A systematic study on leaching property of Nd-doped garnet waste forms under different conditions

The disposal of high-level waste, particularly the management of long-lived actinides after immobilization, requires a thorough assessment of the long-term stability of nuclear waste forms in underground repositories. In this work, the garnet Ca 1.5 Nd 1.5 Zr 1.5 Fe 3.5 O 12 was successfully synthesized via high-temperature solid-phase sintering at 1300°C, exhibiting excellent phase purity and microstructural integrity. The chemical stability of the garnet waste form was evaluated under various conditions, including acidic, alkaline, saline, oxidizing environments, and deionized water. Both static and semi-dynamic leaching methods were employed to investigate the leaching mechanisms in different solutions. In acidic leachate, the normalized leaching rate initially increased before decreasing, as the dominant leaching mechanism shifted from slow dissolution and surface reactions to long-term diffusion. In the other four conditions, surface dissolution and internal diffusion processes primarily controlled the leaching mechanism. Ca 1.5 Nd 1.5 Zr 1.5 Fe 3.5 O 12 demonstrated outstanding thermal stability and corrosion resistance, positioning it as a promising candidate for the immobilization of actinide nuclear waste.