Radon Isotopes Research Articles

Constructing Environmental Radon Gas Detector and Measuring Concentration in Residential Buildings

Background: From the health physics perspective, radon gas is one of the most dangerous gases in residential and business environments. According to the WHO (World Health Organization), radon gas is considered the second cause of lung cancer in societies after smoking. Methods: In this study, the environmental radon gas has been measured using a built radon gas detector on a specific preamplifier circuit and then the perceived results were compared with an Alpha-Guard detector. Specific activity and output ratio on radon concentration in air were measured on three different floors of a residential building covered by different materials. Results: The results showed a good correlation between the outputs and data gathered by the Alpha-Guard. In underground covered by plaster and cement, the detector responses showed approximately double amounts in comparison with the ground floor. The different covered places revealed dissimilar responses, so that the screened granite had greater amounts by 347 ± 37 Bq/m3. Besides, the minimum response was revealed on the first floor using Alpha-Guard by 47 ± 6 Bq/m3. Results confirmed that on each floor, which has a good ventilation system, the exposure due to the radon isotopes can be immensely reduced. Conclusions: This system can also be used to measure the radon concentration changes in the environment and groundwater.

Experimental facility for the production of reference atmosphere of radioactive gases (Rn, Xe, Kr, and H isotopes)

Radioactive gases are of great interest for environmental measurements and can be distinguished in two categories. The natural radionuclides such as the isotopes of radon (222Rn and 220Rn), and the anthropogenic radionuclides coming from fission products (isotopes of Xe and 85Kr) and activation products (3H and 37Ar). Gas monitoring in the environment is an important issue for radioprotection and for the Comprehensive Nuclear-Test-Ban Treaty (CTBT), which both require metrological traceability of these gases. For this purpose, two gas chambers, of 42 L and 125 L, have been conceived and built at the LNE-LNHB to produce reference atmospheres of various gas mixtures. These chambers were created in order to provide any radioactive gas atmosphere with a wide range of activity concentrations (Bq·m−3 to MBq·m−3). The goal of this setup is to be representative of the different environmental conditions for detector qualification and to perform studies of radioactive gas absorption in materials of interest. As a result, the 2 chambers used in this experimental facility are designed to work from vacuum pressure to atmospheric pressure, with a constant activity concentration for any radioactive gas, and under dry to high humidity conditions. It can also be used in a static mode, in which the activity concentration will follow the radioactive decay of the gas. In this paper, the characterization of the chambers will be discussed. These two chambers are combined with different primary standards established by the LNE-LNHB. As the production of the reference atmosphere depends on the primary standard method, we present the details for each atmosphere production, which require a well-known volume, pressure or a direct activity concentration measurement.

Hydrogeological processes and near shore spatial variability of radium and radon isotopes for the characterization of submarine groundwater discharge

Inadequate characterization of variability in natural tracers of submarine groundwater discharge (SGD) introduces large errors into tracer-derived SGD estimates. To address this gap, we investigated spatial variability in the natural SGD tracers 223Ra, 224Ra, 226Ra, 228Ra and 222Rn using a high-density array of piezometers and seepage meters over a nearshore area where discharging groundwater transitioned from fresh to saline. Seepage meters and piezometers were used to sample groundwater and to quantify fluxes and salinity. A series of spatial patterns was distinguished beyond the normal salinity impact on Ra activity. The discharge in the interface between saltwater and freshwater was characterized by higher activities of the longer-lived isotopes (226Ra and 228Ra), while areas dominated by benthic exchange had higher activities of the shorter-lived isotopes (223Ra and 224Ra). Spatial differences in Ra activities were associated with variation in salinity and residence time in the aquifer and were indicative of underlying hydrogeological processes. At the freshwater-saltwater interface, fresh discharge is driven by terrestrial hydraulic gradients and saline discharge is driven by density gradients; both result in long residence times in the aquifer. Benthic exchange of saltwater has shorter residence times, much less than required to enrich long-lived isotopes and reach secular equilibrium. The highest activities of 222Rn were detected in the fresh discharge zone, and the lowest activities in areas dominated by benthic exchange. Direct sampling at discharge points allowed comparison between groundwater collected from inland wells and the water discharging to the bay, and indicated significant differences in the activities despite the short distance from wells to the discharge area. Substantial spatial variability in Ra and Rn was observed on the meter scale, with trends that reflected groundwater origin and residence time. Inadequate characterization of variability, trends, and fluxes introduces large errors into tracer-derived estimates of submarine groundwater discharge. Thus, the study of submarine groundwater discharge with radioactive tracers requires adequate hydrogeological knowledge to identify processes that have strong impacts on Ra and Rn activities and associated fluxes to the ocean.

