ИСТИНА

The radionuclides monitoring in the natural water is an important task for assessing environmental safety and investigating the consequences of nuclear weapons tests and accidents at nuclear power plants. The big interest has isotopes of uranium, plutonium and fission products – iodine and technetium, which are very difficult to detect (existing in small amount even in large volumes of natural water). The aim of this study was to determine the content of 99Tc and 129I in water of Khanka lake and Japan sea. These radionuclides are widely used as an oceanographic tracer to track seawater movement and coastal pollution because of their high mobility. Water samples from 8 points with a volume 100 liters per each were taken in the winter 2021 from the ice. After sampling, the water was consequentially filtrated with pore size 1-5 µm and 0-1 µm and after filtration – acidified (only for 99Tc analyses) with HNO3 for pH 4. Accelerator mass spectrometry was used to determine 129 I. For 99Tc determination, the method of coprecipitation with iron (II) hydroxide followed by TEVA extraction-chromatographic resin separation was used1. The average content of 127I in Khanka lake water is 4.35-9.06 µg/L, and for the Japan sea water – 38.3-43.9 µg/L. The atomic ratio 129I/127I for the fresh water was 1.19-1.34·10-8 and for sea water 1.19-1.67·10-10 which is one order higher than in previous investigations. The 99Tc content for the fresh was 0.32-0.49 mBq/L and for sea water – 0.96-5.0 mBq/L. In the previous investigations, the 99Tc in sea water was identified in amount 0.01-0.1 mBq/L (Japan sea) in 19932. The results show that the level of hard-detected radionuclides increased till last 20-30 years.