French Navy upgrade and discussion


(…) However, the Charles de Gaulle aircraft carrier is supposed to enable the deployment of the Force Aéronavale Nucléaire [FANu], which was created in 1978 and is one of the three strategic forces of the French deterrent.

Unique in the world since American aircraft carriers no longer carry nuclear weapons, the FANu is a "force of circumstance" which, when the aircraft carrier is at sea, is obviously under the sole control of the President of the Republic, Head of the Armed Forces. If GAN
[Naval Air Group] comes under the operational control of Nato, it will not.

"We are in no way going to lose our strategic autonomy. We can recover the mandate at any time" and place the GAN back under national command "during an operation, if necessary", explained Vice-Admiral Maleterre.
/deepl
 
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Namaskaar, in 2016 the FAS published a short ten-pages study
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I am reproducing a few pages here:

Table of contents:
Executive Summary; Introduction: The Advantages of Nuclear Energy for Naval Propulsion; A Brief History of French Naval Nuclear Propulsion; Nuclear Energy in France; Nuclear Safety Rules; Loading and Unloading of the Reactor Core; Enrichment versus Performances; Enrichment and Power of the Core; Enrichment and Lifetime; Enrichment and Maneuverability; Enrichment and Circuit Contamination; Conclusions for Naval Reactors’ Lifetime and Performance; Economic Considerations; Overall Conclusions: France’s Choice


Executive summary
Why did France decide to fuel its nuclear powered submarines and aircraft carrier with low enriched ura- nium (LEU) and switch from using highly enriched uranium (HEU)? While HEU offers very high energy density for compact reactor cores and thus can be used for lifetime cores, the choice for LEU fuel made sense given France’s technical, regulatory, and economic context. In this report, Alain Tournyol du Clos, a lead architect of France’s naval nuclear propulsion program, explains the reasons for France’s decision.

France’s nuclear safety regulations require inspections of civilian and military reactors and their components every 10 years. For the French Navy, these inspections are timed to match overhauls of the nuclear-powered ships and the refueling operations. To make refueling efficient, the submarines’ hulls have brèches (special type of hatches) that allow for relatively quick refueling while also maintaining hull integrity to permit the submarines to dive safely to deep depths.


In the 1970s, in response to the major oil embargo, France decided to invest heavily in nuclear power plants for electricity generation. The French Defense Ministry chose then to couple as closely as possible its own nuclear program to the civilian program in terms of organization and infrastructures. This decision saved considerable money and allowed sharing of operational and organizational experiences.

In 1996, France decided to stop enriching uranium to HEU levels for weapons purposes. 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.


Is LEU fuel the right choice for other nations? The author points out that it depends on the technical and economic context. For non-nuclear weapon states that only want a small nuclear navy, such as Brazil, this choice would be very suitable. For nuclear weapon states with existing large nuclear navies, such as the United States or Russia, this choice could help promote the establishment of a fissile material cutoff and serve as an example to other nations.

(…)

Loading and Unloading of the Reactor Core
(…) a submarine hull will experience during its operational life various pressure cycles due to diving operations; most navies do not like permanent hatches in the hull and hence will cut openings when needed for maintenance and re-weld the hull when maintenance is over. Unloading and reloading the nuclear core at each overhaul would require cutting the hull on top of the nuclear plant pressure vessel and re-weld it every time. Those repeated operations in the same area will weaken the steel and, thus, could limit the maximum depth authorized for the submarine in the long run.

However, as far as French submarines are concerned, this problem does not exist as the designer since the “Arethuse” type — a type of small conventional submarines built in the middle of the 1950s — has incorporated in the hull some specific openings (called “brèches” in French). Brèches are rectangular hatches of sufficient dimension to permit loading and unloading of heavy equipment. The photographs and sketch below define and illustrate these brèches. They can be described as portions of the pressure hull that will fit in such a manner that the external pressure will seal them in the right position. Inside the hull, some safety bolts will ensure that even in severe shocks they will stay in place.
GMKQK2_W4AAo9L3.jpg


Several brèches are positioned all along the hull, one of which being on top of the nuclear plant. Unloading the core is then relatively easy and can be done at any time, even during the short stays in port between patrols (it was effectively demonstrated on SSBN Le Redoutable).

Considering that unloading the core is compulsory at each overhaul to fulfill nuclear safety regulations and that it can be done as often as necessary without affecting the diving performances of the submarine, the need to develop a lifetime core is not of paramount importance for the French Navy. LEU can then be used if it does not degrade the required performances of the submarine as examined in the next section.


