02-23U

Some information about the irradiation-produced defect formation in solid materials including the lava-like fuel-containing materials (LFCM) is represented. The behaviour of defects (their mobility and annihilation) is considered. Some known results of investigations of the diffusion properties of the multicomponent systems, which are interesting for the nuclear engineering, are noted. The simplified version of the task about the void growth in the LFCM due to the vacancy absorption is considered. Using the series of approximations, the time-dependent dynamics of the spherical void radius change in LFCM is estimated numerically. The forecast for nearest twenty years is performed. The factors, which could make certain corrections to the results of calculations for the initial level, are given.