Development of a chloride recovery process by precipitation – Application to molten salt reactors
Molten Salt Reactors (MSRs) represent an innovative option for safer and more sustainable nuclear energy.
They use liquid chloride salts containing actinides, enabling the closure of the nuclear fuel cycle.
During operation, these salts become enriched with fission products and impurities, making chemical treatment necessary.
Enrichment in chlorine-37 aims to limit the formation of chlorine-36, a long-lived radioactive isotope.
Controlling and recycling chloride ions is therefore a major challenge.
The CEA is developing a hydrometallurgical precipitation process to recover enriched chlorine in solid form.
This process is compatible with the La Hague reprocessing plant, in partnership with Orano.
The research focuses on the influence of actinides and fission products on the precipitation reaction and their retention in the solid.
The solubility and purity of the precipitate are studied using various physicochemical techniques.
Purification protocols are optimized when contamination is detected.
Once purified, the solid is recycled to produce reusable chlorine, notably through electrolysis or redox reactions.
This work contributes to the development of innovative reactors and benefits from strong scientific and industrial support.
Characterisation of electrolyte distribution in AEM electrolysers
Anion exchange membrane water electrolysis (AEMWE) is a promising technology for the production of green hydrogen, a pillar of the energy transition. It combines the advantages of proton exchange membrane (PEM) and liquid alkaline approaches while avoiding their chief pitfalls, i.e., an AEM electrolyser can operate at relatively high current-densities (> 1 A cm-2) without the need for critical raw materials in any of its components. Moreover, these devices can run perfectly well if electrolyte is supplied only to the anode side, the cathodic reaction being maintained simply by electrolyte which diffuses across the membrane from the other side of the cell. This approach, known as “dry cathode”, results in hydrogen of greater purity, and facilitates its removal and storage at elevated pressure. Nonethless, this operating mode presents significant challenges in terms of water and gas management to maintain stability at high current-densities.
Development of isotopic and elemental analysis methods on irradiated fuels for the reduction of sample quantities.
The objective of this postdoctoral research is to develop analytical methods for the overall reduction of sample quantities required for high-precision multi-element isotopic analysis (actinides and PF) of spent nuclear fuel, particularly through the use of novel "low-quantity" introduction methods on multi-collector ICPMS. These developments will notably reduce the amount of radioactive waste (consumables and effluents), the dose rate, and the exposure time of analysts/radioactive samples associated with this type of measurements.
To carry out this project, the candidate will conduct analytical developments in a controlled environment to minimize the quantities of elements required for analysis while maintaining or improving uncertainty levels compared to currently available methods.
Modeling and Analysis of Prospective Scenarios for Hydrogen in France and Germany H/F
The use of hydrogen produced by electrolysis, along with its derivatives (such as synthetic methanol and synthetic kerosene), is one of the solutions envisioned to decarbonise certain sectors such as the steel industry and sea and air transport. The development of a European hydrogen transport network is envisaged to support production, access to storage facilities, exchanges between regions with high renewable potential and industrial hubs, and to limit certain electricity grid reinforcement costs.
The propose post doc subject is part of the Franco-German research project CrossHy focuses on analyzing possible deployment pathways for hydrogen transport infrastructure in France and Germany. Post dow work will rely on two complementary modeling tools (REMix, ANTARES)for optimizing development and operation of hydrogen infrstructures at European Level. The project involves regular exchanges between French and German research teams.
Development of catalysts for high-temperature electrolysis applied to ammonia synthesis
The project aims to develop novel catalysts and electrodes for the electrochemical synthesis of ammonia (NH3) at high temperature (400–650 °C), using Solid Oxide Electrolysis Cells (SOEC) and Protonic Ceramic Electrolysis Cells (PCEC). Ammonia is not only a key chemical for fertilizers, but also a promising fuel and a hydrogen carrier. Unlike the energy-intensive and carbon-heavy Haber-Bosch process, the electrochemical route allows for more sustainable production with zero CO2 emissions if powered by clean electricity. The post-doctoral fellow will contribute to the identification and shaping of catalysts (e.g. Ru/YSZ, Fe/YSZ, Mn4N/BCZY), their integration into electrodes, and the evaluation of electrochemical performance. The work combines catalysis, electrochemistry, advanced characterization, and preliminary energy assessment, in close collaboration with CEA teams and academic partners.
Miniaturised analytical method dedicated to the screening of candidate molecules for the capture and removal of radionuclides
This project aims at developing a miniaturized multiplex device dedicated to the screening of the chelating ability of potential molecules for the decorporation of certain radionuclides (RN) from the nuclear power industry, for which current treatments are not satisfactory. The objective is to accelerate the identification of the most promising chelating molecules, while benefiting from the advantages of miniaturisation, such as the consumption of very small quantities of molecules and RN. In a previous project, a phosphated monolith of various lengths has been grafted in situ and characterised in capillaries of 100 µm internal diameter. The quantities of UO22+, Zr4+, Sr2+, Co2+, Cs+ and Ag+ immobilised on these monolithic phases have been measured online by coupling to an ICP-MS.Based on this work, the candidate will be responsible for developing and validating the miniaturised screening method with UO22+, for which data and chelating molecules are available, extending the approach primarily to Zr4+, Sr2+, Co2+, and to fabricate the microfluidic device incorporating parallel microchannels, in order to ultimately screen candidate molecules for distinct RNs in a single fluidic microsystem.
