Search

The integration of geological data obtained through fieldwork, remote sensing and airborne geophysics has been shown to be efficient in creation of precise geological maps. The Vieirópolis region, sited in the west of the Rio Grande do Norte Subprovince of the Borborema Province, is characteristically made up of rocks intensely deformed by transcurrent shear zones and late brittle structures which control the mineralization of gemmological and industrial minerals. ASTER GDEM and airborne geophysical images (magnetometry and gamma-ray spectrometry) were used in order to enhance the geological knowledge of this region and to facilitate the identification and delimitation of structures and lithologies mapped during stages of fieldwork. Thus, a geological map on a scale of 1:50,000 was achieved, made up of six main lithological units and three new shear zones (Vieirópolis, Lastro and São Pedro), as well as the NE-SW-trending Portalegre Shear Zone. Within the newly mapped structures, the Vieirópolis Shear Zone stands out due to its expressiveness. Aeromagnetometry data suggest that this zone originated on the edge of the Brejo das Freiras Subbasin, part of the Portalegre Shear Zone System. NW-SE, ESE-WNW and E-W lineaments were correlated to lesser extent brittle structures which sometimes transversely cut the regional foliation, allowing pegmatite fluids to rise. The RGB ternary composition map (K, eTh, eU) also corroborates the presence of these structures, besides helping to determine lithological units. In this case study, the integration of direct and indirect data showed to be essential for the understanding and producing of local geological map.

Abstract Silicon photomultipliers present saturation effects as they have a limited number of pixels and work in Geiger mode. Their response to light pulses in the nonlinear region is very complex for two reasons: pixel recharging after an avalanche affects the trigger probability and charge multiplication of subsequent avalanches, and non-trivial effects due to crosstalk and afterpulsing. A parametrization of the nonlinear response of silicon photomultipliers was developed where the above effects were readily accounted for. The model was tested on a setup of γ -ray spectrometry using different combinations of scintillation crystals and detectors. The model parameters were interpreted in terms of fundamental characteristics of the setup (e.g., lifetime of the scintillation crystal and pixel recovery time). The proper conversion from signal resolution to energy resolution was provided. [ABSTRACT FROM AUTHOR]

Abstract The γ-radiation emitted by building materials is calculated from the activity indices for 232Th, 226Ra and 40K and expressed as the activity concentration index (ACI). Gamma spectroscopy is a non-destructive technique frequently used to simultaneously determine the indices for several radionuclides. Spectral interpretation poses a number of challenges, including identification of γ-lines subject to summing-in effects, interference from other γ-ray emitting radionuclides and the time required to reach secular equilibrium. These challenges are not fully addressed by Canberra Industries' Genie 2000, the software used by many laboratories to analyse samples. This article describes a Microsoft Excel workbook that exploits Genie 2000 flexibility to program applications with Visual Basic using Canberra's Nuclear Data Access Library and batch procedure tools. The workbook determines 40K activity concentration after correcting for 228Ac interference and 226Ra activity directly from the γ-peak at 186.5 keV. The method proposed was tested by participating in 13 national and international scale inter-comparison exercises. The results were statistically indistinguishable from the reference values at a coverage factor of k = 3 and no statistically significant differences were identified between the respective means by a Student's t pairwise comparison. Highlights • The method developed corrects 228Ac spectral interference in the determination of 40K activity concentration. • The method can be used to determine 226Ra activity from its 186 keV photopeak with no need to wait for secular equilibrium. • Analysts can calculate activities from the CAM file more flexibly, using Genie 2000 in conjunction with Microsoft Excel. [ABSTRACT FROM AUTHOR]

Abstract From late September to early October of 2017, the majority of European networks involved in environmental radiological monitoring – including the environmental monitoring system of the KFKI Campus in Budapest – detected 106Ru isotope of artificial origin in the atmosphere. The reported values higher than the minimum detectable activity (MDA) concentrations were in the range of 0.8 μBq/m3 – 145 mBq/m3. Based on the results of environmental measurements and the available meteorological data, assessments were made to analyze concentration levels of 106Ru activity and to help understand the behavior of radioruthenium in various environmental media. Evaluation of the daily variation of activity levels indicated a maximum of 4 day-long residence time of 106Ru contamination presence in ground level air in Budapest. An average 106Ru activity concentration of 25.6 ± 1.4 mBq/m3 have been observed for the estimated residence time of 106Ru in the air. Deposition of 106Ru was dominantly influenced by rainfall, the major contributor wet deposition which led to an average of 11.3 ± 1.3 Bq/m2 deposition on the ground surface prior to plume passage. Graphical abstract Image 1 Highlights • 106Ru was detected solely in the atmosphere over Europe in the fall of 2017. • Measurement of low-activity, pure β-emitter 106Ru required advanced methods. • 106Ru was detectable in air, deposition, grass, transfer between the elements was shown. • Temporal variation of 106Ru activity indicated short residence time of the plume. • Effective dose in residence time was <0.2 μSv from major contribution of inhalation. [ABSTRACT FROM AUTHOR]

