Methods for investigating Australia's former nuclear test sites

The radiological residues at the former weapons testing sites in Australia at Maralinga, Emu and the Montebello Islands are of ongoing interest in terms of environmental fate, transport, and uptake into the biosphere1. The physical and chemical characteristics of these residues affect their mobility and availability for uptake into living organisms2. At the Taranaki site, Maralinga, substantial body burdens of Pu were observed in mammals, likely due to the presence of respirable particles. Actinides often occur in particulate forms that, for characterisation, require advanced techniques including Accelerator Mass Spectrometry (AMS)3, Scanning electron microscopy and synchrotron X-ray fluorescence microscopy (XFM). Many nuclear test site particles have core-shell, or inhomogenous structures where the surface is dominated by lighter elements sourced from local soils and the Pu concentrated in the interior4. Modelling results suggest that for respirable-sized Pu-containing particles (that can be inhaled and lodged in the lung), most of the alpha emissions escape the particle and are deposited in the surrounding tissue.4 For larger particles, (e.g. >7 µm), which typically do not lodge in the lung but could be ingested, most of the alpha emissions do not escape the particle, but are instead captured within the particle itself (self-shielding) therefore decreasing the effective dose. We are currently using advanced techniques to compare the radionuclide forms from the inland sites (Maralinga and Emu) with the marine site (Montebello Islands).