Browsing by Author "Smodiš, B"
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- ItemAssessing doses to terrestrial wildlife at a radioactive waste disposal site: Inter-comparison of modelling approaches(Elsevier Science BV, 2012-06-15) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Smodiš, B; Twining, JR; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yu, CRadiological doses to terrestrial wildlife were examined in this model inter-comparison study that emphasised factors causing variability in dose estimation. The study participants used varying modelling approaches and information sources to estimate dose rates and tissue concentrations for a range of biota types exposed to soil contamination at a shallow radionuclide waste burial site in Australia. Results indicated that the dominant factor causing variation in dose rate estimates (up to three orders of magnitude on mean total dose rates) was the soil-to-organism transfer of radionuclides that included variation in transfer parameter values as well as transfer calculation methods. Additional variation was associated with other modelling factors including: how participants conceptualised and modelled the exposure configurations (two orders of magnitude); which progeny to include with the parent radionuclide (typically less than one order of magnitude); and dose calculation parameters, including radiation weighting factors and dose conversion coefficients (typically less than one order of magnitude). Probabilistic approaches to model parameterisation were used to encompass and describe variable model parameters and outcomes. The study confirms the need for continued evaluation of the underlying mechanisms governing soil-to-organism transfer of radionuclides to improve estimation of dose rates to terrestrial wildlife. The exposure pathways and configurations available in most current codes are limited when considering instances where organisms access subsurface contamination through rooting, burrowing, or using different localised waste areas as part of their habitual routines. Crown Copyright © 2012 Published by Elsevier B.V
- ItemBiota dose modelling: Little Forest Burial Ground scenario(Australian Nuclear Science and Technology Organisation, 2012-10-16) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Payne, TE; Smodiš, B; Twining, JR; Vandehnove, H; Vives i Batlle, J; Wood, MD; Yankovich, TL; Yu, CRadiation 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.
- ItemDose modelling comparison for terrestrial biota: IAEA EMRAS II Biota Working Group's Little Forest Burial Ground scenario(International Union of Radioecology, 2011-06-19) Johansen, MP; Barnett, CL; Beresford, NA; Brown, JE; Černe, M; Howard, BJ; Kamboj, S; Keum, DK; Smodiš, B; Twining, JR; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yu, CRadiological doses to terrestrial biota have been examined in a model inter-comparison study that emphasised the identification of factors causing variability in dose estimation. Radiological dose rates were modelled for ten species representing a diverse range of terrestrial plant and animals with varying behavioural and physical attributes. Dose to these organisms may occur from a range of gamma (Co-60, Cs-137), beta (Sr-90) and alpha (Th-232, U-234 and U-238, Pu-238, Pu-239/240 and Am-241) emitting radionuclides. Whilst the study was based on a specific site - the Little Forest Burial Ground, New South Wales, and Australia - it was intended to be representative of conditions at sites throughout the world where low levels of radionuclides exist in soil due to waste disposal or similar activities.