Microstructure Characterization of Simulated Tri-Isotropic Particles Embedded in Alkaline Borosilicate Glass

A preliminary study of the encapsulation of tri‐isotropic (TRISO) coated particles in alkaline borosilicate glass (ABG) using melting and casting methods is presented. ABG has been developed to encapsulate simulated TRISO fuel particles that are used as nuclear fuel elements in Very High Temperature Reactors. Encapsulation is an alternative to vitrification and it is a process in which radioactive waste is encapsulated within a composite as a first barrier and a glass matrix as a second barrier. This provides two barriers against leaching and diffusion of the radioactive waste once buried in the geological repository. The study investigates the possibility of achieving high densification of glass–graphite composite by sealing the pores of TRISO particles surrogate (28 wt% CeO2, 70 wt% graphite, and 2 wt% poly‐ethylene glycol) with molten ABG at 600°C. This article follows the carbon phases during the encapsulation and highlights the interaction area between the carbon and glass phases before and after melting, using a polarized laser source (Ar, 514 nm). The laser analysis revealed that the graphite no longer was retained in graphene hexagonal structure and that it was linked with the glass network as disordered carbon atoms.