South Korea's nuclear commission on Thursday approved the restart of three nuclear reactors that were suspended after being found to have used substandard parts approved under fabricated quality certificates.

The Nuclear Safety and Security Commission said it has approved the restart of the Shin Kori Reactor 1 and 2, and Shin Wolsong Reactor 1, effective immediately, as all problematic parts have been replaced. 

The three reactors had been undergoing a special inspection since late May when an internal investigation found that countless substandard control cables with fake quality certificates had been used in their construction.

Nearly 130 former and incumbent of the Korea Hydro & Nuclear Power Co. (KHNP), the state-run operator of nuclear power plants, and its suppliers have since been indicted, with hundreds of others also reprimanded. The scandal raised fears about the safety of nuclear power in South Korea, amid heightened anxiety about the energy source following the Fukushima Daiichi nuclear disaster in Japan.

The restart of the reactors, each generating about 1 million kilowatts of electricity, is expected to significantly improve the country's power supply level during the high-demand winter season.

The Ministry of Trade, Industry and Energy has said the country's peak demand for power is expected to reach 80.5 million kW at the height of the cold season, threatening to nearly deplete its total generation capacity of some 83 million kW before the restart of the three nuclear reactors.

South Korea currently operates 23 nuclear reactors that supply about 30 percent of its total electricity. Two other reactors are also temporarily out of operation for regular inspection and maintenance, according to the nuclear power plant operator.

The KHNP, meanwhile, said the Shin Kori Reactor 1 and Shin Wolsong Reactor 1 are anticipated to be fully normalized starting Tuesday, and the Shin Kori Reactor 2 will also begin full-fledged operation by Jan. 12. (Yonhap News)