Radionuclide mobility in natural porous media: a contribution to reactive transport

The study of radionuclide mobility in natural porous media includes the modeling of reactive transport, which has been the common thread running through my research and development activities at the Commissariat a l'Energie Atomique et aux Energies Alternatives since 2003. This manuscript describes my research approach and my scientific contributions in this field. By means of an experimental approach, this manuscript retraces my activities concerning the choice and validation of transport equations in saturated and unsaturated porous media (chapter 0), including the development of the BEETI device; the consideration of the chemical reactivity of radionuclides in natural porous media, specifically their adsorption process on clay minerals, with a critique of the associated modeling (chapter 3); modelling the transport coupled with the chemical reactivity of trace elements (chapter 4) applied to soils and sedimentary rock. A fourth section (chapter 5) highlights the implications of soil physico-chemical characteristics for simulating the behavior of radioelements in post-accident situations, and for the development of remediation processes such as particle flotation and phyto-remediation. Finally, Chapter 6 gives a succinct presentation of the work in progress and the prospects opened up by our reflections on the data and model gaps identified, with the direction envisaged for the coming years and new fields of application. (author)