Development of U6Fe-Al dispersions for the use of LEU in research and test reactors

For some time now, efforts are being made to develop fuel dispersions that would permit the use of low (∼ 20% 235-U) enriched uranium (LEU) instead of the currently used highly (∼ 93% 235-U) enriched uranium (HEU) in research and test reactors. Since penalties in the performance of the reactor have to be avoided, the 235-U content in the dispersion has at least to be retained at current levels. On account of their high U-densities, the major development effort has been focussed on the uranium silicides [U3Si, U3Si(Al), and U3Si2- based dispersions. With silicides as dispersants, it is possible to fabricate fuel element plates with U-densities in the dispersion of about 6.0 g U/cm3. In comparison to the silicides, the U6Fe-phase offers several advantages namely: - higher U-density (∼ 17.0 g U/cm3); - relative ease of formation compared to U3Si; - possible advantages with regard to reprocessing of the spent fuel due to the absence of silicon. The studies outlined here were therefore performed with a view to investigating the preparation, reaction behaviour and dimensional stability after heat treatment of U6Fe-Al dispersions