Propriétés élastiques des combustibles nucléaires sous conditions extrêmes

par Mara Marchetti

Projet de thèse en Électronique

Sous la direction de Gilles Despaux et de Didier Laux.

Thèses en préparation à Montpellier , dans le cadre de École Doctorale Information, Structures, Systèmes (Montpellier ; 2015) , en partenariat avec IES - Institut d'Electronique et des Systèmes (laboratoire) et de Département Capteurs, Composants et Systèmes (equipe de recherche) depuis le 28-02-2014 .


  • Résumé

    During its in-pile operation, nuclear fuel undergoes dramatic alterations due to fission damage and accumulation of fission products. Fission gas bubbles enhance the fuel swelling process;several micro and macro-structural reorganization processes affect the local morphology of fuel pellets. At a macroscopic level the material cracks and several safety relevant properties are affected. Irradiated fuel is therefore characterized by a high degree of heterogeneity, which includes also the presence of variable stress/strain fields. The local variations of elastic and thermo-mechanical properties can be investigated via high frequency acoustic microscopy. Measurements on relatively homogeneous special irradiation samples allowed determining basic elastic modulus dependence on burn up. These studies must be extended now in order to cover additional fields of interest. These include local variation of properties along the radius of fuel pellet; interface regions such as pellet-cladding interaction layer and the fuel coating layers in the case of TRISO coated particle; alteration of the elastic properties caused by severe fuel degradation and eventually corium formation under extreme (accident) conditions.The objective of these investigation is to establish a basis of data for the understanding of the evolution of the thermo-mechanical fuel properties under irradiation conditions corresponding to normal operation and accident events, as well for the decommissioning of irradiated materials after a severe accident. The development of a 3D image of a coated fuel particle and the characterization of the internal pressure effects in high burn up irradiated particles by analyzing the SiC outside layer will also be contemplated.

  • Titre traduit

    Elastic properties characterization of nuclear fuels under extreme conditions


  • Résumé

    During its in-pile operation, nuclear fuel undergoes dramatic alterations due to fission damage and accumulation of fission products. Fission gas bubbles enhance the fuel swelling process;several micro and macro-structural reorganization processes affect the local morphology of fuel pellets. At a macroscopic level the material cracks and several safety relevant properties are affected. Irradiated fuel is therefore characterized by a high degree of heterogeneity, which includes also the presence of variable stress/strain fields. The local variations of elastic and thermo-mechanical properties can be investigated via high frequency acoustic microscopy. Measurements on relatively homogeneous special irradiation samples allowed determining basic elastic modulus dependence on burn up. These studies must be extended now in order to cover additional fields of interest. These include local variation of properties along the radius of fuel pellet; interface regions such as pellet-cladding interaction layer and the fuel coating layers in the case of TRISO coated particle; alteration of the elastic properties caused by severe fuel degradation and eventually corium formation under extreme (accident) conditions.The objective of these investigation is to establish a basis of data for the understanding of the evolution of the thermo-mechanical fuel properties under irradiation conditions corresponding to normal operation and accident events, as well for the decommissioning of irradiated materials after a severe accident. The development of a 3D image of a coated fuel particle and the characterization of the internal pressure effects in high burn up irradiated particles by analyzing the SiC outside layer will also be contemplated.