Passive device for capturing and treating hydrogen, having an active material based on transition metal oxide

Abstract

The invention relates to a structure for the treatment of hydrogen by recombination, the structure being provided with at least one element (75A, 75B, 75C, 75D) made of a so-called "active" material (20) intended to react with hydrogen, the active material comprising a metal oxide MOx, where M is a transition metal, where 1 < x < 5, the metal oxide MOx being able to undergo reduction in the presence of hydrogen and without the presence of oxygen so as to form water, and to form, as a product of this reduction, another oxide MOx-1 capable of oxidising in the presence of oxygen to reform the metal oxide MOx.

Description

[0001] PASSIVE HYDROGEN CAPTURE AND PROCESSING DEVICE WITH TRANSITION METAL OXIDE-BASED ACTIVE MATERIAL

[0002] DESCRIPTION

[0003] TECHNICAL FIELD AND PREVIOUS ART

[0004] The present invention relates to the field of hydrogen capture and processing, and in particular to passive hydrogen capture and processing devices such as recombiners. It specifically aims at an improved structure comprising a material that enables the recombination of hydrogen into water.

[0005] In several industrial sectors, hydrogen degassing poses a major problem, especially in restricted or confined environments, with potentially serious consequences.

[0006] Such a phenomenon can lead to the swelling of containers or vessels, and the weakening of materials.

[0007] The presence of hydrogen gas is also dangerous in certain situations and locations where hydrogen is likely to interact with oxygen. A significant risk of fire or explosion then exists.

[0008] In certain particularly sensitive locations such as nuclear power plants, fuel storage facilities, or radioactive waste treatment plants, this risk is increased, notably due to the potential for water radiolysis. This phenomenon leads to the formation of both hydrogen and oxygen, which can interact and cause the aforementioned damage.

[0009] Capture devices have been proposed to reduce the concentration of dihydrogen by causing its recombination.

[0010] Among these devices, passive autocatalytic recombiners have been developed. Their operation relies on hydrogen consumption using catalytic plates made of noble metal. One such device is described, for example, in document WO / 2018 / 009092. The advantages of this type of device include its passive nature, its ability to operate without human intervention or even a power supply, particularly electrical, and its long lifespan, requiring little maintenance or plate replacement.

[0011] However, it poses cost problems due to the large quantity of precious metal needed to make the catalytic plates, and the large size of these plates.

[0012] Such a device also has a restrictive limitation in terms of the minimum hydrogen concentration from which it operates, this concentration typically being at least 0.5% v / v (volume on volume) hydrogen.

[0013] DESCRIPTION OF THE INVENTION

[0014] It is therefore an object of the present invention to provide a structure for the treatment of hydrogen by recombination and having one or more elements in an improved "active" material with respect to at least one of the aforementioned disadvantages.

[0015] The inventors discovered, in particular, an active material containing a metal oxide MO X , with M a transition metal, with 1 < x < 5, the metal oxide MO X being capable of undergoing reduction in the presence of hydrogen and without the presence of oxygen so as to form water, and of forming as a product of this reduction another oxide MO x.i capable of oxidizing in the presence of oxygen to reform the metal oxide MO X .

[0016] The treatment implemented can be described as "neutralization" insofar as free hydrogen atoms (in the form of H2) are consumed and lead to the formation of water.

[0017] Metal M is also typically chosen here so that the standard potential E°(MO x / l\ / IO x -i) of the couple M0 x / M0 x -i is located between that E°(H2O / H2) of the H2O / H2 couple and that E°(O2 / H2O) of the O2 / H2O couple. Thus, the metal M is such that the standard potential E°(MO x / l\ / IO x -i) of the couple M0 x / M0 x - is typically between -0.828 V / ESH and +1.229 V / ESH, and preferably between -0.5 and +0.5 V / ESH. An additional criterion for choosing the MOx / MO couple x -i may be the exothermicity of the reduction of MO X by H2(g).

[0018] An element made of such an active material is significantly less expensive than one made solely of noble metal, while also offering good durability and a reduced size.

[0019] It also has the advantage of reacting even at very low concentrations of hydrogen and oxygen. A reaction can be carried out at a dihydrogen concentration below 2% v / v, and in particular below 0.5% v / v and down to at least 0.03% v / v.

[0020] Metal oxide MO X can be WO3OU chosen from the following metal oxides: CuO, MOO3, vanadium oxide (V2O5), Fe2U3, SnCh, NiO.

[0021] Advantageously, the active material is a compound based on said metal oxide MO X and a catalyst or a composite of said metal oxide MO X and said catalyst and / or a mixture or derived from a mixture of said metal oxide MO Xand said catalyst.

