Radon Daughter Products Research Articles

Measurement of the {}^{212}{mathrm{Po}}, ^{214}hbox {{Po}} and ^{212}hbox {{Pb}} half-life time with Timepix3

The half-life times of the relatively short-lived alpha -decaying isotopes ^{212}hbox {{Po}} and ^{214}hbox {{Po}} were measured with a hybrid pixel detector of Timepix3 technology. Radon daughter products were collected at the backside of a 1 mm thick silicon sensor so that subsequent decays inject the polonium isotopes of interest shallowly into the backside of the sensor. The detector’s high spatial and time resolution allow for particle identification and application of the delayed coincidence technique with low systematic uncertainty even at high rates. We find t_{1/2}^{^{212}{hbox {Po}}} = ( 295.02 pm 0.18{_{mathrm{stat.}}} pm 0.17_{mathrm{syst.}} ),hbox {ns} and t_{1/2}^{{}^{214}mathrm{Po}} = ( 163.64 pm 0.038{_{mathrm{stat.}}} pm 0.093_{mathrm{syst.}} ),upmu hbox {s}. Studying the decay of the accumulated radon daughter products after removing the detector from the ^{220}hbox {{Rn}} field, the half-life time of the beta -decay of ^{212}hbox {{Pb}} was measured to be t_{1/2}^{^{212}{mathrm{Pb}}} = ( 10.620 pm 0.011_{mathrm{stat.}} pm 0.014_{mathrm{syst.}} ),hbox {h}. The results are discussed in the context of previous works.

Rainfall Intensity and Quantity Estimation Method Based on Gamma-Dose Rate Monitoring

The features of the atmospheric -background reaction to liquid atmospheric precipitation in the form of bursts is investigated, and various forms of them are analyzed. A method is described for interpreting forms of the measured -background response with the determination of the beginning and ending time of precipitation, the distinctive features of changes in the intensity of precipitation and the number of single (separate) events that form one burst. It is revealed that a change in the intensity of precipitation in one event leads to a change in the -radiation dose rate increase speed (time derivative). A method of estimating the average value of the intensity and amount of precipitation for one event, reconstructing the intensity spectrum from experimental data on the dynamics of the measured dose rate of -radiation, is developed. The method takes into account the radioactive decay of radon daughter products in the atmosphere and on the soil surface during precipitation, as well as the purification of the atmosphere from radionuclides. Recommendations are given for using the developed method to correct for changes (daily variations) in radon flux density from the ground surface, which lead to variations in radon in the atmosphere. Experimental verification of the method shows good agreement between the values of the intensity of liquid atmospheric precipitation, calculated and measured with the help of shuttle and optical rain precipitation gauges.

Hygienic assessment of learning environment conditions (by the example of higher educational institutions of the city of Ufa)

Introduction. The important factors affecting health and performance of young people are the conditions of education, in particular, a comfortable microclimate in the classrooms of higher educational institutions. Materials and methods. In view of the urgency of this problem, an analysis was made of the microclimate parameters of educational organizations of different profiles (Ufa city, the Republic of Bashkortostan). 294 classrooms were studied in 22 buildings of 4 leading universities in Ufa. A total of 3,822 measurements were taken to determine the parameters of the microclimate. The analysis of ionizing radiation in the aerial environment of classrooms. There was performed determination of radon and its affiliated products content. In order to assess the conditions and lifestyle of students of 4 higher educational institutions of the city of Ufa, we conducted an anonymous survey of 1,820 students of I and IV years of education. Results. The average temperature in the classrooms of all universities studied was 23.9±0.09 C. The average relative humidity in all classrooms was 34.2 ± 0.42%. Analysis of ionizing radiation (radon and its daughter products decay) in the aerial environment of the classrooms and sports halls located in the basement determined that the average annual equivalent equilibrium volumetric activity of the radon daughter products (EROA ± Δ222Rn) ranged from 28 ± 14 to 69 ± 34.5 meter, which meets the requirements established by SanPiN. Conclusion. The hygienic assessment of the microclimate parameters of educational institutions of various profile revealed a number of deviations from the regulated norms. The results indicate the need to control the parameters of the microclimate, both from the administration of universities, and from the professors. According to the results of the study, recommendations were prepared for the management of higher educational institutions in Ufa.

