Page 52 - PR 2014 2016 07 Nuclear Science and Technology

194 Nuclear Science and Technology | Progress Report

Mombasa granites indicate limitations when and annual effective dose (D ) were calculat-
ef
applying as surface material. However, consid- ed from the activity concentrations of 226 Ra,
40
ering the gamma exposure index, the granites 232 Th and K. The activity concentration values
Cinza Corumbá, Cinza Andorinha, Amarelo for 226 Ra ranged from under the minimum
Icaraí, Cinza Ocre, Iberê Crema Bordeaux and detectable activity to 38.7 Bq•kg , for 232 Th
-1
Iberê Mombasa have controlled application. from under the minimum detectable activity
In conclusion, the evaluated granites and all to 101.2 Bq•kg and for K from under the
40
-1
-1
marbles evaluated have viable applications minimum detectable activity to 256 Bq•kg .
-1
-1
in different activity sectors and for different Raeq ranged from 1.41 Bq•kg to 203 Bq•kg , Iγ
purposes and the granites that exceeded the ranged from 0.0047 to 0.720, Hin from 0.0076
proposed limits should not be applied in the to 0.653 and Hex from 0.0038 to 0.549. The
interior of residences. absorbed dose rate ranged from 0.170 nGy·h1
to 21.3 nGy·h1 and the annual effective dose
Assessment of natural radioactivity in ranged from 0.83 μSv to 104.2 μSv. The results
wall paints of commercial use in Brazil show that the activity concentrations of the
wall paints studied in this work are below the
Natural radioactivity in soils, rocks and con- recommended limits by Hassan et al. for Raeq
struction materials, due to K and the nat- (370 Bq•kg ), by European Commission for I
-1
40
γ
ural series of 232 Th and 238 U, is the main con- (limit of 2 for superficial materials) and by the
tribution to external exposure in mankind. Organisation for Economic Co-operation and
238
Activity concentrations of 226 Ra ( U series), Development for H and H (both with limit
in ex
232 Th and K were determined for 50 white of 1), for all the 50 samples, assuring the safety
40
latex wall paints samples, commercialized in of these wall paints with respect to radiological
Brazil, namely 15 Economic quality samples, protection.
15 Standard quality samples and 20 Premium
quality samples and for a single titanium di- The use of representative person and
oxide sample. The samples were tightly sealed critical group concepts for environmental
and stored for a minimum period of 30 days, control of nuclear facilities in Brazil
to reach the radioactive secular equilibrium
from U and Th series, then measured by According to the National Commission for
232
238
high resolution gamma-ray spectrometry. The Nuclear Energy, CNEN, the assessment of en-
activity concentration was determined using vironmental radiological impact from the re-
the weighted average concentrations of Pb lease of radionuclides to the environment due
214
212
and Bi for Ra and Ac, Pb and Bi for to normal operation of nuclear facilities, for
212
214
226
228
40
232 Th. The K activity concentration was deter- protecting the public, considers the concept
mined by its single transition of 1460.8 keV. of critical group. In 2006, the International
Self-attenuation correction factors of the sam- Commission on Radiological Protection (ICRP),
ples whose densities are higher than 1.0 g • for the same purpose, proposed the adoption
cm were determined and used to make the of the concept of representative person. Once,
-3
necessary corrections. The radiological indi- at some point, this new concept probably will
ces radium equivalent activity (Ra ), activity be adopted in Brazil. The changes in terms of
eq
concentration index (Iγ), internal exposure procedures for calculating and consequent
risk index (H ) and external exposure risk in- results arising from the application of the rep-
in
dex (H ) and also the absorbed dose rate (D) resentative person methodology are evaluated
ex

Instituto de Pesquisas Energéticas e Nucleares