A hybrid route combining internal gelation and a single-step infiltration was investigated to prepare U 1-yNd yO 2-x sintered microspheres as a surrogate for U 1-yAm yO 2-x transmutation targets. This simplified procedure eliminates the use of successive infiltration and re-calcination steps to reach higher dopant concentrations. The use of starch as a pore-forming agent in the internal gelation process for fabricating porous uranium oxide microspheres has been studied in detail to improve the conditions for an efficient infiltration with dopant solution. While the crystalline structure and composition of dried microspheres was not significantly affected by the process conditions, the onset of the UO 3 to U 3O 8 phase transformation during calcination is shifted from 803 K to 823 K when starch was used. Biphasic mixtures of β-UO 3 and α-U 3O 8 were formed when calcination temperatures between 833 and 853 K were applied. High accessible porosity levels (26–33%) were measured after calcination, and this resulted in efficient infiltration behavior allowing to reach average dopant levels up to y = 30 mol% after sintering. Microstructural features of the sintered microspheres (grain size, porosity distribution, dopant homogeneity) are discussed.
ASJC Scopus subject areas
- Materials Science(all)
- Nuclear and High Energy Physics
- Nuclear Energy and Engineering