Leaching characteristics of glassy waste forms containing two different incineration ashes

Abstract

Several glassy waste forms are fabricated from two different incineration ashes, respectively, at different mixing ratios of ashes to base glass. Incineration ashes used in the experiments are hazardous waste (HW) incineration ash from a paint factory and simulated radioactive waste (RW) incineration ash from a nuclear power plant. To assess the chemical durability, which is known to be the most important factor in the waste form integrity, of glassy waste forms, long-term leaching tests such as MCC-4S (for HW glassy waste form) and ISO (for RW glassy waste form) methods were conducted at 70°C for over 500 days. By observing the initial leach ratio of glass components, it was found that silicon and calcium uniformly leached out after the early leaching of sodium and boron. For sodium and boron, diffusion is a dominant leaching mechanism, while dissolution associated with diffusion affects the leaching of silicon and calcium. Like glass constituents, leaching characteristics of hazardous metals and surrogate nuclides are also dependent upon solubility.