Neutronic Analysis and Performance Assessment of UF4-Based Gas Core Reactors with BeO Reflector

Gas core reactors (GCRs) are considered a key element in Generation IV nuclear systems, expected to surpass all existing and proposed fission technologies in sustainability, resistance to nuclear proliferation, and power conversion efficiency. In this study, the neutron multiplication factor, which is one of the most critical parameters in reactor operation, was found to vary between 0.962 and 1.005. The operation period of the study, governed by the effect of the neutron multiplication factor, was set to 730 days. In the neutronic calculations, the system power was 1000 MW, and the resulting power density at the end of the operation period was 4715 W/cm³. The gaseous core reactor (GCR) configuration utilized a uranium tetrafluoride (UF4)-based gaseous fuel surrounded by beryllium oxide (BeO) reflector and shielding regions. Neutronic analyses performed with the MCNPX code confirmed that BeO improved neutron economy and thermal stability, enhancing overall reactor performance. The cumulative fissile fuel enrichment (CFFE) increased gradually throughout the operation, indicating efficient conversion of fertile isotopes into fissile material. Furthermore, a noticeable accumulation of fission products was observed, reflecting the system’s sustained fission activity. Overall, the findings demonstrate that the GCR system maintained stable subcritical operation, efficient fuel utilization, and long-term neutronic balance, confirming its strong potential for future sustainable nuclear energy applications.