Radon Exhalation Research Articles

Determination of Radium and Radon Exhalation Rate as a Function of Soil Depth of Duhok Province - Iraq

ABSTRACT Radon is a naturally occurring radioactive gas; generated during the decay process of radium, when alpha particles start to be emitted, turning the radium into radon. The rate of radon gas that escapes from the soil into the atmosphere is called radon exhalation rate. In this study, radon, radium, and both radon surface and mass exhalation rates were measured for 40 samples of soil at four sampling depths (10, 20, 30, and 40 cm) in three districts of Duhok province. For the radon measurement, alpha-sensitive RAD7 detector was used. While radium concentration measured by well type NaI (Tl) detector. Analysis, shows radon surface exhalation rate vary from 24 ± 10.7 to 57 ± 2.5 Bq.m−2h−1 with an average value of 38.7 ± 8.9 Bq.m−2h−1. While mass exhalation rate vary from 1.2 ± 0.9 to 6.7 ± 1.6 Bq.kg−1.h−1 with an average of 4.2 Bq.kg−1.h−1. Furthermore, the results showed that radon exhalation rate and radon concentrations in soil have direct proportion to soil depths. Overall, radon concentration, radium content and both surface and mass exhalation rate in all sample points present a good correlation and less than global mean average recommendation [30].

RADON FOOTPRINT FROM THE PHOSPHOGYPSUM WASTE STACK NEAR ZGRPOLCI LOCALITY, VELES, REPUBLIC NORTH MACEDONIA

Five locations and five samples of materials from the phosphogypsum waste stack near Zgrpolci locality, in the vicinity of the city of Veles, were checked for their radon concentrations in air and phosphogypsum radon exhalation rate. The accumulation method using AlphaGUARD DF2000 device was used for specific exhalation rate determinations as well as for radon concentrations in air. The activity concentrations of 222Rn at 5 different sampling locations of the anthropogenically introduced phosphogypsym waste stack near the Zgrpolci locality ranged from 21.02 up to 142.20 Bq kg-3. The 222Rn exhalation rates from these materials (from the same 5 locations) were in the range of 592.27-897.99 mBq m-2 h-1 .

Measurement and spatial distribution pattern of natural radioactivity in a uranium tailings pond in Northwest China

ABSTRACT Numbers of radioactive tailings were produced in the process of uranium mining and milling.In this study,radiation environment monitoring was carried out on a decommissioned uranium mining and milling tailings pond in northwest China, and the governance effect and operation status of the tailings pond was investigated. The soil radionuclide activity concentration and ambient dose equivalent rate (H*(10)) were measured, and soil surface radon exhalation rate was calculated. The results shown that in the tailings pond and its surrounding area, the average soil radionuclide activity concentration was respectively 238U: 42.64±11.17 Bq·kg-1, 226Ra: 45.47±13.56 Bq·kg-1, 232Th: 33.30±7.33 Bq·kg-1, 40K: 631.33±72.05 Bq·kg-1, the average H*(10) was 63.32±6.46 nSv·h-1, and the average radon exhalation rate was 40.46±11.29 mBq·m-2·s-1.Radionuclide activity concentration, H*(10) and radon exhalation rate were within the range of world natural background. Spatial distribution of radioactivity was analyzed by OK interpolation based on the investigated data. According to the measured results and spatial interpolation analysis,the decommissioning governance effect of the uranium tailings reservoir is good, the operation is normal, and there is no migration or diffusion situation of radionuclides in the pond has been found.

Variation in atmospheric air ion and its index of pollution during morning time (06:00 to 08:00 IST) in the sugarcane area at rural station Bhilawadi (16.5oN, 74.2oE)

The present paper reports the diurnal variation in +ve and −ve air ion concentration and pollution index in a sugarcane field [genus: Saccharum spp., variety: CO86032 (NAYANA)] in the vegetation area situated at rural station Bhilawadi (16.5°N, 74.2°E), India. It is a hybrid variety of CO62108 and CO671. The outcomes introduced in this investigation propose that the open ecological air or particularly the sugarcane zone shows enormous convergence of −ve air ions which are basic for human wellbeing. It is due to ionisation, photosynthesis, transpiration and radon exhalation process by sugarcane. The results presented in this study suggest that the open environmental air or especially the sugarcane area exhibits large concentrations of −ve air ions which are essential for human health. Though all living beings interact with the environment, only human beings have less interaction with the environment, so attempts should be made to use natural resources to have better health.

