ML20085F633
| ML20085F633 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 09/10/1974 |
| From: | Sewell R CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| References | |
| 74-73, NUDOCS 8308230076 | |
| Download: ML20085F633 (2) | |
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coo. s o 7 a a osso September 10, 1974 Directorate of Licensing Re:
Docket 50-255 US Atomic Energy Commission License DPR-20 Washington, DC 20545 Palisades Plant Gentlemen:
The attached report describes an event that occurred at the Palisades Plant which was classified as nonreportable in accordance with the derJnition of an abnormal occurrence contained in the Palisades Plant Technical Specifications. Even though not required to be reported, this event is being reported because it is similar in nature to an ab-normal occurrence which was reported September 29, 1972.
This event involved a single control valve failing to operate during exercising of the Main Steam Isolation Valves (MSIV). This control valve did not cause the failure of its associated MSIV to op-erate properly because the control valve actuation system is designed such that a single failure will not cause an MSIV to be inoperable.
The September 29, 1972 report involved six of eight control valves failing which caused the failure to operate of MSIV.
Yours very truly, Ralph B. Sewell (Signed)
RBS/mel Ralph B. Sewell Nuclear Licensing Administrator CC: JGKeppler, USAEC l
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"NONREPORTABLE EVENT" REPORT Palisades Plant 1.
Report Number: 74-73, Docket 50-255 2.
a.
Report Date: July 28, 1974 b.
Occurrence Date: July 28, 1974.
3.
Facility: Palisades Plant.
h.
Identification of Occurrence: Failure to operate of a single control valve on the Main Steam Isolation Valves (MSIV).
5 Condition Prior to Occurrence: Repair outage - plant in cold shutdown.
6.
Description of Occurrence:
During an exercising of the MSIV and their associated control valves, a single control valve failed to operate.
This same valve faile I seven out of ten times during the exercising.
An investigative maintenance test and surveillance was initiated and completed a few days following the reported failure.
During the maintenance test of the control valves, all valves operated success-fully twelve straight times.
7 Analysis of Occurrence: The control valves consist of a solenoid, latch-and-beam mechanism, and valve. Operation of the solenoid re-leases the latch which drops the beam, opening or closing a valve.
The most probable cause of the initial failure was that the latch-and-beam mechanism did not operate with the freenese needed to open the valve to a slight buildup of foreign material that may have occurred during the prolonged plant shutdown. However, any cause can only be speculative since during the maintenance test all control valves operated successfully.
The control valve installation is designed such that the failure of one control valve vill not cause a failure of the MSIV to operate properly.
8.
Corrective Action: A preventive maintenance procedure already exists which calls for cleaning and lubrication of the latch-and-beam mechanism, and testing of the valves at every outage, prior to the next heatup.
All preventative maintenance steps practical are being taken with the present system.
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