New considerations on the kinetics of mass transfer in sodium fast reactors: An attempt to consider irradiation effects and low temperature corrosion

Mass transfer in sodium fast reactors (SFRs) has been extensively studied in the past years, but no consideration on the effect of irradiation on this phenomenon was included in the corrosion equations. Moreover, some discrepancies exist on the mass loss rates obtained at low temperatures and low oxygen content. In this paper, new equations for mass loss are proposed from literature examination, separating the loss by preferential leaching (alloy element dissolution) from general corrosion, and integrating the effect of the diffusion enhancement by irradiation. The effect of irradiation is considered by estimating the diffusion coefficient enhancement due to point defect creation. It is found that the mass losses could be one order of magnitude higher than the values given by several mass transfer models. Depending on the choice of kinetic parameters, the irradiation can account at the most for 70% of the increase. This approach shows that mass transfer codes should take into account elements that were formerly neglected: low temperature corrosion (with correct contributions of preferential leaching and general corrosion), irradiation and saturation.