Method and facility for synthesizing a nuclear fuel salt with recovery of chlorinated compounds having high added value

Abstract

The invention relates to a method and a facility for synthesizing a nuclear fuel salt via chlorination of one or more solid metal oxides MxOy(solid) by means of a chlorinating agent containing CCl4(gas) enriched in 37Cl, wherein M is selected from among plutonium, uranium, magnesium, americium, thorium, curium, aluminium and sodium, at least one of the metal oxides containing a fissile element, the chlorination reaction taking place in a three-phase mixer-reactor (2) or in a two-phase solid / gas reactor receiving the metal oxide(s), optionally a liquid salt (NaCl), and a reactive gas mixture comprising the enriched chlorinating agent and a carrier gas (G). The gaseous headspace from the chlorination reaction is recovered at the outlet of the reactor, and the chlorinated compounds contained therein are isolated using a first series of chlorinated-compound traps (5, 7, 9) operating by selective adsorption, each of the traps being configured to capture a chlorinated compound to the exclusion of non-chlorinated compounds present in the gaseous headspace.

Description

[0001] DESCRIPTION

[0002] TITLE: Process and installation for the synthesis of a nuclear fuel salt with recovery of high-value chlorinated compounds

[0003] This application relates to a process and an installation for the synthesis of a nuclear fuel salt, more specifically a process (and an installation) for the synthesis of a nuclear fuel salt by chlorination of a solid metal oxide MxOy(soiide) using a chlorinating agent enriched in chlorine 37 ( 37 CI).

[0004] A process for the synthesis of a nuclear fuel salt based on UCl3 and UCl4, by chlorination of solid UO2 using a gaseous chlorinating agent enriched in chlorine 37, is described for example by EP 3 241 218.

[0005] In the context of a single-actor synthesis of a chlorine-37 enriched nuclear fuel salt (active), the chlorinated gaseous reagents used as chlorinating agents can only be enriched by chlorine isotope separation. These reagents are therefore particularly expensive. Consequently, the production of an enriched chlorinating agent, its use in the synthesis of the nuclear fuel salt, and its recycling represent significant economic challenges.

[0006] Besides their costs, the known processes for synthesizing nuclear fuel salts by chlorination of a metal oxide MxOy(soiide) have the disadvantage of being very difficult to control and optimize, particularly due to a particularly complex reaction environment.

[0007] Indeed, this reaction medium is usually composed of two or three phases until the end of the chlorination reaction, namely:

[0008] - a gaseous phase, comprising a reactive gas mixture injected into a reactor, the reactive gas mixture being essentially composed of the enriched chlorinating agent and a carrier gas, the gaseous phase becoming increasingly charged with gases produced by the reaction as the chlorination reaction progresses, - a liquid phase comprising a salt in liquid form when a three-phase mixture is considered,

[0009] - a solid phase comprising the metal oxide MxOy(silide) in granular form suspended in the liquid phase (if the medium is three-phase), with an equivalent diameter that changes with the progress of the reaction (core or shrinking grain model assumed applicable), and a binary salt whose composition and rheological properties change with temperature and the progress of the reaction (mixture of salts, here non-Newtonian fluids independent of time). In the case of a two-phase mixture, chlorination occurs in a bed by the contact of a gaseous chlorinating agent with a metal oxide powder in the absence of molten salt: this is a solid / gas reaction.

[0010] Consequently, conducting the synthesis of nuclear fuel salt is particularly delicate and would need to be optimized.

[0011] EP 3 241 218 indicates that the reaction produces gaseous Cl as well as H2 and CO. EP 3 241 218 proposes to recover the gases produced, in particular gaseous Cl, but does not provide any technique for doing so.

[0012] Furthermore, various processes have been proposed for the capture of chlorinated gases in the chemical industry.

[0013] US 3,029,575 discloses a process for purifying the gaseous product resulting from the oxidation of hydrogen chloride (HCl(gas)) in a process known as the Deacon process. In other words, US 3,029,575 discloses a process for recovering chlorine from a chlorinated gaseous product contaminated with oxygen. The disclosed recovery process involves reversibly adsorbing the chlorine from the contaminated gaseous product using a 5A zeolite. In the Deacon process, HCl(gas) reacts with O2(gas) to yield H2O(gas) and Cl2(gas). The proposed purification technique is a temperature-swing adsorption process, also known as the TSA (Temperature Swing Adsorption) process. The adsorber is preheated to 450-480°C, the treated gas being at approximately 25°C and atmospheric pressure in the adsorption phase, desorption taking place at 450-480°C with nitrogen purging if necessary.This allows the Cl2(gas) purity to go from 5 to 20% in the gaseous product to be treated to about 90% at the outlet of the adsorber, with a satisfactory yield for the application concerned.

[0014] In theory, this process could be used to treat chlorinated gaseous products resulting from the synthesis of a nuclear fuel salt by chlorination. However, given the high added value of these enriched products... 37 CI, there would be an advantage to using a treatment process offering better yield and / or better purity.

[0015] Furthermore, when the enriched chlorinating agent used contains Cl2(gas) and / or HCl(gas) and / or CCl4(gas), the synthesis of a combustible salt by chlorination generates non-chlorinated gaseous products that are adsorbed by zeolite 5A (notably O2(gas), CO(gas), CO2(gas), and F(gas)). The purification process proposed by US 3,029,575 therefore does not allow for the isolation and recovery of chlorine from the synthesis reaction of a combustible salt by chlorination, particularly when chlorination is carried out with a chlorinating agent containing Cl2(gas) and / or HCl(gas) and / or CCl4(gas). Known alternative solutions for the selective capture of dichlorine include pressure or cold distillation, such as the US patent 2007 / 0277551, or the absorption / regeneration of chlorine brought into contact with a solvent such as water, as disclosed by US 5,788,743.

[0016] US 5,788,743 discloses a process for separating chlorine from a starting gas containing Cl2 by absorbing the chlorine with an inert absorbing agent and subsequently desorbing the chlorine from the chlorine / absorbing agent mixture. The process includes distilling the chlorine / absorbing agent mixture in a desorption distillation column coupled to a chlorine separation column.

[0017] Finally, US 3,001,607 teaches the adsorption of HCl by an alumino-silicate zeolite with pores between 4 and 5 Å, in order to recover the Cl2 in a mixture of HCl and Cl2.

[0018] When applied to the treatment of chlorinated gases produced during the synthesis of a nuclear fuel salt by chlorination, these processes can denature the background matrix consisting of the carrier gas and the non-chlorinated products of the chlorination reaction. However, as will be explained later, the inventors have shown that there is an advantage to not denaturing this matrix.

[0019] Furthermore, the yield / purity curve of these two processes is unsatisfactory. For example, recovering absorbed chlorine in solution is difficult and energy-intensive, and recovering pure (solvent-free) chlorine from the treated gas requires an additional purification process, such as distillation (as proposed by US 5,788, 743). Distillation requires significant energy to reach the liquid-vapor equilibrium point of the Cl2(gas), and some of the Cl2(gas) is lost at the top of the rectification column.

[0020] Furthermore, the use of such equipment (absorption column, regeneration column, distillation column, compressor, cooler) complicates the purification process in the case of batch production of nuclear fuel salt, where a single-charge adsorption solution would be preferable.

[0021] Description of the invention

[0022] The main objective of the invention is to propose a process for synthesizing a nuclear fuel salt by chlorinating a metal oxide, which has a reduced cost and / or an increased salt production rate and / or an improved yield.

[0023] The invention also aims, and above all, to provide a process for recovering gaseous chlorinated compounds that is less energy-intensive, less expensive and more efficient than known chlorine capture processes and devices that can be used in the synthesis of a nuclear fuel salt by chlorination of a metal oxide, and that is particularly suited to this application.

[0024] To this end, the invention proposes a process for synthesizing a nuclear fuel salt by chlorination using a chlorinating agent enriched in 37CI, the chlorination of one or more solid metal oxides MxOy(soiide) where M is chosen from plutonium (Pu), uranium (U), magnesium (Mg), americium (Am), thorium (Th) and curium (Cm), aluminium (Al) and sodium (Na), at least one of said solid metal oxides containing a fissile element, the chlorination reaction taking place in a reactor (which may be a mixer-reactor or a solid-gas reactor depending on the synthesis route - three-phase or two-phase- chosen) containing a two-phase or three-phase reaction medium which comprises:

[0025] - the solid metal oxide(s) MxOy(silide),

[0026] - a reactive gas mixture comprising said enriched chlorinating agent and a carrier gas selected from noble gases, such as argon and helium, and inert gases, such as nitrogen,

[0027] - and a liquid salt in the case of a three-phase reaction medium, the chlorination reaction producing:

[0028] - at least one metallic chloride MuClv forming the nuclear fuel salt, the metallic chloride MuClv appearing in solid form in solution in the liquid salt in the case of a three-phase reaction medium, and in liquid or solid form in the case of a two-phase reaction medium,

[0029] - a gaseous sky containing one or more chlorinated compounds as well as non-chlorinated compounds, such as for example dioxygen O2(gas) and / or carbon monoxide CO(gas) and / or carbon dioxide CO2(gas) and / or dihydrogen H2(gas) and / or water vapor H2O(gas) (the non-chlorinated compounds generated depending on the enriched chlorinating agent used).

[0030] The process for synthesizing nuclear fuel salt according to the invention is characterized in that:

[0031] - the chlorinating agent used comprises tetrachloromethane gas CCl4(gas) enriched in 37 CI and optionally chlorine gas Cl2(gas) enriched in 37 CI and / or hydrogen chloride gas HCl(gas) enriched in 37 CI, the chlorination reaction according to the reaction scheme g Cl2(gas) + h HCI(gas) +î CO(gas) + j CO2(gas) + k Û2(gas) + I H2(gas) + ITI H2O(gas) with a not zero and b and c which may be harmful

[0032] - The gaseous residue from the chlorination reaction is collected at the reactor outlet.

[0033] - the chlorinated compounds contained in the gaseous headspace exiting the reactor are isolated using a first series of chlorinated compound traps operating by selective adsorption, each of said chlorinated compound traps comprising a selective adsorbent configured to selectively capture one - and preferably only one - chlorinated compound to the exclusion of non-chlorinated compounds present in said gaseous headspace, said first series of chlorinated compound traps comprising, successively and in this order, a selective HCl(gas) trap then a selective Cl2(gas) trap then a selective CCl4(gas) trap.

[0034] These selective traps are based primarily on the principle of separation by molecular sieving, allowing the recovery of each chlorinated compound in a selective manner with very high yield and very high purity.

[0035] In contrast to known methods of capturing chlorinated compounds by absorption (which use a solvent) or by distillation, the use of adsorption traps offers better selectivity so that the products recovered by desorbing said traps have a higher purity, well above 90% and even in the order of 99%, which is an undeniable advantage with regard to the value of the target chlorinated compounds.

[0036] Moreover, such traps are particularly compact and of simple design; likewise, the recovery (by desorption) of the trapped chlorinated compound is very simple and does not require complex and / or bulky equipment.

[0037] As for the zeolite 5A adsorption traps disclosed by US 3,029,575 and by US 3,001,607, they also adsorb some of the non-chlorinated products (in particular CO and CO2) resulting from the chlorination reaction which is the subject of the invention; they are therefore not suitable for this application.

[0038] To promote the direct reaction indicated above and thus maximize the production of fuel salt, the chlorinating agent (and therefore CCl4(gas)) is preferably supplied in excess in the reaction medium, either by using a reactive gas mixture highly concentrated in chlorinating agent, or by injecting the reactive gas mixture into the reactor with a high flow rate, or by combining the two previous techniques (= high flow rate of a reactive gas mixture having a high concentration of chlorinating agent).

[0039] According to Le Chatelier's principle, increasing the amount of CCl4 shifts the reaction equilibrium towards the forward reaction, i.e., towards the production of metal chloride. Furthermore, supplying excess CCl4 promotes the reaction kinetics. Indeed, the diffusion of the CCl4 agent is limiting even under ideal stirring conditions (gain or shrinking core model). In fact, the chemical potential gradient between the metal oxide and the chlorinating agent constitutes the driving force behind mass transfer, governing the reaction kinetics in the case of a perfectly stirred phase.

