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Home   /   Thesis   /   Study of phase transitions in sub-stoichiometric uranium bearing mixed oxides

Study of phase transitions in sub-stoichiometric uranium bearing mixed oxides

Condensed matter physics, chemistry & nanosciences Solid state physics, surfaces and interfaces


Certain, sub-stoichiometric actinide mixed oxides are prone to a low temperature phase separation, which involves the emergence of two phases: a stoichiometric one and another, which carries the entirety of the oxygen deficit. This is the case of MOX fuels ((U,Pu)O2-x) at high Pu concentrations such as those envisaged in generation IV systems. Phase separations at low temperature may also affect mixed oxides with lower average Pu contents, since, depending on the manufacturing route, a certain degree of Pu inhomogeneity may remain. This issue is all the more important in the context of Pu multi-recycling. Thus, local changes in the lattice parameters may lead to an inhomogeneous strain distribution and have deleterious effects during the manufacturing process or with respect to fuel performance. It is noteworthy that cerium (an inoccuous surrogate of plutonium) bearing mixed oxides share remarkable similarities with Pu mixed oxides. There is to our knowledge no current understanding of these phenomena and their predictive modelling, based on a physical understanding of underlying mechanisms constitutes both a technological and scientific challenge. This project therefore aims to characterise these phase separations, to determine their causes and to develop methodologies both experimental and theoretical to interpret them.
This work will mainly be performed at the IRESNE Institute (CEA Cadarache), but will be carried out in collaboration with teams from Marcoule (ICSM) as regards experimental aspects and from Saclay for numerical simulations. Other teams based abroad will also be involved in this work: the JRC in Karlsruhe and a team from ANSTO (Australian Nuclear Science and Technology Organisation) specialising in neutron diffraction. The candidate will benefit from a rich and stimulating scientific environment and will be responsible for proposing and interpreting experiments carried out on large scale scientific facilities. The skills and knowledge he or she will have acquired will be capitalized upon through papers in peer-reviewed journals and presentations at international conferences.


Département d’Etudes des Combustibles
Service d’Analyses, d’Elaboration, d’Expérimentations et d’Examens des Combustibles
Laboratoire de Caractérisation et d‘étude des Propriétés des Combustibles
Aix-Marseille Université
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