The overlying rock of underground laboratories provides excellent radiation shielding necessary for many experiments searching for extremely rare nuclear and astroparticle events. Monte Carlo simulations of HPGe detector background and attenuation of gamma-ray fluxes with different shielding configurations were carried out for an underground laboratory. It has been found that even a small radioactive contamination of the shielding material may increase gamma-ray fluxes in underground laboratory by several orders of magnitude. [ABSTRACT FROM AUTHOR]

Abstract When determining the activity concentration of radionuclides using gamma-ray spectrometry the Full Energy Peak Efficiency (FEPE) for the energies of interest must be known. Determination of the FEPE can be made by means of either experimental calibration or theoretical–mathematical methods, such as Monte Carlo simulations. Given the difficulties related to experimental calibration and improvements in the capabilities of modern computers, Monte Carlo simulation is an increasingly widely used alternative, but requires an accurate model of the detector. The purpose of this work is to generate and validate a computational model, based on Monte Carlo simulation, of an HPGe well detector that permits the performance of FEPE calculations with appropriate precision and accuracy for the measurement of environmental samples. To achieve this, an optimization methodology is applied to the model that minimizes the differences between a set of computational FEPEs and a set of experimental FEPEs used as a benchmark. The resulting optimized model is used to calculate computational FEPEs for 25 different samples with different reference materials and sample heights, which are measured by means of the well detector modeled here. To validate the optimized model, the abovementioned computational FEPEs are used during the calibration of the corresponding spectra, to enable the subsequent comparison of the results of the analyses with the expected values. The measured activities differ from the reference values by less than 10% in most cases and are compatible with these considering the uncertainties involved, thus confirming the validity of the model. Highlights • A HPGe well detector has been modeled using the PENELOPE Code. • Experimental FEPEs have been used as reference. • The model was optimized using the Differential Evolution algorithm. • The model has been validated using reference materials. • Good agreement observed between reference and measured activity concentrations. [ABSTRACT FROM AUTHOR]

Abstract The spatial distribution of heat producing elements (K, U, and Th) in the continental crust has long-term implications for the thermal and physical evolution of orogens. Heat producing elements, in particular Th, are most abundant in metasedimentary rock types. As such, these rock types have a significant control on the spatial distribution of heat production in the crust. The major host of the heat producing element thorium in pelitic metasedimentary rocks is the REE–Th phosphate monazite. We present in-field gamma ray spectrometry (in-field GRS) data integrated with grain-scale electron probe microanalysis data to reveal grain to terrane scale links in thorium distribution. In-field GRS data shows that thorium is not depleted in granulite facies residual rocks that have lost melt with respect to their subsolidus counterparts. Concurrently, the bulk thorium budget of monazite is approximately uniform within samples and if anything increases with increasing metamorphic grade. Monazite average grain size increases with metamorphic grade and prograde cores are largely preserved in granulite facies samples. Thorium is preserved in residual metasediments after melting and melt loss implying that even when melting and melt extraction is efficient it does not strip Th from granulite facies rocks. Highlights • Th preserved in granulite facies residue at both outcrop and micro-scales. • Prograde monazite zoning retained after granulite facies metamorphism and melt loss. • Abundance and total Th contained in monazite increases with metamorphic grade. [ABSTRACT FROM AUTHOR]

During the last days of September to the first days of October in 2017, a unique detection of 106 Ru was observed in air filters sampled at different locations in Sweden via the national air monitoring network. Furthermore, measurements of precipitation also showed the presence of 106 Ru. This initiated soil sampling and in situ gamma-ray spectrometry at one of the locations. [ABSTRACT FROM AUTHOR]

