A view of Hanbit nuclear power plant in Yeonggwang, South Jeolla Province/ Korea Times file

Korea's nuclear safety agency said Friday that it has approved the restart of the Hanbit four reactor upon the completion of maintenance inspections, after the reactor was idle for five years.

The 1,000-megawatt pressurized water reactor, which started commercial power generation in 1996, has been offline since May in 2017 as a number of cracks were found during a regular inspection.

The Nuclear Safety and Security Commission said the reactor in Yeonggwang, 320 kilometers south of Seoul, has met the criteria for resumption and is ready to restart.

Korea Hydro Nuclear Power, the operator of the reactor, said the Hanbit four reactor is expected to reach a "criticality" level on Friday afternoon and will be able to generate power on Sunday.

Criticality refers to the normal operating condition of a reactor, in which nuclear fuel sustains a fission chain reaction.

Currently, Korea operates 25 reactors, which generate about 30 percent of the country's electricity.

The Yoon Suk-yeol government has pledged to reverse the nuclear phase-out policy of the previous administration as part of its long-term plans to reduce its greenhouse gas emissions and better meet carbon neutrality goals.

The Shin Hanul No. 1 nuclear reactor in Uljin, 307 km southeast of Seoul, recently went into full operation, about 12 years after its construction began. (Yonhap)