The main purpose of this paper is the investigation of the rate equations used in the theories of void nucleation and swelling as well as creep, in situations where random displacement cascades are the major source of point defects. The point‐defect concentrations are described by diffusion equations with random source terms to account for the cascades. Using methods from nuclear reactor kinetic theory and averaging over time, the rate equations are derived. It is seen that the rate equations are valid for computing time and spatially averaged point‐defect concentrations, regardless of the cascade statistics, if the observation time is greater than the mean time between cascade events in the irradiated material. An alternate approach is suggested for studying pulsed systems with short pulse widths.