Design and stress analysis of support structure of toroidal field coil for the JT-60SC

The modification of JT-60 to a full superconducting tokamak (JT-60SC) is being planned. The support structures of the TF coils are designed to withstand the large electromagnetic force on the basis of the stress analyses. Shear panels are inserted between the neighboring TF coils against the overturning force and settled after the installation of the peripheral components like NBI ports. The maximum displacement and the Tresca stress of the TF coil have been evaluated in the case of the plasma disruption at the end of plasma current flat-top. In order to analyze the profiles of stress and displacement in detail, the bolts tightening the shear panel are considered in the FEM model. The maximum displacement of a TF coil is evaluated to be about 8.8 mm that is within the design requirement to keep space between the coils and the peripheral ports. The peak Tresca stress of 611 MPa appears at a bolt on the shear panel at the lower midplane. This value is within the allowable stress of SS316LN at 4 K, 667 MPa. In addition, the analyses for the various plasma operations, especially for the high poloidal beta (∼2) plasma operation, were carried out and the validity of the support structure was confirmed.