Radium Content and Radon Exhalation Rates in Beach Sand Samples Collected from Sea Coasts, Egypt using Sealed Cup Technique and LR-115 Detectors

Radium Content and Radon Exhalation Rates in Beach Sand Samples Collected from Sea Coasts, Egypt using Sealed Cup Technique and LR-115 Detectors

A FEASIBILITY TEST FOR QUICK RADON RISK ASSESSMENT BY MEASURING AN IN SITU RADIATION DOSE RATE.

Radon concentration was estimated using an accumulation chamber equipped with AlphaGUARD radon monitor. It varies from 12.6±1.20 to 363±19.3Bqm-3 with a mean value of 180±11.2Bqm-3. A good correlation between radium content and radon concentrations was obtained of R=0.754, which suggests that radium is the main reason of releasing radon to the atmosphere. Radon emanation coefficient and exhalation rate were also calculated. Furthermore, the radiation dose rate was measured with a high-pressure ionization chamber detector. The radiation dose rate was strongly correlated with the radon concentration and exhalation rate of R=0.85 and 0.63. The obtained results support our idea that the radiation dose rate can be a good indicator to the radon level in the atmosphere. In addition, the dependence of radon concentration on the water content was discussed.

Radioactivity of building materials in Mahallat, Iran – an area exposed to a high level of natural background radiation – attenuation of external radiation doses

In this study, mass activity of naturally occurring radioactive materials were measured in twenty-three building material samples, use extensively in the area exposed to a high level of natural background radiation (Mahallat, Iran), to determine the radioactivity index and changes to the level of indoor gamma radiation. The mass activity of 232Th, 226Ra and 40K were within the ranges from 18 ± 3 to 44 ± 10 Bq/kg (average of 27 ± 6 Bq/kg), 22 ± 5 to 53 ± 14 Bq/kg (average of 34 ± 6 Bq/kg) and 82 ± 18 to 428 ± 79 Bq/kg (average of 276 ± 58 Bq/kg), respectively. The gamma dose rates for population were estimated between 48 ± 9 and 111 ± 26 nGy/h with exception of radon exhalation from building materials. Since the air kerma rate in the town varies from 0.8 to 4 μGy/h, the attenuation coefficient was calculated for buildings made of the aforementioned materials. Additionally, the annual gamma radiation doses for inhabitants were calculated based on time spent outdoors and indoors.

A fractal analysis of radon migration in discrete fracture network model

A novel model is proposed to simulate radon migration by combining the fractal theory and the discrete fracture network (DFN) model. In the model, a power-law distribution based on fractal theory is applied to fracture length and aperture and the fracture locations and orientations are modeled with the Poisson distribution and von Mises-Fisher distribution, respectively. The model was applied to produce a computer code that can calculate the radon concentration, flux, and diffusivity of the fractured media. The key issues related to the model were analyzed and the results reveal that: (1) the threshold value of the ratio of the minimum fracture length to the maximum decreases as the fractal dimension of the fracture lengths and the relation between them follows an exponential law; (2) As the fractal dimension of the fracture lengths increases, more connected fractures are generated, resulting in a linear increase of the mean efficient radon diffusivity. (3) The dip angle is the parameter that has the greatest influence on radon migration in determining fracture orientations. (4) The radon exhalation rate increases exponentially with increasing advection velocity. (5) Models with larger fractal dimension for fracture lengths have larger representative elementary volume (REV) size and follow an exponential law.

Experimental study on permeability characteristics and radon exhalation law of overburden soil in uranium tailings pond.

