ML19207B332

Forwards Rept of Reactor Exhaust Sys Malfunction on 790809: Electrical Fire in EF-1 Cubicle of Motor Control Ctr. Caused by Power Surge Due to Failed Transformer.Motor Control Contact Replaced

ML19207B332
Person / Time
Site:	Armed Forces Radiobiology Research Institute
Issue date:	08/15/1979
From:	Tyler P DEFENSE, DEPT. OF, DEFENSE NUCLEAR AGENCY
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
NUDOCS 7908240450
Download: ML19207B332 (2)

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g' g ' DEFENSE NUCLEAR AGENCY ARMED FORCES RADICBIOLOGY PESEARCH INSTITUTE BETHESD A, MARYLAND 20014 DIR AUG 1 ', *N Director, Region 1 Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 631 Park Avenue King af Prussia, PA 19406 i

Dear Sir:

This letter transmits a report of a malfunction of the reactor exhaust system.

My staff will provide any additional information that may be requir d.

C rely, 1 Enci Ugz, i yS t as U Captain, MC, USN Director O

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MALFUNCTION OF REACTOR EXHAUST SYSTEM This report was prepared and fo~ warded to the Nuclear Regulatory Commission (NRC) pursuant to Paragmph 4(a) of Reactor License R-84 and Section I, Paragmph A1. and A3. of the Technical Specifications.

I. Description of Malfunction At 0750, 9 August 1979, a reactor operator discovered that there had been an electrical fire in the EF-1 cubical of the Motor Control Center (MCC), which controls the exhaust fan for the reactor building air handling system. The fire apparently took place between 1545 on 8 August, when a reactor shutdown checklist was completed and the fan was operational, and 0750, 9 August, when during the start-up check the malfunction was noted. The reactor was secured during that entire period with the exception of approximately five minutes prior to the discovery of the malfunction when it was in a shutdnwn state. The reactor was not critical at any time during this period.

II. Cause of Malfunction Probable cause of the malfunction has been determined to have been due to a power surge which resulted in the failure of the transformer in EF-1 cubical of the MCC, thus causing the fire. During the time period cited in Paragraph I there were electrical storms in the AFRRI area which caused electrical power interruptions at 2005 on 8 August, and again at 0555 on 9 August which could have contributed to the failure.

III. Corrective Action Taken Since the ' malfunction resulted in damage, by buming, of the step down transformer, motor control contact and associated wiring, all of those components in the EF-1 cubical of the MCC were replaced. Adjacent sub-systems in the MCC were checked out to insure they had not been damaged as a result of the fire. The EF-1 system was put on line and was functioning properly again at 1450,9 August 1979. A start-up and shutdown check of the reactor was successfully conducted to insure proper operation of the ihgrated systems.

IV. Safety Evaluation The EF-1 sub-system of the MCC controls the exhaust fan which is part of the re ictor building air handling system, which is designed to control the effluent from the reactor building to the outside environment. Since the reactor was secured at the time, and the fact that the electrical transient caused the sealing dampers to close, the air leakage from the reactor building was restrictsd and no safety hazard (other than the fire itself which was contained in the metal cubical of the MCC and self extinguished) was imposed by the malfunction.

V. Safety Review The AFRRI Reactor and Radiation Safety Committee has reviewed this report and recommend forwarding to the NRC.

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