Korea Hydro & Nuclear Power (KHNP) has begun the initial startup phase of Saeul Unit 3, marking a key step toward commercial operation for the new nuclear reactor under construction in Ulsan.
KHNP announced that the 1,400-megawatt-class reactor, located in Ulju County, Ulsan, successfully achieved its “first criticality” on April 12. This milestone signals the start of full-scale test operations and is considered a crucial phase in verifying the plant’s safety following design, construction, and inspection processes.
Saeul Unit 3 received its operating license from South Korea’s Nuclear Safety and Security Commission on December 30 last year. Since then, KHNP has carried out essential pre-operational procedures, including fuel loading and hot functional testing. The successful startup now paves the way for a series of power ascension tests in the coming months.
The development comes at a time when nuclear energy is gaining renewed attention globally amid rising uncertainty in energy markets. Nuclear power is viewed as a relatively stable energy source with less exposure to fuel supply disruptions and price volatility.
Over the next six months, KHNP plans to gradually increase the reactor’s output while conducting comprehensive checks on major equipment and safety systems. Following final performance verification, Saeul Unit 3 is expected to enter full commercial operation at 100% capacity in the second half of this year.
A KHNP official said the initial startup marks a preparatory phase before electricity generation, adding that all subsequent testing will be conducted under strict standards and procedures. The company aims to ensure safety throughout the process and meet the planned timeline for commercial operation.
