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Costas Tsouris - One of the best experts on this subject based on the ideXlab platform.

  • surface charge of environmental and Radioactive airborne particles
    Atmospheric Chemistry and Physics, 2021
    Co-Authors: Gyoung Gug Jang, Sotira Yiacoumi, Costas Tsouris, Alexander I Wiechert, Austin Ladshaw, Tyler L Spano, Joanna Mcfarlane, Kristian G Myhre
    Abstract:

    Abstract. Self-charging of Radioactive uranium oxide particles was measured by comparing the electrostatic surface-charge characteristics of the uranium particles to various airborne dust particulates. Though Radioactive Aerosols can gain charge through various decay mechanisms, researchers have traditionally assumed that the Radioactive Aerosols do not carry any additional charge relative to other atmospheric dust particles as a consequence of charge neutralization over time. In this work, we evaluate this assumption by directly examining the surface charge and charge density on airborne uranium oxide particles and then comparing those characteristics with charging of other natural and engineered airborne dust particles. Based on electric field–assisted particle levitation in air, the surface charge, charge distribution as a function of particle size, and surface charge density were determined for uranium oxide Aerosols (

  • studying the impact of Radioactive charging on the microphysical evolution and transport of Radioactive Aerosols with the tomas rc v1 framework
    Journal of Environmental Radioactivity, 2018
    Co-Authors: Petros Vasilakos, Sotira Yiacoumi, Costas Tsouris, Yongηa Kim, Jeffrey R Pierce, Athanasios Nenes
    Abstract:

    Radioactive charging can significantly impact the way Radioactive Aerosols behave, and as a result their lifetime, but such effects are neglected in predictive model studies of Radioactive plumes. The objective of this work is to determine the influence of Radioactive charging on the vertical transport of Radioactive Aerosols in the atmosphere, through its effect on coagulation and deposition, as well as quantifying the impact of this charging on aerosol lifetime. The TwO-Moment Aerosol Sectional (TOMAS) microphysical model was extended to account for Radioactive charging effects on coagulation in a computationally efficient way. The expanded model, TOMAS-RC (TOMAS with Radioactive Charging effects), was then used to simulate the microphysical evolution and deposition of Radioactive aerosol (containing the isotopes 131I and 137Cs) in a number of idealized atmospheric transport experiments. Results indicate that Radioactive charging can facilitate or suppress coagulation of Radioactive Aerosols, thus influencing the deposition patterns and total amount of Radioactive aerosol mass available for long-range transport. Sensitivity simulations to uncertain parameters affirm the potential importance of Radioactive charging effects. An important finding is that charging of neutral, coarse mode aerosol from background radiation can reduce coagulation rates and extend its lifetime in the atmosphere by up to a factor of 2.

  • incorporating Radioactive decay into charging and coagulation of multicomponent Radioactive Aerosols
    Journal of Aerosol Science, 2017
    Co-Authors: Sotira Yiacoumi, Costas Tsouris, Athanasios Nenes
    Abstract:

    Abstract Compositional changes by the decay of radionuclides in Radioactive Aerosols can influence their charging state, coagulation frequency and size distribution throughout their atmospheric lifetime. The importance of such effects is unknown as they have not been considered in microphysical and global radioactivity transport studies to date. We explore the effects of compositional changes on the charging efficiency and coagulation rates of Aerosols using a set of kinetic equations that couple all relevant processes (decay, charging and coagulation) and their evolution over time. Compared to a coupled aggregation-tracer model for the prediction of the Radioactive composition of particulates undergoing coagulation, our kinetic approach can provide similar results using much less central processing unit time. Together with other considerations, our approach is computational efficient enough to allow implementation in 3D atmospheric transport models. The decay of radionuclides and the production of decay products within Radioactive Aerosols may significantly affect the aerosol charging rates, and either hinder or promote the coagulation of multicomponent Radioactive Aerosols. These results suggest that radiological phenomena occurring within Radioactive Aerosols, as well as subsequent effects on aerosol microphysics, should be considered in regional and global models to more accurately predict radioactivity transport in the atmosphere in case of a nuclear plant accident.

C F Clement - One of the best experts on this subject based on the ideXlab platform.

  • the removal of Radioactive Aerosols by electric fields
    Journal of Aerosol Science, 2009
    Co-Authors: J C Barrett, C F Clement, A B S Virdee
    Abstract:

    Aspects of the motion of Radioactive aerosol in electric fields are discussed. A revised estimate of the self-charging of Radioactive aerosol in confined geometries is presented and used to estimate the self-generated electric field towards the wall. The enhancement of this field and decrease in negative ion concentration near the wall are calculated, but, in contrast to the atmospheric case, the extent of the enhanced region in confined geometries is shown to be very small. Consequently, aerosol removal by this field is likely to be negligible. Estimates are made of the strength of an imposed external field and the dimension of a confined geometry needed for effective removal of a Radioactive aerosol from a gas stream.

