PNO-III-87-082, on 870616,licensee Declared Unusual Event After Concluding That Problems W/Electric Ground Fault Protection Sys Could Result in Common Mode Failure.Licensee Installed 14 Jumpers Around Questionable Detection Devices

PNO-III-87-082:on 870616,licensee Declared Unusual Event After Concluding That Problems W/Electric Ground Fault Protection Sys Could Result in Common Mode Failure.Licensee Installed 14 Jumpers Around Questionable Detection Devices

ML20212E281
Person / Time
Site:	Monticello
Issue date:	06/17/1987
From:	Boyd D, Guldemond W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-87-082, PNO-III-87-82, NUDOCS 9711030128
Download: ML20212E281 (1)

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PRELIMINARY NOTIFICATION OF EVERT OR UNUSUAL OCCURRENCE--PNO-III-87-82 Date June 17, 1987 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without d is basically all that is known by the Region III itaff on this date.

4verificationorevaluation,an Facility: Northern States Power Licensee Emergency Classification:

Monticello X Notification of an Unusual Event Monticello, MN 55362 Alert Site Area. Emergency General Emergency Applicable

Subject:

LOSS OF ELECTRICAL POWER

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The licensee declared an unusual' event at 11:28 a.m. (CST), June 16, 1987, after concluding that problems with,an electrical ground fault protection system could result in a common mode failure, f r-The Unusual Event was in response to two previous notifications of an Unusual Event on June 7 and June 14, 1987. The events were similar in both instances. The two earlier events were declared when a ground fault protection device (a solid state trip device designed to protect equipment by tripping a breaker on a power surge) deenergized the main circuit breaker on the 43A motor control center. The motor control center contains Emergency Core Cooling System equipment, including one train of the Core Spray and the Residual Heat Removal Systems.

When the circuit breaker deenergized, it shut down power to the motor control center, rendering it inoperative.

(The ground detection system had been installed during the June 1986 refueling outage.) Since declaring the June 16 Unusual Event, the licensee has taken corrective action by installing 14 r N jumpers around the questionable detection devices, thereby electrically bypassing them.

fThelicenseebelievesthatthesolidstatedevicescyclesoquicklythatthey

( V trip the main circuit breaker before the load breaker has a chance to open on a grounJ fault.

The licensee terminated the unusual event at 3:55 pai. (CDT), June 16, 1987. The plant is operating at about 100 percent power.

Two NRC specialists have been dispatched to the site to review the problem and the corrective actions. Region III (Chicago) has been monitoring the event.

The Headquarters Duty Officer was first notified of the Unusual Event at 1:10 p.m. (EST),

June 16,;1987. This infonnation is current as of 8 a.m. (CDT), June 18, 1987.

CONTACT: D.Boyd(FTS 388-5546) W.Guldemond(FTS 388-5574)

DISTRIBUTION:

H. St. EDO NRR E/W Willste Mail: ADM:DM8 PA IE NMSS DOT:Trans only Chairman Zech Com. Roberts ELD OIA RES AEOD NRC Ops Ctr Com. Asselstine Com. Bernthal Com. Carr SP Regional Offices ACRS SECY INPO NSAC RIII Resident Office (Corp. Office - Reactor Lic. Only)

[CA PDA Licensee:

9711030128 870617 Region III

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Ih-87-082PDR y

O# U C R Distribution: Chm, Cmrs GC, CA, p , Historian, g gj 3,Y, SEC Records.