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This study investigates the beryllium-7, lead-210 and caesium-137 activity concentrations in aerosol filter samples collected monthly along the 45°N zonal belt over 1991–2019. Sampling was performed in three locations, one in Serbia and two in Slovenia, and the Slovenian data records are published here for the first time. The activity concentrations were determined by standard gamma spectrometry. The obtained results are in general agreement with the literature data for Europe. The data sets at different sites display similarities in measurement ranges, overall means and seasonal cycles. Still, statistical tests show significant differences among the radionuclides’ concentrations across the locations. To investigate underlying processes that affect radioactivity in the surface air in this region, multivariate statistical concepts are applied to the radionuclides’ concentrations and local meteorological parameters. Discriminant analysis shows that all three sites are well separated from each other. Principal component analysis gives common pattern of interconnection between the observables: temperature has a stronger influence on the behaviour of beryllium-7 and lead-210 than that of caesium-137, but a negative correlation of the radionuclides’ concentrations with precipitation seems the strongest for caesium-137. Principal component analysis also shows local differences in the degree of relationship between the meteorological parameters and activity concentrations of the investigated radionuclides. This is an important finding for future atmospheric transport studies.

Optimization of different types of exposure to workers, public, and vegetation is a major issue for several institutions. The main exposure is due to the activities related to various ores of the subsoil such as phosphate which generates heavy metals during its exploitation. This study used the energy-dispersive X-ray spectrometry to investigate the heavy metal pollution that affects life on earth. Fifteen different heavy metals were detected in soil samples from sites dedicated to phosphate ore activities in southern Togo. Results showed that the concentrations of the different heavy metals decreased in the following order: Ca > Fe > K > Ti > Sr > Zn > Zr > Y > Ni > Cu > Pb > U > Br > Rb > Th. Cadmium was not detected while lead remained the most toxic element with a maximum level of 52.4 mg kg−1. Basic statistics depicts strong positive correlations between Ni, Cu, Zn, and Fe which shows that their respective concentrations increased together. Principal component analysis was used to categorize all these data into three groups using two principal axes which recover 88.06% information. The geoacumulation index from Hahotoe-Kpogame-Kpeme soil samples varies from class 0 to class 4 displaying that these areas are moderately polluted and was mainly due to Pb metal concentration. The potential ecological risk levels vary from 157 to 385, which corresponds to moderate and considerable levels. Therefore, these areas could be assumed to be safe regarding these levels. The moderate level observed on these various sites does not present a warning sign but should lead the legislators to establish routine monitoring in order to detect any change in the level of pollution due to heavy metals.

Natural radionuclides activity concentrations of 226Ra, 228Ra, and 40K in soil and grass samples, statistical analysis of these radionuclides and transfer factors (TFs) from soil to the grass were carried out from phosphate mining and processing sites in southern areas of Togo using gamma-ray spectrometry-based High Purity Germanium (HPGe) detector. The average activity concentrations of 226Ra, 228Ra, and 40K were found within the range usually measured worldwide. Statistical analysis was done by investigating the skewness, the kurtosis, and the density distribution of radionuclides in the study areas. Both skewness and kurtosis displayed that the activity concentrations of soil and grass samples in the dischargement waste site (Kpémé) and mining site (Hahotoé) exhibited slightly positively skewed, negatively skewed, leptokurtic, and platykurtic distributions. The TFs for 226Ra, 228Ra, and 40K from dischargement waste soil to grass were evaluated. The average transfer factors of 226Ra, 228Ra, and 40K in the phosphate processing area were found to be 0.16, 0.32, and 8.42, respectively. 226Ra and 228Ra TFs values were found to within the limit of worldwide measure values while that of 40K was to be larger than the values measured in other countries. The average TF value of 8.42 for 40K was 8 times higher than the average value of unity, showing its large intake by vegetables. The high TFs for 40K could be explained by the extensive application of phosphate fertilizers to soils when growing vegetables.

International audience; From early April 2020, wildfires raged in the highly contaminated areas around the Chernobyl nuclear power plant (CNPP), Ukraine. For about 4 weeks, the fires spread around and into the Chernobyl exclusion zone (CEZ) and came within a few kilometers of both the CNPP and radioactive waste storage facilities. Wildfires occurred on several occasions throughout the month of April. They were extinguished, but weather conditions and the spread of fires by airborne embers and smoldering fires led to new fires starting at different locations of the CEZ. The forest fires were only completely under control at the beginning of May, thanks to the tireless and incessant work of the firefighters and a period of sustained precipitation. In total, 0.7–1.2 TBq 137Cs were released into the atmosphere. Smoke plumes partly spread south and west and contributed to the detection of airborne 137Cs over the Ukrainian territory and as far away as Western Europe. The increase in airborne 137Cs ranged from several hundred μBq·m–3 in northern Ukraine to trace levels of a few μBq·m–3 or even within the usual background level in other European countries. Dispersion modeling determined the plume arrival time and was helpful in the assessment of the possible increase in airborne 137Cs concentrations in Europe. Detections of airborne 90Sr (emission estimate 345–612 GBq) and Pu (up to 75 GBq, mostly 241Pu) were reported from the CEZ. Americium-241 represented only 1.4% of the total source term corresponding to the studied anthropogenic radionuclides but would have contributed up to 80% of the inhalation dose.

