Development of the ¹³⁷Cs, ⁹⁰Sr and ³H Concentrations in the Hydrosphere in the Vicinity of NPP Temelín (South Bohemia)

Abstract

The paperfocuses on an analysis of the results of long-term monitoring of the concentrations of 137 Cs, 90 Sr and 3 H in hydrosphere in the vicinity of Temelín Nuclear Power Plant (Temelín plant). The radionuclides were monitored in surface water, river sediments, aquatic flora and fish species. The main objective of the study was to analyze and integrate all of the knowledge on concentrations and behaviour of these radionuclides, which originate mainly from residual contamination, in order to assess the impacts of Temelín Nuclear Power Plant on hydrosphere in these indicators during its standard operation and possible accidents. The radionuclides were analyzed in terms of spatial and temporal variability in their concentrations and their inflows and outflows, mainly into and from Orlík Reservoir. The analysis included standard radioecological characteristics, which were applicable for assessing long-term development and behavior of radionuclides in the environment affected by their possible accidental releases on the territory of the Czech Republic or outside this territory. For all of the components of the environment, the concentrations of 137 Cs and 90 Sr which were used for calculation of their effective and ecological half-time, were decreasing. For 137 Cs in surface water and fish, the rates of the decrease in the first and second monitoring period were different. The rate of the decrease in 90 Sr concentration was invariable. The results of the monitoring showed that 86% of suspended solids and 62% of 137 Cs inflowing into Orlík Reservoir accumulated in the reservoir while accumulation of 90 Sr was not substantiated. Outflows of 137 Cs and 90 Sr activities were assessed in relation to their concentrations that were accumulated in individual basins until 1986 consequently to Chernobyl accident and tests of atmospheric nuclear weapons. The results for the whole area of the Vltava, Luznice and Otava River basins upstream from the Vltava River at Solenice showed that during the period 1986-2013 only 0.49% of 137 Cs activity and 3.6% of 90 Sr activity that accumulated in the basins were washed and flowed out from the area. Distribution coefficients derived from summary analysis of sediments and concentration factors for biota were calculated. Concentrations of 3 H in river sites not affected by Temelín plant were slowly decreasing and their values were substantially below those from the sites affected by the plant.