The radon flux emitted from building material samples and from the surface of building materials could be determined using
a simple and reliable method. This method was based on the use of cellulose nitrate films (LR-115 II). The samples and the
detectors were placed in a closed can of known dimensions. Tracks due to alpha-particles of radon that migrate from the building
material into the air space in the chamber were registered on the LR-115 film. The detectors were chemically etched in 2.5N
NaOH solution at 60±1 °C for 115 minutes. Exhalation rates of various building material samples and of building surfaces of
various building components were determined. The results obtained by this technique could be used to establish a database
for average radon exhalation rates for all available building materials and walls or floors.
Authors:G. Prasad, T. Ishikawa, M. Hosoda, A. Sorimachi, S. Sahoo, N. Kavasi, S. Tokonami, M. Sugino, and S. Uchida
Radon and thoron concentration in the outdoor environment are affected by the magnitude of the exhalation rate that can vary
diurnally and seasonally. This paper presents measurement results of radon and thoron exhalation rates and gamma-ray dose
rate in different season at same location points in Gunma Prefecture Japan. Exhalation rates were measured by the MSZ instrument
which is based on the accumulation method. Three measurement points Katashina Village, Midori City and Takasaki City were
selected for measurement. Soil water saturation and soil temperature were measured to investigate their relationship with
exhalation rate. The diurnal variation of exhalation rate may be correlated with soil temperature but no clear relationship
was found between them. The gamma-ray dose rate do not vary significantly at the same places even in different season. The
average radon exhalation rates were 11 ± 2, 2 ± 1, 5 ± 3 and 11 ± 4 mBq m−2 s−1 for spring, summer, autumn and winter, respectively. Those for thoron were 1,100 ± 100, 120 ± 30, 250 ± 80 and 860 ± 140 mBq m−2 s−1. Thus there was a variation of radon and thoron exhalation rate with different seasons. The radon and thoron exhalation rates
in the summer and autumn surveys are higher than those in the spring and winter surveys which were affected by rainfall. It
indicates that water saturation is an influential factor for radon and thoron exhalation rates.
Laboratory experiment was performed for the measurement of radon exhalation rate from the soil samples collected from Garhwal Himalayas. This study is accompanied by the measurement of soil-gas radon concentration in the same area. Both results were compared with the geological formation and structure of the area. No correlation was observed between soil-gas radon concentration and radon exhalation rate. However, it was found to be controlled by the lithology, geological structure and uranium mineralization in the area. The relationship between radon emanation, geological formation and occurrence of high indoor radon concentration is discussed.
Authors:Deepak Verma, M. Shakir Khan, and Mohd. Zubair
Effective radium content and radon exhalation rates in soil samples have been measured by “Sealed Can Technique” using LR-115
type II plastic track detectors. The soil samples were collected from Farrukhabad city of Utter Pradesh, India. The values
of effective radium content were found to vary from 5.39 to 34.56 Bq kg−1 with an average value of 16.58 Bq kg−1 and a standard deviation of 7.16. The mass and surface exhalation rate has been found to vary from 0.41 × 10−6 to 2.64 × 10−6 Bq kg−1 d−1 and 1.41 × 10−6 to 9.10 × 10−6 Bq m−2 d−1, respectively. All the values of radium content in soil samples of study area were found to be quite lower than the permissible
value of 370 Bq kg−1 recommended by Organization for Economic Cooperation and Development.
Authors:Nabil Hassan, Shinji Tokonami, and Masahiro Fukushi
Indoor radon and thoron concentrations were dominated with their exhalation rate from building materials. Thus, the evaluation
of exhalation rate with highly precise is important. This paper presented a new technique to measure the dependence radon/thoron
exhalation rate, from building materials used in Japan, on absolute humidity. The measurement technique consisted of a solid
state alpha detector equipped a ventilation-type chamber and humidity control system in a flow through method. The exhalation
rate of dried samples (Indian red granite and Japanese gray granite) was measured at various absolute humidity levels in the
range of 1–20 g cm−3. It was found that exhalation rate increased exponential with increasing of absolute humidity for both samples. Furthermore,
the dependence of radon emanation coefficient on building material’s temperature was also studied using an accumulation chamber
equipped with scintillation cell alpha detector. The emanation coefficient of dry sample increased proportionally with increasing
the material’s temperature with a correlation factor of 0.88.
