Radon Emanation Research Articles

Determination of Radon Exhalation Rates and Emanation Factor of Some Soil Samples Collected From Southern Seashore of Kerala, India

Determination of Radon Exhalation Rates and Emanation Factor of Some Soil Samples Collected From Southern Seashore of Kerala, India

Radon Emanation as a Source of Radiation Hazard to the Environment: The Case of the Ukrainian Shield

Radon Emanation as a Source of Radiation Hazard to the Environment: The Case of the Ukrainian Shield

Radioactive disequilibrium in uranium series of core samples from Rasimalai and Pakkanadu areas of Tamil Nadu, India

Uranium mineral in a geological environment may behave like an open system. Various factors such as mobility of radium, α-recoil of 234U causing migration of uranium radioisotopes, and radon emanation lead to disequilibrium in uranium decay series. A study has been carried out to find the disequilibrium status of subsurface samples of Rasimalai area of Vellore district and Pakkanadu area of Salem district, Tamil Nadu. This study has a significance in connection with exploration of atomic minerals. It was observed that samples of Rasimalai area show a disequilibrium in favor of parent uranium whereas samples from nearby Pakkanadu area are in equilibrium.

Implications of alteration processes on radon emanation, radon production rate and W-Sn exploration in the Panasqueira ore district

Alteration processes have strong impacts on the chemical and physical properties of rock masses. Because they can affect the contents and the distribution of U as well as enhance the permeability of the bedrock, they may lead to a significant increase of radon release to the environment. However, their influence on radon emanation and radon production rate has yet to be properly assessed. To investigate the impact of alteration processes on the radiological properties, samples were collected in the Panasqueira region under the influence of surface weathering, deuteric, hydrothermal and fault related alteration. Major and trace elements (U, Th), physical, and radiological properties were measured in metasedimentary and fault rocks. The degree of alteration and weathering progress were assessed through indices of alteration, porosity and bulk density.Overall, an increase of the radon emanation coefficient from (approximately) 0.1 to 0.4 and radon production rate (from 40 to over 160Bq·m−3·h−1) is observed with the progress of physicochemical alteration. Decoupling of physical and chemical alteration however implies both must be quantified towards a proper assessment of the degree of alteration. The behavior of radiogenic elements upon alteration is shown to be complex and contingent upon the alteration process. An atypical increase of radon emanation in the ore district due to U mobilization was caused by hydrothermal alteration. Because radon emanation is not dependent upon the pelitic nature of the metasedimentary rocks, it may thus become a proxy for W-Sn exploration. The dependency of radon production rate from the latter constrains its use for exploration. Nevertheless, it may provide a reliable estimation of the bedrock contribution to indoor radon concentrations. Higher indoor radon concentrations, hence, a higher risk of exposure to radon are expected in the ore district as well as within fault zones.

Control of radon emanation at determination of activity concentration index for building materials

Radon emanation is a well-known source of uncertainty at determination of activity concentration index for building materials and NORM. To reduce this uncertainty both radon emanation coefficient of the sample material and radon leakage from the measuring container should be considered. Two different methods (the rapid method and precise method, which requires to keep the sample sealed for at least three weeks), which are based on the use of only gamma-ray spectrometer, are proposed for testing radon emanation. Both methods also allow simultaneous determination of the specific activity of radium and an assessment of radon exhalation rate from the surface of the finished building products. In addition, the method for determination of radon leakage from the container is proposed. The reliability of the sealing methods of containers is compared and standard PET-flasks with a high radon-tightness are offered. The criteria to control radon leakage and radon emanation coefficient are given for three types of test samples: (a) building materials, (b) natural materials of mineral origin (sands, clays, rocks etc.), and (c) artificial materials, such as absorbents, filters, radioactive wastes. A simplified screening test to control activity concentration index for building materials without a need to keep the sample sealed before the measurement is proposed.

White sand potentially suppresses radon emission from uranium tailings

Uranium tailings represent a huge radioactive waste contaminant, where radon emanation is considered a major health hazard. Many trials have been conducted to minimize radon exhalation rate by using different covering materials. In the present work, three covering materials, commonly available in the local environment, (kaolin, white sand and bentonite) have been used with different thickness 10, 15, and 20mm). 238U, 232Th, 40K and the radon exhalation rate were measured by using gamma spectrometry with a Hyper Pure Germanium (HPGe) detector and solid state nuclear track detectors (CR-39). Radon exhalation rate, calculated before and after covering, ranged from 2.80 ± 0.14 to 4.20 ± 0.21Bqm−2h−1, and from 0.30 ± 0.01 to 4.00 ± 0.20Bqm−2h−1, respectively. Also, the attenuation coefficients of different covering materials and radon emanation were calculated. The obtained results demonstrate that covering of uranium tailings by kaolin, white sand and bentonite has potentially minimized both the radon exhalation rate and the corresponding internal doses.

