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Description
Zadní Chodov is a uranium mine in Český les, some 130 km west from Prague and less than six kilometers from the German border. With 4152 tons of uranium mined between its discovery in 1952 and closing of the mine in 1992, this was the sixth largest deposit in Czech Republic and is a Category III workplace according to the Czech legislation.
Flooding of the mine started in February 1993 and led to the release of the mine water into the surface flow. Until 2010, the concentrations of radionuclides in the discharged water were reduced in the local mine water treatment plant. Given that the measured values of radionuclide concentrations, set in the Monitoring Program DIAMO, s. e. (monitoring of radionuclide concentrations in water and sediments, for which monitoring levels are set), were acceptable, this treatment was stopped with the consent of the SONS in 2010.
The concentration of radionuclides in surface water and stream sediments began slowly to increase. In 2012, an experimental wetland was built here, through which 1/4 of the mine water flowing out is channeled and which actively participates in reducing radionuclide concentrations in the drainage ditch. The 0.25 mSv/y constraint for a representative person was complied with; the situation was stable, and without proven adverse effects/contamination to the surrounding pastures.
In 2024, beavers settled along the drainage ditch and in short time built more than 20 dams, raising the water level, flooding the sections of the surrounding pastures a woods, creating yet another wetland. This contribution presents resulting radionuclide contamination of the ditch surroundings – based on laboratory and in-situ gamma spectrometry, 3D LiDAR scanning and imaging using UAS. Contribution to external and internal irradiation on a representative person was estimated using methodology specified by Czech legislation.