NRC-95-4595, Provides Info to Assist Staff Review of Wgothic Computer Code

Provides Info to Assist Staff Review of Wgothic Computer Code

ML20094L190
Person / Time
Site:	05200003
Issue date:	11/13/1995
From:	Mcintyre B WESTINGHOUSE ELECTRIC COMPANY, DIV OF CBS CORP.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
NTD-NRC-95-4595, NUDOCS 9511200092
Download: ML20094L190 (11)

Text

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y Westinghouse Energy Systems Bu m PObur$ Pennsylvania 15230-0355 Electric Corporatic.:

l NTD-NRC-95-4595 l DCP/NRC0429 i Docket No.: STN-52-003 l .

l November 13,1995 i Document Control Desk j U.S. Nuclear Regulatory Commission j Washington, D.C. 20555

! ATTENTION: MR. T. R. QUAY 4

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SUBJECT:

AP600 WGOTHIC COMPARISON TO GOTHIC I i

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Dear Mr. Quay:

! During the July 27,1995, meeting between Westinghouse and the Containment Systems and Severe i Accident Branch, Westinghouse took an action to provide information to assist the st# review of the l

WGOTHIC computer code. Attachment I to this letter provides the following requested information:

1. A discussion on the applicability of the GOTHIC peer design review package to Westinghouse-GOTHIC,

2. A summary of the peer design review results and a list of the peer design review report sections that are applicable to Westinghouse-GOTHIC,

3. A list of the GOTHIC design review Appendix B results applicable to WGOTHIC, and

4. A comparison of WGOTHIC_S Version 1.2 results to the results from a modified version of the code incorporating the major differences leading to Version 4.0 of GOTHIC _S.

Please contact John C. Butler on (412) 374-5268 if you have any questions coacerning this transmittal.  ;

W Brian A. McIntyre, Manager Advanced Plant Safety and Licensing

/nja ec: T. J. Kenyon, NRC

--- D. Jackson, NRC __.

J. Kudrier.; NRC E. Throm, NRC P. Boehnert, ACRS N. J. Liparulo, Westinghouse

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. i Attachment to NTD-NRC-95-4595 ,

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Applic:bility of GOTHIC Peer Design Revi:w to Westinghouse-GOTHIC In 1991 a peer design group was established by the Electric Power Research Institute (EPRI).

The purpose of this group was to review the GOTHIC coding, supporting documentation, users manuals, and code qualification results in order to establish a reference point for placing the GOTHIC code package under a 10CFR50, Appendix B Quality Assurance program. The review of the code began wbh GOTHIC Version 3.4d. The conclusions of the design review also apply -

to GOTHIC Version 4.0 as indicated in the introduction to the design review final report.

The configured version of Westinghouse-GOTHIC (WGOTHIC) originated with GOTHIC Version 3.4c, the immediate predecessor to the version supplied to the design review team. The differences between Version 3.4c and 3.4d are minor as indicated by the increment in the alpha character of the version stamp and the limited number of differences identified in the tables  ;

provided below.

The results of the design review are applicable to WGOTHIC. The difference between WGOTHIC Version 1.2 and GOTHIC Version 4.0 is demonstrated to be minor in the attached plot and is confirmed by the very few differences identified in letter NTD-NRC-95-4577. Given that GOTHIC Version 4.0 was the result of the peer design review and that WGOTHIC is the same as GOTHIC Version 4.0, with a few identified exceptions, it is concluded that the design review directly applies to WGOTHIC.

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Westingbosse mamerical Applications Inc.

i gggg Westinghouse Purchases GOTHIC -

Version 3.4c t Westinghouse Begins Dedication  ;

1. " of COTHIC Version 3.4c  :

Westinghouse Begins Modifications for AP600 Program. j November f[E r  !$h a boy EPRI Establishes Design Review become AvailaMe 1992 BehsReviewofGOTHICVersion g 3.4d.

May Westinghouse Completes Dedication of GOTHIC Version 3.4c Westinghouse Incorporates COTHIC Error Notices as They become Available Febt Westinghouse Releases WGOTHIC Version 1.0 May NAI Responds to Design Review Gr mp Co m nts July Westinghouse Releases WOOTHIC Version 1.1 September Design Review Complete.

