Institute for Radiation Protection and Nuclear Safety (IRSN)
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A staggered projection scheme for viscoelastic flows
No full textInternational audienceWe develop a numerical scheme for the flow of viscoelastic fluids, including the Oldroyd-B and FENE-CR constitutive models. The space discretization is staggered, using either the Marker-And-Cell (MAC) scheme for structured nonuniform grids, or the Rannacher and Turek (RT) nonconforming low-order finite element approximation for general quadrangular or hexahedral meshes. The time discretization uses a fractional-step algorithm where the solution of the Navier-Stokes equations is first obtained by a projection method and then the transport-reaction equation for the conformation tensor is solved by a finite volume scheme. In order to obtain consistency, the space discretization of the divergence of the elastic part of the stress tensor in the momentum balance equation is derived using a weak form of the MAC scheme. For stability and accuracy purposes, the solution of the transport-reaction equation for the conformation tensor is split into pure convection steps, with a change of variable to the log-conformation tensor, and a reaction step, which consists in solving one ODE per cell via an Euler scheme with local sub-cycling. Numerical computations for the flow in the lid-driven cavity at Weissenberg numbers above one and the flow around a confined cylinder confirm the efficiency of the scheme
Twenty-two years later: consistent dose estimation of an accidental overexposure by retrospective biological dosimetry
No full textInternational audienceThe goal of this study was to retrospectively estimate the exposure dose of a victim from the Lilo radiological accident in Georgia after 22 y and compare it with the original cytogenetics-based analysis performed in our laboratory. Similar types of studies have been published, notably involving victims of the Chernobyl, Goiânia and Tammiku accidents. Nevertheless, their estimations were done after shorter periods of time post-exposure, and in some cases, the exposure might not have been exclusively of an external nature. In this study, Fluorescence In Situ Hybridization (FISH) was used to score chromosomal translocations in lymphocytes from a recent blood sample of the victim and the dose assessment was performed using our laboratory's FISH calibration curve. The resulting whole-body exposure dose of 0.35 Gy [0.12, 0.72] was similar to the one obtained when reanalysing the original scoring data from 1997 (0.38 Gy [0.13-0.75]), suggesting that our current calibration curve could be used for relative dose estimations long time after external exposure
Bayesian transdimensional inverse reconstruction of the Fukushima Daiichi caesium 137 release
No full textInternational audienceThe accident at the Fukushima Daiichi nuclear power plant (NPP) yielded massive and rapidly varying atmospheric radionuclide releases. The assessment of these releases and of the corresponding uncertainties can be performed using inverse modelling methods that combine an atmospheric transport model with a set of observations and have proven to be very effective for this type of problem. In the case of the Fukushima Daiichi NPP, a Bayesian inversion is particularly suitable because it allows errors to be modelled rigorously and a large number of observations of different natures to be assimilated at the same time. More specifically, one of the major sources of uncertainty in the source assessment of the Fukushima Daiichi NPP releases stems from the temporal representation of the source. To obtain a well-time-resolved estimate, we implement a sampling algorithm within a Bayesian framework – the reversible-jump Markov chain Monte Carlo – in order to retrieve the distributions of the magnitude of the Fukushima Daiichi NPP caesium 137 (137Cs) source as well as its temporal discretization. In addition, we develop Bayesian methods that allow us to combine air concentration and deposition measurements as well as to assess the spatio-temporal information of the air concentration observations in the definition of the observation error matrix. These methods are applied to the reconstruction of the posterior distributions of the magnitude and temporal evolution of the 137Cs release. They yield a source estimate between 11 and 24 March as well as an assessment of the uncertainties associated with the observations, the model, and the source estimate. The total reconstructed release activity is estimated to be between 10 and 20 PBq, although it increases when the deposition measurements are taken into account. Finally, the variable discretization of the source term yields an almost hourly profile over certain intervals of high temporal variability, signalling identifiable portions of the source term
Le fer à Notre-Dame de Paris : Nature des alliages, procédés techniques et études de provenance, le cas des fenêtres hautes
