The Entergy (NYSE:ETR) Arkansas Nuclear One Unit 1 facility tripped offline Dec. 15, according to data from the Nuclear Regulatory Commission (NRC).
Unit 1 was manually tripped from 43% power at 5:44 a.m. CST. “The reactor was manually tripped due to operator judgment during control issues with the Integrated Control System (ICS) during a planned down-power for Electro-Hydraulic Control (EHC) system maintenance. CV-2672 B, low load control valve, failed to close,” according to an event report filed with NRC.
“Subsequently, CV-2674 B, low load block valve, began to close and caused a loss of feed to E-24B Steam Generator,” the report indicated.
“No additional equipment issues were noted,” NRC said. All control rods fully inserted. Decay heat is being removed via the steam dump valves to the main condenser. Unit 1 is in a normal shutdown electrical lineup.
Unit 2 was not affected by the transient on Unit 1.Unit 2 continued to run at 100%. Unit 1 was still listed at zero power early Dec. 16. The company notified the State of Arkansas.
Arkansas Nuclear One Units 1 and 2 are both pressurized water reactors (PWRs). Together the two units have a generating capacity of roughly 1,800 MW. Unit 1 completed its last refueling outage in March of this year, according to Nuclear Energy Institute (NEI) data.