Heavy impurities implanted in metals may occupy different sites. In general a substitutional site is possible, as well as sites associated with defects. The interaction of the impurities with the defects produced during the slowing down process is thought to be the reason for the population of the different sites. The incoming atoms are interacting with the correlated damage—interaction with the own damage cascade—and with the uncorrelated damage. The correlated interaction is responsible for the major part of the landing behaviour of the impurities, only the uncorrelated interaction describes the transitions between different sites. With these ideas the evolution of the site populations may be described by means of a set of differential equations. We have solved the equations for the case where all defects are immobile. In order to do so we have introduced spontaneous trapping volumes around every defect configuration. The solutions of these equations produce the evolution of the site populations as a function of dose, trapping volumes, potential between incoming and target atoms, mean displacement energy and range. The site populations are independent of dose rate.