South Korean Submarines, 3,000+ ton KSS-III, Nuclear Potential

See detail on possible South Korean nuclear submarine technology in redded KSS-N sub-heading below.

One of South Korea's (international convention of just "Korea" now used) nine Chang Bogo class (KSS-Is). Korea is completing a sale of three to Indonesia.

---

One of Korea's four Son Won-Il class (KSS-IIs) in commision - five to go. Larger than the KSS-I and AIP equipped. Looks like a pre-launch ceremony. 

---

With the KSS-III being described as a "3,000 tonne submarine" for a decade the above dimensions (very similar to the single hull Collins) may be accurate. The "3,000 t" would be surfaced displacement.

---

A larger KSS-III? If its length is really 83.5 m and breadth/beam 7.7 m, then compared with the Collins (77.4 m, 7.8 m) the KSS-III's displacement appears to be around 3,400 tonnes (surfaced) and 3,800 tonnes (submerged). There are many other variables in estimating displacement of course! Other possibilities are that the above is a "4,000 t" nuclear KSS-N? or 83.5 is propaganda to equal the Soryu's 84 m length.

---

Another model of what the KSS-III may turn out like. It appears to have 6 VLS hatches but a 6 missile Vertical Multi Purpose Lock (VMPL) is more likely.
---

South Korea (international convention of just "Korea" now used) has a long and competitive ship-building tradition. Korea has the world's largest ship-building industry - with 41% of world market share (in first quarter 2015). This has put Korea in a good position to build German TKMS-HDW designed submarines (from kits?) since 1990. Korea has also has submarine export success and is perhaps well prepared to develop a 3,000-4,000 tonne conventional submarine. It faces threats even greater than Japan does - having a land border with North Korea and in much closer proximity to China. The Korean Navy has publicised its creation of a Submarine Command for reasons difficult to discern but perhaps to suggest an eventual capability of a pre-emptive or second strike nuclear deterrent.

South Korea's KSS-I, KSS-II and KSS-III building program suggest a goal of having a rolling average of at least 18 submarines operational and perhaps 22 to match Japan's medium term goal. The so-called "indigenous" submarine (KSS-III) project may still draw heavily on TKMS-HDW technology but "indigenous" also provides ambiguity if Korea needs to develop KSS-III into a nuclear propelled submarine "KSS-N" possibly nuclear armed. 

South Korea's strategy includes the creation of a pre-emptive strike "kill chain" (of threat detection, decision making-authorisation and (mainly missile) pre-emptive strike) against North Korea. Submarines would be a (or the) principal pre-emptive strike and counter-strike platform. Subsonic cruise missiles are generally too slow for these roles - making supersonic+ cruise and ballistic missiles the logical solution.

Used South Korean has two Dolgorae class mini submarines (above) launched 1990 and 1991, 175 tons, with two small 410mm torpedo tubes. They have crews of 14 and may be used for surveillance and perhaps special forces. They were acquired by South Korea to obtain initial experience with the basics of operating a submarine force and to train surface ASW ships in the detection of subs.

In 2011 South Korea indicated it would be building new mini-subs, known as KSS-500As, weighing 510 tons. They may operate only on Lithium-ion Batteries and diesel engines. 

KSS-Is and KSS-IIs

Korea's navy operates:

- 9 Chang Bogo class (KSS-I), a variant of the TKMS-HDW type 209/1200. In 2011 Daewoo Shipbuilding & Marine Engineering (DSME) won a contract to supply Indonesia with two pre-assembled Chang Bogos (to be delivered probably in 2016-2017) with a third Chang Bogo to be assembled in Indonesia (perhaps the beginning of an indigenous Indonesian production line!). The 9 KSS-Is have been regularly upgraded which may extend their service life past the usual 30 years. A major future upgrade may be Lithium-ion batteries fully or partly replacing lead-acid batteries - although such a retrofit may be very difficult. See NTI document for names of specific, commissioned KSS-Is and KSS-IIs up to 2011.

