Tailored Peptide Ligands for Actinide Complexation: From Structure to Selectivity
The processes involved in the nuclear fuel cycle, such as the PUREX process designed to separate uranium and plutonium from fission products, rely on ligands capable of selectively complexing actinide cations to enable their extraction. The chemical functions carried by these ligands play a key role in determining both their affinity and selectivity toward metal cations. Studying the influence of these functional groups, such as carboxylic acids and phosphates, is therefore essential for the design of new extracting molecules, as well as for the development of decorporation strategies.
Over the past decade, cyclic peptides have been developed for their ability to complex uranyl ions with high selectivity over calcium. Organized in ß-sheet conformations, these peptides display a functional face bearing complexing groups (carboxylates, phosphates). Their amino acid composition can be tuned to finely adjust the chemical nature of the coordination site, making these cyclic peptides tailor-made molecular architectures for probing cation complexation. However, while their interaction with uranium is now well characterized, their ability to bind transuranic elements remains largely unexplored.
This PhD project aims to study the complexation of actinides such as plutonium and neptunium by various cyclic peptides. The combination of NMR spectroscopy and classical molecular dynamics simulations will provide detailed structural information on the formed complexes. Complementary techniques, including UV-Vis-nIR and EXAFS spectroscopies, ESI-MS mass spectrometry, and fluorescence spectroscopy, will deepen the characterization. By combining experimental and computational approaches, this work will enhance our understanding of ligand–actinide interactions while paving the way for the design of innovative extracting and decorporating molecules.
Investigation of autocatalysis phenomena occurring in nitric acid dissolution through electrochemical methods
The nuclear fuel recycling process, used at the La Hague plant in France, begins with the nitric dissolution of spent fuel, mainly composed of uranium and plutonium oxides. In a context of plant renewal and widespread of MOX fuel recycling, innovative new dissolution equipment are currently studied. The sizing of such devices is currently limited by the absence of a fully comprehensive model for the dissolution of mixed oxides, which is a highly complex reaction (three-phase involved, self-catalytic, heterogeneous attack, etc.). Despite substantial progress made in previous studies, a number of questions remain unanswered, particularly concerning the reaction mechanisms involved and the nature of the catalyst.
Electrochemical methods (cyclic voltammetry, electrochemical impedance spectroscopy, rotating electrode, etc.) have never been used to understand dissolution, yet they should prove relevant as already demonstrated by the studies carried out on this subject by CEA Saclay in the field of corrosion. Therefore, the aim of this thesis is to apply these experimental methods for the first time to the dissolution of nuclear fuels, through a phenomenological approach. To achieve this, the student will be able to rely on the teams and facilities of Saclay and Marcoule centers, specialized respectively in electrochemical methods for the corrosion studies and the physico-chemical modeling of dissolution.
This cross-disciplinary study, involving materials science, electrochemistry and chemical engineering, will follow a stimulating fundamental research approach, but will also take place in a highly dynamic industrial context. Initially, the work will be carried out on inactive model and noble materials (at the Saclay center), then on real materials containing uranium and/or plutonium (at the Marcoule center).
Study of homogeneous SIMMOX synthesis and dissolution based on hydroxide pathway
The dissolution of spent nuclear fuel is an essential first step in its reprocessing. The kinetics of irradiated (U,Pu)O2 (MOX) dissolution currently hinders industrial-scale reprocessing and therefore requires a better understanding of the mechanisms involved in order to overcome this industrial obstacle. However, studying the dissolution of irradiated MOX fuel in order to identify and model the various stages and mechanisms involved is hampered by the high radiotoxicity of such material and the representativeness of the available samples. In order to simplify these studies and establish representative models, numerous tests have been carried out on model compounds (e.g., non-irradiated UO2 and MOX). Among these, SIMfuel (U,Pu)O2 compounds doped with up to 11 fission products aim to represent the chemical complexity of irradiated fuels. The conventional approach to manufacturing SIMfuel by mixing solid-phase reagents requires sintering of fuel pellets at high temperatures (>1600°C). In order to reproduce the behavior of fission products (reduction-oxidation, distribution, etc.) for irradiated fuels at lower temperatures, an alternative approach has been developed based on the synthesis of oxides via the hydroxide route. This method allows for the simultaneous and homogeneous precipitation of numerous metal cations and significantly lowers the sintering temperature. This approach has already enabled the study of SIMfuel incorporating rare earths, platinoids, and molybdenum under representative conditions. However, this approach has never been implemented for the synthesis of SIMfuel containing both plutonium and all fission products relevant to the study of dissolution.
The objective of this thesis is to implement such syntheses, based on recent results obtained concerning the synthesis of MOx by the hydroxide route. To this end, SIMfuels will be synthesized to represent spent MOx-type fuels (SIMMOx). To represent the different zones present in spent fuel, SIMMOx with different Pu/(U+Pu) ratios will be considered. These SIMMOx will undergo dissolution tests to characterize their behavior during this stage.
