Tohoku applied to the Nuclear Regulation Authority (NRA) in December 2013 for a safety assessment of Onagawa 2 - a 796 MWe boiling water reactor (BWR) - to verify countermeasures applied at the plant meet new safety standards. In late November 2019, the NRA approved a draft screening document that concluded the upgraded plant will meet revised safety standards, introduced in January 2013. In February 2020, the NRA approved the final screening report, clearing the way for the unit to resume operation. Tohoku was required to complete the countermeasure upgrades and obtain the approval of local authorities before restarting Onagawa 2.

Tohoku has now announced that it started fuel loading into the core of Onagawa 2 at 15:00 local time on Tuesday 3 September and that it expects to complete this work next week.

"We will continue to prioritise safety and thoroughly address each and every process, while also carefully communicating our efforts to local residents, as we work hard to restart operations," the company said.

On 18 July, Tohoku announced it had decided to revise the timing of fuel loading as part of the restart process for Onagawa 2 from "around July 2024 to around September 2024". It added: "As a result, we expect the plant to restart power generation around November 2024."

The Onagawa plant was the closest nuclear power plant to the epicentre of the earthquake and tsunami of 11 March 2011, but sustained far less damage than expected. The earthquake knocked out four of the plant's five external power lines, but the remaining line provided sufficient power for its three BWRs to be brought to cold shutdown. Onagawa 1 briefly suffered a fire in the non-nuclear turbine building. The plant was largely unaffected by the tsunami as it sits on an elevated embankment more than 14 metres above sea level, but the basement floors of unit 2 were flooded.