Theory and Simulation Investigation of Low-Energy Neutron Shielding for Different Boron Compounds

Neutron absorbers, especially boron, exhibit a comparatively large neutron absorption cross section, in particular, with regard to thermal neutrons. In this study, four boron compounds, including boron carbide (B4C), boron nitride (BN), boron trioxide (B2O3), and boric acid (H3BO3) were considered for shielding the thermal neutrons, both theoretically and in simulation. The shielding ability and secondary gamma-ray production of compounds were studied, using the MCNP-4C Monte Carlo code. The theory shows that B4C has the greatest and B(OH)(3) the least total neutron macroscopic cross section. Simulation results also show that B2O3 and H3BO3 create more high-energy secondary gamma rays that may cause a significant photoneutron reaction, in addition to unwanted dose radiation. Among these, BN and, especially, B4C, create secondary photons with lower energy. From a shielding point of view, we can confirm that B4C and BN in the second order have the best performance when epithermal and, particularly, thermal neutron absorption is concerned. Result shows that H3BO3 has the worst performance among the candidates considered.