ENS 52568
ENS Event | |
|---|---|
18:40 Feb 20, 2017 | |
| Title | Unanalyzed Condition Due to Potential Failure of Control Room and Control Building Air Handling Units |
| Event Description | During the investigation associated with Event Notification 52566 that was reported on 2/18/17, it has been determined that an unanalyzed condition (new potential single failure concerns) exists. This condition exists only during periods of manually alternating divisions of Control Building Chilled Water systems; in that potential failures of Control Room Air Handling Units (HVC-ACU1A or B) or Control Building Air Handling Units (HVC-ACU2A or B) could fail in a manner that challenges the operability of the alternate division.
As reported in Event Notification 52566, the impact of this event was a loss of safety function cooling to both Division 1 and 2 AC/DC power distribution systems and Divisions 1 and 2 Control Room Fresh Air systems. Contingency actions are in development to address the impact of the potential failure mode. The plant remains in a planned refueling outage, Mode 5 with water level greater than 23' above the vessel flange. Shutdown cooling remains in service and is not affected by this issue. Investigation is ongoing. The NRC Resident Inspector has been briefed on this issue.
The licensee updated information in the first paragraph of the original above with the following: During the investigation associated with Event Notification 52566 that was reported on 2/18/17, it has been determined that an unanalyzed condition (new potential single failure concerns) exists. During periods of alternating divisions of Control Building Chilled Water systems, the potential exists for failures of Control Room Air Handling Units (HVC-ACU1A or B) or Control Building Air Handling Units (HVC-ACU2A or B) that could challenge the operability of the alternate division. The licensee notified the NRC Resident Inspector of this update. Notified R4DO (Gepford)
After further investigation it has been determined that an unanalyzed condition (new single failure concerns) exists with the dampers associated with the Control Room Fresh Air system. The potential exists for damper failures for HVC-FN1A Control Room Booster Fan 1A motor and HVC-FN1B Control Room Booster Fan 1B motor that could challenge the operability of the alternate division. Contingency actions are in development to address the impact of the potential failure mode. The plant remains in a planned refueling outage, Mode 5, with water level greater than 23 feet above the vessel flange. Shutdown cooling remains in service and is not affected by this issue. Investigation is ongoing. The NRC Resident Inspector has been briefed on this issue. Notified R4DO (Pick). |
| Where | |
|---|---|
River Bend  Louisiana (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(ii)(B), Unanalyzed Condition | |
| Time - Person (Reporting Time:+-1.27 h-0.0529 days <br />-0.00756 weeks <br />-0.00174 months <br />) | |
| Opened: | Steven Carter 17:24 Feb 20, 2017 |
| NRC Officer: | Donald Norwood |
| Last Updated: | Feb 22, 2017 |
| 52568 - NRC Website
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