ML20006E096

LER 90-008-00:on 900120,plant Vent Noble Gas Monitor 2R41C Failed Low,Resulting in Closure Signal for Waste Gas Decay Tank Vent Control Valve 2WG41.Caused by Personnel Error. Operator Aid Will Be Posted on panel.W/900215 Ltr

ML20006E096
Person / Time
Site:	Salem
Issue date:	02/15/1990
From:	Miller L, Pollack M Public Service Enterprise Group
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-90-008, NUDOCS 9002220012
Download: ML20006E096 (4)

Text

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k 1 7 C 0 PSEG Public Service Electric and Gas Company P.O. Box 236 Hancocks Bridge, New Jersey 08038

. Salem Generating Station February 15, 1990 U. S. Nuclear Regulatory Commission Document Control Desk Nashington, DC 20555

Dear Sir:

SALEN GENERATING STATION LICENSE NO. DPR DOCKET NO. 50-311 UNIT NO. 2 LICENSEE EVENT REPORT 90-008-00 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.

Sincerely yours, f

L. K. Miller General Manager -

Salem Operations NJP:pc Distribution II 9002220012 900215 FDR ADOCK 05000321 5 PDC The Energy Poopio -

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nest naCr it ,= , . . . ., , ,,. .-. .,, ,. ,, n ei on January 20, 1990, the Radiation Monitoring System (RMS) Plant Vent Radioactive Noble Gas Monitor, 2R41C, channel failed low resulting in a i Containment Purge / Pressure-Vacuum Relief System (CP/P-VRS) isolation

! signal and a closure signal for the 2WG41 valve (Waste Gas Decay Tank Vent Control Valve). At the time of the event, the 2R45A-D channels (Plant Vent noble gas RMS monitors) 2CT-2B Eberline printer was not functioning and was being worked on by Maintenance-I&C. The CP/P-VRS isolation is considered an Engineered Safety Feature (ESF). The root cause of the CP/P-VRS actuation has been attributed to personnel error associated with the 2R45A-D RMS channel work. The 2R45A-D channels have an interlock function with the 2R41 channel. Upon detection of high activity in the plant vent by the 2R45B channel (medium range detector), the 2R41 channels de-energize. This protects the 2R41

, channel detectors and circuitry from being permanently damaged by high l activity. The protective function control circuitry are located in the same cabinet as the control circuitry for the 2CT-2B printer. The technician did not place the 2R41 channel de-energization function in

" block". It has been surmised that the technician had inadvertently caused an electrical pertutbation causing the de-energization of the 2R41 channel. This event has been reviewed with the technician involved in the event. This event will be reviewed with applicable Maintenance Department personnel. The need to maintain attention to detail will be stressed. A controlled Operator aid will be posted on the 2CT-2B panel which will require blocking of the 2R41 interlock function when working on the panel circuitry.

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1

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H I LICENSEE EVENT REPORT (LER) TEXT CONTINUATION {

Salen Generating Station DOCKET NUMBER LER NUMBER PAGE i Unit 2 5000311 90-008-00 2 of 3 i

Ph&NT AND SYSTEM IDENTIFICATION:,  ;

Westinghouse - Pressurized-Water Reactor l

L Energy Industry Identification System (EIIS) codes-are identified in- ,

the text as (xxl  !

LDENTIFICATION OF OCCURRENCE: [

Containment Purge / Pressure-Vacuum Relief Isolation Due To Inadvertent Personnel Error i

Event Date: 1/20/90  ;

Report Date: 2/15/90 This report was initiated by Incident Report No.90-056.

CONDITIONS PRIOR TO OCCURRENCE:

Mode 5 (Cold Shutdown) f

' DESCRIPTION OF OCCURRENCE:_ f On January 20, 1990, at 0508 hours0.00588 days <br />0.141 hours <br />8.399471e-4 weeks <br />1.93294e-4 months <br />, the Radiation Monitoring System 2 (RNS).lIL) Plant Vent Radioactive Noble Gas Monitor, 2R41C, channel failed low resulting in a Containment Purge / Pressure-Vacuum Relief' System (CP/P-VRS) IBFI isolation signal and a closure signal for the 3 2WG41 valve (Waste Gas Decay. Tank Vent Control Valve). At the time of the event, the 2R45A-D channels (high and medium range Plant Vent '

noble gas-RMS monitors) 2CT-2B Eberline printer was not functioning and was being worked on by Maintenance-IEC.

The CP/P-VRS isolation signal is considered an Engineered Safety a Feature (ESF). . Subsequently, within four (4) hours of the 2R41C channel failure and subsequent CP/P-VRS signal, the Nuclear Regulatory Commission was notified of the automatic actuation of CP/P-VRS as required by Code of Federal Regulations .10CFR 50.72 (b) (2) (ii) .

-APPARENT CAUSE OF OCCURRENCE: -

The root cause of the CP/P-VRS actuation has been attributed to -

inadvertent personnel error associated with the 2R45A-D RMS channel work.

The 2R45A-D channels have an interlock function with the 2R41 channel. Upon detection of high activity in the plant vent by the 2R45B channel (medium range detector), the 2R41 channels de-energize.

This protects the 2R41 channel detectors and circuitry from being '

permanently damaged by high activity. The protective function control circuitry is located in the same cabinet as the control circuitry for the 2CT-2B printer. ,

The-functional and calibration procedures for the 2CT-2B printer require the blocking of the interlock circuitry thereby preventing the

[,

• LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salen Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 2 5000311 90-008-00 3 of 3 i

APPARENT CAUSE OF_ OCCURRENCE: (cont'd) inadvertent de-energization of the 2R41 channels. In this event, the general troubleshooting procedure (not specific to any one plant electrical component) was used to investigate the printer concerns.

This procedure does not specify a requirement to de-energize the subject circuitry. Subsequently, the technician did not place the 2R41 channel de-energization function in " block" since he was not directly working on that circuitry. It has been surmised that the technician had inadvertently caused an electrical perturbation which locked up the microprocessor in a state which maintained an active alarm signal resulting in de-energization of the 2R41 channel and the subsequent CP/P-VRS actuation.

ANALYSIS _OF_ OCCURRENCE,_

Isolation of the CP/P-VRS is part of the design Engineered Safety Features (ESFs). It mitigates the release of excessive quantities of radioactive material to the environment after a design base accident.

The 2R41C channel monitor's the plant vent effluent releases for radioactive noble gas via representative sampling. The ESF actuation feature of CP/P-VRS isolation, associated with this channel, is of conservative design. It is redundant to the 2R12A channel. In addition to its ESF function, the channel will cause the isolation of the 2WG41 valve (Waste Gas Decay Tank Vent Control Valve). During the '

2R41C CP/P-VRS isolation signal events, the 2R12A monitor remained operable.

The 2R41C detector is a Victoreen Model 843-22 Beta Scintillator.

The inadvertent actuation of the CP/P-VRS isolation signal was not the result of high activity. Therefore, this event did not affect the health or safety of the public. However, due to the actuation of an ESF function, this event is reportable in accordance with Code of Federal Regulations 10CFR 50.73 (a) (2) (iv) .

CORRECTIVE _ ACTION:

This event has been reviewed with the Maintenance-I&C technician involved in the event.

This event will be reviewed with applicable Maintenance Department personnel. The need to maintain attention to detail will be stressed.

A controlled Operator aid will be posted on the 2CT-2B panel which will require biccking of the 2R41 interlock function when working on the panel circuitry. y G neral Manager -

Salem Operations MJP:pc SORC Mtg.90-014