Shikoku Electric Power Co. restarted on Saturday a reactor at the Ikata nuclear power plant in western Japan after a suspension of nearly one year due to a high court order.
The restart of the No. 3 unit at the plant in the town of Ikata in Ehime Prefecture, announced by the power company after midnight, came after a Japanese high court accepted an appeal by the utility late last month, ruling there are no safety risks associated with potential volcanic activity in the region.
Shikoku Electric said the No. 3 unit reached criticality, a controlled self-sustaining nuclear fission chain reaction, on Saturday evening as planned.
The company said it will start producing and transmitting electricity on Tuesday, before possibly putting the reactor into commercial operation Nov. 28.
The decision by the Hiroshima High Court was an about-face from its provisional injunction issued last December that ordered the power company to halt operation of the No. 3 unit, capable of generating 890,000 kilowatts of electricity, until Sept. 30 following a request from a local opposition group.
The group had argued that Shikoku Electric underestimated the risk of pyroclastic flows reaching the plant if a big eruption occurred at the caldera of Mt. Aso, which is about 130 kilometers away.
The temporary suspension order was the first in which a Japanese high court banned operations at a nuclear plant since the 2011 meltdowns at the Fukushima Daiichi complex.
But the high court said Sept. 25 that the group's claim of a possible destructive volcanic eruption during the plant's operating period has no satisfactory grounds and there is a small chance of volcanic ash and rocks reaching the facility.
The reactor had been idle for maintenance since October last year. Before that, it had gone back online in August 2016 after clearing stricter safety regulations implemented in the wake of the Fukushima nuclear disaster.
Ehime Gov. Tokihiro Nakamura told reporters Friday in the town that the prefectural government will ask the power company to take "thorough safety measures."
"We'd like Shikoku Electric to constantly pursue improvements in safety and reliability, and information disclosure with high transparency," Ikata Mayor Kiyohiko Takakado said in a statement released Saturday.
In front of the main gate of the power plant, which is located where the Sadamisaki Peninsula joins the western part of Shikoku island, about 50 people staged a protest against the restart of the No. 3 unit.
If a serious accident occurred, about 4,500 residents living on the Sadamisaki Peninsula to the west of the power plant would likely be isolated. Also, a major active fault runs near the power plant.
Shikoku Electric had already decided to decommission the aging No. 1 and 2 reactors at the plant.
The No. 3 unit becomes the eighth reactor to be in operation in Japan at a time when a large majority of reactors in the country remain offline following the 2011 nuclear disaster.
At the time of the meltdowns, Japan had 54 nuclear reactors in commercial use.