ITER coils insulation R&D program

The ITER coil insulation systems are required for operating voltages up to 10 kV and to support shear and normal compression loads through the winding pack. Manufacturing considerations and nuclear radiation resistance also influence the choice of suitable systems. A screening program of candidate systems is being conducted in stages. The first stage is reported in this paper. Present R&D data based on small samples indicate a static shear strength of about 85 MPa for a glass or alumina and epoxy resin vacuum pressure impregnation system and 50 MPa for a pre-impregnated glass/epoxy resin system with polyimide interleaved at a temperature of 4 K. The preliminary irradiation results show that coating the steel surface with inorganic materials such as Al/sub 2/O/sub 3/ or ZrO/sub 2//8Y/sub 2/O/sub 3/ is beneficial in increasing the radiation resistance as far as shear strength is concerned. In addition tetrafunctional epoxy (TGDM) systems appear to be more radiation resistant then diglycidyl ether of bisphenol-A (DGEBA) systems. Further R&D work will focus on prototypical samples to continue evaluation of the performance of the insulation systems.