LEANDRO MILHOMENS DA FONSECA

LEANDRO MILHOMENS DA FONSECA

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Self-attenuation factors in gamma-ray spectrometry of samples containing radionuclides of natural origin
2018 - PECEQUILO, B.R.S.; CAVALCANTE, F.; BARROS, L.F.; FERREIRA, A.O.; FONSECA, L.M.; MATEUS, C.
High resolution gamma-ray spectrometry is currently the most widely used analytical technique for qualitative and quantitative determination of radionuclides. Quantification of elements relies on the correct analysis of the spectra, depending strongly on the efficiency calibration of the measurement apparatus, most often performed with aqueous standard multi-radionuclide solutions. For efficiency calibration curves obtained by this method and for samples containing radionuclides of natural origin such as sand, soil, rocks and wall paint with apparent typical densities higher than that of water, self-attenuation correction factors were experimentally determined for hundreds of different samples using the Cutshall transmission technique. The results show that, to obtain more reliable analyses, correction factors for the self-attenuation behaviour, especially in the lower part of the energy spectrum, should be used. Since attenuation depends not only on the density of the sample but also on its chemical composition, correction factors have to be determined for each sample.
Concentrations of 226Ra, 232Th and 40K in Brazilian wall paint
2018 - FONSECA, L.M.; PECEQUILO, B.R.S.
Geological materials used as building materials are a source of radiation exposure due to the presence of radionuclides of natural origin. Wall paint is one of the building materials to be considered for radiological evaluation as it generally contains titanium dioxide pigment obtained from minerals such as ilmenite and rutile which contain 238U and 232Th series radionuclides and 40K. In this work, radionuclide concentrations were determined in 50 commercial Brazilian white latex wall paints using high resolution gamma-ray spectrometry. The following activity concentrations were measured: 1.41–38.7 Bq/kg (226Ra), 0.9–101.2 Bq/kg (232Th) and 5.9–256 Bq/kg (40K). These results demonstrate that the wall paints studied in this work are safe for use.
226Ra, 232Th and 40K concentrations in Brazilian wall paints
2016 - FONSECA, LEANDRO M. da; PECEQUILO, BRIGITTE R.S.
Geological materials used as building materials act as a source of radiation due to primordial radionuclides as the single radioactive isotope of potassium 40K and radioisotopes from the uranium 238U and 232Th series. Wall paints are one of the building materials to be considered for dose rates evaluation, as, beside other components, contain pigments, mainly titanium dioxide. As titanium dioxide is obtained from minerals as rutile and ilmenite, with thorium and uranium traces, the activity concentration of natural radionuclides in wall paints should be determined, for further annual effective dose assessment in a construction. In this work, activity concentrations of 226Ra, 232Th and 40K were determined by high-resolution gamma-ray spectrometry in 50 commercial brazilian white latex wall paints samples. The activity concentration values for 226Ra ranged from 1.41 Bq.kg-1 to 38.7 Bq.kg-1, for 232Th from 0.9 Bq.kg-1 to 101.2 Bq.kg-1 and for 40K from 5.9 Bq.kg-1 to 256 Bq.kg-1. The results show that the activity concentrations of the wall paints studied in this work are in a safe range for use for all the 50 samples.
Self-attenuation factors in gamma-ray spectrometry of NORM samples
2016 - PECEQUILO, BRIGITTE R.S.; CAVALCANTE, FERNANDA; BARROS, LIVIA F.; FERREIRA, ADEMAR O.; FONSECA, LEANDRO M.; MATEUS, CRISLENE
Evaluation of Ra-226, Th-232 and k-40 activities concentrations and radium equivalent index in several brazilian economic wall paints
2015 - FONSECA, LEANDRO M.; PECEQUILO, BRIGITTE R.S.
Natural radioactivity in wall paints: preliminary results
2014 - FONSECA, LEANDRO M.; PECEQUILO, BRIGITTE R.S.