ML20084U139

Ro:On 720504,following Spurious Reactor Scram,Isolation Condenser Valve B-1301-3 Failed to Open Electrically.Caused by Auxiliary Contact B on Closing Circuit for Valve Motor Operator Circuit Breaker Not Consistently Closing Properly

ML20084U139
Person / Time
Site:	Dresden
Issue date:	05/12/1972
From:	Worden W COMMONWEALTH EDISON CO.
To:	Morris P US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084U135	List: ML20084U132 ML20084U139 ML20084U144 ML20084U147 ML20084U377
References
NUDOCS 8306270065
Download: ML20084U139 (2)

Text

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Commonwealth Edison Company 72 WEST ADAMS STREET

• C H I C A G O.

v ILLINOIS A_h Address teely tes POST orrlCE BOX 747

• C H I C A G O, titlNOl$ 60490 Dresden Nuclear Power Station R. R. #1 ,

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Morris, Illinois 60450

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i May 12, 1972

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E N619 Mij%If C t Dr. Peter A. Morris, Director - "

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Division of Reactor Licensing U. S. Atomic Energy Commission

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Washington, D.C. 20545

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Subject:

I.icense DPR-25 DNPS Unit #3 .. .b , . -

_Section 6.6.B.2 of the Icchnical Specifications

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Dear Dr. Morris:

l This is to report a condition relating to the operation of the l station, when isolation condenser volve 3-1301-3 failed to open electrically l

following a spurious reactor scram, thus rendering the isolation condenser inoperable contrary to section 3.5.E.1 of the Dresden Unit #3 Technical Specifications.

PROBI.D1 AND INVESTIGATION On May 4, 1972, Unit #3 was operating in a base load condition at 802 M.Je and 2300 M.lt. At 0911 the unit underwent a scram which was followed by a Group I isolation, causing the reactor pressure to rise. An attempt was made to place the isolation condenser in service, but valve 3-1301-3 would not open. An operator was dispatched to the valve and manually moved the valve off its seat. Once the valve was manually moved off its seat and its breaker reset, it appeared to function properly. The isolation condenser was then used to reduce reactor pressure in an orderly fashion.

CORRt.CTIVr ACTION  !

i d Following the plant shutdown, investigation of the isolation

$ l l ,/ condenser valve 3-1301-3 disclosed that the "B" auxiliary contact on the closing circuit for the valve motor operator circuit breaker was not consis-

}P tently closing properly. This contact is in the electrical interlock circuit f(((

pf, for the open contector. The auxiliary contact arm was adjusted and proper oparation of the valve was verified.

The last surveillance performed on this valve prior to the scram was on 1/15/72 when the valve operated satisfactorily. Subsequent to the  !

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t Dr. Peter A. Morris May 12, 1972 startup following the scram the valve was again operated electrically and performed properly.

ADDITIONAL INFORh TION l The spurious scram on 5/4/72 and the ensuing pressure transient caused an electromatic relief valve to operate. One safety valve prematurely opened at 1108 psig reactor pressure resulting in pressurizing the drywell to 2) psig. There was no drywell damage except for a piece of insultion I which was blown off an adjacent relief valve.

The transient was reviewed by the Station Review Board and the Nuclear Review Board. Following their review, startup was approved and the plant returned to service, a complete report of the event is being developed at this time and will be forwarded to you by 6/1/72.

Sincerely,

h. tut.ck .$. M h W. P. Worden T' ' Superintendent WPW:sds i

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