Radon Emanation Factor Research Articles

Radon exhalation and emanation assessments in the Transdanubian Central Mountain in Hungary

ObjectiveTo determine the radium-226 activity concentration, the massic radon exhalation rate and emanation factor of 55 soil samples from the Central Transdanubian Mountains in Hungary as well as possible radon exhalation hotspots in the sampling area were determined. Further indoor measurements are planned to investigate the possible exposure to radon of the inhabitants. MethodsThe radium-226 activity concentration measurements were carried out with a semiconductor HPGe gamma-ray spectrometer. The massic radon exhalation rate and emanation factor were determined by measuring the radon activity concentrations using the accumulation method with a system developed by our department based on an AlphaGUARD DF2000 portable radon monitor. ResultsThe activity concentrations of radium-226 were between (11.4 ​± ​2.5) and (118.2 ​± ​3.0) Bq/kg, while their average was 39.51 Bq/kg. The massic radon exhalation rates were between (1.02 ​± ​3.64) mBq⋅kg−1⋅h−1 and (275.63 ​± ​4.05) mBq⋅kg−1⋅h−1, while their average was 39.51 mBq⋅kg−1⋅h−1. Finally, the emanation factors were between (0.01 ​± ​0.04) and (0.80 ​± ​0.03) with an average of 0.30. ConclusionsIn our study, the results recorded from the bedrock at the sampling sites were analyzed. 9 samples were taken from sites comprised of limestone bedrock, moreover, the average radium-226 activity concentrations and massic radon exhalation rates at these sampling sites were higher than average. It was also concluded that although no regional correlation can be seen from the results, a possible smaller radon hotspot was identified from our measurements where further sampling will be carried out.

Correction to: Radon emanation factor for soil and external exposure of the public around an atomic power plant narora (U.P.) India

Correction to: Radon emanation factor for soil and external exposure of the public around an atomic power plant narora (U.P.) India

Radon emanation factor for soil and external exposure of the public around an atomic power plant narora (U.P.) India

Radon emanation factor for soil and external exposure of the public around an atomic power plant narora (U.P.) India

MODELING AND EXPERIMENTS TO ESTIMATE RADON EMANATION FACTOR IN SOIL-GRAIN SIZE AND MOISTURE EFFECT.

The influence of soil grain size on its radon emanation mechanism was investigated by developing a Monte-Carlo model. The proposed model supplements the previous formulations by accounting for the effect elicited by specific surface area of the sample. The specific surface area of a sample is governed by its grain size and it strongly influences the emanation rate which is a surface phenomenon. The emanation study was further extended to include the moisture effect. Experiments were carried out with two soil samples; Soil-2 and Soil-4 collected from different terrains, to analyze the role played by moisture in the emanation mechanism. The above model was augmented with provisions to include the moisture input. The model could reproduce the experimental results. There is an abrupt increase in the emanation factor when the moisture content changes from 0 to 2%. Thereafter, the increase is gradual and finally becomes steady when the moisture level reaches 10%. Soil-2 and Soil-4 showed sizeable difference in their radon emanation factor values. This could be explained based on the parent226Ra distribution pattern which stems from the mineralogical composition of the samples. Quartz was predominantly found in Soil-2, whereas Soil-4 shows peaks corresponding to minerals namely ilmenite, Rutile and Zircon confirming relatively higher concentration of heavy minerals than Soil-2. The emanation factor values of the individual minerals reported in the literature were used to decide upon the 226Ra distribution depth and with this input the model to ascertain the experimental observations.

