Radon Progeny Concentrations Research Articles

Estimation of radon progeny concentration based on track morphological parameters.

As the integrated measurements of radon progeny are essential to its risk assessment, a new method based on the morphological analysis of tracks on CR-39 was established for the discrimination of alpha particles emitted from different progenies. The preliminary experiment confirmed its feasibility and revealed its potential for application in long-term surveys of indoor radon progeny. This new attempt was expected be benefit to the improvement of integrated measurements of radon progeny.

Effective dose assessment due to inhalation of 222Rn, 220Rn, and their progeny: highlighting the major contribution of thoron in a thoron-prone area in Cameroon.

To assess public exposure to radon, thoron, and their progeny, measurements were conducted in 50 dwellings within the bauxite-rich area of Fongo-Tongo in western Cameroon. Passive integrating radon-thoron discriminative detectors (specifically RADUET) were employed for radon and thoron measurements. Additionally, concentrations of short-lived radon and thoron progeny were estimated using Direct Radon Progeny Sensors (DRPSs) and Direct Thoron Progeny Sensors (DTPSs) based on LR-115 detectors. The findings revealed indoor radon concentrations ranging from 31 to 123Bqm-3 with a geometric mean (GM) of 62Bqm-3, and indoor thoron concentrations ranging from 36 to 688Bqm-3 with a GM of 242Bqm-3. The Equilibrium Equivalent Radon Concentration (EERC) ranged from 3 to 86Bqm-3 with a GM of 25Bqm-3, while the Equilibrium Equivalent Thoron Concentration (EETC) ranged from 1.2 to 12.5Bqm-3 with a GM of 7.6Bqm-3. Notably, all dwellings recorded radon concentrations below 100Bqm-3. Arithmetic means of radon and thoron equilibrium factors were calculated as 0.47 and 0.04, respectively. To assess annual effective doses from radon and thoron inhalation, equilibrium factors were used along with direct measurements of EERC and EETC. The differences observed in annual effective doses were 4.5% for radon and 42.5% for thoron. Furthermore, the contribution of thoron and its decay products to the annual effective dose from radon, thoron, and their progeny ranged from 12 to 94%, with an average contribution of 58%. Thus, this study found that the effective dose due to thoron inhalation in the study area exceeded that due to radon inhalation. It is concluded that, when evaluating radiation doses and health risks, it is crucial to consider both thoron and its progeny alongside radon and its progeny. This underscores the importance of considering direct measurements for accurately estimating radiation doses.

Activity concentration of indoor radon and its short-lived progeny (218Po, 214Pb, and 214Po) and their effect on atmospheric ionization rate in Sana'a, Yemen

Exposure to ionizing radiation inside houses, especially radionuclides of radon and its progeny, poses serious health risks that can be exacerbated when inhaled as a result of interaction with human lung tissue. Also, air ionization is mainly due to these radionuclides. Therefore, accurate measurements of radon activity concentrations and its short-lived progeny are required to assess dose and environmental pollution and estimate ionization rates in indoor environments. For this purpose, we employed a previously tested and approved reliable method, following the three-count procedure. This method is based on airborne radon progeny sampling on polycarbonate membrane filters and alpha counting using a passive α-dosimetry technique with CR-39 detectors. The method also relies on a PC-based software we developed for solving mathematical equations and calculating all the necessary physical quantities. In this study, the concentrations of radon and individual short-lived radon progeny were measured in 20 houses in Sana'a, Yemen. Measurement conditions and meteorological variables were considered. The average activity concentrations of 222Rn, Equilibrium-Equivalent Concentration (EEC), 218Po, 214 Pb, and 214Po were 73.1 ± 6.0, 29.2 ± 2.4, 44.4 ± 3.6, 30.5 ± 2.5, and 23.2 ± 1.9 Bq.m-3, respectively. The calculated average unattached fractions f1(218Po), f2(214 Pb), and fp were found to be 0.24, 0.04, and 0.07 % respectively. The annual average values of ion-pair production rate caused by 222Rn and their progeny and air ion concentration, were 27.25 ions.cm-3s-1 and 1829 ions.cm-3 respectively. The annual effective dose was estimated to be 1.93 ± 0.16 mSv.y−1, well lower than the recommended 10 mSv.y−1.

