Thibaud Delahaye

Atomic Energy and Alternative Energies Commission | CEA · Département de Radiochimie et de Chimie des Procédés (DRCP)

Ceria (CeO2) is known as a refractory oxide for dissolution in nitric acid, since the leaching reaction is thermodynamically unfavorable, except when it is complexed by nitrates but with very slow kinetics. To enhance dissolution, surface activation was achieved using high-energy milling. With the mechanically-activated cerium oxide, leaching in ni...

The reactivity of the N-(1-adamantyl)acetamide ligand (L = adam) has been evaluated as precipitating agent for the hexavalent uranyl cation ([U] = 20-60 g L-1) in concentrated nitric acid aqueous solution (0.5-5 M). It results in the formation of a crystalline complex (UO2)(adam)2(NO3)2·2(adam) (1), in which the uranyl center is 8-fold coordinated...

(La,Sr)(Ti,Ni)O3 compounds have been characterized as air and hydrogen electrode for symmetrical Solid Oxide Cells. While the materials are thermomechanically compatible with 8YSZ electrolyte, the reactivity tests confirm the formation of an insulating pyrochlore La2Zr2O7, redhibitory for the electrochemical properties. Concerning the electrical be...

The stability of La2xSr1-2xTi1-xNixO3-δ (LSTN) and La7x/4Sr1-7x/4Ti1-xNixO3-δ (25LSTN) materials in high temperature reducing conditions has been studied with a special focus on the Ni exsolution process for SOFC anode / SOEC cathode application. In a general way, LSTN and 25LSTN compounds are stable after treatments at 800 °C in air and wet reduci...

L'invention a trait à un procédé de préparation d une poudre a base d'oxyde(s) comprenant de l'uranium et du plutonium comprenant les étapes suivantes : a) une étape de précipitation d'une solution comprenant de l'uranium à son degré d'oxydation VI et du plutonium à son degré d'oxydation IV par mise en contact de ladite solution avec un mélange com...

Manufacturing of CeO2 ceramics by an aqueous gelcasting shaping process was studied. This study has focused on the identification of critical parameters that influence the properties of suspensions and CeO2 ceramics. It is shown that ethylene glycol diglycidyl ether (EGDGE) and 3,3-diaminodipropylamine (DPTA) are suitable gelling agents for gelcast...

With the scope to develop new electrode materials for Solid Oxide Cells, the (La,Sr)(Ti,Ni)O3-δ system has been studied by Pechini synthesis and heat-treatment in air. Only La2xSr1-2xTi1-xNixO3-δ (LSTN) and La7x/4Sr1-7x/4Ti1-xNixO3-δ (25LSTN) compounds can be prepared as pure phases after synthesis at the minimum temperature of 1000 °C for 12 h. Al...

In the framework of generation IV development for nuclear reactors, actinide mixed oxides are considered for multirecycling plutonium fuels and for transmutation targets of minor actinides. In this context, new processes are being developed for either the synthesis of mixed uranium-plutonium oxide compounds for MOx fuel or uranium-americium target...

Novel NiO/GDC (Gadolinium-doped Ceria) cermet catalysts were developed by the Weak Acid Resin (WAR) method using an ion exchange resin template. In addition, the specific surface area of these tunable materials was enhanced by NiO partial dissolution in aqueous acid solution. The whole procedure highly improved the micro-structural properties of th...

This invention relates to a method for preparing an air electrode based on Pr2-xNiO4 with 0≦x<2, comprising a step consisting in sintering a ceramic ink comprising Pr2-xNiO4 and a pore-forming agent at a temperature above 1000° C. and below or equal to 1150° C. This invention also relates to the air electrode thus obtained and its uses.

Three uranyl amide complexes have been isolated from slow evaporation technique from an aqueous solution of nitric acid (0.5 M), in the presence of N′,N-diethylacetamide (noted dam; compound 1), N-ethylacetamide (noted eam; compound 2) and 2-(2-oxopyrrolidino)acetamide (or piracetam, noted pam; compound 3). It results in the formation of crystallin...

Actinide oxide microspheres are considered as promising substituents to powder precursors for the production of ceramic pellets of nuclear fuel or targets. Porous microspheres of sub-millimetric size are synthesised using the Weak Acid Resin process. Controlling their microstructure and their mechanical properties is essential to predict the micros...

