Shielding Analyses of the ITER NBI Ports

Shielding analyses of the ITER neutral beam injector (NBI) ports have been performed using three-dimensional Monte Carlo and two-dimensional discrete ordinates Sn methods. The biological dose rates inside the cryostat after reactor shutdown are expected to be lower than design target of 100 μSv/h for the current NBI reference design with ∼60 cm thick NBI port walls. It was also observed that the total nuclear heating in the toroidal field (TF) coils satisfies the design limit of 17 kW when the port wall is 40 cm thick. The Sn calculations, performed using a rectangular model of the NBI, overestimate the dose rates at the cryostat and nuclear heating in TF coils by factors of ten and two, respectively, compared to Monte Carlo results obtained using a more accurate representation of the NBI system.