Contribution of Thoron and Its Progeny to the Effective Dose by Inhalation in the Uranium-Thorium Bearing Regions of Mayo Kebbi and Guéra in Chad

Abstract In recent years, technological developments and hypotheses made by some researchers have revealed that the effective inhalation dose from thoron and its progeny was underestimated. This study uses direct measurements to show the significant contribution of thoron progeny to the effective inhalation dose. To achieve this, radon-thoron discriminative detectors (RADUET) and thoron progeny monitors were used for the simultaneous measurement of radon, thoron, and thoron progeny in 150 selected houses in the townships of Bitkine, Mongo, Léré, and Pala in southern Chad. By solid-state detection, concentrations of radon, thoron, and thoron progeny were measured and associated effective doses evaluated. The mean concentrations of radon, thoron, and thoron progeny were 62 (1), 60 (2), and 7.6 (2.1) Bq m−3, respectively. These concentrations are above the corresponding global average values. The equilibrium factor of the thoron varied considerably from one municipality to another. The average total annual effective dose by inhalation was estimated to be 4.23 mSv. The contribution of thoron and its progeny to the total inhalation dose ranged from 5% to 86% with an average of 62%. Considering the above, public exposure to thoron and its associated progeny is a public health concern in a similar way to radon.

Consequences of Violating Conditions of Counting Statistics Are Not Severe when Measuring Radon Progeny Concentrations with the Thomas and Kusnetz Methods.

When analyzing samples of radon progeny using the Thomas or Kusnetz methods, we violate one of the conditions of counting statistics because we use counting times that are not short compared with the half-lives of the radionuclides. The result is that we overestimate the uncertainties of the counts if we use counting statistics without correction. In this work, I describe the method by which I adjusted the values of variance of the counts theoretically to values that are more accurate and calculated the amounts by which I overestimate the values of counting uncertainty by using counting statistics without correction. These values are surprisingly small: 4-5% for the Thomas method and 2-3% for the Kusnetz method. Now, I can correct uncertainty values of radon progeny measurements if it is appropriate to do so. The detailed calculations I present here may be used for determining corrections to the counting uncertainty for a method for measuring radon progeny concentration using different sampling and/or counting times than those described here. Further, they may be used for any sample, not necessarily radon progeny, that requires a long counting time to acquire a significant number of observed counts.

Simultaneous measurements of radon, thoron and thoron progeny and induced cancer risk assessment in Djeno, Pointe-Noire, Republic of Congo.

In this study, the activity concentrations of radon (222Rn), thoron (220Rn) and thoron progeny were measured simultaneously in Djeno (Pointe-Noire, Republic of Congo) using RADUET detectors to evaluate the air quality and the radiological risks due to the inhalation of these radionuclides. Activity concentrations of radon progeny were calculated from those of radon. Indoor radon, thoron and progenies followed a lognormal distribution ranging between 20 and 40, 6 and 62, 8 and 17.6 and 0.4 and 19.6Bqm-3 for radon, thoron, radon progeny and thoron progeny, respectively. Mean values for radon were lower than the worldwide values estimated by the United Nation Scientific Committee on the Effects of Atomic Radiation (UNSCEAR), which are 40Bqm-3 (arithmetic mean) and 45Bqm-3 (geometric mean). Radon concentrations in the dwellings under study were below the World Health Organization and the International Commission on Radiological Protection recommended reference levels, which are, respectively, 100 and 300Bqm-3. The mean concentration of thoron was twice the world average value of 10Bqm-3 estimated by UNSCEAR. Thoron progeny mean concentration was sharply greater than the typical value (0.3Bqm-3) for indoor atmosphere provided by UNSCEAR. Annual effective dose ranges were 0.40-0.87mSv (arithmetic mean, 0.57±0.11mSv) for radon and 0.10-4.14mSv (arithmetic mean, 0.55±0.77mSv) for thoron. The mean value for radon was lower than the value (1.15mSv) estimated by UNSCEAR, while the mean value for thoron was five times higher than the UNSCEAR value (0.10mSv). The study showed that the use of the typical equilibrium factor value given by UNSCEAR to compute effective dose led to an error above 80%. Finally, the results of this study showed that the excess relative risk of radon-induced cancer was low, below 2% for the population under 55y. The results presented in the present study prove that the population of Djeno is exposed to a relatively low potential risk of radon- and thoron-induced cancer.

