TOKYO, Japan — Japan's enforced separation from nuclear power began with the triple meltdown at Fukushima Daiichi last March and was sealed late on Saturday night with the closure of its last working reactor, on the northern island of Hokkaido.
The closure of the 912-megawatt Tomari No. 3 reactor means that Japan, once unrivaled in its enthusiasm for building nuclear power plants, is without atomic energy for the first time since May 1970, when its two reactors briefly went offline for maintenance checks.
While environmental activists celebrated, others warned that the shutdown, combined with the government's failure to reassure the public over safety, has left the world's third-biggest economy susceptible to power shortages during what promises to be long, hot summer.
But for the estimated 5,500 people who marched through central Tokyo on Saturday, severing Japan's ties to nuclear power — the provider of almost 30 percent of its electricity before the March 11 disaster — is an unprecedented opportunity to transform energy policy.
"Now that the number of working reactors is zero, it should stay that way for good," said Kanako Tojo, a medical researcher who attended the anti-nuclear demonstration with her three young children. "I didn't have an opinion on nuclear power before Fukushima, but now I feel strongly that we need to ditch it for the sake of our children."
Satoru Hasegawa, an office worker, believed Japan could prove to other countries that it is possible to wean themselves off nuclear energy. "We have to at least try to make a go of it," he said. "It's now up to us to find an energy policy that works, but which doesn't harm the environment."
Their vision is by no means assured. The prime minister, Yoshihiko Noda, recognizes the need for Japan to lessen its dependence on nuclear power, but is lobbying for the restart of closed reactors to help utilities meet peak demand during the summer, when tens of millions will be turning to air conditions to take the edge off stupefying humidity.
Four of Japan's 54 reactors were damaged beyond repair when a 45-foot tsunami slammed into Fukushima Daiichi on the afternoon of March 11 last year. The remainder have been taken offline to undergo mandatory maintenance checks, with one plant, in Hamaoka, central Japan, shut down over safety fears.
None has been permitted to restart unless they pass stress tests introduced last July to gauge their ability to withstand events such as powerful earthquakes and tsunamis.
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Two reactors in Oi, western Japan, were the first to pass those tests, but Noda and a small team of ministers overseeing the nuclear crisis have failed to win local support for their restart.
To make up the shortfall in power production, Japan has dramatically increased its dependence on liquefied natural gas (LNG), coal and oil for use in thermal power stations. The value of its LNG imports rose 52 percent to 5.4 trillion yen in the 12 months through March this year.
The government hopes to have a clear idea of expected power shortages by the middle of this month. Preliminary data estimates a 5 percent shortage for Tokyo and a 16 percent shortfall in the Kansai region of western Japan — a $1 trillion economy that includes the industrial city of Osaka.
"I have to say we are facing the risk of a very severe electricity shortage," the economy, trade and industry minister, Yukio Edano, said, adding that the extra cost of importing fuel for use in thermal power stations could result in higher electricity bills.
The Japan Business Federation has led calls for the resumption of nuclear power generation, fearing electricity shortages and the rising cost of fossil fuel could derail a fledgling economic recovery. Its chairman, Hiromasa Yonekura, said the economy "could collapse'' unless nuclear reactors are reactivated, while Yoshito Sengoku, the acting president of the governing Democratic Party of Japan, likened the abandonment of nuclear energy to "mass suicide."
The Bank of Japan has warned that inadequate power supplies could hit production over the summer. "We must be mindful not just of such short-term effects but the chance (the power shortages) could hurt Japan's medium- and long-term growth expectations," it said in a recent report.
Importing fossil fuels may have sustained the world's third-biggest economy, but it has also cast doubt on Japan's ability to meet carbon emissions targets it signed up to in Copenhagen in 2009. The environment ministry projects that, without nuclear power, Japan will produce about 15 percent more greenhouse gas emissions this fiscal year than it did in the baseline year of 1990.
But a ministry panel has suggested that the country can still reduce its greenhouse gas emissions by 25 percent by 2030 from 1990 levels without nuclear power, through energy saving and the quicker adoption of renewables.
"Despite the closure of all reactors, the security of the electricity supply is not under threat," said Hisayo Takada, climate and energy campaigner for Greenpeace Japan. "The 2012 summer peak in electricity demand can be managed with energy efficiency, proper load balancing, and energy conservation.
"The Fukushima Daiichi disaster has shown us that Japan's nuclear plants are in no shape to deal with another major earthquake — which experts warn is almost certain to happen in the next few years.
"Should another meltdown occur, it is likely that it will break the back of Japan's economy, and many more people will suffer. It is simply not worth the risk when the clean and safe alternative of renewable energy is at our fingertips."
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