ML20127J568

Forwards Safety Evaluation Approving New Small Break LOCA Model Notrump for TMI Item II.K.3.30,per WCAP-10079 & WCAP-10054.Plant-specific Analysis Due within 1 Yr,Per Item II.K.3.31,if Notrump Used in LOCA Small Break Analysis

ML20127J568
Person / Time
Site:	Wolf Creek
Issue date:	06/14/1985
From:	Youngblood B Office of Nuclear Reactor Regulation
To:	Koester G KANSAS GAS & ELECTRIC CO.
References
TASK-2.K.3.30, TASK-2.K.3.31, TASK-TM GL-83-35, TAC-59057, NUDOCS 8506260694
Download: ML20127J568 (11)

Text

. y JUN 141985 Docket No.: STN 50-482 Mr. Glenn L. Koester Vice President - Nuclear Kansas Gas and Electric Company 201 North Market Street P. O. Box 208 Wichita, Kansas 67201

Dear Mr. Glen L. Koester:

On May 21 1985, the NRC approved the new Westinghouse small break LOCA model, NOTRUMP, for use in satisfying the TMI Action Item II.K.3.30. The Westinghouse model was documented in the two Topical Reports, WCAP-10079 and WCAP-10054. The Westinghouse Owners Group (WOG) references NOTRUMP as the:f r new licensing small break LOCA model to satisfy the requirements of TMI Action Item II.K.3.30. Our Safety Evaluation of II.K.3.30 for the members of WOG is enclosed.

It is our understanding that you are a member of the WOG and that NOTRUMP is to be used in the small break LOCA analysis for the Wolf Creek Generating Station. If this is correct, this completes the TMI Action Item II.K.3.30 for your plant and in accordance with the TMI Action Item II.K.3.31, your plant specific analysis is due within one year of receipt of this letter.

Please advise this office within 60 days if this is not correct and provide your plans and schedule for completing II.K.3.30 and II.K.3.31.

On November 2,1983 in Generic Letter No. 83-35, the NRC provided clarifica-tion and proposed a generic resolution of TMI Action Item II.K.3.31. That is, resolution of II.K.3.31 may be accomplished by generic analysis to demonstrate that the previous analyses performed with WFLASH were conservative. Future plant specific analysis performed for your plant by Westinghouse for reloads or Technical Specification amendments (those beyond 90 days of the date of this letter) should be calculated with the new code, NOTRUMP.

Sincerely, B. J. Youngblood, Chief Licensing Branch No. 1 Division of Licensing

Enclosure:

As stated cc: See next page DISTRIBUTION:

Ipoetet File . MRushbrook EJordan P0'Connor DWigginton NRC PDR~

Local PDR OELD PRC System ACRS (16)

NSIC JPartlow LB#1 R/F BGrimes LB#1/DL M LB#

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8506260694 850614 PDR ADOCK 0500 2

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%, . . . . . .o# JUN 14 25 Docket No.: STN 50-482 Mr. Glenn L. Koester Vice President - Nuclear Kansas Gas and Electric Company 201 North Market Street P. O. Box 208 Wichita, Kansas 67201

Dear Mr. Glen L. Koester:

On May 21 1985, the NRC approved the new Westinghouse small break LOCA model, NOTRUMP, for use in satisfying the TMI Action Item II.K.3.30. The Westinghouse model was documented in the two Topical Reports, WCAP-10079 and WCAP-10054. The Westinghouse Owners Group (WOG) references NOTRUMP as their new licensing small break LOCA model to satisfy the requirements of TMI Action Item II.K.3.30. Our Safety Evaluation of II.K.3.30 for the members of WOG is enclosed.

It is our understanding that you are a member of the WOG and that NOTRUMP is to be used in the small break LOCA analysis for the Wolf Creek Generating Station. If this is correct, this completes the TMI Action Item II.K.3.30 for your plant and in accordance with the TMI Action Item II.K.3.31, your plant specific analysis is due within one year of receipt of this letter.

Please advise this office within 60 days if thie is not correct and provide your plans and schedule for completing II.K.3.5; and II.K.3.31.

