Radiological characterization of granitoid outcrops and dimension stones of the Variscan Corsica-Sardinia Batholith

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. 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 1,177 −304 +408 , 60 −23 +36 and 69 −25 +38 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 −26 +33 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

New gamma-ray spectrometry methods for estimating K, U, TH concentrations in rocks of the Sardinia batholith

In this PhD thesis are collected the results of a research project in the field of nuclear geophysics developed with the scientific collaboration between the Department of Natural and Territorial Sciences of the University of Sassari and the Department of Physics and Earth Sciences of the University of Ferrara. In particular, the research has focused on two main themes: the first part of the work has addressed the problem of the content of natural radionuclides in rocks as an instrument of their lithological characterization, geochemistry and orogenetic, while the second part deal with the realization of a collimated gamma spectrometer for in situ measurements. The abundances of 40K, U and Th in the Corsica-Sardinian Batholith in the N-E of Sardinia were investigated with 545 in situ gamma spectroscopy measurements with portable detectors NaI(Tl) and 167 measurements of natural radionuclides on rock samples using HPGe detectors. On the basis of the data obtained were processed high-resolution thematic maps of the distribution of radionuclides as well as radiometric ternary map, which show excellent agreement with the geological maps of the region. The second part of the thesis describes a new portable and collimated NaI(Tl) spectrometer, which has been calibrated successfully using the FSA method with the NNLS constraint. The results of the measurements show good agreement with the measured concentrations with independent instruments (HPGe)