Study on magnetic property change on neutron irradiated austenitic stainless steel

Nemoto, Yoshiyuki  ; Oishi, Makoto; Ito, Masayasu ; Kaji, Yoshiyuki  

Authors previously reported that Eddy current method and AC magnetization method have potential to be applied for development of diagnostic technics to detect the sign of material degradation before cracking on the austenitic stainless steels used as structural material in nuclear power plants. In typical austenitic stainless steels such as type304, magnetic ferrite phase would exist in the alloy before irradiation, and it is concerned to disturb the magnetic measurement on irradiated material. Magnetic measurements were conducted in this work on type304 austenitic stainless steel specimens irradiated up to different doses. In addition, microstructure observation was conducted on the area including grain boundary to discuss the correlation of magnetization on irradiated austenitic stainless alloy and grain boundary cracking. Obtained magnetic data on irradiated type304 stainless steel were seen clearly different from that on un-irradiated specimen, and showed positive correlation with radiation dose, therefore it was thought that magnetic measurement technics can be applied for the material which contains certain quantity of ferrite phase before irradiation. In the microstructural observation, magnetic phase (FeNi) formation along the grain boundary was revealed.