Influence of the building material and ventilation rate on the concentration of radon, thoron and their progenies in dwelling rooms using SSNTD and Monte Carlo simulation

A new Monte Carlo computer code was developed for determining the detection efficiencies of the CR-39 and LR-115 II solid state nuclear track detectors (SSNTD) for a-particles emitted by radon (²²²Rn) and thoron (²²⁰Rn) series inside the atmosphere of dwelling rooms. Alpha-activities due to radon, thoron and their decay products, were evaluated for the determination of the detection efficiencies of the SSNTD utilized for the emitted a-particles by measuring the corresponding track densities. The influence of the ventilation rate and building material on the concentration of radon, thoron and their progenies was investigated. Equilibrium factors between radon and its progeny and between thoron and its daughters have been evaluated in the air of the rooms.     

Concentrations of radon,thoron and their decay products measured in natural caves and ancient mines by using solid state nuclear track detectors and resulting radiation dose to the members of the public

Alpha- and beta-activities per unit volume of air due to radon (²²²Rn), thoron (²²⁰Rn) and their progenies were measured in the air of natural caves and ancient mines as well as inside different reference atmospheres by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs). In addition, the radon concentration was continuously measured inside one of the studied caves by using the SSNTDs’ method and AlphaGuard counter. Equilibrium factors between radon and its daughters and between thoron and its progeny were evaluated in the studied atmospheres. Alpha-activities due to ²¹⁸Po and ²¹⁴Po short-lived radon decay products were determined in different compartments of the respiratory tract of members of the public. The committed equivalent doses due to the ²¹⁸Po and ²¹⁴Po radon short-lived progeny were evaluated in different tissues of the respiratory tract of the visitors of the considered caves and ancient mines. Annual effective doses due to radon progeny from the inhalation of air by the visitors of the studied caves and ancient mines were evaluated.     

Measurement of radon and thoron progeny size distributions and dose assessments at the mineral treatment industry in Thailand

A new portable type cascade impactor has been developed to determine the activity size distribution of radon and thoron progeny in a natural environment more efficiently. The modified impactor consists of 4 stages with a back up filter stage for the collection of aerosol samples. The aerosol cut points in the impactor are set for 10, 2.5, 1 and 0.5 μm at a flow rate of 4 L min^?1. Five CR-39 chips were used as alpha detectors for each stage. In order to separate α particles emitted from radon and thoron progeny, CR-39 detectors are covered with aluminum-vaporized Mylar films. The thickness of each film is adjusted to allow α particles emitted from radon and thoron progeny to reach the CR-39 detectors. The technique has been successfully tested in field studies, particularly inside a mineral treatment industry in Thailand to estimate doses in the working environment. The dose calculations by lung dose evaluation program showed that activity median aerodynamic diameters played a significant role in determining the particle size distributions of the attached radon and thoron progeny. The dose conversion factor determined from short term measurements due to exposure from the inhalation of thoron and its progeny was found to be 4 times higher than comparable values for radon and its progeny. The effective dose for workers exposed to radon is about 4–6 times higher than thoron.     

Measurements of radon,thoron and their progeny in Gifu prefecture,Japan

Summary Due to the rocky neighborhood, consisting of mostly granite with high radium content, an elevated radon concentration was found in a territory of Gifu prefecture situated in the middle of Japan. Radon concentrations in water were measured and were found to be considerably high. Since indoor radon and radon progeny concentrations might be relatively high, their concentrations were also analyzed. Besides the radon and radon progeny, thoron and thoron progeny concentrations were also investigated. Dose estimations for radon and thoron in indoor air are discussed.     

