ENS 56054
ENS Event | |
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01:08 Aug 18, 2022 | |
Title | Safety System Inoperability |
Event Description | The following information was provided by the licensee via email:
At 2108 EDT on August 17, 2022 the Division 2 Mechanical Draft Cooling Tower (MDCT) fans were declared inoperable due to failure of the over speed fan brake inverter. The brakes prevent fan over speed from a design basis tornado. The MDCT fans are required to support operability of the Ultimate Heat Sink (UHS). The UHS is required to support operability of the Division 2 Emergency Equipment Cooling Water (EECW) system. The Division 2 EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) room cooler and Division 2 Control Center HVAC (CCHVAC) chiller. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. At the time of the event, Division I CCHVAC was inoperable for maintenance (but was running for a maintenance run) and the event caused an inoperability of Division 2 CCHVAC. This resulted in an inoperability of both divisions of CCHVAC. Failure of the Division 2 MDCT Fan brake inverter occurred due to a trip of the DC input breaker. The breaker was reset at 2128 EDT restoring Division 2 UHS Operability. This report is being made pursuant to 10CFR50.72(b)(3)(v)(D) as a condition that at the time of discovery could have prevented the fulfilment of the safety function of structures or systems that are needed to mitigate the consequences of an accident based on a loss of a single train safety system and loss of both divisions of a safety system. The Senior NRC Resident Inspector has been notified |
Where | |
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Fermi Michigan (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
Time - Person (Reporting Time:+0.2 h0.00833 days <br />0.00119 weeks <br />2.7396e-4 months <br />) | |
Opened: | Greg Miller 01:20 Aug 18, 2022 |
NRC Officer: | Brian Lin |
Last Updated: | Aug 18, 2022 |
56054 - NRC Website
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Unit 2 | |
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Reactor critical | Critical |
Scram | No |
Before | Power Operation (100 %) |
After | Power Operation (100 %) |