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).
TREATMENT OF RADIOACTIVE ORGANIC EFFLUENTS
The ECCLOR project (Project labelled 'Investment for the Future') aims to find a management route for challenging radioactive organic effluents. A strategy under investigation is to make the effluents compatible with existing outlets by decontaminating them of radioelements by column filtration. This involves developing ion-selective extractants in a form suitable for use in columns.
Studies are being carried out at CEA to improve the treatment of radioactive aqueous effluents by developing processes capable of achieving "zero discharge" while producing a minimum of waste. The challenge of the ECCLOR project will be to transpose this work to contaminated organic solvents with various radiological compositions and rheological properties. A first post-doctoral contract was dedicated to the development of materials for this application. A number of inorganic supports (silicas, geopolymers, aluminas, etc.) were considered for decontaminating these organic effluents.
The performance of the various materials developed in previous work can be optimised in terms of actinide capacity and selectivity with respect to competitor ions. In particular, the performance of existing materials needs to be studied further on more complex simulated LORs, with the necessary adaptations to the analytical method.
This project is intended for a post-doctoral fellow wishing to develop skills in extraction mechanism comprehension and analytical methods, with an interest in advancing the field of radioactive waste management. It will be will build upon the expertise of two laboratories at CEA Marcoule: the Design and Characterization of Mineral Materials Laboratory for materials elaboration and characterization, and the Supercritical and Decontamination Processes Laboratory for materials grafting and decontamination experiments.
Development of a new generation of reversible polymer adhesives
Polymeric adhesives are generally cross-linked systems used to bond two substrates throughout the lifetime of an assembly, which may be multi-material, for a wide range of applications. At their end of life, the presence of adhesives makes it difficult to separate materials and recycle them. Moreover, it is difficult to destroy the cross-linking of the adhesives without chemical or thermal treatment that is also aggressive for the bonded substrates.
In this context, the CEA is developing adhesives with enhanced recyclability, by integrating recyclability into the chemical structures right from the synthesis of the polymer networks. The first approach involves incorporating dynamic covalent bonds into polymer networks, which can be exchanged under generally thermal stimulus (e.g. vitrimers). A second approach involves synthesising polymers that can be depolymerised under a specific stimulus (self-immolating polymers) and have the ability to cross-link.
The post-doc will develop 2 networks that can be used as adhesives with enhanced recyclability. A first network will be based on a depolymerizable chemistry under stimulus already developed on linear polymer chains, to be transposed to a network. A second vitrimer network will be synthesised on the basis of previous work at the CEA. Activation of the bond exchange in this network will take place via a so-called photolatent catalyst, which can be activated by UV and will make it possible to obtain a UV- and heat-stimulated adhesive. The choice and synthesis of these catalysts and their impact on the adhesive will be the focus of the study. The catalysts obtained could also be used to trigger depolymerisation of the first depolymerisable system under stimulus.
Impact of Microstructure in Uranium Dioxide on Ballistic and Electronic Damage
During reactor irradiation, nuclear fuel pellets undergo microstructural changes. Beyond 40 GWd/tU, a High Burnup Structure (HBS) appears at the pellet periphery, where initial grains (~10 µm) fragment into sub-grains (~0.2 µm). In the pellet center, under high temperatures, weakly misoriented sub-grains also form. These changes result from energy loss by fission products, leading to defects such as dislocations and cavities. To study grain size effects on irradiation damage, nanostructured UO2 samples will be synthesized at JRC-K, using flash sintering for high-density pellets. Ion irradiation experiments will follow at JANNuS-Saclay and GSI, with structural characterizations via Raman spectroscopy, TEM, SEM-EBSD, and XRD. The postdoc project will take place at JRC-K, CEA Saclay, and CEA Cadarache under expert supervision.
Modeling of the MADISON fuel irradiation device for the future JHR reactor
The Jules Horowitz Reactor (RJH), currently under construction at CEA's Cadarache site, will irradiate materials and fuels in support of the French and international nuclear industry, as well as producing radioelements for medical use. To carry out its missions, the reactor will be equipped with numerous experimental devices. In particular, the MADISON device, currently under design, will irradiate 2 or 4 fuel samples under nominal stationary or operational transient conditions. The loop is representative of light-water reactor operating conditions, with single-phase and two-phase forced convection.
The main objective of the Post-Doc is to model the MADISON device and all associated heat exchanges precisely, in order to help determine the overall heat balance during the test and thus improve the accuracy of the linear power imposed on the samples. To this end, a coupled thermal model (describing the fuel rods and device structures) / CFD thermal-hydraulic model (describing the coolant) will be established using the NEPTUNE_CFD/SYRTHES code. The modeling will be validated based on results obtained from similar modeling carried out on the ISABELLE-1 and ADELINE single-rod devices in the OSIRIS and RJH reactors. The proposed approach fits in with the logic of developing digital twins of the RJH experimental devices.