ML17238A728

Unit #3 Section 6.6.B.2 of the Technical Specifications - Relating to the Operation of the Station When Isolation Condenser Valve 3-1801-3 Failed to Open Electronically Following a Spurious Reactor Scram

ML17238A728
Person / Time
Site:	Dresden
Issue date:	05/12/1972
From:	Worden W Commonwealth Edison Co
To:	Morris P US Atomic Energy Commission (AEC)
References
Download: ML17238A728 (2)

Text

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Commonwealth Edison Co~ an;'7'"7.*

72 WEST ADAMS STREET

• CHICAGO, ILLINOIS Addreu Reply to, POST OFFICE BOX 767 *CHICAGO,. ILLINOIS 60690 Dresden Nuclear Power Station R. R. 411 Morris, 60450 May 12, meKEniD WBAliC Dr. Peter A. Morris, Director.

Divi_sion of Reactor Licensing

u. S. Atomic Energy Commission MAY 161972 e.

Washington, D.C. 20545 J:raov OOCKrt CURie

Subject:

License DPR-25 DNPS Unit '#3 Section 6.6.B.2 of the Technical

Dear Dr. Morris:

This is to report a condition relating to the operation of the 1 station, when isolation condenser valve 3-1801.;.3 failed to open electrically following a spurious reactor scram, thus rendering the isolation condenser inoperable contrary to section 3.5.E.l of the Dresden Unit 413 Technical Specifications.

PROBLEM AND INVESTIGATION On May 4, 1972, Unit #3 was operating in a base load condition at 802 MWe and 2300 MWt. At. 09ll, _the. unit underwent'" a .scr.am. which. was followed by a Group I isolation, causing the reactor pressure to rise. An attempt was made to place tli"e 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 s~at. Once the valve was manually moved off its seatr~a!ld its breaker reset, *_ !..'"!.J it appeared to function properly. The isolation condenser was then used to reduce reactor pressure in an orderly fashion.

CORRECTIV~ ACTION Following the plant shutdown, investigation of the isolation condenser valve 3-1301-3 discillosed that the "B" auxiliary contact on .the closing circuib~i6or the valve motor operator circuit breaker was not consis;.

tently closing properly. This contact is in the electrical interlock circuit for the open contactor. The auxiliary contact arm was adjusted and proper op.~ration of the valve was verified.

lhe 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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Dr. Peter A. Morris

• May 12' 1972 sfutup following the scram the valve was aga*in operated electrically and performed properly.

ADDITIONAL INFORMATION

'llle 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. 'lllere was no drywell damage except for a piece of insultion which was blown off an adjaeent relief valve.

'llle transient was reviewed by?the Station Review Board and the Nuclear Review Board. t.FQ__~gi~~~~view, 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, a:JJ.*rvt~

0_,.., W. P. Worden

' \ ' 'Superintendent WPW:sds