Institute for Radiation Protection and Nuclear Safety (IRSN)
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Reactive Transport Modelling of the Aggregate Degradation During ASR
No full textInternational audienceIn the context of massive concrete structure ageing, such as nuclear power plant containments or hydroelectric dams, the study of cementitious material durability is of great interest. In particular, the Alkali-Silica Reaction (ASR) can drastically reduce the durability of such structures. A reactive transport model (species transport and chemical reaction) of ASR able to simulate the progressive aggregate dissolution, the silica gel precipitation and its localization depending on the aggregate characteristics (chemical composition, diffusion properties, size, and morphology) is proposed. The objective is to consider mainly physical measurable parameters and thermodynamic constants. The ion transport is given by Fick's second law of diffusion and the geochemical system models the aqueous complexation and solid reactions. The thermodynamic equilibrium of chemical processes is assumed, except for the dissolution of the reactive silica, that is modeled by a kinetic reaction. Two main reaction products of ASR are considered, a low Ca/Si ratio C-S-H and an expansive alkali-silica gel. The application focuses on the cement paste and aggregate interaction. The results fit well with the experimental observations where the ASR gel forms inside the aggregate particle and the C-S-H precipitates at the interface between paste and the particle. The effect of aggregate composition and particle size on the overall ASR kinetic and gel precipitated localization is investigated
Co-exposure to low-dose gamma irradiation with a chemical stressor causes differential outcomes on brain toxicity parameters in rat
No full textInternational audienceThe various pollutants to which an individual is exposed throughout his or her life can have an impact on brain health. Professional activities involve specific stressors and, regarding nuclear workers, the radiological component of their exposome in the form of low dose gamma irradiations raises a scientific challenge due to potential non-linear effects. The other component takes the form of particulate aerosols, the main source of contamination for nuclear workers. We decided to select tungsten particles to focus on an emerging chemical contaminant linked to the operation of fusion reactors. Our goal is to determine whether differential effects can be observed on brain toxicity parameters when comparing co-exposed groups to single-exposed or control groups, and study underlying mechanisms.Male Sprague-Dawley rats undergo a low dose gamma irradiation (50 mGy, 50 mGy.min-1) and/or a nose-only inhalation of a tungsten particulate aerosol (80 mg.m-3, 30 minutes). Neuronal integrity, cell survival, inflammation, and oxidative stress in the frontal cortex (FC) and olfactory bulb (OB) were analyzed 24 hours and 28 days after exposure.Immunohistological studies reveal significant differences when comparing co-exposed groups to control and single-exposed groups. The occurrence of a neuron suffering phenotype and variations in microglial density in the FC are observed at both time points. In OB, both density and morphological changes are revealed at 28 days. Molecular biology analyses show an increase of antioxidant gene expression in the FC of co- and single-exposed groups compared to the control at 28 days, while no change is observed in OB. At 28 days, as microglial density decreases in FC without increase in cell death, while microglial density increases in OB without proliferation, we can formulate the hypothesis that microglial cells migrate from the FC towards the OB. Consequently, the depletion of microglial cells in FC could contribute to the disruption of the cerebral microenvironment and thus to the increase in the neuronal suffering phenotype. The increased expression of antioxidant genes might be an attempt to compensate this loss. In OB, at 28 days, the reduction of TNFa expression while microglial activation is increased suggests an on-site anti-inflammatory response to our co-exposure.These results suggest a synergy or an additivity between our two stressors and potential persistent effects which are under current investigations
Weak coupling between a discrete element mechanics model and a numerical fluid mechanics model for the assessment of air leaks in cracked reinforced concrete walls
No full textl'ordre des auteurs différe selon les sources et doc; https://lmps.ens-paris-saclay.fr/fr/publications/weak-coupling-between-discrete-element-mechanics-model-and-numerical-fluid-mechanicsInternational audienceTo evaluate nuclear power plant reactor building containment, on-site pressurization tests up to 4 bars relative pressure are performed to measure leakage rates, influencing the French Nuclear Safety Authority's decision to authorize plant operation. Given the concrete's aging nature in the context of lifespan expansion, there is a need for a tool to estimate leakage rates over time, considering potential accidental loadings like coolant loss or seismic events. Experimental studies such as MAEVA (Granger et al.,2001) or VERCORS (Charpin et al., 2021) have assessed the structural scale's leakage ratio