Spatially-resolved analyses of aerodynamic fallout from a uranium-fueled nuclear test

Lewis, Lionel S.; Knight, Kim B.; Matzel, J.; Prussin, S. G.; Zimmer, Mindy M.; Kinman, William S.; Ryerson, Frederick J.; Hutcheon, I. D.

doi:10.1016/j.jenvrad.2015.04.006

Cited by 38 publications

(27 citation statements)

References 26 publications

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“…Recent work analyzing fallout from other nuclear tests focus on determining formation conditions and how device materials incorporated into glassy fallout [54,55,56]. The characterization of stable noble gasses has confirmed that historical fallout preserves a record of the relative volatilities of some fission products, though the distribution was not spatially determined in this study [54].…”

Section: Contemporary Fallout Researchmentioning

confidence: 64%

“…The average major element oxide composition of the interiors of agglomerated fallout objects exhibit a different compositional range than the values found in mm-scale objects [55,56] In the following section, the Si data are not presented, as the Si content across the interfaces and the samples themselves is not highly variable (<2.9% standard deviation for the entire dataset). The K data are also not presented, given their similarity to the Na data (as shown by EDS, Figure 3.26).…”

Section: Epma Analysesmentioning

confidence: 97%

“…In situ secondary ion mass spectrometry (SIMS) analyses of samples from the same test reveal some degree of isotopic enrichment of uranium (residual nuclear fuel) throughout the volume of such fallout glasses [56]. Together, these analyses characterize the degree of heterogeneity observed in actinide distributions between fallout objects and within individual fallout objects (the 235 U/ 238 U ratio ranges from 0.02 to 11.84 [56]). When interpreted in the context of fallout formation models such as the Miller's, the presence of device uranium in the fallout samples is expected, as refractory materials were theorized to condense first and mix volumetrically into molten carriers.…”

Section: Contemporary Fallout Researchmentioning

confidence: 98%

“…Additionally, this study seeks to estimate the time and temperature of mass transport from composition profiles at these interfaces, further constraining fallout formation conditions. In order to explore these interfaces, agglomerated fallout glass samples from a uranium-fueled, near-surface nuclear test were selected, provided from the same anonymous event studied by Eppich et al (2014) and Lewis et al (2015) [55,56]. The Eppich et al (2014) study characterizes the typical samples from this test to be opaque and greenish-black, with no observable crystallinity and often containing visible vesicles.…”

Section: Samples Sample Isolation and Selectionmentioning

confidence: 99%

“…These interactions can be revealed through the study of unfissioned actinides as well as major element compositional variation, including investigation of surface layers preserved in fallout today. By using modern, spatially resolved analytical techniques (e.g., nano-scale secondary ion mass spectrometry (NanoSIMS)), the species, such as residual actinides, that are preserved in these surface layers of glassy fallout can be observed, and subsequently interpreted through the lens of historical fallout formation models (as shown in Lewis et al (2015)). …”

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confidence: 99%

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Mass Transport of Condensed Species in Aerodynamic Fallout Glass from a Near-Surface Nuclear Test

Weisz¹

2016

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In a near-surface nuclear explosion, vaporized device materials are incorporated into molten soil and other carrier materials, forming glassy fallout upon quenching. Mechanisms by which device materials mix with carrier materials have been proposed, however, the specific mechanisms and physical conditions by which soil and other carrier materials interact in the fireball, as well as the subsequent incorporation of device materials with carrier materials, are not well constrained. A surface deposition layer was observed preserved at interfaces where two aerodynamic fallout glasses agglomerated and fused. Eleven such boundaries were studied using spatially resolved analyses to better understand the vaporization and condensation behavior of species in the fireball. Using nano-scale secondary ion mass spectrometry (NanoSIMS), we identified higher concentrations of uranium from the device in 7 of the interface layers, as well as isotopic enrichment (>75% 235 U) in 9 of the interface layers. Major element analysis of the interfaces revealed the deposition layer to be chemically enriched in Fe-, Ca-and Na-bearing species and depleted in Ti-and Al-bearing species. The concentration profiles of the enriched species at the interface are characteristic of diffusion. Three of the uranium concentration profiles were fit with a modified Gaussian function, representative of 1-D diffusion from a planar source, to determine time and temperature parameters of mass transport. By using a historical model of fireball temperature to simulate the cooling rate at the interface, the temperature of deposition was estimated to be ∼2200 K, with 1σ uncertainties in excess of 140 K. The presence of Na-species in the layers at this estimated temperature of deposition is indicative of an oxygen rich fireball. The notable depletion of Al-species, a refractory oxide that is highly abundant in the soil, together with the enrichment of Ca-, Fe-, and 235 U-species, suggests an anthropogenic source of the enriched species, together with a continuous chemical fractionation process as these species condensed.

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