Browsing by Author "Doering, C"
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- ItemThe IAEA handbook on radionuclide transfer to wildlife(Elsevier B.V., 2013-07-01) Howard, BJ; Beresford, NA; Copplestone, D; Telleria, D; Proehl, G; Fesenko, S; Jeffree, RA; Yankovich, TL; Brown, JE; Higley, K; Johansen, MP; Mulye, H; Vandenhove, H; Gashchakk, S; Wood, MD; Takatam, H; Andersson, P; Dale, P; Ryan, J; Bollhöfer, A; Doering, C; Barnett, CL; Wells, CAn IAEA handbook presenting transfer parameter values for wildlife has recently been produced. Concentration ratios (CRwo-media) between the whole organism (fresh weight) and either soil (dry weight) or water were collated for a range of wildlife groups (classified taxonomically and by feeding strategy) in terrestrial, freshwater, marine and brackish generic ecosystems. The data have been compiled in an on line database, which will continue to be updated in the future providing the basis for subsequent revision of the Wildlife TRS values. An overview of the compilation and analysis, and discussion of the extent and limitations of the data is presented. Example comparisons of the CRwo-media values are given for polonium across all wildlife groups and ecosystems and for molluscs for all radionuclides. The CRwo-media values have also been compared with those currently used in the ERICA Tool which represented the most complete published database for wildlife transfer values prior to this work. The use of CRwo-media values is a pragmatic approach to predicting radionuclide activity concentrations in wildlife and is similar to that used for screening assessments for the human food chain. The CRwo-media values are most suitable for a screening application where there are several conservative assumptions built into the models which will, to varying extents, compensate for the variable data quality and quantity, and associated uncertainty. © 2012, Elsevier Ltd.
- ItemModelling the dispersion of radon-222 and radionuclides in dust from the Ranger final landform(South Pacific Environmental Radioactivity Association, 2018-10-06) McMaster, S; Doering, C; Johansen, MPThe Ranger uranium mine, located in the seasonal wet-dry tropics of Australia’s Northern Territory, is scheduled to cease operating by 2021 and be rehabilitated by 2026. The planned rehabilitation of the mine will result in a final landform covered by low uranium grade waste rock and vegetation. The rehabilitation objective is to establish an environment similar to the World Heritage protected area ot Kakadu National Park, which surrounds the mine. Radiological conditions must also not place significant restrictions on the use of the area. Radon-222 gas, and a range of radionuclides bonded to dust emitted from the waste rock substrate of the final landform represent potential radiation exposure pathways to the public. The inhalation dose rates from 222Rn and dust exposure, together with the dose rates from other potential exposure pathways, need to be assessed to determine what. it any, land use restrictions may be required and demonstrate to compliance with dose limits. This study used RESRAD-OFFSITE 3.2 to model the dispersion of 222Rn and radionuclides in dust from a conceptual landform representing the rehabilitated state of the Ranger uranium mine. The predicted dispersion of 222Rn and radionuclides in dust was primarily governed by wind direction frequency. Contour maps of dry and wet season dispersion were developed to aid estimates of potential dose rates to the public from 222Rn and dust exposure. The maps were used to estimate above-background annual doses to hypothetical receptors at the Aboriginal community at Mudginberri (~10 km NNW) and at the town of Jabiru (~7 l
- ItemModelling the dispersion of radon-222 from a landform covered by low uranium grade waste rock(Elsevier, 2018-12) Doering, C; McMaster, SA; Johansen, MPThe dispersion of 222Rn from the planned remediation of the Ranger U mine in the wet-dry tropics of Northern Australia was modelled. Dry and wet season contour maps of 222Rn dose normalised to 226Ra activity concentration in the proposed waste rock substrate on the remediated landform were developed. Three example exposure scenarios were assessed based on an anticipated waste rock 226Ra activity concentration of 800 Bq kg−1. The estimated above-background annual dose from 222Rn to hypothetical receptors at the Aboriginal community at Mudginberri (∼10 km NNW) was 0.005 mSv and at the township of Jabiru (∼7 km W) was 0.033 mSv. The estimated above-background annual dose for the hypothetical worst case scenario, representing a receptor 1 km WNW of the landform centroid during the dry season and at the centroid during the wet season, was 0.13 mSv. Variability analysis on the 20 y meteorological dataset used in the dispersion modelling showed that the dry and wet season 222Rn dose predictions in any single year could be approximately double those of an average year, which suggests that estimates of average 222Rn dose should potentially be doubled if the assessment aim is to demonstrate compliance with the public dose limit. © 2018 Published by Elsevier Ltd.
