The Joint Fact Sheet released following the October 2025 ROK–U.S. summit contained a landmark provision stating that, in addition to reductions in U.S. tariffs on Korean exports and an expansion of South Korean investment in the United States, Washington would approve South Korea’s construction of nuclear-powered submarines. In this regard, National Security Advisor Wi Sung-lac indicated the possible use of an exception under Section 91 of the U.S. Atomic Energy Act, a signal widely interpreted as an intention to pursue a pathway of “military nuclear cooperation” analogous to the Australian case under AUKUS.

To introduce nuclear-powered submarines, South Korea would need to move beyond the framework of Section 123 of the Atomic Energy Act (which governs the ROK–U.S. Atomic Energy Agreement and limits cooperation to peaceful uses) and instead apply Section 91(c) of the Act, which permits nuclear cooperation for military purposes. In the AUKUS case, the United States enacted domestic enabling legislation to facilitate the transfer of nuclear technology to Australia and concluded a separate naval nuclear propulsion cooperation agreement. Australia, for its part, is pursuing a temporary exemption from safeguards on nuclear fuel by invoking the “non-proscribed military activity” provision (Article 14) of its safeguards agreement with the International Atomic Energy Agency. By contrast, cooperation between France and Brazil on the development of nuclear-powered submarines does not involve the transfer of nuclear material or military nuclear technology. Instead, it presumes Brazil’s use of domestically developed nuclear material for submarine propulsion, with the exclusion of safeguards likewise being discussed with the IAEA.

Considering existing precedents for the transfer and development of nuclear-powered submarines—and considering that South Korea would rely on the United States for nuclear fuel and technology—the implementation pathway for South Korea can be summarized in four stages. First, there must be agreement at the leaders’ level between the two countries, a condition that appears to have been met through the issuance of the Joint Fact Sheet. Second, the U.S. President must deliver to Congress a formal determination that the cooperation contributes to U.S. collective defense and security. Third, the two countries must conclude a separate ROK–U.S. Nuclear-Powered Submarine Cooperation Agreement, tailored specifically to military use, to establish the legal basis for technology transfer and security arrangements. Fourth, South Korea must conclude an “Article 14 implementation arrangement” with the IAEA to exempt nuclear fuel from the application of safeguards.

However, because South Korea would seek to construct reactors domestically—unlike Australia, which will import complete reactor units—nonproliferation concerns may be greater. To secure international confidence, South Korea would therefore need to adopt robust transparency measures and rely on high-assay low-enriched uranium (HALEU), among other steps.

This article is an English Summary of Asan Issue Brief (2025-41).

(‘원자력 추진 잠수함 도입 관련 미국법·국제법적 절차와 시사점’)