Radioactivity and radon emanation fraction of the granites sampled at Misasa and Badgastein.

The chemical composition was analyzed and the radioactivity, radon exhalation rate and emanation fraction were measured to investigate the characteristics of the granites sampled at Misasa and Badgastein, world famous for radon therapy. The Misasa granite was probably composed of quartz, albite and microcline. The Badgastein granite was probably composed of quartz and muscovite. The radon exhalation rates and emanation fractions of the Misasa granite were much higher than those of the Badgastein granite, regardless of the (226)Ra activity concentrations.     

NIST 222Rn emission standards.

NIST radon standards are hermetically sealed polyethylene capsules filled with 226Ra solution. Recently, four new series of standards with activities 5, 50, 500, and 5000 Bq were prepared. The measured emanation fraction agrees with a calculation that accounts for the radon accumulated inside the polyethylene walls of the capsule. Obtained solubility of radon in polyethylene is approximately 45 of the solubility of radon in water. The radon diffusion coefficient in low-density polyethylene is 7.2x10(-8)cm2/s.     

Internal exposure from building materials exhaling 222Rn and 220Rn as compared to external exposure due to their natural radioactivity content

The main scope of this paper is to point out the importance of introducing radon and thoron exhalation measurements from building materials in the regulating frame. Currently (2009), such a regulation of this kind of exposure is not explicitly included in the Serbian regulating network. To this end, this work reports concentration measurements of ²²⁶Ra, ²³²Th and ⁴⁰K and radon and thoron exhalation rates from building materials used in Serbia. Following detailed analysis, it was noticed that both internal exposures to radon and/or thoron exhaling from building materials may exceed external exposures to their precursors contained therein.     

Determination of 222Rn emanation fraction and diffusion coefficient in concrete using accumulation chambers and the influence of humidity and radium distribution.

In this paper we present a laboratory method for the determination of diffusion coefficient, D, as well as the 222Rn emanation fraction, f, in concrete core samples. It is based either on the analyses of the growth curves of the radon in the air volume surrounding a sample enclosed in an accumulation chamber (Lucas cell or RADIM device) or using the charcoal adsorption method. Samples used have a special geometry allowing the assumption of a one-dimensional diffusion of radon in material. Radium was enhanced in the concrete samples by adding radium bromide solution or uranium ore. A strong dependence of the emanation fraction on the enhancing method was observed. For the sample enhanced with uranium ore the specific exhalation rate was about ten times smaller. A marked dependence of radon exhalation on the water content was also observed.     

Differences of natural radioactivity and radon emanation fraction among constituent minerals of rock or soil

We examined differences in the radioactive characteristics among the main minerals forming granite materials. Using a non-toxic high-density agent, minerals were separated from rock (granite–gneiss) and soil (weathered granite) samples. The natural radioactivity (²³⁸U and ²²⁶Ra) and radon emanation fraction of the minerals were then studied by gamma-ray spectrometry. The radon emanation fractions (27–43%) of the minerals from the soil were much higher than those (0.6–4.6%) of the rock minerals. Additionally, the emanation fractions differed greatly among the minerals separated from both the bulk rock and soil. These results were discussed in terms of the differences of surface area and radium distribution in the mineral grains. It was noticeable that a higher emanation fraction than expected for quartz was commonly observed in the rock and soil samples. We then estimated the contribution of each constituent mineral to the total radon exhalation from the bulk samples. The result depended not only on the radon emanation fraction, but also on the ²²⁶Ra activity and the mineral content. Furthermore, using the obtained data, we also discussed the effect of grain size on radon emanation and why this has been reported to vary markedly in previous studies.     

Use of three new SSNTD methods for evaluating thorium contents in different building materials and measuring thoron and its progeny concentrations inside dwellings.

Three new methods based on using CR-39 and LR- 115 type II solid state nuclear track detectors (SSNTD) were used for measuring thorium concentrations (in 10(-6)g/g (ppm)) inside different building materials and evaluating the resulting concentrations of thoron and its progenies in dwellings built by the studied materials. The first technique consists of determining the probabilities for alpha-particles emitted by the uranium and thorium series inside the building materials or by the radon and thoron groups inside the dwelling atmosphere to reach and be registered as tracks on the SSNTD utilized and exploiting the resulting track density rates. The second method consists of evaluating the mean critical angles of etching of the CR-39 and LR-115 II SSNTD and measuring the resulting track densities registered on the detectors utilized. The third technique is based on calculating the detection efficiencies of the CR-39 and LR-115 II SSNTD for a-particles emitted by the uranium and thorium series in the building materials or by the radon and thoron groups in air and measuring track density rates registered on these detectors. The influence of the building material's nature and ventilation rate on the thoron and its decay products inside the dwelling rooms studied has been investigated.     

