ISHINOMAKI, Miyagi Prefecture—Tohoku Electric Power Co. announced Nov. 3 that it has shut down the recently restarted No. 2 reactor at the Onagawa nuclear power plant due to unspecified equipment problems.

The company said no radiation leaks occurred in the environment of the factory located in the cities of Onagawa and Ishinomaki in Miyagi Prefecture.

Tohoku Electric restarted the No. 2 reactor on October 29 for the first time in 13 years and seven months. Electricity production was scheduled to begin on November 3.

According to the company, equipment was inserted into the reactor to check whether a detector measuring neutrons was normal. But the inserted equipment stopped working in the middle of the process.

The material was removed and recovered manually.

The company said it had shut down the reactor and would postpone power generation until the cause of the problem was determined.

On October 30, the reactor reached a critical level, in which a fission chain reaction can continue on its own, and the turbine started up on November 1.

Tohoku Electric initially planned to start power generation on November 7. But as inspections and other processes went smoothly, the schedule was moved forward to November 3.