3-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 r adiation environment for machine design and operation planning. Calcul ations were carried out using three-dimensional Sn code TORT and 25 gr oup cross-section data based on the JENDL-3 library, and shielding cha racteristic were examined. Consequently, the radiation leakage effect due to the helical-shaped plasma and coils is necessary to be consider ed in the evaluation of the radiation flux distribution and its relate d 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 m ethod with a suitable conservativeness with regard to the leakage sour ce term calculation. (C) 1998 Elsevier Science S.A. All rights reserve d.