Ambient dose equivalent H*(10) is measured to assess general population exposure to ionising radiation. From its spatial and time variations it is possible to identify sources of exposure. In Slovenia, semi-annual H*(10) is measured routinely with thermoluminescence dosimeters at 66 locations around the Nuclear Power Plant (NPP) Krško and at 50 other locations covering the rest of Slovenian territory. Since the Chernobyl accident contamination had ceased to contribute to ambient dose equivalents, we have been calculating correlation coefficients between annual mean number of sunspots and annual H*(10). These correlation coefficients were calculated for five locations in western Slovenia and for five annual H*(10) extracted from measurements around NPP Krško. Their ranges between –0.64 and –0.38 suggest a clear negative correlation between solar activity and H*(10). Mean annual H*(10) averted by solar activity in the past two solar maxima reached 0.070 mSv around NPP Krško (155 m.a.s.l.) and 0.132 mSv and 0.180 mSv at Kredarica (2515 m.a.s.l.). Quantifying the influence of the solar activity on the ambient dose equivalent helps us to better understand exposure of the general population to ionising radiation., Okoljski dozni ekvivalent H*(10) merimo, da ocenimo izpostavljenost populacije ionizirajočemu sevanju. Iz časovne in prostorske odvisnosti je mogoče ugotoviti vire izpostavljenosti. Polletne dozne ekvivalente H*(10) merimo rutinsko s termoluminiscenčmimi dozimetri na 66 lokacijah v okolici Jedrske elektrarne Krško (NEK) in na 50 drugih lokacijah na teritoriju Slovenije. Ker kontaminacija zaradi Černobilske nesreče ne prispeva več k okoljskemu doznemu ekvivalentu smo izračunali korelacijske koeficiente med povprečnim letnim številom sončnih peg in letnim H*(10). Korelacijske koeficiente smo izračunali za pet lokacij v Zahodni Sloveniji in pet lokacij v bližini NEK. Vrednosti korelacijskih koeficientov so v intervalu od -0.64 do -0.38, kar kaže na močno korelacijo med sončno aktivnostjo in H*(10). Zaradi sončeve aktivnosti so bili povprečni letni H*(10) v zadnjih dveh sončnih maksimumih zmanjšani za 0.070 mSv v okolici NEK (na nadmorski višini 155 m) in za 0.132 mSv in 0.180 mSv na Kredarici (na nadmorski višini 2515 m). Ovrednotenje vpliva sončeve aktivnosti na okoljski dozni ekvivalent boljša razumevanje izpostavljenosti populacije ionizirajočemu sevanju.

The probabilities of locating peaks with a high relative peak-area uncertainty were determined empirically with nine types of peak-location software used in laboratories engaged in gamma-ray spectrometry measurements. It was found that it is not possible to locate peaks with a probability of 0.95, when they have a relative peak-area uncertainty in excess of 50%. Locating peaks at these relatively high peak-area uncertainties with a probability greater than 0.95 is only possible in the library-driven mode, where the peak positions are supposed a-priori. The deficiencies of the library-driven mode and the possibilities to improve the probabilities of locating peaks are briefly discussed. © 2019 Elsevier Ltd

International audience; Traces of particulate radioactive iodine (131I) were detected in the European atmosphere in January/February 2017. Concentrations of this nuclear fission product were very low, ranging 0.1 to 10 μBq m-3 except at one location in western Russia where they reached up to several mBq m-3. Detections have been reported continuously over an 8-week period by about 30 monitoring stations. We examine possible emission source apportionments and rank them considering their expected contribution in terms of orders of magnitude from typical routine releases: radiopharmaceutical production units > sewage sludge incinerators > nuclear power plants > spontaneous fission of uranium in soil. Inverse modeling simulations indicate that the widespread detections of 131I resulted from the combination of multiple source releases. Among them, those from radiopharmaceutical production units remain the most likely. One of them is located in Western Russia and its estimated source term complies with authorized limits. Other existing sources related to 131I use (medical purposes or sewage sludge incineration) can explain detections on a rather local scale. As an enhancing factor, the prevailing wintertime meteorological situations marked by strong temperature inversions led to poor dispersion conditions that resulted in higher concentrations exceeding usual detection limits in use within the informal Ring of Five (Ro5) monitoring network. © 2018 American Chemical Society.

