Determination of the Crystal Structures of Some Uranium Compounds by Means of X-Ray and Neutron Diffraction

摘要

In industrial uranium processing or reprocessing procedures, aqueous uranyl nitrate solutions are an intermediate product. The compounds, whose structures are reported, might prove valuable as alternative crystallization products to existing methods of extracting the uranium from solution. The compounds are obtained by the addition of hydroxylammonium to the uranyl nitrate solution and are of the general formula UO sub 2 (NH sub 2 O) sub 2 .xH sub 2 O) where x can take the values zero, two, three and four. In addition a compound of the formula UO sub 2 (NH sub 2 O) sub 2 .2(NH sub 2 CH).2H sub 2 O was obtained. The UO sub 2 (NH sub 2 O) compound crystallized in a monoclinic crystal form. Crystals large enough for neutron diffraction were not obtained. The structure of the UO sub 2 (NH sub 2 O) sub 2 .2H sub 2 O could not be solved because only disordered crystalline material was available. The structure of UO sub 2 (NH sub 2 O) sub 2 .3H sub 2 O was solved by means of room- and low-temperature neutron diffraction. The unit cell is orthorhombic. The structure of alpha -UO sub 2 (NH sub 2 O) sub 2 .4H sub 2 O was investigated by means of room-temperature x-ray and room- and low-temperature neutron diffraction. The unit cell is triclinic. This compound strongly resembles the trihydrate. The UO sub 2 (NH sub 2 O) sub 2 .2(NH sub 2 OH).2H sub 2 O compound gave crystals large enough for single crystal x-ray but not neutron diffraction. The unit cell is orthorhombic. The characteristic powder patterns (indexed except for the dihydrate compound) of the above compounds are reported. (Atomindex citation 09:390119)