Effects of Aging and Temperature on the Rheological Properties of Simulated Melter Feed Slurries for Nuclear Waste Vitrification

In some vitrification processes, the nuclear waste is first mixed with glass-forming additives to form an intermediate aqueous slurry before being processed through a melter at high temperature (typically 1100-1200°C) to form a glass of the desired composition and properties. The rheological characteristics of such an intermediate melter feed slurry are important for the mixing and transport of the feed slurry to the melter and also in the spreading of the slurry on the surface of the glass melt. In this paper, the effects of aging and temperature on the rheological properties of melter feed slurries have been investigated for various high-sodium waste streams. The apparent viscosity of the melter feeds increases significantly with aging time for relatively high solid content melter feeds. After an aging time of 30 days, the apparent viscosity increased exponentially with solid content. A temperature increase from 25°C to 40°C reduced the apparent viscosity with the reduction becoming more evident at high solids content.