TRANSIENT LIQUID PHASE SINTERING OF UOX AND MOX FUEL PELLETS
The subject is related to the manufacture of UOX and MOX fuels. The main objective is to identify dopant pairs that allow the formation of a transient liquid phase during the fuel sintering step. For this, phase diagram calculations using the CALPHAD method will have to be carried out, also taking into account the requirements related to the irradiation phase once the fuel is loaded into the reactor. The most promising pairs will then be evaluated in the context of the manufacture of a UOX fuel and a MOX fuel. The experiments to be carried out will essentially be: the preparation of a powdery material, the shaping by pressing of this material in the form of cylinders representative of fuel pellets and the study of the high-temperature sintering of these UOX and MOX formulation cylinders. After sintering, a very important step will be the characterization at the macroscopic and microscopic scales of these pellets. The first year of the thesis will take place at the CEA center in Cadarache. The next two will take place at the CEA site in Marcoule. The first year of the PhD will take place at the CEA Cadarache center within the ICPE Uranium Fuel Laboratory. The following two years will be spent at the INB Atalante facility on the CEA Marcoule site. The candidate will work in two facilities unique in Europe and will be able to develop experience working in a nuclear environment with a highly innovative approach that will lead to the publication of original scientific results.
Study of new concepts for miniaturizable and parallelizable liquid-liquid extractors
In the process of developing procedures, their miniaturization represents a major challenge for upstream research and development (R&D). Indeed, the miniaturization of procedures offers numerous advantages in terms of reducing the volume of raw materials, waste management, screening possibilities, automation, and safety for personnel.
To date, the counter-current liquid-liquid extraction process does not have a convincing miniaturization solution, although the applications are numerous: in pharmacy, chemical synthesis, nuclear, or nuclear medicine.
The CEA-ISEC in Marcoule has developed new microfluidic tools to perform these operations in a simple and operational manner, based on a fine understanding of the instabilities of two-phase flows in capillaries.
This 3-year study topic proposes:
- To experiment, understand, and finely model the flows and mass transfers;
- To optimize and then transpose the phenomena to industrially significant volumes;
- To publish and participate in international conferences.
The doctoral student will benefit from learning about the world of research in a team that values quality in the supervision and future of its doctoral students, in a multidisciplinary team ranging from process engineering to instrumentation, with projects ranging from research to industry.
General competencies in chemical engineering and mass transfer are required. Competencies in collaborating with our academic partners will be essential to the success of the study project.
INFLUENCE OF THE DRY GRANULATION ON THE MANUFACTURING OF SFR MOX FUELS
The subject is related to the manufacture of MOX U,Pu)O2 fuel for Fast Neutron Reactors. The current process integrates a co-grinding step of uranium and plutonium dioxides to generate a powder medium which is then shaped by uniaxial pressing to generate cylindrical fuel pellets which are then sintered at high temperature. The collected powder medium has poor flowability which limits the rates of shaping by pressing. The objective of the thesis is therefore to evaluate the impact of mechanical granulation of the powder medium on the flowability, the pressing step and the microstructure obtained after sintering. Dissolution tests in nitric acid will also be carried out on certain very specific microstructures. The thesis will be based on a formal experimental plan developed using specific software (JMP). The PhD will take place at the INB Atalante facility on the CEA Marcoule site. The candidate will work in a unique facility in Europe and will be able to develop expertise in working in a nuclear environment with a highly innovative approach that will lead to the publication of original scientific results.
Towards automated and reconfigurable microfluidic platforms for the study and development of nuclear fuel recycling processes
The main objective of this PhD project is the design and development of the first automatic and reconfigurable microfluidic platform dedicated to research and development on the nuclear fuel cycle. In a context where mastering nuclear processes remains a key challenge, both for energy production and for the sustainable management of nuclear materials, microfluidic devices represent a particularly promising approach. These autonomous laboratories on a chip have already demonstrated their potential in various fields, such as chemistry, materials science, and biology. Their application to nuclear processes would help reduce radiation exposure risks, minimize waste generation, and optimize resources by enabling a larger number of experiments to be performed safely, quickly, and reproducibly. For about a decade, the DMRC has been conducting phenomenological studies on the main stages of the nuclear process (dissolution, solvent extraction, precipitation, etc.) using microfluidic devices. In parallel, it has developed PhLoCs (Photonic-Lab-on-Chips), which allow the miniaturization of several analytical techniques (UV-Vis spectroscopy, LES, holography, etc.) and their integration for online monitoring of the investigated phenomena. Nevertheless, no truly autonomous and fully automated platform currently exists that combines process execution with integrated analytical monitoring.
