Simultaneous Measurement of Radon and Thoron Released from Building Materials Used in Japan (original) (raw)
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Measurement of radon/thoron exhalation rates and gamma-ray dose rate in granite areas in Japan
Radiation Protection Dosimetry, 2012
Radon and thoron exhalation rates and gamma-ray dose rate in different places in Hiroshima Prefecture were measured. Exhalation rates were measured using an accumulation chamber method. The radon exhalation rate was found to vary from 3 to 37 mBq m 22 s 21 , while the thoron exhalation rate ranged from 40 to 3330 mBq m 22 s 21 . The highest radon exhalation rate (37 mBq m 22 s 21 ) and gamma-ray dose rate (92 nGy h 21 ) were found in the same city (Kure City). In Kure City, indoor radon and thoron concentrations were previously measured at nine selected houses using a radon-thoron discriminative detector (Raduet). The indoor radon concentrations varied from 16 to 78 Bq m 23 , which was higher than the average value in Japan (15.5 Bq m 23 ). The indoor thoron concentration ranged from ND (not detected: below a detection limit of approximately 10 Bq m 23 ) to 314 Bq m 23 . The results suggest that radon exhalation rate from the ground is an influential factor for indoor radon concentration.
Environmental Earth Sciences, 2015
Measurement of radium (226 Ra) and thorium (232 Th) content, and exhalation rate of radon (222 Rn) and thoron (220 Rn) from soil and building materials are important in the context of modeling indoor radon and thoron concentration. In this study, exhalation rates of radon and thoron from commonly used building materials in India were measured using active measurement techniques. Also the activity concentrations of 226 Ra, 232 Th and potassium (40 K) in building materials were measured by HPGe gamma spectrometric technique. The activity concentration of 226 Ra, 232 Th and 40 K varied from 16.4 ± 4.4 to 114.7 ± 3.4, 13.3 ± 1.5 to 153.9 ± 16.6 and below detection limit to 1,007 ± 40 Bq/kg with arithmetic mean 40.3, 61.9 and 822 Bq/kg, respectively, for the examined building material samples. The radon exhalation rates from the building materials varied from 0.5 ± 0.01 to 62.9 ± 12.5 mBq/kg/h for powder samples, 73 ± 5 to 6,000 ± 310 mBq/m 2 /h for structural building materials while the thoron exhalation rates varied from 0.07 ± 0.27 to 15.03 ± 2.1 mBq/kg/h for samples in powder form. Radium equivalent activity calculated for coarse aggregate and brick powder samples ranged between 73 and 343 Bq/ kg.
Radon and thoron exhalation rate measurements from building materials used in Serbia
Nukleonika, 2020
The second most important source of indoor radon, after soil beneath dwelling, is building material. With the increase in environmental awareness and new energy-saving policies, residents tend to replace the existing windows with tighter windows, which leads to a decrease in air exchange rate and consequently an increase in indoor radon concentration. In case of low exchange rates, dose caused by inhalation of radon and its progeny can exceed external dose originating from the radium content in the surrounding building material. In this paper, surface exhalation rates of radon (222Rn) and thoron (220Rn) from typical building materials used for construction and interior decoration of houses in Serbia were investigated. Surface exhalation rate measurements were performed using the closed-chamber method, while concentrations of radon and thoron in the chamber were continuously measured using an active device, RTM1688-2, produced by SARAD® GmbH. Finally, the impact of the replacement of...
Arabian Journal for Science and Engineering, 2012
The Singhbhum shear zone is a 200 km long arcuate belt in Jharkhand state situated in eastern India. The central part between Jaduguda-Bhatin-Nimdih, Narwapahr-Garadih-Turamdih is rich in uranium. Presence of uranium in the host rocks and the prevalence of a confined atmosphere within mines could result in enhanced concentration of radon (222 Rn) gas and its progeny. Inhalation of radon daughter products is a major contributor to the radiation dose to exposed subjects. By using high resolution c-ray spectroscopic system various radionuclides in the rock samples, collected from different places of Jaduguda uranium mines have been identified quantitatively based on the characteristic spectral peaks. The activity concentrations of the natural radionuclides, uranium (238 U), thorium (232 Th) and potassium (40 K) were measured in the rock samples and radiological parameters were calculated. Uranium concentration was found to vary from 123 ± 7 Bq kg À1 to 40,858 ± 174 Bq kg À1. Activity of thorium was not significant in the samples, whereas, few samples have shown potassium activity from 162 ± 11 Bq kg À1 to 9024 ± 189 Bq kg À1. Radon exhalation rates from these samples were also measured using ''Sealed Can technique" and found to vary from 4.2 ± 0.05 to 13.7 ± 0.08 Bq m À2 h À1. A positive correlation was found between the radon exhalation rate and the uranium activity. The absorbed dose rates vary from 63.6 to 18876.4 nGy h À1 , with an average value of 7054.2 nGy h À1. The annual external effective dose rates vary from 0.7 to 23.2 mSv y À1. Radium equivalent activities (Ra eq) varied from 134.3 to 40858.0 Bq kg À1. Value of external hazard index (H ex) varied from 0.4 to 110.4 with an average value of 41.2.
