ML20085F924

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RO 75-004:on 750701,control Rod 38 Deviated by 9 Inches. Caused by Shorted Phase Shifting Capacitor in Motor Drive Circuit.Capacitor Replaced
ML20085F924
Person / Time
Site: Palisades Entergy icon.png
Issue date: 07/08/1975
From: Sewell R
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
Office of Nuclear Reactor Regulation
Shared Package
ML20085F925 List:
References
RO-75-004, RO-75-4, NUDOCS 8308230632
Download: ML20085F924 (2)


Text

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US Nuclear Regulatory Commission

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IDCKFT 50-255, LICENSE DPR-20, # /NQ??

PALISADFS PLANT, UE-75 4 Attached in Unusual Event Report No 75 4 covering the explanation for the

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()-inch deviation on control rod No 36.

Ralph B. Sewell (Signed)

Ralph B. Sewell _

Nuclear Licensing Administrator CC: JGKoppler, USNRC I

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COPY SENT REGION [/ON i

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9 9 UNUSUAL EVENT REPORT l

Palisades Nuclear Plant ,

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1. Report Number: UE-75 4, Docket 50-255 Pa. Report Date: July 8,1975 2b. Occurrence Date: July 1, Igr/5 3 Facility: Palisades Plant, Covert, Michigan
4. Identification of Occurrence: 9-Inch Deviation on Control Rod No 38
5. Conditions Prior to Occurrence: Plant operating at steady-state power of 20h.
6. Description of Occurrence: On July 1,1J75 at 0300 hours0.00347 days <br />0.0833 hours <br />4.960317e-4 weeks <br />1.1415e-4 months <br />, the control rods were operating in the automatic mode. The operator received a 3-inch deviation alarm. Control rod No 38 was found to be lower than the rest of the control rods in Group 4. Attempts at raising CR 38 to the level of the rest of the group resulted in its slipping to a lower level (due to the motor-capacitor failure) and caused the remainder of the rods in the group to automatically compensate for the change. The operator p terminated this divergent action by returning the control to " Manual" Q and the 9-inch deviation was noted (CR 38 was at 115.8" and CR 40 was at 124.8").
7. Designation of the Apparent Cause of the Occurrence: The apparent cause for CR 36 failure to withdraw resulted from a shorted phase shifting capacitor in the motor drive circuit.
8. Analysis of Occurrence: PRC review of the incident concluded that plant operation could continue under Section 3.10.4.b of the Technical Specifi-cations. The Technical Specifications state, ". . .if more than one control rod or part-length rod becomes misaligned or inoperable, the reactor shall be placed in the hot shutdown condition within 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br />." The CR could still be tripped in this situation and only one CR was " inoperable."

There were no adverse safety implications of this event because the CR was still capable of being tripped and power distributions were within specified limits.

9 Corrective Action: The phase shifting capacitor was replaced for CR 38 motor-drive circuit. The CR was then tested and found to operate satis-j factorily.

10. Failure Data:

Manufacturer - Aerovox Corp, New Bedford, MA Model - RM0966 C')

i V Part Number - P 150F435 Specs - 6 Microfarad 370 VAC Previous capacitorsFailure has not Data - Plant occurred records indicate that a failure of these before.