Event Notification Report for February 02, 2024

AGREEMENT STATE REPORT - UNDERDOSE CAUSED BY EQUIPMENT FAILURE

The following information was provided by the Wisconsin Radiation Protection Section via email:

"On January 25, 2024, the licensee reported a medical event at 1119 CST which had occurred the same day at 0900 CST, where the dose delivered for a single fraction differed from the prescribed dose by more than 50 percent. This event is also reportable as an equipment failure. A patient was being treated with a Nucletron Corporation Model 106.990 high dose rate remote after loader unit, and during the fraction, the physicist noticed that the timer on the console had frozen while the source remained exposed. The planned treatment time was 6 minutes and 15 seconds over 9 dwell positions, and the timer, counting down, was frozen at 6 minutes and 7 seconds. Once the freeze was noticed, the physicist pressed the emergency stop button on the console to terminate the treatment. The physicist estimated that the total treatment time was approximately 30-40 seconds, all of which was to the first dwell position. The authorized user had prescribed 550 cGy for this fraction and the physicist estimated that only 11 percent of the prescribed dose was delivered. The physicist reported that the timer functioned properly during the daily quality assurance checks prior to treatment. The patient and patient's family were notified by the authorized user. The licensee is contacting the device vendor for emergency service."

Wisconsin Event Number: WI240001

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.

EN Revision Imported Date: 2/1/2024

EN Revision Text: AUTOMATIC REACTOR SCRAM

The following information was provided by the licensee via email:

"At approximately 1202 EST on 01/29/24, unit 2 experienced a reactor scram caused by a main turbine trip. Investigation is still ongoing."

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

All control rods were fully inserted. The licensee indicated that the turbine trip may have been caused by a power load imbalance, however the cause of the incident is under investigation. The scram was not complex.

Decay heat is currently being removed thru bypass valves dumping to the main condenser. Initially unit 2 lost the use of the bypass valves due to lack of condenser vacuum. Unit 2 used the high pressure coolant injection (HPCI) system in the condenser storage tank (CST) to CST mode to remove decay heat. Residual heat removal was used to keep the torus cool. Condenser vacuum was regained and unit 2 is back to removing decay heat with the turbine bypass valves.

There was no impact to unit 3.

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

* * *UPDATE ON 01/29/24 AT 1935 EST FROM PAUL BOKUS TO NATALIE STARFISH* * *

The following information was provided by the licensee via email:

Licensee adds 8-hour non-emergency 10 CFR 50.72(b)(3)(iv)(A) specified system actuation report to original 4-hour non-emergency 10 CFR 50.72(b)(2)(iv)(B) RPS Actuation report.
"At approximately 1202 EST on 01/29/24, unit 2 experienced a reactor scram by a main turbine trip. All control rods inserted. Reactor core isolation cooling system (RCIC) was manually initiated for level control. HPCI was manually initiated for pressure control. Primary containment isolation system (PCIS) Group II and III isolations occurred [specified system actuation]. Investigation is ongoing."

The NRC Resident Inspector has been notified.

OFFSITE NOTIFICATION - WORKPLACE INJURY

The following information was provided by the licensee via email:

"On February 1, 2024, a contract worker was transported offsite for medical treatment due to a work-related injury that required the individual to be admitted to the hospital. The individual was free-released from the site prior to transport.

"The injury and hospitalization were reported by the contract worker's employer to OSHA per 29 CFR 1904.39(a)(2). Based upon that notification to another government agency, Tennessee Valley Authority is reporting this per 10 CFR 50.72(b)(2)(xi).

"The NRC Senior Resident Inspector has been notified of this event."

ACCIDENT MITIGATION - RELIEF VALVES INOPERABLE

The following information was provided by the licensee via email:

"At 1640 CST on February 1, 2024, it was determined that a condition occurred that could have prevented the fulfillment of a safety function due to two of the four steam generator (SG) power-operated relief valves (PORVs) being simultaneously inoperable. In certain accident scenarios, more than two PORVs are needed to mitigate the consequences of an accident; therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v). The first PORV was declared inoperable at 1025 on January 22, 2024, and the safety function is considered to have been lost when the second PORV was declared inoperable at 1902 on January 23, 2024. The safety function was restored at 2234 on January 23, 2024, when the first SG PORV was declared operable. There was no impact to unit 2. 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:

The plant remained in mode 3 for the duration of the condition. The causes for the two PORVs being inoperable were neither related nor systemic in nature. All SG PORVs have been restored to operation.