The Hiroshima High Court on Wednesday revoked a lower court decision and ordered the suspension of a nuclear reactor at Shikoku Electric Power Co.’s Ikata power plant in Ehime Prefecture, dealing a blow to the government and utilities that are aiming to bring more reactors back online.

The high court suspension order — the first in a series of similar injunctions — mandates that the plant operator shutter the No. 3 unit at the Ikata power plant until the end of September next year.

The ruling blocks the planned resumption in January of the unit, which is currently offline for regular checks after it was restarted in August 2016.

Shikoku Electric said the court’s decision is “unacceptable” and plans to file an appeal.

The court questioned a decision by the Nuclear Regulation Authority that potential risks associated with volcanic eruptions would not breach the stricter regulations introduced following the 2011 Fukushima nuclear crisis.

“Specific threats to the lives and health of residents are anticipated,” the court said.

The latest decision follows a ruling by Otsu District Court in March 2016 that ordered Kansai Electric Power Co. to suspend two reactivated nuclear reactors at its Takahama plant. The district court decision was later overturned by the Osaka High Court.

The Fukushima nuclear crisis led to a nationwide halt of nuclear plants, but the government is looking to produce 20 to 22 percent of the country’s electricity supply using nuclear power by 2030.

The focal points of Hiroshima High Court’s decision Wednesday included whether estimates by the plant operator, Shikoku Electric Power Co., of the potential size of possible earthquakes, were reasonable, and whether safety screening conducted under stricter regulations set after the 2011 Fukushima nuclear disaster was credible.

Risks predicted in the event of a nuclear accident or natural disasters such as a volcanic eruptions were also contested.

The plaintiffs claimed that in calculating the size of a potential earthquake, the utility had underestimated the fact that the reactor lies above the epicenter of an anticipated Nankai Trough mega-quake, and that it is located near a geologic fault.

They added that the post-Fukushima regulations cannot ensure safety, and that major damage could occur at the time of an accident or disaster because the regulations were compiled without thoroughly determining the cause of the 2011 disaster.

But Shikoku Electric maintains that it has ensured safety and that there is no danger.

Hiroyuki Kawai, the lawyer representing the plaintiffs said, “Our plea was understood. We could protect the Seto Inland Sea. It is our victory.”

The plaintiffs had said that if the Ikata plant, which faces the Seto Inland Sea, was to be severely damaged, nuclear substances could spread and contaminate waters in the area.

In March, the Hiroshima District Court found that the new regulations set by the Nuclear Regulation Authority and Shikoku Electric’s estimates of a possible earthquake and tsunami were reasonable.

The district court had turned down the request to halt the reactor, saying, “There is no specific risk that residents will suffer severe damage due to radioactive exposure associated with an accident.”

Following the checks, Shikoku Electric had been expected to bring the reactor back online on Jan. 22 and resume operations on Feb. 20.

The plaintiffs were four residents from Matsuyama in Ehime and Hiroshima, located on the opposite side of the Seto Inland Sea to the nuclear plant. Similar injunctions have been contested at the Takamatsu High Court, Oita District Court and the Iwakuni branch of Yamaguchi District Court.