2007 International RERTR Meeting

Abstracts and Available Papers Presented at the Meeting

Transmission Electron Microscopy Investigation of Irradiated U-7 wt% Mo Dispersion Fuel

S. Van den Berghe, W. Van Renterghem and A. Leenaers
Nuclear Materials Science Institute, Microstructural and Non-destructive Analyses
SCK.CEN, Boeretang 200, 2400 Mol, Belgium

ABSTRACT

The microstructural evolution of atomised U-7wt%Mo alloy fuel under irradiation was investigated with transmission electron microscopy on material from the experimental fuel plates used in the FUTURE irradiation. The unsatisfactory irradiation behaviour of this atomised U(Mo) alloy dispersion fuel during this experiment was derived to be related to the properties of the interaction layer formed between the U(Mo) particles and the Al matrix. It is assumed to become amorphous under irradiation and as such cannot retain the fission gas in stable bubbles. As a consequence, gas filled voids are generated between the interaction layer and the matrix, causing the fuel plate to swell, resulting in failure.
The present analysis confirms the assumption that the U(Mo)-Al interaction layer is completely amorphous after the irradiation. The Al matrix and the individual U(Mo) particles, with their cellular substructure, have retained their crystallinity, although evidence for the amorphisation of the low Mo content phase on the cell boundaries is also found.
It was furthermore observed that the fission gas generated in the U(Mo) particles has formed a bubble superlattice which is coherent with the U(Mo) lattice. Bubbles of roughly 1-2 nm size formed a 3-dimensional lattice with a lattice spacing of 6-7 nm.

 

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