Alamos, NM PURPOSE: The purpose of the meeting was was te review the documentation developed by LANL to support the TRAC PF1 Thermal-Hydraulic Code pursuant to the NRC RES Code Scaling Assessment and Uncertainty (CSAU) requirements. The status of the CSAU effort as it relates to the propcsed ECCS Rule revision was also discussed.

MTENDEES: Principal Meeting attendees included:

ACES LANL D. Ward, Chairman T. Knight I

J. Ebersole, Member D. Lyles W. Kerr, Member R. Nelson

• C. Mark, Meaber K. Pasamehmethoglu C. Michelson, Member M. Kappiello

1. Catton, Consultant J. Spore M. Plesset, Consultant L. Guffee V. Schrock. Consultant C. L. Tien, Consultant NRC

• P. Sullivan, Consultant L. Shotkin H. Zuber INEL N. Lauben G. Wilson

• Limited participation due to conflict of interest considerations 8804130438 800218

• PDR ACRS 2547 PDR '

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T/H Phenomena Minutes January 20-21, 1988 4

MEETIl1G HIGHLIGHTS, AGREEMEliTS. AND REQUESTS

1. Mr. Ward noted the following: the ACRS will be advising the Commission on the usefulness of continuing the RES T/H code development Program. He said the NRC needs to avoid abandonment or continuation of the Program by "non-decision." The Subcomittee needs to know if the TRAC code is good enough for current and future regulatory needs; if not, we should ask what can and should be done. The Subcomittee Members will be in a unique position to answer these points.

The Chairman said the QA Report is a monumental and historic effort. LAllt is to be congratulated. He said we are meeting now to gain knowledge for use in our global deliberations on the above points. He asked the Consultants' to keep the "ACRS mission" in mind vis-a-vis their comments on the QA Report.

The Chairman asked the Subcommittee to consider the follcwing questions:

• Is TRAC capable of supporting current regulatory needs; if not why not?

• Is further development appropriate? Are expectations for significant improvement in the code realistic?

2. N. Zuber provided opening remarks. Noting the CSAU effort, he indicated that, for the first time, the Laboratories have been asked to provide a QA Report for the T/H code's models and corre-lations. This Report is vital for exercising the CSAU methodology.

Dr. Zuber solicited Subcommittee coments on the document. l

3. T. Knight (LANL) provided an introduction to the Models and Corre-lations (QA) Report. Key points noted by Dr. Knight included: )

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T/H Phenomena Minutes January 20-21, 1988 The Report supports the TRAC PF1/ MOD-1 Version 14.3 Code.

Version 14.3 was credted in September 1987 and this Code Version was frozen.

There are three objectives for the Report: (1) to provide detailed information on the quality of closure equations, that is, cri correlations, models, and/or criteria used in the code, (2) to describe how these closure relations are coded in the program and to assure that what is listed in the code manual is indeed what the code uses, ard (3) to provide a technical rationale and justification for using these closure relations as coded in the program in the range of interest to NPP safety evaluations. Further, the Report will provide:

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a. The original rrodel, ccrrelation, source or reference, data base, accuracy, and applicability to NPP conditions.

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b. Assessment of effects if the model/ correlation is applied outside its data base. l

c. Implementation of the model/ccrrelation in the code,

d. Description of modifications required to overcome compu-tational difficulties,

e. Assessnient of effects of implementation ard/or modifica- l tion on overall code applicability and accuracy. I i

In response to Mr. Ward, Dr. Knight said the compiling of the l Report resulted in an audit for the "correctness" of the code models and correlations. In response to Dr. Catton, Dr. Zuber said if the QA Report highlights a problem with a particular model or correlation, then the uncertainty has to be increased for this

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. T/H Phenomena Minutes January 20-21, 1988 problem Item or a sensitivity analysis is required. In response to further questions from Dr. Catton, Dr. Knight said that sensitivity calculations of integral plant transients were beyond the scope of the Report.

Mr. Schrock cited a particular heat transfer correlation developed by Theofanous to illustrate the point that LANL has not addressed the issue of sensitivity of correlations to the overall code uncertainty; i.e., The code developer has taken license with correlations to the point the results are meaningless. Dr. Zuber said such a problem would be addressed in the overall uncertainty analysis by requiring a sensitivity analysis of such problem points. Dr. Knight indicated such "errors" point to areas needing additional development. In response to Dr. Kerr, Dr. Knight indicated that "sins of the past" (e.g., tune correlations to get them to run in the code independent of the actual physics involved) are coming to light and "band aid" fixes were used in lieu of addressing the central problem (s) at hand.

Dr. Tien succested the focus of the work be on the key, or most important, phenomena or ,,lements in the code (i.e., what are the key code sensitivities). Mr. Spore (LANL) was in agreement with Dr. Tien's approach, but said such work was, again, outside the secpe of this Report. Dr. Tien asked for documentation that l highlights key phenomena for a given transient. Dr. Zuber said the l

CSAU methodolecy will require such an effort; Dr. Spore said this would probably be done through code applicability reports.

Mr. Schrock noted concerns with the neutronics and neutron kinetics modeling in TRAC. After some discussion, it was noted that input options allow update of the neutronics. Mr. Schrock said such an 1 approach results in the User being the key determinant in the  !

code's ability to calculate a given scenario. There were

, a T/H Phenonena Minutes January 20-21, 1988 additional questions on the code's ability to model different accident scenarios.

LANL considers the following items outside the QA Report scope:

(1) balance-of-plant modeling, (2) trips, control blocks, signal variables, (3) derivation of the code's field equations, and (4) nurerical solution techniques. Dr. Catton felt a discussion of the code's nunerics should be included in the QA Report. Figure 1 '

details the structure of the QA Report.

4 T. Knight began detailed review of the 0A Report by discussing the code's field equatiens (Chapter 2). LANL provided discussion of these equations in order to provide a basis of understanding the rec,uired closure relations in TRAC.

Details of the field eouations were provided (Figs. 2-5). Points noted included:

The condensation heat transfer model has been the subject of extensive NRC/LANL discussion. The model has not been im-proved for some time (6/5 years).

• Mr. Schrock noted that there are errors in the closure parame-ters for the kinetics models and additional instruction tc the user is necessary. LANL indicated agreement with Schrock's concern.

5. The details of the TRAC flow regime maps were provided by D. Liles (LANL). He noted that the flow regime map gives a basis prescrip-tion for determining both interfacial heat transfer and interfacial drag. As a consequence, the most reaningful comparisons are for the interfacial cuantities actually used in the field equations.

Some special purpose maps are used in selected cor?onents such as 4

T/H Phenonena Minutes January 20-21, 1988 the accumulator, pressurizer, turbine, and the core region in the vessel during reflood. Otherwise the basic map is divided into horizcntal and vertical regimes. Figures 6-7 detail the horizontal and vertical maps used in the code. Discussion raised the follow-ing points:

Assessment of the flow regime maps show that the transition from bubbly to slug flow is accurate. The transition to  ;

annular-mist is not very accurate. Recent data also show that slug flow may occur at higher void fractions, but may not occur in larger pipes (D>0.1m). For large diameter pipes, the horizontal flow map underpredicts the vapor velocity at i l

vhich transition cccurs. Dr. Catton indicated that for blowdown modeling, a quite simple flow flow regime rodel will l

suffice. Dr. Catton also said this chapter material does not '

greatly impact the LB LOCA uncertainty.

• Dr. Plesset questioned the usefulness of the vertical flow map. Dr. Liles (LANL) said the code treats the discontinuities by smoothing functions. Dr. Plesset asked if the validity of the code's results are worth the complexity introduced by the modeling. Dr. Liles indicated, in his ,

opinion, it does. Dr. Plesset remained skeptical of the trade i offs involved. In response to Mr. Ward, Dr. Tien said the l code is overly complicated here, and since the code still models ..ie relevant phenomena fairly well, a more global approach (e.g., drift flux modeling) may suffice.

Dr. Zuber showed some slides that give a comparison of the LANL and Dukler flow regime maps. His point was that the code's nap works fairly well as the LANL map results falls within the other regimes. l In response to Dr. Kerr, Dr. Zuber agreed the code is carrying "too 1

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January 20-21, 1988 T/H Phenomena Minutes much Laggage," but the central problem it ..ot in the physics, rather it is in the numerics.

In conclusion, Dr. Liles noted that large scale facilities (i.e.,

UPTF) experimental results suggest that the flow regime is nct well predicted during part of a LOCA transient in the downcomer, upper plenum, and hot-legs. Work is being done in these areas.

6. K. Pasamehmethoglu detailed the fluid energy closure equations used to model interfacial heat transfer. He sumarized the models and constitutive relationships coded within the interfacial heat transfer package of TRAC-PF1/M00-1.

LANL reviewed the details of the various flow regime correlations used in the code (bubbly, slug, bubble-slug transition, annuler- ,

rii st , etc. ) . Highlights of the presentation included:

• Or. Cetton questioned the validity of the bubbly flow model (Figs 8-9). After some discussion, he suggested that a simpler model may be more useful here. Mr. Schreck noted an error in the equation cited here and urged LANL to address it.

