ML032170014

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Emergency Core Cooling System (ECCS) Performance Evaluation Models, 10 CFR 50.46(a)(3)(ii) Annual Report
ML032170014
Person / Time
Site: Palo Verde  Arizona Public Service icon.png
Issue date: 07/23/2003
From: Bauer S
Arizona Public Service Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
102-04971-SAB/TNW/JAP CENPD-279, Suppl 14, Rev 1
Download: ML032170014 (17)
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Text

L Scott A. Bauer Department Leader 10 CFR 50.46 Regulatory Affairs Tel: 6231393-5978 Mail Station 7636 Palo Verde Nuclear Fax: 623/393-5442 P.O. Box 52034 Generating Station e-mail: sbauer~apsc.com Phoenix, AZ 85072-2034 102-04971 -SAB/TNW/JAP July 23, 2003 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555-0001

Reference:

1) APS Letter to NRC, 102-04815-SAB/TNW/JAP, "Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3; Docket Nos. STN 50-528/5291530; Emergency Core Cooling System (ECCS) Performance Evaluation Models; 10 CFR 50.46(a)(3)(ii) Annual Report," July 15, 2002.

Dear Sirs:

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2, and 3 Docket Nos. STN 50-5281529/530 Emergency Core Cooling System (ECCS) Performance Evaluation Models, 10 CFR 50.46(a)(3)(ii) Annual Report Pursuant to 10 CFR 50.46(a)(3)(ii), Arizona Public Service Company (APS) has enclosed the Westinghouse Electric Company's, "Annual Report on Combustion Engineering ECCS Performance Evaluation Models for PWRs, CENPD-279, Supplement 14, Rev. 1, April 2003." This report describes the changes and errors in Combustion Engineering models for Pressurized Water Reactors (PWRs) ECCS performance analysis in calendar year 2002. Appendix A of this report is specific to PVNGS. All other appendices of this report are plant-specific to other Combustion Engineering (CE) designed facilities and have not been included as part of this submittal.

As shown in the table on page 3, the PVNGS large and small break loss of coolant accident (LOCA) analyses utilized the June 1985 and S1 M evaluation models, respectively, at the start of calendar year (CY) 2002. The cumulative effect of changes and errors in these models on calculated peak clad temperature (PCT) is estimated to have been <1 OF and <34 0 F.for large and small break LOCAs, respectively, as previously reported to the NRC in the PVNGS report for CY 2001 (Reference 1).

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance

~ODI Callaway

  • Comanche Peak
  • Oiablo Canyon
  • Palo Verde
  • Wolf Creek

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Emergency Core Cooling System (ECCS)

Performance Evaluation Models, 10 CFR 50.46(a)(3)(ii) Annual Report Page 2 During the first half of 2002, however, large and small break LOCAs (LBLOCAs and SBLOCAs) were reanalyzed for PVNGS with the 1999 and S2M evaluation models, respectively. As of December 31, 2002, there were no known changes or errors that affected the PVNGS PCT calculations performed with these newer evaluation models.

Additionally, because PCT is not calculated as part of the post-LOCA Long-Term Cooling (LTC) analysis, there are no changes or errors in the LTC models that affect PCT.

No commitments are being made to the NRC by this letter.

If you have any questions, please contact Thomas N. Weber at (623) 393-5764.

Sincerely, SAB/TNW/JAP/kg Enclosure cc: Regional Administrator, NRC Region IV J. N. Donohew N. L. Salgado

U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Emergency Core Cooling System (ECCS)

Performance Evaluation Models, 10 CFR 50.46(a)(3)(ii) Annual Report Page 3 Summary of Cumulative Effects on Calculated Peak Clad Temperature (PCT) for PVNGS Due to ChanaeslErrors in LOCA Evaluation Models Notes:

(1) Pursuant to 10 CFR 50.46(a)(3)(j), numerical values In the table represent a cumulation of the absolute magnitudes of the respective changes In PCT, for each change andlor error in the associated LOCA evaluation model.

