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The revised European Directive from 2013 regarding basic safety standard oblige EU Member States to establish a national action plan regarding the exposure to radon. At the same time, International Atomic Energy Agency started technical projects in order to assist countries to establish and implement national radon action. As a consequence, in recent years, in numerous countries national radon surveys were conducted and action plans established, which were not performed before. In this paper, a qualitative overview of radon surveys performed in Europe is given with a special attention to the qualitative and conceptual description of surveys, representativeness and QA/QC (quality assurance/quality control)., Highlights • Literature overview of indoor radon surveys performed in Europe. • Analysis of survey design and representativeness of indoor radon surveys. • Analysis of measurement techniques used in indoor radon surveys. • Analysis of sampling procedure, sampling number and type of locations in indoor radon surveys. • Analysis of quality assurance and quality control in indoor radon surveys.

It is indicated that the exposure to radon originating from the building materials is not negligible and the radon exhalation measurement should get more attention in the future. The experience with four different methods of the exhalation measurement, established in our laboratory for the purpose of the intercomparison is reported. Additionally, a comparison of advantages and disadvantages of used methods is discussed.

Open-faced charcoal canisters have been used for radon measurements for over 40 years. This method is sensitive to temperature, changing radon concentrations, humidity and other parameters, but a comprehensive study dealing with the influence quantities and measurement uncertainty was not available in literature. In this paper, all the identified influence quantities are discussed in detail, uncertainty budget is developed, good practice and bad practice examples are introduced and new recommendations are proposed to optimize the method and reduce uncertainty.

In the aftermath of a nuclear or radiological accident, an extended mapping of reliable dose rate values is of key importance for any governmental decision and countermeasures. Presently, numerous dosimetry network stations, operated by the national governments of the member states in Europe, provide such dose rate data on an hourly basis. Nevertheless, there are large areas in Europe that are not covered at all by these early warning networks and other areas that show only a low density of governmental network stations. Hence, there may be a significant lack of information in case of a nuclear or radiological emergency. As a consequence of the Fukushima Daiichi nuclear power plant accidents in 2011, a number of non-governmental radiation monitoring networks (NRMN) appeared on the internet, providing dose rate data based on stationary as well as on mobile measurements of ionizing radiation by laypersons. Especially the mobile detectors are able to cover large areas in short time. Therefore, it is of considerable importance to investigate the feasibility of using dose rate data from non-governmental networks as a complementary input to the European Radiological Data Exchange Platform (EURDEP). Within the European Metrology Program for Innovation and Research (EMPIR), the project 16ENV04 “Preparedness” has studied the metrological relevance of such non-governmental dose rate data (also called crowd-sourced radiological monitoring) in the most comprehensive way so far. Sixteen different dose rate detector systems (in general 4 of each type, plus 2 types with 2 detectors, i.e. 68 detectors in total) used in NRMN have been investigated for the reliability of their data and the corresponding networks, and their data provision to the public were analyzed. The most relevant performance parameters of dosimetry systems (detector's inherent background, energy dependence and linearity of the response as well as the response to secondary cosmic radiation, the sensitivity to small increases of the dose rate and finally the stability of the detector's indication at various climatic conditions - temperature and humidity) have been investigated for fourteen representative types of non-governmental dose rate measuring instruments. Results of this comprehensive performance study of the simple, light-weighted and cheap dose rate meters used in NRMN, and conclusions on the feasibility of using their data for governmental monitoring in case of a nuclear or radiological emergency are presented. © 2021 The Authors

Results and conclusions of interlaboratory comparison of indoor radon in 2015 in Serbia are presented. The participants were three accredited laboratories from Serbia: Serbian Institute of Occupational Health “Dr Dragomir Karajović”, Laboratory for Radioactivity and Dose Measurements at the Faculty of Sciences, University of Novi Sad and Radiation and Environmental Protection Department, Vinča Institute of Nuclear Science. The laboratories make use of the same method for radon measurement, using charcoal canisters according to US Environmental Protection Agency (EPA) protocol 520/5-87-005. Calibration of detection efficiency was performed using EPA radium standard. Radon activity concentrations were determined on the basis of the intensity of short-living radon daughters, 214Bi and 214Pb, gamma lines. The results of intercomparison were evaluated by using the u-test, which was calculated according to the International Atomic Energy Agency criteria. In this paper, not only limitations but also the advantages and possibilities of application of this method for measuring levels of human exposure to radon are discussed.

