STABILITY ANALYSIS OF THE ITER TF CONDUCTOR

The stability analysis of the reference Nb3Sn conductor for the International Thermonuclear Experimental Reactor (ITER) Toroidal Field (TF) coils is performed using the Mithrandir code. From the point of view of the temperature margin, the most critical conductor in the winding pack, as well as the most critical location along it, is identified by a Vincenta code analysis, which also provides the initial and boundary conditions for the stability study. With this approach, the 1D Mithrandir analysis can be restricted to the most critical conductor, using a much finer grid than Vincenta, in order to capture the details of normal zone initiation and possible recovery to SC state. Two different disturbances are considered: one short in space and time (0.01 m, 1 ms), simulating a disturbance of mechanical nature, the other longer (3 m, 100 ms), corresponding to AC losses (plasma disruption). Both disturbances are applied to the superconducting cable at end-of-burn, in the reference ITER inductive operation scenario. The grid-independence of the results was verified first. Since the results are strongly influenced by the choice of the heat transfer coefficient between strands and helium, this effect has been also parametrically investigated. In all cases, the computed minimum quench energies turn out to be above the level of the expected disturbances