Comparative studies on radon seasonal variations in various undeground environments: Cases of abandoned Beshtaugorskiy uranium mine and Kungur Ice Cave

It is well known that one of the most important risk factors in underground environment is the harmful effects of radon. The reasons for strong seasonal fluctuations in radon content in underground environments remain not fully understood. The purpose of this article is to improve existing ideas about this phenomenon. The article presents the results of a study of radon transport in two different underground spaces – the Beshtaugorskiy uranium mine (North Caucasus) and the Kungur Ice Cave (Middle Ural). We have used the direct measurements of the equilibrium equivalent concentration (EEC) of radon progeny in air, as well as the air flow velocity. A very wide range and strong seasonal variations in the radon levels have been recorded in both cases. The EEC has a range of 11–6653 by Bq m−3 and 10–89,020 Bq m−3 in the Kungur cave and the Beshtaugorskiy mine, respectively. It has been established that seasonal fluctuations in radon levels both in the mine and in the cave are caused by the same process – convective air circulation in the underground space due to the temperature difference between the mountain massif and the atmosphere (so called chimney effect). Overall, these results indicate that due to convective air circulation, underground spaces are periodically intensively ventilated with atmospheric air, and then, on the contrary, they are filled with radon-enriched air that seeps into caves or adits from rocks and ores. In both cases, the EEC of radon progeny exceeds the permissible level for the population and workers. The results of this study highlight the need for the development of measures to limit the presence of people in the surveyed underground spaces.

Assessment of Radiological Risks due to Indoor Radon, Thoron and Progeny, and Soil Gas Radon in Thorium-Bearing Areas of the Centre and South Regions of Cameroon

Indoor radon, thoron and thoron progeny concentrations, along with the equilibrium factor for thoron progeny and soil gas radon concentrations, have been measured to assess radiological risks in the centre and south regions of Cameroon. Indoor radon and thoron concentrations were estimated using radon–thoron discriminative detectors (RADUET), while thoron progeny monitors measured the equilibrium equivalent thoron concentration (EETC). Radon concentrations in the soil were determined using a MARKUS 10 detector. It was found that radon, thoron and thoron progeny concentrations range between 19 and 62 Bq m−3, 10 and 394 Bq m−3 and 0.05 and 21.8 Bq m−3, with geometric means of 32 Bq m−3, 98 Bq m−3 and 4.9 Bq m−3, respectively. The thoron equilibrium factor ranges between 0.007 and 0.24, with an arithmetic mean of 0.06 ± 0.03; this is higher than the world average value of 0.02 provided by the United Nations Scientific Commission on the Effects of Atomic Radiation(UNSCEAR, New York, USA). The level of the soil radon concentration ranges from 4.8 to 57.3 kBq m−3, with a geometric mean of 12.1 kBq m−3 at a depth of 0.7 m. Of the sampling points, 66% fall within normal radon risk areas, and 3% of the sampling areas are high radon risk areas exceeding 50 kBq m−3. The annual effective dose was found to be 0.03 ± 0.01 mSv for radon, 0.08 ± 0.05 mSv for thoron, 0.63 ± 0.12 mSv for radon progeny and 1.40 ± 0.84 mSv for thoron progeny. The total dose is estimated to be 2.14 mSv y−1. The mean estimated indoor excess lifetime cancer risk values due to radon, thoron, radon progeny and thoron progeny are 0.12 × 10−3, 0.31 × 10−3, 2.51 × 10−3 and 5.58 × 10−3, respectively. Thoron progeny contributed 60% to the effective dose. Thus, thoron progeny cannot be neglected in dose assessments, in order to avoid biased results in radio-epidemiological studies.

