This marks the first time the formerly classified program has surfaced as an open national project. Government momentum is accelerating. During the 48th Cabinet Meeting, Defense Ministry official Won Jong-dae confirmed that, pending final consultations with Washington, fuel acquisition is feasible and construction could begin in the late 2020s—setting the stage for the first hull launch in the mid-to-late 2030s.

Domestic Industrial Base: Mostly Ready

South Korea’s shipbuilding and defense sectors already possess much of the capability required to build a nuclear submarine:

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  Pressure Hull Steel: POSCO’s HY-100 steel—used in the Jang Young-sil submarine launched in October—enables dives below 400 meters and is the same grade applied to U.S. Navy Seawolf-class subs.

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  Weapons & Systems: Heavyweight torpedoes, guided weapons, sonar arrays, and combat management systems are largely indigenous.

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  Hydrodynamic Design: Local shipbuilders have already developed next-generation submarine hull concepts suited for sustained high-speed underwater operations. In short, the industrial foundation for hull, sensors, and weapons is largely in place.

  
  The Critical Bottleneck: A Proven Naval ReactorThe defining challenge is the reactor. Concepts include the SMART reactor and several SMR-based derivatives—compact and efficient designs compared to conventional pressurized-water reactors. However, none have been physically demonstrated.A naval reactor must satisfy requirements far beyond a land-based design: Operate within extreme size and weight constraints, Maintain stability under continuous pitch, roll, and yaw, Minimize radiation exposure to the crew, Ensure ultra-low acoustic signature suitable for strategic stealth missions. Because of these constraints, the reactor is the decisive variable that will determine whether the K-SSN succeeds—or stalls.
  
  

Land-Based Prototype Facility: A Mandatory Step

Before the reactor is installed on a submarine, full-scale land-based prototyping and validation is essential. The historical precedent is clear: the U.S. Navy operated the prototype of the USS Nautilus reactor for years at the Idaho National Laboratory, far from urban areas. South Korea will require: A suitable test site, Environmental impact assessments, Agreements with local communities, Long-term nuclear safety and waste protocols, These processes will demand political consensus and transparent communication.

Nuclear-Grade Shipyard & Base Infrastructure

The shipyard tasked with building the K-SSN—and the naval base that will host it—must meet protection and radiation-shielding standards comparable to a nuclear power plant. This represents another major infrastructure challenge and will require early engagement with residents and local governments.

Analysis: The Reactor Will Decide the Future of Korea’s Undersea Deterrent

In defense programs, “the devil is in the details.” Nowhere is this truer than in nuclear propulsion. While hull, steel, sensors, weapons, and shipbuilding capacity are near readiness, the reactor remains the single point of failure—and the single point of opportunity.

If South Korea can successfully design, test, and certify a naval reactor, the K-SSN program will unlock: Continuous submerged endurance, Strategic-level stealth, Blue-water operational reach, A new maritime deterrence architecture for the ROK Navy.

Public support will be essential. As the government transitions the K-SSN into a national strategic program, clear communication and transparent risk management will be critical to securing national consensus.

K-DEFENSE NEWS | Strategic Analysis Desk