South Korea has received President Trump’s blessing to become the seventh country in the world operating nuclear-powered submarines, joining the United States, Russia, China, France, the United Kingdom and India:
South Korea could more effectively counter North Korean or Chinese moves in the waters around the Korean Peninsula; and that would free up the US Navy’s nuclear-powered attack subs to concentrate on patrols in hot spots like the South China Sea and the waters around Taiwan.
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Nuclear-powered submarines (SSNs) come with many advantages. They can stay submerged for long periods of time – essentially for years, if they can carry enough provisions for the crew – whereas most conventionally powered subs must surface for air to run diesel engines, which in turn charge their batteries for running at depth.
They are also generally faster than conventionally powered subs and are in many cases quieter.
Acquiring them has been a decades-long wish of the South Korean government.
But Seoul has faced a key roadblock: under a decades-old nuclear agreement with the US, it is not allowed to reprocess spent nuclear fuel, despite having the technology to do so.
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“There are four-hundred foreign submarines in the world, of which roughly 75% reside in the Indo-Pacific region. One hundred and sixty of these submarines belong to China, Russia, and North Korea,” Davidson told the panel.
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As of July 1, 2025, a US Navy website shows it had 49 attack subs in its fleet, which must cover all the world’s oceans. About two-thirds of that fleet is available to “surge” in an emergency, the acting chief of naval operations said last April, but fewer subs are out on patrol during routine operations.
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“The core issue in Trump’s post was the mention of the Philly shipyard,” said Kim Dong-yeob, South Korean military expert and a professor at the Institute for Far Eastern Studies at Kyungman University.
“What we wanted was not simply to possess nuclear-powered submarines but to secure related technologies and achieve industrial effects through domestic construction,” Kim told CNN.
“Building at the Philly shipyard means losing technology transfer. It is essentially no different from buying weapons built in the US.”
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Shugart, however, questions South Korea’s wish: “It doesn’t make a lot of sense to me from an operational perspective.”
“The primary benefit to nuclear-powered (submarines) is mainly speed, being able to go fast for a long period of time and cross long distances at a rapid clip,” Shugart said.
But “South Korea and Japan are right there where the action is likely to be,” he continued, adding that SSNs could make sense if Seoul’s intention was to carry out aggressive anti-submarine warfare.
A potential South Korean nuclear-powered sub could also exacerbate an arms race in the region. North Korea called South Korea’s pursuit of SSNs “a strategic move for its own nuclear weaponization,” despite Seoul clarifying that the submarine would not carry nuclear weapons.