Radon Emanation Coefficient Research Articles

Variation rules of the radon emanation coefficient in dump-leached uranium tailing sand

This study was intended to determine the variation rules of the radon emanation coefficient in dump-leached uranium tailing sand. A temperature and humidity controllable device for measuring the emanation coefficient was designed. Tailing sand with different grain sizes was selected from uranium tailings in southern China. An orthogonal experimental design was conducted to determine the radon emanation coefficient of the sand under different temperatures, humidities and grain sizes. Experimental results showed that the air temperature, humidity and grain size have significant effects on the emanation coefficient. The variation rules regarding the radon emanation coefficient showed significant reference value.

Analyses of Influencing Factors for Radon Emanation and Exhalation in Soil

The study on radon emanation and exhalation in soil is more and more important for environmental protection, and many influencing factors on radon emanation coefficient and exhalation in soil have been well documented. In order to evaluate the radon change and key influencing factors, this paper made an overall summary based on these studies. The main results show that the change laws of emanation coefficient with elevated temperature of radon can be divided into three types and they relate to the moisture state and content of soil. The normalized radon exhalation has a negative linear correlation with temperature, and the maximum emanation coefficient has a positive linear correlation with heating rate and specific surface. The pores with different size have different effects on the emanation coefficient of radon in the soil, e.g., the micro-pores increase emanation coefficient, and the mezzo-pores decrease emanation coefficient. Taken together, our results offered guiding significance for the evaluation of radon in soil and in air when soil state changes. Lastly, the existing problems and research directions were also given.

Radiometric properties of sepiolite minerals from quarries in central Anatolia of Turkey

Sepiolite is a naturally occurring clay mineral of sedimentary origin and is a magnesium hydrosilicate. Sepiolite has been widely used as an additive raw material in ceramics and cement industry, pharmaceutical, cleaning-detergent, paper, paint, cosmetic agriculture, fertilizer, etc. In this study, the natural radioactivity levels, radon emanation coefficients and radon exhalation rates of 30 sepiolite samples collected from open three sepiolite quarries (Beylikova, Polath and Sivrihisar) in Central Anatolia region of Turkey were determined by using a gamma-ray spectrometry with an HPGe detector. The average absorbed gamma dose rates directly measured in Beylikova, Polath and Sivrihisar open three sepiolite quarries located in Central Anatolia region of Turkey were found as 59, 65, and 64 nGyh?1, respectively. The average activity concentrations of 226Ra, 232Th, and 40K in 30 sepiolite samples collected from those quarries were found as 38.6, 12.4, and 67.4 Bqkg?1, respectively. The average emanation coefficient and exhalation rate of radon of sepiolite samples were determined as 22 % and 0.065 Bqkg?1h?1, respectively. Also, radiological parameters (outdoor absorbed gamma dose rate, annual effective dose rate, external and internal index) were estimated to evaluate the use of sepiolite samples as additive raw materials in the building sector.

Radon Emanation Coefficients of Some Egyptian Rocks

Radon Emanation Coefficients of Some Egyptian Rocks

Radium content and radon exhalation rate from sulfur polymer composites (SPC) based on mineral fillers

Several samples of materials of potential interest as component in building materials, especially in sulfur polymer concrete (SPC) composites, were checked for their radium content and radon exhalation rate. However, the radiation hazard strongly depends on radon exhalation rate from these materials, the influence of SPC composition was investigated concerning radon exhalation and emanation from the composite matrix. The accumulation method using RAD7 device was used for specific exhalation rate determinations. The activity concentrations of Ra-226 in the man-made tiles were in the range of 6.1–593 Bq·kg−1. The Rn-222 exhalation rates from these materials were in the range of 103 mBq·m−2 h−1–9.22 Bq·m−2 h−1, whereas from the SPC composites from 40.2 to 438 mBq·m−2 h−1. SPC manufacture technology and sulfur polymers applied for composites preparation allow for nearly 50-fold decrease of radon emanation coefficient. Different factors (e.g.: physical form of additives or polymer composition and its weight fraction) affecting radon emanation coefficient and its exhalation rate from examined raw materials and composites were discussed. Using a standard room parameters, the Rn-222 concentration resulting from its exhalation from the walls and annual internal doses were estimated indicating for satisfactory results even for raw materials of the highest Ra-226 concentration.

