Event Notification Report for June 26, 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

UNIT 1 MANUAL REACTOR TRIP

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

"At 0014 EDT on 6/24/2025, Sequoyah Unit 1 operators performed a manual reactor trip. All safety systems responded normally, and the plant is currently stable in mode 3 (hot standby) at normal operating temperature and pressure. Unit 1 was manually tripped due to lowering steam generator water levels caused by a secondary control system malfunction.

"Unit 2 is not impacted and remains at 100 percent power in mode 1.

"Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the auxiliary feedwater system.

"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."

UNIT 2 MANUAL REACTOR TRIP

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

"At 0351 EDT on 6/24/25, Sequoyah Unit 2 operators performed a manual reactor trip. All safety systems responded normally, and the plant is currently stable in mode 3 (hot standby) at normal operating temperature and pressure. Unit 2 was manually tripped due to lowering level in the loop 1 steam generator caused by main feedwater regulating valve malfunction.

"Due to the reactor protection system actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the auxiliary feedwater system.

"There was no impact on the health and safety of the public or plant personnel. The NRC Resident Inspector has been notified."