L-PI-12-046, Annual Report of Corrections to the Emergency Core Cooling System (ECCS) Evaluation Models

Annual Report of Corrections to the Emergency Core Cooling System (ECCS) Evaluation Models

ML12178A415
Person / Time
Site:	Prairie Island
Issue date:	06/26/2012
From:	Molden J Northern States Power Co, Xcel Energy
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
L-PI-12-046
Download: ML12178A415 (11)

Text

-e Xcel Energy" L-PI-12-046 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 2 Dockets 50-282 and 50-306 Renewed License Nos. DPR-42 and DPR-60 201 1 Annual Report of Corrections to the Prairie Island Nuclear Generating Plant IPINGP) Emergencv Core Cooling Svstem (ECCS) Evaluation Models Pursuant to IOCFR 50.46, Northern States Power Company, a Minnesota corporation, doing business as Xcel Energy (hereafter "NSPM"), submits the 201 1 annual report of corrections to the PINGP Units 1 and 2 ECCS evaluation models.

Enclosure 1 contains the "Westinghouse Loss of Coolant Accident (LOCA) Evaluation Model Changes" and summarizes the 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 Unit 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 LBLOCA analysis as summarized in Enclosure 2.

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

ames E. Molden

' A i t e Vice President, Prairie Island Nuclear Generating Plant Northern States Power Company - Minnesota Enclosures (2) cc: Administrator, Region Ill, USNRC Project Manager, PINGP, USNRC Resident Inspector, PINGP, USNRC 1717 Wakonade Drive East

• Welch, Minnesota 55089-9642 Telephone: 651.388.1121

ENCLOSURE I Westinghouse LOCA Evaluation Model Changes 4 pages follow

Attachment to LTR-LIS-72-120 February 24,2012 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@)

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

Attachment fo LTR-LIS-12-120 February 24, 2012 RADIATION HEAT TRANSFER LOGIC (Non-Discretionary Change)

Baclrground Two errors were discovered in the calculation of the radiation iteat transfer coefficient in the SBLOCTA computer code. First, existing diagnostics did not preclude non-physical negative or large (negative or positive) radiation heat transfer coefficients from being calculated. These calculations occurred when the vapor temperature exceeded the cladding surface temperature or when the predicted temperature difference was less than 1 degree. Second, a temperature term incorrectly used degrees Fahrenheit instead of Rankine. These eirors have been corrected in the SBLOCTA code and represent a closely-related group of Non-Discretionary Changes in accordance with Section 4.1.2 of WCAP- 13451.

Affected Evaluation Model@)

1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect A combination of SBLOCTA sensitivity calculations and engineering judgment led to an estimated PCT effect of 0°F for existing Small Break LOCA analysis results.

Attachment to LTR-LIS-12-120 February 24,2012 MAXIMUM FUEL ROD TIME STEP LOGIC (Non-Discretionary Change)

Bacicground An error was discovel-ed in the SBLOCTA code that allowed the fuel rod time step to exceed the specified maximum allowable time step. The time step logic has been corrected jn the SBLOCTA code. This change represents a Non-Discretionay Change in accordance with Section 4. I .2 of WCAP- 13451.

Affected Evaluation Model(s) 1985 Westinghouse Small Break LOCA Evaluation Model with NOTRUMP Estimated Effect A combination of SBLOCTA sensitivity calculations and engineering judgment led to an estimated PCT effect of O"Ffor existing Small Break LOCA analysis results.

Attachment to LTR-LIS-12-120 February 24, 2012 GENERAL CODE MaMTENANCE (Discretionary Change)

Baclcground Various changes have been made to enhance the usability of the codes and to help preclude errors in analyses. This includes items such as 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 wiI1. be implemented on a forward-fit basis in accordance with Section 4.1.1 of WCAP-1345 1.

Affected Evaluation Model@)

1985 Westinghouse Small Brealc LOCA Evaluatio~lModel with NOTRUMP Estimated Effect The nature of these changes leads to an estimated PCT impact of 0°F.

