UNDERSTANDING THE MECHANICAL AND HYDROLOGICAL PROPERTIES OF BENTONITE FOR SAFETY ASSESSMENT OF RADIOACTIVE WASTE DISPOSAL

Abstract

Compacted bentonite can be used as an engineered barrier to inhibit radionuclide migration in radioactive waste disposal. Thermal-hydro-mechanical-chemical coupled phenomena occur inside the engineered barrier and change the engineering properties of compacted bentonite, for example, swelling and permeability, for a long-term. Thus far, the properties of bentonite have been investigated in various academic fields, including clay science and mineralogy. The properties of artificially compacted bentonite have also been investigated, specifically to design engineered barriers. Therefore, previous literature and recent findings on the fundamental behavior of compacted bentonite and its influence on the performance of engineered barriers are overviewed from an engineering perspective. The compaction of powdered bentonite and microstructure of compacted bentonite are first introduced. Second, the swelling characteristics and permeability of compacted bentonite are introduced, and microscopic and macroscopic viewpoints on each research subject are distinguished. Furthermore, the effects of chemical alteration under alkaline conditions on the hydro and mechanical properties of compacted bentonite are introduced as an example of a study on thermal-hydro-mechanical-chemical coupled phenomena. An outlook for the further development of the engineering appreciations of bentonite for radioactive waste disposal is provided.