Stability of nano-particles in ODS steel cladding for fast reactor irradiated to about 240 dpa

Oka, Hiroshi   ; Tanno, Takashi  ; Yano, Yasuhide  ; Tachi, Yoshiaki  ; Otsuka, Satoshi   ; Kaito, Takeji 

9Cr-ODS steel was irradiated to approximately 240 dpa at 700 C by using an ion irradiation where the irradiation condition is close to that of a commercial fast reactor cladding tube. Microstructural observation was performed on the nano-sized particles, which is the main factors of the excellent high-temperature strength of 9Cr-ODS steel. The observation revealed that the nano-sized articles of about 5 nm were uniformly dispersed with high density even after irradiation up to 240 dpa. Furthermore, no void formation was observed. Thus, it was concluded that the nano-sized articles of 9Cr-ODS steel exist stably under a high-dose irradiation condition at a practical level at 700 C.