through concrete porosity and cracks. These results are crucial for developing simulation tools within the quasi-brittle material mechanics framework (concrete) and porous/fractured medium transport (diffusion and flow). Numerous investigations have demonstrated that various aspects of crack geometry (e.g., opening, roughness, tortuosity) influence leakage rates within the specimen scale (Akhavan et al., 2012). However, precisely characterizing the three-dimensional geometry of concrete cracks is a significant challenge. A new method has been created that merges Finite Element Analysis, Beam-Particle Modeling, and Computational Fluid Dynamics (CFD) to predict concrete crack geometries and air leakage rates accurately. A first finite element model calculation is performed in the model's first phase, implying macroscopic continuous finite element analysis, not discussed in this article, to handle the high processing needs of discrete simulations. Then, as described in this work, a refined discrete beam-particle model computation will be utilized as input for a CFD model for future work. By predicting the reinforced concrete crack patterns in terms of tortuosity and crack opening variations, the model greatly improves our understanding of crack modeling in nuclear reactor containments with the ability to estimate leakage rates that strengthen safety assessments and regulatory processes
Plant acclimation to ionising radiation requires activation of a detoxification pathway against carbonyl‐containing lipid oxidation products
No full textInternational audienceAbstract Ionising γ radiation produces reactive oxygen species by water radiolysis, providing an interesting model approach for studying oxidative stress in plants. Three‐week old plants of Arabidopsis thaliana were exposed to a low dose rate (25 mGy h −1 ) of γ radiation for up to 21 days. This treatment had no effect on plant growth and morphology, but it induced chronic oxidation of lipids which was associated with an accumulation of reactive carbonyl species (RCS). However, contrary to lipid peroxidation, lipid RCS accumulation was transient only, being maximal after 1 day of irradiation and decreasing back to the initial level during the subsequent days of continuous irradiation. This indicates the induction of a carbonyl‐metabolising process during chronic ionising radiation. Accordingly, the γ‐radiation treatment induced the expression of xenobiotic detoxification‐related genes ( AER , SDR1 , SDR3 , ALDH4 , and ANAC102 ). The transcriptomic response of some of those genes ( AER , SDR1 , and ANAC102 ) was deregulated in the tga256 mutant affected in three TGAII transcription factors, leading to enhanced and/or prolonged accumulation of RCS and to a marked inhibition of plant growth during irradiation compared to the wild type. These results show that Arabidopsis is able to acclimate to chronic oxidative stress and that this phenomenon requires activation of a carbonyl detoxification mechanism controlled by TGAII. This acclimation did not occur when plants were exposed to an acute γ radiation stress (100 Gy) which led to persistent accumulation of RCS and marked inhibition of plant growth. This study shows the role of secondary products of lipid peroxidation in the detrimental effects of reactive oxygen species
Homogenized descriptions for the elastoplastic response of polycrystalline solids with complex hardening laws: Application to neutron-irradiated bainitic steels
No full textInternational audienceHomogenized descriptions are provided for polycrystalline solids deforming in accordance with certain crystal plasticity laws recently proposed for neutron-irradiated bainitic steels. These laws express intragranular plastic slip rates in terms of resolved shear stresses and key microstructural features, such as densities of forest dislocations and of solute clusters, for a wide range of deformation rates, temperatures, and radiation doses. The elastic domain is delimited by thresholds on the resolved stresses that depend on dislocation densities in an intricate manner, and the plastic hardening is described by evolution laws of the Mecking–Kocks type for the dislocation densities with plastic slip. However, thresholds also depend nonlinearly on the resolved stresses themselves. Full-field homogenized descriptions are generated with a Fast Fourier Transform algorithm implemented in the computer code CraFT, while mean-field homogenized descriptions are generated by means of a linear-comparison scheme based on a generalized-secant linearization of the crystal plasticity laws. Multiple ways of accounting for plastic hardening in the mean-field descriptions are explored. Sample results are reported in the form of uniaxial traction curves and concomitant dislocation density evolutions under different scenarios. Overall, the generalized-secant linearization is found to provide an appropriate compromise between precision and mathematical complexity to generate homogenized descriptions for the elastoplastic response of polycrystalline media governed by complex crystal plasticity laws
Chronology of Upper Paleolithic human activities recorded in a stalagmite at Points Cave (Aiguèze, Gard, France)
