Tohoku Electric Power Co. said it needs to inspect the No. 2 reactor at the Onagawa plant in Miyagi Prefecture after problems emerged with monitoring equipment. The reactor had resumed operations Oct. 29 after meeting post-Fukushima safety protocols.
The company said no problems were found in the reactor's core operations.
Workers had to manually extract a neutron detector device after failing to position it correctly inside the reactor.
The boiling water reactor, identical in design to the ill-fated Fukushima Daiichi units, was Japan's 13th reactor to restart under safety guidelines implemented after the 2011 disaster.
The Onagawa facility, located closest to the epicenter of the 2011 magnitude 9 earthquake, survived 13-meter tsunami waves before its shutdown.
The plant received regulatory approval in 2020 and local community support to restart, while its No. 1 reactor faces permanent decommissioning.
