Preparation of UO2, ThO2 and (Th,U)O-2 pellets from photochemically-prepared nano-powders
Journal article, 2016

Photochemically-induced preparation of nano-powders of crystalline uranium and/or thorium oxides and their subsequent pelletizing has been investigated. The preparative method was based on the photochemically induced formation of amorphous solid precursors in aqueous solution containing uranyl and/or thorium nitrate and ammonium formate. The EXAFS analyses of the precursors shown that photon irradiation of thorium containing solutions yields a compound with little long-range order but likely "ThO2 like" and the irradiation of uranium containing solutions yields the mixture of U(IV) and U(VI) compounds. The U-containing precursors were carbon free, thus allowing direct heat treatment in reducing atmosphere without pre-treatment in the air. Subsequent heat treatment of amorphous solid precursors at 300-550 degrees C yielded nano-crystalline UO2, ThO2 or solid (Th,U)O-2 solutions with high purity, well-developed crystals with linear crystallite size <15 nm. The prepared nano-powders of crystalline oxides were pelletized without any binder (pressure 500 MPa), the green pellets were subsequently sintered at 1300 degrees C under an Ar:H-2 (20:1) mixture (UO2 and (Th,U)O-2 pellets) or at 1600 degrees C in ambient air (ThO2 pellets). The theoretical density of the sintered pellets varied from 91 to 97%. 2015 Elsevier B.V. All rights reserved.

Uranium(IV) oxide

UV radiation

EXAFS

Pelletizing

Thorium oxide

Nanoparticles

Author

T. Pavelkova

Czech Technical University in Prague

V. Cuba

Czech Technical University in Prague

E. de Visser-Tynova

Nuclear Research And Consultancy Group

Christian Ekberg

Chalmers, Chemistry and Chemical Engineering, Energy and Material, Nuclear Chemistry

Industrial Materials Recycling

I. Persson

Swedish University of Agricultural Sciences (SLU)

Journal of Nuclear Materials

0022-3115 (ISSN)

Vol. 469 57-61

Subject Categories

Materials Engineering

DOI

10.1016/j.jnucmat.2015.11.041

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12/9/2020