Study of Zn, Cr, Fe, Ni synergies on crystallisation in simplified glasses of nuclear interest
In France, nuclear power-plants used for electricity production generate high-level long-lived radioactive wastes through spent fuel reprocessing. These wastes are confined within a borosilicate glass matrix, whose structure allows for the incorporation at the atomic scale of a large number of elements, and which displays excellent long-term properties. The industry challenges are leading to changes in the nuclear fuel composition, which can thus induce a modification of the spent-fuel composition to be vitrified.
Chromium is as such an element of interest: its relatively low solubility in borosilicate glasses as well as its tendency to crystallise with other elements, such as iron, nickel and zinc, needs to be further investigated. This thesis aims to study the synergetic effect of Cr, Ni, Fe and Zn on crystallisation in simplified peralkaline glasses of nuclear interest in order to better comprehend affinities between these elements, thus identifying both the nature and quantity of the several crystalline phases which may form.
The PhD student will benefit from the recognised skills of the host laboratory in glass formulation as well as the study of their physico-chemical properties. All of the resources made available will enable a global approach to the subject, working on a fast-growing topic with major industrial and societal implications. The experience acquired during this interdisciplinary work will be useful in the field of materials.
Physico-chemical coupling between a bubbles population and the oxido-reduction of glass-forming liquid
The calcination-vitrification process is the solution used in France for more than 30 years for the conditioning of high-level nuclear waste resulting from the reprocessing of spent fuel. During the vitrification process, the waste is incorporated into a borosilicate glass-forming liquid at more than 1000°C. The glass-forming liquid is homogenized in temperature and composition by stirring and gas bubbling. The incorporation of waste into glass-forming liquid can also lead to gas releases, including those of oxygen resulting from redox reactions between species dissolved in the liquid. It is important to properly control the impact of these gases on the glass and the process.
The redox state of glass-forming liquid at equilibrium between the dissolved species has been the subject of various studies at the CEA in the context of the vitrification of nuclear waste. On the other hand, few studies have been devoted to the kinetics of gas reactions in glass-forming liquid. The objective of this thesis aims to study and model the impact of gas bubbles, whatever their nature, on the redox of melting and the kinetics of associated reactions. An approach combining experimentation and digital modeling will be adopted.
The desired candidate will have a taste for experimentation, characterization and interpretation of results addressing different scientific fields (physico-chemistry of materials, electrochemistry). All experiments will be carried out on non-radioactive elements and will involve processing by digital modeling. This PhD thesis will allow acquiring valuable professional experience in the glass and nuclear industry.
Study of plutonium oxalate formation mechanisms – Application to molten salt reactors
Molten salt reactors (MSRs) offer a promising alternative for sustainable nuclear energy production, thanks to their intrinsic safety and their ability to close the nuclear fuel cycle, notably through the use of a fast neutron spectrum. This type of reactor can use liquid chloride salts containing plutonium and other actinides as fuel. As part of the development of this nuclear pathway, the CEA supports the development of a PuCl3 production process. The synthesis of this chloride has already been carried out at small scale at the CEA and elsewhere in the world. Several starting materials can be used for the synthesis of the trichloride, notably plutonium metal, plutonium oxide and plutonium oxalate. The most industrially promising synthesis route is the oxalate route, because it can be transferred to the equipment already present at the La Hague site. This process consists of converting the oxalate into plutonium chloride via a gas–solid reaction with a chlorinating agent, such as HCl for example. However, the reaction mechanism and the decomposition of the oxalate in a chlorinated environment are still poorly understood. A detailed understanding of this transformation would make it possible to optimize operating conditions and facilitate the scale-up of this synthesis. The topic will initially focus on determining the reaction mechanism of Ce oxalate (a surrogate for Pu) to the chloride. Small-scale studies will be performed to identify the various reaction intermediates using analytical techniques such as X-ray diffraction (XRD), thermogravimetric analysis / differential thermal analysis (TGA/DTA) and analysis of the gases produced during the reaction. The kinetics as well as the enthalpy changes will also be studied in order to obtain key data for modelling a large-scale process. Subsequently, an optimization of the PuCl3 synthesis at the scale of a few tens of grams will be carried out. These studies will first be conducted under non-radioactive conditions on a surrogate to validate the experimental approach, before being transposed to radioactive conditions.
