ITER radiation shielding and neutronics analysis

Two dimensional radiation transport calculations have been carried out to determine radiation streaming through the ITER equatorial ports. The NBI port has been identified as the most critical. Shielding requirements were estimated to minimize the nuclear heating rates in the toroidal field (TF) coils and the activation of the cryostat, where hands-on maintenance is anticipated. The shielding efficiency of steel/water port walls was investigated as a function of port and wall dimensions and steel volume fraction. For open ports, i.e. the neutral beam injector ducts, 40–50 cm thick port walls composed of 40% SS-60% H2O–75% SS-25% H2O will reduce the TF coil heating to acceptable levels, while 60–65 cm thick walls are necessary for reducing the dose rates at ∼2 weeks after shutdown to levels of 750 μSv h−1 at the cryostat.