Event Notification Report for June 27, 2025

STOLEN MOISTURE DENSITY GAUGE

The following is a summary of information that was provided by the licensee via phone:

On 6/19/2025, at approximately 1645 EDT, a CPN International MC3 Elite moisture density gauge containing approximately 10 mCi of Cs-137 and 50 mCi of Am-241:Be was stolen from the back of a worker's truck while they were in a store. The moisture density gauge was in its case and the case was locked to the truck; both the case and gauge were missing when the worker discovered the gauge was stolen. The worker notified the police and licensee management of the stolen gauge.

THIS MATERIAL EVENT CONTAINS A 'Less than Cat 3' LEVEL OF RADIOACTIVE MATERIAL

Sources that are "Less than IAEA Category 3 sources," are either sources that are very unlikely to cause permanent injury to individuals or contain a very small amount of radioactive material that would not cause any permanent injury. Some of these sources, such as moisture density gauges or thickness gauges that are Category 4, the amount of unshielded radioactive material, if not safely managed or securely protected, could possibly - although it is unlikely - temporarily injure someone who handled it or were otherwise in contact with it, or who were close to it for a period of many weeks. For additional information go to http://www-pub.iaea.org/MTCD/publications/PDF/Pub1227_web.pdf

MEDICAL EVENT

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

"On 6/12/25 four patients received intradermal administrations of 3 mCi Tc-99m mebrofenin (in three 1-mCi injections at the site) instead of the prescribed 3 mCi Tc-99m sulfur colloid (in three 1-mCi injections at the site) for sentinel lymph node biopsy.

"A physician detected an abnormality on imaging. One patient was also administered the correct (prescribed) dose of 3 mCi Tc-99m sulfur colloid before going to surgery. The other three patients had already gone to surgery when the abnormality was detected. The surgeon detected lymph node counts for two of the patients and resected the nodes (assumed successfully). The surgical status of the third patient is unknown; nuclear medicine will review the pathology results for all four patients when available and follow up accordingly.

"Since 6/12/25, nuclear medicine has been investigating the circumstances that led to dispensing an administration of the wrong radiopharmaceutical and evaluating the dosimetry implications of mebrofenin. Because mebrofenin is typically administered intravenously for liver and gallbladder studies, there is little or no published information on skin dose from intradermal administration. The authorized medical physicist (AMP) does not believe the shallow-dose equivalent (SDE) from 3 mCi intradermal mebrofenin would exceed the documented SDE from 3 mCi intradermal sulfur colloid (105 rad) due to the biokinetics of mebrofenin. Imaging suggests that it quickly migrated away from the injection site. However, on 6/19/25, the radiation safety officer (RSO), in consultation with nuclear medicine and the AMP concluded that the event should be reported to NRC as a potential medical event, because we cannot be certain that the SDE does not exceed 50 rad.

"All patients and their referring physicians have been notified. The authorized user physician does not expect any adverse effects as a result of the dosing error.

"The RSO will contact REAC/TS to determine if an accurate SDE can be calculated or derived for this event."

The licensee notified the NRC Region 3 project manager.

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

A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.

PART 21 REPORT - SOLENOID VALVE DEFECT

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

"Valcor supplied replacement V70900-45 solenoid valves with substitute EM163-80 EPDM O-ring material (due to the obsolescence of the original E0515-80 material) and certified to the original qualification test report based on Delta Qualification report QRSKC26022-1. These replacement solenoid valves were installed at Columbia Generating Station (CGS) in July 2024 as control rod drive scram discharge volume solenoid drain valves. On September 26, 2024, CGS identified this change in material and the issue was entered into the corrective action program. Columbia's review of the Delta Qualification report identified the justification of the thermal life of the new O-ring compound when used in normally energized valves such as those supplied to CGS was not adequate. This issue was communicated to the NRC with an interim Part 21 notification on November 21, 2024 (ML24326A362).

"Valcor's report of additional testing to attempt to justify the new O-ring material as equal to or better than the original material was submitted to CGS on February 24, 2025. Columbia concluded the justification was inadequate and submitted to a third party for evaluation."

The Senior Resident Inspector has been notified.