The sintering behavior of green pellets obtained from nanostructured Ce0.8Gd0.2O1.9 submillimetric microspheres is studied in the present paper. Corresponding shrinkage rate curve shows a two-step densification in dynamic conditions, with the presence of two successive extrema, at 1200 K and 1500 K. To fully understand this non-common densification...

This article draws a state of knowledge of the dissolution of uranium dioxide in nitric acid media. The chemistry of the reaction is first investigated, and two reactions appear as most suitable to describe the mechanism, leading to the formation of monoxide and dioxide nitrogen as reaction by-products, while the oxidation mechanism is shown to hap...

In the frame of minor actinide recycling, (U,Am)O 2 are promising transmutation targets. To assess the thermodynamic properties of the U-Am-O system, it is essential to have a thorough knowledge of the binary phase diagrams, which is difficult due to the lack of thermodynamic data on the Am-O system. Nevertheless, an Am-O phase diagram modelling ha...

The use of CRMP (Calcined Resin Microsphere Pelletization) process for AmBB (Americium Bearing Blankets) fabrication is today a key research axis in americium transmutation domain, where its very high activity requires minimization of powder dissemination. In this aim, the use of oxide microspheres as compaction precursors is a promising clean alte...

In view of aspects such as the leaching behavior of spent nuclear fuel stored in an oxidative environment as well as the potential intermixing of fission products (Pu and minor actinides) with U3O8 as the most stable uranium oxide, the latter is tested by fixing an aqueous solutions of UO2²⁺ and Am³⁺ cations in a 90:10 atomic ratio at a weak-acidic...

One option envisioned for the future management of high level nuclear waste is the transmutation of minor actinides into short-lived fission products in sodium fast reactor. This route requires the development of pellet fabrication processes to prepare Minor Actinide Bearing Blanket (MABB) for the transmutation of americium. Currently, those cerami...

U3O8 is considered to be the most stable phase for uranium oxide. Its structural properties must be accurately understood to foresee and manage aspects such as its leaching behavior when spent nuclear fuel is stored in an oxidative environment. Moreover, as fuel irradiation causes the formation of fission products and activation products such as pl...

UO2 powders were synthesized thanks to oxalic precipitation (platelet morphology) and sol-gel route and completely characterized. A secondary phase was found depending on the calcination atmospheres. This phase has been identified by Raman spectroscopy as graphitic material (i.e. carbon-based secondary compound) and quantified by thermogravimetric...

Mixed actinide (III,IV) oxalates of general formula M2.2UIV1.8AnIII0.2(C2O4)5•nH2O (An = Pu or Am and M = H3O+ and N2H5+) have been quantitatively precipitated by oxalic precipitation in nitric acid medium (yield> 99%). Thorough multiscale structural characterization by XRD and XAS measurements confirmed the existence of mixed actinide oxalate soli...

A possible option to reduce the radiotoxicity of nuclear waste is to transmute minor actinides and notably americium into lighter short-lived elements in fast neutron reactors of fourth generation. It consists in irradiating uranium–americium mixed-oxide compounds named AmBB (Americium-Bearing Blankets) and located at the reactor core periphery. Am...

Uranium-americium mixed oxides are considered as potential targets for americium transmutation in fast neutron reactors. Their thermophysical properties and notably their melting behaviour have not been assessed properly although required in order to evaluate the safety of these compounds under irradiation. In this study, we measured via laser heat...

In U1-xAmxO2±δ compounds with low americium content (x ≤ 20 atom %) and oxygen-to-metal (O/M) ratios close to 2.0, Am(III+) cations are charge-balanced by an equivalent amount of U(V+) cations while the fluorite structure of pure U(IV+)O2 is maintained. Up to now, it is unknown whether this observation also holds for higher americium contents. In t...

This study is devoted to the synthesis and the characterization of porous metal oxide microsphere from metal loaded ion exchange resin. Their application concerns the fabrication of uranium-americium oxide pellets using the powder-free process called Calcined Resin Microsphere Pelletization (CRMP). Those mixed oxide ceramics are one of the material...

