ML20085J949

Ao:On 740504,during Local Leak Rate Testing of LPCI Sys, Valve MO-3-1501-32A Tripped.Caused by Breaker Being Under Sized.Breaker Will Be Replaced

ML20085J949
Person / Time
Site:	Dresden
Issue date:	06/21/1974
From:	Stephenson B COMMONWEALTH EDISON CO.
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
452-74, AO-740621-02, AO-740621-2, NUDOCS 8310190233
Download: ML20085J949 (2)

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Vj C:mmIpcith Edisin s t Or.e First(tnal Plata. CNcago. Ilhnois

\. , , Address Reply to: Post Office Box 767 Chicago, Ilknois 60650 BBS Ltr.f452-74 Dresden R. R. #1 Nuclear [ Power - ',

1. StationI 7 .l' Morris, Illinois June 21, 1974 604504,y@Ml gr, <- p/

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y Mr. J. F. O' Leary, Director \  ?!" [.~r

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Directorate of Licensing- ,

J U. S. Atomic Energy Commission Washington, D. C. 20545

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SUBJECT:

LICENSE DPR-25, DRESD2N NUCLEAR POWER STATION. UNIT #3, REPORT 0?

UNUSUAL EVENT PER SECTION 6.6.B.2 0F THE TEQiNICAL SPECIFICATIONS.

BTJ.AKER TRIP OF HO-3-1501-32A.

Reference:

Dresden Station Deviation Report Number D12-3-74-14 dated l May 4, 1974. 1

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Dear Mr. O' Leary:

This letter is to report a condition relating to the operation of the unit at about 0330 hours0.00382 days <br />0.0917 hours <br />5.456349e-4 weeks <br />1.25565e-4 months <br /> on May 4,1974. At that time, the supply breaker fo* '"" alve MO-3-1501-22A trippod. Th u .. ." - H. . i s cen t r a ry to .%i.lvu 3.3. A.1 414 seguises that the irw. system oe operable unen irradiated fuel is in the core.

l PROBLEM l

On May 4, 1974, local leak rate testing of the LPCI system was in progress. For the test it was necessary to drain the LPCI system which required the operation of MO-3-1501-32A. During the closing of the valve, its supply breaker tripped. At the time of the occurrence, the unit was in shutdown with all control rods inserted.

INVESTICATION AND CORRECTIVE ACTION On investigation, it was discovered that the cause of the breaker trip was due to the breaker being under sized. The supply breaker for MO-3-1501-32A is presently a 10 amp breaker. A recent modification calls for the 10 amp breaker to be replaced with a 25 amp breaker. The 25 amp breaker is presently on order and will be installed immediately upon its arrival.

The increase in breaker size is a satisfactory corrective action in light of cumulative experience. A review of breaker sizing for all motor operated valves at Dresden has been under investigation for about one year. As a QS O p ,

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Mr. J. F. O' Leary June 21,1974 i

result of this investigation, numerous breakers were found to be under sized.

The breaker for HO-3-1501-32A was one found to be under sized, and needed to be changed to a 25 amp breaker.

EVALUATIONS During the failure of LPCI 3-1501-32A valve, the safety of the plant and public was not in jeopardy. At the time of the failure, the unit was in shutdown with all control rods inserted. In addition, the valve was operable as soon as the breaker was reset. Also, at the time of the failure, 4

all other safety systems were operable.

Sincerely, /,

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B. B. Stephenson Superintendent BBS:TEL:do i

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