Assembly design of a fluoride salt-cooled high temperature commercial-scale reactor: Neutronics evaluation and parametric analysis

•A novel assembly neutronics design for the fluoride salt-cooled high temperature commercial scale power reactor is proposed.•The hexagonal assembly design reduces the radioactive graphite waste by employing an innovative refueling strategy which only removes the central cylindrical fueled region, whereas the remaining outer graphite region in the assembly is kept in the core.•The assembly design can achieve the cycle length of 3.55 years (160.6 MWd/kgU) and is proven to be safe with negative reactivity coefficients. In this study, a novel assembly design is proposed for a fluoride salt-cooled high-temperature commercial-scale (FHCR) reactor. It employs tristructural isotropic (TRISO) fuel particles nestled within removable cylindrical beryllium carbide (Be2C) moderator blocks, which are further contained within prismatic graphite blocks. As the name implies, the FHCR is a preconception of a 3400 MW(t) commercial power reactor that uses FLiBe (LiF-BeF2) as the primary coolant of choice. This paper uses the SERPENT 2 code to conduct a parametric neutronics study on the two-dimensional lattice assembly design of the FHCR. The calculations examine the effects of various fuel enrichment levels, TRISO particle packing fractions, fuel compacts’ pitch sizes, and moderating materials on the cycle length, while also determining the neutron spectrum and various nuclide inventories. Finally, a preliminary core is modeled based on the study conducted on the assembly design. Based on the negative values of the fuel temperature coefficients (FTC), moderator temperature coefficients (MTC), and coolant temperature coefficients (CTC) obtained, the design is determined to be safe. This new assembly design is also able to achieve keff>1 for approximately 3.55 years, translating to a burn-up of 160.6 MWd/KgU.