Migration of radionuclides in the geosphere: What can we learn from natural analogues?

Natural analogues give unique qualitative and, in some cases, quantitative information on the migration processes of radionuclides through the geosphere. In this review paper, we show in particular that they help tackle important issues concerning fluid flow paths, water-rocks interactions, chemical forms of radionuclides, processes of elemental retardation, major geochemical parameters and model validation, in varied geological formations. (orig.)