Adsorption of active trace gases by ensemble of ultrafine porous particles with impermeable cores

In the present study, we analyze the combined influence of several factors on the rate of atmospheric trace gas adsorption by an ensemble of porous aerosol particles. The factors include the presence of a non-porous non-adsorbing inner core, kinetic effects, non-uniform distribution of concentration of adsorbed gas inside particles, inert admixtures in the atmosphere, radioactive decay, and particle number density. The particles size has the same order of magnitude as a free path length of molecules in air. The evolution of concentration of adsorbed active trace gas in solid porous particles is described by an integral equation, while the evolution of active trace radioactive gas in a gaseous phase is determined by an integro-differential equation. Numerical calculations are performed to investigate the adsorption of different isotopes of Radon and Iodine by porous particles. The comparison of rates of gas adsorption for radioactive isotopes of Iodine with a stable isotope I-127 shows that radioactive decay alters the scenario of the gas adsorption process by porous particles. The accuracy of the developed model of radioactive gas adsorption by porous particles is validated by available experimental data.

Nutrient dynamics in submarine groundwater discharge through a coral reef (western Lombok, Indonesia)

AbstractSubmarine groundwater discharge (SGD) from tropical volcanic islands locally transports significant amounts of terrestrial nutrients into the coastal ocean, which can affect sensitive coastal ecosystems such as coral reefs. In northwestern Lombok, terrestrial submarine groundwater discharges through several submarine springs at the seafloor into a coral reef. In order to understand the transport mechanisms of nutrients from land into the reef, we investigated nutrient fluxes via SGD within the area using a combination of different methods, including recharge estimates in the coastal catchment area, echosounder profiling of the seafloor, discharge measurements, and hydrochemical analyses (stable isotopes of water, radon, and nutrients). Different types of springs can be distinguished based on their morphology. One spring showed a “crater”‐shaped structure while other springs consisted of fissures. Recharge rates in the coastal catchment amounted to 5 L s−1, while discharge rates from the largest spring were 5 L s−1 for total SGD and 2.5 L s−1 for fresh SGD, which is similar to discharge rates from smaller onshore springs at the slopes of a volcano. SGD was in general a source of nutrients such as dissolved silicon (~ 226 mol d−1), phosphate (0.61 mol d−1), or total dissolved nitrogen (13.4 mol d−1). Nitrate concentrations varied among the different springs, probably due to different sources in the hinterland, transformations (e.g., denitrification), or biological uptake during transport from land into the ocean. As nitrate can considerably affect coral reef health, our findings suggest that especially nitrate should be monitored around submarine springs in Indonesia.

The observation of vibrating pear-shapes in radon nuclei

There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we observed the low-lying quantum states in 224Rn and 226Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.

REVIEW OF RADON AND THORON RESEARCH IN KENYA: 1997-2017.

Six research studies involving radon and thoron in Kenya were carried out between 1997 and 2007. The studies were mainly small scale and involved a few areas scattered across Nairobi, Rift Valley, Coast and Western regions. The results were captured in seven online journal articles. This paper relooks at the journal articles with the view of underscoring the high radon and thoron areas in Kenya, raising awareness on the sources and risks of radon isotopes in indoor environments and highlighting the need for more research on the isotopes in the country.

Rn progeny diffusion, deposition and track distribution in diffusion chamber with permeable membrane

Objective of this work is to define method by which sensitivities of CR-39 and LR-115 in diffusion chamber could be determined. Method is based on initial physical processes that occurs in diffusion chamber: diffusion, deposition and decay of radon (isotopes 222Rn and 220Rn) and their progeny. Cylindrical shape of chamber was considered due to availability of experimental data for validation of presented method. The shape was not limitation factor and can be extended to any geometry. Diffusion equations for radon in two mediums (membrane and chamber volume) and their progeny in volume were solved using Finite Difference Method – FEM, and solutions are their spatial distributions inside of diffusion chamber. Calculation of flux towards the chamber walls determine distribution pattern and deposited progeny fractions. It has been shown that volume and deposited distributions are not uniform. Visible tracks on CR-39 for defined etching conditions are determined by considering range of alpha particles in air and empirical critical angle function θC=θC(E). For LR-115 mean critical angle of 〈θc〉=500 and energy window from Emin=1.7MeV to Emax=4.2MeV was adopted from literature to determine number of visible tracks. The track density distributions on detector are found to be non-uniform and radially dependent.Thickness of permeable membrane has important influence on presence of thoron and its progeny tracks on detector. Sensitivities of CR-39 and LR-115 in diffusion chamber were determined using method presented in this work and compared with other theoretical models and experiment with good agreement. This shown applicability of the presented method.One of important conclusion is that detector sensitivity, given as one simple number, is not the best parameter for calibration due to the existence of radial variation of track density.For cylindrical chamber with 10cm length and 4cm radius, covered with membrane in form of one-layer filter paper 0.25mm thickness, and for equal concentrations of 222Rn and 220Rn in front of the chamber, contribution of 220Rn and its progeny to total track density is about 3%.

