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The potential re-use of red mud in the building and construction industry has been the subject of research of many scientists. The presented research is a contribution to the potential solution of this environmental issue through the synthesis of potential construction materials based on red mud. A promising way of recycling these secondary raw materials is the synthesis of alkali-activated binders or alkali activated materials. Alkali-activated materials or inorganic binders based on red mud are a new class of materials obtained by activation of inorganic precursors mainly constituted by silica, alumina and low content of calcium oxide. Since red mud contains radioactive elements like 226Ra and 232Th, this may be a problem for its further utilization. The content of naturally occurring radionuclides in manufactured material products with potential application in the building and construction industry is important from the standpoint of radiation protection. Gamma radiation of the primordial radionuclides, 40K and members of the uranium and thorium series, increases the external gamma dose rate. However, more and more precedence is being given to limiting the radiological dose originating from building materials on the population these days. The aim of this research was to investigate the possible influence of alkali activation-polymerization processes on the natural radioactivity of alkali activated materials synthesized by red mud (BOKSIT a. d. Milići, Zvornik, Bosnia and Herzegovina) and their structural properties. This research confirmed that during the polymerization process the natural radioactivity was reduced, and that the process of alkali activation of raw materials has an influence on natural radioactivity of synthesized materials.

Presented study deals with the final structure and radiological properties of different fly-ash based geopolymers. Lignite fly-ash (lignite Kolubara – Serbia) and wood fly ash were obtained in combustion process together with commercial fly-ash. Synthesis of the geopolymers was conducted by mixing fly-ash, sodium silicate solution, NaOH and water. The samples were strengthened 60 °C for 48 hours after staying at room temperature in covering mold for 24 hours. The X-ray diffraction, Fourier transform infrared and SAM measurements were conducted on the samples after 28 days of geopolymerization process. The X-ray diffraction measurements of lignite fly-ash samples show anhydrite as the main constituent, while wood fly-ash samples consist of calcite, albite and gypsum minerals. Besides determination of physicochemical properties, the aim of this study was radiological characterization of lignite fly-ash, wood fly-ash and the obtained geopolymer products. Activity concentration of 40K and radionuclides from the 238U and 232Th decay series, in ash samples and fly-ash based geopolymers, were determined by means of gamma-ray spectrometry, and the absorbed dose rate, D, and the annual effective dose rate, E, were calculated in accordance with the UNSCEAR 2000 report.

Various imported building materials commonly used in construction and industry in Serbia were analyzed using gamma spectrometry. Based on the activity concentrations of 226Ra, 232Th, and 40K in the investigated samples, radium equivalent activity, Raeq, absorbed dose rate, D, annual effective dose, DE, and the external hazard index, Hex, were calculated to assess the radiation hazard for people. The Raeq for most of the analyzed samples (416 in total) was lower than the maximum admissible value of 370 Bqkg-1 set in the UNSCEAR report. The absorbed gamma dose rate in air was found to vary from 0.030 mGyh-1 to 1.328 mGyh-1 which in some cases exceeded indoor dose rates in Europe. The obtained values for annual effective dose exceed the limits of 0.41 mSv given in literature for about 5 % of measured samples, while values of Hex were higher than unity for three samples of cement, eight samples of granite, and one sand sample. As a possible source of elevated effective dose, the radon exhalation from building materials was estimated using the parameters given in literature. The internal dose due to 222Rn exhaled from the building material was found to be up to nine times higher than external dose due to 226Ra content in some cases.

A significant amount of red mud generated as a by-product of the Bayer process in the aluminum industry may cause environmental problems if appropriate treatment is not carried out. The presented research dealt with the possibility of application of red mud as a pigment or as raw material for use in the construction material industry. In relation to the aim of this work, the physicochemical characterization was performed and the natural radioactivity of red mud as an industrial waste and a geopolymer sample based on it was determined. The presented research is a contribution to the potential solution for environmental protection through the synthesis of possible construction material based on red mud. The radiological hazard orginating from226Ra,232Th, and40K in the samples was assesed throught the absorbed dose rate and the annual effective dose rate, calculated in accordance with the UNSCEAR 2010 report. Physicochemical characterization of all samples was conducted using X-ray diffraction and diffuse reflectance infrared Fourier transform spectroscopy. © 2018, Vinca Inst Nuclear Sci. All rights reserved.

The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)(3)) and they consists of particles of median particle size 2.1 mu m (sample A) and 2.5 mu m (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from U-238, Th-232, K-40 in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper.

Laundry detergents are chemicals widely used in everyday life, and in numerous industry branches. In order to perceive the radiological aspect of environmental pollution by wastewater, the analysis of laundry detergents available on the Serbian market was undertaken. Laundry detergent samples were measured by means of gamma spectrometry and the results are presented in this paper. Analysis of the obtained activity concentrations showed that laundry detergents in Serbia mostly fulfill the international recommendation and requirements regarding the phosphate content. Besides that, the content of the detected radionuclides in laundry detergent samples indicates the minor radiological risk to the environment via wastewaters.

