A novel approach for managing the excess reactivity at the beginning of the fuel cycle of VVER-1200

Abstract

This work discusses various fuel pellet designs loaded with different types and concentrations of burnable absorbers to suppress the excess reactivity at the early stage of the fuel life in the VVER-1200 fuel assembly. MCNPX, V. 2.7 with the CINDER 90 fuel depletion code was utilized to analyze the neutronic characteristics of the proposed cases. Concentric shells (CS) of integral burnable absorbers are investigated in the fuel tube. Gadolinium and Erbium at different concentrations are investigated in the CS at different operation cycles to manage the excess reactivity. Gadolinium and boron as traditional burnable absorbers (BAs) are investigated in the standard fuel assembly to compare their results with the suggested cases. The infinity multiplication factor (kinf), the concentrations of the fuel composition, reactor-grade plutonium (rgPu), minor actinides (MAs) and some important fission products poisoned were studied with burnup. The radial power and thermal neutron flux distribution through one-six of the VVER-1200 assembly have been analyzed to distinguish the optimum BA and design for flattening the power profile. The neutronic analysis indicates that using Er2O3 in a concentric shell of a fuel pellet is an interesting method for reactivity management.