Evaluation of various calculational models of FA containing burnable absorber rod in the VVER-1000

Abstract The economic performance of a nuclear reactor is fundamentally linked to optimizing fuel efficiency, extending burn-up, and ensuring safe operational parameters. In this regard, this research explores the influence of lattice computational models on macroscopic cross-section generation for VVER-1000 Fuel Assemblies (FAs) containing Burnable Absorber Rods (BARs), focusing on their impact on neutronic parameters throughout the first operational cycle. The study addresses the spectral hardening effect of BARs, which causes distinct neutronic behaviors in fuel rods based on their proximity to the absorber. Three FA simulation arrangements are compared to assess the neutronic consequences of these proximity effects. Results highlight the increased plutonium isotope production and reduced uranium-235 consumption in fuel rods adjacent to BARs. A comparative study of key core parameters during the cycle, such as boron concentration and power peaks, is presented to demonstrate the effects of BAR modeling. The WIMD-D4 transport lattice code, with an updated library by the IAEA, and PARCS, which leverages advanced nodal kernel and CITATION finite difference codes for core calculation, are utilized in this research.