An engineering design of an epithermal neutron generator for boron neutron capture therapy (BNCT) has been completed, which utilizes the spallation reaction by protons accelerated to 50 MeV. The critical issues for realization of the neutron generator are the mechanical structure of a target with cooling capability and its integrity under operating conditions with powers as high as 50 MeVÂ300 mA.The integrity of a target structure design has been confirmed by thermal and stress analyses with a finite element method code ANSYS. Moreover, a target replacement strategy is also studied based on a radioactivity evaluation performed by the IRACM code system.In addition to the target structure design, the neutronics design has been optimized with the Monte Carlo code MCNPX. A high epithermal neutron flux of 1:8Â10 9 cm À2 Ás À1 has been achieved at the aperture of the collimator, which allows a RBE dose of over 30 Gy-eq to be delivered to a brain tumor within 5.9 cm in phantom depth for a therapeutic time of 31 min.

This paper describes shielding evaluation of the measurements around the reactor core ofMonju. The measurements were performed during the system start-up tests at different power levels between 0% and 45%. The measured reaction rates have been obtained radially from the core to the in-vessel storage rack and axially to the reactor vessel upper plenum. The measured values (E) were compared with the calculated values (C) obtained with the FBR shielding analysis methods. Based upon these results, the design margins around the reactor core have been reexamined and reconfirmed .

An engineering design of an epithermal neutron generator for boron neutron capture therapy (BNCT) has been completed, which utilizes the spallation reaction by protons accelerated to 50 MeV. The critical issues for realization of the neutron generator are the mechanical structure of a target with cooling capability and its integrity under operating conditions with powers as high as 50 MeVÂ300 mA.The integrity of a target structure design has been confirmed by thermal and stress analyses with a finite element method code ANSYS. Moreover, a target replacement strategy is also studied based on a radioactivity evaluation performed by the IRACM code system.In addition to the target structure design, the neutronics design has been optimized with the Monte Carlo code MCNPX. A high epithermal neutron flux of 1:8Â10 9 cm À2 Ás À1 has been achieved at the aperture of the collimator, which allows a RBE dose of over 30 Gy-eq to be delivered to a brain tumor within 5.9 cm in phantom depth for a therapeutic time of 31 min.