A Design Study of the Neutron Irradiation Facility for Boron Neutron Capture Therapy

A design study of the neutron irradiation facility for boron neutron capture therapy was performed using two-dimensional transport calculations. Dosedepth distributions in a phantom head were calculated for various neutron energies. The epithermal neutrons having the energies between 10 eV and 0.5 keV are suitable for the therapy. To obtain the epithermal neutron beam, the neutrons leaking downward through the central hole of the annular core TRIGA reactor were moderated through a mixture of heavy water with aluminum whose volume ratio is 15:85. Bismuth and lithium fluoride tile was used to remove gamma rays and thermal neutrons from the beam. Iron, borated polyethylene, and lead were used as the shield surrounding the moderation layer. When the epithermal neutron column is used, the maximum usable depth and irradiation time are 6.9 cm and 7.25 h, respectively, at a 2-MW level.