The Experts below are selected from a list of 1764 Experts worldwide ranked by ideXlab platform
Hyam Nazmy Bader Khalaf - One of the best experts on this subject based on the ideXlab platform.
-
a combined system for Radioactive Aerosol size distribution measurements of radon decay products
Radiation Physics and Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:Abstract To measure the size distribution of Radioactive Aerosols in the widest possible range, a complex system operating on different physical principles was designed. The system consists of a twelve-stage diffusion battery, a five-stage cascade impactor, and a set of three analytical Aerosol filters with established permeability functions. The diffusion battery allows obtaining data on the distribution of Aerosols in the range of 0.5–50 nm, the cascade impactor in the range of 0.8–20 μm, and the standard analytical filters in the range of 0.05–0.8 μm. This system was tested in a standard radon box. At a low Aerosol concentration (less than 1000 cm−3), nearly 45–75% of radon decay product activity was associated with ultrafine particles with an AMTD of ~1 nm (the so-called unattached fraction). Additionally, a mode with a diameter of ~ 5–8 nm was registered. Larger Aerosol particles were not caught by the cascade impactor, instead being deposited on the final filters. This shows that the particles are less than 800 nm in size (the first cut-off diameter of the impactor), which is in good agreement with the literature. When a high concentration of Aerosol particles is created by an additional Aerosol source, the unattached fraction is absent and maximum activity is observed in the cascade impactor and finishing filters.
-
Radioactive Aerosol permeability through russian radiometric analytical pf filters
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:In this work, the permeability of the Radioactive Aerosol particles through different types of Petryanov filters is studied. The experiments were performed with standard radon box, special diffusion battery and AIP-2 cascade impactor. During the experiments a significant breakthrough is observed for different Aerosol filters. The various size modes of the Radioactive Aerosols passing throw the filter are studied. At low Aerosol concentration, the penetration of 1 nm approximately 1% and for 20 nm is varied from 12 to 20%. The different types of filters prevented all unattached radon decay products and the most size activity became with AMTD ~ 10 nm. At high Aerosol concentration, the activity of unattached fraction nearly deleted. The activity of Aerosols with AMTD ~ 10 nm is increased. The filters prevented all particles higher than 0.8 µm.
-
comparison of Radioactive Aerosol size distributions activity number mass and surface area
Applied Radiation and Isotopes, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M E Vasyanovich, M ZhukovskyAbstract:Abstract Information regarding the number, mass, and specific surface area distributions of Aerosols is extremely important for assessments of exposure to radiation due to the intake of Radioactive Aerosols by inhalation. In this study, these distributions were compared with the activity size distributions for radon decay products. The experiments were conducted in a radon chamber under controlled conditions for the Aerosol concentrations and with size distributions in the range from 5 nm to 10 µm. The activity size distributions of the Aerosols were measured by using a diffusion battery and two types of cascade impactors. The Aerosol concentrations during the experiments were in the range from 2 × 103 to 2.5 × 105 cm–3. The measurements obtained with a diffusion battery demonstrated that at the low Aerosol concentration, up to 80% of activity of the radon decay products was connected with Aerosol particles with an activity median thermodynamic diameter (AMTD) ~1 nm (unattached fraction). After injecting the Aerosols into the experimental chamber, the activity of the unattached fraction decreased to practically zero but we observed the presence of the activity of Aerosols with AMTD values ~10–20 nm. After injecting the Aerosols, the distribution of the Aerosol specific surface area exhibited a bimodal distribution, where the median diameter in the accumulation mode was ~120 nm and the geometric standard deviation (GSD) was 1.3. The median diameter in the coarse mode changed with time due to the deposition of Aerosols on the walls of the chamber, where it decreased from 5 µm (GSD = 1.6) at 15 min after injection to 2 µm (GSD = 2.5) at 120 min after injection. The distribution of the Aerosol activity measured by the cascade impactor was virtually independent of the time from the moment when the Aerosols were injected. The parameters used to assess the activity distribution comprised an activity median aerodynamic diameter (AMAD) ~500–650 nm and GSD = 1.5. Comparisons of the activity distributions with the distributions for the number, mass, and specific surface area showed that the closest correspondence was with the average distribution over the specific surface, whereas there were no exact correspondences with the other distributions.
F Gensdarmes - One of the best experts on this subject based on the ideXlab platform.
-
influence of the beta energy decay spectrum and particle size on the Aerosol specific self charging rate of Radioactive Aerosol
European Aerosol Conference EAC, 2019Co-Authors: Gregoire Dougniaux, Mamadou Sow, F GensdarmesAbstract:Nuclear accidents, such as Chernobyl or Fukushima, led to release of Radioactive Aerosols into the environment, which are measured all over the world. During this long-range transport, Aerosols undergo an electrical self-charging due the radioactivity they carry. The specific self-charging rate for particles containing β emitter radionuclides is always considered equal to the specific activity of the particles (Bq/particle) (Clement & Harrison, 1992; Gensdarmes et al., 2001). This assumption is supported by the fact that radionuclides usually considered (Kim et al., 2017), such as 137Cs, 132Te or 131I, have a high mean energy β decay which leads to an electron path length in matter larger than the particle diameter. This study aims to quantify the influence of this assumption by performing calculations of the specific self-charging rate of particles considering the full energy spectrum of β emitter radionuclides. The specific self-charging is treated as the electron escape probability from the particle. Calculations of electron transport in particle matter are realized with Geant4 toolkit (Agostinelli et al., 2003). The particles studied are single spheres with diameters ranging from 20 nm to 200 µm. The simulations are realized for pure iron particles (density 7.87 g/cm3) in vacuum environment (i.e. no interaction of electrons with matter outside the particle). The β emitter radionuclide considered for the calculation, 132Te, is selected from the case studied by Kim et al. (2017). We assume that the radionuclide is homogeneously distributed in the whole particle and random electron emission occurs. The maximum energy of β decay of 132Te is 240.1 keV. The mean energy of β decay is roughly equal to one third of the maximum energy. To calculate characteristic path length of electron in matter, usually a lower value, equal to a quarter of the maximum energy, is considered in order to take account of the higher coefficients of linear energy transfer for low energy electrons of the spectrum (Gensdarmes et al., 2001). The escape probability of electrons is defined for each particle diameter by the ratio of the electrons that exit the particle by the total number of generated electrons. 105 electrons are generated for each diameter and energy considered. An energy size bin of 1 keV is considered for calculation with the full spectrum. The assumption of escape probability equal to 1 for β emitter Radioactive Aerosol studied here leads to an overestimation of specific particle self-charging rate for diameters below 20 µm. The calculations based only on the mean energy could not give accurate results; the discrepancy lies between 10 % and 25 % in comparison to that obtained with the full spectrum for diameters between 1 µm and 10 µm. Specific attention has to be paid for other radionuclides with low energy spectrum like tritium.
-
electrical charging of Radioactive Aerosols comparison of the clement harrison models with new experiments
Journal of Aerosol Science, 2001Co-Authors: F Gensdarmes, D Boulaud, A RenouxAbstract:The electrical charge of beta-active Aerosols was determined using a radial flow DMA and a CNC. The Radioactive Aerosol could evolve and sampled within different geometrical volumes. Our results which are compared with the Clement and Harrison models, show an increase in the mean charge of the Radioactive Aerosol when the intensity of ionisation is reduced by the sampling geometry. In this situation, considering the ion recombination process the models slightly underestimate the electrical charge, while it overestimates the results when ion removal is determined by the diffusion to the walls of the sampling volume. Our results therefore confirm the theoretical studies carried out by Clement and Harrison, in particular the possibility of observing localised enhancement of the electrical charging of Radioactive Aerosols.
M Zhukovsky - One of the best experts on this subject based on the ideXlab platform.
-
a combined system for Radioactive Aerosol size distribution measurements of radon decay products
Radiation Physics and Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:Abstract To measure the size distribution of Radioactive Aerosols in the widest possible range, a complex system operating on different physical principles was designed. The system consists of a twelve-stage diffusion battery, a five-stage cascade impactor, and a set of three analytical Aerosol filters with established permeability functions. The diffusion battery allows obtaining data on the distribution of Aerosols in the range of 0.5–50 nm, the cascade impactor in the range of 0.8–20 μm, and the standard analytical filters in the range of 0.05–0.8 μm. This system was tested in a standard radon box. At a low Aerosol concentration (less than 1000 cm−3), nearly 45–75% of radon decay product activity was associated with ultrafine particles with an AMTD of ~1 nm (the so-called unattached fraction). Additionally, a mode with a diameter of ~ 5–8 nm was registered. Larger Aerosol particles were not caught by the cascade impactor, instead being deposited on the final filters. This shows that the particles are less than 800 nm in size (the first cut-off diameter of the impactor), which is in good agreement with the literature. When a high concentration of Aerosol particles is created by an additional Aerosol source, the unattached fraction is absent and maximum activity is observed in the cascade impactor and finishing filters.
-
Radioactive Aerosol permeability through russian radiometric analytical pf filters
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:In this work, the permeability of the Radioactive Aerosol particles through different types of Petryanov filters is studied. The experiments were performed with standard radon box, special diffusion battery and AIP-2 cascade impactor. During the experiments a significant breakthrough is observed for different Aerosol filters. The various size modes of the Radioactive Aerosols passing throw the filter are studied. At low Aerosol concentration, the penetration of 1 nm approximately 1% and for 20 nm is varied from 12 to 20%. The different types of filters prevented all unattached radon decay products and the most size activity became with AMTD ~ 10 nm. At high Aerosol concentration, the activity of unattached fraction nearly deleted. The activity of Aerosols with AMTD ~ 10 nm is increased. The filters prevented all particles higher than 0.8 µm.
-
comparison of Radioactive Aerosol size distributions activity number mass and surface area
Applied Radiation and Isotopes, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M E Vasyanovich, M ZhukovskyAbstract:Abstract Information regarding the number, mass, and specific surface area distributions of Aerosols is extremely important for assessments of exposure to radiation due to the intake of Radioactive Aerosols by inhalation. In this study, these distributions were compared with the activity size distributions for radon decay products. The experiments were conducted in a radon chamber under controlled conditions for the Aerosol concentrations and with size distributions in the range from 5 nm to 10 µm. The activity size distributions of the Aerosols were measured by using a diffusion battery and two types of cascade impactors. The Aerosol concentrations during the experiments were in the range from 2 × 103 to 2.5 × 105 cm–3. The measurements obtained with a diffusion battery demonstrated that at the low Aerosol concentration, up to 80% of activity of the radon decay products was connected with Aerosol particles with an activity median thermodynamic diameter (AMTD) ~1 nm (unattached fraction). After injecting the Aerosols into the experimental chamber, the activity of the unattached fraction decreased to practically zero but we observed the presence of the activity of Aerosols with AMTD values ~10–20 nm. After injecting the Aerosols, the distribution of the Aerosol specific surface area exhibited a bimodal distribution, where the median diameter in the accumulation mode was ~120 nm and the geometric standard deviation (GSD) was 1.3. The median diameter in the coarse mode changed with time due to the deposition of Aerosols on the walls of the chamber, where it decreased from 5 µm (GSD = 1.6) at 15 min after injection to 2 µm (GSD = 2.5) at 120 min after injection. The distribution of the Aerosol activity measured by the cascade impactor was virtually independent of the time from the moment when the Aerosols were injected. The parameters used to assess the activity distribution comprised an activity median aerodynamic diameter (AMAD) ~500–650 nm and GSD = 1.5. Comparisons of the activity distributions with the distributions for the number, mass, and specific surface area showed that the closest correspondence was with the average distribution over the specific surface, whereas there were no exact correspondences with the other distributions.
Mostafa Y A Mostafa - One of the best experts on this subject based on the ideXlab platform.
-
a combined system for Radioactive Aerosol size distribution measurements of radon decay products
Radiation Physics and Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:Abstract To measure the size distribution of Radioactive Aerosols in the widest possible range, a complex system operating on different physical principles was designed. The system consists of a twelve-stage diffusion battery, a five-stage cascade impactor, and a set of three analytical Aerosol filters with established permeability functions. The diffusion battery allows obtaining data on the distribution of Aerosols in the range of 0.5–50 nm, the cascade impactor in the range of 0.8–20 μm, and the standard analytical filters in the range of 0.05–0.8 μm. This system was tested in a standard radon box. At a low Aerosol concentration (less than 1000 cm−3), nearly 45–75% of radon decay product activity was associated with ultrafine particles with an AMTD of ~1 nm (the so-called unattached fraction). Additionally, a mode with a diameter of ~ 5–8 nm was registered. Larger Aerosol particles were not caught by the cascade impactor, instead being deposited on the final filters. This shows that the particles are less than 800 nm in size (the first cut-off diameter of the impactor), which is in good agreement with the literature. When a high concentration of Aerosol particles is created by an additional Aerosol source, the unattached fraction is absent and maximum activity is observed in the cascade impactor and finishing filters.
-
Radioactive Aerosol permeability through russian radiometric analytical pf filters
Journal of Radioanalytical and Nuclear Chemistry, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M ZhukovskyAbstract:In this work, the permeability of the Radioactive Aerosol particles through different types of Petryanov filters is studied. The experiments were performed with standard radon box, special diffusion battery and AIP-2 cascade impactor. During the experiments a significant breakthrough is observed for different Aerosol filters. The various size modes of the Radioactive Aerosols passing throw the filter are studied. At low Aerosol concentration, the penetration of 1 nm approximately 1% and for 20 nm is varied from 12 to 20%. The different types of filters prevented all unattached radon decay products and the most size activity became with AMTD ~ 10 nm. At high Aerosol concentration, the activity of unattached fraction nearly deleted. The activity of Aerosols with AMTD ~ 10 nm is increased. The filters prevented all particles higher than 0.8 µm.