We describe a calculator for the decision threshold and detection limit, a tool intended for gamma-ray spectrometry. The tool is an Excel file composed of several sheets, containing procedures for calculating the decision thresholds and detection limits under various assumptions. It is publicly available at https://f2.ijs.si/en/laboratories/lmr/calculator . The input data for the calculations are peak-analysis results, usually listed in peak-analysis reports (peak energies, FWHMs, peak areas and their uncertainties). Besides these quantities, data on the total number of counts in the peak region and the numbers of counts in the peaked background (if present) and their uncertainties are needed for the calculation. The calculation procedures implemented in the Excel sheets make it possible to calculate the decision thresholds and detection limits from peak data obtained using the region-of-interest method and the least-squares method. With the least-squares method it is possible to calculate the decision thresholds and detection limits for both isolated and overlapping peaks. An additional sheet enables the calculation of decision thresholds and detection limits for multi-gamma-ray emitters. We show that, in general, the indications corresponding to the decision threshold depend on the observed value of the indication and that those calculated with the region-of-interest method do not depend on it, except through the width of the peak region.

The aim of the research was to obtain first results of tritium in the organic matter of environmental samples in the vicinity of Krsko NPP. The emphasis was on the layout of suitable sampling network of crops and fruits in nearby agricultural area. Method for determination of tritium in organic matter in the form of Tissue Free Water Tritium (TFWT) and Organically Bound Tritium (OBT) has been implemented. Capabilities of the methods were tested on real environmental samples and its findings were compared to modeled activities of tritium from atmospheric releases and literature based results of TFWT and OBT.

In gamma-ray spectrometry the measurement threshold describes the lover boundary of the interval of peak areas originating in the response of the spectrometer to gamma-rays from the sample measured. In this sense it presents a generalization of the net indication corresponding to the decision threshold, which is the measurement threshold at the quantity value zero for a predetermined probability for making errors of the first kind. Measurement thresholds were determined for peaks appearing in the spectra of radon daughters 214Pb and 214Bi by measuring the spectrum 35 times under repeatable conditions. For the calculation of the measurement threshold the probability for detection of the peaks and the mean relative uncertainty of the peak area were used. The relative measurement thresholds, the ratios between the measurement threshold and the mean peak area uncertainty, were determined for 54 peaks where the probability for detection varied between some percent and about 95% and the relative peak area uncertainty between 30% and 80%. The relative measurement thresholds vary considerably from peak to peak, although the nominal value of the sensitivity parameter defining the sensitivity for locating peaks was equal for all peaks. At the value of the sensitivity parameter used, the peak analysis does not locate peaks corresponding to the decision threshold with the probability in excess of 50%. This implies that peaks in the spectrum may not be located, although the true value of the measurand exceeds the decision threshold.

Two effects were identified that induce the dependence of the decision threshold on the uncertainty of the conversion factor. With the first effect, the conversion factor influences the decision threshold directly, through its variability. With the second effect, the variability of the conversion factor influences the decision threshold only when it is not evaluated for the null measurement. Then, the variability of the conversion factor influences the value of the measurand, where the decision threshold is evaluated. Both effects are explained and evaluated.

An account is given on the value of the correlation coefficient between the number of counts in a peak in a gamma-ray spectrum and the number of counts in the background, where the peak resides. It is supposed that the decomposition of the spectrum in the peak and in the background is performed by using the Least Squares method. The values of the correlation coefficient were determined empirically from measurements of gamma-ray spectra under repeatable conditions and from analyses of these spectra using four different kinds of peak-analysis software. These values were compared to the a-priori values, obtained from the Least Squares method.

This article presents yearly mean concentrations of cosmogenic radionuclides 7Be and 22Na occurring in dry and wet depositions (fallout) and aerosols. Time dependencies negatively correlated with the yearly mean number of sunspots. Activity concentrations of 7Be and 22Na in aerosols in the surface air had a correlation of near-unity. 7Be in aerosols exhibited a smoother time dependence than 22Na, implying that the production of 22Na is more sensitive to the solar activity than the production of 7Be. The effect of the measured doses on the general population through internal and external exposure to radiation from cosmogenic radionuclides was small., V članku prikazujemo letne povprečne koncentracije kozmogenih radionuklidov 7Be in 22Na v suhem in mokrem usedu in aerosolih od 1991. do 2018. Med koncentracijami aktivnosti 7Be in 22Na v aerosolih v površinskem zraku je zelo dobra korelacija. Časovni odvisnosti koncentracij aktivnosti kozmogenih radionuklidov sta negativno korelirani s povprečnim letnim številom sončevih peg. Časovna odvisnost 22Na v aerosolih je bolj razgibana kot pri 7Be, zato je nastajanje atomov 22Na v atmosferi bolj povezano s časovnim ciklusom sončeve aktivnosti, kot to velja za atome 7Be v zraku. Prispevka kozmogenih radionuklidov k celotni oceni vpliva na prebivalstvo zaradi notranjega obsevanja in zunanjega sevanja sta majhna.

Non-human biota in radiological risk assessment is typically evaluated using Reference Organisms (ROs) or Reference Animals and Plants (RAPs), for all exposure situations. However, it still remains open whether the use of an increased number of species would improve the ability to demonstrate protectiveness of the environment. In this paper, the representativeness of a broader list of fauna is tested in terms of the geometrical characteristics and habits for radiological risk assessments in the case of routine discharges from a nuclear installation: the Cadarache centre. A list of terrestrial animal species, compiled from ecological inventories carried out around it was evaluated. A first survey around the centre inventoried >400 terrestrial fauna species, which were then filtered to reduce the number to 28 species for which dose assessments were carried out. Despite the differences between geometries for those site-specific species and the ROs (including RAPs), the absorbed dose rates calculated for both were very close (within a factor of two). Regardless of the studied organism, the absorbed dose rates calculated for the discharge scenario were mainly related to internal exposure, particularly for tritium (3H) and carbon 14 (14C), showing that there would be an acceptable dose rates difference between species from the same organism group. Additionally, sensitivity analyses were conducted to determine if the use of generic, predefined ROs was enough to assure an adequate protection of endangered species. It was observed that for every radionuclide the difference between assessments for site-specific species and ROs are unlikely to exceed a factor of 3. Hence, the result of this evaluation indicates that the use of generic ROs for non-human biota radiological risk assessment covers sufficiently other species, including endangered ones.

This study assesses the potential use of different types of stabilized sewage sludge as a soil amendment by considering their physicochemical characteristics, nutritional status, and their trace metal and radionuclide content. The concentrations of trace metals and radionuclides were determined using ICP-OES and gamma-ray spectrometry, respectively. For determining nutritional status and chemical characterization, this study followed standard ISO-recommended procedures. Data analysis revealed that anaerobic sludge contains higher concentrations of Cr, Hg, and Ni compared to aerobic and non-biologically stabilized sludge. A similar observation was observed in the case of 226Ra, 210Pb, 228Ra, and 228Th. Furthermore, the high levels of P and N in aerobic sludge suggest that biologically stabilized sludge has the potential to be a good fertilizer. In addition, the study finds strong evidence that nutrients are involved in the adsorption of metals and radionuclides onto sludge biomass. Overall, eight of the nine studied sludge samples are safe for agricultural use since the concentrations of trace metals fall well below the limits set by Croatian legislation (NN 38/08). In addition, the levels of radionuclides do not pose a radiological risk. This means that soil conditioning with sewage sludge remains a viable strategy for nutrient recovery from municipal waste, although long-term impact assessments of repeated applications are necessary.

Significance A massive atmospheric release of radioactive 106Ru occurred in Eurasia in 2017, which must have been caused by a sizeable, yet undeclared nuclear accident. This work presents the most compelling monitoring dataset of this release, comprising 1,100 atmospheric and 200 deposition data points from the Eurasian region. The data suggest a release from a nuclear reprocessing facility located in the Southern Urals, possibly from the Mayak nuclear complex. A release from a crashed satellite as well as a release on Romanian territory (despite high activity concentrations) can be excluded. The model age of the radioruthenium supports the hypothesis that fuel was reprocessed ≤2 years after discharge, possibly for the production of a high-specific activity 144Ce source for a neutrino experiment in Italy., In October 2017, most European countries reported unique atmospheric detections of aerosol-bound radioruthenium (106Ru). The range of concentrations varied from some tenths of µBq·m−3 to more than 150 mBq·m−3. The widespread detection at such considerable (yet innocuous) levels suggested a considerable release. To compare activity reports of airborne 106Ru with different sampling periods, concentrations were reconstructed based on the most probable plume presence duration at each location. Based on airborne concentration spreading and chemical considerations, it is possible to assume that the release occurred in the Southern Urals region (Russian Federation). The 106Ru age was estimated to be about 2 years. It exhibited highly soluble and less soluble fractions in aqueous media, high radiopurity (lack of concomitant radionuclides), and volatility between 700 and 1,000 °C, thus suggesting a release at an advanced stage in the reprocessing of nuclear fuel. The amount and isotopic characteristics of the radioruthenium release may indicate a context with the production of a large 144Ce source for a neutrino experiment.

