Changes of the surface of SUS316L immersed in high-temperature water caused by -ray irradiation

Nakahara, Yukio ; Yamamoto, Masahiro ; Ishijima, Yasuhiro ; Kato, Chiaki   

500-hour experiments have been done in order to study the effects of -ray irradiation (the absorption rate 30 kGy/h) on the corrosion of 316L stainless steel immersed in high-temperature (288 C) water. Difference between -ray irradiated and non-irradiated specimen surfaces were discussed with the results of surface analyses after the experiments. TEM cross sections of the surfaces of specimens solely immersed in the water show that -ray irradiation made surface oxide film thicker and the formation of oxide grains on the surface more apparent. The change of corrosive environment caused by the irradiation enhanced the precipitation of oxide on the surface. Surface analysis of crevice-simulating specimens was also done by laser Raman spectroscopy. No definite peak was seen in the spectrum of non-irradiated condition. The peaks of compound oxide of Fe, Ni, and Cr were seen in the spectrum of -ray irradiated condition. These results should indicate that the change of corrosive environment inside the crevice caused by the irradiation promoted the corrosion.