-  4 Son Won-Il class (KSS-II) as at April 2015. Five more are due to be commissioned by 2020. These are variants of the TKMS-HDW Type 214 submarines. Hyundai Heavy Industries (HHI) built the first three (commissioned 2007-2009). DSME, HHI and STX Offshore & Shipbuilding are alternately building the second batch of six with one of the six commissioned in December 2014 and the final one due to be commissioned in 2018. Like the KSS-Is the KSS-IIs carry some US built Harpoon missiles for anti-ship and possibly land attack. Like the KSS-Is the KSS-IIs are orientated to a surveillance, anti-shipping, anti-submarine and (a short range) land attack capability. 

KSS-III, 3,000-4,000 tonne Design - Conventional and Potentially Nuclear  

There will be eventually 9 (KSS-III) 3,000-4,000 tonne submarines.  See the 3rd and 4th pictues above that contain varying dimentions attributed to the KSS-III (also called "DSX-3000") which indicate its surfaced displacement may be anywhere between 3,000 and 3,400 tonnes. DSME will be the main designer. The lead KSS-III boat began development in November 2014 at DSME's submarine yard at Okpo. It my be a major step forward in utilising Lithium-ion Batteries (LIBs). The second batch of KSS-IIIs (especially if they use new technology LIBs) may take 8 years to build and launch (2024) and then 3 years to commission (about 2027). 

The larger size of the KSS-III will permit it to include some of the latest submarine technologies, including:

- large diameter unmanned underwater vehicles (LDUUVs)
- Seal/diver delivery vehicles (SDVs)
- dry-wet cells for special forces in dinghies/divers/Seals
- VLS or more probably the major advance of Vertical Multi Purpose Lock (VMPL) capable of launching 1,500+ km cruise and Harpoon missiles,, VMPLs are also capable of launching LDUUVs and SDVs. 

As well as retaining fuel cell (or less likely Stirling) AIP, KSS-IIIs could also incorporate features from the TKMS-HDW Dolphin 2 including the large rudder system and reinforced hull bottom which allow such a large SSK to operate in shallow, littoral waters. Also Germany's TKMS-HDW could provide assistance using features from the so-far drawing board only HDW 216 (intended to be a 3,000+ tonne design). 

One additional reason Korea is going the indigenously developed submarine route is that international political pressure on Germany would probably prevent Germany from openly assisting South Korea to develop the KSS-III in the medium-long term into a nuclear propelled KSS-N submarine, possibly armed with nuclear weapons.

The capability to use Tomahawk or indigenous Hyunmoo-3 series cruise missiles of 1,500+ km (far longer than the 140 km range KSS-I/KSS-IIs UGM-84 Harpoons) potentially makes the KSS-III much more effective against such additional threats as China and Russia. The future KSS-IIIs may also be capable of firing ballastic missiles.

The US may have been politically unwilling to supply the Tomahawk to Korea. Instead Korea appears to have incorporated many of Tomahawk's features into the Hyunmoo-3 series. By building an indigenous missile, warhead ambiguity is introduced. Korea is one of those countries (like Japan) that could develop a nuclear weapon in less than a year. Miniaturisation may be a major hurdle but a Hyunmoo-3 (or other cruise missiles) could trade range to achieve a heavier warhead than 500 kg.

KSS-III could best be described as multi-purpose. For a medium sized navy like Korea's KSS-IIIs (or KSS-Ns) could combine some of the capabilities that larger navies cover more comprehensively with distinctly different types, such as SSKs, SSNs, SSGNs and SSBNs. 

KSS-N, a Nuclear Development of the KSS-III? 

Korea appears to have long maintained an option of a KSS-N (also called KSSX-N and SSX) a 4,000+ ton nuclear propelled development of the KSS-III. On past plans see Globalsecurity.com report. However to date any plan has not occurred due to pressure from all of Korea's neighbours, US opposition and the necessity of building an indigenous submarine rather than a submarine that heavily relies on a foreign country (Germany). Also a nuclear propelled Korean submarine would diminish any chance that North Korea would remove/destroy its nuclear weapons and ballistic missiles. Korea might develop the KSS-N submarine if threats against it sufficiently increase and/or US military support diminishes.

