No abstract

In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

Radionuclides iti the geosphere /Sorption ratios /Colloid formation/Radioactive Cs + ¡Radioactive Sr 2+ /Radioactive Ce 3+ Summary Natural systems comprising sediments and groundwaters of low and of high salinity are investigated with respect to the formation and the influence of coarsely dispersed particles and finely dispersed particles (colloids). Equations are derived for the sorption equilibria in such systems and it is shown that the efficiencies of mutual separation of coarsely dispersed particles, finely dispersed particles and sediments (efficiencies of filtering) strongly influence the sorption ratios that are observed.In groundwater without sediments the formation of colloids of radioactive Ce 3+ is demonstrated, whereas Cs + and Sr ì+ do not form colloids under these conditions, as expected.The amounts of elements and of colloids given off by the sediments into the groundwaters are measured for the samples of low and of high salinity and the influence of agitation is shown.Sorption ratios of radioactive Cs + , Sr î+ , and Ce 3+ are investigated as function of the ratio of the groundwater volume to the mass of the sediment without filtration, after filtration through 0.45 Mm filters and after ultrafiltration. The results are discussed on the basis of the equations derived. It is shown that Cs + ions are sorbed mainly on the clay particles and that the larger amount of these clay particles has grain sizes greater than 0.45 Mm under the experimental conditions of smooth shaking. Sr 2+ ions are mainly sorbed on the sediments with a relatively low sorption ratio. Ce 3+ ions form colloids ("Eigenkolloide") that are retained by ultrafiltration.

Radioactive iodine /Iodine in groundwater / Sorption of iodine/ Carboniferous particles /Organics /Microorganism SummaryThe chemistry of iodine in the hydrosphere is discussed and the sorption of radioactive iodine on sediments from the layers above the salt dome at Gorleben is investigated at low and high salt concentrations. Special attention is paid to the carboniferous particles in the sediments and their influence on sorption of iodine. For this purpose the amount of carboniferous particles in the sediments is varied and the sediments are pretreated by heating and by addition of Η 2 0,. The influence of addition of NaCl is also investigated. The sorption of I ~ on the inorganic components of the sediments (the minerals) is rather small, as expected. It is mainly due to physical adsorption. The sorption of I" in the carboniferous particles, however, is very high. Iodine is taken up by these particles, in particular by the organic compounds and the microorganisms contained therein by very slow irreversible processes.

Cesium /Sorption of Cesium/Colloids/Clay minerals /Ion exchange SummaryCesium is sorbed with relatively high selectivity by clay minerals. Accordingly, in groundwaters Cs is found in high amounts in suspended matter or in colloids, if these consist of or contain clay minerals. The sorption of Cs in sediments is also mainly determined by the presence of clay minerals and the sorption ratio at low salinity is found to be roughly proportional to the clay content in the sediments. Furthermore, with the same sediment the sorption ratio is inversily proportional to the concentration of NaCl which proves that ion exchange on the clay minerals is the prevailing sorption mechanism for Cs.It is shown that the sediments contain small amounts of sorption sites of high selectivity for Cs + which govern the sorption behaviour at very small concentrations of Cs + ions. These sorption sites are also responsible for Cs + sorption on suspended particulates of clay in the groundwaters.