1CAN091001, 10 CFR 50.46 Report - Significant Change in Peak Cladding Temperature

10 CFR 50.46 Report - Significant Change in Peak Cladding Temperature

ML102510656
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/08/2010
From:	David Bice Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
1CAN091001
Download: ML102510656 (5)

Text

Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-4710 David B. Bice Acting Manager, Licensing Arkansas Nuclear One 1CAN091001 September 8, 2010 U. S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001

Subject:

10 CFR 50.46 Report - Significant Change in Peak Cladding Temperature Arkansas Nuclear One - Unit 1 Docket No. 50-313 License No. DPR-51

Dear Sir or Madam:

Pursuant to 10 CFR 50.46(a)(3)(ii), the following information is provided concerning a change to the Arkansas Nuclear One, Unit 1 (ANO-1) Emergency Core Cooling System (ECCS) analyses. On August 9, 2010, AREVA NP Inc. (AREVA) notified Entergy of a change in the ANO-1 ECCS evaluation model that resulted in an increase in the estimated peak cladding temperature (PCT) of greater than 50 °F from the previous temperature calculated for the Small Break Loss of Coolant Accident (SBLOCA). The change is discussed below.

AREVA has informed Entergy that the SBLOCA axial power shape defined in the Loss of Coolant Accident (LOCA) evaluation model may not be bounding for middle-of-cycle (MOC) to end-of cycle (EOC) conditions. Since the SBLOCA analyses are designed to be independent of time-in-cycle, a bounding axial power shape must be used per the requirements of 10 CFR 50, Appendix K. Thus, a bounding EOC 11-foot axial power shape that conservatively meets all requirements was developed and analyzed, resulting in an increase in the reported SBLOCA PCT for all Babcock & Wilcox plants. A revised SBLOCA PCT of 1507 °F has been assigned to ANO-1 to account for the new 11-foot axial power shape. This PCT represents an increase of +225 °F above the previously reported SBLOCA PCT of 1282 °F. The new SBLOCA PCT remains well-below the 10 CFR 50.46 acceptance criteria of 2200 °F, but is greater than the 50 °F PCT change criterion for reporting a model error. Thus, the error requires a 30-day report to the NRC. Additionally, the margin to the limits of local oxidation and whole core hydrogen generation criteria remain sufficient to assure that compliance to these criteria remains unchanged. Consideration of the revised SBLOCA axial power shapes does not impact the conclusions that a coolable core geometry and long-term core cooling can be maintained following any licensing basis SBLOCA.

1CAN091001 Page 2 This error correction is limited to SBLOCA applications; therefore, the PCT for the Large Break Loss of Cooling Accident (LOCA) and the bounding plant linear heat rate limits are unaffected.

The attachment to this report tabulates the effect of the error correction on the SBLOCA PCT for the ANO-1 LOCA licensing basis.

As stated above, the new SBLOCA PCT remains well below the 10 CFR 50.46 acceptance criteria; however, AREVA has also reported that the new estimated PCT of 1507 °F introduces the possibility that fuel clad rupture could be predicted for certain fuel rod conditions. AREVA has scheduled a SBLOCA analysis to determine the PCT effects of the 11-foot axial power shape and to determine if cladding rupture would occur. This analysis is scheduled for completion by December 31, 2010. AREVA has completed an interim evaluation which concludes that the current SBLOCA analysis, that predicts no clad rupture, remains bounding for the current ANO-1 cycle through at least 300 EFPD core burn-up, which is expected to occur no earlier than mid-February 2011.

Should you have any questions regarding this report, please contact me.

There are no new commitments contained in this submittal.

Sincerely, DBB/fpv Attachment - Peak Cladding Temperature Change for SBLOCA Analyses

1CAN091001 Page 3 cc: Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 NRC Senior Resident Inspector Arkansas Nuclear One P.O. Box 310 London, AR 72847 U.S. Nuclear Regulatory Commission Attn: Mr. Kaly Kalyanam MS O-8B1 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Bernard R. Bevill Arkansas Department of Health Radiation Control Section 4815 West Markham Street Slot #30 Little Rock, AR 72205

Attachment to 1CAN091001 Peak Cladding Temperature Change for SBLOCA Analyses

Attachment to 1CAN091001 Page 1 of 1 Peak Cladding Temperature Change for SBLOCA Analyses Loss of Coolant Accident (LOCA) Licensing Activity for Arkansas Nuclear One - Unit 1 Plant Name: Arkansas Nuclear One - Unit 1 Mark- B- HTP LOCA Spectrum Utility Name: Entergy Large Break LOCA Small Break LOCA Reporting Category Description Peak Cladding Temperature (PCT) or PCT Change 2008.1 F 1282 F Previous Licensing Basis Estimated Analyzed End-of-Cycle Small Break Evaluation Model Error N/A +225 F LOCA Axial Power Shape 2008.1 F 1507 F Current Licensing Basis Estimated Estimated