• The basis for using a LANL entrainment model over another .

developed by Kataoka and Ishii was questioned by Dr. Catton (Fig. 10). LANL agreed this model is deficient and needs to be corrected.

• Mr. Schrock questioned the tendency of LANL to adjust the interfacial shear equation. Discussion indicated that the shear equation has been adjusted to obtain agreement with data, i

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T/H Phenomena Minutes January 20-21, 1988

• The condensation equation used by LANL was criticized for employing an inappropriate model (constant Stanton Pember).

Here again, LANL indicated that the correlation used gave fairly acceptable results, which allowed the code to run properly. LANL recognizes the need for a fix here.

In conclusion, LANL noted that:

• A few incensistencies exist within the Interfacial Heat Transport (IHT) package. They have been fixed in M00-2.

• Selection logic between different models is appropriate and well coded.

• The coding used has the merit of allowing future improvements on lHT rrodels with minimum effort.

• In general, IHT models are in agreement with the governing physics of quasi-steady reactor transients.

• Future improvenents of IHT models are required. However, the performence of the IHT package is very much dependent on other I packages, especially the flow-regire map. l

' Transient and/or history-effect correlations must be modified before being implemented into the code.

In response to Dr. Kerr, LANL said the code is "correct" via the basic physics, but improvements are required in IHT models. As a l result of furt5er discussions on this point, it was noted that I while the rrodels may be qualitatively correct, the physics of the I code is somewhat suspect. Dr. Plesset observed that the overall l

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• The condensation equation used by LANL was criticized for employing an inappropriate model (constant Stanton Pember).

Here again, LANL indicated that the correlation used gave fairly acceptable results, which allowed the code to run properly. LANL recognizes the need for a fix here.

In conclusion, LANL noted that:

• A few inconsistencies exist within the Interfacial Heat Transport (IHT) package. They have been fixed in MOD-2.

Selection logic between different models is appropriate and well coded.

• The coding used has the merit of allowing future improvements on IHT nodels with minimum effort.

• In general, IHT models are in agreement with the governing physics of quasi-steady reactor transients, i,

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• Future improvenents of IHT models are required. However, the t

performance of the IHT package is very much dependent on other '

packages, especially the flow-regime map.

• Transient and/or history-effect correlations must be modified before being implemented into the code. ,

In response to Dr. Kerr, LANL said the code is "correct" via the basic physics, but improvements are required in IHT models. As a ,

result of further discussions on this point, it was noted that while the models may be qualitatively correct, the physics of the code is somewhat suspect. Dr. Plesset observed that the overall l

T/H Phenomena Minutes January 20-21, 1988 objective shoulo be to assure that the code can correctly calculate the safety of reactor operations via accidents and transients.

7. The details of the fluid energy closure equations for wall-to-fluid heat transfer were presented by R. Nelson of LANL (Chapter 4). Mr.

Nelsen addressed the following:

- Total wall heat flux and phasic wall heat fluxes

- Methods for defining phasic wall heat fluxes

- Heat-transfer regimes

- Fost-CHF well heat transfer including:

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• Transition boiling

• Film boiling TRAC uses a phasic heat transfer regine approach (Fig.11). In response to Dr. Kerr, Dr. Zuber said that from new on, all NRC sponsored codes will be required to provide a QA Report in order to document the rationale for the models and correlations used. As a J result of further discussion, sparked by questions from Dr. Plesset on the ability to model temperature distribution (wall to fluid),

it was noted that the modeling approach used by LANL introduces a  :

systematic error in the code. It w6s suggested that some of the correlations could be set to zero as these components contribute l

. little to the calculational result. LANL agreed with the Subcommittee's suggestion.

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T/H Phenomena Minutes January 20-21, 1988 The concepts underlying the post-CHF wall heat transfer correlation T

were detailed. This included the derivation of min (mimum CHF temp.) and transition boiling. Dr. Tien congratulated Mr. Nelson on the Tmin model; he said the basic physics of this process are well ha. idled in the code.

LANL showed results of TRAC post-CHF calculations compared with data. The results indicate that the film boiling vapor correlation is acceptable, but the lic,uid correlation has problems (at low void faction). In response to Dr. Zuber, it was noted by LANL that the results of the post-CHF calculations (PCT) give good results, but for the wrong reasons (i.e., the model is deficient).  !

6. The fluN . Tass closure equations were reviewed by R. Nelson. The i recuirements for mass closure were discussed (Fig. 12). Mr. Nelson sumarized his presentation by noted the following:

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- Application of Dalten's law above 1MPa is in c.uestion due to the non-ideal nature of steam. Influence of this non-ideal behavior has not been assessed.

- Evaporation of liquid into a gas mixture is not modeled.  ;

- Modeling of effect of noncondensables on vapor-side heat-transfer is in question.

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9. M. Cappiello described the interfacial drag model used in the fluid

momentum closure equations. Mr. Cappiello noted the currelations and models used are mechanistic quasi-steady state. The apparent mass and Basset force are neglected. Transition criteria are based on the flow regine map (void fraction and mass flux), except for

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the horizontal stratified flow model which is based on critical i s

velocities. LANL detailed the correlations and models for:

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l T/H Phenomena Minutes January 20-21, 1988 interfacial drag, bubbly-slug flow, annular-mist flow, stratified flow, transitions between regimes, the core reflood model, and process models. During discussion of the details of the above information, it was noted that a correlation used in the reflood model (Rosen pool entrainment correlation) did not provide good resul ts . Subcormittee consultants said this correlation is out-dated and should be replaced. LANL agreed.

10. J. Spore discussed the wall drag correlations used in the fluid momentum closure equations. Two wall drag models (ID & 3D) are used (Fig. 13). Sumary remarks were given as follows:

• TRAC-PF1/M00-1 wall-drag model appears to be adequate for most full-scale applications if the homogeneous wall-drag model option is selected.

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• The TRAC annular-flow wall-drag model should not be used. It has been removed from TRAC PF1/ MOD-2. ,

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• Pipe roughness effects must be simulated with an additive friction factor in the TRAC-PF1/ MOD-1 code.

• The TRAC-PF1/M00-2 code accurately models laminar flow regimes and includes accurate models for surface roughness effects. l l

l In response to Dr. Plesset, Mr. Spore indicated that the wall drag term has little irrpact on the overall results. Mr. Schrock said the partitioning of wall drag terms as is done in TRAC is non-physical.

11. The flow process models were reviewed by Ms. L. Guffe of SAIC. The characteristics of the 1-D abrupt area change model used are: (1) l it is turned on at user-specified cell edges, (2) it calculates, i

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T/H Phenomena Minutes January 20-21, 1988 additive loss coefficients - abrupt expansion, abrupt contraction, and thin-plate sharp-edge orifice, and (3) it is added into the momentur equations to correctly predict pressure losses across abrupt area change. Figures 14-17 provide the details. This model calculates correct pressure losses calculated for abrupt expansions and abrupt contractions at interfaces where the model is turned on, but there is a variable error for the case of sharp-edged, thin-plate orifice.

A 1-D critical ficw model is also used in TRAC. Figure 18 details the model. Three critical flow models are used for: subcooled liquid, two-phase two-component fluid, and single phase vapor (either one or two coeponents asneeded). A CCFL model is also available as a User option (Fig. 19).

Mr. Schrock noted a number of problems with the TRAC critical flow model. In particular, he took exception to the interpretation of j Dr. O. Jones' rodel as used in the subcooled liquid correlation.

In response to Mr. Michelson, Dr. Zuber indicated TRAC will not provide a good result for n.odeling the T/H effects seen after valve closure upstream of a pipe break.

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12. The special component models used in TRAC were reviewed by T.

1 Spore. The models are for: the pump, steam / water separator, fill, break, and plenum. Figures 20-26 detail the model descriptions.

13. T. Knight reviewed some of the additional mass field closure ecuations contained in TRAC. Specifically, he reviewed the non-condensable(NC) gas,andliquidsolute(boron)models(Figs.

27-28). The NC gas model is considered by LANL to be sufficient, but is functionally denndent on the specific heat tenn for con-stant pressure. The liquid solute model does not reflect reality

T/P phenomena Minutes January 20-21, 1988 i

at typical (reactor) temperatures. The assumptions used to model plate out are questionable.

1 14 T. Knight provided surrary remarks on the QA Report. Key points noted were:

• The document is well structured and it is relatively easy to fir.d the discussion concerning a given model. Also, each collection of related correlations and models modifies the basic flow-regime map to acccunt for the amount of knowledge available about a given phenomenon.

There is no single, central finding (s) or research result on l which to focus cenclusions. This is good news; it indicates

] that the level of quality in the code is fairly uniforn.

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• The document shows some deficiencies in individual models, j althcugh integral assessment indicates that the o' erall '

i package generally performs well. The integral results also indicate that identifying the correct flow regime is occasion-ally a problem.