The best estimate and its standard deviation are calculated for the case when the a priori probability that the analyte is absent from the test sample is not zero. In the calculation, a generalization of the Bayesian prior that is used in the ISO 11929 standard is applied. The posterior probability density distribution of the true values, given the observed value and its uncertainty, is a linear combination of the Dirac delta function and the normalized, truncated, normal probability density distribution defined by the observed value and its uncertainty. The coefficients of this linear combination depend on the observed value and its uncertainty, as well as on the a priori probability. It is shown that for a priori probabilities larger than zero the lower level of the uncertainty interval of the best estimate reaches the unfeasible range (i.e., negative activities). However, for a priori probabilities in excess of 0.26 it reaches the unfeasible range even for positive observed values. The upper limit of the confidence interval covering a predefined fraction of the posterior is derived.

A method for calculating the decision thresholds for gamma-ray emitters, identified in gamma-ray spectrometric analyses, is described. The method is suitable for application in computerized spectra-analyzing procedures. In the calculation, the number of counts and the uncertainty in the number of counts for the peaks associated with the emitter are used. The method makes possible to calculate decision thresholds from peaks on a curved background and overlapping peaks. The uncertainty in the number of counts used in the calculation was computed using Canberra׳s Standard Peak Search Program (Canberra, 1986, Peak Search Algorithm Manual 07-0064). For isolated peaks, the decision threshold exceeds the value calculated from the channel contents in an energy region that is 2.5 FWHM wide, covering the background in the immediate vicinity of the peak. The decision thresholds vary by approximately 20% over a dynamic range of peak areas of about 1000. In the case of overlapping peaks, the decision threshold increases considerably. For multi-gamma-ray emitters, a common decision threshold is calculated from the decision thresholds obtained from individual gamma-ray emissions, being smaller than the smallest of the individual decision thresholds.

One of the best ways to demonstrate the performance and capabilities of testing laboratories is to participate successfully in different international comparison schemes and proficiency tests. The overview of all results of such schemes in the field of high resolution gamma-ray spectrometry where the Laboratory for Radioactivity Measurements (LMR) of the Jožef Stefan Institute (JSI), Slovenia, participated in years 1986-2014 is presented. Different schemes are compared, strong points and drawbacks of different providers and schemes regarding evaluation procedures, determination of reference values, reporting time, sets of radionuclides included in the samples and range of activities of different radionuclides are discussed. One of the main conclusions is that the comparison and proficiency test samples normally contain substantially larger activities than are usually detected in environmental samples. Therefore the capability of determination of activities close to detection limits is usually covered only by few schemes.

In gamma-ray spectrometric measurements the background is usually taken into account by conducting measurements on a blank sample. However, this method is not appropriate if many different kinds of samples are measured and several types of detectors are used. In such cases it is easier to measure accurately the activities of the blank materials separately and then to subtract the activities of the blank sample from the total sample activities. In order to do this, the measurement function for the activity calculation must be modified.

In 2017, a new revision of the ISO/IEC 17025 standard was issued. One of the important changes is that the uncertainty arising from sampling has to be evaluated. Based on this new requirement, we evaluated the contribution of the sampling procedure to the total uncertainty budget of the high-resolution gamma-ray spectrometry of environmental soil, tap water and aerosol filter samples. We performed statistical analyses of measurements of sets of samples taken from the same target in the same general time period. The determination of sampling uncertainty was based on the evaluation of the standard deviation of the set of measurement results and the combined uncertainty budget of sample preparation and analysis. When the spatial and temporal heterogeneities are low, the sampling uncertainty is estimated to be around 5% (k = 1) for soil samples and 30–40% (k = 1) for air samples. For single tap water samples collected consecutively, sampling uncertainty does not have a significant contribution to the complete uncertainty budget.

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. 21st International Conference on Radionuclide Metrology and itsApplications (ICRM), Argentinian Comis Nacl Energia Atomica, BuenosAires, ARGENTINA, MAY 15-19, 2017

The method for calculating the decision threshold as given by the ISO 11929:2010 standard is not compatible with the definition of the decision threshold given in the same standard. The additional requirement in the method of calculation, that the decision threshold is evaluated at the conventional value of the measurand zero, should be included in the definition. Therefore, a modified definition of the decision threshold that is compatible with the method used for the calculation is proposed.

A table-top exercise on ‘Monitoring a large-scale cross-border contamination in the aftermath of a nuclear accident’ was organized within the FP7-project PREPARE with the focus on the long-term emergency monitoring including transboundary and transnational aspects. From the detailed and content-rich answers from all participants of the table-top exercise, it can be concluded that competent persons with a lot of practical experience in the field were present to play the exercise. Answers were very useful because they were based on the experience from the real situation (e.g . Fukushima accident). It seems that the sampling procedures and measurement strategies are well defined. It was found out that all available communication channels can be established among the crisis centre, teams on the field and other institutions and/or teams involved (e.g . fire brigades, police, army fixed laboratories). From the answers, it comes out that some activities in the emergency are not completely harmonized transnationally, especially dispersion modelling, exchange of data, etc. The majority of the teams claimed that RODOS platform can be applied as the primary tool, but also other dispersion models, in-country developed, would be used in the nuclear emergency. From the answers, it stems out that numbering of specialized teams on the ground and the measurement capacities either in mobile laboratories or fixed laboratories should be concerned in small countries with nuclear installations, and even more pronounced in countries without Nuclear Power Plants (NPPs) on their territories.

