Radon Exhalation Rate Research Articles

Radon and Thoron Exhalation Rate Measurements in Soil Samples Collected from the Vicinity of a Thermal Power Plant

Radon and Thoron Exhalation Rate Measurements in Soil Samples Collected from the Vicinity of a Thermal Power Plant

Studies on Radon and Thorn Exhalation Rates in Beach Sand along East Coastal Region of Tamil Nadu, India

Studies on Radon and Thorn Exhalation Rates in Beach Sand along East Coastal Region of Tamil Nadu, India

Estimation of Exhalation Rates of Radon and Thoron in the Soil Samples Collected from Gurugram, Haryana, India

Estimation of Exhalation Rates of Radon and Thoron in the Soil Samples Collected from Gurugram, Haryana, India

Determination of radon exhalation rate from different mixture of concrete

Determination of radon exhalation rate from different mixture of concrete

Evolution of pore structure and radon exhalation characterization of porous media grouting

Cracks and pores are considered as major sources of radon. Cement is widely used as a grouting material in mines, tunnels, and other projects for reinforcement, seepage prevention, and water plugging. This paper mainly experimentally studied the correlation between the radon exhalation rate of the porous medium after grouting and the sand grain diameter, grouting pressure, and slurry water-cement ratio. The pore characteristics of the samples before and after grouting were also studied based on the low field nuclear magnetic resonance (LF-NMR). The findings of the study show that the porosity of samples increases after the superfine cement solidification with an increase in the water-cement ratio, and the radon exhalation rate is proportional to porosity, the radon exhalation rate increases by 0.0005 Bq·m–2/s at W/C = 1.5, and by 0.0017 Bq·m−2/s at W/C = 2 increases, in comparison to the W/C = 1.The radon exhalation rate of porous media gradually increased after grouting in response to an increase in grouting pressure and the water-cement ratio. The radon exhalation rate of the porous media with larger pores was relatively higher and exhibited a positive correlation with the volume of micropores in porous media，the correlations of coarse, medium and fine media are 0.815, 0.826, and 0.859. The change in pore structure has an influence on radon exhalation. Although grouting changes the pore structure and reduces the connectivity between internal pores, the micropores generated after cement slurry solidification improves the radon exhalation rate by providing new channels, When the water-cement ratio is 1.5 and the grouting pressure is 1.5 MPa, the radon exhalation rate of porous media is 0.00273 Bq·m−2/s. The research results serve as a reference basis for the evaluation of the impact of rock masses on grouting reinforcement and pore sealing.

Estimation of Radon Concentration around Public Spaces and Residential Homes with Altitude within Cities of Delta State, Nigeria

This study evaluates the radon concentrations in public places and private residences with different altitudes in selected locations in Delta State. These measurements were carried out using a professional radon monitoring instrument (Alpha GUARD PQ2000 PRO) and a geographical positioning system (GPS-Garmin GPS Map 76S). The recorded mean radon concentration varied from 11.70 ± 5.20 Bq/m3 to 23.90 ±16.60 Bq/m3, which is within the WHO acceptable range (100 Bq/m3). The basement had greater radon concentrations than the upper floors in most situations, although there were few exceptions. The average values of the estimated radiation risk parameters, which include equilibrium equivalent radon concentration, the potential alpha energy concentration, radon exhalation rates, and excess lifetime cancer risk due to exposure to radon radiation from their progeny are 4.7 Bq/m3 to 9.5Bq/m3, 1.20 × 10-3mWL to 2.60 × 10-3mWL, 0.04 × 10-3WML/y to 0.09× 10-3 WML/y, 3.7Bq/m2/h to 7.52Bq/m2/h and 2.10 × 10-3 to 3.30 × 10-3 respectively. The calculated radiation risk factors were all found to be within the recommended limits based on the data obtained. The research region is deemed safe and poses no threat to people.

