Event Notification Report for November 24, 2025

AGREEMENT STATE REPORT - GAUGE SHUTTER FAILURE

The following information was provided by the Radiation Health Branch of the Kentucky Department for Public Health and Safety (The Department) via email:

"The Department was notified on 11/12/2025, by the radiation safety officer (RSO) from Big Rivers Electric Corporation, that during a routine six-month inventory/shutter checks, two sources were identified to have problems with the shutters closing.

"Both [gauges] measure density in the scrubber material and are mounted on piping. No exposure is possible unless the piping or gauge is removed. Primary action is to notify personnel and modify the red tag system to indicate that until this is resolved, no maintenance can be allowed on the piping because the shutters on the gauges cannot be safely closed.

"Until further notice, the piping where these gauges are mounted cannot have any maintenance activities performed on them. Red tag authorities should make note that the gauges cannot be red tagged because the shutters do not close.

"Maintenance will be performed on the gauges by an authorized contractor."

Gauge 1 information:
Manufacturer: Kay Ray
Model number: 20493
Serial number: 7062BP
Activity: 10 mCi Cs-137

Gauge 2 information:
Manufacturer: Ronan
Model number: SA8-C5
Serial number: 2104CP
Activity: 20 mCi Cs-137

AGREEMENT STATE REPORT - MEDICAL EVENT

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

"The University of California Los Angeles (UCLA) health [center] reported that a patient being treated for liver cancer underwent a Y-90 Sirtex SirSpheres brachytherapy treatment on November 12, 2025. This is a preliminary report of a medical event, per 10 CFR 35.3045.

"The authorized user's (AU) written directive called for two vials of Y-90 activity to treat two different segments of the right lobe via two different arterial branches of the lobe. The first prescription was for 108.11 mCi and 114 mCi (105.73 percent) was successfully delivered.
"The second prescription was for the right lobe, segment 4A using 13.51 mCi but only 10.04 mCi (74.32 percent) was able to be delivered.
"The authorized user believes his patient reached stasis, so he halted the procedure per the Sirtex IFU (instructions for use). Arterial flow is intermittently checked throughout the infusion process.
"The undelivered activity was determined by measuring the exposure rate at a known distance from the post-treatment waste after the administration. UCLA health [center] will submit a 15-day report to the Department."

California 5010 Number: 111225

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.

AUTOMATIC REACTOR TRIP

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

"At 1208 CST on 11/21/2025, with Unit 2 in Mode 1 at 100 percent power, [the] Unit 2 reactor automatically tripped due to a main transformer lockout. The trip was not complex, with all systems responding normally post-trip. One of three essential chillers (chiller 22C) was inoperable at the time of [the] trip due to planned maintenance activities. All other engineered safety feature (ESF) equipment was operable at the time of the event.

"Operations responded and stabilized the plant. Decay heat is being removed by steam generator pressure operated relief valves (PORV). There was no impact to Unit 1.

"All control rods fully inserted.

"Primary pressurizer PORV '655A' opened twice to relieve pressure in response to [the] pressure transient.

"[South Texas Project Unit 2] entered Technical Specification 3.8.1.1.e due to a loss of two off-site power sources, `A' and `C' ESF busses.

"Upon main turbine trip, throttle valves closed as expected.

"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) due to valid actuation of two of the three emergency diesel generators.

"There was no impact on the health and safety of the public or plant personnel, and Unit 2 remains at normal operating temperature and normal operating pressure.

"The NRC Resident Inspector has been notified."


The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
Emergency diesel generators '21' and '23' automatically started upon loss of power as expected. Auxiliary feedwater actuated post-trip as expected. Offsite power to ESF busses has been restored.