It is well known that monitoring of radioactivity released from nuclear medicine departments is necessary to ensure the radiological safety of patients and personnel. Unfortunately, equipment for air sampling is often expensive, loud and is not suitable to use in hospitals. Our goal was to find cheap and simple system for passive monitoring of 131I activity concentration in the air of nuclear medicine departments. Medical activated charcoal tablets were used, because charcoal is excellent material for 131I trapping and tablets are readily available. Our proposed sampling protocol contains tablets preparation, exposure and measurements using HPGe detector. Different methods of tablets preparation (drying, impregnation with KI or NaOH) were tested while an experimental chamber was prepared for estimating 131I (released from Na131I, similar to that used in therapy) trapping efficiency of tablets in different conditions. Finally, tablets were placed in plastic holders and tested in nuclear medicine facilities. [ABSTRACT FROM AUTHOR]

Highlights • We present results of extraction of natural radionuclides from the phosphogypsum. • This separation was based on solubility difference between CaSO 4 and RaSO 4. • The extraction of radionuclides from TENORM phosphogypsum material was achieved. • More than 80% of the gypsum was recovered from the phosphogypsum in the hydrated form. • Benefits of the methodology if implemented in industrial scale. Abstract Phosphate ore is the raw material for the production of fertilizers. Phosphogypsum with a high content of natural radionuclides, specifically those present in the decay series of 238U and 232Th, is a byproduct (waste material) of a chemical reaction between sulfuric acid and phosphate rock in phosphoric acid production. Due to these characteristics, the phosphogypsum is considered a TENORM (Technologically Enhanced Naturally Occurring Radioactive Materials). For each ton of phosphoric acid produced, 4 to 5 tons of phosphogypsum are generated, representing a great environmental liability. Because of the similar chemical properties of phosphogypsum and conventional gypsum, both calcium sulfate, there is a great interest in the scientific community to find technological solutions for reuse of this material. This study aimed to develop methodologies and processes for separating calcium sulfate from the main radionuclides present in the phosphogypsum, based on the difference in solubility between these compounds, among them the radium sulfate. Chemical processes were developed for the recovery of the calcium sulphate in the solid form from the extraction of the radionuclides made by dissolution of the phosphogypsum. This study shows that it is possible to extract radionuclides from waste TENORM - phosphogypsum – obtaining more than 80% of the material in the form of hydrated gypsum. Using gamma-ray spectrometry technique, no signal was detected for the presence of radionuclides in the treated material. The results indicate the benefits that the process used in this work can provide when implemented on an industrial scale. [ABSTRACT FROM AUTHOR]

Abstract Meat is a major component of the daily diet of the Kuwait population. Realizing the negative consequences of the presence of radioactive materials in foodstuffs, various types of meat (fresh and processed lamb and beef) on sale in Kuwaiti markets have been assessed. The interest is in seeking to obtain a measure of the potential radiological impact to human health that results from their consumption. High purity germanium γ-ray spectrometry of the meat has revealed low activities of 226Ra and 228Ra, key indicators of the respective 238U and 232Th natural decay series. While elevated activities of 40K were observed in a number of the fresh meat samples, evidence of the anthropogenic radionuclide 137Cs was found in one sample only. A statistically significant difference was found between the mean value of activity concentration of 40K in fresh and processed beef samples. The total potassium concentration in the meat samples was calculated from observation of 40K activity, values ranging between 2.6 and 17.2 g kg−1. The annual effective dose resulting from meat consumption for a typical adult in Kuwait has been estimated to be 217 µSv y−1, somewhat less than the 290 µSv y −1 assessed by UNSCEAR (2008) to prevail more globally. Findings from this research are intended to underline the importance of periodic monitoring of foodstuffs in efforts towards mitigating radiological risk. [ABSTRACT FROM AUTHOR]