The permeability characteristics of overburden soil have a significant effect on radon exhalation in uranium tailings pond. To understand this change, the effects of dry density, particle size range, and moisture content on the gas permeability and radon exhalation were studied by correlation analysis method. According to the mechanism of radon generation, the permeability characteristics of overburden, and the weather conditions, a theoretical model of radon exhalation was constructed and an experimental setup was designed. A series of tests on different properties of overburden soil were conducted by uranium tailings permeameter, and the radon exhalation rate of corresponding overburden surface was measured by local static method. Results show that the permeability of overburden decreased, which led to the decrease of radon exhalation: (1) At the same moisture content, with the increase of dry density, both the gas permeability and radon exhalation rate decrease. (2) At the same moisture content, with the increase of the particle size range, both the gas permeability and radon exhalation rate increase. (3) At the same dry density, with the increase of moisture content, the gas permeability decreases, while the radon exhalation rate increases slightly at first and then decreases.

Research on radon exhalation characteristics of uranium tailings with cover materials under the coupling load of low-frequency vibration and seepage gradient

In this study, radon (222Rn) measurements were taken at compacted uranium tailings with cover materials by a self-developed coupling testing system under different low-frequency vibration loads and gas seepage rates. The maximum measured value appears at 0.723 Bq m−2 s−1, which is close to the upper limit value of national standard of China (0.74 Bq m−2 s−1). A vibration load significantly damages the compacted uranium tailings sample structure, resulting in a marked increase in the porosity of the porous media thus forming a channel for radon migration. The results presented here may provide a workable approach for simulating geological dynamic load conditions for radon exhalation studies on uranium tailings impoundment.

A study on the three-dimensional unsteady state of indoor radon diffusion under different ventilation conditions

The exhalation of radon from building materials is a serious risk to occupants’ health. This paper studied the indoor radon diffusion under three-dimensional unsteady conditions. The radon exhalation rate of building materials was measured using a radon collection chamber combined with a RAD7-based radon/thoron detector. The indoor radon diffusion under different ventilation patterns were simulated by CFD (Computational fluid dynamics) based on the stabilization of radon concentration after 10 h in a closed environment as an initial condition. The results show that the stabilization time is 20 min, which can be reduced by appropriately increasing the air inlet velocity. Further increase in air velocity from 0.3 m s−1 did not produce any significant changes in the stabilization time and the average radon concentration. Our findings show that the better way to reduce indoor radon concentration is to have the air supply inlet at the top or upper side and the air return outlet on the lower side of the room. The indoor radon can be reduced to a steady level after 20 min using the better ventilation method. The findings would contribute to the control of the indoor radon dispersion, and to alleviate and reduce occupants’ exposure to high radioactive concentration of radon in urban cities.

Radon and thoron exhalation rate, emanation factor and radioactivity risks of building materials of the Iberian Peninsula.

Radon (222Rn) and thoron (220Rn) are radioactive gases emanating from geological materials. Inhalation of these gases is closely related to an increase in the probability of lung cancer if the levels are high. The majority of studies focus on radon, and the thoron is normally ignored because of its short half-life (55.6 s). However, thoron decay products can also cause a significant increase in dose. In buildings with high radon levels, the main mechanism for entry of radon is pressure-driven flow of soil gas through cracks in the floor. Both radon and thoron can also be released from building materials to the indoor atmosphere. In this work, we study the radon and thoron exhalation and emanation properties of an extended variety of common building materials manufactured in the Iberian Peninsula (Portugal and Spain) but exported and used in all countries of the world. Radon and thoron emission from samples collected in the closed chamber was measured by an active method that uses a continuous radon/thoron monitor. The correlations between exhalation rates of these gases and their parent nuclide exhalation (radium/thorium) concentrations were examined. Finally, indoor radon and thoron and the annual effective dose were calculated from radon/thoron concentrations in the closed chamber. Zircon is the material with the highest concentration values of 226Ra and 232Th and the exhalation and emanation rates. Also in the case of zircon and some granites, the annual effective dose was higher than the annual exposure limit for the general public of 1 mSv y−1, recommended by the European regulations.

RADON INHALATION EXPERIMENTS TO TEST RADON EXHALATION KINETICS.

