Radiation shielding for superconductive toroidal field coils around the neutral beam injector duct in the ITER design

Shielding properties were examined for the thinnest duct wall encroached on by toroidal field coils (TFCs) in the ITER (International Thermonuclear Experimental Reactor) design. In superconductive magnets, consideration must be given to shielding properties which include peak nuclear heating rate, electric insulator dose, copper displacement damage and fast neutron fluence for winding packs. The peak nuclear heating rate and the peak dose, multiplied by a safety factor of three become approximately five times larger than the design criteria near the position where the thinnest duct wall is 25 cm at a point encroached on by TFC according to the ITER CDA (Conceptual Design Activity). In order to satisfy the design criteria, therefore, the total thickness composed of 80% stainless steel and 20% H2O should be 35 cm for the left side duct wall near the position encroached on by the TFCs. (orig.)