Dislocation changes under irradiation: a separated effect study
Résumé
Uranium dioxide is currently used as standard fuel for Pressurized Water Reactors. During inpile irradiation the microstructure of the UO2 fuel pellets is drastically modified. Several
phenomena, such as radiation damage accumulation, fission product implantation and
mechanical load occur simultaneously, for temperatures between 500 and 1000°C in normal
conditions, depending on the position in the pellet. Due to the recoil of fission nuclei, extended
defects are produced in the fuel, as well as bubbles. Mechanical stress could also induce
dislocations, dislocation glides and rearrangements. It has been shown experimentally that a
preferential growth of fission gas bubbles is acting on the dislocation line network. Hence, the
study of these extended defects is a necessary step to better understand and in fine to
simulate the behavior of fission gas bubbles under irradiation which is one of the most
important parameter for the PWR safety.
Using a separate-effect approach, the current study attempts to clarify the influence of these
various irradiation parameters (temperature, ion, energy, fluence, stress) on the extended
defect change. This experimental study, performed for several years, is based on ion
irradiations (JANNuS facilities in Orsay and in Saclay) and mechanical tests followed by TEM
characterizations