ML20084T511

Ro:On 721108,during Surveillance Testing of Five Electromatic Relief Valves,Valve 3A Would Not Operate.Caused by Badly Scored Disc Rings Stuck in Valve Guide.Disc Machined & Seat & Disc Lapped.Valve Guide & Rings Replaced

ML20084T511
Person / Time
Site:	Dresden
Issue date:	12/08/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
NUDOCS 8306230234
Download: ML20084T511 (2)

Text

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e o Commonwealth Edison Company 72 WEST ADAMS STREET

• C H I C A G O. f t. L I N O I S A66.an Copy ser POST oPPICE toX 747 4 CMIC AOo, IL LIN Ol8 4069 0 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 Decembet 8, 1972 #

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Mr. A. Giambusso 50-249 kOy b[ I@

Deputy Director for Reactor Projects D

1. h.:h7.f'[h Directorate of Licensing 4 T U. S. Atomic Energy Commission M Washington, D. C.

20545  % y.

SUBJECT:

LICENSE DPR-25. DRESDEN NUCLEAR POWER STATION. UNIT #3, SECTION 6.6.C.1 0F THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This is to report a condition relating to the operation of the unit in which, on November 8,1972, one electromatic relief valve failed to operate as required by Section 3.5.D.l.

PROBLEM AND INVESTICATION On November 8,1972, the unit was operating in a steady state '

condition at 738 MWe. Prior to taking the aigh Pressure Coolant Injection (HPCI) System out of service for repairs, surveillance tests were conducted on the Automatic Pressure Relief System, Core Spray System and the. Isola-tion Condenser as required by the Technical Specifications (4.5.C.2).

M/ During surveillance testing of the five electromatic relief valves, it was jg found that one valve "3A" (serial no. BK 7051) would not operate. Temper-atures downstream of the pilot valve indicated that it was opening, but

'K steam flow to the turbine indicated the main valve was not opening.

b When it was found that the HPCI system and one electromatic relief valve were inoperable, an orderly shutdown was initiated. As the unit was coming down, repairs were made to the HPCI system. After repairs were made, the system was satisfactorily tested. The unit was subsequently brought back up in power and continued operation. The weekly surveillance tests of the HPCI system were conducted while operating with the one inoperable valve. This is required by the Technical Specifications (4.5.D.2).

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Mr. A. Gic a y ,

Decuber 8, 1972 On November 18, 1972, the unit was shutdown to investigate the electromatic relief valve problem and perform other maintenance. Disman- i tling of valve the valve showed badly scored disc rings that were stuck in the guide.

l The stuck rings in the guide caused the valve to malfunction. '

The electromatic relief valve system is designed with one redundant valve.

system capacity is Therefore, when one valve is inoperable the designed still available. Consequently, one inoperable valve presents no unreviewed safety questions, and operation under those s,

conditions is within the limitations of the Technical Specifications.

_ CORRECTIVE ACTION The disc was machined and the seat and disc lapped. The valve guide and rings were replaced. Pilot valve repairs included replacing 3 the disc and stem and lapping the disc and seat. The valve was opera-tionally tested satisfactorily at 500 psig reactor pressure on November 22 while the reactor was heatin8 up. The remaining four valves will be inspected as soon as practical, and no later than the next refueling outage.

Sincerely, Al. hJsbucl.)

fW.P.Worden Superintendent WPW:do i

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