President Donald Trump has come out in support of a future fleet of South Korean nuclear-powered submarines. He says he has signed off on the plan and has claimed that at least some of the boats will be built in the United States. Authorities in South Korea have been open about their nuclear-powered submarine ambitions for years, but have faced pushback, including from the United States, particularly over nuclear proliferation concerns.
Trump has made two posts on his Truth Social social media network discussing South Korean nuclear-powered submarine plans in the past day or so. The U.S. President held a summit with his South Korean counterpart, Lee Jae Myung, yesterday, which was centered heavily on trade negotiations. Trump’s visit to South Korea was part of a larger tour of Asia.
“Our Military Alliance is stronger than ever before and, based on that, I have given them approval to build a Nuclear Powered Submarine, rather than the old fashioned, and far less nimble diesel powered submarines that they have now,” Trump wrote in one post on Truth Social.
“South Korea will be building its Nuclear Powered Submarine in the Philadelphia Shipyards, right here in the good ol’ U.S.A.,” he wrote in a second post. “Shipbuilding in our Country will soon be making a BIG COMEBACK. Stay tuned!!!”
The South Korean Navy already has a substantial fleet of diesel-electric submarines, which currently consists of 12 Jang Bogo class, nine Sohn Won-yil class, and three Dosan Ahn Chang-ho class types. The Jang Bogo and Sohn Won-yil class submarines are German-designed Type 209s and Type 214s, respectively. The Dosan Ahn Chang-ho class, also known as the KS-III Batch I, is a domestically developed design. Just this month, South Korea launched the first of a planned subclass of three KS-III Batch IIs, the country’s largest and most advanced submarine to date, which you can read more about here.
In general, compared to even advanced diesel-electric types like the KS-III Batch II, the key benefit that nuclear-powered submarines offer is functionally unlimited range.
The Trump administration has yet to elaborate on exactly what the current South Korean nuclear-powered submarine plan might entail and the roles that the United States may play.
The shipyard in Philadelphia that Trump mentioned is most likely the Hanwha Philly Shipyard. That yard had been Philadelphia Shipyard Inc. until elements of the South Korean conglomerate Hanwha acquired it last year. That yard has never produced a submarine of any kind or any type of nuclear-powered vessel.
“Asked about Trump’s submarine announcement, Hanwha Ocean, which owns the shipyard with another Hanwha affiliate, said it was ready to cooperate with both countries and provide support with advanced technology, but did not mention specifics,” according to Reuters.
General Dynamics Electric Boat in Groton, Connecticut, and Newport News Shipbuilding, a division of Huntington Ingalls Industries (HII) in Newport News, Virginia, are two current producers of nuclear-powered submarines in the United States.
South Korea’s “Defense Minister Ahn Gyu-back told lawmakers that plans called for South Korea to build its own submarines and modular reactors, and receive a supply of enriched uranium fuel from the United States,” Reuters also reported. “Seok Jong-gun, the minister for the defense acquisition program administration told the same hearing that South Korea had been developing small nuclear reactors for some time and would be able to build one for a submarine in less than the decade usually needed to develop such nuclear-powered vessels.”
“We believe if we use the technologies we have been preparing for the future…we’ll be able to achieve this within a short period of time,” Seok added, per Reuters‘ story.
The South Korean government is known to have conducted at least one detailed design study relating to a miniature nuclear reactor for use on a future submarine, called the 326 Initiative, in the 2003 timeframe. The country also has an established nuclear power industry that develops reactors for non-military purposes, but which could be leveraged for such work.
A key question, in general, when it comes to nuclear-powered submarine designs, is the level of enrichment of the fuel inside their reactors. U.S. Navy nuclear-powered submarines notably have reactors with fuel enriched to the same level as material for nuclear weapons. This is not a requisite, however. The reactors inside current French nuclear-powered submarines use low-enriched uranium. There are reports that Chinese nuclear-powered submarines may also use reactors with LEU fuel.
Still, it is worth noting here that, at least currently, the only countries with operational nuclear-powered submarines are also nuclear weapon states. At the same time, that is already set to change with the Australian Navy’s expected acquisition of nuclear-powered submarines through the trilateral Australia-United Kingdom-United States (AUKUS) defense cooperation agreement.
Since 2015, South Korea has also faced the unique hurdle of a bilateral agreement that bars it from enriching uranium and reprocessing spent fuel without U.S. government approval. Trump appears to have now given that approval. Defense Minister Ahn’s comments, per Reuters, indicate the hurdle has been further cleared by a plan to source the nuclear material directly from the United States.
A South Korean nuclear submarine program could still create proliferation concerns for the country, which is presently a party to the Non-Proliferation Treaty (NPT). As TWZ previously wrote when the possibility of South Korea acquiring nuclear-powered submarines came up in 2018:
The need to build enrichment or other nuclear facilities, or otherwise acquire the highly enriched fissile material, could also draw international criticism that South Korea is abiding by the letter, but not the spirit of the NPT, effectively developing a nuclear weapons program in all but name. These issues are at the core of why South Korea conducted the 326 Initiative in secret and why it abandoned it after it became public, attracting the attention of both the United States and the International Atomic Energy Agency.
South Korean officials have talked in the past about the possibility of changing geopolitical circumstances on the Peninsula, and elsewhere, leading it to start its own nuclear weapons program. North Korea is, of course, a nuclear weapons state, and it may now be pursuing its own nuclear-powered submarines with assistance from Russia.
The South Korean Navy would also have to develop suitable infrastructure to sustain a fleet of nuclear-powered submarines, as well as train personnel in the operational and maintenance of naval reactors. There could be cost and related industrial base concerns, especially depending on how deeply involved the United States needs to be in any such plan. Questions have already been raised about whether the U.S. nuclear-powered submarine industry can support Australia’s needs and U.S. Navy requirements. The U.S. naval shipbuilding industry, as a whole, has faced serious challenges in recent years and continues to despite government-backed efforts to bolster its capabilities and capacity.
There are still larger questions about South Korea’s practical need for a nuclear-powered submarine capability. South Korean President Lee has said that his country fielding nuclear-powered submarines could help reduce operational demands for its American allies. Especially combined with conventionally-armed submarine-launched ballistic missiles (SLBM), it could also give the South Korean Navy more of a true second-strike capability to help deter North Korea.
However, North Korea has limited anti-submarine warfare capabilities, while South Korean diesel-electric submarine designs are only getting more and more advanced. The range and other benefits that nuclear propulsion offers for naval vessels generally point to broader, blue water ambitions. This is certainly the case for Australia, which is situated far from the areas it expects its future nuclear-powered boats to operate.
As such, South Korea’s work to acquire a fleet of nuclear-powered submarines, especially if they are capable of carrying out longer-range strikes on targets at sea and/or ashore, could have broader ramifications. The KSS-III Batch I submarines can already fire conventionally-armed SLBMs (SLBM), a capability that is being expanded upon in the Batch II types.
The Chinese government “hopes that South Korea and the United States will earnestly fulfill their nuclear non-proliferation obligations and do things to promote regional peace and stability, and not the other way around,” Guo Jiakun, a spokesperson for the country’s foreign ministry, said in response to the nuclear-powered submarine news, according to Reuters.
China already has a very large submarine force that includes diesel-electric and nuclear-powered types, and which it continues to expand in both size and capability.
Much still remains to be learned about how, and when, South Korea may expect to finally begin operating nuclear-powered submarines. Regardless, the country’s ambitions in this regard have now gotten a major boost in support from President Trump.
Contact the author: joe@twz.com