Event Notification Report for October 15, 2025

AGREEMENT STATE REPORT - LOST SOURCES

The following information was provided by the Texas Department of State Health Services (the Agency) via phone and email:

"On October 6, 2025, the Agency received notification from the licensee on missing calibration sources. The sources include 2 vials of cesium-137 and cobalt-57. The licensee could not provide details regarding the activities of the sources. According to the licensee, on November 26, 2024, the sources were shipped using [common carrier] to Eckert and Ziegler in California for disposal. At the time, the licensee reportedly they were in the process of closing-up as it was merging with another organization. The licensee stated that it had submitted a request for termination of its license to the Agency's licensing department. In March 2025, the licensing department requested radioactive source transfer records as part of the license termination process, but the licensee could not provide any documentation. The licensee stated that these records could not be found and were lost during the changeover to the new company. Eckert and Ziegler was also contacted but could not find any record of receipt of these sources.

"Additional information will be provided in accordance with SA 300 reporting requirements."

Texas Incident Number: 10236

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

LOSS OF SAFETY FUNCTION

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

"On October 12, 2025, Columbia Generating Station (CGS) was performing a reactor building emergency cooling test. At 1428 [PDT], an air damper associated with the division 1 motor control center (MCC) room cooling failed to perform its intended function to close. This MCC supports the operation of one subsystem of the standby gas treatment system (SGT).

"At 1440, a second air damper, associated with the division 2 MCC room cooling, also failed. This MCC supports the operation of the other SGT subsystem. Field operators were dispatched to investigate the potential cause.

"At 1627, the first air damper that had failed was observed to have closed on its own without further operator action. Operators subsequently determined that failure of the air damper to close rendered the associated emergency room coolers inoperable.

"At 1705, [the division 2 MCC] was declared inoperable and technical specification action statement 3.8.7.A was entered. From 1440 to 1627, CGS was in a condition that required both SGT subsystems to be declared inoperable due to the loss of emergency room cooling to their associated MCCs. This condition constitutes a loss of safety function of SGT and secondary containment. It could have challenged the station's ability to control a radioactive release had one occurred during that time.

"This notification is being made pursuant to 10 CFR 50.72(b)(3)(v)(C) and (D) due to the loss of safety function of both trains of SGT and secondary containment for approximately 2 hours."

The Resident Inspector was notified.

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

At the time of notification, the licensee had exited all technical specification action statements.

CONFIRMED POSITIVE FITNESS FOR DUTY (FFD) TEST

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

"At 1311 EDT on October 13, 2025, it was determined that a non-licensed supervisor had a confirmed positive test as specified by the FFD testing program. The individual's authorization for site access has been terminated at all Duke Energy facilities.

"The NRC Resident Inspectors have been notified."

EN Revision Imported Date: 10/15/2025

EN Revision Text: NOTIFICATION OF UNUSUAL EVENT

The following information was provided by the licensee via phone:

An Unusual Event was declared on October 13, 2025, at 1914 CDT under EAL HU1.1 due to notification of a credible security threat.

State and local agencies were notified. The NRC Resident Inspector was notified.

Notified DHS SWO, FEMA Operations Center, CISA Central Watch Officer, FEMA NWC, DHS Nuclear (email), CWMD Watch Desk (email)

* * * UPDATE ON 10/13/2025 AT 2315 EDT FROM VERONICA ROHAN TO ADAM KOZIOL * * *

The Unusual Event was terminated on October 13, 2025, at 2148 CDT.

Notified DHS SWO, FEMA Operations Center, CISA Central Watch Officer, FEMA NWC, DHS Nuclear (email), CWMD Watch Desk (email)

OFFSITE NOTIFICATION

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

On October 13, 2025, at 2305 CDT, South Texas Project issued a press release on the threat of a potential security concern directed against the licensee's facility and the resultant declaration of an Unusual Event. This media release was reported to the NRC in accordance with 10 CFR 50.72(b)(2)(xi): Any event or situation, related to the health and safety of the public or onsite personnel, or protection of the environment, for which a news release is planned or notification to other government agencies has been or will be made.

AUTOMATIC REACTOR TRIP

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

"At 1552 EDT on October 14, 2025, with Unit 1 in mode 1 at 100% power, the reactor automatically tripped due to a turbine trip. The trip was not complex with all systems responding normally post-trip.

"Operations responded and stabilized the plant. Decay heat is being removed by the emergency feedwater system.