Detailed effects of particle size and surface area on 222Rn emanation of a phosphate rock

The dependency of radon emanation on soil texture was investigated using the closed chamber method. Ground phosphate rock with a large specific surface area was analyzed, and the presence of inner pores, as well as a high degree of roughness and heterogeneity in the phosphate particles, was found. The average radon emanation of the dry phosphate was 0.145 ± 0.016. The emanation coefficient was highest (0.169 ± 0.019) for the smallest particles (<25 μm), decreasing to a constant value (0.091 ± 0.014) for the larger particles (>210 μm). The reduction rate followed an inverse power law. As expected, a linear dependence between the emanation coefficient and the specific surface area was found, being lower than predicted for the large specific surface area. This was most likely due to an increase in the embedding effect of radon atoms in adjacent grains separated by micropores. Results indicate that knowledge of grain radium distribution is crucial to making accurate emanation predictions.

On the claim of modulations in radon decay and their association with solar rotation

Claims were made by Sturrock et al. that radioactive decay can be induced by interaction of the nucleus with solar neutrinos and that cyclic modulations in decay rates are indicative of the dynamics of the solar interior. They analysed a series of measurements of gamma radiation associated with the emanation and decay of radon in a sealed container at the Geological Survey of Israel (GSI) laboratory. The integral count rates in the NaI detector showed strong variations in time of year and time of day. From time-series analysis, Sturrock et al. claim the presence of small oscillations at frequencies in a range between 7.4 a−1 and 12.5 a−1, which they speculatively associated with rotational influence on the solar neutrino flux. In this work, it is argued that the GSI radon measurements are unsuited for studying the variability of decay constants, because the data are strongly influenced by environmental conditions, such as solar irradiance and rainfall. At the JRC and PTB, decay rate measurements of the radon decay chain were performed with ionisation chambers, gamma-ray spectrometers and an alpha spectrometer. No deviation from the exponential-decay law was observed. The existence of cyclic variations in the decay constants is refuted, as well as the concept of measuring solar rotation through radioactive decay.

Emission probability measurement of γ- and X- rays in Ra-226 and Pb-210 decay

The emission intensities of 186.21keV, 46.54keV, XL(Bi) and XK(Rn) photons were measured with calibrated HPGe detectors. The efficiency was computed with the MCNP Monte Carlo code and validated using experimental points. Sources of Ra-226 were prepared from two different radioactive materials. The X-ray emission intensities in Ra-226 decay were determined without X-rays from the daughter decay products using a radon emanation source. The standard CMI source with Pb-210 was used and compared with a source prepared from the NPL solution delivered under the EMRP project “Metrology for processing materials with high natural radioactivity – MetroNORM”.

INTRODUCTION AND TESTING OF A SIMPLIFIED METHOD FOR THE EVALUATION OF THE RADON EMANATION.

The radioactive noble gas radon is identified as the highest risk factor for lung cancer after smoking. The exhalation of radon from building materials can contribute to the radon indoor activity concentration. Therefore, the emanation of radon might be a crucial factor. It is defined as the release of radon from the solid soil matter into the pore space of the material. This article describes a new on-site measurement method for the emanation of radon from building materials at industrial sites. Therefore, a closed vessel with sample material and a passive radon detector inside is used to measure the integrated build-up-curve of the activity concentration. Additionally, a brief overview on existing radon emanation measurement methods is given.

Radon Mitigation Strategy and Results for the SuperNEMO Experiment

SuperNEMO is a modern neutrinoless double beta decay (0νββ) experiment with a design capability to reach half-life sensitivity of T1/2(0ν) >1026 years, equivalent to an effective Majorana neutrino mass of [mββ] < 50 - 100 meV [1]. To achieve this sensitivity, SuperNEMO aims to become a zero background 0νββ experiment in the first Demonstrator phase. This target placed challenging demands on the radiopurity of detector components and the radon activity within the tracker.To minimise radon levels all internal detector components were screened for radon emanation, which was then confirmed through direct measurement of the gaseous tracker. First measurements of tracker indicated that target radon levels of <0.15 mBq/m3 can be achieved.

