Exhalation Rate Research Articles

Theoretical model for calculating and adjusting radon activity concentration in ventilation networks of uranium mines considering pressure drop effect

The radiation dose of workers in underground uranium mines mainly comes from radon and radon progeny. To ensure a healthy and safe work environment, it is necessary and urgent to optimize the design of ventilation systems. As such, based on the simplified radon diffusion-advection migration model of the rocks, this paper proposes 1) two methods for determining the radon exhalation rate modified by pressure drop, 2) three methods for calculating radon activity concentration of single-branch, and 3) the novel adjustment algorithm and solving procedures for calculating and adjusting the radon activity concentration in ventilation networks by modifying the radon exhalation rate, demonstrated on a specific ventilation network in a simulated underground uranium mine with calculation and analysis via MATLAB. The results show that 1) the radon exhalation rate of different branches can be modified by their pressure drop, and 2) the proposed method can be used to reveal the influences of different ventilation methods and fan pressures on the radon activity concentration in the ventilation network and the radon release rate to the atmosphere.

Experimental Study on the Effect of Wetting-Drying Cycles on Crack Development and Radon Retardation of the Covering Soil in Uranium Mill Tailing Impoundments.

The majority of uranium mill tailing impoundments in the southern part of China are located in humid subtropical regions where persistent rainfall and rapid evaporation of water after rain often occur. Under the prolonged influence of alternating wet and dry conditions, the covering soil layer of uranium mill tailing impoundments develops cracks, leading to the issue of degradation or even failure of the radon retardation effect. A beach surface of uranium mill tailing impoundments in the southern part of China is selected as the research object. Through use of a self-made simulation test device, a degradation experiment of uranium mill tailing covering soil models under wetting-drying cycles was conducted indoors. The experimental results indicate that with a constant amplitude of wetting-drying cycles, microcracks characterized by a narrow width and high abundance were mainly generated in the early-to-mid-stage of wetting-drying cycles. The main cracks, characterized by their wide width and less abundance, were mainly formed in the mid-to-late stage of wetting-drying cycles. After seven wetting-drying cycles, the total length of cracks showed a "stair-step" increase and the surface crack ratio exhibited a trend of moving from rapid growth to stable growth and then to a slight decline. The cumulative damage degree showed a rapid increase to stable growth with an increase in the number of wetting-drying cycles. Grey relational analysis revealed that, compared to other surface crack indicators, radon exhalation rate was the most closely correlated with the surface crack ratio. With a constant amplitude of wetting-drying cycles, the radon exhalation rate underwent four stages as the number of wetting-drying cycles increased: stage I witnessed a rapid increase, stage II witnessed a rapid decrease, stage III witnessed a gradual increase, and stage IV witnessed a stable or even slight decrease. With a constant number of wetting-drying cycles, the radon exhalation rate correspondingly increased with the amplitude of wetting-drying cycles, particularly noticeable when the alternation amplitude was 30 ± 20%. From the early mid-stage to the late stage of wetting-drying cycles, the curves of the radon exhalation rate, surface crack ratio, and cumulative damage degree tended to be consistent, showing a gradual increase. The research provided in this study offers valuable insights into radon control measures and environmental assessments on the beach surface of uranium mill tailing impoundments.

Radon exhalation and health hazard assessment for various ceramic tiles used in Bangladesh

Objective: Among various building materials, tiles are the most used decorative materials used worldwide. For the safe use of tiles at home and workplace it is required to select them properly based on radiation dose due to radon and gamma emission.
 Experiments: Among various tiles available in the market, 25 different types of tiles were collected for this experiment. Collected tiles are then ground and stored in sealed cans for secular equilibrium. To measure gamma activity due to the radionuclides 226Ra, 232Th, 40K, High Purity Germanium (HPGe) detector was used. To store radon gas emitting from tiles, a big box was used. The activity concentration was then measured by a radon detector (RadonEye) by placing it inside the box.
 Results and discussion: It was observed that 226Ra, 232Th, 40K activity varies from 45 – 89 Bq/Kg, 77 – 110 Bq/Kg, and 321 – 694 Bq/Kg. The radium equivalent activity varies from 198.32 – 280.46 Bq/Kg, less than the recommended value of 370 Bq/Kg set by UNSCEAR (United Nations Scientific Committee on the Effects of Atomic Radiation). The activity concentration of radon varies from 31 – 71 Bq/m3. This is lower than the 300 Bq/m3 recommended by ICRP (International Commission on Radiological Protection). The radon exhalation rate varies from 0.179 – 0.409 Bqm−2h−1. To assess radiological hazards associated with the tiles samples air absorbed dose rate, internal and external hazard index, gamma index, annual indoor and outdoor effective dose rate, and dose due to radon were also calculated.
 Conclusion: Though the estimated values for external and internal hazards are below the recommended values, they may be safe for adults. As children have thinner skin and breathe more air due to high breathing frequency, they may receive more radiation than adults. Moreover, they are at a greater risk because of their developing bodies and long life expectancy post-exposure.