- ItemPlutonium in wildlife and soils at the Maralinga legacy site: persistence over decadal time scales(Elsevier Science Ltd, 2014-05-01) Johansen, MP; Child, DP; Davis, E; Doering, C; Harrison, JJ; Hotchkis, MAC; Payne, TE; Thiruvoth, S; Twining, JR; Wood, MDThe mobility of plutonium (Pu) in soils, and its uptake into a range of wildlife, were examined using recent and similar to 25 year old data from the Taranaki area of the former Maralinga weapons test site, Australia. Since its initial deposition in the early 1960s, the dispersed Pu has been incorporated into the soil profile and food chain through natural processes, allowing for the study of Pu sequestration and dynamics in relatively undisturbed semi-arid conditions. The data indicate downward mobility of Pu in soil at rates of similar to 0.2-0.3 cm per year for the most mobile fraction. As a result, while all of the Pu was initially deposited on the ground surface, approximately 93% and 62% remained in the top 0-2 cm depth after 25- and 50-years respectively. No large-scale lateral spreading of the Taranaki plume was observed. Pu activity concentrations in 0-1 cm soils with biotic crusts were not elevated when compared with nearby bare soils, although a small number of individual data suggest retention of Pu-containing particles may be occurring in some biotic crusts. Soil-to-animal transfer, as measured by concentration ratios (CRwo-soil), was 4.1E-04 (Geometric Mean (GM)) in mammals, which aligns well with those from similar species and conditions (such as the Nevada Test Site, US), but are lower than the GM of the international mammal data reported in the Wildlife Transfer Database (WTD). These lower values are likely due to the presence of a low-soluble, particulate form of the Pu in Maralinga soils. Arthropod concentration ratios (3.1E-03 GM), were similar to those from Rocky Flats, US, while values for reptiles (2.0E-02 GM) were higher than the WTD GM value which was dominated by data from Chernobyl. Comparison of uptake data spanning approximately 30 years indicates no decrease over time for mammals, and a potential increase for reptiles. The results confirm the persistence of bioavailable Pu after more than 50 years since deposition, and also the presence of larger-sized particles which currently affect CRwo-soil calculations, and which may serve as an ongoing source of bioavailable Pu as they are subjected to weathering into the future. © 2014, Elsevier Ltd.
- ItemPlutonium uptake in biota at former nuclear sites(Australian Nuclear Association, 2013-10-11) Johansen, MP; Child, DP; Doering, C; Harrison, JJ; Hotchkis, MAC; Kamboj, W; Kuhne, WW; Payne, TE; Thiruvoth, S; Twining, JR; Wood, MDPlutonium (Pu) is of ongoing interest as worldwide inventories continue to increase and plans for permanent storage of Pu wastes have stalled in many countries leaving large amounts in temporary storage. Pu also remains as environmental contamination at various locations due to: accidents (e.g., Chernobyl, UKR; Thule, GRL); research and processing releases (e.g., Los Alamos, USA, Mayak, RUS); and former weapons testing (e.g., Nevada Test Site, USA; Semipalatinsk, KAZ; and Maralinga, AUS). We assessed the availability and uptake of Pu in a range of wildlife types at legacy sites with the focus on new data from outside of the remediation zone at the former Taranaki site, Maralinga, South Australia. Of key interest are the uptake and biokinetics of Pu in mammals, particularly from environmental exposure to the undetonated Pu-oxide forms at Taranaki that are representative of much of the worldwide inventory. Our results confirm that environmentally dispersed Pu can remain accessible for uptake by biota over decadal time scales. For example, after more than 50 years since deposition at Taranaki, 62% of Pu has remained in the 0-2 cm surface layer, and nearly 100% in the 0-10 cm of soil depths. Although a small fraction of the Pu is migrating downward at —0.2 cm per year, it appears that most Pu will continue to remain accessible into the future for plants and animals that inhabit the surface, or shallow soil layers. The uptake of Pu into terrestrial animals occurs mainly by inhalation and ingestion, and can be persistent over time as indicated by constant uptake rates for mammals, and a potential increase for reptiles, in data spanning 30 years. The rates of soil-to-animal transfer at Taranaki, align well with those from similar sites where undetonated Pu was tested (e.g., Nevada Test Site, US). However, the uptake values at these sites are lower than general world-wide values, likely due to the presence of less-absorbable forms of Pu. The importance of the physico-chemical form of the Pu on uptake was also seen in data from fish exposed to more absorbable forms of Pu in liquid discharge ponds near processing facilities in the US. These fish had two orders of magnitude higher uptake values than those for similar species receiving Pu solely from atmospheric fallout. The physico-chemical form of the Pu can also influence how it is distributed among mammalian organs. The relatively insoluble forms at Taranaki, which include particulates, led to elevated concentrations of unabsorbed Pu in the lung, gastrointestinal tract, and adhered to skin/fur of mammals. This elevated Pu can provide a secondary source during human, and ecological, food-chain consumption. Of the Pu that was absorbed within the body, much higher accumulation was measured in the skeleton, and much lower in the liver, in mammals at Taranaki as compared with the standard model of 50% skeleton, and 30% liver (ICRP 1986). Our data provides specific quantification of Pu uptake rates in wildlife and the subsequent accumulation in various mammalian organs. These will aid future assessments of the Maralinga site, as well as more general evaluations related to the low-solubility forms of Pu that make up a large share of the worldwide inventory.
