Radioactive particles from a range of past nuclear events: Challenges posed by highly varied structure and composition

• Published in: The Science of the total environment Vol. 842; p. 156755
• Main Authors: Johansen, Mathew P., Child, David P., Collins, Richard, Cook, Megan, Davis, Joel, Hotchkis, Michael A.C., Howard, Daryl L., Howell, Nicholas, Ikeda-Ohno, Atsushi, Young, Emma
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 10.10.2022
• Subjects: Debris; Fallout; Hot particles; Nuclear weapons tests vs nuclear power accidents; Plutonium; Radiological and stable element composition; Nuclear weapons tests vs nuclear power accidents; Radiological and stable element composition; Plutonium; Hot particles; Debris; Fallout
• ISSN: 0048-9697; 1879-1026
• DOI: 10.1016/j.scitotenv.2022.156755

While they have appeared only recently in earth's history, radioactive particles from anthropogenic sources are widespread in global environments and present radiological harm potentials to living organisms. Exposure potentials vary greatly, however few studies examine a wide range of source and particle types. Here we compare a varied set of particles from past nuclear fission and non-fission sources in Australia of highly diverse magnitudes, release modes, and environments. The radiochemistry and microscopy methods revealed that numerous radioactive particles persist in soils 60+ years after their release events. Particles can be distinguished by their Ca/Fe and Si/Fe elemental ratios, which in this study range over orders of magnitude and reflect the materials available during their individual formation events. The particles with Si- and Ca-dominant compositions persisted in corrosive environments (e.g., marine). Internal fracturing is more prevalent than previously reported, and fracturing is greater in Ca-rich vs. Si-dominated matrices. The fractures often form connective pathways from the interior to exterior surfaces, increasing the potential to leach radionuclides into a host organism or the environment. The particles from nuclear testing have dominant 239+240Pu activity concentrations, relative to 90Sr and 137Cs, which increases long-term radiological hazard from alpha emissions if inhaled or ingested, and contrasts with particles from nuclear power accidents (e.g., Fukushima). Additional physical/chemical/radiological measurements are needed to fully understand long-term fate and hazard potentials. [Display omitted] •Numerous and varied radioactive particles persist at all nuclear event sites studied.•Si-,Ca- surface composition enable particle persistence, including in marine conditions.•Our methods reveal a prevalence of interior fractures not previously recognised.•Fractures often connect to particle surfaces and may facilitate radionuclide leaching.•The study weapons-test particles were dominated by Pu (vs 137Cs, 90Sr).