On a fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel

Osaka, Masahiko  ; Takano, Sho*; Yamane, Yoshihiro*; Misawa, Tsuyoshi*

Concept of fast reactor cycle scheme that incorporates a thoria-based minor actinide-containing cermet fuel is given. The present cermet fuel consists of oxide solid solution of Th and minor actinides and Mo inert matrix. It has been proposed as a high-performance device that can enhance minor actinide transmutation in the fast reactor cycle. It is used in an independent small cycle, whereby dedicated cycle process are adopted. Two-steps process for reprocessing of the present cermet fuel was proposed; it consists of pre-removal of Mo-inert matrix and actinide recovery. A preliminary test for pre-removal of Mo-inert matrix using surrogate cermet fuel was carried out. It was done by dissolution in nitric acid at room temperature. Results showed that Mo-inert matrix was largely dissolved, while oxide remained. Burnup characteristics of a fast reactor core loaded with the cermet fuel were investigated by using neutronic calculation codes. It was revealed that a heterogeneous composition of Mo-inert matrix in inner and outer cores could lead to effective transmutation and flattened power density. It was concluded that the present cermet fuel is potentially a promising one as a high-performance transmutation device for the fast reactor.