The profiles of the vertical distribution of the gamma dose rate and activity concentrations of 90Sr, 137Cs, 154Eu, and 241Am in the bottom sediments of Brit Lake were obtained. The lake is located within the dammed section of the Krasnenska floodplain of the Pripyat River in the Chоrnobyl Exclusion Zone (51.44844°; 30.06020°). The values of the dose rate and activity concentration of 137Cs in the sediments reached 23 μGy h−1 and 43 Bq∙cm−3. In the lake Brit radioactive contamination of bottom sediments did not depend on the depth of the lake due to the washing of radionuclides from the water intake. A weak correlation was observed between values of in-situ measured and calculated gamma dose rates in bottom sediments. The average calculated and measured dose rates of gamma radiation in bottom sediments of the lake varied within the range of 1.3-19 μGy h−1 and was compatible with the internal radiation dose to fish (5-15 μGy h−1). Contribution of radionuclide content in water to the gamma dose rate does not exceed 2 nGy h−1. In October 2021, appropriate equipment for acoustic 3-D telemetry and individual dosimetry of various fish species was installed in the lake to reduce uncertainty in estimates of doses of external exposure to aboriginal fish in the lakes

After the accidents at the Chornobyl and Fukushima NPPs, the specific activity of radionuclides in fish in radioactively contaminated reservoirs reached hundreds of kBq kg-1. Over time, as the radiological situation improved, there was a decrease in radioactive contamination of fish, but even now there are cases of exceeding the permissible levels of radionuclides in food. This work aimed to determine in real conditions the content of 90Sr and 137Cs in different species of fish in one of the most radioactively contaminated reservoirs of the Chornobyl Exclusion Zone - Glubokoye lake. As a result of experimental studies conducted from 2016 to 2021, the values of the specific activity of 90Sr and 137Cs in different species of fish were obtained, which were hundreds of times higher than the permissible levels. It is shown that without the use of countermeasures, this situation will persist for several decades. The results show that the internal radiation doses of fish due to the level of their radioactive contamination do not exceed the permissible levels recommended by international organizations for radiation protection of the environment.

When the content of 90Sr and 137Cs in reservoir water is below the permissible level, even for drinking water, the specific activity of radionuclides in fish can be hundreds and thousands of times higher than the established hygienic standards of DR-2006. The purpose of this work was to determine the maximum permissible concentrations of 90Sr and 137Cs in the water of reservoirs depending on the content of calcium and potassium in the water based on the parameters of the metabolism of cesium and strontium in fish, which guarantee that the established hygienic standards of radionuclides in fish (DR-2006) are not exceeded with a probability of 95%. It is shown that in reservoirs with low water mineralization, the maximum allowable concentrations of 90Sr and 137Cs will be too low at the level of Bq units per cubic meter and difficult to measure, unlike radioactive contamination of fish, which makes them, even with minor radioactive contamination of reservoirs, a unique bioindicator for the purposes radiation protection of people and the environment.

No abstract

No abstract