Enrichment and Power of the Core
Criticality and power are two important concepts determining operations of a nuclear reactor core. Criticality will be attained in fuel elements when the number of neutrons produced by fission remains constant over time; criticality does not depend on the number of neutrons present at any moment but only on the fact that it remains constant. Power produced by the core is directly related to the number of fissions generated per instant of time and is thus directly related to the number of neutrons present in the core.

Thus, when the core is critical it can produce any level of power without change; the limit of power that can be produced by a core at any moment is not in relation with the enrichment of the fuel but with the capacity of the circuits (primary coolant circuit and steam generators) to extract the power without the fuel elements’ temperature exceeding their normal operational range.


Enrichment and Lifetime
Limits to the acceptable volume of the core are given by the maximum size of the pressure vessel that can be accommodated inside the hull of a submarine. Given this core volume, by increasing the fuel enrichment, the quantity of U-235 is increased and hence the core lifetime can be increased. However, another factor limiting the potential lifetime of the core is the capacity of the alloy used for the clad- ding of the fuel elements (generally a variety of Zircalloy) to withstand the increased burn-up of the fuel. With an increase of the burn-up, the pressure inside the fuel element (due to gaseous fission products) will increase, and at the same time the cladding will be damaged by the neutron flux; the result will be a swelling of the cladding which can evolve to a rupture. Above a certain value of burn-up it may be necessary to develop new alloys and to qualify them; both operations could be very expensive.

The maximum attainable lifetime of the core will then result from a compromise between fuel enrichment and mechanical resistance of the structures containing the fuel.


Enrichment and Maneuverability
Power changes occurring in the nuclear steam supply system will involve two counter-reactions in the core: the first due to the change in the temperature of the moderator (primary water) and the second due to the change in the temperature of the fuel. The first counter-reaction is called the temperature coefficient of reactivity, or temperature coefficient; this coefficient is negative, meaning negative feedback. Thus, when the power in the core increases, the primary water temperature increases, and its density and its moderation capacity diminish, implying a sub-criticality of the core and hence a halt in the increase of power. If the power in the core decreases, the reverse effect will stop the decrease.

A practical consequence of this characteristic is that the operators can drive the propulsion system by acting on the turbines: an increase in the demand of power will lead to an increase in the steam flow; therefore, this will reduce the coolant temperature and increase the power produced by the reactor until power produced equilibrates the power demand. Diminishing the turbines’ speed or the steam demand will increase the temperature of the primary circuit and diminish the power produced by the reactor. The reactor operator plays then mostly a surveying role and at most has to anticipate the transients to avoid stress on the components.

The second counter-reaction is the power coefficient of reactivity (also called the Doppler Effect); it is also negative. This is due to U-238, the non-fissile isotope of uranium. When the power produced by the core increases, the fuel temperature increases and the absorption cross-section of U-238 (i.e. the proba- bility that neutrons will be absorbed by U-238 instead of provoking fissions in U-235) will increase; that diminishes the core reactivity and thus the power increase. This Doppler Effect is favorable for nuclear safety as it prevents rapid increases of power; it is by all means greater for fuel made with LEU (in which the U-238 proportion is much greater than the U-235 proportion) than for fuel made with HEU (in which the proportion of U-238 is much less than U-235).

However, due to their specific structure, the internal temperature of the fuel elements of a submarine core is lower than for fuel elements made with rods (as used in civilian electricity generation reactors). This significantly reduces the Doppler Effect in the system.

What’s more, it must be remembered that the submarine maneuverability — which is what is sought after — depends also on a certain number of other parameters including: turbines’ capacities to change speed, cavitation phenomenon on the screw propeller, hydraulic inertia of the submarine, etc.


The French Navy, which has experimented on the same types of ships bot h LEU cores and HEU cores, never noticed any difference between them as far as maneuverability was concerned.

(…)

Conclusions for Naval Reactors' Lifetime and Performance
It appears from the above analysis that choosing LEU or HEU for the nuclear core does not influence the immediate performance of the submarine. However, using LEU diminishes the maximum lifetime permitted by the core and will most likely require the use of a greater number of cores during the opera- tional life of the submarine.

The operational life depends principally on the weapon combat system and usually will be comprised between 25 and 35 years but it may go up to 40 years. If the submarine is a “low” consumer of energy — which is the case for SSBNs — one or two cores even with low enrichment fuel will be sufficient for the lifetime; on the contrary, if the submarine is a higher consumer, such as SSNs, a greater number of cores will likely be necessary.