Cs-137 is considered to be the most significant anthropogenic contributor to human dose and presents a particularly difficult remediation challenge after a dispersal following nuclear incident. The Chernobyl Nuclear Power Plant meltdown in April 1986 represents the largest nuclear accident in history and released over 80 PBq of 137 Cs into the environment. As a result, much of the land in close proximity to Chernobyl, which includes the Polessie State Radioecology Reserve in Belarus, remains highly contaminated with 137 Cs to such an extent they remain uninhabitable. Whilst there is a broad scale understanding of the depositional patterns within and beyond the exclusion zone, detailed mapping of the distribution is often limited. New developments in mobile gamma spectrometry provide the opportunity to map the fallout of 137 Cs and begin to reconstruct the depositional environment and the long-term behaviour of 137 Cs in the environment. Here, full gamma spectrum analysis using algorithms based on the peak-valley ratio derived from Monte Carlo simulations are used to estimate the total 137 Cs deposition and its depth distribution in the soil. The results revealed a pattern of 137 Cs distribution consistent with the deposition occurring at a time of flooding, which is validated by review of satellite imagery acquired at similar times of the year. The results were also consistent with systematic burial of the fallout 137 Cs by annual flooding events. These results were validated by sediment cores collected along a transect across the flood plain. The true merit of the approach was confirmed by exposing new insights into the spatial distribution and long term fate of 137 Cs across the floodplain. Such systematic patterns of behaviour are likely to be fundamental to the understanding of the radioecological behaviour of 137 Cs whilst also providing a tracer for quantifying the ecological controls on sediment movement and deposition at a landscape scale. [ABSTRACT FROM AUTHOR]

In this study, activity concentrations of 40K, 226Ra and 232Th in fertilized soil samples and different organic and inorganic fertilizers used in agricultural soil were analysed using gamma-ray spectrometry NaI (Tl) detector in order to access the implications of extended use of fertilizers in 2-3 years. The concentrations of radionuclides in some granular fertilizer brands were discovered to be higher for 40K, 226Ra and 232Th than those obtained in leafy fertilizer, animal fertilizer and fertilized soil samples. From the results, the highest overall mean concentrations of the specific activities of 40K, 226Ra and 232Th were 2301.8 (granular fertilizer), 42.5 (leafy fertilizer) and 327.1 (animal fertilizer) in Bq kg−1, while the lowest values observed in the specific activities of the same radionuclides were 357.7 (leafy fertilizer), 28.1 (animal fertilizer) and 36.5 (animal fertilizer). The radiological hazards of the radium equivalent (Raeq), normative value (NRN), outdoor radium equivalent (Raeq-out), external hazard index (Hext), internal hazard index (Hin), dose rate, annual effective dose rate, activity utilization index and concentration accumulation index (CAI) and RaFZ due to the presence of these radionuclides in the investigated samples were calculated. Nevertheless, some of the fertilizer brands have higher concentration values than the recommended limit, and the values of hazard indices of fertilizer brands used in the selected teaching and research farms were within acceptable limit. Therefore, the fertilized soil samples in the studied farms are safe. [ABSTRACT FROM AUTHOR]

We studied the excitation functions of residual radionuclides produced via proton and deuteron bombardment on natural iridium in the energy ranges of 30–15 MeV and 50–15 MeV, respectively. A conventional stacked-foil activation technique combined with HPGe γ-ray spectrometry was used to measure the excitation functions for 189, 191 Pt and 189, 190g, 192g, 194g Ir radionuclide production. Theoretical thick target yields were estimated to be 172 MBq/µA h and 192 MBq/µA h via the 193 Ir(p,3n) 191 Pt reaction at 29.6–17.5 MeV and the 193 Ir(d,4n) 191 Pt reaction at 40.3–23.8 MeV, respectively. The feasibility of 191 Pt production from an iridium target was discussed, and compared with previously reported methods for the production of 191 Pt. [ABSTRACT FROM AUTHOR]

The CLYC (Cs2LiYCl6:Ce) detector is a scintillator detector sensitive to both neutron and gamma radiation and capable of separating the two types of radiation by pulse-shape discrimination. This feature is interesting as pertains to the development of non-destructive assays for the safeguard of nuclear material, nuclear security, and fast-neutron personal dosimetry. A 1′′×1′′ CLYC detector highly enriched with 6Li was purchased and tested with analog and digital electronics. In this work, we report on the characterization of the detector in terms of linearity, energy resolution, and full-energy efficiency for gamma rays. This characterization was achieved by measurements with calibrated gamma-ray point-sources with an analog measuring chain, in a well-defined, reproducible geometry. The experimental data were also used to validate a model of the detection system that was developed with the Monte Carlo code MCNP-CP. This work is part of a collaborative agreement between SCK•CEN and JRC-Geel. [ABSTRACT FROM AUTHOR]

A simple method for the determination of the radon emanation fraction (EF) from rocks has been studied in this work. Growth and decay curves of radium—radon—daughters and the double counting technique using the same gamma-ray spectrometry were applied to determine the EF from eleven rocks at different lithologies. Aluminium Marinelli beakers were used to prevent the leakage of radon during the equilibration period of around 30 days. And also, nitrogen purging system was constructed to replace the surrounding air of the detector for obtaining a stable background and reducing the interference of radon daughter nuclides from the atmosphere. [ABSTRACT FROM AUTHOR]

