ML20084K308
| ML20084K308 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 07/18/1974 |
| From: | COMMONWEALTH EDISON CO. |
| To: | US ATOMIC ENERGY COMMISSION (AEC) |
| Shared Package | |
| ML20084K292 | List: |
| References | |
| AO-50-254-74-8F, NUDOCS 8305190268 | |
| Download: ML20084K308 (2) | |
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o REPORT NUMBER: A0-50-254/74,8f REPORT DATE: July 18, 1974 OCCURRENCE DATE: May 17, 1974
_ FACI LITY: Quad-Cities Nuclear Power Station Cordova, Illinois 61242 i
IDENTIFICATION OF OCCURRENCE:
Excessive leakage on the drywell personnel air-lock door seals.
CONDITIONS PRIOR TO OCCURRENCE:
Reactor in cold shutdown condition for refueling outage, personnel air-lock doors closed, interior door hold-down bars installed.
DESCRIPT'0N OF'0CCURRENCE:
1 During local leak rate testing of the Unit I drywell personnel air-lock penetration on May 16, 1974, an excessive leakage rate was experienced when pressurized to 10 l
psig.
t The leak rate test was performed by pressurizing the volume enclosed by the single l
gasketed seal drywell personnel air-lock doors. A leakage rate of 287 SCFH meas-ured at a test pressure of 10 psig e xceeded the limit of 5% Lto specified by Technical Speci fication 4.7.A.2. I.2.b.
Subsequent investigation using a soap bubble solution with the air-lock under pressure showed no visible leaks on any welds or on the interior and exterior door
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sealing surfaces.
Four air-lock penetrations are located above the exterior door, one of which was used to pressurize the air-lock volume. The other three penetrations were electri-cal conduit runs, two for lighting and one for the telephone located in the air-lock.
The end plates at the first conduit bends before going to a junction box in the access room were removed from each of the conduit pipes. With the air-lock j
under 10 psig pressure, a leak was audibly detected through the telephone conduit itself. Application of a soap bubble solution confirmed the leakage. The other i
two condult lines showed no leakage.
i Therefore, the leakage path during the test was through the conduit, to a junction box in the personnel access room, and out into the reactor building.
A work request was initiated to repair the telephone conduit internals.
DESIGNATION OF APPARENT CAUSE OF OCCURRENCE:
The air-lock excessive air leakage is attributed to degraded and missing seal material in the telephone line conduit exiting the air-lock, k
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July 18, 1974 A0-50-254/74-8f.
ANALYSIS OF OCCURRENCE:
Although this test was conducted at 10 psig, the likelihood of an actual occurrence of this pressure inside of the air-lock would be minimal due to the redundant inter-nel door. Therefore, in the event of accident conditions in the drywell, the air-lock doors would have performed their design function.
CORRECTIVE ACTION:
As a result of the failure of the telephone conduit sealant, the sealant on this line and on both lines of light fixture conduit pipe was replaced with RTV as a precautionary measure.
On May 18,1974, the Unit I drywell personnel air-lock was retested at a leak rate test pressure of 10 psig. The resultant leakage was found to be 0.0 SCFH which is within the Technical Specification requirements.
t FAILURE DATA:
It has been determined that the telephone conduit installation had been accomplish-ed before the initial pre-operational testing. Evidently, the conduit sealant had not experienced any disintegration at that time.
During pre-operational leak rate testing, a value of 0.0703 SCFH was measured on December 2, 1970. Since this value lies well within the Technical Specificationi limits, the sealant disintegration has occurred since the initial pre-operational testing period.
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