Korea has long and extensive experience building nuclear power reactors - mostly large but still useful in any future development of submarine reactors. Interestingly DSME (as at April 2015) appears to be designing a "nuclear propulsion [surface] ship". This would have the legitimate purpose of meeting market demand for nuclear propelled, very large, ice-breaking, oil and LNG tankers. This activity also provides dual-use potential for submerged nuclear propulsion. 

In terms of an actual reactor technology path the Korea Atomic Energy Research Institute (KAERI) is also operating and further developing a small 100 MW ("SMART") pressurised water reactor with a output (at least) that may suite a 4,000 ton KSS-N. The SMART reactor's main current weakness is that it uses 5% enriched Uranium (U) 235 providing a poor power to size/weight ratio. 5% means SMART presently needs three year (overly frequent) refueling. Korea probably could legitimately develop the SMART at a higher (ice breaker surface ship) U enrichment percentage to make it much more useful as a submarine reactor. Korea has been seeking IAEA-US permission to develop a greater U enrichment capability but has been blocked. Although at a small amount-laboratory level Korea has a proven Uranium enrichment ability.

So Korea's indigenous submarine (KSS-III) program is well worth watching for its potential.

I'll do an article on North Korea's submarine situation in the future.

More Sources

http://www.nti.org/analysis/articles/south-korea-submarine-capabilities/

http://www.defensenews.com/story/defense/show-daily/sea-air-space/2015/04/12/korea-south-north-navy-modernize-coastal-scandal-sub-helicopter-frigate/25512681/

http://www.globalsecurity.org/military/world/rok/kss-n.htm

Pete

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.

------------------

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
---

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

---

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
---------------------

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. 

S Korean nuke sub Reactor likely to be French K15 Variant

India's Bharat Express News December 14, 2021 carries the New York Times (NYT) December 13, 2021 article "South Korea has long wanted nuclear submarines. A new reactor could open a door." without readers having to subscribe to NYT. NYT's article is reproduced by Bharat Express here https://www.thebharatexpressnews.com/south-korea-has-long-wanted-nuclear-submarines-a-new-reactor-could-open-a-door/

SUBMARINE MATTERS BACKGROUND AND COMMENT

South Korea is leaning toward a 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 fueled 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 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, 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 may feature 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.

South Korean SLBMs Possibly Nuclear One Day

South Korea's new KSS-3 SSB, with it nuclear weapons potential and talk of future SK SSBNs amount to major Northeast Asian nuclear proliferation matters. There are implications for all counties in the region, especially for nuclear-have-not-yets Japan and Taiwan. So I hope readers have not become bored with all the articles about these matters  over the last week.

Pete Comment

The KSS-3's AIP will give it the ability to cruise fully submerged for at least 21 days or sit motionless on the seafloor for at least 30 days. In that period one KSS-3 can act as a deterrent threat to North Korea. As SK makes more KSS-3s (perhaps six of them) there will always be one or two KSS-3s sitting on the seafloor ready to perform a first or second strike on North Korea. 

The link between SLBMs and nuclear potential is being increasingly expressed, in seeming concurrence with my own views in articles on September 8,  7,  3, 2021, August 31, 2021,  July 6, 2021,  September 19, 2018 and July 14, 2017  by writers.

ARTICLE

The following are parts of an excellent article, of September 8/9, 2021, by Reuters' Josh Smith, who, in turn, quotes other writers: 

"Analysis: S.Korea blazes new path with 'most potent' conventional missile submarine"

•                     Submarine-launched ballistic missile tested last week

•                     S.Korea only country without nuclear weapons to field SLBM

•                     Missile designed to target bunkers, leadership in N.Korea

•                     New missile raises questions about nuclear goals – analysts

SEOUL, Sept 8 (Reuters) - South Korea's development of a conventional submarine-launched ballistic missile (SLBM) is a ground-breaking move, analysts said, with implications for North Korea, the U.S. alliance, and even the prospect of nuclear weapons in South Korea.

