ML19345G101
| ML19345G101 | |
| Person / Time | |
|---|---|
| Site: | Humboldt Bay |
| Issue date: | 06/02/1975 |
| From: | Crane P PACIFIC GAS & ELECTRIC CO. |
| To: | Goller K Office of Nuclear Reactor Regulation |
| References | |
| 6097, AO-DPR-7-75-2, NUDOCS 8103020325 | |
| Download: ML19345G101 (3) | |
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.R PACIFIC GAS AND ELECTR,IC C O M PANY FO'SIE l
77 B E A l. E S T R E E T. S A N F R A N C I S C O, C A t. l F O R N I A 94106. (415) 781 4211 soHN C. MoRRISSEY j:;f*p;,,,,,,,,
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June 2, 1975
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Mr. Karl R. Goller V
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Washington, D. C. 20555
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Docket No. 50-133 E
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Humboldt Bay Power Plant WJ lut*5 Unit No. 3
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Dear Mr. Goller:
This report is submitted in accordance with Section IX.H.2.a(4) of the Technical Specifications of License No. DPR-7.
Notification of this occurrence was made via telephone to Mr. R. T. Dodds of the Region V Office of Inspection and Enforcement on May 12, 1975, the day of the occurrence.
This notification was confirmed by telecopier on May 13, 1975.
Abnormal Occurrence Report Number:
DPR-7/75-2 Occurrence Date:
May 12, 1975 Facility:
Humboldt Bay Power Plant Unit No. 3, Eureka, California Identification:
The d-c motor operated emergency condenser condensate return valve did not respond to a remote signal to open during the per-formance of a routine test.
This is a 4-inch Chapman 900# WEOS gate valve driven by an SMA-00-10 Limitorque operator with a 125 V D.C. motor.
At the time of the occurrence, the reactor was operating at 180 MWt.
==
Description:==
On May 12, the routine test of the drywell automatically initiated motor operated isolation valve, required by Table IX-1 of the Technical Specifications, revealed that the emergency condenser condensate return valve could not be operated from the control room.
An operator was immediately dispatched to open the valve manually.
The valve was
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q Mr. Karl R. Goller 2
June 2, 1975 then closed electrically from the control room and the valve test was then conducted satisfactorily.
Approximately one and one-half honrs and again ten hours after this occurrence the valve was tested and operated successfully in all respects.
Designation of Anparent Cause:
A similar occurrence took place en March 17, 1975 (Abnormal Occurrence Report DPR-7/75-1).
An inspection at that time did not reveal any apparent condition which could cause the valve to stick shut.
During the period from March 17 to March 27, 1975, satisfactory valve performance was demonstrated by conducting a test program which consisted of daily valve exercising.
The test frequency was decreased to at least twice per week during the period from March 27 to May 12, 1975.
Another inspection of the valve on May 12 did not reveal any apparent cause for the sticking.
Analysis:
If an isolation trip had occurred, the reactor safety valves would have operated to limit the reactor pressure transient and to re-move decay heat.
The emergency condenser would then have been manually initiated in order to remove decay heat.
Since cnly the opening opera-tion was affected, the valve sou3d have closed automatically when re-quired (on high refueling building pressure) if it had been previously opened.
There are no other motor operated valves at the plant that use the same operator.
Therefore, this malfunction has no safety implica-l tions other than thosa analyzed above.
Corrective Action:
An attempt was made to adjust the posit.icn of the valve manually so that it would be open beyond the sticking point with zero leakage, but precision valve position measurements could not be taken due to interference from the high energy line break shields.
Since the valve could not be properly positioned by hand, a return to the program of daily exercising was initiated.
This continued until i
the scheduled May 30 shutdown for refueling.
A thorough investigation will be conducted during the refueling outage to determine the best way to modify the valve to prevent a reoccurrence of this probler A
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report of our findings and modifications will be submitted as soon as practicable following this investigation.
Failure Data:
This is the third occurrence of this type during power l
operation.
The first occurrence was on February 5, 1971.
Following this occurrence the valve motor was rewcund during the 1971 refueling outage to a higher torque rating (rewound from 10 ft-lb output to 18 ft-lb).
The valve motor operated satisfactorily during power l
operation until March 17, 1975.
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Mr. Karl R. Goller 3
June 2, 1975 There were no personnel overexposures, injuries, off-site consequences or damage to the facility as a result of this occurrence.
Very truly yours, CC:
Mr. R. H. Engelken, Director Office of Enforcement and Inspection-Region V I
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