[0040] Furthermore, a high flow rate of concentrated CCK reactive gas mixture promotes agitation of the reaction medium, thereby maximizing the production of combustible salt. It also allows for a reduction in the concentration of the products (favorable to Le Chatelier's principle).

[0041] In a preferred embodiment in which the reaction medium is triphasic, the liquid salt used is sodium chloride NaCl(liquid).

[0042] Note that in the case of a two-phase mixture, the synthesis is carried out in a solid / gas medium and without molten salt (liquid salt). The chlorination reaction follows the same reaction scheme (that indicated above) as in the case of a three-phase reaction medium, with the difference that the metallic chloride MuClv produced by the reaction can be available either in solid or liquid form.

[0043] Throughout, a description of the invention is provided, along with examples applicable to the most complex mixing case, namely a three-phase reaction medium, where the metal chloride(s) are obtained in solution in the liquid salt of the three-phase medium. However, the description also applies to a two-phase solid / gas reaction medium, which leads to the production of metal chlorides in liquid or solid form.

[0044] As defined previously, the invention therefore consists, firstly, in using a chlorinating agent containing CCK, which is preferably injected in excess into the reactor. This use increases the production yield of the fuel salt.

[0045] The invention further consists of recovering the entire gaseous headspace from the chlorination reaction and treating this gaseous headspace selectively so as to extract the enriched chlorinated compounds produced by the chlorination reaction or not consumed by it, without stopping the non-chlorinated compounds resulting from the chlorination reaction.

[0046] First proposed in the context of a nuclear fuel salt synthesis process, the selective capture by adsorption of chlorinated compounds makes it possible to considerably reduce the production costs of nuclear fuel salt since these chlorinated compounds, which are gases enriched in 37These chlorinated compounds, which are very expensive, can be reused to produce more nuclear fuel salt or for other potential applications. It is also thanks to this selective recovery that it is possible, despite the high cost of the chlorinating agent, to inject it in excess into the reactor to promote the fuel salt production reaction.

[0047] Capturing chlorinated compounds also simplifies the venting of the gases produced.

[0048] The recovery of the entire gaseous sky of the chlorination reaction and the selective extraction of the chlorinated compounds it contains makes it possible to exploit the other gaseous products of the reaction, i.e. non-chlorinated compounds such as CO(gas), CO2(gas), H2(gas) and O2(gas) in a noble or inert carrier gas matrix, as explained later.

[0049] Since the chlorinating agent used according to the invention contains CCl4(gas), the gaseous head of the reaction necessarily contains Cl2(gas) and HCl(gas) as reaction products, as well as unreacted CCl4(gas), particularly if the CCl4(gas) is supplied in excess.

[0050] In the case where the chlorinating agent consists exclusively of CCl4(gas), the gaseous products of the chlorination reaction include at least Cl2(g az), CO(g az), CO2(g az), U2(g az), and the gaseous head recovered from the reactor includes at least Cl2(g az), CO(g az), CO2(g az), U2(g az), produced by the reaction, and the unreacted CCl4(gas), as well as possible traces by release of HCl(gas) and H2O(gas).

[0051] In the case where the enriched chlorinating agent includes HCl(gas) in addition to CCl4(gas), the gaseous products of the chlorination reaction include at least Cl2(gas), H2(gas), O2(gas, hHOfgas), as well as HCl(gas) from the secondary (spontaneous) reaction between the products H2(gas) and Cl2(gas), and the recovered gaseous head from the reactor includes at least HCl(g az), Cl2(g az), H2(g az), U2(g az), H2U(g az), products of the reaction, and unreacted CCl4(gas).

[0052] In the case where the chlorinating agent includes Cl2(gas) in addition to CCl4(gas), the gaseous products of the chlorination reaction then include at least O2(gas) and HCl(gas), and the gaseous head recovered from the reactor includes at least Cl2(gas), O2(gas), HCl(gas), produced by the reaction, unreacted Cl2(gas) and CCl4(gas), as well as possible traces by release of H2O(gas).

[0053] Thus, in all scenarios, the gaseous space contains a significant amount of Cl2 (gas) produced by the reaction, and a trace or significant amount of HCl (gas) produced by the reaction, as well as unreacted CCl4 (gas), which can be present in large quantities if the reactive gas mixture is highly concentrated with the chlorinating agent and / or if the reactive gas mixture is injected in excess into the reactor. This is why it is advantageous to include at least one selective trap for HCl (gas), one selective trap for Cl2 (gas), and one selective trap for CCl4 (gas) in the first series of chlorinated compound traps.

[0054] The use of an enriched chlorinating agent containing Cl2(gas) and / or HCl(gas) in addition to CCl4(gas) is not limiting: not only can the chlorinating agent contain only CCl4, but other enriched agents can also be used in combination with CCl4, such as chlorinating agents containing ZrCl4, FeCl4, NH4Cl, etc., enriched in 37 CI.

[0055] Similarly, a carrier salt (liquid) other than NaCl can be used.

[0056] According to particular embodiments of the invention, the process for synthesizing nuclear fuel salt according to the invention further meets the following characteristics, implemented individually or in any technically possible and operational combination.

[0057] Selective separations of HCl(gas), then of Cl2(gas) are preferably carried out by molecular sieving by excluding access to the pores of the sieve of molecules of CCl4(g az), CO(g az), CO2(g az), H2(g az), U2(g az).

[0058] In some embodiments, the HCl(gas) selective trap includes a molecular sieve selected from hydrophobic carbon bases with pores of the order of 3Å to promote the exclusive adsorption of HCl(gas), in particular nanostructured adsorbents such as carbon nanotubes or carbide-derived carbons.

[0059] In some embodiments, the selective Cl2(gas) trap includes a molecular sieve selected from hydrophobic carbon-based adsorbents, in particular carbon nanotubes and carbon-derived carbides, having pores of a size on the order of 4Å to promote the exclusive adsorption of Cl2(g az).

[0060] In some embodiments, the selective CCl4(gas) trap includes an adsorbent medium selected from porous carbonaceous materials with a microporous structure such as microporous activated carbons, the pore size of which is less than 2 nm.

[0061] The process for synthesizing nuclear fuel salt according to the invention can be implemented in the form of a batch process or a continuous process.

[0062] In some embodiments, the chlorination reaction is monitored and controlled by a control system, and the treated gaseous tailings exiting the first series of chlorinated compound traps are sent to an analyzer connected to said control system and configured to measure at least one characteristic, for example, the content, of at least one of the non-chlorinated compounds (CO(g az), CO2(g az), U2(g az), H2(gas)) resulting from the chlorination reaction (and therefore present in the gaseous tailings exiting the first series of chlorinated compound traps since only chlorinated compounds have been extracted, in a very selective manner, from the gaseous tailings exiting the reactor). This characteristic is then used by the control system to access information on the chlorination reaction, such as the progress of the reaction, the reaction kinetics, the understanding of the limiting mechanisms, etc.This information is notably used to control the reaction by regulating certain process parameters including the reactor temperature, the flow rate of the reactive gas mixture injected into the reactor and the content of injected chlorinating agent, etc.

[0063] One of the constraints encountered in the synthesis of nuclear fuel salt lies in the nature of the product obtained: the fission reaction of the produced nuclear fuel salt must not be triggered, meaning that the criticality of the produced nuclear fuel salt must not be reached. This implies working with a reduced reactor volume and necessitates increasing the number of reactors to boost production. Therefore, for the synthesis of nuclear fuel salt to be profitable and feasible on an industrial scale despite the relatively small reactor size, it is preferable to optimize the chlorination reaction in order to increase either the efficiency of this reaction or—preferably—the production rate of nuclear fuel salt.

[0064] Analyzing at least one of the non-chlorinated gaseous products of the chlorination reaction (CO(gas), CO2(gas), O2(gas), H2(gas)) can provide easy access to information about the reaction, enabling the optimization of nuclear fuel salt production. This analysis is facilitated, or even made possible, by the prior selective capture of chlorinated products present in the jet stream exiting the reactor. This capture protects the analyzer's measuring instruments from the risk of material degradation due to exposure to highly corrosive chlorinated compounds. As will be seen later, in certain embodiments, these measuring instruments are also protected from the risks associated with the presence of water or humidity.

[0065] Analytical monitoring can thus be ensured by means of sensitive, fast, reliable and economical gas measurement and analysis instruments, such as a zirconia probe for dioxygen O2(gas) and / or an infrared sensor for CO(gas) and / or CO2(gas) and / or a laser diode for H2(gas).

[0066] Note that the analyzer can be installed in situ or ex situ. If it is ex situ, a sampling system can be provided, ensuring the regulation of pressure, temperature and flow rate of the samples (analytes) feeding the analyzer.

[0067] The analysis of at least one of the non-chlorinated gaseous products present in the recovered reactor gaseous head allows, in continuous production, for real-time monitoring of the chlorination reaction. This enables real-time regulation of the injection rate of the reactive gas mixture into the reaction medium in order to maximize the production rate of nuclear fuel salt. Monitoring the reaction also allows for regulation of the reaction medium temperature not only by controlling the reactor heating system but also by controlling the reactor's stirring system (in the case of a mixer reactor using a three-phase medium) and by controlling the injection rate of the reactive gas mixture (the temperature depending in particular on the progress and rate of the exothermic reaction, as well as the homogeneity of the medium).

[0068] Similarly, in the case of a batch synthesis process, the injection rate of the reactive gas mixture into a batch of metal oxide (possibly with liquid salt) can be regulated to maximize the production rate of nuclear fuel salt; moreover, the information provided by the analysis of non-chlorinated compounds during the production of a batch allows for the improvement of the reactor design (dimensions, heating system, stirring system where it exists, means of injecting the reactive gas mixture and adjustment of these means, etc.).

[0069] It should be noted that a low injection rate of the reactive gas mixture has contradictory effects on the reaction yield: a low flow rate increases the residence time and contact time between the reactant molecules, which is favorable; at the same time, it penalizes the homogeneity of the reaction medium (especially in the case where a homogeneous mixture of the reaction medium cannot be obtained by mechanical means of stirring but requires the use of a bubbling ramp, the effectiveness of which depends on the gas injection rate).Conversely, a high injection rate of the reactive gas mixture improves the homogeneity of the three-phase reaction medium by creating turbulence; however, a high reactive gas mixture flow rate (combined with the necessary small reactor size) reduces the residence time of the chlorinating agent in the reactor, which limits the conversion rate of said chlorinating agent and leads to greater consumption of enriched chlorinating agent, which is an expensive reagent. Thanks to the invention, this last point is no longer a limiting economic factor since the chlorinated compounds are recovered at the reactor outlet.Finally, as previously indicated, the injection rate of the gas mixture will also influence the progress of the reaction and, consequently, the temperature of the reaction medium, which itself has an impact on the homogeneity of the reaction medium (a high temperature reduces the viscosity of the salt and therefore promotes the homogenization of the reaction mixture) and therefore on the yield and kinetics of the reaction, etc.

[0070] As can be seen, the control of the reactive gas mixture injection methods, as well as the reactor's heating and stirring systems (when present), has a significant influence on the chlorination reaction yield and the fuel salt production rate. Consequently, a better understanding of this reaction through the analysis of one or more of the non-chlorinated compounds produced facilitates production optimization, whether for a continuous or batch process.

[0071] In the case of the three-phase synthesis route, the metal oxide MxOy(soiide) can be introduced into the mixing reactor either directly or in suspension in the liquid salt.

[0072] In some embodiments, the chlorination reaction is carried out at a temperature between 400°C and 900°C, ideally between 500°C and 650°C, and at atmospheric pressure within the reactor.

[0073] In certain embodiments, in which the reactor includes a heating system and optionally (in the case of three-phase synthesis) a stirring system, the synthesis process according to the invention further comprises:

[0074] - volumetric counting of the gaseous space to be treated entering the analyzer, using a volumetric gas meter equipped with a pulse emitter instrumented for pressure and temperature,

[0075] - real-time monitoring of the following data:

[0076] -- the molar flow rates of CO(gas) and / or CO2(gas) and / or O2(gas) and / or H2(gas), calculated from the volumetric flow rate provided by the volumetric gas meter and the molar concentrations of CO(gas) and / or CO2(gas) and / or O2(gas) and / or H2(gas) measured by the analyzer,

[0077] -- the temperature of the reaction medium (this temperature can be calculated from the previous molar flow rates and the temperature measured by the volumetric meter, or be measured using a temperature sensor installed in the reactor),

[0078] -- the progress and rate of the chlorination reaction, determined from the temperature and pressure measurements of the volumetric meter and the molar flow rates of CO(gas) and / or CO2(gas) and / or O2(gas) and / or H2(gas), knowing the injection rate of reactive gas mixture into the reactor and the content of enriched chlorinating agent of said reactive gas mixture.

