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on 7/18/25 at 2:07 PM
Argillaceous (i.e. clay-rich) media are being considered in many Nuclear Energy Agency (NEA) member countries as potential host rocks for the long-term, safe, near-surface or at-depth disposal of radioactive waste, as well as serving as major constituents in repository systems into which waste will be placed.
The pore space of clays and shales is dominated by apertures in the range of nanometres, which leads to large mineral-surface areas. Because clay-mineral surfaces are negatively charged, electrostatic interactions with dissolved ions and polar water molecules lead to physico-chemical properties of pore water close to clay surfaces ("bound water") that differ from those of bulk (or "free") water. These microscopic features govern many processes that are observed in clays and shales on a macroscopic scale.
In this report, the focus is on the characterisation of pore-space architecture and on the interaction of pore water molecules with the immediate vicinity of clay surfaces. First, methods and approaches addressing these objectives were reviewed and appraised. On the basis of a literature review pertinent to potentially useful methods, an experimental programme was performed, applying some of the most promising approaches.
In total, 12 samples were obtained from the Clay Club membership, from formations that are studied as potential host rocks for radioactive waste disposal, or from underground research laboratories in clay-rich media.
