Three options of the method to determine microconcentrations of fissile materials in water solutions are developed. They utilize plastic track detectors to measure concentrations. The options are as follows a "wet" method, "thin-layer inorganic sorbents-plastic track detectors", and a method of selective extraction and coprecipitation. These methods are used to check up fuel cladding integrity at the research reactor IVV-2M and liquid radioactive waste contamination by uranium and plutonium at the Beloyarskaya Nuclear Power Plant (BNPP).