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Japan’s nuclear sun to set?

A week can be a long time in politics, so today’s announcement by the Japanese government that it intends to phase out its 50 remaining nuclear reactors by around the 2030s is perhaps much less of a certainty than it might at first appear. Under the plan, existing reactors would be phased out when they reach 40 years of age so causing a gradual fall in nuclear’s share of electricity generation in Japan, as no new reactors are built to replace them.

Many of Japan’s reactors are relatively young meaning that any phase-out will bite hardest quite a fair bit down the line – see the graph belo,w which gives a snapshot of the age of Japan’s power reactors – leaving potential scope for Japan’s nuclear policy to shift in the future under different administrations, and circumstances. (In passing, several of Japan’s reactors were built in the last decade, and two reactors are under construction, so under the 40-year rule would persist beyond 2040). In contrast, Germany which last year decided to phase out its then 17 nuclear reactors intends to do so by 2022 – see “The knock-on effects of Germany’s nuclear phase-out” (almost all of its reactors were built in the 1970’s and are nearing the end of their lifetimes).


Indeed, in the short-term, the pledge to phase-out nuclear energy may provide the Japanese government with political cover to begin restarting reactors, the last of which was shut down in May (see ‘Japan switches off its last nuclear reactor). The reactors, closed for routine maintenance, would usually be reopened immediately after this was completed, but all will need to meet new safety tests and rules to be implemented this autumn before being restarted.

It’s not surprising that Japan is rethinking its energy strategy following last year’s disaster at the Fukushima Daichii power plant (see Nature‘s news special on the Japan earthquake and nuclear crisis). Polls show that the accident has soured public opinion of nuclear energy in Japan, and today’s announcement bows to that public mood.

Few details of how the Japanese plan would be implemented are available but the government is expected to release a detailed strategy by the end of the year. If the zero-nuclear option does comes to pass in Japan, it would be a massive policy turnaround compared with 2010 when the country planned to add 14 new reactors to its fleet of 54, and boost nuclear energy’s share of electricity generation from around 29% to 45% (see ‘Japan plans nuclear power expansion‘). Japan’s nuclear electricity output is not very high as a percentage of the total (see figure below), but in absolute terms with 44215 MW of nuclear output, Japan is third only to France (63130 MW) and the United States 101465 MW) (for statistics on current numbers of reactors by country, and output, see here)


It’s been clear, though, that since the Fukushima disaster occurred nuclear energy was set to play a lesser role in Japan’s electricity mix in the future. A proposal for nuclear energy to be phased out was one of four energy futures scenarios considered by the government in June (see ‘Japan considers nuclear-free future‘). Any large reduction in nuclear power would need to be compensated by increased generation from fossil fuels, and a huge increase in the use of renewable energies, combined with increases in energy efficiency.

It remains to be seen what impact the plan will have on Japan’s pledge to reduce greenhouse gas emissions by 25% by 2020 (see ‘Japan environmental plan includes controversial greenhouse-gas target‘) although World Nuclear News today reported that the new plan could reduce the target to 10% by 2030.


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