Measurements have been made of radon (222Rn), release from diverse quaternary samples collected from different sediment deposits in the Errachidia and Beni-Mellal areas (Morocco). The radon diffusion coefficient as one of some important parameters of radon transport in the soil has been measured using solid state nuclear track detectors (SSNTD). Radon -activity, uranium content and radon exhalation rate have been determined in the studied samples. Uranium concentrations were found to vary from 0.14 to 9.52 ppm whereas the radon exhalation rate varied from 0.003 to 0.145 Bq.m-2.h-1. A positive correlation has been found between radon exhalation rate and uranium content in the studied samples. The average radon diffusion coefficients were found to vary from (1.26±0.09).10-6 m2.s-1 to (4.3±0.36).10-6 m2.s-1. Furthermore, the correlation between 222Rn diffusion coefficient and porosity are also discussed.
Authors:K. Reddy, M. Reddy, Ch. Reddy, P. Reddy, and K. Reddy
Radon and thoron have been identified as potential radiological health hazard and the dose estimation due to their exposure
is an important task. Understanding their behavior in indoor environment helps in calculating the inhalation doses due to
them. Present study aims at the distribution of radon and thoron concentrations in a typical Indian dwelling. Solid state
nuclear track detectors are employed in the study. The concentration of radon is found to be invariant in indoor environment.
The thoron concentration is found to decrease exponentially as a function of distance from the source (wall/floor). Solution
of one dimensional diffusion equation is used for regression fittings for thoron variation, from which the diffusion constants
and the exhalation rates were calculated. The diffusion constants varied from 0.00195 to 0.00540 m2 s−1.
The concentration of radioactive226Ra,232Th and40K in building and ceramic materials of Bangladesh was investigated by γ-spectrometry with two HPGe detectors. Radium equivalent
activities, representative level index values, criterion formula, emanation coefficients and222Rn mass exhalation rates were estimated for the radiation hazard of the natural radioactivity in the materials. The activity
concentrations of the natural radionuclides, radium equivalent activities, emanation coefficients and222Rn mass exhalation rates are compared with the corresponding values for building and ceramic materials of different countries.
The radium equivalent activities in the samples varied between 30.9 (mosaic stone) and 328.0 Bq·kg−1 (gypsum). The emanation coefficient of the materials ranged from 7.83 (cement) to 33.0% (soil) and the222Rn mass exhalation rate ranged from 2.31 (stone chips) to 118.0 μBq·kg−1·s−1 (gypsum).
Authors:K. Holý, I. Sýkora, M. Chudý, A. Polášková, J. Fejda, and O. Holá
The activity concentrations of natural radionuclides in sands, gravels, cements and in different kinds of concretes were measured by -spectrometric methods. The222Rn exhalation rate from concretes was measured by closed chamber method and the emanation coefficient was calculated. Both used methods are described in detail and obtained results are discussed from point of view of allowed hygienic limits.
The radioactivity contents in building materials used in Hong Kong were measured to determine the sources of the high indoor
radon concentrations observed in local buildings. The radium contents and the radon emanation coefficients of different building
materials were measured by high resolution γ-ray spectroscopy using germanium detectors. The radon exhalation rates were measured
using scintillation cells by circulating the exhaled radon from building materials and obtaining the initial growth rates.
The radium content and the radon exhalation rates of concrete and bricks used in Hong Kong were found to be higher than those
in some other countries, resulting in high indoor radon concentrations probably due to the high radioactivity contents in
the aggregates, granitic in nature, used in building materials.