Innovation and qualification of LEU research reactor fuels and materials

Two projects within the Euratom Research and Training Programmes 2014–2018 and 2019–2020 are focused on the innovation and qualification of novel nuclear fuels for conversion from highly-enriched uranium to low-enriched uranium (LEU) and for securing the supply chain of EU research reactors into the future. The LEU-FOREvER project is drawing to a close and has made significant progress in developing and demonstrating the uranium-molybdenum fuel system, demonstrating the viability of a high-density uranium-silicide fuel for EU high-performance research reactors (BR2, RHF, FRM-II, JHR). This project has significantly increased the fabrication know-how and fuel performance understanding of the uranium-molybdenum and high-density uranium-silicide dispersion fuel systems. Further, a new, innovative and increased performance design for the LVR-15 research reactor fuel assembly has been engineered and a demonstration is planned in 2022. In the EU-QUALIFY project, which began in 2020, the planning of four demonstration irradiation tests has been nearly completed and fabrication development of the various fuel systems is ongoing, including the establishment of an EU monolithic uranium-molybdenum fabrication capability. It is expected that the results of this project will begin or complete the data gathering necessary for generic fuel qualification of the LEU uranium-molybdenum dispersion and monolithic fuel systems, and the LEU high-density uranium-silicide fuel system

Aspects mécaniques du changement de phase allotropique à l\u27échelle mésoscopique

La prédiction de létat mécanique de structures en acier soumises à des chargements thermiques ne peut se faire sans modélisation du phénomène de changement de phase allotropique. En effet, le changement de phase induit, pour les aciers, un mécanisme appelé plasticité de transformation conduisant à une déformation irréversible pour des chargements inférieurs à la limite élastique des phases. De nombreux modèles analytiques ont proposé une approche homogénéisée pour la prédiction de létat mécanique. Mais, pour des chargements complexes, ces modèles se révèlent inadéquates. Prenant acte de ces lacunes, nous présentons une modélisation plus proche de sa description heuristique. Léchelle mésoscopique retenue pour ce travail est de lordre de la taille de grain. A cette échelle, nous considérons le comportement de chaque phase comme homogène au sens de la mécanique des milieux continus, par contre, le front de changement de phase est modélisé explicitement. Cette approche mésoscopique du phénomène sest faite expérimentalement et numériquement. Expérimentalement, nous avons mis au point et utilisé une manipulation permettant la traction et le chauffage sous vide partiel dune éprouvette. Lacquisition de la surface de léchantillon pendant la transformation martensitique a conduit, sous certaines hypothèses et grâce à la corrélation numérique dimage, à lidentification partielle des zones affectées localement par la transformation. Numériquement, lutilisation de la méthode des éléments finis étendus appliquée à des champs de déplacement faiblement discontinus. Lutilisation de cette méthode nécessite la modélisation du support de discontinuité -le front. Pour cela, en saidant de la méthode level set, nous avons créé des schémas numériques éléments finis permettant la représentation du support et sa propagation. En sus, nous nous sommes intéressés au calcul des forces motrices définies sur le front à partir du tenseur dEshelby et représentatives de sa vitesse locale

Strain simulation of steel during a heating-cooling cycle including solid-solid phase change

International audienceDesigned for the simulation of transformation induced plasticity in steels occurring on cooling, the model first proposed by Leblond in the middle of 80's works well for constant uni-axial stress test. But further experimental investigation have shown that for non-proportional multi-axial test, the quality of the model is worse. The purpose of this paper is to improve this model through the removal of the hypothesis that plastic flow for the Greenwood–Johnson mechanism occurs only in the ‘weaker’ phase. The improvement, leading to better agreement, enables to use the model on cooling, and shows that for TRIP plastic flowing in harder phase is almost important, even if it is lower than in the ‘weak’ phase

Innovation and qualification of LEU research reactor fuels and materials

International audienceTwo projects within the Euratom Research and Training Programmes 2014–2018 and 2019–2020 are focused on the innovation and qualification of novel nuclear fuels for conversion from highly-enriched uranium to low-enriched uranium (LEU) and for securing the supply chain of EU research reactors into the future. The LEU-FOREvER project is drawing to a close and has made significant progress in developing and demonstrating the uranium-molybdenum fuel system, demonstrating the viability of a high-density uranium-silicide fuel for EU high-performance research reactors (BR2, RHF, FRM-II, JHR). This project has significantly increased the fabrication know-how and fuel performance understanding of the uranium-molybdenum and high-density uranium-silicide dispersion fuel systems. Further, a new, innovative and increased performance design for the LVR-15 research reactor fuel assembly has been engineered and a demonstration is planned in 2022. In the EU-QUALIFY project, which began in 2020, the planning of four demonstration irradiation tests has been nearly completed and fabrication development of the various fuel systems is ongoing, including the establishment of an EU monolithic uranium-molybdenum fabrication capability. It is expected that the results of this project will begin or complete the data gathering necessary for generic fuel qualification of the LEU uranium-molybdenum dispersion and monolithic fuel systems, and the LEU high-density uranium-silicide fuel system

