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International audience; The paper presents the mathematical modelling and computer simulation of static mechanical response of a PWR fuel assembly, with the help of the finite element code CAST3M developed by CEA. In PWR core analysis, the fuel assemblies present non-linear behaviour, which can be explained by the variations of stiffness due to the contact and the slipping between fuel rods and spacer grids as well as to the loss of contact of the rods. In the first part of this paper, a rod-to-grid contact model, based on the Coulomb law and constituted of non-linear springs and hinges, is developed to simulate the holding system of fuel rods inside the grid cells. The results of simulation showed a good agreement with experimental data. The second part aims at applying the domain decomposition methods to the modelling of the fuel assembly with proposed contact model. Due to geometric complexity of the fuel assemblies, the approximation by finite element method leads to a large number of unknowns. The resolution of this system would be prohibitively expensive with the available computation power. By using the domain decomposition methods we are able to reduce a significant amount of computational time and relieve the memory requirement from the advantage of parallel computing.

International audience; In the framework of the CEA scientific research on multiphysics and multiscale coupling in nuclear reactor modeling, our main interest lies within Rod Ejection Accidental situations that may occur in Pressurized Water Reactors (PWR). This accident is characterized by a strong interaction between the different areas of the reactor physics (neutronics, thermal fuel mechanics and thermal hydraulics) and a heterogeneous and dissymmetrical spatial deposit of power on the fuel pin and the coolant, which might jeopardize the fuel pin. In this context, accurate representations of neutron flux distribution are needed. In this paper we focus only on the discipline of neutronics and more precisely on the reconstruction of the coarse power distribution over the whole core in order to obtain the accurate and realistic localization and deposit of the power inside some interesting subdomains of the core.

International audience; Starting from electrical distributed propulsion system concept, the ONERA’s engineers demonstrated the viability of an all electrical aircraft for a small business aircraft. This paper describes the advanced power architecture considering energy conversion and power distribution. The design of this advanced power architecture requires the multi-physic integration of different domains as flight performances, safety and environmental requirements (thermal, electric, electromagnetic). From this analysis, all components of this advanced power architecture have been identified and evaluated.

International audience; We consider an initially spherical capsule freely suspended in a planar hyperbolic flow and study the influence of the wall bending resistance on the capsule dynamics. The capsule wall is assumed to be made of a three-dimensional homogeneous elastic material. The fluid-structure interaction between the capsule and the external flow is modeled numerically by coupling a boundary integral method with a shell finite element method. It is found that, for given three-dimensional wall mechanical properties, the capsule deformability is drastically reduced as the bending resistance is increased. But, if one expresses the same results as a function of the two-dimensional mechanical properties of the mid-surface, which is how the capsule wall is modeled in the thin-shell model, the capsule deformed shape is identical to the one predicted for a capsule devoid of bending resistance. The bending rigidity is found to have a negligible influence on the shape and deformation: the capsule main deformation mode is thus solely a function of the elastic stretching of the mid-surface. The wall bending resistance still plays a role locally in the regions where buckling occurs. Its influence is studied in the low flow strength regime, for which wrinkling of the wall is observed to persist at steady state. We show that the wrinkle wavelength only depends on the bending number, which compares the relative importance of bending and shearing phenomena, and provide the correlation law. This result is interesting as it allows bending resistance to be estimated from experiments on capsules in a planar hyperbolic flow at low flow strength.