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Tomozo Sasaki - One of the best experts on this subject based on the ideXlab platform.
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Radon Emanation Phenomena: A Probabilistic Basis to Estimate Radon Emanation Coefficients Based on Its Zigzag Travel
Journal of Nuclear Science and Technology, 2008Co-Authors: Tomozo Sasaki, Yasuyoshi GunjiAbstract: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 ...
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High Radon Emanation Coefficients of Porous Matters Produced through Filtration and Precipitation
Journal of Nuclear Science and Technology, 2008Co-Authors: Tomozo Sasaki, Yasuyoshi GunjiAbstract: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 comm...
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Uranium-Bearing Wastes and Their Radon Emanation
Transactions of the Atomic Energy Society of Japan, 2007Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Mitsutaka ImamuraAbstract:There are no data available with regard to Radon Emanation coefficients for uranium-bearing wastes; such data are needed for the assessment of radiation exposure from Radon that will be generated in the distant future as one uranium progeny at shallow land disposal sites for uranium-bearing wastes. There are many kinds of uranium-bearing wastes. However, it is not necessary to measure the Radon Emanation coefficients for all of them for two reasons. First, the Radon Emanation coefficients for uranium-bearing wastes contaminated by dissolved uranium are determined by the uranium chemical form, the manner of uranium deposition on the waste matrix, and the size of the particles which constitute the waste matrix. Therefore, only a few representative measurements are sufficient for such uranium-bearing wastes. Second, it is possible to make theoretical calculations of Radon Emanation coefficients for uranium-bearing wastes contaminated by UO2 particles before sintering. In the present study, simulated uranium-bearing wastes contaminated by dissolved uranium were prepared, their Radon Emanation coefficients were measured and Radon Emanation coefficients were calculated theoretically for uranium-bearing wastes contaminated by UO2 particles before sintering. The obtained Radon Emanation coefficients are distributed at higher values than those for ubiquitous soils and rocks in the natural environment. Therefore, it is not correct to just compare uranium concentrations among uranium-bearing wastes, ubiquitous soils and rocks in terms of radiation exposure. The Radon Emanation coefficients obtained in the present study have to be employed together with the uranium concentration in uranium-bearing wastes in order to achieve proper assessment of radiation exposure.
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Theoretical Estimation of Radon Emanation Coefficients for UO2 Particles Deposited on Surfaces of Uranium-bearing Wastes
Journal of Nuclear Science and Technology, 2007Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract: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.
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Theoretical Study of High Radon Emanation
Journal of Nuclear Science and Technology, 2005Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:Radon Emanation coefficients larger than 0.6 have been reported; such large values were unexpected. This led the authors to study how the maximum possible Radon Emanation coefficient (hereafter referred to as ‘maximum Radon Emanation probability’) could be determined. Theoretical calculations were repeated in which the grain configuration was changed in order to get the maximum Radon Emanation probability. Two types of grains were targeted. The first type consisted of two components mixed together; one component was a large amount of mother grains including no radium and the other component was a small amount of very fine grains including radium. For this type, the maximum Radon Emanation probability was obtained as 0.75. The second type consisted of only one grain component including radium. For this type, the maximum Radon Emanation probability was 0.625. In both types, the high coefficients were attributed to the extremely small size of the radium-bearing grains. This finding hinted at a possible count...
Takeshi Okuda - One of the best experts on this subject based on the ideXlab platform.
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Theoretical Estimation of Radon Emanation Coefficients for UO2 Particles Deposited on Surfaces of Uranium-bearing Wastes
Journal of Nuclear Science and Technology, 2007Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract: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.
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Theoretical Study of High Radon Emanation
Journal of Nuclear Science and Technology, 2005Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:Radon Emanation coefficients larger than 0.6 have been reported; such large values were unexpected. This led the authors to study how the maximum possible Radon Emanation coefficient (hereafter referred to as ‘maximum Radon Emanation probability’) could be determined. Theoretical calculations were repeated in which the grain configuration was changed in order to get the maximum Radon Emanation probability. Two types of grains were targeted. The first type consisted of two components mixed together; one component was a large amount of mother grains including no radium and the other component was a small amount of very fine grains including radium. For this type, the maximum Radon Emanation probability was obtained as 0.75. The second type consisted of only one grain component including radium. For this type, the maximum Radon Emanation probability was 0.625. In both types, the high coefficients were attributed to the extremely small size of the radium-bearing grains. This finding hinted at a possible count...
