Institute for Radiation Protection and Nuclear Safety (IRSN)
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Numerical investigation of mechanisms affecting alkali-silica reaction advancement by reactive transport simulations
No full textInternational audienceAlkali-Silica Reaction (ASR) is a long-term chemical degradation induced in concrete by the difference in pH between the aggregate and the cement paste. ASR advancement is thus driven by the combination of the ionic species diffusion and the dissolution of reactive silica. In this paper, the reactive transport model is based on the principal sequence of the ASR-mechanisms: hydroxide, alkali and calcium diffusion, silica dissolution and reaction products precipitation. First, the proposed model highlights the impact of the competition between diffusion and dissolution kinetic on the formation of products in the depth of the aggregate particles according to the calcium concentration. Secondly, the numerical study on the size effect of the aggregate particles highlights the efficacy of this approach to reproduce the dependence of the products type formed during precipitation, allowing for the competition between ASR and pozzolanic effect to be reproduced
Chlorine 36 dry deposition on lettuce and maize crops
No full textInternational audienceChlorine is a mineral nutrient which, in a certain amount in the form of chloride, is essential for plant development. However, the atmosphere-plant transfer of its radioactive isotope, chlorine-36, is still poorly understood. In this study, dry deposition of 36Cl on lettuce and maize was determined experimentally. These two cultures were carried out downwind of Orano La Hague plant (West of France), which chronically emits small quantities of 36Cl. The dry deposition velocities were similar on these two canopies with mean values of and 1.4 × 10− 2 m s− 1 on lettuce and 1.6 × 10− 2 m s− 1 on maize crops. The measured deposition fluxes reflect the importance of the dry deposition mechanism on plants, particularly in situations of anthropogenic discharge. All these results will contribute to improving the knowledge on the fate of 36Cl in environment, and particularly in agrosystems
Characterization and performance of the Apollon main short-pulse laser beam following its commissioning at 2 PW level
No full textInternational audienceWe present the results of the second commissioning phase of the short-focal-length area of the Apollon laser facility, located in Saclay, France. This phase was conducted using the main laser beam (F1), scaled to a peak power of 2 PetaWatts. Under the tested conditions, the F1 beam delivered on-target pulses with a maximum energy of up to 45 J and a duration of 22 fs. Several diagnostics were deployed to assess the facilitys performance. Key measurements included the on-target focal spot and its spatial stability, along with characterizations of secondary sources generated by irradiating solid targets. These evaluations aim at assisting users in designing future experiments. The laser-target interactions were thoroughly characterized, with emissions of energetic ions, X-rays, and neutrons recorded, demonstrating good laser-to-target coupling efficiency. Additionally, we successfully demonstrated the simultaneous operation of the F1 beam with the auxiliary 0.5 PW F2 beam of Apollon, enabling dual-beam operation. This commissioning phase paves the way for the next stage in 2025, which will involve scaling the F1 beam to 8 PW, progressing towards the ultimate goal of achieving 10 PW power
Main outcomes of OECD/NEA THAI-2 project on hydrogen risk and source term investigations: Data application for code validation and containment safety assessment
No full textPart of special issue - 20th International Topical Meeting on Nuclear Reactor Thermal Hydraulics (NURETH-20)International audienceDuring a core-melt accident, apart from hydrogen, radioactive gases and aerosols are released into the containment, the behaviour of which is of significant importance for determining the radiological source term. The investigation of in-containment combustible gases and fission product behaviour was the subject of the OECD/NEA THAI-2 project conducted during 2011–2014. The project focused on experiments on hydrogen behaviour i.e., deflagration in the presence of spray and passive autocatalytic recombiners (PARs) performance in O2-lean atmosphere, on the interaction of molecular iodine with reactive (silver) and non-reactive (tin oxide) aerosol particles to assess the effect on a potential source term, and on the quantification of the release of gaseous iodine from a flashing jet, representing a PWR steam generator tube rupture scenario during reactor shutdown. The project was supported by 11 countries