Statistical Evaluation of the Tritium Content of Aquatic Ecosystems at NPP Sites

The lognormal statistical distribution was used to present the reliable integrated data on the content of various physicochemical forms of tritium in air, natural water, and components of aquatic ecosystems at nuclear facility sites. Statistics of lognormal distributions took into account the left truncation, which reflects the effect of finite sensitivity of measurements. The statistics of lognormal distributions were used to obtain estimates for ecosystems of NPP sites at limited sets of data. Specific activities were estimated for various forms of tritium such as HTO (free water), TFWT (tissue free water tritium), and OBT (organically bound tritium). The measurement results show that the specific activity of tritium in the body in bound forms was, as a rule, higher than its specific activity in free water in the ambient environment. Equilibrium concentration ratios (CRs) (partition coefficients of hydrogen) ranged from 1 to about 20. The results obtained by the Radium Institute research team agree with those obtained by the researchers from Canada and France for the specific activity of tritium in different chemical forms in environmental samples.