The Hiroshima High Court has issued a provisional injunction ordering Shikoku Electric Power Co. to halt operation of the No. 3 reactor at its Ikata Nuclear Power Plant in the western Japan prefecture of Ehime. Both the utility and its government regulator must seriously reflect on this ruling, the second of its kind for the reactor.
In the latest decision, the high court accepted the possibility that the Japan Median Tectonic Line situated off Ikata is an active fault, and deemed operations at the reactor to pose a danger to local residents.
The high court also pointed out that research that the utility conducted to determine whether active faults were situated near the nuclear plant were insufficient. If further, asserted that the Nuclear Regulation Authority (NRA) either made a mistake or failed to sufficiently evaluate risks when concluding that there was no problem with the utility’s research.
In December 2017, the Hiroshima High Court similarly issued a provisional injunction ordering a halt to operations of the same reactor. At the time, the court pointed out that the area where the Ikata nuclear complex was situated was inappropriate as a site for a nuclear plant because pyroclastic flows could hit the premises if Mount Aso in the southwestern Japan prefecture of Kumamoto erupted. The 2017 decision was subsequently overturned on appeal by the utility. In the latest decision, however, the court determined that Shikoku Electric underestimated the impact of a possible eruption of Mount Aso.
Ikata’s No. 3 unit is currently offline because it is undergoing a regular inspection. The utility had planned to resume commercial operation of the reactor on April 27, but the latest injunction stated that the reactor must remain offline until the Iwakuni branch of the Yamaguchi District Court rules on a full-scale lawsuit demanding that operations at the reactor be banned.
The Ikata Nuclear Power Plant in fact faces more serious safety problems than other atomic power stations. It is situated at the base of the Sadamisaki Peninsula, which is about 40 kilometers long and whose narrowest part is only 800 meters wide. If an accident were to occur at the plant, residents’ evacuation routes could be cut off.
Even if the Japan Median Tectonic Line were deemed inactive, another one of Japan’s largest active faults, situated some 6 to 8 kilometers off the coast of the plant site, could still pose a threat to the complex. Moreover, experts have predicted that a powerful Nankai Trough earthquake is highly likely to occur within the next three decades. It is feared that if such a temblor were to strike the area, it could affect the plant.
With these factors in mind, it is understandable that the high court demanded that not only Shikoku Electric, but also the NRA carry out stricter safety inspections at the Ikata plant. The NRA must not make light of the decision.
Currently, six nuclear reactors are in operation in Japan while 12 others are undergoing inspections to see if they meet new regulatory standards implemented after the Fukushima nuclear crisis broke out in March 2011. All possible measures must be taken to ensure the safety of nuclear plants by fully utilizing lessons learned from the crisis.