Buildings materials contain natural primordial radionuclides of 40K, 232Th and 226Ra (238U). The research measures activity concentrations of 40K, 232Th and 226Ra in different types of raw materials with different origins: volcanic, calcareous, zirconium minerals, silico-aluminous etc., used in Romanian building industry. This is important as these materials lead to an exposure of the public and workers from their ionizing radiations. Based on these activity concentrations an estimation of the radiological hazard is also made by analyzing radiological parameters such as radium equivalent activity (Raeq), absorbed dose (D), annual effective dose equivalent (AEDE), external hazard index (Hex), internal hazard index (Hin), gamma and alpha index and dose criterion. Important conclusions can be drawn from the analysis of these indexes in respect with the radiological hazard for the population health by using these materials. Most of materials measured in this work showed fairly low levels of radioactivity. [ABSTRACT FROM AUTHOR]

At the JRC-Geel's RadioNuclide Metrology sector, a Monte Carlo code based on EGSnrc, and a general purpose calculation sheet implemented in Microsoft Excel ® , have been developed to make the quantitative gamma-ray spectrometry analysis of samples simpler and more robust. The further aim is that the software can be used by non-experts in gamma-ray spectrometry e.g. external researchers using JRC-Geel's facilities through the EUFRAT transnational access scheme. This paper presents the developed Monte Carlo software and the functionality included in the calculation sheet. [ABSTRACT FROM AUTHOR]

The National Institute of Standards and Technology (NIST) compared the measured full-energy peak efficiency obtained from a large set of sources to that of a 207 Bi source obtained using three different half-life values. The values of the half-life used for this comparison are published in the Decay Data Evaluation Project (32.9 ± 1.4) years and the Evaluated Nuclear Structure Data File (31.55 ± 0.04) years, and in a recent NIST publication (31.20 ± 0.05) years (or (11395 ± 18) days). [ABSTRACT FROM AUTHOR]

The effect of the intrinsic inhomogeneity of a sample on the efficiency for the measurement of the sample by gamma-ray spectrometry is studied. The difference between the efficiency for the inhomogeneous sample and the efficiency for a sample made from the equivalent homogeneous matrix is evaluated. [ABSTRACT FROM AUTHOR]

Two main non-destructive techniques can be used to measure standard 222 Rn gas ampoules: well-type ionization chambers and gamma-ray spectrometry, the former being used in the Système International de Référence (SIR) for international comparison purposes. The reliability of these techniques requires that the variability of the flame-sealed gas glass ampoules used have a negligible influence on the detector response. This variability is studied in this work by considering three parameters: the volume of the ampoule, the position of the sealing point and the thickness of the glass. Results showed that variability of the gas ampoules induced measurement bias larger than the uncertainty of the standard sources. [ABSTRACT FROM AUTHOR]

This paper presents the results of the absolute measurement of some photon emission intensities in the decay of 166m Ho. Point sources from a reference solution standardized in the frame of the EURAMET.RI (II)-K2. Ho-166m activity comparison were measured by gamma spectrometry. The detection efficiency was obtained by Monte Carlo calculations including the complete decay scheme. Results obtained for 27 gamma and X-ray emissions are compared to reference values. [ABSTRACT FROM AUTHOR]

142 Pr (praseodymium-142), a potential radionuclide for brachytherapy, was produced after irradiating high purity natural Pr 2 O 3 powder in a research reactor. The irradiated powder was then dissolved in acids and diluted for measurement. Several radioactivity measurement methods were used in the standardization of 142 Pr radionuclide. This work reports the results of standardization of 142 Pr with CIEMAT/NIST efficiency tracing method, gamma spectrometry and a calibrated ionization chamber. The activity measured from different standardization methods are compatible with each other within the uncertainty limits. The CIEMAT/NIST efficiency tracing method gives the lowest uncertainty and is a reliable method for the standardization of this radionuclide. [ABSTRACT FROM AUTHOR]

The activity of 158 Tb was measured in waste samples from the Ignalina NPP Unit I RBMK-1500 reactor using gamma-ray spectrometry. The origin of 158 Tb and the other observed gamma-ray emitters has been studied by using SCALE 6.1 modeling and comparing radionuclide ratios in the RBMK-1500 radioactive waste. The results of the calculation of the massic activity of gamma-ray emitters were used for interpretation of the total gamma-ray spectrum and the determination of 158 Tb massic activity uncertainty in the waste of RBMK-1500. [ABSTRACT FROM AUTHOR]

