Development of non-destructive inspection method to predict degradation on internal structural materials in super critical water reactor

Nemoto, Yoshiyuki  

Authors previously reported the leakage magnetic flux density measured by flux gate (FG) sensor depended on the irradiation assisted stress corrosion cracking (IASCC) susceptibility of neutron irradiated austenitic stainless steels. The present study aimed to evaluate a possibility to develop diagnostic method to detect symptom of IASCC by more practical methods such as the eddy current method and AC magnetization method. Magnetic properties of neutron irradiated specimens and mockup specimens were measured and the dependence on IASCC susceptibility was revealed. Microstructure observation using a transmission electron microscope (TEM) was conducted to study the magnetic phase formation by radiation induced segregation (RIS). It was shown that the measurement of magnetic signal changed by magnetic phase formation along grain boundaries caused by radiation induced segregation (RIS) would be a mechanism of the diagnostic method to detect symptom of IASCC.