Interim Report on Task 1.2: Near Equilibrium Processing Requirements - Attrition Milling Part 1 of 2 to Lawrence Livermore National Laboratory for Contract B345772.
Stewart, M. W. A. ; Vance, E. R. ; Day, R. A. ; Eddowes, E. ; Moricca, S.
The objective of Task 1.2 has only partly been achieved as the work on Pu/U-formulations and to a significant degree on Th/U-formulations has been performed under grinding/blending conditions that did not replicate plant-like fabrication processes, particularly in the case with the small glovebox attritor. Nevertheless the results do show that actinide-rich particles, not present in specimens made via the alkoxide-route (equilibrium conditions), occur when the grinding process is not efficient enough to ensure that high-fired PuO(sub 2), ThO(sub 2) and UO(sub 2) particles are below a critical size. Our current perception is that the critical size for specimens sintered at 1350 C for 4 hours is about 5(micro)m in diameter. The critical size is difficult to estimate, as it is equal to the starting diameter of actinide oxides just visible within brannerite regions. Our larger scale attritor experiments as well as experience with wet and dry ball milling suggests that acceptable mineralogy and microstructure can be obtained by dry milling via attritor and ball mills. This is provided that appropriate attention is paid to the size and density of the grinding media, grinding additives that reduce caking of the powder, and in the case of attritors the grinding speed and pot setup. The ideal products for sintering are free flowing granules of(approx) 100(micro)m containing constituents ground to about 1(micro)m to ensure homogeneity and equilibrium mineralogy
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