Modelling of Drop Settling and Coalescence in Mixer-Settlers for Liquid–Liquid Extraction
The energy transition toward low-carbon technologies—such as Li-ion batteries, photovoltaics, and wind power—relies heavily on critical materials like rare earth elements (Dy, Nd, Pr) and metals (Co, Ni, Li). However, their extraction raises serious environmental concerns, and their recycling remains limited due to their low concentrations within complex waste streams, making separation particularly challenging.
Liquid–liquid extraction stands out as an effective technique for purifying such mixtures. Yet, its industrial deployment is hindered by an incomplete understanding of the underlying physico-chemical phenomena, particularly in mixer-settlers—compact devices that combine a mixing chamber with a gravity-based settling zone. While widely used for their high efficiency and compact footprint, current models describing these systems remain semi-empirical and focus mainly on the mixing phase, limiting their predictive capabilities at larger scales. Within the framework of the French national PEPR program "Recyclability and Reuse of Materials", the CEA is leading an initiative to develop a digital twin of mixer-settlers. This postdoctoral position contributes to that project, with a focus on modeling the settler unit. The researcher will conduct experiments using well-characterized emulsions injected into a dedicated transparent mock-up, to study droplet sedimentation and track size evolution over time. These experimental data will serve to validate a model that describes the gravitational and hydrodynamic transport of droplets, as well as coalescence and break-up phenomena. Ultimately, this model will be coupled with an existing model of the mixing chamber (currently under development in a parallel PhD project), leading to the creation of a first-generation digital twin of the complete device.
Solvothermal synthesis of carbon dots for optoelectronic applications
Carbon dots (C-dots) are nano-sized particles of carbon that exhibit unique electronic, optical and chemical properties due to their exceptional physico-chemical properties. These small, high surface-to-volume ratio materials are semiconductors that glow under irradiation, making them ideal for detecting ionizing radiation. Conventional plastic scintillators rely on energy transfer from the ultraviolet to visible light via organic fluorophores. The ability of CDs to absorb photons in the ultraviolet range and emit them in the visible range means that they could potentially replace organic fluorophores in their role as a bridge between ultraviolet and visible light. With low production costs, they can be synthesized either by conventional stepwise organic synthesis or, more rapidly, by top-down or bottom-up single-step approaches using a variety of chemicals. In this context, we have recently developed an interesting synthesis route enabling the preparation of C-dots emitting at different wavelengths, thus covering the entire visible range.
Synthesis, Characterization, and Molecular Modeling of M-(A)-S-H
The main hydration product of Mg/silicate cements is magnesium silicate hydrate (M-S-H), whose composition evolves with time and environmental interactions [refs 1,2], with Mg/Si ratios ranging from 0.67 to 1.5, variable water content, and potential Al incorporation. Atomistic models of M-(A)-S-H remain largely unexplored [ref 4], and most of their properties are still unknown, making it difficult to establish composition–property relationships.
This project aims to elucidate the atomic-scale structure of (alumino)silicate magnesium hydrates (M-(A)-S-H) by combining experimental techniques and atomistic simulations, and to estimate their mechanical properties. The study will focus on M-(A)-S-H compositions relevant to nuclear applications or new low carbon cement matrices.
Modelling and analysis of prospective scenarios for the deployment of hydrogen infrastructure in France and Germany
The use of hydrogen produced by electrolysis or of molecules derived from electrolytic hydrogen (synthetic methanol, synthetic kerosene, etc.) is one of the solutions envisioned to decarbonise certain sectors such as the steel industry and long-distance sea and air transport.
The development of a Europe-wide hydrogen transport infrastructure is considered to facilitate the development of electrolytic hydrogen production on the continent. This infrastructure could provide access to massive underground hydrogen storages unevenly distributed across Europe, facilitate exchanges between regions with high solar or wind energy potential and major industrial hubs and, in certain areas, limit the cost of reinforcing the electricity transmission network.
The goal of the CrossHy project is to analyse the possible deployment pathways for hydrogen transport infrastructure in France and Germany. Two complementary modelling tools (REMix, ANTARES) are going to be used and to develop a European-scale model and a regional-scale model of a cross-border-region.
Regular physical meetings between the French and German research teams are planned during the project; the post-doc will include a 3-month visit to Stuttgart to work and exchange with the DLR team involved in the project.
Decomposition of Fission Fragment Energy from Microscopic Approaches to Provide Input Data for the FIFRELIN Code
The FIFRELIN code (FIssion FRagment Evaporation modeLINg), developed since 2009 at the CEA, simulates the formation and decay of nuclear fission fragments. It contributes to the enrichment of the European nuclear data library JEFF, which is used for reactor simulations. The calculation proceeds in two steps: the generation of fission fragments (with their physical properties), followed by their decay using a Monte Carlo Hauser-Feshbach approach. At the moment of scission into two fragments, the total energy is split between kinetic energy (TKE) and excitation energy (TXE). The TXE is further divided into deformation energy and intrinsic excitation energy, which govern the emission of neutrons and photons. Accurate knowledge of both TXE and TKE is essential to improve FIFRELIN’s performance. Microscopic theoretical approaches (such as Hartree-Fock-Bogoliubov and the Generator Coordinate Method) are used and developed within DES to provide theoretical input supporting evaluated nuclear data. This postdoctoral position aims to use and enhance these models to gain a more detailed understanding of nuclear properties at scission. The desired candidate has several years of experience (3 years or more) in nuclear mean-field theory (such as Hartree-Fock-Bogoliubov, relativistic mean-field, etc.) or in the generator coordinate method.