No full textInternational audienceIn this article, we propose an approach to reconstruct the timing of human activity at Points Cave, an Upper Paleolithic rock art site located in the middle of the Ardèche River Gorge (Rhône valley, France), based on the dating and characterisation of a stalagmite containing soot. Points Cave (‘Grotte aux Points’ in French), also called the ‘little sister of Chauvet Cave’, is famous for its parietal art including a series of dots made of palm prints. A large number of stalagmites formed in the cave during the last 500 ka. However, quarrying of the cave floors during historic times led to the partial destruction of the sedimentary deposits, and many of the stalagmites were found lying on the floor. In particular, one of them (STM‐18‐04) showed the presence of at least four dark layers in cross‐section, which appeared as possible remnants of fire‐related activities in the cave. Despite being present at the same site, no other specific link between STM‐18‐04 and the rock art has been documented. This stalagmite, however, allows us to identify phases of human presence, located at the cave entrance. To do so, we performed a series of analyses to determine its period of growth and the nature of the dark layers that it contains. Scanning electron microscopy and Raman microspectroscopy confirmed that the dark layers include soot, and uranium‐series dating indicated that the fire events occurred, respectively, around 14,200–14,100 and 12,500 years ago, in agreement with the radiocarbon ages of charcoal specimens recovered from the excavation areas nearby. We thus highlighted phases of human activity at the site during the Upper Magdalenian and/or beginning of the Epipaleolithic. By comparing our results with the regional paleoclimatic record, the soot layers trapped in the stalagmite appear to be synchronous with two cold periods, likely the Older Dryas and the Younger Dryas
Main outcomes of the Phebus FPT1 uncertainty and sensitivity analysis in the EU-MUSA project
No full textInternational audienceThe Management and Uncertainties of Severe Accidents (MUSA) project was funded in HORIZON 2020 and is coordinated by CIEMAT (Spain). The project aims at consolidating a harmonized approach for the analysis of uncertainties and sensitivities associated with Severe Accidents (SAs) analysis, focusing on source term figures of merit. The Application of Uncertainty Quantification (UQ) Methods against Integral Experiments (AUQMIE – Work Package 4 (WP4)), led by ENEA (Italy), was devoted to apply and test UQ methodologies adopting the internationally recognized PHEBUS FPT1 test. FPT1 was chosen to test UQ methodologies because, even though it is a simplified SA scenario, it was representative of the in-vessel phase of a severe accident initiated by a break in the cold leg of a PWR primary circuit. WP4 served as a platform to identify and discuss the issues encountered in the application of UQ methodologies to SA analyses (e.g. discuss the UQ methodology, perform the coupling between the SA codes and the UQ tools, define the results post-processing methods, etc.). The purpose of this paper is to describe the MUSA PHEBUS FPT1 uncertainty application exercise with the related specifications and the methodologies used by the partners to perform the UQ exercise. The main outcomes and lessons learned of the analysis are: scripting was in general needed for the SA code and uncertainty tool coupling and to have more flexibility; particular attentions hould be devoted to the proper choice of the input uncertain parameters; outlier values of figures of merit should be carefully analyzed; the computational time is a key element to perform UQ in SA; the large number of uncertain input parameters may complicate the interpretation of correlation or sensitivity analysis; there is the need for a statistically solid handling of failed calculations
Effets physiologiques de l'irradiation gamma combinée à l'infection par Nosema ceranae chez l'abeille domestique, Apis mellifera – BEERAD
No full textInternational audienceRadioactive contamination of the environment is a major ecological challenge. In order to predict accurately the repercussions of nuclear disasters such as Chernobyl or Fukushima, it is essential to deepen our understanding of the effects and dangers that irradiation and contamination by radioactive substances represent for our environment. In this context, the honeybee, Apis mellifera, has been chosen as a model organism for studying the effects of ionizing radiation. Occupying an essential place within ecosystems, bees play a crucial role not only for the environment, but also for society, due to their preponderant role in the economy, the agro-environment and scientific research. The aim of this study is to develop our knowledge of the consequences and processes of action of ionizing radiation on these insects, a domain of study still insufficiently explored. This work is being carried out as part of the ANR BEERAD project, under the direction of IRSN's Laboratory of radionuclide Ecology and eCOtoxicology (LECO) in Cadarache, in collaboration with INRAE's Laboratory of Environmental Toxicology (LTE) bees and environment in Avignon.The first study carried out as part of the BEERAD project in the laboratory aims to assess the combined effect of ionizing radiation and the Nosema ceranae pathogen on honeybees. Bee colony failure, a complex