Study on the formation mechanism of a radon source during coal spontaneous combustion in a goaf

Surface isotope radon detection technology (SIRDT) is an effective physical exploration technology that provides a solution for detecting hidden underground fire sources. However, because of the inaccessibility of deep underground spaces, current research on the formation mechanism of radon sources during coal spontaneous combustion in a goaf is insufficient, which severely restricts the use of SIRDT to detect such fires. In this study, the quantitative relationship between the coal temperature and radon exhalation rate was revealed through radon exhalation experiments during the low-temperature oxidation of coal, which provides measurement data for the radon source term of coal spontaneous combustion in a goaf. A multi-physical, coupled numerical model of coal spontaneous combustion in a goaf was constructed, and the intrinsic dynamics of radon migration and the formation mechanism of the radon source in the process of coal oxidation were thoroughly investigated. The results show that the radon distribution in a goaf is because of the competition between air leakage and the “porous chimney effect.” When the temperature of the coal was low, air leakage dominated the radon transportation in the goaf, causing radon to accumulate in the area close to the air-return side. When the temperature of the coal increased, the thermal buoyancy and vortex phenomena appeared in the high-temperature area of the goaf, at this point, the “porous chimney effect” took the leading role. The updraft generated by the thermal buoyancy effect rapidly carried the radon to the top of the goaf. The vortex promoted airflow from the surrounding area of coal spontaneous combustion into the interior of the “porous chimney,” which accelerated the process of coal spontaneous combustion and increased the amount of radon transported upward; thus, further intensifying the accumulation of radon at the top of the goaf. This accumulation becomes a source of radon that continues to migrate toward the surface.

Study on damage evolution and radon exhalation of uranium-bearing granite under high temperature.

Deep geological disposal of high-level radioactive waste is a feasible method for solving the problem of spent fuel storage in China. High-level radioactive waste releases heat during the decay process, which increases the temperature of the surrounding rock in the repository, resulting in a significant increase in radon concentration. In this study, the surrounding rock (granite) of a high-level radioactive waste repository was taken as the research object and, based on the similarity principle, an orthogonal test designed. Similar materials of uranium-containing granite were prepared in the laboratory and the physical and mechanical properties and cumulative radon concentration of granite samples assessed under different temperatures (25, 50, 100, 150, and 200°C). The results showed that, with increased temperature, the compressive and tensile strengths of samples gradually increased and their pore volume gradually decreased. After heat treatment, the longitudinal wave velocity and thermal conductivity of samples decreased linearly with increased temperature. The radon exhalation rate first increased and then decreased, with the rate reaching a maximum at 100°C. The radon exhalation rate of single-sided and double-sided samples was 0.00914 and 0.00460Bq·m-2·s-1, respectively. When the temperature was 25-100°C, the dominant stage was pore water. The radon exhalation rates of samples were positively correlated with compressive and tensile strengths and negatively correlated with pore volume, longitudinal wave velocity, and thermal conductivity. The temperature of 100-200°C was range of the dominant stage of pore structure. The conclusions obtained in this study can provide theoretical support for radon reduction and radon control of granite in high temperature environments.

Study on the characteristics of radon exhalation from rocks in coal fire area based on the evolution of pore structure

Radon is of great significance as a tracer for the detection of coal fires due to its distinct variations in radon exhalation properties while heating. The research on radon exhalation performance through pore structure is still in its early stages. In this paper, the pore structure and radon exhalation characteristics of heat-treated limestone are studied using indoor tests such as nuclear magnetic and radon measurements. The study's results demonstrate that the radon exhalation rate of limestone initially increases gradually, followed by a steady decline and subsequent increase with the increase in temperature. The radon exhalation rate at 800 °C reaches 2.42 times that at room temperature. The pore structure change within limestone strongly correlates with the radon exhalation rate. The pore volume of micropores (<0.1 μm) plays an essential role in the radon exhalation capacity, which is directly related to the fractal dimension of micropore structure in the heated limestone. The study's findings can be used to identify coal fires.