involving safety organizations, regulatory bodies, research laboratories, universities and industries.The experimental programme of the OECD/NEA THAI-2 project strongly contributed to the validation and further development of advanced lumped parameter and computational fluid dynamic codes used for reactor applications by e. g. providing experimental data for code benchmark exercises. The present paper summarizes the key findings of the project and highlights the importance of project results for mitigation of hydrogen risk and source term related issues. Furthermore, the use of project results by the project partners for code validation and reactor analyses towards management and mitigation of a severe accident in light water reactors is discussed with selected examples
A numerical approach for estimating the probability of earthquake surface rupture
No full textInternational audienceThis study is part of the Probabilistic Fault Displacement Hazard Analysis (PFDHA) framework, which assesses the hazard posed by coseismic surface faulting to infrastructure systems (e.g., lifelines, nuclear power plants, and dams) located on or near an earthquake fault trace. The primary objective of this study is to estimate the probability of surface rupture on the principal fault—the main fault responsible for seismic moment release—based on faulting style, seismogenic thickness, fault geometry, and rupture size (i.e., earthquake magnitude). Current methods for estimating the probability of surface rupture on the principal fault are primarily based on empirical models. These models rely on observations of surface rupture occurrences versus non-occurrences, analyzed through logistic regressions using global or regional datasets of historical crustal earthquakes. However, empirical models have several limitations, including potential biases, catalog incompleteness (i.e., missing surface rupture data), and inconsistencies in fault geometry information and seismotectonic settings (e.g., seismogenic thickness). To overcome these limitations, we propose a numerical approach to compute the Conditional Probability of Surface Rupture (CPSR). This approach incorporates faulting style (normal, reverse, strike-slip), seismogenic thickness, fault dip, magnitude-dependent scaling relations for rupture shape and size, nucleation position within the rupture, and the statistical distribution of hypocenters within the seismogenic crust. These parameters are derived from statistical analyses of global fault rupture databases and earthquake distributions in various non-subduction seismotectonic settings. Our results indicate that CPSR probabilities are strongly influenced by seismogenic thickness and fault dip angle. Moreover, comparison between numerical results and empirical models suggests that CPSR depends on the specific characteristics of the study area. This model can be integrated into PFDHA as an epistemic alternative to purely empirical approaches. Additionally, the numerical code for CPSR computation has been developed and is openly available on GitHub
New approach methodologies to study uranium renal toxicology in low dose exposures
No full textInternational audienceExposure of uranium compounds can occur in several situations including nuclear fuel processing,military activities, and natural exposure. Uranium is a radio element with known radiological (αemitting radionuclide) and chemical (as a heavy metal) toxicities, which accumulates preferentially inthe kidneys and more specifically in proximal convoluted tubules. However significant gaps remain inthe evaluation of the risk of renal cancerous or non-cancerous disease in the case of chronic orrepeated low-dose exposure to uranium
Coupled fluid-structure simulations of a cantilever rod in water turbulent axial flow with different CFD approaches
No full textInternational audienceFluid-structure numerical simulations of an experimental campaign by Cioncolini et al. of a cantilever rod in water axial flow were performed. The experimental configuration aims at representing a nuclear fuel rod, in terms of hydraulic diameter. Water velocity profiles and structure vibrations were measured experimentally. Two of the experimental tests were simulated numerically, one at Re=1.5•10 4 and one at Re=1.9•10 4 . Different CFD approaches were tested, using code Saturne: a wall-resolved two-equation linear viscosity model (k-ω-SST), two wall-modeled Reynolds stress models (SSG and LRR), a wall-resolved Reynolds stress model (EBRSM) and a wall-resolved hybrid URANS/LES model (DDES). The structure was simulated through a onedimensional finite element Euler-Bernoulli beam model. A 2-way coupling was implemented between the two solvers, with an Arbitrary Lagrangian Eulerian