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)

Contribution for the derivation of a soil screening value (SSV) for uranium, using a natural reference soil

In order to regulate the management of contaminated land, many countries have been deriving soil screening values (SSV). However, the ecotoxicological data available for uranium is still insufficient and incapable to generate SSVs for European soils. In this sense, and so as to make up for this shortcoming, a battery of ecotoxicological assays focusing on soil functions and organisms, and a wide range of endpoints was carried out, using a natural soil artificially spiked with uranium. In terrestrial ecotoxicology, it is widely recognized that soils have different properties that can influence the bioavailability and the toxicity of chemicals. In this context, SSVs derived for artificial soils or for other types of natural soils, may lead to unfeasible environmental risk assessment. Hence, the use of natural regional representative soils is of great importance in the derivation of SSVs. A Portuguese natural reference soil PTRS1, from a granitic region, was thereby applied as test substrate. This study allowed the determination of NOEC, LOEC, EC20 and EC50 values for uranium. Dehydrogenase and urease enzymes displayed the lowest values (34.9 and ,134.5 mg U Kg, respectively). Eisenia andrei and Enchytraeus crypticus revealed to be more sensitive to uranium than Folsomia candida. EC50 values of 631.00, 518.65 and 851.64 mg U Kg were recorded for the three species, respectively. Concerning plants, only Lactuca sativa was affected by U at concentrations up to 1000 mg U kg1. The outcomes of the study may in part be constrained by physical and chemical characteristics of soils, hence contributing to the discrepancy between the toxicity data generated in this study and that available in the literature. Following the assessment factor method, a predicted no effect concentration (PNEC) value of 15.5 mg kg21dw was obtained for U. This PNEC value is proposed as a SSV for soils similar to the PTRS1

The Power of Counting Steps in Quantitative Games

We study deterministic games of infinite duration played on graphs and focus on the strategy complexity of quantitative objectives. Such games are known to admit optimal memoryless strategies over finite graphs, but require infinite-memory strategies in general over infinite graphs. We provide new lower and upper bounds for the strategy complexity of mean-payoff and total-payoff objectives over infinite graphs, focusing on whether step-counter strategies (sometimes called Markov strategies) suffice to implement winning strategies. In particular, we show that over finitely branching arenas, three variants of lim sup mean-payoff and total-payoff objectives admit winning strategies that are based either on a step counter or on a step counter and an additional bit of memory. Conversely, we show that for certain lim inf total-payoff objectives, strategies resorting to a step counter and finite memory are not sufficient. For step-counter strategies, this settles the case of all classical quantitative objectives up to the second level of the Borel hierarchy

A new IAEA Technical Report Series Handbook on Radionuclide Transfer to Wildlife

The IAEA Technical Report Series (TRS) handbook on transfer of radionuclides to human foodstuffs from terrestrial and freshwater systems has recently been revised during the EMRAS I programme [1]. The document updates the previous handbook (TRS 364) and constitutes an important source of information for transfer parameters for the human foodchain. Quantification of the rates of transfer of radionuclides through foodchains to humans has long been a key focus of radiation protection. More recently, there has been a move away from radiation protection being solely anthropogenic to one which also considers protection of the environment as recognised by both the IAEA [2] and the ICRP [3] in their Fundamental Safety Principles and revised Recommendations, respectively, both of which now include the need to protect the environment. To address these recommendations and safety principles, the consequences of radiological releases need to be considered in part by estimating an internal dose. To do this, the transfer of radionuclides to wildlife of interest needs to be quantified. In response to the need for a reference source of information on radionuclide transfer to wildlife, the IAEA initiated the development of a TRS handbook, which has been supported by interaction with the EMRAS II Working Group 5, (http://www-ns.iaea.org/projects/emras/emras2/working-groups/working-group-five.asp). The TRS handbook has been finalised and is currently going through the IAEA approval process. The TRS handbook provides equilibrium concentration ratio values for wildlife groups in terrestrial, freshwater, marine and estuarine environments. Wildlife is considered to include all non-domesticated plants, animals and other organisms including feral species (i.e. non-native self-sustaining populations). The TRS handbook provides IAEA Member States with transfer data for use in the radiological assessment of wildlife as a consequence of planned and existing exposure situations [3]. As an equilibrium approach is presented, these data are not directly applicable to emergency situations