[0079] As previously explained, this monitoring makes it possible to characterize the reactor, to identify its ideal operating conditions, and to understand the limiting mechanisms (chemical regime, diffusional regime, mixed regime).

[0080] Understanding the limiting kinetic mechanism allows us to identify the parameter to adjust to improve reactor performance. In a diffusional regime, controlling the gas / solid / liquid contact time and the stirring system improves the fuel salt production rate. In a chemical regime, controlling the concentration of the enriched chlorinating agent and / or the reactive gas mixture flow rate improves the fuel salt production rate. Finally, in a mixed regime, reactor temperature control can also be a valuable variable for maximizing fuel salt production. Given the evolution of the salt's properties in the reactor and the particle size of the metal oxide during the reaction, the limiting kinetic mechanism may change with the extent of the reaction.

[0081] In certain embodiments (continuous or batch production), implemented in an installation comprising a control system, an analyzer and a volumetric meter as previously defined and in which the reactor is equipped with a heating system, as well as an agitation system in the case of a three-phase reaction medium, the synthesis process further comprises:

[0082] - real-time control of the reactor heating system and its agitation system (where applicable),

[0083] - real-time regulation of the temperature of the reactive gas mixture injected into the reaction medium (the installation being equipped with corresponding technical means),

[0084] - real-time regulation of the flow rate (the installation being equipped with corresponding technical means) of the enriched chlorinating agent and / or real-time regulation of the flow rate of the carrier gas at the inlet of a contactor, saturated with enriched chlorinating agent and in which the reactive gas mixture is formed, and / or real-time regulation of the flow rate of the reactive gas mixture at the inlet of the reactor,

[0085] - real-time regulation of the reaction medium temperature by controlling the reactor heating system and the reactor stirring system (when present), and by controlling the flow rate and temperature of the reactive gas mixture introduced into the reactor,

[0086] - and, if the process is implemented continuously, the regulation of the flow rate of liquid salt injected into the reaction medium and of the flow rate of solid metal oxide(s) injected into the reaction medium or introduced into the liquid salt.

[0087] In the case of a batch process, each trap in the first series of chlorinated compound traps is sized to be able to fully process at least a quantity of gaseous space corresponding to one batch. In other words, the trap has a payload sized for the duration of the batch.

[0088] Each of the chlorinated compound traps can then take the form of a cylindrical column containing a selective adsorbent medium, which column has a gas inlet for the introduction into the trap of the gaseous space to be treated, a gas outlet from which the treated gaseous space exits, depleted in trapped chlorinated compound, the adsorbent medium being chosen from among the media capable of selectively stopping the target chlorinated compound while being permeable to the gas matrix consisting of the carrier gas, the non-chlorinated compounds present in the gaseous space of the chlorination reaction and possibly other chlorinated compounds not concerned by the trap in question.

[0089] Each of the chlorinated compound traps (Cl2(gas) or CCl4(gas) or HCl(gas)) can operate in cold conditions from -60°C to 10°C, or at ambient temperature from 10°C to 40°C, or in hot conditions from 40°C to 80°C, and this under vacuum from 0.1 bara to 0.9 bara, or at atmospheric pressure from 0.9 bara to 1.1 bara or under pressure from 1.1 bara to 10 bara. In some embodiments, at the end of the production of a batch: - each of the traps in the first series of chlorinated compound traps is disconnected from the circuit and is regenerated at a temperature between 35°C and 500°C, preferably between 100°C and 300°C, and ideally between 150°C and 200°C, under vacuum (for this purpose, a vacuum pump is connected to the gas outlet of the trap) at an absolute pressure between 0.001 mbara and 900 mbara and preferably between 1 mbara and 100 mbara, with elution by sweeping of the adsorbent medium by means of a carrier gas, called elution gas, noble or inert, clean and dry, injected into the trap through the gas inlet.The vacuum pump - configured to be resistant to corrosive gases - may have PTFE seals and piping; it can also be purged with elution gas to cool the desorbed gas and dilute its chlorine content in order to improve the service life of said vacuum pump;

[0090] - The desorbed chlorinated compounds (gaseous) are compressed and / or cooled for storage in liquid or solid form. The stored product has a purity of approximately 99%.

[0091] The desorbed gas from the HCl(gas) selective trap can thus be cooled to -90°C at atmospheric pressure or compressed up to 70 to 90 bar at ambient temperature, to collect the pure HCl(gas) in liquid form.

[0092] The desorbed gas from the Cl2(gas) selective trap can be cooled to -34°C at atmospheric pressure or compressed up to 6 bar at room temperature, to collect the pure Cl2(gas) in liquid form.

[0093] The desorbed gas from the selective CCl4(gas) trap can be condensed by cooling to ambient or cold temperature, preferably between -20°C and 10°C to collect pure CCl4(gas) in liquid form, or between -30°C and -23°C to collect pure CCl4(gas) in solid form.

[0094] In the case where the synthesis process according to the invention is implemented in the form of a continuous process, each of the traps in the first series of chlorinated compound traps (Cl2(gas), CCl4(gas), HCl(gas)) is preferably a trap, called a VTSA trap, operating according to a vacuum and temperature modulated adsorption process (VTSA being the acronym for the English "Vacuum and Temperature Swing Adsorption").Such a VTSA trap includes an adsorbent medium selective for the target chlorinated compound (Cl2(gas), CCl4(gas), HCl(gas)), a feed inlet for the introduction of the gaseous head to be treated, a production outlet from which the treated gaseous head exits, an elution inlet for the introduction of an elution gas, and a purge outlet for the recovery of a purge gas rich in trapped eluted chlorinated compound, the adsorbent medium being chosen from porous media which, on the one hand, have a satisfactory adsorption capacity of the target chlorinated compound, i.e. of the order of 1 to 60% by mass for concentrations of target chlorinated compound in the gaseous head to be treated which are between 1% and 70% molar, and which, on the other hand, are permeable and resistant to the background gas consisting of the carrier gas and the non-chlorinated compounds present in the gaseous head of the chlorination reaction.The elution gas is preferably a noble or inert gas, clean and dry, for example the carrier gas; alternatively, the treated gaseous head recovered at the outlet of the trap production may be used as the elution gas.

[0095] The purge outlet allows the recovery of the trapped compound enriched to more than 90% molar, the complement gas being a noble or inert gas used to carry out the elution during regeneration.

[0096] In some embodiments, the VTSA chlorinated compound traps each comprise at least two adsorption columns, ideally four (or more) adsorption columns, operating alternately to selectively capture and reject the target chlorinated compound (Cl2(gas), CCl4(gas), HCl(gas)), according to a continuous operating scheme comprising twelve steps with six distinct phases: adsorption, vacuum purging, heated vacuum purging, heated vacuum elution, cooling, and pressurization.

[0097] This alternating operation ensures continuous or near-continuous operation of the fuel salt synthesis process and continuous management, at the trap level, of the inlet flow rates of the gaseous stream to be treated (loaded with the target chlorinated compound), the outlet flow rates of the treated gaseous stream (depleted in chlorinated compound), and the purge flow rate (outlet of gas enriched to more than 90% in chlorinated compound). In some embodiments, the VTSA traps for chlorinated compounds comprise, successively and in this order, a VTSA trap for HCl(gas), a VTSA trap for Cl2(gas), and a VTSA trap for CCl4(gas).

[0098] The selective adsorbent medium of the VTSA trap with HCl(gas) is chosen from:

[0099] - microporous carbon materials, such as carbon nanotubes, carbons derived from carbides, activated carbons, or other carbon molecular sieves,

[0100] - artificial zeolites, in particular 3A zeolites, provided that the gaseous sky to be treated is dry, which have a characteristic pore size between 0.2 nm and 0.6 nm, preferably between 0.3 nm and 0.4 nm, i.e. a pore size favoring the selective capture of HCl(gas) by molecular sieving, said characteristic pore size being determined by the NLDFT method of the non-local density functional theory (NLDFT being an acronym for the English "Non-local Density Functional Theory") with CO2 as the probe molecule at 273 K and with a slit pore type geometric model.

[0101] For an HCl(gas) content of between 1% and 10% molar in the gaseous head to be treated, the adsorbent medium will preferably be chosen from among the aforementioned porous materials which also have a selective adsorption capacity in HCl(gas) of between 0.5% and 60% by mass at temperatures between 10°C and 50°C and at atmospheric pressure, or between 1% and 40% by mass at temperatures between 20°C and 80°C.

[0102] The above-listed HCl(gas) adsorbents have the advantage of being regenerable under vacuum and temperature (VTSA) and of causing no or very little co-adsorption due to the presence of Cl2(gas), CCl4(gas), H2(gas), CO(gas), U2(gas) or CO2(gas) in the gaseous space to be treated, which makes it possible to obtain a purity that has been unmatched until now.

[0103] In some embodiments, the purge gas from the VTSA HCl(gas) trap is reintroduced into the reactive gas mixture upstream of the reactor and / or liquefied in a liquefier for storage, with a purity greater than 99%. The gas phase from this liquefier is then reintroduced into the gas head to be treated at the inlet of the VTSA HCl(gas) trap. In other words, the recovered HCl(gas) is either recycled upstream of the reactor, liquefied and stored in liquid form, or partly recycled and partly liquefied and stored.

[0104] In some embodiments, the selective adsorbent medium of the VTSA Cl2(gas) trap is chosen from microporous carbon materials (carbon nanotubes or carbons derived from carbides or activated carbons or other carbon molecular sieves) and Y-type artificial zeolites, which have a characteristic pore size between 0.3 nm and 0.6 nm, preferably between 0.4 nm and 0.5 nm, as determined by the NLDFT method of non-local density functional theory with CO2 as probe molecule at 273 K and with a slit-type geometric model.

[0105] For a Cl2(gas) content of the order of 1% to 70% molar in the gaseous space to be treated, the adsorbent medium will preferably be chosen from among the aforementioned porous materials which also have a selective adsorption capacity in Cl2(gas) of between 0.1% and 60% by mass, preferably between 1% and 30% by mass, at temperatures between 10°C and 50°C and at atmospheric pressure, and / or between 1% and 40% by mass at temperatures between 20°C and 80°C and at atmospheric pressure.

[0106] These Cl2(gas) adsorbents are regenerable under vacuum and temperature (VTSA); they are also permeable and resistant to CO2(g az), CO(g az), Û2(g az), H2(gas) and CCl4(gas) molecules, so that co-adsorption phenomena due to the presence of CO2(g az), CO(g az), Û2(g az), H2(g az) and CCl4(g az) are negligible.

[0107] The Cl2(gas) captured in the VTSA Cl2(gas) trap and recovered at the trap's purge outlet is reintroduced into the reactive gas mixture upstream of the reactor and / or liquefied in a liquefier for storage. The gaseous phase from this liquefier is then reintroduced into the gas stream to be treated at the inlet of the VTSA Cl2(gas) trap. In other words, the recovered Cl2(gas) is either recycled upstream of the reactor, liquefied and stored in liquid form, or partly recycled and partly liquefied and stored.

[0108] In some embodiments, the adsorbent medium of the VTSA trap with CCl4(gas) is chosen from microporous activated carbons, artificial or natural zeolites, silica gels and activated aluminas, which have a characteristic pore size between 0.3 nm and 2 nm, as determined by the NLDFT method of non-local density functional theory with CO2 as probe molecule at 273 K and with a slit-type geometric model.

[0109] For a CCl4(gas) content of between 1% and 10% molar in the gaseous space to be treated, the adsorbent medium will preferably be chosen from among the aforementioned porous materials which also have a selective adsorption capacity in CCl4 of between 0.5% and 60% by mass at temperatures between 10°C and 50°C and at atmospheric pressure, or of between 1% and 40% by mass at temperatures between 20°C and 80°C and at atmospheric pressure.

