ML20112G025

Special Rept:On 841218,seismic Switches Calibr to Slightly Different Setpoints than Specified in Tech Spec Table 3.3-7, Resulting in Degradation in Threshold Sensitivity to Seismic Events.Cause Under Investigation.Switches Recalibr

ML20112G025
Person / Time
Site:	San Onofre
Issue date:	12/28/1984
From:	Haynes J SOUTHERN CALIFORNIA EDISON CO.
To:	Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION V)
References
NUDOCS 8501160152
Download: ML20112G025 (2)

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Q. MGCVEu Southern California Edison Companyy 95g 3, fy n p 6

SAN ONOFRei. NU C L EA R GENER A TING S T A TION P.o. sox its S AN CLEMENTE. C ALIFORNI A 92672 f@ */ j

. J. G. H AYN ES vetapwoNs

. TA1 oN MANAasa December 28, 1984 m mm.

U.S.-Nuclear Regulatory Commission Office of Inspection and Enforcement Region V 1450 Maria Lane, Suite 210

- Walnut Creek, California 94596-5368 LAttention: Mr. J. B Martin, Regional Administrator

Subject:

Docket Nos. 50-361 and 50-362 Special Report - Seismic Instrumentation San Onofre Nuclear Generating Station, Units 2 and 3 Pursuant to Section 6.9.2 of Appendix A, Technical Specifications to Facility Operating Licenses NPF-10 and NPF-15 for San Onofre Units 2 and 3 respectively, this Special Report is being submitted as required by Action Statement 'a' associated with Limiting Condition for Operation (LCO) 3.3.3.3.

This Action Statement requires that:a Special Report be prepared and submitted to the Commission within 10 days after any of the raismic instrumentation

' listed in Technical Specification Table 3.3-7 is inoperable for more than 30_ days. The cause of the malfunction and plans for restoring the instrument to operate status, are outlined below.

L _0n December-18, 1984, with Unit 2 defueled and Unit 3 in Mode 1, it was p discovered that the Seismic Switches, Items 4a and 4b of Technical Specification _ Table 3.3-7, which are common =to both Units 2 and 3, had been calibrated to slightly different setpoints than those specified in Table 3.3-7 since initial startup of Unit 2 in July 1982. The procedural setpoints used to date are as specified in the original design requirements supplied to the

-vendor.

The_ variance between the Technical Specification setpoints ara the original design requirement setpoints results in a slight degradation in threshold

' sensitivity to seismic events. An investigation as to the source of the present Technical Specification calibration requirements and justification as-

- to why they are different from original design setpoints is in progress. We

.have concluded that.the ability of the instruments to respond to and record a significant seismic event was not affected by this condition. As corrective action, the procedure _has been changed to reflect current Technical Specification calibration requirements and the seismic switches have been recalibrated.

8501140152 841228-1 PDA ADOCK 05000361 [ g-i S._ PDR _

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. Mr. J. B.~ Martin ..

There was no impact on plant operation or the health and safety of plant personnel or the public as a result of the instruments' inoperability. If there are any questions regarding the above, pleast contact me.

Sincerely, t/N - +

cc: F.' R. Huey (USNRC Senior Resident Inspector, Units 1, 2, and 3)

J. P. Stewart (USNRC Resident Inspector, Units 2 and 3)

U.S.; Nuclear Regulatory Commission Document Control Desk Institute of Nuclear Power Operations (INPO) 1 7

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