AbstractA model has been developed to describe the kinetics of void growth in metals during irradiation which explicitly includes the presence of both migrating interstitials and vacancies. It is clear that void growth can occur only when an excess flux of vacancies arrives at the void surface and this can be achieved by taking into account the preferred drift of the interstitials to the dislocation sinks as a result of the long-range size effect interaction. Results of numerical calculations of the vacancy and interstitial average concentration in stainless steel and molybdenum irradiated under typical fast reactor conditions are presented, and these are used to calculate void growth rates as a function of temperature. It is shown that the void growth rate goes through a maximum when plotted against temperature and this is consistent with the experimental swelling data. During the early stages of irradiation, when the number of point defects arriving at voids is negligible compared with those being lost at other sinks, the swelling rate is proportional to (t)3(t = time). Cold work has a beneficial effect in the early stages of irradiation by reducing the void growth rates, but it could have a deleterious effect over a long term by prolonging the period over which the swelling follows the rapid (t)3law.