Ikata Nuclear Power Plant Operation Injunction Lawsuit

In 2026, residents of Ehime Prefecture filed a lawsuit at the Matsuyama District Court seeking a permanent injunction to halt operations of Shikoku Electric Power's Ikata Nuclear Power Plant Unit 3. The plaintiffs argued that the plant's safety measures were insufficient to withstand a potential catastrophic eruption of the nearby Mount Aso caldera, claiming the volcanic ash fall risk and seismic hazards were critically underestimated. They contended that the company's evacuation plans for a pyroclastic flow scenario were unrealistic and would expose residents to impermissible danger, thus violating personal rights to safety and security. The legal action was part of a sustained post-Fukushima citizen movement challenging Japan's nuclear energy policy through the courts, focusing specifically on the unique volcanic threats facing the Ikata facility located in a volcanically active region.

As of 2026, the Matsuyama District Court's decision is pending or has become a subject of intense legal debate. Following precedents from other nuclear injunction cases in Japan, the court was expected to intensely scrutinize the scientific rationality of the volcanic risk assessment. Any ruling either granting or denying the injunction would likely have been immediately appealed to the Takamatsu High Court, continuing a protracted legal battle over the plant's fate.

The central dispute was whether the Nuclear Regulation Authority's approval of Shikoku Electric's volcanic ash countermeasures and the plant's underlying safety assessment met the strict criteria required to protect citizens' personal rights. The case hinged on the predictability and severity of a caldera-forming eruption at Mount Aso, the credibility of the company's event tree analysis for ash ingress disabling critical safety equipment, and the feasibility of simultaneous evacuation for all residents during a massive volcanic disaster.

The lawsuit amplified the national debate on nuclear energy in a disaster-prone archipelago, specifically spotlighting the previously downplayed danger of volcanic caldera collapses. It galvanized anti-nuclear citizen groups and legal professionals, reinforcing the role of civil litigation as a primary check on regulatory decisions. For the host community of Ikata-cho, the case deepened local divisions between economic dependency on the plant and fears for safety, mirroring a nationwide divide and placing immense pressure on local consent politics for nuclear restarts.