A method for the mg scale separation of curium(III) from americium(III) by HPLC using a SCX column

Radon, thoron and their progeny are responsible for more than 50% of the total ionizing radiation dose received by human population. In the present work, radon, thoron and their progeny concentration measurements have been carried out in 150 dwellings in different villages of Faridabad district of Haryana, India. Pin-holes based twin cup dosimeter containing LR-115 type-II film (solid state nuclear track detectors) has been used for the time-integrated passive measurement of radon and thoron concentrations. The dosimeters were deployed for three seasons each having 4 months of exposure period. For measurement of radon and thoron progeny concentration (EERC/EETC), deposition based direct radon/thoron progeny sensors (DRPS/DTPS) were deployed with dosimeters. Based on the gamma exposure rate in different villages during preliminary survey and type of houses available in the regions, numbers of dwellings of different categories have been selected. Radon, thoron and their progeny concentration and total annual effective inhalation dose were calculated and compared with the recommended limits by UNSCEAR, ICRP and WHO.

     

Experimental study of radon and thoron diffusion through barriers

The radon chamber and radon calibration set have been modified for investigation of the diffusion coefficients of the barriers for reduction of radon exposure in the dwellings and for application as filters to separate radon and thoron. The volume radon activities have been measured by continuous monitors with scintillation cell or ionisation chamber. The theory on which the experimental determination of a barrier diffusion coefficient is based, is presented. The diffusion ability of radon has been studied for different materials and the results of the measurements are presented and discussed.     

Seasonal and diurnal variations of radon/thoron exhalation rate in Kanto-loam area in Japan

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.     

Radon,thoron and their progeny concentration variations in dwellings of Gogi region,Yadgir district of Karnataka,India

The radiation dose due to inhalation of radon, thoron and their progenies constitute a major part (50 %) of the total natural background dose received by a man. Thus measurement of indoor radon in dwellings is very important. In the present study, radon, thoron and their decay product measurements were carried out using passive detector systems, namely the pinholes dosimeters and Direct Radon (Thoron) progeny sensors. These measurements were carried out in indoor environments (different dwelling types) during January–April 2013 for 90 days, in the Gogi region. The time-averaged mean radon, thoron and decay product concentrations were found to be within the permissible UNSCEAR limits.     

Radon and thoron progeny levels in air samples at Udagamandalam region of Nilgiris in India

Measurement of concentration of radon and thoron daughter products in various indoor environment covering four seasons of a year in Udagamandalam Taluk of Nilgiris biosphere has been carried out using a high volume air sampler to asses the inhalation dose to the population which delivers higher dose than the radon and thoron gas alone. The potential alpha-energy concentrations of the radon and thoron progeny ranged from 0.97 to 12.72 mWL and from 1.63 to 15.83 mWL with a geometric mean of 6.02 and 7.89 mWL, respectively, taking all seasons into account. These measurements have yielded a wealth of data on the variation among the indoor radon and thoron progeny in various places during different seasons. The radon and thoron progeny levels are higher in winter seasons and are less in summer season with autumn and spring data lie in between winter and summer. Using the dose conversion factor for indoor exposures given in UNSCEAR 93 report the internal equivalent dose to the inhalation of radon progeny is evaluated to be 1357 mSv^.y^–1 and the corresponding annual effective dose equivalent value has been found to be 2.13 mSv^.y^–1. It can be observed that the mean value of radon is higher than the Indian average. Also it is found the radon and thoron progeny levels are higher in the case of houses built with rock and granite and in tiled type houses of nearly 100 years old. The levels are less in the case of houses built with brick and cement. The observed results for different types of houses and seasons are discussed in this paper.     

