South Korea gave the ‍green light on Tuesday (December 30, 2025) for ​the operation of a ‌nuclear reactor ​with an electricity output of 1,400 megawatts, the nuclear watchdog said, starting with a pilot run of six months.

In a statement, the ​Nuclear Safety and ⁠Security Commission said the Saeul 3 unit in the southeastern ​city of ⁠Ulsan, construction of which had begun in 2016, would expand to full operation ‌after its pilot run ‌over the next six months.

Apart from ‍Saeul 3, South Korea has 26 nuclear ‍reactor units and three more under construction, state-run operator Korea Hydro & Nuclear Power says on its website.

Nuclear makes up the bulk of South ⁠Korea’s energy mix, accounting for 31.7% of power ​generation in 2024, followed ⁠by gas and coal at 28.1% each, the industry ministry said in May.