Abstract: The argon space and related structural components of the spent subassembly transfer pot of the China Demonstration Fast Reactor (CFR600) was investigated by computational fluid dynamics program STAR CCM+, and the thermal design of the concrete was verified at normal conditions or accident conditions. The research results show that the maximum temperature of concrete under normal condition meets the design limit requirements, but the temperature distribution of concrete is not uniform in the circumferential direction, and the temperature distribution become non uniformly highly at accident conditions. The radiation heat transfer and convection heat transfer together affect the components of the equipment, in which the radiation heat transfer plays a major role. The emissivity of sodium surface is the main determinant of radiation heat transfer. The results provide technical preparation for operation and safety analysis of spent subassembly transfer pot.