[0110] The above-listed CCl4(gas) adsorbents have the advantage of being regenerable under vacuum and temperature (VTSA) and of causing little co-adsorption due to the presence of CO(gas), O2(gas), H2(gas) and CO2(gas) in the gaseous space to be treated, which makes it possible to obtain a purity that has been unmatched until now.

[0111] The gaseous CCl4(gas) recovered at the outlet of the VTSA CCl4(gas) trap is advantageously recycled upstream of the chlorination reaction, i.e., reintroduced into the reactive gas mixture that feeds the reactor. It can be largely liquefied at temperatures of approximately 10 to 40°C for storage before being recycled upstream of the chlorination reaction or used in other applications.

[0112] In certain embodiments, whether batch or continuous, the gaseous head exiting the first series of chlorinated compound traps or the analyzer (if present) is sent to a second series of non-chlorinated compound traps. These traps are preferably selective adsorption traps or, alternatively, catalysts. The capture of non-chlorinated compounds primarily allows for the recovery of the carrier gas, which can be recycled, further reducing the cost of the synthesis process according to the invention. Furthermore, the capture of CO(gas) specifically ensures safe gas release at the vent. The second series of non-chlorinated compound traps comprises, for example, successively a selective O2(gas) trap, a selective H2(gas) trap, and a selective CO(gas) / CO2(gas) trap.

[0113] In the case of a continuous process, the CO(gas) / CO2(gas) trap is preferably a VTSA type trap (i.e. operating according to a vacuum and temperature modulated adsorption process) whose adsorbent medium is chosen from porous carbon materials (porous activated carbons), type A artificial zeolites, 5A zeolites, silica gels and activated aluminas, which preferably have a CO adsorption capacity of between 0.1% and 10% by mass, for example between 1% and 10% by mass, at temperatures between 20°C and 80°C at atmospheric pressure and in the presence of CO2.

[0114] To improve the compactness of the trap, the adsorber can contain two layers, namely a CO2(gas) filtering layer and then a CO (gas) stopping layer.

[0115] The VTSA CO(gas) / CO2(gas) trap is regenerated using a clean, dry noble or inert gas elution gas, as explained for the VTSA chlorinated compound traps previously described.

[0116] At the outlet of the second series of non-chlorinated compound traps, the treated gaseous residue is essentially, ideally solely, composed of carrier gas (noble or inert). This residue can be recycled. Thus, in the case of a batch process, the treated gaseous residue exiting the second series of non-chlorinated compound traps can be used as an elution gas for the regeneration of the chlorinated or non-chlorinated compound traps. In the case of a continuous process, the treated gaseous sky exiting the second series of non-chlorinated compound traps can be reintroduced into the reactive gas mixture upstream of the reactor and / or used as an elution gas for the regeneration of one or more of the VTSA traps for chlorinated or non-chlorinated compounds, i.e. for the regeneration of the VTSA trap for HCl(gas) and / or the VTSA trap for Cl2(gas) and / or the VTSA trap for CCl4(gas) and / or the VTSA trap for CO(gas) / CO2(gas).

[0117] In certain embodiments, whether batch or continuous, the recovered reactor gaseous head undergoes pretreatment before passing through the first series of chlorinated compound traps. This pretreatment includes passing the reactor gaseous head through a drying device known as a dryer. This dryer prevents potential contamination of the gaseous head due to the degassing of salt into water vapor within the reactor.

[0118] In some embodiments, the dryer is a VTSA-type device, i.e., a vacuum- and temperature-modulated adsorption device, comprising, for example, a zeolite 3A desiccant (a hydrophilic adsorbent with pores approximately 3 Å in size) or a Drierite® desiccant. Zeolite 3A allows the capture of a small proportion of HCl (gas) and retains a large proportion of water; the residual water content after filtration is less than 100 ppbv. Furthermore, the competitive adsorption of water ultimately expels all the HCl (gas) retained in the adsorbent. When using Drierite®, water capture is more selective; nevertheless, the residual water content at the filter outlet is typically in the range of 1 to 10 ppmv. In summary, zeolite 3A has the advantage of not stopping chlorinated compounds other than HCl(gas) in dry media where the amount adsorbed remains low.Furthermore, by definition, the dryer's purpose is to remove water. This adsorbate exhibits strong interaction with zeolite 3A, to the point of occupying sites previously occupied by HCl(gas). Upon water saturation in the zeolite, almost all of the previously retained HCl(gas) has been expelled from the adsorbent. The HCl(gas) expelled from the adsorbent, replaced by water, and the other chlorinated compounds not retained by zeolite 3A are then recovered in the first series of chlorinated compound traps. Zeolite 3A also does not retain non-chlorinated compounds (other than water), which are subsequently analyzed in the analyzer. Drierite® is more selective but allows a few ppmv of water to pass through in the gas exiting the dryer. Both solutions are, however, satisfactory for the application of interest.

[0119] The dryer regeneration conditions are comparable to the regeneration conditions of previous VTSA traps. Thus, for example, the dryer can be regenerated at a temperature between 100°C and 450°C, and preferably between 150°C and 250°C, under vacuum at a pressure between 0.001 mbar and 900 mbar, with purging using a clean and dry noble or inert gas, having a dew point below -80°C, preferably below -100°C.

[0120] In certain embodiments, as an additional safety measure (or in the absence of a CO(gas) / CO2(gas) trap in the installation), in order to eliminate any toxic risk, particularly in the event of gas being released outside, the synthesis process according to the invention includes an additional step of removing carbon monoxide contained in the treated gaseous headspace exiting the second series of non-chlorinated compound traps or, in the absence of a second series of non-chlorinated compound traps, exiting the analyzer or, in the absence of an analyzer, exiting the first series of chlorinated compound traps.

[0121] This step can be carried out by transforming (oxidizing) CO(g) into CO2(gas) using a CuO base in a batch process. For continuous operation, a VTSA-type carbon monoxide trap with a 5A zeolite adsorbent medium can be used. Alternatively, the CO2(gas) is simply flared.

[0122] Finally, if the recovered gaseous sky from the reactor contains dihydrogen, the second series of non-chlorinated compound traps preferably includes a selective H2(gas) trap, which may include a palladium-based catalyst or an MnC base coupled with a drying agent.

[0123] The invention also relates to a nuclear fuel salt synthesis installation characterized in that it is configured to implement the synthesis process described above.

[0124] The invention therefore relates, in particular, to an installation for synthesizing a nuclear fuel salt by chlorination using a chlorinating agent enriched in 37CI, the chlorination of at least one solid metal oxide MxOy(soiide) where M is selected from plutonium (Pu), uranium (U), magnesium (Mg), americium (Am), thorium (Th) and curium (Cm), aluminium (Al) and sodium (Na), at least one of said solid metal oxides containing a fissile element, the installation comprising a reactor containing a three-phase or two-phase reaction medium which comprises the solid metal oxide(s) MxOy(soiide), a liquid salt in the specific case of the three-phase reaction medium and a reactive gas mixture comprising said enriched chlorinating agent and a carrier gas selected from noble gases and inert gases, the chlorination reaction producing at least one metal chloride MuClv forming the nuclear fuel salt,which metallic chloride appears in liquid or solid form within the reactor in the case of a two-phase reaction medium, or in solution in the liquid salt introduced into the reactor in the case of a three-phase reaction medium, as well as a gaseous layer containing one or more chlorinated compounds and non-chlorinated compounds.

[0125] The nuclear fuel salt synthesis installation according to the invention is characterized in that:

[0126] - the chlorinating agent used comprises tetrachloromethane gas CCl4(gas) enriched in 37 CI and optionally chlorine gas Cl2(gas) enriched in 37 CI and / or hydrogen chloride gas HCl(gas) enriched in 37 CI, the chlorination reaction according to the reaction scheme g Cl2(gas) + h HCI(gas) +î CO(gas) + j CO2(gas) + k Û2(gas) + I H2(gas) + ITI H2O(gas) with a not zero and b and c which may be harmed,

[0127] - The reactor includes a gas outlet through which the gaseous headspace from the chlorination reaction is recovered,

[0128] - the installation includes, at the outlet of the reactor, a first series of chlorinated compound traps operating by selective adsorption, each of said chlorinated compound traps comprising a selective adsorbent configured to selectively capture one - and preferably only one - chlorinated compound to the exclusion of non-chlorinated compounds present in said gaseous space, said first series of chlorinated compound traps comprising, successively and in this order, a selective trap for HCl(gas) then a selective trap for Cl2(gas) then a selective trap for CCl4(gas).

[0129] In some embodiments, the synthesis installation also includes:

[0130] - a control system designed to monitor and control the chlorination reaction,

[0131] - downstream of the first series of chlorinated compound traps, an analyzer, which is connected to said control system and into which is introduced the treated gaseous air exiting the first series of chlorinated compound traps, said analyzer being configured to measure at least one characteristic of at least one of the non-chlorinated compounds resulting from the chlorination reaction,

[0132] - optionally, downstream of said analyzer, a second series of non-chlorinated compound traps, each of said non-chlorinated compound traps being configured to capture at least one of the non-chlorinated gaseous compounds (CO(gas), CO2(g az), U2(g az), H2(gas)) present in the gaseous headspace of the chlorination reaction.

[0133] In some embodiments, the installation is configured to implement a three-phase reaction medium and

[0134] - the liquid salt used is sodium chloride NaCl(liquid),

[0135] - The HCl selective trap, the Cl2 selective trap, and the CCl4 selective trap are VTSA traps modulated by vacuum and temperature. Each VTSA trap comprises four adsorption columns containing an adsorbent medium selective for the target chlorinated compound (HCl(gas), Cl2(gas), or CCl(gas)), a feed inlet for introducing the gaseous headspace to be treated, a production outlet from which the treated gaseous headspace exits, an elution inlet for introducing an elution gas to regenerate the adsorbent medium, and a purge outlet for recovering a purge gas rich in the trapped and eluted chlorinated compound. The adsorbent medium is chosen from porous media suitable for adsorbing the target chlorinated compound and which are permeable and resistant to the background gas, which consists of carrier gas, oxygen (O2(gas)), hydrogen (H2(gas)), and carbon monoxide. (CO(gas)) and carbon dioxide (CO2(gas)),the four columns of the VTSA trap operating alternately to selectively capture and reject the target chlorinated compound (HCl(gas) or Cl2(gas) or CCkfgas)) according to a continuous operating scheme comprising twelve steps with six distinct phases: adsorption, vacuum purging, heated vacuum purging, heated vacuum elution, cooling and pressurization,

[0136] - the second series of non-chlorinated compound traps includes a U2(g az) trap, an H2(gas) trap and a CO(gas) / CO2(gas) trap, the CO(gas) / CO2(gas) trap being a VTSA trap whose adsorbent medium is chosen from porous carbonaceous materials, artificial or natural type A zeolites, 5A zeolites, silica gels and activated aluminas capable of stopping CO(gas) / CO2(gas), which preferably have a CO(gas) adsorption capacity of between 0.1% and 10% by mass at temperatures between 20°C and 80°C, at atmospheric pressure and in the presence of CO2(gas),

[0137] - The installation includes a volumetric gas meter arranged immediately upstream of the analyzer, connected to the control system and equipped with a pulse transmitter instrumented for pressure and temperature,

[0138] - the installation includes a contactor, saturated with enriched chlorinating agent and in which the reactive gas mixture is formed, which contactor includes a carrier gas inlet, a temperature sensor and a heating system,

[0139] - the installation includes a flow controller (506) arranged immediately upstream of the contactor's gas inlet,

[0140] - The reactor is a mixing reactor comprising a temperature sensor, a heating system and an agitation system.

[0141] - the control system is configured for

[0142] -- collect temperature measurements from the contactor and reactor temperature sensors,

[0143] -- to control the contactor heating system in real time in order to regulate the temperature of the reactive gas mixture injected into the reaction medium in real time,

[0144] -- regulate in real time the flow rate of the reactive gas mixture introduced into the reactor by controlling the flow rate of the carrier gas introduced into the contactor, -- calculate in real time the temperature of the reaction medium, the molar flow rates of CO(gas) and / or CO2(gas) and / or O2(gas) and / or H2(gas) produced by the chlorination reaction, as well as the progress and rate of the chlorination reaction, -- regulate in real time the temperature of the reaction medium by controlling the heating and stirring systems of the reactor and the heating system of the contactor, and possibly also by controlling the flow rate of the carrier gas introduced into the contactor (the installation then including a flow controller at the carrier gas inlet of the contactor),

[0145] —and to regulate in real time the flow rate of liquid salt injected into the reaction medium and the flow rate of solid metal oxide(s) injected into the reaction medium or introduced into the liquid salt. Various additional features of this installation will be described in more detail with reference to the attached drawings.