Optimization of the conditions for the electrolytic synthesis of metallic uranium
Reprocessed uranium (RepU), derived from the reprocessing of spent nuclear fuel, represents a material whose reuse in power plants would allow for the sustainable management of energy resources. Accordingly, the CEA is supporting the nuclear industry to evaluate the feasibility of enriching this RU via the laser route. This technology requires, as a process input, uranium in the form of a metallic alloy. Consequently, an upstream process for the synthesis of metallic uranium must be developed and optimized to build a sovereign RepU sector.
One of the routes under study for synthesizing metallic uranium is the electrolysis of uranium oxide, previously dissolved in high-temperature molten fluoride salt media. This synthesis, which was previously implemented in the United States using the aluminum synthesis process, now requires a re-appropriation and optimization of experimental conditions.
In a first phase, the PhD student will conduct a systematic study of the electrolyte, in order to understand the influence of key parameters—salt composition, temperature range, redox environment, material compatibility, and oxide solubility—on the behavior of the electrolysis bath. For each parameter, targeted tests will be conducted: thermochemical characterization of the salt (melting point, volatility, purification, etc.), evaluations of the kinetics and the solubility limit of uranium oxide in the bath (a crucial point of the process), electrochemical tests aimed at identifying redox systems of interest, as well as studies on the resistance of materials when in contact with the molten salt and liquid metal. All of these investigations will make it possible to define the optimal experimental conditions for the controlled implementation of metal synthesis by oxide electrolysis.
In a second phase, once these conditions are established, the work will focus on the formation of the metal at the electrode, its recovery, and its characterization. The quantity and quality of the metal produced after electrolysis will be the major criteria for validating the selected experimental parameters.
All acquired data will be utilized for the design of pilot and industrial scale electrolyzers, and will feed into future digital models that will be developed. The results obtained may be the subject of presentations at international conferences and publications.
These studies will be carried out at the laboratory scale using active material, with work phases on simulants to grasp the implementation of the process and scaling up. The host laboratory, which operates in both these environments, specializes in the implementation of thermal processes and pyrochemical tests.
The candidate should ideally have a Master 2 or engineering school degree in chemistry or physics.
At the end of this thesis work, the PhD student will have acquired expertise in experimental techniques related to metallic synthesis by electrolysis, from the design of electrochemical devices to the multi-scale characterization of materials. Furthermore, their involvement in a sovereign project focused on strategic metals will open up numerous employment prospects in academic research or industrial R&D, both in the nuclear sector and in other fields of chemistry and materials.
Potential of magnesium silicate binders for the solidification / stabilization of contaminated soil
Soil contamination by radioactive substances represents a major challenge in terms of public health and environmental protection. Among the various strategies considered for managing such polluted soils, the excavation of contaminated materials offers a pathway to the safe reuse of the site. The excavated soils, when characterized by low to intermediate activity and short-lived radionuclides, must be stabilized prior to disposal. In this context, cementation is widely used due to its moderate cost, ease of implementation, and capacity to confine numerous pollutants. However, its application to soils rich in swelling clays presents two major limitations: poor workability of the fresh material and volumetric instability of the hardened product. To address these issues, this thesis aims to evaluate the potential of magnesium silicate cements as an alternative to conventional calcium silicate cements. These emerging binders are currently attracting growing interest, particularly in the fields of earthen construction and the development of low-carbon materials.
The first objective will be to study the influence of various formulation parameters on the reactivity and properties of magnesium silicate cements. This will be followed by an in-depth investigation of the interactions between the cement phases and the main constituents of contaminated soils. Finally, the long-term durability of the formulated materials will be assessed through leaching tests, which will serve as input for reactive transport modelling, with the aim of gaining a better understanding of the degradation mechanisms and the long-term behaviour of the materials.
