Page 183 - 00. Complete Version - Progress Report IPEN 2014-2016

Nuclear Science and Technology | Progress Report 183

tion of one unit of Brazil nuts is sufficient to contribution of 0.24 mSv. Contribution from
restore the status of selenium in obese women radioactive fallout, fission product 137Cs, was
and the elderly. Selenium is an important part negligible. Based on the data obtained, it can
of antioxidant enzymes that act in the preven- be said that the radioactivity present in Brazil
tion of age-related illnesses such as cancer and nuts does not offer health risks for a daily in-
cardiovascular diseases. In addition to seleni- gestion of one unit. The concentration of Bar-
um, it is known that Brazil nuts also accumu- ium in the analyzed samples ranged from 22
late barium and radium. Due to the presence to 3700 μg g-1. As high concentrations of Ba
of radium in these nuts, the level of radioactiv- were found in some samples, the project is still
ity is 2-4 times higher than that of other veg- in progress for determination of Selenium in
etable foodstuffs, of the same region. This ac- these same samples with the objective of ver-
cumulation of Ba and Ra has been explained ifying the correlation between the concentra-
as a possible formation of organic complexes tions of Ba and Se present in the Brazil nuts.
that increases the mobility of alkaline earth
ions, particularly for these elements, favoring Neutron activation analysis applied to the
their redistribution during fruit development. characterization of different materials
Barium is not considered essential and can be
toxic depending on its chemical form. The Ba2+ Neutron activation analysis is the elemental
ion and the soluble compounds of barium (no- analysis method usually chosen for the char-
tably chloride, sulfide, nitrate and hydroxide) acterization of different matrices because of
are toxic to animals and humans. Several ra- some features such as: small amount of sam-
dioactive substances are considered carcino- ple available, minimal sample handling and
gens (Group 1 agents), according to the Inter- high sensitivity for many elements.
national Agency for Research on Cancer. The
carcinogenic activity is attributed to radiation, Neutron activation analysis applied
224
226
such as the radiation emitted by Ra or Ra in the evaluation of bismuth iodide
or Ra and their decay products. purification methodology
228
In this project, it was proposed to evaluate Bismuth tri-iodide (BiI3) is an attractive ma-
the concentrations of natural ( Ra, Ra, and terial for using as a semiconductor. Howev-
226
228
40K) and artificial (137Cs) radionuclides and er, the behavior of semiconductor devices is
Barium concentration in samples of Brazil strongly influenced by the presence of impu-
nuts acquired at final points of sale, in vari- rities or contaminants remaining due to in-
ous Brazilian regions. Gamma-ray spectrome- complete purification of the semiconductor
try measurements were used to determine the material. Small quantities of impurities pres-
radionuclide activity concentrations and In- ent at concentrations below 1 ppb can have a
strumental neutron activation analysis (INAA) significant effect on quality of semiconductor
was the analytical method used to determine devices. In this project, BiI3 crystals have been
barium concentration. grown by the vertical Bridgman technique
using commercially available powder. Efforts
Among the radionuclides determined in sam- have been concentrated on the purification of
ples of Brazil nuts 137Cs, 40K, Ra and Ra, the BiI3 and, the purification efficiency was as-
228
226
the Ra was the main contributor to the dose sessed by analyzing the crystals, through in-
228
estimated annual intake of 0.27 mSv, with a strumental neutron activation analysis (INAA).