Recent advances and actual status of actinides and Lanthanides research at the IPEN-CNEN/Sao Paulo, Brazil

This paper focuses on the experience acquired with the operation of a pulsed columns solvent extraction unit for the refining of yellowcake produced from the industrial treatment of monazite sand, and the further experimental production of ammonium diuranate, uranium oxides, uranyl tricarbonate and tetra-and hexafluorides of uranium at the pilot plant scale. Special studies have been devoted to the decontamination of the rare earth elements, thorium and zirconium. The refining of thorium in a solvent extraction composite column and the experimental production of crystallized nuclear grade thorium nitrate at the pilot plant scale is also discussed. Thorium hydroxide sludges and crystallized thorium sulphate are used as raw materials, both produced from an alkaline breaking up monazite process. Developmental efforts have also been directed towards the rare earth fractionation using as a first step previous chemical fractionation of the rare earth chlorides and the ion-exchane individual fractionation as the final process step to obtain extremely pure oxides. Finally, the establishment of analytical procedures as an important support to the technical work is emphasized. An extended version of this work will be published elsewhere. (author)