- ItemPlutonium uptake in wildlife at Maralinga, South Australia(Australian Nuclear Science and Technology Organisation, 2012-10-16) Johansen, MP; Child, DP; Collins, RN; Davis, E; Doering, C; Harrison, JJ; Hotchkis, MAC; Payne, TE; Mokhber-Shahin, L; Ryan, B; Thiruvoth, S; Twining, JR; Wilsher, KL; Wood, MDThis study examined accumulation of plutonium (Pu) in wildlife at Maralinga, South Australia, where a 1950s series of experiments dispersed unfissioned Pu onto the landscape. The residual Pu concentrations that remain today are lower than the site clean-up level, but are sufficient to provide a rare opportunity to study wildlife organisms that have been exposed to a food web and soils containing elevated Pu. Analysis was by gamma- and alpha- spectroscopy, and by accelerator mass spectrometry at ANSTO. Uptake of Pu was quantified by concentration ratios, defined as average concentration in the whole-organism, to that of their host soil (CRwo-soil). The geometric mean of CRwo-soil values for all organisms was 0.002 (geometric standard deviation – 4.1E00) with mammals
- ItemRecent developments in the modelling of radionuclide uptake, radiation dose and effects in wildlife(South Pacific Environmental Radioactivity Association, 2014-09) Johansen, MP; Beresford, NA; Howard, BJ; Hinton, TG; Bollhöfer, A; Doering, C; Hirth, GA; Grzechnik, M; Ruedig, E; Payne, TE; Twining, JROf the ~600 scientific publications on the Fukushima event, more than 80% relate to themes of transport of radionuclides in environmental media, transfer to wildlife and foodstuffs, and dose to environmental receptors. This focus reflects a continued need for development and harmonisation of radiological modelling approaches such as has been underway through recent IAEA and ICRP initiatives (e.g. EMRAS I and II, MODARIA). Key developments in improving the understanding of uptake of radionuclides in wildlife include establishing the Wildlife Transfer Parameter Database and related IAEA handbook on transfer to wildlife. These sources provide access to a comprehensive collection of transfer parameters, including input from Australian sources (www.wildlifetransferdatabase.org). Key improvements were highlighted in a recent Journal of Environmental Radioactivity special issue (Vol. 121). Dose modelling for wildlife continues to be challenged by the high diversity of biotic types (plankton to whales) and the breadth of exposure scenarios in diverse ecosystems. Modelling codes (e.g. ERICA Tool, RESRAD-Biota) are undergoing updates of their transfer parameters, improvement of capabilities such as probabilistic analysis (e.g. Monte Carlo), and harmonization of approaches through IAEA model testing exercises (e.g., Little Forest Burial Ground biota dose modelling assessment). A recent development has been the use of voxel dosimetry approaches which build on the standard simplified ellipsoid approach by modelling the absorbed doses in individual organs. Recent improvements in defining dose effects to environmental receptors have focused on updating the FREDERICA Radiation Effects Database. The more comprehensive data have allowed for the updating/development of new Species Sensitivity Distributions that better support the benchmark values for potential dose effects, and for improving estimation of population effects (rather than individuals) upon which the environmental protection strategies are based.