Zeolite and silica fume as enhancers for cementitious solidification of borate radioactive waste

Low- and medium-level borate radioactive liquid wastes are common liquid wastes generated during the operation and decommissioning of nuclear power plants. These wastes pose significant risks to environmental safety and public health, necessitating effective solidification methods for safe disposal. In this study, the use of zeolite and silica fume as additives to increase the performance of cemented forms of waste was investigated. Five formulations were evaluated for compressive strength, impact resistance, freeze‒thaw resistance, gamma irradiation resistance, immersion resistance, and leaching resistance. The results indicate that the combination of 10 % zeolite and 5 % silica fume (Z10-SF5) significantly improved the mechanical properties and durability of the solidified forms of waste under harsh environmental conditions, including freeze‒thaw cycles, gamma irradiation, and immersion. The results also exhibited outstanding leaching resistance, reducing the cumulative boron leaching fraction by 65 % compared with that of the control. X-ray diffraction (XRD), scanning electron microscopy (SEM), and mercury intrusion porosimetry (MIP) analyses revealed that the additives promoted C-S-H gel formation and improved the pore structure and density of the solidified form. These findings highlight the potential of zeolite and silica fume in advancing the long-term stabilization of borate radioactive waste.