ENS 57982
ENS Event | |
|---|---|
00:05 Oct 13, 2025 | |
| Title | Loss of Safety Function |
| Event Description | The following information was provided by the licensee via phone and email:
On October 12, 2025, Columbia Generating Station (CGS) was performing a reactor building emergency cooling test. At 1428 [PDT], an air damper associated with the division 1 motor control center (MCC) room cooling failed to perform its intended function to close. This MCC supports the operation of one subsystem of the standby gas treatment system (SGT). At 1440, a second air damper, associated with the division 2 MCC room cooling, also failed. This MCC supports the operation of the other SGT subsystem. Field operators were dispatched to investigate the potential cause. At 1627, the first air damper that had failed was observed to have closed on its own without further operator action. Operators subsequently determined that failure of the air damper to close rendered the associated emergency room coolers inoperable. At 1705, [the division 2 MCC] was declared inoperable and technical specification action statement 3.8.7.A was entered. From 1440 to 1627, CGS was in a condition that required both SGT subsystems to be declared inoperable due to the loss of emergency room cooling to their associated MCCs. This condition constitutes a loss of safety function of SGT and secondary containment. It could have challenged the station's ability to control a radioactive release had one occurred during that time. This notification is being made pursuant to 10 CFR 50.72(b)(3)(v)(C) and (D) due to the loss of safety function of both trains of SGT and secondary containment for approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />. The Resident Inspector was notified. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: At the time of notification, the licensee had exited all technical specification action statements.
On October 12, 2025, at 2152 PDT, Columbia Generating Station notified the NRC pursuant to 10 CFR 50. 72(b)(3)(v)(C) and (D) due to the loss of safety function of both trains of standby gas treatment (SGT) and secondary containment for approximately 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> under Event Notification 57982. The notification was made due to the failure of two dampers to close during testing of the Reactor Building Emergency Cooling System. The dampers that failed to close were cross-divisional and affected rooms with equipment necessary for both trains of the SGT system which supports the safety function of secondary containment. Following the event, engineering conducted an evaluation to determine if both air dampers remaining open during a loss of cooling accident would have put any safety-related equipment at risk due to potential changes in radiological and environmental conditions within the associated motor control center (MCC) rooms. The engineering evaluation determined temperatures and humidities would not have exceeded limits in the MCC rooms due to the dampers being left open. Additionally, any increase in radiation would be considered negligible and would not affect the ability of the equipment to perform their design functions. Therefore, the safety-related equipment within the MCC rooms would have been available and operable to perform their design function were an accident to occur. Consequently, the failure of two dampers to close during testing is not considered to be an event or condition that could have prevented fulfillment of the safety function of SGT and secondary containment and did not impact the ability to mitigate the consequences of an accident or control the release of radioactive material, therefore, event notification 57982 is retracted. The Resident Inspector has been notified. Notified R4DO (Vossmar) |
| Where | |
|---|---|
Columbia  Washington (NRC Region 4) | |
| Reporting | |
| 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
| Time - Person (Reporting Time:+0.78 h0.0325 days <br />0.00464 weeks <br />0.00107 months <br />) | |
| Opened: | Justin Gerg 00:52 Oct 13, 2025 |
| NRC Officer: | Ernest West |
| Last Updated: | Nov 5, 2025 |
| 57982 - NRC Website
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