A new method for calculating the detection limits of gamma-ray spectrometry measurements is presented. The method is applicable for gamma-ray emitters, irrespective of the influences of the peaked background, the origin of the background and the overlap with other peaks. It offers the opportunity for multi-gamma-ray emitters to calculate the common detection limit, corresponding to more peaks. The detection limit is calculated by approximating the dependence of the uncertainty in the indication on its value with a second-order polynomial. In this approach the relation between the input quantities and the detection limit are described by an explicit expression and can be easy investigated. The detection limit is calculated from the data usually provided by the reports of peak-analyzing programs: the peak areas and their uncertainties. As a result, the need to use individual channel contents for calculating the detection limit is bypassed.

A method was developed for calculating the decision thresholds for gamma-ray spectrometric measurements. At the energies where gamma-ray emitters that are present in the nuclide library, but were not identified in the spectrum, radiate, peaks are supposed to appear. The peak areas are calculated by fitting, using the method of least squares, the spectral region of the supposed peaks with a continuous background and the spectrometer response function at the gamma-ray energies where the supposed peaks are positioned. The null measurement uncertainty of a gamma-ray emitter is obtained as the uncertainty of the weighted average of the activities calculated from the areas of the supposed peaks in a spectrum where the specified activity of the gamma-ray emitter is zero. For the calculation of the decision threshold the null measurement uncertainty is used. These decision thresholds overestimate the critical limits calculated with the Currie formula by about 10% in the case of single gamma-ray emitters. For multi-gamma-ray emitters the decision thresholds yield smaller values than the Currie formula. The presence of a peaked background or peaks that are near the supposed peaks increases the decision threshold considerably.

A method for measuring the total activity of inhomogeneously distributed radioactive waste in a barrel is proposed. The method bases on a measurement of the attenuation of gamma-rays as a function of energy. It can be applied to gamma-ray emitters radiating at several energies over a broad energy range. The method is sensitive enough to measure activities of 104 Bq of 226Ra in 200 L barrels filled with a water-equivalent matrix in one day using a shielded detector with a relative efficiency of 50 %. The sensitivity to 228Ra is better, since here high-energy gamma-rays are emitted with a larger probability.

A method for determining the shielding factors for gamma-ray spectrometers is described. The shielding factors are expressed by decomposing the peaked background of the spectrometer into contributions of the detector, spectrometer shield and ambient radiation to the spectrometer background. The dimensions of the sample and its mass-attenuation coefficient are taken into account using a simple model. For six spectrometers, with contributions to the background quantified, the shielding factors were determined for the background based on the thorium decay series and the radon daughters. For a water sample with a diameter of 9 cm and a thickness of 4 cm and the nuclides of the thorium decay series that are in the spectrometer shields, the values of the shielding factors lie in the interval 0.95–1.00. For a spectrometer exhibiting the diffusion of radon into the shielding material, the values of the shielding factors for the same sample for gamma-rays from the radon daughters lie in the interval 0.88–1.00.

When reporting best estimates as measurement results, systematic influences near the natural limit are introduced that originate not only in the possible inconsistency of the analytical procedure but also in the conversion of the primary measurement results to best estimates. It has been shown that the probability density distribution resembling shifting of values observed in the unfeasible region to the limit of the feasible range (the natural limit) introduces a smaller systematic influence than the Bayesian posterior, resembling censoring with repetition of the measurements that result in observed values in the unfeasible region. The drawback that the uncertainty intervals calculated with the Bayesian posterior do not encompass the natural limit and may not encompass the observed value, although it lies within the feasible region, is avoided by using the probability density distribution resembling shifting. Therefore, such best estimates introduce a smaller systematic influence into the measurement results and are better suited as inputs for subsequent analyses.

A computerized procedure for analyzing high-resolution gamma-ray spectra was improved in three regards: the peak areas having large relative uncertainties were corrected for the possible contribution of statistical fluctuations in the continuous background, the peaks having a negative net peak area after background subtraction were included in the activity calculations and the primary measurement results were converted to the best estimate using an application of the Bayes theorem. It was proven empirically that the improvements that were introduced diminish the probability and severity of type-I errors and that they improve the consistency and accuracy of the measurement results near the decision threshold.

