Browsing by Author "Palmer, T"

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    Characterisation 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, J
    Former 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.
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    Hydride precipitation and its influence on mechanical properties of notched and unnotched Zircaloy-4 plates
    (Elevier Science BV., 2013-05-01) Wang, Z; Garbe, U; Li, HJ; Harrison, RP; Toppler, K; Studer, AJ; Palmer, T; Planchenault, G
    The hydride formation and its influence on the mechanical performance of hydrided Zircaloy-4 plates containing different hydrogen contents were studied at room temperature. For the unnotched plate samples with the hydrogen contents ranging from 25 to 850 wt. ppm, the hydrides exerted an insignificant effect on the tensile strength, while the ductility was severely degraded with increasing hydrogen content. The fracture mode and degree of embrittlement were strongly related to the hydrogen content. When the hydrogen content reached a level of 850 wt. ppm, the plate exhibited negligible ductility, resulting in almost completely brittle behavior. For the hydrided notched plate, the tensile stress concentration associated with the notch tip facilitated the hydride accumulation at the region near the notch tip and the premature crack propagation through the hydride fracture during hydriding. The final brittle through-thickness failure for this notched sample was mainly attributed to the formation of a continuous hydride network on the thickness section and the obtained very high hydrogen concentration (estimated to be 1965 wt. ppm). © 2013, Elsevier Ltd.
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    Radiocarbon dating of linen from an Egyptian mummy
    (GNS Science, 2011-03-24) Jacobsen, GE; Bertuch, F; Sowada, K; Palmer, T; Jenkinson, A
    In the 19th and early 20th centuries, many museums acquired Egyptian coffins containing mummies from private donors who bought them from dealers in Egypt. Owing to the unknown context of such acquisitions, it cannot be assumed that the mummified individual inside the coffin is the same person named on it. Radiocarbon dating is a key diagnostic test, within the framework of a multidisciplinary study, to help resolve this question. The dating of an adult mummy in the Nicholson Museum at the University of Sydney was therefore checked using 14C dating. For over 150 years, mummy NM R28.2 was identified as Padiashaikhet as per his coffin, dated to the 25th Dynasty, c. 725–700 BC. Radiocarbon results from samples of linen wrappings revealed that the mummy was an unknown individual from the Roman period, 68-129 cal AD. The mummification technique can now be understood within its correct historical context. Copyright (c) 2011 AMS12
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    Silver iodide sodalite – wasteform / HIP canister interactions and aqueous durability
    (Elsevier, 2019-04-15) Maddrell, ER; Vance, ER; Grant, C; Aly, Z; Stopic, A; Palmer, T; Harrison, JJ; Gregg, DJ
    The use of silver zeolite for the capture of radioiodine from the vapour phase, followed by thermal conversion now appears to be the most direct route by which a sodalite wasteform can be formed. In addition, consolidation by hot-isostatic pressing (HIP) in sealed canisters has many significant advantages over conventional methods such as sintering or melting these candidate wasteforms. The choice of HIP canister material is important as reaction at the wasteform/HIP canister interface results in an interaction zone that can potentially produce detrimental phases, wasteform porosity and canister thinning. This paper builds on a previous study that demonstrated that iodine could be captured from the vapour phase using silver exchanged zeolite and converted to sodalite by HIPing in Fe HIP canisters. The Cu or Ni metal HIP canisters used in this work result in an ∼100–200 μm thick local interaction zone with a variety of chemistries. Durability studies were conducted using a variety of reducing conditions and clearly demonstrated the redox sensitivity of silver sodalite. While the silver sodalite wasteform produced is, like the popular AgI-based wasteforms, highly leach resistant to leaching by deionised water it was unstable under highly reducing conditions, which are likely to occur in most geological disposal facilities. Post leaching characterisation revealed the redeposition of AgI and the formation of an aluminosilicate alteration layer under some leaching conditions. Appropriate precautions are required should a silver sodalite wasteform for iodine immobilisation be exposed to reducing groundwater conditions. Crown Copyright © 2019 Published by Elsevier B.V.
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    Who's that lying in my coffin? An imposter exposed by 14C dating
    (University of Arizona, 2011-06-01) Sowada, K; Jacobsen, GE; Bertuch, F; Palmer, T; Jenkinson, A
    In the 19th and early 20th centuries, many museums acquired Egyptian coffins containing mummies from private donors who bought them from dealers in Egypt. Owing to the unknown context of such acquisitions, it cannot be assumed that the mummified individual inside the coffin is the same person named on it. Radiocarbon dating is a key diagnostic test, within the framework of a multidisciplinary study, to help resolve this question. The dating of an adult mummy in the Nicholson Museum at the University of Sydney was therefore checked using (14)C dating. For over 150 yr, mummy NM R28.2 was identified as Padiashaikhet as per his coffin, dated to the 25th Dynasty, about 725-700 BC. (14)C results from samples of linen wrappings revealed that the mummy was an unknown individual from the Roman period, cal AD 68-129. The mummification technique can now be understood within its correct historical context. © 2011, University of Arizona