Transmutation of americium in heterogeneous mode through the use of U1-xAmxO2±δ ceramic pellets, also known as Americium Bearing Blankets (AmBB), has become a major research axis. Nevertheless, in order to consider future large-scale deployment, processes involved in the AmBB fabrication have to minimize fine particles dissemination, due to americi...

An electrolyte plate for an electrochemical system including a first face and a second face, being opposite each other, of largest surface area, the first face including linear parallel ribs and the second face including linear parallel ribs. The plate thus exhibits an increased rigidity without substantially increasing the thickness thereof.

The evolution of americium oxide under ambient conditions was monitored using XRD (X-ray diffraction) and Raman spectroscopy. After a thermal treatment under reducing conditions, a polyphasic sample mainly composed of A- and C-type americium sesquioxides is evidenced by XRD and Raman spectroscopy. The sample then evolves through two processes: oxid...

Uranium-americium mixed oxides could be used as transmutation targets to lower Am inventory in spent nuclear fuels. Due to (241)Am activity, these materials are subjected to α-self-irradiation which provokes crystallographic disorder. Previous studies on U-Am mixed oxides gave first insight into α-radiation tolerance of these compounds, but have ne...

The structural evolution under (241)Am self-irradiation of U1-xAmxO2±δ transmutation fuels (with x ≤ 0.5) was studied by X-ray diffraction (XRD). Samples first underwent a preliminary heat treatment performed under a reducing atmosphere (Ar/H2(4%)) aiming to recover the previously accumulated structural defects. Over all measurements (carried out o...

The microstructure of the cathodes plays a crucial role in the performance of the cell and electrocatalytic reduction of steam into hydrogen in SOEC applications. In the present work, a novel ionic-conducting ceramic 1Ce10ScSZ is used for the Ni-1Ce10ScSZ cermet cathode electrode development, as it has better ionic conductivity than the conventiona...

In the framework of minor actinide bearing blanket fuel fabrication, the sintering of uranium/americium (U0.85Am0.15O2±δ) homogeneous mixed-oxide pellets was studied. After the characterization of the U0.85Am0.15O2±δ starting powder (granulometry, X-ray diffraction, and scanning electron microscopy), its densification under a reducing atmosphere wa...

The transmutation of the minor actinides (Np, Am and Cm) in 4th-generation reactors is possible in homogeneous or heterogeneous mode. While reactor experience is already available with homogeneous transmutation, the heterogeneous mode is still largely unknown but has attracted increasing attention in recent years. These studies focus on americium b...

In order to reduce the radiotoxicity of nuclear fuel waste, the transmutation of americium in U1−xAmxO2±δ dedicated fuels is considered. A convenient route to produce such fuels is reactive sintering from a UO2+δ/AmO2−δ green pellet, i.e., a single heat treatment during which both the densification and the formation of the U1−xAmxO2±δ solid solutio...

Partitioning and transmutation (P&T) of minor actinides (MA: americium, neptunium and curium) in fast neutron reactors or accelerator-driven systems is a route envisaged to reduce nuclear waste inventory. Over the years, several modes of P&T were proposed, each being based on the use of dedicated fuels such as inert-matrix fuels, MA-bearing MOX or...

The invention relates to a method for preparing a fuel formed by a solid plutonium and uranium oxide solution having a pre-determined composition. The method comprises the following successive steps: a) bringing into contact a powder of uranium oxide(s) and a plutonium oxide powder; b) compacting the resulting mixture into at least one pellet; c) t...

The invention relates to a method for preparing a fuel comprising a solid uranium oxide solution and at least one minor actinide and, optionally, plutonium and/or thorium, having a pre-determined composition. The method comprises the following successive steps: a) bringing into contact a powder of uranium oxide(s), at least one powder of minor acti...

French DIAMINO (Dispositif d'Irradiation d'Actinides MIneurs dans Osiris) irradiation experiment in OSIRIS reactor (CEA, Saclay) aims to assess the influence of microstructure and Am content on He release and fuel swelling for different irradiation temperatures during heterogeneous transmutation. In this context, Am-bearing blanket fuels with tw...

