This study focuses on the radiological characterization of granitoid outcrops and dimension stone... more This study focuses on the radiological characterization of granitoid outcrops and dimension stones using in-situ gamma-ray spectrometry. Extensive measurements were performed on 210 granitoid outcrops of the Corsica-Sardinia Batholith (C-SB). The large statistical sample allowed us to improve the analysis by considering a log-normal distribution of radioelements and propagating the uncertainties using Monte Carlo method. The activity concentrations of 40K, 226Ra (238U) and 232Th in C-SB area were 1177+408-304 Bq/kg, 60+36-23 Bq/kg and 69+38-25 Bq/kg (at 1σ uncertainty). The median abundance of K, U and Th on the Variscan C-SB was higher than the average values of the upper continental crust and was comparable with Variscan belt. This corresponds to an outdoor absorbed dose rate of 124+33-26 nGy/h at 1σ uncertainty which is 3σ higher than the population-weighted average absorbed dose rate (60 nGy/h). Seven commercial granites (Rosa Beta, Ghiandone, Giallo San Giacomo, Rosa Cinzia, Grigio Malaga, Bianco Sardo and Grigio Perla) were investigated to characterize their radiological hazard through 147 measurements taken in 73 extractive quarries. All of the commercial granites were categorized as A2 material based on their Activity Concentration Indices, excluding (at the 3σ level) any restriction on their utilization as superficial materials. Rosa Beta, Grigio Malaga, Grigio Perla and Bianco Sardo can also be used as bulk materials as they can be included in the A1 category. In the case of Ghiandone, Giallo San Giacomo and Rosa Cinzia, we are confident of an A1 classification only at the 1σ level.
In this paper we report an extensive survey of the natural radioactivity content of rocks of Tusc... more In this paper we report an extensive survey of the natural radioactivity content of rocks of Tuscany Region (Italy): it permitted to elaborate the first total natural radioactivity map of the region. The sampling was planned at the base of the geological map of Tuscany at scale 1:250,000, which contains 45 distinct geological groups recognized by tectonic and stratigraphic features. Each geological group was characterized for the total activity by measuring the activity concentrations of 40K, 238U and 232Th in 865 samples using a high-purity germanium (HPGe) gamma-ray spectrometer. The average areal distribution of samples is approximately one sample per 25 km2. The radiometric map was constructed through the reclassification of each geological formation based on the median value of the total activity. Seven classes of total activity are identified by choosing percentiles almost evenly spread across the range of values. This map represents the starting point for future studies on the natural background radiation, geochemical processes and epidemiological investigations.
In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) obtained with a... more In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) obtained with a multivariate spatial interpolation of airborne γ-ray data using the constraints of the geologic map. The radiometric measurements were performed by a module of four NaI(Tl) crystals of 16 L mounted on an autogyro. We applied the collocated cokriging (CCoK) as a multivariate estimation method for interpolating the primary under-sampled airborne γ-ray data considering the well-sampled geological information as ancillary variables. A random number has been assigned to each of 73 geological formations identified in the geological map at scale 1:10,000. The non-dependency of the estimated results from the random numbering process has been tested for three distinct models. The experimental cross-semivariograms constructed for radioelement-geology couples show well-defined co-variability structures for both direct and crossed variograms. The high statistical correlations among K, eU, and eTh measurements are confirmed also by the same maximum distance of spatial autocorrelation. Combining the smoothing effects of probabilistic interpolator and the abrupt discontinuities of the geological map, the results show a distinct correlation between the geological formation and radioactivity content. The contour of Mt. Capanne pluton can be distinguished by high K, eU and eTh abundances, while different degrees of radioactivity content identify the tectonic units. A clear anomaly of high K content in the Mt. Calamita promontory confirms the presence of felsic dykes and hydrothermal veins not reported in our geological map. Although we assign a unique number to each geological formation, the method shows that the internal variability of the radiometric data is not biased by the multivariate interpolation.
