Neutron dose rate effect on the SCC growth behavior in austenitic stainless steel

Kondo, Keietsu  ; Kaji, Yoshiyuki  ; Ugachi, Hirokazu ; Tsukada, Takashi 

For the safe operation of light water reactors (LWRs), the precise prediction methods for the radiation-induced degradation of core component materials, such as irradiation assisted stress corrosion cracking (IASCC) in austenitic stainless steels, are required. Such prediction methods are developed based on the data experimentally obtained by the accelerated irradiation tests in test reactors. It is, therefore, necessary to assess the neutron dose rate effect on the material degradation behavior for ensuring the validity of prediction methods. In this study, the crack growth test in BWR simulated water and the microstructural observation around SCC crack were performed on type 304 austenitic stainless steel after neutron-irradiation in JMTR with two different (low/high) dose rates. Results of crack growth test showed that irradiation dose rate have little influence on SCC growth rate. Furthermore, plastic strain levels around the crack in both low/high dose rate specimens had little difference. These results might lead to the conclusion that neutron dose rate has little influence on SCC crack behavior.