In this work a rate equations model describing the interstitials (I) diffusion in a trap containing medium is presented. The model takes into account the interstitial injection by implantation and annealing and the surface evaporation. We found an analytical approximated solution of the model which allows clarifying the interplay between the parameters involved and a simple comparison with experimental data obtained by the analysis of boron delta doping arrays broadening. The calculations allow to demonstrate that the I injected into the bulk and toward the surface at the end of the I clusters dissolution does not depend on the detailed time evolution of the I clusters, but only on the total amount of I produced by the implantation. The fitting of the experimental data allows to easily quantifying important physical parameters such as the I evaporation rate at the surface and the density of intrinsic interstitial traps. Applications of the model are shown in the case of MBE materials intentionally doped with substitutional C. The model successfully predicts the TED reduction by MBE intrinsic I-traps and allows to estimate the average composition of Interstitial-Carbon clusters.