ML20084S284

Ro:On 730126,during Local Leak Rate Testing of Rubber Seated Torus Vent Relief Valves,Check Valves 3-1601-31A & 31B Found to Be Leaking Excessively.Cause Not Stated.Valve Seats Cleaned & Smeared W/Thin Layer of Waterless Grease Silicone

ML20084S284
Person / Time
Site:	Dresden
Issue date:	02/23/1973
From:	Worden W COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
150-73, NUDOCS 8306160442
Download: ML20084S284 (2)

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• CommonwealthiltEdison 72 WEST ACAMG STREET CHICAGO. ILLINOIS ComPanv -

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POST OPPICE 801 747

• CHICAGO, attINOIS 60690 WFW Ltr.#150-73 Dresden Nuclear Power Station R. R. #1 Morris, Illinois 60450 February 23, 1973 '[ g s1 q q! ' *#

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Mr. A. Giambusso D. , Of* * .

Deputy Director for Rea ctor Projects '{. f*j 8/y \

Directorate of Licensing ,

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U. S. Atomic Energy Commission .

Washington, D. C. 20545 c); h' , \

SUBJECT:

_ LICENSE DPR-25, DRESDEN NUCLEAR POWER STATION, UNIT #3,_

SECTION 6.6.C.1 OF THE TECHNICAL SPECIFICATIONS.

Dear Mr. Giambusso:

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

] i / ' O- ively.

I,k h g ,r- PROBLEM AND INVESTIGATION On January 26, 1973, rubber seated ventilation valves were being D'.w W leak checked as part of a quarterly surveillance. In order to test valve 3-1601-20A it is necessary to pressurize the volume between this valve and J-0P check vatve 3-1601-3tA te 48 Peends. A simi1ar Precedure is used te test valve 3-1601-20B. In attempting to pressurize these volumes, it was found 4,. g (s ['

that the two check valves were leaking past their seats.

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Valves 3-1601-31A and 31B are part of the torus and drywell to in 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 race

\] 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 57. Lto (48) (29.34 SCF/hr) . Valves 3-1601-20A and 20B are normally closed during operation.

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o Mr. A. Gicmbu'sso Q -

February 23, 1973 f

I 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,were manufactured by Chapman and are the only valves of that kind. Unit 2 has valves manufactured by Atwood i Morrill Company and no leakage has been experienced with these valves. The valves on Unic #3 will be evaluated to determine if they should be modified or replaced.

i (O. . bb W. P. Worden 1 Superintendent WFW:do I

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