The following information was provided by the licensee via phone and email:
At 1001 EST, on November 15, 2024, with Unit 1 in mode 1 at 100 percent power, the reactor was manually tripped due to three control element assemblies fully inserting into the core. The trip was uncomplicated with all systems responding normally post trip. Operations stabilized the plant in mode 3. Decay heat is being removed by the steam bypass control system and main feedwater. Unit 2 was not affected.
This event is being reported pursuant to 10 CFR 50.72 (b)(2)(iv)(B).
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 insertion of the three control rods is suspected to be caused by an electrical failure; however, the cause is still being investigated.