South Korea Pushes for Domestic Nuclear Submarine Construction Amidst U.S. Shipyard Debate

Seoul Prioritizes Indigenous Submarine Development

South Korean officials have recently emphasized their intent to construct nuclear-powered submarines within domestic shipyards, a stance that contrasts with earlier statements made by U.S. President Donald Trump. The debate intensified following a social media post by President Trump on October 29, 2025, which indicated that South Korean nuclear-powered attack boats would be built at the Hanwha Philly Shipyard in Philadelphia, a Korean-owned facility in the U.S.

However, South Korean leaders, including Defense Minister Ahn Gyu-back, have publicly stated that building the submarines at home is 'reasonable' given the nation's accumulated technology and research over 30 years. Minister Ahn also pointed out that the Hanwha Philly Shipyard has 'significant shortcomings in terms of technological capabilities, workforce and facilities' for such a complex military project.

Discrepancy in Summit Interpretations

The differing views emerged after a summit between President Trump and South Korean President Lee Jae Myung during the Asia-Pacific Economic Cooperation (APEC) meetings in Gyeongju. While President Trump's social media announcement suggested U.S. construction, South Korea's presidential office clarified that discussions with Washington were consistently based on domestic construction, with the U.S. providing the necessary enriched uranium fuel.

A South Korean official, speaking anonymously, stated that 'The discussion from start to finish was based on building them here in Korea,' and that the records from the Gyeongju summit confirm President Lee Jae Myung's assertion that the submarines would be built in South Korea.

Strategic Rationale and Challenges

South Korea's pursuit of nuclear-powered submarines (SSNs) is driven by a long-held ambition to bolster its naval deterrence against North Korea's advancing submarine and missile capabilities. These vessels would enable the Republic of Korea Navy to conduct blue-water operations and enhance its role as a security provider in the Indo-Pacific region.

Key considerations for Seoul's domestic program include:

• Fuel Supply: South Korea requires U.S. approval and supply of enriched uranium fuel due to restrictions under the 2015 Atomic Energy Peaceful Uses Agreement.
• Cost Efficiency: Domestic construction is estimated to cost around 3 trillion Korean won per vessel, significantly less than the potential doubling of costs if built in a U.S. shipyard due to labor and supply chain expenses.
• Technological Autonomy: South Korea plans to develop its own reactor model tailored to its security needs, leveraging its existing successful conventional submarine program and shipbuilding expertise.

Alliance Implications and Future Steps

The debate underscores the evolving dynamics of the U.S.-South Korea alliance. While the U.S. has approved South Korea's acquisition of nuclear submarine capability, the location of construction highlights questions of national sovereignty and industrial capacity.

Negotiations are ongoing between Seoul and Washington to finalize a joint fact sheet covering a substantial investment deal and key security issues, including the submarine project. The delay in releasing this document reflects the complex reconciliation of language and logistics between the two nations.