Rheological Characterizations and Modifications of Simple and Complex Melter Slurries: Nuclear Waste Simulant Slurries

Understanding and controlling rheological properties of slurries has been one of the most challenging problems in many industries. For nuclear waste treatment, such as at the U.S. Department of Energy's (DOE) Hanford and Savannah River sites, it is extremely difficult due to the wide distributions of particle size, chemical species, and mass/volume fraction of particles, among others. We investigated rheological characteristics of different simulated nuclear waste melter slurries that are prepared for vitrification of nuclear wastes. These slurries ranged from simple to complex physicochemical systems. It was found that the mixture of glass former chemicals (inorganic oxides consisting mainly of SiO₂) used to prepare melter slurries alter their original particle size distributions significantly, along with an increase in solids content, both of which change rheological characteristics. Our study on rheological modifications of such melter slurries implies that the changes in the particle size distribution may influence not only the efficiency of rheological modifications but also the selection of appropriate rheological modifiers. This work is important to nuclear waste treatment processing, because controlling rheological properties enables us not only to reduce operational cost via an increase in solids content but also to ensure sustainable operations.