Radiological evaluation of industrial residues for construction purposes correlated with their chemical properties

This study characterises the naturally occurring radionuclide (NOR) contents of a suite of secondary raw materials or industrial residues that are normally disposed of in landfills or lagoons but now are increasingly used in green concretes. This includes ashes from a variety of industrial processes and red mud from aluminium production, as well as air pollution control residue and cement kiln dust. The chemical composition of the samples was determined with X-ray fluorescence spectroscopy (XRF). The Ra-226, Th-232 and K-40 activity concentrations were obtained by gamma spectrometry, and the results were compared with recently published NOR databases. The correlation between the NOR contents and the main chemical composition was investigated. The radioactive equilibrium in the U-238 chain was studied based on the determination of progeny isotopes. The most commonly used calculation methods (activity concentration index and radium equivalent concentration) were applied to classify the samples. The radon exhalation rate of the samples was measured, and the radon emanation coefficient was calculated. Significant correlation was found between the NORs and certain chemical components. The massic exhalation demonstrated a broad range, and it was found that the emanation coefficients were significantly lower in the case of the residues generated as a result of high-temperature combustion processes. The results showed a weak correlation between the Ra-226 concentration and the radon exhalation. This emphasises that managing the Ra-226 content of recycled material by itself is not sufficient to control the radon exhalation of recycled materials used in building products. The investigated parameters and their correlation behaviour could be used to source apportion materials found during the process of landfill mining and recovery of material for recycling.

Physical and geometrical parameters controlling measurements of radon emanation and exhalation from soil

The influence of physical and geometrical parameters, such as grain size, volume of the emanation container and mass of the sample, on the emanation coefficient and exhalation rates of radon (with and without consideration of back diffusion effect and effective volume of the emanation container) released from soil have been investigated. Moreover, a method for assessing the flux of radon migrate through soil layers was proposed. This method is based on measurement of the cumulative radon concentration transmitted through five layers of soil. The transmission factor results from the decay of 222Rn over a period of 60 day required for it to migrate through these layers was also determined. The soil samples were collected from Al-Marj city located in northeastern Libya. Radon measurements were carried out by using a closed emanation container based on CR-39 nuclear track detectors (NTDs). The results showed that the radon emanation coefficient clearly increases with grain size, container volume and sample mass. The exhalation rates also increase with grain size and sample mass, but the container volume parameter shows an opposite trend. The radon flux and its transmission factor are significantly decreased throughout that uniform soil when the increase in soil depth retarded exhalation. This study shows that various physical and geometrical parameters were demonstrated to be greatly affected on the emanation coefficient and exhalation rates of radon released from soil.

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

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.

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.

Evaluation of radiological hazards associated with the uses of marble and ceramic as decorative building materials in Egypt

Radon concentrations of 20 samples of marble and ceramic were measured using AlphaGuard and varied from 36.02 ± 2.89 to 614.59 ± 99.40 Bq m−3 with a mean value of 139.12 ± 11.44 Bq m−3. Radon emanation coefficient and exhalation rate were also calculated. Moreover, radiation dose of released radon was calculated using two models, showing good agreement. Its value was varied from 6.3 ± 0.52 to 76.23 ±3.82 μSv year−1 with a mean value of 23.20 ± 1.54 μSv year−1. The results implied that radiation dose was less than safety limit of 1 mSv year−1. Therefore, the selected marble and ceramic types could be safely used as decorative building materials.

Radon exhalation study of manganese clay residue and usability in brick production

The reuse of by-products and residue streams is an important topic due to environmental and financial aspects. Manganese clay is a residue of manganese ore processing and is generated in huge amounts. This residue may contain some radionuclides with elevated concentrations. In this study, the radon emanation features and the massic exhalation rate of the heat-treated manganese clay were determined with regard to brick production. From the manganese mud depository, 20 samples were collected and after homogenization radon exhalation characteristics were determined as a function of firing temperatures from 100 to 750 °C. The major naturally occurring radionuclides 40K, 226Ra and 232Th concentrations were 607 ± 34, 52 ± 6 and 40 ± 5 Bq kg−1, respectively, comparable with normal clay samples. Similar to our previous studies a strong correlation was found between the internal structure and the radon emanation. The radon emanation coefficient decreased by ∼96% from 0.23 at 100 °C to 0.01 at 750 °C. The massic radon exhalation rate of samples fired at 750 °C reduced by 3% compared to samples fired at 100 °C. In light of the results, reusing of manganese clay as a brick additive is possible without any constraints.

