The March 11 disasters sparked a nuclear crisis in the nation and a backlash that postponed plans to reopen reactors shut down because of damage, inspections or unrelated technical problems.

Kyushu Electric Power Co. said it has started generating electricity from the No. 4 reactor on November 1 at the Genkai nuclear power plant in western Japan.

The reactor was taken offline in October after technical problems.

Company officials won approval from a local governor and a mayor to bring the reactor online, Japan's Kyodo news agency reported.

Tokyo Electric Power Co. said on November 2 it detected the chemical element xenon in a nuclear reactor at the crippled Fukushima Daiichi nuclear power plant, a sign that nuclear fission may have occurred.

The power company said it began injecting boric acid into the cooling system and has not seen a temperature change that would suggest nuclear fission has occurred.