Interaction of Hydrogen Peroxide With Carbon Steel and Magnetite

Hydrogen peroxide is considered as one of the main oxidants formed due to the radiolysis of water. In a spent nuclear fuel repository, it is necessary to establish the interaction of hydrogen peroxide with the elements constituting the repository. The objective of this work is to study the consumption of hydrogen peroxide via reaction with the elements of the canister. In this sense, two different series of experiments were conducted, with iron steel an magnetite, respectively. Each series consisted on three different experiments that contained a coupon of the solid and different hydrogen peroxide concentrations (10 −4 moldm −3 , 10 −5 moldm −3 and 10 −6 mol dm −3 ). Hydrogen concentration in solution was measured at different intervals of time by means of chemiluminescence. At the end of the experiments, the coupons were studied by X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) in order to determine the possible secondary solid phases formed on the coupons. In both series of experiments, a decrease of the hydrogen peroxide concentration in solution with time was observed. The determined consumption rates increased with hydrogen peroxide concentration and were higher in steel than in magnetite. The reaction orders relative to hydrogen peroxide concentration were very close to the unity on both solids. The study of the carbon steel coupons by SEM at the end of the experiments showed that they were more attacked at higher hydrogen peroxide concentrations. On the other hand, the XRD measurements in the steel coupons showed that lepidocrocite (γ-FeO(OH)), and magnetite (Fe 3 O 4 ) were formed on the coupon as iron secondary solid phases.