Number and size distribution of aerosols, and diurnal variation of radon progeny concentration during festival fireworks in Madikeri Town, Karnataka, India

Aerosol particles, their size, and number distribution play a key role as they affect the climate, quality of the air, and human health. In the present work, the distribution of aerosol particles was studied using the NanoScan SMPS (TSI 3910) during Deepawali, a festival of lights, at three locations in Madikeri town, Karnataka, India, and the diurnal variation of radon and its progeny was studied at one location. People celebrate this festival by bursting crackers and lighting lamps, which increases aerosol particles leading to pollution of air. The observation showed an increase of nucleation particles of size 11.5 nm and 15.4 nm during this period. The average number of nucleation, Aitken, and accumulation particles at L1 was 48.86, 30.98, and 19.31 cm−3; at L2 was 37.44, 26.75 and 16.21 cm−3; and at L3 was 29.88, 19.95, and 15.192 cm−3. During the study period, the average concentration of 222Rn at L1 was found to be 19.54 Bq m−3. The diurnal studies at L1 showed 222Rn and its progeny to be higher during early morning and late evening hours, whereas lower during daytime. The radon progeny were observed to be lower during the festive period compared to other days, which may be attributed to the increased ion-aerosol recombination processes. The average concentrations of 218Po, 214Pb and 214Po at L1 before and during the festival were 3.06, 1.61, and 1.52 Bq m−3; and 2.09, 0.55, and 0.53 Bq m−3, respectively.

INVESTIGATION OF ENVIRONMENTAL RADIOACTIVITY AT A DECOMMISSIONED URANIUM MINE IN SOUTHERN CHINA.

An environmental radioactivity survey was performed on a uranium mine that has been decommissioned for >10 y. According to the characteristics of this uranium mine, the relevant parameters, such as the surface-absorbed dose rate in air, the radon and radon progeny concentrations in the air, the radon exhalation rate from the soil surface and the concentrations of natural radionuclides in soil and surface water, were measured. The results show that the maximum annual effective doses of residents and employees in the uranium mine caused by radon and radon progenies inhalation were 1.48 and 1.74mSv, respectively, and the maximum annual effective doses of residents and employees caused by gamma-ray external radiation were 1.16 and 1.32mSv, respectively.

Radiological dose estimation due to exposure to attached and unattached fractions of radon and thoron progeny concentrations

Radiological dose estimation due to exposure to attached and unattached fractions of radon and thoron progeny concentrations

Corrections to Kusnetz method for measurements of radon progeny concentrations in air

In 1956, H.L. Kusnetz proposed a quick method for radon progeny concentration measurement in mine atmosphere using a single gross-alpha count of a membrane-filtered air. The method is still widely used today and is based on a number of impractical assumptions. An instantaneous sampling time (less than ten seconds), is one of these assumptions that ignores the build-up and decay of the progeny on the filter paper during the sampling period, which is typically in the order of a few minutes. Of special concern is the 214Bi decay during the sampling period, since 214Po's alphas are lost during the sampling time and cannot be accounted for during the counting time. In addition, the method assumes that 214Bi activity during the counting period is constant. This inaccurate assumption can result in a smaller count rate, especially when counting times are long. Hence, underestimated working levels are expected when using Kusnetz factors without correcting for the sampling and counting times. In this technical report, exact sampling and counting time corrections to the method are provided along with the updated Kusnetz factors that correspond to common equilibrium conditions to correctly estimate the Working Level in air. Additionally, time corrections to the commonly used self-absorption correction formula and the lower level of detectability (LLD) equation used for any sample measurement are given.

Rapid determination of radon progeny concentration based on artificial neural networks

Rapid determination of radon progeny concentration based on artificial neural networks

Estimation of unattached and aerosol-attached activities of airborne short-lived radon progeny in indoor environments

