A model based upon the cluster dynamics approach was proposed in order to describe point defect agglomeration in metals under irradiation. This model was restricted to materials where point defect diffusion was isotropic and was therefore not applicable to anisotropic metals such as Zr. Following an approach proposed by Woo, the model was extended here to the case where self-interstitial atom diffusion was anisotropic. The model was then applied to the loop microstructure evolution of a Zr thin foil irradiated with electrons in a high-voltage microscope. The inputs were first validated by comparing numerical results with experimental results. Further calculations were performed to deduce the effect of thin foil orientation upon the dislocation loop microstructure under irradiation. One result was that it was possible to reproduce, for certain orientations, the so-called unexpected vacancy loop growth which was experimentally observed in electron-irradiated Zr. This effect was directly linked to self-interstitial atom diffusion anisotropy.

Effect of Self-Interstitial Diffusion Anisotropy in Electron-Irradiated Zirconium - a Cluster Dynamics Modeling. F.Christien, A.Barbu: Journal of Nuclear Materials, 2005, 346[2-3], 272-81