A new concept of the radiation-induced microstructural evolution in ionic crystals has been verified experimentally by phenomena observed in heavily irradiated NaCl, such as the formation of large vacancy voids followed by a sudden explosion-like fracture of crystalline samples. The new concept can be a prototype of an adequate description of the long-term behavior of important insulating materials in intense radiation fields, which can be employed for an evaluation of the critical effects expected under conditions of storage of high level nuclear waste and development of radiation resistant materials. In this paper, we present some new data on the microstructural parameters of materials doped with different impurities and summarize the cri...