Should we ignore U-235 series contribution to dose?

Environmental Risk Assessment (ERA) methodology for radioactive substances is an important regulatory tool for assessing the safety of licensed nuclear facilities for wildlife, and the environment as a whole. ERAs are therefore expected to be both fit for purpose and conservative. When uranium isotopes are assessed, there are many radioactive decay products which could be considered. However, risk assessors usually assume 235U and its daughters contribute negligibly to radiological dose. The validity of this assumption has not been tested: what might the 235U family contribution be and how does the estimate depend on the assumptions applied? In this paper we address this question by considering aquatic wildlife in Canadian lakes exposed to historic uranium mining practices. A full theoretical approach was used, in parallel to a more realistic assessment based on measurements of several elements of the U decay chains. The 235U family contribution varied between about 4% and 75% of the total dose rate depending on the assumptions of the equilibrium state of the decay chains. Hence, ignoring the 235U series will not result in conservative dose assessments for wildlife. These arguments provide a strong case for more in situ measurements of the important members of the 235U chain and for its consideration in dose assessments

Radiological dose reconstruction for birds reconciles outcomes of Fukushima with knowledge of dose-effect relationships

International audienceWe reconstructed the radiological dose for birds observed at 300 census sites in the 50-km northwest area affected by the accident at the Fukushima Daiichi nuclear power plant over 2011-2014. Substituting the ambient dose rate measured at the census points (from 0.16 to 31μGy h-1) with the dose rate reconstructed for adult birds of each species (from 0.3 to 97μGy h-1), we confirmed that the overall bird abundance at Fukushima decreased with increasing total doses. This relationship was directly consistent with exposure levels found in the literature to induce physiological disturbances in birds. Among the 57 species constituting the observed bird community, we found that 90% were likely chronically exposed at a dose rate that could potentially affect their reproductive success. We quantified a loss of 22.6% of the total number of individuals per increment of one unit log10-tansformed total dose (in Gy), over the four-year post-accident period in the explored area. We estimated that a total dose of 0.55 Gy reduced by 50% the total number of birds in the study area over 2011-2014. The data also suggest a significant positive relationship between total dose and species diversity. © 2015, Nature Publishing Group. All rights reserved

Effects of radionuclide contamination on leaf litter decomposition in the Chernobyl exclusion zone

The effects of radioactive contamination on ecosystem processes such as litter decomposition remain largely un- known. Because radionuclides accumulated in soil and plant biomass can be harmful for organisms, the function- ing of ecosystems may be altered by radioactive contamination. Here, we tested the hypothesis that decomposition is impaired by increasing levels of radioactivity in the environment by exposing uncontaminated leaf litter from silver birch and black alder at (i) eleven distant forest sites differing in ambient radiation levels (0.22–15 μGy h−1) and (ii) along a short distance gradient of radioactive contamination (1.2–29 μGy h−1) within a single forest in the Chernobyl exclusion zone. In addition to measuring ambient external dose rates, we estimat- ed the average total dose rates (ATDRs) absorbed by decomposers for an accurate estimate of dose-induced eco- logical consequences of radioactive pollution. Taking into account potential confounding factors (soil pH, moisture, texture, and organic carbon content), the results from the eleven distant forest sites, and from the single forest, showed increased litter mass loss with increasing ATDRs from 0.3 to 150 μGy h−1. This unexpected result may be due to (i) overcompensation of decomposer organisms exposed to radionuclides leading to a higher decomposer abundance (hormetic effect), and/or (ii) from preferred feeding by decomposers on the un- contaminated leaf litter used for our experiment compared to locally produced, contaminated leaf litter. Our data indicate that radio-contamination of forest ecosystems over more than two decades does not necessarily have detrimental effects on organic matter decay. However, further studies are needed to unravel the underlying mechanisms of the results reported here, in order to draw firmer conclusions on how radio-contamination affects decomposition and associated ecosystem processes

RETRATO SIN IDENTIFICAR [Material gráfico]

Copia digital. Madrid : Ministerio de Educación, Cultura y Deporte, 201

Modelling the exposure of wildlife to radiation: key findings and activities of IAEA working groups

