Immobilization of Uranium in the Al2O3 Matrix

The immobilization of uranium in the Al2O3 matrix was studied. For the modification of Al2O3 precursors containing 10 wt % UO2(NO3)2 three methods were applied: 1) heating the precursor in air for 5 h at temperatures of 573, 973, and 1273 K, 2) treatment of the precursor with a 0.5 M solution of hydrazine hydrate (HH) for 2 h, drying to dry air moisture content at 383 K, followed by heating in air for 5 h at temperatures of 573, 973, and 1273 K, and 3) treatment of the precursor with a 2.0 M ammonia solution, followed by drying and heating, as in method (2). X-ray diffraction analysis of the synthesized composites revealed UO3 hydrates of various compositions after calcination of the materials to T ~600 K and U3O8 after calcination at T> 950 K. After 24 h of contact of the composites with H2O at 298 K, the leaching of uranium from the studied samples was ~(10–2–10–3) g U/(g day) for the samples calcined at 383 and 573 K and ~(10–4–10–5) g U/(g day) for those calcined at 973 and 1273 K.