This paper outlines the process of characterizing a new NORM material for proficiency testing made of quartz sand with significantly elevated levels of 226 Ra obtained from the backflush of a drinking water treatment facility. Samples of the fully characterized NORM material were sent to European laboratories concerned with radioactivity measurements and environmental monitoring by gamma-ray spectrometry for proficiency testing. The paper discusses the results, specific requirements, problems and solutions that were found during the characterization process and the proficiency test. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

226Ra, 238U, 232Th, and 40K radionuclides have been determined using gamma-ray spectrometry in soil samples collected from urban areas in the southern governorates of Jordan and showed average concentrations of (39 ± 18), (45 ± 20), (23 ± 13), and (233 ± 128) Bq kg−1, respectively. The corresponding radio-elemental concentrations in the existing geological features were obtained and examined for the relative depletion/enrichment processes and state of equilibrium in soils. Radium equivalent activity, hazard indices, and annual gonadal dose equivalent do not exceed the permissible limits. Absorbed dose rates in air outdoor and external effective dose showed average values of 44.0 nGy h−1 and 54.4 μSv y−1, respectively. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

A new set of spectrometric data on γ ray energies and intensities in the decays of the 117g.m Cd isomers (2.5 h and 3.4 h) has been accumulated. Uncertainties in the energies and intensities have been reduced by about an order of magnitude relative to previous studies. Through observation of their time dependence, several transitions are shown as incorrectly assigned in previous studies, and many new transitions were assigned to the respective decays. The placements of other transitions are shown to be doubtful based on poor energy fits. Energies and β -decay intensities have been deduced for the excited states in the 117 In daughter. Some additional γ rays from the decay of daughter 117g In to 117 Sn have also been observed. [ABSTRACT FROM AUTHOR]

Cross sections of reaction products were measured in SiNb reaction using recoil catcher technique involving by off-line gamma-ray spectrometry at beam energies of 105 and 155MeV. At MeV, the contribution from different incomplete mass transfer processes is investigated. Results of the present studies show the contribution from deep inelastic collision (DIC), massive transfer or incomplete fusion (ICF) and quasi-elastic transfer (QET). The contribution from massive transfer reactions was confirmed from the fractional yield of the reaction products in the forward catcher foil. The present results are different from those from the reactions with comparatively higher entrance channel mass asymmetry with lighter projectiles, for which dominant transfer processes are ICF and QET which involve mass transfer predominantly from projectile to target. The values of the products close to the target mass were observed to be in a wide range, starting from of the target (Nb) and extending slightly below the of the composite system, consistent with the contribution from DIC and QET reactions. At MeV, a small contribution from QET was observed in addition to complete fusion. [ABSTRACT FROM AUTHOR]

An X-ray-gamma coincidence measurement method for efficiency calibration of a HPGe–HPGe system, using the methodology for activity standardisation of 125 I, has been developed. By taking one list-mode time-stamped measurement of the 125 I source, six spectra were generated in post-processing: total spectra, coincidence spectra and energy gated coincidence spectra for each of the two detectors. The method provides enough observables for source activity to be determined without a prior knowledge of the detector efficiencies. In addition, once the source is calibrated in this way the same spectra can also be used to perform efficiency calibration of the individual detectors in the low energy range. This new methodology for source activity determination is an alternative to the already established X-ray-(X-ray, gamma) coincidence counting method; with two NaI(Tl) detectors and the sum-peak method using a single HPGe detector. When compared to the coincidence counting method using two NaI(Tl) detectors, the newly developed method displays improved energy resolution of HPGe detectors combined with measurement of only full peak areas, without the need for total efficiency determination. This enables activity determination even in presence of other gamma emitters in the sample. Standard coincidence counting with NaI(Tl) detectors provides lower uncertainties. The method has been used for calibration of a coincidence HPGe spectrometer in the low energy range of 125 I and fine adjustments of a Monte Carlo model of the coincidence system. [ABSTRACT FROM AUTHOR]