  • enhanced localised charging of Radioactive Aerosols
    Journal of Aerosol Science, 2000
    Co-Authors: C F Clement, R G Harrison
    Abstract:

    Abstract The positive self-charging of Radioactive Aerosols by the emission of electrons in the decay process is partly neutralised by the attachment of negative ions from the surrounding gas. The net charging is enhanced if the neutralisation is reduced by lowering the concentration of the ions. This occurs when the ion production rate is reduced by diluting the aerosol or when the aerosol enters a confined geometry, and also when the ions are removed by electric fields. These cases are discussed using an equation derived for the mean charge on the aerosol. An expression for the charging of a particle in a dilute Radioactive aerosol in the environment is obtained allowing for background ionisation and the ion cloud produced by the particle, and conditions for enhanced lung deposition are derived. A comprehensive treatment is given of the ion reduction which rapidly occurs when aerosol enters a confined space, and a simple expression is shown to give adequately the resulting increase in aerosol charge. Ion motion and aerosol charging are briefly discussed for large imposed electric fields and for weak fields produced by movement of decay electrons. Near a negative electrode, enhanced charging of the aerosol arises from reduction of negative ions in the electrode effect, and could lead to greatly enhanced deposition of the aerosol.

  • charge distributions and coagulation of Radioactive Aerosols
    Journal of Aerosol Science, 1995
    Co-Authors: C F Clement, R A Clement, R G Harrison
    Abstract:

    Abstract The self-charging of Radioactive Aerosols will be reduced by background ions, such as those produced by Radioactive gases. The sources of these background ions and their production rates are specified for a reactor containment atmosphere during a possible nuclear accident. Previous theory is extended to calculate the charging of a polydisperse Radioactive aerosol. Gaussian approximations to charge distributions on an aerosol of a given size, and are shown to give a good representation of the exact numerical charge distributions of a Cs aerosol at normal temperatures, and also for highly Radioactive aerosol containing 131I in a containment atmosphere. Extensive calculations are performed for charge-induced modifications to Brownian coagulation rates between steady-state size distributions of these Radioactive Aerosols, and also between small-sized Radioactive aerosol and larger (non-Radioactive) aerosol. The results show considerable enhancements of the coagulation rates between large and small-sized aerosol, but also a strong suppression of coagulation between large particles. Rate modifications calculated using the Gaussian approximations are generally close to the exact values. Time-dependent calculations for a monodisperse α-decaying aerosol reveal enhancements in coagulation rates even when the average charge on the aerosol is positive. Our results are relevant to behaviour in a dusty plasma.

  • the coagulation of Radioactive Aerosols
    Journal of Aerosol Science, 1992
    Co-Authors: C F Clement, R A Clement, R G Harrison
    Abstract:

    Abstract Radioactive Aerosols can become charged by emitting charges during the decay process, and the resulting electrostatic forces will modify coagulation rates. For Brownian coagulation, calculations for nuclear containment Aerosols show that rates averaged over charge distributions can be strongly reduced between particles of the same size, but that increases in average rates can occur for particles of different sizes. The increases arise from small, but significant, negative charging of non-Radioactive and small-sized Radioactive particles, and are sensitive to the asymmetry between the positive and negative ion mobilities.

  • The charging of Radioactive Aerosols
    Journal of Aerosol Science, 1992
    Co-Authors: C F Clement, Richard Harrison
    Abstract:

    Abstract The processes whereby Radioactive Aerosols become charged are examined and their rates are specified in terms of the amount and type of radioactivity present. General equations are obtained for the aerosol charge distribution and ion concentrations. Mean charges found from calculated distributions agree well with more approximate equations used previously by Reed et al. (1977, J. Aerosol Sci. 8, 457–463). The steady-state charge distribution for a monodisperse β-decaying aerosol reduces to an analytic form, and gives a simple result for the mean charge when ion concentrations and mobilities are equal. Mean aerosol charges are found to be large when ion-ion recombination is the dominant ion removal mechanism, and when the aerosol is larger than a critical size. This size is only weakly dependent on the total aerosol mass concentration. Calculations are performed for a β-decaying 198 Au aerosol and an α-decaying 238 PuO 2 aerosol, and reasonable agreement is obtained with experiment.

A Renoux - One of the best experts on this subject based on the ideXlab platform.