Radon and thoron concentrations in offices and dwellings of the Gunma prefecture, Japan

Summary Aone year survey of indoor radon and thoron concentrations was carried out in offices and dwellings of the Gunma prefecture, Japan. A passive integrating radon and thoron discriminative monitor was used in the survey. The annual mean radon concentration was 22±14 Bq ^. m^-3, and ranged from 12 to 93 Bq ^. m^-3 among the 56 surveyed rooms. Radon concentration in offices was generally higher than that in the dwellings, with the arithmetic averages of 29 and 17 Bq ^. m^-3, respectively. Radon concentrations were generally lower in the traditional Japanese wooden houses than those houses built with other building materials. Seasonal variation of indoor radon was also observed in this survey. Compared to summer and autumn, radon concentrations were generally higher in spring and winter. The mean value of thoron to radon ratio was estimated to be 1.3, higher values were observed in the dwellings than in the offices. The annual effective dose from the exposure to indoor radon was estimated to be 0.47 mSv after taking the occupancy factors of offices and dwellings into account.     

Study of radon,thoron and their progeny levels in indoor environment of Firozabad city in U.P., India

Twin cup pin-hole dosimeters having LR-115 as the detector were used to measure the concentration of radon and thoron in the dwellings of Firozabad city of Uttar Pradesh State in India. The mean values of radon, thoron, radon progeny and thoron progeny concentrations were found to be 37.4 Bqm^?3, 13.7 Bqm^?3, 4.0 and 1.5 mWL respectively. The average value of annual effective dose equivalent to the inhabitants of Firozabad city was found to be 1.1 mSv and is below the action level as recommended by the ICRP.     

Study of radon, thoron and toxic elements in some textile dyes

Elemental analysis of textile dyes may provide valuable information concerning the content and concentrations of element, especially the toxic ones. Such information monitors the safety of handling and using these dyes in textile industry. In addition to the safety of wearing of clothes stained with these dyes. In the present work, the specific activity of both radon and thoron were measured in nine textile dyes by using alpha emitters registration which are emitted from radon and thoron gases in CR-39 nuclear track detectors. Unexpectedly, the results obtained reports a high concentration of both radon and thoron gases in some samples (samples D5 and D9). Also the concentration of toxic elements (Cu, Pb, Zn, Mn, Cd and Cr) in textile dyes were determined by flame and graphite furnace atomic absorption spectrometry.     

The influence of the lithology and depth on water recharge of wells in two Moroccan Atlantic coastal regions by using solid state nuclear track detectors and radon as a natural tracer

Uranium and thorium contents as well as radon and thoron -activity concentrations were evaluated inside different underground water samples by using a method based on calculating the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTDs) detection efficiencies for the emitted -particles and measuring the resulting track density rates. The validity of the SSNTD technique utilized was checked by analysing uranium nitrate standard solutions. A relationship between water radon concentration and recharge of wells dug in two Moroccan Atlantic coastal regions, for a given lithology, was found. The influence of the lithology and depth on radon concentration and salinity of well waters studied was investigated.     

Study of the influence of the lithological and hydrogeological parameters of aquifers on the radon emanation from underground waters using solid state nuclear track detectors

Radon-to-thoron ratios as well as radon and thoron activity concentrations in different underground water samples belonging to different aquifers in the Moroccan Middle Atlas area have been evaluated by LR-115 and CR-39 solid state nuclear track detectors (SSNTD) using a new calibration method. The radon isotope (²²²Rn) was used as a tracer for studying the water exchange between different aquifers of the area studied. The influence of the lithological and hydrogeological parameters of the aquifers on radon emanation were investigated.     

Comparison of thoron (220Rn) content and gamma radiation level in high background radiation area of Kollam district in Kerala,India

In order to map the thoron prone areas of the coastal region of Kollam district, a well known HBRA of south India, comparative study of radon and thoron exhalation rate was conducted. The in situ measurement of radon and thoron exhalation has been taken. These studies were correlated with the gamma radiation level. The average value of thoron exhalation is found to 5.55 ± 1.35 Bq m⁻² s⁻¹ along the coastal areas and the radon exhalation rate is found to 107.6 ± 32 Bq m⁻² h⁻¹. The value of thoron exhalation was found 12 times greater than the global values in Neendakara and Chavara region and about 6 times greater in the Alappad region.