GOTHIC Version 4.0 Released.

1994 October Westinghouse Releases WGOTHIC Version 1.2 1995 1995 Westinghouse Updates Wgothic to GOTHIC Version 4.0 Westinghouse _ GOTHIC Code Modification Timeline 00XXG:CFG/XXXX92-3

Summary of Peer Review Results The peer design review group myiewed the documentation, coding, convergence, pre / post processor, code qualification package, and the code's adequacy for containment analysis. The conclusions for these items are presented in section 2.2 of the GOTHIC Design Review Final Repost (NTD-NRC-95-4462, EPRI Report RA-93-10, GOTHIC Design Review Final Report, May 1995).

The design review group concluded that the documentation is adequate to describe the theory and assumptions made in developing the models and logic, the code from a programmer's point of view, how to prepare the input, and how to install the code on supported systems.

The source code was found to be consistent with the documentation. The solution technique used in GOTHIC _S was found to be stable; however, an iterated Newton method was recommended as an option for the future. The pm and post processors were found to be valid for performing the applications required of them.

The code qualification documentation and results were reviewed by the group. It was concluded that GOTHIC _.S is valid to use in performing a wide range of thermal-hydraulic applications. It was noted that although the analyses in the code qualification manual had not been independently reviewed, an impressive array of cases were analyzed with successful comparisons to data and test results.

Overall, the group found the GOTHIC containment analysis package adequate for containment analyses and that the code package offered the ability to provide more accurate and mechanistic results than with other currently available containment codes. This conclusion was qualified with the statements that the nodal and junction treatment as well as the range of the qualification database need to be studied. If the intended application falls outside these ranges then the use of GOTHIC needs to be justified; as was done via the large scale and separate effects tests used to qualify Westinghouse-GOTHIC for use in the licensing of the AP600 (WCAP-14382).

The group had three recommendations at the conclusion of the myiew. The first was the addition

! of dynamic memory allocation so that the code did not need to be re-compiled for different sizes of models. The second was the inclusion of an iterated Newton method to aid in convergence.

The third was to incorporate a fog model to simulate condensation of vapor when regions go from superheated to saturated. None of these issues adversely impact the use of WGOTHIC for AP600 PCS design basis analysis, as discussed below.

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Design Revizw Sections Applic:'. bis to Westinghouse-GOTHIC l There are seven sections and seven appendices contained in the GOTHIC Design Review Final Report. Section 1 is a brief introduction to the code package and the purpose for the review. This section has little applicability to WGOTHIC but it does provide some history of the code.

Section 2 provides a summary of the review and the conclusions reached by the design group.

This'section applies to WGOTHIC in that it presents the results of the review and the recommendations that were made as a result of the review.

Section 3 lists the items that were reviewed by the group as ell as the method of review. This section applies to WGOTHIC since it itemizes the documentation and features that were reviewed.

1 Section 4 presents the results of the review. This section contains the results of the group's j independent tests as well as the assessments of the code against the tests analyzed in the code qualification manual. This section applies to WGOTHIC since the code qualification document I strengthens the justification for using WGOTHIC to analyze the AP600 and supporting tests.

Section 5 indicates that all items from the review have been fully resolved and contains three )

recommendations for improving the code package. The first recommendation, dynamic memory allocation, is a convenience option that applies to WGOTHIC but does not alter its solution. The second recommendation to include an iterated Newton solution option to improve convergence could apply to WGOTHIC; however, satisfactory convergence of the code is supponed by the

. AP600 large scale test comparisons and the GOTHIC code qualification report. The recommendation to include a fog model applies to WGOTHIC. The code qualification case, the CVTR analysis, indicates that the lack of this model results in overpredicting both temperature and pressure. An assessment of fog modeling as it relates to the AP600 has been also performed (NTD-NRC-94-4100, Enclosure 1, Radiation Heat Transfer through Fog in the PCCS, April 1994). Based on these msults it is concluded that although the WGOTHIC code would be

improved by the addition of a fog model it is conservative with respect to temperature and j pressure to ignore the model.

a Sections 6 and 7 provide a listing of the documentation and reference material.

i l Appendix A is a summary of the review coverage for documentation and source code modules.

