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Dijalog Timaj predstavlja jedan od najpoznatijih Platonovih dijaloga koji je izvršio izuzetan uticaj kako na antičke filozofe, tako i na hrišćanske teologe, pa i renesansne, moderne i savremene mislioce. Kosmološki mit koji Platon formuliše u Timaju predstavlja originalnu mešavinu mitskih, prirodno-filozofskih i matematičkih elemenata, te je stoga već od svog pojavljivanja bio predmet raznovrsnih, manje ili više oštrih interpretativnih sporova. Kao jedan od osnovnih pravaca tumačenja može se izdvojiti onaj u kome se teži eliminaciji nekih mitskih aspekata Timaja. Među sledbenike ovog pravca tumačenja spada Aristotel, filozofi stare Akademije, te savremeni istraživači antičke filozofije kao što su Kornford (F. M. Cornford), kod kojeg je prisutna težnja da mitski pojam demijurga (demiourgos) izjednači sa pojmom duše sveta (psyche tou kosmou), ili G. R. Karoni (G. R. Carone), Dž. Dilon (J. Dillon), odnosno O’Brajen (C. S. O’Brien). S druge strane, prema interpretativnom stanovištu koje zastupaju autori kao što su S. Broudi (S. Broadie), L. Brison (L. Brisson), T. Robinson (T. Robinson), ili T. Johansen (T. Kj. Johansen), mitski aspekti Timaja, a naročito pojam demijurga, jesu nužni i suštinski za izgradnju Platonove prirodno-filozofske tj. kosmološke pozicije, što znači da se mitski i naučni aspekti teksta moraju proučavati zajedno i isključivo u međusobnom odnosu. Za Platona, nauka (episteme) podrazumeva znanje o nepromenljivim stvarima, i deli se na matematiku i dijalektiku. Međutim, u dijalogu Timaj, govor (logos) o prirodi i strukturi kosmosa označen je kao mit (muthos), budući da, za Platona, taj govor može u najboljem slučaju biti samo „verovatan“ (eikos), a ne apsolutno izvestan, poput onog o matematičkim entitetima i zakonitostima. I pored toga, Platon u Timaju predlaže matematički model objašnjenja prirodnih pojava, i raspravu o strukturi kosmosa i strukturi duše sveta temelji kako na saznanju matematičkih entiteta, tako i ideja. Platonova kosmologija postavlj, The Timaeus is one of the most famous Plato’s dialogues which exerted enormous influence on ancient philosophers, Christian theologians, as well as various Renaissance, modern and contemporary thinkers. The cosmological myth elaborated in the Timaeus represents an original mixture of mythical, natural-philosophical and mathematical elements, and hence, since its appearance, it has been the subject of various, more or less intense interpretative disputes. According to one basic line of interpretation, some mythical elements in the Timaeus might be eliminated. Supporters of this interpretative stance include Aristotle, Old Academicians, as well as contemporary researchers of ancient philosophy such are F. M. Cornford, who made an attempt to equalize the mythical demiurge (demiourgos) with the world soul (psyche tou kosmou), as well as G. R. Carone, J. Dillon, and C. S. O’Brien. On the other hand, according to the interpretations put forward by S. Broadie, L. Brisson, T. Robinson, and T. Kj. Johansen, the mythical aspects of the Timaeus, particularly the notion of demiurge, are necessary and essential for the constitution of Plato’s natural-philosophical, or cosmological position, which means that the mythical and scientific aspects of the text have to be examined together in mutual relationship. For Plato, science (episteme) is the knowledge of unchangeable things, and consists of mathematics and dialectics. However, in the Timaeus, the speech (logos) about nature and the structure of the universe is called a myth (muthos) because for Plato, this speech is no more than „probable“ (eikos) and not absolutely certain, such as the one about mathematical laws and entities. Still, when it comes to the study of nature, Plato proposes the mathematical model of explanation in the Timaeus, and founds his considerations about the structure of the universe and the world soul upon the knowledge of mathematical entities and ideas. Plato’s cosmology is placed within pronouncedly myt

A method is presented for calculating the expected number of counts in peaks that have a large relative peak area uncertainty and appear in measured gamma-ray spectra. The method was applied to calculations of the correction factors for peaks occurring in the spectra of radon daughters. It was shown that the factors used for correcting the calculated peak areas to their expected values decrease with an increasing relative peak-area uncertainty. The accuracy of taking the systematic influence inducing the correction factors into account is given by the dispersion of the correction factors corresponding to specific peaks. It was shown that the highest accuracy is obtained in the peak analyses with the GammaVision and Gamma-W software.