No full textNational audienceSuite à l’incendie de Notre-Dame de Paris, la mise en place d’échafaudages pour la restauration offre un accès unique à des endroits de la cathédrale qui étaient inaccessibles jusqu’à présent. Ceci a permis de révéler une grande diversité d’usages du mobilier ferreux dans la structure de l’édifice. Un relevé systématique est en cours dans le cadre des travaux de thèse sur les métaux ferreux du monument. Le caractère quasi exhaustif d’un tel inventaire est une première pour l’édifice, dont un des principaux et seuls relevés des armatures en fer remonte aux travaux de Viollet-le-Duc (Viollet-le-Duc, 1858). Mais c’est également un nouveau regard porté sur une cathédrale gothique, car jusqu’`a présent, aucun édifice n’a pu faire l’objet d’un suivi si fin au cours de ses restaurations.Parmi les différents éléments de ce corpus se trouvent des agrafes de fer dans la maçonnerie au niveau des tribunes, des murs gouttereaux, des murs sous les terrasses extérieures ou encore dans des colonnes monolithiques adossées aux bas-côtés de la nef et des chapelles. S’ajoutent à cet inventaire des fers de charpente tels que des clous, des tiges boulonnées et des chevilles clavetées, mais également des crêtes de faîtage, des goujons, ou encore des tirants. Ce poster insistera en particulier sur l’étude des anciennes barres de vitraux des baies hautes de la cathédrale, aujourd’hui supprimées, mais dont subsistent quelques vestiges dans le meneau central des fenêtres. Ces barres transversales, mesurant à l’origine plusieurs mètres de long et d’une section d’environ 3,5 x 4 cm, sont des objets ferreux n’ayant jamais été étudiés auparavant dans un tel édifice car ils sont, le plus souvent, rarement accessibles. Treize échantillons ont été prélevés sur site pour analyses, ainsi que trois éléments entiers sur des pièces destinées à être remplacés. Les premières études métallographiques (attaque Nital, observations macroscopiques et microscopiques) permettent de nous éclairer, en particulier, sur la mise en forme de ce mobilier ferreux, mais aussi sur la qualité de la production métallique. L’étude des inclusions de scories au Microscope Electronique à Balayage en Spectrométrie EDS (Dillmann and L’Héritier, 2007) et l’analyse des éléments traces par LA-ICP-MS (L’Héritier et al., 2020) permettent de préciser les filières techniques et les pratiques opératoires utilisées pour la production du fer et dans la mise en œuvre des barres de vitraux. On peut notamment se questionner sur les méthodes de procédés direct et indirect, mais aussi sur la problématique du recyclage, omniprésente sur les chantiers de construction.En parallèle, l’analyse en éléments traces de scories provenant de différents sites métallurgiques issus de plusieurs secteurs d’Île-de-France (Brie française, sud de la forêt de Rambouillet/Hurepoix, est de la vallée de Chevreuse) jusqu’alors non étudiés chimiquement, nous permet de constituer un inventaire inédit des signatures chimiques de la région de sites susceptibles d’avoir approvisionné Notre-Dame. La comparaison avec la composition des inclusions des armatures métalliques mesurée par LA-ICP-MS contribuera à tester et discuter ces hypothèses de provenance
Avis de l'Anses relatif aux risques pour la santé humaine liés aux proliférations d’Ostreopsis spp. sur le littoral basque
No full textCitation suggérée : Anses (2023). Avis relatif aux risques pour la santé humaine liés aux proliférations d’Ostreopsis spp. sur le littoral basque (saisine 2021-SA-0212). Maisons-Alfort : Anses, 40 p.Au cours des dernières décennies, plusieurs espèces de dinoflagellés du genre Ostreopsis ont été identifiées dans les eaux marines de pays européens tels que l’Albanie, la Croatie, Chypre, l'Espagne, la France, la Grèce, l'Italie, Monaco et le Portugal. Ces microalgues peuvent causer des intoxications humaines lorsque les cellules ou les toxines qu’elles produisent sont présentes dans l’eau de mer, les aérosols ou dans certains produits de la mer. La voie principale d’exposition de l’Homme est l’inhalation d’aérosols sans que l’on sache actuellement si les agents à l’origine des intoxications sont les cellules d’Ostreopsis, les débris cellulaires, des toxines connues produites par Ostreopsis ou d’autres composés non encore identifiés. D’autres voies d’exposition (contact cutané, contact oculaire, ingestion d’eau ou de produits de la mer contaminés) sont possibles.Les intoxications se manifestent par divers signes et symptômes (survenant moins de 48h après l’exposition) : - neurosensoriels et neurologiques : paresthésies (sensation de fourmillements), dysesthésies (sensation de brûlure) et céphalées ; - respiratoires, de la sphère ORL et stomatologiques : dysgueusie à type de goût métallique, rhinorrhée, toux, gêne respiratoire ; - cutanés évoquant de l’urticaire ; - cardiaques : tachycardie, poussée hypertensive ; - digestifs : nausées, vomissements, diarrhée ; - systémiques : fièvre ; - locomoteurs : myalgies et arthralgies (douleurs musculaires et articulaires).Elles surviennent lors de diverses situations : - travail ou activités récréatives dans la mer (baigneurs, maîtres-nageurs, pêcheurs professionnels, surfeurs, etc.) ; - travail ou activités récréatives sur ou à