[0146] The invention, according to examples of embodiment, will be well understood and its advantages will be more apparent upon reading the detailed description that follows, given by way of example and in no way limiting, with reference to the attached drawings in which: o Figure 1 schematically represents a first example of a nuclear fuel salt synthesis installation according to the invention operating in batch production; o Figure 2 schematically represents a second example of a nuclear fuel salt synthesis installation according to the invention operating in continuous production; o Figure 3 schematically represents a VTSA type trap or filtering device with four adsorption columns.

[0147] Identical elements represented in the aforementioned figures are identified by identical numerical references.

[0148] Throughout the description, the expressions "a metal oxide" and "the metal oxide" refer to all the metal oxides involved in the chlorination reaction; it may therefore be a single fissile metal oxide or a mixture of several metal oxides, at least one of which includes a fissile element.

[0149] Figure 1 represents a first example of a nuclear fuel salt synthesis installation by chlorination according to the invention, for the implementation of a synthesis process according to the invention operating in batch production.

[0150] The installation includes a reactor 2, specifically a mixer-reactor in which the chlorination reaction (here three-phase) takes place, leading to the production of nuclear fuel salt. This reactor has a gas inlet 20 through which a reactive gas mixture is introduced, and a gas outlet 22 through which the gaseous headspace formed during the chlorination reaction is collected. The reactor also includes a liquid / solid inlet (not shown) through which a liquid salt, preferably sodium chloride NaCl(iiquid), and a solid metal oxide MxOy(soiid) are introduced at the start of batch production. The solid metal oxide can be introduced into the reactor independently of the liquid salt via another inlet (not shown) or via the aforementioned liquid / solid inlet, or it can be pre-mixed with the liquid salt and carried by it into the reactor via the liquid / solid inlet.At the end of batch production, the fuel salt obtained is extracted from the reactor via a liquid / solid outlet (not shown) or via the aforementioned liquid / solid inlet.

[0151] Reactor 2 also includes a stirring system (not shown) for mixing the reaction medium and a heating system (not shown) for heating the reaction medium.

[0152] The reactive gas mixture, which is introduced into the reactor via gas inlet 20, comprises a carrier gas (denoted G on the attached drawings), either noble (Ar, He, etc.) or inert (N2), clean and dry, and a chlorinating agent enriched in 37 CI which, in the example, includes CCl4(gas), Cl2(gas) and HCl(gas)).

[0153] The chlorination reaction corresponds to the equation: a CCl4(g az) + b Cl2(g az) + C HCI(gas) + d MxOy(solid) — > e MuClv(solution) + f CCl4(gas) + g Cl2(gas) + h HCI(gas) +î CO(gas) + j CO2(gas) + k O2(gas) + I H2(gas) + m H2O(gas)

[0154] The gaseous sky extracted from the reactor by the gas outlet 22 therefore includes carrier gas molecules G, unreacted CCl4(gas), Cl2(gas), unreacted HCl(gas) or resulting from the spontaneous secondary reaction of Cl2(gas) with H2(gas), as well as molecules of O2(gas), CO(gas), CO2(gas), H2O(gas) and H2(gas).

[0155] According to the invention, the synthesis installation comprises, downstream of reactor 2, a first series of selective adsorption chlorinated compound traps, comprising here successively a selective trap for HCl(gas) 4, a selective trap for Cl2(gas) 6 and a selective trap for CCl4(gas) 8.

[0156] It also advantageously includes a dryer 3 at the outlet of reactor 2, that is, between the gas outlet 22 of said reactor and the gas inlet 40 of the HCl(gas) selective trap. Drying the gaseous headspace exiting reactor 2 prevents a potential reaction between HCl(gas) and CCl4(gas).

[0157] Each of the chlorinated compound traps 4, 6, 8, as well as the dryer 3, can be in the form of a cylindrical column with a gas inlet 30, 40, 60, 80 and a gas outlet 32, 42, 62, 82 and containing an adsorbent medium allowing the selective capture of hhOfgas), HCl(gas), Cl2(gas) or CCl4(gas) respectively. The trap can operate at ambient temperature (from 10°C to 40°C) or in cold conditions (from -40°C to 10°C) or in hot conditions (from 40°C to 80°C) and under pressure (from 1.1 to 10 bara) or at atmospheric pressure or under vacuum (from 0.1 to 0.9 bara).

[0158] Dryer 3 is configured to retain the water vapor present in the headspace recovered from the reactor's gas outlet 22. This headspace comprises molecules of G, H2O(gas), HCl(gas), Cl2(gas), CCl4(gas), O2(gas), CO(gas), CO2(gas), and H2(gas). The adsorbent medium for dryer 3 can be zeolite 3A or Drierite® (desiccant products marketed by WA Hammond Drierite Co Ltd).

[0159] The HCl(gas) selective trap 4 is configured to selectively and efficiently trap HCl(gas) present in the treated gas head exiting the dryer's gas outlet 32. This gas head comprises molecules of G, HCl(gas), Cl2(gas), CCl4(gas), O2(gas), CO(gas), CO2(gas), and H2(gas). The adSOTbant medium of said HCl(gas) selective trap can be a carbon molecular sieve, for example, a molecular sieve based on a carbon-derived carbide or carbon nanotubes, with a characteristic pore size between 3 Å and 4 Å, measured according to the NLDFT method as described above.

[0160] The Cl2(gas)6 selective trap is configured to selectively and efficiently trap Cl2(gas) present in the treated gaseous space exiting the gas outlet 42 of the HCl(gas) selective trap. This gaseous space comprises carrier gas molecules G, Cl2(gas), CCl4(gas), O2(gas), CO(gas), CO2(gas), and H2(gas). The adsorbent medium of said Cl2(gas)6 selective trap can be a carbon-based molecular sieve, for example, a molecular sieve based on a carbon-derived carbide or on nanotubes, with a characteristic pore size on the order of 5 Å, measured according to the NLDFT method as described above. The selective trap for CCl4(gas) 8 is configured to selectively and efficiently stop the CCl4(gas) present in the treated gaseous sky exiting the gas outlet 62 of the selective trap for Cl2(gas), this gaseous sky comprising molecules of G, CCl4(gas), O2(gas), CO(gas), CO2(gas) and H2(gas).The adsorbent medium of said CCl4(gas) 8 trap can be a common microporous activated carbon (i.e., with a pore size of less than 2nm).

[0161] At the end of the reaction, each chlorinated compound trap 4, 6, 8 is disconnected from the setup and the extraction of the trapped chlorinated compound is obtained by connecting a vacuum pump to the gas outlet 42, 62, 82 of said trap to create a primary vacuum in the trap, at a pressure between 900 mbar and 0.001 mbar, by heating the {trap + trapped chlorinated compound} system between 35°C and 200°C, possibly up to 450°C, and by eluting the system by sweeping the porous adsorbent medium with a clean and dry noble (He, Ar ... ) or inert (N2) elution gas, introduced into the trap via the gas inlet 40, 60, 80 of the trap.

[0162] At the outlet of the vacuum pump, the elution gas, laden with chlorine compounds, is cooled to condense or solidify the eluted chlorine compound (HCl, Cl₂, or Cl₄). Regeneration is thus performed for each of the chlorine traps 4, 6, and 8. Once disconnected from the trap, the vacuum pump can also be purged with elution gas to cool the desorbed gas and dilute the chlorine content, thereby improving the lifespan of the rotating machine.

[0163] Cooling of the desorbed CCl4(gas) discharged from the vacuum pump outlet is then possible at ambient or cold temperature between -20°C and 10°C to collect pure CCl in liquid form or between -30°C and -23°C to collect pure CCl in solid form.

[0164] Pure CI2 can be collected in liquid form after cooling to -34°C at atmospheric pressure or after compression up to 6 bara at ambient temperature.

[0165] Pure HCl can be collected in liquid form after cooling to -90°C at atmospheric pressure or after compression to 70-90 bar at room temperature. The recovered chlorinated compounds can be reused later, either for the production of another batch after being converted back into gas, or for any other application.

[0166] Figure 2 represents a second example of a nuclear fuel salt synthesis plant by chlorination according to the invention for the continuous production of fuel salt from the chlorinating agent CCl4(gas) alone.

[0167] The installation includes a reactor 2. Here again, it is a mixer-reactor, hosting a three-phase reaction medium; but it could also be a solid-gas reactor for a synthesis of the fuel salt by the two-phase route.

[0168] Reactor 2 has a gas inlet 20, a gas outlet 22, a liquid / solid inlet 24, a liquid / solid outlet 26, an agitation system (not shown), a heating system (not shown) and a temperature sensor (not shown).

[0169] Reactor 2 is monitored and controlled by a control system 500, to which is connected an analyzer 504 described later and a volumetric meter 502 positioned immediately upstream of the analyzer 504. The control system 500 is also connected to the stirring system, the heating system and the temperature sensor of reactor 2, and to the valve(s) of the liquid / solid inlet 24 of the reactor for the purpose of controlling the flow rate of the liquid salt injected into the reaction medium and the flow rate of solid metal oxide(s) injected into the reaction medium or introduced into the liquid salt.

[0170] Upstream of reactor 2, the synthesis unit includes a CCl4(gas) contactor 18, in which the reactive gas mixture is prepared at a temperature between 20°C and 60°C. For this purpose, the contactor 18 includes a heating system (not shown) and a temperature sensor (not shown). The contactor is also equipped with two gas inlets: one for carrier gas G (a clean, dry noble or inert gas), and one for enriched chlorinating agent, i.e., in this case, enriched CCl4(gas).

[0171] In this non-limiting example, the enriched chlorinating agent is CCl4(gas). Of course, alternatively, the enriched chlorinating agent—and consequently the reactive gas mixture—could also include Cl2(gas) and / or HCl(gas) or another chlorinated gas enriched in 37 CI.

[0172] The control system 500 is connected to the contactor 18, in particular to the temperature sensor and the heating system of said contactor, for the control of the temperature of the CCh at liquid / vapor equilibrium.

[0173] The installation also includes a flow controller 506, positioned immediately upstream of the carrier gas inlet of contactor 18 and connected to controller 500, for regulating the noble gas injection rate into contactor 18, which is saturated with CCl4(gas). Combined with flow controller 506, controller 500 ultimately allows for control of the chlorinating agent input into the reaction medium.

[0174] According to the invention, downstream of the gas outlet 22 of the reactor, through which the gaseous sky of the chlorination reaction is extracted from the reactor, the installation includes a first series of chlorinated compound traps.

[0175] This first series of chlorinated compound traps includes a VTSA selective HCl(gas) trap 5, configured to capture (selectively) and continuously desorb HCl(gas) using a vacuum and temperature modulated process, then a VTSA selective Cl2(gas) trap 7, configured to capture (selectively) and continuously desorb Cl2(gas) using a vacuum and temperature modulated process, and finally a VTSA CCl4(gas) trap 9, configured to capture and continuously desorb CCl4(gas) using a vacuum and temperature modulated process.

[0176] Each VTSA chlorinated compound 5, 7, 9 trap includes:

[0177] - at least two, preferably four, adsorption columns, each of the adsorption columns containing a selective adsorbent porous medium capable of trapping the target chlorinated compound (HCl(gas) for trap 5, Cl2(gas) for trap 7 and CCl4(gas) for trap 9),

[0178] - a gas inlet 50, 70, 90, called the feed inlet, through which the gaseous space to be treated is introduced into said trap to be conveyed alternately into one or the other of the adsorption columns,

[0179] - a gas outlet 52, 72, 92, called the production outlet, through which the treated gaseous head from the adsorption columns exits said trap, - an elution inlet 54, 74, 94, through which an elution gas is introduced into the trap to be conducted alternately into one or the other of the adsorption columns so as to sweep the selective adsorbent medium that said column contains, for the purpose of desorption of the trapped chlorinated compound,

[0180] - a purge outlet 56, 76, 96, through which the desorbed chlorinated compound carried by the elution gas is evacuated.

[0181] The installation illustrated in Figure 2 also includes a dryer 12, arranged between reactor 2 and the first series of chlorinated compound traps, and operating according to a VTSA process.

