NSUF 24-5000: Stability limits of the gas bubble superlattice in neutron irradiated U-Mo fuel: A 3D multi-modal and multi-scale study

The proposed research aims to investigate the stability and collapse mechanism(s) of the gas bubble superlattice (GBS) in U-Mo fuel during high burnup structure (HBS) development. The study hypothesizes that the misorientation angle of HBS polygonised sub-domains influences the stability of the GBS, leading to its collapse at high fission densities. To test this hypothesis, a multi-modal and multi-scale approach will be employed, combining 3D focused ion beam (FIB) tomography with sequential back-scattered electron (BSE), sequential electron back-scattered diffraction (EBSD), and transmission electron microscopy (TEM) analysis. Two U-Mo fuel specimens irradiated up to intermediate fission densities will be examined, allowing for the coexistence of intact and collapsed GBS regions. The expected period for experiment execution, data analysis, and reporting will be within three months from award, granted instruments availability. The successful completion of this research is anticipated to significantly advance state-of-the-knowledge regarding fuel behavior during irradiation. Specifically, this study will contribute to the fundamental understanding of fission products behavior and microstructural evolution in U-Mo fuels. By elucidating the mechanisms responsible for the instability of ordered defect nanostructures, this study will provide invaluable data for future development of modeling tools (such as phase field models or atomic kinetic Monte Carlo) simulating defects behavior under irradiation for both fission and fusion applications. The expected scientific outcome from this experiment is two publications in peer-reviewed journals. One publication will focus on the 3D BSE and EBSD reconstruction, which will provide data on grain structure evolution in U-Mo fuel during HBS development. The second one will instead focus on the TEM analysis, which will unveil the connection between GBS stability and grain boundary misorientation.

Additional Info

Field	Value
Award Announced Date	2024-05-29T11:31:29.67
Awarded Institution	Eni S.p.A.
Facility Tech Lead	Alina Montrose
Irradiation Facility
PI	Daniele Salvato
PI Email	[email protected]
Project Type	RTE
RTE Number	None