The effect of γ-ray irradiation on the corrosion of SS 41 carbon steel in high temperature water was studied. The average corrosion rate was measured after 48 or 96hr exposure to distilled water containing different DO (5-700ppb) at 250°C. The amount of Fe ions in the film and that dissolved in water were separately determined by weight measurement combined with a film dissolution technique. The composition of oxide films was determined by X-ray photo-electron spectroscopy (XPS) and X-ray diffraction. After 48hr the corrosion rate with γ-ray irradiation was larger than that without irradiation, whereas after 96hr no detectable difference was observed. By X-ray diffraction the bulk composition of the oxide film was found to be mainly magnetite. XPS showed that γ-ray irradiation forms unknown oxygen compounds, OX, other than O2- and OH-, and also graphite-like substance on the surface. The intensity of the carbon spectra was three to four times higher when γ-rays were irradiated. It is considered that the mechanism of corrosion under γ-ray irradiation is different from that without γ-ray. The corrosion rate and the surface composition showed no clear relationship with DO in the range examined in this work. It is interesting to note, however, that the average dissolution rate of Fe increases with the amount of OH- (without γ-rays) or OX (with γ-rays) on the oxide surface.
