PNO-I-97-019, on 970401,declared Unusual Event at Pilgrim Nuclear Power Station,Due to Inability to Provide Offsite Electrical Power to Safety Related Electrical Busses.Loss of Offsite Electrical Power Resulted from Faults on Lines

PNO-I-97-019:on 970401,declared Unusual Event at Pilgrim Nuclear Power Station,Due to Inability to Provide Offsite Electrical Power to Safety Related Electrical Busses.Loss of Offsite Electrical Power Resulted from Faults on Lines

ML20137J220
Person / Time
Site:	Pilgrim
Issue date:	04/02/1997
From:	Conte R, Laura R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
References
PNO-I-97-019, PNO-I-97-19, NUDOCS 9704030246
Download: ML20137J220 (3)

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' DCS No.: 05000293040197

, Date: 04/02/97 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PN1-97-019 This preliminary notification constitutes EARLY r.otice of events of POSSIBLE safety or public interest significance. The information is as initially received without verification or evaluation, and is basically cll that is known by the Region I staff on this date.

j Facility: Licensee Emergency Classification:

Boston Edison Co. X Notification of Unusual Event l Pilgrim Unit 1 Alert

! Plymouth, Massachusetts Site Area Emergency General Emergency Not Applicable

< Docket No.: 50-293 1

License No.: DRP-35 ,

l Event No.: l

, Event Location Code:

SUBJECT:

UNUSUAL EVENT AT PILGRIM DUE TO LOSS OF OFFSITE ELECTRICAL POWER AND STORM RELATED IMPACT AT OTHER REGION l PLANTS j At 3:49 a.m.,4/1, Boston Edison Co. (BECo) declared an Unusual Event (UE) at the Pilgrim Nuclear  !

Power Station due to the inability to provide offsite electrical power to the safety related electrical i busses. This condition was the result of losing the two 345 kV offsite power lines (i.e., the No. 342 l Canal and the No. 355 Bridgewater lines) to the station's 345 kV switchyard and the offsite power i 4

line supplying the 23 kV shutdown transformer. The plant was in a cold shutdown condition for 9

refueling. Prior to the loss of all offsite power, the plant operators at 2:38 a.m. had started both emergency diesel generators (EDGs) and placed them in service on the station's two emergency busses, at which time these buses were separated from the offsite electrical grid. These actions were the result of high winds (approximately 57 mph) and blizzard conditions from a North-easter storm that were causing instabilities on the offsite power lines.

The loss of the offsite electrical power resulted from electrical faults on the transmission lines. This loss of offsite power also caused the de-energization of the non-safety related buses which caused a thirteen minute temporary loss of shutdown cooling (SDC). No appreciable heatup of the reactor coolant occurred as a result of this loss. As a precautionary measure during the event the plant operators started the station blackout (SBO) diesel. By 11:39 p.m., with both 345 kV transmission lines in service, BECo returned the station to a normal electricallineup using the startup transformer.

The UE was terminated at 11:45 p.m.

The Commonwealth of Massachusetts was notified by the NRC Region l Staff at 7:30 a.m. and the Region i Public Affairs Office is prepared to respond to media inquiries. BECo issued a press release on this event and plant conditions. A resident inspector reported to the site at 6:30 a.m. The Agency entered a monitoring mode for this event at 5:00 'a.m. and exited this mode at 12:00 a.m. on 4/2.

In addition to Pilgrim, the large storm system on the Northeast coast affected the Seabrook and Indian Pont sites in Region 1. The Seabrook station lost two of three of its offsite 345 kV transmission lines es of 8:30 a.m., and made the decision to reduce station power from 100 percent to 30 percent pending the restoration of one of the lines. The State of New Hampshire was notified. At 1:23 p.m.,

a second line was restored and the station was making plans to return the plant to full power.

9704030246 970402 PDR I!*E PNO-I-97-019 PDR g}

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At th3 Inditn point site l storm-rciat:d circtricti faults occurred on soms of the offsits transmission

. linis, howsv:r no idv:rsa imprct on eithsr Unit 2 or 3 occurred. ,

I' This PN is current as of 9:00 a.m. 4/2.

Contact:

Richard J. Conte Richard Laura (610) 337-5187 (508) 747-0565 l 1

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