Tokyo Electric Power Company says it will restart a reactor Monday after an alarm caused it to halt its initial reactivation last month.
TEPCO made the announcement on Friday regarding the No.6 reactor at the Kashiwazaki-Kariwa nuclear power plant in Niigata Prefecture.
The operator had restarted the reactor on January 21, but shut it down about 29 hours later, after an alert sounded while control rods were being extracted.
Officials found a fault in the alarm settings for an inverter that regulates speed on a motor that moves a control rod.
The inverter has no defect, but the alarm was programmed to be set off when it detects rare electric current disruptions that occur when the motor is started.
TEPCO says the alarm was installed in 2023 mainly to be used for inspections, and officials concluded that its removal will not affect the motor and inverter's safety.
The company also says it has deactivated the alarm for all control rods and that the trouble has been resolved.
TEPCO now aims to resume commercial operation of the reactor on March 18. That is 20 days later than initially planned. It submitted a revised schedule to the Nuclear Regulation Authority on Friday.
The chief of the Kashiwazaki-Kariwa plant, Inagaki Takeyuki, says he understands the safety concerns among residents around the facility.
He also says TEPCO will provide them with information and properly handle any problem during steps toward commercial operation.

Quiz 1:
Why did the No.6 reactor at the Kashiwazaki-Kariwa nuclear power plant initially halt its reactivation last month?
A. A defect was discovered in the reactor itself.
B. An alarm sounded while control rods were being extracted.
C. Residents staged a protest against the restart.
D. The Nuclear Regulation Authority ordered the shutdown.

Quiz 2:
What was the nature of the fault identified following the alarm activation?
A. The inverter controlling the motor was defective.
B. The control rods themselves had a mechanical failure.
C. The alarm settings were incorrectly programmed to detect rare electric current disruptions.
D. The motor moving the control rod was experiencing overheating.

Quiz 3:
When does TEPCO now aim to resume commercial operation of the reactor?
A. March 18
B. January 21
C. February 6
D. February 29



[Answer block]
Answers:
Quiz 1: B
Quiz 2: C
Quiz 3: A