ML13317B335
| ML13317B335 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 04/12/1991 |
| From: | Kalman G Office of Nuclear Reactor Regulation |
| To: | Ray H Southern California Edison Co |
| References | |
| TAC-80050 NUDOCS 9105060074 | |
| Download: ML13317B335 (3) | |
Text
o UNITED STATES
- 4.
NUCLEAR REGULATORY COMMISSION A
P WASHINGTON, D. C. 20555 April 12, 1991 Docket No. 50-206 Mr. Harold B. Ray Senior Vice President Southern California Edison Company Irvine Operations Center 23 Parker Street Irvine, California 92718
Dear Mr. Ray:
SUBJECT:
SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1, RESOLUTION OF REACTOR VESSEL REFILL DISCREPANCY (TAC 80050)
On March 28, 1991, the Southern California Edison (SCE) Company notified the NRC by a 10 CFR Section 50.72 report that an error had been discovered in the input model for the San Onofre Unit 1 large break loss-of-coolant-accident (LBLOCA) analysis. The error involved the use of a refill volume of 490 cubic feet instead of the correct volume of 672 cubic feet and was nonconservative in that the time required to refill the reactor vessel following a LBLOCA was underestimated. The longer refill interval would result in a higher calculated peak clad temperature (PCT) following the LBLOCA.
By letter dated March 29, 1991, SCE provided a justification for continued operation at full power based on a sensitivity analysis performed by SCE and Westinghouse. The analysis indicated that the post-accident, PCT would be 210OF higher than the previously calculated value using the smaller (incorrect) reactor volume. The higher temperature would imply that the post-accident PCT limit of 2300'F could be exceeded following a LBLOCA at full power. While this discrepancy was being evaluated, SCE limited reactor power to 75 percent to conservatively remain within allowable PCT limits.
The sensitivity analysis, presented in the March 29, 1991, letter, concluded that calculations using the corrected refill volume do not indicate a higher than allowable post-accident PCT under most operating conditions. However, it was concluded that if operating at full power and with the maximum allowable peaking factor (power offset), PCT could exceed the 2300 degree limit following a LBLOCA. SCE indicated that in practice, the reactor is never operated with the peaking factor near the authorized limit. Administrative controls were established to formally reduce the currently allowed peaking factor (2.78) to a figure (2.38) consistent with the corrected PCT calculations. A Technical Specification (TS) revision will be submitted by SCE to incorporate the new peaking factor into the facility license.
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Mr. Harold B. Ray
-2 The NRC staff has been in telephone communication with SCE during the resolution of the reactor refill issue and has verbally concurred with the subsequent operational restrictions. This issue will be formally concluded after the peaking factor that is currently in the TS is revised to reflect the corrected, post-accident cooling calculations. Within the next 30 days SCE will provide a schedule for submitting the TS revision.
Sincerely, Original Sign 3d By:
George Kalman, Senior Project Manager Project Directorate V Division of Reactor Projects III/IV/V Office of Nuclear Reactor Regulation cc:
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Mr. Harold B. Ray San Onofre Nuclear Generating Southern California Edison Company Station, Unit No. 1 cc:
Mr. Phil Johnson Mr. Richard J. Kosiba, Project Manager U.S. Nuclear Regulatory Commission Bechtel Power Corporation Region V 12440 E. Imperial Highway 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 Mr. Robert G. Lacy Manager, Nuclear Department San Diego Gas & Electric Company P. 0. Box 1831 San Diego, California 92112 Resident Inspector, San Onofre NPS c/o U.S. Nuclear Regulatory Commission P. 0. Box 4329 San Clenente, California 92672 Mayor City of San Clemente 100 Avenida Presidio San Clemente, California 92672 Chairman, Board of Supervisors County of San Diego 1600 Pacific Highway, Room 335 San Diego, California 92101 Regional Administrator, Region V U.S. Nuclear Regulatory Commission 1450 Maria Lane, Suite 210 Walnut Creek, California 94596 Mr. John Hickman Senior Health Physicist Environmental Radioactive Mgmt. Unit Environmental Management Branch State Department of Health Services 714 P Street, Room 616 Sacramento, California 95814 Mr. Don J. Womeldorf Chief, Environmental Management Branch California Department of Health Services 714 P Street, Room 616 Sacramento, California 95814 (9)