Uploaded May 2, 2026 - How France Built Its First Nuclear sub with little US help (except US HEU to fuel a land-based prototype of a nuclear submarine reactor in France). While the US and Soviets dominated the seas, French engineers quietly created the major arm (SSBNs) of then called Force de Frappe. ---
Generally nuclear submarine powers evolve their force from first sub - a prototype - then SSNs then SSBNs or visa versa. Only the US and Soviet Union had the money to build prototypes, SSNs AND SSBNs simultaneously. SSBNs are strategic deterrents.
Australia's SSN-AUKUSs will defend friendly SSBNs (like those of the US, India and eventually South Korea and Japan) and destroy enemy SSNs and SSBNs (like those of China, Russia and North Korea).
Both France and India built SSBNs first. Part of this is because their Bastion range (protected by surface ships and mainly maritime patrol aircraft (MPAs)) can be/were short.
French Redoubtable-class SSBNs and see here and here (in the 1970s to early 2000s) needed to operate close to shore (mainly Bay of Biscay and later some northern European waters). This enabled them to put their relatively short range SLBMs (M1s/M2s/M20s and M4s (see below)) missiles with ranges of 2,500km to 5,000km to hit Moscow and some military-industrial Soviet/Russian/other Warsaw Pact targets including Kyiv (in Soviet Ukraine up to 1991).
"Due to the duration of the [Redoubtable-class] between 1971 and 1986, the main armament, sixteen SLBMs, varied in time, from the M1 to the M4. The M1 was a 1st generation SLBM, and was short-ranged, obliging these subs to patrol along the Norwegian coast or gulf of Genoa. The M1 was retired from service in 1975, replaced by the M2 until 1978, then the M20 with MIRVs, whereas the M4 with a new 6-MIRV warheads entered service in 1985 on FS Inflexible."
Staying close to home in the Bay of Biscay allowed the French Navy to easily protect and maintain constant communication with the SSBNs via the Île Longue nuclear submarine base near Brest.
India
Similarly Indian Arihant-class SSBNs were/are built to operate in the Bay of Bengal, protected by Indian MPAs, to put their K4 SLBMs in range of all Chinese targets up to and including Beijing. India's future SSNs may be in construction for 20 years (until the 2040s) before they are operational to defend the longer range missile SLBM S5 SSBNs.
South Korea (SK)
SK is the only country in the world with SSBs (KSS-III Batch 1s and 2s) large enough to carry full size SLBMs. I conclude SK's first nuclear powered sub will be a prototype/testbed to acquire US nuclear sub technology. SK will then build "SSGNs" (de facto SSBNs) capable of carrying SLBMs in range of North Korean targets. These SLBMs will be notionally conventional warhead but quickly convertible to nuclear warheads.
10 comments:
Fr Ano@8/14/2026 from last blogpost: The SK is a signatory to the NPT and to the U.S.–ROK 123 Civil Nuclear Agreement. Under Article III of the NPT, South Korea is therefore bound by its safeguards obligations, and you cannot simply wish those obligations away.
You cannot just move safeguarded nuclear material around and secretly fuel a test reactor. Such activities have to be reported to the IAEA. The relevant mechanism is Article 14 of INFCIRC/153, which Australia has also adopted. Even under that provision, the state is still required to report the relevant activities to the IAEA.
For highly classified nuclear research, there are essentially three possible pathways: being a P5 nuclear-weapon state, being a non-signatory to the NPT such as India. There is a third option: be like “Eye-ran” (like American pronounce).
So, no, I am quite sure there is no secretly developed research/test-bed ground marine reactor in South Korea. Under its existing NPT and safeguards obligations, such activities cannot simply be conducted without IAEA reporting.
Hi Arpit at 8/14/2026 1:53 PM
The US, great exceptional arbiter of International Law, decided India could be a de facto P6 nuclear weapon state; decided Australia could buy UK and US reactors full of 95+% Bomb grade HEU; and has decided something shady secret, but military nuclear, for SK.
No great power or the UN IAEA dare contradict the USA.