It is well-known that radon is the second important human carcinogen for lung cancer, after smoking. The major sources of indoor radon concentrations are soil and building material. Under certain conditions, a dose received from the inhalation of radon and its progenies can be higher than a dose received from the external exposure due to radium concentration in building materials. In this contribution, the results of the radon and thoron exhalation rate measurement from 9 commonly used building materials are reported. Exhalation rate measurements were performed with accumulation chamber method using active device for measurement of radon concentration. © 2019 RAD Association. All rights reserved.

The coincidence summing effect plays an important role in HPGe spectrometry, especially at low source-detector distances, due to a large solid angle; therefore, the calculation of correction factors is necessary. The aim of the research described in this paper was to compare values of correction factors for a 22Na point source obtained using the GESPECOR software package (Monte-Carlo method) and experimentally obtained values. Measurements were performed using a semiconductor HPGe spectrometer and the point source axially positioned at nine different distances from the detector end-cap. For the purpose of determining correction factors, a system of equations was formed, which, besides nuclear data as the input parameters, uses the experimentally obtained values of the total count in the entire spectrum, as well as the counts in the full energy peaks. The system of equations was solved for each particular case and correction factors were determined. By comparing the results obtained using the experimental and Monte-Carlo method, it was found that the correction factors for the 22Na point source have discrepancies less than 3%. The significance of these discrepancies was also verified from a statistical point of view using a Student's t-test. © 2019 RAD Association. All rights reserved.

Gamaspektrometrija je jedna od najčešće korišćenih metoda za kvalitativno i kvantitativno određivanje sadržaja radionuklida u zemljištu i drugim uzorcima iz životne sredine. Meren je 31 uzorak zemljišta sa teritorije opštine Aleksandrovac, pri čemu su za svaki uzorak korišćene dve različite geometrije (cilindrična kutijica i marineli posuda). Određene su specifične aktivnosti radioizotopa uranovog i torijumovog niza, kao i 235U, 40K i 137Cs. Uzorci zemlje u geometriji cilindrične kutijice mereni sa na dva HPGe detektora različitih efikasnosti i karakteristika, dok su uzorci u marineli posudi mereni samo na jednom HPGe detektoru. U radu su prikazani rezultati poređenja specifičnih aktivnosti istih radionuklida dobijenih merenjem uzoraka u različitim geometrijama na istom HPGe detektoru kao i uzoraka u geometriji cilindrične kutijice merenih na različitim detektorima. Analizirani su uzroci nastalih varijacija., Gamma ray spectrometry is an analytical method that allows the identification and quantification of gamma emitting radioisotopes in soil and other environmental samples. 31 samples of soil were collected from different location in the territory of Aleksandrovac municipality. All soil samples were dried, milled and sealed in two different geometries (500 ml Marinelli beaker and 125 ml cylindrical boxes) and stored for six weeks in order to reach radioactive equilibrium between 226Ra and its descendants. All samples stored in cylindrical boxes were measured by means of two coaxial semiconductor HPGe detectors with different characteristics, while samples stored in Marinelli beakers were measured only by means of one coaxial semiconductor HPGe detector. The activity concentrations of radionuclides 40K, 137Cs, 235U, 226Ra, 238U and 228Ac in all soil samples were determined. Variations in specific activities determination for different geometries measured using one of the detectors, as well as for cylindrical box geometry measured using both detectors, are presented in this paper. The causes of these variations are analyzed.

