title: When the dust settles: stable xenon isotope constraints on the formation of nuclear fallout.
abstract: Nuclear weapons represent one of the most immediate threats of mass destruction. In the event that a procured or developed nuclear weapon is detonated in a populated metropolitan area, timely and accurate nuclear forensic analysis and fallout modeling would be needed to support attribution efforts and hazard assessments. Here we demonstrate that fissiogenic xenon isotopes retained in radioactive fallout generated by a nuclear explosion provide unique constraints on (1) the timescale of fallout formation, (2) chemical fractionation that occurs when fission products and nuclear fuel are incorporated into fallout, and (3) the speciation of fission products in the fireball. Our data suggest that, in near surface nuclear tests, the presence of a significant quantity of metal in a device assembly, combined with a short time allowed for mixing with the ambient atmosphere (seconds), may prevent complete oxidation of fission products prior to their incorporation into fallout. Xenon isotopes thus provide a window into the chemical composition of the fireball in the seconds that follow a nuclear explosion, thereby improving our understanding of the physical and thermo-chemical conditions under which fallout forms.
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA. Electronic address: cassata2@llnl.gov.
authors.forename: W S
authors.initials: WS
authors.lastname: Cassata
authors.affiliation: Department of Nuclear Engineering, University of California - Berkeley, 4113 Etcheverry Hall MC 1730, Berkeley, CA 94720-1730, USA.
authors.forename: S G
authors.initials: SG
authors.lastname: Prussin
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA.
authors.forename: K B
authors.initials: KB
authors.lastname: Knight
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA.
authors.forename: I D
authors.initials: ID
authors.lastname: Hutcheon
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA.
authors.forename: B H
authors.initials: BH
authors.lastname: Isselhardt
authors.affiliation: Berkeley Geochronology Center, 2455 Ridge Road, Berkeley, CA 94709, USA; Department of Earth and Planetary Sciences, University of California - Berkeley, 307 McCone Hall MC 4767, Berkeley, CA 94720-4767, USA.
authors.forename: P R
authors.initials: PR
authors.lastname: Renne
mesh_terms: D008962:Models, Theoretical; D009680:Nuclear Fission; D054043:Nuclear Weapons; D011834:Radiation Monitoring; D011847:Radioactive Fallout / Q000032:analysis*; D013997:Time Factors; D014979:Xenon Isotopes / Q000032:analysis*
chemical_list: D011847:Radioactive Fallout; D014979:Xenon Isotopes
keywords: Chemical fractionation; Fission product; Nuclear fallout; Nuclear fireball; Xenon