Abstract: Process for preventing the extraction of technetium and/or rhenium, particularly during the extraction of uranium and/or plutonium by an organic solvent.This process permitting the extraction of a chemical element, such as uranium or plutonium present in an aqueous solution containing both said element, technetium and/or rhenium and zirconium and/or hafnium consists of contacting the aqueous solution with an organic solvent able to extract said element, wherein for preventing the extraction of the technetium and/or rhenium with said element, to the aqueous solution is added a zirconium and/or hafnium complexing agent in a quantity adequate for complexing all the zirconium and/or hafnium, said agent being soluble in the aqueous solution.

Abstract: Process for the recovery of the uranium present in a phosphoric acid solution by bringing the said solution into contact with an organic solvent suitable for extracting the uranium, wherein the organic solvent comprises a system of extractants constituted by an acid organophosphorus compound and by a neutral phosphine oxide of formula: ##STR1## in which the radicals R.sub.1, R.sub.2 and R.sub.3 are identical or different alkyl, aryl or alkoxyalkyl radicals, at least one of the radicals R.sub.1, R.sub.2 and R.sub.3 being an alkoxyalkyl radical.

Abstract: Process for the separation of americium from curium contained in an aqueous nitric solution, wherein the initial solution undergoes oxidation at ambient temperature in the presence of phosphoric acid or phosphate ions at a concentration at the most equal to 0.1 mol per liter in such a way as to pass the americium at valency VI, the thus treated solution is brought into contact with a slightly reducing organic solvent having a high affinity for americium at valency VI in such a way as to extract the americium in the organic phase, the organic phase containing the americium at valency VI is then washed, followed by the re-extraction of the americium in the organic phase by means of an aqueous solution.

Abstract: The method of selective stripping from plutonium-loaded organic solvents which may also contain uranium consists in passing the organic solvent in countercurrent contact with an aqueous solution of a salt of hydroxylamine and formic acid, the concentration of formic acid in the reaction medium being within the range of 1M to 5M.The method finds an application in the stripping of plutonium from trilaurylamine diluted in an aromatic hydrocarbon such as tert-butyl benzene or in the separation of uranium and plutonium contained in tributylphosphate diluted in an aliphatic hydrocarbon such as dodecane.

Abstract: An anion exchange is carried out between an aqueous solution of a hydroxylamine salt and an organic solution of a formiate of an amine which is insoluble in water in accordance with the reaction:NH.sub.2 OH . HX.sub.aq. + A . HCOOH.sub.org. .fwdarw. A . HX.sub.org. + NH.sub.2 OH . HCOOH.sub.aq.whereA represents the amine which is insoluble in water andX represents the anion of the starting hydroxylamine salt.