ENS 52813
ENS Event | |
|---|---|
02:15 Jun 20, 2017 | |
| Title | Primary Containment Declared Inoperable Due to Failure of Drywell to Suppression Chamber Vacuum Breaker to Fully Close |
| Event Description | This report is being made pursuant to 10 CFR 50.72(b)(3)(v)(D), 'any event or condition that at the time of discovery could have prevented the fulfillment of the safety function of structures or systems that are needed to mitigate the consequences of an accident.'
At time 2115 CDT on June 19, 2017, one torus to drywell vacuum breaker failed to indicate that it was closed after being cycled for surveillance testing. The vacuum breaker had been cycled open and then closed to satisfy SR 3.6.1.8.2 - Perform a functional test of each required vacuum breaker. Failure of the vacuum breaker to indicate closed after the control switch was taken to the closed position represents a failure to satisfy SR 3.6.1.8.2 and SR 3.6.1.8.1 - Verify each vacuum breaker is closed. Primary containment is allowed to have a bypass area between the drywell and suppression chamber less than or equivalent to a one inch diameter hole. The are of bypass was indeterminate while the vacuum breaker did not indicate fully closed. Primary containment was declared inoperable during the time the vacuum breaker did not indicate fully closed. The vacuum breaker control switch was subsequently cycled open and closed one additional time. At time 2311 CDT, the vacuum breaker indicated fully closed. At that time, primary containment was declared operable. Currently, all twelve Drywell to Suppression Chamber vacuum relief valves are closed and in the normal line-up. The NRC Senior Resident Inspector has been notified. |
| Where | |
|---|---|
Cooper  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| LER: | 05000298/LER-1917-004 Regarding Torus to Drywall Vacuum Breaker Failure to Indicate Full Closed Causes Loss of Safety Function |
| Time - Person (Reporting Time:+1.27 h0.0529 days <br />0.00756 weeks <br />0.00174 months <br />) | |
| Opened: | Aric Harris 03:31 Jun 20, 2017 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Jun 20, 2017 |
| 52813 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |