ML20204B091

/03L-0 on 780819:Failure of Check Valve Providing Containment Integrity in 2 Demineralized Water Line Contributed to Containment of Plant Demineralized Water Sys Check Valve Repaired 780905

ML20204B091
Person / Time
Site:	Big Rock Point File:Consumers Energy icon.png
Issue date:	09/15/1978
From:	CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
References
LER-78-032-03L, NUDOCS 7809270337
Download: ML20204B091 (2)

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60 DOCKET NUMSER 69 74 EVENT DATI 76 REPORT DATE 80 EVENT DESCRIPTION AND PROBA8LE CONSEQUENCES O'o F5 m (Failure, between 7/26/78 and 8/19/78, of the check valve providing contain i O Iment integrity in the 2" demineralized water line to containment contrib- i g luted to radioactive contamination of the plant demineralized water system. i (T m ITwenty-five gallons of this water was removed from the plant by employees. l 0 l Containment integrity was established on 8/21/78 and evaluation on 8/23/78 i 1017l trevealed that no undue health hazard exists for any employees or the pub- l 10181 111c .

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1i: 01 IThe check valve was repaired on 9/s/78. Containment integrity had been es-l t

ltablished by valvine on 8/21/78 when the check valve defect became suspect.1

, lReportability is based on T/S 6.9.2.b.(2). Inadequate survey per 10CFR20.-1 g 1201 resulted in unmonitored removal of water from the site and revised ad- I m iministrative i e n controla are being implemented to prevent recurrence. I STA  % POWER OTHER$TATV5 Y ISCO DISCOVERY DESCRIPTION 32 y [E,,J@ l 0 l 8 I Ol@l N/A l l B l@l Trending of Sample Resu1Cs l

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Attachment to LER 032-011-0 Consumers Power Co '

Big Rock Point Plant Docket 050-155 Investigation of abnormally high radioactive materials levels in Lake Michigan water samples between 7/26/78 and 8/19/78 led to the discovery that the samples contained radioactive impurities caused by contamina-tion of the plant demineralized water supply. Demineralized water is used to rinse the sampling hardware. Evaluation on 8/21/78 established that the 2" containment isolation check valve in the demineralized water supply line to containment was defective and that backflow from the fuel pool system was the source of contamination in the demineralized water system.

On 8/21/78, redundant valve CV/4105 was closed to isolate the source of contamination and it was verified leak-tight on 8/25/78 following uri-fication on 8/25/78 that the 2" check valve was defective. Demineraliz-ed water taps and lines in the turbine buildina; were closed and/or caution tagged on 8/21/78 and 8/22/78. All on-site employees were informed of the problem on 8/21/78 and a survey was initiated to determine if unmonitored demineralized water had been used by anyone or removed from the plant.

l The survey revealed that about 25 gallons of water had been removed from )

the site in several containers. Of the fifteen gallons of water retriev-  ;

ed, the highest activity was in the order of 100 120 in one five-gallon l container. Evaluation of each unretrievable use determined that no human l consumption occurred and no undue hazard existed for any empicyee or the public.

The exact mechanism for cross-contamination is not known but the 2" check valve in the demineralized water supply to the containment has been repaired and tested and the design of the valve will be reviewed to determine if reliability can be improved. In addition, manual valves VSFP-20 and VSFP-27 (one in each of the two fuel pool system connections to the demineralized water system) have been placed under lock control to preclude misoperation.

The removal of contaminated water from the plant is the result of inadequate survey practices. Periodic testing of the demineralized water is now being conducted to detect contamination and radiological clearance practice for removal of material from the site is being reviewed for possible improvements.