Nuclear Reactor Threatened by Volcano

Hiroshima High Court on Wednesday approved the appeal of residents around Ikata Nuclear Power Plant in Ehime to halt operation of the plant and ordered its owner, Shikoku Electric Power Company, not resuming the operation of Reactor #3 until the end of next September. It was the first case for a high court in Japan to issue an order of stopping nuclear power plant. The decision may affect other similar lawsuits all around Japan.

The lawsuit was filed by the residents in the cities of Hiroshima or Matsuyama. Hiroshima Regional Court and Matsuyama Regional Court have decided earlier this year that SEPCO did not have to stop the reactor of Ikata Plant, dismissing the demand of the plaintiffs. Hiroshima High Court overturned those decisions of lower courts and new decision was immediately activated. It is inpossible for the company to resume operation #3, which is under usual inspection.

The greatest reason of halting the operation was possibility of great explosion of Mt. Aso, located 130 kilometers away from the plant. The court decision strictly applied internal standard of Nuclear Regulation Authority that regulated operation of nuclear reactor within 160 kilometers from an active volcano. “The possibility of occurrence of a great pyroclastic flow from Mt. Aso, which is paralleled with an old case reaching the location of the site 90 thousand years ago, cannot be regarded as small enough. Building of a nuclear power plant there cannot be approved,” said Chief Judge Tomoyuki Nonoue.

The court indicated that volume of eruption from Mt. Aso would be doubling that of Mt. Kokonoe, which had been assessed by SEPCO, accusing the company of its assessment on accumulation or air pollution of falling ashes as too small. It also criticized NRA of the irrationality of a decision that Ikata Plant had cleared new regulation standard established after the severe accident in First Fukushima Nuclear Power Plant.

SEPCO was surprised with the decision based on a volcanic explosion 90 thousand years ago. “We cannot accept it. It affects our business,” told a board member of SEPCO. “90 thousand years have passed from the catastrophic explosion in Mt. Aso and there is not major structure of magma beneath it. We have concluded that no catastrophic explosion would not happen during the period of its operation,” told one NRA officer. But the court required them to assume the greatest explosion in the past.

Mt. Aso includes other operating nuclear power plants within 160 kilometers of distance. The decision can be applied to those plants, possibly causing new lawsuits to halt the operation. It can also make power companies reluctant to resume nuclear reactors, which cost for safety exceeds ¥100 billion for each. But it is fundamentally unreasonable for a country of volcanic archipelago to have a number of nuclear power plants anyway.