L-PI-10-050, Corrections to Emergency Core Cooling System (ECCS) Evaluation Models

Corrections to Emergency Core Cooling System (ECCS) Evaluation Models

ML101530169
Person / Time
Site:	Prairie Island
Issue date:	06/01/2010
From:	Schimmel M Northern States Power Co, Xcel Energy
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
L-PI-10-050
Download: ML101530169 (11)

Text

JUN 0 1 2010 L-PI-10-050 10 CFR 50.46 U S Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Prairie Island Nuclear Generating Plant Units 1 and 21 Dockets 50-282 and 50-306 License Nos. DPR-42 and DPR-60 Correct~onsto Emergencv Core Cooling Svstem (ECCS) Evaluation Models Enclosed please find enclosure 1, "Westinghouse Loss of Coolant Accident (LOCA)

Evaluation Model Changes," which is the 2009 annual report of corrections to the Pra rie lsland Nuclear Generating Plant (PINGP) Units 1 and 2 ECCS evaluation models. Tt is report is submitted in accordance with the provisions of 10 CFR 50.46 and sumrnarizt!~

changes made to both the large break LOCA (LBLOCA) and small break LOCA (SBLOCA) analyses.

The SBLOCA and LBLOCA peak clad temperature (PCT) assessment sheets for Unil 1 and Unit 2 are included in enclosure 2. The limiting LOCA analysis PCT for PINGP Unit 1 and Unit 2, with consideration of all 10 CFR 50.46 assessments, remains the LBLOA  :

analysis as summarized in enclosure 2.

Neither enclosure 1 nor enclosure 2 need be withheld from public disclosure.

Summary of Commitments This letter contains no new commitments and no revisions to existing commitments.

f l . cx.'*4e/-

Mark A. dchimmel Site Vice President, Prairie lsland Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (2) cc. Administrator, Region Ill, USNRC Project Manager, Prairie Island, USNRC Resident Inspector, Prairie Island, USNRC 1717 Wakonade Drive East Welch, Minnesota 55089-9642 Telephone: 651.388.11;!1

ENCLOSURE I Westinghouse LOCA Evaluation Model Changes 4 pages follow

Attachment to LTR-LIS-10-93 February 3, 201 0 GENERAL CODE MAINTENANCE (Discretionary Change)

Background

Various changes have been made to enhance the usability of codes and to streamline future analyses.

Examples of these changes include modifying input variable definitions, units and defaults; improving the input diagnostic checks; enhancing the code output; optimizing active coding; and eliminating inactive coding. These changes represent Discretionary Changes that will be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-1345 1.

Affected Evaluation Model(s) 1996 Westinghouse B.est Estimate Large Break LOCA Evaluation Model 1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PW& with Upper Plenum Injection 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM ,

Estimated Effect The nature of these changes leads to an estimated PCT impact of 0°F.

Attachment to LTR-LIS-10-93 February 3, 2010 ERROR IN ASTRUM PROCESSING OF AVERAGE ROD BURNUP AND ROD INTERNAL PRESSURE (Non-Discretionary Change)

Background

An error was discovered in the processing of the burnup and rod internal pressure inputs for average corr rods in ASTRUM analyses. The correction of this error has been evaluated for impact on current licensing-basis analyses and will be incorporated into the ASTRUM method at a future time. These changes represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 of WCAP- 13451.

Affected Evaluation Model(s) 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect This error was evaluated to have a negligible impact on PCT, leading to an estimated impact of 0°F for 10 CFR 50.46 reporting purposes.

Attachment to LTR-LIS-10-93 February 3, 2010 DISCREPANCY IN METAL MASSES USED FROM DRAWINGS (Non-Discretionary Change)

Background

Discrepancies were discovered in the use of lower support plate (LSP) metal masses fkom drawings. Tht :

updated LSP metal masses have been evaluated for impact on current licensing-basis analysis results and will be incorporated on a forward-fit basis. This change represents a Non-Discretionary Change in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Model(s)

SECY UP1 WCOBRAITRAC Large Break LOCA Evaluation Model 1996 Westinghouse Best Estimate Large Break LOCA Evaluation Model 1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect The lower support plate mass error is relatively minor and would be expected to have a negligible effect on the Large Break LOCA analysis results, leading to an estimated PCT impact of 0°F for 10 CFR 50.46 reporting purposes.

Attachment to LTR-LIS-10-93 HOTSPOT GAP HEAT TRANSF'ER LOGIC (Non-Discretionary Change)

Background

The HOTSPOT code has been updated to incorporate the following changes to the gap heat transfer logic ::

(1) change the gap temperature fiom the pellet average temperature to the average of the pellet outer surface and cladding inner surface temperatures; (2) correct the calculation of the pellet surface emissivil y to use a temperature in OR (as specified in Equation 7-28 of Reference 1) instead of OF; and (3) revise the calculation of the gap radiation heat transfer coefficient to delete a term and temperature adder not show]1 in or suggested by Equation 7-28 of Reference 1. These changes represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 of WCAP-13451.

