  The disruption and runaway electron analysis model code was extended to
include tungsten impurities in disruption simulations with the aim of studying
the runaway electron (RE) generation. This study investigates RE current
sensitivity on the following plasma parameters and modelling choices: tungsten
concentration, magnetic perturbation strength, electron modelling, thermal
quench time and tokamak geometry: ITER-like or ASDEX-like. Our investigation
shows that a tungsten concentration below 10-3 does not cause significant RE
generation on its own. However, at higher concentrations it is possible to
reach a very high RE current. Out of the two tested models of electrons in
plasma: fluid and isotropic (kinetic), results from the fluid model are more
conservative, which is useful when it comes to safety analysis. However, these
results are overly pessimistic when compared to the isotropic model, which is
based on a more reliable approach. Our results also show that the hot-tail RE
generation mechanism is dominant as a primary source of RE in tungsten induced
disruptions, usually providing orders of magnitude higher RE seed than Dreicer
generation. We discuss best practices for simulations with tungsten-rich
plasma, present the dependence of the safety limits on modelling choices and
highlight the biggest shortcoming of the current simulation techniques. The
obtained results pave the way for a wider analysis of tungsten impact on the
disruption dynamics, including the mitigation techniques for ITER in the case
of strong contamination of the plasma with tungsten.
