South Korean Nuclear Powered Subs by the 2030s: Predicted 2015-2021

Pete's earliest detailed comments on South Korea and its SSN ambitions were April 16, 2015's "South Korean Submarines, 3,000+ ton KSS-III, Nuclear Potential" at https://gentleseas.blogspot.com/2015/04/south-korean-submarines-3000-ton-kss.html 15 comments, 10,155 pageviews.

Pete wrote "S Korean nuke sub Reactor likely to be French K15 Variant" on December 16 2021 at https://gentleseas.blogspot.com/2021/12/s-korean-built-nuke-sub-reactor-likely.html 4 comments, 2,220 pageviews.
Please see text below: 

"...SUBMARINE MATTERS BACKGROUND AND COMMENT [written in 2021]

South Korea is leaning toward a [Low Enriched Uranium (LEU)] reactor solution perhaps initially on a South Korea SSBN - which will be based around the ballistic missile submarine KSS-III SSB. It is not surprising South Korea has long been in talks with France (since 2017 if not earlier) about South Korea building a variant of France's K15 LEU reactor. The K15 is on France's Triomphant class SSBNs and, in slightly smaller form, on the France's Barracuda-Suffren class SSNs. 

In Submarine Matters’ “South Korea seeks Submarine Reactors from US and RUSSIA” of October 22, 2019 South Korea may have concluded it is better to buy an existing submarine reactor or at least a ship reactor than totally reinvent a submarine reactor. 

Since 2017 (if not earlier) South Korea has been considering France’s new Barracuda SSN with its K15 (aka K 15 aka K-15) reactor. With North Korea's buildup of nuclear weapon and missile capabilities South Korea, in October 2019, has been testing any increased US willingness for South Korea to explore nuclear propulsion options. 

The Triomphant-class's 2(?) x K15s and Barracuda's single K15 reactor stands for 150 MWt  power which translates to a total of 30 MWe electrical power (for the French Barracuda’s non-propulsive electrical services hotel load + propulsion).

"In October 2017, the [South Korean] Navy commissioned the Seoul-based Korea Defense Network to conduct a five month study on the feasibility of developing an indigenous nuclear-powered attack submarine. The think tank reported in March 2018 the results to the Navy, suggesting the service build a nuclear attack submarine along the lines of the French 5,300-ton Barracuda-class sub. The French sub is fuelled by low-enriched uranium."

Now that the US and UK have given the green light to supplying Australia with a reactor under the AUKUS deal it is conceivable that France may want [to] supply just the Barracuda’s K15 reactor or transfer technology (including a reactor design) for South Korea to incorporate in its 4,000+ tonne KSS III Batch III building program. 

The Barracuda’s K15 reactor has the:

-  political/regulatory advantage of using LEU ie. less than 20% U-235 which South Korea sees as not being restricted by the NPT or nuclear Safeguards Agreements. This is compared to the political sensitivities and anti-proliferation regulatory restrictions (up until September 2021's AUKUS deal) placed on exporting/importing US and UK HEU submarine reactors. The UK/US reactors use weapons’ grade HEU of 93-97 percent (see p. 20). 

-  technical advantage of being built for a submarine of just over 5,000 tons, ie. in South Korea's KSS III Bach III weight bracket. While the KSS III Batch II with 10 x VLS silos  has diesel-electric (also AIP) propulsion the proposed KSS III Batch III may eventuall have 12 to 16 VLS silos requiring an unusually large propulsion solution. Nuclear has been the solution for SSBNs built by the US, Russia, UK, France, China and India. 

-  Also Naval Group's assistance to Brazil to create a SSN, known as Alvaro Alberto [~5,900 tonnes submerged?], is highly relevant to the South Korean SSN (aka KSS-N) project, Alvaro Alberto's projected launch year (2029) and commissioning (2032-2034) may occur in the same timeframe as the South Korean SSN project.  At Submarine Matter’s 2015 article see the subheading "Brazilian Nuclear Submarine (SN-BR)” “There currently appears to be expectations that SN-BR will be around 100m long and 9m wide. This coincides with France's Barracuda SSN dimensions of: 99.5m long and beam: 8.8m.” 

-  So a A K15 variant first mounted on a South Korean SSBN by the early 2030s may be followed by mounting a K15 reactor variant on a South Korean SSN by the mid 2030s. In terms of vertically launched cruise or ballistic missiles the KSS Batch I features 6 VLS tubes, each with one missile. The KSS III Batch II [now features 10] and the KSS III Batch III perhaps 12 to 16. 

South Korea's neighbour Japan (a part strategic competitor of South Korea) is observing South Korea's interest in nuclear propulsion and ever larger submarines.

India, already having SSBNs, is interested in building 6 x Project 75 Alpha class SSNs with specialised SSN reactors. India is naturally talking to France's Naval Group. Naval Group is already  helping India build the 6 Kalvari-class Scorpenes, and bidding for India's 6 x AIP diesel-electric Project-75I SSK competition. Naval Group produces all of France's SSNs and SSBNs. So India can have far ranging discussions, on many topics, with Naval Group."

SubMatts article ends.

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Very recently, in July 2026, Bill Seney and I have been discussing the above topic:

"Bill Seney [said]

I have seen news reports:
https://www.japantimes.co.jp/news/2026/05/26/asia-pacific/south-korea-nuclear-submarine-2030s/

that South Korea [SK] is looking at a nuclear powered variant of the KSS-III. Given that US nuclear subs seem to be getting further and further away and that UK subs are at least 2 decades away is it worth Australia's while to look at a SK option?

Given that [SK] has yet to build a nuclear submarine I could see the project slipping or even facing cancelation, so it is high risk. On the other hand, we know SK can build diesel boats. Perhaps a mixed fleet, with initial deliveries of conventional KSS-III followed by a nuclear variant when available? If the nuclear option is cancelled Australia would still end up with a powerful fleet of conventional submarines.

7/15/2026 10:41 AM
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Pete2 [said]

Thanks Bill [I agree with your 7/15/2026 10:41 AM comment]]

I'll develop your idea as an article probably tomorrow.

I've long theorised here at SubMatts that SK would look to France's K15 LEU reactor for technology transfer. Also that the last KSS-III Batch 2 or Batch 3s would be nuclear powered.

Cheers Pete

7/15/2026 10:53 AM

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Bill Seney [said]

Thanks Pete

Something I forgot to mention in my earlier comment is that the KSS-III is about the same size as the American Skipjack class SSN, so a nuclear KSS-III variant should be technically feasible.
[Pete comment - Yes the Skipjack-class SSN (1956-1990) was indeed KSS-III sized, at ~ 3,075t (surfaced) & ~3,513t (submerged) and the
French K15 using, Suffren/Barracuda SSN is ~4,765t-5,300t] 

Also, if Australia wanted to partner with South Korea on SSNs we can provide not just uranium [Australia has the 2nd largest Uranium reserves worldwide] but enrichment technology [Australian invented SILEX] as well, something the Koreans may be interested in.

7/15/2026 10:53 PM
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Pete Comment

Whether the US and its changeable Trump card can play a useful part in SK's (at least 11 year old) nuclear powered submarine program follows in a week. 

Certainly the US has an international law "123 Agreement" hold over SK that transactional Trump will maintain unless SK pays the US the price Trump seeks, that may vary from week to week.