Event Notification Report for September 24, 2025

AGREEMENT STATE REPORT - LOST MOISTURE DENSITY GAUGE

The following information was summarized from the State of Florida Bureau of Radiation Control (BRC) via email:

On September 24, 2025, BRC received a report from the licensee regarding the loss of control of a moisture density gauge on the same date. The initial report was that the device had been stolen, but subsequent video footage indicated that the issue was loss of control due to failure to secure the gauge for transport in a truck. The gauge and case are missing but locked. The licensee believes the gauge was lost between a job site in North Port, FL, and Sarasota, FL. The incident has been referred to materials and inspection for investigation.

The device is a Instrotek model number 3500 and contains 10 mCi of Cs-137 and 44 mCi of Am-241/Be.

Florida Incident Number: FL25-094

Notified R1DO (Lilliendahl), NMSS Events Notification (email), and ILTAB (email)



* * * UPDATE ON 09/25/2025 AT 0958 EDT FROM MONROE COOPER TO JON LILLIENDAHL * * *

The following information was summarized from the BRC via email:

The gauge was recovered and returned to ECS Florida.

Notified R1DO (Lilliendahl), NMSS Events Notification (email), and ILTAB (email)



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 - MEDICAL EVENT

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

"The University of California Los Angeles (UCLA) reported to RHB that a reportable medical event (underdose) had occurred on September 24, 2025. A patient was to receive 200 mCi of Lu-177 Lutathera for a neuroendocrine tumor via an intravenous line and a mechanical infusion pump. However, it was calculated that the patient only received 80 mCi of the intended dose.

"The registered nurse starts the IV (3-way connections), and the patient receives amino acids for the first hour. Next, a certified nuclear medicine technologist (CNMT) connects the syringe of Lutathera and connects it to the pump. It takes 45 minutes to complete the infusion, and the pump increases its pressure over time. Upon returning to remove the syringe and restarting the amino acid drip, the CNMT noticed the IV had leaked onto the chux [pad] and a small part of the patient's arm skin. The medical radiation safety officer (RSO) was notified and reported to the patient's treatment room. The patient's arm was decontaminated, and the medical physicist calculated the patient had approximately 2-4 mCi on their skin (estimated 30-60 rem skin dose). The Lu-177 contaminated chux materials were collected and evaluated by the nuclear medicine department to contain approximately 120 mCi of the leaked dose.

"UCLA's initial investigation indicates that the increasing pressure from the infusion pump allowed the IV connection to become loose and leak. RHB will continue to follow-up with UCLA and receive their full event report."

California 5010 Number: 092425

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.

NON-POWER REACTOR - UNPLANNED HIGH-POWER TRIP

The following information was summarized from the licensee via phone and email:

On September 24, 2025, at 1511 MDT, a high-power trip occurred (operation of safety channels 2 and 3). The reactor was being operated by a senior reactor operator (SRO) and a student authorized operator. A positive-period excess reactivity measurement was being performed. The reactor power rose to 5.64 watts. The technical specifications power limit of 6 watts plus was not exceeded, and both safety channels functioned to shut the reactor down.

This prompt notification for a high-power trip is in accordance with current procedures and technical specification 6.9.2.a.7. The proximate cause of this event was operator distraction. The reactor room had two visitors at the time of the event, an NRC inspector and a University of New Mexico nuclear engineering instructor. The instructor was engaging the student authorized operator and the SRO on matters relating to a laboratory activity ongoing in another part of the building. The SRO responded to the rising power too slowly to avoid the high-power trip.

AUTOMATIC REACTOR TRIP

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

"On September 24, 2025, at 1347 CDT, Arkansas Nuclear One, Unit 1, (ANO-1) experienced an issue with the X-01B main phase transformer which led to an automatic trip on reactor protection system (RPS).

"ANO-1 is currently stable in mode 3, maintaining pressure and temperature with the P-1A and P-1B main feedwater pumps and steaming to the main condenser. All rods inserted and systems functioned as expected.

"There is no radiological release on either unit as a result of this event.

"This report satisfies the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A) for the reactor protection system actuation.

"The NRC Senior Resident Inspector has been notified.

"Unit 2 was not affected."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
ANO-1 retains access to all normal sources of offsite power.

MANUAL REACTOR TRIP

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

"On September 24, 2025, at 1829 CDT, Comanche Peak, Unit 1, was manually tripped due to a trip of both main feed water (MFW) pumps. All auxiliary feedwater pumps started due to the trip of both MFW pumps. This event is being reported in accordance with 10 CFR 50.72(b)(2)(iv)(B) for a reactor trip and 10 CFR 50.72(b)(3)(iv)(A) for an actuation of auxiliary feedwater. Unit 1 is being maintained in mode 3 in accordance with integrated plant operating procedures. Decay heat is being rejected to the main condenser via the steam dump valves. The cause of both MFW pumps tripping is unknown and under investigation.

"The NRC Resident Inspector was notified."


The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
No evolutions were ongoing at the time of the event.