HPGe Gamma Spectrometry Research Articles

Study the influences of the radionuclide depth distributions on the FEPE for the measurements of the soil activity using in situ HPGe gamma spectrometry

In this work, the influences of the soil densities and the radionuclide depth distributions (RDD) on the Full Energy Peak Efficiency (FEPE) calculation of the in-situ gamma ray spectrometer using the In Situ Object Counting Systems (ISOCS) software were studied. The data of the RDDs at the sites were investigated by using laboratory HPGe gamma spectrometer. Six different RDDs of 40K, 226Ra and 232Th were found at four studied sites with radionuclide deposition moving from surface to deeper positions. The results show that FEPE values vary strongly for the different RDDs, especially for the low gamma ray energies. Use of the uniform model for calculating FEPEs can result in noticeable errors from 29% to 101% for the realistic RDD of the exponential form (surfaceradionuclide deposition), negative variations from 14% to 30% for the realistic RDD of having a radionuclide deposition at the 30 cm depth, and negligible variations of less than 5 % for the realistic RDD of quasi uniform form in the range of gamma ray energies of interest.

137Cs activity concentration in mosses in the Calabria region, south of Italy

Many studies carried out after the Chernobyl nuclear accident in 1986 showed that mosses are suitable bioindicators of the radioactive fall-out, given their long life expectancy. 137Cs activity concentration was measured through HPGe gamma spectrometry in different mosses (Hypnum Cupressiforme, Hypnum Andoi, Homalothecium Sericeum, Philonotis Fontana), collected, in 2008 and 2015, from four sampling sites in the Calabria region, south of Italy. Experimental specific activities allowed us to determine the effective and the biological half-time of 137Cs for the investigated plants. The effective half-time was found in the range from (4.2 ± 1.1) to (7.4 ± 1.8) years; the biological half-time varied from (4.9 ± 1.3) to (9.9 ± 2.4) years. Data reported in this article provide useful information on the environmental risk of the studied area and can be further used for a radiological mapping.

Search for the decay of nature's rarest isotopeTa180m

$^{\rm {180m}}$Ta is the rarest naturally occurring quasi-stable isotope and the longest lived metastable state which is known. Its possible decay via the $\beta^-$ or the electron capture channel has never been observed. This article presents a search for the decay of $^{\rm {180m}}$Ta with an ultra low background Sandwich HPGe gamma spectrometry setup in the HADES underground laboratory. No signal is observed and improved lower partial half-life limits are set with a Bayesian analysis to $5.8\cdot10^{16}$ yr for the $\beta^-$ channel and $2.0\cdot10^{17}$ yr for the electron capture channel (90% credibility). The total half-life of $^{\rm {180m}}$Ta is longer than $4.5\cdot10^{16}$ yr. This is more than a factor of two improvement compared to previous searches.

Lichens as environmental risk detectors

Several studies carried out after the Chernobyl nuclear accident in 1986 showed that lichens are suitable biomonitors of the fall-out, given their long life expectancy. 137Cs activity concentrations were measured through HPGe gamma spectrometry in different epiphytic lichens (Usnea SPP, Platismatia glauca, Pseudevernia furfuracea, Ramalina SPP), collected from three sampling sites in the Calabria region, south of Italy. Data on variations in the contents of airborne particulates heavy metals, As, Be, Cd, Cu, Hg, Pb and Zn, measured in the thalli of the investigated lichens through inductively coupled plasma mass spectrometry (ICP-MS), were reported in accordance with a lichen thalli naturalness/alteration scale. Energy-dispersive X-ray microanalysis in a scanning electron microscope (SEM-EDX), with an electron beam of 20keV, that interacts with the sample leading to the emission of characteristic X-rays as secondary radiation, was also employed to investigate about the chemistry of the adherent particles to the surface of investigated lichens and about the possible interaction between them and the surrounding environment. Data obtained in this article provide useful information on the environmental risk of the studied area and can be further used for a radiological and chemical mapping.

