Japan has given final approval for the restart of two nuclear reactors, a move that will end a total shutdown of the atomic power sector caused by safety fears raised by last year’s crisis at the Fukushima Daiichi plant.

Utility Kansai Electric Power began preparations on Saturday to bring the reactors at the Oi nuclear power station in western Fukui prefecture back online following the restart announcement by Yoshihiko Noda, prime minister.

“The company is striving to restart the Oi No 3 and No 4 reactors with a perfect system, while putting safety first,” Kansai Electric said.

The restarts will ease concerns about possible electricity shortages this summer in Kansai, an important industrial region. It will also raise the hopes of nuclear advocates in Japan and elsewhere that the long-term impact on the atomic sector of the failure of the tsunami-crippled Fukushima Daiichi plant will be limited.

However, it outraged anti-nuclear activists who say that seismically unstable Japan has not done nearly enough to ensure that surviving plants are truly safe.

Opinion polls suggest that most voters do not agree with Mr Noda’s decision, even though it came after a long and carefully choreographed political process by which the restarts were first backed by atomic regulators and by local and prefectural leaders.

Currently, all of the 54 reactors that supplied nearly one-third of Japan’s electricity before last year’s tsunami are offline, but utilities insist that they have learnt the lessons of the disaster and can ensure future safety.

Kansai Electric said that further tests and checks were required for the two Oi reactors, but it expected to be able to start generating electricity with the No 3 unit in early July, with No 4 following later in the month. It would take each reactor a few days after being restarted to reach full output, the company said.

Kansai Electric is more dependent on nuclear power than any other Japanese power company, with about half of its electricity coming from nuclear before the March 11 disaster last year.

While restarting the two Oi reactors should give Kansai Electric just enough capacity to meet standard summer demand, authorities are likely to be cautious about lifting calls for energy saving by customers given uncertainty about weather and other factors.

Anti-nuclear campaigners’ attention will now shift to other reactors around the country that might be restarted in coming months. Japanese media said leading candidates would be a reactor at Shikoku Electric Power’s Ikata plant in Ehime prefecture and two units at Hokkaido Electric Power’s Tomari plant on the northern island of Hokkaido.

Copyright The Financial Times Limited 2012