A Japanese high court is about to rule whether operations at two reactors at the Genkai nuclear power plant in Saga Prefecture, southwestern Japan should be suspended.
The Fukuoka High Court will hand down its ruling later on Wednesday.
Residents in the host prefecture, the neighboring prefecture of Fukuoka and others had filed a petition for a court injunction against the restart of the plant's No.3 and 4 reactors. The residents say the reactors' safety in the event of powerful earthquakes or mega volcanic eruptions has yet to be ensured.
The appeal to the high court was made by 173 residents after a lower court dismissed their petition in 2017.
The two reactors came back online last year, after Japan's nuclear regulator said in 2017 that they met government requirements introduced after the 2011 accident at the Fukushima Daiichi nuclear power plant.
Currently, the No.3 reactor is offline to undergo regular inspection and will be back online next month. The No.4 reactor is operating but will go offline for inspection next month. The No.1 and 2 reactors are offline and set to be scrapped.
The residents say the operator, Kyushu Electric Power Company, has underestimated the size of tremors from possible quakes. The operator says its estimates are based on rational calculations.
The residents also argue that it is impossible to predict volcanic eruptions, while the operator says it confirmed that a mega-eruption is highly unlikely.
A separate lawsuit filed by residents and others over the use of a plutonium-uranium mixed oxide fuel at the No.3 reactor has already been dismissed.