Coulomb excitation of pear-shaped nuclei

There is a large body of evidence that atomic nuclei can undergo octupole distortion and assume the shape of a pear. This phenomenon is important for measurements of electric-dipole moments of atoms, which would indicate CP violation and hence probe physics beyond the Standard Model of particle physics. Isotopes of both radon and radium have been identified as candidates for such measurements. Here, we have observed the low-lying quantum states in 224Rn and 226Rn by accelerating beams of these radioactive nuclei. We show that radon isotopes undergo octupole vibrations but do not possess static pear-shapes in their ground states. We conclude that radon atoms provide less favourable conditions for the enhancement of a measurable atomic electric-dipole moment.

Измерения эманации изотопов радона в жилых и административных помещениях

The distribution of alpha activity of natural radionuclides in boarding schools located near the tectonic fault zones of Almaty was studied. Measurements were made in boarding schools, which are both residential and administrative buildings. As a result of the measurements, a 2D topology of the distribution of the alpha-radiation flux density of radon isotopes and their daughter decay products from the measurement height (number of storeys) for each boarding school was made. In addition, a 2D topology of the distribution of alpha-radiation flux density from the distance to the tectonic fault was compiled. According to the measurement results, the concentration coefficient of radon was found depending on the distance from the tectonic fault. Using the obtained regularity, it is possible to construct a graph of the dependence of volume alpha activity for other schools, if their distance from the tectonic fault is known.

Radiolysis via radioactivity is not responsible for rapid methane oxidation in subterranean air.

Atmospheric methane is rapidly lost when it enters humid subterranean critical and vadose zones (e.g., air in soils and caves). Because methane is a source of carbon and energy, it can be consumed by methanotrophic methane-oxidizing bacteria. As an additional subterranean sink, it has been hypothesized that methane is oxidized by natural radioactivity-induced radiolysis that produces energetic ions and radicals, which then trigger abiotic oxidation and consumption of methane within a few hours. Using controlled laboratory experiments, we tested whether radiolysis could rapidly oxidize methane in sealed air with different relative humidities while being exposed to elevated levels of radiation (more than 535 kBq m-3) from radon isotopes 222Rn and 220Rn (i.e., thoron). We found no evidence that radiolysis contributed to methane oxidation. In contrast, we observed the rapid loss of methane when moist soil was added to the same apparatus in the absence of elevated radon abundance. Together, our findings are consistent with the view that methane oxidizing bacteria are responsible for the widespread observations of methane depletion in subterranean environments. Further studies are needed on the ability of microbes to consume trace amounts of methane in poorly ventilated caves, even though the trophic and energetic benefits become marginal at very low partial pressures of methane.

Assessment of radiation dose from radon ingestion and inhalation in commercially bottled drinking water and its annual effective dose in Eastern Province, Saudi Arabia

ABSTRACTThe isotopes of radium, uranium, polonium, lead, and short-lived radon are the common radionuclides found in drinking water. The abnormal amount of radon in drinking water causes health risks. In this study, an attempt has been made to estimate the level of radon concentrations and its annual effective dose from bottled water brands and tap drinking water. A total of 77 samples of drinking water sources; 47 bottled water brands and 27 tap water samples including 3 samples from water storage tank supplier were collected and examined. The measurements were performed using active detection method technique called Durridge RAD7-H2O with closed loop. The minimum and maximum level of average radon concentrations was 0.10 ± 0.02 BqL−1 and 9.2 ± 0.02 BqL−1. The results were below the limit recommended by the Environmental Protection Agency (11 BqL−1). The annual effective dose for children and adults was in the range from almost 0.51 µSvy−1 to 46.69 µSvy−1. There are no indications of significant threat from radon concentrations in bottled water brands or tap drinking water, and it is safe as far as health hazard is concerned.

