ENS Event | |
|---|---|
05:00 May 22, 2025 | |
| Title | Part 21 Report - Diesel Generator Jacket Water Pump Failure |
| Event Description | The following information was provided by the licensee via phone and email:
On April 8, 2025, while in Mode 1 and at 100 percent power, during performance of a scheduled monthly surveillance test, Nebraska Public Power District (NPPD) Cooper Nuclear Station (CNS) identified Diesel Generator (DG) 1 jacket water (DGJW) pump may not be providing sufficient cooling water to the DG. The DGJW pump impeller was found to have slipped on the shaft as a result of a failure to achieve the required interference fit during preventive maintenance replacing the pump seal. On May 22, 2025, subsequent investigation identified a deviation in that the originally supplied Cooper-Bessemer DGJW impeller bore was not provided in accordance with the design drawing. Due to the bore dimensional deviation, the required interference fit was not achieved, resulting in shaft rotational and torsional forces challenging the compromised fit until the impeller was able to spin freely on the shaft. On June 19, 2025, NPPD completed an evaluation and determined that the deviation represents a defect that could create a substantial safety hazard as defined in 10 CFR 21, as this pump was approved for use in a safety application. NPPD is not aware of any other plants being impacted by this issue. The NRC Resident Inspector has been notified. A written notification will be provided within 30 days. The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance: Maintenance performed on the DGJW pump was completed on April 9, 2025. |
| Where | |
|---|---|
Cooper  Nebraska (NRC Region 4) | |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+701.9 h29.246 days <br />4.178 weeks <br />0.961 months <br />) | |
| Opened: | Linda Dewhirst 10:54 Jun 20, 2025 |
| NRC Officer: | Bethany Cecere |
| Last Updated: | Jun 20, 2025 |
| 57770 - NRC Website
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WEEKMONTHYEARENS 577702025-05-22T05:00:00022 May 2025 05:00:00
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