Inhalation of the airborne short-lived radon progeny is regarded as the most crucial way of internal exposure to the natural radiation dose delivered to the human lung. In this respect, this study aims to determine the unattached and aerosol-attached activities of radon progeny and to estimate some important physical parameters employed to assess the radiological impact of this radiation on humans. For this purpose, radioactive aerosol samples collected on polycarbonate membrane filters to measure total alpha activity by passive alpha dosimetric technique using CR-39 detectors in sixteen different locations including some houses and workplaces in El Jadida city, in Morocco. In addition, the room-specific parameters and aerosol physical processes that affect the unattached and attached activity concentrations were determined. The obtained experimental results by the three-count method and room model parameters were used as input data on a developed PC-based software that we have developed to solve mathematical equations and calculate required physical quantities. Accordingly, the individual activities of radon progeny namely 218Po, 214Pb, and 214Po as well as radon activity concentration were determined. Simultaneously, the unattached and aerosol-attached activity concentrations (Cju and Cja) of radon progeny were calculated based on the room model calculation. Consequently, some radiological quantities used in the calculation of the lung dose were estimated. The results showed that the indoor radon activity concentration in different targeted locations ranges between 38 and 143 Bq. m−3 with an average value of 84.8 ± 9.5 Bq. m−3. The average obtained values of the equilibrium-equivalent concentration (Ceq), unattached fraction (fp), and equilibrium factor (F) at low and good ventilation rates change respectively from (24 Bq. m−3, 0.08, and 0.25) to (34 Bq. m−3, 0.02, and 0.41). Under normal environmental conditions, the average obtained values of Ceq, fp, and F, in houses and at workplaces were (17 Bq. m−3, 0.07, and 0.25) and (32 Bq. m−3, 0.04, and 0.35) respectively. Depending on the different aerosol conditions and obtained values of unattached fraction fp, the calculated average values of dose conversion factors (DCFs) were 8.70 mSv.WLM−1 and 11 mSv.WLM−1 in houses and workplaces respectively. These values were in good agreement with the recommended values by ICRP, which are in the order of 9 mSv.WLM−1 and 12 mSv.WLM−1 for houses and workplaces respectively.

Optimized method for individual radon progeny measurement based on alpha spectrometry following the Wicke method

Accurate measurement of individual short-lived radon progeny concentrations is very important for dose evaluation and related researches taking radon progeny as radioactive tracers. Different methods have been developed, but higher methodological sensitivity is needed for field measurement under the limitation of size, weight and power consumption of the instrument. For the purpose of developing new measurement method with higher sensitivity, an optimized method based on alpha spectrometry following the Wicke method (Wicke, 1979) is demonstrated, which shortens the measurement cycle to 60 min and make it more suitable for field measurement. For comparison, a series of verification experiments were carried out, and the methodological sensitivity and uncertainty were analyzed in detail in this paper. Results show that the optimized Wicke method can give accurate individual radon progeny concentrations and equilibrium equivalent concentration (EEC) in different environments. The deviation between EEC measured by the optimized Wicke method and the original Wicke method is less than ±2.9%, and the deviation between the optimized Wicke method and the Kerr method is less than ±3.9% in different environment. The methodological sensitivity of the optimized Wicke method is nearly the same as the original method with a much shorter measurement cycle, and 4.3 times higher than that of the Kerr method, which lowers the measurement uncertainty especially in the actual environment.

Exposure to Radon and Progeny in a Tourist Cavern.

The primary objective of this work was to characterize employee exposure to radon and progeny while performing guide/interpretation and concessions duties in a tourist cavern. Radon gas and progeny concentrations, fraction of unattached progeny, and other environmental parameters were evaluated in a popular tourist cavern in Southeastern New Mexico. Alpha-track detectors were used to measure radon gas in several cavern locations during a 9-mo period. Additionally, radon gas and attached and unattached fractions of radon progeny were measured at three primary cavern work locations during a 1-d period using a SARAD EQF 3220. Radon gas concentrations in the cavern were elevated due to extremely low air exchange rates with substantial seasonal variation. Mean measured radon concentrations ranged from 970 to 2,600 Bq m-3 in the main cavern and from 5,400 to 6,000 Bq m-3 in a smaller cave associated with the regional cave system. Measurements of unattached fractions (0.40-0.60) were higher than those commonly found in mines and other workplaces, leading to the potential for relatively high worker dose. Although radon gas concentrations were below the Occupational Safety and Health Administration Permissible Exposure Limit, employees working in the cavern have the potential to accrue ionizing radiation dose in excess of the annual effective dose limit recommended by the National Council on Radiation Protection and Measurements due to a high unattached fraction of radon progeny. There was a strong negative correlation between unattached fractions and equilibrium factors, but these parameters should be further evaluated for seasonal variation. Introduction of engineering controls such as ventilation could damage the cavern environment, so administrative controls, such as time management, are preferred to reduce employee dose.

