Interaction of Embedded Tri-Isotropic Fuel Particles with Melt of Alkaline Borosilicate Glass

A silicon carbide (SiC) layer is an outer-coated layer of spent tri-isotropic (TRISO) fuel particles and it is known to be a pressure vessel for retaining fission products, and preventing contamination in the primary circuit of a nuclear reactor. The goal of this article is to elucidate the chemical bonding and an interface formation of an alkaline borosilicate glass (ABG) with the coating layer of TRISO fuel particles. Particular emphasis is placed on the analysis of the intermediate chemical phase at the interface SiC/glass as a function of the material impurity and thickness of the SiC layer. The findings provide valuable information regarding the restriction parameters of immobilisation TRISO particles in glass. The interaction between the glass and SiC caused a total destruction of a thin SiC layer (10 μm), a random partial interaction to a thick SiC layer (40 μm) and formation of bubbles (CO₂, CO) to an inner pyrolitic carbon (IPYC). The Raman spectroscopy analysis revealed that the interaction of ABG with the SiC layer occurred at a point, where a low excess of carbon was co-deposited during chemical vapour deposition process. The interaction resulted in a formation of a mono-crystal SiC, dispersed in vitreous silica as a crystalline inclusion.