ML20085L520

Ro:On 711230,w/reactor in Run Mode,Condenser Flow Reverse Tests in Progress When Valve 3-5402B Failed to Fully Close. Caused by Valve Disc Binding in Guides Due to Slight Overtravel in Valve.Slug Installed to Reduce Valve Travel

ML20085L520
Person / Time
Site:	Dresden
Issue date:	01/07/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20085L521	List: ML20085L520 ML20085L563
References
NUDOCS 8311010483
Download: ML20085L520 (1)

Text

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o So.an Commonwealth Edison Company ONE FIRST MATIONAL PLAZA

• C H 4 C A 4 0.

ILLINOIS Ashkens Seph so.

POST O FFIC E GOI F 4 7

• C M I C A C O. BLL4NOl8 60400 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 January 7, 1972 68

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Dr. Peter A. Morris, Director V

Division of Reactor Licensing U. S. Atomic Energy Commission

• g Washington, D. C.

20545 F &

SUBJECT:

LICENSE DPR 25 DRESDEN NUCLEAR POWER STATION UNIT #3 k SECTI0r; 6.6.B.3 0F THE TECHNICAL SPECIFICATIONS m.Co l

Dear Dr. Morris:

1 This is to report a condition relating to the operation of the station, when the mechanical vacuum pump suction valve (3-5402B) failed to close, thus rendering the mechanical vacuum pump incapable of being isolated as required by Section 3.8.B.1 of the Dresden Unit #3 Technical Specifications.

Problem and Investigation On December 30, 1971, at 2310, with the reactor in the run mde at 150 We, condenser flow reversal tests were in progress, when valve 3-5402B failed to fully close. The manual suction valve for the mechanical vacuum pump was closed and the reactor placed in a cold shutdown condition. Subsequent investiration revealed that the failure of the valve was the result of the valve disc binding in the guices due to a slight overtravel in the valve.

_ Corrective Action A three inch slug was installed in the valve operator to p[,, d reduce the valve travel in the open direction. After the installation of the slug, the valve was cycled and the anomaly could not be reproduced, fI 31ugs will be added to the remaining similar mechanical vacuum punp g'jl suction valves on Units 2 and 3 at the earliest practical time.

8311010483 720107 Sincerely g= ^"" "

"E u S. w, w p> 4' 9 -

W. P. Worden

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Superintendent

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