[0022] The active material is based on metal oxide MO X and catalyst in the form of an intimate mixture or composite, particularly at the molecular or particulate scale, is a material in which the constituents (the oxide) and (the catalyst) are present together without macroscopic organization into distinct layers, but with distinct phases intimately dispersed at the nano- or micrometer scale. The distribution of metal oxide without the formation of a continuous planar interface typically depends on the manufacturing method employed.

[0023] This catalyst can in particular be a metal from group VIII or group I, preferably chosen from the following metals: Pt, Pd, Ni, Cu, Ag, Au. In this case, the hydrogen recombination reaction to form water vapor can advantageously be carried out at room temperature, without the input of heat.

[0024] In a particularly advantageous way, the metal oxide MO X It could be WO3. Tungsten trioxide is highly reactive with dihydrogen, and in its WO2 form is highly reactive with oxygen, reforming WO3, while exhibiting good thermal and chemical resistance. Such a material is also non-toxic and inexpensive. Advantageously, the active material is a compound or composite and / or a mixture of WO3 as the metal oxide and Pt or Pd as the catalyst. The presence of the catalyst allows recombination at room temperature or even lower. A particular form of the active material based on the transition metal oxide MOx and the catalyst has inclusions or particles of catalyst on the surface of the transition metal oxide and at least partially integrated within the transition metal oxide.

[0025] Advantageously, the active material can be porous, in particular macro-porous and / or mesoporous and / or micro-porous, with pores whose largest dimension or diameter is typically between 10 and 0.1 pm, and even more advantageously in a range of 1 and 0.4 pm.

[0026] In one particular embodiment, the active material can be in the form of a block coated with a porous, water-permeable coating. For example, the porous, water-permeable coating can be in the form of a metallic or polymer foam, or porous glass.

[0027] According to another particular embodiment, the active material can be covered with a coating permeable to hydrogen and oxygen and impermeable to water.

[0028] For example, the porous coating permeable to hydrogen and oxygen and impermeable to water, can be in the form of a functionalized metallic foam having a hydrophobic surface, or a hydrophobic porous polymer.

[0029] According to another particular embodiment, the active material can be in the form of particles or inclusions integrated into a porous material permeable to hydrogen and oxygen.

[0030] According to another particular embodiment, the active material may be in the form of a fibrous support such as glass wool or made of microfibers or nanofibers, in particular SiC microfibers or nanofibers, or of metal or carbon, the fibrous support being coated with the active material or incorporating the active material.

[0031] In another aspect, the present invention relates to a method for producing a structure as defined above, wherein the formation of the active material comprises the preparation of a liquid solution comprising a metal oxide precursor MO X and a catalyst precursor, the metal oxide precursor MO X and the catalyst precursor being dissolved in a solvent. Then, typically at least one drying treatment is carried out to evaporate the solvent.

[0032] Advantageously, a heat treatment step for the coating can be carried out during and / or after drying. A calcination step can be included, particularly after drying, to allow for the removal of a sacrificial agent if such an agent has been introduced into the solution.

[0033] According to another aspect, the present invention relates to a passive dihydrogen recombiner comprising at least one structure for hydrogen treatment and as defined above.

[0034] According to another aspect, the present invention provides an installation for the storage or treatment of nuclear waste or the exploitation of nuclear fuel and comprising at least one passive recombiner as defined above or a structure for the treatment of hydrogen as defined above.

[0035] According to another aspect, the present invention provides a corium catcher comprising at least one structure for hydrogen treatment as defined above.

[0036] According to another aspect, the present invention provides a radioactive waste storage package containing a structure for hydrogen processing as defined above.

[0037] BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be better understood on the basis of the following description and the accompanying drawings, in which:

[0039] [Fig. IA] [Fig. IB] serve to illustrate an example of a recombiner with elements of particular active material based on transition metal oxide and capable of reacting with hydrogen, without the presence of oxygen, and by recombination in order to neutralize the hydrogen by producing water.

[0040] [Fig. 2] serves to illustrate an example of a block of active material based on a transition metal oxide. [Fig. 3] serves to illustrate an example of a particular structure formed from a block of active material based on a transition metal oxide and capable of reacting with hydrogen, this block being coated with a material permeable to hydrogen, oxygen and water.

[0041] [Fig. 4] serves to illustrate an example of a particular structure in which the block of active material is coated with a material permeable to hydrogen, oxygen and impermeable to water.

[0042] [Fig. 5] serves to illustrate an example of a particular structure of active material integrated as particles or inclusions in a material permeable to hydrogen, oxygen and impermeable to water.