[0182] Like the VTSA chlorinated compound traps 5, 7, 9, the dryer 12 preferably comprises four adsorption columns, a feed inlet 120 through which the gaseous head to be dried is introduced into the dryer to be conducted alternately into one or the other of the adsorption columns, a production outlet 122 through which the dried gaseous head from the adsorption columns exits the dryer, an elution inlet 124 through which an elution gas is introduced into the trap to be conducted alternately into one or the other of the adsorption columns so as to sweep the selective adsorbent medium that said column contains, for the purpose of desorption of the trapped water, and a purge outlet 126, through which the water carried by the elution gas is discharged.

[0183] The continuous operation, modulated in vacuum and temperature, of the VTSA chlorinated compound traps 5, 7 and 9 and of the dryer 12 will be detailed later with reference to figure 3.

[0184] In the illustrated example, the CCl4(gas) not consumed by the chlorination reaction and present in the gaseous head recovered from the reactor is directly recycled. The purge gas from the VTSA trap with CCl4(gas) 9, consisting of elution gas G (noble or inert gas) and CCl4(gas), is in fact returned to the CCl4(gas) contactor 18 via a first recycling conduit 21.

[0185] The nuclear fuel salt synthesis installation in Figure 2 further includes a Cl2(gas) liquefier 14 connected to the purge outlet 76 of the Cl2(gas) VTSA trap. This Cl2(gas) liquefier 14 is configured to liquefy, by cooling and / or compression, and to store the Cl2(gas) contained in the purge gas from the Cl2(gas) VTSA trap 7, which purge gas consists of elution gas G (noble or inert gas) and Cl2(gas). The gas remaining after this liquefaction, essentially consisting of elution gas G with possibly some unliquefied gaseous Cl2, is returned to the circuit between the gas outlet 52 of the VTSA trap with HCl(gas) and the gas inlet 70 of the VTSA trap with Cl2(gas) by a second recycling conduit 23, in order to recover all the Cl2(gas) from the chlorination reaction.

[0186] The nuclear fuel salt synthesis plant in Figure 2 further includes an HCl(gas) liquefier 16. This liquefier is configured to liquefy, by cooling and / or compression, and to store the HCl(gas) contained in the purge gas from the HCl(gas) VTSA trap 5, which purge gas consists of elution gas G (noble or inert gas) and HCl(gas). The gas remaining after this liquefaction, essentially consisting of elution gas G with possibly some unliquefied gaseous HCl(gas), is returned to the circuit between the gas outlet 32 ​​of the dryer and the gas inlet 50 of the HCl(gas) VTSA trap via a third recycling line 25, in order to recover all the HCl(gas) resulting from the chlorination reaction.

[0187] The nuclear fuel salt synthesis installation in Figure 2 further includes a liquefier (Ffgas) 19 connected to the purge outlet 126 of the VTSA trap (hhOfgas) (dryer 12). This liquefier (Ffgas) 19 is configured to liquefy, by cooling, and to store the water vapor contained in the purge gas from the VTSA trap (Ffgas), which purge gas consists of elution gas G and Ffgas. The gas remaining after this liquefaction, essentially consisting of elution gas G with possibly some unliquefied H2O gas, is returned to the circuit between the gas outlet 22 of the reactor and the gas inlet 120 of the VTSA trap (hhOfgas) via a fourth recycling line 27, in order to ultimately recover all the carrier gas G initially used to transport the enriched chlorinating agent.

[0188] To optimize the chlorination reaction, the synthesis plant in Figure 2 also includes, downstream of the first series of chlorinated compound traps 5, 7, 9, an analyzer 504 in which certain characteristics of the treated gaseous stream exiting the first series of chlorinated compound traps are measured and / or calculated, including the concentration of O2(gas) and / or H2(gas) and / or CO(gas) and / or CO2(gas) of said gaseous stream. A volumetric meter 502 is connected to this analyzer and is located at its inlet. The analyzer 504 and the volumetric meter 502 are, of course, connected to the controller 500, to which they transmit the measurements and other generated data.

[0189] The synthesis installation in Figure 2 further includes a second series of non-chlorinated compound traps 11, which includes an oxygen trap 11a (not shown in detail) and a VTSA CO(gas) / CO2(gas) trap 11b (see also Fig. 3). This second series of non-chlorinated compound traps 11 includes a gas inlet 110 for its supply of the gaseous space to be treated, a gas outlet 112 through which the treated gaseous space exits, an elution inlet 114 through which an elution gas is introduced into the trap to be conducted either into the O2(gas) trap 11 a or alternatively into one or the other of the adsorption columns of the VTSA CO(gas) / CO2(gas) trap 11 b, a purge outlet 116a through which the O2(gas) captured in the trap 11 a is recovered and a purge outlet 116b through which the CO(gas) / CO2(gas) desorbed from the VTSA CO(gas) / CO2(gas) trap is recovered.

[0190] The second series of non-chlorinated compound traps 1 1 can also include a H2(gas) trap (not referenced) such as a palladium catalyst. Alternatively, H2(gas) capture can be achieved by reacting the H2(gas) with MnO2(soiide) or NiO2(soiide), for example; this generates water that can be captured by adsorption with a zeolite-type medium. In this case, the residual amounts of O2(gas) produced by the chlorination reaction are subsequently captured, for example, by means of a chemical adsorption trap.

[0191] The gaseous sky to be treated which feeds the gas inlet 110 of the second series of non-chlorinated compound traps 11 has been previously cleared of the chlorinated compounds HCl(gas), CCl4(gas) and Cl2(gas), so that it is composed of G (carrier gas), CO(gas), CO2(gas), U2(gas) and H2(gas).

[0192] At the gas outlet 112, the outgoing treated gaseous space contains only pure carrier gas G, which can be recycled. It can thus be returned to the carrier gas inlet of the CCh 18 contactor, more precisely immediately upstream of the flow controller 506, via a fifth recycling conduit 29, and / or to the elution inlet 124 of the VTSA trap at F (gas) via a sixth recycling conduit 31, and / or to the elution inlet 54 of the VTSA trap at HCl(gas) via a seventh recycling conduit 33 and / or to the elution inlet 74 of the VTSA trap at Cl2(gas) via an eighth recycling conduit 35, and / or to the elution inlet 94 of the VTSA trap at CCl4(gas) via a ninth recycling conduit 37 and / or to the elution inlet 114 of the VTSA trap at CO / CO2, via a tenth recycling conduit 39.

[0193] The CO(gas) / H2(gas) / O2(gas) / CO2(gas) produced by the chlorination reaction is analyzed in analyzer 504 to optimize the chlorination reaction. The data provided by the volumetric meter 502 and analyzer 504, as well as by the temperature sensor of contactor CCk 18, allow control system 500 to calculate, among other things:

[0194] - the temperature of the reaction medium (this is also provided by the reactor temperature sensor),

[0195] - the molar flow rates of CO(gas), H2(gas), CO2(gas) and O2(gas) exiting the reactor,

[0196] - the progress of the chlorination reaction, calculated from these molar flow rates, knowing the injection rate of the reactive gas mixture into the reactor and the content of the enriched chlorinating agent in said reactive gas mixture.

[0197] Gas analysis allows real-time monitoring of the chlorination reaction and regulation of the reactant flow to maximize the production rate of combustible salt (formed by MuCIv in solution in liquid NaCl); the reaction being exothermic, the temperature regulation of the reactor is also improved by this system.

[0198] Although not described for the first embodiment illustrated in Figure 1, in the case of batch production, a synthesis installation according to the invention may also include an analyzer such as the 504 analyzer, as well as a second series (not shown) of non-chlorinated compound traps.

[0199] The capture of chlorinated compounds according to the invention essentially eliminates the constraints imposed on the three-phase mixer-reactor in terms of reaction efficiency and agitation. Indeed, given the expected fuel salt production, it is desirable for the reaction to allow for intensive production, which implies that the reaction must be rapid in a compact reactor. In batch production, a maximized efficiency makes it possible to envision zero loss of chlorine-enriched compounds but requires significant experience with the chlorination reaction and the reactor design. In continuous operation, it is accepted that a reaction progress of 100% is not optimal for maximizing fuel salt production rate.In both cases, the capture of chlorinated compounds and the information provided by the analysis of non-chlorinated compounds (in particular CO(gas) / H2(gas) / O2(gas) / CO2(gas)) make it possible to optimize the chlorination reaction, either by optimizing the design of the reactor and the quantities per batch of reactive gas mixture, liquid salt and solid metal oxide in the case of batch operation, or by controlling the chlorination reaction in the case of continuous operation.

[0200] The VTSA process used in the various VTSA traps for F(gas), HCl(gas), Cl2(gas), CCh(gas), and CO(gas) / CO2(gas) will now be described with reference to Figure 3. Each of these traps 12, 5, 7, 9, and 11b ideally comprises:

[0201] - four adsorption columns or adsorbers 100, 200, 300, 400, containing a selective adsorbent medium capable of stopping (capturing) a target compound chlorinated or non-chlorinated (CCl4(gas), HCl(gas) OR Cl2(gas) OR CO(gas) / CO2(gas) OR H2O(gas)),

[0202] - a 600 mm supply line for feeding the gaseous columns to be treated (gas from the reactor or from the previous VTSA trap), the 600 mm supply line being connected to the 120, 50, 70, 90, 110 mm supply inlet of the VTSA trap in question,

[0203] - a production duct 700, connected to the production outlets 122, 52, 72, 92, 112 of the VTSA trap,

[0204] - a purge line 800 for extracting the desorbed target compound from the columns, the purge line being connected to the purge outlets 126, 56, 76, 96, 116 of the VTSA trap,

[0205] - and an elution conduit 900 for the injection into the columns of an elution gas, the elution conduit 900 being connected to the elution inlet 124, 54, 74, 94, 114 of the VTSA trap.

[0206] At one end, each adsorption column 100, 200, 300, 400 is associated on the one hand with a first conduit 101, 201, 301, 401 equipped with a first valve, called the supply valve, which allows the column to be connected to the supply conduit 600, and on the other hand with a second conduit 102, 202, 302, 402, equipped with a second valve, called the purge valve, which allows the column to be connected to the purge conduit 800.

[0207] At its other end, each adsorption column 100, 200, 300, 400 is associated on one side with a third conduit 103, 203, 303, 403 equipped with a third valve, called the production valve, which allows the column to be connected to the production conduit 700, and on the other side with a fourth conduit 104, 204, 304, 404, equipped with a fourth valve, called the elution valve, which allows the column to be connected to the elution conduit 900.

[0208] The VTSA trap operates according to a continuous operating scheme comprising twelve steps with six distinct phases defining a cycle, namely:

[0209] - An adsorption phase: the column is continuously fed with the gas stream to be treated, allowing the gas to circulate in contact with the fixed bed, which consists of an adsorbent medium specifically designed to bind a target compound. Meanwhile, other gases pass through the column along with the noble or inert carrier gas. To this end, the column's feed valve and production valve are opened. At the end of the adsorption phase, the column's adsorbent medium is saturated with the target compound. During the adsorption phase, the pressure in the column is approximately equal to atmospheric pressure, excluding pressure losses in the gas circuit.

[0210] - a vacuum purge phase: At the beginning of the vacuum purge phase, the column production valve is closed, while the feed valve is still in the open position, then, at the same time, the column feed valve is closed, while the feed valve of another (second) column which has just been regenerated is opened in order to send the gaseous sky to be treated into this other column, and the purge valve of the (first) column is opened while the purge outlet of the trap is put in contact with a vacuum pump (not shown).The absolute pressure in the (first) adsorption column drops, and the first molecules trapped in the previous stage are desorbed from the adsorbent medium and then sent to a compressor or liquefier via a vacuum pump discharge (this is the case here for trap 12 with Ff gas), 5 with HCl(gas), and trap 7 with Cl2(gas)) or reinjected into the circuit as explained previously (the case for trap 9 with CCl4(gas) and possibly the trap with HCl(gas) or Cl2(gas) in the unillustrated case where the enriched chlorinating agent contains HCl(gas) or Cl2(gas)). The vacuum pump can be slightly primed with clean, dry inert or noble gas to reduce the chemical potential of the chlorinated gases and thus increase the equipment's lifespan.