Hygienic assessment of learning environment conditions (by the example of higher educational institutions of the city of Ufa)

Introduction. The important factors affecting health and performance of young people are the conditions of education, in particular, a comfortable microclimate in the classrooms of higher educational institutions. Materials and methods. In view of the urgency of this problem, an analysis was made of the microclimate parameters of educational organizations of different profiles (Ufa city, the Republic of Bashkortostan). 294 classrooms were studied in 22 buildings of 4 leading universities in Ufa. A total of 3,822 measurements were taken to determine the parameters of the microclimate. The analysis of ionizing radiation in the aerial environment of classrooms. There was performed determination of radon and its affiliated products content. In order to assess the conditions and lifestyle of students of 4 higher educational institutions of the city of Ufa, we conducted an anonymous survey of 1,820 students of I and IV years of education. Results. The average temperature in the classrooms of all universities studied was 23.9±0.09 C. The average relative humidity in all classrooms was 34.2 ± 0.42%. Analysis of ionizing radiation (radon and its daughter products decay) in the aerial environment of the classrooms and sports halls located in the basement determined that the average annual equivalent equilibrium volumetric activity of the radon daughter products (EROA ± Δ222Rn) ranged from 28 ± 14 to 69 ± 34.5 meter, which meets the requirements established by SanPiN. Conclusion. The hygienic assessment of the microclimate parameters of educational institutions of various profile revealed a number of deviations from the regulated norms. The results indicate the need to control the parameters of the microclimate, both from the administration of universities, and from the professors. According to the results of the study, recommendations were prepared for the management of higher educational institutions in Ufa.

Use of threshold-specific energy model for the prediction of effects of smoking and radon exposure on the risk of lung cancer

Lung cancer is the leading cause of cancer death in both men and women. Smoking causes 80-90% of cases of lung cancer. In this study, an attempt was made to assess the impact of cigarette smoking on the risk of lung cancer by the so-called threshold-specific energy model. This model allows to analyse the biological effects of radon daughter products on the lung tissue, and is based on the assumption that the biological effect (i.e. cell inactivation) will manifest itself after the threshold-specific energy z0 deposited in the sensitive volume of the cell is exceeded. Cigarette smoking causes, among others, an increase in the synthesis of the survivin protein that protects cells from apoptosis and thereby reduces their radiosensitivity. Based on these facts, an attempt was made to estimate the shape of the curves describing the increase in the oncological effect of radiation as a function of daily cigarette consumption.

Radiological impact of phosphate fertilizers on the agricultural areas in Iran

It is common practice to use phosphate fertilizers in the soil to raise crop yield. Natural Radionuclides present in fertilizers are sources of external and internal radiation exposure. External radiation exposure is caused by gamma radiation originating from radionuclides in situ. Internal radiation exposure, mainly affecting the respiratory tract, is due to short-lived daughter products of radon which are exhaled from fertilizers. This paper describes the results of gamma spectrometric measurement of the concentration of the natural radionuclides namely 226 Ra, thorium-232 and potassium-40 in the soil samples from the fields using phosphate fertilizers. The radon concentration and exhalation rate have also been discussed. The values of outdoor annual effective dose are found to vary from 0.07 to 0.09 mSv/year in soil samples containing fertilizers, whereas the outdoor annual effective dose is 0.06 mSv/year in barren soil samples.

Measurement of radon diffusion in polyethylene based on alpha detection

Radon diffusion in different materials has been measured in the past. Usually the diffusion measurements are based on a direct determination of the amount of radon that diffuses through a thin layer of material. Here we present a method based on the measurement of the radon daughter products which are deposited inside the material. Looking at the decay of 210Po allows us to directly measure the exponential diffusion profile characterized by the diffusion length. In addition we can determine the solubility of radon in PE. We also describe a second method to determine the diffusion constant based on the short-lived radon daughter products 218Po and 214Po, using the identical experimental setup. Measurements for regular polyethylene (PE) and High Molecular Weight Polyethylene (HMWPE) yielded diffusion lengths of (1.3±0.3) mm and (0.8±0.2) mm and solubilities of 0.5±0.1 and 0.7±0.2, respectively, for the first method; the diffusion lengths extracted from the second method are noticeably larger which may be caused by different experimental conditions during diffusion.

