ML19319B745

RO NP-33-77-48:on 770727,loss of Power to Containment Spray Valve CS1530 & Vacuum Relief Isolation Valves.Caused by Const Personnel Shorting Cable to Ground.Power Restored within 35 Minutes After Insp

ML19319B745
Person / Time
Site:	Davis Besse
Issue date:	08/23/1977
From:	Lingenfelter J, Miller D TOLEDO EDISON CO.
To:
Shared Package
ML19319B637	List: ML19319B636 ML19319B745
References
NUDOCS 8001270207
Download: ML19319B745 (3)

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• TOLEDO EDISON COMPANY DAVIS-BESSE UNIT ONE NUCLEAR POWER STATION SUPPLEiENTAL INFORMATION FOR LER NP-33-77-48 DATE OF EVENT: July 27, 1977 FACILITY: Davis-Sesse Unit 1 1

IDENTIFICATION OF OCCURRENCE: Loss of power to Containment Spray Pump 1-1 Discharge Valve and to Containment Vacuum Relief Isolation Valves.

Conditions Prior to occurrence: The plant was in Mode 3, with Power (MWT) = 0 and Load (MWE) = 0.

Description of occurrence: At 1145 hours0.0133 days <br />0.318 hours <br />0.00189 weeks <br />4.356725e-4 months <br /> on July 27, 1977, the feed breaker (BElIC1) for Motor Control Center EllC tripped, which resulted in a de-energi:ation of MCC EllC and MCC EllE. MCC EllE is fed from MCC EllC. When MCC EllC tripped, power was lost to the Containment Spray Pump 1-1 Discharge Valve CS 1530, whose feed breaker is Bell 56. Since power was lost to CS1530, Containment Spray Pump 1-1 was declared inoperable. The station entered the Action Statement for Technical Specification 3.6.2.1 which requires two independent Containment Spray Systems to be operable.

Also, when MCC EllC was de-energized, power was lost to five of the Containment Vacuum Relief Isolation Valves. These valves and their breakers are:

VALVE BREAKER CV 5070 BE 1137 CV 5071 BE 1138 CV 5072 BE 1139 CV 5073 BE 1140 CV 5074 BE 1141 Since power was lost to these valves, they would not close on a Safety Features Actuation System signal to maintain Containment integrity. The station entered the Action Statement for Technical Specific =rinn J.6.1.1 which requires Containment inte-grity to be maintained.

Also, as a result of this trip of MCC EllC, both Auxiliary Feedwater Systems were declared inoperable. This was covered in Licensee Event Report NP-32-77-11.

It was found that after investigation no faults existed on MCC EllC or MCC EllE, and they were re-energi ed successfully at 1220 hours0.0141 days <br />0.339 hours <br />0.00202 weeks <br />4.6421e-4 months <br /> on July 27, 1977. This re-l turned the above valves back to operability, and the station was removed from Action Statements for Technical Specifications 3.6.2.1 and 3.6.1.1.

'N Designation of Apoorent cause of Ocettrrence: The cause of the trip of BE 1101 f( ) (feeder for EllC) has ~ceen .ietermined to have been caused by construction personnel (Bisco) working on penetration PAP 2PX in conduit #38357A, which is AP Bell 67. The worker noticed a flash as he was manipulating his equipment around noon on Wednesday July 27, which corresponds to the time BE1167 (Containment Lighting Disconnect Switch BSUX79D3) feeder breaker tripped. This penetration was inspected and no

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TOLri:0 EDISCM CCMPN1Y DA'*IS-3CSSE CIIT 0:lE NUCLEAR POWER STATICN SUPPLEME: ITAL INFORMATION FOR LER NP-33-77-48 PAGE 2 evidence of burns or insulation integrity deterioration was found. It was deter-mined that the construction equipment shorted one of the wires to ground in an area that is now surrounded by the block'out silicone foam sealant which has l

effectively insulated whatever insulation was violated. The containment lighting ,

circuit from BE 1167 was re-energized after some preliminary checks and the fault has not re-occurred. Amperage checks of tne circuits show no problems. A megger check of the cable, AP BE1167, also shows that the cable is good. Since non-Q

! AP BE 1167 (Contain=ent Lighting) was the enly circuit running through the effected conduit and all electrical checks indicate a good cable, removal of the cable from the penetration for further visual inspection will be performed at the first re-i fueling outage. BE 1101 trip is not unusual under a short circuit situation, as selective breaker tripping is only for overload conditions.

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Analysis of Occurrence: Since the reactor had not reached initial criticality, the loss of the Containment Spray Pump 1-1 Discharge Valve and 50?. of the Contain-ment Vacuum Relief Isolation Valves for 35 =inutes posed no threat to the health .

and safety of the public or to station personnel. Containment Spray Pump 1-1 O

was operable, also.

Corrective Action: Power was restored to both MCC E11C and EllE after they were inspected for faults. No future failures .:1:h the same causa are expected in the future.

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Failure Data: No previous similar events have occurred.

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