Shielding design of the ITER NBI duct for nuclear and bremsstrahlung radiation

Three-dimensional Monte Carlo shielding analyses are conducted on the ITER Neutral Beam Injection (NBI) duct for the nuclear and bremsstrahlung radiation. The detailed distribution is evaluated about the nuclear heating rate and surface heat load of the NBI duct wall by the neutron and photon transport calculation. The analytical representations of these nuclear responses are established as a function of the distance from the blanket surface. It is clarified that these representations are different between the duct wall facing the plasma and that hidden from the plasma, and also between the duct wall in the blanket region and that in the vacuum vessel region. These results are very useful for the shielding design of the NBI duct wall in the nuclear fusion reactor.