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

摘要

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 (B_4C), boron nitride (BN), boron trioxide (B_2O_3), and boric acid (H_3BO_3) 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 B_4C has the greatest and B(OH)_3 the least total neutron macroscopic cross section. Simulation results also show that B_2O_3 and H_3BO_3 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, B_4C, create secondary photons with lower energy. From a shielding point of view, we can confirm that B_4C and BN in the second order have the best performance when epithermal and, particularly, thermal neutron absorption is concerned. Result shows that H_3BO_3 has the worst performance among the candidates considered.