Mechanical modeling of the ITER toroidal field coils shear keys behavior. Design and choice of key mock-up for electrical insulation testing on the basis of numerical models

The ITER shear key system is designed to interconnect neighboring toroidal field coils at their inner portions. Due to these keys the coils inner portions resist the torque as a whole structure. On the other hand, the ITER magnet system design provides supporting of the centering load on the TFC by a bucking cylinder. Hence, the keys should not produce any significant wedging during the radial movement of the coils. Numerical modeling of the so called scissors´ action keys that satisfy above requirements has been performed with assembly gaps being taking into account. Cooldown, TFC energizing and poloidal fields coils pulse regimes have been studied. Since the TFC torsion produces high cyclic compression on the key ground insulation, the electrical insulation testing is required. Two mock-up systems for this testing have been proposed and modeled. One system models an effect of the TFC radial movement resulting in higher peak compression on the insulation