Three-dimensional radiation shielding analysis of the large helical device

Three-dimensional radiation shielding analysis around a large helical device (LHD) has been performed in order to confirm the margin of the present shielding design and to provide more detail information on a radiation environment for machine design and operation planning. Calculations were carried out using three-dimensional Sn code TORT and 25 group cross-section data based on the JENDL-3 library, and shielding characteristic were examined. Consequently, the radiation leakage effect due to the helical-shaped plasma and coils is necessary to be considered in the evaluation of the radiation flux distribution and its related evaluation: nuclear heat generation inside the cryostat. The present design method based on two-dimensional calculations was compared with three-dimensional calculations, and turned out to be an appropriate method with a suitable conservativeness with regard to the leakage source term calculation. (orig.)