Radon Emanation Coefficient Research Articles

Radon emanation coefficient and its exhalation rate of wasted petroleum samples associated with petroleum industry in Egypt

Wasted petroleum, scale and sludge, samples associated with petroleum industries have elevated level of radionuclides concentrations which increase the radiation dose received to the workers. Radon concentration, emana- tion coefficient and exhalation rate give good information about the radioactivity levels. Twelve samples of scale, sludge and sand, collected from different oil fields in the Red Sea Refineries company for petroleum services in the eastern desert of Egypt, were selected for this study. Radon concen- tration released from selected samples was measured using AlphaGUARD radon monitor. Radon emanation coefficient and its exhalation rate were calculated based on the measured value of radon concentration. Correlation among radon exhalation rate with radium content and ''emanated radon concentration'' (radium concentration 9 emanation coeffi- cient) as well were found to be of 0.94 and 0.99, respectively. Therefore, radon exhalation rate could be useful index for both radium concentration and emanated radon. Radon emanation coefficient was increased more than twice due to water content within material of less than of 10 %.

Evaluation of radionuclide concentrations and associated radiological hazard indexes in building materials used in Egypt

Radionuclide concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in different types of building materials used in Egypt were measured using gamma-ray spectroscopy. The results showed relatively moderate radionuclide concentrations for all samples except granite, which showed extremely high concentrations of 78.75 ± 2.36, 2.82 ± 0.11 and 2.37 ± 0.07 kBq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The radiological hazard indexes of radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin), due to the presence of those radionuclides in the investigated building materials, were calculated. The released radon from the selected samples was measured using the AlphaGUARD radon monitor in order to use its value to calculate the radon emanation coefficient and the radon exhalation rate. The alpha equivalent dose (dose from indoor radon generated from building materials) was calculated using the measured values of the radium concentration and the radon emanation coefficient.

Radiological investigation of the effects of red mud disaster

On 4 October 2010, the gate of a red mud waste dump of a Hungarian alumina factory was damaged and ∼800.000 m(3) of alkaline red mud flooded the vicinity of the dumps. Red mud samples were collected from the contaminated area and they were investigated from the radiological point of view. The activity concentrations were as follows: (232)Th: 264 (194-337) Bq kg(-1), (238)U: 265 (197-332) Bq kg(-1), (226)Ra: 180 (143-237) Bq kg(-1), (40)K: 283 (228-360) Bq kg(-1). As a function of the moisture content (0-28 %), the obtained radon emanation coefficients were relatively high (7.6-20 %) and, consequently, the radon exhalation also increased.

Does the utilization of coal fly ash in concrete construction present a radiation hazard?

The advantages of utilization of coal fly ash in concrete construction, as well as the technological and environmental problems caused by an elevated content of chemical/radioactive contaminants, are discussed. The paper deals with the question whether the utilization of coal fly ash in concrete construction presents a radiation hazard. The analysis of the experimental studies shows that although radon exhalation rate of concrete containing coal fly ash can be sometimes slightly higher, than that of the reference concrete, radon emanation coefficient is lower. In view of this, the standards regulating radioactivity of building materials, but not addressing the decrease of radon emanation coefficient properly could be detrimental to the utilization of fly ash in concrete construction. Drawing direct comparisons between results presented in different papers is challenging because of varying methodologies, sample sizes, material properties, such as age, moisture and porosity, and experimental goals. The need in the systematic study considering different factors, which can influence the radon release of a concrete, is emphasized.

Granulation effects on the radon emanation rate

The radon emanation and the granulation effect on the emanation rate of several building materials (ceramic plates, sand, red brick and siporex brick) with different (226)Ra concentrations were investigated. A ball mill was used to achieve different granulations of the materials. The particle size distributions were determined by a particle size analyser (Mastersizer 2000). The increase in the (222)Rn concentration inside a closed chamber (volume ≈5.4 × 10(-3) m(3)) due to emanation from each material with different granulations was measured by an alpha spectrometer (RAD7). Thus, time-dependent curves for radon concentrations were obtained. The highest radon emanation coefficient (27 %) was obtained for the siporex sample with the smallest grain size (0.34 µm). For the ceramic pads, the granulation effect was negligible and the emanation coefficient was very low (∼0.4 %). The strongest influence of granulation on the radon emanation rate was found for the siporex brick sample.

