Recent Results of Microstructural Characterization of Irradiated Light Water Reactor Fuels using Scanning and Transmission Electron Microscopy

Recent electron microscopy investigations are presented with an emphasis on properties related to the safe extended operation of nuclear fuel. In particular, this article considers the formation of the high burnup structure (HBS), the prevailing microstructural aspects associated to spent fuel aging, and the release of fission products under accidental condition. Examples of microstructures associated with transient-tested samples but also with very high burnup fuel or heterogeneous mixed oxides (MOX) are presented together with results on damage formation in UO 2 samples doped with 238 Pu to study the specific effect of alpha damage on the microstructure during the cooling/storage time of irradiated fuel. Examples of single-effect studies (e.g., on the behavior of tellurium, a typical volatile fission product) using ion implantations are also presented.