proximité de la plage (estivants, secouristes, agents en charge du nettoyage des plages, restaurateurs, etc.) ; - séjour ou résidence à proximité immédiate du bord de mer ; - consommation de produits de la mer contaminés.En France, la présence d’Ostreopsis est identifiée de façon récurrente sur les côtes méditerranéennes depuis une quinzaine d’années alors qu’elle est beaucoup plus récente sur les côtes basques française et espagnole. Deux espèces ont été identifiées sur la côte basque : O. cf. siamensis et O. cf. ovata. Si la première, O. cf. siamensis, est observée sur cette côte depuis 2018, la seconde, O. cf. ovata, a été observée dans cette partie du golfe de Gascogne pour la première fois en 2021.Le bilan épidémiologique montre que près de 900 personnes ont développé des signes et des symptômes associés aux proliférations d’Ostreopsis sur la côte basque française depuis 2020. Ce bilan montre par ailleurs qu’il n’existe pas de différence clinique avec les effets observés lors des épisodes de prolifération d’Ostreopsis cf. ovata du pourtour méditerranéen.[Saisines liées n°2007-SA-0227 et 2007-SA-0303
Bayesian hierarchical approach to account for radon exposure measurement error when estimating the risk of death by several cancers in an occupational cohort of uranium miners
No full textInternational audienceIntroduction: Radon exposure is a factor increasing the risk of death by lung cancer. Its part is still being studied for death by kidney cancer, death by brain and nervous central system (CNS) cancer and death by leukaemia. The population of uranium miners is a reference population for studying the impact of chronic low-dose radon exposure. However, radon exposures in the French uranium miners’ cohort are error-prone. Not taking those errors into account leads to a bias in the risk estimate and in the variance of this estimator. Standard correction methods, like regression calibration or SIMEX, often lack the flexibility to account for complex patterns of errors whose type and magnitude may change over time, as found in the cohort. Methods: We proposed several Bayesian hierarchical models, combining a survival submodel with time-dependent covariates, a measurement submodel and an exposure submodel, to obtain a corrected estimate of the potential association between chronic exposure to radon and cancer mortality in the French cohort of uranium miners. The Bayesian paradigm allows to include information a priori information of the general French male population. Factor modifying the dose-response relationship, such as time since exposure or period of exposure, are included in the survival submodel. An adaptive Metropolis-Within-Gibbs algorithm was developed in Python to fit the proposed hierarchical models whose explicative performances were compared using the Widely-Applicable Information Criterion.Results: In our application, one observed a marked increase in the excess risk estimate for lung cancer mortality when compared with an approach where radon exposure measurement error was not accounted for. As expected, the width of the credible intervals increased after accounting for measurement error but the estimated excess risk remained statistically significant. Concerning the other cancers, the risk of death associated with radon exposure is not significant with or without measurement error correction. A sensitivity analysis showed that the posterior distribution of the excess risk depends on the magnitude of the exposure measurement error. A study on the inclusion of a priori information in the survival submodel found a common bias in epidemiology, “a healthy worker effect”: information of the French general masculine cannot be extrapolated to the uranium miners’ population. Conclusion: Measurement errors must be taken into account when studying a health risk in the French cohort of uranium miners. Modelling exposure measurement error in a retrospective cohort study is often limited due to loss of information
EDITORIAL NOTE AT THE SPECIAL ISSUE: NEA/CSNI/WGAMA specialists meeting on nuclear thermal-hydraulics in water cooled reactors
No full textInternational audienceA Specialists Meeting on Transient Nuclear Thermal-Hydraulics (NTH) in water cooled reactors (SM-TH) was organized by the OECD Nuclear Energy Agency (NEA) Committee on the Safety of Nuclear Installations (CSNI) Working Group on the Analysis and Management of Accidents (WGAMA) together with the Consejo de Seguridad Nuclear (CSN). Initially, it was intended to be hosted by CIEMAT in Madrid (Spain) in December 2020, but was finally held virtually in March 2022 due to the COVID-19 (NEA/CSNI/R (2023)1). The key goal of the SM-TH was to summarize the current status in NTH and to formulate recommendations to CSNI for activities in the area.The meeting gathered nearly 70 experts from industry, safety authorities, research institutes and universities in 16 countries to discuss the achievements and the needs of safety research in nuclear reactor accident thermal-hydraulics. About 70 papers have been presented at the meeting, discussing the state of the art and maturity of NTH for evaluating safety of existing reactors, identifying strengths and drawbacks of the current analysis approaches, and defining the needs and priorities of research on safety-related NTH, particularly under accident conditions.This special issue is a collection of the selected papers that summarizes the key outcomes of the SM-TH, after a careful peer reviewer process
