ENS 53173
ENS Event | |
|---|---|
01:02 Jan 18, 2018 | |
| Title | |
| Event Description | At 2002 EST on January 17, 2018, annulus differential pressure exceeded its pressure limit. At that time, the Shield Building was declared inoperable requiring entry into Technical Specification 3.6.15, Conditions A and B. Action was taken by field operators to swap annulus vacuum control dampers to restore annulus differential pressure. At 2024 EST, annulus differential pressure was restored to required limits, the Shield Building was declared operable, and LCO 3.6.15, Conditions A and B were exited.
The temporary loss of the Shield Building resulted from a failure of the annulus vacuum control system to maintain the required differential pressure. Manual swap-over of pressure control to the backup damper restored differential pressure to required limits allowing exit from TS LCO 3.6.15 and restoration of the Shield Building safety function. The Shield Building ensures that the release of radioactive material from the containment atmosphere is restricted to those leakage paths and associated leakage rates assumed in the accident analysis during a Loss of Coolant Accident (LOCA). The Emergency Gas Treatment System (EGTS) would have automatically started and performed its design function to maintain annulus vacuum within required limits. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). The NRC Resident Inspector has been notified. |
| Where | |
|---|---|
Watts Bar  Tennessee (NRC Region 2) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+-2.35 h-0.0979 days <br />-0.014 weeks <br />-0.00322 months <br />) | |
| Opened: | Andrew Waldmann 22:41 Jan 17, 2018 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Jan 17, 2018 |
| 53173 - NRC Website
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Unit 1 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |