Factors Affecting Microbial Activity in Compacted Clay-Based Sealing Materials Proposed for Use in a Deep Geologic Repository for Used Nuclear Fuel

Abstract

Microbial activity in clay-based barriers immediately adjacent to metal used-fuel containers in a repository could affect the longevity of such containers. The current emphasis is, therefore, on reducing or minimizing microbial activity in such clay-based barriers through material composition design. Factors affecting microbial activity in clay-based materials were studied in large-scale and smaller-scale experiments. Results suggested that keeping water activity (aw) values below ∼0.95 may minimize microbial activity in clay-based barrier materials. A considerably higher effective montmorillonite dry density (EMDD), which partially controls a w, is achievable for 100% bentonite than for previously proposed reference buffer materials, which contain only 50% bentonite.