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• The process of writing the document identified minor inconsis-j tencies within the code that should be fixed.

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• TRAC-PF1/ MOD-1 is a very useful analysis tool capable of j j simulating many trensients. This document supports applica- l tions of the code and aids in understanding the results. i i

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' The closure relations, together with the flow-regime map, must

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be worked as a complete package to improve results.

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T/H Phenomena Minutes January 20-21, 1988 Figures 29-31 lists the errors found in the 14.3 Version to date as a result of compiling the QA Report.

15. The Subcomittee Members and Consultants were asked by the Chairman to provide their comments on the TRAC QA document. Mr. Ward said that, at L. Shotkin's suggestion, Dr. D. Liles will provide a ,

presentation on the history of TRAC development.

Highlights of the Members and Consultants' coments on the report er.d. (at the Chairman's request) response to the question of whether or not the report supports closecut of the LB LOCA issue, were:

Dr. Plesset - Supports closure of the LB LOCA issue. He said the QA Report was "pedestrian". LAiil did not live up to their reputa-tior for high technical work with this product. The work on TRAC should be ended. The code is difficult to use and puts a trenendous burden on the user. All work on it should end.  ;

Dr. Mark agreed TRAC is difficult to use. He asked Dr. Plesset if  !

l he knew of a simple code one could use for LB LOCA calculation.

Dr. Plesset felt that LANL could have been more critical in their i analysis of the code via this Report. In response to Mr.

Michelson, Dr. Plesset said some more code work is needed on a global, simpler, plane. A code for use in training operators would be of great value. Dr. Mark said a simpler code of some sort will be needed for analysis of the hydrodynamics of the advanced LWR designs.

Dr. Tien - The QA Report is useful and informative for a first-time effort. It is necessary. TRAC models complex phenomena; consider-i ing this, LANL has done well with it. Some of the areas (e.g.,

flow regimes) are very challenging to model. There is, even today, e a lack of needed data to further develop and verify these models.

T/H Phenomena Minutes January 20-21, 1988 1 1

In other areas,1ANL was too detailed in their modeling. A major problem with the code was a lack of a more global modeling ap-proach. The results of calculations with TRAC show a more simple approach will work. The LB LOCA effort should be closed out. NRC should keep the code frozen, but correct the known significant errors. Some further research on code simplification is called for, but not on a major scale.  ;

In response to Mr. Ward, Dr. Tien clarified his remarks to note that research on flow regime modeling and interfacial transport is still needed. The research effort here can be modest.

Mr. Schrock - Is in substant161 agreement with Drs. Plesset and Tien. He said he shares the view noted in a recent meeting report from Dr. Catten that the QA Report is disappointing. The report fails to address problems identified by the Advanced Code Review Group as long as 10 years ago. The problem here is with the  !

philosophy of the code developer which results in creation of correlations on an ad-hoc basis. He agrees that there is no need for further develooment of the advanced codes; what is needed is work to demonstrate that TRAC can indeed "scale up" calculations to a full size plant. NRC RES will have a difficult problem with the error assessment for TRAC. Mr. Schrock was concerned with the lack of a rigorous statistical assessment of the TRAC calculational uncertainty. He agreed with Dr. Plesset's coment on the lack of critical assessment by LANL via model and correlation use in TRAC.

Noding is also a problem. Mr. Schreck indicated that the TRAC l

i noding is not user friendly. The success of the code use should not rest on such user options as noding selection.

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T/H Fhenomena Minutes January 20-21, 1988 On closure of the LB LOCA issue, Mr. Schrock said he doesn't feel it can be declared a dead issue. He said we need to put the issue in perspective end decide what we need to do via reactor safety.

Mr. Ward oefined wFat he means by "closure" of the LB LOCA Issue, be iritially believed the issue had been closed by the regulatione, (10 CFR 50.46 and Appendix K). Recently, Cor.gress indicated that something should be done with the LOCA related research knowledge gainedovertheyears,e.g.,allowuseofrealistic(bestestimate) analysis to relax licensing restrictions and increase power output.

The ACRS has stated that use of realistic analysis enhanced reactor safety. However, use of BE models requires evaluation of the uncertaintics associated with use of realistic models - hence the problems we see here. In this sense, we have "reopened" the LB LOCA issue.

Dr. Kerr asked Mr. Schrock if we can be confident in predicting a PCl that will give a reasonable damage estimate. Mr. Schrock said the CSAU riethod may show we can get a "good" PCT estimate, but based on the QA P.eport, he is uneasy. He felt that the Report should have addressed the code's sensitivity. He is not confident one can calculate to within 3-400*F.

Dr. Catton said test data sFows one can evaluate the blowdown tests, minus the codes, to obtain a 1 150 F uncertainty on PCT. He also said part of the problems the code developers have had resulted from choices made by the NRC many years ago.

Dr. Catton - The QA document will tell one what's in the code. The "dirty laundry" is all there. There should be a sensitivity study done as well. He was surprised at the number of ad-hoc corre-lations in TRAC. The report needs to address numerics and nodali-zation. One cannot draw any conclusions on code uncertainty via this report above. There are too many violations of physics. You

T/H Phenomena Minutes January 20-21, 1988 I

must compare TRAC with experiments on a consistent basis. The CSAU method has done this with amazingly good results. One does not need to use TRAC for LB LOCA analyses. Dr. Catton ob,iects to putting incorrect physics in a code. The report also needs to adoress SB LOCA as well.

Mr. Schreck reiterated his belief that TRAC cannot analyze T/H phenomena post-blowdown. He noted the recent concern with long term cooling post-LOCA with W plants and doubted TRAC could cor-rectly model this. He said TRAC is not the first principle code it was touted to be. He also criticized the assessment progran as it failed to identify problem areas needing additional experimental

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vork or further analytis.

Dr. D. Liles yovided coments on TRAC development and future plans. Development of the code becan in 1974 with the P-1 version.

Figure 32 details the development history. Dr. Liles noted that after the PFl/M00-1 version was frozen, LANL was prohibited from ,

revising models that they knew were in need of change. Work has continued on a pre-release version of MOD-2.

The current development plans for TP.AC (PF1-MOD-1 Version 14.3) were discussed (Fig. 33). In addition, there will be an evaluation of some models for possible revision before release of MOD-2 in June 1989 (Fig. 34).

I i Mr. Ward asked if TRAC code users should be "qualified". Dr. Liles

] indicated that by use of users guidelines, the friendlessness

problem can be mitigated. Other efforts in this area can be done, pending availability of more funding. Dr. Tien seid the develop-ment is too far ahead of the physics in the code. NRC should stop and reevaluate this before more development is done. Dr. Liles was i in gereral agreement with this point, but said some development is a

T/H Phenomena Minutes January 20-21, 1988 i

justified if you want to run certM n transients at all, albeit the results may be "bare bones". D . Catton indicated LANL is way out en a limb here and more data is needed to firm up the modeling.

16. h. Zuber introduced the discussion on the CSAU methodology.

G. Wilson provided a status report on the CSAU developraent and deronstraticn effort. Mr. Wilson began by overviewing the CSAU L n.ethodology (Fig. 35). The methudology is considered a general l process but, in its use, is specific in application (i.e., for a given code modeling a Diven scenario).

The initial application of CSAU to a four-loop W plant for a LB LOCA gave a 95% probability bcunding PCT value of 1379'F for the blowdown peak only. RES is currently working on the PCT demon-

stration for the reflood peak.

The details of the above calculation, as keyed to the various CSAU i steps noted in Figure 35, were shown. Figures 36-46 provide the 1 details. Key points noted during the discussion were: -

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• In respense to Mr. Schrock, Dr. Zuber said the procedure used to evaluate the code uncertainty was the top-down approach; i.e., the everall uncertainty was determined, not the uncer- l

] tainty for each rodel in the code. Dr. Tien said the uncer-tainty for the inputs to the code should be evaluated. Dr. j Zuber said the number of parameters involved precludes such an .

appreach.

• There was a bias of 100*F added to the evaluation of total code uncertainty to account for the uncertainties not expli-

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citly evaluated in the CSAU method. Dr. Catton said he

believes this bias is too high.

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• G. Wilson observed that he believes the CSAU method works, and is general in rature. The method can be successfully used to develop an uncertainty calculation for any code.

Dr. Catton provided ccmrents on the Peer Review Group Meeting held on January 12-13, 1988 to review the CSAU methodology. He noted that, overall, the Group appeared to find the method acceptable, subject to the following reservations / comments:

• A more prescriptive statement of the CSAU method is needed.

• More work is needed on the code nodalization.

• The Group was skeptical of the argument that no scale effect

, is evident for the LB LOCA blowdown experiments analyzed.

• For the code uncertainty eralysis, there was concern that NRC did not perform a simultaneous variance of the T/H paraneters.

Also the CSAU uncertainty analysis should be compared with a similar effort underway by W for their new BE (OCA Podel.

• The code's inability to converge should be evaluated by 4 additional conparison to experimental results.