Analysis and risk estimates to workers of Brazilian granitic industries and sandblasters exposed to respirable crystalline silica and natural radionuclides

Occupational exposure to respirable crystalline silica and to radiation emitted by natural radionuclides present both in rocks and sands was studied in the Brazilian extractive process and granite product manufacture. Respirable airborne dust samples were collected in working environments, where workers perform different tasks with distinct commercial granites types, and also in places where sandblasters work with sands from different origins. The free crystalline silica contents were determined using X-ray diffraction of the respirable particulate fraction of each sample. Dust samples from granite cutting and sandblasting ambient had the natural radionuclides concentrations measured by gamma spectrometry. Dust concentrations in the workplaces were quite variable, reaching values up to 10 times higher than the respirable particle mass threshold limit value (TLV) set by the American Conference for Governmental Industrial Hygienists of 3 mg m −3 . Also the free crystalline silica concentrations were high, reaching values up to 48 times the TLV of 0.025 mg m −3 . Additionally, our results suggest that the risk of radiation-induced cancer in the granite or marble industries is negligible. However, the combined exposure to dust, gamma radiation, and radon daughter products could result in the enhancement of lung cancer risks associated to sandblasting activities.

Radon exhalation rates from zircon sands and ceramic tiles in Italy

Naturally occurring radionuclides in building materials are sources of external and internal exposure in dwellings. External radiation exposure is caused by the gamma radiation originating from members of uranium and thorium decay chain and from 40 K. Internal radiation exposure, mainly affecting the respiratory tract, is due to the short-lived daughter products of radon which are exhaled from building materials into room air. The objective of this study is to measure the radon exhalation rates from zircon materials, flours and sands, used as raw materials in the porous fired tiles body and from the final products (porcelain tiles usually commercialized in Italy). The radon exhalation rates for the zircon flours and sands ranged from 0.17 to 1.9 Bq kg-1 h-1 , and from 0.090 to 0.20 Bq kg-1 h-1 ; 222 Rn exhalation rates for most of the porcelain stoneware tiles are near or below the minimum detectable limit (LLD) of 0.0004 Bq kg-1 h-1 .

Measurement of natural radioactivity and radon exhalation rate from rock samples of Jaduguda uranium mines and its radiological implications

The Singhbhum shear zone is a 200km long arcuate belt in Jharkhand state situated in eastern India. The central part between Jaduguda–Bhatin–Nimdih, Narwapahr–Garadih–Turamdih is rich in uranium. Presence of uranium in the host rocks and the prevalence of a confined atmosphere within mines could result in enhanced concentration of radon (222Rn) gas and its progeny. Inhalation of radon daughter products is a major contributor to the radiation dose to exposed subjects. By using high resolution γ-ray spectroscopic system various radionuclides in the rock samples, collected from different places of Jaduguda uranium mines have been identified quantitatively based on the characteristic spectral peaks. The activity concentrations of the natural radionuclides, uranium (238U), thorium (232Th) and potassium (40K) were measured in the rock samples and radiological parameters were calculated. Uranium concentration was found to vary from 123±7Bqkg−1 to 40,858±174Bqkg−1. Activity of thorium was not significant in the samples, whereas, few samples have shown potassium activity from 162±11Bqkg−1 to 9024±189Bqkg−1. Radon exhalation rates from these samples were also measured using “Sealed Can technique” and found to vary from 4.2±0.05 to 13.7±0.08 Bq m−2h−1. A positive correlation was found between the radon exhalation rate and the uranium activity. The absorbed dose rates vary from 63.6 to 18876.4nGyh−1, with an average value of 7054.2nGyh−1. The annual external effective dose rates vary from 0.7 to 23.2mSvy−1. Radium equivalent activities (Raeq) varied from 134.3 to 40858.0Bqkg−1. Value of external hazard index (Hex) varied from 0.4 to 110.4 with an average value of 41.2.

Radon Effects in Ground Gamma-ray Spectrometric Surveys

The effect of emanation radon is shown to be a significant problem for estimating uranium concentration from ground-based gamma-ray spectrometric surveys. Radon gas (a daughter product in the U238 decay series) escapes from rocks and soils near the Earth's surface into the lower atmosphere. Under early morning, still-air conditions, radon concentrates as a thin layer near the Earth's surface. If ground radiometric surveying is undertaken before this radon layer is mixed into the lower atmosphere, large errors in U concentration estimates result.This paper shows the effect of early-morning radon accumulation on a gamma-ray spectrometric survey near Boorowa, NSW. Paddocks surveyed in the early morning show much higher apparent uranium concentrations than those surveyed later in the day. We demonstrate the radon diurnal effect by monitoring the equivalent U concentration at a fixed site over several weeks. Typically, there is a build-up of radon near the Earth's surface overnight. Radon concentration reaches a maximum at about one hour after sunrise, before slowly dispersing over a period of 2-3 hours. By reporting both the Boorowa survey and the radon monitoring results in the same units of equivalent uranium concentration, we demonstrate that the anomalous effects seen in the Boorowa survey are consistent with that of a radon diurnal.The monitoring data also show the effect of rainfall on apparent U concentrations. Rain deposits radioactive daughter products of atmospheric radon onto the ground, resulting in a significant increase in apparent U concentration. These short-lived daughter products decay to insignificant concentrations within about 3 hours. Ground surveys should not be conducted during or within 3 hours of the cessation of rain, or under early-morning, still-air conditions. Also, because high moisture concentrations in soil reduces the gamma-ray fluence rate at the Earth's surface, surveys should not be conducted after prolonged or heavy rainfall where the soil profile is saturated.

