Effect of neutron irradiation on microstructure of ODS cladding tube developed for fast reactor

Yamashita, Shinichiro   ; Yano, Yasuhide  ; Akasaka, Naoaki; Otsuka, Satoshi   ; Kaito, Takeji ; Inoue, Masaki 

Neutron irradiation behavior of 9Cr- and 12Cr-ODS steels cladding tubes developed for fast reactor was investigated to understand the effect of neutron irradiation on their microstructures. These ODS steels cladding tubes were irradiated at fuel-free condition and at 683 to around 1,100 K to fast neutron fluences ranging from 3.0 to 6.6 10 n/m (E0.1 MeV) in JOYO. Metallurgic examination and TEM observations revealed that the radiation-induced defect cluster formation was suppressed and that each matrix structure of 9Cr- and 12Cr-ODS steels possessed relatively high microstructural stability during irradiation at elevated temperature. These results attributed to a high density of defect sink site existed in each of their initial matrices and also to microstructural stabilization effect of thermally stable oxide dispersion, that is, the suppression effects of oxide on microstructural evolutions, such as dislocation recovery and grain growth, during irradiation.