ML20084S036

Supplements Info to RO Re Primary Containment Isolation Valve Leakage Reported on 720518.Henry Pratt Co,Manufacturer of Valves,Has Concluded Cause of Leakage Due to Improper Assembling of Valve Operator

ML20084S036
Person / Time
Site:	Dresden
Issue date:	10/24/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
References
776-74, NUDOCS 8306160120
Download: ML20084S036 (2)

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BBS Ltr.#776-74 Dresden Nuclear Power Station R. R. fl g' Morris, Illinois 60 3-October 24, 1974 <

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e A;49 rd Mr. James G. Koppler, Regional Director Directorate of Regulatory Operations-Region III

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799 Roosevelt Road Glen Ellyn, Illinois 60137

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SUBJECT:

LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT C.

SUPPLEENPARY IUFOPFATION TO REPORT CP U'iUS'JAL EVENT PER SECTION 6.6.B.2 OF THE TECEiICAL SPECIFICATIC::S.

PRIFARY CO!7 PAD ~rl?P ISOLATION VALVE LEAKAGE.

References:

1) Letter from Mr. W. P. Worden to Dr. P. A. Morris dated May 18, 1972.

2) Letter from Mr. W. P. Wordet. to th . J. P. O' Leary da',,cd December 19, 1973

3) Drawing P&ID M-356 ,

Dear Mr. Keppler:

In the letter sent to you from Mr. W. P. Worden dated December 19, 1973, concerning primary conteunment isolation valve leakage, it was stated that leakage through the rubber seated butterfly valves had been a recurring problem. At that time, it was not known whether the leakage was associated with the rubber seats or another problem.

Since that time the manufacturer of the valves, the Henry Pratt Co., wao asked to investigate this problem. They concluded that the cauco of the leakage was due to improper assembling of the valve operator. They had checked the valves with the operators off and found them to be bubble-tight, and leakage did not occur until after the operators were assembled to the valves and installed in line.

The valves had been cent to the manufacturer to be rerubbered with an Ethylene-Propylene Terpolymer rubber, a high temperature radiation resistance rubber ccat material after the original seats failed because of heat deterioraticn.

However, the operators remained at the station. According to the company, when the operators were reassembled at the station, clearances existed between the operator plate bearings and the shaft lover, and scme set screws in the operator lever that -lock it agaltmt the valve shaft were missing. Thesc ocmponents help to position th; valvo disc. , Therefore, the clearanece between the operator plate bearints cnd the loading cauacd by the assembly of the J operator to the valve allcwed the disc to move alons the axial center line of the valve shaft. This movement resulted in leakase at the hub area.

8306160120 741024 J-.W7 PDR ADOCK 05000249 Kd, S PDR /# COPY SENT REGION = l 00T- _5}19H ///1 ^/// " j

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m O O Mr. James G. Keppler October 24, 1974 i The llenry Pratt Co. has sent the station drawings on the assembly of the valve and operator, and these drawings have been sutxnitted to the mainten-ance department.

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Sincere 1' .// l

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Super endent BBS:ELS:do

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