Missions

After passing through the reactor, spent nuclear fuel assemblies are stored in pools for several years. In the event of accidental cladding failure, the fuel, which is in direct contact with the pool water, will be subject to alteration mechanisms that must be understood and controlled. The objective of the project supported by the CEA and EDF is to propose, in the medium term, a model of chemical interaction of fuels under water and under radiolysis under pool storage conditions in order to quantify the radionuclide source terms and to determine the nature and location of the precipitated phases in the fuel assembly.
The physical-chemical fuel degradation model developed in this project will be based on the CHESS-HYTEC chemistry-transport code. HYTEC is a modular and scalable simulation platform developed by the Ecole des Mines ParisTech, consisting of a hydrodynamic module, a reaction module (CHESS) and a coupler. This code makes it possible to numerically simulate all chemical processes in solution and at interfaces with gases and solids, at thermodynamic equilibrium or under kinetic control in a geometry and for representative boundary conditions.
As part of this project, the successful candidate will be required to use the CHESS-HYTEC code and test the potential of the COMSOL Multiphysics code to model the alteration processes of spent fuel in pools. The successful candidate will be required to interact and collaborate with team members and other partners involved in the project (CEA, EDF, Ecole des Mines ParisTech).

Activities

After an initial phase of litterature review and enrichment of the thermodynamic database, the modeling approach will be based on the gradual complexification of the system, which will initially integrate gamma radiolysis into homogeneous chemistry, then temperature, before moving on to a more complex geometry that is representative of the damaged fuel rod. Taking radiolysis into account requires the use of the Chemsimul code: one of the postdoctoral researcher's tasks will be to develop Python tools to improve its use and the exploitation of results, as well as to enable linking with the CHESS-HYTEC code. The development of this numerical model will be based on experimental data available in the literature or obtained in the laboratory. The postdoctoral researcher will be able to participate in defining experimental plans to acquire missing data.
The successful candidate will be required to produce presentations and progress reports as part of project management and to disseminate the results of their research at conferences and in scientific articles.

Skills

The candidate must hold a PhD in chemistry, materials science or geochemistry. Advanced skills in multi-physics modeling and in the development of scientific tools in Python are required, and experience in using the CHESS-HYTEC code chosen for this study would be appreciated. In addition, knowledge of nuclear fuel cycle chemistry and materials will be necessary. The candidate must have good communication skills, both oral and written, in English and French, and be able to work in a multidisciplinary environment interacting with different teams and an industrial partner.

Work Context

The CDD researcher will be attached to the Laboratory of Evolving Interface of Materials within the Institute of Separative Chemistry of Marcoule (ICSM, UMR 5257, CEA/CNRS/UM/ENSCM). This study is being conducted in close collaboration with the Active Materials and Processes Laboratory at CEA Marcoule (CEA/ISEC/DPME/SEME/LMPA). The geographical proximity of the two laboratories involved will allow for regular exchanges. Finally, several assignments are planned at the École des Mines de Paris (Fontainebleau site).

The position is located in a sector under the protection of scientific and technical potential (PPST), and therefore requires, in accordance with the regulations, that your arrival is authorized by the competent authority of the MESR.

Constraints and risks

There are no particular risks associated with the duties of a fixed-term researcher.