Prompt and delayed radiation shielding calculations for the zephyr deuterium-tritium ignition experiment

Results of discrete ordinates radiation transport calculations are presented for the proposed tokamak ignition and burn control experiment ZEPHYR. As a first step, baryte concrete with 0.15 wt% B4C was identified as an optimum concrete for the shielding fitting tightly around the torus and some attached devices. This shielding material with a maximum thickness of 70 cm allows personnel to enter the experiment hall just a few hours after termination of a worst-case burn discharge sequence. Inside the vacuum vessel, delayed dose rates amount to several tens of rem/h after only 50 s of plasma burn for waiting times that are typical for maintenance and repair, thus, remote handling equipment is required. Bootstrapped radiation transport calculations for neutral beam injectors show them to be strongly activated after the worst-case discharge sequence with typical dose rates of some rem/h. Thus shielding is required around the injector boxes and most repair tasks have to be performed remotely. Delayed dose rates outside the torus shielding in front of typical straight diagnostic ducts with diameters of 15 to 25 cm are shown to be significant but ''hands-on'' maintenance of the diagnostic equipment will be possible with some restrictions on working time