U radu je merena ekshalacija radona iz bigra iz Niške Banje poznatom po povišenoj koncentraciji 226Ra. Bigar zbog svoje velike poroznosti i visoke koncentracije radijuma je idealan materijal za testiranje parametara od kojih zavisi brzina ekshalacije. U radu je razmatrana zavisnost ekshalacije u odnosu na vlažnost kao i na sprašenost uzorka. Brzina ekshalacije je merena metodom zatvorene komore, a sama koncentracija radona aktivnim uređajem. Dobijeni rezultati ukazuju da brzina ekshalacije raste sa povećanjem vlažnosti uzorka i smanjenjem veličine zrna., In this contribution, radon exhalation rate from travertine originating from Niška Banja, Serbia was measured. This particular travertine, with a high 226Ra concentration and high porosity, is ideal for testing various parameters that can influence radon exhalation rate. The radon exhalation rate was investigated for different sizes of grains. Grain sizes were dived into 4 groups: 1) 2.1 - 1.6 mm, 2.) 1.6 - 1.2 mm, 3.) 1.2 - 0.7 mm i 4.) < 0.7 mm. Influence of the humidity on radon exhalation rate was also investigated. Samples with the smallest grain size were exposed to 3 different levels of humidity (dry sample, and two samples in which water content was around 10% and 20% of the mass of dry sample. An accumulation chamber method with an active device RTM1688-2 was used to estimate radon exhalation rate from continuous measurement of radon in the chamber. Obtained results indicate that radon exhalation rate is increasing with an increase of humidity of the sample and with an decrease of grain size.

Prikazan je pregled najnovijeg gama metoda za merenje ekshalacije radona iz građevinskih materijala, koji pored ekshalacije omogućava merenje faktora emanacije i merenje difuzione dužine radona u datom materijalu, što nije moguće u standardnim merenjima ekshalacije radona. Takođe su prikazana i još tri standardna metoda merenja ekshalacije radona i dato je uporedno objašnjene prednosti i mana ovih metoda. Biće dat i pregled dosadašnjih merenja u Srbiji., A review of a new radon exhalation measurement method is presented. This method provides also a measurement of the radon diffusion length and the radon emanation coefficient, which is not possible by standard radon exhalation measurement methods. Besides, three standard radon exhalation measurements are presented: closed chamber with an active instrument, closed chamber with a solid state nuclear track detector and a charcoal canister method. An intercomparison of advantages and disadvantages is also given. A short review of previous measurements of radon exhalation from comercial building materials in Serbia will be given in the presentation.

In order to compare three different techniques and estimate radiological impact, activity concentration of Pb-210 in coal, slag and ash samples from thermal power plant Nikola Tesla, Serbia, were measured, and results are presented in this study. Determination of Pb-210 was carried out in three ways: using HPGe gamma spectrometer and via in-growth of Po-210 and Bi-210 by alpha-particle spectrometry and proportional counting, respectively. The results obtained for three different techniques were compared. Statistical analysis and comparison of methods were carried out by combination of Z score and chi (2) statistical tests. Tests results, as well as values of measured activities concentrations obtained by alpha and gamma spectrometry, showed that gamma spectrometry is a valid alternative to time-consuming alpha spectrometry for low level activity measurements of Pb-210. This remark is also valid even for gamma spectrometers with poor efficiency in low energy region.

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.

In the era of the energy saving policy (i.e. more air tight doors and windows), the radon exhaled from building materials tends to increase its concentration in indoor air, which increases the importance of the measurement of radon exhalation from building materials. This manuscript presents a novel method of the radon exhalation measurement using only a HPGe detector or any other gamma spectrometer. Comparing it with the already used methods of radon exhalation measurements, this method provides the measurement of the emanation coefficient, the radon diffusion length and the radon exhalation rate, all within the same measurement, which additionally defines materials radon protective properties. Furthermore it does not necessitate additional equipment for radon or radon exhalation measurement, which simplifies measurement technique, and thus potentially facilitates introduction of legal obligation for radon exhalation determination in building materials. (C) 2016 Elsevier Ltd. All rights reserved.