-
comparison of Radioactive Aerosol size distributions activity number mass and surface area
Applied Radiation and Isotopes, 2019Co-Authors: Hyam Nazmy Bader Khalaf, Mostafa Y A Mostafa, M E Vasyanovich, M ZhukovskyAbstract:Abstract Information regarding the number, mass, and specific surface area distributions of Aerosols is extremely important for assessments of exposure to radiation due to the intake of Radioactive Aerosols by inhalation. In this study, these distributions were compared with the activity size distributions for radon decay products. The experiments were conducted in a radon chamber under controlled conditions for the Aerosol concentrations and with size distributions in the range from 5 nm to 10 µm. The activity size distributions of the Aerosols were measured by using a diffusion battery and two types of cascade impactors. The Aerosol concentrations during the experiments were in the range from 2 × 103 to 2.5 × 105 cm–3. The measurements obtained with a diffusion battery demonstrated that at the low Aerosol concentration, up to 80% of activity of the radon decay products was connected with Aerosol particles with an activity median thermodynamic diameter (AMTD) ~1 nm (unattached fraction). After injecting the Aerosols into the experimental chamber, the activity of the unattached fraction decreased to practically zero but we observed the presence of the activity of Aerosols with AMTD values ~10–20 nm. After injecting the Aerosols, the distribution of the Aerosol specific surface area exhibited a bimodal distribution, where the median diameter in the accumulation mode was ~120 nm and the geometric standard deviation (GSD) was 1.3. The median diameter in the coarse mode changed with time due to the deposition of Aerosols on the walls of the chamber, where it decreased from 5 µm (GSD = 1.6) at 15 min after injection to 2 µm (GSD = 2.5) at 120 min after injection. The distribution of the Aerosol activity measured by the cascade impactor was virtually independent of the time from the moment when the Aerosols were injected. The parameters used to assess the activity distribution comprised an activity median aerodynamic diameter (AMAD) ~500–650 nm and GSD = 1.5. Comparisons of the activity distributions with the distributions for the number, mass, and specific surface area showed that the closest correspondence was with the average distribution over the specific surface, whereas there were no exact correspondences with the other distributions.
X Ortega - One of the best experts on this subject based on the ideXlab platform.
-
analysis of outdoor radon progeny concentration measured at the spanish Radioactive Aerosol automatic monitoring network
Applied Radiation and Isotopes, 2009Co-Authors: Delia Arnold, A Vargas, X OrtegaAbstract:An analysis of 10-year radon progeny data, provided by the Spanish automatic radiological surveillance network, in relation to meteorology is presented. Results show great spatial variability depending mainly on the station location and thus, the surrounding radon exhalation rate. Hourly averages show the typical diurnal cycle with an early morning maximum and a minimum at noon, except for one mountain station, which shows an inverse behaviour. Monthly averaged values show lower concentrations during months with higher atmospheric instability.
-
analysis of the natural radon progenycontribution to Radioactive Aerosol monitoringin the automatic spanish surveillance network
Artificial Intelligence Review, 2006Co-Authors: Delia Arnold, A Vargas, G Cortes, X OrtegaAbstract:Continuous monitoring of Radioactive pollutants in the air is provided by environmental radiological surveillance networks. In Spain, continuous and automatic control is carried out by the REA network, which comprises a set of 25 automatic stations. Most of these stations are run together with meteorological stations, belonging to the Spanish Meteorological Institute. The monitor for measuring the artificial Radioactive Aerosol concentration is the BAI 9850 from Berthold Company. An important contribution to the uncertainty of its measurements is due to natural air radioactivity, mainly from radon progeny. A statistical study using the data from the REA and the INM radiological and meteorological stations has been carried out in order to characterize the natural radioactivity at each station and to improve the quality of the artificial radioactivity air concentration measurements. This study shows that natural radioactivity concentration varies both daily and seasonally, and is significantly correlated to meteorological parameters and the geological properties of station surroundings. Radon progeny concentration commonly shows a daily cycle with a maximum in the early morning and a minimum in the afternoon, according to the behaviour of meteorological parameters. However, at a station situated at a higher altitude, the radon progeny pattern is completely different, due to the evolution of the planetary boundary layer above this complex terrain. Stations have been classified into coastal, inland and mountain according to the behaviour of the natural radioactivity at each location. A representative station from each category has been selected and a simulation study is being carried out using the MM5 code coupled with the atmospheric transport code FLEXPART.