Defect formation processes in superionic crystals under irradiation have been theoretically studied. Two basic mechanisms of radiation defect formation are distinguished: elastic displacement at scattering of a fast particle and ionization mechanism at decay of Coulomb-unstable regions, formed in an Auger cascade from deep-level holes in negative ions. It is shown that the presence of a fast quasi-liquid component affects radically the run of elementary destruction processes. Aspects of increasing the radiation resistance of these crystals are discussed.