New Korean reactor cleared for start up

In January 2014, the government authorised construction of two APR1400 units as Saeul units 3 and 4 (formerly known as Shin Kori 5 and 6). Construction was originally scheduled to start in September 2014, but was then delayed. The regulator issued a construction licence in June 2016, and site works began immediately. Construction of unit 3 commenced in April 2017. However, following the change in government in June 2017, Korea Hydro & Nuclear Power (KHNP) decided to suspend work for three months. In October 2017, a government-organised committee voted 59.5% in favour of resuming construction of the two units. The committee stated that stability of power supply had been cited as a primary reason for the choice in survey responses. In September 2018, construction of unit 4 commenced.

Prior to the delay, commercial operation of the units was due in March 2021 and March 2022, respectively. In late December 2025 the Nuclear Safety and Security Commission (NSSC) issued an operating licence for Saeul 3, with fuel loading and approximately eight months of testing to follow. Commercial operation is expected around August 2026. Saeul 4 is expected to follow in late 2026.

"Since the operating licence was issued last year, the NSSC has been conducting pre-operational inspections (5 stages) on Saeul unit 3," the regulator said. "During this process, inspections were conducted on items that must be performed before criticality, such as nuclear fuel loading inspections and high-temperature functional tests. As a result, it was confirmed that reactor criticality can be safely achieved."

The NSSC said it plans to finally confirm the safety of the unit by conducting follow-up inspections, including power increase tests, from the time Saeul 3 achieves first criticality - a sustained chain reaction - until it enters commercial operation.

Once commercially operational, Saeul 3 will account for about 1.7% of South Korea's total power generation and 37% of Ulsan's electricity demand.

South Korea has four operational APR1400 units - Saeul units 1 and 2 (formerly Shin Kori 3 and 4) and Shin Hanul units 1 and 2, plus the APR1400s under construction as Saeul units 3 and 4. Four APR1400 units have also been built at the Barakah nuclear power plant in the UAE, which are all now in commercial operation.