Determine the Contaminations of Radon in the Drinking Water Using NTDs (CR-39) and RAD7 Detectors

This presented study was performed to determine the contaminations of radon in twenty-five drinking tap water samples in Penang/Malaysia. The concentration of 222Rn, specific activity of 226Ra, radon emanation factor, equilibrium radon concentration, annual effective dose and mass exhalation rate were measured in drinking water samples available under study by using two methods, passive method (NTDs (CR-39) and active method (RAD7 monitoring). Also, the pH and electrical conductivity of the samples were measured. The results showed that the maximum concentration of radon was found in sample 7 to be 98.154 Bq m−3 and the minimum concentration of radon was found in sample 4 to be 39.715 Bq m−3 with an average of 66.521 Bq m−3. The maximum concentration of radium was found in sample 7 to be 1266.036 × 10−3 Bq kg−1, and the minimum concentration of radium was found in sample 4 to be 530.729 × 10−3 Bq kg−1 with an average (899.999 × 10−3 Bq kg−1). The results obtained from the passive technique (CR-39) and active technique (RAD7) were in good agreement together (66.521, 63.533) Bq m−3, because the passive method and active method are simple and reliable analytical methods. An average annual effective dose (0.770 mSvy−1) was found to be below the value (3–10 mSvy−1) that was reported by the ICRP (1993), therefore, there is no evidence of health problems. Significant strong positive correlations found (r = 1, Pearson Correlation, p < 0.000) in concentrations of radon, radium and annual effective dose. All the results obtained were within the international levels as given by UNSCEAR (United Nations Scientific Committee on the Effect of Atomic Radiation).

A study on natural radioactivity and potential of 222Rn, 220Rn exhalation from Deccan table land of Kolhapur district, Maharashtra, India

In this study, an investigation has been carried out on the potential of radon, thoron and natural radioactive content by collecting soil samples from the Deccan land of Kolhapur district, India. The mean value of radon mass exhalation rates is 12.66 ± 1.07 mBqkg−1h−1 and mean thoron surface exhalation rate is 2300 ± 261 Bqm−2h−1. The mean value of Radon emanation factor is 5.18%. The mean activity concentrations of 238U, 232Th and 40K in the soil samples are 9.33 ± 0.45 Bqkg−1, 16.60 ± 0.77 Bqkg−1 and 66.15 ± 4.33 Bqkg−1 respectively and well below the value recommended by UNSCEAR 2000.

Radiometric characterization of zeolite minerals used in many industries and assessment of radiological risks

Zeolites are important additives materials which are widely used in different industries such as construction, paper, paint, agriculture, textile, and fertilizer. In this study, radiometric characterization of natural zeolite samples collected from four zeolite open quarries in Western Anatolia in Turkey were determined using a gamma-ray spectrometry with high purity germanium detector. The radiological risks due to the use of zeolite samples as raw materials in cement and concrete production was assessed for adult people by estimating activity concentration index and annual effective dose due to external exposure in indoor. Also, annual effective radiation dose in outdoor and the corresponding lifetime cancer risk were estimated for quarry workers. Average activity concentrations of 226Ra, 232Th and 40K measured in seventy-seven zeolite samples were found as 85 ± 4, 129 ± 2 and 1030 ± 24 Bq kg−1, respectively. The radon emanation factor and radon mass exhalation rate of zeolite samples varied from 1 to 9% with an average of 4% and 1.8–15.1 μBq kg−1 s−1 with an average of 7.2 ± 0.3 μBq kg−1 s−1, respectively. The data were compared with criteria or limit values. The results revealed that usage of the examined zeolite samples as building raw materials would not cause any significant radiological risk.

Application of zeolitic rocks in the environment: assessment of radiation due to natural radioactivity

The 238U, 226Ra, 210Pb, 228Ra, 228Th and 40K concentrations have been measured beside to radon emanation factor due to sample granulometric using γ-spectrometry. The radiological hazards of zeolitic rocks application in the environment as soil improvements, diet supplements and building materials have been studied. No γ-radiation hazards occur for soil improvements since up to 0.13 mSv year−1 estimate. No radiation hazards arise for diet supplements since 0.21 μSv day−1 g−1 of zeolite intake is estimated. Instead, the application as cement and bricks give external annual effective dose up to 1.19 mSv, while the internal radiation rises to 3.45 mSv.

