ML20085F770

AO AO-11-74:on 740609,100-amp Dc Control Breaker 72-203 on 1D Bus Tripped.Cause Under Investigation.Breakers Checked Electrically & Visually W/No Abnormalties Found.Breaker Reset W/Local Fuses & Tripped When Second Fuse Added

ML20085F770
Person / Time
Site:	Palisades
Issue date:	07/20/1974
From:	Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:	Oleary J US ATOMIC ENERGY COMMISSION (AEC)
References
AO-11-74, NUDOCS 8308230180
Download: ML20085F770 (2)

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') L U General Offices: 212 West Mechegan Avenue Jackson. Michegan 49201. Area Code 517 788-0550 June 20, 1974 Mr. John F. O' Leary, Director Re: Docket 50-255 Directorate of Licensing License DPR-20 US Atomic Energy Commission Palisades Plant Washington, DC 20545 A0-ll-Th

Dear Mr. O' Leary:

Attached is Abnormal Occurrence Report A0-ll-74 covering the d-c control breaker trip on June 9, 1974. Investigations as to the cause are still under way. The final results of the investigation will be analyzed and transmitted to you before returning the plant to service.

Yours very truly, Ralph B. Sewell (Signed)

RBS/ map Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC 4

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v ABNORMAL OCCURRENCE REPORT PALISADES PLANT

1. Report Number: A0-11-74, Docket 50-255 2a. Report Date: June 19, 1974 2b. Occurrence Date: June 9, 197h 3 Facility: Fulisades Plant

4. Identification of Occurrence: 100 amp d-c control Breaker 72-203 on 1D bus tripped.

5 Conditions Prior to Occurrence: Plant in cold shutdown condition.

6. Description of Occurrence: On June 9,1974, at approximately 1600, the operator reported to the shift supervisor that the indicating lights for the circuit breakers on Bus 1D vere out.

The local lights at 1D bus were also out and d-c control power Breaker 72-203 (100 amp) was tripped and attempts to reset failed.

7 Designation of Apparent Cause of Occurrence: Still under investigation.

8. Analysis of Occurrence: This is an isolated incident and there has been no history of this type of occurrence. Efforts to simu-late this incident were not successful.

9 Corrective Action: Breakers vere checked electrically as well as visually fbr any grounds, shorts, loose wires, cable breaks, etc.

The resistance was checked at each individual fuse block. No abnormalities were found. Breaker was reset with local fuses removed and then with the addition of the second fuse, breeker tripped. But this incident could not be repeated.

10. Failure Data: Unable to determine cause of breaker trip at this time. Occurrence is still under investigation.