ML20217H567
| ML20217H567 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/09/1997 |
| From: | Krieger R SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9710160141 | |
| Download: ML20217H567 (2) | |
Text
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SOUTHikN CAlllOR%M ll. W. Krieger b
EDISON n?;L An i UlSON l\\ll R\\ A f 80%41 Canpany October 9,1997 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket Numbers 50-361 & 50-362 l
Voluntary Report - ABB-CE LOCA Evaluation Model San Onofre Nuclear Generating Station, Units 2 & 3 l
l l
In response to an NRC request, this letter provides a San Onofre specific update of the effects of the recently reported ABB-CE error regarding their Loss of Coolant Accident (LOCA) evaluation model.
On July 11,1997, ABB issued InfoBulletin 97-04 (Rev. 01), indicating that ABB was re-evaluating Energy Redistribution Factors (ERF) used in emergency core cooling systeni (ECCS) performance models for large and small break loss of coolant accidents (LBLOCA and SBL9CA). The evaluation was initiated due to an apparent omission of voiding effects when determining the ERF, ABB issued their preliminary evaluation findings on August 15,1997, confirming volding had been in:orrectly omitted when determining ERF for LBLOCA and SBLOCA ABB estimated the ERF were understated by 0.5 to 1,5%, and when corrected, would increase the calculated peak fuel clad temperature between 20 and 60 degrees F. ABB reported this error to the NRC on August 15,1997, under 10 CFR 21.
ABB concluded this omission occurred circa 1975 when generating ERF curves as a function of pin / Lox peaking factor. ABB-CE has recalculated these curves using the MCNP Monte Carlo coce for both the 14x14 and 16x16 lattice types. For the SONGS 16x16 lattice configuration, the not difference between the 1975 ERF PCT and the MCNP PCT is less than 50 degrees F. SCE is voluntarily providing this report due tn NRC interest.
The CE InfoBulletin 97-04 also recommended that Utilities administratively limit Peak j
Linear Heat Generation Rate (PLHGR) about 0.2 KW/FT below that allowed by the NRC to Iy maintain safety analysis conservatism.
A For the current SONGS cycles, the Linear Power Density (LPD) penalties implemented
/f(D/
were more restrictive than that required by the safety analysis. This self-imposed conservatism was sufficient to account for the ABB-recommended 0.2 KW/FT reduction in PLHGR However, based on the final values for SONGS, this additional administrative margin reservation is not required for the cycle 9.
P.O.lb 128 San Clemente, CA 92674-0128 71 & 368 6255 N R Elng 9710160141 971009 rn 714168+183 DR ADOCK 0000 1
,88 Ell,I%Isl a
Document Contrst Desk
- SQE evaluated all previous cycle fuel designs to determine the impact of the error on PCT in each cycle for both Units, it was determined that sufficient margin existed for each cycle to ensure that the PCT was maintained below the required 2200 degrees F.
If you have any questions, please let me know.
Sincerely, i
i l
b cc:
E. W. Merschoff, Regional Administrator, NRC Region IV K. E. Perkins, Jr., Director, Walnut Creek Field Office, NRC Region IV J. A. Sloan, NRC Senior Resident inspector, San Onofre Units 2 & 3 M. B. Fields, NRC Project Manager, D1 Onofre Units 2 & 3 Institute of Nuclear Power Operations (INPO) c j