Comparison of Hexagonal and Square Fuel Pin Arrangement with UN-PuN Fuel in PWR

Indonesia is experiencing an increasing demand for electrical energy, which can be met through alternative sources such as nuclear energy generated in nuclear reactors at Nuclear Power Plants (NPPs). Small Modular Reactors (SMRs) can be implemented in Pressurized Water Reactors (PWRs). The fuel can be arranged in hexagonal or square pin configurations in such reactors, each potentially influencing the reactor’s neutronic performance. This research aims to determine the multiplication factor (keff) and excess reactivity, as well as the characteristics of neutron flux, fission rate, and minor actinide production resulting from using hexagonal and square fuel pin arrangements. This research was conducted by performing a neutronic analysis on the 300 MWth PWR using UN-PuN fuel with a comparison between the two fuel pin configurations. Neutronic calculations were carried out using OpenMC code based on the Monte Carlo method with the ENDF/B-VIII.0 library. The results indicate that different fuel pin arrangements yield distinct neutronic characteristics. The hexagonal fuel pin arrangement results in lower keff and excess reactivity values while exhibiting higher neutron flux, fission rate, and minor actinide concentrations compared to the square fuel pin arrangement.Keywords: Fuel Pin Arrangements, OpenMC, PWR, UN-PuN