Browsing by Author "Vandenhove, H"

Now showing 1 - 7 of 7
  • Thumbnail Image
    Item
    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
  • Thumbnail Image
    Item
    Best practices for predictions of radionuclide activity concentrations and total absorbed dose rates to freshwater organisms exposed to uranium mining/milling
    (Elsevier, 2022-02) Goulet, R; Newsome, L; Vandenhove, H; Keum, DK; Horyna, J; Kamboj, S; Brown, JE; Johansen, MP; Twining, JR; Wood, MD; Černe, M; Beaugelin-Seiller, K; Beresford, NA
    Predictions of radionuclide dose rates to freshwater organisms can be used to evaluate the radiological environmental impacts of releases from uranium mining and milling projects. These predictions help inform decisions on the implementation of mitigation measures. The objective of this study was to identify how dose rate modelling could be improved to reduce uncertainty in predictions to non-human biota. For this purpose, we modelled the activity concentrations of 210Pb, 210Po, 226Ra, 230Th, and 238U downstream of uranium mines and mills in northern Saskatchewan, Canada, together with associated weighted absorbed dose rates for a freshwater food chain using measured activity concentrations in water and sediments. Differences in predictions of radionuclide activity concentrations occurred mainly from the different default partition coefficient and concentration ratio values from one model to another and including all or only some 238U decay daughters in the dose rate assessments. Consequently, we recommend a standardized best-practice approach to calculate weighted absorbed dose rates to freshwater biota whether a facility is at the planning, operating or decommissioned stage. At the initial planning stage, the best-practice approach recommend using conservative site-specific baseline activity concentrations in water, sediments and organisms and predict conservative incremental activity concentrations in these media by selecting concentration ratios based on species similarity and similar water quality conditions to reduce the uncertainty in dose rate calculations. At the operating and decommissioned stages, the best-practice approach recommends relying on measured activity concentrations in water, sediment, fish tissue and whole-body of small organisms to further reduce uncertainty in dose rate estimates. This approach would allow for more realistic but still conservative dose assessments when evaluating impacts from uranium mining projects and making decision on adequate controls of releases. © 2022 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license.
  • Thumbnail Image
    Item
    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.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    The estimation of absorbed dose rates for non-human biota: an extended inter-comparison
    (Springer, 2011-05-01) Vives i Batlle, J; Beaugelin-Seiller, K; Beresford, NA; Copplestone, D; Horyna, J; Hosseini, A; Johansen, MP; Kamboj, S; Keum, DK; Kurosawa, N; Newsome, L; Olysaegers, G; Vandenhove, H; Ryufuku, S; Lynch, SV; Wood, MD; Yu, C
    An exercise to compare 10 approaches for the calculation of unweighted whole-body absorbed dose rates was conducted for 74 radionuclides and five of the ICRP's Reference Animals and Plants, or RAPs (duck, frog, flatfish egg, rat and elongated earthworm), selected for this exercise to cover a range of body sizes, dimensions and exposure scenarios. Results were analysed using a non-parametric method requiring no specific hypotheses about the statistical distribution of data. The obtained unweighted absorbed dose rates for internal exposure compare well between the different approaches, with 70% of the results falling within a range of variation of +/- 20%. The variation is greater for external exposure, although 90% of the estimates are within an order of magnitude of one another. There are some discernible patterns where specific models over- or under-predicted. These are explained based on the methodological differences including number of daughter products included in the calculation of dose rate for a parent nuclide; source-target geometry; databases for discrete energy and yield of radionuclides; rounding errors in integration algorithms; and intrinsic differences in calculation methods. For certain radionuclides, these factors combine to generate systematic variations between approaches. Overall, the technique chosen to interpret the data enabled methodological differences in dosimetry calculations to be quantified and compared, allowing the identification of common issues between different approaches and providing greater assurance on the fundamental dose conversion coefficient approaches used in available models for assessing radiological effects to biota. © 2011, Springer.
  • No Thumbnail Available
    Item
    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.
  • No Thumbnail Available
    Item
    Uranium : radionuclides
    (John Wiley & Sons, 2010-05) Vandenhove, H; Hurtgen, C; Payne, TE
    This article describes the occurrence, chemistry, and bioavailability of uranium (U) in terrestrial and aquatic environments, its analysis in environmental samples, and remedial measures applicable to uranium-contaminated water and soil. Uranium is widely distributed throughout the world. There are three main isotopes present in natural uranium, which comprises 234U (0.0055%), 235U (0.72%), and 238U (99.27%). Uranium can occur either in its reduced state (U(IV)), which is generally highly immobile, or in its more soluble and mobile (U(VI)) state. Uranium mobility and bioavailability are governed by oxidation state, complexation by organic and inorganic ligands, pH, sorption by minerals including clays and hydroxides, and interactions with organic matter. In uncontaminated surface waters uranium content is generally low (<1 ppb). Most groundwaters are low in uranium but the concentration range is large (<0.001–2600 ppb), resulting from the interaction of groundwater with naturally occurring uranium-bearing materials or anthropogenic contamination sources. Since groundwater is a major source for drinking water, various methods have been developed to remove uranium from potable water. Similar methods are applied in wastewater treatment. Extraction and processing of uranium ore or minerals containing natural radionuclides has resulted in the generation of waste streams. The major challenge associated with these contaminated waste streams, residues, or sites is typically the larger volumes of material and the relatively low specific activities. © 2011 John Wiley & Sons, Ltd.