  • electrical charging of Radioactive Aerosols comparison of the clement harrison models with new experiments
    Journal of Aerosol Science, 2001
    Co-Authors: F Gensdarmes, D Boulaud, A Renoux
    Abstract:

    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.

  • experimental study of the electrical charging of Radioactive Aerosols
    Journal of Aerosol Science, 2000
    Co-Authors: F Gensdarmes, D Boulaud, A Renoux
    Abstract:

    F. GENSDARMES1,2, D. BOULAUD1, A. RENOUX2 1 Institut de Protection et de Surete Nucleaire, Departement de Prevention et d’Etude des Accidents, Service d’Etudes et de Recherches en Aerocontamination et en Confinement.CEA/Saclay, Bat 389, 91191 Gif-sur-Yvette cedex, France. 2 Universite Paris XII, Laboratoire de Physique des Aerosols et de Transfert des Contaminations. Av. du General de Gaulle, 94010 Creteil cedex, France.

R G Harrison - One of the best experts on this subject based on the ideXlab platform.

  • enhanced localised charging of Radioactive Aerosols
    Journal of Aerosol Science, 2000
    Co-Authors: C F Clement, R G Harrison
    Abstract:

    Abstract The positive self-charging of Radioactive Aerosols by the emission of electrons in the decay process is partly neutralised by the attachment of negative ions from the surrounding gas. The net charging is enhanced if the neutralisation is reduced by lowering the concentration of the ions. This occurs when the ion production rate is reduced by diluting the aerosol or when the aerosol enters a confined geometry, and also when the ions are removed by electric fields. These cases are discussed using an equation derived for the mean charge on the aerosol. An expression for the charging of a particle in a dilute Radioactive aerosol in the environment is obtained allowing for background ionisation and the ion cloud produced by the particle, and conditions for enhanced lung deposition are derived. A comprehensive treatment is given of the ion reduction which rapidly occurs when aerosol enters a confined space, and a simple expression is shown to give adequately the resulting increase in aerosol charge. Ion motion and aerosol charging are briefly discussed for large imposed electric fields and for weak fields produced by movement of decay electrons. Near a negative electrode, enhanced charging of the aerosol arises from reduction of negative ions in the electrode effect, and could lead to greatly enhanced deposition of the aerosol.

  • charge distributions and coagulation of Radioactive Aerosols
    Journal of Aerosol Science, 1995
    Co-Authors: C F Clement, R A Clement, R G Harrison
    Abstract:

    Abstract The self-charging of Radioactive Aerosols will be reduced by background ions, such as those produced by Radioactive gases. The sources of these background ions and their production rates are specified for a reactor containment atmosphere during a possible nuclear accident. Previous theory is extended to calculate the charging of a polydisperse Radioactive aerosol. Gaussian approximations to charge distributions on an aerosol of a given size, and are shown to give a good representation of the exact numerical charge distributions of a Cs aerosol at normal temperatures, and also for highly Radioactive aerosol containing 131I in a containment atmosphere. Extensive calculations are performed for charge-induced modifications to Brownian coagulation rates between steady-state size distributions of these Radioactive Aerosols, and also between small-sized Radioactive aerosol and larger (non-Radioactive) aerosol. The results show considerable enhancements of the coagulation rates between large and small-sized aerosol, but also a strong suppression of coagulation between large particles. Rate modifications calculated using the Gaussian approximations are generally close to the exact values. Time-dependent calculations for a monodisperse α-decaying aerosol reveal enhancements in coagulation rates even when the average charge on the aerosol is positive. Our results are relevant to behaviour in a dusty plasma.

  • the coagulation of Radioactive Aerosols
    Journal of Aerosol Science, 1992
    Co-Authors: C F Clement, R A Clement, R G Harrison
    Abstract:

    Abstract Radioactive Aerosols can become charged by emitting charges during the decay process, and the resulting electrostatic forces will modify coagulation rates. For Brownian coagulation, calculations for nuclear containment Aerosols show that rates averaged over charge distributions can be strongly reduced between particles of the same size, but that increases in average rates can occur for particles of different sizes. The increases arise from small, but significant, negative charging of non-Radioactive and small-sized Radioactive particles, and are sensitive to the asymmetry between the positive and negative ion mobilities.

