ML19332C617

LER 89-018-00:on 891024,25 & 1112,control Room Received Train a High Radiation Alarm,Initiating Automatic Start of Auxiliary Bldg Special Ventilation Sys.Caused by Spike of Radiation Monitor.Monitor replaced.W/891122 Ltr

ML19332C617
Person / Time
Site:	Prairie Island
Issue date:	11/22/1989
From:	Hunstad A, Parker T NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM), Office of Nuclear Reactor Regulation
References
LER-89-018-01, LER-89-18-1, NUDOCS 8911280351
Download: ML19332C617 (4)

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Northem States Pouw % ,

414 NicoHet Mall &

Minneapolis, Minnesota 554011927 3 Telephune (612) 330-5500 i

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November 22, 1989 10 CFR Part 50 Section 50.73 i Director of Nuclear Reactor Regulation U S Nuclear Regulatory Commission  ;

Attn: Document Control Desk Washington, DC 20555 i

I PRAIRIE ISLAND NUCLEAR CENERATING PIANT t Docket Nos. 50 282 License Nos. DPR 42 50-306 DPR 60 Auto-starts of Train A of Auxiliary Building Special Ventilation System As a Result of Radiation Monitor Soikes The 1.icensee Event Report for these occurrences is attached.

.This; events were reported via the Emergency Notification System in accordance with 10 CFR Part 50, Section 50.72, on October 24, 1989, October 25, 1989, and November 12 -1989. Please contact us if you require additional information related to this event.

l Thomas M Parker Manager Nuclear Support Services c: Regional Administrator - Region III, NRC NRR Project Manager, NRC Senior Resident Inspector, NRC MPCA Attn: Dr J W Ferman f ,

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$UOMe&stON VI$ fif y.e. c.mp.efe (Ji*lCTIO JUdef/33704 DA Tif NO j l j A. T R ACT a-,, ic ,m .... . ., . . -. , n ei During the events, both units were operating at 100% power. The control room received a Train A High Radiation alarm, which initiated an automatic start of the Auxiliary Building Special Ventilation System on three 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; 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, radiation monitor 2R.37, which actuates the Auxiliary Building Special Ventilation System, was found to ba 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 raturned the Auxiliary Building Normal Ventilation System to service. This radiation monitor module will be replaced with an upgraded monitor module.

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L EVENT DE klIPTION ,

During the events, both units were operating at 100% power. The control room received a Train A High Radiation alarm, which initiated an automatic start of the Auxiliary Building Special Ventilation System on three separate cecasions: 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; and at 0659 hours0.00763 days <br />0.183 hours <br />0.00109 weeks <br />2.507495e-4 months <br /> on N'ovember 12, F 1989. Those were non ESF actuations of an ESF system. In each case, radiation monitot 2R-37 (EIIS Component Code Identifier MON), which actuates the Auxiliary Building Sp:cial 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 c:ndition in the Auxiliary Building, the control room operator reset the alarm on the r diation monitor and returned the Auxiliary Building Special Ventilation System to the n:rral standby condition and returned the Auxiliary Building Normal Ventilation System to service.

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use of each event was a spike on radiation monitor 2R-37, causing a.

! high radiation alarm and actuation of the Auxiliary Building Special Ventilation l System. Cause of the spiking could not be conclusively identified, though the first

!- two events occurred while maintenance was taking place on an adjacent radiation

etnitoring channel.

ANALYSIS OF THE EVENT Th3 functional response of the auto-start actuation of the Auxiliary Building Special V:ntilation. System was according to design, which is to deactivate the Auxiliary Building Normal Ventilation and actuate the Auxiliary Building Special Ventilation l System. .The Auxiliary Building Special Ventilation System is used to decrease l- rcdiological impact of a radiological release to the Auxiliary Building through

, increased filtration and monitoring of the air in the ventilation system. Since this l sv2nt 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.

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CORRECTIVE ACTION  !

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Immediate actions included troubleshooting and inspection of the radiation monitoring ch:nnel.

This radiation monitor module will be replaced by an upgraded monitor module

= nufactured by Nuclear Measurements Corporation (NMC). This module upgrade will  ;

oliminate spiking caused by either intermittent component failure or poor connectors  !

within the module. The new modules also provide circuitry that will prevent actuation -

cf a control function even if a spike is generated within the radiation monitor 1 ch:nnel. '

kh n t.he previous LER was written, Unit 1 LER 89 016, we expected this module upgrade i to be complets by December 31, 1989. The vendor has now informed us that the upgrade c:dules will not be available until at least February 1990. Therefore, we now expect  ;

,ths modifications to be complete '

in March 1990.

COMPONENT IDENTIFICATION j Nuclear Measurements Corporation Model APM 625 gas monitor with totalis:er  ;

PREVIOUS SIMIIAR EVENTS Previous aimilar 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, f

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