ML20024G700

LER 91-002-00:on 910323,auto-start of Control Room Special Ventilation Sys Occurred.Caused by Spike on Newly Installed Radiation Monitor.Wiring Changed to Provide Time Delay Feature for Remaining Four modules.W/910422 Ltr

ML20024G700
Person / Time
Site:	Prairie Island
Issue date:	04/22/1991
From:	Hunstad A, Parker T NORTHERN STATES POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-91-002-01, LER-91-2-1, NUDOCS 9104250386
Download: ML20024G700 (5)

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Northem States Power Company 414 Nicollet Mall Minneapohs, Minnesota 65401 1927 Telepone (612) 3345500 April 22, 1991 10 CFR Part 50 Section 50.73 U S Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555 PRAIRIE ISLAND NUCLEAR GENERATING PLANT Docket Nos. 50 282 License Nos. DPR 42 50 306 DPR 60 Auto start of Control Room Special Ventilation System Due to Spike on Newiv installed Rndlation Monitor 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 March 23, 1991. Please contact us if you require additional information related to this event, hM9 " v 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 Attachment 9104250386 910422 PDR ADOCK 05000282

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On March 23, 1991, both units were operating at full power. At 0019 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> a spike on radiation monitor R 23 caused control room annunciation of control room liigh Radiation Train A, which resulted in auto start of No. 121 Control Room Cleanup Fan and isolation of the control room outside air supply.

Several unplanned actuations of ESF ventilation systems had taken place over a period of several years as a result of spiking in the circuitry of radiation

_ monitors. To help prevent recurrences, upgraded monitor modules.had been ordered from the manufacturer. Upgraded monitor modules had been recently received and installed. Spurious high radiation alarms occurred in these new

- monitors in the first few hours of operation. No spurious alarms occurred on any of the new modules after 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of operation. In communication with the manufacturer, it was determined that the 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> f actory burn in" test specified in the purchase order had not been done. llad the burn in requirement been moti no spurious alarms would have occurred after installation.

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z =ncPlant e m ., eUnit tixt EVENT DESCRIPTION At 0019 hours2.199074e-4 days <br />0.00528 hours <br />3.141534e-5 weeks <br />7.2295e-6 months <br /> a both units were operating at full power.MON) caused identifier:

On March 23, 1991, spike on radiation monitor R 23 (Ells Component Train A, which isolation of control room annunciation of control room High Radiat tonre ter reading at the control room outside air supply. h operator found radiation monitor R 23 in alarm with t e rneRedundant monitor R 24 w normal background levels,When operators had determined thatd the monitor actions returned background were spurious,Icvels.they removed radiation monitor R 23 from service an the control room ventilation system to normal. (Auxiliary Several unplanned actuations of Engineered Safety Feature ilation) systems had Building Special Ventilation and Spent ruel pool l Special Ventf spiking in the taken place over a period of several years as a resu t oThese events were reported as Unit 1 circuitry of radiation monitors. To help prevent h anufacturer 88 007, 88 011, 89 008, 89 016, 89failures 018orand poor 90 005. recurren Nuclear Measurements Corporation.

ld provide unwanted actions caused by either intermittent comuonentconn time delay circuitry to prevent actuation of contro was generated, f these were Four upgraded monitor modules were recently received and three o installed in radiation monitors R 23 (Control Room Air Supply Radiation Building Monitor), R 25 (Spent Fuel Monitor PoolR 23, Airwhich Monitor) and 1R was installed on 37 March(Auxiliary 22, Ventilation Cas Monitor). few hours of service.

produced a spurious high radiation alarm in its first d le had not t rt of No, Since viring changes to provide the time delay feature of the mo u yet been made, the spurious high radiation100 alarm produced an auto s aAddi hours of service, 121 Control Room Cleanup Fan.

h produced on monitors R 23 and IR 37 within their firstbut the ti actuation of ESF equipment was prevented.

a fourth module Because of the spurious alarms seen on the installed monitors,Two spurious high radia was bench tested from March 27 through April 8. 100 hours0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> of 0

alarms occurred on this test module, both within the first operation, No spurious alarms occurred on any of the new mo hours of operation. hours prior to installation while being bench tested.)

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% u , . ..e , .mn As a result of these findings and communication with the manufacturer, it was determined that the factory " burn in" test specified in the purchase order had not been done. The manufacturer was requested to withhold shipment of the other four modules ordered until the requested 100. hour burn in test at the factory was documented.

CAUSE OF THE EVENT The manufacturer had not provided a 100 hour0.00116 days <br />0.0278 hours <br />1.653439e-4 weeks <br />3.805e-5 months <br /> burn in test at the factory before shipment, as specified in the purchase order. Thiw burn in time was requested to expose any design deficiencies prior to shipment and to provide time for electronic components to settle into their operational characteristics, llad the burn in requirement been met, no spurious alarms would have occurred after installation, llad the time delay feature of monitor R 23 been enabled before placing the monitor in service, the spurious alarm would not have caused an unplanned actuation of ESr equipment. The installation procedure did not provide for making the wiring changes to enable the time delay feature before placing the monitor in service. This order of' installation was intentional and was a result of evaluation of the risks of inadvertently causing an ESF actuation during all parts of the modification process.

ANALYSIS OF THE EVQiI The functional response of the automatic actuation of the control room cleanup fan and isolation of the outside air to the control room was according to design. The purpose of this isolation is to protect control room personnel from exposure to airborne radioactivity. Since this occurrence was not triggered by the presence of airborne radioactivity, there was no threat to the operation of the plant. Therefore, this event did not affect the health and safety of the public.

GQERECTIVE ACTION After experiencing multiple spurious alarms in two of the three installed new modules, the fourth was bench tested for several days. The manufacturer was then requested to withhold shipment of the other four modules ordered until the requested 100. hour burn in test at the factory was documented. Those four modules have now been received and will be installed shortly. Wiring changes to provide the time delay feature for the remaining four modules have been made.

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We had previously reported that the monitor improvements would be completed by March 31, 1991. As discussed above, the codificatfons were interrupted March 23, 1991, pending resolution of the problems. The monitor improvements both to the modules and the time delay circuits now appear to be offective if the burn.in time specification is observed, Therefore, the remaining modules will be installed shortly. l l

The failure of the vendor to comply with the purchase order requirements will be pursued by our vendor quality assurance group. t FAILED COMPONENT 1 DENT 1rICATIQB Nucicar Measurements Corporation Model APM 625 gas monitor with totalir.cr. <

HEVIOUS SitillAR EVENTS Similar events were reported as Unit 1 LLR's 88 007, 88 011 E9 008, 89 016, 89 018 and 90 005.

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