Decay Product Concentrations Research Articles

Radon Equilibrium Factor and the Assessment of the Annual Effective Dose at Underground Workplaces

The equilibrium factor F is one of the parameters that should be considered when assessing the effective dose based on radon activity concentration. Since the equilibrium factor in various environments ranges theoretically from a value close to 0 to 1, it is expected that dose assessment based on one recommended coefficient value may lead to an underestimation or overestimation of the dose. That is why it is essential to measure this quantity if the basis for dose assessment is the radon concentration and not the concentration of radon decay products. The equilibrium factors were determined based on measurements of radon activity concentration and potential alpha energy concentration and varied from 0.15 to 0.94, with an arithmetic mean of 0.55. The average effective dose calculated for the employee taking into account these values was 31 mSv, assuming an annual working time of 1800 h. In turn, the average effective dose calculated for the equilibrium factor of 0.2 as recommended by the International Commission on Radiological Protection (ICRP) was equal to 13 mSv.

The method of Pb-212 measurements in air with the application of the LSC technique

This paper describes a method enabling the measurement of the potential alpha energy concentration (PAEC) of thoron decay products based on the determined concentration of lead 212Pb (T1/2 = 10.64 h) in the air [Lever et al., 2003]. A liquid scintillation spectrometer was used to determine the concentration of the 212Pb isotope, and the sample was taken by pumping air through a filter where thoron decay products were stored. This method can be classified as integrating because the sample takes several hours, and the measurement results in one value for the entire sampling period. Measurements were carried out in laboratory conditions, in a climatic chamber where a constant supply of thoron was maintained, and in environmental conditions, in the basement of the family house and outdoors. Sampling took from 12 to 48 h. This article presents the preliminary results of the study. The obtained results were in the range of 170–195 Bq/m3 in the case of laboratory measurements and from 0.04 to 0.79 Bq/m3 in the case of environmental measurements. Based on the obtained results, the potential alpha energy concentration (PAEC) was calculated. The application of the low-level LS spectrometer allows for the achievement of a lower limit of detection (LLD) at level 0.04–0.05 Bq/m3, while the use of the portable LS spectrometer allows for the measurement of deficient 212Pb concentrations in the range of 0.4–0.5 Bq/m3. The obtained results confirm that the method is suitable for determining the concentration of 212Pb and, consequently, assessing exposure to thoron progeny.

Analysis of variations in concentration of radon decay products in near surface layer of the atmosphere

In the last few years an increase in the amplitude of seasonal pressure wave and heavy radioactive nuclides concentration at Baksan Neutrino Observatory of INR RAS in the North Caucasus is being observed. The foregoing tendency, as well as the anomalies observed in the detectors data in autumn-winter, 2017 and winter-spring, 2021 are investigated. Hypotheses of the anomalies reasons and their connection to observed trends are presented.

Modeling: Activity Concentration of Radon, Thoron, and Their Decay Products in Closed Systems

The article presents a model for simulating changes in the activity concentration of radon and thoron as well as their progeny in closed or poorly ventilated systems. A system can be considered closed when a stream of radon and thoron flows into a space, but nothing comes out. It was also assumed that there may be devices or installations with a filtering system that would reduce the concentration of radon and thoron decay products. These assumptions may, therefore, correspond to a situation in which, in an isolated chamber, the calibration of radon hazard-monitoring devices is carried out, and nuclides are supplied from an emanation or flow through sources or well-isolated spaces in an environment where the source of nuclides is, for example, radon and thoron exhalation. The differential equations were formulated on the basis of the assumption that the activity concentration of radionuclides of concern in the space is uniform. The equations do not consider possible losses due to diffusion or the inertial or gravitational deposition of aerosols. If these phenomena have a limited impact on changes in the activity concentration of nuclides, the solutions provided may be used to simulate the activity concentration of radon and thoron and their decay products in any confined space assuming different boundary conditions.