One of the main problems in quantitative gamma-ray spectroscopy is the determination of detection efficiency, for different energies, source-detector geometries, and composition of samples or sources. There are, in principle, three approaches to this issue: experimental, numerical, and semiempirical. Semiempirical approach is based on the calculation of the efficiency for the measured sample on the basis of an experimental efficiency measured on the same detector, but with a calibration source that can be of different size, geometry, density, or composition—the so-called efficiency transfer. The aim of this paper is to analyze the semiempirical approach, using EFFTRAN and MEFFTRAN software as a typical example. These software were used in the Department of Radiation and Environmental Protection, Vinča Institute of Nuclear Sciences, on three HPGe detectors. The results were compared to the experimentally obtained efficiency, and further validation is performed by measuring reference materials issued within the framework of several interlaboratory intercomparisons. The analysis of the results showed that the efficiency transfer produces good results with the discrepancies within the limits of the measurement uncertainty. Also, for intercomparison measurement, utest criterion for the trueness of the result was applied showing that the majority of the obtained results were acceptable. Some difficulties were identified, and the ways to overcome them were discussed.

An indirect method of metal content determination in drinking water based on a study of scale, showed precision, reliability and reproducibility of the obtained results. Results showed that the water quality, based on the metal content in the water, is quite constant and metals are in a concentration allowed by the Regulations. An increase of Uranium in drinking water (mainly the isotope 238U) was determined and its anthropogenic origin is proven based on the results of fractional extraction. Based on the content of macro- and microelements it is determined type of tested water as HCO3- Ca-Mg. In the examined period the concentration of macro- and microelements was below the MAC (Maximum Allowable Concentration) values. Ratio of Ca/Mg according to the Regulations should be between 3 and 4, while in the period of examination was varied in the range of 10.67 to 16.76, which means that the content of Mg in water is very low. Regarding to the period of 2011-2015 the input of heavy metals via drinking water was significantly increased (even 10 times) in comparison to the period of 2008-2011. As result of increased concentrations of Fe and Zn is a high growth of heavy metals. Calculated data showed that the risk of input microelements: Al, Fe and Pb, which are in studied water much higher than allowed by the Regulations, is not having any short-term risk to human health. Data analysis of the risk on the long-term health showed that the only real danger is the presence of Pb in drinking water. The risk of cancer is present in 23-58 population of 1000 people who are using this water for drinking. Indirektna metoda određivanja sadržaja metala u vodi za piće bazirana na ispitivanju kamenca pokazala je preciznost, pouzdanost i reproduktivnost dobijenih rezultata. Rezultati ispitivanja potvrdili su da je kvalitet vode, baziran na sadržaju metala u vodi, konstantan i da se metali nalaze u koncentraciji koja je dozvoljena pravilnikom. Utvrđen je porast urana u vodi za piće (uglavnom izotopa 238U), a na osnovu rezultata frakcione ekstrakcije dokazano je njegovo antropogeno poreklo. Na osnovu sadržaja makro- i mikroelemenata utvrđeno je da je ispitivani tip vode HCO3-Ca-Mg. U ispitivanom periodu koncentracija makro- i mikroelemenata bila je ispod MDK (Maksimalno dozvoljena koncentracija) vrednosti. Odnos Ca/Mg po pravilniku treba da iznosi između 3 i 4, dok je u ovom periodu varirao u opsegu 10,67-16,76, što znači da je sadržaj Mg u vodi jako nizak. Unos teških metala preko vode za piće u periodu od 2011-2015. godine značajno je povećan (čak 10 puta) u odnosu na period od 2008-2011. godine. Ovako visok porast teških metala posledica je povećane koncentracije Fe i Zn. Proračunati podaci ukazuju da rizik od unošenja mikroelemenata: Al, Fe i Pb, koji se u ispitivanim vodama nalaze u vrednosti višoj od one dozvoljene pravilnikom, ni za jedan metal ne pokazuju kratkoročni zdravstveni rizik po zdravlje ljudi. Analiza podataka o dugoročnom zdravstvenom riziku ukazuje da jedina realna opasnost postoji od prisustva Pb u vodi za piće. Rizik od pojave kancera prisutan je kod 23-58 stanovnika od 1000 stanovnika koji koriste ovu vodu za piće.

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.

