Cross Section Doppler Broadening prediction using Physically Informed Deep Neural Networks

Temperature dependence of the neutron-nucleus interaction is known as the Doppler broadening of the cross-sections. This is a well-known effect due to the thermal motion of the target nuclei that occurs in the neutron-nucleus interaction. The fast computation of such effects is crucial for any nuclear application. Mechanisms have been developed that allow determining the Doppler effects in the cross-section, most of them based on the numerical resolution of the equation known as Solbrig's kernel, which is a cross-section Doppler broadening formalism derived from a free gas atoms distribution hypothesis. This paper explores a novel non-linear approach based on deep learning techniques. Deep neural networks are trained on synthetic and experimental data, serving as an alternative to the cross-section Doppler Broadening (DB). This paper explores the possibility of using physically informed neural networks, where the network is physically regularized to be the solution of a partial derivative equation, inferred from Solbrig's kernel. The learning process is demonstrated by using the fission, capture, and scattering cross sections for $^{235}U$ in the energy range from thermal to 2250 eV

CFD validations of ballooning effects during LOCA against MASCARA experiments

International audienceThis study investigates the thermal–hydraulic behavior through deformed fuel assemblies during LOCAs using CFD simulations. The MASCARA experiments uses a dedicated mock-up and Magnetic Resonance Velocimetry (MRV) to study how ballooned nuclear fuel rods affect coolant flow. We consider CFD validation against MASCARA experimental data. Employing the Code_Saturne solver, we reproduce flow redistribution and extrapolate thermal behavior in a 7x7 fuel rod bundle with different blockage configurations of 4x4 balloons. The chosen turbulence models with carefully designed meshes capture critical flow phenomena, including intense transverse velocities upstream and recirculation zones downstream of blocked regions. Validation against MRV data confirms the reliability of Code_Saturne in replicating experimental observations across various blockage conditions. Thermal simulations reveal the recirculation-driven heat accumulation and evacuation based on different geometry of deformed subchannels. The study is dedicated to improving sub-channel code predictions in ballooning effects and demonstrating the potential of high-fidelity CFD for multiscale nuclear safety assessments

Propriétés thermiques du béton armé des enceintes de confinement de réacteurs nucléaires pour les études de pressurisation enceinte : état de l'art et proposition pour des valeurs enveloppe et "best-estimate"

International audienceIn case of loss of coolant accident or severe accident in a nuclear pressurised water reactor, the containment pressure must remain below the design pressure to prevent radioactive releases. The evolution of containment pressure can be estimated by computer codes such ASTEC or MAAP. However, especially for severe accident, the pressurisation kinetics during the first 24 hours is very sensitive to the thermal properties of the containment concrete, which stores most of the decay heat. A wide range of thermal properties (thermal conductivity, specific heat and density) of concrete and reinforced concrete can be found in the literature, depending on the concrete temperature, composition and relative humidity. This paper presents a review of available thermal properties for concrete and reinforced concrete and makes some proposals for best estimate and conservative properties to calculate the evolution of the containment pressure during the first 24 hours after the accident initiator.En cas d'accident de perte de réfrigérant ou d'accident grave dans un réacteur nucléaire à eau pressurisée, la pression dans l'enceinte de confinement doit rester inférieure à la pression de dimensionnement afin de minimiser les rejets radioactifs. L'évolution de la pression dans l'enceinte de confinement peut être estimée à l'aide de codes informatiques tels que ASTEC ou MAAP. Cependant, en particulier dans le cas d'un accident grave, la cinétique de pressurisation au cours des premières 24 heures est très sensible aux propriétés thermiques du béton de l'enceinte de confinement, qui stocke la majeure partie de la chaleur résiduelle. La littérature scientifique fait état d'une grande variété de propriétés thermiques (conductivité thermique, chaleur spécifique et densité) du béton et du béton armé, qui dépendent de la température, de la composition et de l'humidité relative du béton. Cet article présente une revue des propriétés thermiques disponibles pour le béton et le béton armé et formule quelques propositions pour une estimation "best-estimate" et des propriétés enveloppes permettant de calculer l'évolution de la pression dans l'enceinte de confinement pendant les premières 24 heures suivant le déclenchement de l'accident

Iron Metallurgy in Ancient Cambodia: Production Dynamics, Traditions and Chronologies in a Southeast Asian Context (9th–14th centuries CE)

International audienceCollaborative studies in iron archaeometallurgy in Cambodia over the past decade, particularly through the IRANGKOR project, have advanced our understanding of iron production dynamics during the Angkorian period (9th–15th centuries CE). This research examines metallurgical remains and artifacts within a systemic framework, linking them to production sites, geological contexts, and usage settings, such as iron clamps in monumental constructions. Studied diachronically and across multiple spatial scales, these remains provide insights into production practices and “recipes,” production dynamics, and the circulation and supply of iron, particularly within the central production territory of Phnom Dek, historically recognized for its metallurgical tradition.The study explores the relationships between resources, production processes, metallurgical practices, and iron circulation. Central to the research is the use of provenance analyses, direct dating of the metal itself, and the examination of comparative patterns, providing precise chronological and spatial benchmarks. Combining historical and archaeological sources with material analysis of artifacts and smelting debris establishes a framework for interpreting these dynamics across the Angkorian territory.The resulting datasets reveal changes in metallurgical “recipes” as well as in supply strategies and demands over more than 1,400 years. This presentation synthesizes recent results, highlighting the contribution of compositional and chronological data to frameworks for understanding continuities and changes in ancient metallurgical practices. Situating these findings within a broader Asian context highlights similarities in practices and recipes and their implications for regional technical dynamics

First wheat certified reference material for organically bound tritium measurement in the environment