Естественный радиационный фон в жилых и общественных зданиях в районах проведения горных работ в Арктике

Natural background radiation (NBR) largely contributes to the human inhalation of radionuclides originating from the decay of U-238, U-235 and Th-232 isotopes. This problem is of particular importance for public health in the areas with high seismicity induced by mining operations. The purpose of this article was to assess the impact of mining activities on NBR in the residential and public buildings located in the immediate vicinity of the apatite-nepheline ore mining operations in the Arctic. Materials and methods. The measurements were taken in residential and public buildings of Kirovsk (Murmansk Region) adjacent to open-pit and underground mines. The following were measured: total radioactivity dose of samples of raw ores and their concentrates, their spectral characteristics, as well as the aerosol concentration of radon decay products, and volumetric radon concentration in the basements of residential and public buildings located within 3 km from the mining area. Results. The radioactivity of open-pit ore was significantly (7.3 times) higher than that from underground mines (107,300 ± 9823 and 14,615 ± 1980 Bq/kg, respectively). However, the radioactivity of the final product (apatite concentrate) did not depend on the extraction technique (59,792 ± 865 and 61,827 ± 1022 Bq/kg, respectively). Indoor air concentrations of radon in the basements of buildings located up to 3 km from the mines, increased linearly by an average of 0.15 Bq/m3 for each ton of explosives used in ore breaking. The levels of radon and its decay products in residential and public buildings in areas adjacent to the mining operations did not exceed 100 Bq/m3. Thus, mining and blasting operations in the stress-strain state of ore-bearing rocks might have an important impact on the intensity of radionuclide emissions and changes in NBR inside residential and public buildings located in Arctic settlements adjacent to the areas of apatite-nepheline ore mining.

Particle radioactivity from radon decay products and reduced pulmonary function among chronic obstructive pulmonary disease patients

BackgroundRadon (222Rn) decay products can attach to particles in the air, be inhaled, and potentially cause airway damage. Research questionIs short-term exposure to particle radioactivity (PR) attributable to radon decay products emitted from particulate matter ≤2.5 μm in diameter (PM2.5) associated with pulmonary function in chronic obstructive pulmonary disease (COPD) patients? Study design and methodsIn this cohort study, 142 elderly, predominantly male patients with COPD from Eastern Massachusetts each had up to 4 one-week long seasonal assessments of indoor (home) and ambient (central site) PR and PM2.5 over the course of a year (467 assessments). Ambient and indoor PR were measured as α-activity on archived PM2.5 filter samples. Ratios of indoor/ambient PR were calculated, with higher ratios representing PR from an indoor source of radon decay. We also considered a measure of outside air infiltration that could dilute the concentrations of indoor radon decay products, the indoor/ambient ratio of sulfur concentrations in PM2.5 filter samples. Spirometry pre- and post-bronchodilator (BD) forced expiratory volume in 1 s (FEV1) and forced vital capacity (FVC) were conducted following sampling. Generalized additive mixed models were adjusted for meteorologic variables, seasonality, and individual-level determinants of pulmonary function. We additionally adjusted for indoor PM2.5 and black carbon (BC). ResultsPR exposure metrics indicating radon decay product exposure from an indoor source were associated with a reduction in FEV1 and FVC. Patients in homes with high indoor PR (≥median) and low air infiltration (<median) compared to others had a −26.9 (95% CI: −61.4, 7.7) mL and −75.4 (95% CI: −128.6, −22.2) mL reduction in post-BD FEV1 and FVC, respectively. These associations remained similar after PM2.5 and BC adjustment. InterpretationOur findings raise concern about the harmful effects of PR exposures attributable to residential radon on pulmonary function in patients with COPD.

Dosimetry of indoor alpha flux belonging to seasonal radon, thoron and their EECs.

Radon (222Rn) and thoron (220Rn) are ubiquitous radioactive noble gases present in the earth's crust. The source term for these gases includes soil and building materials as well. The radiological impact of radon/thoron gases and their decay products on human life is a matter of concern and has been given due attention in research and policy. The present study aims to measure and quantify residential radon/thoron gas and the decay product's concentration and to discuss the associated interpretations for Ludhiana district of Punjab, India. Passive measurement techniques employing a single-entry pinhole dosimeter for gases and direct progeny sensors for the decay product's concentration have been used in this work. The obtained data from these measurements have been analysed using appropriate statistical techniques. The variations have been linked with the changes in the ventilation conditions, building material, room type and altitude. A higher concentration of radon and thoron gas was observed in the winter season for the study region. It was estimated that the contribution of radon and thoron decay products towards the annual average inhalation dose is 75% and 25%, respectively.

