HIROSHIMA -- The Hiroshima High Court ruled on Sept. 25 to allow the restart of the No. 3 reactor at the Ikata nuclear power plant in western Japan's Ehime Prefecture.

The ruling overturns an injunction the same court issued in December last year ordering the reactor's operations suspended due to the potential impact from future eruptions of Mt. Aso to the southwest.

The high court's reversal of its earlier ruling could have far-reaching repercussions because similar legal battles seeking the suspension of nuclear power plants are ongoing nationwide. Many such lawsuits have been filed since the March 2011 triple-meltdown disaster at Tokyo Electric Power Co.'s Fukushima No. 1 Nuclear Power Plant, which resulted in extensive radioactive fallout. The incident triggered massive evacuations and rendered large swaths of land around the facility difficult to return to for former residents.

The December 13 injunction by the Hiroshima High Court made a strict application of Nuclear Regulation Authority rules, and stated that for volcanoes within a 160-kilometer radius of a nuclear station, operators must consider the possibility of an eruption equivalent to the biggest one in the past. The court determined that pyroclastic flows from Mt. Aso in southern Japan's Kumamoto Prefecture could reach Ikata, some 130 kilometers away, should the mountain have a catastrophic eruption similar to one it had about 90,000 years ago, and ruled the plant's location "inappropriate."

The high court also judged back then that its injunction would be valid until the end of September this year, out of consideration for the possibility that the Hiroshima District Court could issue a different decision on a similar lawsuit seeking the suspension of the Ikata plant.

In two hearings before the high court issued its Sept. 25 decision, Shikoku Electric argued that Mt. Aso does not have a major pool of magma under its caldera and therefore is "extremely unlikely" to cause a catastrophic eruption during the operational life of the plant's No. 3 reactor. The high court, presided over by Judge Masayuki Miki, accepted the utility's assertion.

Residents near the Ikata plant, who are suing to suspend the plant's operation, countered that the possibility of such an eruption cannot be denied as no reliable long-term prediction method exists for volcanic eruptions. The plaintiffs also emphasized that it was "common sense" to consider that pyroclastic flows from the Mt. Aso eruption 90,000 years ago reached the place where the Ikata plant now stands.

Another issue of contention in the case was that earthquakes may damage the facility. Shikoku Electric argued that their understanding of possible temblors affecting the plant is based on detailed research and is thus sufficient. The residents insisted that the power utility underestimated the intensity of possible earthquakes and the damage they could cause.

A separate lawsuit seeking the suspension of the Ikata plant from Oct. 1 is pending in the Hiroshima District Court. Similar legal actions opposing the resumption of the nuclear power station are underway at the Takamatsu High Court in Kagawa Prefecture, the Iwakuni branch of the Yamaguchi District Court in Yamaguchi Prefecture, and the Oita District Court in the southern Japan prefecture of Oita. The Oita court is scheduled to issue a decision on Sept. 28.

(Japanese original by Misa Koyama, Hiroshima Bureau)