A Review of Key Wasteform Properties for Radioactive and Heavy Metal Mixed Waste: Leaching Behavior and Radiological Stability

Abstract

Mixed waste produced by nuclear facilities is difficult to dispose of, as it comprises both radiological and chemical hazards. Considering that most mixed wastes are designated as low-level waste and that heavy metals are the major chemical hazards, it is highly likely that the difficulties associated with mixed waste disposal can be resolved by solidification and stabilization (S/S) treatment. The primary material used for S/S treatment of low-level radioactive and hazardous materials is ordinary Portland cement (OPC). Conversely, vitrification is recommended for high-level radioactive waste, especially nuclear fuel material. Additionally, geopolymers with comparable performance to OPC have gained considerable attention recently. This report reviews the binding mechanisms associated with S/S of OPC, geopolymer, and glass wasteform with radionuclides and hazardous material, as well as structural degradation, leaching resistance, mechanical changes, and irradiation effects in irradiation environments. It also introduces a multi-scale modeling approach for quantitative evaluation of the physical, chemical, thermal, and mechanical properties of heterogenous OPC, geopolymers, and glass. Studies on S/S that consider the properties of mixed waste can enable safe and efficient mixed waste treatment and enhance the sustainability of nuclear power generation.