L-2007-092, Emergency Core Cooling Systems in Light Water Nuclear Power Reactors - 30-Day Special Report
| ML071870339 | |
| Person / Time | |
|---|---|
| Site: | Turkey Point  |
| Issue date: | 06/25/2007 |
| From: | Jefferson W Florida Power & Light Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| L-2007-092 | |
| Download: ML071870339 (2) | |
Text
FPL June 25, 2007 L-2007-092 10 CFR 50.46 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, D. C. 20555- 00001 Re:
Turkey Point Units 3 and 4 Docket Nos. 50-250 and 50-251 10 CFR 50.46, "Acceptance Criteria for Emergency Core Cooling Systems in Light Water Nuclear Power Reactors" Day Special Report By letter L-2007-082 dated May 23. 2007, Florida Power & Light (FPL) submitted the 10 CFR 50.46 Annual Report for 2006. There were no changes in Peak Clad Temperature (PCT) in the Small Break Loss of Coolant Accident (SBLOCA) or the Large Break Loss of Coolant Accident (LBLOCA) for Turkey Point Units 3 and 4 during 2006. The reported total estimated LBLOCA PCT was 2064 OF and the SBLOCA PCT was 1689 OF.
Westinghouse notified FPL via letter NF-FP-07-126 dated June 4, 2007, of a computer code error in their design basis analysis of the LBLOCA PCT for Turkey Point Units 3 and 4.
Specifically, the error occurred in the HOTSPOT code. At the axial node where fuel rod burst is predicted to occur, a fuel relocation model in HOTSPOT is used to account for the likelihood that additional fuel pellet fragments above that elevation may settle into the burst region. It was discovered that the effect of fuel relocation on local linear heat rate was being calculated, but then cancelled out later in the coding. Westinghouse determined that the error has an adverse impact of +40 OF on predicted PCT. Therefore, the current Turkey Point Units 3 and 4 design basis LBLOCA PCT of 2064 OF is being changed to 2104 OF. This is still well below the 10 CFR 50.46 limit of 2200 OF.
10 CFR 50.46(a)(3)(ii) requires that licensees report within 30 days to the Commission significant changes to, or errors discovered in, the Emergency Core Cooling System (ECCS) evaluation models, or in the application of such models that affect the peak clad temperature calculation and their effect on the limiting ECCS analysis. 10 CFR 50.46 (a)(3)(i) defines a significant change or error as one which results in a calculated peak fuel cladding temperature different by more than 50 OF.
Including the impact of this error in the HOTSPOT code, the cumulative changes to the Turkey Point Units 3 and 4 LBLOCA Evaluation Model PCT is 153 OF.
In accordance with 10 CFR 50.46 this issue is reportable to the NRC within 30 days. This letter meets the 30-day reporting requirement. In addition to reporting, 10 CFR 50.46 also requires that a schedule be proposed for reanalysis or for taking other actions as may be needed to show compliance with the requirements of the regulation. Including the impact of this error, Westinghouse has determined that the Turkey Point Units 3 and 4 LBLOCA design basis analysis maintains compliance with 10 CFR 50.46 requirements. Accordingly, no schedule for reanalysis is required. Nevertheless, FPL is assessing options, including reanalysis with improved methodology, to gain additional margin to the 10 CFR 50.46 criteria.
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g L-2007-092 Page 2 of 2 Should there be any questions, please contact James Connolly, Licensing Manager, at 305-246-6632.
Very truly yours, William Jefferson, Jr.
Vice President Turkey Point Nuclear Plant OIH Attachment cc:
Regional Administrator, Region II, USNRC Senior Resident Inspector, USNRC, Turkey Point Plant