[0043] [Fig. 6] serves to illustrate an example of a particular structure in which the active material is integrated as particles or inclusions in a material permeable to hydrogen, oxygen and water.

[0044] [Fig. 7] serves to illustrate a functionalized fibrous support incorporating the active material.

[0045] [Fig. 8] serves to illustrate an example of recombination kinetics of a particular active material.

[0046] [Fig. 9] serves to illustrate an example of a corium catcher comprising several zones of active material based on transition metal oxide and capable of reacting with hydrogen by recombination to produce water.

[0047] [Fig. 10A] [Fig. 10B] [Fig. 10C] respectively illustrate the integration of active material into a waste storage facility containing at least one radioactive package, and the integration of active material into at least one radioactive waste storage package.

[0048] Identical, similar or equivalent parts of the different figures carry the same numerical references in order to facilitate the transition from one figure to another.

[0049] The different parts represented in the figures are not necessarily shown on a uniform scale, in order to make the figures more legible.

[0050] DETAILED DESCRIPTION OF SPECIFIC METHODS OF IMPLEMENTATION

[0051] An example of a recombiner 10 according to the invention, comprising at least one structure of so-called "active" material capable of reacting with hydrogen, is schematically represented in Figures IA and IB. The recombiner 10 can be suspended in a site or enclosure to be protected, for example a nuclear power plant, or a storage site for nuclear waste or material likely to generate hydrogen outgassing or even hydrogen outgassing by water radiolysis, or a site for the production and / or use of hydrogen as an energy carrier.

[0052] In the example shown in Figure IA, the recombiner 10 is designed for wall mounting. Alternatively, it can be supported and suspended by another type of structure, for example a bracket, or simply placed on a support, for example on the floor.

[0053] The recombiner 10 comprises a chassis 13 housing, in the illustrated example, one or more elements 15A, 15B, 15C, 15D of active material 20, the composition of which will be detailed later. The elements 15A, 15B, 15C, 15D are, for example, in the form of blocks or plates made of active material 20 or comprising at least one zone or layer of active material 20.

[0054] The chassis 13 is internally equipped with at least one conduit 14 in which elements 15A, 15B, 15C, and 15D are arranged, extending between at least one inlet opening 17 and at least one outlet opening 19. During operation, hydrogen H2 is passively drawn in (arrow(s) Fl) through at least one inlet opening 17, and a reduction reaction occurs with the active material of elements 15A, 15B, 15C, and 15D to generate water vapor (arrow(s) F2). This vapor exits through the upper end of the conduit via the outlet opening 19. Arrows Fl and F2 in Figures IA and IB show a preferred flow direction resulting from natural circulation, further enhanced by a thermal gradient due to heat release during the reaction. The operation of the recombiner 10 is thus based on physico-chemical principles to initiate and maintain the recombination reaction.Recombiner 10 is described here as a "passive" recombiner because it can operate autonomously without an external power source, particularly without electricity, and requires no control, intervention, or actuation during its operation. Such a passive recombiner operates, in particular, without the need for a pressurized supply to force a gas into the recombiner and without the need for a draw-off to extract the gas from the extraction opening 19.

[0055] The elements 15A, 15B, 15C, 15D can be integrated in various ways into the chassis 13 of the recombiner 10, typically in a removable manner, for example by means of a sliding structure.

[0056] The active material 20 here has the particularity of being a transition metal oxide MO X(with M a transition metal such as for example: W, Mo, Ce, Ni, Sn, Cu and with x typically greater than 1 and less than 5) chosen so that it can be reduced in the presence of hydrogen and recombine to create water molecules.

[0057] In particular, a metal is chosen, such as the M0 couple. x / M0 x -i exhibits a standard electrochemical potential E°(MO x / MO x -i) between the standard potential of the H2O / H2 couple and that of the O2 / H2O couple which are between -0.8 and +1.22 V / ESH respectively.

[0058] Advantageously, the metal M is chosen such that the standard electrochemical potential E°(MO x / MO x -i) of the couple M0 x / M0 x .i is in a range between -0.6 V / ESH and +1.0 V / ESH and even more advantageously in a range between -0.5 V / ESH and +0.5 V / ESH.

[0059] Two other physicochemical characteristics can be taken into account in order to select the metal oxide MO X , namely the activation energy (E a ) of the reaction between the metal oxide (MO X ) and hydrogen (H2( g and the exothermicity of the reduction and oxidation (these reactions corresponding to reactions 2 and 3 given below). The higher the E value a The lower the concentration, the higher the reaction kinetics. The higher the exothermicity of the reduction and oxidation of the metal couple by H2(g), the more efficient the principle.