International audienceMeasuring the radioactivity of organically bound tritium in environmental samples is difficult. For the past twenty years, many laboratories have been working on the development of reliable tritium measurement methods. In this context, several interlaboratory comparisons have been organised to develop these methods and enable laboratories to compare themselves. However, the trueness of the measurement methods has never been estimated due to the lack of certified reference materials available for use during the analyses. This document presents the production of the first certified reference material for the measurement of organically bound tritium radioactivity in environmental samples

Diffusivity in metallic beryllium: The case of the H, C, N and O species

International audienceThe insertion and diffusivity of interstitial species in metallic beryllium are discussed in this work using a multi-scale methodology, coupling first-principles calculations and a multi-site approach. Emphasis is placed on the main interstitial species, i.e., H, C, N and O atoms. The results show that the most stable site is strongly dependent on the nature of the interstitial atom. Indeed, carbon is most stable in octahedral sites and hydrogen tetrahedral sites, while oxygen and nitrogen are most stable in basal tetrahedral sites. From the stable insertion sites and symmetrical saddle points identified, a number of migration pathways were mapped. The diffusion pathways were then completed using nudged elastic band (NEB) calculations. The diffusivity of the atoms shows an isotropic behavior as expected for carbon, which shows a strong anisotropic behavior with faster diffusivity along the basal plane. These theoretical results are in agreement with known experimental data, especially for hydrogen diffusion. The discrepancy between theory and experiment is corrected by the vacancy trapping effect. Finally, this paper theoretically determines the Arrhenius parameters of each diffusing species, in particular carbon and oxygen, for which no data were available

Modélisation des courbes d’évolution des mesures nucléaires dégradées par des aérosols.

International audienceIn nuclear facilities, the mandatory airborne contamination surveillance is operated by dedicated Continuous Air Monitors (CAM) that collect all airborne aerosol on a filter, measure the radioactivity and trig an alarm when a predetermined activity concentration is exceeded. This measurement and therefore the alarms are very integrated by the variations in size and concentration of the aerosols. A new adjustment process can be used to establish a relationship between the mass deposited on a sampling filter and the evolution of the nuclear measurement, based on a previously assembled data set. This relationship has been established for one aerosol dimension and requires extension to the other aerosol dimensions in the database. This represents the first explicit relationship between changes in nuclear measurements and changes in aerosols.Dans les installations nucléaires, la surveillance obligatoire de la contamination aéroportée est opérée par des instruments dédiés (CAM - Continuous Air Monitor) qui collectent les aérosols sur un filtre, mesurent la radioactivité déposée et déclenchent une alarme lorsqu'un seuil prédéterminé en activité est dépassé. Cette mesure et donc les alarmes sont très influencées par les variations en taille et concentration des aérosols. Sur la base d'un ensemble de données préalablement constitué, un processus d'ajustement nouveau permet de chercher à mettre en relation la masse déposée sur un filtre de prélèvement et l'évolution de la mesure nucléaire. Cette relation a pu être établie pour une dimension d'aérosol et doit être étendue aux autres dimensions d'aérosols de la base de données. Il s'agit ici de la première relation explicite entre les évolutions des mesures nucléaires et celle des aérosols

Numerical investigation of mechanisms affecting alkali-silica reaction advancement by reactive transport simulations

International 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

Exploring the safety and performance of molten salt reactors for their deployment in the European Union: the MIMOSA and ENDURANCE projects

International audienceMolten Salt Reactors (MSR) are Generation IV nuclear systems in which the fuel is dissolved in a molten salt circulating through the primary system. There is growing interest in this advanced technology in Europe, but also in the US, China, South Korea, Japan and Russia, due to their inherently high safety level, flexibility, reliability, load-following capabilities, and potential for multi-recycling of materials contained in light-water reactors’ spent nuclear fuels. These advantages could position MSRs as ideal complements to other decarbonized energy sources in a future sustainable energy mix. In this respect, it is probably one of the most promising advanced technologies and, at the same time, the least mature and studied one. Two ongoing EURATOM-funded projects, MIMOSA and ENDURANCE projects are exploring molten salt reactors’ safety and performance features, as well as fuel cycle aspects, in order to assess and demonstrate their potential for future deployment in Europe. The MIMOSA and ENDURANCE projects have the common objective of improving the maturity of MSR technology. The MIMOSA project develops and analyses multi-recycling strategies for the European Union based on the use of MSR and demonstrates several key aspects of their technical feasibility and performance by both calculations and experimental investigations. The ENDURANCE project supports the safe operation and the development of Critical Technology Elements by connecting design developers and industry with universities and research centres while ensuring alignment with regulatory requirements. Whereas ENDURANCE is in its starting phase, MIMOSA has already delivered important results

Analyse paléosismologique des failles de la terminaison NE cévenole après le séisme du Teil : qu’avons-nous appris ?

National audienceLe séisme du Teil en 2019, dont l’épicentre est situé le long de la faille de la Rouvière à proximité des centrales nucléaires de Cruas et de Tricastin, est apparu comme un séisme sans précédent en France métropolitaine. Il a généré une rupture de surface inédite (4.5 km de long, 10 cm de déplacement du sol en moyenne avec un mouvement inverse), de fortesaccélérations du sol (1g le long de la faille) et est situé à une profondeur superficielle (~1 km).Cet événement a soulevé un ensemble d’interrogations auxquelles la communauté scientifique tente de répondre par le biais de nombreuses observations et recherches, notamment dans le cadre de l'axe Failles actives France de l'Action transverse sismicité d'Epos-France. Début 2025, toutes les failles de la terminaison NE cévenole n’ont pu être étudiées. Il est donc fondamental de poursuivre ces études paléosismologiques pour mieux contraindre l’aléa sismique associé aux réseau de failles situé dans une partie de la vallée du Rhône, fortement peuplée et industrialisée