The calcination-vitrification process is the solution used in France for more than 30 years for the conditioning of high-level nuclear waste resulting from the reprocessing of spent fuel. During the vitrification process, the waste is incorporated into a borosilicate glass-forming liquid at more than 1000°C. The glass-forming liquid is homogenized in temperature and composition by stirring and gas bubbling. The incorporation of waste into glass-forming liquid can also lead to gas releases, including those of oxygen resulting from redox reactions between species dissolved in the liquid. It is important to properly control the impact of these gases on the glass and the process.
The redox state of glass-forming liquid at equilibrium between the dissolved species has been the subject of various studies at the CEA in the context of the vitrification of nuclear waste [1, 2]. On the other hand, few studies have been devoted to the kinetics of gas reactions in glass-forming liquid [3, 4]. The objective of this thesis aims to study and model the impact of gas bubbles, whatever their nature, on the redox of melting and the kinetics of associated reactions. An approach combining experimentation and digital modeling will be adopted.
A taste for experimentation, characterization and interpretation of results addressing different scientific fields is important to carry out this work. All experiments will be carried out on non-radioactive elements and will involve processing by digital modeling.