Dissolution of Iron Chromium Oxide Using Foam Decontaminating Agent

Radioactive corrosion oxides in pressurized light water reactors consist of an inner layer formed of crystals of Fe, Ni and Cr ions developed through the oxidation of a metal element at the interface between the oxide film and metal, and an outer layer formed through diffusion into the boundary between the coolant and oxide film through the pores of the oxide film and precipitated. Because the Cr³⁺ component present in the inner layer of the corrosion oxide film has insoluble characteristics, an oxidizing agent has to be added to oxidize into soluble Cr⁶⁺. The weight loss and SEM/EDX of the specimens was measured before and after decontamination, and the concentration of Fe and Cr ions in the solution after decontamination was analyzed using AA spectroscopy. The decontamination performance of a foam decontaminating agent mixed with a chemical decontaminating agent was investigated as a part of the development of a foam decontaminating agent. The following conclusions were obtained. At lower concentrations of 0.1M Ce (IV), the amounts of Fe and Cr dissolved increased by 25% and 67%, respectively, as the HNO₃ concentration was doubled, whereas the amounts of Fe and Cr dissolved were increased at higher concentrations of 0.5M Ce (IV) by 2.6- and 1.3-fold, respectively. It can be seen that the Ce (IV) concentration, rather than the nitric acid concentration, plays an important role in the dissolution behavior.