Measurement of Effective Radium Content and Radon Exhalation Rates in Soil Samples of Adigrat, Tigrai Region, Ethiopia

The predominant source of radiation exposure for the global population is natural radiation, originating from radioactive elements present in the Earth's soil, air, and water. These elements, such as uranium, radium, and radon, have existed since the planet's formation. Prolonged exposure, particularly in specific geographic locations, significantly contributes to radiation risks for populations. Exposure routes include inhaling radon gas, ingesting radioactive substances in food and water, and direct exposure to terrestrial gamma radiation. While natural radiation exposure generally remains within safe limits, certain factors can elevate risks, such as geological formations rich in radioactive minerals or proximity to nuclear facilities. Environmental conditions and geological factors can also influence radiation levels, leading to fluctuations in exposure risks. Monitoring and regulating radiation exposure are crucial to prevent surpassing permissible levels, which can result in health hazards like an increased risk of cancer. Effective management requires ongoing research, stringent regulations, and public awareness efforts to mitigate the risks associated with natural radiation exposure and protect public health. Effective radium content and radon exhalation rates in soil samples collected from Adigrat in Tigrai state of Ethiopia were experimentally measured by ‘‘Sealed Can Technique’’ using LR-115 type II plastic track detectors. The values of effective radium content were found to vary from16.11 Bq/kg to 34.24 Bq/kg with an average value of 25.93 Bq/kg and a standard deviation of 6.10. The mass and surface exhalation rate has been found to vary from 1.61x10<sup>-6</sup> Bq kg<sup>-1</sup> d<sup>-1</sup> to 3.42 x10<sup>-6</sup> Bq kg<sup>-1</sup> d<sup>-1</sup> and 0.81x10<sup>-4</sup> Bq m<sup>-2</sup> d<sup>-1</sup> to 1.71x10<sup>-4</sup>Bq m<sup>-2</sup> d<sup>-1</sup>, respectively. The radium content in soil in the study area is below the permissible value of 370 Bq/kg as recommended by Organization for Economic Cooperation and Development.

Assessment of radon transportation and uranium content in the tectonically active zone of Himalaya, India

The study shows how geology and tectonic activity affect the soil gas 222Rn concentration. The tectonically active zone, namely the Ghuttu region, which is located within the Himalayan seismic belt, was studied to decipher its impact on soil gas 222Rn concentrations. A soil gas 222Rn study was performed in the soil at a depth of 30 cm, and it varied from 426 ± 156 Bq m−3 to 24,057 ± 1110 Bq m−3 with an average of 5356.5 ± 1634.6 Bq m-3, and at 60 cm below the soil surface, the concentration varied from 1130 ± 416 Bq m−3 to 30,236 ± 1350 Bq m−3 with an average of 8928.5 ± 2039.5 Bq m−3. These concentrations vary in soil from −3.4 % to 437.3 % as the depth moves from 30 cm to 60 cm. The variation in uranium content also shows anomalies, and higher values of uranium content in the soil affect the radon concentration in the study area. The average soil gas 222Rn concentration in the Ghuttu window was found to be higher than that in its surrounding region. This is likely due to transportation from daughter products of uranium. 222Rn mass exhalation rate measurements were also carried out, and a weak correlation with the soil gas 222Rn concentration was observed. A significant variation in the mass exhalation rate was noticed in tectonically active areas. This study is vital to understanding the behavior of radon and uranium in tectonic regions.

