In all these studies, the association between the transition and lateral cracking in the oxide layer depicts some interaction between the mechanical behaviour of the system, and its corrosion kinetics, but does not provide a clear understanding of the morphology of the metal:oxide interface during the corrosion process, at the nanometre level. Understanding why this transition behaviour happens is critical when modelling the rate of growth of oxide, and therefore to the lifetime prediction of Zr clads, and ultimately to the safety of nuclear power reactors. No model will be complete without a nanoscale understanding of what is going on during oxidation. Thus, it is essential that the oxide scale and the top layers of the metal are studied at nanometre resolution to reveal the detailed structural and chemical changes associated with diffusion of oxygen and the resulting oxidation of the metal. Whilst a number of techniques have been employed for this purpose, it is clear that various techniques within transmission electron microscopy (TEM) will be among the most versatile and informative for this purpose, although additional information can be added by techniques such as atom probe tomography.
