South Korea clears key inspections for Saeul 3 startup milestone

South Korea’s Saeul 3 has cleared the nine inspections that had to be completed before initial criticality, putting Korea Hydro & Nuclear Power’s latest APR1400 on the last technical stretch between construction and commercial generation. The Nuclear Safety and Security Commission said the reactor had finished the pre-operational checks that gate fuel loading, high-temperature functional testing, and the final run-up to first criticality.

That matters because initial criticality is the point at which the core reaches a self-sustaining chain reaction for the first time. It is the moment every commissioning schedule is built around, the last real proof that the unit is ready to move from a licensed project to a working power plant. For Saeul 3, the commission said another 31 follow-up inspections, including power ascension tests, will still come before commercial operation.

Saeul 3 received its operating licence on December 30, 2025, nearly two years after the last new nuclear plant licence in South Korea, Shin Hanul 2 in September 2023. KHNP had applied for operating licences for Saeul Units 3 and 4 in August 2020, after receiving the original construction licence for Saeul 3 in June 2016 and starting construction the same year. The project has been delayed by South Korea’s earlier nuclear phase-out policy and the public deliberation process under the Moon Jae-in administration.

Once in commercial operation, Saeul 3 is expected to provide about 1.7% of South Korea’s total electricity generation and 37% of Ulsan’s power demand. KHNP said the project involved about 760 companies and generated jobs and related-industry production across equipment manufacturing, construction and maintenance, a reminder that these starts are industrial events as much as they are regulatory ones. KHNP also said Saeul 3 entered full-scale test operation on April 12 after the commission completed pre-use inspections on April 10.

The reactor is a 1,400-MW APR1400 pressurized-water reactor with a 60-year design life and added safety features, including thicker reactor and auxiliary building walls, earthquake protection, backup generators and spent-fuel storage for the plant’s full operating life. South Korea already has four operating APR1400 units, Saeul 1 and 2 and Shin Hanul 1 and 2, and the same design was exported to the Barakah nuclear power plant in the United Arab Emirates. For South Korea’s build schedule and export story, Saeul 3 is now close enough to touch the grid, but still one round of testing away from claiming it.