The probability density of Type-I errors in the peak-locating step of the spectra-analyzing procedure was empirically determined at a low value of the sensitivity parameter for peak recognition as a function of the height of the continuous spectral background and peak width. On the basis of this probability density, the number of Type-I errors for any spectral shape and FWHM calibration can be estimated. A criterion that is based on the relative peak-area uncertainty and the relative difference between the peak width obtained from the FWHM calibration and the width reported by the peak-analyzing program, as a measure of the believability that a located peak presents a Type-I error, is established. In addition, we demonstrate that the peaks having the largest believability are most likely to originate from Type-I errors. Using this criterion, the number of peaks, not identified in the identification step of the spectra analyzing procedure, to be checked for their origin can be reduced in accordance with the number of estimated Type-I errors.

A method for calculating the approximate value of the detection limit for measurements of ionizing radiation is presented. The method can be applied when the indication corresponding to the detection limit and its uncertainty are given as explicit functions. Then also the detection limit can be calculated explicitly, which means that the iteration procedure for its calculation can be avoided. The advantage of the method becomes apparent when the iteration process for calculating the detection limit is difficult to apply.

International audience; Several methods for reporting outcomes of gamma-ray spectrometric measurements of environmental samples for dose calculations are presented and discussed. The measurement outcomes can be reported as primary measurement results, primary measurement results modified according to the quantification limit, best estimates obtained by the Bayesian posterior (ISO 11929), best estimates obtained by the probability density distribution resembling shifting, and the procedure recommended by the European Commission (EC). The annual dose is calculated from the arithmetic average using any of these five procedures. It was shown that the primary measurement results modified according to the quantification limit could lead to an underestimation of the annual dose. On the other hand the best estimates lead to an overestimation of the annual dose. The annual doses calculated from the measurement outcomes obtained according to the EC's recommended procedure, which does not cope with the uncertainties, fluctuate between an under- and overestimation, depending on the frequency of the measurement results that are larger than the limit of detection. In the extreme case, when no measurement results above the detection limit occur, the average over primary measurement results modified according to the quantification limit underestimates the average over primary measurement results for about 80%. The average over best estimates calculated according the procedure resembling shifting overestimates the average over primary measurement results for 35%, the average obtained by the Bayesian posterior for 85% and the treatment according to the EC recommendation for 89%. © 2016 Elsevier Ltd.

Two simple methods for calculating the correlations between peaks appearing in gamma-ray spectra are described. We show how the areas are correlated when the peaks do not overlap, but the spectral regions used for the calculation of the background below the peaks do. When the peaks overlap, the correlation can be stronger than in the case of the non-overlapping peaks. The methods presented are simplified to the extent of allowing their implementation with manual calculations. They are intended for practitioners as additional tools to be used when the correlations between the areas of the peaks in the gamma-ray spectra are to be calculated. Also, the correlation coefficient between the number of counts in the peak and the number of counts in the continuous background below the peak is derived.

Activity concentrations of 40K and 3H in drinking water from four sources in the vicinity of NPP Krsko and their correlation with geological data are presented. The data extends from the year 1996 until present. In addition, activity concentrations of 40K in drinking water at randomly selected sources in Slovenia are presented on a map. These activity concentrations vary by more than an order of magnitude with the largest values in northeastern part of the country.

Metals can form several kinds of oxides. Iron forms wustite (FeO), magnetite (FeO + Fe2O3 or Fe3O4) and haematite (Fe2O3). Iron oxides, especially magnetite, are used for insulation between the lamellas of an electromotor made of electromagnetic sheet. In this work, iron oxide layers were characterized on industrial samples of electromagnetic sheet by AES depth profile analysis, and iron oxides with known chemical composition were used as reference samples, i.e. a magnetite mineral and a standard haematite reference sample. The magnetite mineral was chosen because it can be found in nature in a very pure form. The selection of reference samples was also verified on samples with an oxide layer of known composition, which were prepared by sputter deposition. The composition of the sputtered oxide layers was analysed by the weight-gain method and Rutherford backscattering without the use of standard reference materials (SRM), and the results were then compared with those obtained by AES depth profile analysis.

Environmental dosemeters were benchmarked against various dosimetry systems in realistic environmental conditions. For the first time, the dosemeters, provided by two institutions from two different countries, were deployed at 20 sites in Slovenia and Croatia (near the Nuclear Power Plant, NPP Krsko, Slovenia) during two semi-annual periods: summer-autumn and winter-spring. The results obtained using the different dosimetry systems show interesting features concerning local environmental peculiarities. The results of the intercomparison demonstrate an excellent agreement of the ambient doses measured independently by two different institutions and three passive dosimetry systems. Such consistency is crucial for the environmental dosimetry.

