Fuel Selection of Long Life Small Natural Circulation Lead-based Fast Reactor

Aiming at design goals for long life, miniaturization and natural circulation of lead-based fast reactors, a lead-based fast reactor core model was constructed and fuel selection was carried out. U-Pu and Th-U cycle fuels, oxides, nitrides, carbides and metal fuels were selected to be researched, and the physical parameters of different fuels, the physical characteristics of cores under different energy spectra were analyzed and compared. The results show that in the soft energy spectrum, Th-based fuel core has the larger breeding ratio, and the larger negative reactivity coefficient, the larger thermal safety margin and the stronger fission product retention capacity. PuN-ThN fuel core has the best burnup characteristics, can obtain the higher breeding ratio under loose grid conditions, reduce fuel load, ensure inherent safety, and meet the design requirements of long core life, miniaturization and natural circulation; however, the effective delayed neutron fraction of the core is small, which is not conducive to reactivity control.