EFFECTS OF CRYOGENIC IRRADIATION ON ELECTRICAL STRENGTH OF CANDIDATE ITER INSULATION MATERIALS

Candidate International Thermonuclear Experimental Reactor toroidal fi eld coil insulation materials were subjected to irradiation at 4 K by a fast neutron fluence of 3.1 x 10(22) n m(-2). Electrical strengths o f the irradiated materials were evaluated at 76 K and are compared to electrical strengths of unirradiated control specimens. Materials eval uated include several classes of organic matrix insulation, barrier ma terials including mica paper and polyimide film, and selected hybrid i nsulation systems. Radiation at these levels had little significant ef fect on the electrical strength of most of these materials. Inclusion of a barrier had a small effect on preirradiation electrical strength, but improved the postirradiation electrical strength of hybrid system s over that of the associated primary insulation systems. The selectio n of insulation systems may be made based upon parameters including fa brication method and mechanical performance, and this selection is not necessarily limited by radiation induced electrical strength degradat ion.