Monte Carlo evaluation of gamma and neutron shielding performance of rare-earth hexaborides and advanced concrete materials

Advanced radiation shielding materials are essential for improving safety and structural efficiency in next generation nuclear power plants. In this study, the gamma ray and neutron shielding performances of selected rare earth hexaborides, including GdB₆, NdB₆, SmB₆, LaB₆, and CeB₆, together with advanced concrete materials, were investigated using MCNP6.2 Monte Carlo simulations. Monoenergetic gamma photons with an energy of 0.662 MeV and neutrons with an energy of 0.1 MeV were used to represent typical reactor related radiation fields. Linear attenuation coefficients for photons and total macroscopic cross sections for neutrons were evaluated as functions of material thickness and compared with conventional shielding materials such as ORNL, Missouri, magnetite and steel, and Luminite Portland Colemanite Baryte concretes. The results indicate that GdB₆ exhibits superior gamma and neutron attenuation performance among the investigated hexaborides, primarily due to the high neutron absorption capability of gadolinium. Advanced concretes, particularly MO and LPCB, also demonstrate improved neutron shielding compared to ordinary concrete. Energy dependent transmitted neutron flux analyses further confirm the strong attenuation capability of hexaboride materials, especially at low and intermediate energies. These findings highlight the potential of rare earth hexaborides combined with advanced concretes as effective shielding materials for compact and efficient nuclear reactor designs.