Event Notification Report for May 30, 2025

AGREEMENT STATE REPORT - STOLEN GAUGE

The following information was provided by the California Department of Public Health, Radiologic Health Branch via email:

"Sequoia Consulting Inc. called the Radiologic Health Branch to report the theft of a CPN MC-3 moisture density gauge (serial number 31118). The device contains a 10 mCi cesium-137 sealed source and a 50 mCi americium-241/beryllium sealed source. A gauge operator finished a night job in Valencia, CA, and traveled to their home for a restroom break and snack. While the operator was occupied, a man driving a blue Bronco was recorded cutting the security lock securing the gauge case to the vehicle and stealing the device. The Radiologic Health Branch will continue to follow-up on this investigation.

"Local law enforcement was notified."

California 5010 Number: 052325

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

MANUAL REACTOR TRIP AND AUXILIARY FEEDWATER ACTUATION

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

"At 1253 EDT, on May 28, 2025, with Unit 1 in mode 1 at 100 percent power, the reactor was manually tripped due to a loss of main feedwater pump `A'. The trip was not complex, with all systems responding normally post-trip.

"Operations responded and stabilized the plant. Decay heat is being removed by discharging steam through the steam dumps to the main condenser. Units 2, 3, and 4 are not affected. An automatic actuation of auxiliary feedwater (AFW) also occurred. The AFW auto-start is an expected response from the reactor trip.

"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). This event is also being reported as an eight-hour, non-emergency notification per 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."

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

All control rods inserted on the trip. A main feedwater pump lube oil evolution was in progress at the time of the trip.