ML20002D892
| ML20002D892 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 10/08/1970 |
| From: | Haueter R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | Morris P, Skovholdt D US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| NUDOCS 8101230324 | |
| Download: ML20002D892 (3) | |
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Dr. P. A. Morris, Director Re : Docket 5 3-155 Division of Eeactor Licensing License No EPR-6 United States Atomic Energy Commission Washington, DC 205h5 Nar Dr. Morris :
Att:
Mr. D. J. Skovholt This letter is written to apprize you of the failure of the emergency generator to "come-up" to voltage during routine bi-monthly testing on August 6, 1970 and the failure of the emergency generator to start automatically during routine bimonthly testing on October 1, 1970 at our Big Rock Point Plant.
On August 6,1970, the emergency diesel generator was started for a routine test run. The normal power supply breaker to station power Bus 2-B was opened de-energizing Bus 2-B.
The emergency generator was then connected to the de-energized bus and, shortly afterward, an operator noted the generator output voltage indicated zero. The generator was disconnected from station power Bus 2-B and the bus was energized from its normal power supply. The diesel engine was shut down and maintenance personnel were assigned to troubleshoot and repair the unit. After about six hours, the problem was traced to two diode units in the same phase of the ex-citer. These two diodes had shorted which shorted the generator field. These diodes were replaced and the emergency generator was test-operated satisfactorily.
Investigation subsequent to the diode failure has been conducted. The generator vendor was contacted and requested to pro-vide recommendations to increase the reliability of this generator.
The vendor recommended replacing all six diodes with a similar diode from a different manufacturer than those originally installed in the exciter circuitry. The generator and exciter circuitries were studied to determine if transient effects during start-up and/or shutdown could have caused premature failures of these diodes. No possible causes for failure could be determined as a result of these studies. The failed diodes were visually inspected. No apparent defects were detected. The failure of these diodes is felt to be due to old age and/or moisture.
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Dr. P. A. Morris 2
Octob2r 8, 1970 With respect to the August 6 failure, corrective actions have been instituted and are as follows:
l.
All six diodes in the exciter circuit have been replaced by diodes with similar. operating characteristics but, of a different manufacturer. Spares are being stocked for these diodes.
2.
The operators have been reinstructed in the importance of checking for proper generator voltage as prescribed by the plant operating procedure prior _ to placing the generator in service.
In conclusion, no damage to equipment resulted from the diode failure. The actions of the operating personnel were prompt and. proper, and it is felt that the corrective action taken will pre-clude recurrence.
On October 1,1970, the diesel engine driver for the emer-gency generator failed to ctart automatically during routine testing.
The engine was primed with the installed hand pump by an operator.
It then started immediately. Following the test run, the engine was shut down and started in automatic mode two times on October 1, 1970 and once on October 2,1970. The results of these three tests were satisfactory. The failure to start in the automatic mode was at-tributed to loss of prime to the injection system. An investigation ic being conducted to determine and correct the cause of this failure of the diesel engine to start. Further information will be submitted when the investigation is completed.
Yours very truly, e-.2 M
RBS/dmb Robert L. Haueter Electric Production Superintendent -
Nuclear 3315
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