This study focuses on the radiological characterization of building materials manufactured in Alb... more This study focuses on the radiological characterization of building materials manufactured in Albania by using a high-resolution gamma-ray spectrometer. The average activity concentrations of 40K, 226Ra and 232Th were, respectively, 644.1 ±64.2 Bq/kg, 33.4 ±6.4 Bq/kg and 42.2 ±7.6 Bq/kg in clay bricks and 179.7 ±48.9 Bq/kg, 55.0 ±5.8 Bq/kg and 17.0 ±3.3 Bq/kg in the cements. The calculated Activity Concentration Index (ACI), varied from 0.48 ± 0.02 to 0.63 ± 0.04 in the clay bricks and from 0.29 ± 0.03 to 0.37 ± 0.02 in the cements. Based on the ACI, all of the clay bricks and cements were categorized as A1 materials. We can exclude (at 3σ level) any restriction of their utilization as bulk materials.
Materials containing radionuclides of natural origin, which is modified by human made processes a... more Materials containing radionuclides of natural origin, which is modified by human made processes and being subject to regulation because of their radioactivity are known as NORM. We present a brief review of the main categories of non-nuclear industries together with the levels of activity concentration in feed raw materials, products and waste, including mechanisms of radioisotope enrichments. The global management of NORM shows a high level of complexity, mainly due to different degrees of radioactivity enhancement and the huge amount of worldwide waste production. The future tendency of guidelines concerning environmental protection will require both a systematic monitoring based on the ever-increasing sampling and high performance of gamma ray spectroscopy. On the ground of these requirements a new low background fully automated high-resolution gamma-ray spectrometer MCA_Rad has been developed. The design of Pb and Cu shielding allowed to reach a background reduction of two order of magnitude with respect to laboratory radioactivity. A severe lowering of manpower cost is obtained through a fully automation system, which enables up to 24 samples to be measured without any human attendance. Two coupled HPGe detectors increase the detection efficiency, performing accurate measurements on sample volume (180 cc) with a reduction of sample transport cost of material. Details of the instrument calibration method are presented. MCA_Rad system can measure in less than one hour a typical NORM sample enriched in U and Th with some hundreds of Bq/kg, with an overall uncertainty less than 5%. Quality control of this method has been tested. Measurements of certified reference materials RGK-1, RGU-2 and RGTh-1 containing concentrations of K, U and Th comparable to NORM have been performed, resulting an overall relative discrepancy of 5% among central values within the reported uncertainty.
This study focuses on the radiological characterization of granitoid outcrops and dimension stone... more This study focuses on the radiological characterization of granitoid outcrops and dimension stones using in-situ gamma-ray spectrometry. Extensive measurements were performed on 210 granitoid outcrops of the Corsica-Sardinia Batholith (C-SB). The large statistical sample allowed us to improve the analysis by considering a log-normal distribution of radioelements and propagating the uncertainties using Monte Carlo method. The activity concentrations of 40K, 226Ra (238U) and 232Th in C-SB area were 1177+408-304 Bq/kg, 60+36-23 Bq/kg and 69+38-25 Bq/kg (at 1σ uncertainty). The median abundance of K, U and Th on the Variscan C-SB was higher than the average values of the upper continental crust and was comparable with Variscan belt. This corresponds to an outdoor absorbed dose rate of 124+33-26 nGy/h at 1σ uncertainty which is 3σ higher than the population-weighted average absorbed dose rate (60 nGy/h). Seven commercial granites (Rosa Beta, Ghiandone, Giallo San Giacomo, Rosa Cinzia, Grigio Malaga, Bianco Sardo and Grigio Perla) were investigated to characterize their radiological hazard through 147 measurements taken in 73 extractive quarries. All of the commercial granites were categorized as A2 material based on their Activity Concentration Indices, excluding (at the 3σ level) any restriction on their utilization as superficial materials. Rosa Beta, Grigio Malaga, Grigio Perla and Bianco Sardo can also be used as bulk materials as they can be included in the A1 category. In the case of Ghiandone, Giallo San Giacomo and Rosa Cinzia, we are confident of an A1 classification only at the 1σ level.
In this paper we report an extensive survey of the natural radioactivity content of rocks of Tusc... more In this paper we report an extensive survey of the natural radioactivity content of rocks of Tuscany Region (Italy): it permitted to elaborate the first total natural radioactivity map of the region. The sampling was planned at the base of the geological map of Tuscany at scale 1:250,000, which contains 45 distinct geological groups recognized by tectonic and stratigraphic features. Each geological group was characterized for the total activity by measuring the activity concentrations of 40K, 238U and 232Th in 865 samples using a high-purity germanium (HPGe) gamma-ray spectrometer. The average areal distribution of samples is approximately one sample per 25 km2. The radiometric map was constructed through the reclassification of each geological formation based on the median value of the total activity. Seven classes of total activity are identified by choosing percentiles almost evenly spread across the range of values. This map represents the starting point for future studies on the natural background radiation, geochemical processes and epidemiological investigations.
