ML20002E358

LER 81-001/01T-0:on 810102,while Performing Monthly Ventilation Sys Test,Supply Breaker for Safeguards Motor Control Ctr 1B42 Tripped.Caused by Dust in Instantaneous Trip Valve on Breaker.Breaker Cleaned & Tested

ML20002E358
Person / Time
Site:	Point Beach
Issue date:	01/16/1981
From:	Fay C WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
Shared Package
ML20002E357	List: ML20002E356 ML20002E358
References
LER-81-001-01T, LER-81-1-1T, NUDOCS 8101270564
Download: ML20002E358 (3)

Text

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7 8 EVENT DATE 74 EVENT DESCRIPTION AND PROBA8LE CONSEQUENCES h 10121 l At 0139 hours0.00161 days <br />0.0386 hours <br />2.29828e-4 weeks <br />5.28895e-5 months <br /> on 01-02-81 the supply breaker for safeguards motor I iO i3i l control center 1B42 tripped while performing a monthly ventilation l 10 l 41 l system test. The unit was at about 70% steady state power at the time. l _

i O i s i l The loss of 1B42 resulted in a loss of the lYO4 instrument bus. The l 10 is I l loss of the lYO4 bus resulted in a momentary violation of the minimum l l0l2l l degree of redundancy required by Technical Specifications and is l 1 O t8 i i reportable IAW Tech. Spec. 15.6.9.2.A.2. 1 E O S SC E COMPONENT CODE SU8 0'E S E g l E l B l@ J@ W @ l C l K l T l B l R l K l@ y@ [Z_j @

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44 47 CAUSE DESCRIPTION AND CORRECTIVE ACTIONS h li l O I l The lYO4 instrument bus was shifted to its alternate power supply at I ii ii i l 0140 hours0.00162 days <br />0.0389 hours <br />2.314815e-4 weeks <br />5.327e-5 months <br /> and power was restored to 1B42 at 0141 the same day. The I g i cause of the breaker trip was found to be dust in the instantaneous I g l trip valve on the breaker. The Westinghouse type DB-50 breaker was l

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.t ATTACHMENT TO LICENSEE EVENT REPORT NO. 81-001/0lT-0 Wisconsin Electric Power Company Point Beach Nuclear Plant, Unit 1 Docket No. 50-266 During normal operation at 0139 hours0.00161 days <br />0.0386 hours <br />2.29828e-4 weeks <br />5.28895e-5 months <br /> on January 2, 1981 with Unit 1 operating at approximately 70% power, the supply breaker for safeguards motor control center 1B42 tripped. The breaker tripped during a monthly ventilation system test. Loss of the motor control center rasulted in a loss of the lYO4 instrument bus for a short period of time. A turbine runback was also initiated by the loss of the lYO4 instrument bus from a power level of 70% to approximately 50%.

The 1YO4 instrument bus was shifted to its alt:ernate power supply at 0140 hours0.00162 days <br />0.0389 hours <br />2.314815e-4 weeks <br />5.327e-5 months <br /> and power was restored to the 1B42 motor control center within two minutes of the event by resetting the supply breaker. Unit 2 was not affected by this event. Unit 1 was returned to 70% power at 0511 hours0.00591 days <br />0.142 hours <br />8.449074e-4 weeks <br />1.944355e-4 months <br /> on January 2, 1981.

The momentary loss (approximately one minute) of the lYO4 instrument bus constituted a violation of the minimun degree of redundancy required by the Technical Specifications for contain-ment spray actuation and steam line isolation. Containment pressure channel PC-950 is powered by lYO4 and requires power to generate a high-high pressure trip signal.

The loads on 1B42 which were de-energized for approximately two minutes are shown on the attached list.

The breaker trip was caused by dust on the instantaneous trip valve seat which lowered the current required to trip the valve. During the ventilation system surveillance testing, the starting current for the additional equipment caused the breaker to trip. The Westinghouse type DB-50 breaker was cleaned, tested, and returned-to-service later the same day. There have been no previous events related to DB-50 breakers due to this cause.

This event is being reported in accordance with Technical Specification 15.6.9.2.A.2.

MOTOR CONTROL CENTER 1B42 LOADS j l

'MOV-850B Containment sump "B" isolation MOV-852B Reactor vessel injection isolation l MOV-866B Safety injection hot leg isolation MOV-860B Containment spray isolation

- MOV-8968 "B" safety injection pump suction isolation MOV-878C Safety injection loop " A" isolation MOV-878B Safety injection loop "B" isolation MOV-860D Containment spray isolation MOV-851B Containment sump "B" isolation MOV-856B Residual heat removal pump "B" suction MOV-870B Spray pump "B" suction MOV-871B' Containment spray pump "B" recirc line MOV-825B Safety injection header to refueling water storage tank isolation MOV-841B Accumulator "B" isolation MOV-738B Cooling to residual heat removal heat exchanger "B" MOV-701 Residual heat removal to loop " A" ,

MOV-5 9 9 Loop "B" drain _

MOV-826 A Boric acid supply to safety injection pump MOV-826B Boric acid supply to safety injection pump MOV- 35 0 Emergency boration MOV-719 Containment cooling MOV-1298 Charging line isolation MOV-427 Letdown line isolation MOV-596 Pressurizer relief tank drain MOV-516 Power-operated relief isolation P12B Spent fuel pool cire pump l MOV-4021 Auxiliary feed pump P38B discnarge i MOV-4006 Service water to turbine driven auxiliary - feed pump Boric acid heat tracing transformer 1GYO4 Instrument bus AC M-G set Diesel generator G01 starting air compressor 1

W12C Diesel room supply fan

! MOV-2908 Service water from containment vent coolers

_MOV-2880 Service water to spent fuel pit heat exchanger MOV-29 30 Spent fuel cooling service water supply MOV-3931- Fuel oil to Diesel day tank "B" W21A Auxiliary building stack vent fan

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