[0211] - A heated vacuum purging phase: At the beginning of the heated vacuum purging phase, a heating element is activated to indirectly heat the adsorbent medium and the remaining adsorbed load, either at the column wall or within the column itself. The overall setup (open / closed state of the various valves, connection of the trap's purge outlet to the vacuum pump) remains identical to that of the previous step. The heating temperature ramp can be between 0.1 and 20°C / min and preferably between 1 and 5°C / min. The maximum temperature reached during the step can be between 50 and 500°C, preferably between 150°C and 250°C. There may be a temperature ramp-up phase and a stabilization phase with a plateau at the high temperature.

[0212] - A heated vacuum elution phase: During this phase, with the column purge valve still open and the trap purge outlet still in contact with a vacuum pump, the column elution valve opens and a clean, dry noble or inert gas is injected into the elution line via the trap's elution inlet. This allows for a counter-current vacuum flow of the gas, in the opposite direction to the flow of the gas during the adsorption phase, to elut the molecules trapped in the column under heat. Under vacuum, the consumption of elution gas is minimized for the same actual gas exchange rate during this regeneration step, thus minimizing noble or inert gas consumption and maximizing the average purity of the recovered chlorinated compounds.The temperature is maintained between 50°C and 500°C, and preferably between 150°C and 250°C. The gas exchange rate is between 0.5 and 100 times the adsorber volume per hour, and ideally between 10 and 50 times the adsorber volume per hour. A cooling phase follows: in principle, the adsorbent is perfectly regenerated at the end of elution under heated vacuum. The column cooling is initiated by switching off the heating element, and then, once a certain low temperature is reached, all the bottom valves (feed and drain valves) and top valves (production and elution valves) of the column are closed.

[0213] - A pressurization phase: At the end of the cooling stage, the elution valve or the column feed valve opens, and clean, dry noble gas or the gaseous space to be treated pressurizes the system to the desired pressure. The column is then ready to start a new cycle.

[0214] As previously mentioned, each VTSA trap operates according to a twelve-step scheme:

[0215] - Step No. 1: Adsorber 100 begins an adsorption phase (and therefore a new cycle); this adsorber 100 is therefore connected to the supply duct 600 and production duct 700 while being isolated from the elution duct 800 and purge duct 900; Adsorber 200 is in the vacuum purge phase, this adsorber is therefore connected to the purge duct 800 while being isolated from the supply, production and elution ducts, moreover the purge outlet of the trap is in contact with a vacuum pump; Adsorber 300 is in the cooling phase (all its valves are closed), Adsorber 400 is in the pressurization phase (its elution or supply valve is open while its production and purge valves are closed).

[0216] - Step 2: Adsorber 100 is still in the adsorption phase (its valves therefore remain in the same state as in step 1); adsorber 200 is in the heated vacuum purging phase (its valves remain in the same state as in the previous step and its heating device is switched on); adsorber 300 is still in the cooling phase; adsorber 400 is still in the pressurization phase;

[0217] - Step No. 3: Adsorber 100 is still in the adsorption phase; Adsorber 200 enters the heated vacuum elution phase (its elution valve opens, its purge valve remains open, its supply and production valves remain closed, its heating device remains running, as does the vacuum pump at the purge outlet of the trap); Adsorber 300 is still in the cooling phase; Adsorber 400 is still in the pressurization phase;

[0218] - Step No. 4: Adsorber 100 enters the vacuum purge phase (its feed and production valves close, its elution valve remains closed and its purge valve opens, the purge outlet of the trap remains connected to the vacuum pump); Adsorber 200 enters the cooling phase (all valves closed); Adsorber 300 enters the pressurization phase (its elution or feed valve opens, its purge valve closes, its production valve remains closed); Adsorber 400 enters the adsorption phase (its elution valve closes, its feed and production valves open, its purge valve remains closed);

[0219] - Step No. 5: Adsorber 100 enters the heated vacuum purging phase (its valves remain in the same state as in the previous step and its heating device is switched on); Adsorber 200 is still in the cooling phase; Adsorber 300 is still in the pressurization phase; Adsorber 400 is still in the adsorption phase;

[0220] - Step No. 6: Adsorber 100 enters the heated vacuum elution phase (its elution valve opens, its purge valve remains open, its supply and production valves remain closed, its heating device remains in operation, as does the vacuum pump at the purge outlet of the trap); Adsorber 200 is still in the cooling phase; Adsorber 300 is still in the pressurization phase; Adsorber 400 is still in the adsorption phase;

[0221] - Step No. 7: Adsorber 100 enters the cooling phase (all its valves are closed and its heating device is switched off); Adsorber 200 enters the pressurization phase (its elution or supply valve is opened, the other valves remain closed); Adsorber 300 enters the adsorption phase (its elution valve is closed, its supply and production valves are opened, its purge valve remains closed) and Adsorber 400 enters the vacuum purging phase (its supply and production valves are closed and its purge valve is opened);

[0222] - Step No. 8: Adsorber 100 remains in the cooling phase; Adsorber 200 remains in the pressurization phase; Adsorber 300 remains in the adsorption phase; Adsorber 400 enters the heated purging phase (its heating device is activated);

[0223] - Step No. 9: Adsorber 100 remains in the cooling phase; Adsorber 200 remains in the pressurization phase; Adsorber 300 remains in the adsorption phase; Adsorber 400 enters the elution phase under heated vacuum (opening of its elution valve and maintenance of its heating device);

[0224] - Step No. 10: Adsorber 100 enters the pressurization phase (its elution or supply valve is opened, the other valves remain closed); Adsorber 200 enters the adsorption phase (its elution valve is closed, its supply and production valves are opened, its purge valve remains closed); Adsorber 300 enters the vacuum purging phase (its supply and production valves are closed and its purge valve is opened); Adsorber 400 enters the cooling phase (all its valves are closed and its heating device is switched off);

[0225] - Step No. 11: Adsorber 100 remains in the pressurization phase; Adsorber 200 remains in the adsorption phase; Adsorber 300 enters the heated purging phase (its heating device is activated); Adsorber 400 remains in the cooling phase;

[0226] - Step No. 12: Adsorber 100 remains in pressurization phase; Adsorber 200 remains in adsorption phase; Adsorber 300 switches to heated elution phase (opening of its elution valve and maintenance of its heating device); Adsorber 400 remains in cooling phase.

[0227] At the end of step No. 12, the operating procedure resumes at step No. 1 above.

[0228] The operating steps described above for the four-column VTSA traps of the installation in Fig. 2 are summarized in the following table:

[0229] [table]

[0230] The method and installation according to the invention can be the subject of numerous variations provided they remain within the scope of the appended claims. By way of example, the installation may further include means for separating the 35 CI and the 37 CI in the recovered chlorinated compounds.

Claims

44 / 54 DEMANDS 1. Process for synthesizing a nuclear fuel salt by chlorination using a chlorinating agent enriched in 37CI, the chlorination of one or more solid metal oxides MxOy(soiide) where M is selected from plutonium (Pu), uranium (U), magnesium (Mg), americium (Am), thorium (Th), curium (Cm), aluminum (Al), and sodium (Na), at least one of said solid metal oxides containing a fissile element, the chlorination reaction taking place in a reactor (2) containing a three-phase or two-phase reaction medium comprising the solid metal oxide(s) MxOy(soiide), a liquid salt in the case of a three-phase reaction medium, and a reactive gas mixture, which reactive gas mixture comprises said enriched chlorinating agent and a carrier gas (G) selected from noble gases, such as argon and helium, and inert gases, such as nitrogen, the chlorination reaction producing at least one metal chloride MuClv forming the nuclear fuel salt, thus that a gaseous sky containing one or more chlorinated compounds (HCl(g az) , Cl2(g az),CCl4(g az )) as well as non-chlorinated compounds (CO(gas), CO2(gas), O2(gas), H2(gas), H2O(gas)), the process of synthesizing nuclear fuel salt being characterized in that:, - the chlorinating agent used comprises tetrachloromethane gas CCl4(gas) enriched in 37 CI and optionally chlorine gas Cl2(gas) enriched in 37 CI and / or hydrogen chloride gas HCl(gas) enriched in 37 CI, the chlorination reaction according to the reaction scheme g Cl2(gas) + h HCI(gas) +î CO(gas) + j CO2(gas) + k O2(gas) + I H2(gas) + ITI H2O(gas) with a not zero, and b and c which may be harmed, - said gaseous cloud from the chlorination reaction is recovered at the outlet of reactor (2), - the chlorinated compounds contained in the headspace exiting the reactor are isolated using a first series of chlorinated compound traps (4, 6, 8; 5, 7, 9) operating by selective adsorption, each of said chlorinated compound traps being configured to selectively capture a chlorinated compound to the exclusion of non-chlorinated compounds present in said headspace, said 45 / 54 first series of chlorinated compound traps includes, successively and in this order, a selective trap for HCl(gas) (4; 5), then a selective trap for Cl2(gas) (6; 7) then a selective trap for CCl4(gas) (8; 9).

2. A synthesis process according to claim 1, wherein the chlorinating agent is supplied in excess in the reaction medium, either by using a reactive gas mixture highly concentrated in chlorinating agent, or by injecting the reactive gas mixture into the reactor with a high flow rate, or by combining the two preceding techniques.

3. Synthesis process according to any one of claims 1 or 2, wherein the reaction medium is triphasic and the liquid salt used is sodium chloride NaCl(liquid).

4. A synthesis process according to any one of claims 1 to 3, wherein: - the chlorination reaction is monitored and controlled by a control system (500), - the treated gaseous sky exiting the first series of chlorinated compound traps (4, 6, 8; 5, 7, 9), is sent into an analyzer (504) connected to said control system and configured to measure at least one characteristic of at least one of the non-chlorinated compounds (CO(gas), CO2(gas), O2(gas), H2(gas)) produced by the chlorination reaction, characteristic which is then used by the control system (500) to access information on the chlorination reaction.

5. Synthesis process according to claim 4, implemented in an installation in which the reactor (2) is equipped with a heating system, as well as an agitation system in the case of a three-phase reaction medium, the synthesis process comprising: - volumetric counting of the treated gaseous space entering the analyzer, using a volumetric gas meter (502) equipped with a pressure- and temperature-instrumented pulse emitter, - real-time monitoring of the following data: -- the temperature of the reaction medium, -- the molar flow rates of CO(gas) and / or CO2(gas) and / or O2(gas) and / or H2(gas), calculated from the volumetric flow rate measured by the volumetric meter and the 46 / 54 molar concentrations of O2(gas) and / or CO(gas) and / or CO2(gas) and / or H2(gas) measured by the analyzer, -- the progress and rate of the chlorination reaction, determined from temperature and pressure measurements provided by the volumetric meter and molar flow rates of O2(gas) and / or CO(gas) and / or CO2(gas) and / or H2(gas), knowing the injection rate of the reactive gas mixture into the reactor and the content of the enriched chlorinating agent in said reactive gas mixture, - real-time control of the reactor heating system, as well as the reactor agitation system where it exists, - real-time temperature control of the reactive gas mixture injected into the reaction medium, - real-time regulation of the flow rate of the enriched chlorinating agent and / or real-time regulation of the flow rate of the carrier gas at the inlet of a contactor (18), saturated with enriched chlorinating agent and in which the reactive gas mixture is formed, and / or real-time regulation of the flow rate of the reactive gas mixture at the inlet (20) of the reactor, - real-time regulation of the reaction medium temperature by controlling the reactor heating system (2) and the reactor stirring system when they exist, and by controlling the flow rate and temperature of the reactive gas mixture introduced into the reactor, - and, if the process is implemented continuously, regulation of the flow rate of liquid salt injected into the reaction medium and of the flow rate of solid metal oxide(s) injected into the reaction medium or introduced into the liquid salt.

6. A synthesis process according to any one of claims 1 to 5, implemented as a batch process, and wherein, at the end of the production of a batch: - each of the traps (4, 6, 8) of the first series of chlorinated compound traps is disconnected from the circuit and regenerated at a temperature between 35°C and 500°C, under vacuum at an absolute pressure between 0.001 mbar and 900 mbar, with elution by sweeping of the adsorbent medium using a clean and dry noble or inert elution gas, - the chlorinated compounds thus desorbed are compressed and / or cooled to be stored in liquid or solid form.

