ML17252A999

Letter Reporting a 01/26/1973 Occurrence Relating to Excessive Leaking of Check Valves 3-1601-31A and 31B - Dresden Unit 3

ML17252A999
Person / Time
Site:	Dresden
Issue date:	02/23/1973
From:	Worden W Commonwealth Edison Co
To:	Giambusso A US Atomic Energy Commission (AEC)
References
WPW Ltr. #150-73
Download: ML17252A999 (2)

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Commonwealth Edison Company

• 50-249 72 WEST ADAMS STREET

• CHICAGO, ILLINOIS Addreu Reply to._*~-~

POST 0 ....-'ft.:t~'~_rN'-..~ CHICAGO, ILLINOIS 60690 WPW Ltr./1150-73 (;{ Dresden Nuclear Power Station U;>At..; R. R. #1 Morris, Illinois 60450 I

-~ B 2 7 1973

.: L t> 1*, ~. February 23, 1973 REGULATORY Ji{7 ;:.:._"

MAIL SECTION If'\ "'

DOCKET CLERK 6 Mr. A. Giambusso en Deputy Director for Reactor Projects Directorate of Licensing U. s. Atomic Energy COtimlission Washington, D. C. 20545

SUBJECT:

. LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3, SECTION 6.6.C.l OF THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

This is to report a condition relating to the operation of the unit, when during local leak rate testing of the rubber seated torus vent relief valves, check valves 3-1601-31A and 31B were found to be leaking excess-ively.

PROBLEM AND INVESTIGATION On January 26, 1973, rubber seated ventilation valves were being leak checked as part of a quarterly surveillance. In order to test valve 3-1601-20A it is necessary to pressurize the vo~ume between this valve and check valve 3-1601-31A to 48 pounds. A similar procedure is used to test valve 3-1601-20B. In attempting to pressurize these volumes, it was found that the two check valves were leaking past their seats.

Valves 3-1601-31A and 31B are part of the torus and drywell to reactor building vent system as shown on piping and instrument drawing M-356. The leakage through the check valves had no safety effects since the two valves associated with the check valves, 3-1601-20A with check valve 31A and 3-1601-20B with check valve 31B, were found to have a leak rate within* Technical Specification Limits. Valve 20A exhibited a leak rate of 3.12 SCF/hr while 20B was zero SCF/hr. The Technical Specification Limit for any one isolation valve is 5% Lt:<> (48) .. (29. 34 SCF /hr) ~',valves 3-1601-20A and 20B are normally closed during operation.

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1348

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...... Mr. A. Giambusso February 23, 1973 CORRECTIVE ACTION The valve seats were .cleaned and a thin layer of silicone base waterless grease placed on the seat. The volume between 20A and 31A and the volume between 20B and 31B was then pressurized and both 20A and 20B had leak rates within allowable limits.

Check valves 3-1601-31A, and B,~_!"'~(manufactured by Chapman and are the only valves of that kind. Unit 2 has *valves manufactu-ned by Atwood Morrill Company and no leakage has been experienced with these valves. The valves on Unit #3 will. be evaluated to determine if they should be modified or replaced.

W. P. Worden Superintendent WPW'fl"do

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