  • self charging of Radioactive Aerosols
    Journal of Aerosol Science, 1991
    Co-Authors: C F Clement, R G Harrison
    Abstract:

    Abstract Radioactive Aerosols become charged by internal ionisation which accompanies ejection ofRadioactive particles. The slowing down of these particles produces external ions, which diffuse back onto the aerosol and may cause electrical neutralisation. We have formulated general equations to allow the resulting aerosol charge distributions to be calculated. Approximations for mean aerosol charge levels can also be obtained from simpler equations (Reed et al 1977). Calculations have been performed for beta-emitting Radioactive Aerosols to investigate the consistency of the two approaches, and establish the conditions under which significant aerosol charging is likely to occur. The mean charge on the aerosol becomes large when the ion loss is dominated by recombination and the aerosol concentration is sufficiently small.

Sotira Yiacoumi - One of the best experts on this subject based on the ideXlab platform.

  • surface charge of environmental and Radioactive airborne particles
    Atmospheric Chemistry and Physics, 2021
    Co-Authors: Gyoung Gug Jang, Sotira Yiacoumi, Costas Tsouris, Alexander I Wiechert, Austin Ladshaw, Tyler L Spano, Joanna Mcfarlane, Kristian G Myhre
    Abstract:

    Abstract. Self-charging of Radioactive uranium oxide particles was measured by comparing the electrostatic surface-charge characteristics of the uranium particles to various airborne dust particulates. Though Radioactive Aerosols can gain charge through various decay mechanisms, researchers have traditionally assumed that the Radioactive Aerosols do not carry any additional charge relative to other atmospheric dust particles as a consequence of charge neutralization over time. In this work, we evaluate this assumption by directly examining the surface charge and charge density on airborne uranium oxide particles and then comparing those characteristics with charging of other natural and engineered airborne dust particles. Based on electric field–assisted particle levitation in air, the surface charge, charge distribution as a function of particle size, and surface charge density were determined for uranium oxide Aerosols (

  • studying the impact of Radioactive charging on the microphysical evolution and transport of Radioactive Aerosols with the tomas rc v1 framework
    Journal of Environmental Radioactivity, 2018
    Co-Authors: Petros Vasilakos, Sotira Yiacoumi, Costas Tsouris, Yongηa Kim, Jeffrey R Pierce, Athanasios Nenes
    Abstract:

    Radioactive charging can significantly impact the way Radioactive Aerosols behave, and as a result their lifetime, but such effects are neglected in predictive model studies of Radioactive plumes. The objective of this work is to determine the influence of Radioactive charging on the vertical transport of Radioactive Aerosols in the atmosphere, through its effect on coagulation and deposition, as well as quantifying the impact of this charging on aerosol lifetime. The TwO-Moment Aerosol Sectional (TOMAS) microphysical model was extended to account for Radioactive charging effects on coagulation in a computationally efficient way. The expanded model, TOMAS-RC (TOMAS with Radioactive Charging effects), was then used to simulate the microphysical evolution and deposition of Radioactive aerosol (containing the isotopes 131I and 137Cs) in a number of idealized atmospheric transport experiments. Results indicate that Radioactive charging can facilitate or suppress coagulation of Radioactive Aerosols, thus influencing the deposition patterns and total amount of Radioactive aerosol mass available for long-range transport. Sensitivity simulations to uncertain parameters affirm the potential importance of Radioactive charging effects. An important finding is that charging of neutral, coarse mode aerosol from background radiation can reduce coagulation rates and extend its lifetime in the atmosphere by up to a factor of 2.

  • incorporating Radioactive decay into charging and coagulation of multicomponent Radioactive Aerosols
    Journal of Aerosol Science, 2017
    Co-Authors: Sotira Yiacoumi, Costas Tsouris, Athanasios Nenes
    Abstract:

    Abstract Compositional changes by the decay of radionuclides in Radioactive Aerosols can influence their charging state, coagulation frequency and size distribution throughout their atmospheric lifetime. The importance of such effects is unknown as they have not been considered in microphysical and global radioactivity transport studies to date. We explore the effects of compositional changes on the charging efficiency and coagulation rates of Aerosols using a set of kinetic equations that couple all relevant processes (decay, charging and coagulation) and their evolution over time. Compared to a coupled aggregation-tracer model for the prediction of the Radioactive composition of particulates undergoing coagulation, our kinetic approach can provide similar results using much less central processing unit time. Together with other considerations, our approach is computational efficient enough to allow implementation in 3D atmospheric transport models. The decay of radionuclides and the production of decay products within Radioactive Aerosols may significantly affect the aerosol charging rates, and either hinder or promote the coagulation of multicomponent Radioactive Aerosols. These results suggest that radiological phenomena occurring within Radioactive Aerosols, as well as subsequent effects on aerosol microphysics, should be considered in regional and global models to more accurately predict radioactivity transport in the atmosphere in case of a nuclear plant accident.