multifactorial phenomenon, results from the interaction of many factors [1]. Among these factors, biological causes such as the N. ceranae pathogen, a microsporidian parasite naturally affecting bees, target the midgut and cause a disease known as nosemosis. This parasite, by invading and growing in the epithelial cells of the gut, weakens the bee and, by extension, the colony [2]. The present study therefore aims to examine the joint effects of an abiotic stress, here represented by ionizing radiation, and a biotic stress, embodied by the N. ceranae pathogen, on individual bees. The objective is to simulate as closely as possible a nuclear accident situation affecting a hive parasitized by N. ceranae, in order to study the multi-stress effect. To do this, newborn bees were infected and then irradiated in small cages of 50 individuals for 15 days, which, given a bee's lifespan (between 13 and 38 days during the summer season), is equivalent to chronic exposure. The bees were irradiated at a dose rate considered high (14 mGy/h), simulating a typical dose just after a nuclear accident. Several samples were taken throughout the irradiation period (0, 2, 4, 8 and 14 days of irradiation) for kinetics, to determine whether the effects observed were early or late.The first results of this study suggest a synergistic effect of the combination of stressors (irradiation and infection) on food consumption, with a significant decrease observed in the consumption of both infected and irradiated bees. An antagonistic effect was observed for survival,with a significant decrease in survival in bees only irradiated and bees only infected, but not in bees both infected and irradiated. This indicates that the combination of the two stressors does have an impact on the bees. These first results, as well as the effects of the combination of stressors on N.ceranae spore counts and on tissue activity of enzymes of interest targeting metabolic integrity, oxidative stress control, immunity and neural activity will be presented in this poster.La contamination radioactive de l’environnement constitue un enjeu écologique majeur. Afin de prévoir avec précision les répercussions des catastrophes nucléaires telles que Tchernobyl ou Fukushima, il est essentiel d’approfondir notre compréhension des effets et des dangers que représentent l’irradiation et la contamination par des substances radioactives pour notre environnement. Dans ce contexte, l’abeille domestique, Apis mellifera, a été choisie comme organisme modèle pour l’étude des effets des rayonnements ionisants. Occupant une place essentielle au sein des écosystèmes, les abeilles jouent un rôle crucial non seulement pour l’environnement, mais aussi pour la société, de par leur rôle prépondérant dans l’économie, l’agro-environnement et la recherche scientifique. L’objectif de cette étude est de développer nos connaissances sur les conséquences et les processus d’action des rayonnements ionisants sur ces insectes, domaine d’étude encore insuffisamment exploré. Ces travaux sont menés dans le cadre du projet ANR BEERAD, sous la direction du Laboratoire d'écologie des radionucléides et d'eCOtoxicologie (LECO) de l'IRSN à Cadarache, en collaboration avec le Laboratoire de toxicologie environnementale (LTE) abeilles et environnement de l'INRAE à Avignon.La première étude réalisée dans le cadre du projet BEERAD au laboratoire vise à évaluer l'effet combiné des rayonnements ionisants et du pathogène Nosema ceranae sur les abeilles domestiques. La défaillance des colonies d'abeilles, phénomène multifactoriel complexe, résulte de l'interaction de nombreux facteurs [1]. Parmi ces facteurs, des causes biologiques comme le pathogène N. ceranae, un parasite microsporidien affectant naturellement les abeilles, cible l'intestin moyen et provoque une maladie appelée nosémose. Ce parasite, en envahissant et en se développant dans les cellules épithéliales de l'intestin, fragilise l'abeille et, par extension, la colonie [2]. La présente étude vise donc à examiner les effets conjoints d'un stress abiotique, ici représenté par des rayonnements ionisants, et d'un stress biotique, incarné par le pathogène N. ceranae, sur des abeilles individuelles. L'objectif est de simuler au plus près une situation d'accident nucléaire affectant une ruche parasitée par N. ceranae, afin d'étudier l'effet multi-stress. Pour cela, des abeilles nouveau-nées ont été infectées puis irradiées dans de petites cages de 50 individus pendant 15 jours, ce qui, compte tenu de la durée de vie d'une abeille (entre 13 et 38 jours pendant la saison estivale), équivaut à une exposition chronique. Les abeilles ont été irradiées à un débit de dose considéré comme élevé (14 mGy/h), simulant une dose typique juste après un accident nucléaire. Plusieurs prélèvements ont été effectués tout au long de la période d'irradiation (0, 2, 4, 8 et 14 jours d'irradiation) pour la cinétique, afin de déterminer si les effets observés étaient précoces ou tardifs.Les premiers résultats de cette étude suggèrent un effet synergique de la combinaison de stresseurs (irradiation et infection) sur la consommation alimentaire, avec une diminution significative observée dans la consommation des abeilles infectées et irradiées. Un effet antagoniste a été observé pour la survie,avec une diminution significative de la survie chez les abeilles uniquement irradiées et les abeilles uniquement infectées, mais pas chez les abeilles infectées et irradiées. Cela indique que la combinaison des deux stresseurs a bien un impact sur les abeilles. Ces premiers résultats, ainsi que les effets de la combinaison de stresseurs sur le nombre de spores de N. ceranae et sur l’activité tissulaire d’enzymes d’intérêt ciblant l’intégrité métabolique, le contrôle du stress oxydatif, l’immunité et l’activité neurale seront présentés dans ce poster
