Institute for Radiation Protection and Nuclear Safety (IRSN)
Not a member yet
7928 research outputs found
Sort by
Sediment pollution: An assessment of anthropogenic and geogenic trace element contributions along the central Algerian coast
No full textInternational audienceSediment cores from the central Algerian coast were collected to investigate the distribution, sources and risk oftrace metals. The local geochemical background of metals was defined from the core S collected in an uncontaminatedarea of the coast. The anthropogenic inputs in Algiers Bay elevated Ag, Cd, Pb and Zn concentrationsas their maximum were 3.1, 3, 2.1 and 1.8 times the background values, respectively. Meanwhile, increasedcontents of Arsenic (up to 21.1 mg/kg) were detected in all sites. Correlations and PCA suggest that lithogenicsources controlled metal deposition, while most sediment arsenic was agriculture-derived. Organic matter actedas a sink or source for some trace metals. According to EFs, the study area showed slight to moderate enrichmentwith respect to Ag, As, Pb, Cd, Zn and Cu, whereas they remained uncontaminated with Cr, V, Co and Ni. Thisstudy provides a needed baseline for future environmental investigations
Identification of the origin of radiocesium released into the environment in areas remote from nuclear accident and military test sites using the Cs/Cs isotopic signature
No full textInternational audienceThe isotopic signature of radionuclides provides a powerful tool for discriminating radioactive contamination sources and estimating their respective contributions in the environment. In this context, the Cs/Cs ratio has been tested as a very promising isotopic ratio that had not been explored yet in many countries around the world including France. To quantify the levels of radioactivity found in the environment, a new method combining a thorough radiochemical treatment of the sample and an efficient measurement by ICP-MS/MS has been recently developed. This method was successfully applied, for the first time, to soil and sediment samples collected in France in two mountainous regions preferentially impacted either by global fallout from nuclear weapons testing (i.e., the Pyrenees) or by the Chernobyl accident (i.e., the Southern Alps). The Cs/Cs ratios measured on twenty-one samples ranged from 0.66 ± 0.04 and 4.29 ± 0.21 (decaycorrected to January 1 st , 2022) corresponding to the characteristic signatures of the fallout from Chernobyl and global fallout associated with the nuclear weapons testing, respectively. Moreover, large variations of both the Cs mass activity and the studied isotopic ratio recorded by most samples from the southern Alps suggest varying proportions of these two Cs sources. For these samples, the contribution of each source was estimated using this new tracer (Cs/Cs) and compared with the mixing contribution given by activity ratio: Pu/Cs. This work has successfully demonstrated the applicability of the Cs/Cs isotopic signature to nuclear forensic studies and could be extended to better evaluate the environmental impact of nuclear facilities (i.e., NPP, waste reprocessing)
Experimental validation in a neutron exposure frame of the MINAS TIRITH for cell damage simulation
No full textInternational audienceIn the domains of medicine and space exploration, refining risk assessment models for protecting healthy tissue from ionizing radiation is crucial. Understanding radiation-induced effects requires biological experimentations at the cellular population level and the cellular scale modeling using Monte Carlo track structure codes. We present MINAS TIRITH, a tool using Geant4-DNA Monte Carlo-generated databases to study DNA damage distribution at the cell population scale. It introduces a DNA damage location module and proposes a method to convert double-strand breaks (DSB) into DNA Damage Response foci. We evaluate damage location precision and DSB-foci conversion parameters. MINAS TIRITH’s accuracy is validated against γ -H2AX foci distribution from cell population exposed to monoenergetic neutron beams (2.5 or 15.1 MeV) under different configurations, yielding mixed radiation fields. Strong agreement between simulation and experimental results was found demonstrating MINAS TIRITH’s predictive precision in radiation-induced DNA damage topology. Additionally, modeling intercellular damage variability within a population subjected to a specific macroscopic dose identifies subpopulations, enhancing realistic fate models. This approach advances our understanding of radiation-induced effects on cellular systems for risk assessment improvement
Les fers médiévaux de Notre-Dame de Paris : Chronologie, pratiques artisanales et économie du chantier
No full textNational audienc
Étude numérique de la rupture d'éprouvettes mini-C(T) d'aciers de cuves dans le domaine de transition ductile-fragile
