Progress of the engineering analyses for the JT-60SA toroidal field coils structures

Abstract

JT-60SA is a fully superconducting tokamak presently being built at the JAEA Naka site, in the framework of the JA-EU Satellite Tokamak Project under the Broader Approach (BA) Programme and JAEA's national Programme. The mission of the JT-60SA project is to contribute to the early realization of fusion energy, supporting the exploitation of ITER and research towards DEMO by addressing key physics issues.The whole magnet system of JT-60SA has a cold mass of more than 670tonnes and rests entirely on the toroidal field (TF) magnet which is made of 18 D-shaped NbTi superconducting coils, each enclosed in a stainless steel casing, which are supported toroidally by a fully bolted outer intercoil structure (OIS), and which are connected to one another by complex bolted and pinned inner intercoil structures (IIS).Due to the demanding electromagnetic loads experienced by the tokamak magnet system during operation, together with the tight space requirements around the coils, the intercoil structures have to transfer massive shear and normal forces, in excess of several MN, while providing enough flexibility to avoid unnecessary internal reactions to the immense centripetal and wedging forces at the magnet centre vault.This paper illustrates the engineering analyses carried out to define the requirements for the coil casings and intercoil structures, to assist the development of the technological solutions in view of the manufacturing of the components, and to predict the behaviour of the components from their assembly through to off-normal and fault conditions during operation.The latest results obtained from the global electromagnetic and structural analyses, briefly presented in the paper, show that the magnet system is suitable to perform the intended number of cycles in the operating conditions. More emphasis is given to the results of the multiple detailed analyses of the TF intercoil structures, which show that each individual component can withstand the operating loads with a comfortable safety margin.