Host rock heterogeneities may represent a source of uncertainty for the long-term safety of the deep geological disposal of high-level radioactive waste (HLW) in argillaceous formations if they are not captured adequately and at the relevant scale in the derivation of transport parameters. The DR-D experiment contributes to assessing the extent to which rock heterogeneity affects radionuclide diffusion at the meter scale (i.e., around a 1 m diffusion interval). This study focuses on the sandy facies of Opalinus Clay (SF-OPA) from the Mont Terri rock laboratory (Switzerland), which exhibits a significantly higher degree of heterogeneity compared to the more commonly investigated shaly facies. In that respect, SF-OPA offers insight into heterogeneous argillaceous formations that might be encountered in different national contexts for instance in Germany or Belgium, where a range of clay formations are being considered. The closely related DR-C experiment addresses the impact of a temperature gradient on radionu-clide diffusion via two diffusion experiments conducted at ambient temperature and at 80 °C. While this paper provides an overview of laboratory and in-situ activities supporting both DR-D and DR-C, the focus is placed on DR-D, as DR-C is described in a separate contribution (Pochet et al. 2026).
Ratnayake et al. (Thu,) studied this question.
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