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Квалитет гама спектрометријских мерења у општем сучају директно зависи од познавања ефикасности детекције за посебне случајеве геометрије мерења и карактеристика мереног узорка. С обзиром на то да узорци који се мере могу бити веома различити по хемијском саставу и геометрији, калибрација није доступна у свакој ситуацији. Поред тога, код мерења у контактној геометрији, што је најчешћи случај приликом мерења узорака из животне средине, феномен коинцидентног сумирања пертурбује спектар и мења површине испод пикова у спектру што резултује нетачним резултатима мерења. Тада се јавља потреба за развијањем различитих метода за калибрацију и специфичних референтних материјала за сваки појединачни случај. Методе калибрације могу подразумевати мерење сертификованих извора или секундарних референтних материјала, одређивање параметара потребних за израчунавање ефикасности или симулирање спектралног одговора инструмента. У овом раду представљено je и примењено неколико различитих приступа калибрацији ефикасности мерног система. То су: - Експериментални метод, који подразумева мерење секундарних референтних материјала који су по геометрији и хемијском саставу најприближнији узорцима који се мере. Овај метод даје најтачније резултате али истовремено захтева дуго време припреме секундарних референтних материјала и дуго време мерења. Све ово може бити извор низа мерних несигурности које су последица управо те припреме. -Аналитички метод, који подразумева успостављање аналитичке зависности између ефикасности и геометријских карактеристика мереног узорка и детектора. Овај метод је апроксимативан с обзиром на то да су интеграли који описују зависност за цилиндричне геометрије врло компликовани и њихово решавање је могуће једино нумеричким путем. Уведене апроксимације доприносе мерној несигурности али у оквирима потреба мерења узорака из животне средине могу бити прихватљиве. -Полуемиемпиријски метод (представљен у овом раду програмом за трансфер ефикасности, EFFTRAN) користи зависност, The quality of the gamma spectrometry measurements is in general directly dependent on determining of the efficiency for the specific measurement geometry and measured sample characteristics. Due to the fact that measured samples can be very versatile in terms of geometry and chemical composition, the efficiency calibration is not readily available. That is when the need for developing different efficiency calibration methods and specific reference materials becomes obvious. Methods of efficiency calibration may consist of measurement of certified sources and secondary reference materials, determination of the parameters needed for efficiency calculation or simulation of the detector system response. Besides, the measurement in contact geometry, such is the case in measurement of environmental samples, implies the perturbation of the spectrum via coincidence summing effect, which leads to incorrect results of the measurement. Several methods for efficiency calibration of the measurement system are presented and utilized in this thesis. These are: - Experimental method, which implies the measurement of the secondary reference materials that are similar to the realistic samples in terms of geometry and composition. This method produces high accuracy results but at the same time requires long time for production of the secondary reference materials and long measurement time. All this can be the source of large measurement uncertainty. -Analytical method, which implies the existence of analytical dependence between the efficiency and geometrical characteristics of the measured sample and detector. This method is approximate, due to the fact that the integrals describing the efficiency dependence for cylindrical geometry are very complex and their solution is only possible by using a numerical integration. The approximations introduced in the calculation contribute to the uncertainty of the results, but can be acceptable in case of environmental samples. -Semi empirical

The homogeneity of fertilizer samples for interlaboratory gamma-ray spectrometry comparison was tested by determination of the total. count rate and the count rates for two U-238. lines, one K-40 line and one common U-235 and Ra-226 line. Homogeneity testing was accomplished by determination of the minimum, maximum, mean and standard deviation for each parameter and comparison of their standard deviations with predefined tolerances, by Cochrans test, and by a one-way ANOVA. The standard deviations were all less than these tolerances. All samples passed Cochrans test and the one-way ANOVA test for homogeneity.

