The permits had been granted by the country’s nuclear regulator, the Nuclear Regulation Authority. According to Kyodo news agency this is the first time a Japanese court has challenged safety assessments by the regulator under tougher safety standards imposed after the 2011 Fukushima-Daiichi disaster.
The court ruled in favour of about 130 plaintiffs who claimed that the Ohi-3 and -4 reactors are vulnerable to major earthquakes, according to Kyodo.
The court said the NRA’s decision had not taken into account necessary considerations in assuming the magnitude of earthquakes, Kyodo said.
The NRA, which said in 2017 that the reactors met new safety standards, will discuss with the Ministry of Justice whether it will appeal the ruling, a spokesman said.
“The court ruling is regrettable and unacceptable,” Kansai Electric said in a statement. “We will study details of the court decision and take appropriate actions after swiftly coordinating with the government.”
Ohi-3 and -4 are both 1,127-MW pressurised water reactor units. Ohi-3 began commercial operation in 1991 and Ohi-4 in 1993.
The two plants been offline for scheduled maintenance since earlier this year.
Japan has a total of 62 nuclear power units, but shut down all 42 reactors that were operating at the time after Fukushima-Daiichi. Thirty-three units have a licence to operate, although before units return to service they need to meet stricter safety standards introduced after the accident.
Nine units have been returned to service, but seven of those are offline again for regular maintenance or upgrades.
Before the Fukushima-Daiichi accident in March 2011 Japan’s nuclear fleet generated about 30% of the country’s electricity. According to the International Atomic Energy Agency that figure was about 7.5% in 2019.
Japan’s Nuclear Status
The nine units that have returned to service since Fukushima are Sendai-1 and -2, Genkai-3 and -4, Ikata-3, Ohi-3 and -4 and Takahama-3 and -4.
Sendai-1 Operational. Had been shut down earlier this year after failing to meet deadlines for safety improvements.
Sendai-2 Shut down earlier this year after failing to meet deadlines for safety improvements.
Genkai-4 Offline for regular maintenance.
Ikata-3 Offline after the Hiroshima High Court granted a provisional disposition order in January to stop the unit because it ruled Shikoku Electric’s preparations for a potential eruption of a nearby volcano, Mount Aso, are inadequate.
Ohi-3 Offline for regular maintenance.
Ohi-4 Offline for regular maintenance.
Takahama-3 Offline for regular maintenance and work to upgrade security measures.
Takahama-4 Offline for work to upgrade security measures.