Experimental Investigation on the Photopeak Efficiency of a Coaxial High Purity Germanium Detector for Different Geometries

Purpose: Gamma spectrometer systems are complex instruments, and the quality of the numerical results they provide strongly depends on their reliable calibration. In this study, it was aimed to determine the full-energy peak efficiencies of a 40% p-type High Purity Germanium HPGe detector for point source, Marinelli beaker, and cylindrical container geometries in the 200-1500 keV energy range. Methods: The efficiency calibration of the HPGe gamma spectrometry system was performed using certified calibration sources. Efficiency values were determined using the gamma ray spectrum acquired for every calibration source.Results: Two different efficiency curves, at the linear scale and logarithmic scale-fitting, experimental efficiencies were plotted. The functions and parameters that fitted the efficiency curves were obtained by a computer program.Conclusion: The photopeak efficiencies decrease as energy increases and the observed efficiency curves were closely with similar studies

Diagnostics techniques and dosimetric evaluations for environmental radioactivity investigations

A comprehensive study was conducted about the investigation of the natural/anthropo-genic radioactivity of various environmental matrices. Different diagnostics techniques were employed: high resolution HpGe gamma spectrometry, to quantify the activity concentration of radionuclides that emit gamma photons; alpha spectrometry, for the determination of the specific activity of α -emitters radioisotopes; liquid scintillation, to measure the activity concentration of tritium, radon and total alpha/beta in liquid samples; alpha spectrometry through the Rad7 setup, to estimate the gas radon activity concentration in air, water and soil; total alpha/beta counter, for the activity concentration quantification of radionuclides, in solid samples, emitting alpha/beta particles. From the dosimetric point of view, knowledge of the radioactivity level in the environmental matrices allows to evaluate any possible radiological hazard for the population, through the calculation of the appropriate parameters of radioprotection and their comparison with the safety limits reported by the literature.

Thoron emanation and exhalation of Slovenian soils determined by a PIC detector-equipped radon monitor

Abstract The health risk from thoron (Rn-220) is usually ignored owing to its short half-life (55.6 s), but the generated thoron decay products can cause a significant dose contribution. In this study, altogether 51 Slovenian soil samples were investigated using an accumulation chamber technique to obtain information about thoron exhalation features. The obtained (massic) thoron exhalation results varied between 6.9 and 149 mBq·kg−1·s−1 (average: 55.2 mBq·kg−1·s−1). The Th-232 content was determined using HPGe gamma spectrometry. The Th-232 activity concentration ranged between 9.3 and 161.7 Bq·kg−1 (average: 64.6 Bq·kg−1). The thoron emanation features were also calculated from the obtained results (2.9 to 21.2% with an average of 8.6%). The thoron exhalation and emanation properties were compared with the radon exhalation and emanation features determined in a previous study. It was found that there was no correlation between the radon and thoron emanation features, according to the obtained data. This can be explained by the different Ra-224 and Ra-226 distributions in the soil grains. As a result, the thoron emanation factor cannot be predicted from radon emanation and vice versa.

Radiological maps for fallout 7Be in forest soil horizons in a mountainous area of Turkey

ABSTRACTDue to the paucity of data on separate spatial distribution of cosmogenic 7Be radionuclide activities in forest soil layers, a spatial study was performed in Mount Ida (Kazdagi)/Edremit, Turkey. In this study, it was aimed to examine the 7Be spatial variability and depth distribution in the surface soil layers. The 7Be activity concentrations were determined by HPGe gamma spectrometry system and the distributions of 7Be activities in the OL and OF + OH horizons throughout the region were mapped separately. Activity concentrations of 7Be in OL horizons and OF+OH horizons varied as 35 ± 23–701 ± 40 Bq kg−1 and 0.96 ± 0.63–197 ± 11 Bq kg−1, respectively. 7Be inventories (0.20 ± 0.06–5.69 ± 0.75 kBq m−2) in the study area were relatively higher when compared with the other regions of the world. 7Be inventories increased with altitude, slope and the thickness of the humus layer in some of the investigated area. Average 7Be activity level in deciduous forest stand type was significantly higher than that for coniferous and mixed stand types. Our limited data could not provide a latitudinal distribution pattern of 7Be soil inventory or precipitation dependence and further investigation is needed.