In this article, the X-ray and gamma-ray coincidence summing effect in Eu-152 is studied. Coincidence summing corrections and peak and total efficiencies of point and volume sources were determined using the direct matrices multiplication (DMM) method. The theoretically evaluated peak count rates were found to be in good agreement with the experimentally obtained values. Validation was performed by comparing the calculated efficiency curves and the corresponding correction factors with the results obtained using GESPECOR 4.2 software. (C) 2015 Elsevier Ltd. All rights reserved.

Ugalj,iporedsve intenzivnijeg razvoja i korišćenja obnovljivih izvora energije, ima i dalje značajnu ulogu u proizvodnji električne energije širom sveta. U Republici Srbiji prema godišnjem izveštaju “Elektroprivrede Srbije” za 2013. godinu u termoelektranama, čije jepogonsko gorivo lignit, proizvedeno je 26 537GWhod ukupno37 433 GWh električne energije[1]. Proizvodnja uglja, koji se koristi u termoelektranama “Elektroprivrede Srbije”, odvija se na površinskim kopovima rudarskih basena Kolubara (75 %) iKostolac(25 %) [2]., Coal as the fossil fuel contains naturally occurring radionuclides and belongs toNORM (Naturally Occurring Radioactive Materials). On the other hand, slag and fly-ash belong to TENORM (Technically Enhanced Naturally Occurring Radioactive Material), and if they are released into the environment an increase and/or redistribution of natural radionuclide content can occur. For the purposes of this study, six sets of samples (18 in total) of “Kolubara” coal, slag and fly-ash were collected during the periodical emission tests in May 2012th at steam boilers K3 and K4 of TPP “Kolubara”, Serbia. Coal, slag and fly-ash samples were prepared for analysis (milled, dried, sieved and weighed) by appropriate standard methods. Prepared samples were placedin 125 mL PVC cylindrical boxes, weighted and sealed with natural wax. Sealed samples were measured with a semiconductor HPGe spectrometer (37 % relative efficiency) after the radioactive equilibrium was reached. The obtained values of specific activity for coal (Ac), slag (As) and fly-ash (Af) do not differ significantly compared to the values available in the literature. Analysis of determined mutual ratiosAs/Ac andAf/Ac are consistent, taking into account uncertainties ofactivity concentrations, with values of approximately 2 and 4, forK3, and1.5 and 4, forK4. Discrepancies were notedonly for40K (bothsteam boilers) ofAs/Ac.Results indicate that further investigation with more samples should be undertaken, and also correlation between radiological and proximate analysis should be determined.

Naturally occurring radionuclide (uranium, actinium and thorium series and 40K) are widespread in the environment. In addition, significant amount of 137Cs may also be present in the soil as a result of accidents, such as Chernobyl accident. Thus, monitoring of radionuclides content in soil is of great importance. Aleksandrovac is small town in the western part of central Serbia and Župa is identified as the administrative territory of Aleksandrovac municipality. Nature of Aleksandrovačka Župa is under the long-lasting influence of anthropogenic factors, and therefore dominates altered natural landscape. Activity concentration of 226Ra, 232Th, 40K and 137Cs in 26 soil samples collected from different location in the territory of Aleksandrovačka Župa were determined and presented. All soil samples were milled and sealed in 0.5 l Marinelli beakers, and stored for six weeks in order to reach radioactive equilibrium between 226Ra and its descendants. All samples were measured by means of coaxial semiconductor HPGe detector (ORTEC GEM-30, 37% relative efficiency and 1.8 keV resolution for 60Co at 1332 keV line). The detector was calibrated using the standards in the same geometry spiked with common mixture of gamma-ray emitters certified by Czech Metrological Institute. The activity concentrations of radionuclides 40K and 137Cs in soil samples were determined directly by analyzing full-energy peaks of their principal energies at 1460.83 keV and 661.66 keV, respectively. The activity of 40K was corrected for the contribution of 228Ac (1459.14 keV). The activity of 226Ra was determined by analyzing full-energy peak at 186.21 keV, corrected for the contribution of 235U (185.72 keV) evaluated via 235U photo-peak at 143.77 keV and additionally approved by analyzing activity concentrations of its descendants (214Bi and 214Pb). Furthermore, the activity concentration of 232Th was determined by using the evaluated activity of its descendants (228Ac, 212Bi, 212Pb, and 208Tl). All

