Browsing by Author "Barnett, CL"

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    Assessing 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, C
    Radiological 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
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    Biota 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, C
    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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    Dose 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, C
    Radiological 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.
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    Ensuring robust radiological risk assessment for wildlife: insights from the International Atomic Energy Agency EMRAS and MODARIA programmes
    (Published on behalf of the Society for Radiological Protection by IOP Publishing Limited, 2022-05-03) Beresford, NA; Beaugelin-Seiller, K; Barnett, CL; Brown, JE; Caffrey, EA; Johansen, MP; Melintescu, A; Ruedig, E; Vandenhove, H; Vives i Batlle, J; Wood, MD; Yankovich, TL; Copplestone, D
    In response to changing international recommendations and national requirements, a number of assessment approaches, and associated tools and models, have been developed over the last circa 20 years to assess radiological risk to wildlife. In this paper, we summarise international intercomparison exercises and scenario applications of available radiological assessment models for wildlife to aid future model users and those such as regulators who interpret assessments. Through our studies, we have assessed the fitness for purpose of various models and tools, identified the major sources of uncertainty and made recommendations on how the models and tools can best be applied to suit the purposes of an assessment. We conclude that the commonly used tiered or graded assessment tools are generally fit for purpose for conducting screening-level assessments of radiological impacts to wildlife. Radiological protection of the environment (or wildlife) is still a relatively new development within the overall system of radiation protection and environmental assessment approaches are continuing to develop. Given that some new/developing approaches differ considerably from the more established models/tools and there is an increasing international interest in developing approaches that support the effective regulation of multiple stressors (including radiation), we recommend the continuation of coordinated international programmes for model development, intercomparison and scenario testing. © 2022 Society for Radiological Protection.
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    The 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, C
    An 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.
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    Recent development of wildlife transfer databases
    (International Union of Radioecology, 2014) Beresford, NA; Copplestone, D; Hosseini, A; Brown, JE; Johansen, MP; Hirth, GA; Sheppard, S; Dagher, E; Yankovich, T; Uchida, S; Napier, J; Outola, I; Wells, C; Barnett, CL; Wood, MD; Howard, BJ
    The transfer of radionuclides to wildlife in the environmental radiological assessment models developed over the last two decades is most often described by the whole organism concentration ratio (CRwo-media). This parameter relates whole organism activity concentrations to those in environmental media (typically soil for terrestrial ecosystems and water for aquatic ecosystems). When first released in 2007, the ERICA Tool contained the most comprehensive and well documented CRwo-media database available for wildlife. It was subsequently used in the US DOE RESRAD-BIOTA model and formed the initial basis for the international wildlife transfer database (WTD; www.wildlifetransferdatabase.org/?) developed to support IAEA and ICRP activities. Subsequently, many additional data were input to the WTD, including the outputs of a review of Russian language literature and data from Canadian monitoring programmes associated with nuclear power plants, U-mining and related industries. Summarised data from the WTD in 2011 were used to provide CRwo values in ICRP 114 and the IAEA's handbook on wildlife transfer parameters (http://www-ns.iaea.org/projects/emras/emras2/working-groups/working-group-five.asp?s=8&l=63). This paper provides an update on the development of the WTD subsequent to 2011 and its application to derive revised default CRwo-media parameter values of the ERICA Tool. Since 2011, some circa 17,000 additional CRwo-media values have been added to the WTD. The new inputs include original data for: representative species of the ICRPs Representative Animals and Plants (RAPs) from a UK forest; monitoring data from Japanese estuaries and Finland; Canadian wildlife; plutonium uptake data from US weapons testing programme sites; wild plants and invertebrates from north western USA; refereed literature published after 2011. Additionally, data already in the WTD from Australia were reviewed with reference to original source reports not previously considered and amended where required. The revised WTD was quality checked by considering the degree of variation in the data for each organism-element combination and the change between the WTD versions. This identified a number of errors (e.g. double entry of data, unit conversion errors and entries based on a dry matter rather than the required fresh weight basis) all of which have now been rectified. Statistical analyses of the WTD have demonstrated that there is currently no justification to subdivide CRwo-media from e.g. mammal to mammal herbivore and mammal carnivore etc.. In revising the ERICA Tool, a more generic categorisation of organisms has subsequently been used. Even with the increase in available data, there are still many radionuclide-organism combinations for which data are lacking. To provide default values where there are no data, a set of rules have been derived including the use of Bayesian statistics. (authors)
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    Whole-body to tissue concentration ratios for use in biota dose assessments for animals
    (Springer, 2010-11) Yankovich, TL; Beresford, NA; Wood, MD; Aono, T; Andersson, P; Barnett, CL; Bennett, P; Brown, JE; Fesenko, S; Fesenko, J; Hosseini, A; Howard, BJ; Johansen, MP; Phaneuf, MM; Tagami, K; Takata, H; Twining, JR; Uchida, S
    Environmental monitoring programs often measure contaminant concentrations in animal tissues consumed by humans (e.g., muscle). By comparison, demonstration of the protection of biota from the potential effects of radionuclides involves a comparison of whole-body doses to radiological dose benchmarks. Consequently, methods for deriving whole-body concentration ratios based on tissue-specific data are required to make best use of the available information. This paper provides a series of look-up tables with whole-body:tissue-specific concentration ratios for non-human biota. Focus was placed on relatively broad animal categories (including molluscs, crustaceans, freshwater fishes, marine fishes, amphibians, reptiles, birds and mammals) and commonly measured tissues (specifically, bone, muscle, liver and kidney). Depending upon organism, whole-body to tissue concentration ratios were derived for between 12 and 47 elements. The whole-body to tissue concentration ratios can be used to estimate whole-body concentrations from tissue-specific measurements. However, we recommend that any given whole-body to tissue concentration ratio should not be used if the value falls between 0.75 and 1.5. Instead, a value of one should be assumed. © 2010, Springer.