The Fukuoka High Court upheld Wednesday a lower court decision rejecting an injunction request by local residents to suspend operation of nuclear reactors in Saga Prefecture, southwestern Japan.

Around 170 residents had appealed the Saga District Court's decision in 2017 rejecting an injunction to halt operation of the Nos. 3 and 4 reactors at Kyushu Electric Power Co.'s Genkai nuclear power plant due to safety concerns.

"I cannot recognize that the nuclear reactor facility lacks safety features and there are specific risks that could result in serious damage," said Presiding Judge Noriyuki Yamanouchi.

The plaintiffs argued that the utility has underestimated the potential effects of seismic ground motion, a key factor in a reactor's quake-resistance design, while degraded piping could lead to serious accidents.

In the appeal trial, the plaintiffs argued there was an additional volcanic risk from Mt. Aso in neighboring Kumamoto Prefecture, claiming that pyroclastic flows from possible large-scale eruptions could reach the plant.

The utility argued it adopts scientific methods based on experts' views to predict seismic shaking and is implementing necessary safety measures such as renewing piping when needed.

Units 3 and 4 at the plant have cleared Nuclear Regulation Authority screenings in accordance with safety standards revamped after the Fukushima nuclear disaster, which was triggered by the March 2011 earthquake and tsunami.

In dismissing the local residents' request in June 2017, the Saga District Court said the new standards were "reasonable" as they were based on the latest scientific knowledge and found no safety issues with the reactors.

The Nos. 3 and 4 reactors at the Genkai plant were reactivated in March and June last year, respectively. Operation of the No. 3 unit has been suspended since May this year due to regular inspections.

The No. 1 unit is undergoing decommissioning work due to aging and the utility has decided to decommission the No. 2 reactor.

Another group of local residents had filed for an injunction with the district court to stop operation of the nuclear plant, but the court rejected the request in March last year. A hearing of the appeal trial at the Fukuoka High Court was concluded in March.