Assessment of exhalation rates of radon and thoron in soil from the Jaunsar-Bawar region of the Indian Himalayas

Assessment of exhalation rates of radon and thoron in soil from the Jaunsar-Bawar region of the Indian Himalayas

Estimation of soil Rn-222 exhalation rate and its dependence on meteorological parameters in Purulia District, West Bengal, India

Estimation of soil Rn-222 exhalation rate and its dependence on meteorological parameters in Purulia District, West Bengal, India

Assessment of primordial radionuclides and radon exhalation in granitic terrain of Bengaluru, India

This study delves into an investigation of primordial radionuclides and radon exhalation potential in natural soil and rock samples collected from the granitic terrain of Bengaluru, Karnataka, India. Employing a Smart RnDuo monitor and HPGe-based gamma spectrometry, the analysis reveals significantly elevated average specific radium, thorium, and potassium activities compared to the global averages documented by UNSCEAR. The research work evaluates radiological parameters in these samples, confirming compliance with global safety limits. Absorbed dose rates, hazard indices, and dose levels align with recommended standards, underscoring the safety of the assessed environment. Notably, the radon exhalation potential of these samples spans a range of 17 ± 1.3 mBq/kg/h to 179.42 ± 10.6 mBq/kg/h, accompanied by corresponding radon emanation factors varying from 5.1 ± 0.3 % to 45.4 ± 3.1 %, with an arithmetic mean of 18.0 ± 1.1 %. Intriguingly, a positive correlation emerges between the radon exhalation rate and both radium content and emanation factor. This research sheds light on the unique radiological characteristics of the Bengaluru granitic terrain, offering insights into the local radon risk and contributing to the broader understanding of radionuclide distribution in geologically diverse regions.

Comprehensive Study of Natural Radioactivity in Building Materials: A Case Study in Ica, Peru

This study evaluates radon exhalation rates and assesses the potential radiological risks of external exposure to primordial radionuclides in building materials employed in the Ica region of Peru, particularly those with high uranium content. The radon exhalation rates are currently measured using a combination of a closed chamber and an active monitor. We proposed a novel method that effectively ensured a hermetic seal for the closed chamber and guaranteed that the efficient maintenance of secular equilibrium. The obtained results ranged from below the detection limit (BDL) to a maximum of 52.3 mBq · kg−1h−1. Gamma spectrometry was employed to measure the concentrations of radionuclides by utilizing a 3′ × 3′ NaI detector. The analysis of cement samples revealed a strong positive correlation between the activity concentration of radium and the radon exhalation rate. The activity concentrations for radionuclides varied, with values ranging from BDL to 60.6 mBq · kg−1h−1 for 226Ra, BDL to 22.3 mBq · kg−1h−1 for 232Th, and BDL to 1074 mBq · kg−1h−1 for 40K. These findings contribute valuable insight to decision-making processes in the Peruvian construction industry, particularly regarding material safety and radiological risk management.

Novel approaches for accurately measuring radon exhalation rate and mechanism interpreted by numerical simulation

Measurements of radon exhalation rate using traditional methods can be affected by back-diffusion or differential pressure in the accumulation chamber, resulting in deviations between the measured and the true values. To obtain an accurate radon exhalation rate for evaluation of radon-risk regions, two novel approaches of measurements based on traditional methods were proposed. Repeated experiments were implemented on a self-designed stainless cylindrical vessel filled with uranium tailings sand. The measured radon exhalation rates on average were 0.51 ± 0.02 and 0.52 ± 0.02 Bq m−2 s−1 for the two proposed methods, with 0.02% and 0.04%, respectively, deviations from the theoretical value. In addition, numerical techniques were employed to interpret the defects of traditional methods and mechanisms of proposed approaches to measure accurate values. Two novel approaches have significantly reduced the impact of back diffusion and differential pressure inside the chamber and consumed less time.

