Validation of a Radionuclide Transfer Model in Brackish Lake

In order to simulate the behavior of radionuclides in a brackish lake, Lake Obuchi, adjacent to the first commercial spent nuclear fuel reprocessing plant in Japan, we constructed a transfer model for radionuclides using a three-dimensional hydrodynamic model coupled with an ecosystem model. To validate the hydrodynamic model using actual field data, the concentration of tritium (³H) was measured in water samples collected in and around the lake from 2005 to 2008. The samples collected from 2006 to 2008 occasionally showed higher concentrations than background when high concentration seawater flowed into the lake with the tide. ³H concentrations in the lake water estimated by the model were generally within 10% of the observations, although the observed values were overpredicted by a factor of 2 in a few cases.