Biota dose modelling: Little Forest Burial Ground scenario
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Date
2012-10-16
Journal Title
Journal ISSN
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Publisher
Australian Nuclear Science and Technology Organisation
Abstract
Radiation doses to terrestrial wildlife were examined in a model inter-comparison study on a diverse range of terrestrial plants and animals at the Little Forest Burial Ground, NSW, Australia. This inter-comparison was one in a series conducted under the IAEA Environmental Modelling for Radiation Safety Programme (EMRAS), which indicated general agreement among available biota dose models in the use of dose conversion parameters for standard organisms and geometries. However, notable variation in dose estimates emerged when the models were applied to a terrestrial deposition scenario (Chernobyl exclusion zone, Ukraine); a freshwater aquatic scenario (Perch Lake, Canada; a low-level burial ground scenario (Little Forest Burial Ground, Australia;), as well as additional aquatic (Beaverlodge, Canada) and wetlands (various locations) scenarios currently underway. Given the range in outcomes from the various modelling approaches of the previous EMRAS studies, the Little Forest Burial Ground scenario focused on quantifying the factors causing variation. The dominant variable factor (up to orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides. Additional variation was associated with: exposure configurations (two orders of magnitude when considering trees growing on the waste trenches); inclusion/exclusion of progeny in Th and U isotopes (typically less than one order of magnitude); and radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). At Little Forest, results suggest radionuclide uptake is occurring in wildlife, but at low levels as most organisms only access the relatively clean surface soils above the buried wastes. Doses to acacia tree were elevated, however, due to its deeper roots having direct access to the buried wastes, with predictions of 95th percentile doses above the screening levels indicating further study is warranted. Our study confirms and adds to the outcomes of previous EMRAS studies in quantifying the sources of variation in biota dose modelling, and highlights soil to-organism transfer as a key source of uncertainty. It prompts continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife.
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Keywords
Radiation doses, Wild animals, Ground disposal, Radioactive wastes, ANSTO, New South Wales, Australia, Fresh water, Trees
Citation
Johansen, M. P., Barnett, C. L., Beresford, N. A., Brown, J. E., Černe, M., Howard, B. J., Kamboj, S., Keum,. D. K., Payne. T. E., Smodiš, B., Twining, J. R., Vandenhove. H., Vives I Battle, J., Wood, M.D., Yankovich, T. L. & Yu. C. (2012). Biota dose modelling: Little Forest Burial Ground scenario. Paper presented to the 12th South Pacific Environmental Radioactivity Association Conference (SPERA 2012), Tuesday 16 October – Friday 19 October 2012, Sydney, Australia. Lucas Heights, NSW: Australian Nuclear Science and Technology Organisation. (pp. 48-49).