• The issue of applying CSAU to BWR analyses was raised. The Group wondered why this had not been explored, and al:o questioned whether a sufficient experimental data base exists

to successfully apply CSAU hs-*.

Concern was expressed that NRC may not possess the technical enmpetence to audit an industry BE LOCA code submittal.  :

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T/H Phenomena Minutes January 20-21, 1988

• The Group indicated general satisfaction with the results presented for blowdown, but cautioned that the reflood analysis will be mort difficult.

I N. Zuber discussed the schedule for completion of the CSAU method demonstration. Figures 47-48 provide details. The entire CSAU development effort should be complete with issuance of a report by i

June 30, 1988. Dr. Zuber also comented that the QA report was disappointing to him on a technical level. The report is rieeded however to determine code uncertainty. He also believes that the CSAU demonstration has been, and will ultimately be, successful.

He also said he does not believe further TRAC development work is necessary - the code is adequately mature for use on reactor licensing issues, i

17. Mr. N. Lauben (NRC/RES) reviewed the status of CE, GE and W activ-ities relatt:d to use of best estimate (BE) ECCS licensing method- ,

ologies. The list of vendor methodologies currently in-house for NRC review is given in Figure 49. Currently, CE, GE & }{ are using the "BE" method described in SECY Paper 83-472.

The chronology / status of the GE BE model review was described (Fig.

50). GE had submitted a new model to cover their non-jet pump plants which, at our choice, ACRS did not review. Details of the new GE LOCA model were provided (Figs. 51-53).

The W, and CE, UPI LOCA medels were reviewed. Need for these new models arose because the original UPI LOCA codes modeled ECC injection into the cold legs instead of the upper plenum as is the actual case. W and CE submitted new models for NRR Staff review in 1986-87. In response to questions from Messrs. Catton and liichelson, Mr. Lauben indicated that he felt the CSAV methodology

R T/H Phenomena Minutes January 20-21, 1988 was needed in order to assure sufficient consistency and discipline in NRR reviews of the various BE LOCA models.

The status of the W BE LOCA model described above was noted. ACRS review of the rrodel and its application to 2-loop plants is scheduled for NJune 1988. Figure 54 shows the calculational

scheme for the W BE LOCA model.

The schedule for the CE BE code review by NRC was described (Fig.

55). NRR had requested RES assistance for this review, fir. Lauben indicated that the current version of the CE code has significant problers and will require additional work. He said the quality of the submittal was disappointing. This message will be transmitted to NRR from RES by letter in the near future.

In response to Mr. Ward, Mr. Lauben said the proposed ECCS Rule 1 dovetails very well with the recuirements of SECY 83-472 vis-a-vis the use of BE codes for LOCA licensing calculations.

1 i 18. L. Shatkin (RES) discussed the NRC-RES research on advanced LWR designs. There are four Projects for large ( " 1000 kWe) plants, and two (W AP-600 and GE SBWR) mid size (*600 We) plant projects.

For the large plants, RES currently sees no need for new T/H j experiments or code assessment, because there are no new design i features. NRR will review the T/H design aspects in FY 88-89.

I J

For mid size plants, the basic approach is that Industry will do ]

all necessary research; NRC will perform confirmatory research as needed. The T/H research areas that need to be addressed for the j ABWR include:

l (1) TRAC /G (GE version of TRAC-BWR) modifications inde and analyses completed.

i [

T/H Phencmena Minutes January 20-21, 1988 L

(2) Gravitydrivencoolingsystem(GDCS). ,

(3) Steam injcetor system.

(4) Depressurization valve to allow depressurization so GDCS can operate.

s Itens ?-4 are new features that may require confirraatory research on a T/f! basis.

The W AF-600 plant design has the following new features:

' High inertic canned motor pump development ar.d testing.

• Hydroball incore instrumentation system (ICIS) development and testiro. t

- Strings of metal balls inserted and removed from core by reactor coolant and scanned for activation levels outside Core.

• Additioncl development of RCS design sper:ifics, e.g., passive safety injection system Mr. Ward asked if RES expects some confirmatory research will be needed for these advanced designs. Dr. Shotkin said he believes there will be sore needs here.

19. L. Shotkin cemented on the T/H code development vis-a-vis the RES T/H Five Year Plan. He provided a time chart for the on-going l

and/or planned T/H research products (Fig, 56). All code develop-ment work is scheduled to end in June 1989, although other related l

T/H Phenomene Minutes January 20-21, 1988  ;

T/H research will continue beyond this date. Points noted includ-ed:

)

• There are two ICAP Consortia agreements: one with the FRG using RELAP-5 M00-3 and another with several countries using TFAC-PF1/ MOD-2.

• In response to Mr. k'ard, Dr. Shotkin noted that the M00-2 version of TRAC was developed to meet cormitments to the ICAP participents. The modifications to be made to the PF1/M00-1 version were done to address contaitments to the 2D/3D Program.

• RES is starting work on "accident management." The current versions of TRAC and PELAP-5 are being used for evaluation of in-vessel accident concerns via this research area. RES plans e Software Experts' Meeting to help define what additional code development, if any, is needed.

• RES is expecting to be working on advanced reactors 1/H research starting in late FY 89.

20. The meeting was adjcurned at 3:30 p.m. on January 21, 1988.

NOTE: Additional meeting details can be obtained from a transcript of this meeting available in the NRC Public Document Room, 1717 H Street , N.W. , Washington, D.C., or can be purchased from ACE-Federal Reporters, 444 North Capitol Street, Suite 402, Washington, D.C. 20001,(202)347-3700.

u

Document Structure Chapter '

1: Introduction 2: Field Equations 3: Flow-Regime Map 4: Fluid Energy Closure 5: Fluid Mass Closure 6: Fluid Momentum Closure 7: Heat-Structure Process Models 8: Flow Process Models 9: Special Component Models 10: Additional Mass-Field Closure 11: Summary and Conclusions Appendix A: Water Properties Appendix B: Material Properties l

l l

l l

j TRAC PF1/M001 CorroIntions and Models: Introduction 1120i68 9

Basic Definitions TRAC-PF1/ MOD 1 Two Fluid: liquid and gas Three Component: water, noncondensable gas, liquid solute 1D and 3D thermal hydraulics 1D and 2D heat conduction Point reactor kinetics Independent Variable t= time, and f = position.

Subscripts a= term applying to noncondensable gas, g= term applying to a general mixture of water vapor l and noncondensable gas, t= term applying to liquid water, and v= term applying to water vapor.

I l

l TRAC.PF1/ MOD 1 Correlations and Models: Field Equations 1/20/88 5 J

jhbh

Total Energy Equation (2-1) 6 l(1 - a)ptet + apg eg; V. (1 - a)ptet N t + agg ge9g at , _

= -pv .  ;(1 - a)Ve + aV a.,

+ qwe + qwo + Gdt + qdo Combined-Gas Energy Equation (2-2)

ON"P0'0} + V (apg geV)=-P g g -PV ' (a a)

+ qwo + qdo + qio + Th',

Liquid Mass Equation (2-3) 6((1-a)p[. 9, _9)p p = _p 8t Combined-Gas Mass Equation (2-4) 6(apg) 7, p_p at l

Total Mass Equation (2-7)

S [(1 - a)pt + agg. 9, 1 - a)ptNe + agg9; g =0 8t

• TRAC PF1/ MOD 1 Correlations and Models: Flaid Equations 1/20/88 6

Liquid Equation of Motion (2-5)

- <- 1 c'-

BVe + Ve VVe = - pt Vp + (V (1 g - V )

- a)pt t Vg - Ve 8t c,e r- -

g t

Ve Vi +y (1 - a)pe (V - V ) - (1 - a)pt Combined-Gas Equation of Motion (2-6)

- - 1 BV* + aV VV o = - -Vp o t Vo - Vi Ot Po GPoc'- (V - V )

g t

• • gV Vg +y GPo(V-V) GPo Noncondensable-Gas Mass Equation (2 -- 13) ,

8(apa) + V * (aPaVo ) = 0 8t Liquid-Solute Concentration Equation (2-17) 8 '(1 - a)mpt

+ V ;(1 - a)mptVe, = Sm l 8t 1

l Heat Conduction (2-91)

BT pcp g = V - (kVT) + q"'

TRAC PF1/ MOD 1 Correlations and Models: Fleid Equations 1/20/88 7 -

Point-Reactor Kinetics Thermal Power (2-113) dP R-p S dt

=

A P + [ Ai Ci + A(1 - R) t=1 Delayed-Neutron Concentrations (2-114) dC'- = - A< Ce + 0;P , fo r 2 = 1, 2, . . . , I dt A Decay Heat (2-115) dHj = - A Hj + EjP , fo r j = 1, 2, . . . , J l

EfTective Power (2-116) f J ) J Peg = 1 - [Ej P + [ Af Hj + S

( j=1 ) i=1 l TRAC PF1/ MOD 1 Correlations and Models: Field Equetions 1/20/888

I HORIZONTAL MAP (Taite and Dukler) 1-D Components only t

• For the case of liquid upflow, allowed to  :

occur in pipe angles of up to 10 from the horizontal. j For the case of liquid downflow, allowed to i occur in pipe angles of up to 90 from the  !

horizontal.