Simultaneous determination of 222Rn and 220Rn exhalation rates from building materials used in Central Italy with accumulation chambers and a continuous solid state alpha detector: influence of particle size, humidity and precursors concentration.

A method to determine simultaneously the rates of 222Rn and 220Rn released from building materials quarried in Central Italy is presented. The method makes use of a continuous monitor equipped with a solid state alpha detector, in-line connected to a small accumulation chamber. The effects of chamber leakage and back diffusion on 222Rn free exhalation rate is evaluated. The influence of available exhalation surface, humidity content and precursors concentration on radon and thoron exhalation rates is investigated.     

A source for measurement of the absolute intensities of 226Ra gamma-radiation in equilibrium with decay products.

The design and production techniques of a gamma-ray spectrometric source of 226Ra in equilibrium with its daughter decay products have been developed. The radon emanation coefficient of the source did not exceed 0.1%. The 226Ra activity in the gamma-ray spectrometric source was measured relative to that in an alpha-particle spectrometric source by comparison of the intensities of the main gamma rays using a semiconductor gamma-ray spectrometer. The total uncertainty of the activity measurement results was 0.5% for a coverage factor of k = 2.     

Radon, thoron and their progenies measured in different dwelling rooms and reference atmospheres by using CR-39 and LR-115 SSNTD.

Detection efficiencies of the CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD) for alpha-particles emitted by radon, thoron and their decay products inside the air of different dwelling rooms and in various reference atmospheres were determined by using a Monte Carlo computer code. Alpha- and beta-activities per unit volume of air due to radon, thoron and their progenies were measured in the studied atmospheres by exploiting data obtained for the detection efficiencies of the SSNTD and measuring the resulting track density rates. Equilibrium factors between radon and its progeny and thoron and its daughters were evaluated in the studied atmospheres.     

Distribution of radionuclides in the river sediments and coastal soils of Chittagong, Bangladesh and evaluation of the radiation hazard

The concentrations and distribution of natural and anthropogenic radioactive materials in sediments and soils from around the two major rivers and coastal area of Chittagong, Bangladesh were investigated with an aim of evaluating the environmental radioactivity and radiation hazard. In the sediment and soils in general, the concentration of ²³²Th was found to be higher than that of the ²³⁸U and the activities of ²³²Th and ²³⁸U in this area are higher than the world average. ¹³⁷Cs was observed in all the samples, ranging from 0.4 to 3.88 Bq kg⁻¹. The radium equivalent activities, emanation coefficients and radon exhalation rates were estimated for the sediment and soils; the emanation coefficients, radon exhalation rates and dose rates were found to be higher than the world average values.     

Procedures for the determination of 222Rn exhalation and effective 226Ra activity in soil samples.

Two methods for measuring 222Rn exhalation and effective 226Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of 226Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of 222Rn exhalation and effective 226Ra in environmental samples.     

A new method for evaluating radon and thoron alpha-activities per unit volume inside and outside various natural material samples by calculating SSNTD detection efficiencies for the emitted alpha-particles and measuring the resulting track densities.

A Monte Carlo computer code for determining detection efficiencies of the CR-39 and LR-115 II solid-state nuclear track detectors (SSNTD) for alpha-particles emitted by the uranium and thorium series inside different natural material samples was developed. The influence of the alpha-particle initial energy on the SSNTD detection efficiencies was investigated. Radon (222Rn) and thoron (220Rn) alpha-activities per unit volume were evaluated inside and outside the natural material samples by exploiting data obtained for the detection efficiencies of the SSNTD utilized for the emitted alpha-particles, and measuring the resulting track densities. Results obtained were compared to those obtained by other methods. Radon emanation coefficients have been determined for some of the considered material samples.     

Correlation of radon anomalies with seismic events along Mat fault in Serchhip District,Mizoram, India

Radon emanation from the soil gas was studied using a deep red coloured cellulose nitrate LR-115 type II film. The study was carried out from March 2012 to February 2013 at Mat Bridge (23°18΄ N, 92°48΄ E) along Mat Fault in Serchhip district, Mizoram (India). Changes in radon concentrations have been observed. Effects of meteorological parameters on radon emission were also studied. The measured radon data shows a moderate positive correlation with relative humidity but no specific relation with air temperature and rainfall. Data obtained have been correlated to the earthquakes that occurred around the measuring sites.     

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.     

Automated measurement of 224Ra and 226Ra in water.