Radiation Protection Dosimetry, 2015
This paper reports the natural radioactivity of Brazilian igneous rocks that are used as dimension stones, following the trend of other studies on the evaluation of the risks to the human health caused by the rocks radioactivity as a consequence of their use as cover indoors. Gamma-ray spectrometry has been utilized to determine the 40 K, 226 Ra and 232 Th activity concentrations in 14 rock types collected at different quarries. The following activity concentration range was found: 12.18-251.90 Bq/kg for 226 Ra, 9.55-347.47 Bq/kg for 232 Th and 407.5-1615.0 Bq/kg for 40 K. Such data were used to estimate Ra eq , H ex and I g , which were compared with the threshold limit values recommended in literature. They have been exceeded for Ra eq and H ex in five samples, where the highest indices corresponded to a rock that suffered a process of ductile-brittle deformation that caused it a microbrecciated shape. The exhalation rate of Rn and daughters has also been determined in slabs consisting of rock pieces $ 10 cm-long, 5 cm-wide and 3 cm-thick. It ranged from 0.24 to 3.93 Bq/m 2 /h and exhibited significant correlation with eU (¼ 226 Ra), as expected. The results indicated that most of the studied rocks did not present risk to human health and may be used indoors, even with low ventilation. On the other hand, igneous rocks that yielded indices above the threshold limit values recommended in literature may be used outdoors without any restriction or indoors with ample ventilation.
Exhalation rate study of radon/thoron in some building materials
Radiation Measurements, 2001
Indoor radon=thoron have been recognised as one of the health hazards for mankind. Common building materials used for construction of houses, which are considered as major sources of these gases in indoor environment, have been studied for exhalation rate of radon=thoron. 'Can' technique using plastic track detector LR-115 type-II has been used for measurement. Exhalation rates for radon and thoron have been found to be varying from a minimum value of 0.024 and 29:4 Bq m −2 h −1 for cement plastered brick to a maximum value of 0.16 and 692:2 Bq m −2 h −1 for unÿred brick, respectively. Exhalation rate for thoron has been found to be several times higher than that for radon. Measured exhalation rates for thoron indicate signiÿcant presence of thoron in indoor environment which is also supported by indoor measurements of thoron and its progeny.
Radiation Measurements, 2011
Building materials used in Japan were collected from several companies and their radionuclide concentrations were measured. Fifteen granite samples with high activity concentrations were selected for the present study. To investigate the effect of water content on the radon emanation coefficient, the coefficient was measured under 3 different conditions (dry, normal, and wet). The emanation coefficients were then used to calculate the alpha equivalent dose (dose from indoor radon generated from building materials), assuming a simple room model. The radon emanation coefficient for the dry condition ranged from (3.7 AE 0.1)% to (27.2 AE 3.9)%, with an average value of (10.5 AE 1.4)%. The emanation coefficients were 2e5 times that size for the wet condition. Similarly, the alpha dose became larger, owing to its proportion to the emanation coefficient, indicating that water content in building materials is an important factor for the emanation coefficient as well as the radiation dose. The radon exhalation rate was also measured for the dry samples. Radon exhalation rate and radium concentration had a relatively low correlation (R 2 ¼ 0.40). However, the correlation between radon exhalation rate and "emanated radon concentration" (radium concentration  emanation coefficient) was much higher (R 2 ¼ 0.84). Therefore, emanated radon concentration could be a useful index for exhalation rate and alpha equivalent dose, but radium concentration in building materials alone is not.
Measurement of radon exhalation rate in various building materials and soil samples
Journal of Earth System Science, 2017
Indoor radon is considered as one of the potential dangerous radioactive elements. Common building materials and soil are the major source of this radon gas in the indoor environment. In the present study, the measurement of radon exhalation rate in the soil and building material samples of Una and Hamirpur districts of Himachal Pradesh has been done with solid state alpha track detectors, LR-115 type-II plastic track detectors. The radon exhalation rate for the soil samples varies from 39.1 to 91.2 mBq kg −1 h −1 with a mean value 59.7 mBq kg −1 h −1. Also the radium concentration of the studied area is found and it varies from 30.6 to 51.9 Bq kg −1 with a mean value 41.6 Bq kg −1. The exhalation rate for the building material samples varies from 40.72 (sandstone) to 81.40 mBq kg −1 h −1 (granite) with a mean value of 59.94 mBq kg −1 h −1 .
