ML18095A373

LER 90-018-01:on 900528,control Room Air Intake Radiation Monitoring Sys Monitor Alarm Circuitry Failed & on 900701, Channel 1R1B Failed Resulting in Actuation of ESF Function. Caused by Spurious High Channel spike.W/900724 Ltr

ML18095A373
Person / Time
Site:	Salem
Issue date:	07/24/1990
From:	Miller L, Pollack M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-018, LER-90-18, NUDOCS 9008010012
Download: ML18095A373 (4)

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. .. *0 PS~G Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038 Salem Generating Station July 24, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Washington, DC 20555

Dear Sir:

SALEM GENERATING STATION LICENSE NO. DPR-75 DOCK~T NO. 50-272 UNIT NO. 1 LICENSEE EVENT REPORT 90-018-01 This Licensee Event Report is being submitted pursuant to the requirements of the Code of Federal Regulations 10CFR 50.73(a} (2) (iv}. This report is required within thirty (30) days of discovery.

L. K. Miller General Manager -

Salem Operations MJP:pc Distribution The Energy People 95-2189 ~10M) 12-89

U.I. NUCUAll RIGULATOAY CQllM-LICENS.EE EVENT REPORT (LERI I

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SALEM GENERATING STATION UNIT 1 TIT'J.ls1' ACTUATION: AU'.OOMATIC

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' l YES (ff;,... tt>mp/*tr EXl'ECTED SU61l11$$10N DA TEI NO DATE 1111 I I I ANT II ACT (Limit ID 1400 111>><*. /.._, lppl'OICltNtrly f i ' - ri11fl**111>><* fyP1wrimn tiMC} (1 II On May 28, 1990 at 0834 hours0.00965 days <br />0.232 hours <br />0.00138 weeks <br />3.17337e-4 months <br />, with the plant in Mode 5 (Cold Shutdown), the Control Room air intake Radiation Monitoring System (RMS*) monitor' (lRlB} alarm *circuitry failed. This resulted in the automatic switching of the Control Room Ventilation from normal operation to the accident mode of operation (100% recirculation) for both Salem Unit 1 and Salem Unit 2 (by design). The switching of the Control Room Ventilation system to the emergency mode of operation is an Engineered Safety Feature (ESF). The switching of the ventilation resulted from a spurious high channel spike. On July 1, 1990 at 2309 hours0.0267 days <br />0.641 hours <br />0.00382 weeks <br />8.785745e-4 months <br />, during power operation, the iRlB channel failed again resulting in actuation of its ESF function. The lRlB channel detector is an LFE-Trapelo MD12C(V-ll) geiger-mueller tube. A channel functional test was successfully completed on June 11, 1990 for the first event.

No specific problem was identified by Maintenance personnel during their investigation of that.event. As a result of the second event the root cause of the channel failures has been identified as an equipment failure. The alarm/warning module was found cracked causing intermittent channel spiking. The module was replaced on July 2, 1990 and the channel was functionally tested and declared operable.

NllC For"' 3M 111-431

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 90-018-01. 2 of 3 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Water Reactor Energy Industry Identification System (EIIS) codes are identified in the text as {xxl IDENTIFICATION OF OCCURRENCE:

Engineered Safety Feature Actuation - Automatic Switching of the Control Room Ventilation to the Emergency Mode of Operation due to an equipment failure Event Dates: 5/28/90 and 7/1/90 Report Date: 7/17/90 This report was initiated by Incident Report Nos.90-351 and 90-455.

CONDITIONS PRIOR TO OCCURRENCE:

5/28/90: Mode 5 (Cold Shutdown) 7/01/90: Mode 1 Reactor Power 75% - Unit Load 799 MWe DESCRIPTION OF OCCURRENCE:

On May 28, 1990 at 0834 hours0.00965 days <br />0.232 hours <br />0.00138 weeks <br />3.17337e-4 months <br />, with the plant in Mode 5 (Cold Shutdown), the Control Room air intake Radiation Monitoring System (RMS) {ILi monitor (lRlB) alarm circuitry failed. This resulted in the automatic switching of the Control Room Ventilation from normal operation to the accident mode of operation (100% recirculation) for both Salem Unit 1 and Salem Unit 2 (by design).

On July 1, 1990 at 2309 hours0.0267 days <br />0.641 hours <br />0.00382 weeks <br />8.785745e-4 months <br />, during normal power operations, the lRlB RMS channel failed again causing the automatic switching of the Control Room Ventilation from normal operation to the accident mode of operation *

. The switching of the Control Room Ventilation system to the emergency mode of operation is an Engineered Safety Feature (ESF). Therefore, on May 28, 1990 at 0849 hours0.00983 days <br />0.236 hours <br />0.0014 weeks <br />3.230445e-4 months <br /> and on July 2, 1990 at 0003 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />, the Nuclear Regulatory Commission was notified of the ESF actuations in accordance with the Code of Federal Regulations 10CFR 50.72(b) (2) (ii)o APPARENT CAUSE OF OCCURRENCE:

The switching of the Control Room Ventilation (both times) resulted from a spurious high channel spike. Investigations have determined that the root cause of the spikes can be attributed to an equipment failure. The alarm/warning light module wa*s _found_ cracked.

ANALYSIS OF OCCURRENCE:

The lRlB channel continuously monitors the air from the HVAC intake duct into the Unit 1 control room. This monitor consists of four

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 90-018-01 3 of 3 ANALYSIS OF OCCURRENCE: (cont'd)

Geiger-Mueller (GM) tubes (LFE-Trapelo MD12C(V-11)) in parallel. ,

When any of the four GM tubes reaches the alarm setpoint the monitor will actuate an alarm and initiate closure of the intake valve to prevent airborne activity from entering the control room.

The lRlA channel (Control Room General Area Monitor) is used as the corroborating channel to provide indication of ajrborne activity in the control room. This channel .has the same automatic isolation function as the lRlB ctiannel. This channel did not indicate any abnormal activity during this event.

As indicated previously, the automatic switching of the Control Room ventilation system to the accident mode of operation, was caused by failure of the lRlB radiation monitoring channel alarm circuitry and not by an actual high radiation signal. Therefore, the health and safety of the public was not affected by this event. However, since the switching to the accident mode of operation by the control room ventilation system is considered an ESF actuation, this event is reportable in accordance with the Code of Federal Regulations 10CFR 50e 73 (a) (2) (iv).

CORRECTIVE ACTION:

As identified in the original issue of this LER, a channel functional test was successfully completed on June 11, 1990 for the first event (May 28, 1990). No specific problem was identified, at that time, by Maintena~ce personnel during their investigation of the event.

Investigation of the second event (July 1, 1990) has identified the root cause of both channel failures (May 28, 1990 and July 1, 1990) to be a cracked alarm/warning module. The module was replaced and a channel functional test was successfully completed on July 2, 1990.

General Manager -

Salem Operations MJP:pc SORC Mtg.90-092