An improved analysis of the OECD/NRC PWR MOX/UO₂ core transient benchmark with PARCS/Serpent

This paper presents an improved analysis of the OECD/NRC PWR MOX/UO₂ core transient benchmark using the two-step method combining the Monte Carlo code Serpent 2 and nodal kinetics code PARCS. Analyses of the following important factors that can affect the PARCS/Serpent calculations were performed: diffusion coefficients attained with the B₁ leakage corrected out-scatter approximation and cumulative migration method (CMM), reflector cross-sections generated with 1D and 3D reflector models, thermal cut-offs for two-group structure (0.625 eV, 1.3 eV, 2.02 eV and 4.0 eV), and nuclear data libraries (ENDF/B-VI.8, ENDF/B-VII.1 and ENDF/B-VIII.0). The results showed that using the CMM method and 3D reflector model alongside the 0.625 eV cut-off is the best choice while using the 4.0 eV cut-off or ENDF/B-VIII.0 library leads to the most conservative transient results. Thus, it is highly recommended that the two-step approach with PARCS/Serpent proposed be applied to improve further transient calculations of PWR MOX/UO₂ cores.