  Runaway electrons (REs) present a high-priority issue for ITER but little is
known about the extent to which RE generation is affected by the stochastic
field intrinsic to disrupting plasmas. RE generation can be modelled with
reduced kinetic models and there has been recent progress in involving losses
due to field stochasticity, either via a loss-time parameter or radial
transport coefficients which can be estimated by tracing test electrons in 3D
fields. We evaluate these terms in ITER using a recent JOREK 3D MHD simulation
of plasma disruption to provide the stochastic magnetic fields where RE markers
are traced with the built-in particle tracing module. While the MHD simulation
modelled only the current quench phase, the case is MHD unstable and exhibits
similar relaxation as would be expected during the thermal quench. Therefore,
the RE simulations can be considered beginning right after the thermal quench
but before the MHD relaxation is complete. The plasma is found to become fully
stochastic for 8 ms and the resulting transport is sufficient to overcome RE
avalanche before flux surfaces are reformed. We also study transport mechanisms
for trapped REs and find those to be deconfined as well during this phase.
While the results presented here are not sufficient to assess the magnitude of
the formed RE beam, we show that significant RE losses could be expected to
arise due to field stochasticity.