No full textInternational audienceCe travail cherche à simuler numériquement des essais de rupture d'éprouvettes C(T) (Compact Tension) miniatures d’aciers de cuves de réacteurs nucléaires. Les simulations reposent sur le code XPER développé à l’IRSN et dédié à la simulation numérique de la fissuration complexe à l’aide de modèles de zones cohésives [1]. En particulier, l’approche générale par zone cohésive de [2] est utilisée pour modéliser la transition ductile-fragile des aciers de cuve (procédure générale pour obtenir une dépendance des paramètres du modèle de zone cohésive à la température). Ce travail est réalisé dans le cadre du projet européen FRACTESUS (Fracture mechanics testing of irradiated RPV steels by means of sub-sized specimens [3] [4]).[1] Perales F., Dubois F., Monerie Y., Piar B. and Stainier L. A NonSmooth Contact Dynamics-based multi-domain solver : Code coupling (Xper) and application to fracture European Journal of Computational Mechanics (2010), 19 (4), pp. 61-66.[2] Chakraborty P. and Bulent Biner S. A unified cohesive zone approach to model the ductile to brittle transition of fracture toughness in reactor pressure vessel steels Engineering Fracture Mechanics (2014), 131, pp. 194-209.[3] Cicero S., Lambrecht M., Swan H., Arffman P., Altstadt E., Petit T., Obermeier F., Arroyo B., Álvarez J.A. and Lacalle R. Fracture mechanics testing of irradiated RPV steels by means of sub-sized specimens : FRACTESUS project Procedia Structural Integrity (2020), 28, pp. 61-66.[4] FRACTESUS | Fractesus H2020 (fractesus-h2020.eu). This project has received funding from the Euratom research and training programme 2020-2024 under grant agreement No 900014
Microstructure Characterization of EU INCEFA-SCALE 316L Stainless Steel Fatigue Specimens – Mechanistic Understanding
No full textInternational audienceA pressurized water reactor (PWR) primary environment can have a deleterious effect on the fatigue lifetime of austenitic stainless steels. One of the main goals of a five-year INCEFA-SCALE (INcreasing safety in NPPs by Covering gaps in Environmental Fatigue Assessment — focusing on gaps between laboratory data and component SCALE) project, kicked off in October 2020 and supported by the European Commission HORIZON2020 programme, is to develop an improved mechanistic understanding behind the effect of a PWR primary environment on the fatigue behavior of austenitic stainless steels through coordinated extensive characterization of as-machined and tested specimens at partner organizations. This work focuses on the microstructure characterization of as-received austenitic stainless steel 316L plate material and as-machined fatigue specimens, as well as the preparation of guidelines on post-mortem characterization for the consortium. The presented microstructure characterization is carried out using light optical microscopy (LOM), scanning electron microscopy (SEM), and analytical electron microscopy (AEM) (including electron backscatter diffraction (EBSD), scanning/transmission electron microscopy (STEM/TEM), X-ray energy dispersive spectroscopy (EDS) and electron diffraction). The hardness, grain structure, inclusions, and delta-ferrite of the as-received 316L material were investigated. The surface roughness, machining-induced deformation layers, and ultra-fine-grained structure of as-machined ground and polished specimens were studied. A ground surface finish leads to significantly higher machining-induced deformation, and surface roughness, with plenty of machining-induced cracks and defects extending a few microns into the bulk material, compared to a polished finish. The guidelines on the post-mortem characterization for the whole consortium can guide partner organizations in their posttest analysis for a direct comparison of the characterization data, which facilitates the mechanism interpretation
Tornando a krigagem consistente com as equações de fluxo: aplicação da krigagem com covariâncias numéricas para estimar uma pluma de contaminação
No full textInternational audienceWhen the data are few, kriging hydraulic head or concentration with usual variogrammodels can lead to physically inconsistent results, because the non-stationarityinduced by the flow or transport equations is not taken into account properly. Severalmethods have been proposed to account for these equations in the geostatisticalestimation. A recent and general approach consists in incorporating them throughspecific covariance models. A set of random fields sampling uncertain parameters (e.g.conductivity) is first used as input of a flow simulator. Empirical “numerical” spatialcovariances are then calculated between pairs of points and for the variable ofinterest (e.g. hydraulic head, concentration) on the corresponding set of flow simulatoroutputs. These non-stationary “numerical” covariances are consistent with the specificspatial variability of hydraulic head or concentrations. They are used in the estimation.In this paper, flow-and-transport simulations are thus combined with kriging to estimatecontaminant concentrations in groundwater. A non-stationary Gaussian anamorphosisin introduced for non-linear estimation so that the estimate of the concentration ispositive.The method is first validated on synthetic data and then on real data from a twodimensional cross-section of an aquifer downstream of a trench containing radioactivewaste in the Chernobyl area. Kriging with the output of a simplified flow model asexternal drift and kriging with numerical covariances reproduce the spatial variability ofthe contaminant plume much better than usual (ordinary) kriging based onobservations only. The comparison between the two best estimators is discusse