Background simulations for the ECHo experiment

ECHo-1K is an experiment designed to measure the electron neutrino mass from the spectrum of the electron capture on 163Ho using an array of 100 magnetic micro calorimeters each loaded with 10 Bq of 163Ho. In this article, we present the results of our activities in the investigation of possible backgrounds to the electron capture spectrum using GEANT4 based Monte-Carlo simulations of the sources 166mHo, 40K, 210Pb and the 238U decay chain. For standard contaminations of the used materials, the contribution of the investigated sources is well below the background induced by the pile-up of 163Ho decays. Nonetheless, care has to be taken to avoid accidental contamination during the manufacturing and storage of the detectors, since a few mBq in total on the surface of all 100 detectors of either 40K (∼ 12 mBq) from residual potassium, or 210Pb (∼ 4 mBq) from radon emanation yield a background as large as the expected signal.

Radon emanation coefficients of several minerals: How they vary with physical and mineralogical properties

The escape rates of radon gas from rocks and minerals are of great relevance to many branches of geosciences, and it is, thus, important to understand the physical and mineralogical properties that control radon emanation rates. Mechanisms of radon loss from minerals have direct bearing on the reliability of U-Pb and U-Th-He geochronology. Fourteen minerals from three different mineral groups and with localities spanning three continents were selected for this study. The radon emanation coefficients (REC) for each mineral were measured as a function of grain size, temperature, 238 U and 232 Th activities, total absorbed α-dose, density, and mineral melting temperature. The measured 238 U and 232 Th activities ranged from 0.01 to 6487 Bq/g and from below detection limit to 776 Bq/g, respectively. The REC values for unheated, pulverized samples ranged from 0.083 to 7.0%, which is comparable to previously reported ranges (except for zircon). An inverse correlation between grain size and REC was observed. Full annealing of fission tracks resulted in an overall decrease in REC values, suggesting that nuclear tracks could possibly act as conduits for radon release. While activity, α dose, density, and melting temperatures are not strongly correlated with REC values, it was observed that minerals with high melting points (≥1400 °C) have lower REC values, most likely due to inhibition of radon release by compact crystal-lattice structures. This is the first attempt, to our knowledge, to correlate REC values with melting temperature, and this study reports six minerals for which no REC values have been previously reported.

Radon emanation from fresh, altered and disturbed granitic rock characterized by 14C-PMMA impregnation and autoradiography

Radon emanation from intact samples of fresh (“BG”), altered (“Fract”) and disturbed (“EDZ”) Finnish granitic rock from Kuru (Finland) and its dependence on humidity and rock structural factors was studied. The pore network of the rock was characterized by microscopy and impregnation with 14C-PMMA (polymethylmethacrylate) resin and autoradiography. The radon emanation factor was increasing linearly with the relative humidity. 14C-PMMA autoradiography of the altered zones and the EDZ indicated significant, mineral-specific increase of porosity and porosity gradients towards the fracture surfaces (Fract) and microcracks within the EDZ. For small samples in the cm-scale emanation was not diffusion, but source term controlled.

Online ^{222}Rn removal by cryogenic distillation in the XENON100 experiment

We describe the purification of xenon from traces of the radioactive noble gas radon using a cryogenic distillation column. The distillation column was integrated into the gas purification loop of the XENON100 detector for online radon removal. This enabled us to significantly reduce the constant ^{222}Rn background originating from radon emanation. After inserting an auxiliary ^{222}Rn emanation source in the gas loop, we determined a radon reduction factor of R,>,27 (95% C.L.) for the distillation column by monitoring the ^{222}Rn activity concentration inside the XENON100 detector.

