Integrated analysis of the effects of runaway electrons on plasma facing components in ITER

The effect of the runaway electrons impinging at the vessel walls is strongly dependent on the energy gained in the tokamak toroidal electric field. Few experimental and theoretical investigations exist to predict the main parameters of the runaway electrons. Runaway electrons can cause severe damage to plasma-facing and structural materials; seriously affecting the operations of the reactors. In contrast to the ITER report predictions, our preliminary analysis showed the importance influence of the tangential part of the runaway kinetic energy on the energy deposition, material thermal response, and wall damage. Most previous calculations considered the initial runaway electron beam direction as parallel to the magnetic field flow. The energy deposition models were further enhanced in our HEIGHTS package for the runaway electron deposition by taking into account the various interactions mechanisms of electrons with surface target atoms. Earlier, we found that in the previous ITER Be/Cu wall geometry, the beryllium can melt at the interface with the structural Cu material. Using tungsten wall instead caused significant surface melting and vaporization for all the parameters of runaway electrons considered in this study. Because the wall design optimization needs numerous simulations, the upgraded HEIGHTS full 3D computer package provided significant insights into the effects of runaway electrons damage and potential design mitigations.