Mechanical Modeling and First Case Study on ITER TF CICC Loading Cases With Upgraded Finite Element Code Simulations

The strands of the Cable-In-Conduit Conductors (CICCs) for the ITER magnet system TF coils are made of Nb3Sn, which is a brittle and strain-sensitive superconducting material. The strain distribution in the filaments is driven by the cool-down process and the electromagnetic forces acting on the strands in operation. The impact of electromagnetic and thermal warm-up-cool-down cycles on the conductor performance degradation has been investigated experimentally both on short samples in the SULTAN facility and in the solenoidal configuration of the TF Insert tests in the CSMC facility. A deeper understanding on how cyclic loading of the conductor affects its electrical performance could allow one to identify the best working conditions so as to limit the degradation. In this paper, a mechanical model of one last sub-cable (petal) of the TF CICC is presented. The strain distribution in the strands is simulated via a new version of the MULTIFIL finite element code. The effects of the alternate application of thermal and electromagnetics cyclic loading are tentatively analyzed, similarly to experiments performed in the SULTAN facility in the tests of the TFIO1 conductor sample. An upgrade of the model is implemented, concerning the thermal cycle simulation.