Radionucleides, which are commonly released into the atmosphere after accidents on nuclear plants, by atmospheric precipitation fall onto the earth, are deposited in the soil, an consequently contaminate the environment, getting into the food chain. Considering that milk represents a kind of food that is consumed by all people, especially children, with the aim to protect the population after Cernobil accident, from then to today, constant long-term monitoring of antropogenic radionucleide (137Cs) presence in milk samples has been carried out, at almost complete territory of Serbia. Beside that, immediately after the nuclear accidents in Fukushima power plants, during march and april 2011. laboratory for radiation hygiene at the Faculty of veterinary medicine in Belgrade, carried out a special monitoring of radioactivity (40K , 131I 137Cs) in dairy cow, sheep and goat milk, at 30 localities in Serbia. The obtained results showed that the activity of 137Cs, as a consequence of Chernobyl accident, in milk at the territory of Serbia was below limit detection. Despite a large distance between Japan and Serbia, traces of 131I and 137Cs were detected in sheep and goat milk samples in april 2011., but considering their low activity, they do not represent a radiation risk for population in Serbia. Radionuklidi koji se oslobađaju u atmosferu posle nesreća na nuklearnim postrojenjima putem padavina se talože na zemljinu površinu, dospevaju u životnu sredinu i ugrađuju se u lanac ishrane ljudi. Mleko je namirnica koja je zastupljena u ishrani svih kategorija stanovništva, a posebno dece. U cilju očuvanja bezbednosti stanovništva, posle černobiljske katastrofe do danas, vršeno je višegodišnje praćenje prisustva radionuklida, antropogenog porekla (137Cs) u uzorcima mleka, na skoro celokupnoj teritoriji Srbije. Pored toga, neposredno posle katastrofe na nuklearnim reaktorima u Fukušimi tokom marta i aprila 2011. godine, Laboratorija za radijacionu higijenu Fakulteta veterinarske medicine u Beogradu, sprovela je vanredni program praćenja radioaktivnosti (40K, 131I, 137Cs) mleka krava, ovaca i koza na 13 lokaliteta na teritoriji republike Srbije. Dobijeni rezultati su pokazali da se aktivnost 137Cs poreklom iz černobiljske katastrofe u mleku, na teritoriji Srbije, danas nalazi na granici detekcije. Uprkos velikoj razdaljini Japana i Srbije tragovi 131I i 137Cs detektovani su u uzorcima ovčijeg i kozijeg mleka u aprilu 2011. god, ali s obzirom na njihovu nisku aktivnost ne predstavljaju radijacioni rizik za stanovništvo Srbije.

Investigation of the natural radioactivity levels in water around power plants, as well as in plants, coal, ash, slag and soil, and to assess the associated radiation hazard is becoming an emerging and interesting topic. This paper is focused on the results of the radioactivity analysis in waste water samples from five coal fired power plants in Serbia (Nikola Tesla A, Nikola Tesla B, Kolubara, Morava and Kostolac), which were analyzed in period 2003–2015. River water samples taken upstream and downstream from the power plants, drain water as well as overflow water were analyzed. In the water samples gamma spectrometry analysis was performed as well as determination of gross alpha and beta activity. Natural radionuclide 40 K was detected by gamma spectrometry, while the concentrations of other radionuclides, 226 Ra, 235 U and 238 U usually were below the minimum detection activity (MDA). 232 Th and artificial radionuclide 137 Cs was not detected in these samples. Gross alpha and beta activity were determined by α / β low level proportional counter Thermo Eberline FHT 770 T. In the analyzed samples, gross alpha activity ranged from MDA to 0.47 Bq L − 1 , while the gross beta activity ranged from MDA to 1.55 Bq L − 1 .

Radon problem has a special attention in many countries in the world and the most of them have established national radon programmes. The radon issues in Serbia have not been approached in a systematic and organized way. Currently, there are many research groups and institutions working in radon field, and it is a good basis to integrate all these activities into a comprehensive national programme to define the strategic objectives and action plan for the next few years. Also, Serbia as a candidate for membership in the EU is obliged to harmonize its legislation, including the field of radiation protection in which the radon issues has an important role. In this report, a brief history of radon research, present status and plans for the future activity on radon issues in Serbia are presented. Regarding the long-term plans, the establishment and implementation of the Radon Action Plan with the primary goal of raising awareness about the harmful effects of public exposure to radon and implementing a set of measures for its reduction. In that sense, the synergy between the national, regional and local organizations responsible for public health and radiation protection must be achieved.

The results referring to radioactivity analysis in soil, water, plant, coal, slag and flying ash samples from the environment around two power plants Nikola Tesla A and Kolubara for 2015 are explained. The analysis of samples was performed by gamma spectrometry using HPGe detector. In the investigated soil, flying ash, slag and coal samples, naturally occurring radionuclides Ra-226, Th-232, K-40, U-235, U-238, as well as the man-made radionuclide Cs-137, were detected. The highest values of natural radionuclides were obtained in flying ash samples, which is known for the effect of concentrating the combustion of coal. In plant samples, beside these radionuclides, Pb-210 and 7Be were also detected. In water samples, Ra-226 and K-40 were detected, while the concentrations of Th-232, U-235, U-238 and Cs-137 were below the minimum detectable concentration. In water (river, drinking, drain and overflow) samples, beside the gamma spectrometry analysis, gross alpha and gross beta activity was also determined. The obtained values for gross alpha and beta activity in these water samples are in accordance with the current legislation in Serbia (Official Gazette 86/11), which refers only to drinking water. The results presented in this paper showed that there was no significant difference in the activity of radionuclides in all investigated samples compared to the values obtained in previous years. 4th International Conference on Radiation and Applications in Various Fields of Research (RAD), Proceedings, May 23-27, 2016, Nis, Serbia

