Towards a shared method to classify contaminated territories in the case of an accidental nuclear event: the PRIME project

The analysis of the management of the accidentally radioactive contaminated areas such as those around Chernobyl nuclear power plant highlights the fact that the current spatial classification methods hardly help in recovering proper use of the contaminated territory. The cause is mainly to be searched for in the traditional construction of risks assessment methods; these methods rest on criteria defined by institutional experts, which are not applicable in practise because they are not shared by all the stakeholders involved in the management of the contaminated territories. Opposite such top-down tentative management, local efforts supported by Non-Governmental Organizations to restore life in the contaminated area seem to be more fruitful but very time and resources consuming and limited to the specific areas where they are experimented. The aim of the PRIME project, in progress at the French Institute for Radioprotection and Nuclear Safety, is to mix the advantages of both approaches in building a multicriteria decision tool based on the territorial specificities. The criteria of the method are chosen and weighted with representatives of the territory’s stakeholders (decision makers, local actors and experts) to warrant that all the points of view are taken into account and to enable the risk managers to choose the appropriate strategy in case of an accident involving radioactive substances. The area chosen for the pilot study is a 50 km radius territory around the nuclear sites of Tricastin-Pierrelatte in the lower valley of Rhône (France). One of the exploration questions of the PRIME project is whether a multicriteria method may be an appropriate tool to treat the data and make them visible and accessible for all the stakeholders

Screening the importance of soil micro-organisms on radionuclides mobility

Abstract. In surface soils, the native physical and chemical properties of the abiotic components control most of the sorption-desorption processes. Moreover, micro-organisms may significantly modify the speciation of trace elements and/or radionuclides and subsequently determine their fate, to a large extent. Micro-organisms, mainly bacteria and fungi, develop many strategies that may affect indirectly or directly the behaviour of trace elements. Due to their activity, changes in the pore-water composition, e.g. pH, redox-potential, may occur in relation with organic acid production or solid phase alteration, reduction or oxidation of metallic oxi-hydroxides, and mineralization of organo-metallic complexes. Micro-organisms may also directly modify the speciation of radionuclides as a result of bio-accumulation in living cells, biosorption on cellular components, direct reduction or oxidation, biomethylation, etc. Each one of these microbial processes may either increase or decrease radionuclide mobility, depending on the element, the soil reactivity and the environmental conditions. The resulting effect of these processes is still poorly known. This literature review intends to present a comprehensive overview of the role of micro-organisms on radionuclide mobility. It aims at classifying these elements, regarding to their potential sensitivity to these microbial processes. It summarizes the theoretical effect of these mechanisms, resulting in a potential increase or decrease of the solid-liquid distribution. The environmental significance of such processes for various biogeochemical radionuclides cycles still remains to be confirmed by experiments. (This study is part of a research program supported by Andra)

Evaluation of

The dosimetric consequences of 14C dissemination resulting from the radioactive fall-out of atmospheric nuclear-weapons testing conducted in the 50s have been estimated. Owing to the lack of 14C measurements in food consumed in France over the past 60 years, this evaluation is based on the standard modelling of the isotopic equilibrium: it is assumed that the specific activity (14C/C) of living plants is in equilibrium with that of CO2 in the air. It is also considered that this isotopic ratio remains constant in animals and their production. The specific activities of 14C in the biosphere were drawn from reference publications. Since the 1950s, the effective dose for adults has risen from 12.1 µSv y-1 to a maximum of about 22.3 µSv y-1 in 1964, before falling to 12.9 µSv y-1, which is slightly higher than the initial value. The excess dose due to atmospheric testing reached about 10 µSv y-1 in the sixties. The generation of 1940 was exposed to the highest dose: 190 µSv in 60 years due to nuclear-weapons testing, which remains low in relation to natural exposure

