South Korea - United States ANS for Seoul

Unanimously behind Vice-Admiral Kim Myung-Soo, Chairman of the Republic of Korea's Joint Chiefs of Staff, Korean leaders and public opinion want their country to acquire nuclear attack submarines as soon as possible. These appear to be already under consideration, derived from the KS III submarines currently in service, whose dimensions are comparable to those of French attack submarines. By 2035, the estimated date of their commissioning, Seoul, whose nuclear reactors are among the best in the world, will be able to design the naval nuclear boiler room and obtain the loads of highly enriched uranium they need. The price to be paid will be the arm wrestling with Washington. Seoul doesn't seem to mind. It even plans to go so far as to acquire nuclear-powered ballistic missile submarines, the core of a future deterrent force.

On November 24, 2023, when questioned by a committee of the South Korean Parliament in connection with his appointment as Chairman of the Joint Chiefs of Staff, Admiral Kim Myung-Soo called for the construction of nuclear attack submarines (NAS) to be launched by his country, and denounced the United States as the main opponent of the development of weapons necessary for South Korea's security. Admiral Kim Myung-Soo was requesting that his country acquire a fleet of SNA* . He was not alone in wanting to bring about what is nothing less than a minor revolution.

Alongside him, Professor Jeeyong Kim of the South Korean Naval Academy asserts: "The strategic role of the K-SSN* would be unparalleled as a deterrent to China, Russia and North Korea. Pyongyang will no longer be able to threaten the South, once the Republic of Korea is equipped with a sufficient fleet of nuclear submarines, whereas today its growing nuclear capabilities pose a direct threat, not only to South Korea, but also to the USA1 ." The South Korean population follows them. Recent polls have shown that the majority of South Koreans consider the availability of nuclear-armed SNAs* to be a vital necessity, rather than an option. As Yulgok Kim, Secretary General of the Republic of Korea's Nuclear Strategy Forum, reminds us.

A major long-term program is launched

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Seoul is about to embark on a great technological and industrial adventure. Building a nuclear submarine is a technological challenge. The United Kingdom could not meet it alone. It had to enlist the help of the United States, and as part of the mutual defense agreement it signed, it was able to benefit from a "considerable" transfer of information for the development of the Rolls-Royce nuclear reactor on its Astute submarines. The fuel for these reactors is highly enriched uranium, between 93% and 97%.

In principle, South Korea will be alone in this endeavor, and will have a long and demanding road ahead of it. What are the first steps? The US Navy has the answer.

The future third-generation KSS III class submarines, which may give rise to the nuclear submarine, are scheduled to enter service in 2030. They will displace around 3,600 tons on the surface and 3,950 tons underwater, and measure 89 meters in length2 . This is more than France's first nuclear attack submarine, the Rubis, which displaced 2,385 tons on the surface and 2,670 tons underwater, and was 73.60 meters long, but significantly less than the Redoutable, France's first ballistic missile submarine, which displaced 8,080 tons on the surface, 8,920 tons underwater, and was 129 meters long.
These submarines will be equipped with ten vertical missile-launching systems (VLS) made by Hanwha Ocean, which are already capable of firing SLBM missiles with a range of 500 kilometers for land attack. They will be designed to fire ten-tonne missiles3 . This is still a long way from the performance expected for intermediate-range nuclear missiles, in the region of 30 tonnes.

So much for the hulls, but the hardest part remains to be designed and built: first and foremost, the nuclear boiler room. This is not the simple reactor that South Korea is so good at - it builds civil nuclear power plants that have recorded the lowest number of emergency shutdowns in the world - but a compact, low-noise naval reactor. What's more, it will require highly, or very highly, enriched uranium, whereas South Korea's nuclear fuel supply agreements with the USA are for civilian applications only.

There are a lot of hurdles to overcome, and they make it hard to hope for the launch of a nuclear attack submarine before 2035 (a date found in American estimates). But Seoul's nuclear ambitions should not stop there. Korean naval authorities make no secret of the fact, declaring: "The technologies and experience acquired during the construction of the K-SSN* will serve as a keystone when South Korea decides to build a nuclear-powered ballistic missile submarine." Fair enough, but we don't see that happening before 2040. All the more so as South Korea will also have to equip itself with industrial facilities capable of producing miniaturized nuclear warheads.

For the United States, South Korea is on the wrong track

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It's unlikely that Washington will go along with South Korea's nuclearization. This could be a breaking point between the two countries.

For the USA, Korea's ambition is unwelcome and Seoul must give up.

• The project is ruinous. If Seoul were to launch a submarine program, it would have to build at least three of them to be sure of having a vessel permanently at sea on patrol.  A program costing over 10 billion dollars, if logistical support is included. What's more, it will stretch out over time. The Australian submarine delivery schedule set out in the AUKUS program is a benchmark which shows that at least a decade will have to elapse before a single South Korean nuclear submarine takes to the seas.
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• These submarines will be of no use, as for operational reasons conventionally-powered submarines remain preferable. The waters surrounding the Korean peninsula are relatively shallow, which favors the use of quiet conventional submarines. South Korea currently operates seven Son-Won II class diesel-electric submarines. These submarines are ideally suited to operations around the Korean peninsula4 . In short, nuclear submarines are unnecessary, as the South Korean navy does not need to venture far afield. The high seas are reserved for others, for AUKUS vessels.

Towards an arm wrestling match

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Is this not a serious error of judgment? Can we ask a country to resign itself to being a second-rate nation? For the South to give way to the North? South Korean politicians of all persuasions do not accept this, and are united in their desire to emancipate themselves from American tutelage. The former president, Moon Jae-in, took a first step in 2017 when he wanted to create an independent military force that would no longer rely exclusively on the United States. In 2022, President Yoon Suk Yeol declared that he wanted to equip his country with nuclear weapons. He was immediately called to order by Joe Biden. And tomorrow it's the mayor of Seoul, Oh Se-hoon, a potential future presidential candidate, who in turn calls for the development of these weapons to meet South Korea's security needs.

NATO's and the USA's announced setback in the Ukraine should finally convince Seoul of the fragility of the security agreement linking them to the USA, which has led them to renounce their nuclear capabilities. Although the USA is committed to using all its strategic assets and nuclear weapons to defend its ally against North Korea, this arrangement has lost all credibility over the past two years. Pyongyang has a large number of nuclear missiles, which threaten South Korea, but above all place the USA under the threat of retaliation if they were to act. In a situation of mutually assured destruction, Washington is condemned to nuclear impotence.

For the time being, on November 13, 2023, Seoul is acting "as if". It assures the United States of its loyalty when South Korean Defense Minister Shin Won-sik and his American counterpart Lloyd Austin sign an update to the TDS agreement* . At the same time, however, it seems that South Korea is quietly heading for a showdown with the United States5 . It has little to lose, and to keep up appearances, it will always be able to claim that, alongside the US Navy, the K-SSNs will be a useful asset in countering China and North Korea. Submarines that will serve the interests of both South Korea and the United States.

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1. South Korean Admiral Claims That Nuclear-Powered Submarines Are Necessary, Naval News, 24/11/2023.
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2. South Korea's Sophisticated KSS-III Submarines, USNI.org, 06/2023.
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3. South Korea to develop new VLS and SLBM for its Submarines, Naval News, 24/11/2023.
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4. South Korea does not need nuclear subs, The Hill, 24/11/2023.
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5. Pour se doter un flotte de SNA sud-coréens, Séoul se dirige vers un bras de fer avec Washington, meta-defense.fr, 24/11/2023.