(2) By letter dated May 3,2002 (1102-04699-CDMiTNWIJAP), APS informed the NRC that LOCA analyses had been performed for PVNGS with the 1999 EM (LBLOCA) and S2M (SBLOCA) evaluation models. Although these analyses had primarily been performed to support the Introduction of Zaiow fuel cladding Into the Unit 2 Cycle 11 reload core (which achieved criticality on April 16, 2002), the APS letter stated that "... These analyses are also bounding for PVNGS Units 1 and 3...." Section 6.3 of the PVNGS UFSARwas subsequently revised, pursuant to 10 CFR 50.71(e), to remove the previously reported June 1985 EM (LBLOCA) and SIM (SBLOCA)

PCT values.

(3) CENPD-279, Supplement 14, Revision 1, states that STRIKIN-I1 computer code errors were Identified and corrected In CY 2002, Involving a time step algorithm and the Coffman plastic strain model. The PVNGS LBLOCA analyses performed with the 1999 EM, however, utilized a corrected version of STRIKIN-11. Therefore, these errors had no effect on calculated PCT for PVNGS. There Is no previous accumulated effect on PCT for the 1999 EM LBLOCA model.

(4) CENPD-279, Supplement 14, Revision 1, states that there Is no previous accumulated change In cladding temperature for the S2M SBLOCA evaluation model.

Furthermore, the S2M analyses performed for PVNGS used a corrected version of CEFLASH-4AS.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway

  • Comanche Peak
  • DOablo Canyon
  • Palo Verde
  • Wolf Creek

ENCLOSURE Annual Report on Combustion Engineering ECCS Performance Evaluation Models for PWRs, CENPD-279, Supplement 14, Rev.1, dated April 2003

CENPD-279 Supplement 14, Rev. 1 ANNUAL REPORT ON COMBUSTION ENGINEERING ECCS PERFORMANCE EVALUATION MODELS for PWRs April 2003 0 Copyright 2003, Westinghouse Electric Company LLC. All rights reserved.

Westinghouse Electric Company LLC

CENPD -279, Supp. 14, Rev. I LEGAL NOTICE This report was prepared as an account of work performed by Westinghouse Electric Company LLC. Neither Westinghouse Electric Company LLC nor any person acting on its behalf:

A. Makes any warranty or representation, express or implied including the warranties of fitness for a particular purpose or merchantability, with respect to the accuracy, completeness, or usefulness of the information contained in this report, or that the use of any information, apparatus, method, or process disclosed in this report may not infringe privately owned rights; or B. Assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, apparatus, method or process disclosed in this report COPYRIGHT NOTICE This report has been prepared by Westinghouse Electric Company LLC (WEC) and bears a Westinghouse Electric Company LLC copyright notice. Information in this report is the property of and contains copyright information owned by WEC and/or its subcontractors and suppliers. It is transmitted to you in confidence and trust, and you agree to treat this document and the information contained therein in strict accordance with the terms and conditions of the agreement under which it was provided to you.

You are permitted to make the number of copies of the information contained in this report which are necessary for your internal use in connection with your implementation of the report results for your plant(s) in your normal conduct of business. Should implementation of this report involve a third party, you are permitted to make the number of copies of the information contained in this report which are necessary for the third party's use in supporting your implementation at your plant(s) in your normal conduct of business if you have received the prior, written consent of WEC to transmit this information to a third party or parties. All copies made by you must include the copyright notice in all instances and the proprietary notice if the original was identified as proprietary.

The NRC is permitted to make the number of copies beyond those necessary for its internal use that ame necessary in order to have one copy available for public viewing in the appropriate docket files in the NRC public document room in Washington, DC if the number of copies submitted is insufficient for this purpose, subject to the applicable federal regulations regarding restrictions on public disclosure to the extent such information has been identified as proprietary.

Copies made by the NRC must include the copyright notice in all instances and the proprietary notice if the original was identified as proprietary.

Westfighouse ElectrIc Company LLC

CENPD -279, Supp. 14, Rev. 1 ABSTRACr This report describes changes and errors in the ECCS performance evaluation models for PWRs developed by Combustion Engineering in calendar year (CY) 2002 per the requirements of 10CFR50.46. For this reporting period, errors were found in the evaluation models (EM) or application of the models that affect the cladding temperature calculation. In particular, errors in the STRIK-H code used in the large break LOCA evaluation models were found and corrected.