approach. Unexpectedly, wall-modeled Reynolds-stress models were found to calculate higher amplitudes of vibration than the higher-resolution EBRSM and DDES. The frequency domain analysis allowed to identify high energy flow velocity and flow-induced force harmonics at relatively low frequency calculated by LRR and SSG, not present in the EBRSM and DDES results, which explain the numerical results in terms of vibration response. This specific behavior of LRR and SSG seems to be linked to the wall function boundary condition. LRR and SSG calculate a rms amplitude of vibration close to the experiments, whereas EBRSM and DDES underestimate them by a factor of 2.5. A hypothetical small permanent deformation (4% of the hydraulic diameter) of the rod was simulated and found to increase the calculated vibration amplitudes by a factor of 2. 1-way coupling was also tested to assess the influence of damping and added mass on the results
Numerical investigations on size effects and mini-CT applications for master-curve determination
No full textInternational audienceThis paper presents a comprehensive numerical study on size effects and the application of mini-compact tension (mini-CT, or MCT) specimens within the Master Curve methodology for determining fracture toughness, particularly in irradiated nuclear materials. This study, conducted as part of the FRACTESUS project, involves collaboration among several European laboratories to estimate the efficacy of mini-CT specimens through extensive finite element modelling (FEM) and inter-laboratory simulations. The research addresses critical factors, including the consistency of FEM codes, the impact of crack length on displacement conversion factors, and the application of the Beremin model for brittle fracture analysis. The good consistency between the results obtained by the different laboratories validates the numerical approach. The comparison of the macroscopic and local mechanical fields between 1T-CT and MCT specimens highlights the in- and out-plane loss of constraint and the deterioration in the plane strain state in MCT, resulting in the apparent fracture toughness shift on the measured value. The numerical analysis of this shift using the Beremin model show that: (i) numerical simulations can accurately replicate experimental results obtained with MCT specimens, (ii) a size effect is observed on the Beremin fracture parameters, (iii) the use of cross-parameter sets between geometries does not yield satisfactory results, and (iv) the value, using the same parameters for both specimen geometries, is lower is the MCT compared to 1T-CT suggesting that MCT can lead to non-conservative results with respect to 1T-CT
Avis de l'Anses relatif à un « projet d’arrêté relatif aux conditions de production et d’utilisation des eaux usées traitées pour des usages urbains »
No full textCITATION SUGGÉRÉEAnses. (2024). Avis relatif à un « projet d’arrêté relatif aux conditions de production et d’utilisation des eaux usées traitées pour des usages urbains » (saisine 2023-SA-0156). Maisons-Alfort : Anses, 67 p.L’Anses a été saisie le 4 août 2023 par la Direction générale de la santé (DGS) pour une demande d’avis portant sur un projet d’arrêté relatif aux conditions de production et d’utilisation des eaux usées traitées pour des usages urbains.CONTEXTE ET OBJET DE LA SAISINELes ressources en eau subissent des pressions de plus en plus importantes au niveau mondial, dues à diverses causes comme le dérèglement climatique, l’augmentation de la démographie (humaine et animale), l’urbanisation et l’industrialisation, qui affectent le cycle de l’eau (IPCC, 2022[1]). La raréfaction de la ressource en eau est considérée comme un risque majeur par le groupe d’experts intergouvernemental sur l’évolution du climat (GIEC). En France, la fréquence plus élevée des épisodes de sécheresse et des vagues de chaleur imposent des mesures de restriction d’eau avec des limitations de son utilisation, marquées par le risque de multiplication des conflits d’usage (CGAAER, 2023 [2]).L’objectif 2 du pacte des Assises de l’eau [3], qui est d’économiser et de mieux partager l’eau, s’appuie sur plusieurs actions, dont l’action 7 qui vise à « tripler les volumes d’eaux non conventionnelles [4] réutilisées d’ici 2025 en facilitant leurs usages » et d’adapter la réglementation pour « autoriser de nouveaux usages des eaux non conventionnelles(nettoiement, arrosage d’espaces verts...), lorsqu’une qualité d’eau potable [5] n’est pas nécessaire et que les risques sanitaires sont maîtrisés ».Dans ce contexte, le plan d’action gouvernemental pour une gestion résiliente et concertée de l’eau [6] décline 53 mesures. Les objectifs de celles qui visent à « valoriser les eaux non conventionnelles » sont de « massifier la