Design Studies of an Epithermal Neutron Beam for Neutron Capture Therapy at the Musashi Reactor

Studies were carried out to design an epithermal neutron beam for neutron capture therapy at the Musashi reactor, a TRIGA-II of 100kW. The idea in this design is to use spent fuel elements as a converter assembly to convert thermal neutrons from the core to fission neutrons which would then be moderated to epithermal neutrons. In the design, 43 elements were placed outside of the graphite reflector but inside the tank. These elements could be cooled by water in the reactor tank and also be easily removed for inspection. Monte Carlo computations indicated that by using a 63 cm-thick A1 2 O 3 moderator, an epithermal neutron beam with an intensity of 0.34x10 9 n·cm −2 ·s −1 and fast neutron and γ-doses per epithermal neutron of 4.3 x 10 −11 cGy·cm 2 ·n −1 and 0.3x10 −11 cGy·cm 2 ·n −1 , respectively, could be produced. The multiplication factor of the 43 spent fuel elements was