Leaching Behavior and Mechanism of Ceramic Waste Forms

Abstract

The radionuclides in high-level radioactive waste (HLW) forms may be leached out over geological time and enter the human environment with groundwater circulation after deep geological disposal. This is likely the potential way for radionuclides to enter the biosphere. Therefore, the long-term chemical durability of HLW waste forms is the key issue for selecting suitable waste forms. Ceramic waste forms, regarded as the second generation of HLW forms, are of long-range ordered structures, whose physical properties can be easily characterized quantitatively. It is of great importance and significance to study the leaching mechanism of ceramic waste forms. However, not only the studies of leach mechanisms, but also the evaluation methods of ceramic waste forms are in their infancy. There is also lack of the standards of ceramic waste forms received by the repository. The present paper summarizes the research methods and key points of chemical durability, reviews the research status of hydrothermal alteration of related ceramics, and analyzes the leaching rate of radionuclides. In addition, the paper also discusses the influencing factors and their influencing modes, and finally concludes the leaching mechanisms and existing problems.

Zirconia/garnet multiphase ceramics with high immobilization capacity for Nd confers better physical and chemical stability

“…In addition, the leaching agent used here was weakly alkaline simulated Bei Shan groundwater (pH≈8.10), while the leaching agent previously used was deionized water (pH≈7). The effect of temperature on the normalized leaching rate can be explained by Arrhenius's formula 49 : $$$$\begin{equation}k = A{{\mathrm{e}}}^{ - {E}_{\mathrm{a}}/\left( {RT} \right)},\end{equation}$$$$…”