In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) obtained with a... more In this paper we present maps of K, eU, and eTh abundances of Elba Island (Italy) obtained with a multivariate spatial interpolation of airborne γ-ray data using the constraints of the geologic map. The radiometric measurements were performed by a module of four NaI(Tl) crystals of 16 L mounted on an autogyro. We applied the collocated cokriging (CCoK) as a multivariate estimation method for interpolating the primary under-sampled airborne γ-ray data considering the well-sampled geological information as ancillary variables. A random number has been assigned to each of 73 geological formations identified in the geological map at scale 1:10,000. The non-dependency of the estimated results from the random numbering process has been tested for three distinct models. The experimental cross-semivariograms constructed for radioelement-geology couples show well-defined co-variability structures for both direct and crossed variograms. The high statistical correlations among K, eU, and eTh measurements are confirmed also by the same maximum distance of spatial autocorrelation. Combining the smoothing effects of probabilistic interpolator and the abrupt discontinuities of the geological map, the results show a distinct correlation between the geological formation and radioactivity content. The contour of Mt. Capanne pluton can be distinguished by high K, eU and eTh abundances, while different degrees of radioactivity content identify the tectonic units. A clear anomaly of high K content in the Mt. Calamita promontory confirms the presence of felsic dykes and hydrothermal veins not reported in our geological map. Although we assign a unique number to each geological formation, the method shows that the internal variability of the radiometric data is not biased by the multivariate interpolation.
This study focuses on the radiological characterization of building materials manufactured in Alb... more This study focuses on the radiological characterization of building materials manufactured in Albania by using a high-resolution gamma-ray spectrometer. The average activity concentrations of 40K, 226Ra and 232Th were, respectively, 644.1 ±64.2 Bq/kg, 33.4 ±6.4 Bq/kg and 42.2 ±7.6 Bq/kg in clay bricks and 179.7 ±48.9 Bq/kg, 55.0 ±5.8 Bq/kg and 17.0 ±3.3 Bq/kg in the cements. The calculated Activity Concentration Index (ACI), varied from 0.48 ± 0.02 to 0.63 ± 0.04 in the clay bricks and from 0.29 ± 0.03 to 0.37 ± 0.02 in the cements. Based on the ACI, all of the clay bricks and cements were categorized as A1 materials. We can exclude (at 3σ level) any restriction of their utilization as bulk materials.
Materials containing radionuclides of natural origin, which is modified by human made processes a... more Materials containing radionuclides of natural origin, which is modified by human made processes and being subject to regulation because of their radioactivity are known as NORM. We present a brief review of the main categories of non-nuclear industries together with the levels of activity concentration in feed raw materials, products and waste, including mechanisms of radioisotope enrichments. The global management of NORM shows a high level of complexity, mainly due to different degrees of radioactivity enhancement and the huge amount of worldwide waste production. The future tendency of guidelines concerning environmental protection will require both a systematic monitoring based on the ever-increasing sampling and high performance of gamma ray spectroscopy. On the ground of these requirements a new low background fully automated high-resolution gamma-ray spectrometer MCA_Rad has been developed. The design of Pb and Cu shielding allowed to reach a background reduction of two order of magnitude with respect to laboratory radioactivity. A severe lowering of manpower cost is obtained through a fully automation system, which enables up to 24 samples to be measured without any human attendance. Two coupled HPGe detectors increase the detection efficiency, performing accurate measurements on sample volume (180 cc) with a reduction of sample transport cost of material. Details of the instrument calibration method are presented. MCA_Rad system can measure in less than one hour a typical NORM sample enriched in U and Th with some hundreds of Bq/kg, with an overall uncertainty less than 5%. Quality control of this method has been tested. Measurements of certified reference materials RGK-1, RGU-2 and RGTh-1 containing concentrations of K, U and Th comparable to NORM have been performed, resulting an overall relative discrepancy of 5% among central values within the reported uncertainty.
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