The Hiroshima High Court on Friday revoked a lower court decision and ordered Shikoku Electric Power Co. to suspend its only operable nuclear reactor in Ehime Prefecture because its preparations for a potential eruption of Mount Aso are inadequate.
The utility has previously claimed the reactor is safe to run because it would have enough advance warning of an eruption to take safety measures.
The high court also said the Nuclear Regulatory Agency's regulations were unreasonable.