Bruit de fond du tritium en milieu terrestre

National audienceSamples of tree leaves and terrestrial foodstuffs, obtained from French non-influenced zones were measured for tissue free water tritium (TFWT) and organically bound tritium (OBT) content, over the period 2007-2012. The background level determined from these data does not vary significantly over the 5 years of the survey and displays a mean value of 1.4 ± 1.2 Bq/L for both tritium forms. © 2014 EDP Sciences.Des résultats de mesures de tritium libre et organiquement lié ont été acquis de 2007 à 2012, en France métropolitaine, pour des échantillons de végétaux et de denrées prélevés en milieu terrestre, hors de l’influence potentielle d’un rejet. Le bruit de fond, déduit de ces données, n’évolue pas significativement; il est en moyenne de 1,4 ± 1,2 Bq/L pour le tritium libre et pour le tritium organiquement lié

Données utiles à l’interprétation des mesures de carbone 14 en milieu terrestre

L’examen des résultats de mesure de 14C, notamment dans le cadre de la surveillance environnementale requiert la connaissance de certaines spécificités du comportement du carbone. Les principaux paramètres susceptibles d’influer sur les mécanismes d’incorporation du carbone dans les matrices environnementales et donc sur les niveaux mesurés en 14C sont succinctement rappelés. Des résultats de mesure d’échantillons biologiques ont été acquis par l’IRSN dans des zones non directement influencées par des rejets d’installations nucléaires; ces chroniques permettent de présenter les valeurs du bruit de fond naturel et rémanent, exprimé en activité spécifique (Bq 14C/kg C), hors de l’influence contemporaine d’un rejet local de 14C

Effet de traitements alimentaires de légumes et de céréales sur la radioactivité des produits transformés

La diminution de radioactivité de 134Cs, 85sr, 106Ru, 57Co, 110mAg au cours de traitements alimentaires de légumes et de céréales a été mesurée. Les opérations de lavage et de blanchiment de légumes contaminés directement par un dépôt unique d'aérosols induisent une réduction de l'activité massique (variable selon le végétal, le radionucléide et le stade végétatif du végétal au moment du dépôt), qui peut atteindre 90 % pour le césium. L'efficacité de ces traitements est moindre sur des légumes contaminés par voie racinaire, à l'exception du parage des légumes racines. La mise en conserve après parage et blanchiment de légumes contaminés en césium, strontium, cobalt et ruthénium par transfert indirect s'avère être assez efficace, avec une radioactivité résiduelle allant de 30 à 50 % pour le haricot vert et de 5 à 20 % pour la carotte. Des mesures d'isotopes stables du césium et du strontium effectuées sur des céréales avant et après traitements industriels mettent en évidence une diminution importante de l'activité massique des produits transformés ; les facteurs de transformation sont de 0,1 à 0,2 pour la transformation du blé en farine et de 0,1 à 0,4 pour le blanchiment du riz

Comportement de radionucléides (Cs, I, Sr, Se, Tc) dans le sol: Proposition de valeurs de Kd par défaut

The simplest and most common parameter for modelling radionuclide mobility in soils is the distribution coefficient, Kd. In reverse, the empirical Kd value accounts for several bio-chemical and physical mechanisms, influenced by numerous correlated variables. Moreover, Kd values vary with radionuclide and soil types. Consequently, the use of default Kd values in assessment models to predict the behaviour of radionuclide in soils can result in significant uncertainties. Five radionuclides (Cs, I, Sr, Se, Tc) were systematically assessed regarding their behaviour in the soil, e.g., main processes, kinetics, sorption reversibility/irreversibility... A data base of Kd values was completed for each radionuclide, including the data used for establishing the most common default values and new data from recent publications. A summary form summarizes the most important parameters, proposes a default Kd value for and suggests pertinent experiments that could be carried out in order to acquire more relevant Kd values. © 2005 EDP Sciences