The Direct Matrices Multiplication (DMM) method was developed by D. Novkovi as theoretical model for coincidence summing of X-and gamma rays of radionuclides with complex decays schemes. This method enables: a) identification of allpossible decay paths and decay paths outcomes; b)calculation of particular path outcome, probabilities and corresponding energy deposited in the detector; c) determination of theoretical expressions for count rates of single and summing peaks as well as for total count rate, where the unknown quantities are the total and peak detection efficiencies. This method can be applied to the point sources and for small source-to-detector distances. lt was successfully applied to the decay of 13e6", 576o, '338., and 75Se. The DMM method was tested on the equivalence with other methods for calculation of coincidence summing corrections by G. Kanisch, T. Vidmar and O. Sima and a good agreement with the GESPRECOR program was confirmed for point sources of 133Ba, 13aCs and, 152Er. ln the case of the volume sources, calculations of coincidence summing corrections, peak and total efficiencies are more complex than for point sources. Laboratory for Nuclear and Plasma Physics participated in the intercomparison, organized by the Gamma-ray Spectrometry working group of the lnternational Committee for Radionuclide Metrology (ICRM). Volume iorr.", filled by radioactive solution ("'Er, 134Cs) and with different absorbers have been considered. Results obtained by DMM method showed satisfactory agreement with the mean values.

Coal as fossil fuel mainly contains naturally occurring radionuclides from the uranium and thorium series and K-40. Use of coal, primarily in industry, as a result has dispersion of radioactive material from coal in and through air and water. The aim of this study was to determine the activity concentrations of natural radionuclides in coal samples from open pit mines Kolubara and to evaluate its effect on population health. The results showed that all measured and calculated values were below the limits recommended in international legislation. (c) 2013 Elsevier Ltd. All rights reserved.

Ugalj predstavlja glavni izvor energije u Srbiji. Jedan od problema koji prati proizvodnju energije iz uglja je problem tzv. “energetskog otpada”, kao što su leteći pepeo i šljaka, koji predstavljaju nesagorivi i nesagoreli ostatak pri sagorevanju uglja. Leteći pepeo i šljaka predstavljaju TENORM (Technically Enhanced Naturally Occurring Radioactive Material), a u slučaju kada se odlažu u životnu sredinu mogu dovesti do uvećanja i/ili promene raspodele sadržaja prirodnih radionuklida. Da bi se odredio eventualni uticaj “energetskog otpada” na životnu sredinu analizirani su uzorci uglja, pepela i šljake iz termoelektrana “Nikola Tesla” i “Kolubara”. U radu su prikazani rezultati koncentracije prirodnih radionuklida (uranovog i torijumovog niza, kao i 40K) u uzorcima uglja, kao i šljake i pepela nastalih sagorevanjem uglja. Zatopljeni uzorci su mereni nakon uspostavljanja radioaktivne ravnoteže na poluprovodničkom HPGe spektrometru (37% relativne efikasnosti). Spektri uzoraka su snimljeni i analizirani pomoću programskog paketa GENIE 2K, uz dodatnu analizu korišćenjem programa ANGES. Dobijene vrednosti specifičnih aktivnosti ne odstupaju značajno u odnosu na vrednosti dostupne u literaturi. Svi dobijeni rezultati su dodatno statistički obrađeni u cilju određivanje mogućih korelacija., Coal is the main energy source in Serbia. One of the problems associated with the production of energy from coal is the so-called “energy waste”, such as fly-ash and slag (bottomash), which are incombustible and unburt residue from combustion of coal. Fly-ash and slag are TENORM (Technically Enhanced Naturally Occurring Radioactive Material), and if they are released into the environment an increase and/or redistribution of natural radionuclide content can occur. To determine the potential impact of “energy waste” on the environment, samples of coal, fly-ash, and slag from thermal power plant “Nikola Tesla” and “Kolubara” were analyzed. The measured concentrations of natural radionuclides (uranium and thorium series and 40K) in samples of coal as well as in slag and fly-ash produced by combustion of coal are presented in this paper. Sealed samples were measured with a semiconductor HPGe spectrometer (37% relative efficiency) after the radioactive equilibrium was reached. Spectra were recorded and analyzed using software package GENIE 2K, with additional analysis performed by ANGES software. The obtained values of specific activity do not differ significantly compared to the values available in the literature. All the results were further statistically analyzed in order to determine the possible correlation.