[0060] Transition metal oxide MO X This allows for recombination to occur both in the presence and absence of a catalyst, according to one of the following reactions 1 or 2: (without catalyst) Reaction 1 (with catalyst) Reaction 2 Q and Q' correspond respectively to heat released during reaction 1 and during reaction 2.

[0061] The reaction without a catalyst occurs particularly at temperatures on the order of several hundred °C, for example between 400 °C and 600 °C. The active material 20 also has the unique characteristic and advantage of being able to react with hydrogen even when the oxygen concentration is low, for example on the order of 4% v / v, or even in the total absence of oxygen.

[0062] For example, with a composite active material made of Pt (6 atomic percent) as a catalyst and WO3 in an orthorhombic phase as a metal oxide, hydrogen neutralization with the same efficiency can be achieved between 20 and 3.5% O2.

[0063] Another advantage of using a transition metal oxide MO X as defined above, in the presence of oxygen, a metallic oxide MO x-i produced by a reduction reaction defined above, capable of oxidizing to reform the metal oxide MO X Re-oxidation occurs to regenerate the reactant, in other words, the transition metal oxide MO X The starting point can be implemented as follows, and according to the following reaction:

[0064] This contributes to the durability of elements 15A, 15B, 15C, and 15D. The transition metal oxide-based material can be, for example, one of the following metal oxides: tungsten oxide (WO3), molybdenum oxide (MoOs), vanadium oxide (V2O5), CuO, Fe2O3, tin oxide (SnO2), or NiO. The various metal oxides mentioned have optimal standard potentials around 0 V / ESH.

[0065] Another advantage of the aforementioned active material 20 is that it allows reaction with hydrogen at low hydrogen concentrations typically between 1.81 and 0.03% v / v, and which can thus be less than 0.5% v / v.

[0066] According to a particularly advantageous embodiment, the active material 20 can be based on tungsten trioxide (WO3). In the specific case where the active material elements 15A, 15B, 15C, 15D are based on tungsten trioxide (WO3), the following reaction can be carried out:

[0067] Reaction 4 (special case where the active material is devoid of a catalyst)

[0068] The catalyst-free metal oxide material can be used in high-temperature environments, particularly between 400°C and 600°C.

[0069] According to an advantageous embodiment, the active material 20 is based on MO Xand a catalyst. In this case, advantageously, the reduction reaction can take place at room temperature without the input of heat. The catalyst is typically metallic and based on at least one metal from group VIII or I, in particular chosen from the following metals: Ru, Rh, Ir, Pd, Pt, Ni, Cu, Ag, Au.

[0070] In ascending order of preference (an order which may be dictated by both cost and melting temperature criteria), the metal is chosen from the following list: Au, Ag, Cu, Ni. More advantageously, the catalyst can be based on Platinum (Pt) or Palladium (Pd).

[0071] Thus, according to a particularly advantageous embodiment, elements 15A, 15B, 15C, 15D can be based on tungsten trioxide (WO3) and a catalyst such as, for example, Platinum or Palladium.

[0072] The following reaction can then be implemented:

[0073] (with catalyst, with Q being the heat released by the chemical reaction in kJ / mol). The reduction reaction (reactions 4 and 5) of tungsten trioxide is exothermic.

[0074] With or without a catalyst, when the active material 20 is tungsten trioxide (WO3), the following reaction can be implemented at elements 15A, 15B, 15C, 15D:

[0075] Thus, when tungsten trioxide is reduced by hydrogen to form tungsten dioxide, the latter is rapidly re-oxidized by the presence of oxygen. This reaction (reaction 6) is also exothermic. The two types of reaction (reaction 4 or reaction 5 on the one hand, and reaction 6 on the other) occur simultaneously and allow for continuous consumption when hydrogen and oxygen are present in significant quantities.

[0076] Typically, the formation of the active material involves the use of a liquid solution comprising at least one metal oxide precursor MO X and a catalyst precursor, the metal oxide precursor MO X and the catalyst precursor being dissolved in a solvent.

[0077] This can be achieved, for example, by adding the catalyst precursor present in solution to a solid metal oxide, or by suspending the solid metal oxide, for example in powder form, in a solution containing the catalyst precursor. The catalyst precursor itself can be introduced as a metal powder (catalytically active form) into a liquid solution.

[0078] Optionally, the resulting solution can then be deposited onto a support. Typically, at least one drying treatment is performed to evaporate the solvent. The metal oxide MO Xand the catalyst active material are thus mixed into the material obtained.

