ML20087L655

Ro:On 730208,during Performance of Functional Test on Purge Valves,Two Containment Purge Inlet Valves Open When Placing Manual Switch to Open Position But Did Not Close.Caused by Loose Screw on Switch.Mod Made to Valve Circuits

ML20087L655
Person / Time
Site:	Point Beach
Issue date:	03/09/1973
From:	Burstein S WISCONSIN ELECTRIC POWER CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8403270330
Download: ML20087L655 (2)

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March'9, 1973 Mr. John F. OSImary, Director Directorate of Licensing U. S. Atenic Energy Commission Washington, D. C. 205h5

Dear Mr. O'Imary:

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DOCKEf NOS. 6 AND 50-301 POIllT BEACH'HUCLEAR PIANT UN1T 2 CONTAINEENT PURGE SUPPLY VALVE SWITCH MALFUNCTION In accordance with Section 15.6.6.A.3.d of the Technical Specifications for Point Beach Nuclear Plant, Units 1 and 2 (Facility Operating License Nos. DPR-2h and DFR-27), .this report is submitted with respect to a switch malfunction and an investigation which disclosed that under certain specific condi-tions a single equipment failure could conceivably result in the containment purge si t pal.

inlet valves failing to close on initiation o* a containment isolation On February 8,1973, following maintenance of the Unit 2 contain-ment purge valves, a functional test was performed on the purge valves to con-firm their operability. In the Point Beach arrangement, these purge valves are air operated and controlled by a single switch. Since placing the manual switch to the open position would cause both valves to open simultaneously, instrument air was secured to one valve while cycling the second valve. This procedure provides containment thatintegrity.

one valve remains shut at all times during the test to maintain Upon testing the outboard of the two containment purge inlet valves (number 32hh), the valve opened when placing the manual switch to the open position, but did not close when the switch was returned to the closed position.

An investigation of the switch revealed that a small screw which

. secures the contact closing cam to the manual portion of the switch had become aloose and backed off. This permitted the cam to stay in the " contacts closed"

position and prevented further manual operation of the switch from opening the contacts and closing the valve. It is our opinion that the failure of this switch is an isolated case and is not generic in nature.

I)uring the review of the electrice.1 drawings following the switch malfunction, it was noted that if the switch failed in the manner dencribed above a containment valves isolation if both were opensignal would at that time.not be capable of closing the oped valve or h /

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Mrt Jchd F. O'Imary - 2 o o March 9, 1973 -

l To correct this condition whereby the malfunction of a single switch, under the given conditions, could conceivably result in the loss of the capability of the two purge supply valves to perform their containment isolation function the control systems for each individual valve will be modified to include a switch which will operate that valve only. A malfunction of a single switch can thus result in one valve failing to close, mntainment integrity being maintained by the redundant valve.

A similar modification will be made to the valve control circuits of the Unit 2 purge axhaust valves and the Unit 1 purge supply and purge exhaust valves.

Very truly yours, , ,

Senio Vice President Sol Burstein cca Mr. Boyce H. Grier, Regional Director Directorate of Regulatory Operations, Region III 6

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