Laboratorija za nuklearnu i plazma fiziku Instituta „Vinča“, Laboratoriji za metrologiju radionuklida (LMR), ovlašćena je i akreditovana za gamaspektrometrijska ispitivanja sadržaja radionuklida u uzorcima različitog porekla. Da bi se obezbedila tačnost i pouzdanost rezultata merenja, a po zahtevima standarda ISO 17025, vrše se periodična interna etaloniranja HPGe poluprovodničkih spektrometara. Zbog raznovrsnosti uzoraka koji se mere kalibracija se mora izvršiti za više različitih geometrija i matriksa. U većini Laboratorija za ispitivanje radioaktivnosti, zbog specifičnosti ispitivanih uzoraka i geometrija merenja, nedostatka materijalnih sredstava i sl., uglavnom postoji problem adekvatnosti i mogućnosti nabavke komercijalno dostupnih radioaktivnih standarda i referentnih materijala. Program internog etaloniranja se u LMR sprovodi pomoću radnih standarda napravljenih u skladu sa potrebama i iskustvima proizišlim iz dugogodišnje prakse, a pouzdanost merenja proverena je uspešnim učešćem na više međunarodnih interkomparacija i PT šema. Zbog konačnog veka trajanja radioaktivnih standarda, određenog vremenima poluraspada radionuklida prisutnih u standardu, u LMR su u više navrata pripremani setovi radnih standarda pomoću standardnog rastvora miksa radionuklida gama emitera [1], a po proceduri detaljno opisanoj u literaturi [2,3]. U radu će sumarno biti prezentovana iskustva stečena tokom primene procedura pripreme radnih standarda., In the Laboratory for Radionuclide Metrology at Vinča Institute, activity concentration measurements are routinely performed and numerous calibration standards are required. Thus, a variety of calibration standards whose measurement geometry and chemical composition and density are similar to those of the measured samples were prepared. The standardized solutions of a common mixture of gamma-emitting radionuclides (241Am, 109Cd, 139Ce, 57Co, 60Co,137Cs, 203Hg, 113Sn, 85Sr, 88Y and 210Pb) purchased at the Czech Metrological Institute were used to prepare working standards for efficiency and energy calibration of gamma-ray semiconductor HPGe spectrometer in accordance with the IAEA recommendations. Calibration standards were prepared in different geometries (PVC cylindrical boxes, Marinelly beakers and PVC cylindrical bottles) and with various matrices (mineralized grass, activated carbon, surface soil, water, sand and ached filter paper). The matrix materials were spiked by using the activated carbon as the activity carrier, and homogenized mechanically. A comprehensive review of the procedures and techniques used for working standard preparation is presented in this paper.

Učešćem u interkomparaciji organizovanoj od strane Gamaspektrometrijske radne grupe u okviru ICRM, već razvijeni teorijski model za potrebe rešavanja problema koincidentnog sumiranja primenjen je na zapreminske izvore. Analizirana je vrlo složena šema 152Eu i formiran sistem jednačina. Rešavanje tako formiranog sistema zahtevalo je uvođenje određenih aproksimacija. U radu su prikazani izračunati korekcioni faktori za geometriju cilindrične PVC kutijice i radionuklid 152Eu u kombinaciji sa bakrom i pleksiglasom kao apsorberom., A theoretical model for solving the problem of coincidence summing based on matrix formalism was applied to the volume sources in the intercomparison exercise, organized by the Gamma-spectrometric working group within the International Committee for Radionuclide Metrology. A complex decay scheme of 152Eu was analyzed and the system of equations was formed. Solving this system required the introduction of some approximations. The calculated correction factors for a cylindrical geometry box and radionuclide 152Eu in combination with copper and plexiglas as absorber are presented in this paper.

