ENS 52618
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ENS Event | |
|---|---|
06:20 Mar 9, 2017 | |
| Title | Containment Airlock Function Lost Due To Equalizing Valve Not Closing |
| Event Description | On March 9, 2017 at 0120 EST, the equalizing valve for the Watts Bar Nuclear Plant (WBN) Unit 2 upper containment airlock inboard door was found not closed while the outboard airlock door was open. This created a containment bypass with leakage potentially greater than allowed by the design. The operator immediately identified, after opening the outer door of the elevation 757 Air Lock, the pressure equalizing valve for the inner door was not fully closed. The outer door was promptly shut to isolate the airlock. The inner door was then cycled which closed the equalizing valve. The total time that a containment bypass was present is estimated at five minutes.
This condition was initially recognized as being potentially reportable. However, the assessment performed at the time, based on operator control of the outer airlock door, concluded there was a reasonable assurance of meeting the safety function. A subsequent independent review of this condition identified that this should have been reported under 10 CFR 50.72(b)(3)(v)(C) within eight hours of the event. The NRC Resident Inspector has been informed of this event. The licensee is planning on replacing the equalizing valve in the near future. |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(C), Loss of Safety Function - Release of Radioactive Material | |
| LER: | 05000391/LER-2017-001 |
| Time - Person (Reporting Time:+203.8 h8.492 days <br />1.213 weeks <br />0.279 months <br />) | |
| Opened: | Brian Mcilnay 17:08 Mar 17, 2017 |
| NRC Officer: | Mark Abramovitz |
| Last Updated: | Mar 17, 2017 |
| 52618 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
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