I 1

Ua > c1 (pe - pg)g cos p Aa- 1/2 pg

' ( - 1)

. dAe/dhe ,

= he C1 1 D (3-2) l l

dAe =

dhe d2 - (2he - d)2 , (3-3)  !

TRAC PF1/M001 Correlations and Models flow Regime Map 3 m

[p/4.4)

t VERTICAL FLOW REGIME MAP

/

YLYN 7

o .

5 /

/

C sf

$ sumy

~

N o.o o.s g ho$Atio'Awwti.R'"5l o.5 0J5 to l Vapor Fraction a '

Applies to all pipe inclinations if the flow is not stratified.

• Slug flow uses linear weighting between a l l

void fraction of 0.3 and 0.5 for the bubble diameter. The bubble diameter is allowed to .'

i grow up to the size of the hydraulle diameter I

at a void fraction of 0.5. ,

l

• The interpolated region uses a cubic spline between the Interfacial values calculated for

bubbly-slug and annular-mist. Void fraction is used as the indeperidant variable.

l

\ TRAC.PF1/ MOD 1 Correlations and Models Flow Reginvr Map 4

. . _ _ _ _ . . _ _ ~- - - - _ _ _ _ . . _ _ _ .-. . - - - _ - - -

3C33LY FLCW "

i G -

mo-

• A i 6 a vol/D 3 , , , .

Is i where Wes = 7.5  ;

l 3 10" < Da < % .

O di O2 03 04 05 OS N7 OS $9 1 a

• If Ty > L, hig K.

1000 W/m  :

If Ty < L, hig 10,000 W/m K (Brucker and Sparrow,197/)

k

\ -

BCB3LY FLOW (cont.)

• :M T i < L St(Var) i 0. 02 If "i > L Xui(D3} YAX; Xu1, Xua ;

where Nu1: Lee and Ryley (1968)

Xu e: Plesset-Zwick (195?)

T N

h .

n ANXCLAR MST FLOW ALV = EEQxALVmist + (1 - EEQ)xALVmm CHTI = EEQxCHTImist + (1 - EEQ)xCHTImm 0 < EEQ = MAX (EEQ1, EEQ2) < 1 1

EEQ1: Kataoka and Ishii (1982)

EEQ2 = 1 - exp[0.5 (1 - V,/Vou)] (Los Alamos) e ,, ,. . . . . . . . . . . . . .....

/

c  :.

w n. m l

-- si N /

/

E

==-

p .

,/

%=Qtm eet: IshH and

. Kataoka g er = 0. 75 g (195$ 3 e = 0. 066 3%n pe = 9000 8

= ""

e i r

• I A = 20 o e's s'2 es o's es o'a e'7 es oo :

• a M N a y

t .

TRACiPF1-MOD 1 H'nt-Trrnsfor Regimea <

Regime Correlations Liquid vapor laminar & turbulent zero natural convection to liquid Rohsenow-Choi, Dittus-Boelter zero forced convection to liquid Chen natural convection, Dougall-Rohsenow nucleate boiling

/

Biasi CHF Griffth's interpolation on T, natural convection, Dougall-Rohsenow transition boiling minus the vapor portion Tg Henry-type Tm using homogeneous nucleation as contact temperature mod. Bromley, mod. Forslund- natural convection, Doty =11-Rohsenow film boiling Rohsenow zero turbulent natural convection,Sieder-Tate single-phase vapor i%-

zero; laminar & turbulent natural condensation laminar & turbulent natural convection, Nusselt convection,Chen(S=0);

b o(-interpolation x -

-'I L _ ---- __-_--_-_-_--__ _ --_

Required For Mass Closure Interfacial heat transfer models (reviewed under section 4.1)

- Subcooled boiling model

- Effect of noncondensables

. Dalton's law

. Influence of noncondensables on evaporation / condensation

<l l

1 1

l l

l

_l

/9/e.4A/ l

i%

WALL DRAG 1D Wall-Drag Model a), Homogeneous Single-Phase Model b) Homogeneous Two-Phase Model c) Annular Flow Single-Phase Model d) Annular Flow Two-Phase Model e) Horizontal Stratified Flow Two-Phase Model 3D Wall-Drag Model (a) Single-Phase Model '

(b) Two-Phase Model l

I 1

TRAC PF1/ MOD 1 Correlations and Models: Wall Drag 1/20/88 2 j $b*

GENERAL hODI\G: .

ASSUME: Horizontal, e e . .

steady, incompressible 3_g j_g gg gg flow, neglect friction.

F2 P1 j #1 P2

.1-D Momentum Equation:

.. 1/p (ap/ax) + V (aV/ax) = 0 integration + minor irreversible losses yields:

Apj ri = 0.5p(Vai 2 - Vj 2) + 0.5K,i.no.,epV.2 where V, is the velocity at the smaller x-section.

TRAC equilvalent it>' ng staggered finite diff. scheme):

Apav2 - pan = pV33 (Vai - Vj) + 0.5KwepV.2 l IMPORTANT RESULT:

K t.na.,4 # Kmc

l l

ABlUPT EXPANS ON POSmVE FIDW =

t e o e e j -M J - V2 j + V2 j+W j-2 j-1 j j+1 j+2 STANDARD: K i.ne.,e = ( 1 - Aj / Ari )2 Apj.i. j = 0 Apj.gi = pVai(Vri - Vj)

TRAC: KTRAC = 0 Apj w 4 ev2 = 0 Apav2 - nsn " P V ri(Vri - V 3) l RESULTS: Correct pressure drop in TRAC. 1 Shifted by 1 cell. j l

j O'

l: .  ;

l- ABRUPT CONTRACTION:

l POSITIVE FLOW =

e e o e j - 3/a j-@ j+@ j + 3/2 j+1 j+2 j-2 j-1 j STANDARD: K t.no.ro = experimental data (i.e. Massey,1968)

= 0.5 - 0.7(Aj/Aj.1) + O2(A /A 3

.3)2 3

Apj_i j = 0.5p(16Vj2- 0.7VjVj.i - 0.8V .3 3 2

)

Ap; pi = 0  ;

1 j

TRAC: Kwe = - 0.5 + 13(A;/Aj.i) + 0.8(A /Aj.i)2 3 1

2 Ap; v2 -. av2 = 0.5p(1.5Vj - 0.7VjV 3.i - 0.8V .,2) 3 Apj+v2 4 3+s/2 = 0 RESULTS: Correct pressure drop in TRAC.

Fitted to experimental data. -.

TH Y-P,_ ATE, SHARP-EDGED OR lCE:

1 l

POSITIVE FLOW =

e e e o j - 3/2 j-1/2 j + 1/2 j A 3/2

~

j-2 j-1 j j+1 j+2 l l

l l

STANDARD: K,1.no.ro = experimental data (i.e. Idel'Chik,1960)

= { 1 + 0.707[1 - (Aj/ Api)]v2 - (A/ Api) }2 l Apj.i.pi = 0.5pK(Vj - Vpi)2 1

F TRAC: KTRAC = - ( 1 - Aj / A3i )2 Apj.v2-as/2 = 0.5p(Vj - Vpi)2 RESULT: Variable error introduced in TRAC.

Full pressure drop calculated over 2 cells.

Error decreases as Aj approaches 0 or Aj.i.  !

l ll=M. >7]

l', ,

1-D CRmCAL FLOW IVODEL-l 9 Based on RELAP5 critical flow model.

l l

9 Turned on at user-specified cell interfaces.

i e UPPER UMIT to momentum sol'n velocities.

l l

e At Each Time Step:

_- 1. Calculate momentum sc!'n velocities.

2. Calculate critical flow velocities.

3. Compare momentum solution values to critical flow values.

4. New time step velocities =

MIN 4 Momentum, Critical D.

4 4

ffM15] 1

Counter Current Flow Limitation (CCFL)

• Available as an option to the user. This model is applied at user chosen axial cell edges in the 3-D Vessel component only.

• The user supplies CCFL correlation constants, and the code calculates an interfacial drag coefficient that is consistent with the liquid flux prescribed by the correlation.

Example, for a typical CCFL correlation:

VJ g + m VJi = C the constants m, and C are input.

• The input is general so that Wallis-scaling, '

Kutateladze-scaling, or a combination (Bankoff) can be used.

• Comparisons against tie-plate flooding data (Bankoff, et. al.) show good agreement for both  !

saturated and subcooled conditions.

TRAC-PFt/ MODI Correlallons and Models Flow Process Models

l PUMP COMPONENT The TRAC 1D momentum equation includes the pump head as a momentum source.

Because the flow is assumed to be homogeneous at the pump, only a mixture momentum equation is solved.

Wall shear is neglected within the pum p momentum solution and is assumed to be included within the pump head curves.