Use of radon isotopes, gamma radiation and dye tracers to study water interactions in a small stream in Brazil

In this study, natural (222Rn) and fluorescent (uranin) tracers were used to investigate the interactions between surface and subsurface waters in a small hydrographical basin located in the southeast region of Brazil. Levels of 222Rn were measured in 117 water samples with the use of an alpha solid-state detector. After the identification of the probable discharge sections along the stream, a measurement of the natural flows, upstream and downstream of these sections, was done with the use of a fluorimeter and fluorescent tracers. Also, scanning was done to verify a correlation between the natural gamma radiation and the 222Rn in the areas where its activity was higher. The results showed some sections where the 222Rn activity is more significant and contributed to the growth of the flows along the stream. It was possible to confirm a correlation between the discharge sections and the natural gamma radiation, what can be used as a preliminary approach to finding these sections in scenarios similar to the one studied here.

HYGIENIC EVALUATION OF EXPOSURE DOSES FOR THE VORONEZH REGION POPULATION FROM THE NATURAL AND TECHNOGENOUSLY MODIFIED BACKGROUND

The purpose of the study was to estimate the doses to the Voronezh region population from natural sources of ionizing radiation and the technologically altered background in the territory of Voronezh Region. The data of forms of state statistical observation No. 4-DOZ “Information on the doses of population exposure due to natural and technologically altered background” for 20102017 and the radiation and hygienic passport of the territory of the Voronezh Region were used. The average annual per caput effective dose due to all types of ionizing radiation remains stable with a slight upward trend and lies in the range from 2.925 (2010) to 3.656 mSv (2017). Natural sources are the main dose-forming factors for the population. Their annual contribution to the annual effective dose ranges from 74.96 to 83.65%. The leading contribution to the total dose from natural sources is the exposure due to the inhalation of radon isotopes: it ranges from 37.6 to 51.1%. In second place,there is the share of external exposure from sources of terrigenous origin, which ranges from 21.2 to 28.9% of the total dose. The average annual effective dose of natural exposure to humans varies from 2,355 to 2,980 mSv / year, the exposure from radon – from 0,83 to 1,65 mSv / year. The dose from technogenic-altered radiation background, including global radioactive fallout due to atmospheric nuclear tests and due to past radiation accidents are insignificant (0,062 mSv / year). Its annual contribution to the total dose is less than 2%. Based on the results of the assessment of the indicators characterizing the level of exposure of sources of ionizing radiation to natural and technogenic-altered radiation background, no excess of radiation safety standards has been recorded. The situation associated with exposure to ionizing radiation sources in the Voronezh region has been described as safe for the last 8 years.

Submarine groundwater discharge and chemical behavior of tracers in Laizhou Bay, China

Naturally occurring radon (222Rn) and radium isotopes are widely used to trace water mixing and submarine groundwater discharge (SGD) in the coastal zones. However, their activities in groundwater are variable both spatially and temporally. Here, time series sampling of 222Rn and radium was conducted to investigate their behavior in intertidal groundwater of Laizhou Bay, China. The result shows that groundwater redox conditions have an important impact on the behavior of tracers. The activities of tracers will decrease under oxidizing conditions and increase under reducing conditions. Radon and radium mass balance models were used to evaluate the flushing time and SGD based on spatial surveys in Laizhou Bay. The flushing time is estimated to be 32.9–55.3 d with coupled models, which agrees well with the result of tidal prism model. The trace-derived SGD in the whole bay ranges from 6.1 × 108 to 9.0 × 108 m3/d and the re-circulated seawater (RSGD) ranges from 5.5 × 108 to 8.5 × 108 m3/d. The average SGD and RSGD fluxes are 22.8 and 21.1 times greater than the Yellow River discharge in April 2014, respectively. The study provides a better understanding of the dynamics of coastal groundwater and behavior of tracers in a well-studied bay system.

The mandate and work of ICRP Committee 2 on doses from radiation exposure.

The practical implementation of the International Commission on Radiological Protection's (ICRP) system of radiological protection requires the availability of appropriate methodology and data. Over many years, ICRP Committee 2 has provided sets of dose coefficients to allow users to evaluate equivalent and effective doses for radiation exposures of workers and members of the public. The methodology being applied in the calculation of doses is state-of-the-art in terms of the biokinetic models used to describe the behaviour of inhaled and ingested radionuclides, and the dosimetric models used to model radiation transport for external and internal exposures. This overview provides an outline of recent work and future plans, including publications on dose coefficients for adults, children, and in-utero exposures, with new dosimetric phantoms in each case. For the first time, ICRP will publish dose coefficients for intakes of radon isotopes calculated using dosimetric models. Committee 2 is also working with Committee 3 on dose coefficients for radiopharmaceuticals, and leading a cross-committee initiative to provide advice on the use of effective dose. The remit of Committee 2 has now been widened to include all data requirements for the assessment of doses to humans and non-human biota.

