NeuG4: Developing a Geant4-Based Monte Carlo Framework for Nuclear Reactor Analysis

We developed a Geant4 (Geometry and Tracking 4)–based Monte Carlo framework, NeuG4 (Neutronics with Geant4), primarily to calculate the k-eigenvalue for fissile materials of spherical geometry. Geant4 is a C++–based Monte Carlo simulation toolkit. Using Geant4, NeuG4 was programmed to determine the effective multiplication factor, neutron flux spectrum and distribution, depletion analysis, and Shannon entropy convergence test using continuous-energy cross sections provided by the Geant4 nuclear data library. Hypothetical uranium spheres with varying radii, enrichment levels, and criticality conditions were used to demonstrate the proposed approach. The performance of NeuG4 for criticality evaluations was compared with the neutron transport code OpenMC.