Abstract The fuels used in first generation advanced heavy water reactor (AHWR) are mixed oxides (MOX) of 238U– 239Pu and 232Th– 233U. The reprocessing of spent MOX fuel and partitioning of minor actinides from waste generate high level waste (HLW) raffinates. Sodium borosilicate glass matrix was developed for immobilization of simulated HLW raffinate. Waste oxide loadings upto 25 wt% was achieved. The matrix was studied for physico-chemical characteristics like processing temperature, density, microhardness and chemical durability. The glass transition temperatures were estimated by differential scanning calorimeter (DSC). Homogeneity and glass structure was analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transform infra red (FTIR) spectroscopy. The detailed data on preparation and characterization of the glasses are presented.