ENS 56542
ENS Event | |
|---|---|
04:00 May 25, 2023 | |
| Title | Part 21 Interim Evaluation - Mechanical Draft Cooling Tower Fan Brakes Design Flaw |
| Event Description | The following is a summary of the information provided by the licensee via email:
As previously reported under Fermi LER 2023-001-00, submitted on May 22, 2023, 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 the speed switch not functioning over its published voltage and frequency ranges. The MDCT fan brakes are required to prevent fan overspeed from a design basis tornado. On May 25, 2023, Fermi completed its 10 CFR Part 21 discovery process and determined the need to perform a 10 CFR Part 21 evaluation. The vendor (Engine Systems Inc. (ESI)) was contacted and the purchaser (Fermi) assumed responsibility for performing the Part 21 evaluation for the supplied mechanism. This Part 21 evaluation is being tracked by Fermi CARD 23-20075. It has been determined the direct cause of the event was due to the Dynalco speed switch model SST-2400A-1, supplied by ESI, not functioning over its published voltage and frequency ranges. Corrective actions were taken to develop a design change to correct MDCT fan speed control system returning the MDCT fans, ultimate heat sink, and the service water subsystems to service on March 24, 2023. The root cause evaluation is ongoing, and written follow-up will be provided in 30 days by providing a supplement to the original LER by June 24, 2023. No new commitments are being made in this submittal. |
| Where | |
|---|---|
| Fermi Michigan (NRC Region 3) | |
| Reporting | |
| 10 CFR 21.21(a)(2), Interim Report for Comply or Defect in Component | |
| Time - Person (Reporting Time:+34.27 h1.428 days <br />0.204 weeks <br />0.0469 months <br />) | |
| Opened: | Eric Frank 14:16 May 26, 2023 |
| NRC Officer: | Donald Norwood |
| Last Updated: | May 26, 2023 |
| 56542 - NRC Website
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Unit 2 | |
|---|---|
| Reactor critical | Critical |
| Scram | No |
| Before | Power Operation (100 %) |
| After | Power Operation (100 %) |
WEEKMONTHYEARENS 565422023-05-25T04:00:00025 May 2023 04:00:00
[Table view]10 CFR 21.21(a)(2), Interim Report for Comply or Defect in Component Part 21 Interim Evaluation - Mechanical Draft Cooling Tower Fan Brakes Design Flaw 2023-05-25T04:00:00 | |