! This section applies to WGOTHIC.

} Appendix B is a listing of the review findings and responses. This section applies to WGOTHIC.

i g Appendix C is a summary of the installation survey, Appendix D is a summary of the applications survey, and Appendix E is a summary of the preprocessor survey. These sections do not apply to WGOTHIC.

Appendix F contains the resumes of the design review group and Appendix G is an inventory

of the design myiew.

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Design Review Appendix B Findings cnd Rel:v:nca to Westinghouse-GOTHIC 11 of the findings presented in Appendix B of the GOTHIC Design Review Final Report (NTD-NRC-95-4577, " Updated GOTHIC Documentation," 12 October,1995) apply to Westinghouse-GOTHIC.

The results of a detailed comparison of WGOTHIC_S Version 1.2 and GOTHIC _S Version 4.0 are presented in the next section. The comparison encompasses all differences between the two code versions, including the findings identified in the Design Review Final Report as well as other corrections and enhancements made by the code developer that had not been incorporated into WGOTHIC by Westinghouse. The negligible effect of these differences is presented via a comparison of results which is also included in the next section.

Comparison of WGOTillC_S Version 1.2 with GOTHIC _S Version 4.0 The Westinghouse _ GOTHIC code was developed based on GOTHIC Version 3.4c. During the course of developing our code for use on the AP600 program a number of modifications and error corrections were made based on continuous dialog with the code developers, Numerical Applications, Inc. As a result of this close interaction, a number of code errors identified early in our development program were corrected prior to configuring WGOTHIC. This process is responsible for the very limited number of differences between the two versions of the code, the bulk of which were introduced to GOTHIC _S at the time that version 4.0 was created.

j To determine- the differences between WGOTHIC_S Version 1.2 and GOTHIC Version 4.0, a detailed comparison of the two codes was performed. This line-by-line comparison of the two codes was condensed into the two tables presented in letter NTD-NRC-95-4577. Tables 1 and i 2 from that trference are presented below along with an additional explanation as to why specific items were determined to be negligible.

4 To verify that the differences would not alter the results or conclusions of the AP600 analyses

( presented to date, all of these differences were incorporated into a temporary version of WGOTHIC_S. The AP600 containment pressure transient for the cold leg break case was reanalyzed to show the differences in the two versions. The figure below illustrates the differences in peak pressure results for the two versions of WGOTHIC_S.

I The only difference in results occurs during blowdown when the improved droplet model is

, activated. The pressure predicted by the modified code is slightly less than that predicted with the configured version of WGOTHIC_S Version 1.2. Based on this result it is concluded that the differences between the configured version of WGOTHIC and GOTHIC Version 4.0 are slightly conservative and permit the continued interim use of WGOTHIC_S Version 1.2 Incorporation of GOTHIC Version 4.0 into WGOTHIC The currently configured version of WGOTHIC will be upgraded to be consistent with GOTHIC 4.0. This will occur prior to performing the final calculations for the AP600 containment in'.egrity analyses.

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AP600 Containment Pressure Transient i Wgothic_s Ver 1.2

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Table 1: Identified Diffemnces Between GOTHIC _S Version 4.0 and WGOTHIC_S Version 1.2 Determined to be Negligible ,

ROUTINE DESCRIITION GOTIIIC Version 4.0 WGOTIIIC Version 1.2 REASON bikdat.f Coefficient used to 0.005245502294 0.005245502234 Small numerical difference in a calculate saturated liquid single factor of the equation used enthalpy to calculate the saturated liquid enthalpy.

boiling.f Film thickness calculation [0.5 'dh *( 1.-( 1 -liq _ frac )' ')]/ wet _fr [0.25*dh* liq _fracl/ wet _ frac This regime is not predicted to for use in calculating the ac occur during the transients single phase liquid heat calculated for the containment transfer coefficient analyses supporting the AP6(X).

boiling.f Version 4.0 deleted the hspl=(0.023*rel'*prl')* xkliq/de hspl= max (3.66. 023*rel **prl')* xkl Rese regimes are not predicted logic setting the minimum hspv=(.023* reg '*prmix *)*cmix/d iq/de to occur during the transients single liquid and vapor heat e hspv = max (3.66, calculated for the containment transfer coefficient to .023* reg'*prmix')*cmix/de analyses supporting the AP600.

