It’s not immediately intuitive to think of an explosion as a reducing environment. After all, a conventional explosion is an oxidative process. In the case of a nuclear explosion; however, it has been known since 1975 that large amounts of iron in the surrounding environment can be reduced to its ferrous form. 1. An explanation for this is not readily available based on mass balances and equilibrium redox conditions. There has been speculation as to the nature of actinide oxidation states under these conditions based on condensation temperatures and fractionation. 2. This work is the first direct measurement of the oxidation state of plutonium in historic fallout and improves upon previous measurements of uranium and iron. 3. In addition to the oxidation state, the local chemistry surrounding the actinides in fallout debris will ultimately dictate its long-term stability. To investigate what phase contains these actinides in fallout we combined autoradiography with scanning electron microscopy – energy dispersive spectroscopy to map which elements co-locate with plutonium. This lead to some insight into the factors that ultimately drive plutonium concentrations in fallout debris.
Kiel Holiday is Group Leader for the Chemistry of Nuclear Materials Group in the Materials Science Division. He received his Ph.D. in Radiochemistry from University of Nevada, Las Vegas in 2009. He completed a two-year post-doc with the Institut für Nukleare Entsorgung (INE) in Karlsruhe, Germany before joining the Lawrence Livermore National Laboratory in 2011. Kiel has experience in solid-state synthesis and characterization of actinide materials by various X-rays and electron techniques. Kiel currently performs research in the chemical processing of nuclear materials for stockpile stewardship, nuclear forensics, and innovations in manufacturing.