ML20138N556

Forwards LERs 84-002-02,84-023-01 & 85-019-01

ML20138N556
Person / Time
Site:	San Onofre
Issue date:	11/01/1985
From:	Morgan H SOUTHERN CALIFORNIA EDISON CO.
To:	NRC OFFICE OF ADMINISTRATION (ADM)
Shared Package
ML20138N558	List: 05000361/LER-1984-023, :on 840524,spurious Actuation of Control Room Isolation Sys Occurred Because of Noise Spike on Control Room Airborne Radiation Monitor.Monitor Detector Replaced & Preamplifier Properly Grounded 05000361/LER-1985-019, :on 850517,fuel Handling Isolation Sys Actuated by Spurious Airborne Monitor Alarm.Probably Caused by Radiation Monitor Detector Sensitivity.Spurious Actuations Also Occurred on 850519,26 & 0607 ML20138N556
References
NUDOCS 8511050226
Download: ML20138N556 (2)

Text

f [5 Southem Califomia Edison Company SAN ONOFRE NUCLEAR GENERATING STATION P. O. BOX 128 SAN CLEMENTE, CALIFORNIA 92672

.H.E. MORGAN TELEPHONE CTAT60N MANAGER (714)368 6241 November 1, 1985 U.S. Nuclear Regulatory Commission Document Control Desk Washington, D.C.

20555

Subject:

Docket Nos. 50-361 and 50-362 Licensee Event Report No.84-002, Revision 2 (Docket No. 50-361)

Licensee Event Report No.84-023, Revision 1 (Docket No. 50-361)

Licensee Event Report No.85-019, Revision 1 (Docket No. 50-362)

San Onofre Nuclear Generating Station, Units 2 and 3

References:

(1) Licensee Event Report No.84-002 (Docket No. 50-361);

J. G. Haynes (SCE) to USNRC Document Control Desk, dated February 28, 1984 (2) Licensee Event Report No.84-023 (Docket No. 50-361);

J. G. Haynes (SCE) to USNRC Document Control Desk, dated June-21, 1984

.(3) Licensee Event Report No.85-019 (Docket No. 50-362);

J. G. Haynes (SCE) to USNRC Document Control Desk, dated June 14, 1985 (4) Letter, J. G. Haynes (SCE) to USNRC Document Control Desk, dated August 30, 1984; Licensee Event Report No.84-002, Revision 1 (5) Letter, J. G. Haynes (SCE) to USNRC Document Control Desk, dated December 27, 1984; Licensee Event Report Nos.84-002 and 84-023 References (1), (2), and (3) provided the required 30-day Licensee Event Report (LER) for occurrences involving the spurious actuation of the Containment Purge' Isolation System (CPIS), the Control Room Isolation System (CRIS), and Fuel Handling Isolation System (FHIS) which were apparently due to noise spikes.. Reference (4) stated that revisions to LER 84-002 and LER 84-023 would be submitted by December 31, 1984, at the conclusion of our investigation of the cause of the spurious actuations and identification of corrective action.

Reference (5) stated the most probable cause of the noise spikes was ground currer:t surges traveling to the monitors through the ground system, during transients caused by the switching of heavy current equipment; however, testing and evaluation 'of the ground system was required to confirm p

this.

8511050226 851101gl '

g DR ADOCK O

/

U."S. Nuclear Regulatory Commission

• We have completed our review of the grounding system and have determined that noise spikes in the process and effluent monitors are most probably being

. picked up by the detectors due to improper grounding. We plan to inspect each noise susceptible detector in the monitoring system to ensure it is properly grounded. This inspection will be completed as access to each detector becomes available dur.ing unit shutdowns or other corrective maintenance activities.

Improvements in the grounding of the monitors are also being implemented to ensure other po,tential points for noise are eliminated.

It is expected upon completion.of the inspections, the frequency of noise spikes t

will be reduced.

If-you require any additional information, please so advise.

Si erely, I

l5 x

t.

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

J. B. Martin (Regional Administrator, USNRC Region V)

Institute of Nuclear Power Operations (INPO)

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