Abstract <p>The aging of collision cascades with damaging energies of 1–50 keV at temperatures of 300–900 K in BCC metals Fe and V has been simulated by an object kinetic Monte Carlo method. The metals under study are of interest as the basis for low-activation structural steels and alloys for fusion reactors and hybrid fission–fusion systems. The initial spatial distributions of self-point defects surviving after the cascade region cooling (20 ps from the beginning of the cascade development) have been taken from previously obtained molecular dynamics data. The evolution of the system, which includes the processes of diffusion, recombination, clustering, and dissociation of radiation defects, has been surveilled for 5 ns. The temperature and damaging energy dependences of the number of surviving self-point defects after aging and the corresponding size distributions of their clusters have been obtained. During the aging process, cascade efficiency decreases by 12–40% from the initial values, depending on the material, temperature, and damaging energy. The physical mechanisms underlying the observed features of the calculated dependences have been determined.</p>