Following Submarine Matter's articles France’s Future SSBN “SNLE 3G” Starts Production of March 28, 2024; France's New K22 reactor for Carrier & 3G SSBN of December 27, 2023; and French LEU Reactor & SSN Implications of March 24, 2023:
The USN, and partly the UK RN, rely on the US' massive HEU naval reactor industrial
base to develop new reactor technology and to create the 94+% HEU fuel.
In contrast France developed LEU naval reactors. HEU requires a
specialized and expensive naval reactor fuelling program, while dual civilian-naval LEU fuel is less expensive.
But it was not always so. Alain Tournyol du Clos in a Federation of American Scientists (FAS) study of December 2016, reported https://uploads.fas.org/2016/12/Frances-Choice-for-Naval-Nuclear-Propulsion.pdf on page 2:
"[The Redoubtable-class SSBNs always used HEU reactors. They] were equipped with nuclear plants identical to" [France’s land based prototype HEU reactor known as “PAT”].
“Yet, very soon after the start of
the first SSBN, the scientists working in CEA (the French Atomic Energy Commission) who were in charge of developing nuclear propulsion, realized
that [French nuclear submarine classes after the Redoubtables] could use LEU, in dioxide form, to produce cores which would
provide energy to the SSBNs four to five times (20 to 25 years) greater than
with the first generation of cores. This was possible, on the one hand, because
the conception of the first generation cores included high margins and, on the
other hand, because SSBNs are low consumers of energy due to the nature of the
slow, steady speed of patrolling.”
“After [the Redoubtables], the French Navy decided to adopt cores using
low-enriched uranium dioxide for all the following classes of nuclear ships:
SSN Rubis class, SSBN Le Triomphant class, SSN Barracuda class, and CVN Charles
de Gaulle."
Alain Tournyol du Clos further reports:
"In 1996, France decided to stop
enriching uranium to HEU levels for weapons purposes [A secret - France by 1996
then mainly relied on Pu and Tritium for its all 2-stage thermonuclear weapon
arsenal]. If the Navy had wanted to use HEU fuel, it would have had to invest
significant money to have its own HEU enrichment facility. By choosing to only
use LEU fuel with enrichments much less than 20 percent in the fissile isotope
uranium-235, France has saved money by purchasing from the commercial
market. Moreover, France’s decision to use LEU fuel for naval propulsion has
not degraded the operational performance of the ships."
France’s new K22 220
MW (thermal) about 37 MW (electrical?) naval reactor
Regarding France’s latest naval
reactor, the K22 French Anonymous commented
(along the lines) the K22 is not a major problem. It has been tested in land
based prototype form at the new RÉS facility https://inis.iaea.org/search/search.aspx?orig_q=RN:38002931. This K22
prototype went critical in 2018 at France’s major nuclear reactor research
centre at Cadarache._CIA_World_Factbook_map.png)
The K22’s engineering may have been completed
in 2023 with actual construction of the sea based K22 being started at Naval
Group’s Nantes-Indret complex https://www.navalnews.com/naval-news/2021/06/naval-group-signs-first-industrial-orders-for-future-french-navys-third-generation-ssbns/ . K22s
will initially go into France’s future SSBNs (SNLE 3Gs).
More interesting on the Naval Group
video [Alas Pierre (Pete) cannot find it!?] is the computerized thick steel plates water jet
cutting in a swimming pool sized facility (very high precision and no thermal
stresses).
Two x K22s will later go into France’s future nuclear powered aircraft carrier PA-NG (see video here and below) with construction
beginning in France’s Saint Nazaire shipyard in the mid 2020s to early 2030s.
Significantly the K22 is a development of the K15 with 50% more power and perhaps a 25% increase in size. The K22 will use the same LEU refuelling and inspection processes as the K15 – that is using robots.
A Nuclear Threat Initiative 2010 paper https://www.nti.org/analysis/articles/expanding-nuclear-propulsion-challenges/ makes some interesting points about LEU "Caramel" fuel in French Navy reactors including the K15 and presumably the K22:
"...French nuclear vessels are able to extract more energy from LEU than are U.S. vessels by taking advantage of a more LEU-efficient fuel design. The French navy uses a uranium-dioxide composite embedded in a zirconium alloy grid, an arrangement known as "caramel" fuel.
CARAMEL fuel increases the efficiency of the burn-up of uranium-235 so that lower enrichment levels and/or smaller reactor volumes can be employed with a greater energy yield. Studies have shown that a design in which small spheres of uranium dioxide are embedded in a zirconium matrix can boost the efficiency of the fission reaction even further.[32]"