On November 2,1983 in Generic Letter No. 83-35, the NRC provided clarifica-tion and proposed a generic resolution of TMI Action Item II.K.3.31. That is, resolution of II.K.3.31 may be accomplished by generic analysis to demonstrate that the previous analyses performed with WFLASH were conservative. Future plant specific analysis performed for your plant by Westinghouse for reloads or Technical Specification amendments (those beyond 90 days of the date of this letter) should be calculated with the new code, NOTRUMP.

Sinc e y, l i

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3. J. oungbl od, Chief Life ing Br nch No. 1 Di' vision of Licensing

Enclosure:

As stated cc: See next page

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JUN 141985 WOLF CREEK Mr. Glenn L. Koester Vice President - Nuclear Kansas Gas and Electric Company 201 North Market Street Post Office Box 208 Wichita, Kansas 67201 cc: Mr. Nicholas A. Petrick Ms. Wanda Christy Executive Director, SNUPPS 515 N. 1st Street 5 Choke Cherry Road Burlington, Kansas Rockville, Maryland 20850 l C. Edward Peterson, Esq.

Jay Silberg, Esq. Legal Division Shaw, Pittman, Potts & Trowbridge Kansas Corporation Commission 1800 M Street, N. W. State Office Building, Fourth Floor Washington, D. C. 20036 Topeka, Kansas 66612 Mr. Donald T. McPhee John M. Simpson, Esq.

l Vice President - Production Attorney for Intervenors l Kansas City Power & Light Company 4350 Johnson Drive, Suite 120 l 1330 Baltimore Avenue Shawnee Mission, Kansas 66205 l Kansas City, Missouri 64141 l Regional Administrator l Ms. Mary Ellen Salava U. S. NRC, Region IV Route 1, Box 56 611 Ryan Plaza j Burlington, Kansas 66839 Suite 1000

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Arlington, Texas 76011 A. Scott Cauger Assistant General Counsel Mr. Allan Mee Public Service Commission Project Coordinator P. O. Box 360 Kansas Electric Power Cooperative, Inc.

Jefferson City, Missouri 65101 Post Office Box 4877 Gage Center Station Mr. Howard Bundy Topeka, Kansas 66604 Resident Inspector / Wolf Creek NPS c/o U.S.N.R.C Regional Administrator Post Office Box 311 U.S.N.R.C. - Region III Burlington, Kansas 66839 799 Roosevelt Road Glen Ellyn, Illinois 60137 Mr. Robert M. Fillmore State Corporation Commission Brian P. Cassidy, Regional Counsel State of Kansas Federal Emergency Management Agency Fourth Floor, State Office Bldg. Region I Topeka, Kansas 66612 J. W. McCormack POCH Boston, Massachusetts 02109

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WOLF CREEK cc: Terri Sculley, Director Special Projects Division Kansas Corporation Commission State Office Building, Fourth Floor Topeka, Kansas 66612 Mr. Gerald Allen Public Health Physicist Bureau of Air Quality & Radiation Control Division of Environment Kansas Dept. of Health & Environment Forbes Field Bldg. 321 Topeka, Kansas 66620 Mr. Bruce Bartlett Resident Inspector / Wolf Creek NPS c/o U.S.N.R.C Post Office Box 311 Burlington, Kansas 66839 l

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Enclosurs SAFETY EVALUATION TMI ACTION ITEM II.K.3.30 FOR WESTINGHOUSE PLANTS NUREG-0737 is a report transmitted by a letter from D. G. Eisenhut, Director of the Division of Licensing, NRR, to licensees of operating power reactors and applicants for operating reactor licenses forwarding TMI Action Plan requirements which have been approved by the Commission for implementa-tion.Section II.K.3.30 of Enclosure 3 to NUREG-0737 outlines the Commission requirements for the industry to demonstrate its small break loss of coolant accident (SBLOCA) methods continue to comply with the requirements of Appendix K to 10 CFR Part 50.

The technical issues to be addressed were outlined in NUREG-0611, " Generic Evaluation of Feedwater Transients and Small Break Loss-of-Coolant Accidents in Westinghouse-Designed Operating Plants." In addition to the concerns listed in NUREG-0611, the staff requested licensees with U-tube steam generators to assess their computer codes with the Semiscale S-UT-08 experimental results.

This request was made to validate the code's ability to calculate the core coolant level depression as influenced by the steam generators prior T.o loop seal clearing.