Radionuclide geochemistry of groundwater in the Eastern Desert, Egypt

Radionuclides have been recognized as a limiting factor of groundwater quality in the Middle East and Northeastern Africa. High levels of naturally occurring radioactivity, mostly from radium and radon isotopes, have been reported in waters from the Nubian Sandstone Aquifer System (NSAS) in several countries in the Middle East including the Sinai Peninsula of Egypt. This study aims at extending the existing data coverage by investigating radionuclide concentrations and their potential geological and hydrogeochemical controls in groundwater of the NSAS and the overlying alluvial aquifers in the Eastern Desert of Egypt. Radium isotope activities (226Ra and 228Ra) and uranium concentrations were analyzed in 39 groundwater samples from these aquifers. The shallow Nubian aquifer has 226Ra and 228Ra activities ranging from 0.016 to 0.750 and 0.018–1.421 Bq/L, respectively. The deep Nubian aquifer has 226Ra and 228Ra activities ranging from 0.019 to 0.051 and 0.014–0.248 Bq/L, respectively. The shallow alluvial aquifers have 226Ra and 228Ra activities ranging from 0.008 to 0.086 and 0.006–0.081 Bq/L, respectively. Groundwater in the Nubian aquifer may have Ra activities substantially in excess of the drinking water MCL values of the US Environmental Protection Agency (EPA), the European Union (EU), and the World Health Organization (WHO). The concentration of U varies from 0.06 to 33.06 μg/L, 0.06–15.46 μg/L, and 0.01–13.19 μg/L for the shallow Nubian aquifer, the deep Nubian aquifer, and the shallow alluvial aquifers, respectively. U concentrations exceed the EPA and WHO MCL values in some wells, mostly from the shallow Nubian aquifer.

Determination of groundwater discharge rates and water residence time of groundwater‐fed lakes by stable isotopes of water (18O, 2H) and radon (222Rn) mass balances

AbstractLacustrine groundwater discharge (LGD) and the related water residence time are crucial parameters for quantifying lake matter budgets and assessing its vulnerability to contaminant input. Our approach utilizes the stable isotopes of water (δ18O, δ2H) and the radioisotope radon (222Rn) for determining long‐term average and short‐term snapshots in LGD. We conducted isotope balances for the 0.5‐km2 Lake Ammelshainer See (Germany) based on measurements of lake isotope inventories and groundwater composition accompanied by good quality and comprehensive long‐term meteorological and isotopic data (precipitation) from nearby monitoring stations. The results from the steady‐state annual isotope balances that rely on only two sampling campaigns are consistent for both δ18O and δ2H and suggested an overall long‐term average LGD rate that was used to infer the water residence time of the lake. These findings were supported by the good agreement of the simulated LGD‐driven annual cycles of δ18O and δ2H lake inventories with the observed lake isotope inventories. However, radon mass balances revealed lower values that might be the result of seasonal LGD variability. For obtaining further insights into possible seasonal variability of groundwater–lake interaction, stable water isotope and radon mass balances could be conducted more frequently (e.g., monthly) in order to use the derived groundwater discharge rates as input for time‐variant isotope balances.

Human exposure to radon radiation geohazard in Rong Cave, Dong Van Karst Plateau Geopark, Vietnam

Human exposure to radon radiation geohazard in Rong Cave, Dong Van Karst Plateau Geopark, Vietnam

Spectroscopy of the long-lived excited state in the neutron-deficient nuclides Po195,197,199 by precision mass measurements

Direct mass measurements of the low-spin $3/2^{(-)}$ and high-spin $13/2^{(+)}$ states in the neutron-deficient isotopes $^{195}$Po, $^{197}$Po, and high-spin $13/2^{(+)}$ state in $^{199}$Po were performed with the Penning-trap mass spectrometer ISOLTRAP at ISOLDE-CERN. These measurements allow the determination of the excitation energy of the isomeric state arising from the $\nu$i$_{13/2}$ orbital in $^{195,197}$Po. Additionally, the excitation energy of isomeric states of lead, radon, and radium isotopes in this region were obtained from $\alpha$-decay chains. The new excitation energies complete the knowledge of the energy systematics in the region and confirm for the first time that the $13/2^{(+)}$ states remain isomeric, independent of the number of valence neutrons.