Application of Ferrite Film Formation Process to BWR Plants

Abstract

The formation process of a ferrite oxide film, which can effectively suppress radioactive nuclide deposition on piping surfaces of BWR reactor water recirculation system, was evaluated from the viewpoints of scale-up from a 1 liter flask scale to a 10 m³ plant scale. To get a thin and closely packed oxide film, the pH and oxidation-reduction potential values should be maintained within the magnetite stability domain in the Pourbaix diagram of the iron-water system by controlling the hydrazine concentration. The selected film forming conditions were confirmed using the flow system apparatuses of 1/500 and 1/10 actual plant scales. This film formation process could be evaluated taking into consideration the charge balance and chemical equilibrium equations of each reaction involved in the film formation. The method was applied to an actual plant just after the chemical decontamination.