PNO-III-83-032, on 830426,scram Circuitry Failed to Operate Properly When Mode Switch Moved from Refuel Position to Shutdown Position.Caused by Three Loose Wires in Rectifier Bridge

PNO-III-83-032:on 830426,scram Circuitry Failed to Operate Properly When Mode Switch Moved from Refuel Position to Shutdown Position.Caused by Three Loose Wires in Rectifier Bridge

ML20204G478
Person / Time
Site:	Duane Arnold
Issue date:	04/27/1983
From:	Jordan M, Shafer W NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
To:
References
PNO-III-83-032, PNO-III-83-32, NUDOCS 8305020511
Download: ML20204G478 (1)

PRELIMINARY NOTIFICATION OF EVENT OR UNUSUAL OCCURRENCE--PNO-III-83-32 Date: 4/27/83 This preliminary notification constitutes EARLY notice of events of POSSIBLE safety or public interest significance. The information is as initially received without veri-fication or evaluation, and is basically all that is known by the staff on this date.

Facility: Iowa Electric Light & Power Co. Licensee Emergency Classification:

Duane Arnold Energy Center Notification of Unusual Event Docket No. 50-331 Alert Palo, IA 52324 Site Area Emergency General Emergency X Not Applicable

Subject:

FAILURE OF SCRAM FUNCTION DURING MODE SWITCH SURVEILLANCE TESTING The licensee reported that during a surveillance test on April 26, 1983, the scram circuitry failad to operate properly when the mode switch was moved from the refuel position te the shutdown position. the switch position should have resulted in a reactor trip (scram) signal. Changing (All control rods were fully inserted prior to the surveillance test of the mode switch.) When the mode switch position was changed, the "B" train scram circuitry tripped normally, but the parallcl "A" train failed to trip. A trip of both the "A" and "B" trains is required to scram the control rods. A manual scram was initiated and both trains tripped normally.

The reactor has been shut down for refueling since February 11, 1983. The pre-liminary investigation by the licensee determined that three loose uires in a rectifier bridge caused the problem. The investigation by the licensee also determined that the portion of the Reactor Protective System (RPS) which was affected would not have prevented any of the automatic or normal scrams. associated with the mode switch in startup or run position. The mode switch positions startup and run are the positions which permit withdrawal of rods for a reactor startup and normal position for the mode switch during reactor operation respectively. The Senior Resident Inspector returned to the site from the Region III (Chicago) Office and the Quad Cities Senior Resident Inspector from the Quad Cities Station was also dispatched to Duane Arnold to review the matter. Reactor restart is presently scheduled for April 30, 1983, but restart will not occur until RIII completes its review.

Neither the Licensee nor Region III plans to issue a news announcement.

The State of Iowa will be nofitied.

Region III was notified of the incident by the Headquarters Duty Officer at 6:00 a.m.

(CDT), April 26 983. This information is current as of 8:00 a.m. (CDT) A;;ril 27, l' -

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Contact:

M. ordan FTS 384-2565 W. Shafer 384-2656 [(

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