Calculation and experimental analysis of BN-800 neutron-physical characteristics during the transition to mixed oxide fuel loading

The BN-800 reactor with a hybrid core has been in commercial operation in Russia since 2016. During the initial period, the layout of the hybrid core was constantly changed, including variations in the ratios of fuel assemblies with uranium and mixed oxide fuel, as well as the number of fuel assemblies in medium and high enrichment zones. In 2021, the transition of the BN-800 core to full mixed oxide fuel loading began. The transition was carried out in stages: during the reloading period, fuel assemblies with mixed oxide fuel (one third of the total amount of fuel assemblies in the core) was loaded into the core. In 2022, the reactor was brought to its minimum controlled power level at full mixed oxide fuel loading. During BN-800 operation, a large amount of experimental data on the main neutron-physical characteristics of the core has been accumulated. The adequacy of the computational prediction of the BN-800 neutron-physical characteristics was confirmed by comparing the neutron-physical values. The experimental results were evaluated using a set of critical BFS assemblies for modeling the reactor core. A comparative analysis of calculated values between the neutron-physical characteristics, which were obtained by various calculation codes within the framework of a reactor operation support, and the experimental data, was carried out.