Radiological and material characterization of high volume fly ash concrete

The main goal of research presented in this paper was the material and radiological characterization of high volume fly ash concrete (HVFAC) in terms of determination of natural radionuclide content and radon emanation and exhalation coefficients. All concrete samples were made with a fly ash content between 50% and 70% of the total amount of cementitious materials from one coal burning power plant in Serbia. Physical (fresh and hardened concrete density) and mechanical properties (compressive strength, splitting tensile strength and modulus of elasticity) of concrete were tested. The radionuclide content (226Ra, 232Th and 40K) and radon massic exhalation of HVFAC samples were determined using gamma spectrometry. Determination of massic exhalation rates of HVFAC and its components using radon accumulation chamber techniques combined with a radon monitor was performed. The results show a beneficial effect of pozzolanic activity since the increase in fly ash content resulted in an increase in compressive strength of HVFAC by approximately 20% for the same mass of cement used in the mixtures. On the basis of the obtained radionuclide content of concrete components the I -indices of different HVFAC samples were calculated and compared with measured values (0.27–0.32), which were significantly below the recommended 1.0 index value. The prediction was relatively close to the measured values as the ratio between the calculated and measured I-index ranged between 0.89 and 1.14. Collected results of mechanical and radiological properties and performed calculations clearly prove that all 10 designed concretes with a certain type of fly ash are suitable for structural and non-structural applications both from a material and radiological point of view.

Mechanisms of radon loss from zircon: Microstructural controls on emanation and diffusion

Understanding how radon escapes from minerals is important for many fields in Earth science, yet few studies have focused on the mechanisms for radon escape. We measured radon emanation rate and radon loss upon heating for crushed aliquots of three large zircon crystals from three localities: Mud Tank (Australia), Bancroft (Canada), and Malawi (Africa). Our study, in conjunction with published data, shows that the room temperature radon emanation coefficient (REC) varies over 5 orders of magnitude in zircon. For low U zircon, Mud Tank, there are variations in REC that appear to be related to annealing at different temperatures, possibly due to annealing of fission tracks, however, all REC values for Mud Tank zircon are within error of one another. Bancroft and Malawi zircons have higher U content and do not show any systematic relationship of REC to annealing temperature. Results from Mud Tank zircon suggest that partial annealing of fission tracks decreases REC, but when all fission tracks are annealed REC reaches a maximum. REC in zircons with high U content, Bancroft and Malawi, is slightly higher than in zircon with lower U, although results are within error. Results of measurements of radon loss upon heating suggest that radon diffusion is slow, ∼30% of the radon is lost during heating at 975°C for 48h. Samples heated a second time yield less fractional radon loss, ∼10%, suggesting that diffusion parameters are changed during heating at temperatures ⩾975°C, which is likely the result of annealing of radiation damage. Diffusion parameters calculated from the fractional loss experiments reflect diffusion in highly radiation damaged or metamict zircons. Our results indicate that internal microstructures in zircon, such as fission tracks and alpha-radiation damage, influence radon escape for diffusion and recoil mechanisms, and hence if these effects can be further characterized, measurements of 222Rn escape have the potential to be useful for probing the internal structure of zircon, and other U-bearing minerals.

NORM, radon emanation kinetics and analysis of rocks-associated radiological hazards

Analysis of naturally occurring radioactive material (NORM) and environmental (radiological) hazard associated with radionuclides in rocks from northeastern Nigeria was carried out and the results are presented. NORMs analysis on rock samples was undertaken with gamma-ray spectroscopy, while radon isotopes were analyzed using an electric radon measurement device (RAD 7). Activity concentration (Bq kg−1) of 226Ra, 232Th and 40K ranges from 11.4 ± 2.6 to 74.6 ± 4.8, 26.6 ± 0.8 to 183.4 ± 3 and 30.1 ± 4.6 to 1120.3 ± 16.4, respectively. Ranges for annual effective dose (mSv) are 0.03–0.20; radium equivalent (Bq kg−1) is 5.7.33–358.36; external hazard index is 0.16–0.99; 222Rn and 220Rn exhalation rates (Bqm−3 h−1) are 2.60–6.25 and 0.50–7.10, respectively. For radon emanation coefficient, the working month level and related dosages ranges are 0.012–0.058, 0.25–0.00 and 1.38–3.30 mSv, respectively. The results reveal that the possible radionuclides enrichment in the rocks is potentially an environmental (radiation) hazard to the inhabitants of the area.

