[en] The ANDRA has just completed its feasibility study of an HLLL disposal facility concept implanted in the middle of the roughly 130 m thick Callovo-Oxfordian formation in a several hundred km² zone located at the eastern edge of the Paris basin. For study purposes, the facility was hypothesized to be located at the same depth (∼ 500 m) and position as ANDRA's URL at Bure (Meuse/Haute-Marne). An essential part of the performance assessment of the proposed concept is proper modeling of radionuclide migration in the pore-water contained in the porosity of the engineered barrier (EB) materials (compacted bentonite, concrete), the clay-rock constituting the geological barrier system and the over and underlying water-bearing geological formations (Oxfordian, Dogger). In order to accurately predict migration of a given radionuclide in each of these materials it is essential to have well founded conceptual models for (i) its solubility and dissolved speciation for the prevailing local physical-chemical conditions, (ii) its solid-solution partitioning by sorption on material surfaces and (iii) dominating transport phenomena (diffusion, convection..). The conceptual models for each of these processes in each material were established based on the results of studies carried out over the last decade, generally by a process of identification and mathematical formulation of the predominant physical-chemical processes, followed by measurement or estimation of representative values and associated uncertainties for the corresponding parameters, for the range of conditions expected for the material under repository conditions. The essential features of the main migration models called upon for the Normal Evolution Scenario (NES) performance assessment are briefly reviewed here