I am an editorial writer at The Korea Times, focusing on foreign policy, North Korea and domestic politics. My key areas of interest include North Korea, foreign interference in elections, election integrity, cyberattacks and human rights. Prior to joining the Editorial Board, I served as both Politics Desk editor and Culture Desk editor. During my career, I have reported on the Presidential Office under the Lee Myung-bak administration, the Ministry of Foreign Affairs and the National Assembly.
Untangling South Korea's quest for nuclear-powered submarines
US Los Angeles-class nuclear-powered attack submarine USS Alexandria is seen in the oceans near Busan, Feb. 10. Yonhap
By Kang Hyun-kyung
President Lee Jae Myung’s opening remarks at his Oct. 29 summit with U.S. President Donald Trump in the historic southeastern city of Gyeongju, North Gyeongsang Province, came as a surprise to many foreign policy watchers.
Lee — long accused by political opponents of being overly sympathetic to China since his “xie xie” (thank you) remark stirred controversy during his presidential campaign — explicitly cited China, alongside North Korea, as a key reason his administration is pursuing multiple nuclear-powered submarines.
Diesel-powered submarines are too slow for South Korea’s Navy to effectively track and outmaneuver North Korean and Chinese submarines, he said. He requested U.S. support in supplying the uranium fuel necessary for naval reactors, adding that South Korea hopes to build several conventionally armed, nuclear-powered attack submarines to defend its maritime borders in the East and West Seas. “Should this happen,” he said, “the U.S. would be able to ease part of the defense burden it currently carries.”
As expected, his nuanced pitch drew a swift rebuke from Beijing.
“China hopes that South Korea and the United States will earnestly fulfill their nuclear nonproliferation obligations and do things that promote regional peace and stability, not the opposite,” Chinese Foreign Ministry Spokesperson Guo Jiakun said during a press briefing on Oct. 30.
At home, Lee’s identification of China as a maritime security threat immediately triggered speculation about his motives. Until now, he has been notably cautious about criticizing China and has even reacted sharply to anti-China rallies held near the Chinese Embassy in Seoul, calling the protesters “racists” and warning of punitive measures. His stance stood in stark contrast to his silence on anti-U.S. protests outside the U.S. Embassy in Seoul, fueling claims that he is sympathetic toward China.
His sudden shift — publicly naming China as a security challenge — therefore raised eyebrows.
Retired Navy Capt. Park Bum-jin, now a professor at Kyung Hee University in Seoul, said Lee’s rhetoric reflects calculated messaging aimed at securing U.S. approval for the submarine program.
“He intentionally mentioned China, along with North Korea, because he knew Washington is preoccupied with China and focused on containing it,” Park said. “It appears his strategy worked, given that the U.S. approved the plan. When it comes to nuclear-powered submarines, bipartisan support is essential. There should be no policy reversal on an issue of national security.”
In the joint fact sheet released last week following Trump’s summit with Lee, the U.S. gave South Korea the green light. “The United States has given approval for the ROK to build nuclear-powered attack submarines. The United States will work closely with the ROK to advance requirements for this shipbuilding project, including avenues to source fuel,” the document states. ROK is the acronym for the Republic of Korea, South Korea’s official name.
President Lee Jae Myung shakes hands with U.S. President Donald Trump before a dinner hosted by Lee in Gyeongju, North Gyeongsang Province, Oct. 29. Yonhap
Civilian use of nuclear energy vs. naval reactors
Nuclear-powered submarines rely on nuclear reactors for propulsion, which require enriched uranium. Naval reactors can use either low-enriched uranium (LEU) or highly enriched uranium (HEU). U.S. nuclear submarines operate with HEU-based reactors, while others — such as those used by France — are powered by LEU.
Based on Lee’s remarks, South Korea’s aim is to develop naval reactors using LEU, a technology the country already employs extensively. Under the U.S.-ROK Agreement for Peaceful Nuclear Cooperation, widely known as the “123 Agreement,” South Korea uses LEU to fuel its commercial nuclear power plants. The country operates dozens of reactors across multiple sites, supplying over 30 percent of its national electricity.