Last week, South Korea conducted ejection tests of the SLBM from its recently launched Dosan Ahn Chang-ho KSS-III submarine, Yonhap news agency reported, showcasing a unique capability. It is the only nation to field such weapons without nuclear warheads. read more

Seoul says the conventionally armed missile is designed to help counter any attack by North Korea. Analysts say the unusual weapon also checks many other boxes, including reducing South Korea's reliance on the United States and providing a foundation if it ever decided to pursue a nuclear arsenal.

South Korea's ministry of defence declined to confirm the tests, but said it is pursuing upgraded missile systems to counter North Korea.

South Korea's sub-launched missile, believed to be a variant of the country's ground-based Hyunmoo-2B ballistic missile, with a flight range of about 500 kilometres (311 miles), is smaller than the nuclear-tipped SLBMs developed by the North.

...Ankit Panda, a senior fellow at the U.S.-based Carnegie Endowment for International Peace.[says]  "The SLBM is nominally justified in these terms, granting South Korean planners a highly survivable conventional second strike option in the face of North Korean attack; these missile systems would punish North Korea's leadership in the case of an attack on the south,"

...Although submarine-launched ballistic missiles are usually associated with nuclear weapons, that does not mean South Korea has them or is pursuing them, he said.

"However, should the alliance with the United States fray in the future or South Korea's national defences needs drastically shift, these SLBMs would provide an immediately available foundation for a limited, survivable nuclear force," he added.

A Political Issue

For now it is just an academic debate, but one that has made its way into the current South Korean presidential campaign, with some conservative candidates arguing that the country should seek a nuclear deterrent either on its own or by hosting American weapons, as some NATO allies do.

The United States removed its battlefield nuclear weapons from South Korea in 1991, but has continued to protect its ally under a "nuclear umbrella."

But recent years were tumultuous for the U.S.-South Korea alliance, with then-U.S. President Donald Trump pressing Seoul to pay more for the American military presence there, and even suggesting that countries, including South Korea and Japan, may need to develop their own nuclear weapons.

“It is unrealistic to prevent us from our own nuclear armament when North Korea has not given up its nuclear weapons yet," presidential candidate Yoo Seung-min said last month.

The SLBM programme doesn't appear to be part of elaborate plan to hedge toward nuclear weapons, said Joshua Pollack, a researcher at the James Martin Center for Nonproliferation Studies who co-wrote a report last year warning that advances in conventional missiles in both Koreas have helped create a new pathway for a crisis.

"It simply looks like South Korea is trying to catch up with North Korea," he said. "For decades, each side has been determined to show that it is more advanced and capable."

...Later [in 2019] North Korea said it had successfully test-fired a new SLBM from the sea, and in January [2021] it showcased a new SLBM design during a military parade in Pyongyang.

One Western diplomatic source said it was likely that other countries would follow South Korea's lead.

So far the test launch has not elicited public responses from officials in North Korea, Japan, China or other nearby countries, but South Korea’s neighbours are bound to ask tough questions, Pollack said.

"The loser here is the entire region, in the throes of a multi-sided missile race," he said.

Reporting by Josh Smith. Editing by Gerry Doyle.”

S Korea richer than Russia: So SK SSBN might be Affordable

Below Japan's Nuclear Weapon Breakout Capability of August 27, 2021 Gessler  commented on August 30, 2021. Also note my redded responses/suggestions. Gessler said:

Looking at [South] Korea's Joong Ang Daily of August 29, 2021 "Expectations are rising that the Korean military will announce the development of an indigenous nuclear submarine within the year, according to military sources who spoke on the condition of anonymity..."

