ML13331A243
| ML13331A243 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 02/08/1988 |
| From: | Medford M Southern California Edison Co |
| To: | NRC Office of Administration & Resources Management (ARM) |
| References | |
| IEB-80-20, NUDOCS 8802120205 | |
| Download: ML13331A243 (2) | |
Text
Southern.California Edison Company P. 0. BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M. 0. MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING February 8, 1988 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D.C. 20555 Gentlemen:
Subject:
Docket No. 50-206 IE Bulletin 80-20:
Failures of Westinghouse Type W-2 Spring Return to Neutral Control Switches San Onofre Nuclear Generating Station Unit 1
Reference:
Letter from J. G. Haynes, SCE, to R. H. Engelken, NRC Region V, Dated September 5, 1980, regarding IE Bulletin 80-20 In response to IE Bulletin 80-20 regarding failures of Westinghouse Type W-2 Control switches, SCE provided to the NRC the referenced letter. As stated therein, monthly continuity checks of Westinghouse Type W-2 switches for three of the Safety Injection System (SIS) control valves would be performed. The tests would consist of an initial continuity check of the neutral contacts and again after each manipulation of the switch from its neutral position. In addition, continuity checks would be performed every 31 days whenever the safety injection system is required to be OPERABLE. This testing was to continue until completion of any necessary long term corrective actions.
The Westinghouse design review of Type W-2 switches was completed and documented in Westinghouse Technical Bulletin WSD-TB-80-1 Revision 1 dated February 16, 1981.
The review concluded that no generic failure mechanism exists and that the switch failure at Zion was a random occurence. Upon receipt of this technical bulletin, SCE submitted a supplemental response to IE Bulletin 80-20 by letter dated November 18, 1981 to indicate that the recommended actions proposed by the technical bulletin did not provide a satisfactory long term solution and that SCE would pursue resolution of the matter with Westinghouse. Pending development of an acceptable long term solution testing as specified in our initial bulletin response would be continued.
After several years, the continuity tests performed on the Type W-2 switches on the SIS control valves have not revealed any failures. In addition, a review of the INPO industry database was performed and no other failures of the W-2 switches have been reported by the nuclear industry. In light of this data, and the results of the Westinghouse design review, SCE believes that 8802120205 680208 PDR ADOCK 05000206 I0 G
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Document Control Desk February 8, 1988 continued testing of the W-2 switches is not necessary. The operability of the switches is verified through the normal SIS technical specification surveillance tests and further testing has not demonstrated the existence of design deficiencies. Consequently, SCE has discontinued monthly continuity tests and testing subsequent to switch manipulation, and will rely on system surveillance tests to identify switch malfunctions.
If you have any questions or require additional information regarding the above, please let me know.
Very truly yours, cc:
- 3. B. Martin, Regional Administrator, NRC Region V F. R. Huey, NRC Senior Resident Inspector, San Onofre Units 1, 2 and 3