South Korea’s push for nuclear-powered submarines could transform it from a US security client into an undersea strategic power, while at the same time accruing steep financial, technological and proliferation risks.
This month, multiple media outlets reported that South Korea’s Ministry of National Defense unveiled a historic blueprint to build and launch its first domestic nuclear-powered attack submarine (SSN) by the mid-2030s, a move aimed at countering North Korea’s escalating underwater nuclear and ballistic missile capabilities.
Dubbed the “Jangbogo-N Project (KSS-N),” the multi-decade national initiative will see the vessels designed and constructed entirely within South Korea, leveraging the country’s advanced civilian nuclear and commercial shipbuilding sectors.
Under the plan, the submarines will utilize low-enriched uranium fuel to enable long-cycle operations while strictly adhering to international non-proliferation standards. To secure fuel autonomy, South Korea is coordinating closely with the US and working to establish a joint safeguards system with the International Atomic Energy Agency (IAEA), while reiterating that it will not develop nuclear weapons.
South Korean President Lee Jae-myung and Defense Minister Ahn Gyu-back championed the project as a vital step toward defense autonomy and regional peace. Following the announcement, shares of major domestic shipbuilders Hanwha Ocean and HD Hyundai Heavy Industries surged nearly 10%.
While the US previously signaled political support for South Korea’s procurement plans, significant hurdles remain, including the need for final nuclear fuel agreements, stringent regulatory safeguards and immense long-term budgetary pressures.
Delving into South Korea’s nuclear submarine strategy, a January 2026 podcast by The Korea Society outlines how it could deploy such vessels.
The Korea Society’s James Holmes notes that these nuclear submarines could be deployed in a three-submarine flotilla, ensuring that at least one boat is continuously at sea to maintain a continuous maritime presence.
Holmes adds that these submarines could be employed for both surface and anti-submarine warfare, using nuclear propulsion to remain submerged indefinitely, maximizing elusiveness and endurance.
Sanghyun Lee notes they will be deployed around North Korean coastal waters, employed as an always-on covert tracking mechanism to monitor missile test areas and logistics. Similarly, Minkyung Jung emphasizes their role in persistently tracking and neutralizing North Korean undersea platforms at their home ports.
North Korea’s alleged development of nuclear submarines may be a major contributor to South Korea’s urgency to build such vessels. Asia Times has previously reported on North Korea’s alleged nuclear submarine program, mentioning that the country is pursuing a dual-track approach to build a sea-based nuclear deterrent.
The first track involves conventionally powered, nuclear-armed submarines, highlighted by the March 2025 unveiling of the Hero Kim Kun Ok, a modified Soviet Romeo-class vessel. However, the vessel may have significant technical flaws, including high noise levels and stability issues, making it highly vulnerable to detection.
The second track focuses on true nuclear-powered strategic submarines. In December 2025, North Korean state media showcased the welded hull of an estimated 6,000- to 8,700-ton vessel. While completion of the hull suggests a reactor may be installed, significant skepticism remains regarding North Korea’s ability to master reactor safety, acoustic quieting, and long-term sustainment.
These advancements may be accelerated by Russian tech transfers, including decommissioned nuclear submarine modules, provided in exchange for North Korean support in the Ukraine War.
While these developments are significant, they should be taken with skepticism, as North Korea is known for bombastic military propaganda. Hinting at the limitations of North Korea’s nuclear submarine program, Asia Times noted in April 2026 that the country’s introduction of the Choe Hyon destroyer could serve as a vital interim sea-based nuclear deterrent, given the program’s possible technical immaturity.
Beyond countering North Korea’s emerging sea-based deterrent, Lee argues in a November 2025 Lowy Institute article that the logic behind the KSS-N project shifts the country from a passive buyer of US security to an active partner building deep industrial and strategic interdependence.
Lee points out that, unlike the AUKUS pact with Australia and the UK, which strains US shipyards, South Korea acts as an industrial contributor. He notes that through a US$350 billion investment package—including Hanwha Group’s revitalization of the Philadelphia shipyard—South Korea embeds its advanced engineering and capital directly into the US defense-industrial base.
He says that by helping resolve US naval shipbuilding shortages, South Korea creates an alliance so deeply intertwined that nuclear submarine cooperation becomes strategically and politically difficult to reverse.
However, the project could crowd out near-term investment in advanced air-independent propulsion (AIP) conventional submarines such as the Dosan Ahn Changho KSS-III class.
Jim Halsell argues in an October 2025 Proceedings article that conventionally powered submarines are far cheaper to build, with a single nuclear-powered submarine costing as much as multiple conventional units.
By comparison, in 2026, the Dosan Ahn Changho KSS-III class costs about US$829 million per unit, while a US Virginia-class SSN costs roughly $5 billion. Halsell adds that conventional submarines feature lower maintenance costs with simpler refueling logistics that bypass expensive nuclear-servicing infrastructure.
That affordability, he says, enables a larger, distributed fleet that spreads offensive power across multiple positions, enhancing targeting options while mitigating strategic risks if a unit is lost. He notes that conventional submarines require smaller crews with less specialized training and can use simpler forward-basing facilities built at relatively low cost.
Beyond cost concerns, the KSS-N risks lagging behind advances in undersea detection technologies due to its long lead time. As Roger Bradbury and other writers noted in a March 2023 article for The Conversation, advances in non-acoustic sensing technologies threaten submarines’ vital stealth, potentially making the oceans “transparent” by the 2050s.
Bradbury and others note that while Western submarines traditionally relied on quietness to evade sonar, newer tech can detect physical, chemical, and biological ocean disturbances, as well as radiation and magnetic field changes caused by moving subs. Their Intelfuze software assessment predicts a 75% to 90% probability of transparent oceans by the 2050s.
Beyond operational and technological concerns, the project also raises sensitive questions about nuclear proliferation.
Sharon Squassoni argues in a December 2025 article for the Bulletin of the Atomic Scientists that since naval reactors require enriched uranium — and military fuel applications are often restricted by international agreements — the indigenous development of these sensitive fuel-cycle technologies gives South Korea the exact technical infrastructure and material needed to quickly resuscitate a clandestine nuclear weapons program if it chooses to do so.
South Korea may already have a precedent for suspicious nuclear behavior. In 1979–1981 and 2000, South Korea conducted undeclared laboratory-scale uranium enrichment experiments, producing small amounts of enriched uranium, some of which reached weapon-grade levels. They also secretly separated 0.7 grams of plutonium in 1982.
Those activities violated South Korea’s IAEA safeguards agreement, though subsequent investigations found no evidence of ongoing violations.