When measurement results with values near the decision threshold are being considered, a relative uncertainty of 60% is expected. Since such measurement results can be reported, the performance of the peak-analysing software for gamma-ray spectra needs to be examined for peaks that have a large relative uncertainty. The investigation was performed on a series of spectra measured with a HPGe detector under identical counting conditions. It was found that under a limit value of the relative peak area uncertainty the peak-analysis results are reliable with respect to both the peak location and the peak area evaluation. At relative uncertainties exceeding this uncertainty, the probability of type-II errors increases and a systematic influence on the peak area occurs, which originates in fluctuations of the continuous background in the vicinity of the peak. For the counting conditions used in this investigation, the limit relative uncertainty is about 35%, and whereas a systematic influence can be taken into account by a correction factor, the frequency of the type-II errors can only be reduced at the expense of increasing the frequency of the type-I errors.

In the presence of radon daughters, gamma rays from (88)Y with energies at 898.0keV or 1836.1keV appear on a high, continuous background or overlap with other peaks. Therefore a calculation of the decision threshold from the sum peak at 2734.1keV represents a useful alternative, because here the continuous background is low. The decision threshold calculated from this peak can attain a value being comparable to the decision threshold calculated from the gamma-ray peak at 898.0keV.

Determination of gamma ray dose in mixed neutron+gamma ray fields is still a demanding task. Dosemeters used for gamma ray dosimetry are usually in some extent sensitive to neutrons and their response variations depend on neutron energy i.e., on neutron spectra. Besides, it is necessary to take into account the energy dependence of dosemeter responses to gamma rays. In this work, several types of thermoluminescent detectors (TLD) placed in different holders used for gamma ray dose determination in the mixed fields were examined. Dosemeters were from three different institutions: Ruđer Boskovic Institute (RBI), Croatia, Jožef Stefan Institute (JSI), Slovenia and Autoridad Regulatoria Nuclear (ARN), Argentina. All dosemeters were irradiated during the International Intercomparison of Criticality Accident Dosimetry Systems at the SILENE Reactor, Valduc, June 2002. Three accidental scenarios were reproduced and in each irradiation the dosemeters were exposed placed on the front of phantom and ‘free in air’. Following types of TLDs were used: 7 LiF (TLD-700), CaF 2 :Mn and Al 2 O 3 :Mg,Y—all from RBI; CaF 2 :Mn from JSI and 7 LiF (TLD-700) from ARN. Reported doses were compared with the reference values as well as with the values obtained from the results of all participants. The results show satisfactory agreement with other dosimetry systems used in the Intercomparison. The influence of different types of holders and applied corrections of dosemeters' readings are discussed.

We have implemented a fast switching electrostatic system on the actinides beamline on the ANTARES accelerator at ANSTO, to improve the precision of analyses by accelerator mass spectrometry. This high-energy bouncing system is based on a pair of deflector plates, deflecting in the orbit plane, set at the entrance and exit of the analysing magnet. The design of deflector plates is unique, and it was modelled by SIMION in order to minimize field inhomogenity and fringe field effects. The pair of deflector plates are supplied by a high-voltage amplifier driven by an EPICS-enabled control unit, with two 4 W power supplies providing up to ±10 kV modulation. The high-energy bouncing system is synchronized with the existing low-energy bouncing system. To measure the isotopic ratio with the new system, the magnetic fields of the injector and analysing magnets are set to transmit selected isotopes along the beam line with zero voltage applied. The other isotopes of interest are transmitted by keeping the magnetic fields constant and modulating the voltages on the injector magnet chamber and on the high-energy deflector plates.

After the Fukushima accident aerosol and rain water samples collected within regular national monitoring programmes were carefully analysed. In rain water samples, aerosol and iodine filters collected in the second half of March and in April 2011 I-131, Cs-134 and Cs-137 were detected. In May 2011 the activities of I-131 and Cs-134 were close or below the detection limit and Cs-137 reached values from the period before the Fukushima accident. Additionally plutonium and americium activity concentrations in aerosol filters were analysed. These measured data were compared with measured data after the Chernobyl contamination in Slovenia in 1986. We can conclude that with adequate regular monitoring programmes influences of radioactivity contamination due to nuclear accidents worldwide can be properly assessed.

The uranium-induced background in eight high-resolution gamma-ray spectrometers was analyzed in order to identify the locations of its sources. On the basis of the energy dependence of the peak count rates, normalized to units of emission probability and detection probability, the contributions of the molecular sieve and the beryllium window were extracted. Based on the uncertainties achieved the contribution of the detector shields could not be observed. However, some correlations between the construction of the detectors and the values of the parameters describing the energy dependence were observed and the uranium activity in the beryllium windows was assessed.

A programme of harmonization of individual dosimetry quality control organized in the framework of a distributed metrology system is presented as seen from the experiences gained in Slovenia. As a part of the programme intercomparison of dosimetry services was organized and basic characteristics of dosimetry systems compared. Results are discussed with suggestions for further improvements of quality assurance.