Tracking Radionuclide Fractionation in the First Atomic Explosion Using Stable Elements

Compositional
analysis of postdetonation fallout is a tool for
forensic identification of nuclear devices. However, the relationship
between device composition and fallout composition is difficult to
interpret because of the complex combination of physical mixing, nuclear
reactions, and chemical fractionations that occur in the chaotic nuclear
fireball. Using a combination of in situ microanalytical techniques (electron
microprobe analysis and secondary ion mass spectrometry), we show
that some heavy stable elements (Rb, Sr, Zr, Ba, Cs, Ba, La, Ce, Nd,
Sm, Dy, Lu, U, Th) in glassy fallout from the first nuclear test,
Trinity, are reliable chemical proxies for radionuclides generated
during the explosion. Stable-element proxies show that radionuclides
from the Trinity device were chemically, but not isotopically, fractionated
by condensation. Furthermore, stable-element proxies delineate chemical
fractionation trends that can be used to connect present-day fallout
composition to past fireball composition. Stable-element proxies therefore
offer a novel approach for elucidating the phenomenology of the nuclear
fireball as it relates to the formation of debris and the fixation
of device materials within debris.