Distribution of radionuclides and activity utilisation index estimation of construction materials using in Mangalore district, India

ABSTRACT The present investigation involved the collection of various construction materials from several sites throughout the Mangalore District, Karnataka, India. The concentration of radionuclides in each sample was then determined using a NaI(Tl) detector. The passive ‘Can’ technique method was used to determine the rate of radon exhalation in the collected samples. The activity concentration of 40K ranges from 36.53 Bq kg−1 to 80.68 Bq kg−1. The activity concentration of 226Ra ranges from 23.30 Bq kg−1 to 80.87 Bq kg−1. The 232Th activity concentration found to be lowest is 15.06 Bq kg−1 and a maximum of 38.65 Bq kg−1 in different samples. The estimated Activity Utilisation index (AUI), dose rate (D) and gamma index (Iγ) which is lower than the recommended limit. The hazard index values are below the Indian, World average and below the safety limit, which indicates that construction materials are safe to use for construction purposes. The present investigation gives insight on radiation hazards to the human population used in the selected location.

Study on the influence of sampling methods for measuring soil radon exhalation rates

Soil is the primary source of radon in the atmosphere, and soil radon exhalation rate (E) is a key indicator to evaluate the radon hazard in soil. Radon can also be used as a tracer to analyze atmospheric processes and monitor greenhouse gas emissions. Therefore, improving the accuracy of measuring E is significant for radon protection and radon pollution management as well as public health. In this study, three different sampling methods were compared to determine the most suitable sampling method for E measurement under different conditions. The results indicated that the closed-loop gas-flow method can be used to measure E and required correction for leakage and counterdiffusion; E was found to vary from 13.25 ± 1.44 to 30.46 ± 2.19 mBq·m−2 s−1. For the open-loop gas-flow method, a low sampling flow rate was selected, and the sampling flow rate derived from this experiment was less than 0.2 l min−1; E varied from 36.11 ± 0.99 to 52.67 ± 1.68 mBq·m−2 s−1. For the activated-carbon adsorption method, the counterdiffusion effect had a negligible influence on the measurement results, and the measurement error due to the uneven distribution of radon in the carbon layer could be eliminated by changing the waiting time for the measurement; the measurement showed E of about 23 mBq·m−2 s−1. Moreover, the influence of water absorption of the activated carbon on the measurement results should be considered, and the water absorption rate should be less than 9%. The obtained values will serve as a reference for the rapid and accurate measurement of E.

Estimation of radon in groundwater and analysis of radon and thoron exhalation rates of the soil in Mokokchung district, Nagaland, India

The present study of the analysis of radon in groundwater and its exhalation rates in soil was carried out in 19 selected locations in Mokokchung district, Nagaland, India. The survey was carried out by employing a portable scintillation-based smart RnDuo monitor. The radon (222Rn) mass exhalation rates of the soil were found to vary from 27 mBqKg−1h−1 to 40 mBqKg−1h−1 with an average of 31 ± 0.8 mBqKg−1h−1. While the thoron (220Rn) surface exhalation rate of the soil was found to vary from 714.6 Bqm−2h−1 to 2166.6 Bqm−2h−1 with an average of 1009.9 ± 77.1 Bqm−2h−1. The radon (222Rn) in drinking water was found to vary from 1.48 BqL−1 to 2.22 BqL−1 with an average of 1.82 ± 0.04 BqL−1 and is below the world average values as set by USEPA (1991), WHO (2004) and UNSCEAR (2008). Furthermore, the total effective dose range is below the WHO (2003) recommendation.

Radiological assessment of radon concentration, radon exhalation rate, and annual effective dose of building materials used in Erbil city Kurdistan region, Iraq