Pre-breakdown Phenomena and Influence of Aging Byproducts in Thermally Aged Low Pour Point Ester Fluids Under AC Stress

Application of low pour point esters in transformers insulation serving in cold climatic regions is still a challenge. To address this concern, the pre-breakdown and breakdown analyses of thermally aged low pour point ester fluids are investigated. The breakdown measurements are performed at different aging conditions under AC stress. Needle-plane electrode geometry (with varying radii of the tip) is employed since this configuration is necessary for any practical diagnostic based on partial discharge (PD). This allows studying the effect of the chemical impurities (aging by-products) as assessed by some physicochemical properties (acidity, particles count, turbidity, and dissolved decay products) on the partial discharge and breakdown characteristics. The complete analysis is carried out for liquids having the pour points less than -50 °C, including a mineral oil (MO) and two synthetic ester liquids (SE1 and SE2). Changes in the streamer properties, such as partial discharge inception voltage (PDIV), breakdown-streamer inception voltage, and breakdown voltage are reported as a function of the needle tip radius and aging condition. It is observed that the breakdown properties of SE1 are better than that of SE2 and are comparable to MO. To understand the influence of aging on the PD, correlations between decay products, acidity, BSIV, and PDIV are reported. It is observed that the acidity and concentration of decay products directly impact the PD characteristics.

Determination of 226Ra in TENORM Sample Considering Radon Leakage Correction

Background: Phosphogypsum is material produced as a byproduct in fertilizer industry and is generally used for building materials. This material may contain enhanced radium-226 (226Ra) activity concentration compared to its natural concentration that may lead to indoor radon accumulation. Therefore, an accurate measurement method is proposed in this study to determine 226Ra activity concentration in phosphogypsum sample, considering the potential radon leakage from the sample container.Materials and Methods: The International Atomic Energy Agency (IAEA) phosphogypsum reference material was used as a sample in this study. High-purity germanium (HPGe) gamma spectrometry was used to measure the activity concentration of the 226Ra decay products, i.e., 214Bi and 214Pb. Marinelli beakers sealed with three different sealing methods were used as sample containers. Due to the potential leakage of radon from the Marinelli beaker (MB), correction to the activity concentration resulted in gamma spectrometry is needed. Therefore, the leaked fraction of radon escaped from the sample container was calculated and added to the gamma spectrometry measured values.Results and Discussion: Total activity concentration of 226Ra was determined by summing up the activity concentration from gamma spectrometry measurement and calculated concentration from radon leakage correction method. The results obtained from 214Bi peak were 723.4 ± 4.0 Bq· kg-1 in MB1 and 719.2 ± 3.5 Bq· kg-1 in MB2 that showed about 5% discrepancy compared to the certified activity. Besides, results obtained from 214Pb peak were 741.9 ± 3.6 Bq· kg-1 in MB1 and 740.1 ± 3.4 Bq· kg-1 in MB2 that showed about 2% difference compared to the certified activity measurement of 226Ra concentration activity.Conclusion: The results show that radon leakage correction was calculated with insignificant discrepancy to the certified values and provided improvement to the gamma spectrometry. Therefore, measuring 226Ra activity concentration in TENORM (technologically enhanced naturally occurring radioactive material) sample using radon leakage correction can be concluded as a convenient and accurate method that can be easily conducted with simple calculation.

Low Radon Cleanroom for Underground Laboratories.

