  Avoidance of the harmful effects of runaway electrons (REs) in
plasma-terminating disruptions is pivotal in the design of safety systems for
magnetic fusion devices. Here, we describe a computationally efficient
numerical tool, that allows for self-consistent simulations of plasma cooling
and associated RE dynamics during disruptions. It solves flux-surface averaged
transport equations for the plasma density, temperature and poloidal flux,
using a bounce-averaged kinetic equation to self-consistently provide the
electron current, heat, density and RE evolution, as well as the electron
distribution function. As an example, we consider disruption scenarios with
material injection and compare the electron dynamics resolved with different
levels of complexity, from fully kinetic to fluid modes.