Legislative aspects of radiation hazards from both gamma emitters and radon exhalation of concrete containing coal fly ash

Utilization of coal fly ash in concrete construction has clear environmental, technological and economical advantages. At the same time, fly ash is known to have enhanced concentrations of Naturally Occurring Radioactive Materials (NORM). Legislative issues related to the utilization of coal fly ash in concrete construction are analyzed. Different approaches implemented in standards regulating gamma radiation and radon emanation of concrete and other building materials are reviewed. Although radon exhalation rate of concrete containing coal fly ash can be sometimes slightly higher than that of the reference concrete, radon emanation coefficient is usually lower. In view of this, the standards regulating radioactivity of building materials, but not addressing radon emanation properly could be detrimental to the utilization of fly ash in concrete. At the same time, the evaluation of the excess dose caused by building materials for the radon pathway is complicated, and much more research work is required to justify the assumptions of the physical models in the future standards.

Evaluation of radiation level and radon exhalation rate of rock samples from Mahd Ad Dahab mine in Saudi Arabia

Mahd Ad Dahab mine is the largest and oldest gold mine in the middle East, situated in the western region of Al-Madina Al-Munawara in Saudi Arabia. By using a high-resolution gamma-ray spectroscopy system, various radionuclides in about 20 rock samples, collected from four different locations of the Mahd Ad Dahab mine, have been identified quantitatively based on their characteristic spectral peaks. The activity concentrations of the natural radionuclides uranium (238U), thorium (232Th), and potassium (40K) as well as some radiological parameters were measured in the rock samples. The activity concentration of uranium was found to vary from 7.94 to 38.52 Bq/kg, thorium from 3.14 to 17.79 Bq/kg and potassium activity from 93.51 to 175.83 Bq/kg. The radon emanation coefficient of the rock samples was estimated. It ranged between 0.48 and 0.55. Moreover, the radium equivalent activity in the samples ranged between 19.3 and 77.49 Bq/kg, which is lower than the allowed maximum value for worker safety. The external and internal hazard indices and gamma-radiation hazard index were found not to exceed the permissible limits.

Preliminary Study on a Regional Radon Concentration in Surface Soil Prediction Method

A reformulated mathematical equation for predicting radon concentration in surface soil has been established based on the diffusive and convection theory. The parameters in the equation, such as radon emanation coefficient, convection velocity, diffusion coefficient, porosity of soil and so on, are closely related to the soil types. In order to determine these parameters, field measurement were carried out in totally 31 sites covering four types of soil in Chengdu Area, China. And least squares fitting algorithm and inversion fitting computation were also used. The prediction equation is ultimately applied to map the radon concentration in surface soil of Chengdu Area along with the geochemical databases of uranium content distribution in soil and soil texture distribution. According to the field measurement results on 17 sites in Chengdu, the prediction was verified to work property. About 50% of the natural radiation dose which people accepted is contributed from radon and its short-life progenies. And more and more attentions are paid on the issue of the health risks from them. In fact, radon in the ambient air is mainly released from the radioactive elements uranium and radium in the soil and rocks underground. Therefore, it is of significance for radon control to delineate the potential high radon zone combining the local geological background. Especially in China, the environmental radon survey started relatively late. A large-scale indoor radon measurement has not been conducted yet. However, the database based on regional geological survey has been built in many localities. A great number of geochemical data such as the uranium content and the distribution of soil texture are available. It is a feasible way to predict the regional radon distribution quickly and efficiently by combining these data with radon migration theory. Based on a steady-state radon transport model in porous materials 1) , combined with the local geological and pedological parameters, several methodologies were also developed for predicting a regional radon concentration 2-4) . In this paper, a methodology for predicting the radon distribution in surface soil of Chengdu Area was introduced. First, a reformulated simplified mathematical equation for the prediction was established by using a new boundary condition, i.e., the flux density of radon on ground-air interface is continuous and equal. Second, the parameters in the radon concentration equation, such as radium content, soil porosity and so on, were measured by field samples. The theoretical radon value was calculated and compared with the measured value. The ultimate prediction equation was derived by corrected and verified by field measured results.

