Hanwha Ocean plans to complete the basic design phase of its nuclear-powered submarine development project by 2026. The South Korean government has announced its intention to “develop and build nuclear-powered submarines domestically,” and domestic defense shipbuilders have already completed about half of the necessary preparatory work.
According to recent reports from South Korean media, the Agency for Defense Development (ADD) signed a basic design contract with Hanwha Ocean for a nuclear-powered submarine development project in 2022. Hanwha Ocean plans to complete the basic design by the end of 2026 and calculate the required operational capabilities (ROC) and construction costs. This marks the official launch of South Korea’s nuclear-powered submarine development project. If completed on schedule, the project will proceed to critical phases such as detailed design and the construction of the lead vessel.
It is reported that if the South Korean government secures the necessary budget starting in 2027, the country’s nuclear-powered submarine development program will be able to move into the detailed design phase.
South Korean officials believe that the development of a small nuclear reactor for nuclear-powered submarines marks a major breakthrough in the country’s domestic technology. The development of this reactor is being led by the Agency for Defense Development, with participation from Doosan Energy, the Korea Atomic Energy Research Institute, and the Korea Electric Power Corporation.
As progress is made on the design of nuclear-powered submarines, the South Korean government has revealed that it expects to launch its first nuclear-powered submarine in the mid-2030s and put it into service by the late 2030s. The government has made it clear that the nuclear-powered submarines will be built at a domestic shipyard, which effectively points to Hanwha Ocean’s Geoje Shipyard.
It is understood that Hanwha Ocean is South Korea’s most prolific submarine builder, having previously constructed the 1,200-ton “Jangbogo-I,” the 1,800-ton “Jangbogo-II,” and the 3,000-ton “III Batch-II” class submarines.
Although South Korea has made it clear that its nuclear-powered submarines will be built by domestic shipyards, when U.S. President Trump approved South Korea’s nuclear-powered submarine project in October 2025, he stated that “South Korea’s nuclear submarines will be built at the Hanwha Philly Shipyard in the United States.”
However, South Korea argues that Hanwha Philly Shipbuilding, a U.S.-based shipyard majority-owned by a South Korean company, currently lacks the capability to build nuclear-powered submarines due to significant shortcomings in technology, personnel, and facilities.
Currently, there are only two defense shipbuilders in the United States with the actual capability to design and build nuclear-powered submarines: Huntington Ingalls Industries (HII), the nation’s largest defense shipbuilding group, and General Dynamics Electric Boat (GDEB). If nuclear-powered submarines are to be built at Hanwha Philly Shipyard, additional investment will be required to address the shipyard’s capacity gaps in terms of technology, personnel, and facilities.