ML13308B509
| ML13308B509 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 01/14/1974 |
| From: | Coe R SOUTHERN CALIFORNIA EDISON CO. |
| To: | Oleary J US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8103060672 | |
| Download: ML13308B509 (2) | |
Text
Southern California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 January 14, 1974 Mr. John F. O'Leary, Director Directorate of Licensing Regulation U. S. Atomic Energy Commission Washington, D. C. 20545 Docket No. 50-206 San Onofre Unit 1
Dear Mr. O'Leary:
At 1:47 PM, December 18, 1973, while conducting sphere penetration leak rate tests, excessive leakage was observed on the sphere equalizing and instrument vent header penetration.
Computer analysis determined the leakage to be 138% of the allowable 0. 2% of the containment volume in 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />. If containment isolation had been initated, leakage would have been within design limitations as indicated below. The unit was in a cold shutdown configuration with the containment sphere open when the condition was observed.
A visual inspection revealed that CV-116, the sphere equalizing valve, which is located inside the sphere, was leaking around the valve seat.
CV-10, the redundant isolation valve, located outside the sphere, performed properly.
A blank flange was bolted on the valve and the penetration re-tested. The leakage dropped to 0. 5% of the allowable.
This verified that CV-116 was leaking and that CV-10 outside the sphere wa s operating properly.
The sphere equalizing valve, CV-116, operates in conjunction with CV-10 to minimize the pressure differential between atmospheric and containment sphere pressures.
The valve is a normally open butterfly and seats on both sides of the valve disc.
The valve seat is a neoprene material, exposed to the containment atmosphere and will dry out and bind the valve unless lubricated properly.
The valve seat was subsequently cleaned and lubricated.
The penetration was leak tested satisfactorily on December 21, 1973, with a final leak rate of. 85%
of the allowable.
c1:I
~ Gu 4 2
-2 Mr. John F. O'Leary January 14, 1974 The inspection and lubrication requirements for CV-116 have been added to the addressograph preventive maintenance system.
It should be recognized that CV-10, the redundant isolation valve, tested and operated satisfactorily throughout the incident.
Sincerely, Robert N. Coe Senior Vice President cc: R. H. Engelken, Director Region V, Regulatory Operations Office