Institute for Radiation Protection and Nuclear Safety (IRSN)
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Editorial trend: adverse outcome pathway (AOP) and computational strategy — towards new perspectives in ecotoxicology
No full textCorrection to: Editorial trend: adverse outcome pathway (AOP) and computational strategy — towards new perspectives in ecotoxicology (Environmental Science and Pollution Research, (2023), 31, 5, (6587-6596), 10.1007/s11356-023-30647-w) : 10.1007/s11356-025-36073-4International audienceThe adverse outcome pathway (AOP) has been conceptualized in 2010 as an analytical construct to describe a sequential chain of causal links between key events, from a molecular initiating event leading to an adverse outcome (AO), considering several levels of biological organization. An AOP aims to identify and organize available knowledge about toxic effects of chemicals and drugs, either in ecotoxicology or toxicology, and it can be helpful in both basic and applied research and serve as a decision-making tool in support of regulatory risk assessment. The AOP concept has evolved since its introduction, and recent research in toxicology, based on integrative systems biology and artificial intelligence, gave it a new dimension. This innovative in silico strategy can help to decipher mechanisms of action and AOP and offers new perspectives in AOP development. However, to date, this strategy has not yet been applied to ecotoxicology. In this context, the main objective of this short article is to discuss the relevance and feasibility of transferring this strategy to ecotoxicology. One of the challenges to be discussed is the level of organisation that is relevant to address for the AO (population/community). This strategy also offers many advantages that could be fruitful in ecotoxicology and overcome the lack of time, such as the rapid identification of data available at a time t, or the identification of “data gaps”. Finally, this article proposes a step forward with suggested priority topics in ecotoxicology that could benefit from this strategy
Diffusion model uniform manifold filtering for classification of small datasets with underrepresented classes: Application to chromosomal aberration microscopy detection
No full textInternational audienceA frequent problem in biomedical machine learning is the issue of imbalanced classes, especially when datasets are small, which restricts the performance of deep learning methods. To address this issue, generative models are often used to generate additional synthetic data. Specifically, image-to-image models can transform input images to match the characteristics of target images. However, training such models on small datasets can affect the quality of synthetic samples. We propose a new method to filter generative outputs of an image-to-image Brownian Bridge Diffusion Models (BBDMs) using Uniform Manifold Approximation and Projection (UMAP) dimension reduction of a real data classifier's feature space. We apply this methodology to filter synthetic chromosomal aberrations generated from the blue DAPI-colored channels in the context of cytogenetic Fluorescence In Situ Hybridization (FISH) microscopy. Our method shows that such filtered synthetic data significantly enhance classification performance compared to the state of the art CycleGAN and could potentially be applied to a variety of other generative models
Sensitivities of Configurations with Missing Fuel Rods
No full textInternational audienceRecent results described a new method paving the way towards a consistent approach of criticality safety of fuel assemblies with missing fuel rods. The proposed approach made use of a pair of descriptive variables, that are then used to browse among the large diversity of situations associated to the problem. In the present work, it is shown that the proposed coordinate system can also be used to describe the variations of the sensitivity profiles observed on a fuel assembly with different configurations of missing fuel rods, this showing that the variables are truly relevant for describing the physics of the problem. We then go on to discuss a few prospects for the realization of integral experiments, illustrating how the variables used could help and guide the choice of new experiments involving configurations of fuel rods on a regular lattice
Investigation of Uncertainty Propagation in the Resolved Resonance Range
No full textInternational audienceThis paper presents a comparative study using the first-order formula (also called "sandwich") and the multivariate sampling methodologies for propagating uncertainty in the resolved resonance region. A distinctive aspect of this work is the generation of random cross sections by sampling Resonance Parameters (RPs) taking in consideration their correlations provided in nuclear data libraries via the Resonance Parameter Covariance Matrix (RPCM). SCOOBY (Sampling COvariance OBservatorY), a newly developed sampling tool, is presented in this paper. This tool relies on the GAIA-2 nuclear data processing code to read and correct the RPCM and generate random cross sections. The study compares the sandwich method that relies on sensitivity coefficients and covariance matrices, with the sampling method, which involves numerous Monte Carlo simulations with random cross sections. The comparison is tested on an ICSBEP benchmark, PU-MET-MIXED-002, chosen for its sensitivity to 239 Pu cross sections. The results indicate that both methods quantify similar uncertainties, confirming the reliability of both the SCOOBY module and the GAIA-2 code. By using the PU-MET-MIXED-002 benchmark and sampling 239 Pu resonance parameters, this work demonstrates the effectiveness of these methodologies in estimating uncertainty in criticality safety calculations. The findings highlight the robustness of these approaches in uncertainty propagation, suggesting the need for further research on additional benchmarks and expanded uncertainty propagation studies
Datations « absolues » en archéologie
No full textNational audienceAbsolute dating has become indispensable to archaeological research. Its results make it possible to anchor chronologies within the timescale and to refine the duration of historical processes, thereby placing past events more precisely in time. The discovery of the regular decrease over time of carbon-14 radioactivity, and its use as a “chronometer” to estimate the age of materials submitted for dating, was a small revolution at the dawn of the 1950s. Combined with other so-called relative methods such as stratigraphy, seriation and typology, radiocarbon dating profoundly transformed our understanding of the past. Since then, research has made it possible to considerably improve both the reliability and the precision of results. At the same time, other methods have been developed in response to the growing diversity of excavated materials (dendrochronology, potassium–argon, uranium–thorium, archaeomagnetism, thermoluminescence and optically stimulated luminescence, etc.). With the development of preventive archaeology, the volume of data accumulated is now considerable, and raises questions about how best to manage and make these data accessible. Moreover, the analysis of large numbers of dates relating to a cultural phenomenon or to the spread of an artefact type makes it possible to process information using statistical and spatial approaches, thus opening up new research perspectives. In archaeology, the implementation of these methods generally involves recourse to researchers specialised in other disciplines (biology, chemistry, Earth sciences, nuclear physics, etc.), or to archaeometrists trained in laboratory settings. The range of actors and expertise mobilised is broad—even within the archaeological community itself—and it was therefore important for Inrap to provide a forum for interdisciplinary encounters, the exchange of experience, and collective reflection on the future of these methods and the collaborations they entail. The aim is to reflect jointly on the evolution of field protocols (sampling), on awareness-raising or training initiatives to be undertaken, and on the need to centralise and share results. Finally, these meetings will provide an opportunity to discuss the different methodological approaches and to assess their strengths and weaknesses.Les datations absolues sont devenues indispensables à la recherche archéologique. Leurs résultats permettent de caler les chronologies sur l’échelle du temps. Elles précisent la durée des phénomènes historiques en œuvre et situent dans le temps les événements du passé. La découverte de la décroissance régulière au fil du temps de la radioactivité du carbone 14 et de son usage comme « chronomètre » pour estimer l’âge des matériaux soumis à datation a été une petite révolution à l’orée des années 1950. Combinées avec d’autres méthodes dites relatives comme la stratigraphie, la sériation et la typologie, la datation par le radiocarbone a en effet modifié profondément notre connaissance du passé. Depuis, la recherche a permis de considérablement affiner la fiabilité et la précision des résultats. Parallèlement, d’autres méthodes ont été développées en lien avec la diversification des matériaux mis au jour (dendrochronologie, Potassium-Argon, Uranium-Thorium, archéomagnétisme, thermoluminescence et luminescence stimulée optiquement…). Avec le développement de l’archéologie préventive, la masse de données accumulées est aujourd’hui considérable et nécessite de s’interroger sur la manière de gérer et de rendre accessible ces données. Par ailleurs, l’analyse d’un grand nombre de datations relatives à un phénomène culturel ou à la diffusion d’un type d’objet permet de traiter l’information à l’aide de la statistique et de manière géographique, offrant ainsi de nouvelles perspectives de recherche.La mise en œuvre de ces méthodes, en archéologie, se traduit généralement par le recours à des chercheurs spécialisés dans d’autres disciplines (biologie, chimie, sciences de la Terre, physique nucléaire…) ou à des archéomètres formés dans les laboratoires. La multiplicité des acteurs et des compétences mises à contribution est grande, même au sein de la communauté archéologique, et il était donc important, pour l’Inrap, de proposer un lieu de rencontre interdisciplinaire, d’échanges d’expériences et de réflexions sur l’avenir de ces méthodes et des collaborations qu’elles impliquent. Il s’agit de réfléchir, collégialement, sur l’évolution des protocoles de terrain (échantillonnage), les actions de sensibilisation ou de formation à entreprendre et la nécessité de centraliser et de partager les résultats. Enfin, ces rencontres seront l’occasion d’aborder les différentes approches méthodologiques et d’évaluer leurs atouts ou faiblesses
Towards a highly efficient and unbiased population-control algorithm for kinetic Monte Carlo simulations
No full textInternational audiencePopulation-control methods are key to non-stationary Monte Carlo simulations of multiplying systems: they prevent either the unbounded growth or the disappearance of neutrons, occurring respectively in supercritical and subcritical conditions; furthermore, they contribute to an efficient allocation of computational resources by addressing the unbalance between the neutron and the precursor populations. In this paper, we present two alternative populationcontrol algorithms: the legacy implementation in TRIPOLI-4®, the Monte Carlo code developed at CEA, and an improved version that is currently under investigation, based on the use of a simplified point-kinetics solver. We assess the performance of these methods through the simulation of a $2.2 step reactivity insertion in a fast system (Flattop-Pu), leading to an increase of the neutron population by a factor 200, which is benchmarked against point kinetics. We show that the new implementation not only suppresses the slight bias that was present in the legacy method due to a stochastic normalization factor, but also outperforms the previous algorithm in terms of variance reduction and improvement of the figure of merit
Entrainment in variable-density jets