The aim of this PhD work is therefore to make a decisive step by designing a modular device where several functional chips can be assembled, some dedicated to process operations (e.g., uranium/plutonium separation) and others to online measurements, within a flexible configuration adapted to nuclear environments. In addition, the research will focus on integrating new instrumental techniques directly on chips, such as FTIR and UV-Vis-NIR spectroscopies, which are crucial for studying critical process steps, including solvent degradation. This project thus aims to establish the foundations of next-generation microfluidic platforms that combine safety, modularity, and performance to advance nuclear fuel cycle research. At the end of the PhD, the candidate will have developed unique expertise in microfluidics applied to nuclear processes, combining optical instrumentation and automation. These skills will offer strong career opportunities in research and advanced process engineering.
Design and Optimisation of an innovative process for CO2 capture
A 2023 survey found that two-thirds of the young French adults take into account the climate impact of companies’ emissions when looking for a job. But why stop there when you could actually pick a job whose goal is to reduce such impacts? The Laboratory for Process Simulation and System analysis invites you to pursue a PhD aiming at designing and optimizing a process for CO2 capture from industrial waste gas. One of the key novelties of this project consists in using a set of operating conditions for the process that is different from those commonly used by industries. We believe that under such conditions the process requires less energy to operate. Further, another innovation aspect is the possibility of thermal coupling with an industrial facility.
The research will be carried out in collaboration with CEA Saclay and the Laboratory of Chemical Engineering (LGC) in Toulouse. First, a numerical study via simulations will be conducted, using a process simulation software (ProSIM). Afterwards, the student will explore and propose different options to minimize process energy consumption. Simulation results will be validated experimentally at the LGC, where he will be responsible for devising and running experiments to gather data for the absorption and desorption steps.
If you are passionate about Process Engineering and want to pursue a scientifically stimulating PhD, do apply and join our team!
Understanding the mechanisms of oxidative dissolution of (U,Pu)O2 in the presence of Ag(II) generated by ozonation
The recycling of plutonium contained in MOx fuels, composed of mixed uranium and plutonium oxides (U,Pu)O2, relies on a key step: the complete dissolution of plutonium dioxide (PuO2). However, PuO2 is known to dissolve only with great difficulty in the concentrated nitric acid used in industrial processes. The addition of a strongly oxidizing species such as silver(II) significantly enhances this dissolution step—this is the principle of oxidative dissolution. Ozone (O3) is used to continuously regenerate the Ag(II) oxidant in solution.
Although this process has demonstrated its efficiency, the mechanisms involved remain poorly understood and scarcely documented. A deeper understanding of these mechanisms is essential for any potential industrial implementation.
The aim of this PhD work is to gain insight into the interaction mechanisms within the HNO3/Ag/O3/(U,Pu)O2 system. The research will be based on a parametric experimental study of increasing complexity. First, the mechanisms of generation and consumption of Ag(II) will be investigated in the simpler HNO3/Ag/O3 system. In a second phase, the influence of various parameters on the oxidative dissolution of (U,Pu)O2 will be examined. The results will lead to the development of a kinetic model describing the dissolution process as a function of the studied parameters.
At the end of this PhD, the candidate—preferably with a background in physical chemistry—will have acquired advanced expertise in experimental techniques and kinetic modeling, providing a strong foundation for a career in academic research or industrial R&D, both within and beyond the nuclear sector.
Monitoring and modeling the evolution of microstructural properties during the fabrication of MOX fuel
The nuclear fuel MOX (Mixed OXide), a ceramic obtained from a mixture of uranium and plutonium oxides, represents a strategic alternative for the valorization of plutonium resulting from the reprocessing of spent fuel. MOX pellets are produced industrially using a powder metallurgy process combined with material densification through high-temperature sintering. The rejected products are reintroduced into the process in the form of "chamotte" powder. Yet, the influence of the content and nature of this chamotte on the microstructural stability of the material remains poorly understood, particularly during the pressing and sintering stages. This aspect is critical for both the mechanical integrity and the in-reactor behavior of MOX fuels. A better understanding of these phenomena, combined with refined modeling, would make it possible to optimize industrial processes and ultimately improve the reliability of these fuels.
The objective of this PhD project is to study and model the evolution of the microstructural properties of MOX fuel as a function of the proportion and nature of the chamotte added during fabrication. The thesis strategy will rely on an integrated approach combining experimental studies with numerical simulations. It will be based on multi-scale characterization of the microstructure, coupling imaging and spectroscopy techniques, as well as on the three-dimensional reconstruction of the microstructure from experimental 2D images. The ultimate goal is to establish a link between the elastic properties of the material and its microstructure. This work will build on a combined experimental and modeling approach, bringing together the expertise of the supervisory team for experiments on plutonium-bearing materials, and for numerical modeling (micromechanical modeling, FFT-based calculations).
At the end of this PhD, the graduate student, with initial training in the physical chemistry of materials, will master a wide range of experimental techniques as well as advanced numerical modeling methods applied to ceramic materials. These skills will open up many job opportunities in academic research or industrial R&D, both within and outside the nuclear sector.