Design of fuel assembly for molten-salt-cooled reactors

Abstract Background: Molten salt reactor(MSR), a fourth generation reactor, possesses good economy and inherent safety properties. By using the fuel assembly in molten-salt-cooled reactor, it is expected that the fuel load and release can be easier and reliable, which is similar to that widely used in LWR(Light Water Reactor). Purpose: Based on spherical TRISO(Tristructural Isotropic) coated particle fuel elements, this study aims to design a fuel assembly model for the high-temperature molten-salt-cooled reactor. Methods: The MCNP(A Monte Carlo N-Particle Transport Code) is employed to investigate the feasibility and behavior of the fuel assembly by analyzing the infinite multiplication factor K_inf, the reactivity temperature coefficient(RTC) and the void reactivity(VR) of the FLiBe coolant as a function of the composition, density and wall thickness of the assembly material, the TRISO coated particles packing factor and the enrichment of ⁷Li in FLiBe salt. Results and Conclusion: The results show that carbon-based materials are significantly better than silicon-carbide-based materials for fuel assembly. Increasing the TRISO packing factor and enrichment of ⁷Li helps to improve neutron economy and security properties of the reactor. (authors)