Effects of -ray irradiation and crevice-like shape on the corrosion of type 316L stainless steel in high-temperature water

Nakahara, Yukio ; Kato, Chiaki   ; Yamamoto, Masahiro ; Watanabe, Atsushi*; Fuse, Motomasa*

The irradiation effect to high-temperature water in nuclear power plant has been regarded as one of important issues for preventing corrosion and stress corrosion cracking of plant materials. However, the effects of surface reaction and configurations of material on irradiated high-temperature water chemistry have been studied little because of the difficulty of measuring the environment. In this work, we have done a series of corrosion tests of Type 316L stainless steel in high-temperature water in order to estimate the effects of -ray irradiation and crevice-like shape on the water chemistry. Test specimens immersed in high-temperature water of 288 C were -ray irradiated for 500 hours. The absorbed dose rate of -ray irradiation was estimated to be 30 kGy h. The dimensions of the disk-like specimens were 16 mm in diameter by 0.5 mm in thickness. The surfaces of the specimens were mechanically finished with #800 emery paper. Sets of two specimens attached closely in order to simulate a crevice-like environment were also immersed. The surfaces of the specimens were analyzed using SEM, TEM, and laser Raman spectrometer. The results of surface analyses indicated that -ray irradiation enhanced the precipitation of iron oxide on the surface and the thickness of inner oxide layer became thicker by -ray irradiation. -ray irradiation also changed the morphology of oxide on the surface faced to the crevice-like environment.