BEERAD - Évaluation des effets des radiations ionisantes chez l'abeille
No full textInternational audienceThe risk assessment linked to the radiocontamination of the environment after a nuclear accident is a major ecological issue. However, it is still surrounded by controversial results and conclusions on the real impact of such events on flora and fauna inhabiting the targeted zones. Moreover, the potential underlying mechanisms of the action of ionizing radiation （IR） are poorly known. Therefore, it is important to acquire data on the potential effects of IR on ecosystems both in experimental and realistic conditions. The objective of the BEERAD project is, using a pluri-disciplinary approach, to increase the knowledge of effects and mechanisms of action of IR on physiology and populations of honeybees in the context of chronic exposure （i.e., exposure of a significant period of time relative to the lifespan of exposed organisms） and at low dose rates （sublethal ecotoxicity） in realistic conditions, i.e., on the field and in the laboratory. However, very few data exist on this subject, and it seems important to conduct studies that will serve as a basis to better evaluate the impacts of IR on animal health using honeybees. The presentation will focus on the experiment of implantation of hives realized around the Fukushima Nuclear Power Plant from April to October 2023.L’évaluation des risques liés à la radiocontamination de l’environnement après un accident nucléaire constitue un enjeu écologique majeur. Cependant, elle est encore entourée de résultats et de conclusions controversés sur l’impact réel de tels événements sur la flore et la faune peuplant les zones ciblées. De plus, les mécanismes potentiels sous-jacents à l’action des rayonnements ionisants (IR) sont mal connus. Il est donc important d’acquérir des données sur les effets potentiels des IR sur les écosystèmes à la fois dans des conditions expérimentales et réalistes. L’objectif du projet BEERAD est, par une approche pluridisciplinaire, d’accroître la connaissance des effets et des mécanismes d’action des IR sur la physiologie et les populations d’abeilles domestiques dans le cadre d’une exposition chronique (i.e., exposition d’une durée significative par rapport à la durée de vie des organismes exposés) et à de faibles débits de dose (écotoxicité sublétale) dans des conditions réalistes, c’est-à-dire sur le terrain et en laboratoire. Cependant, très peu de données existent sur ce sujet, et il semble important de mener des études qui serviront de base pour mieux évaluer les impacts de l’IR sur la santé animale en utilisant les abeilles domestiques. La présentation portera sur l’expérience d’implantation de ruches réalisée autour de la centrale nucléaire de Fukushima d’avril à octobre 2023
The burrowing and casting dynamics of earthworms are influenced by litter presence as evidenced by repeated scans and a new marker of bioturbation
No full textInternational audienceThe importance of earthworms for soil functioning is widely accepted and is mainly linked to their burrowing, feeding and casting behaviours. However, our knowledge of earthworm behavior is still limited by the lack of efficient and easy-to-use methods. In this work, we describe and test a new marker of earthworm bioturbation. Dense particles of tungsten, visible in X-ray images, were located at a certain depth in repacked soil cores inoculated by either Lumbricus terrestris or Aporrectodea caliginosa, alone or in combination. This marker was compared to the classical luminophore method (i.e. colored sand particles) generally used in aquatic ecology. The dynamics of both the burrow systems and the casting activities was followed using X-ray tomography every two weeks for a period of 10 weeks. Below ground casting activities could be assessed since parts of the casts excreted by the earthworms were marked by tungsten and appeared white in the images. The time dynamics of both burrow and cast productions were almost linear and significantly influenced by the earthworm species and the presence of litter. As expected, L. terrestris created larger (up to 50 cm3) and deeper burrow systems and made fewer macropores compared to A. caliginosa. Surprisingly, both species were equally influenced by the presence of litter, and this highlighted their behavioral plasticity. For example, A. caliginosa decreased by 32 % the volume of burrows in the presence of litter and the resulting burrow system was significantly shallower which showed that this endogeic species is indeed able to partly feed on surface litter. The use of tungsten particles is a promising new tool to accurately characterize the casting activities of earthworms in the soil and to study behavioral plasticity under the influence of environmental factors