"Due to the reactor protection system actuation while critical, this event is being reported as a 4-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and an 8-hour, non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for valid actuation of the reactor protection and emergency feedwater systems. There was no impact on the health and safety of the public or plant personnel. The NRC resident inspector has been notified."

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

A generator field breaker lockout occurred. In addition, a small fire was observed in the generator field breaker and extinguished in less than 15 minutes by the onsite fire brigade. The unit is stable in hot standby with emergency feedwater and main condenser steam dumps in-service.

AGREEMENT STATE REPORT - GAUGE SHUTTER FAILURE

The following information was provided by the Texas Department of State Health Services (the Agency) via phone and email:

"On October 10, 2025, the Agency received a notification from the licensee regarding a failure of the shutter mechanism on a level measurement gauge. The gauge is a Vega Americas SHRM-B model, containing a 300 millicurie cesium-137 sealed source. The licensee stated that the roll pin, which attaches the shutter handle to the shutter shaft, had detached, resulting in the separation of the handle from the shaft. The shutter shaft connects the handle to the shutter allowing it to be opened or closed. The shutter is currently stuck in the open position, which is the normal operating position. The licensee stated that there is no risk of additional radiation exposure to members of the public or radiation workers due to this mechanism failure. The licensee has notified a licensed service provider to repair the unit. Additional information will be provided in accordance with SA-300 reporting requirements."

Texas Incident #: 10237
Texas NMED #: TX250054

AGREEMENT STATE REPORT - GAUGE SHUTTER FAILURE

The following information was provided by the Minnesota Department of Health (MDH) via email:

"The radiation safety officer (RSO) was attempting to lock-out an Ohmart, Cs-137 fixed gauge when they found that the shutter was stuck open. The RSO stated that while trying to close the shutter, they chipped it. At that point, they removed the gauge and attempted to close the shutter in their workshop and were still unsuccessful. The RSO stated that, during continued attempts to close the shutter, they further damaged the shutter. At this point, the RSO fixed a 6-inch steel plate over the beam and put the device in storage. The RSO took surveys and determined the source was adequately shielded. The device will remain in storage, and the gauge manufacturer will be consulted for next steps.

"The RSO reported the event to MDH at approximately 1200 CDT on October 9, 2025."

Manufacturer: Ohmart
Model: unknown at this time
Source: Cs-137
Activity: approximately 80 millicuries

Minnesota Event ID: MN250007

PART 21 - POWER DRIVEN POTENTIOMETER WITH LOOSE RELAY SOCKETS

The following is a summary of information provided by Engine Systems Inc. (ESI) via email:

Relay sockets used to retain relays 'K1' and 'K2' on a power driven potentiometer (PDP), part number: ESI 50258, were found to have low retention force. Without both relays installed, the raise and lower function of the PDP is inoperable, thus preventing adjustment of the generator output voltage.

There is a scenario where if the PDP is adjusted to a value other than the normal voltage setpoint and if the K1 or K2 relays were to dislodge during a subsequent emergency event, the PDP would not return to its preposition setpoint and therefore the generator terminal voltage would not return to its desired voltage setpoint, in which case the ability of the emergency diesel generator to carry its safety-related loads could be impacted


Affected Plants
Region 3: Prairie Island

ESI contact information:

Dan Roberts
Quality Manager
Engine Systems Inc
175 Freight Rd 175
Rocky Mount, NC 27804

CONCURRENT REPORT

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

"A 24-hour report was made to New Mexico Environment Department in accordance with discharge permit condition 30 and New Mexico Administrative Code (NMAC) 20.6.2.1203 on 10/15/2025 for an unauthorized discharge. This is a concurrent report in accordance with 10 CFR 70 Appendix A(c). On 10/14/2025, work to empty laboratory rinse water into an approved discharge route commenced in accordance with procedure. This routes the rinse water to a lined retention pond, as approved in Urenco USA's discharge permit. During transfer of the rinse water, it was identified that the rinse water was not being put into the intended location. It was determined that it was being put into a cement vault for a domestic water flowmeter. The contents of the tote are approximately 330 gallons of rinse waster from non-radiological labware for reagent preparation from the chemistry laboratory, containing primarily deionized water with dilute acids, detergents, and neutralized with sodium bicarbonate. It was analyzed to be within allowable limits for uranium concentration and pH in accordance with the discharge permit and NMAC 20.6.2.3103, prior to removal from the laboratory. This event has been put into the corrective action program and corrective actions are ongoing."