Discovery of uranium mineralizations in the rhyolite-granite complex in the Jabal Eghei area of southern Libya

During investigation of the Jabal Eghei area in southern Libya and the production of geological maps at a scale of 1:250 000 (Tibesti sector, sheet Wadi Eghei NF 34-1 and NF 34-2), regional prospecting for mineral raw materials was performed. Radiometric survey of observed targets at the sites indicated two significant uranium mineralizations in rhyolites, and some smaller ones in granites that are in close contact with rhyolites. Rhyolites are located in the central part of the investigated region. They cut through granite rocks. The first mineralization is in the central part of the rhyolite region, which is mostly composed of silificated rhyolites. The second one was discovered near the granite-rhyolite contact zone, characterized by the presence of silicified breccia rocks. These findings were confirmed by laboratory measurements of more than seventy samples collected in the area, using high resolution gamma-ray spectrometry. The concentrations of uranium in these mineralizations were found to range from approx. 50 mg kg-1 to more than 600 mg kg-1. The latter value is about 240 times above the Earth’s average. Besides uranium, these measurements have also given concentrations of thorium and potassium. Additional geochemical analysis was performed on samples taken from locations where uranium anomalies were discovered using ICP-MS technique, in which concentrations of more than forty elements were determined. Uranium mineralizations are accompained by increased contents of silver (up to 17 times), arsenic (up to 8 times), molybdenum (up to 50 times), mercury (up to 9 times), and lead (up to 14 times), in regard to the Clark’s values. These results warrant a continued investigation of this region because of potential interest in the discovery of nuclear mineral raw materials

Prirodni radionuklidi u mahovinama iz istočne Srbije u razdoblju 2008.-2013.

The results of the study on natural radionuclide content in 102 samples of the moss species randomly collected in 2008-2013 at 30 locations of eastern Serbia are presented in the paper. The activity concentration values of 238U, 226Ra, 232Th, 40K, and 7Be determined by gamma spectrometry were within the intervals: 238U (1.1–50) Bq kg-1, 226Ra (1.1–41) Bq kg-1, 232Th (1.4–28) Bq kg-1, 40K (64–484) Bq kg-1 and 7Be (88–227) Bq kg-1, not standing out of the average data reported for this region. The distribution of the obtained data for 226Ra, 232Th, and 238U activity concentration in the analysed mosses has shown values up to 10 Bq kg-1 with frequencies 47.1 %, 54.9 % and 48.0 %, respectively. The obtained activity concentration values of primordial 40K and cosmogenic radionuclide 7Be were up to 500 Bq kg-1 and about 90 % of all the results for 7Be uptake by mosses were in the 200-250 Bq kg-1 concentration range.U radu su prikazani rezultati ispitivanja sadržaja prirodnih radionuklida u 102 uzorka mahovine prikupljene metodom slučajnoga uzorka u razdoblju 2008.-2013. na 30 lokacija u istočnoj Srbiji. Vrijednosti koncentracija (specifične aktivnosti) radionuklida 238U, 226Ra, 232Th, 40K i 7Be, određene primjenom spektrometrije gama zračenja, nalaze se u opsegu: 238U (1,1 – 50) Bq kg-1, 226Ra (1,1 – 41) Bq kg-1, 232Th (1,4 – 28) Bq kg-1, 40K (64 – 484) Bq kg-1 i 7Be (88 – 227) Bq kg-1 te ne odstupaju značajno u odnosu na ostale rezultate dobivene za ovu regiju. Distribucija dobivenih podataka o koncentracijama 238U, 226Ra i 232Th u analiziranoj mahovini pokazuje vrijednosti do 10 Bq kg-1, s učestalošću 54,9 %, 48,0 % i 47,1 %. Dobivene vrijednosti koncentracija primordijalnoga 40K i kozmogenoga 7Be bile su do 500 Bq kg-1, pri čemu je oko 90 % svih rezultata za 7Be akumuliranog u mahovinama bilo u opsegu koncentracija 200 – 250 Bq kg-1

One numerical method for determining the absorbed dose of gamma and X radiation in the ZrO2 dielectric within the MOS capacitor

At present, advanced microelectronics devices with Metal-Oxide-Silicon (MOS) structures are used to improve the functional characteristics of devices used in nuclear technology, radiation dosimetry and radiation protection in aerospace engineering, nuclear industry and radiotherapy equipment. Among other things, it is often the goal of new research to find new materials for the dielectric oxide such as of zirconium oxide (ZrO2) with higher dielectric constant (high-k) and testing its characteristics in an environment with radioactive radiation. The paper presents the application of a numerical method for the determination of the absorbed dose of gamma and X radiation in the dielectric thin layer of zirconium oxide, which is located in the structure of the MOS capacitor. The relation on the basis of the numerically calculated absorbed dose of radiation is obtained by using the theory of the physical transport of photons in a thin layer of dielectric. In doing so, it is necessary to know the spatial dependence of the photon flux of gamma or X-ray in a volume of the dielectric, as well as the values of the total mass attenuation coefficient and total energy absorbed mass coefficient for ZrO2 as a radiation characteristic of the material from which is made a dielectric. Based on the results of our research, it can be concluded that ZrO2 has satisfactory radiation characteristics as an alternative to the selection of dielectrics in MOS structures that are incorporated in dosimeters and radiation monitors.VII International Conference on Radiation in Various Fields of Research : RAD 2019 : book of abstracts; June 10-14, 2019; Herceg Novi, Montenegr

