Intitulé du poste : Post-doc - Time-resolved in-situ study, by X-ray diffraction under synchrotron radiation, of structural evolutions in a high temperature oxidized zirconium alloy
Ville : Gif-sur-Yvette
Laboratoire/Institut : CEA-Saclay (DEN/DANS/DMN/SRMA)
Description du poste : In certain hypothetical accident situations in pressurized-water nuclear reactors (PWRs), the zirconium alloy cladding of fuel rods, which constitutes the first barrier for the containment of radioactive products, can be exposed for a few minutes to water vapor at high temperature (up to 1200 ° C), before being cooled and then quenched with water. The cladding material then undergoes numerous structural and metallurgical evolutions: formation of an oxide layer (zirconia), diffusion of oxygen in the underlying metal, phase transformations of the metal and the oxide. These evolutions introduce internal stresses likely leading to damaging of the material weakened by the oxidation. These structural evolutions are still not well known, in particular because they are difficult to study under these conditions.
In order to follow the high temperature oxidation process of a zirconium alloy (Zircaloy-4), first in-situ measurements of X-ray diffraction under synchrotron radiation on the French CRG D2AM beamline at the ESRF have recently been carried out using a prototype furnace that allows to control very precisely the atmosphere composition. The structural and microstructural evolutions of zirconia as a function of temperature and time during heating, high temperature oxidation and cooling have thus been measured.

The postdoctoral fellow will perform two tasks:
1. Deepen the analyzes made following the experiments already carried out, to:-Determine the evolution of phase volume fraction (monoclinic zirconia / tetragonal zirconia) as a function of time and temperature;-Analyze the internal stresses generated during the growth of the oxide;-Analyze the oxidized samples at different temperatures (measured at 900 ° C, 1000 ° and 1100 ° C).
2. Prepare a new proposal for complementary experiments in 2020, just after the reopening of the ESRF.

To carry out this project, we will work in collaboration with the two essential laboratories for this type of experiment: IRCER (University Limoges) and the laboratory PIMM (ENSAM Paris) and respectively René Guinebretière and Olivier Castelnau.

Skills: Good knowledge of X-ray diffraction, experimental approach and data analysis (Rietveld refinement, texture analysis, residual stresses ...). Experience in using synchrotron radiation sources will be also appreciated.

Qualification:Thesis, expected profile: PhD thesis in materials science or condensed matter physics with an expertise on experimental studies of crystallographic structures.
Durée du contrat : 12 mois
Date de prise de fonction : 01-01-2020
Personne à contacter : Raphaëlle GUILLOU, Jean-Luc BÉCHADE
Téléphone :
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