Molten Salt Fast Reactors (MSFRs) have been the subject of periodic investigations since the early 1960s. MSFRs can be employed to extend fissile resource availability through uranium-plutonium and thorium-uranium breeding, and are highly flexible to be configured into modified open or full-recycle configuration. A single reactor core design may be capable of performing both fissile resource extension and waste disposition missions. The safety aspects of MSFRs are also innovative. So, in order to use the natural resources more efficiently while offering options for a better management of the nuclear waste, there is currently a renewed interest in MSFRs. In France, a conceptual design of reference MSFR with a fast neutron spectrum and based on the Thorium fuel cycle has been proposed.
For improving and optimizing the design of the MSFR, in the present research, several different fluorides salts are chosen as fuel carrier salts to be evaluated. The evaluation scheme is based on the Scale5.1 code system. And the impact of different carrier salts on neutron spectrum and temperature reactivity coefficient has been evaluated in detail. The results indicate that the LiF-NaF-ThF4-UF4 (47.40-30.10-19.95-2.55) composition may be best in all recommended compositions. A significant amount of design work remains to be performed to develop a workable MSFR system, this work can provide a reference for choosing suitable fuel carrier salts in the design process of the MSFR in the future.