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ST 2.1 –
Radiación natural, NORM y TENORM
VALIDATION OF INDOOR RN-222 MEASUREMENT USING SOLID STATE
NUCLEAR TRACK DETECTOR
Leite das Chagas, Eduardo Galvão
Universidade Federal de Alfenas – UNIFAL. Brasil.
Responsible author, email: duglchagas@hotmail.com
Radon is a radioactive, colorless and odorless noble gas and its best known isotope is Rn-222
which emerges from the decay chain of uranium 238. This element is found in soils, rocks and
building materials. Part of the radon gas generated amid these media and materials escapes to
indoor environments through cracks and differential pressure. This way, radon is found in all
places with various concentration levels, from the lowest in Middle Eastern countries to more
elevated concentrations in European countries. With a half-life of 3.8 days, Rn-222 decays in
radioactive metals, as Polonium, Lead and Bismuth, also known as radon daughters. This
decay chain is the main concern related to the concentration levels of this gas in the air, since
radon and its daughters can be inhaled and retained in the respiratory system, discharging an
internal radiation dose. The annual effective dose due to radon gas and its decay products
represents 50% of the effective dose of ionizing radiation from natural sources to which the
world population is subjected. An atmosphere with radon excess is correlated to diseases of the
respiratory system such as lung cancer. This relationship emerged from the records of high
mortality observed in underground mine workers on the first decades of the 20th century. In the
1970’s the existence of radon in human environments was confirmed, and since then this
element has been considered a problem for public health. The measurement of this radionuclide
in the interior of residences can be accomplished using various techniques, including solid state
nuclear trace detector -SSNTD. This technique has been used by the Laboratory of Poços de
Caldas/CNEN in evaluations of Rn-222 concentrations inside residences within the plateau of
Poços de Caldas. A quality assurance program was implemented as a necessary and expected
component of high quality radon measurements. The SSNTD validation procedure was the first
stage of this process. The proceedings employed and the results obtained in this validation are
presented in this paper. The following tests were performed: Repeatability / Precision, Accuracy
/ Bias, Linearity, Detection limit and Robustness.