Event Notification Report for August 21, 2025

EN Revision Imported Date: 8/21/2025

EN Revision Text: PART 21 - INTERIM REPORT FOR REGULATING TRANSFORMER

The following is a synopsis of information provided by AMETEK Solidstate Controls Inc. (AMETEK) via email:

During regulating transformer system operations, the transformer may be experiencing short circuiting between coils to ground.

Visual inspection for severe darkening or charring of coils, magnetic shunts, or core, and/or the use of thermal probes or infrared guns monitoring for excessive temperatures greater than 180 degrees Celsius or 355 degrees Fahrenheit may detect affected regulating transformer systems.

Affected systems exhibit signs of transformer insulation system deterioration, increased audible noise from the units, blackening on any areas of the transformer, or signs of electrical shorting between windings or coil to core.

The cause of the short circuiting is unknown. Component failure impact analysis and regulating transformer system electrical testing are in progress.

Recommend all units currently in service with internal components, which include but are not limited to capacitors, wire harnesses, and transformer materials, with temperatures in excess of 180 degrees Celsius or 355 degrees Fahrenheit be removed from service.

COMPONENT DESCRIPTION:
The AMETEK SCI model numbers listed are for regulating transformers that are intended to take in AC power at 460 VAC plus or minus 10 percent and output AC power at 120 VAC plus or minus 2 percent with low harmonic distortion.

Models: 85-IS0075-12 and 85-IS0150-14

AFFECTED PLANTS:
Southern Nuclear Company - Vogtle
Constellation Energy - Ginna

* * * UPDATE ON 03/11/25 AT 1530 EDT FROM ZACHARY RUMORA TO KERBY SCALES * * *

The following is a synopsis of the information provided from Ametek:

Test were performed on both models (85-IS0075-14 and 85-IS0075-12).

Model 85-IS0075-12 was found to be functioning as expected during testing and did not present a failure mode. Therefore, Ginna is not affected by this component.

Regarding model 85-IS0075-14, dielectric testing was performed and the apparent source of the failure was a short-circuit between the secondary coil of the transformer and the magnetic shunts and center leg of the transformer core. The suspected cause of this short circuit is the design of the magnetic shunt. Various actions are being reviewed to enhance model 85-IS0150-14 specifically regarding the insulation system of the transformer around the coils and magnetic shunts. An updated report is expected to be completed in May/June.

Notified R1DO (Schussler), R2DO (Pearson), Part 21 Group (email)

* * * UPDATE ON 08/20/2025 AT 0748 EDT FROM ZACHARY RUMORA TO ROBERT THOMPSON * * *

The following is a synopsis of the information provided from Ametek:

AMETEK is submitting the final report on the potential defect. A design change is being implemented to enhance the insulation system of the transformer used in model 85-IS0150-14. This design change is expected to be released by August 31, 2025. Additionally, an alternative regulating transformer design is available that can replace the existing design.

AFFECTED PLANTS:
Southern Nuclear Company - Vogtle

Notified R1DO (Dimitriadis), R2DO (Bacon), Part 21 Group (email)

AGREEMENT STATE REPORT - MEDICAL EVENT

The following is a summary of information provided by the Nebraska Department of Health and Human Services via phone and email:

The licensee reported that on August 12, 2025, a patient was to receive a 200 mCi Lu-177 (Pluvicto) treatment for prostate cancer per a written directive, but was administered a 156 microcurie Ra-223 (Xofigo) treatment for metastatic prostate cancer instead. The licensee's initial estimate is that the patient received a 13 rem whole-body dose and 665 rem to the bone marrow. There were no immediate implications for patient health reported. The referring physician and patient have been notified of the event.

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.

LOST MOISTURE DENSITY GAUGE

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

The licensee reported the loss of a Troxler model 3440+ moisture density gauge (8 mCi Cs-137, 40 mCi Am-241/Be). The gauge was last positively accounted for at Fort Carson, CO, on June 29, 2023, prior to shipment to Fort Hood, TX. Despite extensive investigation at both locations, its current location remains unknown. Both Troxler and the common carrier have been contacted in attempts to locate the gauge. Efforts to locate the gauge are ongoing, including planned on-site surveys at Fort Hood and Fort Carson.

The loss stemmed from a series of procedural failures, including inadequate communication regarding shipment details, insufficient tracking documentation (due to expired shipment tracking data), and a lack of positive control over the asset during redistribution. The potential for radiation exposure to the public is considered minimal due to the sealed source design.

