Preparation and Characterization of Nano porous Silica Glasses for Nuclear waste Immobilization

In the current study, crystallization and phase separation of a borosillicate glass composition in the system Na۲O–CaO–Al۲O۳–B۲O۳–SiO۲ used for nuclear waste immobilization have been investigated. At first, base glass composition was prepared by mixing and homogenizing of pure raw materials, melting in an alumina crucible and then casting in a stainless steel mold. Mo۲O۳ was added in constant values of ۰.۵, ۱.۵, ۲.۵ and ۳.۵ %mole. XRD analysis was carried out to ensure no crystalline phases were formed. Heat treatment was performed at temperature intervals of ۶۲۰, ۶۵۰, ۶۸۰ and ۷۱۰°C. To study phase separation creation, SEM analysis was carried out. In the next step, acid leaching of phase separated glasses was performed. Porosity analysis and measurement of specific surface area by BET were performed on acid-leached samples. The results show that all samples show different amounts of phase separation. Also, the highest specific surface area was related to the sample containing ۱.۵ %mole Mo۲O۳ with two acid washing steps.