Abstract
One of the most important consequences of plasma disruptions is the formation of runaway electron (RE) beams and the resulting damage to the first wall of the tokamak reactor. An increase in tokamak power leads to an increase in the power of the RE flux and energy deposition into the first wall in the case of a loss of plasma stability. While significant efforts are being pursued to find reliable and robust ways to predict and mitigate such events, a credible design must withstand a few of these transient events without significant damage. Therefore, accurate modeling and prediction of RE parameters, heat loads on internal components, and resulting damage are critical to assess. This paper investigates and compares the performance of the actual ITER design during the potential RE impact using the current predicted ITER parameters. The HEIGHTS comprehensive 3D computer package is used in these simulations. The resulting heat loads lead to severe melting and vaporization of the tungsten armor under ITER-relevant conditions. The role of vapor or plasma layers formed during transient events is examined to evaluate whether potential shielding or mitigation can exist. Due to the large penetration depth of the relativistic electrons, these vapor layers, either from residue of transient disruption events or from an inert gas injection, provide negligible shielding. We demonstrated that mitigation based on low-Z protective layers can significantly spread the spatial energy deposition over a larger volume and reduce peak surface temperatures. These results highlight the limitations of current tungsten first wall designs and emphasize the need for integrated mitigation strategies combining material design and disruption control.