The objective of this article is to provide a better understanding on the transport of radioelements through a porous medium (cementitious material). We focus on electrokinetic methods where an external current and a lixiviant solution accelerate the transport of the radionuclides from the porous medium to the exterior. This work sheds light on the interactions between the porous medium and the radionuclide of interest. A numerical model is developed in order to describe the concentration profiles inside the porous medium during a decontamination test, and to predict the decontamination rate of the sample. The final objective of this work is to assist the development of industrial processes of decontamination.

This paper describes a transport model for the nuclear decontamination of cementitious materials by electromigration. The porous medium is assumed to be saturated and reactive with the radioelement of interest, cesium. The transport of ions is described by a Nernst–Planck equation, in the framework of a multi-species approach to the problem. The overall electrical field accounts for the electrical field applied externally, and for the membrane potential. Two extreme cases are detailed: irreversible cesium binding, and reversible cesium sorption. It is shown that cesium interactions with the solid phase have a strong effect on the decontamination rate. In addition, the influence of the initial cesium content in the pore solution and the relevance of accounting for the membrane potential in the transport equations, are discussed.

A numerical model was developed in order to describe the electromigration of radioelements through contaminated concrete. The transport of several ionic species across a saturated sample of material, is described by the Nernst-Planck relation. The multi species approach provides a better understanding of the phenomena involved: it stresses the need to know, as precisely as possible, the material characteristics and the history of the contamination. The approach also sheds lights on the way the radionuclide (cesium 137) is carried away from a concrete sample during a decontamination simulation.