ENS 57753
ENS Event | |
|---|---|
05:00 May 2, 2025 | |
| Title | Part 21 - Thermal Sleeve Defect |
| Event Description | The following information is a summary provided by the licensee via phone and email:
The affected component is the thermal sleeve in the control rod drive mechanism (CRDM) penetration tube in the replacement Reactor Vessel Closure Head (RVCH) provided to the Callaway plant in 2014. The reportable defect is the unanticipated wear rate of the CRDM thermal sleeve flanges supplied to Callaway as part of the replacement RVCH that was installed in the fall of 2014. During the Callaway refueling outage in the spring of 2025, the thermal sleeve at location H08 was found resting on the upper internals. A ring shaped remnant of the thermal sleeve flange had become separated and was present in the CRDM adapter. Measurements were performed on the remaining CRDM thermal sleeves to determine the amount of thermal sleeve descent from the nominal design configuration. Descent distances ranged from 0.03 to 1.7 inches, with four thermal sleeves having descent of 0.9 inches or more. The failure of a thermal sleeve resulting in a detached flange segment can impact the performance of the corresponding CRDM with the potential to impede or prevent control rod insertion. This issue was first reported under 10 CFR 21 by Westinghouse. Since the identification of the thermal sleeve flange wear issue by Electricite de France (EdF) in 2018, Framatome is unaware of any instances of a control rod failing to insert due to CRDM thermal sleeve events, even at plants which have experienced multiple locations with complete thermal sleeve flange separation. Framatome is conservatively making this notification because the undetected simultaneous failure of multiple thermal sleeves could potentially create a safety hazard if multiple control rods fail to fully insert. Although the causal analysis in still in process, Framatome has reviewed the other replacement RVCHs supplied by Framatome to the US fleet and have not identified any other plants which contain an equivalent combination of conditions that would indicate the potential for accelerated thermal sleeve flange wear. For the other US plants with Framatome supplied replacement RVCHs with thermal sleeves, Framatome will provide a notification to continue using the current and future inspection guidance published by industry bodies. Affected plants: Callaway Energy Center Framatome Contact Information: Gayle Elliott Director, Licensing Regulatory Affairs Framatome Inc. gayle.elliott@framatome.com |
| Where | |
|---|---|
Callaway  Fulton, Missouri (NRC Region 4) | |
| Organization: | Framatome, Inc |
| Reporting | |
| 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect | |
| Time - Person (Reporting Time:+964.08 h40.17 days <br />5.739 weeks <br />1.321 months <br />) | |
| Opened: | Gayle Elliot 09:05 Jun 11, 2025 |
| NRC Officer: | Ernest West |
| Last Updated: | Jun 11, 2025 |
| 57753 - NRC Website
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WEEKMONTHYEARENS 577532025-05-02T05:00:0002 May 2025 05:00:00
[Table view]10 CFR 21.21(d)(3)(i), Failure to Comply or Defect Part 21 - Thermal Sleeve Defect ENS 529982017-10-02T16:15:0002 October 2017 16:15:00 10 CFR 21.21(d)(3)(i), Failure to Comply or Defect Initial Part 21 Notification - Cameron Model 752B Differential Pressure Transmitters 2025-05-02T05:00:00 | |