It seems the South Koreans are intent on following-up the KSS-3 with a nuclear-powered multi-purpose [called KSS-N aka KSSX-N] submarine of approx. 5,000 tons displacement & 100-meters in length. [This coincides with my October 25, 2019 report where an SK study looked at the option of using a French Barracuda class nuclear sub design, which just happens to be 5,000+  tons and is 99.5m long.]  Not that different in size & scope from India's Arihant-class SSBN [Arihant is an estimated 6,000 tonnes and 111m long]. Plus as per the article they'd want to put up to 10 x SLBMs on it, though these are much smaller/shorter-ranged ones than what are carried by the Indian subs.

Two points of note:

1) If they are serious about submarine-launched ballistic missile capability, conventional explosives don't make much sense, only nuclear warheads do. I believe you wrote a good piece on this very topic a while back.

[Yes in my article S Korea Hedging with its KSS-3 Ballistic Missile Submarines of July 7, 2021 I wrote: "(SK) deploying its KSS-3 ballistic missile submarines shows an intention to eventually arm the ballistic missiles with a deterrent warhead - which can only be nuclear...If the SK warheads remained just conventional high explosive this would confuse North Korea (NK) (and everyone else) as to why SK is building ballistic missile submarines of 3,500-4,000 tonnes armed with ballistic missiles with a TOTAL high explosive throw-weight of only 6 to 10 tonnes."]

2) If SK decides to go nuclear (both in terms of warheads & submarine propulsion), then Japan cannot be expected to sit back & watch considering they have a direct rivalry with the Koreans and the mutual distrust seems to be growing in recent times.

[Indeed. My article Japan's Nuclear Weapon Breakout Capability of August 27, 2021 talks about Japan having the 3 major components (delivery platforms, U and Pu explosives and nuclear device knowledge) for a nuclear capability for decades. Also see my S. Korean & Japanese Nuclear Submarine Propulsion & Weapons of April 12, 2020. At the DSME website is Nuclear Propulsion Ship]    

A declining & increasingly isolationist US might prompt both of its East Asian treaty-bound & nuclear umbrella-sharing Allies to decide to go nuclear independently as they might think the US can no longer be depended upon to fulfill its obligations.

[Very true. The US's surprisingly quick withdrawal (looking more like a retreat) from Afghanistan worries many/most allies of the US.] 

This is going to be an interesting decade, that's for sure.

[True. US isolationism or, at least, downgraded relationships with Indo-Pacific allies, may be more than just a Trump policy. There is a risk it may become a US bi-partisan policy, now led by Biden, with US public support, for years.] 

PETE COMMENT

It is difficult to assess how imminent an OFFICIAL South Korean plan to build SSBNs might actaully be. There has been speculation that South Korea might be interested in developing nuclear propelled submarines (presumably nuclear armed) since 2009 if not earlier. Normally South Korea press speculation comes from anonymous South Korean military tip-offs of the type in this August 2021 instance.

There are numerous addition articles at Submarine Matters on South Korean SSBNs, SSBs and nuclear warhead ambiguous SLBMs. Just click on https://gentleseas.blogspot.com/search?q=nuclear+south+korea+submarine+KSS and you'll see more than 10 artcles, particularly if you scroll down and click on "Next Posts".

I would say the US retreat from Afghanistan is one tip-off prompter. Ongoing North Korean nuclear threats another. 

But what may be worrying South Korea most is North Korea restarting its Yongbyon reactor in July 2021 with Yongbyon believed mainly there to produce Pu for nuclear weapons. Also the Yongbyon complex hosts a laboratory which may have been reprocessing spent reactor fuel since March 2021. Any IAEA and US protests seem muted with international attention focussed on Afghanistan.

At a minimum South Korea may be reminding the US of the US nuclear umbrella promise against North Korea. Although as South Korea is ramping up its vertical launch plans toward 10 missile silos for its KSS-3 (future) Batch 2s a later Batch with nuclear propulsion might be a logical step. I also flag South Korea's nominal GDP is equal to or greater than Russia's. So a South Korea SSBN is not as outlandish as many might think.

