Cassata W S, Prussin S G, Knight K B, Hutcheon I D, Isselhardt B H, Renne P R
Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, CA 94550, USA.
Department of Nuclear Engineering, University of California - Berkeley, 4113 Etcheverry Hall MC 1730, Berkeley, CA 94720-1730, USA.
J Environ Radioact. 2014 Nov;137:88-95. doi: 10.1016/j.jenvrad.2014.06.011. Epub 2014 Jul 9.
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.
核武器是大规模杀伤性的最直接威胁之一。如果一枚获取或研制的核武器在人口密集的大都市地区爆炸，就需要及时、准确的核法医分析和沉降物建模，以支持溯源工作和危害评估。在此，我们证明，核爆炸产生的放射性沉降物中保留的裂变成因氙同位素对以下方面提供了独特的限制：（1）沉降物形成的时间尺度；（2）裂变产物和核燃料融入沉降物时发生的化学分馏；（3）火球中裂变产物的形态。我们的数据表明，在近地表核试验中，装置组件中存在大量金属，再加上与周围大气混合的时间较短（数秒），可能会阻止裂变产物在融入沉降物之前完全氧化。因此，氙同位素为核爆炸后数秒内火球的化学成分提供了一个窗口，从而增进了我们对沉降物形成时的物理和热化学条件的理解。
