Validation of the neutron cross section processing code MGGC3.0 via JOYO-70 reactor physics experiments

Fast neutron reactor is a critical design within the Generation IV nuclear reactor systems. In this study, a high-precision neutron cross-section processing code named MGGC3.0 was developed. It directly applies HFG (hyperfine group:∼400000) cross-section data for resonance calculations and utilizes problem-dependent HFG neutron energy spectrum for energy group merging to produce the UFG (ultrafine group:∼2000) cross-section to take into account the complicated resonance self-shielding effect between isotopes. The computation of UFG elastic scattering matrix is expedited through prefabricated scattering function method. For the production of few-group cross section, MGGC3.0 conduct critical buckling searches and employs a two-region approximation for fuel and non-fuel assemblies, respectively. This process calculates the neutron energy spectrum for energy group merging to obtain the few-group cross section. Initially, verification was conducted using three fuel assemblies: MOX, UO2, and U-TRU-Zr. This involved comparing the UFG macroscopic cross-sections produced by MGGC3.0 with those obtained from OpenMC calculations. Subsequently, the code underwent verification using a series of fast reactor benchmarks in ICSBEP. This entailed comparing the eigenvalues computed based on cross sections produced by MGGC3.0 with those calculated by RMC. Lastly, validation of the code was conducted using the JOYO MK-I series zero-power experimental setup. This involved comparing the calculated and experimental values of control rod worth, sodium void reactivity, and fuel replacement reactivity. The computational results of the verification and validation processes indicate that the neutron cross sections produced by the MGCC3.0 code exhibit high accuracy, thereby furnishing precise cross-sectional data for fast reactor.