Gessler and Pete

S. Korean & Japanese Nuclear Submarine Propulsion & Weapons

Hi Tri-ring and Anonymous (your August 11, 2020 comments on Japanese and South Korean submarines nuclear propulsion possibilities).

1.  Tri-ring I think it much more likely Japan and South Korea will further develop what they have already achieved that is Pressurized Water Reactors (PWRs) that are small enough to fit on small ships. The fusion and other advanced engines (you mention) are for the US and China in coming decades.

Anonymous, I agree with you that South Korea will eventually move to nuclear propulsion, but suspect it will build SSBNs before SSNs.

As a technical and political EVOLUTIONARY process South Korea has been at looking at the issue of a nuclear or conventionally propelled ballistic missile launching First and Second Strike platform for more than 10 years. South Korea would have been looking at the nuclear issues even earlier: since 2003 when North Korea withdrew from the NPT and since 2006 North Korea's first nuclear weapon test.  

Japan, in 1972, completed the Mutsu small nuclear propelled ship, working nuclear reactor and all. 

South Korea has had a less visible marine reactor program with a view to using a modified civilian SMART reactor (note mention of an even smaller "SMART-P(SMART pilot plant, 1/5 scale)") 

or equivalent since 1997. At the DSME website is Nuclear Propulsion Ship. Meanwhile South Korea likely has a parallel program with plans for a smaller reactor for a submarine. 

Since these major advances in reactor miniaturisation for Japan (48 years ago) and South Korea (23 years ago) these advanced civilian reactor countries will have made substantial gains in knowledge on how to further miniaturise.

Also Japan and South Korea have overt and covert intelligence programs to gain knowledge from existing submarine reactor countries (US, UK, France, Russia, China, India and Brazil) on how to further miniaturise.

2.  Meanwhile South Korea is technically and politically evolving submarines as First and Second Strike weapons against discreet targets in North Korea's cities and nuclear weapons facilities. South Korea is developing its KSS-III (3,360+ ton) submarines to each eventually vertically fire 10 missiles (cruise and eventually ballistic). The 9 x KSS-IIIs planned have air independent propulsion (AIP) and from the Batch II subclass onwards they may have Lithium-ion Batteries (LIBs). AIP + LIBs may give a KSS-III the ability to lie in wait, sitting on the seafloor, for 6 weeks without surfacing. 

KSS-IIIs being commissioned up to the mid 2030s may be a credible deterrent against North Korea but not against China. North Korea, would generally assume that 500+kg warhead incoming missiles may well have nuclear warheads. North Korea would therefore deliver a nuclear response. South Korea going to the trouble of building whole submarines with only 10 relatively small (500kg) warhead missiles is only explicable if these missiles eventually have nuclear warheads.

A South Korean nuclear propelled ballistic missile class (lets call them "KSS-BNs") being launched from the late 2030s may be sufficient against China and Russia (and against India, the US and Japan for that matter). 

Can South Korea afford nuclear weapons and nuclear propelled submarines? When you look at nominal GDP for South Korea its GDP is equal to or greater than Russia's. South Korea's nuclear military aspirations have been held back by US promises of a nuclear umbrella against North Korea and China. This umbrella and US, Russian and Chinese political power has not stopped North Korea from nuclear arming. South Korea will feel even more desperate to build a true deterrent in 12 years time when North Korea will have fleshed out its nuclear triad.

South Korean Submarines KSS-II, KSS-IIIs and Nuclear "KSSX-N" Option

Simplified cutaway of Germany's HDW U-214 AIP (designated KSS-II by South Korea). South Korea has announced it will order/build a new batch of 6 AIP KSS-IIs.

-----------------

Please connect with Submarine Matters latest South Korea update South Korean Submarines, 3,000 Ton KSS-III, Nuclear Potential of April 15, 2015

The following Submarine Matters article was originally drafted in September 2009. 

