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Specific activity of tritium (H-3) in precipitation and specific activity of Cs-137 in ground-level air were monitored at three locations in Belgrade (Meteorological Station of Belgrade at Zeleno Brdo (ZB), Meteorological Station Usek (USEK), and Vina Institute of Nuclear Sciences (VINS)). Data presented cover the period 1985-1997 for Cs-137 for all locations and 1985-2009 (ZB), 1988-1997 (USEK), and 1988-2009 (VINS) for H-3. Concentrations of H-3 in precipitation have been determined using electrolytic enrichment and liquid scintillation spectrometer LKB-Wallac 1219 RackBeta. The activity of Cs-137 in air was determined on an HPGe detector (Canberra, relative efficiency 23 %). H-3 concentrations in precipitation ranged from 0.40 +/- 0.08 to 74.6 +/- 5.2 Bq l(-1) decreasing with distance from the nuclear facilities. Significantly higher tritium levels were measured in samples in VINS compared with those from an off-site location. The observed seasonal variations of tritium concentration indicate the stratospheric source of tritium. Increases in activity concentration of Cs-137 in the atmosphere were observed after the nuclear plant accident at Chernobyl in April 1986. The concentrations obtained for Cs-137 in 1986 were compared with the integrated air concentrations of Cs-137 in the region. The increases of Cs-137 air concentrations in 1987 and 1988 were attributed to local resuspensions from the ground. Since 1989, the activity level before the accident has been obtained. The average monthly concentrations of Cs-137 in ground-level air were shown spread maximum in spring-summer period and pronounced maximum during winter. The obtained results were statistically analyzed, i.e., the following parameters were determined: tritium deposition, monthly activities of H-3 and Cs-137, seasonal indices, radionuclide loading indices, and linear correlation coefficients.

Disertacijoje nustatyti 137Cs patekimo į Ignalinos AE aplinkos orą šaltiniai ir įvertinti ilgamečiai 137Cs aktyvumo koncentracijų ore pokyčiai. Radionuklidų aktyvumo koncentracijos ore ir iškritose matuotos nuo 2004 iki 2009 metų Ignalinos AE poveikio zonoje. Gauta, kad metinės 137Cs aktyvumo koncentracijos pažemio ore pastaraisiais metais kinta su 30 metų mažėjimo pusiau trukme. Stebėta, kad šuoliški 137Cs aktyvumo koncentracijų pažemio ore padidėjimai koreliuoja su oro masių pernašos trajektorijomis, kertančiomis teritorijas, užterštas po avarijos Černobylio AE. Nustatytas radioaktyvių aerozolio dalelių augimas prisotintuose vandens garuose veikiančio RBMK reaktoriaus kondensatoriuje. Vieno kontūro atominės elektrinės aušinamame vandens gare inertinių dujų radionuklidai, skildami virsta šarminių ir žemės šarminių metalų elementais, tampa aerozolio gamybos centrais, absorbuoja vandens molekules ir per keliolika minučių ant jų, kaip kondensacijos branduolių, išauga radioaktyvios aerozolio dalelės. Klasikinis radionuklidų aktyvumo aerozolio dalelių, surinktų filtrais, bandiniuose nustatymas papildytas išplovimo distiliuotu vandeniu eksperimentais, matuojant radionuklidų aktyvumą bandiniuose iki ir po eksperimento. Gauta, kad 137Cs ir 60Сo dalis aerozolio dalelių, surinktų veikiančio reaktoriaus ventiliaciniame ore, tirpioje frakcijoje buvo 74  22 % ir 67  17 %, atitinkamai, o neveikiančio reaktoriaus ventiliaciniame ore – 24  5 % ir 20  5 %. 60Co aktyvumo koncentracijos AE... [toliau žr. visą tekstą] Investigations on the determination of 137Cs sources in the Ignalina NPP environment air and the evaluation of changes of the long-term trend of 137Cs activity concentrations in the Ignalina NPP ground-level air were carried out in this dissertation. Radionuclide activity concentrations in the air and deposition were measured in the Ignalina NPP impact zone in 2004-2009. Results show, that in recent years annual 137Cs activity concentrations in the ground-level air in the Ignalina NPP region change with the half-time of 30 years. Observed episodic increases in 137Cs activity concentrations in the air correlate well with air mass transport trajectories that intersect territories, polluted with 137Cs after the accident at the Chernobyl NPP. The growth of radioactive aerosol particles in the oversaturated water vapour of the operating RBMK reactor has been investigated. In the one contour nuclear power plant coolant water steam, noble gas radionuclides decay into alkaline and earth-alkali metals, which become condensation nuclei and due to the absorption of water molecules in several minutes grow into radioactive aerosol particles. The classical method of the radionuclide activity determination in aerosol particle samples, collected on filters, was supplemented with experiments on the leaching of aerosol particles using the distilled water and measurements of radionuclide activities in samples before and after the experiment. Results show that the quantity of 137Cs and 60Сo in... [to full text]