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

AGREEMENT STATE REPORT - DAMAGED MOISTURE DENSITY GAUGE

The following information was provided by the Washington State Department of Health, Office of Radiation Protection (WADOH) via email:

"At 0100 PDT [on 08/14/2025] an intoxicated driver collided with several pieces of equipment in a roadside construction zone, including a nuclear portable gauge. This event occurred on SR 16 eastbound directly before the Tacoma Narrows Bridge in Gig Harbor, Washington. The nuclear gauge that was damaged was a licensed Troxler model 3450. The damage appeared to consist of the handle being separated from the body of the gauge. The gauge was not in use at the time.

"The radiation safety officer (RSO) cordoned off the area and prevented individuals from coming within 150 feet of the source. The timeline of this event is still being investigated. The RSO contacted WADOH at 0205 PDT. Emergency response, consisting of fire and hazmat personnel, arrived on site at approximately 0500 equipped with a Geiger Mueller radiation detection instrument. Two individuals donned Tyvek [suits] and proceeded towards the source, with WADOH directing their response via telephone communication. The highest radiation levels were 15 mR/hr, measured approximately one foot from the source, which indicated that the sources were likely still within the shielded position. The two emergency responders used a shovel to pick the source handle and gauge body up and place the pieces back into the Troxler type 'A' shipping container. This took approximately 8 minutes and the dose received is assumed to be less than 2 mrem each. The container was then closed, and additional radiation surveys were taken. The on contact dose on the exterior of the container was 2 mR/hr, which is below the expected dose rate while within the container. WADOH arrived on-site at approximately 0730 PDT and took contamination surveys on the source assembly, which was visibly intact. No contamination was detected.

"Under Troxler's guidance, the licensee transported the material within the type 'A' container back to their calibration facility to perform leak tests. Leak tests have been performed and are being sent out for counting prior to shipment back to Troxler. The gauge will remain in a secured position until it is shipped back to Troxler. The licensee will follow Troxler guidance and all applicable DOT regulations. A full report will be delivered to WADOH within 30 days. WADOH will continue conversations with the licensee to determine the full scope of the situation, and additional details will be provided as they are found."

Gauge sources: 9 mCi Cs-137, 44 mCi Am-241/Be, and 66 microcuries Cf-252

WA Incident Number: WA 25-009

MAJOR LOSS OF EMERGENCY ASSESMENT CAPABILITY

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

"At 2030 EDT on 08/19/2025, it was discovered that the main control room master fire control panel '10-C-672' had faulted and could no longer receive information from any remote panel. Due to this condition, the panel, and thereby the main control room, is unable to receive fire alarms.

"This is an eight-hour, non-emergency notification for a loss of emergency assessment capability. This event is reportable in accordance with 10 CFR 50.72(b)(3)(xiii) because the condition affects the evaluation of all emergency action levels for an emergency initiating condition.

"There is no impact to the health and safety of the public or plant personnel.

"The NRC Resident Inspector has been notified. The Lower Alloways Creek Township will be notified."

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

Fire watches have been posted at remote panels and other required areas as a compensatory measure until the fire computer is returned to service.

FITNESS-FOR-DUTY

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

"A non-licensed employee had a confirmed positive for alcohol during a random fitness-for-duty [test]. The employee's access to the plant has been terminated."

The NRC Resident Inspector has been notified.

INOPERABLE CONTAINMENT UNIT COOLERS

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

"On August 20, 2025, at 1020 CDT, River Bend Station (RBS) was operating at 100 percent reactor power when it was discovered that previously implemented enhancement compensatory measures were determined to have rendered containment unit cooler `A' (HVR-UC1A) and containment unit cooler `B' (HVR-UC1B) inoperable.

"On August 14, 2025, RBS placed 'HVR-UC1A' and 'HVR-UC1B' in lockout as a compensatory measure to enhance operability following a Part 21 notification from General Electric.

"On August 20, 2025, it was discovered that the lockout function would delay the start of a time relay needed for load sequencing in the event of an accident. This condition would prevent the unit coolers from starting within their required sequence timing following a loss of offsite power. 'HVR-UC1A' and 'HVR-UC1B' were declared inoperable. By 1219 CDT, these compensatory measures were no longer in place.

"This event is being reported under 10 CFR 50.72(b)(3)(ii)(B) as any event or condition that results in the nuclear power plant being in an unanalyzed condition that significantly degrades plant safety, as well as 10 CFR 50.72(b)(3)(v)(C) and 10 CFR 50.72(b)(3)(v)(D) as an event or condition that could have prevented fulfillment of a safety function that is needed to control the release of radioactive material and mitigate the consequences of an accident.

"The NRC Resident Inspector has been notified."