ML19329A649
| ML19329A649 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 12/17/1976 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19329A643 | List: |
| References | |
| RO-287-76-20, NUDOCS 8001090633 | |
| Download: ML19329A649 (2) | |
Text
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0 DUKE POWER COMPANY
'. O OCONEE UNIT 3 V
Report No.: R0-287/76-20 Report Date: December 17, 1976 Occurrence Date: November 21, 1976 Facility: Oconee Unit 3, Seneca, South Carolina Identification of Occurrence: Feedwater containment isolation valve 3FDW-108 inoperable Conditions Prior to Occurrence: Unit at 90 percent full power Description of Occurrence:
On November 21, 1976, following chemical sampling of the "3B" once-through steam generator, feedwater containment isolation valve 3FDW-108 failed to close under system pressure. This valve, located outside the Reactor Building, is part of the chemical sampling system and provides containment isolation following an ES actuation. The redundant valve, 3FDW-107, located inside the Reactor Building was closed and locked as required by Oconee Technical Specific. tion 3.6.4.b.2.
Apparent Cause of Occurrence:
The cause of this occurrence has not been determined.
The valve remained inoperable after it had been lubricated, the spring had been replaced and an inspection had determined that the solenoid was operating correctly.
Previous problems with valve 3FDW-108, which were discussed in reports UE-287/74-4, UE-287/75-7 and R0-287/76-13, transmitted by our letters of November 29, 1974, July 1, 1975 and September 21, 1976, respectively, have been analyzed. This analysis and the above ineffective corrective actions indicate that the problem lies in the valve internals instead of the operator. The internal valve parts cey be defective or the valve stem i
may have been bent.
Investigation of these possibilities is described under corrective action.
Analysis of Occurrence:
Valve 3FDW-108 was properly isolated in compliar.e with Technical Specifica-tion 3.6.4.b.2 by securing redundant valve 3FDW 107 in the closed position.
In the event that containment isolation had been required prior to securing valve 3FDW-107, valve 3FDW-107 would have closed upon an ES actuation.
Con-tainment integrity was not affected by this incident and it is thus concluded that the health and safety of the public were not affected.
Corrective Action:
Valve 3FDW-108 was lubricated, the spring was replaced and the solenoid was tested for operability. Parts have been ordered to replace the stem, disc and ~ canopy ring of the valve internals. After receipt of these parts, the valve internals will be examined and the new parts will be installed.
If no damage to the valve stem or to other internal valve parts is observed, 8001090[ g
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1 further investigation will be conducted.
No similar recurrences have been observed on identic31 valves on Units 1 or 2.
In the interim, valve.3FDW-107, the redundant valve,will be locked closed.
Also, valve 3FDW-108 is being rech;cked and a gage is being fabricated to measure the pressure on the valve operator after the valve is closed in order to assure that there is no remaining pressure which is keeping the valve from fully closing.
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