ENS 52669
ENS Event | |
|---|---|
20:20 Apr 6, 2017 | |
| Title | Temporary Loss of Control Room Envelope Boundary |
| Event Description | At 1620 EDT on April 6, 2017, a Main Control Room (MCR) door was found ajar. At that time, both control room ventilation filtrations trains (CREVS) were declared inoperable in accordance with Technical Specification 3.7.10, condition B, due to the inoperability of the Control Room Envelope (CRE). At 1623 EDT, the door was closed, CREVS was declared operable and LCO 3.7.10, Condition B was exited.
The safety function of the CRE boundary is to ensure the in-leakage of unfiltered air into the CRE will not exceed the in-leakage assumed in the licensing basis analysis of Design Basis Accident (DBA) consequences to CRE occupants. Additionally, it ensures that the occupants are protected from hazardous chemicals and smoke. This event is being reported pursuant to 10 CFR 50.72(b)(3)(v)(D). NRC Resident Inspector has been notified.
Event Notification EN 52669, made on 4/06/2017, is being retracted because additional reviews have been performed supporting that a loss of safety function did not occur. Watts Bar Unit 2 has concluded that there was no loss of safety function, because when the door was found open it was capable of being closed and able to support the control room envelope function. A simulation performed on 04/07/17 also showed that with the door in question opened 1-2 inches that the control room pressure would have remained above the TS required positive pressure of 0.125 inches of water. The control room envelope is designed such that the door is expected to be opened to allow personnel entry and exit, and thus positive pressures in the control room will fluctuate. The event that occurred is similar to a number of individuals entering and exiting the control room in series. Since the control room envelope function was not lost, this event is not reportable and NRC Event 52669 is being retracted. The basis for this conclusion will be provided to the NRC Resident Inspector." The licensee informed the NRC Resident Inspector. Notified R2DO (Blamey). |
| 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:+2.33 h0.0971 days <br />0.0139 weeks <br />0.00319 months <br />) | |
| Opened: | Charles Broesche 22:40 Apr 6, 2017 |
| NRC Officer: | Jeff Rotton |
| Last Updated: | May 18, 2017 |
| 52669 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Not Critical |
| Scram | No |
| Before | Hot Shutdown (0 %) |
| After | Hot Shutdown (0 %) |