Effect of Oxide Film Formed During Gamma-ray Irradiation on Pitting Corrosion of Fuel Cladding in Water Containing Sea Salt

摘要

In Fukushima Daiichi Nuclear Power Station (1F), seawater was injected into spent fuel pools in March 2011. Zircaloy-2 is adopted for the fuel cladding at 1F. Zirconium alloys including Zircaloy-2 are susceptible to pitting corrosion in oxidizing chloride solutions. In this study, we investigated the effect of oxide film formed during gamma-ray irradiation on pitting corrosion of fuel cladding in water containing sea salt. The pitting potentials of Zircaloy-2 were measured using the water containing artificial sea salt. Changes in the composition of water containing sea salt were analyzed before and after gamma-ray irradiation. The characteristics of the oxide films formed on Zircaloy-2 were evaluated by X-ray photoelectron spectroscopy. Solution analyses for water containing sea salt showed that hydrogen peroxide was generated by the irradiation. The pitting potential of Ziracloy-2 with oxide film formed under gamma-ray irradiation was higher than that with oxide film formed without irradiation. X-ray photoelectron spectroscopy indicated that the oxide film was composed of zirconium oxide and the growth of oxide film was enhanced during the irradiation. It could thus be explained that the enhanced growth of oxide film under gamma-ray irradiation caused the higher pitting potential.