Extreme environment in nuclear reactor are known to change microstructure and hence the performance of nuclear fuels during their operation. One of the main mechanisms in guiding the microstructural changes of fuels is damage associated with the formation and migration of fission products<sup>1,2</sup>. During irradiation at aggressive reactor conditions, interaction can occur between the fuel particle and the matrix in a dispersion fuel that results in development of an interaction layer that is unstable under irradiation, which can contribute to fuel plate failure. Thus, understanding of microstructural evolution and correlation with performance is crucial in the developments of nuclear fuels. Atom Probe Tomography (APT) provide unique access to 3D distribution of microstructural features in materials at nano length scale along with near accurate chemical mapping of the elements. However, there has been limited work carried out to visualize distribution of fission products in irradiated Uranium based fuels. In current study, APT is used to elucidate microstructural changes in fuel and to quantify fission products formation after irradiations. Systematic APT study is carried out on UMo alloy fuel particles coated with a diffusion barrier layer of ZrN and dispersed in Al matrix. APT analysis on irradiated U-Mo fuel reveals uniform distribution spherical shaped clusters enriched with fission products (Figure 1). While APT might offer very high chemical and spatial resolution that no other technique can match<sup>3</sup>, challenges remain for multicomponent materials and interfaces in terms of chemical and spatial resolution. More on recent developments and challenges in elucidating complex fuel system with APT will be presented.

Challenges and opportunities in analyzing nuclear material with atom probe tomography

256th National Meeting (2018)

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