The VVV term from the TRAC momentum equation is neglected for the pump.

The steady-state solution for the TRAC momentum equation for the pump is that the aressure rise across the aump is equal to the pump head from the pump-head 1omologous curve.

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88 - 3

PUMP ASSESSMENT Accuracy of the pump modelis dependent upon accuracy of homologous curves.

Treatment of frictional torque is limited and should be generalized.

Assumption of homogeneous flow leaving the pump is not appropriate for stratified flow regimes, locked rotor pumps, or pumps at low pump speed.

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88 - 7

SEPARATOR COMPONENT MODEL The SEPD component has three phases:

1. Determination of the appropriate carryover

• and carryunder** returning for a given set of conditions.

2. Determination of the resulting separator exit flows and steam qualities, based on quasi-steady mass and momentum balances.

3. Circumvention of the normal solution so as to achieve those flows and qualities.

• Carryover is the liquid mass flow rate leaving the top of the separator divided by the total mass flow rate leaving the top of the separator.

• • Carryunder is the vapor mass fiow rate leaving the separator return divided by the total mass flow rate leaving the separator return.

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88 8

SEPARATOR COMPONENT MODEL CALCULATION OF CARRYOVER (XCO) &

l CARRYUNDER (XCU) l User Options

1. Constant user input values for xco and xcu.  ;

2. Mechanistic model supplied by INEL for GE steam / water separators. Default geometry is available or user may supply geometry.

3. User supplied performance data supplied in tabular l form. User can supply xco and xcu as function of l essentially any parameter or combination of parameters that is calculated by TRAC and stored as a signal variable. l I

(

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88 9 f/d E

l*

FILL COMPONENT The FILL component replaces the TRAC momentum equations at the cell edge connected to the fill with user-specified velocities.

Velocities can be user specified directly or inferred from user-specified mass fiow rates.

Velocities inferred from user-specified mass flow rates will be based on old time densities and void fractions; therefore, the inferred velocities may not duplicate the user-specified mass flow rates at the end of a given time step.

For flow into the component adjacent to the fill, the thermodynamic properties convected into the adjacent component are determined from the user-specified thermodynamic conditions in the fill.

l l

l l

l TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88- 10 l8d{

BREAK COMPONENT The BREAK component supplies a pressure boundary

( condition to the component to which the break is connected.

For flosv into the component adjacent to the break, the thermodynamic properties convected into the adjacent component are determined from the user-specified thermodynamic conditions in the BREAK component.

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88- 11 2

6

PLENUM COMPONENT MODEL Simple generalization of the one-dimensional flow modeling to a single-cell component with an arbitrary number of connections to other components.

Momentum flux within the PLENUM component is set to zero, therefore flow l

l l

TRAC PF1/ MOD 1 Correlations and Models: Special Component Models 1/20/88 12

l-Noncondensable Gas Single species: Air or Hydrogen, by input Thermodynamic properties:

Ideal gas o p constant Transport properties:

Viscosity; polynomial fit (Ref.10-1)

Thermalconductivity: constant d

r u...msca ar, 1noisa s rucmucos car.i.e.n. .nes.u.: aue p,H >0

Liquid Solute Single species: defaults to Boron for use with the reactivity feedback; can be changed ,

through input l Requires only a specification of solubility Special treatment of the field eqiiation i

l i

t 1/20188 6 TRAC-PFtM001 Caneletions and Modele: AddttionslNeen field Closure

-f flh* h

Code Errors in Version 14.3 Inconsi, stent average relative-velocity vector for interfacial drag in 3-D inconsistent lower limit in 3-D and 1-D as relative velocity goes to 0.0 (to prevent divide by zero)

Void fraction limits for momentum equations inconsistent among 1-D and three 3-D equations (to prevent divide by zero)

Application of inverted annular flow model inconsistent between 1-D and 3-D SEPARATOR model has a bug that causes code failure when it goes through an on, off, on cycle inconsistencies in the definitions of cell velocities -

in the 3-D ruce,mos ca.e-am m.ac.-w. uwes a jg Q

Code Errors (cont.)

Axial-fine mesh index in the ROD is off by 1 (only affects the calculation of H 2 mass production; does not feed back to thermal-hydraulic calculation)

Signal variables 25 and 26 incorrect - fuel rod centerline and outside temperatures in the critical flow model, for a mixture of gas and vapor, code checks gas (and vapor) temperature against saturation T based on total pressure instead of partial pressure of vapor For critical flow model, code uses mixture specific heat at constant volume instead of vapor parameter For critical flow model, code uses steam R instead of mixture R (gas constant)

In water properties, very small error in calculating steam enthalpy because of offset in reference point temperature p-

Ccde Errors (cont.)

Error in shifting tables when a single signal variable is used in more than one table One error and poor conversions in the material properties for electrically heated rods Need to resolve in the references inconsistencies on coefficients in front of a heat-transfer correlation Wall shear in the Z direction is also used for radial direction For the core wall drag, model attempts to account for liquid film, but as entrainment goes to zero or one, total wall drag is wrong 1

'f l 1/20188 6

- or11Mcos corntonions and sodok

summuy and conchoniene Jm.s] __

TRAC DEVELOPMENT HISTORY (Begun 11/97). p' TRAC 1 VERSION BELEASED APPLICATION FEATURES P1 12/77 LBLOCA 5 EQ. drift flux modelin pipes P1 A 3/79 LBLOCA Improved mass conservation PD2 10/80 LBLOCA & Two-fluid model in some SB 3D VESSEL, new LOCAs reflood modle.

PD2/ MOD 1 Error corrections small improvements PF1 7/81 LBLOCA & Two-fluid model most SB with two-step LOCAs numerics in 1D, noncondensable gas, trips, critical flow model.

l PF1/ MOD 1 12/83 LBLOCA & Full set of trips &

SBLOCAs, controllers and l operational full balance of  ;

transients, plant.

PF1/ MOD 1 was frozen 1/85 (only cerror corrections for the modelsw9a permitted). This was done to support ICAP assessment activities. Error corrections were no longer allowed after 9/87.

TRAC Development History and Plans 1/20/88 - 2 fjf/g, 3 ~

1 w_ .- .__ _ _---_ _ - - _ - - _ - - - - -

TRAC DEVELOPMENT PLANS G

CURRENT MODEL DEV.LOPMENT ACTIVITIES Improvements designed to improve UPTF predictions Replace Weber number sizing criteria with Ishii model for bubbles and droplets.

Use Ishii entrainment model only.

Redo Stanton number and examine interfacial area relations for condensation.  !

l Restrict slug diameter and examine basic drag correlations 1 Change Dukler horizontal flow critierion.

l Replace linear averaging for annular-mist flow.

Cleanup interfacial drag and heat transfer models (small l inconsistencies revealed during Q/A document research).

Examine the necessity of a special flow map for hutze (ECC HL nozzle), downcomer, lower plenum, a:1d upper plenum.

TRAC Development History and Plans 1/20/88 - 4 l

^^

FIVE-STARRED ITEMS FOR 2D/3D (planned improvements)

Downcomer penetration CCFL at tie plate Upper plenum entrainment Hot and cold leg injection Cleanup interfacial drag (small changes based on Q/A document)

TF. AC Development History and Plans 1/20/88- 6 l$. 31

l s -~ SCENAmo j

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i i.

P TOTAL (5+Ct4f AINTY TO CALCutATs 13 SPtCIP C $CENAR10 LN A setC:sc wee 2 C006 SCAUNG, APPtiCA8tuTY ANO UNCMTAINTY (CSAW M WtTN000000Y o  !

o CB N .

M lk.&

l THE IMPORTANT PHENOMENA / PROCESSES HAVE BEEN IDENTIFIED  !