3.66*k/dh condin.f Corrected conversion factor 0.08805 0.317 The analyses supporting the from Watts /m2 to AP600 containment analyses Btu /hr*ft2 when specifying have been performed exclusively a fixed surface heat flux in English units.

intfr.f Corrected the calculation of rbub= min (rbub,0.5'dhyd,0.02) thub= min (rbub.l.0*dhyd,0.G4) A bubbly flow regime is not the average small bubble predicted to occur in the AP600 radius containment analyses.

inttr.t Deleted a small bubble heat h shlv=(2.0+0.74

• reb' 5* prl" '")* yk hshiv= max [(2.0+0.74* reb' 5* A bubbly flow regime is not transfer coefficient f*dbubi prl* '")* ykf*dbubi, predicted to occur in the AP600 calculation option rip * (ht t-h f)*y k f* dbubi/(rvp *(h f.hg containment analyses.

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intfr.f Corrected the minimum cdd=4.0 cdd-0.45 These changes are a result of droplet interfacial drag improvements in the droplet coefficient regimes considered in the code.

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ROUTLNE DESCRIPTION GOTHIC Version 4.0 WGOTHIC Wrsion 1.2 REASON '

intfr.f Added logic to determine laminar Rese changes are a result of ,

terminal velocities for solid sphere improvements in the droplet '

droplets in various regimes distorted regimes considered in the code.

drop limit drop limit intfr.f Reinstituted droplet Available Not available Rese changes are a result of deentrainment on horizontal improvements in the droplet surfaces regimes considered in the code. ,

solids.f Version 4.0 permits a time His is an improvement over dependent multiplier on the earlier wrsions of the code. This ice heat transfer coefficient. feature is not used in AP600 analyses.

tpress.f Calculation of liquid and d321(jj,j)=d321(jj,j)+0.25 *dvdzl d321(jj,j)=d321(jj,j)+0.125*dvdzl His is a factor in the turbulence vapor strain rates d32v(ii.j)=d32v(ii j)+0.25'dvdzy d32V(ii.j)=d32v(ii,j)+0.125*dvdzy models used only for the i distributed parameter model. The assumption made in that analysis is equivalent to perfect mixing within the cells so this item has very little effect.

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4 Table 2: Identified Differences Between GOTHIC _S Version 4.0 and WGOTHIC_S Version 1.2 Shown to be Insignificant . ,,

ROUTINE DESCRIPTION GOTHIC Version 4.0 WGOTHIC Version 1.2

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healf Modified the method used to calculate the [0.5 'dh * ( 1.-( 1 -liq _ frac )")lAvet_ frac [0.25*dh* liq _fracl/ wet _ frac minimum effective film thickness heat.f Corrected modifier on smoothing method for htcru=htevu+ htevu=htevu+

the Uchida correlation (htevt-htevu)*exp'**** (htevt-htevu)*exp'**'*)

heat.f Removed old time weighting from direct htevs(isd.n)=xvap*hyl htcys(isd,n)=(xvap*hvi)*'*

wall condensation and Tagami max (one.htevs(isd.n))"

newdit.f Gravity driven flow time step limit logic delgmx=delt*0.5/dgmx delgmx=delt*l.0/dgmx increased post 3d.f Calculation of vertical mass flow rates within Vertical mass flow rate is updated Forces the change in vertical mass a cell with respect to changes in pressure flow per change in pressure to rero for cells connected to a pressure for all cells connected to a pressure boundary condition boundary condition.

post 3d.f Update of gas densities prior to solution of Recalculates gas densities Recalculates gas densities  ;

state equation. accounting for pressure change and accounting for gas mass error gas mass error setin.f Revised the lower limit for the Uchida heat humin =2. humin =15.

transfer coefficient

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