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

Attachment to LTR-LIS-12-120 February 24,2012 Westinghouse LOCA. P e a i r Clad Temperature Summary for Appendix K Small Brealc Plant Name: Prairie Island Unit 1 Utility Name: Xcel Energy, 111c Revision Date: 2/24/20 12 Analvsis Information Eh4: NOTRUMP Analjlsis Date: 1/21/2008 Limiting Brcalc Size: 3 inch FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage + SGTP (%): 10 Notes: Zirlo@ (14X14), Framatome RSG Clad Temp (OF) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 359 1 PCT ASSESSMENTS (Delta PCT)

, A. PRIOR ECCS MODEL ASSESSMENTS I . None B. PLANNED PLANT MODIFICATION EVALUATIONS 1 None 0 C. 2011 ECCS MODEL ASSESSMENTS 1 .None D. OTHER*

I . None LICENSING BASIS PCT. +P a ASSESSMENTS PCT= 959

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

Rcferenccs:

1. LTR-LIS-08-158, "Transmittal ofFuture Prairie Island Units 1 and 2 PCT Summaries," Febiuary 2008.

Notes:

None

Attachment to LTR-LIS-72-120 February 24, 2012 Westingbouse LOCA Peak Clad Temperature S u m m a r y for ASTRUM' Best Estimate Large Brealc Plant Name: Prairie Tsland Unit 1 Utility Name: Xcel Energy, Inc Revision Date: 21241201 2 Annlvsis Information EM.: ASTRUM (2004) Analysis Date: 11/30/2007 Limiting Brealc Size: Split FQ: 2.5 FdH: 1.77 Fuel: 422 Vantage t SGTP (%): 10 Notes:

Clad Temp ( O F ) Ref. Notes LICENSING BASIS Analysis-OERecord PCT 1765 1 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 . None B. PLANNED PLANT MODIFICATION EVAJXATIONS 1 .None C. 201 1 ECCS MODEL ASSESSMENTS 1 , None D. OTIIER*

1 .None LZCENSlNG BASIS PCT + PCT ASSESSMENTS PCT= 1765 V t is recommended that the licensee determine if these PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

1. 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

~ttachmentto LTR-LIS-I 2-120 February 24, 2012 Westinghouse LOCA Peak CIad Temperature Sum~nitryfor Appendix K Small Brealc PIant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Inc Revision Date: 2/24/2012 Analysis Information EM: NOTRUMP Analjlsis Date: 1/21/2008 Limiting Brealc Sizc: 2 inch FQ: 2.5 FdII: 1.77 Fuel: 422 Vantage + SGTP (%): 25 Notes: ZirloQ (14x14)

Clad Tenip ( O F ) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 965 1 PCT ASSESSMENTS (Delta PCT)

A. PRIOR ECCS MODEL ASSESSMENTS 1 .None B. PLANNED PLANT MODIFICATION EVALUATIONS 1 . None C. 2011 ECCS MODEL ASSESSMENTS 1 .None D. OTHER*

1 . None LICENSING BASIS PCT -I-PCT ASSESSMENTS PCT= 965

+ It is recommended (hat the licensee determine if these PCT allocations should be considered with respect to 10 CFR 50.46 reporting requirements.

References:

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

None

Attachment to LTR-LIS-12-120 February 24, 2012 Westinghouse LOCA Peak Clad Temperature Summary for ASTRUM Eest Estimate.Large Brealc Plant Name: Prairie Island Unit 2 Utility Name: Xcel Energy, Tnc Revision Date: 2/24/2012 Analj~sisInformation EM: ASTRUM (2004) Analysis Date: 11/30/2007 Limiting Break Size: Split FQ: 2.5 FdB: 1.77 Fuel: 422 Vantage + SGTP ( O h ) : 25 Notes:

Clad Temp ( O F ) Ref. Notes LICENSING BASIS Analysis-Of-Record PCT 1623 1 PCT ASSESSMENTS (Delta PCT) ,

A. P N O R ECCS MODEL ASSESSMENTS 1 . None 0 B. PLANNED PLANT MODlFXCATION EVAWATIONS 1 None C. 2011 ECCS MODEL ASSESSMENTS 1 . None D. OTHER*

1 None LICENSING BASIS PCT + PCT ASSESSMENTS PCT= 1623

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

References:

1. WCAP-16891-P, "Best-Estimate Analysis of the Large-Break Loss-of-Coolant Accident for the Prairie Island Nuclear Plant Unit 2 Using ASTRUM Methodology," 612008.

Notes:

None