The sum of the absolute magnitude of the generic peak cladding temperature (PCI) changes for the large break LOCA June 1985 EM from all reports to date continues to be less than 10 F excluding plant specific effects. The generic impact on the peak cladding temperature for the large break LOCA 1999 EM is less than 12F. The generic sum of the absolute magnitude of the peak cladding temperature changes for the small break LOCA S1M evaluation model from all reports to date is less than 30 F. There is no generic accumulated change in peak cladding temperature for the small break LOCA S2M evaluation model. No change occurred in the PCT due to post-LOCA long term cooling issues. The total effect relative to the 500 F definition of a significant change in PCr for each evaluation model is the sum of the generic effects for that model and plant specific effects, if any, described in Appendices A-G.

Westinghouse Electric Company LLC i

CENPD -279, Supp. 14, Rev. 1 TABLE OF CONTENTS Section Title Page

1.0 INTRODUCTION

1 2.0 COMBUSTION ENGINEERING ECCS EVALUATION MODE[S AND CODES 3 3.0 EVALUATION MODEL CHANGES AND ERROR CORRECTIONS 4 3.1 STREKIN-H Code Errors 4

4.0 CONCLUSION

S 6

5.0 REFERENCES

7 APPENDICES (Plant Specific Considerations)

A. ARIZONA PUBIUC SERVICE COMPANY (PVNGS Units 1-3)

B. CALVERT CLIFFS NUCLEAR POWER PLANT INCORPORATED (Calvert Cliffs Units 1 & 2)

C. SOUTHERN CALIFORNIA EDISON COMPANY (SONGS Units 2 & 3)

D. DOMINION RESOURCES (Millstone Unit 2)

E. ENTERGY OPERATIONS, INCORPORATED

1. Arkansas Nuclear One Unit 2
2. Waterford Unit 3 F. FLORIDA POWER AND LIGHT COMPANY (St. Lucie Unit 2)

G. CONSUMER ENERGY COMPANY (Palisades)

Westinghouse Electric Company LLC ii

CENPD -279, Supp. 14, Rev. I 1.0 INTRODUCMION This report addresses the NRC requirement to report changes or errors in ECCS performance evaluation models. The ECCS Acceptance Criteria, Reference 1, spell out reporting requirements and actions required when errors are corrected or changes are made in an evaluation model or in the application of a model for an operating licensee or construction permittee of a nuclear power plant.

The action requirements in 10CFR50.46(a)(3) are:

1. Each applicant for or holder of an operating license or construction permit shall estimate the effect of any change to or error in an acceptable evaluation model or in the application of such a model to determine if the change or error is significant. For this purpose, a significant change or error is one which results in a calculated peak fuel cladding temperature (PCI) different by more than 50F from the temperature calculated for the limiting transient using the last acceptable model, or is a cumulation of changes and errors such that the sum of the absolute magnitudes of the respective temperature changes is greater than 50SF.
2. For each change to or error discovered in an acceptable evaluation model or in the application of such a model that affects the temperature calculation, the applicant or licensee shall report the nature of the change or error and its estimated effect on the limiting ECCS analysis to the Commission at least annually as specified in 10CFR50.4.
3. If the change or error is significant, the applicant or licensee shall provide this report within 30 days and include with the report a proposed schedule for providing a reanalysis or taking other action as may be needed to show compliance with IOCFR5O.46 requirements. This schedule may be developed using an integrated scheduling system previously approved for the facility by the NRC. For those facilities not using an NRC approved integrated scheduling system, a schedule will be established by the NRC staff within 60 days of receipt of the proposed schedule.
4. Any change or error correction that results in a calculated ECCS performance that does not conform to the criteria set forth in paragraph (b) of 10CFR50.46 is a reportable event as described in 10CFR50.55(e), 50.72 and 50.73. The affected applicant or licensee shall propose immediate steps to demonstrate compliance or bring plant design or operation into compliance with 10CFR50.46 requirements.

This report documents all the errors corrected in and/or changes to the presently licensed ECCS performance evaluation models for PWRs developed by Combustion Engineering, made in the Westinghouse SElectric Company LLC 1

CENPD -27, Supp. 14, Rev. 1 year covered by this report, which have 'not been reviewed by the NRC staff. This document is provided to satisfy the reporting requirements of the second item above. Reports for earlier years are given in References 2-15.