[0079] A heat treatment step during and / or after drying, particularly calcination heat treatment, may then be implemented. This step may be optional when the catalyst precursor is in the form of a catalytically active metal powder.

[0080] A particular embodiment of the active material 20 involves the use of a sol-gel type process.

[0081] The document: “Electrochromic properties of sol-gel derived WO3 coatings”, by P. Judeinstein and J. Livage, in Sol-Gel Optics, SPIE, 1990, p. 344-351. doi: 10.1117 / 12.22573, gives an example of the realization of WO3 by sol-gel process.

[0082] An example of the fabrication of a WO3 and Pd compound is given in the document "A fiber-optic evanescent-wave hydrogen gas sensor using palladium-supported tungsten oxide", by S. Sekimoto et al., Sens. Actuators B Chem., vol. 66, no. 1, pp. 142-145, 2000, doi: 10.1016 / 50925-4005(00)00330-0. The document "Fiber optic hydrogen sensors with sol-gel WO3 coatings", by Yang, Z. Yang, J. Dai, and D. Zhang, Sens. Actuators B Chem., vol. 166-167, p. 632-636, 2012, doi: 10.1016 / j.snb.2012.03.026, gives an example of the realization of a compound of WO3 and Pt as a catalyst.

[0083] A specific example of the process sequence for manufacturing an active material coating using the Sol-Gel method will now be presented. In this particular case, the active material can be deposited onto a substrate, such as a plate, or a fibrous substrate made of nanofibers and / or microfibers of glass, SiC, or polymer. Alternatively, the active material can be formed directly as an active powder following solvent evaporation.

[0084] In the first step, a solution containing a metal oxide is acidified. This acidification can be achieved, for example, using a cation exchange resin, which is brought into contact with the solution. For instance, a 13 mL solution of 0.5 M sodium tungstate (ISwC) can be acidified to obtain a solution containing a precursor, in this case, FbwCaq. A solvent, typically organic, is then added. This solvent could be ethanol, for example, in a volume of approximately 8 mL for the aforementioned volumes of precursor and catalyst solutions.

[0085] The solution containing this precursor is collected and to which another solution containing a catalyst is added. In one particular example, this other solution could be a solution of FbPtCle. A volume of 4 mL at 0.125 M could be used, resulting in an atomic proportion of 1:13 of catalyst: WO3. This proportion corresponds to an optimal ratio for a good reaction while minimizing the amount of catalyst required.

[0086] A MO oxide-based coating is then formed. Xin amorphous form, here amorphous WO3, using the previously obtained solution. A process commonly known as "Dip-Coating," in which the substrate is immersed in the previously obtained solution, can be used to deposit the coating onto the substrate. Alternatively, a process such as "Spin-Coating" can be used to deposit the coating onto a flat surface. The active coating in powder form can be obtained through solvent evaporation. To accelerate the evaporation process, the solution can be heated to a temperature, for example, between 50°C and 60°C and / or placed under vacuum using, for example, a rotary evaporator.

[0087] Such a process typically includes a coating drying stage, which can be carried out in ambient air or heated to a temperature of, for example, between 50°C and 60°C in order to accelerate the process, for example for a period of several hours, for example 2 hours.

[0088] A calcination step is then typically carried out. The purpose of this step is twofold: first, the tungsten trioxide is converted into a crystalline form, creating vacancies. The presence of these vacancies promotes the reactivity of the material. Finally, if the catalyst is introduced as FbPtCle or any other form in solution, calcination is performed to break the bonds between the chlorine and platinum and to reduce the platinum to its metallic, catalytically active form. This heat treatment is typically carried out at a temperature of several hundred degrees Celsius, for example, typically between 300°C and 650°C, for a duration of at least several tens of minutes, for example, typically between 10 and 90 minutes. Advantageously, such treatment is carried out between 450°C and 550°C for a duration of between 30 and 60 minutes.

[0089] According to an advantageous embodiment, an active material can be provided that is 20 porous and in particular meso- and / or micro-porous.

[0090] In order to increase the specific surface area of ​​the material obtained and to increase or create porosity, a "Soft-Tern plating" (i.e. "soft matrix") or "hard-templating" (i.e. "hard matrix") type method can be used and possibly integrated into a process as described above.

[0091] It is thus possible to introduce molecules or molecular assemblies to form a so-called "sacrificial" phase in a solution, as previously described, containing a precursor, for example, H2WO4aq. The precursor is then solidified, for example, during a cooking step such as calcination, as previously described, to form a composite material where sacrificial regions are embedded in an inorganic matrix or skeleton based on MO2 oxide.x or based on MO oxide x and the catalyst.