No full textInternational audienceThe entrainment of ambient fluid into a variable-density jet is typically quantified using an entrainment coefficient . Here, we investigate the dependence of on the ratio of the jet's density and that of the ambient fluid . Current parametrisations of rely on a scaling inferred from early laboratory experiments (Ricou & Spalding, J. Fluid Mech. , vol. 11, 1961, pp. 21–32). We demonstrate analytically that the experiments preclude definitive conclusions regarding the dependence of on and that the underlying physical processes therefore warrant closer attention. To investigate the physics behind the dependence of entrainment on the density ratio we use a Favre-averaged entrainment decomposition. The decomposition is applied to data from large-eddy simulations of jets characterised by density ratios spanning over two orders of magnitude that have been verified against experimental data. Changes in the shape of the velocity profile are a significant contributor to entrainment in the near field due to the breakdown of the potential core, and persist over larger streamwise distances in heavy releases than in light releases. Therefore, to focus exclusively on the effects of density ratio, we study the region where the shape changes have become small but the density ratio is still significant. We show that the dimensionless turbulent kinetic energy production and mean kinetic energy flux depend strongly on the density ratio, both for our large-eddy simulation data and for recent experiments. Despite this, the entrainment coefficient is practically constant in this region and has value for all simulations
An Optimization Approach to Improve Thermal Scattering Law Using Experimental Total Cross Section Data
No full textInternational audienceThe objective of this research is to present an optimization approach to improve thermal scattering cross section data for moderator materials. This study leverages on chi-square minimization technique, aiming to minimize the inconsistencies found in different evaluations of thermal scattering cross sections. The efficiency of this methodology has been demonstrated on improving the thermal scattering law for light water, a key moderator in thermal nuclear systems. Comparative analyses of the TSL for light water with a comprehensive experimental total cross section data set reveal that the existing evaluations have discrepancies up to 5 % with JEFF-3.3 and 2 % with ENDF/B-VIII.0 in the energy regions significant for thermal nuclear s ystems. Utilizing a chi-square minimization technique, the present work achieves a significant reduction in these discrepancies, closely aligning with the experimental total cross section data. This provides a solid foundation for future work and has immediate applications in improving thermal scattering laws for light water. The robust methodology established in this paper can be extended to improving thermal scattering law for other moderator materials
AOP report: Development of an adverse outcome pathway for deposition of energy leading to learning and memory impairment
No full textInternational audienceUnderstanding radiation‐induced non‐cancer effects on the central nervous system (CNS) is essential for the risk assessment of medical (e.g., radiotherapy) and occupational (e.g., nuclear workers and astronauts) exposures. Herein, the adverse outcome pathway (AOP) approach was used to consolidate relevant studies in the area of cognitive decline for identification of research gaps, countermeasure development, and for eventual use in risk assessments. AOPs are an analytical construct describing critical events to an adverse outcome (AO) in a simplified form beginning with a molecular initiating event (MIE). An AOP was constructed utilizing mechanistic information to build empirical support for the key event relationships (KERs) between the MIE of deposition of energy to the AO of learning and memory impairment through multiple key events (KEs). The evidence for the AOP was acquired through a documented scoping review of the literature. In this AOP, the MIE is connected to the AO via six KEs: increased oxidative stress, increased deoxyribonucleic acid (DNA) strand breaks, altered stress response signaling, tissue resident cell activation, increased pro‐inflammatory mediators, and abnormal neural remodeling that encompasses atypical structural and functional alterations of neural cells and surrounding environment. Deposition of energy directly leads to oxidative stress, increased DNA strand breaks, an increase of pro‐inflammatory mediators and tissue resident cell activation. These KEs, which are themselves interconnected, can lead to abnormal neural remodeling impacting learning and memory processes. Identified knowledge gaps include improving quantitative understanding of the AOP across several KERs and additional testing of proposed modulating factors through experimental work. Broadly, it is envisioned that the outcome of these efforts could be extended to other cognitive disorders and complement ongoing work by international radiation governing bodies in their review of the system of radiological protection
Nouveau dispositif de fluage pour l'évaluation de l'effet de la précontrainte biaxiale sur les déformations différées du béton
No full textInternational audienceDe nombreux ouvrages en béton sont atteints de réactions de gonflement internes (RGI) pouvant affecter leur tenue en service. Pour être capable de modéliser l'évolution de leur comportement, des recherches doivent étudier les couplages avec des sollicitations mécaniques. De telles études demeurent néanmoins complexes à mettre en oeuvre en laboratoire. Ceci est d'autant plus vrai pour un chargement en compression biaxiale représentatif des enceintes de confinement nucléaires précontraintes suivant deux directions. Or, le fluage du béton provoque des pertes de précontraintes pouvant compromettre leur fonction d'étanchéité si elles s'avéraient trop élevées dans certaines conditions. Un bâti original de fluage biaxial a été conçu pour tester des dalles en béton de 20x20x15 cm. Leurs déformations sont mesurées suivant les trois directions grâce à des capteurs à fibre optique noyés résistants aux conditions sévères nécessaires pour accélérer les RGI. L'analyse des résultats des essais réalisés montre que les déformations de fluage dépendent fortement des conditions de chargement. La distribution asymétrique des contraintes révèle l'importance de l'effet Poisson entre les deux directions. Les essais avec RGI étant toujours en cours, les résultats disponibles de fluage biaxial sans RGI constituent une base de données originales permettant de tester les modèles