The production of solute enriched (or depleted) regions has been observed in Fe³Al, Cu⁵Zn⁸, and Ni⁵Zn²¹ subject to neutron irradiation. The formation of those regions is due to the separation of the alloy components in the path of the atomic collision cascade, at the thermal stage of its development. A mechanism of formation of a region of different concentration in the collision cascade is proposed. Analyses of the kinetics of recovery of the in-cascade induced defect distribution show that the annealing of that damage can lead to the redistribution of the alloy components. Enrichment of one atomic species results in the depleted zone. The preferential flux of an atomic species toward the depleted zone is determined by the difference in the atomic mobilities and the characteristics of the interstitial configurations and migration mechanisms. A computer simulation of the separation confirmed the possibility of precipitation of a new phase at a sink, such as a depleted zone, which exists for a very short period of time.