A simulation study on beam property of 124Sb-Be isotope-based neutron for BNCT

The Be-9(gamma,n) neutrons with the energies at 21-24 keV generated by 1.691 MeV photons from Sb-124 was investigated as a source of epithermal neutrons for BNCT, using PHITS code. A beam shaping assembly composed of 13 mm thick Be target, a gamma ray shield made of 30 cm thick Bi, and a reflector of 30 cm thick Pb satisfied the beam requirements of IAEA-TECDOC-1223. The needed Sb-124 activity was estimated in the order of 10(16)-10(17) Bq. Feasibility of BNCT using Sb-124-Be neutrons would be influenced by the capability of periodic supply of short-lived Sb-124 (half-life: 60 days) with such high activity.