Simulated high-level liquid waste (HLLW) slurries were prepared by combining a series of soluble stock solutions composed of commonly available chemical reagents. The properties simulated included acidity, nitrate concentration, quantities and composition of undissolved solids, density, and viscosity of HLLW at various degrees of evaporation. Limits of concentration by evaporation and stability during storage were studied. Settling rates and particle sizes of the undissolved solids were estimated for stored HLLW. While considerable effort was expended to closely simulate actual reprocessing wastes, these data should be confirmed under actual process conditions.