RS-07-068, Updated Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors from November 4, 2005 Through November 3, 2006

Updated Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors from November 4, 2005 Through November 3, 2006

ML071100413
Person / Time
Site:	Clinton
Issue date:	04/19/2007
From:	Simpson P AmerGen Energy Co
To:	Document Control Desk, NRC/NRR/ADRO
References
RS-07-068
Download: ML071100413 (7)

Text

www.exe1oncorp corn An Exelon Company AmerGen Energy Company, LLC 4300 Winfield Road Warrenville, IL 60555 April 19, 2007 10 CFR 50.46 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, D.C. 20555-0001 Clinton Power Station, Unit 1 Facility Operating License No. NPF-62 NRC Docket No. 50-461

Subject:

Updated Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station

Reference:

Letter from K. M. Nicely (Exelon Generation Company, LLC) to U. S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 3,2006 In the referenced letter, AmerGen Energy Company, LLC (AmerGen) submitted the annual report of the Emergency Core Cooling System (ECCS) evaluation model changes and errors for Clinton Power Station (CPS), Unit 1 in accordance with 10 CFR 50.46, "Acceptance criteria for emergency core cooling systems for light-water nuclear power reactors," paragraph (a)(3)(ii). The report covered the period from November 4,2005 through November 3,2006.

We recently identified that the peak clad temperature evaluation for the core shroud repair performed in the Spring 2006 refueling outage was not reported in the CPS 10 CFR 50.46 annual report provided in the referenced letter. The issue associated with this oversight has been entered into the corrective action program.

The attachment to this letter provides an updated annual report of the CPS ECCS evaluation model changes and errors. The attached report continues to cover the period from November 4,2005 through November 3,2006.

April 18, 2007 U. S. Nuclear Regulatory Commission Page 2 Should you have any questions concerning this letter, please contact Mr. Timothy A. Byam at (630) 657-2804.

Respectfully, Patrick R. Simpson Manager - Licensing Attachments:

1. 10 CFR 50.46 Report

2. 10 CFR 50.46 Report Assessment Notes

Attachment 1 Clinton Power Station Unit 1 10 CFR 50.46 Report Page 1 of 2 PLANT NAME: Clinton Power Station, Unit 1 ECCS EVALUATION MODEL: SAFEWGESTR - LOCA REPORT REVISION DATE: 313 1I07 CURRENT OPERATING CYCLE: 11 ANALYSIS OF RECORD Evaluation Model Methodology: The GESTR-LOCA and SAFER Models for the Evaluation of the Loss-of-Coolant Accident; Volume Ill, SAFERIGESTR Application Methodology, NEDC-23785-1-PA, Revision 1, General Electric Company, October 1984.

Calculation: Clinton Power Station, SAFEWGESTR-LOCA Analysis Basis Documentation, NEDC-32974P, GE Nuclear Energy, October 2000.

Fuel: GE 14 Limiting Fuel: GE 14 Limiting Single Failure: High Pressure Core Spray (HPCS) Diesel Generator Limiting Break Size and Location: 1.0 Double Ended Guillotine of Recirculation Pump Suction Piping Reference Peak Cladding Temperature (PCT):

MARGIN ALLOCATION A. PRIOR LOCA MODEL ASSESSMENTS 10 CFR 50.46 report dated November 13,2000 (See Note 1) APCT = 0°F 10 CFR 50.46 report dated November 08,2001 (See Note 2) APCT = 5°F 10 CFR 50.46 report dated November 05,2002 (See Note 3) APCT = 35°F 10 CFR 50.46 report dated November 05,2003 (See Note 4) APCT = 5°F 10 CFR 50.46 report dated November 05,2004 (See Note 5) APCT = 0°F 10 CFR 50.46 report dated November 04,2005 (See Note 6) APCT = 0°F 10 CFR 50.46 report dated November 03,2006 (See Note 7) APCT = 0°F Net PCT 1595°F

