Page 198 - 00. Complete Version - Progress Report IPEN 2014-2016

198 Nuclear Science and Technology | Progress Report

IPEN showed lower concentration of radionu- Durolon ® were used. The last one was char-
clides analyzed when compared with plants acterized for this purpose using a technique
grown by the producer, as these were grown called double exposure and sensitivity intrin-
in pots with organic substrate and addition sic factor. The characterized plastic was effi-
of fertilizer, whose analysis showed low con- cient for the application and the calibration
centrations of radionuclides studied. Based on factor corresponded to 1.60 ± 0.10 tracks·c-
data from national literature who studied the m2·(kBq·m3·day)1 in relation to the CR39
Brazilian fertilizer, it can be concluded, to the factor, equivalent to 2.8 ± 0.2 tracks·cm2·(k-
plants from the producer, the fertilizer has a Bq·m3·day)1. The detector showed a higher
great influence in the concentration of radio- efficiency at a higher dose. The activities de-
nuclides studied. termined by passive detection varied from
100 ± 10 Bq·m3 up to (2,4 ± 0,3)·103 Bq·m3,
Assessment of natural radioactivity in commercial highlighting the biggest exhalation rates for
marble and granite of Espírito Santo State granite Iberê Mombasa. Considering the mar-
bles, activity values varied from 80 ± 10 Bq·m3
226
Concentrations of natural radionuclides Ra, up to 200 ± 25 Bq·m3 highlighting only the
232 Th and 40K in granite and marble samples Cintilante and Branco Extra with higher val-
were determined, considering the main ex- ues. The values obtained for surface exhala-
traction mining of Espírito Santo state, south- tion rate were approximately equal, except
eastern Brazil. For all studied sites, three for granites Iberê Mombasa and Iberê Prado
samples were sealed in 100 mL high density with values above 1 Bq·m2·h1. The measures
polyethylene bottles. Each sample rested for 4 by gamma spectrometry showed that the Ra
226
weeks to reach the secular equilibrium of U concentrations varied from 1.9 ± 0.2 Bq·kg1
238
and Th series before measured by high reso- up to 483 ± 55 Bq·kg1, with the highest val-
232
lution gamma spectrometry, and the acquired ue for granite Iberê Mombasa. The Th con-
232
spectra were analyzed with the software Win- centrations ranged from 3.2 ± 0.4 Bq·kg1 to
nerGamma. The self-absorption correction 224 ± 6 Bq·kg1, whose largest value was ob-
was considered for all samples, using an ex- served for the gray granite Corumbá. The 40K
pression and method specially developed for concentrations ranged from 8.8 ± 1.8 Bq·kg1 up
this purpose. The concentration of 226 Ra was to 1642 ± 67 Bq·kg1, with the largest value ob-
determined by the weighted arithmetic mean served for granite Iberê Vitara. The radio equiv-
of 214Pb and 214Bi concentrations, the con- alent value showed that most samples can be
232
centration of Th by the weighted arithme- defined as category I, below 370 Bq·kg1, except
tic mean of 228 Ac, 212Pb and 212Bi concen- for the granites Cinza Corumbá, Iberê Crema
trations, and the concentration of 40K by its Bordeaux and Iberê Mombasa that can be clas-
single 1460 keV transition. The radium equiv- sified as class II (up to 740 Bq·kg1). The evaluat-
alent and gamma index were calculated from ed granites show internal and external expo-
232
the activity concentrations of Ra, Th, and sure rates below 1.0 mSv·y1 except the granites
226
40K. The emanated radon was measured using Cinza Corumbá, Iberê Crema Bordeaux and
an exhalation chamber and the passive detec- Iberê Mombasa that exceed the value range of
tor technique, with a solid state nuclear tracks 1.0 to 3.2 mSv·y1 for this index. For the annual
detectors (SSNTD) being exposed in NRPB/SSIH exposure dose, only the granites Gray Corum-
dosimeters. During exposure, a commercial bá, Iberê Crema Bordeaux and Iberê Momba-
detector CR39 ® and a national plastic called sa exceeded 1.5 mSv·y1. For the alpha expo-

Instituto de Pesquisas Energéticas e Nucleares