Modélisation du comportement des combustibles à particules : caractérisation d'un volume élémentaire représentatif pour un milieu hétérogène aléatoire

HTR fuel is based on spherical coated particles of uranium dioxide inserted in graphite blocks. To take into account the effects of the random distribution of fuel particles on local thermomechanical fields, the simulation propose a multi scale approach based on the Finite Element Square method. This method make use of a two scale discretization: a finite element computation on the Representative Volume Element (RVE) is carried out simultaneously at each integration point of the homogeneous macrostructure. The first characterization of the random geometry is given by a distribution indicator: the minimal distance between centres of particles. After, we used finite element computation to obtain the effective behaviour, which have been compared with an analytic model. Finally, we define thermal and mechanical representativity criteria, inspired by particles failure under irradiation. Mots-clefs : Homogeneisation ; Volume Elementaire representatif ; Combustible a particules