Abstract
A first-principles model is developed for defining the combustive explosion of ignited plutonium droplets during free-fall in air and for quantifying fractions of plutonium aerosolization. The model, which is based on literature data and a conceptual description of the combustion and explosion processes, determines heat accumulation and temperature of a droplet over time using the rates of oxidation and heat loss, as well as physical and thermochemical properties of plutonium metal and oxide. Self-heating during combustion leads to fusion of the oxide layer and pressurization of the droplet by plutonium vapor that ultimately vents through the molten oxide to produce fume aerosol and a hollow spherule of residual oxide. Observed dependencies of time-to-explosion and aerosolized fraction on droplet size are accurately calculated by the model. All ignited droplets with sizes greater than a threshold diameter (approximately 0.01 cm) explode with aerosolization of residual plutonium (68–75%), if the free-fall period or distance is sufficient for the droplet temperature to exceed 3300°C. A practical size window for explosion is bounded by the threshold value and by the diameter (about 0.13 cm) of a droplet that attains the explosion temperature during a free-fall distance of ten meters. Calculations show that a 1.0 cm-diameter drop heated initially to 1000°C is 0.3% oxidized after free-falling for this distance in 1000°C air and reaches a maximum temperature of 1560°C. Since minimum diameters of one centimeter are observed for naturally occurring plutonium drops during containment failures at 1000°C and the amount of dispersible plutonium is limited by the extent of oxidation, the reliability of large aerosol release fractions recommended in the literature for fuel-fire scenarios are questionable. Effects of independent variables on combustion and explosion are discussed and application of the model in predicting aerosol fractions released by plutonium fragments formed during highly energetic events is described.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
