This work presents a Monte Carlo simulation of the spontaneous recovery of damage in a silicon target periodically exposed to a beam of energetic ions. Each exposure is supposed to generate vacancy-interstitial pairs with a random distribution and the transient following each flash is analysed by simulating the random walks of defects. The occurrence of events such as clustering and annihilation is examined in terms of dose and damage growth-rate. The results of the simulation are compared with TEM observations.