Measurements of 222Rn exhalation rates, effective 226Ra contents, and radiological risks from geological samples of Kopili Fault Zone and gneissic complex of Shillong Plateau, India

Abstract This report unveils the outcomes of measurements of 222Rn exhalation rates, effective 226Ra content, and the annual effective dose for rocks and soil collected in the vicinity and far from the seismically active Kopili Fault Zone, India. LR-115 (II) nuclear track detector has been used to investigate radiation exposure in the seismically active fault zone and gneissic complex of the Shillong Plateau, which have significant geological characteristics and frequently produce earthquakes. In this study, 222Rn mass exhalation rates for granite, gneiss, and soil samples collected near and far from the fault were calculated to be in the ranges of 73.2–83.0, 11.0–14.8, 21.1–70.7 and 34.3–65.5, 6.4–9.9, 19.1–28.9 mBq kg−1 h−1, respectively. Surface exhalation rates of 222Rn for granite, gneiss, and soil samples collected near and far from the fault varied between 2428.8–2751.7, 365.6–491.9, 698.3–2345.9, and 1138.6–2172.7, 211.9–328.2, 634.9–960.0 mBq m−2 h−1, respectively. The 226Ra contents of granite, gneiss, and soil collected in similar distributions were found to vary from 9.76–11.06, 1.47–1.98, 2.8–9.4, and 4.58–8.74, 0.85–1.32, 2.6–3.6 Bq kg−1, respectively. The annual effective doses attributed to 222Rn inhalation from exposure to the samples were calculated to be in the ranges of 176.3–199.8, 26.5–35.7, 50.7–170.3 and 82.7–157.7, 15.4–23.8, 46.1–69.7 μSv y−1, respectively, for granite, gneiss, and soil. The lifetime fatality-risks have also been analysed in this study. The samples that were collected in close proximity to the fault showed higher values than those that were collected farther away. However, the results reveal that the measured values are within the globally recognised permissible range.

Temperature-humidity evolution and radon exhalation mechanism of red clay-bentonite covering layer in uranium mill tailings pond

To ensure the safety and stability of the beach surface of the decommissioned uranium mill tailings pond, this paper uses red clay-bentonite and red clay (1:1) to carry out covering layer radon reduction simulation experiments to study the temperature, humidity, and radon reduction effect of the covering layer under natural conditions. The results show that the radon exhalation rate of red clay-bentonite cover layer is only 0.32 times that of red clay, which has a better radon reduction effect. The red clay-bentonite cover layer has better water retention and comparable heat preservation effect than red clay cover layer. The red clay-bentonite and red clay temperature curves follow the same evolution trend and were close together in the same outdoor conditions, and the humidity curves showed a difference of 1% to 3%. Soil temperature is the dominant factor affecting the variation of radon exhalation of red clay-bentonite and red clay covering layer with unsaturated water content.

Skin temperature influence on transcutaneous carbon dioxide (CO2) conductivity and skin blood flow in healthy human subjects at the arm and wrist.

Objective: present transcutaneous carbon dioxide (CO2)-tcpCO2-monitors suffer from limitations which hamper their widespread use, and call for a new tcpCO2 measurement technique. However, the progress in this area is hindered by the lack of knowledge in transcutaneous CO2 diffusion. To address this knowledge gap, this study focuses on investigating the influence of skin temperature on two key skin properties: CO2 permeability and skin blood flow. Methods: a monocentric prospective exploratory study including 40 healthy adults was undertaken. Each subject experienced a 90 min visit split into five 18 min sessions at different skin temperatures-Non-Heated (NH), 35, 38, 41, and 44°C. At each temperature, custom sensors measured transcutaneous CO2 conductivity and exhalation rate at the arm and wrist, while Laser Doppler Flowmetry (LDF) assessed skin blood flow at the arm. Results: the three studied metrics sharply increased with rising skin temperature. Mean values increased from the NH situation up to 44°C from 4.03 up to 8.88 and from 2.94 up to 8.11 m·s-1 for skin conductivity, and from 80.4 up to 177.5 and from 58.7 up to 162.3 cm3·m-2·h-1 for exhalation rate at the arm and wrist, respectively. Likewise, skin blood flow increased elevenfold for the same temperature increase. Of note, all metrics already augmented significantly in the 35-38°C skin temperature range, which may be reached without active heating-i.e. only using a warm clothing. Conclusion: these results are extremely encouraging for the development of next-generation tcpCO2 sensors. Indeed, the moderate increase (× 2) in skin conductivity from NH to 44°C tends to indicate that heating the skin is not critical from a response time point of view, i.e. little to no skin heating would only result in a doubled sensor response time in the worst case, compared to a maximal heating at 44°C. Crucially, a skin temperature within the 35-38°C range already sharply increases the skin blood flow, suggesting that tcpCO2 correlates well with the arterial paCO2 even at such low skin temperatures. These two conclusions further strengthen the viability of non-heated tcpCO2 sensors, thereby paving the way for the development of wearable transcutaneous capnometers.