The aim of the present study was to investigate distribution of (137)Cs in leg and breast meat of broilers and pheasants following single alimentary contamination and administration of two protectors (AFCF and clinoptilolite). The birds were administered a single dose of (137)CsCl, with an activity of 750 Bq. Protectors were given via gastric tube or mixed in the forage pellets. AFCF given via gastric tube decreased the (137)Cs concentration by a factor of 7.8 in broilers leg meat and 7.4 in broilers breast meat. When AFCF was mixed in pellets, the (137)Cs concentration was 19.5 times lower in broilers leg meat and 22.1 times lower in broilers breast meat, than in the control group. In pheasants, AFCF administered via gastric tube decreased the (137)Cs concentration by a factor of 12.4 in leg meat and by a factor of 13.7 in breast meat, respectively. In group 4, where pheasants were administered AFCF mixed in pellets, the (137)Cs concentration was 3.7 times lower in leg and breast meat, than in the control group. For comparison, clinoptilolite administered via gastric tube decreased the (137)Cs concentration 1.8 times in broilers leg meat and 2.0 times in breast meat, compared to the control group. In pheasants, (137)Cs concentration was 2.9 times lower in leg meat and 2.6 times lower in breast meat. Clinoptilolite mixed in the feed had relatively low efficiency of protection in broilers ((137)Cs concentration was 1.4 times lower in leg meat and 1.6 lower in breast meat). A similar trend was observed in pheasants ((137)Cs concentration was 1.6 lower in leg and breast meat).

Radio-ecological monitoring of the environment encompasses the measures of specific radionuclide activity in the samples from the environment that is relevant for the exposure of inhabitants, first of all in air, drinking water, food and in some typical representatives of flora and fauna with characteristic features of radioactive contamination (the ability of radionuclide to concentrate). The aim of monitoring is: a) timely detection and identification of all uncontrolled radiation sources or radiation contamination; b) assessment of real and possible exposure of the critical group or inhabitants to radioactive matters in the environment due to use of any radiation sources; c) keep the record on the radioactivity level in the environment; d) check if all the legislative regulations and other restrictions are fulfilled; e) inform the public. According to the final results of measuring different samples form the territory of the Republic of Serbia in the period 1986 to 2008, it may be concluded that the level of natural and artificial (long-lived) radionuclides (originating from Chernobyl) was low, in tolerant and acceptable levels.

The analysis of water quality, regarding the content of metals, especially heavy and radioactive ones, has been carried out in an indirect way, by testing scale formed in a hot-water heater, using water from the water-supply network of the city of Belgrade – the district of New Belgrade. The determination of the composition and the structure of the scale has resulted in its complete identification, and its crystallochemical formula has been defined. It has unequivocally been established that the obtained results are within the tolerance boundary with the results acquired by a conventional analysis of water, when it is a matter of very low concentrations. The presence of radioactive elements of uranium and strontium in a scale sample has been found and the way of their penetrating its composition and structure has been explained. Applying the fractional extraction method, uranium has been established to be of an anthropogenic origin.

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.

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.

The homogeneity of fertilizer samples for interlaboratory γ-ray spectrometry comparison was tested by determination of the total γ count rate and the count rates for two 238U γ lines, one 40K line and one common 235U and 226Ra 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 Cochran’s test, and by a one-way ANOVA. The standard deviations were all less than these tolerances. All samples passed Cochran’s test and the one-way ANOVA test for homogeneity.

Measurement of the gross alpha and beta activity concentrations in various matrices is suitable as a preliminary screening procedure to determine whether further analysis related to specific radionuclide is necessary. In Serbia, according to current regulations, radioactivity concentrations in drinking water for gross alpha and gross beta should be < 0.5 and < 1.0 Bq L−1, respectively. The generally accepted methods for gross alpha and beta activity analysis of drinking water in different countries are: EPA 900.0 and ISO methods (ISO 9696, water quality – measurement of gross alpha activity in non-saline water – thick source method, and ISO 9697, water quality – measurement of gross beta activity in non-saline water). This paper describes comparison of preparations and measurement gross alpha and beta activity in bottled mineral waters as well as in tap waters in Serbia using two methods: EPA 900.0 with and without ash, and ISO methods. Concentration of total dissolved solids (TDS) in investigated water samples was determined. Based on obtained TDS, certain volume was evaporated. The instrumentation used to count the gross alpha and gross beta activities for both methods is α/β low level proportional counter Thermo Eberline FHT 770 T.