Aim of a low radon cleanroom technology is to minimize at the same time radon, radon decay products concentration and aerosol concentration and to minimize deposition of radon decay products on the surfaces. The technology placed in a deep underground laboratory such as LSM Modane with suppressed muon flux and shielded against external gamma radiation and neutrons provides “Zero dose” space for basic research in radiobiology (validity of the LNT hypothesis for very low doses) and for the fabrication of nanoelectronic circuits to avoid undesirable “single event effects.” Two prototypes of a low radon cleanroom were built with the aim to achieve radon concentration lower than 100 mBq·m3 in an interior space where only radon-free air is delivered into the cleanroom technology from a radon trapping facility. The first prototype, built in the laboratory of SÚRO Prague, is equipped with a standard filter-ventilation system on the top of the cleanroom with improved leakproofness. In an experiment, radon concentration of some 50 mBq·m−3 was achieved with the filter-ventilation system switched out. However, it was not possible to seal the system of pipes and fans against negative-pressure air leakage into the cleanroom during a high volume ventilation with the rate of 3,500 m3·h−1. From that reason more sophisticated second prototype of the cleanroom designed in the LSM Modane uses the filter-ventilation system which is completely covered in a further improved leakproof sealed metal box placed on the top of the cleanroom. Preliminary experiments carried out in the SÚRO cleanroom with a high radon activity injection and intensive filter-ventilation (corresponding to room filtration rate every 13 s) showed extremely low radon decay products equilibrium factor of 0.002, the majority of activity being in the form of an “unattached fraction” (nanoparticles) of 218Po and a surface deposition rate of some 0.05 mBq·m−2·s−1 per Bq·m−3. Radon exhalation from persons may affect the radon concentration in a low radon interior space. Balance and time course of the radon exhalation from the human body is therefore discussed for persons that are about to enter the cleanroom.

A novel method based on 220Rn (thoron) exhalation rate of indoor surfaces for robust estimates of 220Rn concentration and equilibrium factor to compute inhalation dose

The research into 220Rn (thoron) has generated an increasing interest in recent times due to the realisation of its radiological importance in many indoor environments. Though it is assumed that the contribution of 220Rn, per se, to the inhalation dose is negligible in comparison with that of its decay products, this may not be always true. Correct estimation of inhalation dose due to thoron requires a reliable method to measure the concentration of both 220Rn and its decay products in indoor air. However, due to its very short half-life (55.6 s) 220Rn shows large variation in its indoor activity concentration. This makes it difficult to have a robust value of 220Rn concentration which can be considered representative of a house, thus making the dose estimation unreliable. This issue has been addressed in the present study by developing a novel method that utilises the 220Rn exhalation rate from indoor surfaces as the basis for estimation of average 220Rn concentration in indoor air. The 220Rn concentration estimated in this manner can be converted to decay products concentration using a suitable equilibrium factor and finally the inhalation dose using appropriate dose conversion factors. A wall mounting accumulator setup has been developed for easy in-situ measurement of 220Rn exhalation from room surfaces. The method has been validated through comprehensive measurements in 25 dwellings in two different regions of India. The developed method is very good for large scale field surveys because of fast and easy applicability.

RADON IN MINES OF KRYVYI RIH IRON ORE BASIN IN UKRAINE.

The first studies of radiation exposure in old mines of Kryvyi Rih Iron Ore Basin (Kryvbas) began relatively recently, about 20years ago. The results of these studies have shown that the problem of radon is present in the major part of the Basin mines. In 6 of 8 mines tested, an excess of radiation safety standards for the equilibrium equivalent decay products concentration (EEC) of Radon-222 was observed. According to the sum of the main measured parameters of radiation situation, a preliminary assessment of doses to underground workers was made and a classification of the Basin mines according to radiation danger was developed. Results of the recent radiation surveys of these mines are shown in this article. Data on the incidence of lung cancer among the miners are presented and classified into age groups. Measures to improve the radiation situation in the mines of Kryvbas are considered.

THE INFLUENCE OF THE EQUILIBRIUM FACTOR ON THE ESTIMATED ANNUAL EFFECTIVE DOSE FROM INHALED RADON DECAY PRODUCTS IN SELECTED WORKPLACES.

Measurements of activity concentration of radon gas and radon decay products were carried out in several workplaces including schools, radium spas, swimming pools, water treatment plants, caves and former mines. Based on these measurements, annual effective doses to workers were estimated and values of the equilibrium factor, F, were calculated. This paper describes the different approaches used to estimate the annual effective dose based on the dose coefficients recommended by the International Commission on Radiological Protection. Using the measured F values as opposed to the default F value of 0.4 changed the doses by about 5-95% depending mainly upon the ventilation conditions of the workplace.