Cheers Pete
Article X of the NPT allows countries to withdraw on 3 months notice.
South Korea operates 3 CANDU heavy water reactors (one of the original 4 has been retired). The CANDU produces tritium (required for boosted fission weapons) and can, once IAEA safeguards are removed, be used to breed plutonium.
The CANDU is capable of online refueling, allowing it to maximize use of U-235. This capability can also be used to move fuel bundles through the reactor in such a way as to maximize production of Pu-239 (something the IAEA watches out for).
I would note that India used similar reactors in their nuclear weapons program.
For Australia, building a power plant with 4 CANDU reactors could replace an existing coal power plant, helping reduce CO2 emissions, and giving Australia the option to become a nuclear power without committing Australia to follow that path.
There may be value in Australia having the option but not using it as it will give the US an incentive to keep Australia under its nuclear umbrella so Australia does not feel it needs nuclearweapons. Whichever way it goes Australia would still have the electricity from the reactors.
Fr ano
I hear what you say,You are looking at it from a legal stanpoint
I am looking at it from an engineering logic
In tha AIEA SMR catalogue ther are 3 S Korean models.the most advanced the I-Smart is ready for commercializtion which are very close to SM need
170 mW T, integral type ,with the steam generator above the core and allowing for natural circulation, in case of low power /pump failure. Life time is 24/36 monthg before refuelin wit UO2 material à 5% enr;
A modificartuion of the fuel , loading , planar etc will allow to have a 10 year life while l the safety /hydrodynamics /thermal would be alredy tested which is usually the majoir issue
KAERI has published public papers on planar high loadig fuel plates in 2024
As an engineer I know that critical experiments , well planned, on a bench in a lab reduces orders of magnitude the risk
But I must admit I have no proofs
I, Arpit Kanodia, comment:
Pete2: Indeed, you are correct about it. But the US has always allowed it under the legal framework; the exception was the A.Q. Khan network.
And it is not that simple to move safeguarded nuclear material around or refuel a reactor. The US might not say a thing, but Russia, China, or Japan would have reported it.
Or perhaps there is some secret source of uranium that no other country knows about.
But I get your overall point: if the US wants it, the IAEA won’t be able to do much. However, I don’t think the US would allow it to operate in secrecy.
Fr Ano: Firstly, treating a civilian reactor as a military one is one of the biggest red flags people should avoid. It is essentially like assuming that all P5 countries were completely fools and that the laws of physics somehow work differently for South Korea.
Every nation that develops a nuclear-powered submarine typically builds a land-based reactor test facility, often resembling a partial or full-scale section of the submarine. This is not merely for testing the reactor itself; it is also critical for validating the reactor-control system, ruggedising the reactor and its associated systems against shock and vibration, and operating it across different power levels and transient conditions.
The certification and qualification of every component to the required MilSpec are equally essential. This includes everything from individual pieces of equipment, from rods to piping, valves, pumps, electrical systems, and safety-critical components.
So, the idea that South Korea could simply use a civilian reactor to accomplish all of this is highly questionable. If that is the assumption, then best of luck to them.
Hi Arpit at 8/15/2026 6:19 PM
Evidence seems to be SK is bursting to break out a nuclear weapons capability. Only US offers, like helping to build KSS-N, are holding SK back.
A similar scenario, export of 8 AUKUS Pillar 1 SSNs, seems to apply to Australia.
On SK history, see:
https://en.wikipedia.org/wiki/South_Korea_and_weapons_of_mass_destruction is interesting including:
https://en.wikipedia.org/wiki/South_Korea_and_weapons_of_mass_destruction#Early_nuclear_ambitions
https://en.wikipedia.org/wiki/South_Korea_and_weapons_of_mass_destruction#Previously_unreported_experiments
https://en.wikipedia.org/wiki/South_Korea_and_weapons_of_mass_destruction#Russian_nuclear_program_proposal "Russian nuclear program proposal
In 2025, a South Korean declassified document confirmed that Russia offered nuclear programs to repay debt inherited from the Soviet Union. In 1992, Russia offered advanced nuclear and plant life-extending technology. In 1994, Russia offered 50 tons of highly enriched uranium [HEU] originating from Ukrainian nuclear warheads plus 150 tons of low-enriched uranium annually for 10 years.[31][32]"
Also see https://www.theguardian.com/world/2025/oct/23/south-korea-monster-missile-hyunmoo-5-balance-power-north
Cheers Pete
Hi Bill at 8/14/2026 3:48 PM
Australian invented SILEX might offer even a quicker, easier, U enrichment path.
