Analytical Sciences

Selective Extraction of Uranium from a Mixture of Metal or Metal Oxides by a Tri-n-butylphosphate Complex with HNO₃ and H₂O in Supercritical CO₂

Takashi SHIMADA,*^,*** Sinya OGUMO,*** Kayo SAWADA,* Youichi ENOKIDA,* and Ichiro YAMAMOTO**

*EcoTopia Science Institute, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
**Department of Materials, Physics and Energy Engineering, Nagoya University, Furo-cho, Chikusa, Nagoya 464-8603, Japan
***Nuclear Energy Systems Engineering Center, Mitsubishi Heavy Industries, Ltd., 16-5 Konan 2-chome, Minato, Tokyo 108-8251, Japan

In order to study the decontamination nature of the reactive extraction of uranium in the presence of some metal chemicals using a single-phase mixture of HNO₃, H₂O and tri-n-butylphosphate (TBP) in supercritical carbon dioxide (SC-CO₂), we measured the decontamination factors (DFs) of Sr, Zr, Mo, Ru, Pd, Ce and Nd from their mixture with U. These elements were originally added to U₃O₈ as SrO, ZrO₂, MoO₃, RuO₂, Pd, CeO₂ and Nd₂O₃, and the extraction was performed at 18 MPa and 323 K with the single-phase mixture. The DFs for these elements were determined to be greater than 10³ when the molecular ratio of U to TBP in the extracted complex was greater than 0.3. Dilution by SC-CO₂ effectively increased the DFs.

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