Condensation of Humid Air during Loss of Insulation Accident in a LH2 tank (CHALIA Project)
Liquid hydrogen is increasingly becoming the key energy vector for industrial decarbonization in heavy mobility. It is stored at 20K in a double-walled tank with an insulating vacuum. Any compromise to the integrity of the outer wall will allow hot air to enter the insulating vacuum. Nitrogen, oxygen, and water vapor will condense or even desublimate on the cold wall of the inner tank, thereby transferring heat to the cryogen, which will begin to boil. This boiling causes a pressure increase, leading to the opening of safety valves to prevent tank rupture. To better understand these complex phenomena, the CEA, Fenex Collaborative Research Center, and the University of Western Australia have submitted the CHALIA project to the Franco-Australian Center for Energy Transition. This project was approved in October. The post-doctoral position offered by the CEA involves setting up an analytical experiment using an existing glass cryostat to study in detail the various phenomena and measure the heat fluxes transmitted to the cryogen during the different phases of the accident. A gradual approach is proposed, starting with nitrogen entry before progressing to a binary mixture (synthetic air) or a ternary mixture (humid air). The project also aims to identify and quantify the phases involved in the process using various optical methods. The work will be conducted in close collaboration with researchers from the University of Western Australia, who will focus on scaling up the findings.
Thermodynamic study of photoactive materials for solar cells
The development of solar photovoltaic electricity generation requires the development of new materials for converting solar radiation into electron-hole pairs. Organic-inorganic hybrid perovskites (HOIPs) of the CsPbI3 type, with substitutions of Cs by formamidinium (FA) and/or methylammonium (MA) ions, have emerged as very promising materials in terms of performance and manufacturing. Substitutions of Cs with elements such as Rb, Pb with Sn, and I with Br are also being considered to improve stability or performance. The synthesis and optimization of the composition of layers of such materials require a better understanding of their thermodynamic equilibrium properties and stability. The objective is to construct a thermodynamic model of the Cs-Rb-FA-Pb-Sn-I-Br system. The project began with the ternary Cs-Pb-I system, which resulted in a paper [1]. The next step will focus on the ternary Cs-Pb-Br system, followed by the quaternary Cs-Pb-I-Br system. The approach uses the CALPHAD method, which focuses on building a database and an analytical formulation of the phases Gibbs energy, capable of reproducing thermodynamic and phase diagram data. A critical review of the data in the literature will enable this database to be initialized and the missing data will be evaluated by experiments and/or DFT calculations.
Microfluidics applied to the separation of actinides in nuclear samples by chromatography
The main objective of this post-doctoral position is to develop a method for separating the fission products, plutonium and uranium in nuclear samples by chromatography with a resin volume of 200 µL or less. This project is structured around three research axes.
The first one consists in optimising the miniaturised separation method. The resin packing protocol, the pressure applied during the separation and the eluant compositions will be studied by comparing the chromatograms and by calculating the associated decontamination factors. These developments will be carried out using simulated samples first, and then with plutonium-containing samples. Control over the redox adjustment step will be necessary to maximize the decontamination factors. A second development axis will focus on the conception of a user-friendly system, minimizing interventions in the glovebox in order to reduce the user's exposition to ionizing radiation. The experience of the laboratory in terms of experimental setup miniaturisation and micro-fabrication will be useful for this post-doctoral position. The third research axis consists in applying the developments of the first two axes to the determination of isotopic composition of nuclear samples by TIMS or MC-ICP-MS with a per-mil level of uncertainty in a radiation-controlled laboratory.
Robust path-following solvers for the finite element simulation of cracking in complex heterogeneous media: application to reinforced concrete structures
Path-following (or continuation) procedures are used to describe the unstable responses of structures exhibiting snap-back or snap-through phenomena. These methods consist in adapting the external load during the deformation process in order to satisfy a control constraint, by introducing an additional unknown, the load multiplier. Several variants exist depending on the controlled quantity: degrees of freedom, strain measures, or variables related to energy dissipation.
In addition to enabling the tracing of unstable responses, a major advantage of these approaches lies in improving the convergence of incremental Newton-type solvers by reducing the number of iterations required. This gain often compensates for the additional computational cost associated with the continuation algorithm. Some formulations have proven both efficient and simple to implement.
However, no objective criterion yet allows one to determine which formulation is best suited for the simulation of reinforced concrete structures, where multiple dissipation mechanisms coexist along with a strong spatial variability of the material properties.
The proposed postdoctoral work aims to develop robust path-following algorithms for such structures, building upon previous research carried out at CEA. It will include a critical analysis of existing formulations, an evaluation of their performance (monolithic or partitioned solvers), followed by their implementation. Finally, representative test cases of industrial structures will be simulated to assess the gain in robustness and computational cost compared to standard solvers.