Photo/IllutrationLawyers hold up signs that say a request for a temporary injunction on the Ikata nuclear plant had been rejected on March 30 by the Hiroshima District Court. (Koichi Ueda)

HIROSHIMA--The district court here on March 30 rejected a request for a temporary injunction halting operations of the No. 3 reactor at the Ikata nuclear power plant in Ehime Prefecture, upholding the operator's anti-seismic designs.

The main point of contention in the closed court sessions was if the basic earthquake ground motion figure used by Shikoku Electric Power Co., the plant operator, was appropriate as the basis for its anti-seismic design for the reactor.

The four plaintiffs, who are residents of Hiroshima and Matsuyama, argued that the Ikata plant is located in the region that is vulnerable to a potentially massive Nankai Trough earthquake. The plant also faces a second quake risk because it is located close to the Median Tectonic Line, the longest fault system in Japan.

Based on those circumstances, the plaintiffs argued that the maximum 650 gals, a measure of ground acceleration, used by Shikoku Electric as the basic earthquake ground motion, was an underestimation when compared to the figures used for safety inspections of other nuclear plants that have been made stricter following the 2011 accident at the Fukushima No. 1 nuclear power plant.

However, the Hiroshima District Court ruled that Shikoku Electric used reliable measures in calculating the basic earthquake ground motion. The court also ruled that there were no irrational points in the decision made by the NRA to approve the safety screening for the Ikata reactor based on the new standards.

The temporary injunction request, filed on March 11, 2016, the fifth anniversary of the Great East Japan Earthquake, was rejected because the court ruled that the rights of the plaintiffs were not likely to be violated by the safety measures.

The ruling follows a decision on March 28 by the Osaka High Court that overturned a ruling in March 2016 by the Otsu District Court that issued a temporary injunction against the No. 3 and No. 4 reactors at the Takahama nuclear plant in Fukui Prefecture.

Other residents have submitted requests for similar temporary injunctions against the Ikata plant in the Matsuyama and Oita district courts as well as the Iwakuni branch of the Yamaguchi District Court.

The plaintiffs in the Hiroshima case have also filed a separate lawsuit with the Hiroshima District Court seeking to halt operations of the No. 1 to No. 3 reactors at the Ikata plant. No ruling has yet been made on that lawsuit.