South Korean Navy to Legalize Nuclear Submarine "Jangbogo-N" through Special Law Aiming for Commissioning in the Mid-2030s

The legislative announcement made by the South Korean Ministry of National Defense on July 29 is not merely a notification of a submarine program. It outlines the framework of a "special law" that will encompass the nuclear-powered attack submarine "Jangbogo-N" from both the weapon system and nuclear safety perspectives. Public comments are being accepted until September 7, and the Ministry of National Defense has set a policy goal of passing the bill by the end of 2026.

Special Law as a "Standalone Project"

According to the Ministry of National Defense, the current legal framework does not allow for the oversight of nuclear submarines as a single project. This is because the military's weapon systems and nuclear propulsion are overlapping for the first time. The bill stipulates the establishment of a "Nuclear Submarine Strategy Committee" directly under the Prime Minister and the formulation of a basic plan, incorporating procurement, operation, and safety regulations into a dedicated framework. Furthermore, it allows for exemptions from feasibility studies essential for large projects and shortens testing and evaluation periods, thereby accelerating development.

Defining Denuclearization and U.S. Approval

Noteworthy is the non-proliferation clause included in the bill. It specifies that the purpose is not to develop, manufacture, possess, or use nuclear weapons, that nuclear materials will not be diverted for weapon purposes, and that compliance with the NPT and cooperation with IAEA verification are to be upheld. Seoul is attempting to institutionally separate "nuclear propulsion" from "nuclear armament."

This move is predicated on the U.S.-South Korea joint fact sheet from November 2025. The U.S. has approved the construction of South Korea's nuclear-powered attack submarines and indicated a willingness to cooperate on requirements including the procurement of nuclear fuel. On May 26, 2026, the basic plan will be announced, marking the transition to a stage where it is backed legally.

Implications for Japan's Maritime Self-Defense Force

Japan does not possess nuclear submarines, and the Maritime Self-Defense Force has been responsible for anti-submarine warfare with conventionally powered submarines, primarily the "Taigei" class, which utilize air-independent propulsion (AIP). If South Korea commissions a nuclear attack submarine in the mid-2030s, the underwater combat power balance in East Asia will qualitatively change. Vessels equipped for long-term submersion and high-speed maneuverability will become operational in both the Sea of Japan and the East China Sea.

In the author's view, Japan's challenge lies not in "what to do about submarines" but in "how to uphold the alliance's non-proliferation regime." Given that the U.S. has permitted nuclear propulsion by non-nuclear allies, managing this precedent becomes a significant issue. The reality is that the Maritime Self-Defense Force has very limited political and technical room to consider similar options.

The true challenge lies not in the submarines themselves but in the nuclear fuel cycle. If the enrichment levels and supply routes for naval nuclear fuel proceed without transparency, it will create an unaddressed blind spot in the non-proliferation regime in Northeast Asia.