A novel approach to estimate the power peaking factors in a complex geometry iPWR inspired by CAREM 25 using GEANT4 toolkit

CAREM 25 is considered one of the early versions of Small Modular Reactors (SMRs) worldwide. Despite efforts to simulate CAREM using black box Monte-Carlo codes, this paper is the first to simulate CAREM 25 or any other core reactor with full complex geometries using open-source software, such as GEANT4. Recent studies have demonstrated that GEANT4 can effectively analyze neutron transport in nuclear physics and engineering. This study aimed to illustrate the potential of GEANT4 in evaluating power peaking factors (PPFs) in the CAREM reactor compared to previous studies. We calculated the power peaking factors (PPFs) of the fuel assemblies and fuel rods using the UserAction classes and the built-in ROOT toolkit in GEANT4. The results showed a flattening of the power distribution, which ensures less disparity between regions with the highest power density (the central fuel assembly with a PPF of 1.502) and other fuel assemblies. This promotes stable reactor behavior while maintaining safety margins. We calculated the detailed PPFs of the 108 fuel rods in both the hottest assembly and the average assembly (with a PPF of 1.005), revealing a flattened power distribution across the fuel assemblies. While direct validation against MCNPX was not achievable due to variations in conditions, our investigation identified consistent trends in the PPFs of both GEANT4 and MCNPX, suggesting similar behavior across the fuel assemblies. This research takes an important step in employing open-source codes like GEANT4 in reactor physics with complex core geometries, with further investigations needed to enhance its effectiveness and alignment with other Monte Carlo codes.