ENS 40221
ENS Event | |
|---|---|
19:16 Oct 3, 2003 | |
| Title | Accident Mitigation System Degraded Due to Both Trains of Auxiliary Building Gas Treatment System Inoperable |
| Event Description | The following information was obtained from the licensee via facsimile:
On 10/03/2003, Watts Bar Nuclear Plant Unit 1 was in Mode 6 during a refueling outage with core re-load in progress. At 1516 [hrs EDT], the control room became aware that an activity in preparing for an upcoming test had placed the B Auxiliary Building Gas Treatment System (ABGTS) 480v Breaker in the off position. An operator was immediately dispatched to close the ABGTS breaker and the breaker was closed at 1521 [hrs], restoring the train to OPERABLE status. The opening of this breaker at about 1324 [hrs] caused the B ABGTS train to be INOPERABLE at a time when the A ABGTS train was available to start but technically INOPERABLE due to the emergency power supply ( A Train Diesel Generator) and a room cooler being out of service. The ABGTS system is required for the mitigation of a postulated fuel handling accident. Site emergency procedures require the operator to promptly confirm ABGTS is in operation, indication is provided in the control room on ABGTS status and breaker restoration can be quickly performed. In addition, with off site power available, the A ABGTS train would have immediately responded to an event and begun to perform the filtration function while the otherwise operable B train was manually restored. However, at the time of discovery, the system could not have performed its function in the event of a postulated accident coincident with a loss of off site power. Accordingly, TVA has determined this event is reportable in accordance with 10 CFR 50.72 (b)(3)(v)(D). The licensee has notified the NRC Resident Inspector. |
| 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:+0.97 h0.0404 days <br />0.00577 weeks <br />0.00133 months <br />) | |
| Opened: | Mike Earles 20:14 Oct 3, 2003 |
| NRC Officer: | Howie Crouch |
| Last Updated: | Oct 3, 2003 |
| 40221 - NRC Website | |