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Analysis of recently available archive materials regarding the liquid radioactive waste storage and reprocessing at the "Mayak" Production Association in 1949-1956 has led to a more accurate reconstruction of radionuclide releases into the Techa River. Radionuclide concentrations in the Techa River water, bottom sediments and floodplain soils in 1949-1951 were reconstructed with the use of a purposely-developed Techa River model. Model calculations agree with the measurements of the specific activity in the river water and bottom sediments conducted since 1951. The model output for the (90)Sr concentration in the river water shows a good agreement with the retrospective estimates derived from (90)Sr measurements in teeth and the whole body of the Techa riverside residents. Modeled (137)Cs-contamination of the floodplain shows agreement with the values reconstructed from (137)Cs measurements in the floodplain soils obtained in later years. Reconstructed contamination levels by radionuclides in the Techa River water and floodplain are being used to refine internal and external doses and risk estimates of late effects in the population chronically exposed to radiation.

The purpose of this work was detailed physicochemical, radiological, and toxicological characterization of the composite sample of water intended for human consumption in the Cameron/Tuba City abandoned uranium mining area before and after a combined electrochemical/advanced oxidation treatment. Toxicological characterization was conducted on human lymphocytes using a battery of bioassays. On the bases of the tested parameters, it could be concluded that water used for drinking from the tested water sources must be strictly forbidden for human and/or animal consumption since it is extremely cytogenotoxic, with high oxidative stress potential. A combined electrochemical treatment and posttreatment with ozone and UV light decreased the level of all physicochemical and radiological parameters below the regulated values. Consequently, the purified sample was neither cytotoxic nor genotoxic, indicating that the presented method could be used for the improvement of water quality from the sites highly contaminated with the mixture of heavy metals and radionuclides.

The efficiency of ozone treatment in the degradation of organic compounds of nuclear laundry water is presented. Ozonation experiments were performed in different combinations of pH, hydrogen peroxide and ultraviolet radiation. The degradation of non-ionic surfactant and other organic compounds was analysed by chemical oxygen demand, total organic carbon, biochemical oxygen demand and the molecular weight distribution measurements. The optimal degradation circumstances were found to be at pH 7 with ozone, UV radiation and hydrogen peroxide addition. The transfer of ozone increased substantially thus resulting in decreased treatment time compared to our previous experiments. The reductions of chemical oxygen demand, total organic carbon and biochemical oxygen demand were about 46%, 32% and 70%, respectively.