(STEP 3): 1 o 'C0l#10N TO BLOWDOWN, REFILL & REFLOOD l STORED ENERGY, FUEL ROD TO FLUID BREAK CONVECTIVE FLOW, HEAT TRANSFER, PUMP TWO-PHASE FLOW o ADDITIONAL DURING REFILL & REFLOOD STEAM BINDING, ECCS BYPASS & DOWNCOMER PENETRATION, REFLOOD HEAT TRANSFER

~

COMPARISDN OF THE IMPORTANT PHENOMENA (STEP 3) WITH THE i

C0 tie CAPABILITY (OA REPORT & ASSESSMENTS) HAS IDENTIFIED THE NECESSARY UNCERTAINTY QUANTIFICATION (STEP 6)

IMPORTANT PHENOMENA IMPORTANT L'NCERTAINTY FROM PIRT PARAMETERS BREAK FLOW =-CD STORED ENERGY - GAP CONDUCTANCE

= PEAKING FACTOR l

- FUEL CONDUCTIVITY I FUEL R0D TO FLUID i = HT COEFICIENT CONVECTIVE HT =TMIN PUMP 2-PHASE FLOW  : HEAD CURVES i

- TORQUE CURVES l STEAM BINDING, ECCS = INTERFACIAL DRAG BYPASS & PENTRATION i

i

\ .

i THE CODE ASSE$SMENT MATRIX (STEP 7) IDENTIFIES THE SOURCE OF INFORMATION NEEDED TO COMPLETE STEPS 8 THROUGH 11 AREA 0F DATA BASE CON"FIBUTION DATA NPP CODE SCAL:: tG NF'P INPUT BASl! N0DALIZATION ACCURACY EFFECTS SENSITIVIII X X MARVIKEN SEMISCALE X ,

LOFT X X X X )

SCTF X i X X X CCTF X X UPTF THE STANDARD NPP liODEL HAS BEEN DEVELOPED TO CAPTURE IMPORTANT PHENOMENA BASED ON BOTH SET & IET ASSESSMENT STUDIES (STEP 8) o MODEL

SUMMARY

4 LOOPS (240 CELLS)15 LEVEL, 3 RING (180 CELLS)

VESSEL: 4-THETA 8GUIDETUBES(46 CELLS) -

FUEL RODS: 8 AVG, 22 SUPPLEMENTAL 460 TOTAL CELLS o NPP MODEL C'OMPARES FAVORABLE WITH LOFT IET MODEL a

[pa.5]

. 1 1

f THE CODE PLUS EXPERIMENT ACCURACY HAS BEEN ESTIMATED FO BOTH BLOWDOWN & REFLOOD (STEP 9)

NO. DATA POINTS BIAS STD DEVIATION DATA BASE BLOWDOWN:

27 23 of 120 of LOFT REFLOOD:

20 -3 of 120 of i CCTF & SCTF (BIAS = TCODE - TEXP)  !

i i

THE POTENTIAL FOR SCALE EFFECTS, DURING BLOWDOWN, HAS BEEN EVALUATED WITH EXPERIMENTAL DATA (STEP 10) o DATA BASE:

l 5 FACILITIES l 1/30000 < SCALE RANGE < 1/48  !

216 DATA POINTS  !

UNCERTAINTY AT 95 % C.L. = 360 0F o NO DISCERNIBLE SCALE EFFECT WITHIN ABOVE UNCERTAINTY NO CONSISTENT TREND WITH RESPECT TO SCALE RESULTS TEND TO CONFIRN OPINION THAT EXPERIMENTS ARE FULL SCALE WITH RESPECT TO FUEL RODS I

{F/6.31;

Maximum measured clad temperaturo from.sey rci scciad l

[Jdp. ggo n 00 fy N on /,/

I experimental f acilities (216 data points) 2300 . ... .... ......... - - - - - - - - --

- -- - APPENDIX K LIMIT mw

- i, v..e..SCALE

,A ciut y scAuNo ca:TERiote -

e _ v ,., Ro=~mvu .. .

!S

- O t$

..**,{

E 1800 a

- &lu; ;n;' ' -

e

- .. .. - e + Jr o y

- . .  ; g 3

~

1300

, . '.. .ge

,e,*d*

ey T3

. ... +' - .

• *f*

, t .....-

-sa'*

a  : ., +e.

d ' ,,g-4' ,3,.. -

l 800 af ...-

~

4 ~

',. ' 95% CONFCEPvCE . APCS

,,- _ Lih( AR REGRES$4CN LINE 300 O 5 10 15 20 UNEAR HE AT GENERATION R ATE (KWIFT)

THE POTENTIAL UNCERTAINTIES RESULTING FROM THE IMPORTANT PHENOMENA DETERMINED IN STEP 3 ARE QUANTIFIED WITH NPP MODEL CALCULATIONS (STEP 11) o INDIVIDUAL PARAMETERS ARE RANGED WITH EXPERIMENTAL DATA 1

l o 7 COMPUTER RUNS FOR BLOWDOWN PCT l o 140 PCTs SINGLE PARAMETER SELECTED CROSS PRODUCTS DOUBLE PARAMETER TRIPLE PARAMETER m

flb $f_

Calculation to Determine Effect on PCT by Core External and Core Internal Parameters r

= Supplemental Rods -

' Merage & Stored Cross Peaking Nominal  !

Energy Products Hot Rod Factors a

Nominal

{

cc CD Pump s r Trnin

' 22 Rods--

l~ 9 Rods -;:

an.

Uncertainty Results PCT (k) Nament APCT(k) 832 4 Nominal Case Critical Flow 938 106 1r 97 929 2r Pump 14 846 1r 36 868 2r Tmin 0 832

-20 8 840

+100 ,,s .....

P ft& 90

1 Uncertainty Results PCT APCT  ;

832 NOMINAL CASE STORED ENERGY 798 -34 l HGAP +80*4 916 84 i

-80%

770 -82 HCONV +25% 886 54

-25%

828 -4 KFUEL + 10 %

836 4

- 10 %  ;

1 PEAKING FACTOR 840 8 l

+6% -16 816

-6%

I CROSS PRODUCT - WORST CASE H 346 1178 H GAP CONV (-(80%)

-25%)

BREAK CD 1C Maximum calculated clad temperature vs. linear heat generation rate for nuclear power plant (23 calculated points).

2300 -

i

~ A PCT .t mid-pl.no

- 9 /CT .t other et.v.tlone

$ 1800 -

y -

a:

w a.

s -

1. 1300 -

o.s; J .

u $ *A .W*..... *.. -

o 3

800 -

g* ,*..... ....- n.or... ion iin. .no unc.rtainty b.nd from l

X - e,, . m p. rim.ni .: e.i.

j . ,,,,... ,... _

I....' ' ' ' ' ' ' ' ' ' ' ' ' '

300 5 10 15 20 0

LINEAR HEAT GENERATION RATE (KW/FT) f/6N/l;

, r ,- -

f '

l PROCEDURE TO OBTAIN UNCERTAINTY FRC "-= c> *ULATIONS WITH IMPORTANT PHENOMERA

' CODE ASSESSMENT 7 PARAMETERS 9

'

• SCALING e UNCERTAINTY ,

RANGE

• DISTRIBUTION i

NPP SENSITIVITY CALCULATIONS gi 140 PCT POINTS T

RESPONSE

SURFACE l 12

\

PCT : pdf S l RESul.T3 LGHR: 6-10 KWIFT 12 l IMEAN = 1106'F T.95 O g379ep a = 172'F l

EEiPARING THE RESPONSE SURFACE

• 7 PARAMETERS BASED ON P.IRT, RANGE BASED ON DATA. AND DISTRIByTIQNS TAKEN AS UNIFORM .

• UNIFORM DISTRIBUTION BEcAUSE IT IS THE DISTRIBUTION OF MAXIMUM LACK OF KNOWLEDGE

• 140 TRAC DATA POINT 5 CALCULATED FOR VARIOUS VALUES ON THE DISTRIBUTIONS 25% TRIPLE CROSS PRODUCTS 60% DousLE CROSS PRODUCTS lf/4.Oa]

~

PREPARING THE RESPONSE SURFACE (CONT D)

• VARIOUS FITTING SURFACES IN SEVEN VARIABLES

- LINEAR = 8 COEFFICIENTS LINEAR + QUADRATIC TERMS

= 15 COEFFICIENTS

- FULL SECOND DEGREE

= 36 COEFFICIENTS

• EFFECT oF VARYING DISTRIBUTIONS FINAL TRAC NPP 8 LOWDOWN UNCERTAINTY DISTRIBUTION r.eie 1 I

1tg Uncrtainty PartMtte lange, i

Paepete* NEf ael Vatue 4fafmue 88 8 s 1 % 9 0.$44 LV 1.056 LV Petala9 Fetter LOC 41 f alwe (LV)

Lv 0.2 Lv 1.8 LY 340 Coeductance 0.9 LY 1.1 LY Fwei Conductivity LV LV 0.75 Lv 1.5 Lf M

gyy f LV if . 20% LV

• 100%

ugg c3 c3 23' 03 + 25 Ire sa ,

Puse mo del (Mi 4 3.6t* M + 3.61

+ The eierest'en for 5 come, ,ro. Brocanavee and were pre,ented earlier.

.e.,.....,,

1,. ,,, . ..e. ,. ...,,...... ...

