ML19325C749

LER 89-016-00:on 890908,control Room Received Train B High Radiation Alarm,Which Initiated Automatic Start of Auxiliary Bldg Special Ventilation Sys.Caused by Spike on Radiation Monitor 2R-30.Monitor Upgrade Being pursued.W/891010 Ltr

ML19325C749
Person / Time
Site:	Prairie Island
Issue date:	10/10/1989
From:	Hunstad A, Parker T NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
LER-89-016-01, LER-89-16-1, NUDOCS 8910170243
Download: ML19325C749 (4)

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Northem States Power Company  ;

.t 414 Nicollet Mall l

- ' Minneagrdis, Minnesota 664011927 .

' Telephone (612) 330 5500 l 6

October 10, 1989 10 CFR Part 50- -

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- Section 50.73 t

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Director of Nuclear Reactor Regulation

,U.S Nuclear Regulatory Commission l Attn: Document Control Desk Washington, DC 20555 t

PRAIRIE ISLAND NUCLEAR GENERATING PIANT ,

Docket Nos. 50-282 ' License Nos. DPR-42 i 50 306 DPR-60 Auto Start of Train B of the Auxiliary Building Special Ventilation System as a Result of a Radiation Monitor Soike

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The Licensee Event Report for this occurrence is attached.

This event was reported via the Emergency Notification System in accordance with 10 CFR Part'50, Section 50.72, on September 8, 1989. Please contact us if you

-; require additional information related to this event.

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Thomas M Parker-Manager-Nuclear Support Services

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c: Regional Administrator - Region III, NRC NRR Project-Manager, NRC Senior Resident Inspector, NRC L MPCA.

! Attn: Dr J W Ferman

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Special Ventilation System as a Result of a Radiation Monitor Spike

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On September 8, 1989, both units were operating at 100% power. At 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br />, the control room received a Train B High Radiation alarm, which initiated an automatic l'

l start of the Auxiliary Building Special Ventilation System (ABSVS). This was a non Engineered Safeguards Feature actuation of an ESF system. Radiation monitor 2R-30, which actuates the ABSVS, was found to be in alarm. Since there was in fact no high radiation condition in the Auxiliary Building, the control room operator l-rsset the alarm on the radiation monitor and returned the ABSVS to the normal standby

j. condition and returned the Auxiliary Building Normal Ventilation System to service.

The radiation monitor detector tube and one electronics card were replaced and the monitor tested satisfactorily.

A radiation monitor module upgrade is planned.

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EVENT DESCRIPTION On September 8, 1989, both units were operating at 100% power. At 1555 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.916775e-4 months <br />, the centrol room received a Train B High Radiation alarm, which initiated an automatic ctart of the Auxiliary Building Special. Ventilation System (ABSVS). This.was a n:n Engineered Safeguards Feature actuation of an ESF system. Radiation monitor 2R 30.(EIIS Identifier MON), which actuates the ABSVS, was found to be in alarm.

Since there was in fact no high radiation condition in the Auxiliary Building, the centrol room operator reset the alarm on the radiation monitor and returned the ABSVS to the normal standby condition and returned the Auxiliary Building Normal Vsntilation System to service.

CAUSE E IllE EVENT Ccuse of the event was a spike on radiation monitor 2R 30, causing a high radiation alarm and actuation of the ABSVS. The cause of the spiking could not bo conclusively identified. The detector cable, detector failure or poor electrical etnnections are suspected to be the cause of the spiking. Corrosion was observed on the outside of the detector tube.

. ANALYSIS E IllE EVENT The functional response of the auto start actuation of the Auxiliary Building Special Vantilation System was according to design, which is to deactivate the Auxiliary Building Normal Ventilation and actuate the ABSVS. The ABSVS is used to decrease rcdiological impact of a radiological release to the Auxiliary Building through incressed filtration and monitoring of the air in the ventilation system. Since this ovenc was not triggered by a radiological event, there were no radiological concerns cnd there was no effect on the health and safety of the public, s

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CORRECTIVE ACTION

.Immediate actions included troubleshooting and inspection of the radiation monitoring

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on September 13th the tube and one electronieri card were replaced and the monitor ,

tested satisfactorily.

A radiation monitor module upgrade is being pursued with the monitor manufacturer, NMC. This module upgrade vill eliminate spiking caused by either intermittent ,

cc:ponent failure or poor connectors within the module. The new modules also provide

-circuitry that will prevent actuation of a control function when a spike is generated within the radiation monitor channel. We expect this module upgrade to be complete '

by December 31, 1989.

Ma'are also working with the detector tube manufacturer to develop a program for prcdicting end of tube life. .

COMPONENT IDENTIFICATION i Nuclear Measurements Corporation Model APM 625 gas monitor with totalizer LND Incorporated #719 G M Detector Tube PREVIOUS SIMIT.AR EVENTS i Pravious similar events were reported as Unit 1 LER's S8-007, 88 011 and 89-008, though this is the first event caused by this particular monitor, 2R 30. The provious events were caused by monitor 1R 37.

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