South Korea's nuclear regulator said Friday that it had renewed the operating license of its second-oldest nuclear power plant until 2022, in a decision that upset opponents of nuclear energy.

The Nuclear Safety and Security Commission said that seven of nine commissioners voted to approve to restart the Wolsong No. 1 reactor located in Gyeongju city, 275 kilometers (170 miles) south of Seoul.

It was the first such decision in South Korea since safety concerns about older plants and nuclear energy were raised following the meltdowns at Japan's Fukushima Daiichi reactors in 2011.

The nuclear regulator said in a statement that it reviewed the plant's safety in the event of natural disaster and other legal standards. Two commissioners who asked for more time to review the reactor's safety abstained from the vote at the end of the 14-hour meeting.

South Koreans were sharply divided over the fate of the plant that had operated for 30 years until its license expired in 2012. The plant, which began operation in 1982, is South Korea's first nuclear power plant using Canada's heavy water technology.

Opponents to the restart of the plant said it had failed to meet the latest safety standards that came into effect after the plant went into operation, and that residents near the power plant want it to shut down. Supporters said the safety concerns were overblown and that South Korea, which imports oil and gas, needs the cheap energy source.

Korea Hydro and Nuclear Power, the state-owned monopoly nuclear plant operator, spent 560 billion won ($509 million) to upgrade the reactor before seeking the approval.

Nuclear energy provides about one-third of the country's electricity.