~ In response to TMI Action Item II.K.3.30, the Westinghouse Owners Group (WOG) has elected to reference the Westinghoue NOTRUMP code as their new licensing small break LOCA model. Referencing the new computer code did not imply deficiencies in WFLASH to meet the Appendix K requirements. ,The decision was based on desires of the industry to perform licensing evaluatio'ns with a computer program specifically designed to calculate small break LOCAs with greater phenomenological accuracy than capable by WFLASH.

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The following documents our evaluation of the WOG response to TMI Action Item II.K.3.30 confirmatory items.

II.

SUMMARY

OF REQUIREMENTS NUREG-0611 required licensees and applicants with Westinghouse NSSS designs to address the following concerns:

A. Provide confirmatory validation of the small break LOCA model to adequately calculate the core heat transfer and two phase coolant level during core uncovery conditions.

B. Validate the adequacy of modeling the primary side of the steam generators as a homogeneous mixture.

C. Validate the condensation heat transfer model and affects of non-condensible gases.

D. Demonstrate, through noding studies, the adequacy of the SBLOCA model to calculate flashing during system depressurization.

E. Validate the polytropic expansion coefficient applied in the accumu-lator model, and F. Validate the SBLOCA model with LOFT tests L3-1 and L3-7. In addition, validate the model with the Semiscale S-UT-08 experimental data.

Detailed responses to the above items are documented in WCAP-10054,

" Westinghouse Small Break ECCS Evaluation Model Using the NOTRUMP Code."

III. EVALUATION The following is the staff's evaluation of the TMI Action Ite'm require-ments outlined above.

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! A. Core Heat Transfer Models

. The Westinghouse Owners Group (WOG) referenced the NOTRUMP computer code as their new computer program for small break loss of coolant accident (SBLOCA) evaluation. NOTRUMP was benchmarked against~ core uncovery experiments conducted at the Oak Ridge National Laboratory (ORNL). These tests were performed under NRC sponsorship. The good agreement between the calculations and the data confirmed the adequacy of the drift flux model used for core hydraulics as well as the core heat transfer models of clad temperature predictions.

The staff finds the core thermal-hydraulic models in NOTRUMP accept-able. This item is resolved.

B. Steam Generator Mixture Level Model

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NUREG-0611 requested licensees and applicants with Westinghouse

$ designed NSSSs to justify the adequacy of modeling the primary system of the steam generators as a homogeneous mixture. This question was l directed to the WFLASH code. NOTRUMP, the new SBLOCA licensing code j models phase separation and incorporates flow regime maps within the steam generator tubes. The adequacy of this model was demonstrated through benchmark analyses with integral experiments, in particular with Semiscale test S-UT-08.

The staff finds the steam generator model in NOTRUMP acceptable.

This item is resolved.

C. Noncondensible Affects On Condensation Heat Transfer NUREG-0611 requested validation of the condensation heat transfe.-

correlations in ',he Westinghouse SBLOCA model and an assessment cf 3

e-the consequences of noncondensible gases in the primary coolant.

The condensation heat transfer model used in NOTRUMP is based on steam experiments performed by Westinghouse on a 16-tube PWR steam generator model. For two phase conditions, an empirical correlation developed by Shah is applied.

The staff finds the condensation heat transfer correlation in NOTRUMP acceptable.

, The influences of noncondensible gases on the condensation heat transfer was demonstrated by degrading the heat transfer coefficient in the steam generators. The heat transfer degradation was calculated using a boundary layer approach. For this calculation, the noncon-densible gases generated within the primary coolant system were col-1ected and deposited on the surface of the steam generator tubes.

The sources of noncondensibles considered were:

(i) Air dissolved in the RWST.

(ii) Hydrogen dissolved in the primary system.

(iii) Hydrogen in the pressurizer vapor space.

(iv) Radiolytic decomposition of water.

With a degradation factor on the heat transfer coefficient, the limiting SBLOCA was reanalyzed for a typical PWR. The WOG, thereby, concluded that formation of noncondensible gases in quantities that may reasonably be expected for a 4-inch cold leg break LOCA presents no serious detriment on the PWR system response in terms of core uncovery or system pressure. What perturbation was observed was minor in nature.

