South Korea will seek Washington’s cooperation to develop or acquire nuclear-powered submarines (SSN), South Korea’s new Minister of Foreign Affairs Cho Hyun stated during a successful confirmation hearing on 18 July.
According to South Korean reports, Cho is specifically seeking to amend the US-ROK Peaceful Nuclear Cooperation Agreement, often referred to as the 123 Agreement, which is seen as the major impediment to procuring a domestic nuclear submarine capability.
The 123 Agreement prohibits US-sourced nuclear materials from being used by South Korea for military purposes including naval propulsion. It also bars Seoul from enriching uranium above 20 per cent, and reprocessing spent nuclear fuel, without authorisation from Washington.
Cho’s SSN plans are understood to be supported by the current director of the National Intelligence Service (NIS) Lee Jong-seok, a member of the “pro-autonomy faction”, which advocates for less reliance on the US alliance.
There is broader political support in Seoul for developing nuclear latency, defined as the capacity to rapidly build nuclear weapons, which could also be facilitated by amending the 123 Agreement.
South Korean media has reported that non-proliferation advocates in the US Department of Energy and the State Department strongly oppose South Korea developing a military-use nuclear capability.
Former US Secretary of Defense Lloyd Austin has also stated that the burden of Washington’s obligations to transfer SSN technology to Australia under the AUKUS SSN pact make it “very, very difficult” for the US to support South Korea “on top of what we do right now.”
The recent decision by the Trump administration to review the AUKUS pact has also been cited as a negative for Seoul’s prospects, with fears that Washington is refocusing on domestic capability building.
However, the bigger impediment is seen to be Washington lacking sufficient trust in South Korea’s newly elected left-leaning president, Lee Jae Myung.
A former Australian diplomat, speaking on the condition of anonymity, said that the US would be unlikely to share nuclear submarine technology with South Korea due to the strong presence in Seoul of pro-China political factions. Lee has been frequently accused of being “pro-China” by his political opponents – claims he has denied.
The source also stated that in terms of sharing sensitive technology, South Korea falls far short of the level of trust the US has in its AUKUS partners Australia and the United Kingdom, all of whom are part of the Five Eyes intelligence alliance.
Despite foreseen difficulties, Cho has raised the possibility of adopting a “transactional approach” to US President Trump to secure a deal, while adding that Seoul could convince the US that its enrichment and reprocessing would not be military in nature, but rather industrial and environmental.
It has also been noted that President Trump, and US Under Secretary of Defense for Policy Elbridge Colby, have previously hinted that they could be willing to tolerate a nuclear-armed South Korea.
While there are concerns that the US may be unable to concurrently transfer SSN technology to Australia and South Korea, it has been pointed out that the ROK already possesses most of the requisite conditions for developing such a capability, including large civilian nuclear and shipbuilding industries, nuclear engineering institutions, as well as a submarine force trained in SLBM operations.
An exclusive report from Chosun Online, published August last year, claimed that South Korea has already made inroads in developing a land-based test site for a small modular reactor (SMR).