Evaluation of insulation shear stresses in the ITER central solenoid

CS insulation system binds the conductor jackets into a an important structural element of bucked ITER magnet system. The CS must accommodate bucking pressures, and the flexural motions of the TF case. Shear stresses in the CS are computed in a large ANSYS global model of the magnet system. The local structural response of the jacket also adds shear stresses at the bonds between neighboring conductors. Each of the six stress components of the "smeared" CS stress state from the global model induces additional local shears and normal stresses within the insulation between conductors. In this study, the detailed behavior of the local models is coupled with the global stresses within the CS, yielding a detailed picture of insulation stresses. ITER Project insulation performance and criteria are more restrictive now than when the current magnet system concept was chosen, putting a portion of the CS in violation of the criteria. Insulation systems which use etched Kapton tapes have shown some promise in static shear tests. Cyclic tests of these materials are needed. Array testing with applied shear loading is recommended. Other insulation systems without Kapton should be considered.