This research project is intended for a PhD candidate interested in advancing his/her expertise in materials physical chemistry and contributing to the development of innovative solutions for contaminated soil management and low-impact binder technologies.
Development of machine learning algorithms to improve image acquisition and processing in radiological imaging
The Nuclear Measurements Laboratory at the LNPA (Laboratory for the Study of Digital Technologies and Advanced Processes) in Marcoule consists of a team specializing in nuclear measurements in the field. Its activities are divided between developing measurement systems and providing technical expertise to CEA facilities and external partners (ORANO, EDF, IAEA).
The LNPA has been developing and using radiological imagers (gamma and alpha) for several years. Some of the developments have resulted in industrial products, while other imagers are still being developed and improved. Alpha imaging, in particular, is a process that allows alpha contamination zones to be detected remotely. Locating the alpha source is an important step in glove boxes, whether for a cleanup and dismantling project, for maintenance during operation, or for the radiation protection of workers. The alpha camera is the tool that makes alpha mapping accessible remotely and from outside glove boxes.
The objective of the thesis is to develop and implement mathematical prediction and denoising solutions to improve the acquisition and post-processing of radiological images, and in particular alpha camera images.
Two main areas of research will be explored in depth:
- The development of real-time or post-processing image denoising algorithms
- The development of predictive algorithms to generate high-statistics images based on samples of real images.
To do this, an experimental and simulation database will be established to feed the AI algorithms.
These two areas of research will be brought to fruition through the creation of a prototype imager incorporating machine learning capabilities and an image acquisition and processing interface, which will be used in an experimental implementation.
Through this thesis, students will gain solid knowledge of nuclear measurements, radiation/matter interaction, and scientific image processing, and will develop a clear understanding of radiological requirements in the context of remediation/decommissioning projects.
Physicochemical Properties of Antimony-containing Photovoltaic (PV) Glass
The proposed PhD thesis is part of the ANR GRISBI project (2026–2030), which aims to optimize the recycling of glass from photovoltaic (PV) panels. These glasses, predominantly manufactured in China, are doped with antimony oxide (Sb2O3) to ensure high transparency while keeping production costs low. However, the presence of antimony currently prevents the recycling of these glasses within the European flat glass industry, which would otherwise greatly benefit from this secondary raw material to reduce its environmental footprint — particularly its greenhouse gas emissions, in line with the carbon neutrality targets set by the Paris Agreement (2015). To make the recycling of PV glass into flat glass production feasible, it is therefore essential to gain a deeper understanding of the physicochemical behavior of antimony in glass, and more generally, within the float process, which involves a hot glass / liquid tin interface.
The core scientific objective of the PhD is to determine the redox equilibria between the multivalent species present in PV glasses, in particular the Sb2O3/Sb and Fe2O3/FeO couples. The work will involve preparing glasses with different Sb2O3 contents, then determining the mechanisms of antimony incorporation into the glass structure, as well as the temperature and oxygen partial pressure (pO2) conditions leading to the reduction of Sb³? to metallic Sb°. Experimental results, based on advanced materials characterizations such as SEM, XRD, EXAFS, and XANES, will be used to enrich thermodynamic databases and to develop a methodology enabling the recycling of Sb-doped PV glasses in flat glass production.
The PhD will be conducted at CEA Marcoule, in collaboration with IMPMC (Sorbonne Université) — two laboratories internationally recognized for their expertise in glass science. All glass samples will be synthesized by the PhD student, and their characterization will primarily rely on facilities available at CEA and IMPMC.
A background in Materials Science is required. This research project will provide the PhD candidate with the opportunity to develop strong expertise in applied glass science and industrial recycling technologies.