Surface rupturing earthquakes along the eastern Rhine Graben Boundary Fault near Ettlingen-Oberweier (Germany)
No full textInternational audienceThe eastern Rhine Graben Boundary Fault (eastern RGBF) forms the eastern margin of the Upper Rhine Graben (URG), the most seismically active area in the plate interiors of Europe. Despite seismic activity posing a significant threat to the densely populated URG and critical facilities therein, only a few studies have documented the paleoearthquake history and associated seismic hazard, focusing mainly on the western margin. We present the results of the first paleoseismological trenching ever conducted on the central section of the eastern RGBF. Following high-resolution near-surface geophysical studies, we excavated six trenches near Ettlingen-Oberweier (south of Karlsruhe, Germany) on one of its secondary fault strands. The nearly-vertical fault is transtensional left-lateral and splits into several NNW-SSE en échelon branches, forming a negative flower structure. Stratigraphic and structural relationships along with radiocarbon and Optically Stimulated Luminescence dating reveal a minimum of three surface-rupturing paleoearthquakes with a Mw of potentially 6.5 ± 0.5, occurring from old to young, >56 ka (EX), between 54 and 19 ka (EY), and between 15 and 1 ka (EZ). The events are poorly constrained in age due to erosional unconformities. Based on the cumulative vertical separation of 1.2 ± 0.3 m, we calculate an average vertical slip rate of 0.02 ± 0.005 mm/yr. From a horizontally offset alluvial channel, we infer a cumulative left-lateral slip of 5.9 ± 0.7 m and derive an average horizontal slip rate of 0.1 ± 0.01 mm/yr. The average net slip rate is 0.1 ± 0.02 mm/yr for the past 59.5 ± 3.8 ka. This value represents a minimum slip rate for the eastern RGBF, considering slip distribution within the different fault strands of the fault system. Our findings highlight the seismic potential of the eastern RGBF, providing new evidence of the Late Pleistocene and Holocene tectonic activity of its central section
The European Radiation Dosimetry Group—a 40 year success story
No full textInternational audienceAbstract The European Radiation Dosimetry Group (EURADOS) was founded in 1982. Since then, the group has continuously developed and is currently a network of 80 institutions and more than 600 individual scientists across Europe, including exchange with the scientific community outside of Europe. EURADOS supports research and development of dosimetry and harmonising dosimetric practices. This paper describes the major milestones in the history of the organization. It starts from the very beginning when the idea was born and describes periods during which the role and strategy of the network had to be defined, elaborated and refined. Finally, it ends to date where EURADOS appears as an independent self-sustainable association, which is a reliable partner for various international organisations in radiation research and radiation protection. Major activities of EURADOS are highlighted such as (1) establishment and coordination of Working Groups, (2) regular organization of dosimetric intercomparisons for quality assurance of dosimetry procedures, (3) development and organization of education and training events, and (4) contributions towards the development of strategic and integrated radiation research in Europe
Experience with NORM waste disposal in different European countries
No full textInternational audienceIndustrial processes generate various quantities of waste that can be contaminated with radionuclides of natural origin (naturally occurring radioactive material (‘NORM waste’)). The efficient management of this waste is essential for any industries affected by NORM waste generation. To obtain an overview of current practices and approaches in Europe, the IRPA Task Group on NORM conducted a survey among task group members and other experts from European countries. The results revealed significant differences in methods and approaches in the European countries. In many countries, landfills are used to dispose of small- and medium-sized quantities of NORM waste with limited activity concentration. But our survey indicated that despite a uniform reference basis for national legislation in Europe, there are different framework conditions for the disposal of NORM waste in practice. In some countries, the disposal is hampered because the interface between the radiation protection system and the waste regime is not yet clearly regulated. Particular practical problems include the lack of acceptance of waste because of the ‘radioactivity’ stigma and only vague specifications by the legislators on acceptance obligations of the waste management sector