ABSTRACT Radon gas has long been connected with human public health risks. Building materials, one of the biggest producers of this gas in enclosed areas, are thought to be among the most important channels of this gas. The radon concentration, radon exhalation rate as well as the annual effective dose for 52 building material samples (granite, ceramic, marble, mosaic, building stones, gypsum, gypsum board, block, lightweight block, sand, aggregate, limestone, concrete, siporex, cement, white cement, brick and red brick) in Erbil city were assessed by applying a radon detection system consisting of a length-pipeline approach using CR-39 SSNTDs as an inactive mode and an electronic RAD7 solid-state detector as a can way. The outcomes of passive and active approaches were found to be very comparable. The highest values of radon exhalation rate, radon concentration and indoor yearly effective dosage were recorded, respectively, as 0.546 ± 0.032 Bq.m−2.h −1, 290.2 ± 17 Bq.m−3 and 7.32 ± 0.43 mSv.y −1 for granite samples, while the lowest values were 0.057 ± 0.003 Bq.m−2.h −1, 30.2 ± 1.8 Bq.m −3 and 0.76 ± 0.05 mSv.y −1 for the gypsum board samples. The results also revealed that the radon exhalation rate was lower than the global average of 57.600 Bq.m −2.h −1, and the indoor annual effective dose for all samples except for granite samples was less than the allowed threshold of 1–5 mSv.y−1. The annual effective dose for all samples was above the average world value of 1.2 mSv.y −1 reported by UNSCEAR and WHO except for gypsum board samples. The radon concentrations in granite samples were within the ICRP’s suggested activity ranges of 200 to 600 Bq.m−3.

A study of grain size effect on radon exhalation rate and uranium content of a phosphate rock

A study of grain size effect on radon exhalation rate and uranium content of a phosphate rock

Comparison of two models for measuring radon exhalation rate with a ventilation chamber by numerical simulation

Two models can be used to measure the radon exhalation rate with a ventilation chamber. The first is the custom model with a flow meter, and the second is the improved model without flow meter. As the established radon exhalation standard facilities can't simulate any medium to be measured by adjusting the radon exhalation rate and effective decay constants as required, numerical simulation is useful to compare the two models for measuring radon exhalation rate under different effective decay constants. Three different effective decay constants and two different radon exhalation rates were simulated for measuring radon exhalation rates, and the simulation results confirmed that the improved model is quick and accurate even when the radon exhalation rate is very low. While the custom model can only be used to calculate the radon exhalation rates when the ventilation rate is far larger than the effective decay constant, and it takes a long time for the radon concentration inside the ventilation chamber to be stable. Therefore, the improved model without flow meter is more accurate to measure the radon exhalation rate under different effective decay constants.

Measurement of Radium and Radon Exhalation Rate in Marble Samples used in Al-Bayda City Market-Libya

The aim of the present study is to measure the activity concentrations of 226Ra, 222Rn, the mass exhalation rate of 222Rn, and the annual effective dose of radon in marble samples collected from Al-Bayda city local market –Libya. Samples were measured by using a low-background NaI (Tl) detector. The average activity concentrations of 226Ra and 222Rn were 72.57 Bq.kg-1 and 597.85 Bq.m-3.The radon exhalation rate in marble samples vary from 0.05-0.30 Bq.kg-1.S-1 with an average of 0.13 Bq.kg-1.S-1. The annual effective dose of radon was calculated in samples under investigation. For most samples, the values were lower than the maximum permissible dose limits. It can be concluded that marble samples under investigation do not pose any radiological hazard to the dwellers of buildings used in their construction.

Radon Exhalation Rate and Annual Effective Dose for Different Rock Types and Excess Lifetime Cancer Risk from Radon Exposure

Purpose: Radon (222Rn) and its decay products clinging to airborne particles settle in the lungs when inhaled and can lead to lung cancer. The main source of 222Rn is rocks and soil in the Earth's crust and causes indoor radon exposure when local geological material is used as a building material. Accordingly, the primary objective of the study is to determine the radon activity concentrations (CRn) and exhalation rates (EA and EM) from different rock types taken from the Aliağa-İzmir region. The study also estimates the annual effective dose (AED) and the excess lifetime cancer risk (ELCR).&#x0D; &#x0D; Material and Methods: For the measurement of the CRn, EA, and EM in different rock types, the can technique with LR-115 detector was utilized. The AED and the ELCR were estimated using the CRn in the samples.&#x0D; &#x0D; Results: It was found that the CRn, EA, EM, AED, and ELCR values for the examined rock samples were ranged between 66±4 and 1711±13 Bq m−3, 51±3 and 1309±10 mBq m-2 h-1, 2.68±0.18 and 64.02±0.47 mBq kg-1 h-1, 1.67 and 43.16 mSv y−1, and 0.006 and 0.151, respectively.&#x0D; &#x0D; Conclusion: The higher radiological risks in terms of radon exposure were related to the rocks of volcanic origin.

