ML13310B078

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Forwards Rev 2 to PWR Safety & Relief Valve Test Program, PORV Block Valve Adequacy Rept for Southern California Edison,San Onofre,Unit 1
ML13310B078
Person / Time
Site: San Onofre Southern California Edison icon.png
Issue date: 11/17/1983
From: Medford M
SOUTHERN CALIFORNIA EDISON CO.
To: Crutchfield D
Office of Nuclear Reactor Regulation
Shared Package
ML13310B080 List:
References
TAC-44128, NUDOCS 8311280367
Download: ML13310B078 (2)


Text

Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD. CALIFORNIA 91770 M.O. MEDFORD TELEPHONE MANAGER, NUCLEAR LICENSING (213) 572-1749 November 17, 1983 Director, Office of Nuclear Reactor Regulation Attention: D. M. Crutchfield, Chief Operating Reactors Branch No. 5 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

Subject:

Docket No. 50-206 PORV Block Valve Adequacy Report San Onofre Nuclear Generating Station Unit 1

Reference:

Letter, K. P. Baskin, (SCE), to D. M. Crutchfield, (NRC),

PORV Block Valve Adequacy Report, July 13, 1983 The referenced letter provided you with the information available to date on the PORV block valves at San Onofre Unit 1. We indicated that we needed to verify some assumptions in the Anchor/Darling prepared portion of the subject report. It is the purpose of this correspondence to provide you with the completed report.

In compliance with our commitment, please find enclosed the "PORV Block Valve Adequacy Report for San Onofre Unit 1."

The report provides adequate justification for the San Onofre Unit 1 PORV block valves.

The report concludes that the block valves-are capable of performing the design pressurizer PORV relief blocking function. Accordingly, no modifications other than those defined below are planned.

As described in the referenced letter, certain as-built design parameters were verified. The results are as follows:

1. The supply air pressure range is 84.5 to 92.75 psig. This is sufficient air pressure to assure valve operability, as further described in the enclosed report.

8311280367 831117 PDR ADOCK( 05000206 P

PDR

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Mr. D. M. Crutc'hfield November 17, 1983 The backup air supply for the PORV block valves is provided by a bottled nitrogen system which has a set point of 80 psig. As illustrated in Figure 4-1 of the enclosed report, this will allow the valves to close to within 5 percent of full closure. This would reduce the full discharge of the PORV's to what is considered a leakage level. This conclusion i.s based on the fact that with the valve 5 percent open (.125 inch) the valve gate has not yet cleared the seat of the valve. Accordingly, the blocking function of these valves is assured when the backup nitrogen system is used.

2. The bonnet bolting torque value was found to be less than the required 640 ft-lbs. Since the verification, the bolting has been torqued to 640 ft-lbs.
3. The spring used in the valve operator was found to be a nested spring arrangement with a spring rate of approximately 1,850 lbs. per inch. In order to support the assumptions in the enclosed report, a check with the actuator manufacturer has verified that a new spring, with a spring rate of 1,035 lbs. per inch, can be purchased and will be installed during the next maintenance interval, but no later than prior to return to power from the current outage. Although this is not the 1,020 lbs. per inch assumed in the enclosed Westinghouse report, a Westinghouse verification analysis has determined this to be an acceptable application.

The above discussion completes our action on the requirements of NUREG-0737, Item II.D.l - Performance Testing of PWR Safety and Relief Valves. If you have any questions or desire additional information, please let me know.

Sincerely, Enclosure