"The Hamaoka plant is indispensable for us to achieve a stable supply of electricity and carbon neutrality," President Kingo Hayashi told a news conference.

The plant has been idle since 2011 when the nuclear disaster at Tokyo Electric Power's Fukushima Daiichi power station led to an eventual shutdown of all reactors in Japan.

Nearly 10 years since Chubu Electric submitted its first application to restart the No.4 unit at Hamaoka a review by the Nuclear Regulation Authority (NRA) is still ongoing with the timing of an approval uncertain.

The utility has been locked in a dispute with the regulator for years over disaster resilience measures at the Hamaoka plant, which is located near a major tectonic plate boundary.

"The review is progressing steadily, but there are still many issues to be addressed, including a plant review and consensus from local communities," Hayashi said.

Asked when it aims to restart the unit, Hayashi said: "We don't have a timeline of when yet."

(Reporting by Yuka Obayashi; editing by Jason Neely)