The Mito District Court ruled Thursday that Japan Atomic Power Company (JAPC) cannot reactivate its idled Tokai No. 2 nuclear power plant in Ibaraki Prefecture. The No. 2 unit has been idled since the 2011 Tohoku earthquake, which also heavily damaged the Fukushima Daiichi Nuclear Power Plant Complex.

The Tokai station originally contained two reactors, the first of which has been dismantled. However, JAPC sought to continue operation of No. 2, arguing that updated safety procedures and facilities for managing serious accidents had been developed. No. 2 was built in 1978 and is approaching its 40-year operational lifespan. However, aged nuclear reactors in Japan can be granted a single extension of up to 20 additional years, pending regulatory approval from the Nuclear Regulatory Authority.

Among the safety upgrades that JAPC planned to install were extra tsunami protection for power supplies and water pumps, newly constructed seawalls, and diversified power and water sources to protect reactor safety in the event of a power failure. Such concerns address shortcomings that played a major role in the Fukushima Daiichi disaster, where power failures caused a loss of reactor core cooling and subsequent meltdowns.

While JAPC argued that Tokai No. 2 was safe, and the Nuclear Regulatory Authority had previously approved the reactor restart, the Mito court was not persuaded by the company’s assertions and ordered an injunction against reopening the plant, with Judge Eiko Maeda finding that JAPC’s evacuation planning “lacks safety.” JAPC has announced that they plan to appeal the decision to the Tokyo High Court.