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A hybrid atomistic-empirical numerical twin to predict the fuel microstructure evolution

Vacancy details

General information


The French Alternative Energies and Atomic Energy Commission (CEA) is a key player in research, development and innovation in four main areas :
• defence and security,
• nuclear energy (fission and fusion),
• technological research for industry,
• fundamental research in the physical sciences and life sciences.

Drawing on its widely acknowledged expertise, and thanks to its 16000 technicians, engineers, researchers and staff, the CEA actively participates in collaborative projects with a large number of academic and industrial partners.

The CEA is established in ten centers spread throughout France



Description de l'unité

The Unit of Study and Simulation of the Fuel Behaviour (SESC) is a team of about 70 engineers and researchers as well as ~30 PhD students that hosts each year about 20 trainees: Students from Master and License (Bachelor) of science as well as Engineer schools. This Unit belongs to the Fuel Study Department (DEC) and the IRESNE Institute (Research Institute for Nuclear Systems for Low Carbon Energy Production), a part of the Division of Energies of the French Atomic and Alternative Energy Commission (CEA). The CEA is committed to carrying out the R&D necessary for the implementation of a low-carbon energy mix in France, and as such is positioned at the top of the world rankings for the filing of patents concerning technological innovation for low-carbon energyThe SESC is located at the CEA Cadarache site, the major European research centre devoted to low-carbon energy: nuclear fission and fusion, solar energy and biofuels. The CEA Cadarache is located in the south of France about 40 kilometres from Aix-en-Provence.

Position description


Materials, solid state physics



Job title

A hybrid atomistic-empirical numerical twin to predict the fuel microstructure evolution


Like other industrial sectors, the nuclear industry is developing 'digital twins', applications that simulate the behaviour of an industrial component, such as a car, plant, reactor or, in our case, a fuel rod. The proposed work is part of this approach and contributes to the development of a digital twin of a grain that can be used to simulate its microstructural evolution under irradiation.

Contract duration (months)


Job description

The microstructure of nuclear fuel (uranium oxide) is severely damaged during irradiation in a reactor: the atoms produced by the fission of uranium nuclei displace the atoms in the material in a cascade, creating irradiation defects (vacancies and interstitials) whose aggregation leads to the gradual appearance of cavities and dislocation loops. These extended defects influence the volume of the material, its creep and its retention of fission gases. The physical model of the phenomenon is cluster dynamics: a set of kinetic equations representing the chemical reactions of defect aggregation by diffusion in the material.

Most of the model parameters are derived from atomistic calculations (defect formation and migration energies, irradiation damage). However, some of them have not been calculated and are practically impossible to measure directly. The approach proposed for this internship is twofold:


a.Fitting the missing parameters using the model to simulate the results of experiments (already available in the laboratory) in which the microstructure is affected, such as transmission electron microscopy characterisation of dislocations and voids (size, concentration). Innovative techniques will be used:
•Sensitivity analysis to determine which parameters affect the measured values
•Optimisation (genetic algorithms) to fine-tune these parameters. The URANIE™ platform developed by the CEA will be used for the statistical analysis of the data.
•Kinetic Monte Carlo for the damage simulation

b.Validate this fitted model by comparing its results with measurements from other experiments. The model will then be applied to new situations, such as irradiation of fuel material to predict fission gas release, or the density of loops and dislocation lines.

This modelling project involves a variety of tasks:
•Interpretation of experiments
•simple computational development of optimisation scripts for URANIE
•simulation of experimental or industrial situations

This internship offers the candidate the opportunity to contribute to the development of numerical physics applied to multiscale modelling, taking a central position and a synthetic point of view. It is also an opportunity to discover for oneself how microscopic computational approaches ultimately help to solve complex practical problems.


R. Skorek, Étude Par Dynamique d’Amas de l’influence Des Défauts d’irradiation Sur La Migration Des Gaz de Fission Dans Le Dioxyde d’uranium, PhD Thesis, Univ. Aix-Marseille, 2013.

E. Gilabert, D. Horlait, M.-F. Barthe, P. Desgardin, M.-L. Amany, G. Carlot, M. Gérardin, S. Maillard, and T. Wiss, D2.2 - Behaviour of Fission Gases and Helium in Uranium Dioxide, EC report, 2020.

Methods / Means

Using/improving simulation codes, simple coding of physical mechanisms

Applicant Profile

Master's degree or equivalent in materials physics, modelling or numerical physics

Position location



Job location

France, Provence-Côte d'Azur, Bouches du Rhône (13)


Saint Paul lez Durance

Candidate criteria

Prepared diploma

Bac+5 - Master 2

Recommended training

Master's degree or equivalent in materials physics, modelling or numerical physics

PhD opportunity



Position start date