PNO-III-86-052, on 860601,both Feedwater Pumps Tripped During Surveillance Test,Causing Reactor Water Level to Decrease Below Scram Level.Investigation to Determine If ATWS Occurred or If Instrumentation Faulty Underway

PNO-III-86-052:on 860601,both Feedwater Pumps Tripped During Surveillance Test,Causing Reactor Water Level to Decrease Below Scram Level.Investigation to Determine If ATWS Occurred or If Instrumentation Faulty Underway

ML20198N507
Person / Time
Site:	LaSalle
Issue date:	06/02/1986
From:	Guldemond W, Wright G NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-86-052, PNO-III-86-52, NUDOCS 8606060113
Download: ML20198N507 (1)

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PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-86-52 Date Jure 2, 1986 This preliminary notification constitutes EARLY notice of events of FOSSIBLE 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: Commonwealth Edison Co.

LaSalle Unit 2 Licensee Emergency Classification:

Notification of an Unusual Event MD Marseilles, IL 61341 XX Alert Site Area Emergency Docket No: 50-374 General Emergency Not Applicable

Subject:

POSSIBLE ATWS EVENT At 4:21 a.m. (CDT), June 1,1986, while operating at about 83 per cent power, both feedwater punps tripped during a surveillance test, causing the reactor water level to decrease. A preliminary review of this incident indicates that the water level may have decreased to about four inches above instrument zero (which is 13_.7 feet above the top of the fuel), but which is below the automatic scram setpoint of 12.5 inches. Yet, no scram occurred (the normal operating water level is 36 inches above instrument zero). Control room operators, tho apparently did not recognize the rotential " Anticipated Transient Without Scram" (ATWS),

restarted the feedwater pumps in about two minutes.

The possible ATWS was not identified until about two hours after the event when an oncoming shif t engineer apparently noticed an abnormal trace on one of the reactor water level recorders. After analyzing the situation, the licensee initiated a shutdown at 2:40 p.m. (CDT),

June 1,1986, and declared an " Alert" under its emercency classification system on the basis of the potential ATHS at about 6:30 p.m. (CDT) June 1,1986.

LaSalle Unit 1 is currently shut down for refueling.

The licensee is investigating the event to determine whether there may have been an ATWS, or whether instrumentation indicating the low water level may have been faulty.

Region III (Chicago) will issue a Confirmatory Action Letter documenting the licensees commitment to obtain the Regional Administrator's concurrence before restarting the unit. An Augmented Inspection Team (AIT) composed of regional inspectors including the Oyster Creek resident inspector (the Oyster Creek design is similar to LaSalle) and a representative from the Office cf Nuclear Reactor Regulation has been dispatched to the site and is expected to arrive in the early afternoon of June 2.

The State of Illinois will be notified. Region III first learned of this event at 5:48 p.m.

(CDT), June 1, 1986. This information is current as of 12:00 p.m. (CDT), June 2, 1986.

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RIII Resident Office PDR Licensee: /,.T/,4.)b (Corp. Office - Reactor

&_Lic.Only) 8606060113 860602 N-II-86-52 PDR g g Rev. November 1985

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