Comportement du 210Po en milieu terrestre: Revue bibliographique

International audienceThis bibliographical review illustrates the behaviour of 210 polonium in the terrestrial environment. Sources of 210Po in the atmosphere vary especially with the geographical localization and the occurrence or the absence of mining activities. In soils, polonium, because of its atmospheric origin, is concentrated in the first upper centimeters. 210Po is rather immobile and adsorbed on mineral surfaces; it can (co)precipitate with metallic (oxi)hydroxides or in the form of sulphide. The main transfer pathway of 210Po to vegetation is foliar deposit, which is not, or only slightly, followed by incorporation or translocation. 210Po is transferred to animals mainly by ingestion, with relatively high transfer factors. In freshwaters, 210Po is generally immobile in the form of insoluble Po(IV) and/or associated with the particulate or colloidal phase. Plankton, invertebrates and fish concentrate the 210Po, especially in soft tissues. Polonium, which is an omnipresent natural radionuclide, is likely to occasion a significant exposure to man, compared with other natural or artificial radioisotopes. Nearly all studies derive from in situ measurements and are very descriptive, therefore experimental work aiming at a better knowledge and modeling of its behaviour in the terrestrial environment would be useful. © EDP Sciences, 2004.Cette synthèse bibliographique décrit le comportement du polonium-210 dans l'environnement terrestre. Les sources du 210Po dans l'atmosphère varient notamment avec la localisation géographique et la présence ou l'absence d'activités minières. Dans les sols, le polonium, du fait de son origine atmosphérique, est concentré dans les premiers centimètres. C'est un élément peu mobile qui s'adsorbe sur les surfaces minérales et peut (co)précipiter avec les (oxy)hydroxydes métalliques ou sous forme de sulfure. La voie d'entrée majoritaire du 210Po dans la végétation est le dépôt foliaire qui n'est pas, ou peu, suivi d'incorporation ou de translocation. Le transfert du 210Po aux animaux s'effectue principalement par ingestion, avec des facteurs de transfert relativement élevés. Dans les hydrosystèmes dulçaquicoles, le 210Po est généralement immobilisé sous forme de Po(IV) insoluble et/ou associé à la phase particulaire ou colloïdale. Le plancton, les invertébrés et les poissons concentrent le 210Po, surtout dans les tissus mous. Le polonium, radioélément naturel omniprésent dans l'environnement, est susceptible d'induire pour l'homme une exposition significative par rapport à d'autres radionucléides naturels ou artificiels. Les études – essentiellement des mesures in situ – qui lui sont consacrées restent très descriptives, aussi, des travaux expérimentaux permettant de mieux comprendre et de modéliser son comportement dans le milieu terrestre seraient utiles

Distribution coefficient Kd of transuranics in soils: Experimental determination and consequences for dose assessment

The distribution coefficient (or Kd) of 241Am between soil and soil solution was estimated on the basis of experiments carried out under controlled conditions for soils displaying pH and organic matter content (which are the relevant parameters for transuranic nuclides sorption ability) found in cultivated soils. In these experiments, designed with five experimental units (batches) per studied contact time, 10 g of dry soil are contaminated with 50 mL of osmosed water containing proper concentrations of the radionuclide. The tracer, initially in nitric form, is neutralized prior to addition with the water, to ensure a constant ionic strength and avoid disturbance of the soil chemistry. After shaking and sedimentation, for each batch, the supernatant is sampled and analyzed by either liquid scintillation or alpha spectrometry. The sorption-desorption kinetic time necessary to reach apparent equilibrium is evaluated (> 10 days). Fixation curves, e.g. activity of the soil vs activity of the solution are established, after measurements, for a single delay representative of the equilibrium, and for a range of several orders of magnitude for radionuclide concentrations. On the basis of several assumptions, Kd values are evaluated by simple linear adjustment. A numerical application to retention half lives in soil is made. Finally, the weight of using site-specific Kd values instead of default parameters, on the doses due to ingestion of terrestrial foodstuffs is discussed for different scenarios