An Electromagnetic and Structural Finite Element Model of the ITER Toroidal Field Coils

The ITER magnet system consists of 18 toroidal field (TF) coils, a central solenoid (CS), six poloidal field (PF) coils, and a set of 18 correction coils. The TF coils provide the required toroidal magnetic field of ≈5.3 T at the plasma radius R = 6.2 m mainly needed to confine the plasma. Since the magnets are under manufacturing, nonconformity-reports (NCR) and/or deviation requests (DR) can be provided by the manufacturers. Fast checks on the impact of those design updates on the structural behavior of the system are needed before accepting their implementation. With this aim a detailed finite element model of the TF system has been developed representing two TF coils and is described in this paper. It is a three-dimensional cyclic symmetric finite element model giving a representation of the two types of coils characterizing the TF magnet: one TF coil type A (the one that supports the six PF coils) and one TF coil type B (the one that supports four out of six PF coils and the CS). The model allows computing the magnetic field during the different operating scenario of the magnet and the related Lorentz forces acting on the TF coil system. It also permits to simulate how the TF system will mechanically behave during operation. Updates of the FE mesh can be easily implemented since the model has been built in a modular way, small subcomponents of the system can be isolated and geometrically updated if needed. This is the key feature of the model, which has allowed to study in a very fast way possible NCR's and DR's produced during the manufacturing. An intensive usage of the ANSYS APDL language has been implemented in such a way that the entire analysis cascade can be executed in a completely automatic way. Due to its versatility, this tool has become the reference TF coils model in the ITER Magnet Division.