Leaching kinetics of Cs+ and Co2+ under dynamic conditions

The possibility of retaining Cs+ and Co2+ bound by immobilization processes in the cement matrix is defined as the subject of its investigation: the cement matrix formulation, the water/ cement ratio, the amount of waste, and the porosity of such a structure. Implementing the standard leaching method by Hespe the possibility of comparing different authors’ results was achieved. Diffusion and semi-empirical model were used to investigate the transport phenomenon in order to predict the leaching level for a long period of time. Leaching of Co2+ and Cs+ ions under dynamic conditions immobilized in the cement matrix dynamic conditions decreases with the increase of the sludge content, regarding porosity increase. The effects of the diffusion and surface washing are equalized, and the contribution ofthe matrix dissolution to the Cs + and Co2+ transport in the cement porous media increases, on average, for one order of magnitude. The semi-empirical model gives a better approximation for Co2+ and Cs+ leaching process for the duration ofthe experiment while both models significantly approximate leaching results in dynamic conditions. © 2019, Vinca Inst Nuclear Sci. All rights reserved

Radioactivity of sand from several renowned public beaches and assessment of the corresponding environmental risks

The radiological risk due to the presence of natural and man-made radionuclides in beach sands from several renowned seaside and riverbank public beaches was estimated in this study. The exposure levels to terrestrial radiation of the beaches were determined, as well as hazards due to human use of the analyzed sands in industry and in building constructions. Specific radionuclides concentrations in the sand samples were determined by standard gamma-spectrometry. The corresponding radiation hazards arising due to the use of sand as a building material were estimated by three different radiological hazard indices. The total absorbed gamma dose rate in the air was determined and the corresponding annual effective dose outdoors was estimated. The obtained data are relevant both from human health and environmental monitoring aspects

Characterization of PM(2.5)sources in a Belgrade suburban area: a multi-scale receptor-oriented approach

Designated as the most harmful for health, PM(2.5)aerosol fraction was a subject of our study. It was collected for all four seasons during 2014/15 in the suburban area of Belgrade (Serbia) and analysed for Al, Si, P, S, Cl, K, Ca, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Br, As, Ba and Pb elements and for NH4+, NO(3)(-)and SO(4)(2-)ions by particle-induced X-ray emission and ion chromatography techniques, respectively. Obtained concentrations have been treated by a combination of several receptor-oriented models to reveal source contributions to the suburban PM(2.5)at different spatial scales. Applied positive matrix factorization analysis indicated five main groups of emission sources: biomass burning (14.5%), traffic (3.9%), regional combustion/secondary sulphates (28.8%), local combustion/secondary nitrates (29.7%) and soil (5.4%). Local heating units had been pointed out as dominant contributors by long-range transport and ground-wind circulation analyses. Air masses circulating over the Balkan Peninsula denoted regional emissions as responsible for the high concentrations of secondary sulphates. Local and long-range transport analyses combined suggested that the BB and the LC/NO(3)originated from the wider urban area. Several Saharan dust episodes were detected as well. Presented results might be a basis for the development of air pollution mitigation strategies in the continental Balkan area, considered one of the most polluted and under-investigated European regions

JSCS–3847 Original scientific paper

Radioactivity of sand from several renowned public beaches and assessment of the corresponding environmental risk

Leaching kinetics of Cs+ and Co2+ under dynamic conditions

The possibility of retaining Cs+ and Co2+ bound by immobilization processes in the cement matrix is defined as the subject of its investigation: the cement matrix formulation, the water/ cement ratio, the amount of waste, and the porosity of such a structure. Implementing the standard leaching method by Hespe the possibility of comparing different authors’ results was achieved. Diffusion and semi-empirical model were used to investigate the transport phenomenon in order to predict the leaching level for a long period of time. Leaching of Co2+ and Cs+ ions under dynamic conditions immobilized in the cement matrix dynamic conditions decreases with the increase of the sludge content, regarding porosity increase. The effects of the diffusion and surface washing are equalized, and the contribution ofthe matrix dissolution to the Cs + and Co2+ transport in the cement porous media increases, on average, for one order of magnitude. The semi-empirical model gives a better approximation for Co2+ and Cs+ leaching process for the duration ofthe experiment while both models significantly approximate leaching results in dynamic conditions. © 2019, Vinca Inst Nuclear Sci. All rights reserved

JSCS–3921 Original scientific paper

Physical and chemical characterization of the particulate matter suspended in aerosols from the urban area of Belgrad

Toxicity evaluation of two polyoxotungstates with anti-acetylcholinesterase activity

A toxicity evaluation of two Keggin-type heteropolytungstates, K-7[Ti2PW10O40].6H(2)O and K6H [SiV3W9O40].3H(2)O, with different inhibitory potencies toward acetylcholinesterase activity (IC50 values of 1.04 x 10(-6) and 4.80 x 10(-4) mol/L, respectively) was performed. Wistar albino rats were orally treated with single doses (5 and 50 mg/kg) of both investigated compounds. The biochemical parameters of renal (serum urea and creatinine) and liver function (direct and total bilirubin, alanine transaminase, and aspartate aminotransferase) were determined after 24 h and 14 days. A histopathological analysis of liver tissue was carried out 14 days after the polyoxotungstate administration. Both applied doses of the investigated compounds did not induce statistically significant alterations of the renal function markers. However, the polyoxotungstate treatment caused an increase in the activities of serum alanine transaminase and aspartate aminotransferase in a time- and concentration -dependent manner, although statistically significant changes in bilirubin concentrations were not observed. Furthermore, the detected hepatotoxic effect was confirmed by histhopathological analysis that suggested some reversible liver tissue damage two weeks after the treatment, especially in the case of K6H [SiV3W9O40]-3H(2)O. Accordingly, the toxicity of these two polyoxotungstates with anti-acetylcholinesterase effect cannot be considered as a severe one, but their potential clinical application would require a more complex toxicological study