valorisation des eaux non conventionnelles (REUT [7], eau de pluie, eaux grises...) », de « développer 1 000 projets de réutilisation sur le territoire, d’ici 2027 » et de lever les « freins réglementaires ».Au niveau communautaire, plusieurs directives ou règlements encouragent et encadrent une utilisation durable de l’eau :- l’article 12 de la directive 91/271/CEE du Conseil du 21 mai 1991 relative au traitement des eaux urbaines résiduaires mentionne que les eaux usées traitées peuvent être réutilisées chaque fois que cela se révèle approprié ;- la directive 2000/60/CE du Parlement européen et du Conseil du 16 décembre 2020 établit un cadre pour une politique communautaire dans le domaine de l'eau, qui promeut une utilisation durable de l’eau et contribue à atténuer les effets des inondations et des sécheresses ;- le règlement (UE) 2020/741 du Parlement européen et du Conseil du 25 mai 2020, relatif aux exigences minimales applicables à la réutilisation des eaux usées traitées, rappelle que cette réutilisation vise à contribuer aux objectifs de développement durable des Nations-Unies, en particulier l’objectif 6 sur la disponibilité et la gestion durable de l’eau et de l’assainissement pour tous et l’objectif 12 sur la consommation et la production durable. Si ce règlement s’applique à la réutilisation des eaux urbaines résiduaires traitées à des fins d’irrigation agricole, il précise, au considérant 29, que[1] Intergovernmental Panel on Climate Change.[2] Conseil général de l’alimentation, de l’agriculture et des espaces ruraux[3] Assises de l’eau – Un nouveau pacte pour faire face au changement climatique. Dossier de presse 1erjuillet 2019. https://www.ecologie.gouv.fr/assises-leau, consulté le 28 septembre 2023.[4] Plusieurs termes coexistent dans la réglementation et dans le langage professionnel pour désigner leseaux qui ne sont pas des « eaux potables » ou des « eaux minérales naturelles » au sens du code dela santé publique (CSP) : « eaux non potables » et « eau(x) impropre(s) à la consommation humaine », ces deux termessont employés l’un pour l’autre dans le CSP :- « eaux non potables », terminologie utilisée au chapitre II bis du titre II du livre III de lapremière partie du CSP pour désigner les « eaux impropres à la consommationhumaine » ;- « eau(x) impropre(s) à la consommation humaine », terminologie employée dans lesarticles L. 1321-1 et L. 1322-14 du CSP, qui regroupe les catégories d’eaux qui nerespectent pas la réglementation relative aux eaux destinées à la consommationhumaine ; « eaux non conventionnelles », terminologie introduite dans le pacte des Assises de l’eau (2019)qui regroupe les eaux usées traitées, les eaux de pluie, les eaux d’exhaure et les eaux grises(ensemble des eaux usées domestiques à l’exception des eaux-vannes, i.e. eaux issues destoilettes).[5] Les eaux potables sont également nommées eaux destinées à la consommation humaine (EDCH).[6] Plan d’action pour une gestion résiliente et concertée de l’eau - 53 mesures pour l'eau - Dossier depresse 30 mars 2023. https://www.gouvernement.fr/preservons-notre-ressource-en-eau/les-53-mesures-du-plan-eau, consulté le 28 septembre 2023.[7] REUT : réutilisation des eaux usées traitées. https://www.ecologie.gouv.fr/plan-eau-gouvernement-accelere-reutilisation-des-eaux-usees-traitees-reut, consulté le 28 septembre 202
Évaluation de la sûreté des réacteurs à eau pressurisée lors d'événements internes et externes et des stratégies de mitigation
No full textInternational audienceThis paper describes the main objectives and outcomes of two funded European projects(R2CA & BESEP), which have been recently finalized. They were dedicated to the safety analyses ofdesign basis accidents and design extension conditions scenarios, covering a broad spectrum of accidentsand analysis methodologies.The R2CA project covering deterministic safety analyses set out to reduce some of the conservatisms anddecoupling factors currently used for design basis accidents in safety studies or licensing calculations andto optimize emergency operating/accident management procedures. To this end, simulation tools and theircoupling in calculation chains were enhanced to provide a better quantification of safety margins and abetter evaluation of the radiological consequences of accident scenarios.The BESEP project aims to develop best practices for the verification of stringent safety requirementsagainst external hazards. The aim is achieved using an efficient and integrated set of safety engineeringpractices and probabilistic safety assessment. The efficient and integrated set of safety engineering practicessupports the safety margins determination and safety requirement verification helping the licensing processof nuclear power plant new builds and upgrades