Westinghouse Electric Company LLC 2

CENPD -279, Supp. 14, Rev. 1 2.0 COMBUSTION ENGINEERING ECCS EVALUATION MODELS AND CODES Five evaluation models (E) for ECCS performance analysis of PWRs developed by Combustion Engineering are described in topical reports, are licensed by the NRC, and are covered by the provisions of I0CFR50.46. The evaluation models for large break LOCA (LBLOCA) are the June 1985 EM and the 1999 EM. There arm two evaluation models for small break LOCA (SBLOCA): the SBLOCA Evaluation Model (SIM) and the S2M SBLOCA EM.

Post-LOCA long term cooling (LTC) analyses are performed with the LTC evaluation model.

Several digital computer codes are used to do ECCS performance analyses of PWRs for the evaluation models described above that are covered by the provisions of 10CFR50.46. Those for LBLOCA calculations are CEFIASH-4A, COMPERC-L, HCROSS, PARCH, STREON-H, and COMZIRC. CEFLASH4AS is used in conjunction with COMPERC-IL STRKIN-I, and PARCH for SBLOCA calculations. The codes for post-LOCA LTC analyses are BORON, CEPAC, NATFLOW, and CELDA.

Westinghouse Electric Company LLC 3

CENPD -279, Supp. 14, Rev. 1 3.0 EVALUATION MODEL CHANGES AND ERROR CORRECTIONS This section discusses all error corrections and model changes to the ECCS performance evaluation models for PWRs described in Section 2.0 that may affect the calculated PCL.

3.1 STRII-I Code Errors Errors in the implementation of the time step algorithm and the Coffman plastic strain model were identified and corrected in 2002.

3.1.1 Time Step Algorithm The algorithms used in the automatic time step selection method for STRIKIN-HI arx described in Appendix C of Reference 16. They are designed to automatically adjust the time step length such that STRIKIN-I calculates an appropriate solution for the fuel, cladding and coolant temperature and the heat flux to the coolant by limiting the Courant number. They are designed to ensure that the Courant number, Rj, defined for Eq. H.2-6 in Reference 17, never exceeds 1.0 which ensures conservation of energy. That is, Rj Gj eAt/(pj*Az)<1.0 where GI = Mass flux at axial node j (lbmfft2 -sec)

At = Time step interval (sec) pj = Coolant density at axial node j (lbm/f 3 )

Az = Axial node lerigth (ft).

While the numerical limit for the Courant number is 1.0, the time step algorithm in STRIKN-Il further limits it to a value of 0.5. An error in the implementation of the algorithm bypassed this test which could allow the Courant number to exceed the normal limit. This error was corrected.

An additional problem that could produce a Courant number greater than 1.0 was found with the implementation of a user input for the minimum time step length. When the user input for the minimum time step is less than the value calculated by the automatic time step algorithm, the minimum time step length is used. An error test was added to stop the code with an error message if the minimum time step specified by the user would allow the Courant number to exceed 0.99.

Westinghouse Eectric Company LLC 4

CENPD -279, Supp. 14, Rev. 1 3.1.2 Coffman Plastic Strain Model for Cladding A problem with the implementation of the Coffmnan plastic strain model for fuel cladding in STRIKN-I1 was discovered. The model is only used when the heating rate and the cladding temperature are within bounds set for application of the model. The calculated plastic strain is continuous except when the cladding conditions are outside these bounds and later return within the bounds at a higher cladding temperature. In order to address the resulting discontinuity, a ramp function is used to introduce the strain over several time steps. The problem occurred when the heating rate fell below the lower bound for the model within the time duration of the ramp. This was corrected by terminating the ramp when the conditions for the use of the model described above are not satisfied.

3.1.3 Effect of Conrecting STRIM-H Errors Analyses of several plants with the 1985 EM for Zircaloy4 cladding shows that the effect on PCT is less than l 0.2-F l. Analyses of plants with the 1999 EM for Zircaloy4 and ZERLOw cladding show that the effect on cladding PCT is less than l 1.20 F I.

Westnghouse Electric Company LLC 5

CENPD -279, Supp. 14, Rev. 1

4.0 CONCLUSION

S There were two errors in the ECCS evaluation models for PWRs in CY 2002. Both of the errors were in STRIKEN- code models that affect the results of LBLOCA analyses using either the 1985 or 1999 EM. The sum of the absolute magnitude of the changes in PCT calculated using the June 1985 EM for BLOCA, including those from previous annual reports, References 2-15, remains less than 1F. The total 1985 EM LBLOCA impact on PCI for a given plant remains

<10 F. The maximum impact on PCI with the 1999 EM is less than 1.2F. Plant specific LBLOCA considerations for each plant are discussed in Appendices A through 0.