A method for the simultaneous measurement of radon and thoron PAEC concentrations in air using a TLD monitor

The idea of using a device with thermo-luminescent detectors (TLD) for the simultaneous measurement of radon (Rn-222) and thoron (Rn-220) decay products’ concentrations was invented and developed in the Silesian Centre for Environmental Radioactivity at the Central Mining Institute, Katowice, Poland. The results of a preliminary analysis of the technical applicability, the required minimum period of air sampling and the optimised time schedule proved that such measurements can provide information about the potential alpha energy concentrations (PAECs) of radon and thoron decay products (TnDP).Following the analysis, preliminary measurements were performed at several locations—in a thoron chamber, in dwellings and even outdoors. Surprisingly, the maximum PAEC of the TnDP in the basement of a twin house in the Upper Silesia region was as high as 0.68 ± 0.15 µJ m−3. This paper presents the results of those measurements.

Statistical inferences from measured data on concentrations of naturally occurring radon, thoron, and decay products in Kumaun Himalayan belt.

Regional averages of radon, thoron, and associated decay product concentration are reported to be higher than their respective global averages in recent studies conducted in Indian Himalayan belt. The present study explores another region in Indian Himalayan belt by conducting measurements of radon, thoron, and decay product's activity concentration in 92 dwellings of Bageshwar district. The year-long measurements were performed in all 3 seasons distinguishing dwellings as per their construction material. The average radon and thoron concentration for the study region was measured as 57Bq/m3 and 66Bq/m3, respectively. Analysis of the measured data in terms of seasonal effects and construction material led to well established inferences, i.e., higher concentration for mud houses and for winter season. In addition, the present study focuses on lesser probed statistical inferences. One of them is related to the appropriateness of frequency distribution function for the measured data and other dwells upon the correlation analysis of inter-related factors for high concentration cases. Three distribution functions (Lognormal, Weibull, and Gamma) were found to be following the trend of frequency distribution curve of the measured data. For mud houses in winter season, variations of radon/thoron concentration were attempted to correlate with mass/surface exhalation rate, emanation rate, and source term content. More than 80% of the dwellings of the study region were found to have gas and decay product's concentration levels, higher than the respective global average values. However, these values were mostly within the reference levels for residential environments. Nevertheless, this region requires further studies to pinpoint the causes for elevated levels and suggest simple remedial modifications if required.

Response of an automatic air monitoring gamma-spectrometry station based on sample retention to rainfall-caused dosimetric alterations and to environments with a wide range of radon levels

An increase in ambient dose equivalent rate during precipitation events is a well known phenomenon that is easily identified by dose rate monitoring networks. Despite the invaluable information these monitors usually provide, they cannot identify the radioisotopes involved in these radiological alterations nor quantify their activity concentrations. Commercial systems based on passive gamma spectrometry using scintillation detectors allow to identify the radionuclides that increase during rainfall events but they cannot infer if they are deposited on ground or linked to the airborne particles. In 2016 an air monitoring station based on sample retention and scintillator gamma spectrometer was custom-designed and integrated into the automatic and quasi-real-time Radiological Alert Network of Extremadura (RARE) in south western Spain. In this work, it is presented how the capabilities of our system take advantage of the distinction between the radionuclides that are deposited and the radionuclides that are presented in airborne during rainy events.However, during the operation of RARE's homemade monitoring station based on sample retention and gamma-spectrometry, some shortcomings to meet the requirements appertained to real-time radiological networks, such as efficiency, were identified. Concretely, the station was targeted at monitoring the activity of gamma-emitting radioisotopes in airborne, but the relatively poor energy resolution of the gamma scintillation detectors employed meant that exceptionally high concentrations of radon decay products (such as 214Pb) in the area made it very difficult to identify and quantify the activity levels of some anthropogenic radioisotopes such as 131I, with there being a significant number of false positives and substantial increase in those isotopes' minimum detectable activities. This paper describes the simple approach that has been implemented in order to overcome the aforementioned analytical difficulty in situations where the activity concentration of radioiodine in air could be of the order of natural radon concentration, for example, when effluent releases from nuclear facilities permitted under authorities’ regulations.