...ii. ,, i L .

l 9

N4 f53 ,

PROCEDURE TO OSTAM TOTAL UNCERTANTY FOR LBLOCA BLOWDOWN DO&MNANT 3 ,

PHENOMENA (PRT) i f f -

hET ] 8 [TEY }

• i f I f f

CODE ASSESSMENT TEST DATA CODE ASSESSMENT S 2T LOFT PCT 3 21s PCT T PARAMETERS S FACILITIES 10

• SCALING

• UNCERTAINTY

• BIAS

• SCALING

• t#4 CERTAINTY

• MEAN PCT RANGE p

• UNCERTAINTY

• DISTfufMITION RESULTS Nf'P GENSITIVITY BfAS = 23*F g RESULTS CALClt.ATIONS 11 Lum: 0-10 KWIFT

, 140 PCT POINES e = 1204

• MO SCALE EFFECT y 1340*F 4 18*5 - 15404 10 9804 = ,,,

4 11904 RESPONSE CNN l 2e = 361 SURFACE 12 ~ UNCERTAINT ES PCT : pdf 12 L 2e = 41T*F

• LE ACCOUNTMO RESULTS * -319T - APCT - 619T LGi#t: 6-f 0 KWIFT 12 TMEAN = 1106T 10 95 ,337g9 -

e= 1T2T TOTAL UNCERTANTY SIA3 : -190 4 13 I

e, T ...

e = 1F24

, , , 9,

% I COMBINATION OF UNCERTAINTIES IF DIFFERENT ASPECTS ARE INDEPENDENT THEN CONSINE

• IF DIFFERENT ASPECTS ARE HIGHLY DEPENDENT THEN COMPARE, DO NOT C9M53NE IF ONE INSISTS ON COMBINING. THEN ROOT SUN OF SQUARES OR ASSOLUTE ADDITION ADDITION EXCEEDS KNOWN DATA RANGE -

ADDITION fXCEEDS 100% OF TRAC NPP UNCERTAINTY DISTRIBUTION CONCLUDE THAT ADDITION IS OVERLY CONSERVATIVE COMBINATION OF UNCERTAINTIES (CONT'D)

ROOT SuH OF SQUARES EXCEEDS KNOWN DATA RANGE AND COVERS 99.6% OF TRAC NPP UNCERTAINTY RANGE CQNCLUDE THAT RSS IS QVERLY CONSERVATIVE

• THESE PRODUCE OVERLY CONSERVATIVE RESULTS BECAUSE OF EXTENSIVE DOUBLE COUNTING 1

)

i l

l COMBINATION OF UNCERTAINTIES (c0NT'D) '

1

• COMPARE RANGES

• CoNcLuog; 95% CENTRAL INTERVAL OF DISTRIBUTION ACCEPTABLE AND oNE-SIDED 95% LsMIT Is PR (T < 1379 F) = 0.95 9

l i

j lE!6 4't

-l l

CSAU SCHEDULE

) .

[

o PERFORM NPP CALCULATIONS BLOWDOWN

+ NOMINAL CASE COMPLETED

! + VARIATIONS FOR CRITICAL FLOW, COMPLETED i PUMP, THIN

+ VARIATION 5 FOR STORED ENERGY COMPLETED .'

+ CROSS PRODUCES FOR CRITICAL FEB 08, 1988 I FLOW AND PUMP

+ EVALUATE HOT CHANNEL MAR 01, 1988 I

REFLOOD i

l + NOMINAL CASE COMPLETED l + RANGE REFLOOD PARAMETERS MAR 01, 1988 l + CODE UPDATES MAR 15, 1988 l + VARIATIONS FOR ECC BYPASS, MAY 15, 1988 ENTRAINMENT, REFLOOD HEAT k* TRANSFER

+ .

D -

, %i N

l ,q l

CSAU SCHEDULE (CONTINUED)

I

o DEFINE CODE BIAS AND UNCERTAINTY BLOWDOWN MAR 15, 1988 REFLOOD JUN 01, 1988 l

o DOCUMENTATION l

PIRT MAR 01, 1988 CSAU JUN 30, 1988 LESSONS LEARNED JUN 30, 1988 1

i l

j

VENDOR B. E. METHODOLOGIES COMPLETE

+ GE - JET PUMP & NON-JET PUMP BWRs LB & SBLOCA UNDER REVIEW

+ W - TWO LOOP W UPI PWR LBLOCA UNDER REVIEW

+ CE - TWO LOOP W UPI PWR LBLOCA ON HOLD

+ CE - SBLOCA CE PWRS ON HOLD

+ ANFC- PWR LBLOCA AFTER 2 LOOP

+ W - 3,4 LOOP W PWR LBLOCA h

4

GE CHRONOLOGY / STATUS 12/81

+ GESTR-LOCA AND SAFER SUBMITTALS 8/83

+ GESTR/ SAFER CODE REVIEW SER

~

6/84 jeg,, g ,f ,, ,7 f ,-

+ GESTR/ SAFER METHODOLOGY REVIEW SER 7/86

+ SAFER /CORECOOL JET PUMP /NON-JET PUMP SUBMITTAL 2/87

+ SAFER /CORECOOL CODE REVIEW SER 5/87

+ SAFER /CORECOOL METHODOLOGY REVIEW SER

+ ACRS DID NOT REVIEW SAFER /CORECOOL

+ ALL GE REVIEWS DONE BY NRR WITHOUT RES OR CONTRACTOR ASSISTANCE v> .

a s,

LAM 8 SAFER SHORT TERM THERMAL.

LONG-TERM THERMAL- p HYDRAUUC TRANSIENT HYDRAUUC TRANSIENT MODEL MODEL 1P F 3 OUTPUT:

CORE AVERAGE PRESSURE, CORE INLET FLOW, a

CORE INLET ENTHALPY

( )

TIME OF BotuNG TRANSI-U qy OUTPUT: m

- SCAT CORE UNCOVERY TIME, HEAT TRANSIENT CRITICAL ,

TRANSFER COEFFICIENTS POWER MODEL FOLLOWING BoluNG TRANSITION, VESSEL PRESSURE, ECCS FLOW FMTES, CORE REFLOODING TIME, PEAK CLADDING TEMPERATURE 1I r 3 OUTPUT:

MINIMUM CRITICAL POWER RATIO CONVECT!VE HEAT TRANSFER COEFFICEINTS V J i

(_.

l I CHASTE OR 4 l l GESTR

-, CORECOOL l LOCA GAP l CORE HEATUP MODEL l CONDUCTANCE I

I I I I I I i

! I I I I I U I I

r 3 I OUTPUT l PUX CLADDING TEMPERATURE, 'I PEAK CLADDING OXIDATION l l MAXIMUM AVERAGE PLANAR UNEAR HEAT GENERATION RATE j i I L__________________J 1 Flow Diagram of loss of Coolant Accident Analysis Using New Enhanced SAFEit gjg, y

1-.--- _ _ _ _ _ - _ _ . - - - -m__m w

• SAFER REVISIONS

+ INCREASE CORE NODES FROM 7 TO T2

+ NEW JAPANESE DATA BASED CCFL MODEL IN UPPER PLENUM TO CENTRAL BYPASS AND BETWEEN GUIDE TUBE AND BYPASS REGIONS

+ ISOLATION CONDENSER FOR BWR-2

+ NEW CONVECTIVE H.T.MODEL BASED ON GE, ASEA AND CISE DATA

+ 2 FUEL ROD REGION RADIATION MODEL

e #

w

• NEW CORECOOL CODE

+ SINGLE PIN, NON-EQUILIBRIUM, ONE DIMENSIONAL

+ USED FOR BWR-2 (NON-JET PUMP)

+ ADVANCED CODE TYPE HEAT TRANSFER

+ ASSESSMENT USED TLTA, FIX-II, ROSA-Ill, FIST, HITACHI, TOSHIBA, ATOMENERGI s

o ,

WESTINGHOUSE SCHEME FOR BEST-ESTIMATE LBLOCA PAD 4L r 3 INITIAL STORED ENERGY v J r 3

~

W COBRA / 2 HOT ROD

' PCT TRAC

'l ,

i 4L l r 3 BREAK MASS r 3 i CONTAINMENT AND ENERGY I

BACK PRESSURE q FLOW j q ESTIMATE j 1F

< L COCO

CE UPI CHRONOLOGY / STATUS

+ NRC/CE Meeting 1 -87

+ CEUPR Submitted 4 87

+ NRR Request for RES revisw of CEUPR S-87

+ RES Contracts LANL to assistin review 10 - 87 *

~

+ LANL provide pro!iminary CEUPR model review 11 - 87 re: 1985 sttsf guidance

> + LANL providss additional reshw including review of CEUPn assessmeit 2 - 88

+ NRR arranga rneet!ng with CE and utilities SOON l

1 1

i i

1 j I 2

FM.ST, Q

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- , - - - , - - , , , . , , - ~g - n- ge , , --n 7 -% p-gp --

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88 89 90 91 92 l ROSA-IV lm Tk"d@'TTENTNk m w' 2D/3D , l l

% . with industry .

< B&W OTSG + MIST , ,

O z ICAP and , ,

o Code Consortia . .

oc w

E TRAC-B (MOD 2) l-m m m' DICTATED M RELAP5 (MOD 3) l, m s m m BY REGULATORY

$ NEE s

,8 TRAC-P (MOD 2) y, 'm m m s , ,

CS1U l ECCS RULE l In-Vessel Acc.Mgmt, , ,

(Software Expert mig) a s' "

• CONTAINMENT =

m u a Z o GENERIC ISSUES =

mmmmmmm, TECH SUPPORT priorityissues U CENTER E TTC

< NUCLAAM PLANT AEOD('39G) & NRR ANALY7.ER l

AUDIT INDUSTRY

! SUBMITTALS I i

j ADV. REACTORS

h! 47

- - . - . _