Radioactivity, granulometric and elemental analysis of river sediments samples from the coast of Calabria, south of Italy

River sediment samples from different sites of the coast of Calabria, south of Italy, were analyzed to determine the natural radioactivity concentration of the studied area and to investigate about their geological provenience. The radioactivity investigation was performed by using HPGe gamma spectrometry. Activity concentration data were reported and the influence of the particle size on the radionuclides concentration was investigated. X-ray fluorescence spectrometry (XRF) measurements were performed for the quantitative elemental analysis of the river sediments, revealing the major and minor elements present in the investigated samples. From XRF experimental results it was possible to estimate the geological provenience of the analyzed river sediments. Data obtained in this article provide useful information on the background radioactivity of the studied area and can be further used for radiological mapping of the coast of the Calabria rivers.

Technologically elevated natural radioactivity and assessment of dose to workers around a granitic uranium deposit area, China

Gamma dose rates in a uranium site in Guangdong, China were measured based on different functioning areas (mining area, milling area, tailings area and downstream area); four representative soil profiles were measured with HP Ge gamma spectrometry. The gamma dose rates as well as annual effective dose overall exceeded the relevant values reported from other countries. Both the external and the internal hazard index overwhelmingly exceeded the recommended value. Some areas were heavily polluted with technologically elevated concentrations of 238U and 226Ra, while others were observed with extremely high background level of natural radioactivity, mainly stemming from granitic lithology.

The radioactivity of bricks produced in Serbia

Natural radioactivity of the brick, one of the most used building materials was investigated. The content of natural radionuclides in the samples was measured by HPGe gamma-spectrometry. The average values of specific activities of 226Ra, 232Th and 40K in the samples are: 31 ? 9, 40 ? 11 and 460 ? 118 in Bq kg-1, respectively. The absorbed dose in the air was computed by the method of buildup factors for the standard model of the room. The obtained values for the absorbed dose are in the range of 9 - 47 (nGy h-1), with the average of 36 ? 9 nGy h-1. The radiation hazard was estimated calculating the corresponding gamma index and the effective dose. The gamma index belongs to the range of 0.11 to 0.56, and the effective dose is in the range of 0.044 - 0.23 (mSv), far below the reference limit of 1 mSv.

The dose of gamma radiation from building materials and soil

Abstract The radioactivity of some structural building materials, rows, binders, and final construction products, originating from Serbia or imported from other countries, was investigated in the current study by using the standard HPGe gamma spectrometry. The absorbed dose in the air was computed by the method of buildup factors for models of the room with the walls of concrete, gas-concrete, brick and stone. Using the conversion coefficients obtained by interpolation of the International Commission on Radiobiological Protection (ICRP) equivalent doses for isotropic irradiation, the corresponding average indoor effective dose from the radiation of building materials of 0.24 mSv·y−1 was determined. The outdoor dose of 0.047 mSv·y−1 was estimated on the basis of values of the specific absorbed dose rates calculated for the radiation of the series of 238U, 232Th and 40K from the ground and covering materials. The literature values of the effective dose conversion coefficients for ground geometry were applied as well as the published data for content of the radionuclides in the soil.

