A nuclear reactor in northeastern Japan, hit by the devastating 2011 earthquake and tsunami, was restarted Wednesday after a temporary suspension due to an instrument problem, the plant operator said. In late October, the Onagawa plant's No. 2 unit became the first reactor to operate in eastern Japan since the natural disaster, but it was halted earlier this month after a checking device became stuck inside the containment vessel. File photo taken on Oct. 24, 2024, shows the Onagawa nuclear power plant in Miyagi Prefecture. (Kyodo)

SENDAI - Tohoku Electric Power Co., the operator of the Onagawa nuclear plant in Miyagi Prefecture, said it detected that a nut on a joint of a guide tube -- designed to send devices into the reactor -- was not tightened adequately when it was replaced in May.