Potential of tropical expansive clays as natural sealing layer in nuclear waste repository system: a preliminary study

Abstract

The issue of radioactive waste disposal in Malaysia is frequently debated, particularly in terms of human and environmental long-term well-being. The creation of a repository with minimal hazard risk and cost implications is a major environmental concern related to nuclear waste. Expansive clay has distinct characteristics that are readily available in the environment and can serve as a natural barrier (sealing system) against the migration of radioactive and chemical pollutants. In this study, the physico-chemical and microstructural properties of 2 types of tropical soils with dominant clays mineral (vermiculite and montmorillonite) were investigated to better understand the potential of these clays as natural sealing in nuclear waste repository systems. Based on preliminary findings, both types of soil have been classified as alkaline soil (>7) with high swelling capacity (FSI) (>80%) and high consistency (LL>50%; PI>30%). The microstructural study demonstrates that vermiculite clays have a noticeable flaky morphology and a porous structure as compared to montmorillonite, indicating that the soil can absorb more water, hence decreasing its infiltration capability. Pinhole dispersion analysis reveals that montmorillonite clay is more prone to dispersion due to the presence of sodium ions and has a higher erosion potential than vermiculite clay. Future Malaysian stakeholders may employ this research to establish a long-term plan for the management of radioactive waste through the usage of natural resources.