Event Notification Report for July 24, 2026

AGREEMENT STATE REPORT - STUCK RADIOGRAPHY SOURCE

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

"An iridium-192 sealed source contained in a QSA Delta 880 camera [failed to retract into the shielded position]. The radiation safety officer (RSO) reported that the radiography crew was performing the first exposure of the day at a fabrication shop at approximately 0930 CST when the source failed to retract into the shielded safe position. The crew immediately secured the area and notified the licensee, who dispatched a source recovery team. The source recovery team successfully returned the source to its shielded position at approximately 1320 CST. The RSO stated that a faulty guide tube caused the failure to retract and a new guide tube has been purchased for the camera. No individual received any significant exposure from this event.

"Additional information will be made available in accordance with SA300 reporting requirements."

Texas incident number: 10309
Texas NMED Number: TX260025

INVALID SPECIFIED SYSTEM ACTUATION

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

"On May 25, 2026, with Unit 2 at 100 percent power in mode 1, personnel were preparing to calibrate two area radiation monitoring (ARM) power supplies, each associated with an ARM trip unit. During the task preview, it was identified that one ARM trip unit had previously been removed (de-energized) for repair. At 1452 EDT, as part of the calibration activity, the power supply associated with the remaining ARM trip unit was de-energized. Having both ARM trip units simultaneously de-energized caused a partial system isolation. The partial isolation was not in response to an actual plant condition or parameter satisfying the requirements for initiation of the system. Therefore, the actuation was invalid.

"This event is reportable per 10 CFR 50.73(a)(2)(iv)(A) because it was not part of a pre-planned sequence and resulted in the invalid, partial actuation of containment isolation valves (CIVs) in both the primary containment and secondary containment systems, with all systems responding normally.

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

PART 21 - THERMAL OVERLOAD FOR EMERGENCY DIESEL GENERATOR

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

On July 15, 2026, Cook Nuclear Plant completed a Part 21 evaluation concerning an issue with the thermal overload (TOL) used in the electric starter for the Unit 1 emergency diesel generator (EDG) room exhaust fan.
Failure investigation determined that a TOL line-side conductor had a loose electrical connection causing a high-resistance condition and elevated temperature on one phase.
The defect caused the Unit 1 'AB' EDG room exhaust fan to trip and resulted in the associated EDG being declared inoperable and unable to perform its safety-related function.

The starter was replaced and the preventative maintenance and testing procedure was revised to check the TOL for proper assembly prior to installation.

Cook Nuclear Plant is the only facility known to be affected at the time of this report.

The NRC Resident has been notified.

INVALID ACTUATION

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

"This 60-day optional telephone notification is being made in lieu of a licensee event report (LER) as allowed by 10 CFR 50.73(a)(1). This notification is made pursuant to the reporting requirements specified in 10 CFR 50.73(a)(2)(iv)(A) for an invalid actuation of one of the systems listed in 10 CFR 50.73(a)(2)(iv)(B).

"At approximately 0634 MST on 5/30/2026, Palo Verde Nuclear Generating Station Unit 2 had an invalid actuation of the train 'B' balance of plant engineered safety feature actuation system (BOP ESFAS). This resulted in an auto start of the train 'B' essential chiller, spray pond pump, essential cooling water pump, high pressure safety injection, low pressure safety injection, containment spray, and auxiliary feedwater pump. No valves actuated and the plant remained stable. This event was the result of an invalid BOP ESFAS actuation due to a load sequencer failure.

"Since the actuation was not initiated in response to actual plant conditions, it was not an intentional manual initiation, and there were no parameters satisfying the requirements for initiation of the systems, this event has been determined to be an invalid actuation.

"There was no impact on the health and safety of the public or plant personnel.

"The NRC Resident has been notified."