ARC Disruption Physics and Strategy

Commonwealth Fusion Systems is designing a 400 MW net electric tokamak fusion power plant called ARC. The high-level preliminary disruption targets for the ARC Version 3A power plant are (1) to reduce the average mitigated disruption rate to one-per-day or lower, (2) to mitigate disruptions sufficiently to allow rapid restart in 20 s, and (3) to ensure unmitigated disruptions are rare. Physics scoping and fluid modeling suggests that using 12 valves, each the same design as the SPARC massive gas injection valves, will meet ARC requirements. Axisymmetric electromagnetic loads from mitigated and unmitigated disruptions are assessed using M3D-C1 as well as a flexible, forward modeling workflow that leverages the ThinCurr code. The sideways force is evaluated with a filament representation of the plasma inside a COMSOL vessel model. DREAM simulations of runaway electron generation post impurity injection find that gas injection alone might not prevent beam formation, and runaway impact studies find millimeter melt depths, so a non-insulated runaway electron mitigation coil option is scoped. Radiation flash forward modeling using HEAT suggests that avoiding tungsten melt during mitigated disruptions is likely achievable, greatly increasing the likelihood of rapid restart.

Work funded by Commonwealth Fusion Systems. This material is based upon work supported by the U.S. Department of Energy, Office of Science, Fusion Energy Sciences, under the Milestone-Based Fusion Development Program.