ENS 56429
ENS Event | |
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15:45 Mar 23, 2023 | |
Title | Design Flaw Discovered in Mechanical Draft Cooling Tower Fan Brakes |
Event Description | The following information was provided by the licensee via fax:
While in Mode 1 at 100 percent power at 1145 EDT on March 23, 2023, it was determined that all mechanical draft cooling Tower (MDCT) fan brakes would not perform their design function during a tornado due to a design flaw with the control system. The MDCT fan brakes are required to prevent fan overspeed from a design basis tornado. The MDCT fans are required to support the operability of the ultimate heat sink (UHS). At the time of discovery, the provisions of LCO 3.0.9 were being utilized for loss of the 'D' MDCT fan brake (barrier loss). When it was identified the condition was a design flaw common to all MDCT fan brakes, the 24-hour allowance for restoration was entered. A design change is currently being implemented to restore MDCT fan brake operability. This condition is reportable per 10 CFR 50.72(b)(3)(v)(A), (B), & (D). The NRC Resident Inspector has been notified. |
Where | |
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Fermi ![]() Michigan (NRC Region 3) | |
Reporting | |
10 CFR 50.72(b)(3)(v)(A), Loss of Safety Function - Shutdown the Reactor 10 CFR 50.72(b)(3)(v)(B), Loss of Safety Function - Remove Residual Heat 10 CFR 50.72(b)(3)(v)(D), Loss of Safety Function - Mitigate the Consequences of an Accident | |
Time - Person (Reporting Time:+2.75 h0.115 days <br />0.0164 weeks <br />0.00377 months <br />) | |
Opened: | Justin Wilhelm 18:30 Mar 23, 2023 |
NRC Officer: | Donald Norwood |
Last Updated: | Mar 27, 2023 |
56429 - 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 %) |