Effect of particle size distribution on slurry rheology: Nuclear waste simulant slurries

Controlling the rheological properties of slurries has been of great interest in various industries such as cosmetics, ceramic processing, and nuclear waste treatment. Many physicochemical parameters, such as particle size, pH, ionic strength, and mass/volume fraction of particles, can influence the rheological properties of slurry. Among these parameters, the particle size distribution of slurry is especially important for nuclear waste treatment because most nuclear waste slurries show a broad particle size distribution. We studied the rheological properties of several different low activity waste nuclear simulant slurries having different particle size distributions under high salt and high pH conditions. Using rheological and particle size analysis, it was found that the percentage of colloid-sized particles in slurry appears to be a key factor for rheological characteristics and the efficiency of rheological modifiers. This behavior was shown to be coupled with an existing electrostatic interaction between particles in a low salt concentration. Our study suggests that the particle size distribution is a critical factor in understanding and controlling the rheological properties in nuclear waste treatment plants, such as the U.S. Department of Energy's Hanford and Savannah River sites, because the particle size distributions vary significantly for different types of nuclear waste slurries.

Changes in yield stress of three AW-101 LAW simulants and the AZ-101 pretreated HLW simulant owing to changes in particle size distribution.Figure optionsDownload as PowerPoint slideHighlights
► For nuclear waste slurries, the percentage of particles smaller than 5 μm is likely correlated to increases in yield stress for these slurries.
► We use shear-repulsion number and shear-attraction number to understand the rheological behavior of nuclear waste simulant slurries.
► The effect of particle size distribution is closely correlated with modification of rheological properties.
► Slurries with a low salt concentration revealed that the effect of particle size distribution could be strongly coupled with the existence of repulsive electrostatic interactions.