Five U1-xAmxO2±δ homogeneous solid solutions (with 0.075 ≤ x ≤ 0.49) were succesfully produced using solid-state reactions. The evolution of the lattice parameter of these solid solutions under self-irradiation was monitored by regular XRD analysis and this paper presents the first conclusive results obtained for the U0.925Am0.075O2±δ and U051Am0.4...

U1–xAmxO2±δ blanket fuels for heterogeneous transmutation in fast reactors, and more precisely their fabrication via sintering, were for the first time studied by dilatometry. Several experiments, performed at up to 2023 K and under a controlled atmosphere, are analyzed to understand and characterize the densification behaviour of such materials. T...

The transmutation of minor actinides (MA) in 4th-generation reactors can be envisioned in homogeneous or heterogeneous mode. Minor actinide-bearing blankets (MABB) -- fuel for heterogeneous transmutation comprising 10 to 20% MA dispersed in a UO2 matrix -- are largely unknown and warrant further research on the fabrication and properties of the mat...

The DIAMINO irradiation program aims to assess the influence of Am content and microstructure on He release and fuel swelling for different irradiation temperatures during heterogeneous transmutation in the OSIRIS reactor. Such irradiation programs call for ceramic fuels compliant with strict specifications. In the case of the DIAMINO experiment, A...

In the frame of the heterogeneous transmutation of minor actinides in MABB (Minor Actinides Bearing-Blanket) fuels, the CEA program DIAMINO aims to assess the influence of americium content and microstructure on helium release and fuel swelling. For DIAMINO experiment, four sets of U1-xAmxO2±δ ceramic fuels, namely two compositions (x = 0.075, 0.15...

In the framework of minor actinide transmutation in heterogeneous mode, its application to americium through U1 xAmxO2±δ MABB (Minor Actinide-Bearing Blanket) fuels represents a major research focus. Recently, two experimental irradiations of U1 xAmxO2±δ fuels were programmed: MARIOS and DIAMINO, for which dense fuels were fabricated using two diff...

In the framework of minor actinide, and especially americium, transmutation, a new fabrication process was developed to produce highly dense U1-xAmxO2±ϕ fuels. This process, called UMACS, is based on the dissociation of the solid solution formation and its densification, by means of a conventional sintering. The competition that occurs during a rea...

Uranium-americium mixed oxides are promising fuels for achieving an efficient Am recycling. Previous studies on U0.85Am0.15O2±x materials showed that the high α activity of 241Am induces pellet swelling which is a major issue for cladding materials design. In this context, X-Ray Diffraction and X-ray Absorption Spectroscopy measurements were used t...

A promising route to recycle americium is transmutation in fast neutron reactors via U1 xAmxO2±δ fuels. Other mixed-oxide fuels, such as MOX, i.e., U-Pu mixed oxides, are industrially fabricated by reactive sintering from single dioxide precursors. However, because of the differences in properties between uranium and americium oxides, and due to th...

A new La0.5Sr0.5Ti0.75Ni0.25O3 (LSTN25) titanate was proposed as a hydrogen electrode for Solid Oxide Cells (SOCs) with electrochemical performance given by Ni nanoparticles exsoluted at the surface of a conducting oxide. As only in-situ reduction at 800 °C has been proposed in literature to perform Ni exsolution, the reduction at higher temperatur...

To improve U1-xAmxO2±δ pellet characteristics and avoid americium sublimation, a new process implying a conventional sintering was developed. By dissociating solid state reaction and sintering steps, dense U0.85Am0.15O2±δ pellets (d > 94% TD) were obtained. This process was successfully used at the CEA Marcoule ATALANTE facility to produce dense U0...

In order to reduce the nuclear waste inventory and radiotoxicity, U(1-x)Am(x)O(2±δ) materials are promising fuels for heterogeneous transmutation. In this context, they are generally fabricated from UO(2+δ) and AmO(2-δ) dioxide powders. In the subsequent solid solution, americium is assumed to be trivalent whereas uranium exhibits a mixed-valence (...

Materials of the titanate type of perovskite or derived structure and their uses for the production of electrodes, more particularly in the cell elements of an SOFC cell or the cell elements of a high-temperature steam electrolysis cell.