South Korea (hereinafter called "Korea") is planning a large future conventional submarine, known as KSS-III and/or "Jangbogo III" displacing 3,000 tons (submerged). 

-

Korea plans to design and build the KSS-III locally. The KSS-III will involve some advanced design and Korean production solutions of particular interest. The first KSS-III will also be built (launch date perhaps 2022) slightly ahead of Australia's future submarine (likely launch date 2027).

-

The increased tonnage of the future KSS-III suggests that Korea is looking at a larger AIP system,  much longer range or a vertical launch system (VLS) (for first or second strike against North Korea using Hyanmoo III missiles) or a combination of the three.

-

Korea's main submarine opponent is almost certainly North Korea. As North Korea is a nuclear and conventional threat to Korea and a constant infiltrator South Korea's main submarine task would probably constant intelligence gathering - including monitoring of intruding North Korean submarines. Korea also considers China a threat and (less likely) Japan or Russia.

-

Korea's advanced nuclear power industry and the announcement that France is to assist Brazil in creating a nuclear powered Scorpene raises the possibility that Korea might consider nuclear propulsion in the distant future. Only a nuclear powered submarine has the sustained speed to chase/shadow one of China's emerging SSBNs or SSNs. Cooperative tactics with US SSNs would therefore be essential.

Background on KSS-III Development

From The Korea Times, May 10, 2009 reports:

"The Ministry of National Defense plans to deploy 3,000-ton [surfaced, 3,500 ton submerged] attack submarines after 2020, a two-year delay from the original Defense Reform 2020 initiative, a report said Sunday. ...The development of an [indigenous] 3,000 ton KSS-III submarine is a key part of the Navy's modernization programs. The KSS-III sub is to be fitted with domestically built submarine combat systems aimed at automating target detection, tracking, threat assessment and weapon control, according to Navy officials. The 1-trillion-won heavy attack submarine will also be armed with indigenous ship-to-ground cruise missiles and be capable of underwater operations for up to 50 days with an advanced Air Independent Propulsion (AIP) system, they said. The AIP system has improved the submarine's underwater performance and gives it stealth capability." full article

On South Korea's past consideration of a 4,000 ton nuclear propelled submarine (various names including "KSSX-N") option see this globalsecurity.com report. 

Pete

South Korea Looking At France's Barracuda SSN or Just the K15 Reactor

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, designs 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. 

"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 fueled by low-enriched uranium."

It is conceivable that France may want to sell a complete French built Barracuda to South Korea, 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. Thus KSS III Batch III would become the nuclear propelled KSSN or KSSX-N.

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 placed on exporting/importing US and UK submarine reactors (with weapons’ grade HEU of 93-97 percent (see p. 20)) and Russian naval reactors (reported to use 20 to over 90 percent HEU (p. 20)). 

-  and technical advantage of the Barracuda's reactor being built for a submarine of just over 5,000 tons, ie. in the KSS III Bach III weight bracket. The Barracuda's K15 reactor stands for 150 MWt which translates to 30 MWe for Barracuda’s hotel load + propulsion.

It is significant that France, for over a decade, has been assisting Brazil in designing the non-nuclear aspects of Brazil’s future SN-BR SSN (to be called Álvaro lberto). 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.” Such non-nuclear assistance could be extended to South Korea and perhaps with a more quiet transfer of some K15 technology.

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 may feature 10 and the KSS III Batch III perhaps 12 to 16. If  the KSS III Batch III were nuclear propelled and had 12 to 16 VLS tubes this would amount to a middle naval power mini-SSN/SSBN solution. This would avoid the much higher great power expense of building separate specialised SSN and SSBN classes.

Neighbouring Japan (a part strategic competitor of South Korea) and Australia with its future conventional Barracuda (known as the Attack-class) are closely observing South Korea's interest in nuclear propulsion and ever larger submarines.

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

Pete