Radon Mass Exhalation Rates of Selected Building Materials in Tanzania
This study aimed at determining the mass radon exhalation rate of Tanzania Portland cements and their raw materials for assessment of the radiological hazards due to use of those materials in residential construction. The radon mass exhalation rate was measured by closed chamber coupled with the Pylon AB5 ™ and varied from 0.3 to 13 %. The estimated indoor radon concentrations and annual effective dose for tightly closed standard room were within the safe limits of radon potential health hazards of 600 Bq m-3 for dwellings and 1500 Bq m-3 for workplaces recommended by International Commission on Radiological Protection (ICRP). 1. Introduction Radon 222 Rn, thoron 220 Rn and actinon 219 Rn are naturally existing radioactive noble gases with half-lives of 3.83 d, 55.6 s and 3.96 s respectively. The source of the radioactive gases in the dwellings is the occurrence of the radium isotopes from the uranium and thorium series in the soil, rocks and building materials. From the radiological point of view and due to the half-life period the hazard of the 222 Rn is significantly larger than those of 220 Rn and 219 Rn, therefore 220 Rn and 219 Rn are omitted in this study. At homes and building offices 222 Rn emigrates from the walls, floor and ceilings and can accumulate to harmful levels. The primary concern of the health effects is related to the potential alpha energy concentration and that is exactly associated with the alpha particles emitted from the short–lived decay products of radon such as 218 Po and 214 Po (UNSCEAR 1988). The atoms of these isotopes at the creating moment often appear in the ion forms chemically reactive and rapidly attach to the aerosols such as particles of dust and water vapor get inside the body through the process of inhalation. When inhaled may be deposited on respiratory tract tissues, decay and emit the alpha particles acting and damaging cells near the deposition site, contributing to increase the risk of lung cancer (Nazaroff 1992; Darby et al. 2005).The concentration of the radon daughters in the dwelling air are governed by the radon concentration in the air, but the last is upon to radium concentration in the building materials including with floor, their construction, radon exhalation rate, attachment and recombination, deposition, and transport by diffusion and air ventilation condition and so on (Durrani 1997;Akerblom 1994;Jonsson 1995;Bossew 2003). The release of the radioactive gas from the materials into the atmosphere is controlled by three processes: emanation, transport and exhalation. The illustration of the mentioned processes is presented in Figure 1. Emanation is the escape of the radon gas from the solid medium into the air filled pore spaces (interstitial space), governed by the momentum and recoil energy of alpha particles from the radioactive decay of radium. The recoil distance for 222 Rn ranges 20-70 nm in common minerals, 100 nm in water, and 63µm in air (Nazaroff 1992). From the pores spaces (interstitial space), radon can migrate through diffusion process or seepage. The diffusion of radon is a process controlled by radon gas concentration gradient across the radon gas sources (rocks, soils, building materials, and other different materials) and the surrounding air. Finally, a fraction enters the atmosphere before undergoing radioactive decay the process known as exhalation. The exhalation rate is the radon fraction in the free air originated from the radon created by the radium decays in the inside of the materials. It was revealed that, the value of exhalation rate depends on air condition and on the physical properties of the material samples such as moisture, grain sizes, and so on (De Martino 1998). The radon exhalation rate ranges from 0 (in the case of no radon release from the material), to 1 (where all radon escapes). A number of studies have been conducted to establish the radium concentrations in raw and industrial building materials and their radon exhalation rate (EC 1999; Hassan et al. 2009; Sakoda et al. 2010; IAEA 2013). The 226 Ra concentration of the most typical building materials in the World is summarized in Table 1 (IAEA 2002). The Portland cements are typically the products derived from sedimentary or weathered rocks such as: sandstones, clay, limestone, shale, gypsum, pozzolan (UNSCEAR 2008). Portland cement clinker is manufactured by heating a calcareous material, typically limestone, and an argillaceous like clay or shale. The final product of Portland cement is gained by intergrading gypsum (sulphate minerals) with the clinker (Taylor 1997). The production processes also influences the radionuclide activity concentration of final products and thus determine the activity concentrations in the construction materials. Generally, the radium concentration in the final product should be controlled by the radium activity of the raw materials and calculated by formula:
Radiation Protection Dosimetry, 2013
It is very important to determine the levels of the natural radioactivity in construction materials and radon exhalation rate from these materials for assessing potential exposure risks for the residents. The present study deals with 22 different granite samples employed as decoration stones in constructions in Turkey. The natural radioactivity in granite samples was measured by gammaray spectrometry with an HPGe detector. The activity concentrations of 226 Ra, 232 Th and 40 K were found to be in the range of 10-187, 16-354 and 104-1630 Bq kg 21 , respectively. The radon surface exhalation rate and the radon mass exhalation rate estimated from the measured values of 226 Ra content and material properties varied from 1.3 to 24.8 Bq m 22 h 21 with a mean of 10.5+ + + + +1.5 Bq m 22 h 21 and 0.03-0.64 Bq kg 21 h 21 with a mean of 0.27+ + + + +0.04 Bq kg 21 h 21 , respectively. Radon concentrations in the room caused from granite samples estimated using a mass balance equation varied from 23 to 461 Bq m 23 with a mean of 196+ + + + +27 Bq m 23. Also the gamma index (I g), external indoor annual effective dose (E g) and annual effective dose due to the indoor radon exposure (E Rn) were estimated as the average value of 1.1+ + + + +0.1, 0.16+ + + + +0.02 mSv and 5.0+ + + + +0.7 mSv, respectively, for the granite samples.