In the framework of Partitioning & Transmutation (P&T), U1−yAmyO2±x materials are promising fuels for Am recycling. In this context, these materials were fabricated in the ATALANTE facility by a process which consists of pelletizing and reactive sintering. Since it was effective in studies conducted on UO2+x, sintering in overstoichiometric conditi...

This study deals with the preliminary development of a powder-free process called calcined resin microsphere pelletization (CRMP) used for the fabrication of metallic oxide pellets. This dustless process could be used for the fabrication of mixed U1−yAmyO2±x pellets dedicated to the transmutation of Am in fast neutron reactors. In this study, porou...

In the search for new air electrode materials for Proton Conducting Cells (PCC), the case of basic (rare earth and/or alkaline earth containing) oxocobaltites has been considered to find materials exhibiting mixed electron and proton conductivity. The stability in dry and wet air of classical (cubic and derived) as well as hexagonal 2H perovskite s...

MOX fuel pellets containing up to 1.4 wt% of Minor Actinides (MA), i.e. Am, Np and Cm, were fabricated to demonstrate the technical feasibility of powder metallurgy process involving, pelletizing and sintering in controlled atmosphere. The compounds were then characterized using XRD, SEM and EDX/EPMA. Dense pellets were obtained which closed porosi...

The invention relates to compounds of formula LaxSr1-xTi1-y-zMnyNizO3-δ and to the uses thereof. In particular, the invention is suitable for use in the following fields: electrodes, fuel cells, electrolysers and electrochemical cell

A method for producing a porous fuel including uranium, optionally plutonium, and optionally at least one minor actinide, the method including: a) compacting a mixture including a first type of agglomerate including uranium oxide in a form of uranium dioxide UO2, optionally plutonium oxide, and optionally at least one minor actinide oxide, and a se...

An electrolyte plate for an electrochemical system including a first face and a second face, being opposite each other, of largest surface area, the first face including linear parallel ribs and the second face including linear parallel ribs. The plate thus exhibits an increased rigidity without substantially increasing the thickness thereof.

This paper describes the developments and results of the fabrication of Am bearing blankets for the MARIOS experiment in the High Flux Reactor (HFR, Petten). This irradiation program aims to asses the influence of the microstructure on the helium release and then fuel swelling for different irradiation temperatures during heterogeneous transmutatio...

Method of preparing an electrochemical half-cell with support electrode comprising a step consisting in subjecting a raw electrode layer on which is deposited a precursor gel of the electrolyte or a precursor of the latter, to a sintering at a temperature of less than or equal to 1350°C.

BaIn0.3Ti0.7O2.85 (BIT07) is a promising electrolyte for solid oxide fuel cells, due to its chemical compatibility with most of the cathode electrode material such as LSM and Ln2NiO4. The present work is aimed on the fabrication of anode-supported half cells with thin BIT07 electrolyte. For this, Ni-8YSZ cermet was chosen due to its excellent mecha...

The perovskite La0.75Sr0.25Cr0.5Mn0.3Ni0.2O3−δ (LSCMMn0.30Ni0.20) was evaluated as potential electrode for solid oxide fuel cells. The electrochemical performances of LSCMMn0.30Ni0.20 for hydrogen oxidation and oxygen reduction reactions were studied at 800°C. Symmetrical cells LSCMMn0.30Ni0.20/YSZ/LSCMMn0.30Ni0.20 were studied by electrochemical i...

Typical microstructures of LSM/YSZ, NiO/YSZ, Ni/YSZ composite electrodes are simulated by the discrete element method. The numerical microstructures are generated by taking into account in a realistic manner the sintering process. This allows complex microstructures such as bilayers or microstructures containing pore formers to be obtained. NiO par...

The perovskite La 0.75 Sr 0.25 Cr 0.5 Mn 0.3 Ni 0.2 O 3−δ (LSCMMn 0.30 Ni 0.20) was evaluated as potential electrode for solid oxide fuel cells. The electrochemical performances of LSCMMn 0.30 Ni 0.20 for hydrogen oxidation and oxygen reduction reactions were studied at 800 °C. Symmetrical cells LSCMMn 0.30 Ni 0.20 /YSZ/LSCMMn 0.30 Ni 0.20 were stu...

