Concerns over safety in event of eruption at nearby Mount Aso The Ikata nuclear power station in southwest Japan. The Hiroshima High Court on Friday revoked a lower court decision and ordered Shikoku Electric Power Company to suspend operation of the Ikata-3 nuclear power unit in Ehime Prefecture, southwest Japan, because the company’s preparations for a potential eruption of a nearby volcano, Mount Aso, are inadequate.

The utility had claimed the reactor is safe to run because operators would have enough advance warning of an eruption to take safety measures.

The ruling marks the second time the high court has ordered a halt of Ikata-3.

The reactor had been shut for regular maintenance work since late December and was scheduled to restart within a couple of months, but now must remain offline pending an appeal.

In a statement, Shikoku Electric said the decision by the Hiroshima High Court is “extremely regrettable” and pledged to “promptly file an appeal so that the order can be revoked as soon as possible”.

In making its decision, the court considered whether the operator and the regulator’s regulations and risk estimates for a potential eruption at Mount Aso, about 130 km to the west of the station, were adequate.

Ikata-3, an 846 MW pressurised water reactor unit that began commercial operation in 1994, is the only unit in commercial operation at the Ikata station. Two others have been permanently shut down.

It resumed commercial operation in 2018 under stricter safety regulations introduced after the 2011 Fukushima-Daiichi nuclear crisis led to a nationwide shutdown of nuclear power plants.