Onagawa N-Plant’s No. 2 Reactor Likely to Shut Down Next Dec.; Company Cites Construction Delays of Antiterrorism Facilities

The Yomiuri Shimbun

14:32 JST, October 18, 2025

SENDAI — Tohoku Electric Power Co. said Friday it will likely shut down the No. 2 reactor at the Onagawa nuclear power plant in Miyagi Prefecture in December next year due to the company’s inability to meet a key construction deadline.

The company had initially planned to build mandatory facilities related to counterterrorism by Dec. 22 next year, but construction delays have pushed that date back to August 2028.

The reactor at the plant, which straddles Onagawa and Ishinomaki in the prefecture, resumed operations last October after 13 years and 7 months of inactivity, becoming the first reactor in eastern Japan to be brought back online since the 2011 Great East Japan Earthquake.

Installing facilities to deal with terrorism, including aircraft crashing into the facilities, is mandatory under new regulatory standards formulated in the wake of the 2011 accident at Tokyo Electric Power Company Holdings, Inc.’s Fukushima No. 1 nuclear power plant.

Installations must be completed within five years from the approval of a construction plan, and the reactor’s construction plan was approved on Dec. 23, 2021. A backup direct current power supply system is also required to be installed within the same timeframe, but its completion is expected to be delayed until March 2028.

Tohoku Electric cited labor shortages in the construction industry and the impact of overtime restrictions as reasons for the delay.

“We deeply regret having to shut down the plant, as the local community had high expectations for its stable operation,” Hiroaki Aoki, who heads Tohoku Electric’s Nuclear Power Division, said at a press conference in Sendai on Friday.

The company plans to increase the operating rate of its thermal power plants to cope with the shutdown period, saying that it will “firmly ensure its ability to supply power.”