Modelling of Thermo-Fluid Phenomena in the Plasma Nozzle of the ELIPSE Process
The ELIPSE process (Elimination of Liquids by Plasma Under Water) is an innovative technology dedicated to the mineralization of organic effluents. It is based on the generation of a thermal plasma fully immersed in a water-filled reactor vessel, enabling extremely high temperatures and reactive conditions that promote the complete decomposition of organic compounds.
The proposed PhD research aims to develop a multiphysics numerical model describing the behavior of the process, particularly within the plasma nozzle, a key zone where the high-temperature gas jet from the torch interacts with the injected liquids.
The approach will rely on coupled thermo-aerodynamic modeling, integrating fluid dynamics, heat transfer, phase change phenomena, and turbulence effects. Using Computational Fluid Dynamics (CFD) tools, the study will characterize plasma–liquid interaction mechanisms and optimize the geometry and operating conditions of the process. This modeling will be compared and validated against complementary experimental data obtained from the ELIPSE setup, providing the necessary input for model calibration and validation.
This work will build upon previous research that has led to the development of thermal and hydraulic models of both the plasma torch and the reactor vessel. Integrating the new model within this framework will yield a comprehensive and coherent representation of the ELIPSE process. Such an approach represents a decisive step toward process optimization and industrial scale-up.
The ideal candidate will be a Master’s or final-year engineering student with a background in process engineering and/or numerical simulation, demonstrating a strong interest in physical modeling and computational approaches.
During this PhD, the candidate will develop and strengthen skills in multiphysics numerical modeling, advanced CFD simulation, and thermo-aerodynamic analysis of complex processes. They will also acquire solid experience in waste treatment, a rapidly expanding field with significant industrial and environmental relevance. These skills will provide strong career opportunities in applied research, process engineering, energy, and environmental sectors.
Multi-criteria Navigation of a Mobile Agent applied to nuclear investigation robotics
Mobile robots are increasingly deployed in hazardous or inaccessible environments to perform inspection, intervention, and data collection tasks. However, navigating such environments is far more complex than simple obstacle avoidance: robots must also deal with communication blackouts, contamination risks, limited onboard energy, and incomplete or evolving maps. A previous PhD project (2023–2026) introduced a multi-criteria navigation framework based on layered environmental mapping and weighted decision aggregation, demonstrating its feasibility in simulated, static scenarios.
The proposed thesis aims to extend this approach to dynamic and partially unknown environments, enabling real-time adaptive decision-making. The work will rely on tools from mobile robotics, data fusion, and autonomous planning, supported by experimental facilities that allow realistic validation. The objective is to bring navigation strategies closer to real operational conditions encountered in nuclear dismantling sites and other industrial environments where human intervention is risky. The doctoral candidate will benefit from an active research environment, multidisciplinary collaborations, and strong career opportunities in autonomous robotics and safety-critical intervention systems.
Origins and consequences of the heterogeneous alteration of nuclear glasses
This PhD project focuses on the long-term behavior of nuclear glasses used to confine long-lived radioactive waste.
In aqueous environments, these glasses generally undergo homogeneous alteration: the transformation into alteration products occurs at a uniform rate across the entire surface.
However, cases of heterogeneous alteration also exist, where the glass/gel interface becomes irregular, forming pits or cavities.
Two key questions arise: what are the mechanisms responsible for that behavior, and what are the consequences for the long-term durability of the glass?
Several hypotheses have been suggested in the literature, such as local fluctuations in solution composition or mechanical stress at the glass surface, but no definitive explanation has yet been established.
The proposed approach combines accelerated experiments with chemical, mechanical, and structural characterizations, as well as modeling (e.g., mesoscopic and Monte Carlo models).
Experiments will be conducted on glasses with various surface states (polished, irradiated, fractured, etc.) using analytical tools such as SEM, TEM, and nanoSIMS.
Once the mechanisms are identified, the long-term impact of these heterogeneous alteration patterns can be assessed.
The project seeks candidates with a background in chemistry or materials science, strong interest in modeling, and solid theoretical knowledge.