One of the major difficulties in gamma spectrometry of voluminous environmental samples is the efficiency calibration of the detectors used for the measurement. The direct measurement of different calibration sources, containing isolated gamma-ray emitters within the energy range of interest, and subsequent fitting to a parametric function, is the most accurate and at the same time most complicated and time consuming method of efficiency calibration. Many other methods are developed in time, some of them using Monte Carlo simulation. One of such methods is a dedicated and user-friendly program PHOTON, developed to simulate the passage of photons through different media with different geometries. This program was used for efficiency calibration of three HPGe detectors, readily used in Laboratory for Environment and Radiation Protection of the Institute for Nuclear Sciences Vinca, Belgrade, Serbia. The simulation produced the spectral response of the detectors for fixed energy and for different sample geometries and matrices. Thus obtained efficiencies were compared to the values obtained by the measurement of the secondary reference materials and to the results obtained by GEANT4 simulation, in order to establish whether the simulated values agree with the experimental ones. To further analyze the results, a realistic measurement of the materials provided by the IAEA within different interlaboratory proficiency tests, was performed. The activities obtained using simulated efficiencies were compared to the reference values provided by the organizer. A good agreement in the mid energy section of the spectrum was obtained, while for low energies the lack of some parameters in the simulation libraries proved to produce unacceptable discrepancies. (C) 2015 Elsevier B.V. All rights reserved.

This paper is focused on the results for activity concentrations of Be-7 in depositions recorded in Vina Institute of Nuclear Sciences, as part of radioactivity monitoring in Institute from 1994 to 2013. year. Samples were collected on a monthly basis and activities were present on sampling day (middle of the month). The activities were determined on HPGe detectors by standard gamma spectrometry, and they ranged from 0.05 to 10.4 Bq m(-2). The obtained results were statistically analyzed. The Be-7 activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter.

This work presents a comprehensive study of natural radioactivity in 720 building materials imported in Serbia in 2012. Radioactivity concentrations of Ra-226, Th-232 and K-40 in the studied samples range from LT 5 to 4,938, LT 3 to 763 and LT 10 to 3,192 Bq kg(-1), respectively. The maximum values of Ra-226 and Th-232 activity concentrations were found in zirconium mineral, while the highest K-40 activity concentration was in the feldspar. Based on the obtained radionuclide concentrations, radium equivalent activity, air absorbed dose rate, annual effective dose, external and internal hazard indices, gamma and alpha index due to radon inhalation were evaluated to assess the potential radiological hazard associated with these building materials.

To assure that radiological monitoring is reasonably valid, organisations performing such measurements have found it necessary to establish quality assurance (QA) and quality control (QC) programs. These programs are needed to identify deficiencies in the sampling and measurement processes. In addition, validation of the monitoring aims to prove whether the results are acceptable. The major aim of QA and QC in analytical laboratories is to address measures used to verify the validity of the final results. In the document ISO 17025 the requirements on how to achieve QA and QC in analytical laboratories is described. All proposed measures for QC/QA are implemented in the Radiation and Environment Protection Department of Institute for Nuclear Sciences in Vinča, Belgrade. This paper presents the summarisation and analysis of QC and QA measures undertaken by the Laboratory for Environmental and Radiation Protection of the Vinča Institute of Nuclear Sciences. Total of 6 months of QC/QA charts are presented in this paper for 2 HPGe gamma spectrometry detectors and one gross alpha/beta detector. The data were analysed and conclusions were made concerning the stability of the measurement systems. In cases of unsatisfactory behaviour of the system, some correctional measures are proposed and conducted and the effect on the measurement system is discussed.

Active charcoal detectors are used for testing the concentration of radon in dwellings. The method of measurement is based on radon adsorption on coal and measurement of gamma radiation of radon daughters. The contributions to the final measurement uncertainty are identified, based on the equation for radon activity concentration calculation. Different methods for setting the region of interest for gamma spectrometry of canisters were discussed and evaluated. The obtained radon activity concentration and uncertainties do not depend on peak area determination method. (C) 2013 Elsevier Ltd. All rights reserved.

The determination of radionuclide activity concentration requires a prior knowledge of the full-energy peak (FEP) efficiency at all photon energies for a given measuring geometry. This problem has been partially solved by using procedures based on Monte Carlo simulations, developed in order to complement the experimental calibration procedures used in gamma-ray measurements of environmental samples. The aim of this article is to apply GEANT4 simulation for calibration of two HPGe detectors, for measurement of liquid and soil-like samples in cylindrical geometry. The efficiencies obtained using a simulation were compared with experimental results, and applied to a realistic measurement. Measurement uncertainties for both simulation and experimental values were estimated in order to see whether the results of the realistic measurement fall within acceptable limits. The trueness of the result was checked using the known activity of the measured samples provided by IAEA.

