Event Notification Report for October 30, 2024

AGREEMENT STATE REPORT - MEDICAL UNDERDOSE

The following information was provided by the Pennsylvania Department Bureau of Radiation Protection (the Department) via email:

"On October 23, 2024, the licensee informed the Department of a medical event involving a treatment with SirSpheres. It is reportable per 10 CFR 35.3045.

"On October 22, 2024, a patient was receiving a SirSphere treatment. During the course of administration of the Y-90 spheres, the microcatheter became blocked, and the procedure was stopped. The remaining dose/waste was assessed, and it was calculated that the patient received approximately 30 mCi out of a prescribed 50 mCi. This represents an approximate 40 percent underdose. The authorized user (AU) was satisfied with that amount, believing it to be therapeutic and does not expect any harmful effects to the patient. Both the patient and AU were notified.

"The Department will perform a reactive inspection. More information will be provided as received."

Event Report ID No: PA240020

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.

LOSS OF ITEM RELIED ON FOR SAFETY

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

"Loss or degradation of items relied on for safety that results in failure to meet the performance requirement of 10 CFR 70.61.

"A temperature interlock, designated as item relied on for safety (IROFS), failed to actuate at setpoint.

"NRC Region II has been notified."

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

The licensee is troubleshooting the cause, and the system was placed in safe shutdown.

AGREEMENT STATE REPORT - STUCK OPEN GAUGE SHUTTER

The following information was provided by the Tennessee Division of Radiological Health via email:

"During a scheduled six-month shutter check, it was discovered that a gauge shutter was stuck in the open position. The technician took surveys to verify the shutter was stuck in the open position. The open position is the normal operating position. No abnormal levels of radiation were detected. A VEGA field technician has been contacted to service the gauge.

"Corrective actions or reports, as well as additional information, will be updated with a NMED report within 30 days."

Manufacturer: Ohmart/Vega
Source Holder Model: SHF2
Source Holder SN: 99949B
Isotope: Cs-137, 24.4 mCi

Tennessee Event Report ID Number: TN-24-081

FITNESS FOR DUTY

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

A non-licensed contract supervisor violated the station's fitness-for-duty program. The employee's access to the plant has been terminated.

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.

PART 21 INTERIM REPORT - POTENTIAL DEFECT WITH CIRCUIT BOARD

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

The licensee received two alarms due to direct current (DC) output voltage fluctuating between 127.4 to 131.3 volts. After troubleshooting, the DC output voltage fluctuations were caused by the battery charger printed circuit board. The part has been sent to the vendor, Ametek, for evaluation. Catawba is the only plant known to have this issue at this time.

The evaluation is expected to be completed on January 31, 2025.

Catawba condition report 02526388

Ametek Part Number: 80-921-4031-90
Ametek failure analysis number: 24-006

AUTOMATIC REACTOR TRIP

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

"At 1023 CDT, on 10/29/2024, with Unit 2 in Mode 1 at 100 percent [reactor] power, during the performance of surveillance procedure 2047, CONTROL ROD QUARTERLY EXERCISE, Unit 2 experienced an automatic reactor trip [followed by a] turbine trip. All control rods fully inserted into the core following the reactor trip. The cause of the Unit 2 reactor trip is being investigated.

"Operations responded and stabilized the plant. Auxiliary feedwater actuated as expected. Decay heat is being removed by the steam generators through the main steam dumps to the condenser. The Unit 2 reactor trip was not complex with all systems responding normally post trip.

"Due to the actuation of the reactor protection system (RPS) of Unit 2, this event is being reported as a RPS Actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(2)(iv)(B).

"Due to the actuation of the auxiliary feedwater system following the Unit 2 reactor trip, this event is being reported as a specified system actuation in accordance with the reporting criteria of 10 CFR 50.72(b)(3)(iv)(A).

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

INOPERABILITY OF DIVISION 3 DIESEL GENERATOR SUPPORTING HIGH PRESSURE CORE SPRAY

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

"At 1152 EDT, on 10/29/2024, the division 3 diesel generator was declared inoperable due to variations in steady state voltage during a planned monthly surveillance run. Troubleshooting of the issue is in progress. This condition could prevent the fulfillment of a safety function; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). All other emergency core cooling systems were operable during this time.

"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:

Limiting condition for operations (LCO) 3.8.1.b was entered as a result of this event.

OFFSITE NOTIFICATION

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

"At 1730 [EDT], on 10/29/2024, Vistra authorized a report to the State of Ohio in accordance with NEI 07-07, 'Industry Groundwater Protection Initiative,' of a liquid spill to the plant's outdoor ground from an outdoor cask holding radioactive waste. This spill contained radionuclides cobalt-60 and manganese-54 with activities greater than the site procedural limits for state reporting. The outdoor cask has been removed from the onsite storage area; remediation and causal investigation activities are being performed. This exceedance did not exceed any NRC regulations or reporting criteria. There was no impact on the health and safety of the public or plant personnel.

"This notification is being made solely as a four-hour, non-emergency notification for a Notification of Other Government Agency. This event is reportable in accordance with 10 CFR 50.72(b)(2)(xi).

"The NRC Resident Inspector has been notified."

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

No EPA limits were exceeded