ML20084L748
| ML20084L748 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 04/18/1974 |
| From: | COMMONWEALTH EDISON CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084K292 | List: |
| References | |
| AO-254-74-8B, NUDOCS 8305230683 | |
| Download: ML20084L748 (2) | |
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r-REPORT NUMBER: A0 254/74-8b REPORT DATE: July 18, 1974 OCCURRENCE DATE: Aprii 10,1974 i
FACILITY: quad-Cities Nuclear Power Station Cordova, 1IIInois 61242 IDENTIFICATION OF OCCURRENCE:
Primary containment oxygen analyzer valve A0-1-88028 ex<.essive leakage.
CONDITIONS PRIOR TO OCCURRENCE:
Reactor in the cold shutdown condition for refueling outage, oxygen analyzer valves closed.
4 DESCRIPTION OF OCCURRENCE:
i Local leak rate testing of the Unit One primary containment oxygen analyzer valves l
was in progress on April 10, 1974. Valve A0-1-88028 was placed in the closed position by actuating the control room switch, and valve A0-1-88018 was opened in the same manner. The oxygen analyzer sample valve at. the local rock was manually closed.
The leak rate test itself was performed by pressurizing the volume of i-inch piping, enclosed by the 88028 valve and the manual sample valve, through a tee located in the local oxygen analyzer cabinet to a pressure of 48 psig. However, the 48 psig value could not be attained in this case. The 88028 valve was then cycled open and l
closed three times. A subsequent pressurization attempt was made without success; l
the volume could only be pressurized to approximately 35 psig.
l The 88028 valve was taken out of service and repairs were initiated. Local leak rate tests were performed on the other oxygen analyzer valves with the following results:
VALVE LEAKAGE (SCFH) 8803 1.175 8804 0.98 8801A 0.28 8802A 2.05 88018 0.09 8801C 0.38 8802C 0.40 88010 0.09 88020 0.66 All of these leakage values were well within the limit of 18.36 SCFH (5% Lto) for
l any primary containment isolation valve as given by Technical Specification 4.7.A.
2.1.(2) (b).
8305230683 740418 PDR ADDCK 05000254 s
PDR J
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A0 254/74-8b July 18,1974 DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:
Upon investigation of the valve operation prior to actual repairs, it was observed that the valve was extremely sluggish in closing.
It appeared that the valve was not fully seating itself, although the position Indication in the control room showed that the valve was fully closed. The valve packing was noticed to be ex-tremely tight, thus accounting for the sluggish valve closure operation.
Therefore, the apparent cause of the valve leakage was the fact that the valve was not fully closed during the pressurization, and was unable to sustain a 48 psig test pressure. The leakage path was through the 88028 valve, through the open 88018 valve, and back into the drywell.
,A,NAlYSIS OF OCCURRENCE:
Although the leakage through the A0-1-8802B valve did exceed the Technical Specifi-r cation limitation for any one primary containment isolation valve, the leakage through the inboard valve in that pipe was minimal. Since A0-1-8801B leaked only 0.0? SCFH, the actual volumetric leakage from the drywell through that particular sample pipe was equal to that through the inboard valve. Therefore, in the case of a Group 2 Isolation, both valves in the analyzer line would have closed and leakage i
f rom the drywell to the local sample rack would have been minimal.
In this case, no safety-related systems or components would have been rendered inoperable.
Therefore, equipment damage and excessive personnel exposure would not have resulted due to the excessive leakage through the A0-1-88028 valve.
I CORRECTIVE ACTION:
r Maintenance personnel dismantled the valve operator and thoroughly cleaned the valve seating surfaces. The valve stem was also cleaned. After the valve was re-assembled, the packing was adjusted to facilitate smooth valve operation. The valve was cycled open and closed three times from the control room, and the valve operated smoothly and seated properly when closed.
On April 16, a local leak rate test was performed on A0-1-88028. The measured leakage was 6.58 SCFH, which was within Technical Specification limits. The valve l
was then returned to service by the maintenance department.
Fall.URE DATA:
l l
This valve was leak tested for the first time during the current Unit One refueling l
l outage. No pre-operational local leak rate test was performed on this or on any I
other oxygen a slyzer valves. Therefore, no excessive leakage volumes have been l
obtained from ttis valve previously.
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