[Gyeongju APEC] Achievement in Nuclear Submarine Introduction... Further Negotiations Remain

The Lee Jaemyung administration achieved a long-standing goal of the South Korean military-the introduction of nuclear-powered submarines-during the South Korea-U.S. summit held on the occasion of the 2025 Gyeongju Asia-Pacific Economic Cooperation (APEC) Summit. While challenges remain, such as revising the South Korea-U.S. Nuclear Cooperation Agreement, securing technology, and actual construction, South Korea must also overcome opposition and checks from neighboring countries such as China and Russia.

Amid Naval Buildup by North Korea and China... A 30-Year Ambition Realized

On October 30, one day after the South Korea-U.S. summit, U.S. President Donald Trump stated on his social media platform, Truth Social, "The South Korea-U.S. military alliance is stronger than ever," adding, "Based on this, I have authorized South Korea to build nuclear-powered submarines instead of outdated diesel submarines." This was in response to President Lee’s request during the summit to "make a decision allowing South Korea to receive fuel for nuclear-powered submarines."

With this, South Korea has become the seventh country in the world capable of possessing and operating nuclear-powered submarines. The introduction of nuclear-powered submarines has been a major aspiration of the South Korean military, officially and unofficially pursued since the era of civilian governments, but it had seen little progress for over 30 years. This was due to the South Korea-U.S. Nuclear Cooperation Agreement, which prohibits the use of nuclear fuel for military purposes, as well as the consistently negative stance of the United States. Even if South Korea were to push for the introduction of nuclear-powered submarines on its own, U.S. technology and fuel support-such as small reactors and enriched uranium-are essential.

The Lee Jaemyung administration’s formalization of the nuclear-powered submarine program is seen as a response to the significant naval buildup by neighboring countries such as China and North Korea. China is rapidly expanding its naval power in the Yellow Sea and East China Sea, while North Korea has been working to secure a "nuclear-powered strategic guided-missile submarine" since the 8th Congress of the Workers’ Party in 2021. The nuclear-powered strategic guided-missile submarine is believed to be a ballistic missile submarine (SSBN) capable of carrying submarine-launched ballistic missiles (SLBMs) with nuclear warheads.

The submarines currently operated by the South Korean military are powered by diesel engines, which have limitations. Due to the limited amount of fuel, their submerged endurance is about two weeks, and their actual underwater speed remains at around 4-5 knots. In contrast, nuclear-powered submarines face far fewer restrictions in terms of submerged endurance, depth, and speed. A military official stated, "Because they are powered by small reactors, operations can continue until supplies such as food are depleted," adding, "Even if detected by enemy anti-submarine forces, they can rapidly evade at depths of 200-300 meters, greatly enhancing survivability."

To Be Built at a U.S. Shipyard... Expected to Take 10 Years Until Deployment

The nuclear submarine will be constructed at the Hanwha Ocean Philadelphia Shipyard, the core of the "Make American Shipbuilding Great Again (MASGA) Project," which symbolizes South Korea-U.S. shipbuilding cooperation. President Trump stated, "South Korea will build nuclear-powered submarines right here at this excellent Philadelphia shipyard," adding, "American shipbuilding is about to experience a big comeback."

With the introduction of nuclear-powered submarines confirmed, attention is also focused on the Jangbogo-III Batch-III project currently being pursued by the South Korean military. The Jangbogo-III Batch-III is reportedly being developed with a displacement of over 5,000 tons, equivalent to that of nuclear submarines. On October 30, during a comprehensive parliamentary audit by the National Defense Committee, Chief of Naval Operations Kang Donggil responded to a question from Assemblyman Yoo Yongwon of the People Power Party regarding the construction timeline for Jangbogo-III Batch-III, saying, "The start date has not been decided," and "Once a decision is made, it will take about 10 years, so completion is expected in the mid-2030s."

Admiral Kang also projected that the displacement of the nuclear-powered submarines to be built in the future "will be over 5,000 tons," and regarding nuclear fuel, he added, "It should be at a level that can be used peacefully, so the enrichment of uranium is expected to be below 20%." The scale of the nuclear submarine introduction is expected to be at least three to four vessels. Minister of National Defense Ahn Kyubaek, in response to a related question from Assemblyman Kang Daesik of the People Power Party, said, "We will have to consult with the Navy, but I believe at least four submarines will be necessary."

Minister Ahn further emphasized the significance of introducing nuclear-powered submarines, stating, "Diesel submarines simply cannot surpass the nuclear submarines North Korea is preparing in terms of submerged endurance and speed, so this is highly significant," adding, "As a strategic asset, this will be a decisive opportunity for us to secure the conditions necessary for self-reliant national defense."

Follow-Up Negotiations and Managing Regional Tensions Remain Challenges

Yonhap News Agency

The key issue is the follow-up procedures. In addition to revising the South Korea-U.S. Nuclear Cooperation Agreement to prevent the military use of nuclear fuel, concrete negotiations are needed to secure small reactors and low-enriched uranium required for nuclear submarines. At a briefing on October 29, National Security Office Director Wi Sunglak was asked whether a separate agreement with the United States would be necessary regarding the introduction of nuclear-powered submarines. He responded, "We need to review the legal procedures," adding, "The current South Korea-U.S. Nuclear Cooperation Agreement also prohibits the use of nuclear fuel for military purposes, so adjustments are needed."

Opposition from neighboring countries such as China and Russia also remains a challenge. At a regular press briefing, Chinese Foreign Ministry spokesperson Guo Jiakun commented on South Korea’s nuclear submarine program, saying, "China hopes that South Korea and the United States will faithfully fulfill their nuclear non-proliferation obligations and work to promote peace and stability in the region." Although the tone was moderated in consideration of President Xi Jinping’s planned visit to South Korea and the South Korea-China summit, underlying discomfort was evident.

The South Korean government continues to emphasize that the introduction of nuclear-powered submarines is being carried out within the framework of the Nuclear Non-Proliferation Treaty (NPT). Minister of Foreign Affairs Cho Hyun stated at a press conference on October 30, "This is entirely separate from nuclear weaponization and is not intended to enhance potential nuclear capabilities," adding, "We make it clear that South Korea is complying with the Nuclear Non-Proliferation Treaty (NPT)."

Experts advise that managing potential conflicts will be essential as nuclear-powered submarines are introduced. Kim Heungkyu, professor of political science and diplomacy at Ajou University and director of the U.S.-China Policy Institute, said, "With China making its 'an eye for an eye, a tooth for a tooth' stance clear, and South Korea moving closer to the U.S.-led containment framework against China, regional instability is likely to increase." He added, "Fortunately, with President Xi’s visit to South Korea, a basis has been established for President Lee’s visit to China, so efforts should be made to manage conflicts going forward."