[0092] The sacrificial regions are then removed, leaving only the MO oxide-based material. X and catalyst.

[0093] When using a hard-templating method, the sacrificial phase is typically inorganic. For example, silicon or silica (SiC>2) in powder form, with a grain size typically less than 1 pm, can be used to form the sacrificial phase, which is then added to a solution containing an FbWC aq precursor and the FbPtCle catalyst.

[0094] A catalyst-doped oxide coating, here WCh / Pt, is then formed in free spaces around the sacrificial phase, for example, Si or SiCh. After calcination, the sacrificial phase is typically removed by dissolution using a hydrofluoric acid (HF) solution, for example, 10%. This yields a metal oxide that can be further catalyst-doped, in this case a WOi / Pt composite material with porosity formed by the removal of sacrificial regions, here silicon or silica.

[0095] The document "Nanostructured Tungsten Oxide - Properties, Synthesis, and Applications," by H. Zheng, et al., Adv. Funct. Mater., vol. 21, no. 12, pp. 2175-2196, 2011, doi: 10.1002 / adfm.201002477, provides an example of the fabrication of porous WO3 using a "Soft Templating" method. The fabrication of a WO1 / Pt composite material using a similar method is also conceivable.

[0096] The active material 20 is based on metal oxide MO X ^ advantageously associated with a catalyst can be in the form of a block as illustrated in figure 2.

[0097] In one embodiment, the active material block 20 is at least partially covered with a coating 30 that is permeable to gases, in particular to hydrogen and oxygen, and permeable to water.

[0098] In this case, the water produced during the reaction of hydrogen with the active material 20 can be more easily removed. This permeable coating 30 can be a porous material, advantageously with high porosity, and with a skeleton or matrix that can be metallic, ceramic, or polymeric. For example, the coating 30 can be a metallic foam, for example, made of copper, or a stainless steel, for example, type 304L or 316L. Such a foam can be produced, for example, by 3D powder bed printing or by a conventional technique for manufacturing metallic foam or porous filters. As another example, the coating 30 can be based on a hydrophilic porous polymer, for example, polyvinyl alcohol (CAS: 9002-89-5). Another embodiment involves a coating based on porous glass, typically sintered glass.

[0099] In the particular embodiment illustrated in Figure 3, the active material 20 is in the form of a block entirely covered by the permeable coating 30.

[0100] According to another embodiment, the active material 20 is at least partially covered with a coating 40 permeable to hydrogen and oxygen but this time impermeable to water.

[0101] In the particular embodiment illustrated in Figure 4, the active material 20 is arranged to form a sheath of a channel covered by the coating 40 which is permeable to hydrogen and oxygen and impermeable to water.

[0102] In this case, the water produced during the reaction of hydrogen with the active material can be retained in the channel or discharged through it. The water-impermeable coating 40 can, for example, consist of a single layer of molecules ("self-assembled monolayer" or SAM), such as an alkanethiolate layer, or be based on alkylphosphonic acid(s). In one particular embodiment, the coating 40 can be a porous metallic material rendered hydrophobic, such as porous steel or hydrophobic porous copper. A low-carbon steel, such as 316L steel with less than 0.03% carbon, can be functionalized, for example, with octadecanethiol (ODT; C18H37SH: CAS No. 2885-00-9) after first quenching the steel in hydrochloric acid to remove the passivation layer.The coating 40 can also be in the form of hydrophobic or hydrophobically rendered cotton or a functionalized foam with a hydrophobic surface, in particular a metallic foam or a hydrophobic porous polymer-based foam, for example a fluorocarbon polymer such as Teflon™, or a polymer such as polyvinylidene fluoride (CAS: 24937-79-9). A process such as the one described, for example, in the document "The nature of self-assembled octadecylphosphonic acid (ODPA) layers on copper substrates" by Zhao et al., Journal of Colloid and Interface Science Volume 581, Part B, 1 January 2021, Pages 816-825, can be used, for example, to functionalize and render hydrophobic copper or another metal or even a metal oxide using an alkylphosphonic acid (ODPA).

[0103] As an alternative to either of the embodiments described above, rather than being in the form of block(s) or layer(s), the active material 20, based on transition metal oxide MO X or based on a transition metal oxide compound MO X and catalyst, can be in the form of inclusions or particles integrated into a porous material permeable to hydrogen and oxygen.

