The microstructure of nuclear graphite

The microstructure of graphite and its oxidation have been individually investigated at length. When catalytic impurities are removed from graphite, oxidative attack takes place preferentially from the exposed edges, or active sites of the graphite crystallites. This provides valuable insights regarding the underlying crystallography and fundamental structure of graphite which are not immediately evident from a raw topographical examination using, for example, microscopy. Using new techniques, such as field emission guns and sensitive detectors, modern scanning electron microscopes are capable of operating down to a few hundred volts. When surface features and effects are being considered this is absolutely critical as the low voltages imply low sample penetration of the electrons, thus the true surface morphology of the material can be resolved. In combination, these methods provide a valuable technique for investigating the microstructures found in graphite. The approach has been applied to natural but is even more relevant to synthetic graphite and therefore nuclear materials, which have an exceedingly complex microstructure. The revealed structural qualities can be related to the manufacturing processes in order to gain additional insights into the material and uncover potential options for improving the properties.