A Hiroshima court ruled on 13 December that a nuclear reactor in southwestern Japan should not be allowed to operate because it is too close to an active volcano and could be affected by a major eruption.
The injunction ordered by the high court is likely to force the Unit 3 reactor at the Ikata nuclear plant in Ehime prefecture to stay offline after its regular inspection ends in February. The court said the nuclear regulators' risk estimate for Mount Aso, 130 km southwest of the plant, was inadequate, citing an eruption thousands of years ago that caused pyroclastic flows that exceeded that distance.
Judge Tomoyuki Tanoue ruled that the plant's operator, Shikoku Electric Power Co., had underestimated the potential impact of a ‘cauldron’ explosion at the volcano (that is, in the volcano’s crater), and said the possibility of a pyroclastic flow reaching the reactor is "not small enough." The judge also said that the Nuclear Regulation Authority's safety approval of the reactor was "irrational" and that the lives of the plaintiffs could be endangered by radiation in the event of a major accident.
The decision reverses a lower court ruling and upholds the plaintiffs' request for an injunction through September to protect the safety of residents while their lawsuit demanding a permanent shutdown is pending.
An extended closure of Unit 3 would be a major business loss for Shikoku Electric, and the utility said it will appeal the decision. Shikoku had earlier decided to decommission the 40-year-old Unit 1 reactor, while the Unit 2 reactor has been shut down since the 2011 Fukushima disaster.
All operating reactors in Japan were temporarily stopped for safety checks after Fukushima. Five reactors, including Ikata No. 3, have since resumed operation under a tougher 'post-Fukushima' safety standard, with seven others in the final stages of restarting. Dozens of lawsuits and injunction requests have been filed in Japan over safety concerns since the Fukushima disaster, slowing down a government push for more reactors to be put into operation.