Estimation of radionuclides concentration and average annual committed effective dose due to ingestion for some selected medicinal plants of South India

Eight medicinal plants and soil samples from the Malnad area of Karnataka in South India (N 13°29′35.4″; E 75°18′02.4″) were analysed for activity concentrations of natural and artificial radionuclides using HPGe gamma spectrometry. The average annual committed effective dose (AACED) due to the ingestion of radionuclides from medicinal plants were also estimated. The activity concentrations of 226Ra, 210Pb, 232Th, and 40K were found to vary in the range of 32.27–60.12 Bqkg−1, 56.09–160.56 Bqkg−1, 49.61–98.46 Bqkg−1, and 241.57–712.85 Bqkg−1, respectively, in the soil samples and 2.66–11.27 Bqkg−1, BDL to 87.03 Bqkg−1, 2.42–8.72 Bqkg−1, and 93.79–6831.40 Bqkg−1, respectively, in the medicinal plants corresponding to the soil samples. The activity concentration of artificially produced radionuclide 137Cs was BDL to 12.34 Bqkg−1 in the soil and it was below detectable level (BDL) in all the plant samples. The soil to plant transfer factors (TF) varied from 0.07 to 0.27, BDL to 0.80, 0.04 to 0.13 and 0.17 to 23.80, respectively, for 226Ra, 210Pb, 232Th, and 40K. The AACED due to the ingestion of radionuclides from the medicinal plants varied from 0.0075 to 0.1067 mSvy−1. The AACED values reported in this study are much below the world average value of 0.30 mSvy−1 for an individual. This indicates that there is no radiological health risk in using these plants for medicinal purposes. This study may also contribute data on local medicinal plants to formulate regulations related to radiological healthcare.

Analysis of essential elements in Ethiopian finger millets (eeleusine coracanda) by instrumental neutron activation analysis (INAA)

The objective of this study was to determine essential elements in white, black and mixed species of Ethiopian finger millets using neutron activation analysis (NAA). The samples were collected from the local market of Bahirdar city, in Northwest Ethiopia. After the samples were dried, milled, heat sealed in a polythene sheet and put in a vial, they were irradiated in the irradiation channels of the Nigeria research reactor. The activities of the samples were measured using HPGe gamma spectrometry and analyzed by Winspan 2004 software. A total of 16 elements (Ca, Mg, K, Cl, V, Al, Ba, Na, Mn Fe, Zn, La, Sc, Sm, Br and Rb) were analyzed in three of the samples. According to the analyzed data Ca, Mg and K as macronutrients were found in range of 592 ± 21 ppm to 4876 ± 36 ppm, elements Fe, Al, and Cl as micronutrient were obtained in the range of 156 ± 18 to 775 ± 42 ppm with all others elements measured in traces. The results, therefore, showed that black and mixed finger millets are significantly enriched in essential elements. In addition, finger millets have also medicinal properties for controlling diabetes, blood pressure, anemia, stomach cancer and Alzheimer because they contained in pharmacological elements: Mg, Fe, Zn, V and Mn.

Quality assurance and quality control in environmental radioactivity monitoring

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

Radiological mapping in the granodiorite area of Bergama (Pergamon)-Kozak, Turkey

As higher radiation levels are associated with granodiorite area and the maps are more practical to interpret the results of radiological survey, the distributions of the specific activities of 226Ra, 232Th, 40K in soil-granite samples and indoor 222Rn activities throughout the granodiorite area of Bergama (Pergamon) were mapped in detail. Samples from the granites and soils underlying Kozak-Bergama (Pergamon) granodiorite area were collected and analyzed by HPGe gamma spectrometry system, while indoor radon levels in 20 dwellings of rural areas at this area were measured by the alpha track etch integrated method. This paper represents the baseline maps of natural radioactivity levels (226Ra, 232Th, 40K and 222Rn) and corresponding absorbed dose rates from outdoors terrestrial gamma radiation.

The influence of particle size on radionuclide activity concentrations in Tejo River sediments

Sediment samples from Tejo River were analyzed for 228Ra, 226Ra, 137Cs and 40K by HPGe gamma spectrometry. The activity concentration data were statistically analyzed. The activity concentrations values were in the range of about two orders of magnitude for each radionuclide. The influence of the particle size on the radionuclide concentrations was observed. The different environmental origins of the radionuclides 228Ra, 226Ra, 137Cs and 40K, in the sediments were demonstrated through correlation analysis. Cluster analysis showed a close relationship between 228Ra and 226Ra and a different behavior for 40K. The data obtained in this study provides useful information on the background radioactivity of the studied area and can be further used for radiological mapping of the Tejo River.