Three experiments were conducted with a volunteer to test the kinetics of the 222Rn exhalation after a short-time exposure to an elevated 222Rn air concentration. Radon concentration in an exhaled air was measured, complemented by whole body counting of 222Rn decay products in a body. Exhaled activities are compared with the prediction of the recent ICRP biokinetic model for radon. While a rapid equilibration of the exhaled radon activity concentration with that in the air inhaled corresponded with the model, the measured 222Rn exhalation rate was significantly less than modelled. Five hours after termination of the inhalation phase, the radon concentration in the exhaled air decreased to levels expected for non-elevated indoor radon activity concentration. Whole body activities of the 222Rn decay products were found higher than expected. Inhalation of the unattached fraction or residual activity of decay products in the air inhaled may be the explanation.

Measurement of Alpha Activity in Several Types of Iraqi Ceramic and Cement in the Iraqi Markets

In this study fifteen samples of ceramic and cement collected from Iraqi markets have been determined for the radium efficacy and radon exhalation rates using the CN-85 plastic track detectors. For the estimation of the effective radium content and exhale rate, these samples comprised 15 different Iraqi materials. The effective radium content values ranged from 2.108 to 21.689 Bq / kg to an average of 9.399 Bq / kg and standard devolution of 6.950. The mass exhalation levels for radon ranged from 0.106 to 1.092 mBq / kg.day, with an average value of 0.473 mBq / kg. day and standard deviation of 0.312 Bq / kg. The exhalation rate for the radon surfaces ranged from 1.889 to 19.44 mBq / kg.day. The mean radon exhalation levels, which are an effective radium element, were found to fall below the world average of 57600 Bq / m2 in the samples of ceramic and concrete materials and Soil: 35 Bq / kg, In addition, the study’s showed that the effective radium content in this study and the associated radon exhalation do not pose a human health risk when they are used in daily life in Iraqi markets.

VARIATIONS OF INDOOR RADON CONCENTRATION IN TRADITIONAL RUSSIAN RURAL WOODEN HOUSES.

Continuous indoor radon measurements were carried out in two traditional Russian rural houses located in different villages of the Moscow region in summer of 2017 and 2018. In additional, in the summer of 2017, continuous measurements of soil gas radon activity concentration at depth 0.8m and radon exhalation rate from the ground surface near the house were performed simultaneously. It was found that the indoor radon concentration in rural houses is subject to strong daily variations, which are characterized by highs at night and lows during the day. Indoor radon concentration is directly proportional to indoor and outdoor temperature difference and inversely proportional to wind speed. While the radon exhalation rate from the ground surface, as well as the ventilation of premises (opening doors and windows) practically do not affect the concentration of radon in Russian rural wooden houses.

INDOOR RADON MEASUREMENTS FOR THE SOUTH AFRICAN WEST COAST PENINSULA.

Granite commonly contains high concentrations of uranium, with consequent high exhalation of radon. The geology of the West Coast peninsula of South Africa is dominated by granite, and a recent article predicted potentially high indoor radon concentrations in this region's two largest towns, Vredenburg and Saldanha. This research aimed to measure indoor radon levels in these towns. Measurements were first done for a minimum of 3d during warmer months, with houses typically being more ventilated. Thirty-four homes in Vredenburg and 27 in Saldanha were measured, and the average indoor radon determined to be 40 and 58Bqm-3, respectively. The measurements were then repeated during the colder months, and an increase in average radon concentration of 173Bqm-3 for Saldanha and 153Bqm-3 for Vredenburg was found. The granite geology and lifestyle of occupants during the colder months seem to contribute towards elevated levels of indoor radon concentrations.

Evaluation of the effect of cover layer on radon exhalation from building materials

Radium, which is naturally present in many building materials, decays to the radioactive gas radon, which is exhaled from the surface of concrete block and is a major source of human exposure to radioactivity. In this study, an experimental evaluation of radon exhalation was conducted on a concrete block covered with mortar and acrylic render. Factors such as sand aggregates content and water content of the mortar cover layer, the thickness of the double cover layer were considered. Results showed that the radon exhalation rate was increased with an increase of sand content in mortar cover layer, and the radon exhalation rate was reduced with an increase of the thickness and water content. Besides, indoor radon concentration and effective dose estimation involving concrete block with cover layer were evaluated. The calculated indoor radon concentration was reduced from 234.9 to 201.1 Bq m−3 as the thickness of the cover layer was increased from 15 to 35 mm, and the effective dose was reduced by 0.61 mSv y−1. Therefore, the addition of a cover layer on the indoor walls, floors and ceilings could reduce the indoor radon concentration and the radon dose on exposure to occupants.

