ML20084J189

Ao:On 721021,during Operability Test,Core Spray Pump 1B Failed to Start.Caused by Pump Breaker Not Closing.Interlock Cam in Breaker Housing Filed

ML20084J189
Person / Time
Site:	Quad Cities
Issue date:	10/31/1972
From:	Palmer F COMMONWEALTH EDISON CO.
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20084J183	List: ML20084J180 ML20084J189 ML20084J193
References
FAP-72-197, NUDOCS 8305120225
Download: ML20084J189 (3)

Text

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'" " Quad-Cita R- ar Power Station (M(a g[^%{ P,ost Othee De< P16,,,

p v af voidova,1;hnoo ulc .c Qy/ Tclephone 309/654-2241 50-254 FAP-72-197 Oct ober 31, 1972

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14r. A. Giambusso 5 Noyl$,ygycr e.s.

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?O Deputy Director for Reactor Projects - teaj Directorate of Licensing 6 As m .,

U.S. Atomic Energy Commission qg "

Washington, D. C. 20545 Re feren ce : Quad-Cities Nuclear Power Station Unit 1 License DPR-29, Appendix A, Sections 1.0.A.2, 3 5.A.1, and 6.6.B.3

Dear f4r. Giambusso:

The purpose of this letter is to report a condition relating to the operation of the station in which the 1B Core Spray Pump failed to start during an operability test. This abnormal occurrence was reported to you by telegram on October 21, 1972.

DESCRIPTION OF INCIDENT On October 19, 19 72 the No. 1/2 Diesel Generator was made inoperable for modification work in the Condensate Pump Room.

Prior to removing the diesel from service low pressure core cooling systems, containment cooling systems, and the unit diesel generators were tested and proven operable on Units 1 and 2. During a subsequent daily operability test at 2159 on October 21, 1972 the 1B Core Spray Pump failed to start.

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fg A weekend load reduction from 907 power which had been started at 2000 was continued while the core spray problem was investigated.

Dr b(L INVESTIGATION AND REP AIR

fk g)y The initial investigation revealed that the pumn breaker was er not closing. The closing spring was discharged and could not d# be charged with the breaker in the operate position. The breaker was then racked to the test position and it operated satisfactorily. When the breaker was racked back in to the 8305120225 721103 DR ADOCK 05000254 i V PDR G O E,

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Mr. A., Giambusso October 31, 1972 operate position, however, it still would not close. A spare

, breaker was then substituted with similar results. With the problem apparently in the breaker housing, station raaintenance personnel were called in.

The switchgear involved is a General Electric MC fl.76 Horizontal Drawout type. In order to move the breaker from one position to another a sliding shutter must first be pushed aside to in-sert the crank handle. This shutter is part of the interlock mechanism and it cannot be moved unless the breaker is open.

When the shutter is open the mechanism holds the breaker in the tripped position. Linkage also actuates a limit switch and lowers a roller nut to engage an interlock cam in the breaker housing. The limit switch opens contacts which prevent energizing the breaker closing coil or the spring charging motor.

The roller nut rides under the interlock cam as the breaker is racked in or out. If the breaker is stopped in an intermediate position, the nut is held down by the cam and through the link-age the sliding shutter is held open and thus the breaker held tripped.

During the original installation of these bret.kcrs the interlock cam must be positioned and _ cut to allow the roller nut to come up when the breaker has reached the full in or operate position.

In this case maintenance personnel suspected that the can was not allowing the interlock mechanism to reset when the breaker was full in and they filed the edge of the cam for insurance that the roller nut was not hLnging up. The breaker was then racked in and it operated satisfactorily. The B Core Spray system was declared operational at 0115 on October 21, 1972.

CONCLUSIONS Since the breaker spring could not be charged on either the original or the spare breaker, it is apparent that the inter-lock cam in the housing prevented closure of the limit switch I actuated by the shutter slide. It is theorized that the limit switch was close to its opening point when the pump was last started and that the breaker action jarred the interlock mechanism and the roller nut hung up j ust far enough out of its engaged pc31 tion to keep the limit switch open.

The problem with the breaker housing was corrected by filing the cam. While this type of problem had been encountered L during construction, this is the first occurrence during

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Mr. A. Giamb usso October 31, 1972 plant operation. Any reoccurrence of the problem uould be readily detected by normal surveillance.-

Very truly yours ,

COMMONWEALTH EDISON COMPANY QUAD-CITIES NUCLEAR POWER STATION jyg/, /

F. A. Palmer Superintendent FAP/zm l

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