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demonstration of a method to suppress Radon Emanation from uranium bearing wastes
Journal of Nuclear Science and Technology, 2004Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:The authors have previously done a theoretical study of Radon Emanation and quantitatively demonstrated that a small pore of even nanometer size with moisture in its microscopic grain structure can give as high a Radon Emanation coefficient as around 0.18. Therefore, it was concluded necessary to remove pores of any size in the grain in order to suppress Radon Emanation. Melting of uranium-bearing wastes is one of the best technologies for this purpose. In order to verify this theoretical finding, a series of experiments was carried out using three test samples; unprocessed, cemented and vitrified calcium superphosphate. Calcium superphosphate was chosen because it resembles a uranium-bearing waste like sludge in terms of both radioactive nuclide adhesion on the grain surface of the waste matrix (surface contamination) and the grain geometric shape. As expected from the theory, Radon Emanation from the vitrified sample was extremely low compared to the unprocessed sample. On the other hand, Radon emanatio...
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Mathematical Modeling of Radon Emanation
Journal of Nuclear Science and Technology, 2004Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:It is well known that Radon Emanation is affected by moisture. The models which explain Radon Emanation can be considered to come in three types. One is to predict the maximum possibility of Radon Emanation assuming uniform distribution of radium in a solid grain independent of moisture. The other two are to explain moisture effect on Radon Emanation, but their aims are different from each other. The first of them aims to demonstrate a theory explaining microscopic phenomena of Radon Emanation employing observed macroscopic phenomena of Radon Emanation under moist condition. The second aims to predict the leveling-off value of Radon Emanation under moist conditions employing an observed data of Radon Emanation under dry condition. The present paper develops a close-packed spherical grain model which belongs to the last type of model just mentioned. This model is oriented to contribute to the safety assessment of uranium-bearing waste disposal. Uranium-bearing waste generates Radon as one of the uranium de...
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Radon Emanation Dependence on Grain Configuration
Journal of Nuclear Science and Technology, 2004Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:Very small pores called ‘nanopores’ play an important role in enhancement of Radon Emanation in grains. The concept of nanopores was originally proposed by Rama and Moore. The present paper has evolved this concept into more specific grain configurations to estimate Radon Emanation coefficients by theoretical calculations. These configurations cover combinations of nanopore geometry and radium distribution in grains. Radium is the parent nuclide of Radon. Assuming isotropic emission of Radon from its birthplace with recoil energy imparted by the decay of radium, the present calculation led to nearly the same high Radon Emanation coefficients as measured; these were as high as 0.18 under moist conditions. Therefore, it was theoretically verified that even small pores of nanometer size may contribute to high Radon Emanation.
Yasuyoshi Gunji - One of the best experts on this subject based on the ideXlab platform.
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Radon Emanation Phenomena: A Probabilistic Basis to Estimate Radon Emanation Coefficients Based on Its Zigzag Travel
Journal of Nuclear Science and Technology, 2008Co-Authors: Tomozo Sasaki, Yasuyoshi GunjiAbstract: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 ...
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High Radon Emanation Coefficients of Porous Matters Produced through Filtration and Precipitation
Journal of Nuclear Science and Technology, 2008Co-Authors: Tomozo Sasaki, Yasuyoshi GunjiAbstract: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 comm...
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Uranium-Bearing Wastes and Their Radon Emanation
Transactions of the Atomic Energy Society of Japan, 2007Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Mitsutaka ImamuraAbstract:There are no data available with regard to Radon Emanation coefficients for uranium-bearing wastes; such data are needed for the assessment of radiation exposure from Radon that will be generated in the distant future as one uranium progeny at shallow land disposal sites for uranium-bearing wastes. There are many kinds of uranium-bearing wastes. However, it is not necessary to measure the Radon Emanation coefficients for all of them for two reasons. First, the Radon Emanation coefficients for uranium-bearing wastes contaminated by dissolved uranium are determined by the uranium chemical form, the manner of uranium deposition on the waste matrix, and the size of the particles which constitute the waste matrix. Therefore, only a few representative measurements are sufficient for such uranium-bearing wastes. Second, it is possible to make theoretical calculations of Radon Emanation coefficients for uranium-bearing wastes contaminated by UO2 particles before sintering. In the present study, simulated uranium-bearing wastes contaminated by dissolved uranium were prepared, their Radon Emanation coefficients were measured and Radon Emanation coefficients were calculated theoretically for uranium-bearing wastes contaminated by UO2 particles before sintering. The obtained Radon Emanation coefficients are distributed at higher values than those for ubiquitous soils and rocks in the natural environment. Therefore, it is not correct to just compare uranium concentrations among uranium-bearing wastes, ubiquitous soils and rocks in terms of radiation exposure. The Radon Emanation coefficients obtained in the present study have to be employed together with the uranium concentration in uranium-bearing wastes in order to achieve proper assessment of radiation exposure.
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Theoretical Estimation of Radon Emanation Coefficients for UO2 Particles Deposited on Surfaces of Uranium-bearing Wastes
Journal of Nuclear Science and Technology, 2007Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract: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.
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Theoretical Study of High Radon Emanation
Journal of Nuclear Science and Technology, 2005Co-Authors: Tomozo Sasaki, Yasuyoshi Gunji, Takeshi OkudaAbstract:Radon Emanation coefficients larger than 0.6 have been reported; such large values were unexpected. This led the authors to study how the maximum possible Radon Emanation coefficient (hereafter referred to as ‘maximum Radon Emanation probability’) could be determined. Theoretical calculations were repeated in which the grain configuration was changed in order to get the maximum Radon Emanation probability. Two types of grains were targeted. The first type consisted of two components mixed together; one component was a large amount of mother grains including no radium and the other component was a small amount of very fine grains including radium. For this type, the maximum Radon Emanation probability was obtained as 0.75. The second type consisted of only one grain component including radium. For this type, the maximum Radon Emanation probability was 0.625. In both types, the high coefficients were attributed to the extremely small size of the radium-bearing grains. This finding hinted at a possible count...
M.a. Misdaq - One of the best experts on this subject based on the ideXlab platform.
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The influence of the lithology and granulation on Radon Emanation in a sedimentary phosphatic deposit using solid state nuclear track detectors
Journal of Radioanalytical and Nuclear Chemistry, 1999Co-Authors: M.a. Misdaq, A. Bakhchi, A. Ktata, J. LamineAbstract:Samples have been collected from different layers in a sedimentary phosphatic deposit and sieved. Different granulometric fractions have been selected. The uranium and thorium contents have been determined in each phosphate sample and its corresponding selected fractions. Radon (222Rn) α-activities per unit volume have been evaluated inside and outside each phosphate sample and its corresponding selected fractions by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD). The Radon Emanation coefficient in each phosphate layer has been determined and the global Radon alpha activity outside a parallelepipedic block of the layers studied was evaluated. The influence of the lithology and granulation on the Radon Emanation has been studied.
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Study of the influence of porosity on the Radon Emanation coefficient in different building material samples by combining the SSNTD technique with Monte Carlo simulations
Radiation Physics and Chemistry, 1998Co-Authors: M.a. Misdaq, H. Khajmi, A. KtataAbstract:Abstract Radon alpha-activities per unit volume have been measured inside and outside different building material samples by using CR-39 and LR-115 type II solid state nuclear track detectors (SSNTD). Radon Emanation coefficients of the studied building materials have been evaluated. The porosities of the building material samples studied have been determined by using a Monte Carlo calculational method adapted to the experimental conditions and compared with data obtained by the Archimedes's method. The influence of the building material porosity on the Radon Emanation coefficient has been investigated.
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A new method for determining the Radon Emanation coefficients and Radon production rates in different building materials using solid state nuclear track detectors
Journal of Radioanalytical and Nuclear Chemistry, 1997Co-Authors: M.a. Misdaq, H. MoustaaidineAbstract:Radon α-activity concentrations have been measured inside and outside various building materials by combining a calculational method with the solid state nuclear track detector (SSNTD) technique. Radon Emanation coefficients of the studied materials have been evaluated. A new calibration method for determining the radium (^226Ra) and thorium (^232Th) specific activities of the considered building materials has been developed. The Radon production rates per unit volume of the studied materials have been evaluated. The influence of the material porosity on the Radon Emanation coefficient and Radon production rate have been investigated.
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A new method for studying the influence of pollution and soil nature on the Radon Emanation from water samples by using solid state nuclear track detectors
Journal of Radioanalytical and Nuclear Chemistry Articles, 1996Co-Authors: M.a. Misdaq, C. SatifAbstract:Radon Emanation from surface water and groundwater samples has been studied by using CR-39 and LR-115 solid state nuclear track detectors (SSNTD). A calibration method for determining the thoron and Radon concentrations of the water samples studied has been developed. The effect of pollution due to coal fly ashes, cement and granite dusts on the Radon Emanation from water samples has been investigated. The influence of the Radon source on the Radon Emanation rates from water samples has been studied.
Patitapaban Sahu - One of the best experts on this subject based on the ideXlab platform.
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Radon Emanation from backfilled mill tailings in underground uranium mine.
Journal of environmental radioactivity, 2014Co-Authors: Patitapaban Sahu, Devi Prasad Mishra, Durga Charan Panigrahi, Vivekananda Jha, R. Lokeswara Patnaik, Narendra Kumar SethyAbstract: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.
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Radon Emanation from low grade uranium ore
Journal of Environmental Radioactivity, 2013Co-Authors: Patitapaban Sahu, Devi Prasad Mishra, D C Panigrahi, V N Jha, Lokeswara R PatnaikAbstract:Estimation of Radon Emanation in uranium mines is given top priority to minimize the risk of inhalation exposure due to short-lived Radon progeny. This paper describes the Radon Emanation studies conducted in the laboratory as well as inside an operating underground uranium mine at Jaduguda, India. Some of the important parameters, such as grade/226Ra activity, moisture content, bulk density, porosity and Emanation fraction of ore, governing the migration of Radon through the ore were determined. Emanation from the ore samples in terms of Emanation rate and Emanation fraction was measured in the laboratory under airtight condition in glass jar. The in situ Radon Emanation rate inside the mine was measured from drill holes made in the ore body. The in situ222Rn Emanation rate from the mine walls varied in the range of 0.22–51.84 × 10−3 Bq m−2 s−1 with the geometric mean of 8.68 × 10−3 Bq m−2 s−1. A significant positive linear correlation (r = 0.99, p < 0.001) between in situ222Rn Emanation rate and the ore grade was observed. The Emanation fraction of the ore samples, which varied in the range of 0.004–0.089 with mean value of 0.025 ± 0.02, showed poor correlation with ore grade and porosity. Empirical relationships between Radon Emanation rate and the ore grade/226Ra were also established for quick prediction of Radon Emanation rate from the ore body.
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Radon Emanation from low-grade uranium ore
Journal of environmental radioactivity, 2013Co-Authors: Patitapaban Sahu, Devi Prasad Mishra, V N Jha, Durga Charan Panigrahi, R. Lokeswara PatnaikAbstract:Estimation of Radon Emanation in uranium mines is given top priority to minimize the risk of inhalation exposure due to short-lived Radon progeny. This paper describes the Radon Emanation studies conducted in the laboratory as well as inside an operating underground uranium mine at Jaduguda, India. Some of the important parameters, such as grade/226Ra activity, moisture content, bulk density, porosity and Emanation fraction of ore, governing the migration of Radon through the ore were determined. Emanation from the ore samples in terms of Emanation rate and Emanation fraction was measured in the laboratory under airtight condition in glass jar. The in situ Radon Emanation rate inside the mine was measured from drill holes made in the ore body. The in situ222Rn Emanation rate from the mine walls varied in the range of 0.22–51.84 × 10−3 Bq m−2 s−1 with the geometric mean of 8.68 × 10−3 Bq m−2 s−1. A significant positive linear correlation (r = 0.99, p
