Modeling an Unmitigated Quench Event in an ITER Toroidal Field Magnet

An unmitigated quench of a toroidal field (TF) magnet has been proposed as an extremely unlikely event for International Thermonuclear Experimental Reactor (ITER) Engineering Design Activity safety analysis. While the frequency of such an event is highly improbable (<1 × 10^-6/yr), the public safety consequences of this event must be explored because the TF magnets are located midway between the two primary confinement barriers of the ITER design. These confinement barriers are the vacuum vessel (VV) and the cryostat. An unmitigated quench has the potential for producing melting of the magnet. If molten material from the magnet were to impinge on the walls of the VV and cryostat, these walls could fail, resulting in a pathway for release of radioactive material to the environment from the VV. A model has been developed at the Idaho National Engineering and Environmental Laboratory called MAGARC to investigate the consequences of this accident. This model is described in detail, and results from this model used in ITER safety analysis are presented.