Event Notification Report for October 28, 2024

MEDICAL EVENT

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

The licensee's radiation safety officer (RSO) was notified on 12/20/2024, at approximately 1130 CST of a medical event that occurred at Franciscan Health Munster in Munster, IN on 10/28/2024. A patient was prescribed a Y-90 TheraSphere treatment with a prescribed dose of 23.5 Gbq. The calculated administrated dose was 18.32 Gbq. This indicates an approximate 22 percent underdose. The licensee is continuing to investigate.

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.

* * * RETRACTION ON 12/26/2024 AT 0907 EST FROM WALEED AL-NAJJAR TO SAMUEL COLVARD * * *

The following information was provided by the licensee via phone:

The event is being retracted due to the following reasons. The activity initially documented as prescribed corresponded to the quantity requested from the manufacturer. This activity is intended to decay to a specific dose by the time the procedure occurs. On the day of the procedure, the prescribed dose was 110 Gy, while the dose delivered was 89.1 Gy. The difference between these amounts is less than 20 percent, thus not subject to reporting.

Notified R3DO (Nguyen), and NMSS Events Notification (email).

CRITICALITY ACCIDENT AND ALARM SYSTEM OUT OF SERVICE FOR TESTING

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

"The American Centrifuge Plant (ACP) Criticality Accident and Alarm System (CAAS) is designed to detect a nuclear criticality accident, and provide audible and visual alarms that alert personnel to evacuate the immediate area, as required by 10 CFR 70.24, criticality accident requirements.

"Periodic maintenance and testing, of the CAAS, is scheduled to commence on Monday, October 28, 2024, at approximately 0700 EDT. The maintenance and testing is expected to last approximately 48 hours and affect the X-3001, including the North area. The CAAS will be temporarily taken out of service and declared inoperable, to perform the periodic maintenance and testing in accordance with approved plant procedures.

"In accordance with License Application Section 5.4.4 compensatory measures will be implemented for the ACP. These measures include, but may not be limited to the following:
 Presence of essential personnel during the maintenance and testing activities;
 Evacuation of non-essential personnel from affected areas and the immediate evacuation zone prior to taking CAAS equipment out of service;
 Limiting access to the area by restricting material movements, including fissile material movement, while the CAAS is inoperable;
 Use of personal alarming dosimeters for personnel authorized to access the area during the CAAS outage;
 Compensatory measures will remain in place until CAAS coverage is verified to be operational and the CAAS is declared operable in accordance with approved plant procedures.

"American Centrifuge Operating, LLC (ACO) will notify the NRC when CAAS coverage is returned to normal operation.

"The licensee has notified the NRC Project Manager and Region II Senior Inspector.

"ACP condition notification number: 12198

"The Department of Energy has been notified."

LOSS OF BOTH TRAINS OF CONTROL ROOM VENTILATION

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

"On October 28, 2024, at 0533 EDT, it was discovered both trains of the unit 1 and unit 2 control room ventilation system booster fans were simultaneously inoperable due to trip of the supply breaker to the motor control center (MCC) supplying the normally closed motor operated intake dampers for both trains. Therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). At 1059 EDT, one train of the unit 1 and unit 2 control room ventilation system booster fans was restored to operable. 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:

Although the control room ventilation affects both units 1 and 2, unit 1 is currently defueled and outside the mode of applicability during the timeframe of this event.

For clarification regarding train separation, both trains for control room ventilation have separate power supplies for their booster fans. However, power for both of their inlet dampers and one of the booster fans are all fed from the same MCC supply breaker that tripped. Therefore, both trains were simultaneously inoperable at 0533 EDT. The loss of power to the MCC is still under investigation. Procedurally, Oconee was able to restore one train to service, the train that still had power to its booster fan, at 1059 EDT, by manually opening its inlet damper in the fail-safe position.