According to information recently circulated by open sources, the South Korean Navy would begin construction in 2028 of the first of its future KSS-III Batch-III nuclear-powered submarines, marking a turning point in the evolution of its conventional submarine program and in the structural transformation of its submarine force.
Regarding the latter, the report states that the necessary technological developments for this new variant of the KSS-III program have reportedly been completed, allowing construction to begin as scheduled in 2028, while the supply of nuclear fuel would be carried out through the United States via the appropriate legal mechanisms. In parallel, this information aligns with recent reports indicating that South Korea’s Ministry of National Defense has established a specific team for the acquisition of nuclear submarines, institutionally consolidating the project after years of technical and political planning.
A program developed over two decades
In line with this, South Korea has been working for at least two decades on the development of nuclear capabilities applied to the naval domain, both in technological and regulatory terms, with the aim of transitioning from conventional diesel-electric submarine platforms to those powered by nuclear reactors.
However, this project has a key dimension to consider: the United States plays a central role in this South Korean initiative. In this regard, toward the end of 2025 the White House signaled that both countries were engaged in discussions to begin developing the new nuclear submarines, a matter that was channeled into an understanding with the United States allowing South Korea to explore the development of nuclear-powered submarines under strict guidelines for the peaceful use of nuclear material.
More specifically, the decision comes after extensive discussions with Washington, a central actor in many initiatives related to nuclear technologies. Although Seoul has reiterated that its interest is limited to nuclear propulsion—and not nuclear weapons—the project requires the approval and cooperation of the United States within the framework of South Korea’s commitments under the Nuclear Non-Proliferation Treaty (NPT).
A key aspect to understanding the scope of this initiative is that South Korea already possesses a considerable submarine force, albeit entirely based on conventionally powered platforms. Unlike future nuclear-powered submarines, however, these units rely on conventional systems that limit their endurance, sustained speed, and time spent in deep submersion—critical factors in prolonged surveillance scenarios and the tracking of enemy submarines. In this context, Seoul’s interest in incorporating nuclear submarines does not seek to replace its current fleet, but rather to complement it by adding a new long-range strategic and strike capability it currently lacks, through a platform with greater endurance, extended submerged operations, and patrol capacity in areas far from its shores.
The information disclosed so far not only confirms that nuclear fuel would be supplied by the United States, in line with the bilateral cooperation framework, but analysts also suggest that Washington could provide support in critical areas such as technical assistance related to nuclear reactors, regulatory frameworks, safety procedures, and long-term maintenance.
An evolution of the KSS-III program
On the other hand, it is worth noting that the specific design of this new nuclear submarine variant has not yet been fully defined. However, analysts suggest that it would represent a direct evolution of the KSS-III program.
As previously mentioned, the South Korean Navy operates submarines from the Batch-I (Dosan Ahn Chang-ho class) and Batch-II lots, the latter being an enlarged version currently in production, with the first unit already launched. The new Batch-III variant, in addition to featuring nuclear propulsion capability, is expected to have an approximate displacement of 8,300 tons, which would make it the largest submarine ever built by South Korea. This would also imply greater endurance and extended submerged operational capability.
You may also like: For more than US$ 2.8 billion, the U.S. awarded the modernization contract for the South Korean Air Force’s F-15K fighters
