Long-term alteration of bentonite; For safety evaluation of deep geological disposal

Tanaka, Tadao ; Sakamoto, Yoshifumi; Yamaguchi, Tetsuji ; Takazawa, Mayumi; Akai, Masanobu; Negishi, Kumi; Iida, Yoshihisa ; Nakayama, Shinichi 

Highly alkaline environments induced by cementitious materials in radioactive waste repositories are likely to dissolve and to alter montmorillonite, the main constituent of bentonite buffer materials. For the prediction of the long-term variations in permeability of compacted sand-bentonite mixtures, long-term alteration of bentonite should be quantified based on information accumulated by using the compacted or powdered bentonite materials, with batch experiments or column experiments. In this study, we summarize distinctive information obtained from various experimental systems, and propose functional and effective integration of experimental approaches to prediction of bentonite alteration.