Simulation of radioactive plume transport in the atmosphere including dynamics of particle aggregation and breakup

Journal Article · Tue Apr 04 00:00:00 EDT 2023 · Journal of Environmental Radioactivity

DOI:https://doi.org/10.1016/j.jenvrad.2023.107167· OSTI ID:1968698

Wiechert, Alexander I. ^[1]; Ladshaw, Austin P. ^[1]; Kim, Yong-ha ^[2]; Tsouris, Costas ^[3]; Yiacoumi, Sotira ^[1]

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1. Georgia Institute of Technology, Atlanta, GA (United States)
2. Louisiana State Univ., Baton Rouge, LA (United States)
3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Accurate prediction of the atmospheric transport of debris particles relies heavily on our knowledge of the size distribution of the particles within a debris cloud. Assuming a fixed particle size during simulations is not always viable since the size distribution of the debris can change during transport. Various microphysical processes, such as aggregation and breakup, influence debris particles and dictate any changes to the size distribution. To track those changes that can occur, a population balance model can be adopted and instituted within a model framework. Nonetheless, many of the models that simulate the transport of radioactive debris following a device-driven fission incident have historically neglected to consider these processes. As such, this work describes our effort to develop a modeling framework capable of simulating the transport and deposition of a radioactive plume generated from a fission incident with a dynamic population balance including particle aggregation and breakup. Herein the impact of aggregation and breakup, individually and collectively, on the particle size distribution is explored using the developed framework. When simulating aggregation, for example, six mechanisms, including Brownian coagulation, the convective enhancement to Brownian coagulation, van der Waals-viscous force correction for Brownian coagulation, gravitational collection, turbulent inertial motion, and turbulent shear, are considered. Brownian coagulation and its corrections have, as one would expect, a large impact on relatively small aggregates. Aggregates with a diameter that is less than or equal to 1.0 μm, for instance, comprise 50.6 vol % of all aggregates in the absence of aggregation and 31.2 vol % when Brownian coagulation and its corrections are considered. Gravitational collection and, to a much lesser extent, turbulent shear and turbulent inertial motion are, conversely, of great importance to relatively large aggregates (i.e., diameter greater than 3.0 μm). Additionally, the individual effects of atmospheric and particle parameters, such as wind speed and particle density, are examined. Of the parameters examined, turbulent energy dissipation and aggregate fractal dimension (i.e., aggregate shape with lower values representing more irregular particles) were of substantial importance since both terms directly impact aggregate stability and, by extension, the breakup rate. Large-scale transport and deposition simulations in a dry atmosphere are also presented and discussed as a proof of concept.

• Research Organization: Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: Defense Advanced Research Projects Agency (DARPA); USDOD; USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC05-00OR22725
• OSTI ID: 1968698
• Journal Information: Journal of Environmental Radioactivity, Journal Name: Journal of Environmental Radioactivity Journal Issue: July Vol. 263; ISSN 0265-931X
• Publisher: Elsevier
• Country of Publication: United States
• Language: English

Related Subjects

98 NUCLEAR DISARMAMENT, SAFEGUARDS, AND PHYSICAL PROTECTION
fallout modeling
population balance
radioactive aerosols
radionuclide transport