Neutronics analysis of the ITER NB system: Nuclear responses of the components and shutdown dose around the NB injector

Neutronics of the neutral beam (NB) injector for international thermonuclear experimental reactors (ITER) was analyzed by two- and three-dimension (3-D) codes, and their results were then compared. The neutron flux on the beam line axis obtained by the 2-D code agrees with that by the 3-D code within 30%. The shutdown dose rate around the NB injector was estimated by the 2-D model developed by taking into consideration both the plasma operation pattern and the scenario. The dose rate at 106 s after the shutdown around the NB injector was estimated to be 40 μSv/h, which allows for hands-on maintenance during the shutdown period.