ML070170468

Report of Changes or Errors Discovered in the Current Acceptable Emergency Core Cooling System Evaluation Models

ML070170468
Person / Time
Site:	Nine Mile Point
Issue date:	01/11/2007
From:	Harland G Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML070170468 (2)

Text

Lycoming, NY 13093 Nine Mile Point Nuclear Station Constellation Energy P.O. Box 63 January 11, 2007 U. S. Nuclear Regulatory Commission Washington, DC 20555-0001 Attention: Document Control Desk

Subject:

Nine Mile Point Nuclear Station Unit Nos. 1 & 2; Docket Nos. 50-220 & 50-410 Report of Changes or Errors Discovered in the Current Acceptable Emergency Core Cooling System Evaluation Models

Reference:

General Electric Letter, A. Lingenfelter to Nine Mile Point Nuclear Station, Unit 2 - 10 CFR 50.46 Notification Letter 2006-01, "Impact of Top Peaked Power Shape for Small Break LOCA Analysis," July 28, 2006 The purpose of this letter is to submit a 30-day report in accordance with 10 CFR 50.46(a)(3)(ii) for a calculated Peak Cladding Temperature (PCT) change of more than 50 degrees for Nine Mile Point Nuclear Station, Unit 2 (NMP2). In the referenced letter, General Electric (GE) identified a change in the calculated PCT of more than 50 degrees. The evaluation of the change by Nine Mile Point Nuclear Station, LLC occurred on December 13, 2006. In the notification letter, GE reported a newly discovered sensitivity to the assumed axial power shape for small break loss-of-coolant accident (LOCA) cases. This sensitivity may result in higher calculated PCT values for top-peaked axial power shapes. The PCT impact of the new power shape sensitivity was estimated to be 90 degrees for the limiting analysis. The current peak clad temperature calculated for NMP2 is 1370'F for GE14 fuel. With this change, the PCT is estimated to be 1460'F (1370'F plus 90'F) which is 740'F below the 2200'F limit for the limiting analysis. Due to the large margin remaining, no reanalysis or other actions are planned.

No other changes or errors to the emergency core cooling system (ECCS) evaluation models used for Nine Mile Point Nuclear Station, Unit 1 (NMPI) or NMP2 were identified during 2006. Thus, this letter also serves as the annual report of changes or errors to the NMP1 and NMP2 ECCS evaluation models required by 10 CFR 50.46(a)(3)(ii). Additionally, no changes or errors to the ECCS evaluations models were identified in 2005 for NMP1 or NMP2.

Based on the above, for NMP1, the maximum increase in PCT due to changes or errors in the limiting analysis is 0°F. For NMP2, the maximum increase in PCT is 90'F. The sum of the absolute values of the effect on PCT of all changes or errors in the latest approved limiting ECCS analysis is 0°F for NMP 1 and 90'F for NMP2. The maximum anticipated PCT due to the limiting analysis remains less than 2200'F for NMP1 and NMP2.

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Document Control Desk January 11, 2007 Page 2 Should you have any questions regarding this submittal, please contact M. H. Miller, Licensing Director, at (315) 349-5219.

Very truly yours, Gary Harland Manager Engineering Services cc: D.V. Pickett, NRC S. J. Collins, NRC Resident Inspector, NRC