Beginning Sunday, Kansai Electric Power planned to gradually take offline the No. 4 reactor at its Oi nuclear plant in Fukui prefecture in western Japan. Officials at the utility expected the reactor to stop power generation after several hours, before coming to a complete stop early Monday.

Industry projections for a restart vary from December this year to mid-2014. It's not clear when the 12 Japanese reactors currently seeking permission to restart might receive it, with some of the stations also approaching the end of their recommended 40-year lifespans.

Prime Minister Shinzo Abe supports nuclear power, which used to supply around 30 percent of Japan's energy, but public opposition to atomic energy is strong after the 2011 Fukushima meltdown. The disaster was triggered by the major March 11 earthquake and tsunami, when water flooded and disabled Fukushima's cooling systems. Nobody is known to have died as a result of the meltdown, although thousands of people were forced to leave their homes and some are yet to return.

Since Fukushima, Japanese safety standards have been tightened and operators also need the green light from local governments to put idle plants back on the grid.

The stricken Fukushima site remains in the headlines owing to problems storing radioactive water that was used to cool the reactor. Abe famously told the International Olympic Committee last week that the situation at Fukushima was "under control," and would have no effect on the 2020 Olympics awarded to Tokyo this month. With the government assisting Fukushima operator TEPCO in its bid to keep the contaminated water in protective tanks and out of the sea, Abe's comments prompted some critical domestic headlines.

No blackouts, but higher bills

Japan last went without nuclear energy in May and June 2012, when the country's 50 commercial reactors stopped for maintenance. Public protests then opposed restarting the plants. Government and industry officials voiced concerns that Japan could experience major blackouts without nuclear power, particularly in the western region, which relies heavily on nuclear energy. Those fears proved unfounded, albeit at the cost of steeply rising electricity bills as Japan imports other power sources.

The 2012 halt in nuclear power production ended when the government gave approval for Kansai Electric to restart the No. 3 and No. 4 reactors at the Oi plant in July 2012, arguing that the energy demands of the coming winter would require nuclear power. Japan's previous government had pledged to phase out nuclear power after Fukushima, but then lost to Abe in last year's general election.

Japan has turned to expensive fossil-fuel imports and other solutions, tying to fill the gap left by the shutdown of atomic plants. Utilities have raised power fees to cover increased fuel costs. In 2011 and 2012, Japan posted two consecutive years with a trade deficit after more than three decades of uninterrupted surpluses, with power, quake rebuilding efforts and difficult ties with China among the key factors for this change.

mkg/msh (AFP, AP, dpa, Reuters)