President Lee Jae Myung listens to defense minister Ahn Gyu-back’s briefing on the ministry’s plan on developing nuclear-powered submarines at a comittee meeting held in Changwon, South Gyeongsang Province, Monday.
South Korea’s plans to build nuclear-powered submarines by the mid-2030s will spur a U.S.-allied network of advanced underwater capabilities near the first island chain, strengthening deterrence against potential adversaries such as China and North Korea, analysts say.
The South Korean defence ministry this week announced its basic plans to build the country’s first nuclear-powered submarine, giving its first detailed outline of the programme since U.S. President Donald Trump granted initial approval in October.
According to the plan, South Korea will launch the first of the vessels by the mid-2030s and deliver them to the Republic of Korea Navy by the late 2030s.
The submarines, which are expected to be in use for at least 30 years, will be powered by low-enriched uranium instead of high-enriched uranium that could be used to build nuclear weapons.
However, in contrast to Trump’s approval, which required the South Korean submarines to be built at Hanwha Ocean’s shipyard in Philadelphia, the plan said South Korea would develop and build the submarines within its own territory using the country’s “world-class” nuclear energy and shipbuilding technology.
“Nuclear-powered submarines possess significantly improved operational capabilities, such as long-term submerged endurance and high manoeuvrability, compared to existing diesel submarines, and will play a key role in responding to North Korea’s submarine-based nuclear and missile threats,” the ministry plan released on Tuesday said.
While it did not specify the number and size of the submarine fleet to be built, media reports quoted the South Korean Joint Chiefs of Staff as saying in a meeting before the plan’s announcement that they had decided to build up to four nuclear-powered submarines, each with a displacement of 8,000 tons.
Nuclear-powered submarines – also known as SSNs, or “submersible ship nuclear” – are powered by nuclear reactors but are not necessarily armed with nuclear weapons.
Compared with conventional diesel-electric submarines, which require frequent resurfacing for refuelling, nuclear reactors allow a submarine to operate underwater at higher speeds for extended periods, essentially with unlimited range. They have played a crucial role in navies around the world as strategic assets projecting maritime deterrence in blue waters.
Seoul’s submarine plan comes amid rising tensions on the Korean peninsula, especially since 2021, when North Korean leader Kim Jong-un declared his country’s plans to build its own nuclear-powered submarine.
While doubts were raised over Pyongyang’s lack of technological capabilities, the programme appeared to be progressing when Kim visited the shipyard reportedly building an 8,700-ton “nuclear-powered strategic guided-missile submarine” in March and December last year.
China is also ramping up its submarine development. A February report by the London-based think tank International Institute for Strategic Studies said Beijing had “rapidly expanded” its nuclear-powered submarine production, surpassing U.S. launch numbers and tonnage between 2021 and 2025.
During this period, China launched 10 submarines with an estimated displacement of 79,000 tons, while the U.S. launched seven boats displacing 55,000 tons, according to the report.
President Lee Jae Myung listens to defense minister Ahn Gyu-back’s briefing on the ministry’s plan on developing nuclear-powered submarines at a comittee meeting held in Changwon, South Gyeongsang Province, Monday.
Bence Nemeth, a senior lecturer in defence studies at King’s College London and executive director of the King’s Centre for Defence Economics and Management, said a South Korean SSN would “change the underwater balance” around the Korean peninsula, by giving the South Korean navy “much greater submerged endurance and mobility”.
“This would make it harder for North Korea to plan around South Korean submarine operations and would strengthen Seoul’s ability to track and threaten North Korean naval forces, including submarine-launched missile capabilities,” Nemeth said.
Benjamin Blandin, a non-resident research fellow at the Yokosuka Council on Asia-Pacific Studies in Japan, said that having nuclear subs would serve as the “last resort” to deter an adversary – such as North Korea, Russia or China – as it demonstrated the “means to inflict devastating damage, with or without the U.S”.
South Korea’s nuclear-powered submarine would primarily aim at North Korea, Blandin said, but added: “I would be surprised [if] Moscow and Beijing don’t get the message that helping North Korea to attack South Korea would be interpreted as direct co-belligerence.”
According to Blandin, in addition to South Korea, Japan could build its own SSNs within a decade, with both countries able to produce their own nuclear reactors and “good quality” submarines.
Collin Koh, a senior fellow at the Institute of Defence and Strategic Studies at the S. Rajaratnam School of International Studies in Singapore, noted that while South Korea’s SSN operation was likely to be confined to waters around the Korean peninsula, the possibility of their involvement in the first island chain conflict “cannot be ruled out completely”, depending on how the U.S. alliance system evolved.
The first island chain in U.S. defence policy is a strategic arc of islands and archipelagos in East Asia, running from Japan to the Philippines. The series includes Taiwan, which Beijing views as part of China to be reunited by force if necessary. Most countries, including the U.S. and its allies, do not recognise self-governed Taiwan as an independent state, but Washington is opposed to any forcible change to the status quo and is legally bound to supply Taipei with weapons.
Koh said South Korea’s possession of SSNs could anticipate a “few potential ramifications”, such as China and North Korea using the strengthening of Seoul’s underwater capabilities as an “excuse” to ramp up their own naval forces, and spurring Japan’s push to develop its own nuclear-powered submarine.
Japanese Defence Minister Shinjiro Koizumi said in November that Tokyo would consider acquiring nuclear-powered submarines.
South Korea and Japan’s potential possession of nuclear-powered submarines, as well as Australia’s ongoing Aukus submarine programme with the U.S. and Britain, “will tie together with the broader U.S. alliance system in the region”, according to Koh.
“I think in a way this U.S. ally network of nuclear-powered submarines armed with strategic and substrategic weapons could actually have a significant boost when it comes to deterrence in the region against perceived common adversaries like China or North Korea,” he said.
It was likely to spark “at least some type of naval arms dynamic” Koh said, “not necessarily only confined to submarine versus submarine”.
“But we’ll be looking at a more structural, more systemic type of naval arms dynamic, whereby it will be an across-the-board type of modernisation effort.”
Read the article at SCMP.