Determination of <sup>224</sup>Ra and <sup>226</sup>Ra in drinking water
The content of natural isotopes of radium <sup>224</sup>Ra and <sup>226</sup>Ra in various types of natural drinking water was studied. For the separation of radium from natural waters, an improved analysis technique has been developed, including the preliminary separation of radium by granulated titanium dioxide, followed by the preparation of a thin alpha-spectrometric source by sorption with a thin layer of manganese dioxide (МnO<sub>2</sub>-CTA). It is shown that the time of sorption of radium on МnO<sub>2</sub>-CTA should be 1 day, while the degree of sorption of the order reached 75 %. At longer contact of the layer МnO<sub>2</sub>-CTA with a solution, the degree of sorption increases to 85 %, But the quality of the resulting alpha spectrum is worsened by diffusion of radium into the layer and an increase in the thickness of the source. 24 samples of mineral waters, as well as 4 samples of water from springs and 4 samples of water from wells in the vicinity of Ekaterinburg were analyzed. The results of the analysis showed that the mineral waters are characterized by a higher activity of <sup>226</sup>Ra (0,4-125 MBq/L), than for fresh (0,529 MBq/L), at the same time the level of interference was not exceeded in any sample (490 MBq/L). Activity of <sup>224</sup>Ra (the presence of this radionuclide in the waters unambiguously indicates the presence in the water of its parent radionuclide <sup>228</sup>Th) in freshwater was from 0,5 до 20 MBq/L, which is also less than the level of intervention.