Event Notification Report for December 10, 2025

AGREEMENT STATE REPORT - LOST RADIOACTIVE SAMPLES

The following information was provided by the Colorado Department of Public Health and Environment (the Department) via email:

"The licensee prepared a shipment of samples in petri dishes containing Pu-239 (0.0869 uCi) and Sr-90 (0.0865 uCi) evenly distributed on 32 planchets with TDS [technical data sheet(s)] on November 3, 2025. The samples were sealed in a box which was vacuum sealed and labeled with a label detailing the package contained radioisotopes. On November 4, 2025, a shipping tracking number could not be located. The shipping department lead contacted the radiation safety officer. Efforts were made following this communication to find the missing package by contacting customers who had received other dangerous goods shipments from that day. No samples were found before the incident was reported by phone and in writing to the Department on December 1, 2025. Corrective actions have not been determined by the licensee at this time and further investigation by the unit is ongoing."

Colorado Event Number: CO250045

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

CERTIFICATE OF COMPLIANCE VIOLATION

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

"On December 8, 2025, at 1424 EST, it was confirmed that a primary neutron source assembly (NSA) was loaded into a multi-purpose canister contrary to the requirements stated in the Certificate of Compliance (CoC, Renewed Amendment 11). Specifically, one primary NSA was loaded in the incorrect fuel storage location. Table 2.1-1 of the CoC requires fuel assemblies containing NSAs to be loaded in fuel storage locations 13, 14, 19, and/or 20. The primary NSA, however, was loaded into fuel storage location 32 in April, 2024. This condition is reportable in accordance with Section 2.2 of the CoC.

"It has been verified that the total heat load of the fuel cask remains bound by the requirements of the CoC. There are also no adverse impacts to criticality since the primary NSA is in the outer region of the fuel cask, which is more conservative than the inner region. All other NSAs were verified to be in their approved fuel storage locations. All offsite and occupational dose remain within regulatory limits.

"This condition poses no impact to the health and safety of the public or plant personnel.

"The NRC Resident Inspector has been notified."

FITNESS FOR DUTY VIOLATION

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

"At 0818 EST on December 9, 2025, it was determined that a contract supervisor failed a test specified by the fitness for duty testing program. The individual's authorization for site access has been terminated.

"The NRC Resident Inspector has been notified."

60-DAY REPORT OF INVALID ACTUATION OF CONTAINMENT ISOLATION VALVES

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

"This sixty-day telephone notification is being made per 10 CFR 50.73(a)(2)(iv)(A) under the provision 10 CFR 50.73(a)(1), as an invalid actuation of containment isolation valves in more than one system. On October 11, 2025, while in mode 5 for a refueling outage, an invalid actuation signal occurred while performing preventative maintenance on a 120V AC inverter.

"At the time of the event, one channel of the refuel floor exhaust (RFE) high radiation monitor was tripped due to a scheduled electrical bus outage. This electrical bus outage, in combination with the unexpected loss of power from the 120V AC inverter on another channel, caused the actuation of containment isolation valves in more than one system. The actuation was not the result of an actual plant condition and, therefore, is invalid.

"The containment isolation valves functioned as designed for the actuation signal received. There was no impact on the health and safety of the public or plant personnel.

"The NRC Resident Inspector has been notified."