The aim of this paper is to characterize two HPGe gamma-ray detectors used in two different laboratories for environmental radioactivity measurements, so as to perform efficiency calibrations by means of Monte Carlo Simulation. To achieve such an aim, methodologies developed in previous papers have been applied, based on the automatic optimization of the model of detector, so that the differences between computational and reference FEPEs are minimized. In this work, such reference FEPEs have been obtained experimentally from several measurements of the IAEA RGU-1 reference material for specific source-detector arrangements. The models of both detectors built through these methodologies have been validated by comparing with experimental results for several reference materials and different measurement geometries, showing deviations below 10% in most cases. [ABSTRACT FROM AUTHOR]

This paper presents a Monte Carlo method to obtain the full energy peak efficiency (FEPE) curve for a High Purity Germanium (HPGe) detector, as it is difficult and time-consuming to measure the FEPE curve experimentally. The Geant4 simulation toolkit was adopted to establish a detector model since detector specifications provided by the nominal manufacturer are usually insufficient to calculate the accurate efficiency of a detector. Several detector parameters were optimized. FEPE curves for a given HPGe detectors over the energy range of 59.50–1836 keV were obtained and showed good agreements with those measured experimentally. FEPE dependences on detector parameters and source-detector distances were investigated. A best agreement with experimental result was achieved for a certain detector geometry and source-detector distance. [ABSTRACT FROM AUTHOR]

The absolute intensity for the 803-keV γ ray of 210Po was evaluated by α-γ coincidence technique. A liquid sample with a known amount of 210Po embedded in scintillation fluid was measured in a coincidence-based system that comprises a Liquid Scintillator (LS) detector and a High-Purity Germanium (HPGe) detector. A photo-reflector assembly that contains the 210Po sample provides 100% efficiency for detecting the α particles. The combination between the HPGe and the LS detectors allows to reject non-coincident α-γ events while maintaining high resolution γ spectroscopy. Consequently, the faint 803-keV photopeak from 210Po could be observed in a background-free environment, and its intensity could be evaluated with good accuracy. Sample measurements were carried out over nine months to gather statistics and verify the reliability of the experimental procedure. The absolute intensity of the 803-keV line was found to be (1.22 ± 0.03) × 10−5, in excellent agreement with the adopted value in a recent data compilation and consistent with previous experimental works. • The intensity of the 803-keV γ-ray emitted from 210Po was evaluated using a α-γ measurement system. • Result is in very good agreement with values from previous works. • Measurement uncertainty is competitive with other more traditional methods. • The method may be applicable to other low-intensity α-γ emitters. [ABSTRACT FROM AUTHOR]

A method has been developed to purify and measure platinum radioisotopes in the presence of fission products and environmental constituents. The method uses a combination of cation exchange and anion exchange chromatography and selective precipitation steps to remove other radioisotopes from the sample. The addition of stable platinum carrier allows for a gravimetric determination of the chemical yield of the procedure. Overall, the method is fast, simple, and potentially applicable for rapid turnaround of unknown samples. Using this method, multiple platinum radioisotopes were measured in two different irradiation experiments. The measured ratios of the platinum radioisotopes clearly reflect the neutron spectrum of the irradiation, suggesting that platinum radioisotopes could be valuable signatures in nuclear forensic analyses. [Display omitted] • Measurement of radioactive platinum activation products in environmental samples. • Effective decontamination against fission product interferences. • Platinum radioisotope ratios depend on the neutron spectrum of the irradiation. [ABSTRACT FROM AUTHOR]

A ground-level prototype system for low-background measurements was developed and tested. The system consists of a high-purity germanium (HPGe) detector used for detecting γ rays and coupled to a liquid scintillator (LS) used for detecting α and β particles. Both detectors are surrounded by shielding materials and anti-cosmic detectors ("veto") used to suppress background events. The energy and timestamp of detected α, β and γ emissions are recorded event-by-event and analyzed offline. By requiring timing coincidence between the HPGe and LS detectors, background events originating from outside the volume of the measured sample can be effectively rejected. The system performance was evaluated using liquid samples containing known activities of an α emitter (241Am) or a β emitter (60Co) whose decays are accompanied by γ rays. The LS detector was found to provide a solid angle of almost 4π for α and β particles. Compared to the traditional γ-singles mode, operating the system in coincidence mode (i.e., α-γ or β-γ) reduced the background counts by a factor of ∼100. Consequently, the minimal detectable activity for 241Am and 60Co was improved by a factor of 9, being 4 mBq and 1 mBq for an 11-d measurement, respectively. Furthermore, by applying a spectrometric cut in the LS spectrum that corresponds to α emission from 241Am, a background reduction factor of ∼2400 (compared to γ-singles mode) was achieved. Beyond low-background measurements, this prototype exhibits additional compelling features, such as the ability to focus on certain decay channels and study their properties. This concept for a measurement system may be of interest to laboratories that monitor environmental radioactivity, studies involving environmental measurements and/or trace-level radioactivity. • A low background measurement system was developed and tested. • The developed system is capable of detecting α, β and γ emissions. • The solid angle for detecting α/β-particles was found to be nearly 4π. • Operation in coincidence mode leads to background reduction factor of 100 compared to γ-singles. • The gross background count rate in coincidence mode was found to be 0.018 kgGe−1·s−1. [ABSTRACT FROM AUTHOR]