Numerical simulations of radon exhalation from surrounding rocks of single and double underground roadways

The radon exhalation rate of surrounding rocks in underground roadways is an important parameter in determining radon exhalation capacity and ventilation flowrate for radon removal. By approximating the roadways as thick-walled, porous cylinders, this study investigates radon exhalation from their surrounding rocks via simulations using computational fluid dynamics (CFD). Radon exhalation rates of single and double underground roadways were computed and analysed under different pressure differences, radon diffusion coefficients, permeabilities of rocks, single roadway locations and additional parallel roadway orientation. The radon regulating zone was presented and the effect of pressure difference on it was analysed. By fitting the data from simulation results, an estimation model was obtained for the radon exhalation rate of a single roadway. For two adjacent parallel roadways with a distance greater than or equal to 50m, the model is also suitable for estimating the radon exhalation rate when the rock permeability is less than 1 × 10−14 m2 and the ratio of permeability to diffusion coefficient is less than 5 × 10−9.

A portable low-cost device to quantify advective gas fluxes from mofettes into the lower atmosphere: First application to Starzach mofettes (Germany)

In this study, we introduce a portable low-cost device for in situ gas emission measurement from focused point sources of CO2, such as mofettes. We assess the individual sensors’ precision with calibration experiments and perform an independent verification of the system’s ability to measure gas flow rates in the range of liters per second. The results from one week of continuous CO2 flow observation from a wet mofette at the Starzach site is presented and correlated with the ambient meteorological dynamics. In the observed period, the gas flow rate of the examined mofette exhibits a dominant cycle of around four seconds that is linked to the gas rising upwards through a water column. We find the examined mofette to have a daily emission of 465 kg ±16 %. Furthermore, two events were observed that increased the flow rate abruptly by around 25 % within only a few minutes and a decaying period of 24 hours. These types of events were previously observed by others at the same site but dismissed as measurement errors. We discuss these events as a hydrogeological phenomenon similar to cold-water geyser eruptions. For meteorological events like the passages of high pressure fronts with steep changes in atmospheric pressure, we do not see a significant correlation between atmospheric parameters and the rate of gas exhalation in our one-week time frame, suggesting that on short timescales the atmospheric pumping effect plays a minor role for wet mofettes at the Starzach site.

Radon and thoron exhalation rate from building materials: experimental evaluations and theoretical models

Radon and thoron exhalation rate from building materials: experimental evaluations and theoretical models

Optimized helical intermedium-period fiber grating for breathing monitoring.

The investigation into the spectral properties and refractive index (RI) sensitivities at low RI region of helical intermedium-period fiber gratings (HIPFGs) with varied periods ranging from 10-48 μm is presented in detail for the first time. The structure of HIPFG is optimized for RI sensing in the RI range of 1.3-1.33 by comparing the optical properties of HIPFGs with different grating periods. The HIPFG with optimized structure is demonstrated to have a high average sensitivity of 302.5 nm/RIU in the RI ranging from 1.3 to 1.33, which is two orders more elevated than the traditional long-period fiber gratings. The improved HIPFG is also experimentally applied to breath monitoring in different states. Normal breath, slow breath, fast breath, and unhealthy breath are distinguished based on breathing rate, intensity, and time of exhalation and inhalation. The fastest response time is determined to be 10 ms. The results demonstrate that the optical fiber's sensitivity in the low RI region can be increased by shortening its period, offering a special strategy for improving detection performance of HIPFGs. By verifying its performance in breathing monitoring, it is proved that the optimized HIPFG sensor has the great potential to expand medical applications.

Assessing Radon (222Rn) Exhalation Rates from Building Tiles in Duhok, Iraq

Assessing Radon (222Rn) Exhalation Rates from Building Tiles in Duhok, Iraq

Radon gas concentrations and exhalation rates in soil samples of Al-Muthanna governorate, Iraq

Radon gas concentrations and exhalation rates in soil samples of Al-Muthanna governorate, Iraq

Numerical simulations for radon migration and exhalation behavior during measuring radon exhalation rate with closed-loop method

Numerical simulations for radon migration and exhalation behavior during measuring radon exhalation rate with closed-loop method