ML20005D707

LER 89-018-01:on 891024,25,31 & 1112,control Room Received High Radiation Alarm Which Initiated Automatic Start of Auxiliary Bldg Special Ventilation Sys.Caused by Radiation Monitor Spikes.Monitor Modules replaced.W/891130 Ltr

ML20005D707
Person / Time
Site:	Prairie Island
Issue date:	11/30/1989
From:	Hunstad A, Parker T NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-018, LER-89-18, NUDOCS 8912140275
Download: ML20005D707 (4)

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Northem States Power Company (

414 Nicollet Mall Minneapolis, Minnesota $54011927 Telephone (612) 330-5500 i J

November 30, 1989- 10 CFR Fart 50 Section 50.73' ,

Director.of Nuclear Reactor Regulation  ;

U S Nuclear Regulatory Commission '

Attn: Document Control Desk l Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50 282 License Nos. DPR 42 50 306 DPR 60 Auto starts of Auxiliary Building Special .

Ventilation System Ar a Result of Radiation Monitor Soikes -

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The Updated Licensee Event Report for these occurrences is attached. This update includes an additional event which occurred on October 31, 1989. At the time that the original Licensee Event Report was submitted, the cause of ,

this event was not known. Subsequently, the cause of this event has been determined to be the same as that of the three previous similar events reported in Licensee Event Report 1-89 018. Since this event occurred within the 30 days following the earliest event reported in 1-89-018, it is included in this update to Licensee Event Report 1 89 018. _  ;

This additional event was reported via the Emergency Notification System in-L accordance with 10 CFR Part 50, Section 50.72, on October 31, 1989. Please contact us if you require additional information related to this event.

i Thomas M Parker '

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Nuclear Support Services l

l c: Regional Administrator - Region III, NRC NRR Project Manager, NRC Senior Reaident Inspector, NRC MPCA Attn: Dr J V Forman f,h '

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During these even". both units were operating at 100% power. The control room l

received a High Rouiation alarm, which initiated an automatic start of the Auxiliary j i Building Special Ventilation System on four separate occasions: at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on l October 24, 1989; at 1626 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.18693e-4 months <br /> on October 25, 1989; at 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br /> on October 31, 1989; and at 0659 hours0.00763 days <br />0.183 hours <br />0.00109 weeks <br />2.507495e-4 months <br /> on November 12, 1989. These were non-ESF actuations of an ESF system. In each case one of the radiation monitors which actuates the Auxiliary Building Special Ventilation System, was found to be in alarm with a normal response indicated by the meter located on the monitor. Since there was in fact no high radiation condition in the Auxiliary Building, the control room operator reset the alarm on the radiation monitor and returned the Auxiliary Building Special Ventilation System to the normal standby condition and returned the Auxiliary Building Normal Ventilation System to service. These radiation monitor modules will be replaced with upgraded monitor modules.

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PrCirie Island Unit 1 o p ;o ;o jo l2 i 8 ; 2 '8 ; 9 O;1;8 .,_ 0;1 0 92 or 0 ;3 var v . -.c .,mi EVENT DESCRIPTION During the events, both units were operating at 100% power. The control room received c High Radiation alarm, which initiated an automatic start of the Auxiliary Building Special Vent.ilation System on four separate occasions: at 1320 hours0.0153 days <br />0.367 hours <br />0.00218 weeks <br />5.0226e-4 months <br /> on October 24, 1989; at 1626 hours0.0188 days <br />0.452 hours <br />0.00269 weeks <br />6.18693e-4 months <br /> on October 25, 1989; at 1210 hours0.014 days <br />0.336 hours <br />0.002 weeks <br />4.60405e-4 months <br /> on October 31, 1989; and at 0659 hours0.00763 days <br />0.183 hours <br />0.00109 weeks <br />2.507495e-4 months <br /> on November 12, 1989. These were non-ESF actuations of an ESF system. In each cese one of the radiation monitors (EIIS Component Code Identifier MON), which-actuates the Auxiliary Building Special Ventilation System, was found to be _ in alarin with a ntrmal response indicated by the meter located on the monitor. Since there was in fact no high radiation condition in the Auxiliary Building, the control room operator reset the alarm on the radiation monitor and returned the Auxiliary Building Special Vantilation System to the normal standby condition and returned the Auxiliary Building Normal Ventilation System to service.

CAUSE OF THE EVENT Catuse of each event was an electronic spike on the radiation monitor, causing a high l rcdiation alarm and actuation of the Auxiliary Building Special Ventilation System.

Cause of the spiking could not be conclusively identified, though the first two events occurred while maintenance was taking place on an adjacent radia*, ion monitoring channel.

ANALYSIS OF THE EVENT l

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.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 Ve'ntilation and actuate the Auxiliary Building Special Ventilation l System. The Auxiliary Building Special Vent,ilation System is used to decrease l radiological impact of a radiological release to the Auxiliary Building through l increased filtration and monitoring of the air in the ventilation system. Since this event was not triggered by a radiological event, there were no radiological concerns end there was no effect on the health and safety of the public.

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Prcirie Island Unit.1 oIsIololo1 2;8l2 8;9 _

0 l1l8 Oi l 0 13 or 0 l3 virr,, . - nac w .m.unn CORRECTIVE ACTION L Immediate actions included troubleshooting and inspection of the radiation monitoring

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Thsse radiation monitor modules will be replaced by an upgraded monitor module m nufactured by Nuclear Measurements Corporation (NMC). This upgrade will eliminate spiking caused by either intermittent component failure or poor connectors within the module. The new modules also provide circuitry that will prevent actuation of a control function even if a spike is generated within the radiation monitor channel.

' When the previous LER was written Unit 1 LER 89-016, we expected this upgrade to be l completa by December 31, 1989. The vendor has now informed us that the upgrade modules will not be available until at least February 1990. Therefore, we now expect the

.modificatic,ns to be complete in March 1990. l COMPONENT IDENTIFICATION ,

Nuclear Heasurements Corporation Model APM 625 gas monitor with totalizer PREVIOUS SIMILAR EVENTS l Pravious similar events were reported as Unit 1 LER's88-007, 88-011 and 89-008, caused by monitor 1R-37, and LER 89 016 caused by monitor 2R 30.

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