Browsing by Author "Cook, M"

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    Assessment of radioactive ‘Hot Particles’ and marine sediment plutonium and americium levels from the Montebello Islands, Western Australia
    (South Pacific Environmental Radioactivity Association, 2018-11-06) Hoffman, M; Johansen, MP; Cook, M; Howell, NR; Kleinschmidt, R; Clegg, JK
    The Montebello islands are an archipelago off the Western Australian coast that to this day display an artificial radioactive legacy. The legacy is the result of nuclear testing from 1952-1956. that produced long-lived radionuclides such as americium (Am-241) and plutonium (Pu-239/240). This study investigated the extent and characteristics of radioactive contamination in marine sediments near the former Operation Hurricane and Operation Mosaic G2 detonation sites in hopes of contributing to future management strategies and updated assessment of health risks to native flora, fauna and human populations. The project was conducted with samples collected in 2015 by the Australian Nuclear Science and Technology Organisation (ANSTO) as two series; Series 1 chosen to monitor the activity from the Operation Mosaic G2 detonation and Series 2 aiming to determine residual activity from the Operation Hurricane HMS Plymouth detonation. Samples were initially sieved to separate the bulk samples into four size-based fractions for analysis of activity fractionation among sediment grain sizes. Radiation counting processes included alpha spectrometry and gamma spectrometry, back-scatter electron mode scanning electron microscopy (BEI-SEM) and photo-stimulated luminescent (PSL) autoradiography to evaluate the overall radiative status of the sediment locations and to investigate the presence of ‘hot’ particles or heterogenous dispersion of radioactivity. Both spectrometry processes revealed that Series 1 Am-241 and Pu-239/240 activity was dispersed preferentially in the two larger fractions (>500 um and 500-200 um). Activity determined as Am241 and Pu-289/240 vi/as observed across Series 2 as well but as values an order of magnitude lower. Environmental plutonium from Series 1 was present in hot particle form, specifically within particles from the more active >500 um [largest] fraction which revealed gamma emissions of the plutonium progeny Am241. imaging and subsequent analysis by BE!-SEM and energy dispersive X-ray spectroscopy (EDS) of the particles revealed that the majority of the particle material was calcium carbonate, indicative of the dominant geology at the detonation site. Study results provide insights into the radioactive characteristics of hot-particles and bulk sediments at the Montebello site. it is believed and hoped that this investigation will aid decisions on the future management of the Montebello wildlife resources and marine park management, and provide insights into potential risks and protective measures for site visitors and researchers.
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    Comparison of radium-228 determination in water among Australian laboratories
    (Elsevier, 2017-11) Zawadzki, A; Cook, M; Cutmore, B; Evans, F; Fierro, D; Gedz, A; Harrison, JJ; Loosz, T; Medley, P; Mokhber-Shahin, L; Mullins, S; Sdraulig, S
    The National Health and Medical Research Council and Natural Resource Management Ministerial Council of Australia developed the current Australian Drinking Water Guidelines which recommend an annual radiation dose value of 1 mSv year−1. One of the potential major contributors to the radiation dose from drinking water is radium-228, a naturally occurring radionuclide arising from the thorium decay series. Various methods of analysing for radium-228 in water have been established and adapted by analytical radiochemistry laboratories. Seven laboratories in Australia participated in analysing radium-228 spiked water samples with activity concentrations ranging from 6 mBq L−1 to 20 Bq L−1. The aim of the exercise was to compare and evaluate radium-228 results reported by the participating laboratories, the methods used and the detection limits. This paper presents the outcome of the exercise. Crown Copyright © 2017 Published by Elsevier Ltd.
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    Radioactive 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, EL
    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. Crown Copyright © 2022 Published by Elsevier B.V.