Event Notification Report for October 13, 2023

AGREEMENT STATE REPORT - MEDICAL UNDERDOSE

The following information was provided by the Colorado Department of Public Health and Environment (the Agency) via email:

"On October 4, 2023, the radiation safety officer of the University of Colorado Hospital reported a medical event to the emergency response line. The medical event occurred during the administration of a Y-90 TheraSphere treatment that took place that day. The authorized user stated that high back pressure was observed during administration so only 71.2 percent of the prescribed dose was delivered to the treatment area. This is the third medical event (May 18, 2023 - CO230012 and May 24, 2023 - CO230014) with Y-90 TheraSpheres at this facility in the last six months. Different authorized users and IR [Interventional Radiology] technologists were present at each medical event. The Agency is currently waiting for additional information from the hospital and the Agency intends to follow up with an in-person investigation."

Event Report ID No.: CO2300034

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.

AGREEMENT STATE REPORT - FIXED GAUGE STUCK SHUTTER

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

"On October 5, 2023, Covestro LLC (the licensee) reported to the Agency that on September 26, 2023, during routine 6-month checks, the shutter on one of its VEGA SHLG-1 fixed nuclear gauges, containing 1.5 curies cesium-137, was found stuck in the open position. Open is the normal operating position for this gauge. There were no [personnel] exposures and none are anticipated as the gauge is mounted on the side of a vessel and secured from access. The licensee has contacted the manufacturer and is trying to make arrangements for repair or replacement. An investigation into this event is ongoing. More information will be provided as it is obtained in accordance with SA-300."

Texas Incident Number: 10056

60 DAY NOTIFICATION FOR AN INVALID SPECIFIED SYSTEM ACTUATION

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

"This 60-day telephone notification is being made per the reporting requirements specified by 10 CFR 50.73(a)(2)(iv)(A) and 10 CFR 50.73(a)(1) to describe an invalid specific system actuation of the North Anna Power Station Unit 1 Emergency Core Cooling System (ECCS).

"On 6/18/2023, a comparator card power supply associated with 1-CH-PC-1121A, charging pressure low-standby pump start signal comparator, failed and caused the `A' and `B' charging pumps to auto-start and the previously running `C' charging pump to trip and lock-out.

"This event is considered an invalid system actuation because the actuation was not initiated in response to actual plant conditions or parameters and was not a manual initiation. The ECCS pumps functioned as expected in response to the actuation. The `A' Charging pump was shut down in accordance with plant procedures following replacement of the comparator card. There was no impact on the health and safety of the public or plant personnel.

"The reportability requirement was determined beyond the 60-day notification requirement on 9/21/2023. The NRC Resident Inspector has been notified."

PART 21 REPORT - EMERGENCY DIESEL GENERATOR DIGITAL REFERENCE UNIT PROBLEM

The following information was provided by the licensee via email:

"Donald C. Cook Nuclear Power Plant completed an internal Part 21 evaluation concerning an issue with an Emergency Diesel Generator (EDG) Digital Reference Unit (DRU) supplied by Engine Systems Incorporated (Appendix B Supplier for Woodward Governors). [On August 8, 2023,] a potential defect was identified [during a surveillance test] concerning a marginal solder joint on the DRU electronic circuit board that can result in a loss of continuity between the termination strip and the electronic board, causing a loss of setpoint output from the DRU to the Electronic Governor, and a subsequent loss of fuel to the EDG and inability to support any load. A formal failure analysis is ongoing at the time of this notification. A written notification will be provided within 30 days.

"Affected known plants include only Donald C. Cook Nuclear Power Plant Units 1 and 2 at the time of notification.

"The NRC Resident has been notified."

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

The EDG DRU was replaced after discovery of the potential defect and the EDG is currently operable.

MANUAL REACTOR TRIP

The following information was provided by the licensee via email:

"On 10/12/23 at 2127 EDT, with the Unit 1 in Mode 1 at 100% Power, operators identified degrading condenser vacuum and manually tripped the reactor. All control rods inserted as expected. The trip was not complex, and all systems responded normally post-trip. The cause of the degraded condenser vacuum was an unexpected closure of the condenser air ejector regulator. The cause of the air ejector regulator going closed is not fully understood and is being investigated.

"Following the SCRAM, Operators responded and stabilized the plant. Decay heat is being removed by the Main Steam System through the Atmospheric Relief Valves (ARVs) and Auxiliary Feed Water (AFW) systems. Due to the Reactor Protection System (RPS) actuation while critical, this event is being reported as a four-hour, non-emergency notification per 10 CFR 50.72(b)(2)(iv)(B) and an eight-hour non-emergency notification per 10 CFR 50.72(b)(3)(iv)(A) for a valid specified system actuation.

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