Effective radium-226 concentration in meteorites

The analysis of noble gases in meteorites provides constraints on the early solar system and the pre-solar nebula. This requires a better characterization and understanding of the capture, production, and release of noble gases in meteorites. The knowledge of transfer properties of noble gases for each individual meteorite could benefit from using radon-222, radioactive daughter of radium-226. The radon-222 emanating power is commonly quantified by the effective radium-226 concentration (ECRa), the product of the bulk radium-226 concentration and of the emanation coefficient E, which represents the probability of one decaying radium-226 to inject one radon-222 into the free porous network. Owing to a non-destructive, high-sensitivity accumulation method based on long photomultiplier counting sessions, we are now able to measure ECRa of meteorite samples, which usually have mass smaller than 15g and ECRa<0.5Bqkg−1. We report here the results obtained from 41 different meteorites, based on 129 measurements on 70 samples using two variants of our method, showing satisfactory repeatability and a detection limit below 10−2Bqkg−1 for a sample mass of 1g. While two meteorites remain below detection level, we obtain for 39 meteorites heterogeneous ECRa values with mean (min–max range) of ca. 0.1 (0.018–1.30)Bqkg−1. Carbonaceous chondrites exhibit the largest ECRa values and eucrites the smallest. Such values are smaller than typical values from most terrestrial rocks, but comparable with those from Archean rocks (mean of ca. 0.18Bqkg−1), an end-member of terrestrial rocks. Using uranium concentration from the literature, E is inferred from ECRa for all the meteorite samples. Values of E for meteorites (mean 40±4%) are higher than E values for Archean rocks and reported values for lunar and Martian soils. Exceptionally large E values likely suggest that the 238U-226Ra pair would not be at equilibrium in most meteorites and that uranium and/or radium are most likely not uniformly distributed. ECRa of meteorites is correlated with E and seems to mainly reflect the gas permeability of the meteorite, which could be one important property, preserved in the meteorite, of its parent body, characterizing its history in space, possibly modified by alteration, shock metamorphism, and eventually weathering on Earth. Larger radon emanation values are associated with larger concentrations of the heaviest noble gases (argon, krypton, xenon), and larger 20Ne/22Ne and 36Ar/38Ar ratios, suggesting Earth’s atmosphere contamination or solar wind implantation, and probably a similar carrier phase such as Q phase. An unclear correlation is observed with 40Ar, which may rule out a purely radiogenic effect on radon emanation. Thus, larger radon emanation suggests a larger capacity of collecting solar and terrestrial gases, which should imply higher loss of gases generated in the meteorite and larger dispersion of Pb/U ratios for age determination. This study provides the first quantification of natural radon-222 loss from meteorites and opens promising perspectives to quantify the relationship between pore space connectivity and the transfer properties for noble gases in meteorites and other extraterrestrial bodies.

Radiometric and seismic study of Chidvinskaya kimberlite pipe (Arkhangelsk diamondiferous province, North of the East European Craton, Russia)

Surface geophysical measurements were carried out on Chidvinskaya diamond pipe of the Arkhangelsk diamondiferous province (North of the East European Craton, Russia). Geophysical measurements included a high-precision gamma-spectrometric survey, radon emanation survey in soil air, and microseismic sounding method. Radiometric measurements were used to found radioactivity anomalies of the surface layer over the Chidvinskaya pipe which could be a result of impact of the kimberlite body on a host medium. Deep structure of the kimberlite pipe and host medium was imaged by means of microseismic sounding method. Results indicate that the pipe appears as a high-velocity body. The host medium is low-velocity that is typical for rocks with excessive fissuring. Increased values of total gamma-ray radiation of near surface layer are observed within the pipe contour and exceeded the background values by 2-4 times. Anomalous radon emanation in the soil air was found at the pipe boundaries. According to the microseismic sounding data near-contact zone is a gas-penetrable structure with excessive fissuring. The results of the used methods are in good agreement with each other. The proposed complex of methods has allowed to identify the pipe distinctive feature.

Study on active tectonic faults using soil radon gas method in Viet Nam

Study on active tectonic faults using soil radon gas method in Viet Nam

Residual radioactivity of treated green diamonds

Treated green diamonds can show residual radioactivity, generally due to immersion in radium salts. We report various activity measurements on two radioactive diamonds. The activity was characterized by alpha and gamma ray spectrometry, and the radon emanation was measured by alpha counting of a frozen source. Even when no residual radium contamination can be identified, measurable alpha and high-energy beta emissions could be detected. The potential health impact of radioactive diamonds and their status with regard to the regulatory policy for radioactive products are discussed.

Periodic variations in time of atmospheric radioactive nanoparticles

In the article the authors present the data of periodic variations in time of radon emanations in the ground layerof the atmosphere, which were measured for the period from January 1 to August 3, 2016. Harmonics ofdiurnal, 4-day and longer periods are revealed. The authors interpreted the 4-day variations, which can occurdue to "lunar tides", that is, from soil uplifts due to the increase in gravitational tidal forces. The mechanism ofradon emanation to the Earth's surface is complex. The mechanism of radon emanation to the Earth's surface iscomplex. In particular, the transportation of radon from the inner surfaces of the earth's crust is carried out bythe diffusion of aerosols onto the surface, to which the radon atoms coagulate, due to electrostatic attraction.Such radioactive aerosol nanoparticles located in the surface layer of the atmosphere have the greatest impacton the risks of cancer, since the probabilities of their settling on the lung tissues are several orders of magnitudehigher than the radon itself in the atomic form.