  Neutron irradiation induces in steels nanostructural changes, which are at
the origin of the mechanical degradation that these materials experience during
operation in nuclear power plants. Some of these effects can be studied by
using as model alloy the iron-carbon system.
  The Object Kinetic Monte Carlo technique has proven capable of simulating in
a realistic and quantitatively reliable way a whole irradiation process. We
have developed a model for simulating Fe-C systems using a physical description
of the properties of vacancy and self-interstitial atom (SIA) clusters, based
on a selection of the latest data from atomistic studies and other available
experimental and theoretical work from the literature. Based on these data, the
effect of carbon on radiation defect evolution has been largely understood in
terms of formation of immobile complexes with vacancies that in turn act as
traps for SIA clusters. It is found that this effect can be introduced using
generic traps for SIA and vacancy clusters, with a binding energy that depends
on the size of the clusters, also chosen on the basis on previously performed
atomistic studies.
  The model proved suitable to reproduce the results of low (<350 K)
temperature neutron irradiation experiments, as well as the corresponding
post-irradiation annealing up to 700 K, in terms of defect cluster densities
and size distribution, when compared to available experimental data from the
literature. The use of traps proved instrumental for our model.