Affected Evaluation Model@)

1996 Westinghouse Best ~ s t k n a t Large e Break LOCA Evaluation Model 1999 Westinghouse Best Estimate Large Break LOCA Evaluation Model, Application to PWRs with Upper Plenum Injection 2004 Westinghouse Realistic Large Break LOCA Evaluation Model Using ASTRUM Estimated Effect Sample calculations showed a minimal impact on PCT, leading .to an estimated effect of 0°F.

Reference(s)

1. WCAP- 12945-P-A, Volume 1, Revision 2, "Code Qualification Document for Best Estimate LOCA Analysis, Volume I: Models and Correlations," March 1998.

ENCLOSURE 2 LBLOCA and SBLOCA Peak Clad Temperature Assessment Sheets 4 pages follow

Attachment to LTR-LIS-10-93 February 3,20'0 Westinghouse LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 1 127110 Analysis Information EM: ASTRW (2004) Analysis Date: 11130107 Limiting Break Size: Split FQ: 2.5 FdEk 1.77 Fuel: 422 Vantage + SGTP (%): 10 Notes:

Clad Temp (OF) Ref. Not6 s LICENSING BASIS Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None B. PLANNED PLANT MODIFICATION EVALUATIONS 1 . None C. 2009 ECCS MODEL ASSESSMENTS 1 . None I). OTHER*

1 . None LICENSING BASIS PCT + PCT ASSESSMENTS PCT = 1765

• It IS recommended that the licensee determine ifthese PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

! WCAP-16890-P, Revision 1, "Best-Estimate Analysis of the Large-Break Loss-of-Coolant Accident for the Prairie Island Nuclear Plant Unit 1 Using ASTRUM Methodology," June 2008.

Notes:

None

Attachment to LTR-LIS-10-93 February 3, 20'0 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 1 /27/10 Analvsis Information EM: NOTRUMP Analysis Date: 1/21/08 Limiting Break Size: 3 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage + SGTP (%): 10 Notes: Zirlom (14X14),Frarnatome RSG Clad Temp (OF) Ref. Notc s LICENSING BASIS Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None B. PLANNED PLANT MODIFXCATION EVALUATIONS 1 . None C. 2009 ECCS MODEL ASSESSMENTS 1 . None D. OTHER*

1 . None LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 959

• It is recommended that the licensee determine ifthese PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

I LTR-LIS-08-158, "Transmittal of Future hairie Island Units 1 and 2 PCT Summaries," February 2008.

Notes:

None

Attachment to LTR-LIS-10-93 February 3,20'0 Westinghouse LOCA Peak Clad Temperature Summary for ASTRUM Best Estimate Large Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 1 /27/10 Analvsis Information EM: ASTRUM (2004) Analysis Date: 6/1/06 Limiting Break Size: Split FQ: 2.5 F a 1.77 Fuel: OFA SGTP (Yo): 25 Notes:

Clad Temp (OF) Ref. Notc s LICENSING BASIS Analysis-Of-Record PCT PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None B. PLANNED PLANT MODIFICATION EVALUATIONS 1 . None C. 2009 ECCS MODEL ASSESSMENTS 1 . None D. OTHERX 1 . None LICENSING BASIS PCT -tPCT ASSESSMENTS PCT= 1546 It is recommended that the licensee determine ifthese PCT allocptions should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

I WCAP-16508-P, "Best-Estimate Analysis ofthe Large-Break Loss-of.Coolant Accident for the Prairie Island Nuclear Plant Unit 2 Using ASTRUM Methodology," 6i2006 Notes:

None

Attachment to LTR-LIS-10-93 February 3, 2010 Westinghouse LOCA Peak Clad Temperature Summary for Appendix K Small Break Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 1 127110 Analvsis Information EM: NOTRUMP Analysis Date: 9/1/00 Limiting Break Size: 3 inch FQ: 2.8 FdFk 2 Fuel: OFA SGTP (%): 25 Notes: ZirloTM(14x14)

Clad Temp (OF) Ref. Note s LICENSING BASIS Analysis-Of-Record PCT 1142 1 (a1 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . No Items for 2000,2001 & 2002 Reports 2 . NOTRUMP Bubble Rise 1 Drift Flux Model Inconsistency Corrections 35 6,7 B. PLANNED PLANT MODIFICATION EVALUATIONS 1 . None C. 2009 ECCS MODEL ASSESSMENTS 1 . None D. OTHER*

1 . Evaluation for Reduced Auxilary Feedwater Flow Rate LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 1177

• It is recommended that the licensee determine ifthese PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

1 NSP-00-045, "SBLOCA Re-analysis with Revised NOTRUMP Code," October 2,2000.

2 NSP-01-006, "Northern States Power Company Prairie Island units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2000," March 6,2001.

3 NSP-02-36, "SBLOCA Limited FSAR Update and Evaluation for Revised Auxiliary Feedwatw Flow Rate," October 2002.

4 NSP-02-5, "Nuclear Management Company Prairie Island Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2001," March 2002. .

S NSP-03-19. "Nuclear Management Company Prairie Island Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2002," March 2003.

6 NSP-03-58, "10 CFR 50.46 Mid-Year Notification and Reporting for 2003," November 2003.

7 NSP-03-38, "Nuclear Management Company Prairie Island Units 1 and 2 10 CFR 50.46 Annual Notification and Reporting for 2003," March 2004.

Notes:

(a) Accumulator water volume sensitivity of+/- 30 cubic feet included