Experimental Study on Unsteady Radon Exhalation from the Overburden Layer of the Uranium Mill Tailings Pond under Rainfall

In order to find out radon reduction performance of the overburden layer on uranium mill tailings (UMTs) pond beach surface after rainfall, the rainfall simulation experiment of the overburden layer was carried out with the self-developed equipment. Based on the radon migration model of the overburden layer on the UMTs pond beach surface, the change rule of radon exhalation in four types of compactness of the overburden layer within 120 hours after rainfall was studied, and the corresponding moisture content was also analyzed. The results show that the radon concentration in the overburden layer of UMTs increases nonlinearly; the dynamic change in moisture content of the overburden layer on the beach surface leads to the unsteady radon exhalation. The variation of radon exhalation shows three stages: increase, linear decrease, and stability tendency. After rainfall, radon exhalation rate increases due to water vapor and there is free radon seepage in pores. With the decrease of free radon production rate, radon exhalation rate gradually decreases until it reaches stability again. When the thickness of the overburden layer reduces, the porosity decreases with the increase in compactness of the overburden layer. While the decrease in radon reduction is more obvious, the less time it takes for radon exhalation to vary from unstable to stable overburden after rainfall.

INFLUENCE OF SAMPLING FLOW RATE ON THORON EXHALATION RATE MEASUREMENTS BY THE CIRCULATION METHOD.

Researchers have used various methods to obtain the exhalation rates of radon and thoron from soil and building materials. One of the typical methods for radon exhalation rate is the circulation method using an accumulation container, an external or internal sampling pump and a continuous radon monitor. However, it is necessary to consider sampling flow rate if this method is applied to exhalation rate measurement for thoron due to its short half-life. Based on a calibration experiment, the measured thoron concentrations obtained by an electrostatic collection type radon and thoron monitor (RAD7) were found to be influenced strongly by the sampling flow rate. It was also found that the thoron exhalation rate from a soil sample depended on the pressure difference which was proportional to the increasing sampling flow rate. The thoron exhalation rate measured at the generally used sampling flow rate of the internal sampling pump of the RAD7 was overestimated compared with the value at 0 L min-1.

Factors affecting the radon (222Rn) emanation from aquifer rock materials: Implications for radiological and groundwater tracer studies

Groundwater discharge (GD) is an important component of the water budget in large urban areas with high water demands. Radon is a routinely used groundwater tracer in mass-balances for evaluating GD to surface water bodies. The diffusion of 222Rn from aquifers' sediments parameter is important for GD's assessments. Sediment equilibration experiments were employed with various sediment and rock materials, including sand, granite, gneiss and loess that constitute the Pampeano Aquifer (PA) in the Buenos Aires Province, Argentina. These experiments allowed the 222Rn concentration determination in pore fluids at secular equilibrium and to examine the factors affecting the magnitude of radon 222Rn emanation from the materials under study. We found that radon emanation decreases in a power function (R2 = 0.9, n = 6) with the particle size of the tested PA sediment and rock materials. Based on our results, loess sediments with the smallest particle size and the largest particle surface area have the highest radon emanation. This strongly suggests that these two parameters are the parameters that govern the radon diffusive fluxes' magnitude in the PA. On the other hand, we found that PA basement rocks, primarily granite and gneiss, showed an exhalation rate of radon of 8.1 ± 0.81 Bq∙m−2∙h−1 and 13.2 ± 1.32 Bq∙m−2∙h−1. These rates are two orders of magnitude higher than loess sediments (0.3 ± 0.1 Bq∙m−2∙h−1), owning to the higher natural content of radon's parent isotopes from the 238U natural decay series. These high radon levels are consistent with currently available radon concentrations measured in groundwater in contact with the PA basement rock formations. This study demonstrates the importance of considering site-specific aquifer properties in the radon diffusive fluxes when utilizing radon as a groundwater tracer in hydrological studies. This is the first quantitative study that examines the aquifer characteristics affecting radon emanations in this large hydrogeological system.