Neste trabalho foram determinadas as concentrações dos radionuclídeos naturais 226 Ra, 232 Th e 40 K em amostras de areias superficiais para 16 localizações ao longo da costa da Grande Vitória, região metropolitana do estado do Espírito Santo, sudeste do Brasil. As áreas de estudo compreendem as praias de Manguinhos e Jacaraípe no município da Serra,
Abstract. Radon ( 222 Rn) is the most important cause of exposure to mankind due to natural radioactivity. Radon exhalation depends not only on the 226 Ra concentration in the material, but also on other factors such as mineralogy of the region, size and density of grains and porosity of the material. As building materials are one of the major sources of environmental radon, the radiological implications of the use of materials with great content of uranium must be always assessed. In this work, radon exhalation from several undamaged granitic building materials used as ornamental rocks or coating tiles is determined using the "sealed-can technique" and CR-39 solid state nuclear track detectors (SSNTD). Preliminary results for radon concentrations showed values of the same order that literature values, in a range from 99 Bq.m −3 to 1100 Bq m −3 . Further, the methodology will be validated with standard sources of 222 Rn.
In this work, the concentrations of natural radionuclides 226 Ra, 232 Th and 40 K in granite and marble samples were determined, considering the main extraction mining of Espirito Santo state, southeastern Brazil. For all study sites, three samples were sealed in 100 ml high density polyethylene bottles. Each sample rested for 4 weeks to reach the secular equilibrium of 238 U and 232 Th series before measured by high resolution gamma spectrometry, and the acquired spectra were analyzed with the software WinnerGamma. The self-absorption correction was considered for all samples, using an expression and method specially developed for this purpose. The concentration of 226 Ra was determined by the weighted arithmetic mean of the concentrations of 214 Pb and 214 Bi, the concentration of 232 Th by the weighted arithmetic mean of the concentrations of 228 Ac, 212 Pb and 212 Bi and the concentration of 40 K by its single 1460 keV transition. The radium equivalent and gamma index were calculated from the activity concentrations of 226 Ra, 232 Th, and 40 K. The emanated radon was measured using an exhalation chamber and the passive detector technique, with a solid state nuclear tracks detectors (SSNTD) being exposed in NRPB/SSI-H dosimeters. During exposure, a commercial detector CR-39 ® and a national plastic called Durolon ® were used, the last was characterized for this purpose using a technique called double exposure and sensitivity intrinsic factor. The characterized plastic was efficient for the application and the calibration factor corresponded to 1.60 ± 0.10 tracks•cm²•(kBq•mˉ³•day)ˉ¹ in relation to the CR-39 factor, equivalent to 2.8 ± 0.2 tracks•cm²•(kBq•mˉ³•day)ˉ¹. The detector showed a higher efficiency at a higher dose. The activities determined by passive detection varyed from 100 ± 10 Bq•m-³ up to 2400 ± 300 Bq•m-³, highlighting the biggest exhalation rates for granite Iberê Mombasa. Considering the marbles, activity values varyed from 80 ± 10 Bq•m-³ up to 200 ± 25 Bq•m-³ highlighting only the Cintilante and Branco Extra with higher values. The values obtained for surface exhalation rate were approximately equal, except for granites Iberê Mombasa and Iberê Prado with values above 1 Bq·m-2 ·h-1. The measures by gamma spectrometry showed that the 226 Ra concentrations varyed from 1.9±0.2 Bq.kg-1 up to 483±55 Bq.kg-1 , with the highest value for granite Iberê Mombasa. The 232 Th concentrations ranged from 3.2±0.4 Bq.kg-1 to 224±6 Bq.kg-1 , whose largest value was observed for the gray granite Corumbá. The 40 K concentrations ranged from 8.8±1.8Bq.kg-1 up to 1642±67 Bq.kg-1 , with the largest value observed for granite Iberê Vitara. The radio equivalent value showed that most samples can be defined as category I, below 370 Bq.kg-1 , except for the granites Cinza Corumbá, Iberê Crema Bordeaux and Iberê Mombasa that can be classified as class II (up to 740 Bq.kg-1). The evaluated granites show internal and external exposure rates below 1.0 mSv•yˉ¹ except the granites Cinza Corumbá, Iberê Crema Bordeaux and Iberê...
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