PNO-III-87-111, on 870821,severe Thunder Storms & Lighting Caused Grid Disturbance & Tripped Main Generator on High Vibration.Expected Automatic Isolation of Steam Supply Did Not Occur.Caused by Faulty Pressure Switch.Switch Repaired

PNO-III-87-111:on 870821,severe Thunder Storms & Lighting Caused Grid Disturbance & Tripped Main Generator on High Vibration.Expected Automatic Isolation of Steam Supply Did Not Occur.Caused by Faulty Pressure Switch.Switch Repaired

ML20238B040
Person / Time
Site:	Davis Besse
Issue date:	08/24/1987
From:	Guldemond W, Mcgregor L NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-87-111, NUDOCS 8709010041
Download: ML20238B040 (1)

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-87-111 Date August 24, 1987 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without-verification or evaluation, and is basically all that is known by the Region III staff on this date.

Facility: Toledo Edison Company Licensee Emergency Classification:

Davis-Besse Notification of an Unusual Event Oak Harbor, OH 43449 Alert Site Area Emergency Docket No. 50-346 General Emergency X Not Applicable

Subject:

PLANT SCRAM DUE TO SEVERE THUNDER STORMS AND LIGHTNING l On August 21, 1987 at about 11:00 p.m. (EDT) severe thunder storms and lightning caused a grid disturbance and tripped the main generator on high vibration at the Davis-Besse Nuclear Power Station. This actuated the Anticipatory Reactor Trip System which tripped the reactor from 100% power.

During and after the trip all safety systems functioned normally. However, immediately after the trip the expected automatic isolation of the steam supply to the Moisture Separator Reheaters did not occur. causing a steam demand on the steam generators and a subsequent 60 degree cooldown of the roactor coolant system. Operator intervention about one minute after the trip terminated the transient with normal pressurizer pressure and level being restored in approximately nine minutes. The faulty pressure switch that controls the steam supply valves was repaired and the reactor was taken critical at 2:07 a.m. (EDT) on August 23, 1987.

The main generator was paralleled to the grid at 11:18 a.m. (EDT) of-the same day.

The resident inspector was notified of this incident and reported to the site to assess the '

licensee's course of action.

The State of Ohio will be notified.

Region III (Chicago a informe ff t.is event a .

PM (EDT) ugus 21 0 1987. T e i tion is u -rent a of,5- i

. EDT on gust 24 4987.

CONTACT L. M g . d F 8 -5141 FR 8- 74 '

DISTRIBUTION:

H. St. ED0 NRR E/W Willste Mail: ADM:DMB Chairman Zech PA IE NMSS D0T:Trans only Comn. Roberts ELD OIA RES Comm. Bernthal AE0D NRC Ops Ctr & M Comm. Carr Comm. Rogers ACRS SP $lD Regional Offices L SECY f

CA INP0 %)6 NSAC 8;/ 7 PDR RIII Resident Office Licensee: 7<GO (Corp. Office - Reactor Lic. Only)

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8709010041 870024 Region III PDR 18cE Rev. August 1987 PNO-III-87-111 PDR

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