Structural investigation of UO₂ films prepared by spraying-assisted combustion synthesis

With the climate change and the energy crisis that is currently upon us, nuclear energy is in the forefront once more. Most commercial nuclear power plants use uranium dioxide (UO₂) as the primary nuclear fuel due to its high melting point (2865 °C), its compatibility with cladding materials, as well as its high chemical and radiation stability. During reactor operations, UO₂ fuel becomes more radioactive, evolves chemically due to the ²³⁵U fission and the neutron capture of ²³⁸U followed by β-decay, and undergoes considerable morphological changes. The exact mechanisms behind these structural changes are unknown due to difficulties in investigating highly radioactive spent fuel. Ion irradiation of thin films of UO₂ is a suitable alternative for exploring such structural evolutions. However, the lack of simple, safe and efficient film deposition methods impede the irradiation-induced structural investigation of UO₂ at the nanoscale level.

I will report on a new target production method that utilizes the use of electrospray techniques to deposit chemically reactive layers that can be converted to actinide oxides by simple heat treatments. This method allows the control of the layer thicknesses while it provides excellent uniformity. Furthermore, this method uses the very minimum in starting materials. The targets produced were tested with a 1.7 MeV Ar²⁺ beam and measurements were made of the structural changes that took place and the overall stability of the targets. These measurements allowed us to reveal links between synthesis conditions and irradiation-driven structural changes including the origin of reduced radiation tolerance of nanoscale UO₂.