Corrosion mechanism of iron-based materials adsorption Cl in high level radioactive waste packaging containers

Abstract

BackgroundThe packaging container is critical to the safe disposal of high-level radioactive waste. The study of Cl adsorption and corrosion behavior of iron-based materials is of guiding significance for the selection of packaging materials for high-level radioactive waste.PurposeThis study aims to clarify the effect of Cl adsorption on the corrosion of iron-based materials in radiation environment.MethodsBased on the first principle of density functional theory, the separation and co-adsorption models of Cl on Fe(100) surface were constructed. Parameters, such as ariations of adsorption energy, Fe-Cl bond length and electronic structure, etc., in the process of Cl adsorption were studied by using Medea-VASP code. Effects of water radiation decomposition products (O, H and OH free radicals) on the stability of Cl adsorption were analyzed emphatically.ResultsThe calculation results show that the length of Fe-Cl bond is shortened by the absence of surface atoms and the existence of free radicals. In the four co-adsorption systems, the adsorption energies of Fe/(Cl-H2O), Fe/(Cl-H), Fe/(Cl-OH) and Fe/(Cl-O) decrease successively, while the charge transfer number of Bader increase successively.ConclusionsAdsorption of Cl on the defect Fe surface is more stable in the radiation environment, and the radiation decomposition products of H2O promote the adsorption of Cl on the defect Fe(100) surface, revealing the microscopic mechanism of corrosion of iron-based materials in the radiation-chlorine-containing groundwater coupling environment.

Keywords

• hlw-packaging container
• radiation decomposition
• defect iron surface
• cl adsorption
• first principles