The charcoal canister method of radon measurement according to US Environment Protection Agency protocol 520/5-87-005 is widely used for screening. This method is based on radon adsorption on coal and measurement of gamma radiation of radon daughters. For the purpose of gamma spectrometry, appropriate efficiency calibration of the measuring system must be performed. The most usual method of calibration is using standard canister, a sealed canister with the same matrix and geometry as the canisters used for measurements, but with the known activity of radon. In the absence of standard canister, a different method of efficiency calibration has to be implemented. This study presents the results of efficiency calibration using the EFFTRAN efficiency transfer software. Efficiency was calculated using a soil matrix cylindrical secondary reference material as a starting point. Calculated efficiency is then compared with the one obtained using standard canister and applied to a realistic measurement in order to evaluate the results of the efficiency transfer.

In the 1999 bombing of the Federal Republic of Yugoslavia, NATO forces used ammunition containing depleted uranium. The cleaning of depleted uranium that followed was performed in southern Serbia by the Vinca Institute of Nuclear Sciences between 2002 and 2007 at the locations of Pljackovica, Borovac, Bratoselce, and Reljan. This paper presents detailed results of radioactivity monitoring four years after cleaning (2011), which included the determination of gamma emitters in soil, water, and plant samples, as well as gross alpha and beta activities in water samples. The gamma spectrometry results showed the presence of natural radionuclides Ra-226, Th-232, K-40, U-235, U-238, and the produced radionuclide Cs-137 (from the Chernobyl accident). In order to evaluate the radiological hazard from soil, the radium equivalent activity, the gamma dose rate, the external hazard index, and the annual effective dose were calculated. Considering that a significant number of people inhabit the studied locations, the periodical monitoring of radionuclide content is vital.

Determination of full energy peak efficiency is one of the most important tasks that have to be performed before gamma spectrometry of environmental samples. Many methods, including measurement of specific reference materials, Monte Carlo simulations, efficiency transfer and semi empirical calculations, were developed in order to complete this task. Monte Carlo simulation, based on GEANT4 simulation package and EFFTRAN efficiency transfer software are applied for the efficiency calibration of three detectors, readily used in the Environment and Radiation Protection Laboratory of Institute for Nuclear Sciences Vinca, for measurement of environmental samples. Efficiencies were calculated for water, soil and aerosol samples. The aim of this paper is to perform efficiency calculations for HPGe detectors using both GEANT4 simulation and EFFTRAN efficiency transfer software and to compare obtained results with the experimental results. This comparison should show how the two methods agree with experimentally obtained efficiencies of our measurement system and in which part of the spectrum do the discrepancies appear. The detailed knowledge of accuracy and precision of both methods should enable us to choose an appropriate method for each situation that is presented in our and other laboratories on a daily basis. (C) 2014 Elsevier B.V. All rights reserved.

Activities of Be-7 and Pb-210 were monitored in surface air in Belgrade, Serbia, from 2004 to 2012. The measurements were taken from two locations, in an open field of a city suburb and in the central city area. The activities were determined on HPGe detectors by standard gamma spectrometry. The Be-7 activity shows a pronounced seasonal pattern, with the maximum in spring-summer and minimum in winter, while the Pb-210 activity exhibits two maxima, in autumn and late winter. The mean monthly concentrations measured at both sites are below 9 mBq/m(3) and 1.3 mBq/m(3) for Be-7 and Pb-210, respectively. The obtained correlation of the Be-7 activity with the number of sun-spots is not statistically significant. Relations of the radionuclides activities with climate variables (precipitation, temperature, relative humidity, cloud cover, sunshine hours, and atmospheric pressure) are also investigated, but the only significant correlations are found for the Be-7 activity with temperature and sunshine hours, and the Pb-210 activity with atmospheric pressure. The maximum Be-7 and Pb-210 activities corresponding to binned total monthly precipitation data imply different modes of the radionuclide scavenging from the atmosphere. During dry periods, accumulation of the radionuclides in the atmosphere leads to their increased activities, but no correlation was found between the activities and the number of consecutive dry days.