Assessment of ambient gamma dose rate around a prospective uranium mining area of South India – A comparative study of dose by direct methods and soil radioactivity measurements

Indoor and outdoor gamma dose rates were evaluated around a prospective uranium mining region – Gogi, South India through (i) direct measurements using a GM based gamma dose survey meter, (ii) integrated measurement days using CaSO4:Dy based thermo luminescent dosimeters (TLDs), and (iii) analyses of 273 soil samples for 226Ra, 232Th, and 40K activity concentration using HPGe gamma spectrometry. The geometric mean values of indoor and outdoor gamma dose rates were 104nGyh−1 and 97nGyh−1, respectively with an indoor to outdoor dose ratio of 1.09. The gamma dose rates and activity concentrations of 226Ra, 232Th, and 40K varied significantly within a small area due to the highly localized mineralization of the elements. Correlation study showed that the dose estimated from the soil radioactivity is better correlated with that measured directly using the portable survey meter, when compared to that obtained from TLDs. This study showed that in a region having localized mineralization in situ measurements using dose survey meter provide better representative values of gamma dose rates.

Purification of cerium, neodymium and gadolinium for low background experiments

Cerium, neodymium and gadolinium contain double beta active isotopes. The most interesting are 150 Nd and 160 Gd (promising for 02 search), 136 Ce (2 + candidate with one of the highest Q 2). The main problem of compounds containing lanthanide elements is their high radioactive contamination by uranium, radium, actinium and thorium. The new generation 2 experiments require development of methods for a deep purification of lanthanides from the radioactive elements. A combination of physical and chemical methods was applied to purify cerium, neodymium and gadolinium. Liquid-liquid extraction technique was used to remove traces of Th and U from neodymium, gadolinium and for purification of cerium from Th, U, Ra and K. Co-precipitation and recrystallization methods were utilized for further reduction of the impurities. The radioactive contamination of the samples before and after the purification was tested by using ultra-low- background HPGe gamma spectrometry. As a result of the purification procedure the radioactive contamination of gadolinium oxide (a similar purification efficiency was reached also with cerium and neodymium oxides) was decreased from 0.12 Bq/kg to 0.007 Bq/kg in 228 Th, from 0.04 Bq/kg to <0.006 Bq/kg in 226 Ra, and from 0.9 Bq/kg to 0.04 Bq/kg in 40 K. The purification methods are much less efficient for chemically very similar radioactive elements like actinium, lanthanum and lutetium.

Prototype studies on the nondestructive online burnup determination for the modular pebble bed reactors

The online fuel pebble burnup determination in future modular pebble bed reactor is implemented by measuring nondestructively the activity of the monitoring nuclide Cs-137 with HPGe detector on a pebble-by-pebble basis. Based on a full size prototype the feasibility is investigated. The prototype was first tested by using double sources to show that a precision of 2.8% (1σ) can be achieved in the determination of the Cs-137 net counting rate. Then, the relationship between the Cs-137 activity and the net counting rate recorded in the HPGe detector is calibrated with a standard Cs-137 source contained in the center of a graphite sphere with the same dimension as a real fuel pebble. Because the self attenuation of the calibration source differs with a fuel pebble, a correction factor of 1.07±0.02 (p=0.95) to the calibration is derived by using the efficiency transfer method. Last, by analyzing the spectra generated with KORIGEN software followed by Monte Carlo simulation, it is predicted that the relative standard deviation of the Cs-137 net counting rate can be still controlled below 3.5% despite of the presence of all the interfering peaks. The results demonstrate the feasibility of utilizing HPGe gamma spectrometry in the online determination of the pebble burnup in future modular pebble bed reactors.