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After U.S. approval of nuclear-powered submarines, Korea faces a series of challenges

Published: 06 Nov. 2025, 00:04

Yu Ji-hoon

The author is a research fellow at Korea Institute for Defense Analyses

U.S. President Donald Trump has signaled that Washington will approve Korea’s longstanding wish to build nuclear-powered submarines. For Seoul, acquiring submarines capable of remaining submerged for extended periods, operating far from home waters and moving rapidly with sustained endurance would mark a qualitative leap in military capability. Beyond a simple enhancement of naval power, nuclear-powered submarines could become a core asset that supports Korea’s self-reliant defense and strengthens the combined deterrence of the Korea-U.S. alliance.

The Jang Yeong-sil, the first submarine of the Jangbogo-III Batch-II class, is seen during its launch ceremony at Hanwha Ocean in Geoje, South Gyeongsang, on Oct. 22. The 3,600-ton vessel is a diesel-electric submarine equipped with vertical launch tubes and is considered one of the most advanced of its kind. [YONHAP]

Yet, securing such strategic assets comes with serious constraints. Because these submarines use nuclear material as a power source, legal, technical and diplomatic hurdles are deeply intertwined. A political statement alone does not guarantee the actual deployment of nuclear-powered submarines. Still, the agreement between the two leaders provides political momentum and creates conditions for addressing issues ahead.

The first barrier lies in law and regulation. Under the current Korea-U.S. Atomic Energy Agreement, revised in 2015, Korea is prohibited from enriching uranium or reprocessing spent nuclear fuel without prior U.S. consent. Trump’s approval can be seen as a political signal to relax parts of this restriction. To translate that into reality, approval from the U.S. Congress and possibly a special bilateral agreement would be needed to legally permit nuclear propulsion for naval use.

Technical challenges are no less daunting. Building a nuclear-powered submarine requires far more than shipbuilding skills. It demands expertise in small marine reactor design, integration with propulsion systems, radiation shielding, cooling technology and precision welding, along with specialized facilities for construction and maintenance. Trump also suggested the idea of building Korean submarines at the U.S. Navy’s Philly Shipyard as part of a broader plan to revive U.S. shipbuilding. But the shipyard does not currently have the facilities to construct nuclear-powered submarines, raising questions about practical feasibility.

A more realistic solution may be a hybrid model that combines the strengths of both countries. In such a division of labor, the United States would take responsibility for reactor and nuclear fuel technology, while Korea would handle hull design, assembly and systems integration. Core nuclear components could be produced in the United States, with final assembly, outfitting and sea trials conducted in Korea. This approach would require a separate bilateral agreement specifying the construction site, technology transfer terms and division of responsibilities.

Diplomatic implications must also be considered. North Korea could exploit the move as justification for further military provocations or nuclear expansion. China may view Korea’s acquisition of nuclear-powered submarines as part of a U.S.-led containment effort. Japan, observing regional shifts in naval power, may accelerate its own defense modernization. Seoul would need to make clear to the international community that its nuclear-powered submarines are nonnuclear weapons platforms used solely for defensive purposes.

Alliances are built on trust, but they function through mutual interest. The more Washington sees Korea’s submarine project as aligned with U.S. industrial and security interests, the more likely the Trump administration will expand legal, technical and diplomatic support. Building bipartisan backing in the United States will be essential. Close cooperation between the two navies will also be critical. If the project is widely perceived as contributing to regional maritime security and allied naval operations, policy-level support is more likely to grow.

North Korean leader Kim Jong-un inspects the construction of a nuclear-powered submarine, the Korean Central News Agency reported on March 8. [KOREAN CENTRAL NEWS AGENCY/YONHAP]

Securing nuclear-powered submarines will require significant time and resources. Institutional mechanisms must ensure continuity if U.S. leadership changes. In Seoul, the Ministry of National Defense, Ministry of Foreign Affairs, Ministry of Trade, Industry and Energy and Ministry of Science and ICT must work together through a permanent consultative body. A comprehensive road map linking defense, technology, diplomacy and industry is essential.

Washington’s approval offers an opportunity to deepen mutual trust and strategic cooperation within the alliance. But political declarations alone are not enough. What is needed now is national resolve, diplomatic confidence and a long-term strategic vision.

This article was originally written in Korean and translated by a bilingual reporter with the help of generative AI tools. It was then edited by a native English-speaking editor. All AI-assisted translations are reviewed and refined by our newsroom.