What We Have Learned from RENEB Inter-Laboratory Comparisons Since 2012 With Focus on ILC 2021
No full textInternational audienceInter-laboratory exercises are important tools within the European network for biological dosimetry and physical retrospective dosimetry (RENEB) to validate and improve the performance of member laboratories and to ensure an operational network with high quality standards for dose estimations in case of a large-scale radiological or nuclear event. In addition to the RENEB inter-laboratory comparison 2021, several inter-laboratory comparisons have been performed in the frame of RENEB for a number of assays in recent years. This publication gives an overview of RENEB inter-laboratorycomparisons for biological dosimetry assays in the past and a final summary of the challenges and lessons learnt from the RENEB inter-laboratory comparison 2021. In addition, the dose estimates of all RENEB inter-laboratory comparisons since 2013 that have been conducted for the dicentric chromosome assay, the most established and applied assay, are compared and discussed
Swarms and mainshock-aftershocks sequences are both triggered by fluids in the Ubaye Region (Western Alps)
No full textInternational audienceThe Ubaye Region (French Western Alps) is one of the most seismically active regions in France. It is regularly struck by mainshock–aftershocks sequences like in 1959 (ML 5.3), seismic swarms (2003–2004), and complex sequences (2012–2015) characterized by successive mainshocks clustered in time and space. This diversity of seismic behaviour highlights the complex processes at play in this area. To improve our understanding of these processes, in this study, we compile a regional catalogue of existing focal mechanisms, completed by 100 new calculated focal mechanisms of aftershocks following the 07/04/2014 mainshock (ML 5.1). The oriented stress-state we reconstruct for different periods and subareas are similar to each other and to previous published values focusing on swarm periods. We then calculate fluid pressure required to trigger the earthquakes. Most of the events (65 per cent) need fluid overpressure between 15 and 40 MPa (17 to 40 per cent of the hydrostatic pressure) with a median value of 24 per cent. Moreover, even the largest events, like the mainshocks in the 2012–2015 sequence, appear to be triggered by fluid pressure, similarly as events within swarm sequences. However, while fluid overpressure decreases with time in an aftershock sequence, it varies randomly at high levels during a swarm sequence. Therefore, based on a fault-valve model, we propose that: (1) the fluids trapped in the fault plane tend toward lithostatic pressure and trigger the mainshock rupture and (2) part of the aftershocks are induced by the diffusing fluid pressure. On the contrary, swarms need external, likely deep, fluid pressure feedings. Fluid pressure is likely to be a common triggering mechanism of the seismicity in the Ubaye Region, even if the involved processes should differ to explain the different types of seismic sequences
Modélisation micromécanique du comportement de matériaux du nucléaire
No full textCes activités de recherche s’articulent autour de l’étude du comportement mécanique de matériaux poreux dunucléaire par la modélisation, de l’échelle microscopique locale à l’échelle macroscopique de la structure. Lesmilieux poreux étudiés dans le cadre de ces recherches sont des céramiques de combustibles nucléaires et desaciers utilisés dans les réacteurs nucléaires à eau sous pression.Les thématiques de recherche portent globalement sur la mécanique théorique et numérique (solide, structure,matériaux), avec, d’une part, l’homogénéisation et les méthodes de changement d’échelles en mécanique dessolides, et d’autre part, les couplages entre l’endommagement et la plasticité ou la viscoplasticité et la simulationde la fissuration des matériaux.Les deux types de matériaux étudiés, céramique pour les combustibles en dioxyde d’uranium et oxydes mixteset métallique pour les matériels appelés "internes" de cuve, subissent, durant leur utilisation, des températuresélevées et de fortes doses d’irradiation, ce qui modifie leur microstructure et leur comportement mécanique.Ce travail de recherche a pour objectif appliqué de fournir des modèles de comportement tridimensionnelscapables de prendre en compte le plus explicitement possible les effets de l’irradiation, tout en restant intégrableset utilisables dans des codes de calculs "métiers". Leur utilisation en réacteur peut notamment amener à laformation de cavités dans ces matériaux, ce qui introduit une compressibilité globale à ces matériaux. Desmodèles de comportement tridimensionnels avec prise en compte de la triaxialité des contraintes sont recherchés