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 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.

Importance of radon studies in rural areas and correlation of indoor radon level with radon inventory

The measurement of indoor radon in villages is very important as 50% of the world populations live in villages, and rural houses normally have very low air exchange rates. This study has estimated the possible indoor radon level from five types of rocks, which are readily available to build houses in Eastern Singhbhum district of India. In the process to calculate this radon inventory, radium content and radon flux rate were measured in the selected rocks. Then calculated radon emanation factor was compared with the possible indoor radon concentration computed from the available air ventilation rate of typical Indian houses. It was found that granite generated low radon level and it can be a good alternative choice as building material instead of other regionally used rocks. This study also suggests that important geological parameters, which develop and increase porosity, can effectively increase radon inventory.

Radon emanation from backfilled mill tailings in underground uranium mine

Coarser mill tailings used as backfill to stabilize the stoped out areas in underground uranium mines is a potential source of radon contamination. This paper presents the quantitative assessment of radon emanation from the backfilled tailings in Jaduguda mine, India using a cylindrical accumulator. Some of the important parameters such as 226Ra activity concentration, bulk density, bulk porosity, moisture content and radon emanation factor of the tailings affecting radon emanation were determined in the laboratory. The study revealed that the radon emanation rate of the tailings varied in the range of 0.12–7.03 Bq m−2 s−1 with geometric mean of 1.01 Bq m−2 s−1 and geometric standard deviation of 3.39. An increase in radon emanation rate was noticed up to a moisture saturation of 0.09 in the tailings, after which the emanation rate gradually started declining with saturation due to low diffusion coefficient of radon in the saturated tailings. Radon emanation factor of the tailings varied in the range of 0.08–0.23 with the mean value of 0.21. The emanation factor of the tailings with moisture saturation level over 0.09 was found to be about three times higher than that of the absolutely dry tailings. The empirical relationship obtained between 222Rn emanation rate and 226Ra activity concentration of the tailings indicated a significant positive linear correlation (r = 0.95, p < 0.001). This relationship may be useful for quick prediction of radon emanation rate from the backfill material of similar nature.

A model to predict radon exhalation from walls to indoor air based on the exhalation from building material samples

In recognition of the fact that building materials are an important source of indoor radon, second only to soil, surface radon exhalation fluxes have been extensively measured from the samples of these materials. Based on this flux data, several researchers have attempted to predict the inhalation dose attributable to radon emitted from walls and ceilings made up of these materials. However, an important aspect not considered in this methodology is the enhancement of the radon flux from the wall or the ceiling constructed using the same building material. This enhancement occurs mainly because of the change in the radon diffusion process from the former to the latter configuration. To predict the true radon flux from the wall based on the flux data of building material samples, we now propose a semi-empirical model involving radon diffusion length and the physical dimensions of the samples as well as wall thickness as other input parameters. This model has been established by statistically fitting the ratio of the solution to radon diffusion equations for the cases of three-dimensional cuboidal shaped building materials (such as brick, concrete block) and one dimensional wall system to a simple mathematical function. The model predictions have been validated against the measurements made at a new construction site. This model provides an alternative tool (substitute to conventional 1-D model) to estimate radon flux from a wall without relying on 226Ra content, radon emanation factor and bulk density of the samples. Moreover, it may be very useful in the context of developing building codes for radon regulation in new buildings.

Radon exhalation studies in an Indian uranium tailings pile

A study was taken up to quantify the source term arising due to radon exhalation from Uranium(U) tailings pile at Singbhum shear zone in Jharkhand state of India. In-situ experiments were conducted at 40 locations of the U tailings pile in three seasons namely summer, rainy and winter to measure the radon fluxes. The fluxes were also predicted by a diffusion model using the measured parameters such as Ra-226 content, bulk density, diffusion coefficient, radon emanation factor, moisture content and temperature in the U tailings. It was observed that the predicted fluxes using the in-situ diffusion length and emanation factor were closer to measured values by accumulator technique than that predicted using empirically estimated diffusion coefficient and emanation factor. A conversion factor has been established between radon fluxes and Ra-226 content in U tailings for Jaduguda. The source term arising due to the radon exhalation from U tailings pile at Jaduguda has determined using the measured data of radon fluxes.

