Borosilicate glasses are used to contain long-lived radioactive waste resulting from the reprocessing of spent nuclear fuel. Predicting their long-term behavior in deep geological storage relies on models that describe, in a disjointed manner, the physico-chemical processes from the molecular scale (molecular dynamics) to the macroscopic scale (geochemical model), passing through an intermediate scale known as mesoscopic (Monte Carlo, phase field model, and gel maturation model).
Molecular and mesoscopic scale models deal with simple cases (glasses with 3 or 4 oxides altered in pure water). They have significant explanatory power but limited predictive scope because the actual situation is more complex: nuclear glass consists of about thirty oxides. It undergoes the effects of irradiation and will evolve in an environment influenced by the claystone of the site, iron, corrosion products from metal casings, and the filling material.
The geochemical model allows simulating the behavior of complex glasses under realistic alteration conditions but currently relies on a simplified description of basic processes, sometimes distant from real processes.
The thesis will contribute to bridging the gap between simplified approaches and more realistic complex systems. It focuses on three main axes:
1 - Validation of gel maturation phenomenological laws for glasses of increasing complexity.
2 - Consideration of irradiation effects.
3 - Consideration of environmental effects.
Profile sought: Master's degree (M2) or engineering degree in solid-state physicochemistry/materials science. The thesis will provide the candidate with advanced skills in the field of glasses, modeling, and project management in multidisciplinary research, in collaboration with industrial and academic partners. Numerous employment opportunities are available after the thesis, in the nuclear sector, glass industry, or academia.