In order to assure Quality Control in accordance with ISO/IEC 17025, it was important, from metrological point of view, to examine the long-term stability of calibration standards previously prepared. Comprehensive reconsideration on efficiency curves with respect to the ageing of calibration standards is presented in this paper. The calibration standards were re-used after a period of 5 years and analysis of the results showed discrepancies in efficiency values. (C) 2012 Elsevier Ltd. All rights reserved.

A study of coincidence summing of X- and gamma rays of Se-75 has been presented in this paper. The computation of the Se-75 spectra was performed by application of the previously published theory by Novkovi et al. The method enables the treatment of all possible single and sum peaks of Se-75. The calculation gave the 419 decay path outcomes, resulting in 84 peak count rate equations and also the total count rate equation. By HPGe spectrometers with 15% and 18% relative efficiency, 20 and 30 peaks were recorded, respectively. Some simplification of the decay scheme was introduced and existing metastable level had to be treated separately. Nevertheless, the experimental values of the peak count rates were in good agreement with the theoretical evaluation. (C) 2011 Elsevier Ltd. All rights reserved.

The direct measurement of the activities of Co-57 sources by application of the sum-peak method recently developed by Novkovic et al., is described in this paper. The comprehensive assessment of the uncertainty budget of the activity of the measured sources has been analyzed. The presented method is successfully tested using an HPGe spectrometer with efficiencies of 50%. The accuracy of this method is confirmed to be comparable with the commonly used methods of the activity measurement of Co-57. (C) 2012 Elsevier Ltd. All rights reserved.

The second part of an intercomparison of the coincidence summing correction methods is presented. This exercise concerned three volume sources, filled with liquid radioactive solution. The same experimental spectra, decay scheme and photon emission intensities were used by all the participants. The results were expressed as coincidence summing corrective factors for several energies of Eu-152 and Cs-134, and different source-to-detector distances. They are presented and discussed. (C) 2012 Elsevier Ltd. All rights reserved.

Artificial radionuclides are product of different human activities and their presence in the environment is negative side effect of civilization progress. They have been spread in the environment by events such as nuclear weapon tests, nuclear accidents and by deliberate and negligent discharge of radioactive waste from nuclear and other installation. Once released in to the nature, the artificial radionuclides start to circle in the same manner as naturally occurring ones, and finally they fall out from air and water onto the ground and build into the foodstuff and drinking water resulting in radiation doses to human beings. The short overview of presence of artificial radioactivity in human environment and its impact on human life is presented in this paper.

Coal as the most widely used fossil fuel contains traces of naturally occurring radioactivity from uranium and thorium series and 40K. The United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) estimated that average concentrations in coal worldwide are 50 Bq/kg for 40K and 20 Bq/kg for both 238U and 232Th (range 5 Bq/kg – 300 Bq/kg). [1] Activity concentrations of naturally occurring radionuclide 40K, 238U and 232Th for tree groups of samples of coal and mineral matter mixed with coal (I (2008 year – 30 samples), II (2009 year – 26 samples) and III (2010 year – 26 samples)) are presented in this paper. Representative samples of different coal quality were especially collected at different locations at open pit mines in RB “Kolubara” which has annual production of 29 millions tones of lignite for the power generation at TPP “Nicola Tesla”, Obrenovac. The samples were pulverized, dried and sealed in Marinelli plastic boxes 0.5 l, and stored for forty days until radioactive equilibrium between 226Ra and its decay products were achieved. All samples were measured by means of coaxial germanium HPGe detector (ORTEC GEM-30, 30 % relative efficiency and 1.8 keV resolution for 60Co at 1332 keV line). The detector was calibrated using standard solutions with radionuclide activities certified by CMI [2]. The experimentally obtained spectra were processed using Canberra’s Genie2000 software. The activity concentrations of 238U and 232Th were determined indirectly from the gamma-rays emitted by their progenies while 40K was determined directly by its gamma-line of 1460.8 keV. It can be seen from this table that the measured coal samples have low activity concentrations and the artificial radionuclides were not detected. The obtained activity concentrations of naturally occurring radionuclides in analyzed coal samples are comparable with those in coals from other countries [3, 4]