The effect of water content on the radon emanation coefficient for some building materials used in Japan

Abstract Building materials used in Japan were collected from several companies and their radionuclide concentrations were measured. Fifteen granite samples with high activity concentrations were selected for the present study. To investigate the effect of water content on the radon emanation coefficient, the coefficient was measured under 3 different conditions (dry, normal, and wet). The emanation coefficients were then used to calculate the alpha equivalent dose (dose from indoor radon generated from building materials), assuming a simple room model. The radon emanation coefficient for the dry condition ranged from (3.7 ± 0.1)% to (27.2 ± 3.9)%, with an average value of (10.5 ± 1.4)%. The emanation coefficients were 2–5 times that size for the wet condition. Similarly, the alpha dose became larger, owing to its proportion to the emanation coefficient, indicating that water content in building materials is an important factor for the emanation coefficient as well as the radiation dose. The radon exhalation rate was also measured for the dry samples. Radon exhalation rate and radium concentration had a relatively low correlation ( R 2 = 0.40). However, the correlation between radon exhalation rate and “emanated radon concentration” (radium concentration × emanation coefficient) was much higher ( R 2 = 0.84). Therefore, emanated radon concentration could be a useful index for exhalation rate and alpha equivalent dose, but radium concentration in building materials alone is not.

Radiological characterization of commercially available “radon spa sources”

Nowadays, artificial “radon spa sources” for home baths are commercially available. Although these sources could give a potential radiation exposure to the users, few studies have been reported on their radiological measurements. In the present study, five types of radon spa sources were collected and their radiological characterization was investigated. The followings were estimated for these samples: (1) radon emanation coefficients (dry and water-saturated conditions), (2) surface γ-ray dose rate, (3) surface count rates for α- and β-rays, (4) activity concentrations of 226Ra, 232Th and 40K, and (5) concentrations of radon and thoron generated from the sources located in an air flow system. The activity concentrations were very high (except for one sample (named “sample B”), although radon emanation coefficient was low compared with soil. This leads to high concentrations of radon/thoron generated from the sample. The maximum surface γ-ray dose rate was observed for sample A (2.7 μGy h−1). If people stay very close to the sample for a long time, the exposure might be significant.

Determination of the emanation coefficient and the Henry’s law constant for the groundwater radon

The radon emanation coefficient (e) from aquifer rock and the Henry’s law constant (H) of radon were determined by measuring activity concentrations using liquid scintillation counter (LSC). For the evaluation of the method, the coefficients were measured at 0, 10 and 20 °C and the temperature dependency of the coefficients was compared with others. The radon emanation coefficients from the rock particles used in this work are 0.0845, 0.1007 and 0.1308 at 0, 10 and 20 °C, respectively. The dimensionless Henry’s law constants for the groundwater used in this work are 0.994, 1.153 and 2.641 at 0, 10 and 20 °C, respectively. The results show a good agreement with those in literatures.

A simple technique for studying the dependence of radon and thoron exhalation rate from building materials on absolute humidity

Indoor radon and thoron concentrations were dominated with their exhalation rate from building materials. Thus, the evaluation of exhalation rate with highly precise is important. This paper presented a new technique to measure the dependence radon/thoron exhalation rate, from building materials used in Japan, on absolute humidity. The measurement technique consisted of a solid state alpha detector equipped a ventilation-type chamber and humidity control system in a flow through method. The exhalation rate of dried samples (Indian red granite and Japanese gray granite) was measured at various absolute humidity levels in the range of 1–20 g cm−3. It was found that exhalation rate increased exponential with increasing of absolute humidity for both samples. Furthermore, the dependence of radon emanation coefficient on building material’s temperature was also studied using an accumulation chamber equipped with scintillation cell alpha detector. The emanation coefficient of dry sample increased proportionally with increasing the material’s temperature with a correlation factor of 0.88.