We present a new simple approach for automated, non-destructive measurement of the alpha-emitting radium isotopes ((223)Ra, (224)Ra, and (226)Ra) in water based on the emanation of their respective radon daughters ((219)Rn, (220)Rn, and (222)Rn). The method combines the high adsorption uptake of MnO(2) Resin for radium (K(d)=2.4 x 10(4)ml/g) over a wide pH range with the simplicity of the activity registration using a commercial radon-in-air analyzer (RAD7, DURRIDGE Company, Inc). Radium is first adsorbed onto the MnO(2) Resin by passing a water sample through the resin packed in a gas-tight glass cartridge. The same cartridge is then connected to the radon analyzer via a simple tubing system to circulate air through the resin and a drying system. The efficiency of the proposed system is determined by running standards prepared in the same manner. Our results indicate that the efficiency for (226)Ra is >22% if both (218)Po and (214)Po counts are collected. This is comparable with typical efficiencies for alpha spectrometry but with much less sample preparation. We estimate that an MDA of 0.8 pCi/L for (226)Ra may be obtained with this new approach using a 1L water sample and less than 4h of counting.     

Seasonal levels of radon and thoron in the dwellings along southern coastal Orissa,Eastern India

Inhalation of radon (²²²Rn) and thoron (²²⁰Rn) are a major source of natural radiation exposure. Indoor radon–thoron study has been carried out in some dwellings of Ganjam district, southern coastal Orissa, India using LR-115 type II plastic track detectors. Seasonal variation of indoor radon and thoron shows high values in winter and low values in both summer and rainy. The inhalation dose lies in the range of 0–0.06 μSv h^?1 and is not high from those found elsewhere in India.     

Radon exhalation rate and uranium estimation in rock samples from Bihar uranium and copper mines using the SSNTD technique.

Widespread uranium mineralization is associated with copper, nickel and other sulphides in the Singhbhum shear zone developed at the northern margin of the Singhbhum craton in the state of Bihar of India. The south-eastern part of the shear zone between Surda-Mosabani-Badia is rich in copper mineralization while the central part between Jaduguda-Bhatin-Nimdih and Narwapahar-Garadih-Turamdih is enriched in uranium. In the present study, trace uranium concentration in geological samples from the Mosabani copper mine and the Narwapahar and Jaduguda uranium mine areas have been determined using fission track registration technique. For the measurement of the radon exhalation rate, the 'can technique' using alpha sensitive LR-115 type II plastic track detectors were used. Uranium concentrations were found to vary from 1.5 to 2097.9 ppm whereas the radon exhalation rate varied from 0.2 to 19.2 Bq m-2 h-1. The values of radon exhalation rate from crushed rock and soil samples are found to correspond with the measured values of uranium in the corresponding samples. A positive correlation has been found between radon exhalation rate and uranium concentration in the samples. The linear coefficients are found to be 0.40, 0.98 and 0.95 in the Mosabani, Narwapahar and Jaduguda mine areas respectively. High values of radon exhalation in subsurface mines like Jaduguda (depth approximately 800 m) and Mosabani (depth > 1000 m) seem to emphasize the need for adequate ventilation for the removal of radon and its progenies from the mines.     

Procedures for the determination of Rn exhalation and effective Ra activity in soil samples

Two methods for measuring ²²²Rn exhalation and effective ²²⁶Ra in soil samples were studied. In the first determination, the method employed was based on the adsorption of radon onto activated charcoal and subsequent measurement of the activity of its daughters with an HPGe (high-purity germanium) detector. In the second, vials containing an aqueous suspension of the sample, mixed with an insoluble high efficiency mineral oil scintillation cocktail, were measured using a low-level liquid scintillation counter. Studies of optimum sampling time, efficiency in both procedures, variation of ²²⁶Ra efficiency with quenching, as well as the effect of sample amount and granulometry upon the quenching parameter, were carried out. The two methods were applied to the determination of ²²²Rn exhalation and effective ²²⁶Ra in environmental samples.     

226Ra and 228Ra determination in mineral waters—Comparison of methods

A comparison of different radiochemical separation procedures and measurement techniques used to determine the activity concentration of ²²⁶Ra and ²²⁸Ra in water is made with respect to accuracy, detection limits and turn-around time. Radium-226 activity concentration was determined by the radon emanation technique, alpha-particle and gamma-ray spectrometry. To determine the ²²⁸Ra activity concentration, four different techniques were used: low-level liquid scintillation counting, low-level proportional counting, alpha-particle and low-level gamma-ray spectrometry.     

我国部分地区土壤氡析出率的理论模型

目的 本研究旨在通过理论研究和实验验证初步建立我国部分地区土壤氡析出率的理论模型。方法 通过对氡在土壤中扩散理论的分析，建立土壤氡析出率数学模型，该模型考虑了土壤的镭含量、射气系数、孔隙度和含水饱和度等因素对氡析出率的影响。为验证此模型，我们在北京、贵阳和内蒙古3个不同土壤类型的地区，共30处进行了氡析出率及土壤相关物理性质的实际测量。结果 有近1／3的样品理论值与实测值吻合比较好。结论 实测结果初步显示出模型的有效性。笔者对误差分布规律及产生原因进行了分析，提出了今后土壤氡析出率模型的改进方向。