[0104] In the embodiment illustrated in Figure 5, particles 120, with a maximum size or width dim, for example, between 1 micrometer and 1 decimeter, advantageously between 50 µm and 2 cm, of active material 20 are integrated into a porous material 400, permeable to hydrogen and oxygen but impermeable to water. This material 400 can, for example, be of the type used to form the coating 40 described previously in connection with Figure 4.

[0105] One method for obtaining this configuration in which the active material 120 is incorporated into a functionalized, hydrophobic metallic foam includes additive manufacturing or a sintering technique.

[0106] In the embodiment illustrated in Figure 6, particles 120' of active material 20 with a maximum dimension or width d2m, for example, between 1 micrometer and 1 decimeter, advantageously between 50 µm and 2 cm, are embedded in a porous material 300, permeable to hydrogen, oxygen, and water. This material 300 can, for example, be of the type used to form the coating 30 described previously in connection with Figure 3.

[0107] In the embodiment illustrated in Figure 7, the active material 20 is arranged as particles on a functionalized fibrous support 52. The fibrous support 52 forms a filter and is, for example, made of glass fibers or composed of SiC microfibers or nanofibers, or of metal or carbon. The support 52 may have pores, for example, of micrometric size, such as between A and B. The particles of active material 20 can be incorporated into the pores.

[0108] In the particular embodiment shown, the fibrous support 52 has a circular plate shape, but other shapes, possibly flat, are possible. The active material 20 on the fibrous support 52 can, for example, be deposited in powder form.

[0109] According to one variant, the active material 20 can be arranged on the support 52, for example, by depositing a sol-gel solution containing the material 20 on one face of the support 52 and creating a vacuum on the opposite face. Drying for a period of, for example, at least 24 hours can then be provided. In order to accelerate this drying step, the functionalized support 52 can be heated to a temperature, for example, between 50°C and 80°C for a period of, for example, between 2 and 24 hours, or placed under vacuum for a period of, for example, between 5 and 24 hours. The support 52 can then be subjected to a calcination step at a temperature, for example, between 300 and 600°C, advantageously between 450 and 550°C, for a period of 30 to 90 minutes.

[0110] The choice of configuration depends on the application and context. An active material coating can be used in a device or installation where the water produced by the reaction is released, as well as in a device or installation where the water is retained by a sponge effect.

[0111] Figure 8 shows a Ci curve illustrating the recombination kinetics of a given active material introduced into a measurement cell. In this example, the active material consists of 7 mg of a Pt / WCh compound with a molar ratio of 1 / 13, exposed to a volume of 625 mL of hydrogen at atmospheric pressure. 1 81 ± °- 04 % v / vof hydrogen. On the left y-axis, the estimated temperature (in °C) of the active material 20 is indicated, while on the right y-axis, the estimated hydrogen concentration (in % v / v) is given. The portion of the curve Ci located before 0 s corresponds here to a gaseous air purge at 1.81% v / v for a flow rate of 300 L / h. From 0 s onward, this gaseous purge is stopped and the cell is then closed at both the inlet and outlet. A static measurement is thus performed. In an active material 20 based on a metal oxide and a catalyst, as described previously, the metal oxide and the catalyst are intimately associated and mixed, since they are typically formed from a liquid solution comprising a precursor of the metal oxide and a precursor of the dissolved catalyst.An active material structure 20 thus obtained is structurally and performance-wise distinct from an arrangement in which a layer of metal oxide would be coated with another layer of catalyst.

[0112] An active material 20 such as previously presented can be used in multiple applications and / or installations in which an undesirable emission of dihydrogen is likely to occur.

[0113] A hydrogen-active material such as the one presented earlier is, for example, particularly advantageous in a core catcher installed in a nuclear power plant to mitigate a case of reactor core meltdown.

[0114] An example of a corium catcher is shown schematically in Figure 9.

[0115] The condenser here includes sacrificial structures 71a, 71b, for example made of concrete, and in particular a sacrificial separation structure 71b with a discharge channel 72 whose walls are coated with a protective layer 73. In the event of a reactor core meltdown and rupture of the sacrificial structure 71b, the corium falls by gravity into the discharge channel 72, which communicates with a spreading chamber 74 designed to promote cooling. The spreading chamber 74 can be partially filled with water and equipped with cooling plates 77. During the release of the corium, significant hydrogen production can occur due to the high temperature rise of various metallic parts, for example zirconium cladding, and when water is present in the vapor phase. The water is then likely to oxidize certain metals by forming hydrogen.