Understanding the weathering intensities can provide answers for environmental issues, soil, and geoscience studies. Recently, geophysical approaches and machine learning techniques have been applied in soil science to access weathering. This study aimed to model weathering intensity using combined data from geophysical sensors, satellite images, and morphometry associated to machine learning algorithms. We also we evaluated the efficiency of nested-leave one out cross-validation applicability in a small geodata set evaluated the importance of covariates and the resulting weathering intensity map in relation to pedogeomorphological processes. Our study focused on a 184-ha area in southwest Brazil, where we conducted soil analysis at 71 sites. We applied principal component analysis and determined the ideal number of clusters to determine the classes of weathering intensity. We used six geophysical sensor parameters, including equivalent uranium, equivalent thorium, potassium 40, magnetic susceptibility, and soil apparent electrical conductivity, along with the weathering index to create the clusters. Then, four machine learning algorithms were used to infer different weathering intensities in soils formed from the same parent materials. To validate our results, we used the nested-leave-one-out-cross-validation ("nested-LOOCV") method, which is suitable for small datasets. Our findings showed that the random forest model performed the best with three clusters as the ideal number. We also found that the geophysical data, clusterization, and machine learning algorithm contributed significantly to identifying different weathering intensities. The results indicated that weathering operated at different intensities on both the diabase/Rhodic-Nitisols and the siltite/metasiltite Rhodic and Xanthic Lixisols areas, with the highest intensities occurring in the west Xanthic Lixisols and the lowest intensities occurring in the Rhodic and Lixisols in the east area. The siltite/metamorphosed siltite and Lixisols areas presented moderate weathering rates. We found that the all-geophysical variables used were related and affected by weathering intensity, which contributed to the modeling and clusterization processes. • Combined use of geophysical sensors in modeling soil weathering intensity. • Nested Leave One Out Cross-Validation for external validation in small dataset. • Use pedoenvironmental covariates and satellite image to determine ideal number of clusters. • Geophysical data, machine learning and clustering identified different weathering intensities. • Use of clusters in modeling processes. [ABSTRACT FROM AUTHOR]

The study of spatial distribution of activity concentration of 238U, 226Ra, 210Pb, 232Th, 40K, and 137Cs radionuclides in the surface soil samples (n = 42) collected in the vicinity of four coal-fired power plants in Serbia is presented. Radioactivity measurements in soils performed by gamma-ray spectrometry showed values [Bqkg-1] in the range: 15-117 for 238U, 21-115 for 226Ra, 33-65 for 210Pb, 20-69 for 232Th, 324-736 for 40K, and 2-59 for 137Cs. Surface soil radio-activity that could have resulted from deposition of radionuclides from airborne discharges or resuspension of ash from disposal sites showed no enhanced levels. It was found that variation of soil textural properties, pH values, and carbonate content influenced activity levels of natural radionuclides while radiocesium activities were associated with soil organic matter content. Modification of some soil properties was observed in the immediate vicinity (

The application of the principal component analysis and artificial neural network method in forecasting 137Cs behaviour in the air as the function of meteorological parameters is presented. The model was optimized and tested using 137Cs specific activities obtained by standard gamma-ray spectrometric analysis of air samples collected in Belgrade (Serbia) during 2009-2011 and meteorological data for the same period. Low correlation (r = 0.20) between experimental values of 137Cs specific activities and those predicted by artificial neural network was obtained. This suggests that artificial neural network in the case of prediction of 137Cs specific activity, using temperature, insolation, and global Sun warming does not perform well, which can be explained by the relative independence of 137Cs specific activity of particular meteorological parameters and not by the ineffectiveness of artificial neural network in relating these parameters in general. [Projekat Ministarstva nauke Republike Srbije, br. TR34034]