Kinetics of ³H, ⁹⁰Sr and ¹³⁷Cs content changes in hydrosphere in the Vltava River system (Czech Republic)

The paper presents results and interpretation of long-term monitoring of occurrence and behaviour of radioisotopes ³H, ⁹⁰Sr, and ¹³⁷Cs in the vicinity of the Temelín Nuclear Power Plant. ³H, ⁹⁰Sr, and ¹³⁷Cs originate predominantly from residual contamination due to atmospheric nuclear weapons tests and the Chernobyl disaster in the last century. Monitoring of radionuclides comprised surface waters, river sediments, aquatic plants, and fish. This enables an up-to-date appraisal of the Temelín Nuclear Power Plant impact on the hydrosphere in all indicators at standard power plant operation, as well as at critical situations. The time and spatial variability of these radionuclide concentrations were monitored in the hydrosphere at in- and out-flow of the Orlík Water Reservoir. The basic evaluated radioecological characteristics can be used in assessing the long-term kinetics of decline and behaviour of radionuclides and their potential release into the environment. A very slow decline in ³H concentration at unaffected sites was observed. At sites downstream from the power plant the ³H concentrations were significantly higher, an evident impact of the power plant operation. A decline in ⁹⁰Sr and ¹³⁷Cs concentrations was observed in all the monitored indicators. Also, the characteristic effective and ecological half-lives were evaluated.