The distribution of radionuclides in the ground during the hypothetical serious damage to an underground nuclear power station is considered. A set of filtration gas equations and convective diffusion equations are used to describe the transport of radionuclides. Processes of nuclear decay and nonequilibrium adsorption are taken into account. The results of mathematical modeling of the distribution of 90 and 137 isobaric radionuclide chains, and zones of probable pollution of the environment by these radionuclides, are presented.