Radon and thoron progeny levels in air samples at Udagamandalam region of Nilgiris in India

Measurement of concentration of radon and thoron daughter products in various indoor environment covering four seasons of a year in Udagamandalam Taluk of Nilgiris biosphere has been carried out using a high volume air sampler to asses the inhalation dose to the population which delivers higher dose than the radon and thoron gas alone. The potential alpha-energy concentrations of the radon and thoron progeny ranged from 0.97 to 12.72 mWL and from 1.63 to 15.83 mWL with a geometric mean of 6.02 and 7.89 mWL, respectively, taking all seasons into account. These measurements have yielded a wealth of data on the variation among the indoor radon and thoron progeny in various places during different seasons. The radon and thoron progeny levels are higher in winter seasons and are less in summer season with autumn and spring data lie in between winter and summer. Using the dose conversion factor for indoor exposures given in UNSCEAR 93 report the internal equivalent dose to the inhalation of radon progeny is evaluated to be 1357 mSv.y–1 and the corresponding annual effective dose equivalent value has been found to be 2.13 mSv.y–1. It can be observed that the mean value of radon is higher than the Indian average. Also it is found the radon and thoron progeny levels are higher in the case of houses built with rock and granite and in tiled type houses of nearly 100 years old. The levels are less in the case of houses built with brick and cement. The observed results for different types of houses and seasons are discussed in this paper.

Measurement of Mobility of Radioactive Air Ions in Atmosphere

A method for measuring the mobility of radon daughter products, 218Po, in gas medium is described. The mobility of the daughter products was measured using the flow-through technique of air ion detection. The flow-through technique is based on precipitation of ions from Rn-containing air flow on the surface of a semiconductor detector. Precipitation occurs in an electrostatic field of a plane capacitor. Upon precipitation, alpha radiation of 218Po is detected. The dependence of ion mobility on the absolute humidity of air was determined (the age of ions was about 1 s). It was shown that, within a range of humidity from 3.4 to 13.6 g/m3, this dependence is negligible. The mean mobility of 218Po was found to be 1.05 ± 0.05 cm2/(sV).

Monitoring Radioactive Aerosols in the Object “Cover”

The results of an investigation of aerosols in the rooms of the object “Cover” at the Chernobyl nuclear power plant in November–December 2000 are presented. Using packets of Petryanov three-layer filtering materials, the dynamics of the volume activity of the products of the accident in the No. 4 unit and the daughter products of radon and thoron is traced, and the size of the carrier particles in room 207/5 is determined. It is shown that the 137Cs concentration varied from 0.2 to 20 Bq/m3. The median aerodynamic diameter of carrier particles ranged from 0.5 to 6 μm for 137Cs and from 0.08 to 0.8 μm for the daughter products of radon. The sources of the coarsely dispersed cesium aerosols at maximum concentration were determined in both cases.

Results of radon concentration measurements in some regions of Russia

Inhalation of radon and its daughter products makes the major contribution to the total exposure of the population to natural radiations. In implementing a complex ecological survey, concentrations of radon and its daughter products were measured in different regions of Russia, namely, in the St Petersburg Region, the Central Territories and the Altay Territory. Two suitable low price versions of the dosimeters for measuring environmental radon concentrations based on track-etch and activated-charcoal detectors were used. The radon daughter product activity and the effective dose equivalents were calculated with an equilibrium factor of 0.5 and a recommended effective dose equivalent factor of 0.061 mSv (Bq m −3) −1. Indoor measurements were taken in more than 1000 dwellings and public and industrial buildings of 21 towns and villages. The track chambers were exposed for about 2–3 months and the charcoal detectors for 6–10 days, mainly during the summer. The actual radon and daughter product concentration levels and effective dose equivalents (EDE) are presented and analyzed.