See my https://gentleseas.blogspot.com/2025/09/australian-invented-silex-process-also.html In it I wonder whether the Bomb Development Factory that is Los Alamos (and maybe Sandia) might have a program for SILEX enrichment to 95% HEU. This would be a secret parallel program to the Paducah, Kentucky public program to <20% LEU.
What do the SILEX inventing Lucas Heights Aussie scientists in Australia and maybe in the US(?) think of all this?
Cheers Pete
I dont think Ano Engineer was seriously implying you could just plonk a civilian reactor into a sub - if nothing else the power-draw profile and fuel cycling methods are completely at odds. I think the point was that once you have mastered the massive challenges of building any kind of a viable compact reactor, the engineering challenges of militarising the fundamental technology is substantially less of of a challenge. IE learning to walk is hard, learning to run, having mastered walking, doesn't take long. (As any parent knows!)
From Fr Ano
Yes it was exactly my point.As I said, I have no proof that a complete on shore was actually operatedHowever all the critical elements are public.Putting it together is not a major issue in my opinion..if it has not been done
The SK SMR is a very comptct 170 Mw vertical fully integrated reactor (The steam generator is directly locared above the fuel assembly w/o any piping but probably vertical baffles to have ,as a claim ,an intrisic safety thru natual convection in case of pump failure /shut down..(low power silent pump free..?)
The critical elements of hydrodyamics/thermal exchange in a compact 170 Mw th system is tested
.Thre robotized system to open the top ,remove the steam gen, the fuel assenbly, replace it ..quick is also tested..
Changing the fuel assembly toward a plate system with high loading to reach 10 years life at 5 %to 7% wir the same power density is needed.KAERI has published papers in 2004 about its technology in this area on a lab scale
Again I am expressing an engineering opinion
Interesting to note that TechnicAtome, (partial sub of Naval Group,), the Fr Engineering company behind 60 years of naval military reactors is proposing exactly the reverse path in the Nuward civilian SMR project with various power levels starrting at 170 Mw
As a piece of info the K 15 (150 Mw th) in within a container 5 m tall and 3 m in diameter. assembly and has a similar set up, the fuel "chemistry" and the plates mfg process might be different however if you look at KAERI paper
Hi CDD at 8/19/2026 2:57 PM and Fr Ano at 8/19/2026 7:07 PM
A little research I've just done yields this titbit. https://en.wikipedia.org/wiki/French_submarine_Gymnote_(S655) advises:
"The French planned a nuclear propelled submarine in the late 1950s and laid down a hull (no Q244). Because France had not developed uranium enrichment facilities at the time, the planned power plant was to be a heavy water reactor, which could utilize natural uranium. But French engineers were unable to produce a reactor small enough to fit into the submarine, which led to the project being cancelled in 1959.[1] "
[[1] is long French document https://web.archive.org/web/20091014011143/http://www.stratisc.org/ihcc_nuc1_Gempp.html ]
"In the early 1960s the French government decided to develop an independent nuclear deterrent based on SLBM's. Hull Q244 was redesigned as a trials submarine with diesel-electric propulsion and four missile tubes in an extended casing. Re-designated Q251 and christened Gymnote, she was commissioned in 1966 and fired the first M-1 missile in 1968. The M-1 missile was subsequently deployed aboard the Redoutable-class submarines. She was extensively rebuilt in 1977-79 to enable trials of the new M-4 missile. In the 1980s, as part of a general re-numbering of the French submarine fleet. Gymnote was re-designated S655.
Gymnote/S655 was decommissioned in 1986."
Cheers Pete
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