Event Notification Report for December 19, 2023

AGREEMENT STATE REPORT - STUCK SOURCE

The following information was provided by the Georgia Radioactive Material Program via email:

"On December 6, 2023, the radiography crew experienced an issue with retracting the source assembly into the shielded position and notified their radiation safety officer (RSO). The RSO removed an excessive bend in the guide tube. During disassembly it was determined that the guide tube was not connected to the exposure device. This resulted in creating a small gap that caused binding when retracting the source assembly. The radiographer's pocket dosimetry read 18 millirem and the assistant's read 11 millirem at 1057 [EST] and later at 1120 read 21 millirem for the radiographer and the assistant's read 11 millirem. At the shop, the guide tube was inspected, cleaned, and then challenged to verify its function. The radiation safety department identified that the radiographic operations did not notify the State of performing radiography in Cummings, Georgia. Corrective actions have been taken."

Manufacturer: Source Production
Model: Spec-150
Serial Number and Source Serial Number: 1880, EK1501

Georgia Incident Number: 74

EN Revision Imported Date: 12/18/2023

EN Revision Text: AUTOMATIC SCRAM DUE TO TURBINE TRIP
The following information was provided by the licensee via email:

"On December 16, 2023, at 0350 CST, Grand Gulf Nuclear Station was operating in mode 1 at 81 percent power when an automatic scram occurred due to a turbine trip signal. Before the scram the unit was performing a rod sequence exchange, and no critical work was underway. The cause of the turbine trip signal is not known at this time and is being investigated. All control rods fully inserted, there were no complications, and all plant systems responded as designed. Reactor water level is being maintained by main feedwater and condensate. Reactor pressure is being maintained with main turbine bypass valves. No radiological releases have occurred due to this event.

"This event is being reported under 10 CFR 50.72(b)(2)(iv)(B) and 10 CFR 50.72(b)(3)(iv)(A), as any event or condition that results in actuation of the reactor protection system when the reactor is critical and specified system actuation due to expected reactor water level 3 isolation signals on a reactor scram. The NRC Senior Resident Inspector has been notified of this event."

The following additional information was obtained from the licensee in accordance with Headquarters Operations Officers Report Guidance:
Group 2 and Group 3 isolations occurred on the Level 3 isolation signal.

HIGH PRESSURE COOLANT INJECTION SYSTEM INOPERABLE

The following information was provided by the licensee email:

"At 0223 EST, on 12/18/2023, while Unit 2 was at 100 percent power in mode 1, the high pressure coolant injection (HPCI) outboard steam isolation valve closed resulting in the HPCI system being declared inoperable. The cause of the outboard steam isolation valve closing is under investigation. HPCI does not have a redundant system, therefore, this condition is being reported as an eight-hour, non-emergency notification per 10 CFR 50.72(b)(3)(v)(D). The safety function was restored at 0512, on 12/18/23, and HPCI has been declared operable. Reactor core isolation cooling (RCIC) and low pressure emergency core cooling systems (ECCS) 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."

60 DAY NOTIFICATION FOR AN INVALID SPECIFIED SYSTEM ACTUATION

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

"At 2011 EDT on 11/01/23, with Unit 2 in Mode 3 at 0 percent power, Unit 2 received multiple spurious actuations. These actuations consisted of a partial group 1 and a partial group 5 primary containment isolation and a partial secondary containment isolation. The partial Group 1 isolation resulted in the closure of two main steam isolation valves (MSIVs); all other MSIVs were already closed. The partial group 5 isolation auto closed one of the reactor water cleanup (RWCU) isolation valves. The partial secondary containment isolation resulted in the closure of the inboard refueling floor and reactor building secondary containment isolation valves (SCIVs).

"Additionally, at 2238 EDT, Unit 2 again received multiple spurious actuations. These actuations consisted of a partial group 5 primary containment isolation and a partial secondary containment isolation. The partial group 5 isolation auto closed one of the RWCU isolation valves The partial secondary containment isolation resulted in the closure of the inboard refueling floor and reactor building SCIVs.

"And again, at 2354 EDT, Unit 2 received spurious actuations which consisted of a partial secondary containment isolation which resulted in the closure of the inboard refueling floor and reactor building SCIVs.

"The spurious actuations seen on 11/1/23 are triggered at -35 inches reactor water level (RWL) for group 5 and secondary containment isolations and at -101 inches RWL for group 1 isolations. It was determined that a combination of the RWL fluctuating above and below the wide range instrument reference leg tap, the reactor vessel pressure being lowered, and reactor core isolation cooling introducing colder water conditions near the reference leg tap of the wide range instrument caused the spurious actuations. Using multiple RWL indications for each of the instances mentioned above, the actuations were confirmed to be spurious as RWL was being controlled in a band of +55 inches to +85 inches at the time of the actuations.

"This event is being reported in accordance with 10 CFR 50.73(a)(2)(iv)(A) as an event that resulted in an invalid actuation of a partial group 1, a partial group 5, and partial secondary containment logic."

The NRC Resident has been notified.