The aim of this study was to investigate the Cs+ ions sorption on natural minerals clinoptilolite. The analysis of clinoptilolite and clinoptilolite with adsorbed Cs+ ion was con- ducted by X-ray diffraction, scanning electron microscopy, X-ray fluorescence, and gamma spectrometry. The specific activity of naturally occurring radionuclides in clinoptilolite was determined by gamma spectrometry by using the HPGe semiconductor detector. Obtained activity concentrations ranged from 49 Bq/kg to 810 Bq/kg for 40K, 5.7 Bq/kg to 10 Bq/kg for 238U, 5.8 Bq/kg to 70 Bq/kg for 232Th(228Ac), and the presence of artificial radionuclides was not detected (137Cs < 0.02 Bq/kg). The study of the thermal decomposition of raw clinoptilolite and Cs adsorbed clinoptilolite by differential thermal analysis is presented in this paper. The activation energy of the reaction phase transformation of raw clinoptilolite is 156.7 kJ/mol, while Cs adsorbed clinoptilolite is 121.7 kJ/mol. The lower value of activation energy reaction of the phase transformation Cs adsorbed clinoptilolite indicates that Cs which is adsorbed destabilizes the crystal structure of clinoptilolite and thus facilitates the transition to the amorphous state. [Projekat Ministarstva nauke Republike Srbije, br. 45012]

The exposure of human beings to ionizing radiation from Cs-137 is a continuing and inescapable feature of life on Earth. Artificial radio nuclides are widely distributed in various geological formations and ecosystems such as rock, soil, groundwater, and foodstuffs. In the presents study, the distribution of Cs-137 was measured in soil samples collected from different lithological units of the Rudovci, Lazarevac, Serbia. Analysis of the vertical soil profiles indicated that the activity of Cs-137 was not extremely changed with depth. The activity concentrations of the Cs-137 in measured soil samples ranged from below minimal detectable concentrations up to 38.1 Bq/kg. In order to evaluate the radiological hazards due to Cs-137 in the samples, the absorbed dose rate and the annual effective dose were calculated in accordance with recommendations given in the UNSCEAR 2000 report. The distribution of radionuclides depends upon the rock composition, chemical and physical properties of the soil. The external absorbed gamma dose rates due Cs-137 were found to vary from 0 to 1.16 nGy/h.

The direct measurement of Ba-133 source activity by the application of the theoretical count rate equations has been recently developed by Novkovic et al. The analytical and Monte Carlo calculation of activity measurement uncertainties were described in previously published papers for the case of one recorded spectra. The procedure of uncertainty calculation for a sequence of successively recorded spectra, enabling the determination of the correlation between peak count rates, is presented in this paper. The uncertainty of activity obtained by the described method is caused by the uncertainty of the experimentally obtained input data and uncertainties of the used nuclear decay data.

This paper introduces the distribution background and unique characteristics of 137Cs in cultivated and undisturbed areas. The samples were taken from three measuring points of the depth of 1 m. We examined all visible horizons and determined their classifications. There were four horizons in one profile. All four horizons had a different zone thickness. 137Cs is an artificial radionuclide that has been produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950. Also, the great amount of 137Cs (~85 PBq) was released in the atmosphere during the Chernobyl accident. So, 137Cs has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of 137Cs in soil is primarily controlled by soil erosion processes, such as processes caused by water, wind, and tillage. Thus, 137Cs is a valuable tracer to study soil erosion. The specific activity of 137Cs in soil and sediment samples was determined by using the gamma-spectrometric method., U ovom radu prikazana je rasprostranjenost i jedinstvene karakteristike cezijuma-137 kako u obradivim tako i u neobradivim zemljištima. Uzorkovanje je vršeno na tri merna mesta do 1 m dubine. Ispitani su svi vidljivi horizonti i utvrđeno je postojanje 4 horizonta u jednom profilu, koji su različitih debljina. Cezijum-137 je veštački radioizotop koji je nastao kao posledica termonuklearnih reakcija ispitivanog oružja u atmosferi zemlje kao i neželjeni proizvod nuklearnih akcidenata (Černobil, 1986). Ovaj radioizotop je široko rasprostranjen u celom svetu, gde se njegova migracija u zemljištu prati pomoću intenziteta erozije potpomognutim vodom i vetrom. Stoga je cezijum-137 važan faktor pri određivanju intenziteta erozije kako u zemljištu tako i u sedimentima, te je određena njegova specifična aktivnost korišćenjem gama spektrometrije.

This paper introduces the distribution background and unique characteristics of Cs-137 in cultivated and undisturbed areas. The samples were taken from three measuring points of the depth of 1 m. We examined all visible horizons and determined their classifications. There were four horizons in one profile. All four horizons had a different zone thickness. Cs-137 is an artificial radionuclide that has been produced primarily as a result of atmospheric thermonuclear weapon tests since the 1950. Also, the great amount of Cs-137 (similar to 85 PBq) was released in the atmosphere during the Chernobyl accident. So, Cs-137 has been globally distributed, with fallout rates generally related to latitude and precipitation depth. The movement of Cs-137 in soil is primarily controlled by soil erosion processes, such as processes caused by water, wind, and tillage. Thus, Cs-137 is a valuable tracer to study soil erosion. The specific activity of Cs-137 in soil and sediment samples was determined by using the gamma-spectrometric method.

The results of experimental testing of the digital multichannel analyzer which digitalizes the signal after a preamplifier are presented. The recordings of some of the characteristics of the spectrometer containing a digital MCA, such as full-peak efficiency, net-area ratio of the two peaks and the stability of the peak position, were carried out under different input counting rates, with different radioactive sources. The tested MCA has shown some excellent features, like the stability of the peak position over a long-term period and flexibility in the adjusting of optimum measurement conditions. However, the performed tests have also shown some serious and unexpected disadvantages of the digital MCA when it operates under certain circumstances, one of them having to do with the automatic tuning of live-time correction at low-input counting rates.