Super homogenization method applied in diffusion calculation for pebble-bed fluoride-salt-cooled high-temperature reac

Abstract Background: The control rods of pebble-bed fluoride-salt-cooled high-temperature reactor (PB-FHR) are located in the side reflector. Neutron diffusion calculation in those control rods has difficulties of no fission source in the control rod region and strong effect from the core leakage spectrum. Purpose: This study aims to apply super homogenization (SPH) method in diffusion calculation for PB-FHR. Methods: SPH method is applied in the diffusion calculation for the strong absorber in control rod region located in the reflector area of the PB-FHR, through which the local area of control region is homogenized. The spectra of different places of the reactor core except the control rod region are calculated to modify its cross sections. SPH factors calculation is accomplished by an iteration procedure between SPH and spectra modification (SM). Results: Reactivity worth of the control rod and neutron flux distribution are calculated accurately. Conclusion: Compared with the fine mesh transport reference solution, the verification results demonstrates that the method proposed can accurately model the control rod including the reactivity worth and flux distribution, and it is more suitable for the situation with interference effect between different control rods compared with regular SPH method. (authors)