Thesis defense “Influence of redox conditions and composition on iodine incorporation mechanisms in borosilicate glasses: Experimental and spectroscopic approaches” of Sami Soudani

As the demand for energy is increasing and the energy mix needs to evolve towards general decarbonisation, renewable and nuclear energy sources are the main options. For countries with a developed nuclear industry, a key issue is the management of radioactive waste. Although the vitrification of waste is a well-established process, certain radioisotopes remain problematic. Among these, volatile elements are lost in the gaseous phase during the fusion process. A new protocol has recently been developed at the laboratory scale to vitrify these volatile elements using technologies that enable glass to be synthesised under high pressure condition. After preliminary experiments on this subject, the present study pursues this research in three main directions: 1) Analysis of the effect of pressure on volatile-free glasses in order to improve our understanding of this mechanism in simplified nuclear glass compositions; 2) Study of the impact of variations in chemical composition on the final retention of volatile substances. We thus compared the differences in the iodine affinity with different cations. 3) Analysis of iodine-containing glasses to determine how iodine modifies the glass structure. Finally, we identified the reactions potentially involved in the dissolution of iodine in the glass, revealing that the introduction of iodine into the network induces polymerisation.