Natural resources such as ores contain radioactive nuclides at various concentrations. Therefore it is important to investigate the radioactivity in these resources as well as in the soil at the locations of ore deposits. For that reason we conducted preliminary measurements in the soil samples taken from the locations of lead and zinc ore deposits in Bosilegrad and Raska and from the locations of phosphate ore deposits in Bosilegrad to estimate the environmental conditions prior to the ore excavation. The activity concentrations of radionuclides in soil, water and plant samples were determined by gamma spectrometry (HPGe detector, relative efficiency 23%). Results showed the presence of natural radionuclides Ra-226, Th-232, K-40, U-235, U-238 as well as the produced radionuclide Cs-137 (from the Chernobyl accident). Ambient gamma radiation dose rate in ground level air was also measured. In order to estimate the influence of subsequent mining on the working and living environment, radium equivalent (Ra-eq), external hazard index (H-ex), external gamma absorbed dose rate ((D) over dot) and annual effective dose (D-E) were determined.

After the accident in Fukushima reactors, a daily monitoring programme was initiated in two laboratories in Belgrade, one at the VinD degrees Institute for Nuclear Sciences and the other at Institute for Occupational Health Karajovic. Samples of aerosol and fallout, as well as the random samples of food and water, were collected and analysed, using gross alpha/beta and gamma spectrometry, in order to establish the presence of traces of isotopes indicating Fukushima fallout. Gamma spectrometry measurement of these samples showed clear evidence of fission products I-131, Cs-134 and Cs-137 wtihin 2 weeks after the accident. The activity diminished with time due to dispersion in air and, in case of I-131, short half-life.

A considerable number of primordial radioisotopes are present in almost all the samples extracted from the Earths crust, such as oil, rock, soil or other materials. Their concentrations are often determined by gamma spectrometry. Although the relative concentrations of isotopes often fluctuate within a narrow range, it is not always the case. Some natural materials (such as naturally occurring radioactive material) show unusual activity ratio between U-238 and Th-232, while technologically processed materials (technologically enhanced naturally occurring radioactive material) might also introduce significant disequilibrium hi radioactive chains. Knowing that primordial radioisotopes emit in total more than a thousand gamma and characteristic X-ray photons and that many of them interfere with each other, a question arises whether for some activity ratios commonly used photopeaks become useless for quantitative analysis, due to interferences with other photopeaks. A computer program was developed in order to calculate full energy photon interferences for any chosen photopeak. The calculations are based on the inputs in the form of isotope activities and detector calibration equations and its characteristics are presented in this paper.

The radioactivity monitoring in the Nikola Tesla, Kolubara, Morava and Kostolac coal-fired power plants was performed by the Radiation and Environmental Protection Laboratory, Vinca Institute of nuclear sciences in the period 2003-2010. Monitoring included the analysis of soil, water, flying ash, slag, coal and plants. This paper presents the results of the radioactivity analysis of coal, ash and slag samples. Naturally occurring radionuclides Ra-226, Th-232, K-40, U-235, U-238, and Pb-210 as well as the man-made radionuclide Cs-137 were determined by gamma spectrometry using HPGe detector. The concentrations of pairs of radionuclides were statistically tested to determine the corellation between them. Based on the obtained results, health effect due to the activity of these radionuclides was estimated via radium equivalent (Ra-eq), external hazard index (H-ex), external gamma absorbed dose rate ((D) over dot) and annual effective dose.

Radioactive emissions into the atmosphere from the damaged reactors of the Fukushima Dai-ichi nuclear power plant (NPP) started on March 12th, 2011. Among the various radionuclides released, iodine-131 ((131)I) and cesium isotopes ((137)Cs and (134)Cs) were transported across the Pacific toward the North American continent and reached Europe despite dispersion and washout along the route of the contaminated air masses. In Europe, the first signs of the releases were detected 7 days later while the first peak of activity level was observed between March 28th and March 30th. Time variations over a 20-day period and spatial variations across more than 150 sampling locations in Europe made it possible to characterize the contaminated air masses. After the Chernobyl accident, only a few measurements of the gaseous (131)I fraction were conducted compared to the number of measurements for the particulate fraction. Several studies had already pointed out the importance of the gaseous (131)I and the large underestimation of the total (131)I airborne activity level, and subsequent calculations of inhalation dose, if neglected. The measurements made across Europe following the releases from the Fukushima NPP reactors have provided a significant amount of new data on the ratio of the gaseous (131)I fraction to total (131)I, both on a spatial scale and its temporal variation. It can be pointed out that during the Fukushima event, the (134)Cs to (137)Cs ratio proved to be different from that observed after the Chernobyl accident. The data set provided in this paper is the most comprehensive survey of the main relevant airborne radionuclides from the Fukushima reactors, measured across Europe. A rough estimate of the total (131)I inventory that has passed over Europe during this period was LT 1% of the released amount. According to the measurements, airborne activity levels remain of no concern for public health in Europe.

