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~ 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

/

Dr. Peter A. Morris, Director Division of Reactor Licensing U. S. Atomic Energy Commission Washington, D. C. 20545

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SUBJECT:

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

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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 reduce the valve travel in the open direction. After the installation p[,, d 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

(, Superintendent

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