Improving phase field damage models - Application to vitroceramic materials subjected to self-irradiation
The vitrification of nuclear waste is a solution currently adopted for the storage of nuclear waste. The vitroceramic materials considered for this application consist of a glass matrix and inclusions of crystalline phases. Rich in radioactive elements, these inclusions undergo self-irradiation resulting in their swelling, which may cause cracking of the glass matrix. It is necessary to know the maximum amount of inclusions below which the material does not crack. An experimental study on radioactive materials, produced and monitored over time, is excessively expensive and the development of a numerical approach could make it possible to better target the materials to be studied.
Following Gérald Feugueur's thesis work on the subject, which highlighted the difficulty of current models in dissociating crack initiation and propagation, the main goal is to develop and test an improved phase field model incorporating an elasticity-independent crack nucleation criterion, based on regularized models of softening plasticity. The model will be implemented using the finite element method (FEniCS code) and an alternative method using Fourier transforms (AMITEX code). Following cross-validation, the most efficient implementation will be selected for application to large-scale 3D microstructures. Close exchanges with CEA Marcoule will enable us to characterize the microstructure of the materials, and an experiment currently underway should enable us to analyze the potential cracking of these materials under self-irradiation.
Characterization methods for LMJ’s layered cryogenic targets
Inertial Fusion on the Laser Megajoule facilty requires to form a spherical DT layer at cryogenic temperature. A major topic of interest for fusion experiments is the characterization of the layer quality and thickness. The characterization will be done using two technics : optical shadowgraphy and X-ray phase contrast analysis. A cryostat developed by CEA is already available to work on future target designs and layer characterization.
The objectives of the PhD are to understand and model (theorically and numerically) the physics of the layer observation and to develop the characterization test bench in the cryostat’s environment and the image analysis for the 3D description of the layer.
The student will have to learn to use the cryostat, its command system and its simple actual characterization system. After a bibliography research, he will have to study the physics governing the characterization (multiple reflections, refractions, phase contrast, …) and develop the acquisition and image analysis system allowing the 3D description of the layer using images obtained during experiments with the cryostat. Lastly, the coupling between the command of the cryostat and the characterization will be developed. For all these developments, the student will have access to extensive bibliographical data and the expertise of the host team
Compréhension et modélisation du transport des gaz dans un combustible UO2 présentant plusieurs familles de porosités
Sans objet (candidats français uniquement pour cette thèse)
Radiological large-scale accident dosimetry: use of EPR spectroscopy for population triage by measurements of smartphone screens
In the event of a large-scale radiological emergency involving sources of external irradiation, methods are needed to identify which members of the population have been exposed and require priority care. To date, there are no operational methods for such sorting. Smartphone touch screen lenses retain traces of ionizing radiation through the formation of so-called “radiation-induced” defects.Measuring and quantifying these punctual defects, in particular by electron paramagnetic resonance (EPR) spectroscopy, makes itpossible to estimate the dose deposited in the glass, and thus the exposure associated with irradiation. The thesis work proposed herefocuses in particular on the alkali-aluminosilicate glasses used in cell phone touch screens, which are currently the best candidates fordeveloping new measurement capabilities in the context of accidents involving large numbers of victims.
We will focus in particular on identifying point defects as a function of the glass model used in smartphones by simulating EPR spectra in order to optimize the proposed dosimetry method.
Integrated System for Adaptive Antenna Tuning and Synthesized Impedance in the Sub-6 GHz Band for Next-Generation RF Systems.
The growing adoption of sub-6 GHz RF systems for 5G, IoT, and wearable technologies has created a critical demand for compact, efficient, and adaptive solutions to enhance energy transfer, mitigate environmental detuning effects, and enable advanced sensing capabilities. This thesis proposes an innovative system-on-chip (SoC) that integrates an Antenna Tuning Unit (ATU) and a Synthesized Impedance Module (SIM) to address these challenges. By combining in-situ impedance measurement and dynamic re-adaptation, the system resolves a key limitation of miniature antennas—their extreme sensitivity to environmental perturbations, such as proximity to the human body or metal surfaces. Moreover, the integration of a Synthesized Impedance Module brings additional versatility by enabling the emulation of complex loads. This capability not only optimizes energy transfer but also allows for advanced functionality, such as material characterization and environmental sensing around the antenna.