Estimation of radon emanation factor in Indian building materials

Results of estimation of radon ( Rn 222 ) emanation factors of the commonly used building materials in India are presented. All the samples were analyzed for Ra 226 , Th 232 and K 40 contents by gamma spectrometric method. Rn 222 mass exhalation rates of the various samples were determined using an Alphaguard, a continuous radon monitoring system. From the Ra 226 content and Rn 222 mass exhalation rate obtained, the Rn 222 emanation factor was evaluated for the samples. Results showed that the estimated Rn 222 emanation factors of the studied building materials and soil samples under dry condition and in powder form varied from 0.1% to 20.8 %.

An empirical radon emanation model for residential premises

Based on an averaging technique, a methodology has been established to estimate an effective radon emanation factor M for residential premises. The model shows that the new term M and the ventilation rate are the essential parameters in estimating the level of indoor radon. M includes two components: the radon emanation rates of internal surface materials and the ratio of surface areas of applicable materials to premises volume. The value of M can be determined from on-site measurements. Different ventilation modes of a sampled residential unit during daytime and nighttime, with air conditioner on, window-open, and window-closed were included in site measurements. Each ventilation mode was measured twice during daytime and twice at night. During the investigation, air exchange rate, and indoor and outdoor radon levels were monitored simultaneously. The results of measurements were then used to verify the model. The value of M was found to be 31.7 Bq m −3 h −1. The model is valid if the air exchange rate is larger than 0.2 h −1.

Measurement of radon emanation factor from granular samples: effects of additives in cement

Two methods for radon emanation factor determination were performed and compared regarding their measuring accuracy: (a) by hermetically closing the sample in an airtight container and measuring the induced radon activity, and (b) by mixing charcoal and sealing the sample hermetically and after placing the sample in an open vessel with no charcoal addition, measuring each time the 226Ra content using gamma-spectrometry. Measurements of radon emanation factor of cement and pozzolanic additives, i.e. fly ash and phosphogypsum were also performed.

An experimental method for measuring the radon-222 emanation factor in rocks

An experimental method, based on a 21-day accumulation technique, is proposed for measuring the radon-222 emanation factor in undisturbed consolidated materials. The leakage rate is determined from the form of the radon growth curve in the measurement chamber. It was comparable to the radon decay. In order to obtain the “true” radon emanation factor, the thickness of the sample must be less than the radon diffusion length in the porous material. The method was used to measure the radon emanation factor in water-saturated claystones (argillites). The radon emanation factor, determined from experiments on a rock sample with a thickness of 5 mm , was 15%, a value typical for this kind of material.

Results of a simple intercomparison of natural radioactivity measurements using a ‘blue concrete’ sample

A simple intercomparison of natural radioactivity and radon emanation factor measurements co-ordinated by the Medical Physics Department of the University of Cantabria UC, Spain, has been carried out during 1998 in the framework of the EU Concerted Action ERRICCA (European Research into Radon in Construction Concerted Action). All the measurements have been made on a ‘blue concrete’ sample kindly donated by Dr G. Akerblom from the Swedish Radiation Protection Institute. In addition to UC, two other participant laboratories, STUK from Finland and ZVD from the Republic of Slovenia, have contributed to the development of the intercomparison exercise. Considering the uncertainties of the measurements, a good agreement between the results obtained by the three participating laboratories has been ascertained. However, in accordance with experimental results obtained by other authors, data reported by UC show a significant decrease of the radon emanation factor as moisture content of the sample decreases below 5% (per weight).