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. 2nd International Conference on Radiation and Dosimetry in Various Fields of Research RAD and The 2nd East European Radon Symposium (SEERAS), May 27-30, 2014, Nis, Serbia

Herbal teas are an important part of traditional medicine in Serbia. The objective of the present study was to determine the activity concentrations of (40)K and (137)Cs in herbal tea, using the gamma spectroscopy method. The samples were collected during the period 2011-2012 in three mountain regions in Western and Central Serbia. The activity concentrations of (40)K and (137)Cs were found to be in the range of 130-1160 and 0.7-124 Bq kg(-1), respectively. The average annual effective dose equivalents from ingestion of (40)K and (137)Cs for an adult person consuming one cup of herbal tea daily were found to be 588.4-5250.2 nSv for (40)K and 4.0-706.1 nSv for (137)Cs. Our investigation showed that the herbal teas originating from Maljen, Zlatibor and Tara mountains are radiologically safe for human consumption.

The proposed and validated method for determination of Sr-90 content in environmental samples (water, soil and plant) is based on the radiochemical analytical separation of Y-90 from the sample and measuring its activity after the establishment of radioactive equilibrium with Sr-90. Validation is the confirmation by examination and provision of objective evidence that they meet the individual requirements stipulated for a specific use. Validation of method was done based on the blank samples for water by adding Sr-90 known activity and using reference materials of soil (IAEA-326) and plant (IAEA-330). Content of Sr-90 in environmental samples was determined by alpha/beta low level proportional counter. The accuracy and the precision of the applied method are confirmed and the method is validated and can be used for determination of Sr-90 in environmental samples. On the other hand, participations in interlaboratory comparisons are confirmed that the adequacy of the validated method is ensured.

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 Vinca, Belgrade. This paper presents the summarisation and analysis of QC and QA measures undertaken by the Laboratory for Environmental and Radiation Protection of the Vinca 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.

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.

The activity concentrations of (40)K, (238)U, (232)Th and (137)Cs have been measured using a gamma spectrometric method in different samples from the environment of two mountains in Serbia (altitude 1000-1100 m), during the period 2002-2007. The mountains Maljen and Tara (popular tourist destinations) are near Belgrade. On mountain Maljen, samples were taken at 4 different altitudes (200 m, 650 m, 1000 m and 1100 m), and on mountain Tara at altitudes of 1000 m and 1100 m. On mountain Maljen it was found that the level of (137)Cs activity increased with altitude in samples of soil, grass, hay and cow, sheep and goat milk. On the contrary, (40)K activity decreased with altitude in samples of soil, grass and hay. The highest activity concentrations of (137)Cs were found in bioindicators: sheep meat, venison, wild boar meat, moss and mushrooms. These results indicate that (137)Cs is present in mountain region of Serbia even 20 years after the nuclear accident in Chernobyl. Deposition of (137)Cs was almost two times higher on the Maljen mountain compared to Tara mountain. An average annual dose arising from (137)Cs was 7.4 microSv due to ingestion of cow milk and 6.3 microSv due to ingestion of mushrooms at the Maljen mountain.

A new Certified Reference Material (CRM) for radionuclides in sediment (IAEA-385) is described and the results of the certification process are presented. Eleven radionuclides ((40)K, (137)Cs, (226)Ra, (228)Ra, (230)Th, (232)Th, (234)U, (238)U, (238)Pu, (239+240)Pu and (241)Am) have been certified and information mass activities with 95% confidence intervals are given for seven other radionuclides ((90)Sr, (210)Pb((210)Po), (235)U, (239)Pu, (240)Pu and (241)Pu). Results for less frequently reported radionuclides ((60)Co, (99)Tc, (134)Cs, (155)Eu, (224)Ra and (239)Np) and information on some activity and mass ratios are also reported. The CRM can be used for quality assurance/quality control of the analysis of radionuclides in sediment samples, for the development and validation of analytical methods and for training purposes.

Natural radioactive materials were used for detector calibration. We found that KCl is a very suitable material for this purpose. The efficiency curve shape was derived by using γ ray lines of 214Bi normalised using a known quantity of KCl in the same geometry. The best fit was found by the least squares method. The summing correction coefficients for 214Bi are determined.