SEOUL — South Korea's Ministry of National Defense unveiled a blueprint to build and launch its first domestic nuclear-powered attack submarine by the mid-2030s. The initiative, known as the Jangbogo-N Project (KSS-N), will involve designing and constructing the submarines entirely within South Korea.

The KSS-N submarines will use low-enriched uranium fuel to enable long-duration operations while complying with international non-proliferation standards. South Korea is coordinating with the United States and working to establish a joint safeguards system with the International Atomic Energy Agency to ensure fuel autonomy. Officials reiterated that the program does not involve nuclear weapons development.

President Lee Jae-myung and Defense Minister Ahn Gyu-back championed the project as a vital step toward defense autonomy and regional peace. "This project is not about escalating tensions but about ensuring our sovereignty and contributing to stability in the region," Lee said.

Critics have raised concerns about cost, technological feasibility, and strategic implications. Jim Halsell, writing in the October 2025 issue of Proceedings, argued that a single nuclear-powered submarine costs as much as multiple conventional units. He added that conventional submarines feature lower maintenance costs, simpler refueling logistics, and require smaller crews with less specialized training.

Sharon Squassoni, in a December 2025 article for the Bulletin of the Atomic Scientists, warned that indigenous development of naval nuclear fuel-cycle technologies could give South Korea the infrastructure to quickly restart a clandestine nuclear weapons program. "Naval reactors require enriched uranium, and mastering the full fuel cycle blurs the line between civilian and military capabilities," she wrote.

The announcement follows increased naval activity from North Korea, which unveiled the Hero Kim Kun Ok, a modified Soviet Romeo-class submarine, in March 2025. Skepticism remains about North Korea’s ability to master reactor safety and acoustic quieting for nuclear submarines. Hurdles also face South Korea’s program, including finalizing nuclear fuel agreements, regulatory safeguards, and managing long-term budgetary pressures.