STUDIES OF RADON LEVELS, RADIUM CONCENTRATION, AND ESTIMATED EFFECTIVE DOSE IN DWELLINGS AND SOILS IN GOLD MINING TOWNS IN ABIREM OF EASTERN REGION OF GHANA.

Studies have been carried in 126 dwellings for indoor radon levels and 43 soil samples for radium and radon exhalation rate of Abirem communities in Eastern region of Ghana. The measurements were done using CR-39 and HPGe techniques. Indoor radon and mean concentration ranged from 23.8 to 125.7Bq/m3, 54.7±23.7Bq/m3. Bedroom, kitchen, and sitting varied from 30.8 to 125.7Bq/m3, 23.8-63.9Bq/m3 and 23.8 to 58.4Bq/m3. Strong and weak Pearson correlation were found between radium and radon in soil, radium and indoor radon concentration. Radium concentration and mean were found to be varied from 19.5 to 38.9Bq/kg, 29.0±16.0Bq/kg. The radon exhalation rate and mean in soil were also found to be varied from 21.3 to 112.1 μBq/m2h, 65.1±27.6 μBq/m2h. Indoor radon values and radium concentration in dwellings and soil recorded 8% and 38%, respectively, more than action proposed by WHO and UNSCEAR 2000. The estimated annual effective doses and cancer risk were less than the average values recommended by UNSCEAR and ICRP.

Carcinogen soil radon enrichment in a geothermal area: Case of Güzelçamlı-Davutlar district of Aydın city, western Turkey

Radon gas is noble gas formed from the normal radioactive decay series of 238U. Uranium is present in almost all rocks but enriched in silica-rich rocks like granites, gneisses, schists, volcanics, pegmatites, migmatites. The study area extends over metamorphic, volcanic, and clastic sedimentary rocks. Soil radon was measured in 34 measuring points and its concentrations reach 3700 Bq/m3. The mean values decrease due to seawater penetrations or to collections of atmospheric waters in a basin. Those water saturates the soil and prevents radon emanation and exhalation. The emanation of radon to the surface requires transporting agents. In geothermal fields, hot water or fluids take on this task. For that reason, geothermal fields can represent high soil radon. As radon was classified as a human carcinogen, our study area and whole Aydın province which has rich geothermal potential must be surveyed for public health.

The results of long-term simultaneous measurements of radon exhalation rate, radon concentrations in soil gas and groundwater in the fault zone

The regular monthly radon measurements were carried out in the fault zone on the Western slope of the Beshtau magmatic massif (North Caucasus). The radon exhalation rate from the soil surface, as well as radon concentrations in soil gas at a depth of 0.5 m and in groundwater discharged at a spring located nearby have simultaneously been measured. High seasonal fluctuations in radon exhalation and radon concentration in soil gas, characterized by highs in summer and lows in winter, were registered. In summer, the radon exhalation reached 23.8 Bq m−2s−1, and the radon concentration in the soil gas reached 166 kBq m−3. In winter, both the radon exhalation and the radon concentration in the soil dropped to 0.025 Bq m−2s−1 and <3 kBq m−3, respectively. The concentration of radon in ground water varied over the year in a relatively narrow range (100–210 Bq l−1), and there were no seasonal fluctuations. A sharp increase in soil radon and radon exhalation in spring and a fall in autumn are timed to the moments when the temperature of the atmospheric air becomes, respectively, higher and lower than the temperature of the rock massif. Both the soil radon concentration and the radon exhalation show a close correlation with the temperature of atmospheric air, but in the first case the relationship is linear, and in the second – exponential. The obtained data confirm the assumption that the seasonal radon variations are caused by atmospheric air circulation in the shallow area of the fault due to the temperature difference between the atmosphere and the rock massif.