ENS 52958

v t e ENS Event
14:00 Sep 9, 2017
Title	Mechanical Draft Cooling Tower Fans Declared Inoperable
Event Description	At 1000 EDT on September 9, 2017, 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 EECW system cools various safety related components, including the High Pressure Coolant Injection (HPCI) system room cooler. An unplanned HPCI inoperability occurred based on a loss of the HPCI Room Cooler. Investigation into why the Division 2 MDCT fan over speed brake inverter failed is in progress. 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 fulfillment of a safety function needed to mitigate the consequences of an accident based on a loss of a single train safety system. The licensee entered two (2) LCO Action Statements (AS); 14-day LCO AS 3.5.1 for ECCS (HPCI Inoperable) and 72-hour AS 3.7.2 for UHS. The licensee has two spare inverters on-site. After replacement and successful post-maintenance testing the licensee expects to exit both AS before 72-hours. The NRC Resident Inspector has been notified.

ENS 52958 +/-
Where
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:+1.07 h0.0446 days <br />0.00637 weeks <br />0.00147 months <br />)
Opened:	Greg Miller 15:04 Sep 9, 2017
NRC Officer:	Steve Sandin
Last Updated:	Sep 9, 2017
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v • d • e

v t e Emergency Notification System
Fermi with 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident
WEEKMONTHYEAR2025-07-07T19:45:00 [Table view]
[ENS list for Fermi]

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