A hydrogen-producing cell comprising a cell of a high temperature steam electrolyzer or HTSE comprising a porous cathode (404) and a porous anode (402) on either side of a dense and gases-impervious anion conducting electrolyte (403), wherein said cell of the high temperature steam electrolyzer is directly coupled, in series, with a cell of an elec...

Improvement of performances of SOFCs/SOECs demands the development of novel materials for its commercially viability and practicability in operations. For air electrode applications novel materials like cobalt based compounds, which offer both ionic and electronic conductivity (MIECs), to achieve high performance are very promising. Among these Pr1...

The invention relates to a method for the catalytic dehydrogenation of saturated hydrocarbons into unsaturated hydrocarbons and hydrogen, which includes at least one step of synthesizing unsaturated hydrocarbons that comprises combining a catalyzed dehydrogenation reaction, an electrochemical pumping in a proton-conductivity cell, and a continuous...

A metal-supported electrochemical cell is provided. The cell may contain a porous metal support comprising a first- and a second-main surfaces, a porous thermomechanical adaptive layer on the second main surface, a porous layer that is a barrier against the diffusion of chromium on the porous thermomechanical adaptive layer, this porous barrier lay...

The invention relates to a supporting electrolyte for an electrochemical system made from a single material comprising first and second substantially parallel surfaces (4) separated by at least 80 μm, representing the thickness of the supporting electrolyte, at least one of the surfaces (4) comprising recesses (6) that define projections (8) with a...

The method for fabricating a nickel-cermet electrode comprises the steps of formation of a mixture comprising an organic nickel salt in solid state and at least one ceramic material in solid state at ambient temperature, followed by shaping of the mixture and heat treatment of the shaped mixture, preferably under reducing conditions, to form the ni...

The invention relates to an electrolyte plate for an electrochemical system, comprising a first (4) and a second (6) surface opposite larger surfaces, the two surfaces (4, 6) being separated by a given distance (e), the first surface (4) including linear protrusions (8) and the second surface (6) including linear recesses (10), the protrusions (8)...

The invention relates to the use of a ceramic of formula (I) Ba2(1-χ)M2χIn2(1-y)M'2yO4+δ(OH)δ, where M represents at least one metal cation of degree of oxidation II or III or a combination of these, M¢ represents at least one metal cation of degree of oxidation III, IV, V or VI, or a combination of these, 0 < x < 1, 0 < y < 1, δ < 2 and 0 < δ' < 2...

BaIn0.3Ti0.7O2.85 (BIT) exhibits high anionic conductivity above 700{degree sign}C. Electrolyte-supported as well as anode-supported single cells based on BIT were fabricated and tested. A Ni/BIT cermet was used as anode and La0.7Sr0.3MnO3-d as cathode. Electrolyte-supported cells were fabricated by coating slurries of anode and cathode materials o...

Electrolyte supported as well as anode supported single-cells based on BaIn0.3Ti0.7O2.85 (BIT) electrolyte were developed. In these cells, Ni-BIT cermet was used as anode and La0.8Sr0.2MnO3 as cathode. Electrolyte supported cells were fabricated by coating slurries of anode and cathode materials on the circular faces of sintered electrolyte discs....

Ni-based cermets were prepared and reduced from mixtures of NiO and Ba2In0.6Ti1.4O5.7□0.3. A cermet containing 18.7 vol.% of Ni exhibits promising characteristics: 40% of open porosity and a lower DC resistivity than a Ni/YSZ cermet with a larger Ni content (30 vol.%). Its thermal expansion coefficient is 11.4 × 10− 6 K− 1 whereas that measured for...

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In this paper, we wish to present an overview of the research carried out in our laboratories with low-cost transition metal oxides (manganese dioxide, iron oxide and vanadium oxide) as active electrode materials for aqueous electrochemical supercapacitors. More specifically, the paper focuses on the approaches that have been used to increase the c...

The radiotoxicity of spent nuclear fuel is mainly due to the content of minor actinides, which could be substantially reduced by Partitioning and Transmutation. A possible transmutation method would be to employ americium-bearing uranium oxide materials as blanket fuels in fast neutron reactors. In order to maintain fuel performance and reactor saf...