Fault analysis of plasma facing component mounts using multiphysics simulation

Plasma facing components like the ITER blanket shield modules (BSMs) often consist of a first wall and a shield block that are mounted to a vacuum vessel wall. The ITER mount is comprised of an Inconel bolt, Ni-Al-bronze collar, insulating layers of alumina and a flexible Inconel cartridge that allows compliance to reduce stress. Here we describe our efforts to perform multiphysics simulations on the flexible mount using current densities calculated for ITER halo scenarios and off-normal disruption events over various size faults or breaks in the insulator layers. This effort also entailed a study of fault size and simulations of high current flow over small area faults that would likely lead to melting. In addition to ohmic heating and thermal analysis, melting and solidification physics were included using computational fluid dynamics to track the solid/liquid interface and the degree of melting near the fault. Temperature dependent conductivities were used for the solid and liquid phases of all the materials. We concluded that for the anticipated off-normal conditions in ITER, the flexible mount is very fault tolerant for both large and small area faults.