武蔵工大炉医療用照射場の中性子ビーム設計

抄録

Design studies were carried out for the Musashi reactor (TRIGA-II, 100kW) with a view to generating epithermal and thermal neutron beams applicable to boron neutron capture therapy (BNCT). By Monte Carlo calculations, the thermal neutron beam intensity 1.1×10⁹n/cmcm2·s and the epithermal neutron beam intensity 4.1×10⁸n/cmcm2·s at the operation power of 100kW have been obtained at the irradiation ports in the thermal and thermalizing columns, respectively. These beams are little adulterated with fast neutrons and gamma-rays, and are relatively forward-directed. Depth-dose calculations in a tissue phantom showed that above thermal and epithermal neutron beams would be useful to treat superficial (-4cm) and deeper (-6.5cm) tumors, respectively. The full-dose treatment time is estimated about 2.5h. These neutron beam designs suggest how TRIGA reactors could be modified for BNCT, and the produced neutron beams, if built into the Musashi reactor, will significantly increase the chance of success of BNCT in Japan.