VALERIAN: caracterizing electron transport for the ITkPix modules of ATLAS
A precise description of the transport of electrons and photons in matter is crucial in several of the CEA's flagship fields, notably radiation protection and nuclear
instrumentation. Their validation requires dedicated parametric studies and measurements.Given the scarcity of public experimental data, comparisons between calculation codes are also used. The challenge for the coming years is to qualify these codes in a broad energy domain, as certain discrepancies between their results have been identified during preliminary SERMA studies involving the coupled transport of neutrons, photons and electrons. The VALERIAN project involves seizing the opportunity created by a unique data collection Campaign planned for 2025-2026 at the IRFU (DRF) to better characterise these discrepancies. The IRFU has undertaken to check at least 750 pixel modules for the new trajectograph of the ATLAS experiment, as part of the rejuvenation of the large detectors at CERN. Numerous measurements with beta sources will be carried out in 2025-2026 for the qualification of these modules.
Study of the Thermodiffusion of Small Polarons in UO2
The position is published on the CEA website at the following address:
https://www.emploi.cea.fr/job/emploi-post-doctorat-etude-en-ab-initio-de-la-thermodiffusion-des-petits-polarons-dans-UO2-h-f_36670.aspx
PV module designed for repair and recycle using ultrasonic delamination
PV panels, crucial for producing decarbonized electricity, have a limited lifespan due to performance degradation, failures, or economic factors. In the next decade, millions of tons of PV panels will become waste, posing significant environmental and societal challenges. Europe has recognized this problem through the WEEE directive (Waste Electrical and Electronic Equipment) to manage electronic waste, including PV.
PV modules are complex devices containing critical materials such as silver and long-life pollutants like fluorinated polymers. On top of that, the glass sheet and the silicon solar cells show a high carbon footprint, making the reuse essential to mitigate environmental impact. Various dismantling techniques have been explored in R&D labs to obtain pure fractions of metals, polymers and glass, but these methods require further improvement. Key objectives include selectivity and purity, material yield and control of residual pollution. To boost the sustainability of photovoltaic energy, managing module lifespans in a circular economy vision is essential.
The LITEN institute is leading research into delamination and separation methods to enhance the quality of recycled materials. In this postdoc opportunity, we will explore the implementation of ultrasonic waves for dismantling or repairing PV modules. The development of a numerical model to understand vibration phenomena in PV panels will support the design of a tool for efficient wave coupling. Beside modelling ant tool set-up, we will explore new PV architectures based on "design to recycle" and "design to repair" principles, focusing on composite layers sensitive to ultrasound. Evaluating various phenomena induced by these layers, such as optical transmission and thermo-mechanical behaviour, will be a key aspect of the study. The research will leverage a high-level scientific environment, with expertise in thermo-mechanical numerical modelling, PV module design and prototype’s fabrication.
Study of the Velocity-Vorticity-Pression formulation for discretising the Navier-Stokes equations.
The incompressible Navier-Stokes equations are among the most widely used models to describe the flow of a Newtonian fluid (i.e. a fluid whose viscosity is independent of the external forces applied to the fluid). These equations model the fluid's velocity field and pressure field. The first of the two equations is none other than Newton's law, while the second derives from the conservation of mass in the case of an incompressible fluid (the divergence of velocity vanishes). The numerical approximation of these equations is a real challenge because of their three-dimensional and unsteady nature, the vanishing divergence constraint and the non-linearity of the convection term. Various discretisation methods exist, but for most of them, the mass conservation equation is not satisfied exactly. An alternative is to introduce the vorticity of the fluid as an additional unknown, equal to the curl of the velocity. The Navier-Stokes equations are then rewritten with three equations. The post-doc involves studying this formulation from a theoretical and numerical point of view and proposing an efficient algorithm for solving it, in the TrioCFD code.
Modelling of prospective deployment scenarios for hydrogen in France and Europe M/F
One of the major energy transition leverages at the horizon 2050 is decarbonation of uses such as electricity production, transport or industry. If electrification of some uses is part of the solution, a potential is also foreseen in using decarbonized intermediate vectors such as hydrogen, produced by electrolysis, and which can be leveraged both as an energy vector and as a substitute molecule in carbon-emitting industries like chemistry, steel production, etc.
However, the potential high development of hydrogen creates underlying needs for electricity production, leading to questions about the sustainability aspects of such deployments, a possible criteria when choosing between different possible deployment options.
As part of a “PEPR Hydrogène” research project, the study aims at 1/ developing possible quantitative hydrogen deployment scenarios consistent between different geographic scales (from the French regions to the national and European level), in collaboration with project partners, 2/ assessing the consequences of these scenarios on the European electrical production system and consequently on the characteristics of the electricity used for the hydrogen production – in particular from the sustainability point of view (e.g. electricity cost and greenhouse gas emissions).