Modeling of atmospheric dispersion of sodium fire aerosols for environmental impact analysis during accidental leaks. (November 2019)

• Record Type: Journal Article
• Authors: Srinivas, C.V.; Subramanian, V.; Kumar, Amit; Usha, P.; Sujatha, N.; Bagavath Singh, A.; Rakesh, P.T.; Baskaran, R.; Venkatraman, B.
• Is Part Of: Journal of aerosol science. Volume 137(2019)
• Publication Date: 2019-11
• Subjects: Sodium fires -- Aerosols -- Atmospheric transport -- FLEXPART -- Chemical kinetic model; Aerosols -- Periodicals; Aerosols -- Periodicals; Aérosols -- Périodiques; 541.34515
• DOI: 10.1016/j.jaerosci.2019.105432
• Languages: English
• ISSNs: 0021-8502

Abstract

Abstract: In this study a chemical kinetic model which converts sodium oxide aerosols to sodium carbonate aerosols as a function of CO2 and humidity is implemented in the FLEXPART atmospheric dispersion model for impact assessment during sodium fire accidents in sodium cooled fast reactors. The model is validated with open environment aerosol dispersion experiments conducted at Kalpakkam coastal site. Simulated total aerosol concentrations and deposition agree with experimental data. Simulations indicate rapid conversion of NaOH to Na2 CO3 during atmospheric transport under high humidity levels (57–80%) at Kalpakkam. Parametric tests with different particle size indicated that a particle diameter of 5 μm produced realistic aerosol deposition closely comparing with observations. A series of simulations were conducted for various meteorological conditions to assess the chemical impact in a range of 25 km during a postulated accident. Simulations for extended 8-h release scenarios in different seasonal flow conditions indicate the concentrations beyond 1.5 km fall to very low values (≤0.1 mg/m 3 for NaOH and ≤4 mg/m 3 for Na2 CO3 ) indicating no chemical impact. Short-duration (1 h) releases during worst environmental conditions (sea breeze, low winds) indicate that the aerosol concentrations during sea breeze are about 4–5 times high compared to winter time calm winds due to wide diffusion of aerosols in winter. The concentrations in these two cases are found to be higher (∼0.2 mg/m 3 for NaOH and 6 mg/m 3 for Na2 CO3 ) in the site distance range but thereafter rapidly fall, thus indicating no inhalation hazard during sodium fire scenarios at the coastal site. Highlights: A chemical kinetic model is incorporated in FLEXPART for modeling atmospheric dispersion of sodium fire aerosols. Model is validated with open atmosphere sodium aerosol dispersion experiments at Kalpakkam. Simulations indicate rapid conversion of NaOH to Na2 CO3 during atmospheric transport in agreement with field data. Sensitivity tests indicated that particle diameter 5 μm produced realistic aerosol deposition. Simulated aerosol concentrations for postulated accidents are below TLV under various meteorological conditions.