Results of radon concentration measurements in some regions of Russia

Inhalation of radon and its daughter products makes the major contribution to the total exposure of population to natural radiations. In implementing a complex ecological survey, concentrations of radon and its daughter products were measured in different regions of Russia, namely, in St.-Petersbourg Region, in Central Territories, and in Altay Territory. Two most suitable low-price versions of the dosimeters for measuring environmental radon concentrations based on track-etch and activated-charcoal detectors were used. The radon daughter product activity was calculated with an equilibrium factor of 0.5. Indoor measurements were taken in more than 1000 dwellings and public and industrial buildings of 21 towns and villages. The track chambers were exposed for about 2–3 months, and the charcoal detectors for 6–10 days. The actual radon and daughter-product concentration levels is presented and analyzed.

Determination of alpha-emitters in Brazilian tobacco

The decay products of uranium and thorium natural series are widely distributed in all the terrestrial crust. Their concentrations are considerable in the phosphates utilized as fertilizer in the Brazilian agriculture. In this work analysis was performed on238U,234U,232Th,238Th,226Ra and210Po in 22 Brazilian tobacco samples. The results showed238U and234U are in isotopic activity equilibrium (0.5±0.2 mBq/g). The equilibrium was not reached in the case of thorium isotopes: the228/232Th ratio was about 6.4. The average values obtained were 34.3 mBq/g for228Th and 5.4 mBq/g for232Th. The226Ra values were higher than its radioactive precursor,238U. This can be explained by the high affinity of radium to tobacco plant and the uranium removal during physical and chemical processes. The high concentration of210Po (20 mBq/g) in tobacco samples may be due to radon daughter products being electrically charged and then attaching themselves to inert dusts, which then become attached to tiny hairs on tobacco leaves. The results of this work are consistent with values presented in specialized literature.

Monitoring genotoxic exposure in uranium mines.

Recent data from deep uranium mines in Czechoslovakia indicated that mines are exposed to other mutagenic factors in addition to radon daughter products. Mycotoxins were identified as a possible source of mutagens in these mines. Mycotoxins were examined in 38 samples from mines and in throat swabs taken from 116 miners and 78 controls. The following mycotoxins were identified from mines samples: aflatoxins B1 and G1, citrinin, citreoviridin, mycophenolic acid, and sterigmatocystin. Some mold strains isolated from mines and throat swabs were investigated for mutagenic activity by the SOS chromotest and Salmonella assay with strains TA100 and TA98. Mutagenicity was observed, especially with metabolic activation in vitro. These data suggest that mycotoxins produced by molds in uranium mines are a new genotoxic factor for uranium miners.

Monitoring genotoxic exposure in uranium miners.

Recent data from deep uranium mines in Czechoslovakia indicated that in addition to radon daughter products, miners are also exposed to chemical mutagens. Mycotoxins were identified as a possible source of mutagenicity present in the mines. Various methods of biomonitoring were used to examine three groups of miners from different uranium mines. Cytogenetic analysis of peripheral lymphocytes, unscheduled DNA synthesis (UDS) in lymphocytes, and lipid peroxidation (LPO) in both plasma and lymphocytes were studied on 66 exposed miners and 56 controls. Throat swabs were taken from 116 miners and 78 controls. Significantly increased numbers of aberrant cells were found in all groups of miners, as well as decreased UDS values in lymphocytes and increased LPO plasma levels in comparison to controls. Molds were detected in throat swabs from 27% of miners, and 58% of these molds were embryotoxic. Only 5% of the control samples contained molds and none of them was embryotoxic. The following mycotoxins were isolated from miners' throat swab samples: rugulosin, sterigmatocystin, mycophenolic acid, brevianamid A, citreoviridin, citrinin, penicilic acid, and secalonic acid. These data suggest that mycotoxins are a genotoxic factor affecting uranium miners.

Radiation Measurement Systems and their Impact on the Estimation of Miners Exposure

This paper presents the results of measurements made simultaneously using different and independent systems of measurement for assessment of miners exposure to radon daughter products. The field grab-air sampling and ‘passive’ etched track environmental dosemeters were compared with a so-called ‘reference system’. Which is based on the individual dosemeters worn by a randomly selected group of miners. This study revels that no correlation exists between the annual miners exposures evaluated using the grab-air-sampling, environmental dosimetry system and the individual dosimetry system. Some regularities were observed, e.g. the effect of ‘avoiding’ higher concentrations in measurements obtained with the grab-air sampling system usually dominates. The conclusion to be drawn from observation and comparison of these systems is that a correct and true evaluation of miners exposure to radon progeny is very sensitive and dependent on the strategy of sampling and its implementation.