The national survey of natural radioactivity in concrete produced in Israel

The main goal of the current survey was to collect the results of the natural radiation tests of concrete produced in the country, to analyze the results statistically and make recommendations for further regulation on the national scale.Totally 109 concrete mixes produced commercially during the years 2012–2014 by concrete plants in Israel were analyzed. The average concentrations of NORM did not exceed the values recognized in the EU and were close to the values obtained from the Mediterranean countries such as Greece, Spain and Italy.It was also found that although the average value of the radon emanation coefficient of concrete containing coal fly ash (FA) was lower, than that of concrete mixes without FA, there was no significant difference between the indexes of both total radiation (addressing gamma radiation and radon together), and gamma radiation only, of the averages of the two sub-populations of concrete mixes: with and without FA.

Assessment of natural radioactivity in fertilizers and phosphate ores in Egypt

Radionuclide concentrations of uranium (238U), thorium (232Th) and potassium (40K) maintained in 10 phosphate ore and 5 fertilizer samples were measured using a high-purity germanium detector. The concentrations of these radionuclides in the phosphate ore samples were relatively high for 226Ra at 871.37±91.90Bqkg−1 and relatively low for 232Th and 40K at 19.21±2.42Bqkg−1 and 176.06±17.66Bqkg−1, respectively. The concentrations of these radionuclides were low in the fertilizer samples. The radiological hazards of the radium equivalent activity (Raeq), external (Hex) and internal (Hin) indices and annual effective dose due to the presence of these radionuclides in the investigated samples were calculated. The released radon from the selected samples was measured using the Alpha Guard radon monitor. Subsequently, the radon emanation coefficient and its exhalation rate were calculated.

Parameter Ranking System of Indoor Radon Concentration in South Korea, Case Studies: Dokdo Island, Yang Pyeong and Nae Gi

Indoor Radon concentration (IRC) is among the emerging environmental and health issues in Republic of Korea. Due to lack of epidemiological studies and insufficient public awareness about Radon, effective parameter ranking system is required to establish protocols for future field sampling and settlement construction. This research propose the IRC parameter ranking system based on field measurements and laboratory experiments. Dokdo Island, Yang Pyeong and Nae Gi were selected as the case studies in South Korea. The Radon transport equations and statistical analyses are modelled with Simulink and Matlab. IRC model accounts for exhalation of Radon from soil, building material and outdoor air and also considers the major mitigation methods like ventilation, air cleaners and filtration. The PAWN sensitivity analysis method has been applied to determine the sensitivity of each parameter. The results indicates that soil gas radon concentration, radium concentration, emanation coefficient and ventilation rate have the most dominant role on IRC. Based on these results, field sampling patterns and indoor mitigation strategies can be established for restricted access areas and probabilistic studies.

Background radiation and radiological hazard associated with local building materials around Zaria, Nigeria

Activity concentrations of 226Ra, 232Th, and 40K in building materials used for the construction of a neutronics laboratory at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria have been determined using γ-ray spectrometry. Radon and thoron exhalation and emanation were determined using an electronic radon detector connected to a closed loop vessel. The materials studied include cement (CMT), sharp sand (SPS), plaster sand (PLS), concrete bricks (CBK), and gravel aggregate (GAT). The ranges of the measured activities (Bq kg−1) for 226Ra, 232Th, 40K, and thoron were determined and presented. The annual external radiation dose (mGy) of the samples ranged from 0.148 to 1.082 with a mean of 0.77. The radon emanation coefficient of the samples ranged from 0.36 to 3.88%. The highest estimated radium equivalent concentration for the samples is 46 ± 4 Bq kg−1 and is comparable with the reported values for many countries in the world. These radiation values can contribute to background radiation that should be taken into consideration for its effect on research results and facilities resident in the building. The values obtained are also within acceptable levels and suggest that the use of these materials does not pose radiological hazard.