Seasonal variation on radon emission from soil and water

Radon is being measured continuously in spring water and soil-gas at Badshahi Thaul Campus, Tehri Garhwal in Himalayan region by using radon Emanometer since December 2002. An effort was made to correlate the variance of radon concentrations in spring water and soil-gas with meteorological parameters at the same location. The main meteorological parameters that affect the radon emanation from host material is surrounding temperature, barometric pressure, wind velocity, rain fall and water level of the spring. The correlation coefficient between radon concentration in spring water and different atmospheric parameters was computed. The correlation coefficient between radon concentration in spring water and the maximum atmospheric temperature was 0.3, while it was 0.4 for minimum atmospheric temperature at the monitoring site. The correlation coefficient for radon concentration in spring water with minimum and maximum relative humidity was 0.4. Spring water radon concentration was found positively correlated (0.6) with water discharge rate of the spring. A weak correlation (0.09) was observed between the radon concentration in spring water and rain fall during the measurement period. As temperature of near surface soil increases, the radon emanation coefficient from the soil surface also increases. The possible effects due to global warming and other climatic changes on environment radiation level were also discussed in detail.

Radon Emanation Phenomena: A Probabilistic Basis to Estimate Radon Emanation Coefficients Based on Its Zigzag Travel

Previous theoretical approaches based on mathematical models by other researchers to the subject of radon emanation assumed straight linear travel of radon generated in grains constituting rocks or soils. However, it is difficult for these approaches to explain high radon emanation coefficients for rocks or soils without the introduction of the ideas of radon indirect recoil or a threshold for imbedding into grains. Unlike them, the present authors proposed anotherhypothesis based on the idea of radon zigzag travel and elucidated high radon emanation in a previous paper. The radon zigzag travel is caused by many collisions of radon with atoms constituting the grains. The results of the theoretical calculation successfully supported the claims of nanopore presence by Rama and Moore and radium layer presence near grain surfaces by Krishnaswami and Seidemann in a unified manner. However, the present authors think there is still room to improve their theory and they want to entice researchers toward a better explanation of high radon emanation for rocks or soils. Therefore, they give a probabilistic basis for their hypothesis and make a comparison between radon emanation coefficients obtained on straight linear and zigzag travel models, before concluding with a validity check of the models.

High Radon Emanation Coefficients of Porous Matters Produced through Filtration and Precipitation

Previous theoretical predictions of high radon emanation coefficients were verified in experiments using porous matters artificially produced through filtration and precipitation. Such porous matters were prepared by replicating uranium-bearing waste generating processes used in fuel fabrication facilities in Japan except that radium was employed instead of uranium. In the replication, a liquid containing a trace amount of naturally occurring radium was processed by filtration or precipitation, resulting in radium adsorption on the surfaces of the matrices used as agents for the processing. The matrices were diatomaceous earth for filtration and iron (III) hydroxide for precipitation. Radon emanation coefficients of these matrices were measured and proved to be very high as expected from the authors' previous theoretical calculations which predicted that chemical procedures like filtration or precipitation could lead to very high radon emanation coefficients. Filtration and precipitation are the most common processes employed in chemical industries. Therefore, the present study also provides important information on radon emanation coefficients for workers in those chemical industries which handle substances containing naturally occurring radium. The findings further imply that man-made artificial industrial products containing naturally occurring radium should be distinguished from ubiquitous minerals, rocks and soils containing naturally occurring radium from a radiological exposure viewpoint, because the radon emanation coefficients of the former are generally higher than those of the latter.