The International Atomic Energy Agency (IAEA) established the Biota Working Group (BWG) as part of its Environmental Modelling for Radiation Safety (EMRAS) programme in 2004 (http://www-ns.iaea.org/projects/emras/emras-biota-wg.htm). At that time both the IAEA and the International Commission on Radiological Protection (ICRP) were addressing environmental protection (i.e. protection of non-human biota or wildlife) within the on-going revisions to the Basic Safety Standards and Recommendations respectively. Furthermore, some countries (e.g. the USA, UK) were already conducting assessments in accordance with national guidelines. Consequently, a number of assessment frameworks/models had been or were being developed. The BWG was established recognising these developments and the need to improve Member State’s capabilities with respect to protection of the environment from ionizing radiation. The work of the BWG was continued within the IAEA’s EMRAS II programme by the Biota Modelling Group (http://wwwns. iaea.org/projects/emras/emras2/working-groups/working-group-four.asp)

STAR deliverable (D-No. 3.3). International wildlife dosimetry workshop

This report summarises the main issues related with the International Wildlife Dosimetry Workshop, organized by STAR in June 2014. All the information of the workshop: the agenda, the presentations of all the speakers and the minutes of the discussion sessions can be freely downloaded from the STAR web page: https://wiki.ceh.ac.uk/display/star/ Wildlife+Dosimetry+Workshop. The workshop addressed a wide spectrum of questions related to the ionising radiation dose estimation in animals and plants, involving world leading experts in each of the subjects treated. There were 30 participants from 12 countries (Belgium, Canada, USA, Spain, France, Germany, Japan, Norway, Portugal, United Kingdom, Russia and Sweden)

The Radioecology Exchange

The Radioecology Exchange (www.radioecology-exchange.org) was created in 2011 under the EU FP7 STAR (STrategy for Allied Radioecology, www.star-radioecology.org) Network of Excellence; (2011-2015). This project aims to integrate radioecological research efforts of European organisations into a sustainable network. In 2013, the EU FP7 COMET (COordination and iMplementation of a pan-European instrumenT for radioecology (2013- 2017); www.comet-radioecology.org) project commenced; COMET will build upon the work initiated under STAR. The Radioecology Exchange has therefore become the web resource for activities from both projects which will ultimately be maintained by the European Radioecology Alliance (ALLIANCE; www.er-alliance.org). The Radioecology Exchange is intended to become a ‘gateway’ for information related to European (and wider) radioecological research

Estimating radiological exposure of wildlife in the field

The assessment of the ecological impact due to radionuclides at contaminated sites requires estimation of the exposure of wildlife, in order to correlate radiation dose with known radiological effects. The robust interpretation of field data requires consideration of possible confounding effects (e.g., from the tsunami at Fukushima) and an accurate and relevant quantification of radiation doses to biota. Generally, in field studies the exposure of fauna and flora has often been characterised as measurements of the ambient dose rate or activity concentrations in some components of the environment. The use of such data does not allow the establishment of a robust dose-effect relationship for wildlife exposed to ionising radiation in the field. Effects of exposure to radioactivity depend on the total amount of energy deposited into exposed organisms, which is estimated by adding doses (or dose rates) for all radionuclides and exposure pathways. Realistic dose estimation needs to reflect the entire story of the organisms of interest during their whole exposure period. The process of identifying and collecting all the related information should allow the “W” questions (Which organisms are exposed, Where, When and hoW) to be answered. Some parameters are well known to influence dose (rate): the organism life stage, its ecological characteristics (e.g. habitat, behaviour), the source term properties (e.g. discharging facility, nature of radiation), etc. The closer the collated data are to the ideal data set, the more accurate and realistic the dose (rate) assessment will be. This means characterising each exposure pathway (internal and external), the activity concentration in each exposure source, the time each organism spends in a given place, as well as the associated dose. In this paper the process of data collation in view of dose reconstruction is illustrated for Japanese birds exposed to radioactive deposition following the Fukushima accident. With respect to the Chernobyl Exclusion Zone we will also consider variability under field conditions, availability of relevant datasets and options for better estimating internal and external doses received by wildlife