On 10 April, South Korea’s Nuclear Safety and Security Commission (NSSC) said that it had completed all nine inspections required to be performed prior to the reactor’s initial criticality during the pre-operation inspection of Saeul unit 3.
Korea Hydro & Nuclear Power (KHNP) announced that the reactor had “successfully entered the ‘first start’ phase” by achieving first criticality on 12 April.
Output from the unit will gradually be increased over the next six months, KHNP said. “Once its final performance and safety are verified, it will begin commercial operation at 100% output in the second half of the year.” 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.
“The initial start-up is a preparatory phase prior to full-scale electricity production, and test operations will proceed in accordance with strict standards and procedures,” a KHNP official said in a statement. “We will prioritise safety throughout the entire process and conduct thorough inspections to ensure that commercial operation can commence in the second half of the year.”
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 NSSC issued an operating licence for Saeul 3, with fuel loading and approximately eight months of testing to follow.
South Korea has four operational APR1400 units. Saeul 1 and 2 (formerly Shin Kori 3 and 4) entered commercial operation in December 2016 and August 2019, respectively, while Shin Hanul units 1 and 2 entered commercial operation in December 2021 and April 2024. Four APR1400 units have also been built at the Barakah nuclear power plant in the UAE, which are all now in commercial operation.