Decontamination of Sludgelike Uranium-Bearing Wastes: Decontamination Feasibility Judgment Using Radon Emanation Coefficients and Development of Decontamination Methods

It is difficult to decontaminate sludgelike uranium-bearing wastes by wet methods, such as employing nitric acid for selective uranium dissolution. This is because these uranium-bearing wastes have very small pores inside which uranium is deposited, and the decontamination liquid cannot get inside the pores and so cannot dissolve the uranium. The present study found that radon emanation coefficient measurements can be employed to judge if decontamination liquid can get inside the pores. In fact, the difficulty of decontamination was corroborated by these measurements. Accordingly, wet decontamination methods of selective uranium dissolution were abandoned. Instead two newly developed decontamination methods were considered: one employing ClF3 gas and the other employing adsorbent for uranium in a solution of completely dissolved sludgelike uranium-bearing wastes. These two methods were derived as a natural consequence of the difficulty in wet decontamination methods. In the former method, a high degree of decontamination below 3.3 ppm (0.3 Bq/g for 4.5% enriched uranium) was achieved by ClF3. In the latter, complete dissolution was achieved by the addition of NaOH and H2SO4 to the wastes. As a next research step, efforts to develop adequate adsorbents for uranium are desired.

Measurements of radiation level in petroleum products and wastes in Riyadh City Refinery

Recent concern has been devoted to the hazard arising from naturally occurring radioactive materials (NORM) in oil and gas facilities. Twenty-seven petroleum samples were collected from Riyadh Refinery. Fourteen samples were products and 13 were waste samples; three of them were scale samples and 10 were sludge samples. The specific radioactivities of 238U, 232Th, 226Ra, 224Ra, 40K, and 235U for all samples were determined using high-resolution gamma-ray spectrometry. The radium equivalent activity, radiation hazard indices and absorbed dose rate in air for all waste samples were estimated. The radon emanation coefficient of the waste samples was estimated. It ranged between 0.574 and 0.154. The age of two scale samples was determined and found to be 2.39 and 3.66 years. The chemical structure of the waste samples was investigated using X-ray florescence analysis (XRF) and Mg, Al, Si, S, Cl, Ca and Fe were found in all samples. From this study, it was noticed that the concentrations of the natural radionuclides in the petroleum wastes were higher than that of the petroleum products.

High Radon Emanation Coefficients of Porous Matters Produced through Filtration and Precipitation

Previous theoretical predictions of high radon emanation coefficients were verified in experiments using porous matters artificially produced through filtration and precipitation. Such porous matters were prepared by replicating uranium-bearing waste generating processes used in fuel fabrication facilities in Japan except that radium was employed instead of uranium. In the replication, a liquid containing a trace amount of naturally occurring radium was processed by filtration or precipitation, resulting in radium adsorption on the surfaces of the matrices used as agents for the processing. The matrices were diatomaceous earth for filtration and iron (III) hydroxide for precipitation. Radon emanation coefficients of these matrices were measured and proved to be very high as expected from the authors' previous theoretical calculations which predicted that chemical procedures like filtration or precipitation could lead to very high radon emanation coefficients. Filtration and precipitation are the most common processes employed in chemical industries. Therefore, the present study also provides important information on radon emanation coefficients for workers in those chemical industries which handle substances containing naturally occurring radium. The findings further imply that man-made artificial industrial products containing naturally occurring radium should be distinguished from ubiquitous minerals, rocks and soils containing naturally occurring radium from a radiological exposure viewpoint, because the radon emanation coefficients of the former are generally higher than those of the latter.

Decontamination of Sludgelike Uranium-Bearing Wastes: Decontamination Feasibility Judgment Using Radon Emanation Coefficients and Development of Decontamination Methods

Decontamination of Sludgelike Uranium-Bearing Wastes: Decontamination Feasibility Judgment Using Radon Emanation Coefficients and Development of Decontamination Methods

Theoretical Estimation of Radon Emanation Coefficients for UO2 Particles Deposited on Surfaces of Uranium-bearing Wastes

In nuclear fuel fabrication facilities, fine particles of UO2 deposit on the surfaces of walls, equipment, ventilation filters, etc. which may finally become uranium-bearing wastes when these items are removed or replaced. Radon is one progeny of uranium and emanates from those wastes. It is very difficult to experimentally simulate such radon emanation, which means it is difficult to measure radon emanation coefficients for those wastes. The present paper theoretically calculated radon emanation coefficients for them assuming UO2 particles remain on the surfaces of such wastes in the distant future when radon is formed in these particles. The calculated average radon emanation coefficient was 0.03. With more complete information about particle size distribution from fuel manufacturers, this method would be able to provide better predictions.