Effects of γ-radiation on Steel Corrosion

Abstract

An important factor influencing the aging of nuclear reactor coolant piping and the transport of activation products in the piping is the chemical effects of ionizing radiation on steel corrosion. In the presence of ionizing radiation (e.g., gamma radiation), water decomposes into both oxidizing and reducing species (e.g., •OH, H₂O₂, O₂⁻) whose net interactions with steels are not fully understood. The effect of radiation on the corrosion kinetics of carbon steel was studied by following the corrosion potential, ECORR, of a carbon steel electrode during its exposure to γ-radiation. The changes in the surface film composition and morphology due to radiation were studied using Electrochemical Impedance Spectroscopy (EIS). The gas and aqueous samples were analyzed for H₂, O₂, and H₂O₂ using a GC-MS/TCD (Gas Chromatography-Mass Spectrometer/Thermal Conductivity Detector) and UV-visible spectrophotometer, respectively. The results of the radiation study were then compared with those obtained with carbon steel exposed to H₂O₂ under non-irradiation conditions. The comparison indicates that the main influence of gamma radiation on carbon steel corrosion is via the radiolytic production of H₂O₂ in the aqueous phase.