The joint fact sheet nevertheless prompted questions about the need for additional U.S.-South Korea consultations. Why would South Korea, with decades of experience in the peaceful use of nuclear energy, require special procedures to gain U.S. approval for naval reactors that would rely on the same LEU technology used in its power sector?
Retired Lt. Gen. Chun In-bum says this requirement stems directly from the bilateral civilian nuclear energy pact. “If you look at the 123 Agreement, there is a section requiring the two countries to sit down and discuss any new developments, such as enrichment and the recycling of spent fuel,” he said.
The 123 Agreement establishes a “High-Level Bilateral Commission” to coordinate cooperation on issues including spent fuel management, stable fuel supply, nuclear security and collaboration between the U.S. and South Korean nuclear industries. It notes that the commission will “allow for deepened cooperation and more regular interaction between our two governments on the state of nuclear energy in both countries and allow us to account for new developments in technology, spent fuel management, security and safety.”
Under the agreement, South Korea may begin building nuclear-powered submarines only after Washington and Seoul finalize the required procedures in detail.
Partnering with third country?
But there is another potential path for South Korea to acquire nuclear-powered submarines.
Lee Jeong-ik, a professor of nuclear and quantum engineering at KAIST, said partnering with a third country could be an alternative.
“The 123 Agreement is a bilateral pact between South Korea and the U.S. on nuclear material and technology. Therefore, if South Korea partners with countries other than the U.S., it would not be bound by this agreement,” he wrote in an article titled “Misunderstanding and Facts about South Korea’s Nuclear-Powered Submarine Project,” published by the Korea Institute for Maritime Strategy.
Lee noted that countries such as France and Russia operate nuclear-powered submarines based on their own reactor technologies.
Chun said cooperation with France, for example, is technically possible but strategically risky. “If South Korea does that, its alliance with the U.S. will be hurt seriously,” he said. “Look at Australia. It initially planned to partner with France to replace its aging submarines but later changed course, opting to purchase U.S. nuclear-powered submarines.”
Under the AUKUS security partnership, Australia committed to purchasing three Virginia-class nuclear-powered submarines from the United States beginning in the early 2030s.
Proliferation woes
Park agreed that pursuing a third-country partnership would be counterproductive given the potential fallout for the U.S.-ROK alliance. “The key is how to source the fuel,” he said.
Park added that the road ahead will be difficult for other reasons as well, including domestic anti-nuclear sentiment.
“In South Korea, there are people who oppose anything related to nuclear power,” he said. “In the U.S., there are people worried about proliferation. Convincing both groups to support South Korea’s development of nuclear-powered submarines will be a tough job.”
Bryan Clark, a senior fellow at the Hudson Institute in Washington, D.C., argued that constructing naval reactors for ship propulsion does not constitute nuclear proliferation.
“It is an approved use under the Nuclear Non-Proliferation Treaty (NPT),” he said. “South Korea would not need a separate agreement to enrich uranium.”
Still, some in the U.S. question South Korea’s intentions, raising additional concerns.
Bruce Bennett, an adjunct senior international and defense researcher at RAND and a professor at the RAND School of Public Policy, warned that U.S. technology transfer could entail risks.
“The challenge with nuclear submarines is how the fuel for the reactor will be provided. For the U.S., this fuel is reportedly about 95 percent highly enriched uranium, which is roughly the same level used for nuclear weapons,” he said. “South Korea specifically asked for permission to create the fuel for the reactors in its nuclear-powered submarines. If it is given that permission and uses a U.S. design, it would be producing highly enriched uranium that could be diverted to nuclear weapons.”
However, concerns about nuclear proliferation via naval reactors are, to some extent, overstated. Clark noted that South Korea is not permitted to enrich uranium to high levels.
“The NPT limits non-nuclear weapon states to enriching uranium only to low levels that are not useful for nuclear weapons,” he said.