     

Investigation of radon and thoron concentrations in a landmark skyscraper in Tokyo

The temporal variation of the radon concentration, and the radon and thoron concentrations every 3 months for a year were measured using two types of devices in a landmark skyscraper, the Tokyo Metropolitan Government Daiichi Building. In the measurement of temporal variation of the radon concentration using a pulse type ionization chamber, the average radon concentration was 21 ± 13 Bq m^?3 (2–68 Bq m^?3). The measured indoor radon concentration had a strong relationship with the operation of the mechanical ventilation system and the activities of the office workers. The radon concentration also increased together with temperature. Other environmental parameters, such as air pressure and relative humidity, were not related to the radon concentration. In the long-term measurements using a passive radon and thoron discriminative monitor, no seasonal variation was observed. The annual average concentrations of radon and thoron were 16 ± 8 and 16 ± 7 Bq m^?3, respectively. There was also no relationship between the two concentrations. The annual average effective dose for office workers in this skyscraper was estimated to be 0.08 mSv y^?1 for 2000 working hours per year. When considering the indoor radon exposure received from their residential dwellings using the annual mean radon concentration indoors in Japan (15.5 Bq m^?3), the annual average effective dose was estimated to be 0.37 mSv y^?1. This value was 31 % of the worldwide average annual effective dose.     

Short- and long-term monitoring of radon, thoron and carbon dioxide in soil-gas at Altos de pipe, Venezuela

We have measured radon and thoron activities in soil-gases since July 9, 1997 Cariaco earthquake (Mw=6.9) until the end of 2000. Carbon dioxide concentrations were also monitored between 1998–2000. The soil-gas was collected between 50–55 cm depths at two sampling points at Altos de pipe (Instituto Venezolano de Investigaciones Cientificas-IVIC) near Caracas, Venezuela. The radon and thoron measurements were performed daily employing radiation monitors with scintillation cells and the carbon dioxide was monitored with portable gas analyzers. Average weekly and monthly values were calculated and plotted for this three-four year period. In general, both the radon and carbon dioxide values showed sinusoidal trends due to seasonal changes. During the dry season the radon and carbon dioxide values decreased, while the radon activity was relative constant (flat) during the rainy season at one of the sampling points. Only two monthly radon values were seen to be anomalous in the graphs in respect to seven anomalous periods for the average weekly values. No anomalous periods were clearly seen for carbon dioxide. Finally, it was difficult to try to relate these radon anomalous periods with specific earthquakes due to the large number of minor earthquakes during these years, but it seem that the minor earthquake (Mb=5.9) of October 4, 2000 could be associated with the radon anomalous period in September, when there were no other minor earthquakes (Mb≥4.0). This revised version was published online in July 2006 with corrections to the Cover Date.     

Spatial and vertical distribution of radon and thoron in a typical Indian dwelling

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.     

Dose assessment from exposure to radon,thoron and their progeny concentrations in the dwellings of sub-mountainous region of Jammu & Kashmir,India

The present work deals with the assessment of annual inhalation dose due to exposure of indoor radon, thoron and their progeny concentrations in the villages situated in sub-mountainous region of Jammu & Kashmir, India. The distribution of the data and the homogeneity of medians among different seasons and dwellings were assessed with the Shapiro–Wilk test and the Mann–Whitney test. The estimated total annual inhalation dose in these villages varied from 0.5 to 1.9 mSv year^?1 which is less than the prescribed limit by ICRP (2008). Thus, the investigated area is safe from irradiation of radon, thoron and their progeny.     

A new method for studying the influence of pollution and soil nature on the radon emanation from water samples by using solid state nuclear track detectors

Radon emanation from surface water and groundwater samples has been studied by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). A calibration method for determining the thoron and radon concentrations of the water samples studied has been developed. The effect of pollution due to coal fly ashes, cement and granite dusts on the radon emanation from water samples has been investigated. The influence of the radon source on the radon emanation rates from water samples has been studied.