Vertical distribution of 137Cs and natural radioactivity in core sediments of Thermaikos Gulf, northwestern Aegean Sea

Sub-superficial sediments have been collected from the Thermaikos Gulf, located in the NW Aegean Sea, in order to determine sedimentation rates using vertical distributions of 137Cs and 210Pb. In addition measurements of the characteristic radionuclides of the 238U and 232Th natural series has also been performed to better understand the transport and the sedimentation process in a marine environment, which is strongly influenced by the main North Greece rivers. The sedimentation rates of the five selected cores using the two methods were consistent and varied from 0.20 ± 0.01 till 0.30 ± 0.02 cm y-1. The mean sedimentation rates derived with both methods are enhanced during the last ten years compared to previous values at the studied region by one order of magnitude, due to human implications. The activity concentration of the 238U decay products does not exhibit variation along the depth. The activities of 226Ra are enhanced (~30 %) compared to the activities of radon daughters (214Pb, 214Bi) especially at the surface layer. The results of the correlation between 232Th decay products and 40K indicate that there is positive correlation between their averaged activities. The good proportionality between 232Th and 40K concentrations may be attributed to the fact that thorium is a particularly insoluble element in water.

Spatial and Temporal Variations of Indoor Airborne Radon Decay Product Dose Rate and Surface-Deposited Radon Decay Products in Homes.

The temporal variations of the airborne radon decay product dose rate and deposited radon decay product activities, as well as the within-house and house-to-house variations of radon concentrations, were evaluated through repeated field measurements. Long-term average radon and surface-deposited radon decay product concentrations were measured in 76 rooms of 38 houses. Temporal variation of radon, as well as airborne and surface-deposited radon decay products, were measured in 11 of the 38 houses during two different seasons. Environmental factors that have the potential to influence airborne dose rate and deposited radon decay products were also studied. Airborne dose rates were calculated from the unattached and attached potential alpha energy concentrations using two dosimetric models. For one model, the observed dose variations were 103%, 74%, 58%, and 60% for the total, house-to-house, within-house, and within-room temporal variations, respectively. For the other model, the dose variations were 100%, 66%, 61%, and 46%, respectively. Surface-deposited Po showed variations of 79%, 57%, 42%, and 48%, respectively. These substantial radon decay product concentration variations suggest that multiple locations and time-integrated measurements are needed to make an accurate assessment of the chronic radon-related doses in homes. Smoking was the environmental factor that had the largest temporal and spatial effect on airborne radon decay product dose rates.

Measurements of radon (222Rn) and thoron (220Rn) exhalations and their decay product concentrations at Indian Stations in Antarctica

During the 33rd summer expedition to the two Indian Stations at Antarctica, Bharati and Maitri, radon and thoron progeny concentrations in indoors and outdoors were measured along with radon (222Rn)/thoron (220Rn) exhalation rate measurements of soil samples, radionuclide content and 222Rn emanation coefficient. This investigation was based on the reports of the higher gamma radiation levels reported around these stations. The results will give an estimate of the radioactivity level as well as the total dose received by personnel carrying out long-term measurements at these stations. Radon and thoron progeny concentrations were measured using direct radon and thoron progeny sensors (DRPS and DTPS). The soil radionuclide content was measured using HPGe gamma spectrometry while radon/thoron exhalation rates were measured using the accumulation method by scintillation radon/thoron monitor. In contrast to a higher radiation field and radioactivity content, studies showed the radon/thoron exhalation rates and progeny concentration to be similar to that measured in normal background areas of other parts of the world. This could be attributed to the ice deposits and the larger atmospheric dispersion, and also to the soil nature which is mainly loamy sands with low clay content contributing to a lower emanation. The results are discussed.

Effect of Residential Radon Decay Product Dose Factor Variability on Reporting of Dose.

Guidelines for occupational exposure to radiation are based on annual absorbed or effective dose. Guidelines for Rn exposure are currently based on air concentrations of Rn or decay products. Models of bronchial dose from decay product exposure are based on calculations that have five major parameters with parameter variabilities ranging from 20 to 50%. Many countries currently use the ICRP dose conversion convention, which is a ratio of lifetime Rn lung cancer risk to lifetime atomic bomb dose risk. The results of ongoing epidemiology changed both lifetime risk values, and the dose conversion convention has increased by a factor of 2. Therefore, the current dose conversion convention risk ratio is to be replaced by biokinetic dosimetric models. The main effect of variability in the value of Rn dose factors on industry is that the workplace atmosphere must be characterized accurately, and at present, this is not possible. A history of the dose factor models is central to factor development. The values of the dose model parameters are described illustrating the difficulty in calculation of a dose factor with universal applicability. The objective is to show the range of each parameter and the effect of the dose factor used when reporting occupational or residential bronchial dose.