There are no errors for SBLOCA in CY 2002. Previous plant specific PCI effects for both the SIM and S2M SBLOCA evaluation models are discussed in Appendices A through G of Reference 15. In addition, there is a generic effect on maximum cladding temperature for the SBLOCA SIM (due to the change in application of the SBLOCA SIM described in Reference

11) that is less than 30 F. There is no previous accumulated change in cladding temperature for the S2M.

There is no PCT effect for the post-LOCA long term cooling evaluation model.

Westinghouse Electric Company LLC 6

CENPD -279, Supp. 14. Rev. 1

5.0 REFERENCES

1. "Acceptance Criteria for Emergency Core Cooling Systems for Light Water Nuclear Power Reactors," Code of Federal Regulations, Title 10, Part 50, Section 50.46.
2. 'Annual Report on C-E ECCS Codes and Methods for 10CFR50.46," CENPD-279, April, 1989.
3. 'Annual Report on C-E ECCS Codes and Methods for IOCFR50.46," CENPD-279, Supplement 1,February, 1990.
4. "Annual Report on C-E ECCS Codes and Methods for IOCFR50.46," CENPD-279, Supplement 2, April, 1991.
5. "Annual Report on C-E ECCS Codes and Methods for 10CFR50.46," CENPD-279, Supplement 3, April, 1992.
6. "Annual Report on C-E ECCS Codes and Methods for 10CFR50.46," CENPD-279, Supplement 4, April, 1993.
7. 'Annual Report on C-E ECCS Codes and Methods for IOCFR50.46," CENPD-279, Supplement 5, February, 1994.
8. "Annual Report on ABB C-E ECCS Performance Evaluation Models," CENPD-279, Supplement 6, February, 1995.
9. "Annual Report on ABB C-E ECCS Performance Evaluation Models," CENPD-279, Supplement 7, February, 1996.
10. "Annual Report on ABB CE ECCS Performance Evaluation Models," CENPD-279, Supplement 8, March, 1997.
11. "Annual Report on ABB CE ECCS Performance Evaluation Models," CENPD-279, Supplement 9, February, 1998.
12. "Annual Report on ABB CE ECCS Performance Evaluation Models," CENPD-279, Supplement 10, February, 1999.
13. "Annual Report on ABB CE ECCS Performance Evaluation Models," CENPD-279, Supplement 11, March, 2000.
14. "Annual Report on Combustion Engineering ECCS Performance Evaluation Models for PWRs," CENPD-279, Supplement 12, April, 2001.
15. "Annual Report on Combustion Engineering ECCS Performance Evaluation Models for PWRs," CENPD-279, Supplement 13, Rev. 1, April, 2002.

Westinghouse Electric Company LLC 7

CENPD -279, Supp. 14, Rev. 1

16. "STRED A Cylindrical Geometry Fuel Rod Heat Transfer Program," CENPD-135-P, Supplement 5, April 1977.
17. "STRIKWN-, A Cylindrical Geometry Fuel Rod Heat Transfer Program," CENPD-135P, August 1974.

Westinghouse Electric Company LUC 8

CENPD -279, Supp. 14, Rev. 1 APPENDIX A ARIZONA PUBLIC SERVICE COMPANY Plant Specific Considerations for Palo Verde Units 1, 2 and 3 The total effect on PCKU due to the STRIKiN- errors described in Section 3 is less than 1IT for LBLOCA analyses of Palo Verde Units 1, 2 and 3 done with the 1985 EM. There is no effect on the LBLOCA analyses for ZIRLOh cladding and revised heat sinks done in March 2002 with the 1999 EM because the corrected version of STRIN-H1 was used.

Plant specific effects for analyses done with the SIM SBLOCA methodology from previous reports are described in this appendix of Reference 15. There is no plant specific effect for the bounding S2M SBLOCA analysis of Palo Verde Units 1, 2 and 3 completed in March 2002 because it uses a corrected version of CEFLASH-4AS.

Westinghouse Electric Company LLC A.1

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