Radiation Resistant Electrical Insulation Qualified for ITER TF Coils

Abstract

The Toroidal Field (TF) coils for the ITER device will represent the largest superconducting magnet system assembled to date, and thus creates several challenges related to the manufacture of these magnets. Most notably, the electrical insulation for the TF coils must address four simultaneous constraints: high radiation, large mechanical stresses, high voltage operation, and operation in a vacuum. In addition, these materials must meet all shipping and local environmental regulations for use in large quantities in both Europe and Japan. The TF coil insulation will undergo fast neutron fluences up to 3.2 × 1021n/m2, which is equivalent to 10 MGy, and still be able to withstand the estimated operation in-plane shear stress in the range of 45 MPa. To address this need, CTD has developed and qualified two epoxy/cyanate ester resin systems, CTD-425 and CTD-435. These materials meet the processing requirements, mechanical strength after 30 000 load cycles, and radiation exposure specifications established by ITER IO. Both materials are qualified for use in constructing the ITER TF coils, and are supplied to European and Japanese customers by Lord Corporation. This paper summarizes the performance characterization, qualification tests, and supply chain for these materials.