ML20084U961

Ao:On 720911,containment Sump Isolation Valve CV-3030 Failed to Respond to Open Signal.Caused by Leakage Between Valve Seating Surfaces & Pressure Regulator Drift from 150 Psi to 90 Psi.Pressure Restored to 150 Psi & Valve Stroked

ML20084U961
Person / Time
Site:	Palisades
Issue date:	09/21/1972
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U963	List: ML20084U961
References
NUDOCS 8306290672
Download: ML20084U961 (2)

Text

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[! If cenerai omcer oi2 we.t Michigan Avenue, hekson. Michigan WOf . Area Code 517 78H-0550 September 21, 1972

, , x Mr. John F. O' Leary, Director h/ QyA \ Re: , Docket No 50-255 Directorate of Licensing US Atomic Energy Commission k} g

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Washington, DC 205h5 M hy f . f/

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Dear Mr. O' Leary:

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On September 11, 1972 during qua gyncMting

~crlylt of the contain-ment sump isolation valves as required by Article 4.6.h(a) of the Tech-nical Specifications, CV-3030 failed to respond to an open signal. The other containment sump isolation valve (CV-3029) tested satisfactorily.

At the time the incident occurred, the reactor was operating at a power level of approximately 1320 E4 t. Generator output was approx- .

"imately 425 KJeg. This incident was similar to one involving CV-3029 reported by our letter dated February 11, 1972.

CV-3030 is a double-acting piston, air-operated, 24-inch gate valve. Air to operate the valve is supplied from a 325 psi air system.

Air to the closing side of the piston operator is provided from the air system through a solenoid valve and a 325 to 40 psi pressure regulator.

Air to the opening side of the piston operator is provided by the air system through a solenoid valve and a 325 to 150 psi pressure regulator.

The cause of the failure was twofold. The closing side pres-sure regulator had very slight leakage between the valve seating sur-faces, allowing air pressure to build up against the closing side of the piston operator pushing the valve harder into its seat. In addi-tion, the pressure regulator on the opening side of the valve operator 1 j had drifted from its normal 150 psi setting to 90 psi. This allowed

/ a smaller than normal force to be built up on the opening side of the

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piston operator. At the time the testing was performed, it had been approximately three months since the valve had been operated.

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'/ Shortly after the valve failed to operate, the pressure was

/cl )l/ bled off the closing sido md the opening side pressure restored to g'* q g the normal 150 psi and th; ;alve stroked open. The valve was then stroked normally several more times, jo f nj Wo 4W 8306290672 ypo9 pRADOCK05000h5 Y I ;

5254 PDR COPY SENT REGION. N - 3 ,

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1. h Mr. John F. O' Leary 2 Docket No 50-255 License No DPR-20 September 21, 1972 Both the containment sump isolation valves were tested success-fully daily for one week following this failure. They will be tested weekly until a means can be provided that will prevent an air pressure buildup on the closing cylinder. Concurrent with the above testing, the pressure regulators will be checked to insure their set points are not dri fting.

Two completely redundant containment sump isolation valves are provided. Therefore, the failure of one valve does not impair the ability of the safety injection system to perform its design function in the recirculation mode of operation. In addition, the Technical Speci-fications provide appropriate rules governing plant operation with inoperable components present in the safety injection system. A single component being inoperable does not negate the ability of the safety injection system to perform itt Eunction, but it does reduce the redun-dancy provided by design. The time limits for operation with an inoperable component provide assurance that the reactor vill not be operated for an extended time period with an inoperable component.

In the unlikely event this valve were again to stick in the closed position, it could be opened by manually increasing the air pressure supplied to the opening side of the valve operator. The valve operator is designed to withstand 400 psi. The air systems installed in the engineered safeguards rooms provide 325 psi air.

Yours very truly, Ralph B. Sewell (Signed)

RBS/ map Ralph B. Sewell Nuclear Licensing Administrator CC: BHGrier, USAEC