ENS 50378
ENS Event | |
|---|---|
13:53 Aug 18, 2014 | |
| Title | Ultimate Heat Sink System Inoperable |
| Event Description | Conditions were met that require immediate NRC notification per 10 CFR 50.72(b)(3)(v)(B) and 10 CFR 50.72(b)(3)(v)(D) due to both trains of the Ultimate Heat Sink (UHS) system being inoperable for approximately 83 minutes. This condition resulted from a planned system outage of train B Component Cooling Water (CCW), as a subsystem of the Train B UHS, and an unexpected trip of a Train A Auxiliary Component Cooling Water (ACCW) Wet Cooling Tower (WCT) fan, which is also a subsystem of the Train A UHS.
CCW Train B was declared inoperable at 0820 CDT and removed from service for a planned relay replacement, resulting in entry of 72 hour8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> shutdown Technical Specification (TS) LCO 3.7.3, and associated cascading TS on Train B, including TS LCO 3.7.4 Action a. Subsequently, at approximately 0853 [CDT], the 6A ACCW WCT fan tripped, rendering the redundant Train A UHS inoperable, causing entry into 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> TS LCO 3.7.4 Action b, which states, 'With both UHS trains inoperable, restore at least one UHS train to OPERABLE status within 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> or be in at least HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />.' At approximately 0948 CDT the WCT Fan 6A electric motor thermal overload relays were reset, the fan restarted, and operated properly. At 1016 CDT, CCW train B had been restored from the planned maintenance and was declared operable, exiting TS LCO 3.7.3 and associated cascading TSs on Train B. Although a plant shutdown was not commenced following expiration of the one hour specified in TS LCO 3.7.4 ACTION b, Operations was preparing for a power reduction and TS required plant shutdown. During this reported condition, an outside air intake valve of the Control Room Emergency Filtration system was inoperable for planned maintenance, for which TS 3.7.6.1 mitigating actions were in place. This valve was restored to Operable at 1210 CDT. Other safety systems remained available. The plant remained stable at 100% during this time. The NRC Resident Inspector was notified. |
| Where | |
|---|---|
Waterford  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+3.5 h0.146 days <br />0.0208 weeks <br />0.00479 months <br />) | |
| Opened: | Joe Williams 17:23 Aug 18, 2014 |
| NRC Officer: | Daniel Mills |
| Last Updated: | Aug 18, 2014 |
| 50378 - NRC Website
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Unit 3 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |