Browsing by Author "Young, EL"
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- ItemCharacterisation of anthropogenic radioactive particles from former weapon test sites in Australia(South Pacific Environmental Radioactivity Association, 2018-11-06) Young, EL; Johansen, MP; Child, DP; Hotchkis, MAC; Howell, NR; Pastuovic, Z; Howard, DL; Palmer, T; Davis, JFormer nuclear test sites on Australian territories such as those at Maralinga and the Montebello islands have been remediated to varying extents but wide-spread radioactivity still remains. Fission and neutron-activation products at the test sites have been decaying over time but long-lived radioisotopes such as uranium and plutonium persist within the environment, predominantly in the form of discrete particles. These particles vary widely in composition depending upon the detonation characteristics and local geology, and are widely dispersed around each site. Radioactive particles are the dominant form of radionuclides at the former test sites and the future distribution of radioactive contaminants in the environment at these sites is largely dependent upon their fate and behaviour. The weathering of particles in the environment and the potential release of the radioactivity they contain is influenced by a range of factors including particle morphology, elemental composition and chemical form, and the prevailing environmental conditions. Radioactive particles have been isolated from soils and sediments from Australian test sites and characterised using photostimulated luminescence (PSL)-autoradiography, scanning electron microscopy energy dispersive X-ray spectroscopy (SEM-EDS), Synchrotron X-ray fluorescence microscopy (XFM) and particle-induced X-ray emission (PIXE). The characteristics of the particles and potential implications for their long term fate will be discussed in the context of the techniques applied and the environments in which the particles were found.
- ItemComparing results of X-ray diffraction, µ-Raman spectroscopy and neutron diffraction when identifying chemical phases in seized nuclear material, during a comparative nuclear forensics exercise(Springer Nature, 2018-01-24) Rondahl, SH; Pointurier, F; Ahlinder, L; Ramebäck, H; Marie, O; Ravat, B; Delauney, F; Young, EL; Blagojevic, N; Hester, JR; Thorogood, GJ; Nelwamondo, AN; Ntsoane, TP; Roberts, SK; Holliday, KSThis work presents the results for identification of chemical phases obtained by several laboratories as a part of an international nuclear forensic round-robin exercise. In this work powder X-ray diffraction (p-XRD) is regarded as the reference technique. Neutron diffraction produced a superior high-angle diffraction pattern relative to p-XRD. Requiring only small amounts of sample, µ-Raman spectroscopy was used for the first time in this context as a potentially complementary technique to p-XRD. The chemical phases were identified as pure UO2 in two materials, and as a mixture of UO2, U3O8 and an intermediate species U3O7 in the third material. © The Author(s) 2018. This article is an open access publication.
- ItemA new class of fluorinated 5-pyrrolidinylsulfonyl isatin caspase inhibitors for PET imaging of apoptosis(Royal Society of Chemistry, 2012-11-12) Krause-Heuer, AM; Howell, NR; Matesic, L; Dhand, G; Young, EL; Burgess, L; Jiang, CD; Lengkeek, NA; Fookes, CJR; Pham, TQ; Sobrio, F; Greguric, I; Fraser, BHThirteen compounds in a new class of fluorinated 5-pyrrolidinylsulfonyl isatin derivatives were synthesised that have potent and selective inhibitory activity against effector caspases-3 and -7. With in vivo animal PET imaging studies of cerebral ischemia being planned, N-benzylation with selected para-substituted benzylic halides allowed systematic variation of lipophilicity (logP 1.94–3.31) without decreasing inhibition potency (IC50). From this series the p-methoxybenzyl analogue was selected for initial ‘proof-of-concept’ [18F]-fluoride radiolabelling which proceeded in good yield and purity with no need for a protection/deprotection strategy. © 2013 Royal Society of Chemistry
- ItemNuclear forensics: scientific analysis supporting law enforcement and nuclear security investigations(American Chemical Society, 2015-12-24) Keegan, EA; Kristo, MJ; Toole, K; Kips, R; Young, ELNuclear forensic science, or "nuclear forensic", aims to answer questions about nuclear material found outside of regulatory control. In this Feature, we provide a general overview of nuclear forensics, selecting examples of key "nuclear forensic signatures" which have allowed investigators to determine the identity of unknown nuclear material in real investigations. © 2015 American Chemical Society
- ItemPlutonium and other radionuclides persist across marine-to-terrestrial ecotopes in the Montebello Islands sixty years after nuclear tests(Elsevier, 2019-11-15) Johansen, MP; Child, DP; Cresswell, T; Harrison, JJ; Hotchkis, MAC; Howell, NR; Johansen, A; Sdraulig, S; Thiruvoth, S; Young, EL; Whiting, SDSince the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg−1 of 239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their 240/239Pu and 241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms. Crown Copyright © 2019 Published by Elsevier B.V
- ItemRadioactive particles from a range of past nuclear events: challenges posed by highly varied structure and composition(Elsevier B. V., 2022-10-10) Johansen, MP; Child, DP; Collins, RN; Cook, M; Howell, NR; Ikeda-Ohno, A; Young, ELWhile 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. Crown Copyright © 2022 Published by Elsevier B.V.
- ItemRecent survey of plutonium at the Montebello Islands nuclear test sites: uptake in marine and terrestrial organisms in a radioactive-particle environment(South Pacific Environmental Radioactivity Association, 2018-11-06) Johansen, MP; Child, DP; Cresswell, T; Harrison, JJ; Hotchkis, MAC; Howell, NR; Thiruvoth, S; Young, EL; Sdraulig, S; Whiting, SDThe plutonium (Pu) residues from the former nuclear weapons tests at the Montebello Islands, Australia, provide unique opportunities for radioecological science. The area has important ecological and conservation values and supports marine and terrestrial threatened species. Local fallout from the l95Os tests left a legacy of fission products and actinides, often in the form of radioactive particles. Plutonium is penvasive and persistent at the sites. Of the nuclear test residues, it remains the primary exposure hazard to wildlife, human visitors and researchers. The highest totalPu measurement in soil found by our limited 2015 sampling (25,050 Bd kg-1) is well above post-cleanup levels at Maralinga and international benchmarks (e.g. the 100 Bq kg-1 IAEA benchmark for the release of material to the public). Other residual radionuclides are present and generally rank (highest-to-lowest activity concentrations): totalPu > 137Cs > 90Sr > 241Am > 152Eu > totalU > 230Th > 60Co although some local variation exists. Across ecological zones, radionuclide levels generally rank: island soils > dunes > beach above high tide (turtle nesting zones) > sea sediments > and intertidal zone. The intertidal beach is the least contaminated zone as many of the radionuclides have been washed into the nearby waters and sea sediments by daily waves as well as frequent storms. However, higher activity concentrations occur below the surface sands, with the maximum occurring at ~1 m at Burgundy Bay beach near the Mosaic G2 test site. At the ground-zero areas, gamma dose rates have reduced by about lOO-fold since 1962 due to the depletion of short-lived neutron activation products. The gamma emissions are easily detected by hand-held devices. Away from these areas, the Pu, in particular, is persistent but is not readily detectable in the field. The use of hand-held detectors or radiation badges alone does not effectively detect the Pu, 90Sr, and other key radionuclides, and therefore may provide a false sense of security to researchers and island visitors. Radionuclide activity concentrations were measured for representative ecological organisms including: algae, oysters, sea cucumbers, crabs, stingrays, fish, and sea turtles. The Pu isotopic signatures from the three tests are distinct from each other, and from world-wide fallout. These signatures could aid in determining local vs regional occupancy and may be useful, along with stable isotopes and other markers, in migration and habitat usage studies for turtles and other species.