THE REACTIVITY OF BENTONITES - A REVIEW - AN APPLICATION TO CLAY BARRIER STABILITY FOR NUCLEAR WASTE STORAGE

The thermal stability of bentonites is of particular interest for cont ainment barriers in nuclear waste storage facilities. The kinetics of smectite reactions have been investigated under laboratory conditions for some time. The variables of time, chemical composition and tempera ture have been varied in these experiments. The results of such an ass essment are that there are about as many kinetic values deduced from e xperiments as there are experiments. Experiments using natural bentoni te to study the smectite-to-illite conversion have been interpreted as a progressive transformation of montmorillonite to illite. It is high ly probable that the initial reaction product is not illite but a high -charge beidellite + saponite + quartz mineral assemblage which gives, then, beidellite-mica interstratified mixed-layer minerals. These exp erimental reactions are noticeably different from those of diagenesis, being closer to reactions in hydrothermal systems.