[0116] The active material 20 mentioned previously is, in the specific embodiment illustrated, distributed across different zones 75A, 75B, 75C, 75D of the installation to allow for passive hydrogen recombination. According to another application example, a hydrogen-based active material 20 such as the one presented earlier can also be integrated into a deep geological repository for radioactive waste, particularly of the High-Level (HLW) or Intermediate-Level Long-Lived (ILW-LL) type.

[0117] In the context of deep geological disposal of high-level (HLW) or intermediate-level long-lived (ILW-LL) radioactive waste, some waste is likely to emit hydrogen within waste packages. This emission is problematic due to the risks of fire (typically starting at 4% v / v hydrogen) or explosion (generally starting at 13% v / v hydrogen), but also due to the degradation of the metal container at concentrations even lower than those mentioned above for a fire.

[0118] The hydrogen-based active material 20 presented previously can be placed in different areas of a waste storage facility.

[0119] Thus, in the specific embodiment shown in Figure 10A, regions 85A, 85B of active material 20 are arranged on the internal walls of a cell 80 for receiving radioactive waste packages 82, typically located underground. As illustrated in Figures 10B and 10C, the active material 20 can also be incorporated into radioactive waste packages 84, 86.

[0120] Thus, in Figure 10B, a package 84, called "compacted", of radioactive waste, for example of type MA-VL, contains on an internal wall a region 85D of active material 20. In Figure 10C, a package 86, called "vitrified", of radioactive waste, for example of type HA, contains on an internal wall a region 85E of active material 20.

Claims

DEMANDS 1. A recombination hydrogen processing structure having at least one element (15A, 15B, 15C, 15D, 75A, 75B, 75C, 75D, 85A, 85B, 85C, 85D) of an "active" material (20) designed to react with hydrogen, the active material comprising a metal oxide MO X , with M a transition metal, with 1 < x < 5, the metal oxide MO X being capable of undergoing reduction in the presence of hydrogen and without the presence of oxygen so as to form water, and of forming as a product of this reduction another oxide MO x -i capable of oxidizing in the presence of oxygen to reform the metal oxide MO X .

2. Structure according to claim 1, The metal M is such that the standard potential E°(M0 x / M0 x i) of the couple M0 x / M0 x . is between -0.828 V / ESH and +1.229 V / ESH, preferably between -0.5 and +0.5 V / ESH.

3. Structure according to claim 1 or 2, the metal oxide MO X being WO3OU chosen from CuO, MOO3, vanadium oxide (V2O5), Fe2Û3, SnCh, NiO.

4. Structure according to any one of claims 1 to 3, in which the active material (20) is a compound based on said metal oxide MO X and a catalyst or composite based on said metal oxide MO X and a catalyst and / or a mixture of said metal oxide MO X and said catalyst, the catalyst being in particular a metal of group VIII or group I, preferably chosen from among the following metals: Pt, Pd, Ni, Cu, Ag, Au.

5. Structure according to claim 4, the catalyst being Pt or Pd.

6. Structure according to any one of claims 1 to 5, the active material (20) being porous, in particular microporous and / or mesoporous.

7. Structure according to any one of claims 1 to 6, wherein said active material (20) is in the form of a block coated with a water-permeable porous coating (30), such as a metallic or polymer-based foam or a porous glass.

8. Structure according to any one of claims 1 to 7, wherein said active material (20) is covered with a coating (40) permeable to hydrogen and oxygen and impermeable to water, such as a functionalized metallic foam having a hydrophobic surface, or a hydrophobic porous polymer.

9. Structure according to any one of claims 1 to 5, wherein said active material (20) is in the form of particles or inclusions integrated into a porous material (300, 400) permeable to hydrogen and oxygen.

10. Structure according to any one of claims 1 to 5, comprising a fibrous support such as glass wool or formed of microfibers or nanofibers of SiC, or of metal or carbon, the fibrous support being coated with the active material (20) or incorporating the active material (20).

11. Passive recombiner (10) of dihydrogen comprising at least one structure (15A, 15B, 15C, 15D) according to any one of the preceding claims.

12. Installation for the storage or treatment of nuclear waste or the operation of nuclear fuel comprising at least one passive recombiner (10) according to claim 11 or a structure according to any one of claims 1 to 10.

13. Corium catcher comprising at least one structure according to any one of claims 1 to 10.

14. Radioactive waste storage package(s) containing a structure according to one of claims 1 to 10.

15. A method for producing a structure according to any one of claims 1 to 11, wherein the formation of the active material comprises the preparation of a liquid solution comprising a metal oxide precursor MO X and a catalyst precursor, the metal oxide precursor MO X and the catalyst precursor being dissolved in a solvent, then, - carry out at least one drying treatment to evaporate the solvent.

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