ENS 46972
ENS Event | |
|---|---|
20:10 Apr 21, 2011 | |
| Title | Invalid Primary Containment Isolation System Actuation Due to Conflicting Work Activities |
| Event Description | This event is reportable under 10 CFR 50.73(a)(2)(iv)(A) as an automatic actuation of general containment isolation signals affecting containment isolation valves in more than one system. This 60-day telephone notification is being made in accordance with 10 CFR 50.73(a)(1) for invalid actuations reported under 10 CFR 50.73(a)(2)(iv)(A). This actuation was invalid since it was caused by maintenance activities and not by any actual plant condition warranting containment isolation.
On April 21, 2011, at 1310 hours0.0152 days <br />0.364 hours <br />0.00217 weeks <br />4.98455e-4 months <br />, upon de-energization of the Reactor Protection System (RPS) Bus A for maintenance, an unexpected actuation of the Groups 3 and 4 outboard containment isolation valves occurred. Outboard isolations occurred in the reactor building drain and ventilation systems, and reactor closed cooling systems. Control room emergency ventilation and standby gas treatment systems also started. All systems functioned as designed, excluding those components that were already removed from service. Following the event, the RPS Bus A was re-energized and the plant was restored to normal operating condition for the current configuration per plant procedures. The subsequent investigation found that personnel involved with work planning and control did not recognize that de-energizing RPS Bus A would create a condition which completed the Nuclear Steam Supply Shutoff System outboard isolation logic. An associated relay for the second channel had been previously de-energized to support ongoing maintenance. The cause of allowing this conflicting work to occur was determined to be inadequate procedural guidance. Planned corrective actions will enhance procedures to identify logic impacts, conflicting equipment and recommended protection schemes. There were no actual safety consequences associated with this event since all affected equipment responded as designed. The NRC Resident Inspectors have been notified. |
| Where | |
|---|---|
Columbia Generating Station  Washington (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.73(a)(1), Submit an LER, Invalid Actuation | |
| Time - Person (Reporting Time:+1433.33 h59.722 days <br />8.532 weeks <br />1.963 months <br />) | |
| Opened: | Rick Garcia 13:30 Jun 20, 2011 |
| NRC Officer: | Steve Sandin |
| Last Updated: | Jun 20, 2011 |
| 46972 - NRC Website | |
WEEKMONTHYEARENS 566252023-05-17T10:39:00017 May 2023 10:39:00
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