Importantly, for the French Navy, as unloading is required at every major overhaul and several times without compromising the diving performances, the choice between LEU and HEU does not rely on operational considerations but only on economic considerations as examined next.

(…)

Overall Conclusions: France's Choice
The specific elements — which are developed in the previous paragraphs — that have driven France’s choice can be summarized as follows:


1. French nuclear safety regulation requires periodic unloading of the naval cores.

2. The specific architecture of the French submarines permits unloading in short periods of time without lessening the strength of the pressure hull.

3. The immediate operational performances of a submarine are not affected by the choice of low enrichment for the uranium used in the cores.

4. France has during the past years built major facilities to fulfill the needs of its electricity generation reactors (mainly enrichment plant and reprocessing plant) that the French Navy can use for its purposes.

Taking into account these conditions, a reasonable choice for France was to develop nuclear propulsion cores using a technology very close to the one used in the electricity generation reactors. This choice — which has had been said is very dependent on the economic and technical context — can nevertheless be taken as an example for other nations that want to acquire nuclear submarines. Such nations could be non-nuclear weapon states such as Brazil.

Finally, it should be noted that the halt decided in 1996 of the production of weapons-grade uranium, joined with the halt decided in 1992 of the production of plutonium for nuclear weapons, allowed France’s government to advocate a treaty forbidding the production of fissile materials for nuclear weapons. The blueprint of such a treaty, called the Fissile Material Cut-Off Treaty, has been tabled in April 2015 as an official document to the Disarmament Conference in Geneva.


© 2016 by the Federation of American Scientists. All rights reserved.
France's Choice for Naval Nuclear Propulsion: Why Low-Enriched Uranium Was Chosen - Federation of American Scientists
 
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#LOG
New French navy Logistic support ship, BRF Jacques Chevallier
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supplying the aircraft carrier Charles de Gaulle with Aster missiles (VLS):
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Unfortunately, neither a frigate nor a destroyer can carry a truck crane...
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But there are French bases in Djibouti in the Red Sea, and on Reunion Island in the Indian Ocean.

Here supplying a Rubis class SSN:
GLMBaSBWoAAzTRg
 
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nmskar 🙏
it's been a long time since I last posted here

2 news items since June dated 13&12 of july:

1/ #F_IOR // La Reunion Island
Reaper drones may be deployed on an ad hoc basis on Réunion

i read that at La Reunion Island: Intervention capabilities will benefit by 2030 from the possibility of carrying out inter-theatre airlift with the permanent cover of A400Ms in the Indian Ocean", states the Military Planning Law_2024-30.

i also read: Air Force Base 181 "Lieutenant Roland Garros" [La Réunion Island] will see its capabilities "strengthened", with the possibility of "punctually" hosting "MALE drones of the [MQ-9] Reaper (1) type, Dassault Falcon 2000 surveillance and reconnaissance aircraft and A400M transport aircraft or [A300MRTT] tankers".

Finally, General Mabin at a recent hearing in the Senate [upper Chamber] dedicated to the strategic environment of Mayotte and Réunion saying: … the bases on Réunion and Mayotte are "safe" support points, in the sense that they "are not subject to the potential political versatility of third countries, nor to direct threats that could affect our forces pre-positioned in Djibouti or the United Arab Emirates.

(1) i therefore assume that these facilities will be "interoperable" with IN's SeaGuardians, in the same way that MN's port facilities on Réunion are already interoperable with Indian vessels.


2/ #subs #SNA_Tourville (Suffren SSN class n°3)
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Third unit of the Suffren class, the Tourville nuclear attack submarine begins sea trials
(...) On 12 July, the Tourville made its first sea voyage, marking the start of the test campaign prior to its delivery to the DGA and then to the French Navy. Like its two predecessors, the SNA Suffren and the SNA Duguay-Trouin, the Tourville crossed the Cherbourg roadstead to venture into the Bay of Becquet (…). This is where it will undergo its first periscope immersion in order to validate its watertightness, stability and the operation of its main equipment. Its exact mass will also be determined.

If everything is normal, the Tourville will then go on to undergo 'dynamic' trials in the open sea, supervised by the DGA and the Military Applications Division [DAM] of the French Atomic Energy and Renewable Energies Commission [CEA]. During this period, and until delivery, it will remain the property of Naval Group and TechnicAtome
(...)