Concentrations of beryllium-7 (Be-7), lead-210 (Pb-210) and caesium-137 (Cs-137) were measured at two sites in the city of Belgrade (Serbia). One monitoring site was located in the central city area with heavy traffic and the other within the Institute of Nuclear Sciences Vinca, in the suburbs. Presented data cover the period 2004-9. Activity of the radionuclides was determined on an HPGe detector (Canberra, relative efficiency 23%) by standard gamma spectrometry. Activities of Be-7 and Pb-210 exhibit a similar seasonal pattern. The mean monthly concentrations of Be-7 did not exceed 7 mBq m(-3). The maxima are correlated with the seasonal increase in temperature, whereas the minima are linearly correlated with the amount of precipitation. The activity of Pb-210 was below 0.9 mBq m(-3). The activities of both radionuclides were very low in winters and were largely affected by precipitation and snow coverage. Concentrations of Cs-137 were mainly below the limit of detection.

To assess the validity of the moss bag monitoring technique in the radioactivity control of ground level urban air, a study on radionuclide contents in moss was performed in the city of Belgrade, Serbia. From May 2006 to May 2007, moss (Sphagnum girgensohni, Dubna, Russia) was exposed to the aero pollution in a location in the central area of the city. The activity of K-40, Pb-210, and Cs-137 was measured on an HPGe detector (Canberra, relative efficiency 23%) by standard gamma spectrometry. The activities 245 +/- 25 Bq/kg for K-40, 315 +/- 34 Bq/kg for Pb-210, and 28 +/- 4 Bq/kg for Cs-137 are in the range of values reported for the region; the differences are due to the moss species, local climate and measuring technique. Taking into consideration the time of the exposure and appropriate calibration procedure, moss bag biomonitoring could be used as a complementary method for determination of radionuclides in urban air.

Three sets of data covering the 2004-2007 period are examined: two beryllium-7 series and ozone measured in ground level air. The measuring sites are at three different locations in Belgrade, Serbia. The temporal evolution of beryllium-7 and ozone is presented, as well as their mutual correlations. Beryllium-7 data for Belgrade agree well with the results for other locations in the region. The correlation between two beryllium-7 data sets is 0.57. The results for ozone indicate that Belgrade is not a common continental site, as the maximum in ozone distribution is reached in springtime. The overall correlation between beryllium-7 and ozone is good, but varies over different seasons. A large correlation (0.67) is noted between beryllium-7 measured at the site in Vinca, Serbia, and the monthly maximum ozone in autumn. An analysis which assumes the transport of air masses from the stratosphere, along which the only process changing the air mass composition is radioactive decay of beryllium-7, does not conclusively confirm the high correlation between beryllium-7 and ozone in autumn.

Generalized coupled two-level model is applied in different gas mixtures and investigated for high fluence regime. Functional dependences of mean number of absorbed photons per molecule LT n GT (total) on buffer-gas pressure (P-buff) are presented, used to confirm or predict some possible physical and chemical processes, like enhanced absorption and/or dissociation. Limitations of proposed models are analyzed depending on both gas pressure and laser fluence. Results are compared with other previously obtained by the same experimental technique, but for different absorbing molecule.

Influence of the buffer gas on the multiphoton absorption and dissociation in different mixtures was investigated. Simple method based on the empirical and theoretical vibrational energy distribution is applied for high fluence regime. Collisional effects of buffer gas (Ar) are introduced to enhance the absorption and relaxation of irradiated molecules (SF6 and C2H4). Functional dependences of mean number of absorbed photons per molecule ( LT n GT (total)) on the Molecular excitation level are presented, enabling us to confirm or predict the level of excitation, number of molecules directly involved in the absorption process and dissociated during the laser pulse.

Measuring the vibrational-to-translational relaxation time tau(V-T) in gases is one of the applications of pulsed photoacoustic spectroscopy. Unfortunately, the spatial profile of the laser beam can significantly influence the accuracy of these measurements. Namely, minor changes in the spatial profile of the laser beam cause significant errors in the tau(V-T) measuring. We present a method for simultaneous determination of the spatial profile of the laser beam and vibrational-to-translational relaxation time. It is based on the temporal shape of the photoacoustic pulse and utilizes a mathematical algorithm developed for photoacoustic tomography.