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Nuclear submarines potential game-changer for South Korea

Published: 30 Oct. 2025, 19:02

A Jang Bogo III-class submarine [HANWHA OCEAN]

South Korea’s bid to acquire nuclear-powered submarines took a step closer to reality on Wednesday, as the leaders of South Korea and the United States reached a consensus on the issue for the first time during their summit in Gyeongju.

U.S. President Donald Trump further fueled expectations the following day, writing on his social media platform Truth Social, “I have given them approval” for the construction of nuclear-powered submarines.

If finalized, South Korea is likely to become the world’s eighth nation to possess such vessels. The move would not only elevate South Korea’s global strategic standing but also invite greater scrutiny from neighboring powers such as China and Russia.

Defense minister says four subs needed

The topic was raised at the National Assembly’s Defense Committee audit on Thursday. Defense Minister Ahn Kyu-back said, “Rather than calling it ‘approval,’ it’s more accurate to say that we had already prepared the conditions to build nuclear-powered submarines, and that fuel was the final piece.”

His remarks suggest that the project had already been underway at the government level, with nuclear fuel as the final hurdle.

“We’ll have to coordinate with the Navy, but we likely need at least four submarines,” Ahn added.

If South Korea proceeds, it could join Australia as the eighth or ninth country operating nuclear-powered submarines. Outside of the five declared nuclear powers under the Non-Proliferation Treaty (NPT) — the United States, China, Russia, the United Kingdom and France — only India, a declared nuclear power but not a party to the NPT, currently possesses them. Australia plans to acquire five such submarines under the Aukus pact by the 2040s, and Brazil is pursuing a similar program.

Britain’s 7,400-ton Astute-class submarine [SCREEN CAPTURE]

Nuclear-powered submarines, or SSNs, are powered by enriched uranium fuel, including uranium-235. Unlike diesel-electric submarines, which must surface roughly every 20 days, SSNs can remain submerged almost indefinitely, drastically reducing the risk of detection.

The U.S. Navy’s Virginia-class submarine can operate for up to three months, with a range that extends into deep ocean territories. Traveling at speeds of 25 to 30 knots, they can reach Guam — about 4,000 kilometers (2,485 miles) away — within three to five days.

This is why nuclear-powered submarines have long been the South Korean Navy’s aspiration as it seeks to become a true blue-water navy.

Previous administrations under presidents Roh Moo-hyun and Moon Jae-in quietly pursued nuclear-powered submarines but failed to gain traction due to domestic and international concerns over nuclear nonproliferation.

The USS Blue Ridge, the U.S. Navy's 7th Fleet command and control ship, is seen entering the Busan Naval Operations Command's Busan base in Nam-gu, Busan on Sept. 25. [SONG BONG-GEUN]

On Thursday, Choi Jong-kun, a professor at Yonsei University and a former first vice foreign minister under the Moon administration, said on the news radio program that “Moon raised the issue when he first met Trump,” adding that Trump once told Moon, “Why just one? Buy two.”

The remark suggests Trump had been supportive during his first term, though the plan was ultimately scrapped due to opposition from the U.S. government. Still, Seoul quietly pursued the program under a classified project.

At the audit, Ahn said when asked about the project’s progress, “We’ve made substantial advances in small modular reactors (SMRs), and we’re now at a significant level of development.”

“Testing must occur on land first before we go underwater, and we’ve already completed much of that process,” Ahn added.

The USS Alexandria, the U.S. Navy's Los Angeles-class nuclear-powered submarine, is seen entering the Busan Naval Operations Base in Nam-gu, Busan on Feb. 10. [SONG BONG-GEUN]

U.K.'s Astute-class, France’s Barracuda-class considered

Based on Navy assessments, the South Korean model would likely be in the 6,000 to 6,500-ton range. The Navy has long aimed for nine Jang Bogo III-class submarines since deciding to acquire them in 2005.

Six vessels — including the 3,600-ton ROKS Jang Yeong-sil — have been confirmed under the Jang Bogo III Batch-I and II programs. There are calls to convert the remaining three under Batch-III into nuclear-powered submarines.

Britain’s 7,400-ton Astute-class and France’s 5,000-ton Barracuda-class submarines are being floated as viable models. The United States uses weapons-grade highly enriched uranium, above 90 percent enrichment, for its submarines, which the South Korean government considers unrealistic to adopt.

Instead, France’s model, which uses high-assay low-enriched uranium (HALEU) under 20 percent, is seen as a more feasible option. The Barracuda-class uses fuel enriched to around 5 to 7 percent.

“The government requested U.S. approval to enrich uranium to 3 to 5 percent and to insert fuel rods, and the U.S. response was to propose joint construction,” said Democratic Party lawmaker Park Sun-won, citing an unnamed source.

Past cases suggest it would take at least a decade to develop and build such submarines. Navy Chief of Staff Kang Dong-gil said during the audit, “If the decision is made, it will take around 10 years. We’re looking at the mid-2030s.”

“So far, we’re still at the level of political declarations,” said Naval Chief of Staff Kim Tae-hoon.

The Virginia-class submarine USS North Carolina pulls into Naval Station Norfolk following a brief deployment in this file photo [JOONGANG ILBO]

Implications for China and Russia

Multiple hurdles remain, including approval from the U.S. Congress. Experts also note that acquiring nuclear-powered submarines would mark a significant shift in South Korea’s military posture.

South Korea’s military reach could extend beyond the peninsula, especially if the United States supports the initiative on the condition that South Korea helps check the influence of China and Russia.

In a written response to People Power Party lawmaker Kang Dae-sik, the Navy said, “Nuclear-powered submarines would be a game-changer against threats from North Korea and surrounding countries,” implying a broader strategic role.

The U.S.-South Korea alliance is also at a turning point over the long-standing issue of transferring wartime operational control (Opcon) to Seoul.

U.S. Secretary of Defense Pete Hegseth told reporters at the Asean Defense Ministers’ Meeting-Plus (ADMM-Plus) in Malaysia on Thursday that South Korea’s plan to complete the Opcon transition during President Lee Jae Myung’s term was “great,” according to Yonhap News Agency.

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.
BY LEE YU-JUNG,CHUNG YEONG-GYO [[email protected]]