PNO-II-86-029, on 860411,reactor Tripped While Unit Operating at 70%,due to Loss of Permanent Magnet Generator in Exciter Unit.Repairs Will Be Completed by 860415.During Shutdown, Cooldown Rate Higher than Expected

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PNO-II-86-029:on 860411,reactor Tripped While Unit Operating at 70%,due to Loss of Permanent Magnet Generator in Exciter Unit.Repairs Will Be Completed by 860415.During Shutdown, Cooldown Rate Higher than Expected
ML20203C365
Person / Time
Site: North Anna Dominion icon.png
Issue date: 04/14/1986
From: Brownlee V, Ignatonis A
NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
To:
References
PNO-II-86-029, PNO-II-86-29, NUDOCS 8604210128
Download: ML20203C365 (1)


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I April 14, 1986 PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE PNO-II-86-29 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without verifi-cation or evaluation, and is basically all that is known by the Region Il staff on this date.

i FACILITY: Virginia Electric & Power Co. Licensee Emergency Classification:

North Anna Unit 2 X Notification of Unusual Event Docket No. 50-339 Alert Mineral, Virginia Site Area Emergency General Emergency Not Applicable

SUBJECT:

UNSCHEDULED SHUTDOWN GREATER THAN 48 HOURS Virginia Power expects by tomorrow to complete repairs of the permanent magnet generator in the exciter unit of North Anna Unit 2. Loss of this component caused a main generator trip and a subsequent turbine trip, followed by a reactor trip, at 1:44 a.m. (EST) on Friday, April 11, while the unit was operating at 70 percent power.

During the shutdown, the unit cooldown rate was higher than expected but less than the maximum of 100 degrees per hour allowed by technical specifications. The additional cooldown -- following the reactor trip and before the main steam isolation valve closed -- i resulted from greater steam flow through the three-inch opened manual bypass (warming) i valves to the moisture separator reheaters and from additional' auxiliary feedwater flow through the main feedwater bypass valves. In accordance with the plant emergency plan, Virginia Power declared an unusual event at 2:03 a.m. after the trip, and terminated it at 3:45 a.m.

North Anna Unit 1 is operating at 100 percent power.

Virginia Power is prepared to respond to media inquiries.

The Commonwealth of Virginia has been informed.

This infomation is current as of 2:30 p.m. (EST) today.

Contact:

A. Ignatonis, 242-5509 V. Brownlee, 242-5583 DISTRIBUTION:

H. Street MNBB Phillips E/W Willste MAIL:

Chairman Palladino TDT NRR T hMSS IDYiTIMB Com. Roberts PA OIA RES D0T: Trans Only Com. Asselstine MPA AE00 Applicable State Com. Bernthal ELD Com. Zech Air Rights INP0 - N 74 SECY SP NSAC ACRS CA PDR Regions: 31~~/dlF//.% M #/# pg5 g g Licensee: /z3c (Reactor Licensees)

Applicable Resident Site - //8

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P W h 28 860414 PND-II-86-029 pg i 0 L - _ _ _ _ _ -