Design of neutron beams for boron neutron capture therapy for TRIGA reactor

Reflector and moderator arrangements were studied for the TRIGA-II type reactor with a view to generating epithermal and thermal neutron beams for application to boron neutron capture therapy (BNCT). The beams are delivered from thermal and thermalizing column exits situated on opposite faces of the reactor. Several prospective arrangements for the reflector were examined for their ensuring adequate reactor criticality. The reflector arrangements were then combined with various moderator arrangements for obtaining sufficiently intense epithermal and thermal neutron beams separately and little adulterated with neutrons of extraneous energy ranges and with gamma rays. Monte Carlo calculations indicated that, with a suitable reflector-moderator arrangement, little-adulterated epithermal and thermal neutron beams respectively attaining 5x108 n·cm-2·s-1 and 1.5x109 n·cm-2·s-1, and presenting good beam directionality, should be obtainable from the thermal column with the reactor operating at 100 kW. Compared with the thermal column, the thermalizing column would deliver neutron fluxes of distinctly lower intensity, but raising reactor power to 250 kW should ensure the generation of epithermal and thermal neutron beams of intensities adequate for BNCT application at both thermal and thermalizing columns. The present study should serve to indicate how a TRIGA reactor could be modified for generating beams suited to BNCT. (author)