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

: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

ML20138N568
Person / Time
Site:	San Onofre
Issue date:	11/01/1985
From:	Morgan H SOUTHERN CALIFORNIA EDISON CO.
To:
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
LER-85-019, LER-85-19, NUDOCS 8511050229
Download: ML20138N568 (1)

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

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(v), Loss of Safety Function 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(viii)(B) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(x)
3611985019R00 - NRC Website

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NRC Form 3..

U.S$ NUCLEAR REGULATO!JY COMMIS$10N IU'3I APPROVED OM8 NO. 31504104 LICENSEE EVENT REPORT (LER)

EXPtRES: $/31/55 Paesury.aus (i) oocumv nuusun (a)

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SAN ON0FRE NUCLEAR GENERATING STATION, UNIT 3 o 1510101013 16 12 1 l0Fl011 vev6s ( )

SPURIOUS FUEL HANDLING ISOLATION SYSTEM (FHIS) ACTUATIONS EVENT DATE (5)

LER NUMBER (6)

REPORT DATE (7)

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LICENSEE CONTACT FOR THIS LER (12)

TELEPHONE NUMBER.

anEmCoDE H. E. MORGAN. STATION MANAGER 71114 3 16 18 l-16 12 14 11 COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13) c.

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Abstract (umit to 1400 spaces, La., approximately fif teen single-space typewritten lines) (16)

On 05/17/85, at.1803 and -1817, with Unit 3 at 100% power, an actuation of the Fuel Handling Isolation System (FHIS)(EIIS System Code VG) Train 'A' occurred when Airborne Monitor (EIIS Component Code DET) 3RE-7822 spuriously alarmed. Additional spurious actuations of the Unit 3 FHIS occurred on 05/19/85, 05/26/85 and 06/07/85.

In each case, all FHIS components functioned properly. The actuations were verified to be spurious by c:nfirming the monitor readings were below the alarm setpoint. Following each spurious actuation, FHIS was promptly reset.

The cause of the spurious actuations is believed to be radiation monitor sensitivity to random electrical noise. No radiation monitoring system maintenance or repairs were in progress which could have generated the spurious signals. There is no fuel in the Unit 3 Fuel Handling Building. Actual airborne activity remained at background levels.

An investigation of the' cause of the electrical spikes concluded that the most probable entry point of the noise spikes is via the detector. An inspection will be made of the detectors and, i.f necessary, repairs will be made to ensure p. roper grounds are in place.

8511050229 851101 PDR ADOCK 05000361 S

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