LMA - Laboratoire de Mécanique et d’Acoustique

R. Riccioli - Mechanical modelling of superconducting cables for fusion under cyclic electromagnetic and thermal loads

Keywords : Fusion machines, ITER, superconductors, composite materials, strain-sensitive strands

Abstract

The strands of the Cable-In-Conduit Conductors for the ITER magnet system TF coils are made of Nb3Sn, which is a brittle and strain sensitive superconducting material. Nb3Sn composite strands exhibit a critical current density that strongly depends on the strain state of the superconducting filaments. During the machine operation, the conductors are submitted to several electromagnetic and thermal cycles affecting the Nb3Sn mechanical state and consequently the capacity of the conductors to transport current. Different studies based on both macroscopic and microscopic approaches have been performed so far to identify the mechanisms determining the conductors’ behavior. Nevertheless, so far, no theory has been developed permitting to predict the electrical performance of cyclically loaded conductors. Therefore, a solid electromechanical model able to tackle the analysis of CICC and other fusion cables when they undergo thousands of cyclic loadings would be very useful. The main goal of this PhD is the development of an advanced mechanical model to study the mechanical behavior of ITER TF CIC conductors based on a new version of the MULTIFIL finite element code. At the same time, experimental activities will take place to enrich and improve the numerical model. An assessment of the electromagnetic behavior based on the mechanical analysis will be also performed to make a preliminary comparison between the simulated results and the experimental ones obtained for TFIO1 samples by the SULTAN facility.

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