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International audience; Exposure to radiation is a potential hazard to humans and the environment. The Fukushima accident reminded the world of the importance of a reliable risk management system that incorporates the dose received from radiation exposures. The dose to humans from exposure to radiation can be quantified using a well-defined system; its environmental equivalent, however, is still in a developmental state. Additionally, the results of several papers published over the last decade have been criticized because of poor dosimetry. Therefore, a workshop on environmental dosimetry was organized by the STAR (Strategy for Allied Radioecology) Network of Excellence to review the state of the art in environmental dosimetry and prioritize areas of methodological and guidance development. Herein, we report the key findings from that international workshop, summarise parameters that affect the dose animals and plants receive when exposed to radiation, and identify further research needs. Current dosimetry practices for determining environmental protection are based on simple screening dose assessments using knowledge of fundamental radiation physics, source-target geometry relationships, the influence of organism shape and size, and knowledge of how radionuclide distributions in the body and in the soil profile alter dose. In screening model calculations that estimate whole-body dose to biota the shapes of organisms are simply represented as ellipsoids, while recently developed complex voxel phantom models allow organ-specific dose estimates. We identified several research and guidance development priorities for dosimetry. For external exposures, the uncertainty in dose estimates due to spatially heterogeneous distributions of radionuclide contamination is currently being evaluated. Guidance is needed on the level of dosimetry that is required when screening benchmarks are exceeded and how to report exposure in dose-effect studies, including quantification of uncertainties. Further research is needed to establish whether and how dosimetry should account for differences in tissue physiology, organism life stages, seasonal variability (in ecology, physiology and radiation field), species life span, and the proportion of a population that is actually exposed. We contend that, although major advances have recently been made in environmental radiation protection, substantive improvements are required to reduce uncertainties and increase the reliability of environmental dosimetry. © 2017 Elsevier Ltd

For the first time, a system for specific consideration of radiological environmental protection has been applied in a major license application in Sweden. In 2011 the Swedish Nuclear Fuel & Waste Management Co. (SKB) submitted a license application for construction of a geological repository for spent nuclear fuel at the Forsmark site. The license application is supported by a post-closure safety assessment, which in accordance with regulatory requirements includes an assessment of environmental consequences. SKB's environmental risk assessment uses the freely available ERICA Tool. Environmental media activity concentrations needed as input to the tool are calculated by means of complex biosphere modelling based on site-specific information gathered from site investigations, as well as from supporting modelling studies and projections of future biosphere conditions in response to climate change and land rise due to glacial rebound. SKB's application is currently being reviewed by the Swedish Radiation Safety Authority (SSM). In addition to a traditional document review with an aim to determine whether SKB's models are relevant, correctly implemented and adequately parametrized, SSM has performed independent modelling in order to gain confidence in the robustness of SKB's assessment. Thus, SSM has used alternative stylized reference biosphere models to calculate environmental activity concentrations for use in subsequent exposure calculations. Secondly, an alternative dose model (RESRAD-BIOTA) is used to calculate doses to biota that are compared with SKB's calculations with the ERICA tool. SSM's experience from this review is that existing tools for environmental dose assessment are possible to use in order to show compliance with Swedish legislation. However, care is needed when site representative species are assessed with the aim to contrast them to generic reference organism. The alternative modelling of environmental concentrations resulted in much lower concentrations compared to SKB's results. However, SSM judges that SKB's in this part conservative approach is relevant for a screening assessment. SSM also concludes that there are big differences in dose rates calculated to different organisms depending on which tool that is used, although not systematically higher for either of them. Finally, independent regulatory modelling has proven valuable for SSM's review in gaining understanding and confidence in SKB's assessment presented in the license application.

Many wetlands support high biodiversity and are protected sites, but some are contaminated with radionuclides from routine or accidental releases from nuclear facilities. This radiation exposure needs to\ud be assessed to demonstrate radiological protection of the environment. Existing biota dose models cover\ud generic terrestrial, freshwater, and marine ecosystems, not wetlands specifically. This paper, which was\ud produced under IAEA's Environmental Modelling for Radiation Safety (EMRAS) II programme, describes\ud an evaluation of how models can be applied to radionuclide contaminated wetlands. Participants used\ud combinations of aquatic and terrestrial model parameters to assess exposure. Results show the importance of occupancy factor and food source (aquatic or terrestrial) included. The influence of soil saturation conditions on external dose rates is also apparent. In general, terrestrial parameters provided\ud acceptable predictions for wetland organisms. However, occasionally predictions varied by three orders\ud of magnitude between assessors. Possible further developments for biota dose models and research\ud needs are identified.

The present work has been done within the IAEA Environmental Modelling for Radiation Safety Programme. EMRAS-II aims to improve the capabilities in the field of environmental radiation dose assessment by means of acquisition of improved data for model testing, comparison, reaching consensus on modelling philosophies, approaches and parameter values, development of improved methods and exchange of information.

In parallel with a renewed interest in nuclear power and its possible environmental impacts, a new environmental radiation protection system calls for environmental indicators of radiological stress. However, because environmental stressors seldom occur alone, this study investigated the combined effects of an ecological stressor (larval density) and an anthropogenic stressor (ionizing radiation) on amphibians. Scaphiopus holbrookii tadpoles reared at different larval densities were exposed to four low irradiation dose rates (0.13, 2.4, 21, and 222 mGy d(-1)) from (137)Cs during the sensitive period prior to and throughout metamorphosis. Body size at metamorphosis and development rate served as fitness correlates related to population dynamics. Results showed that increased larval density decreased body size but did not affect development rate. Low dose rate radiation had no impact on either endpoint.

After the Chernobyl accident, high activity concentrations of (137)Cs (>1 MBq m(-2)) were detected in a riparian swamp in the central-eastern part of Sweden. The objective of this study was to clarify the redistribution processes behind the accumulation of (137)Cs in the wetland. A mass balance budget of (137)Cs was calculated based on soil and sediment samples and reports in the literature. Results showed that accumulation occurred over several years. Of all the (137)Cs activity discharged between 1986 and 2002 from the upstream lake, 29% was estimated to be retained in the wetland. In 2003, measurements showed that 17 kBq m(-2) sedimented on the stream banks of the wetland. Continuing overbank sedimentation by spring flooding prolongs the time that the wetland will contain high activity concentrations of (137)Cs. Consequently, organisms living in wetlands serving as sinks for (137)Cs may become exposed over long time periods to high activity concentrations.

Currently, there is no established methodology to estimate radiation doses to non-human biota. Therefore, in this study, various dose models were used to estimate radiation doses to moor frogs (Rana arvalis) in a wetland ecosystem contaminated with (137)Cs. External dose estimations were based on activity concentrations of (137)Cs in soil and water, considering changes in habitat over a life-cycle. Internal doses were calculated from the activity concentrations of (137)Cs measured in moor frogs. Depending on the dose model used, the results varied substantially. External dose rates ranged from 21 to 160 mGy/y, and internal dose rates varied between 1 and 14 mGy/y. Maximum total dose rates to frogs were below the expected safe level for terrestrial populations, but close to the suggested critical dose rate for amphibians. The results show that realistic assumptions in dose models are particularly important at high levels of contamination.