7. A synthesis process according to any one of claims 1 to 5, implemented as a continuous process and wherein: - Each of the traps (5, 7, 9) in the first series of chlorinated compound traps is a trap, called a VTSA trap, operating according to a vacuum and temperature modulated adsorption process. Each VTSA trap comprises an adsorbent medium selective for the target chlorinated compound (Cl2(gas), CCl4(gas), HCl(gas)), a feed inlet (50, 70, 90) for introducing the gaseous stream to be treated, a production outlet (52, 72, 92) from which the treated gaseous stream exits, an elution inlet (54, 74, 94) for introducing an elution gas to regenerate the selective adsorbent medium, and a purge outlet (56, 76, 96) for recovering a purge gas rich in the trapped and eluted chlorinated compound. The adsorbent medium is chosen from porous media suitable for adsorption. selectively targets the chlorinated compound and is permeable and resistant to the background gas consisting of the carrier gas (G) and non-chlorinated compounds present in the gaseous space of the chlorination reaction, - The VTSA chlorinated compound traps (5, 7, 9) each comprise four adsorption columns (100, 200, 300, 400), operating alternately to selectively capture and reject the target chlorinated compound (Cl2(gas), CCl4(gas), HCl(gas)), according to a continuous operating scheme comprising twelve steps with six distinct phases: adsorption, vacuum purging, heated vacuum purging, heated vacuum elution, cooling and pressurization.

8. A synthesis process according to claim 7, wherein the VTSA traps for chlorinated compounds comprise successively and in this order, a selective VTSA trap for HCl(gas) (5), a selective VTSA trap for Cl2(gas) (7) and a VTSA trap for CCl4(gas) (9), and wherein: - the selective adsorbent medium of the HCl(gas) selective VTSA trap (5) is chosen from among microporous carbon materials, such as carbon nanotubes or carbons derived from carbides or activated carbons or other carbon molecular sieves, and artificial zeolites, in particular 3A zeolites, which have a characteristic pore size between 0.3 nm and 0.4 nm, - the selective adsorbent medium of the Cl2(gas) selective VTSA trap (7) is chosen from microporous carbon materials, such as carbon nanotubes or carbons derived from carbides or activated carbons or other carbon molecular sieves, and Y-type artificial zeolites, which have a characteristic pore size between 0.4 nm and 0.5 nm, - the adsorbent medium of the VTSA trap with CCl4(gas) (9) is chosen from among microporous activated carbons, artificial or natural zeolites, silica gels and activated aluminas, which have a characteristic pore size between 0.3 nm and 2 nm.

9. A synthesis process according to claim 8, wherein: - the purge gas from the VTSA trap with CCl4(gas) (9) is reintroduced into the reactive gas mixture upstream of the reactor (2), - the purge gas from the VTSA selective Cl2(gas) trap (7) is reintroduced into the reactive gas mixture upstream of the reactor (2) and / or liquefied in a liquefier (14) for storage purposes, the gaseous phase from this liquefier being reintroduced into the gaseous head to be treated at the inlet of the VTSA selective Cl2(gas) trap (7), - the purge gas from the VTSA selective HCl(gas) trap (5) is reintroduced into the reactive gas mixture upstream of the reactor (2) and / or liquefied in a liquefier (16) for storage purposes, the gas phase from this liquefier being reintroduced into the gaseous head to be treated at the inlet of the VTSA selective HCl(gas) trap (5).

10. A synthesis process according to any one of claims 1 to 9, wherein: - the gaseous space exiting the first series of chlorinated compound traps (4, 6, 8; 5, 7, 9) or exiting the analyzer (504) is sent into a second series (11) of non-chlorinated compound traps, said traps being selective adsorption traps, - the treated gaseous sky exiting the second series (11) of non-chlorinated compound traps is reintroduced into the reactive gas mixture upstream of the reactor (2) and / or is used as an elution gas for the regeneration of one or more of the chlorinated (4, 6, 8; 5, 7, 9) or non-chlorinated (11 b) compound traps.

11. A synthesis process according to claim 10, carried out continuously and in which the second series (11) of non-chlorinated compound traps comprises a selective O2(gas) trap (11a), a selective H2(gas) trap, and a selective VTSA CO(gas) / CO2(gas) trap (11b) the adsorbent medium of which is selected from porous carbonaceous materials, artificial or natural type A zeolites, 5A zeolites, silica gels and activated aluminas.

12. A synthesis process according to any one of claims 1 to 11, wherein: - the gaseous head recovered from reactor (2) is subjected to pretreatment before passing through the first series of chlorinated compound traps (4, 6, 8; 5, 7, 9), which pretreatment includes passing the gaseous head from reactor (2) through a dryer (3; 12); - the dryer (3; 12) includes a desiccant of the zeolite 3A type or of the Drierite® type, capable of retaining H2O( gaZ ) and permeable and resistant to HCl(gas), CCl4(gas), Cl2(g az), Û2(g az), CO(g az), CO2(g az) and H2(g az); - if the synthesis process is a batch process, the dryer (3) is regenerated at a temperature between 100°C and 500°C, preferably between 150°C and 250°C, under vacuum at a pressure between 0.001 mbar and 900 mbar, with purging by means of a clean and dry noble or inert gas, having a dew point below -80°C, preferably below -100°C, - if the synthesis process is a continuous process, the dryer (12) is a VTSA type device comprising at least two adsorption columns (100, 200, 300, 400), operating alternately to selectively capture and reject water continuously.

13. Synthesis process according to any one of claims 1 to 12, comprising an additional step of removing carbon monoxide contained in the treated gaseous head exiting the second series (11) of non-chlorinated compound traps or, in the absence of a second series of non-chlorinated compound traps, exiting the analyzer (504) or, in the absence of an analyzer, exiting the first series of chlorinated compound traps (4, 6, 8; 5, 7, 9).

14. Installation for the synthesis of a nuclear fuel salt, by chlorination of one or more solid metal oxides MxOy(silicon) using a 50 / 54 chlorinating agent enriched in 37CI, where M is selected from plutonium (Pu), uranium (U), magnesium (Mg), americium (Am), thorium (Th), curium (Cm), aluminum (Al), and sodium (Na), at least one of said solid metal oxides containing a fissile element, the installation comprising a reactor (2) containing a three-phase or two-phase reaction medium comprising the solid metal oxide(s) MxOy(silicon), a liquid salt in the case of a three-phase mixture, and a reactive gas mixture, which reactive gas mixture comprises said enriched chlorinating agent and a carrier gas (G) selected from noble gases, such as argon and helium, and inert gases, such as nitrogen, the chlorination reaction producing at least one metal chloride MuClv(silicon) forming the nuclear fuel salt, and a gaseous cloud containing the carrier gas (G), one or more chlorinated compounds (HCI(g az), Cl2(g az), CCl4(g az )) and non-chlorinated compounds (CO(gas), CO2(gas), O2(gas), H2(gas)),the installation being characterized in that: - the chlorinating agent used comprises tetrachloromethane gas CCl4(gas) enriched in 37 CI and optionally chlorine gas Cl2(gas) enriched in 37 CI and / or hydrogen chloride gas HCl(gas) enriched in 37 CI, the chlorination reaction according to the reaction scheme g Cl2(gas) + h HCI(gas) +î CO(gas) + j CO2(gas) + k O2(gas) + I H2(gas) + ITI H2O(gas) with a not zero and b and c which may be harmed, - the reactor (2) includes a gas outlet (22) through which the gaseous headspace from the chlorination reaction is recovered, - the installation includes, at the outlet of the reactor (2), a first series of chlorinated compound traps (4, 6, 8; 5, 7, 9) operating by selective adsorption, each of said chlorinated compound traps comprising a selective adsorbent configured to selectively capture a chlorinated compound to the exclusion of non-chlorinated compounds present in the gaseous space, said first series of chlorinated compound traps comprising, successively and in this order, a selective trap for HCl(gas) (4; 5), then a selective trap for Cl2(gas) (6; 7) then a selective trap for CCl4(gas) (8; 9).

15. Installation according to claim 14, further comprising: - a control system (500) designed to monitor and control the chlorination reaction, - downstream of the first series of chlorinated compound traps, an analyzer (504), which is connected to said control system and into which is introduced the treated gaseous head exiting the first series of chlorinated compound traps (4, 6, 8; 5, 7, 9), said analyzer (504) being configured to measure at least one characteristic of at least one of the non-chlorinated compounds (CO(gas), CO2(gas), U2(gas) H2(gas)) produced by the chlorination reaction, - optionally, downstream of the analyzer (504), a second series (11) of non-chlorinated compound traps, each of said non-chlorinated compound traps being configured to capture at least one of the non-chlorinated gaseous compounds (CO(g az), CO2(g az), U2(g az), H2(gas)) present in the gaseous headspace of the chlorination reaction.

16. Installation according to claim 14, configured to implement a three-phase reaction medium and to operate continuously, and in which: - the liquid salt is sodium chloride NaCl(liquid), - The first series of chlorinated compound traps comprises, successively and in this order, a VTSA trap selective for HCl(gas) (5), then a VTSA trap selective for Cl2(gas) (7), and then, optionally, a VTSA trap for CCl4(gas) (9). These VTSA traps are modulated in vacuum and temperature and each comprises four adsorption columns containing an adsorbent medium selective for the target chlorinated compound (HCl(gas), Cl2(gas), or CCl4(gas)), a feed inlet (50, 70, 90) for introducing the gaseous stream to be treated, a production outlet (52, 72, 92) from which the treated gaseous stream exits, an elution inlet (54, 74, 94) for introducing an elution gas for regenerating the adsorbent medium, and a purge outlet. (56, 76, 96) for the recovery of a purge gas rich in trapped chlorinated compound eluted,the adsorbent medium being chosen from porous media which are capable of adsorbing the target chlorinated compound and which are permeable and resistant to the background gas consisting of carrier gas, dioxygen (O2(gas)), carbon monoxide (CO(gas)), carbon dioxide (CO2(gas)) and, 52 / 54 dihydrogen (H2(gas)), the four columns of the VTSA trap operating alternately to selectively capture and reject the target chlorinated compound (HCl(gas), CCl4(gas) or Chfgas)) according to a continuous operating scheme comprising twelve steps with six distinct phases: adsorption, vacuum purging, heated vacuum purging, heated vacuum elution, cooling and pressurization, - the second series (11) of non-chlorinated compound traps includes an O2(gas) trap (11a), an H2(gas) trap and a CO(gas) / CO2(gas) trap (11b), the CO(gas) / CO2(gas) trap (11b) being a VTSA trap whose adsorbent medium is chosen from porous carbonaceous materials, artificial or natural type A zeolites, 5A zeolites, silica gels and activated aluminas capable of stopping CO(g az ) / CO2(g az), - the installation includes a volumetric gas meter (502), arranged immediately upstream of the analyzer (504), connected to the control system (500) and equipped with a pressure and temperature instrumented pulse transmitter, - the installation includes a contactor (18), saturated with enriched chlorinating agent and in which the reactive gas mixture is formed, which contactor includes a carrier gas inlet (G), a temperature sensor and a heating system, - the installation includes a flow controller (506) arranged immediately upstream of the contactor's gas inlet, - the reactor (2) is a mixing reactor (2) comprising a temperature sensor, a heating system and an agitation system, - the control system (500) is configured for -- collect temperature measurements from the temperature sensors of the contactor (18) and the mixing reactor (2) or the solid-gas reactor depending on the synthesis route chosen, -- to control the contactor heating system in real time in order to regulate the temperature of the reactive gas mixture injected into the reaction medium in real time, -- to regulate in real time the flow rate of the reactive gas mixture introduced into the mixer-reactor or the solid-gas reactor according to the synthesis route chosen 53 / 54 by controlling the flow of carrier gas introduced into the contactor (18), -- calculate in real time the temperature of the reaction medium, the molar flow rates of CO(gas) and / or CO2(gas) and / or O2(gas) produced by the chlorination reaction, as well as the progress and rate of the chlorination reaction, -- regulate in real time the temperature of the reaction medium by controlling the heating and stirring systems of the reactor-mixer (2) and the heating system of the contactor (18), and possibly also by controlling the flow rate of carrier gas introduced into the contactor, -- and regulate in real time the flow rate of the liquid salt injected into the reaction medium and the flow rate of solid metal oxide(s) injected into the reaction medium or introduced into the liquid salt.

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