In December 2025, North Korean leader Kim Jong-un toured a shipyard and inspected the completed hull of a supposed 8,700-ton nuclear-powered “strategic guided-missile submarine.” North Korea’s state-controlled media hailed this sub as a breakthrough in Pyongyang’s naval nuclear ambitions.
Just weeks earlier, U.S. President Donald Trump announced that the United States would share closely held nuclear propulsion technology with Seoul, clearing the way for South Korea to build its own nuclear-powered attack submarines (SSNs).
Trump’s announcement was a long-overdue recognition of a strategic reality: in an era of nuclear-armed adversaries on the Korean Peninsula and a rapidly modernizing Chinese navy, South Korea cannot deter aggression with diesel-electric submarines alone.
For decades, Seoul has operated some of the world’s most sophisticated conventional submarines. South Korea’s KSS-III-class subs are quiet, heavily armed with vertical-launch cruise and ballistic missiles, and equipped with advanced air-independent propulsion. They represent a remarkable indigenous achievement.
However, diesel-electric submarines have significant limitations. Range and time at sea are limited by their diesel fuel. These subs must periodically surface to recharge their batteries, limiting their time submerged to days or weeks at best. In the shallow, confined waters around the Korean Peninsula—and in any broader Indo-Pacific contingency—the KSS-III subs are vulnerable to detection and cannot sustain the persistent, high-speed patrols required for naval deterrence today.
South Korean nuclear-powered submarines can change that equation. An SSN can remain submerged for months, travel at sustained high speeds, and operate across vast distances without fuel constraints. For South Korea, this capability is a necessity. North Korea’s growing fleet of ballistic-missile submarines already threatens to complicate Seoul’s defense planning. Beijing’s expanding submarine force, designed to project power far beyond the first island chain, poses an even larger challenge.
The good news is that South Korea is ready. Its “Big Three” shipbuilders — HD Hyundai Heavy Industries, Samsung Heavy Industries, and Hanwha Ocean — are global leaders in the shipbuilding industry. They already produce world-class conventional submarines and have invested heavily in US shipyards, including the Philadelphia facility acquired by Hanwha. Transferring US naval nuclear propulsion technology would help bring South Korea’s advanced shipbuilding industry to the next level.
However, building and sustaining a nuclear submarine fleet requires far more than hulls and reactors. South Korea must gain access to the full nuclear fuel cycle: the ability to enrich uranium to produce nuclear fuel and to reprocess spent fuel rods into advanced nuclear fuel. Without this, both its submarine program and civilian nuclear industry would remain dependent on foreign suppliers.
Access to the full nuclear fuel cycle would also be a boon to South Korea’s broader civilian nuclear ambitions. South Korea relies on nuclear power for about 30 percent of its electricity. It is also a leading producer of advanced nuclear reactors. Granting South Korea access to enrichment and reprocessing would boost its efforts in next-generation nuclear power technology, such as the production of high-assay low-enriched uranium (HALEU) and advanced nuclear fuel needed for Small Modular Reactors (SMRs) and new reactor designs.
Moreover, providing South Korea with access to the full nuclear fuel cycle is not only a strategic imperative but also a matter of basic fairness and logic.
Source: Korea Times News