The staff finds acceptable the Westinghouse submittal on the influences of noncondensible gases on design bases SBLOCA events. Our ccnclusion is based on the limited amount of noncondensible gases available dur-ing a design basis SBLOCA event, as well as results obtained from Semi-scale experiments which reached similar conclusions while injecting noncondensible gases in excess amount expected during a SBLOCA design basis event. This item is resolved.

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D. Nodalization Studies For Flashing During Depressurization As a consequence of the staff's experience with modeling SBLOCA events with NRC developed computer codes (in particular the THI-2 accident), the staff questioned the adequacy of the nodalization in the licensing model to calculate the depressurization of the primary system. The staff therefore requested validation of the Westinghouse Evaluation Model to properly calculate the depressurization expected during a SBLOCA event.

Through nodalization. studies and validation of the NOTRUMP licensing model with integral experiments (e.g., LOFT and Semiscale), Westing-house demonstrated the acceptability of the nodalization and nonequi-librium models.

The staff finds the W estinghouse model acceptable for calculating depressurization during SBLOCA events. This item is resolved.

l E. Accumulator Model WFLASH, the previous Westinghouse small break loss of coolant accident (SBLOCA) analysis code, applied a polytropic gas expansion coefficient of 1.4 to the nitrogen in the accumulators. The WOG was requested to validate this accumulator model in light of data obtained through the LOFT experimental programs for SBLOCAs. Westinghouse reviewed the f applicable LOFT data and determined the need to perform full scale i

accumulator tests. Based upon these tests, Westinghouse modified the polytropic expansion coefficient to a more realistic value. Of inter-est is Westinghouse's conclusion that the selection of either a high or low expansion coefficient had negligible effect on the calculated peak clad temperature (PCT). This insensitivity is only appropriate to NOTRUMP, with its nonequilibrium assumptions.

t The staff finds acceptable the polytropic expansion coefficient in

the NOTRUMP code. This item is resolved.

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F. Code Validation Following the Taree Mile Island event of 1979, staff analyses with NRC developed computer codes led to concerns that detailed nodali-zation was required to simulate realistic systems responses to postu-lated SBLOCAs. As a consequence, licensees and applicants with Westing-house plants were requested to validate their licensing tools with integral experiments. In specific, the NRC requested that the computer codes be validated with the LOFT L3-1 and L3-7 experimental data. In addition, the staff also requested that the code be benchmarked with the Semiscale S-UT-08 experimental data.

Westinghouse performed the above benchmark analyses. For the LOFT tests, Westinghouse showed good agreement between the NOTRUMP calcu-lations and the experimental data. For the S-UT-08 test, Westinghouse demonstrated that NOTRUMP did a reasonable job calculating the experi-mental data. However, this required a more detailed nodalization of the steam generators then used in the licensing model. With the less detailed licensing nodalization, the pre-loop-seal-clearing core level depression phenomenon, as observed in the S-UT-08 data, was not con-servatively calculated for very small breaks. However, the calculated peak clad temperature was demonstrated to be higher (more conservative)

! with the coarse nodalization. The staff, therefore, finds acceptable the NOTRUMP computer code and the associated nodalization for SBLOCA i design basis evaluation.

This item is resolved.

IV. CONCLUSION The Westinghouse Owners Group (WOG), by referencing WCAP-10079,and WCAP-10054, have identified NOTRUMP as their new thermal-hydraulic c'omputer program for calculating small break loss of coolant accidents (SBLOCAs). The staff finds acceptable the use of NOTRUMP as the new Westinghouse licensing tool for calculating SBLOCAs for Westinghouse NSSS designs.

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The responses to NUREG-0611 concerns, as evaluated within this SER, have also been found acceptable.

This SER completes the requirements of TMI Action Item II.K.3.30 for licensees and applicants with Westinghouse NSSS designs who were members of the WOG and referenced WCAP-10079 and WCAP-10054 as their response to this item.

Within one year of receiving this SER, the licensees and applicants with Westinghouse NSSS designs are required to submit plant specific analyses with NOTRUMP, as required by TMI Action Item II.K.3.31. Per generic letter 83-35, compliance with Action Item II.K.3.31 may be submitted generically. We require that the generic submittal include validation that the limiting break location has not shifted away from the cold legs to the hot or pump suction legs.

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