Attachment 1 Clinton Power Station Unit 1 10 CFR 50.46 Report Page 2 of 2 B. CURRENT LOCA MODEL ASSESSMENTS Core Shroud Repair (Note 8) APCT = 6°F Total PCT change from current assessments , CAPCT = 6°F Cumulative PCT change from current assessments c I APCT I = 6 " ~

Net PCT 1601OF

Attachment 2 Clinton Power Station Unit 1 10 CFR 50.46 Report Assessment Notes Page 1 of 3 NOTES:

1. Prior LOCA Model Assessments The referenced letter reported a new analysis of record for Clinton Power Station (CPS).

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Reference:

Letter from M. A. Reandeau (AmerGen Energy Company) to U.S. NRC, "Report of a Change to the ECCS Evaluation Model Used for Clinton Power Station (CPS)," dated November 13, 2000.1

2. Prior LOCA Model Assessments An inconsistent core exit steam flow was used in the pressure calculation in the SAFER code when there is a change in the two-phase level. The incorrect calculated pressure may result in premature termination of ECCS condensation and will impact the second peak clad temperature (PCT). GE evaluated the impact of this error and determined that the impact is an increase of 5°F in the PCT. This error was reported to the NRC in the referenced letter.

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Reference:

Letter from K. A. Ainger (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 8, 2001 .]

3. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the Low Pressure Coolant Injection (LPCI) and Low Pressure Core Spray (LPCS) minimum flow valve flow diversion was reported and was found to have a 0°F impact. Also in the referenced letter GE LOCA errors were reported all of which had a 0°F PCT increase except for a SAFER Core Spray sparger injection elevation error that resulted in a 15°F increase in the PCT. The Extended Power Uprate (EPU) has resulted in an increase of 20°F in the PCT. The EPU was implemented in Cycle 9 Reload.

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Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2002.1

4. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of an error found in the initial level/volume table for SAFER was reported. The levellvolume tables were generated with incorrect initial water levels. This resulted in an incorrect volume split in the nodes above and below the water surface, and incorrect initial liquid mass. This error resulted in a 5°F increase in the PCT for all fuel types (i.e., GE 10 & GE14).

Attachment 2 Clinton Power Station Unit 1 10 CFR 50.46 Report Assessment Notes Page 2 of 3

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Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2003.1

5. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of a GE postulated new heat source applicable to the LOCA event was reported. This heat source is due to recombination of hydrogen and excess oxygen drawn into the vessel from containment during core heatup. The PCT impact for all fuel types was 0°F and the effect on local oxidation was negligible.

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Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 5, 2004.1

6. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the 24-month cycle operation was reported. The evaluation determined that the LOCA analysis of record was performed with bounding assumptions and hence is not impacted with the 24-month cycle. A zero degree PCT impact was assigned.

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Reference:

Letter from Patrick R. Simpson (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 4, 2005.1

7. Prior LOCA Model Assessments In the referenced letter to the NRC, the impact of the top peak axial power shape on the small break LOCA was reported. The impact of the top peak axial power shape on the licensing basis PCT was zero degrees for GE 14 fuel for CPS.

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Reference:

Letter from Kenneth M. Nicely (Exelon Generation Company) to U.S. NRC, "Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors for Clinton Power Station," dated November 3,2006.1

8. Current LOCA Model Assessments During the CPS Cycle 11 reload outage in the Spring 2006 (i.e., C1RlO), a core shroud repair was performed.

The leakage flows through the repair holes result in slightly increased time to core recovery, following core uncovery. The effect has been conservatively assessed to increase the PCT for the limiting LOCA by less than 6°F. The Cycle 11 Reload evaluation for the GE 14 fuel did not have any impact on the PCT for CPS. The combined impact on the licensing basis PCT is reported as 6°F for CPS.

Attachment 2 Clinton Power Station Unit 1 10 CFR 50.46 Report Assessment Notes Page 3 of 3

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Reference:

GENE-0000-0023-6259-05, Revision 1, Amergen Energy Co, LLC Clinton Power Station BWRVIP-04A Core Shroud Repair Design Submittal to the NRC, March 2005.1