Innovation and qualification of LEU research reactor fuels and materials

Two projects within the Euratom Research and Training Programmes 2014–2018 and 2019–2020 are focused on the innovation and qualification of novel nuclear fuels for conversion from highly-enriched uranium to low-enriched uranium (LEU) and for securing the supply chain of EU research reactors into the future. The LEU-FOREvER project is drawing to a close and has made significant progress in developing and demonstrating the uranium-molybdenum fuel system, demonstrating the viability of a high-density uranium-silicide fuel for EU high-performance research reactors (BR2, RHF, FRM-II, JHR). This project has significantly increased the fabrication know-how and fuel performance understanding of the uranium-molybdenum and high-density uranium-silicide dispersion fuel systems. Further, a new, innovative and increased performance design for the LVR-15 research reactor fuel assembly has been engineered and a demonstration is planned in 2022. In the EU-QUALIFY project, which began in 2020, the planning of four demonstration irradiation tests has been nearly completed and fabrication development of the various fuel systems is ongoing, including the establishment of an EU monolithic uranium-molybdenum fabrication capability. It is expected that the results of this project will begin or complete the data gathering necessary for generic fuel qualification of the LEU uranium-molybdenum dispersion and monolithic fuel systems, and the LEU high-density uranium-silicide fuel system

Innovative and safe supply of fuels for reactors

Within the Euratom research and training program 2014–2018, three projects aiming at securing the fuel supply for European power and research reactors have been funded. Those three projects address the potential weaknesses – supplier diversity, provision of enriched fissile material – associated with the furbishing of nuclear fuels. First, the ESSANUF project, now terminated, resulted in the design and licensing of a fuel element for VVER-440 nuclear power plant manufactured by Westinghouse. The HERACLES-CP project aimed at preparing the conversion of high performance research reactor to low enriched uranium fuels by exploring fuels based on uranium-molybdenium. Finally, the LEU-FOREvER pursues the work initiated in HERACLES-CP, completing it by an exploration of the high-density silicide fuels, and including the diversification of fuel supplier for soviet designed European medium power research reactor. This paper describes the projects goals, structure and their achievements

Simulation éléments finis étendus du phénomène de plasticité de transformation

International audienceUsual models designed for transformation induced plasticity (TRIP) mechanical simulation makes an essential use of analytical homogeneisation. This implie to use a simplificate topology of different phase while transformation is occuring. One of there weakness is that they are unable to simulate TRIP under complex loadings. In order to overcome this limitation, we design an Xfem simulation which enable the mechanical simulation of TRIP under complex loading while taking into account the real phase change.Les modèles actuels de plasticité de transformation sont essentiellement des modèles d'homogénéisation analytique utilisant une topologie simpliste de changement de phase. Or ils s'avèrent inefficaces pour modéliser des problèmes sous chargement complexe. Pour pallier ce problème on a mis au point une modélisation fine du changement de phase par la méthode des éléments finis étendus en association avec l'observation optique de la topologie des phases durant la transformation

A Finite Element Method for Level Sets

chapitre 7Level set methods have recently gained much popularity to capture discontinuities, including their possible propagation. In this contribution we present a finite element approach for solving the governing equations of level set methods. After a review of the governing equations, the initialisation of the level sets, the discretisation on a finite domain and the stabilisation of the resulting finite element method will be discussed. Special attention will be given to the proper treatment of the internal boundary condition, which is achieved by exploiting the partition-of-unity property of finite element shape functions

Nature-Based Solution along High-Energy Eroding Sandy Coasts: Preliminary Tests on the Reinstatement of Natural Dynamics in Reprofiled Coastal Dunes

International audienceThis paper describes a large-scale experiment designed to examine if reinstating natural processes in the coastal dune systems of Southwest France can be a relevant nature-based adaptation in chronically eroding sectors and a nature-based solution against coastal hazards, by maintaining the coastal dune ecological corridor. An experiment started in late 2017 on a 4-km-long stretch of coast at Truc Vert, where experimental notches were excavated and intensively monitored in the incipient and established foredunes. Preliminary results indicate that most of the excavated notches did not develop into blowout. Only the larger elongated notches subsequently excavated in the established foredune in 2018 showed evidence of development, acting as an effective conduit for aeolian landward transport into the dunes. All notches were found to have a statistically significant impact on vegetation dynamics downwind, even those that did not develop. The area of bare sand landward and within the elongated notches notably increased implying a loss of vegetation cover during this first stage of development. Observations of a nearby coastal dune system that has been in free evolution over the last 40 years also indicate that, although the dune migrated inland by more than 100 m, it is now mostly made of bare sand. Further work is required to explore if and how dunes maintained as dynamic systems can become an efficient nature-based solution along this eroding coastline