Event Notification Report for June 12, 2025

AGREEMENT STATE REPORT - DAMAGED MOISTURE DENSITY GAUGE

The following information was provided by the Illinois Emergency Management Agency (the Agency) via phone and email:

"The Agency was contacted on 6/3/25 by the radiation safety officer for Hanson Professional Services, Inc. to report that a Troxler 3440 moisture density gauge (8 mCi Cs-137, 40 mCi Am-241/Be) had been damaged on a construction site in Pekin, IL. [The licensee reported that] approximately a half-hour earlier, a truck backed over the gauge damaging the case and electronics. The source rod was not extended when the incident occurred. The licensee did not have a survey meter, but the gauge user had isolated the area and was maintaining direct surveillance of the device.

"Agency staff arrived to assess the gauge approximately 90 minutes later. Both sources were undamaged, and exposure rates were consistent with the sealed source and device registry sheet. The source rod was fully retracted, and the shutter closed. The transport case was not damaged and was used to package and prepare the gauge for return to the licensee's storage vault. Area surveys were taken, and the incident did not result in contamination, loss of radioactive material or exposures in excess of regulatory limits. That evening, the gauge was returned to the licensee's secure storage and will be leak tested prior to being shipped to the manufacturer for repair/disposal.

"Investigation findings indicate the gauge user walked away from the gauge momentarily when returning to their vehicle. A vehicle on the site then backed over the device, crushing the housing, but not damaging either source or its shielding. The root cause of the event is failure of the gauge user to maintain constant surveillance and prevent unauthorized access to licensed material. This report will be kept open pending receipt of the licensee's written report identifying corrective actions."

Illinois item number: IL250023

AGREEMENT STATE REPORT - SOURCE UNABLE TO BE RETRIEVED

The following report was received by the Louisiana Department of Environmental Quality (LDEQ) via email:

"On June 5, 2025, LDEQ was notified by CF Industries Nitrogen, LLC that, while retracting the source cable during an outage, one source came off the cable and remains inside the reactor. The facility was retracting a Berthold Model P2608-100, serial number LB 7674, with three cobalt-60 sources on the cable. Two sources were retracted and secured. One source came off the cable and remains inside the reactor. There were no radiation exposures to personnel.

"Berthold has been called to perform a source retrieval for the source inside the reactor. The facility is in a shutdown and there is a lockout tag-out in place until the source is retrieved. The disconnected source activity is one of either three sources: 197.3 mCi, 120.3 mCi, or 106.8 mCi. The source serial numbers are 41-01-15, 42-01-15, and 43-01-15."

Louisiana Event Number: LA20250004

PART 21 - GATE VALVE STEM FAILURE

The following information was provided by the licensee via phone and email:

"On June 4, 2025, the Tennessee Valley Authority (TVA) determined there are manufacturing non-conformances associated with the stem failure on a 10-inch, Class 900 Anchor Darling double-disc gate valve, used as a high pressure coolant injection system (HPCI) isolation valve in Browns Ferry Nuclear Plant, Unit 3 (vendor drawing: W0025604; serial number: E125T-2-2).

"On May 9, 2024, the vendor, Flowserve, was contacted and assumed responsibility for performing the Part 21 Evaluation for this valve. On October 28, 2024, Flowserve provided a 10 CFR 21.21(b) notification to TVA, stating that they were not capable of evaluating the existence of a defect. TVA procured additional engineering expertise to complete the required evaluation. These evaluations were tracked by TVA under CR 1942523. An independent failure analysis by BWXT was provided to Flowserve. BWXT concluded that 'the most likely cause of failure was brittle overload fracture due to a combination of tensile and bending forces that were exacerbated by the presence of shallow outer diameter initiated cracks and a significant loss of material ductility due to thermal embrittlement.' TVA also procured a second independent technical evaluation from MPR Associates, Inc., and provided their report to Flowserve to help with their evaluation. This report concluded that the event was apparently caused by an improper upper wedge-to-stem joint, and the resulting mismatch in mating surface diameters resulted in the bending stress which led to the valve failure, in conjunction with thermal embrittlement and excessive torques. TVA is providing notification of the existence of the defect and its evaluation.

"This event was entered into the corrective action program as condition report 1914295.

"The NRC Resident Inspector has been notified of this event, and a written report will be submitted within 30 days. Previous interim reports regarding this issue were submitted on June 23, 2024; August 22, 2024; and
November 27, 2024."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:

The non-conforming part is no longer in service. There are similar parts in service at the Browns Ferry site, but it has been determined that the risk is low. Discussion will follow in the 30-day report.

FITNESS FOR DUTY

The following information is a summary provided by the licensee via phone and email:

At 1230 EDT on June 10, 2025, a non-licensed supervisor failed a fitness for duty test. The NRC Resident Inspector has been notified.

PART 21 - THERMAL SLEEVE DEFECT

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