ML19340A220
| ML19340A220 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 11/05/1976 |
| From: | DUKE POWER CO. |
| To: | |
| Shared Package | |
| ML19340A217 | List: |
| References | |
| RO-270-76-12, NUDOCS 8001140837 | |
| Download: ML19340A220 (2) | |
Text
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63 l
. DUKE POWER COMPANY l
OCONEE UNIT 2 P
Report'No.: R0-270/76-12 Report Date: November 5, 1976 L
Occurrence Date: October 7, 1976 H
Facility: Oconee Unit 2, Seneca, South Carolina Identification of Occurrence:
Containment isolation valve 2 LWD-1 discovered' inoperable l
Conditions Prior to Occurrence: Unit at 100 percent full power l.
Description of Occurrence:
On October 7,-1976, after draining the Reactor Building normal sump, con-tainment isolation valve 2:13m+1 was discovered inoperable.
This valve, which is the first isolation valve in the Reactor Building normal sump drain line, provides containment integrity following an ES actuation.
Valve 20WD-1 and the redundant. containment isolation valve, 20WD-2 are both located outside the Reactor Building.
Valve 2 LWD-1 was promptly isolated by locking clo ed redundant isolation valve 2 LWD-2 pursuant to Oconce Technical Specification 3.6.4^.b.2.
Investigation revealed that the valve internals were defective. To maintain containment integrity lduring repair of 2 LWD-1, a freeze plug was applied between 2 LWD-1 and the Reactor Building normal sump. Additionally, a' blind
' flange was bolted onthe valve body during the period when the valve internals l,
were removed. The valve was ' repaired but the motor operator and internals were damaged while attempting to cycle the valve prior to _ return to service.
i Af ter reverifying the integrity of the freeze plug and again utilizing the l
L blind flange, the valve was repaired, successfully tested, and returned to ~
service.
Designation of Apparent Cause of Occurrence:
The apparent cause of this occurrence was a broken compression foot roll pin in the. internals of 2 LWD-1, a' pneumatic diaphragm valve.
The motor.
-failure which followed initial repair of the valve resulted from an incorrect stroke setting,and in a subsequent. attempt to manually cycle the valve, the newly installed roll pin was broken.
JAnalysis of Occurrence:
- Valve-20WD-1-was properly isolated.in compliance with Oconee Technical
. Specification 3.6.4.b.2 by securing redundant valve 2 LWD-2 in the closed
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8001-140Ah 25
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l-position. Containment integrity was continuously maintained during the repair of the valve by a freeze plug located in the drain line between the Reactor Building normal sump and 2 LWD-1.
A safety evaluation conducted on the use of the freez?. plug determined that this method of scaling the drain line met the requirements of Oconee Technical Specification 3.6.4.b.3.
The freeze plug was also leak tested at 60 psi to verify its capability to maintain containment integrity in the event of an ES actuation.
In addition, a blind flange was used to isolate the valve opening while repairs were made.
Containment integrity was not affected by this incident and it is, therefore, concluded that the health and safety of the public were not affected.
Corrective Action:
Valve 2 LWD-1 has been repaired and its operability verified. To assure that a thorough electrical inspection of diaphragm valves is properly conducted prior to return to service, the procedure for repair and replacement of diaphragm valves will be revised by December 1,1976.
Also, an invei tigation of continuing problems encountered with Grinnell-Saunders diaphragm valves with Limitorque operators will be conducted prior to January 1,1977.
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