Irradiation effects of ADS target window materials on corrosion in liquid metal

Okubo, Nariaki   ; Fujimura, Yuki; Kitamura, Akane; Okuno, Yasuki

Japan atomic energy agency has been conducting research activities for developing the accelerator driven system (ADS), which is expected to reduce and transmute radioactive wastes involved in spent fuels by nuclear power plants. The ADS adopts a liquid metal of lead-bismuth eutectic (LBE) as a coolant and also spallation target to produce high energy neutrons. In this study, effect of irradiation on corrosion behavior was evaluated for 316L stainless steel and T91 ferritic martensitic steel, which are candidate materials of ADS target window, through the immersion test under LBE with saturated and low oxygen concentration followed by ion irradiation experiment. In the case of soaking in LBE with saturated oxygen concentration for SS316L steels at 450C, 330 hrs, non-irradiated region did not show clear oxide layer, however, irradiated region showed bi-layers of magnetite and spinel type oxides. The formation rate of oxide layer for irradiated region, 26 m/year, was about twice faster than that of non-irradiated region, 12 m/year. This result suggests that diffusion behavior after irradiation and mass transfer in the interface between LBE and steel surface is important for understanding of irradiation effect on liquid metal corrosion.