One-Year Continuous Measurement of Outdoor Radon Progeny Concentration in Beijing Area

Background: Compared with reported data of radon concentration, data of radon progeny concentration is limited in general, especially in outdoor environment. Materials and Methods: To know both the level and the variation of radon progeny concentration in outdoor environment in Beijing area, one-year continuous measurement with a cycle of 60 minutes was carried out by a step-advanced filter (SAF) monitor for radon progeny measurement. The observation site was located in a park in Eastern Beijing area, and the observation period was from October 17, 2018 to September 29, 2019. Results and Discussion: The equivalent equilibrium concentration (EEC) of radon progeny varies from 0.7 to 19.1 Bq·m-3, with an annual average of 4.9 ± 2.7 Bq·m-3. A clear diurnal variation of EEC, higher in the early morning and lower in the late afternoon, is observed due to the high sensitivity of the SAF monitor. Conclusion: Vertical convection of atmospheric boundary layer is thought to be the main reason of this phenomenon. For annual variation, the lowest monthly average EEC appeared in April, while the highest appeared in November, which might attribute to the atmospheric stability in different seasons.

Measurements of 222Rn, 220Rn and their progeny concentrations indoors around a coal/gas-based power plant and estimation of annual inhalation dose to the public

In the present study, indoor radon (222Rn), thoron (220Rn), radon progeny (214Po) and thoron progeny (212Po) activity concentration have been measured in a region around the National Capital Power Station, Dadri, Uttar Pradesh, India. The mean values of the 222Rn, 220Rn and their progeny in the studied region are found to be 22.1 ± 10.0 Bqm−3, 48.6 ± 13.5 Bqm−3, 8.8 ± 4.8 Bqm−3 and 0.49 ± 0.15Bqm−3 respectively. The annual inhalation dose estimated from the observed concentrations varies from 0.29 ± 0.04 to 2.06 ± 0.121 mSv with a mean value of 0.75 ± 0.32 mSv and is well within the reference level. It has also been observed that 212Po is a significant contributor (= 18.7%) to the total annual inhalation dose. Seasonal variations of 222Rn, 220Rn, and their progeny have also been reported.

Comparison measurement of unattached radon progeny concentration in three different environments

Accurate measurement of unattached radon progeny is important for dose evaluation of radon exposure. For quality control of field surveys, a series of comparison measurements were carried out using three commercial unattached radon progeny monitors in real environments as well as in a radon chamber. The results show that the radon equilibrium equivalent concentrations (EECs) of different monitors agree very well, mostly within ±3.0% where there is no thoron progeny interference in the radon chamber. However, the unattached fraction of radon progeny is not so consistent, and the relative difference is 3.3% ~ 39.5% in different environments. The unattached fraction of radon progeny is affected by aerosol concentration. Anomalously high unattached fraction was found in the environment with extremely high humidity and low aerosol concentration. For accurate measurement of unattached radon progeny, specific attention should be paid to the collection efficiency of unattached radon progeny and the interference of attached radon progeny on a wire screen.

Exposures from radon, thoron, and thoron progeny in high background radiation area in Takandeang, Mamuju, Indonesia

Abstract The exposure from radon, thoron, and thoron progeny was measured for 45 dwellings in high background radiation area in Takandeang, Indonesia with ambient dose equivalent rate ranging from 0.34 μSv h−1 to 1.90 μSv h−1. The measurement was taken using passive radon and thoron discriminative detector and thoron progeny detector. This measurement was taken from November 2018 to October 2019, and within one month the detector would be replaced with a new detector. The concentrations of radon, thoron, and thoron progeny were calculated as 42–490 Bq m−3, 20–618 Bq m−3, and 4–40 Bq m−3, respectively. The concentrations for outdoor were 49–435 Bq m−3, 23–457 Bq m−3, and 4–37 Bq m−3, respectively, and the annual effective dose was 9.8–28.6 mSv y−1. Based on the result of Spearman’s correlations analysis between the indoor radon and thoron concentrations and between the indoor thoron progeny and thoron concentrations, we suggest that exposure to thoron cannot be predicted from exposure to radon, and the equilibrium equivalent thoron concentration has a large uncertainty when it is estimated from thoron concentration assuming a single thoron equilibrium factor.