A central focus of this research is the co-integration of a Vector Network Analyzer (VNA) with a broadband post-matching network (PMN) and a Synthesized Impedance Module. This combined architecture provides real-time impedance monitoring, dynamic tuning, and the generation of specific impedance profiles critical for characterizing the antenna's response under various scenarios. Guaranteed operation in the 100 MHz–6 GHz band is achieved while maintaining low power consumption through efficient duty cycling.
. Profile Sought : are you passionate about electronics and microelectronics and eager to contribute to a major technological breakthrough? We are looking for a motivated and curious candidate with the following qualifications:
. Education
Graduate of an engineering school or holder of a master’s degree in electronics or microelectronics.
Technical Skills
Strong knowledge of transistor technologies (CMOS, Bipolar, GaN…).
Expertise in analog/RF design.
Experience with design tools such as ADS and/or Cadence.
Programming
Basic skills in Python, MATLAB, or similar programming languages.
Additional Experience
Prior experience in integrated circuit design would be a valuable asset.
. Why Apply: you will have the opportunity to work on cutting-edge technologies in an innovative and collaborative research environment. You will be guided by renowned experts in the field to tackle exciting scientific and technical challenges.
Contacts: PhD. Ghita Yaakoubi Khbiza: ghita.yaakoubikhbiza@cea.fr, HDR. Serge Bories: serge.bories@cea.fr
Development of highly reactive bio-based polyhydroxyurethanes for the substitution of isocyanates in polyurethanes
Polyurethanes are thermosetting materials with significant environmental impacts. They are primarily synthesized from isocyanates, which are highly hazardous substances (toxic, sensitizing, and some even classified as CMR - Carcinogenic, Mutagenic, or Reprotoxic) and are subject to REACH restrictions. In this context, polyhydroxyurethanes (PHUs) offer several advantages: (i) they are more easily bio-based compared to conventional PUs, (ii) their synthesis does not involve isocyanates, but (iii) instead allows for CO2 sequestration. However, the precursors used in the synthesis of PHUs (cyclic carbonates and amines) exhibit much lower reactivity than isocyanates, resulting in curing times that are currently incompatible with the temperatures and production rates required for this type of material.
Several research directions have been proposed to optimize PHU curing kinetics, focusing on the identification of (i) new cyclic carbonate and amine precursors chemically substituted at the a or ß positions of the reactive group, and (ii) new high-performance catalysts capable of activating both types of precursors used in synthesis.
In this context, the PhD candidate will be tasked with synthesizing new cyclic carbonate and amine precursors and studying their reactivity to identify the most favorable conditions for the synthesis of highly reactive PHUs. The results obtained during this work will then be analyzed using symbolic Artificial Intelligence models developed at CEA.
This PhD project is part of the PHURIOUS project, funded by the PEPR DIADEM program, which aims to integrate high-throughput synthesis and characterization techniques in polymer chemistry with digital tools, including DFT calculations, molecular dynamics simulations AI approaches.
Development of a multi-criteria comparison tool for electrochemical stationary storage systems
Use of stationary storage systems is now essential to keep pace with changes in the electricity grid and the growing integration of intermittent renewable energies such as solar and wind power. The choice of a storage solution is based on a number of criteria, including performance, lifetime, environmental impact, safety, regulatory constraints and, of course, economics.
The laboratory possesses comparative data on these different criteria, via experimental studies and feedback on existing systems. In addition, an initial software tool has been developed to assess environmental impact using LCA (Life Cycle Assessment). The aim of this thesis work is to integrate these different components into a broader comparison tool with a multi-criteria approach, targeting specific case studies and a limited number of storage technologies that have reached sufficient maturity for the available data to be reliable.
High yield strength austenitic stainless steels for nuclear applications: numerical design and experimental study
The PhD thesis is part of a project that aims at designing new austenitic stainless steels grades for nuclear applications, which are specifically suitable to in-service conditions encountered by the components and to the manufacturing process. More precisely, the subject deals with bolt steels achieved by controlled nitriding of powders which are then densified by hot isostatic pressing. Indeed, current bolt steel grades may suffer from stress corrosion cracking, while nitriding allows to increase the chromium content, which is beneficial from that point of view.
The study will start by the definition of specifications and associated criteria, then CALPHAD calculations in the Fe-Cr-Ni-Mo-X-N-C system will be done to define promising compositions. Then, selected compositions will be supplied as powders. The behaviour of powders during nitriding will be studied and modelled. Samples will be nitrided, densified and heat treated. One grade will be then selected and fully characterised: mechanical properties and deformation mechanisms, corrosion behaviour. One important objective is to demonstrate the advantages of the new grade compared to the industrial solution.