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Thesis
Home   /   Thesis   /   Impact of chemical disorder on the behaviour of fission gases in mixed-oxide nuclear fuels

Impact of chemical disorder on the behaviour of fission gases in mixed-oxide nuclear fuels

Condensed matter physics, chemistry & nanosciences Green and decarbonated energy incl. bioprocesses and waste valorization Solid state physics, surfaces and interfaces Technological challenges

Abstract

The extreme weather events occurring worldwide are a clear sign that the transition to low-carbon energy supply technologies cannot be delayed any further, as the latest IPCC report* has highlighted. This implies the urgent need for improving electricity production and storage, including resource optimization and recycling. One of the critical elements in this effort is the development of more efficient materials, which relies on the synergy between testing experiments and computational modeling aimed at predicting their properties and behavior.

Nuclear energy, which emits little greenhouse gases, is an important asset in this context. Fuel optimization, in particular mixed uranium-plutonium oxides (MOX), is necessary to further improve reactor safety and reduce the amount of radioactive waste. Simulations at all scales allow for a detailed characterization of the fuel behavior under irradiation, and the development of reliable predictive models. For instance, fission gas release caused by the atomic-scale diffusion of gas atoms is a relevant phenomenon that affects fuel integrity and performances.

The goal of the thesis is to investigate the effect of chemical disorder on the gas diffusion properties in MOX, for which no experimental measurements are currently available. One of the main challenges in the modeling of these systems is sampling the vast number of possible atomic configurations. The candidate will define and implement effective sampling strategies, possibly based on artificial intelligence algorithms, and use automatic techniques of diffusion-path search based on the ART-nouveau method. This will be combined with diffusion models, electronic structure calculations, and molecular dynamics simulations performed on HPC (High Performance Computing) resources. The outcome of this work will allow for the improvement of the gas-release models currently included in the fuel performance codes that describe fuel behavior in a nuclear reactor.

The project will take place in a collaborative framework between several CEA teams. The candidate will present the results of their research in international conferences, and publish them in peer-reviewed scientific journals. The candidate will acquire an in-depth expertise of multiple modeling tools applicable to many classes of materials. This will be a valuable asset for a career in academic or industrial research, as well as in materials engineering.

* IPCC = Intergovernmental Panel on Climate Change (https://www.ipcc.ch/report/ar6/wg1/)

Laboratory

Département d’Etudes des Combustibles
Service d’Etudes de Simulation du Comportement du combustibles
Laboratoire de Modélisation Multi-échelles des Combustibles
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