Dissymmetric N,N-dialkylamides, the synthesis thereof and uses of same

A method for separating totally or partially uranium(VI) from plutonium(IV), uranium(VI) and plutonium(IV) being in an acid aqueous solution, comprising the following steps:

• a) a co-extraction of uranium and plutonium from the aqueous solution, the co-extraction comprising at least one contacting of the aqueous solution with an organic solution comprising an N,N-dialkylamide or mixture of N,N-dialkylamides of formula(I):
• where R is a linear or branched alkyl group having 8 to 15 carbon atoms, as extractant in solution in an organic diluent, followed by a separation of the aqueous solution from the organic solution;
• b) a stripping of plutonium, in oxidation state +IV, and of a fraction of uranium from the organic solution resulting from step a), the stripping comprising at least one contacting of the organic solution with an aqueous solution comprising from 0.1 mol/L to 0.5 mol/L of nitric acid, followed by a separation of the organic solution from the organic solution;
• and
• c) an extraction of all or part of the uranium fraction contained in the aqueous solution resulting from step b), the extraction comprising at least one contacting of the aqueous solution with an organic solution identical to the organic solution of step a), followed by a separation of the aqueous solution from the organic solution;
• whereby there are obtained an aqueous solution comprising either plutonium without uranium, or a mixture of plutonium and uranium, and an organic solution comprising uranium without plutonium.

A single-cycle method for processing an aqueous solution resulting from a dissolution of a spent nuclear fuel in nitric acid, the aqueous solution comprising uranium, plutonium, americium, curium and fission products including technetium, the cycle comprising the following steps:

• a) a co-extraction of uranium and plutonium from the aqueous solution, the co-extraction comprising at least one contacting, in an extractor, of the aqueous solution with a first organic solution comprising a N,N-dialkylamide or mixture of N,N-dialkylamides of formula (I):
• where R is a linear or branched alkyl group having 8 to 15 carbon atoms, as extractant in solution in an organic diluent, followed by a separation of the aqueous solution from the organic solution;
• b) a decontamination of the organic solution resulting from step a) with respect to americium, curium and fission products, the decontamination comprising at least one contacting, in an extractor, of the organic solution with an aqueous solution comprising from 0.5 mol/L to 6 mol/L of nitric acid, followed by a separation of the organic solution from the organic solution;
• c) a partitioning of the uranium and plutonium contained in the organic solution resulting from step b) into an aqueous solution comprising either plutonium without uranium, or a mixture of plutonium and uranium, and an organic solution comprising uranium without plutonium, the partitioning comprising:
• c1) a stripping of plutonium, in oxidation state +IV, and of a fraction of uranium from the organic solution resulting from step b), the stripping comprising at least one contacting, in an extractor, of the organic solution with an aqueous solution comprising from 0.1 mol/L to 0.5 mol/L of nitric acid, followed by a separation of the organic solution from the organic solution;
• c2) an extraction of all or part of the uranium fraction contained in the aqueous solution resulting from c1), the extraction comprising at least one contacting, in an extractor, of the aqueous solution with a second organic solution identical to the organic solution of step a), followed by a separation of the aqueous solution from the organic solution;
• d) a decontamination of the organic solution resulting from c1) with respect to technetium, the decontamination comprising:
• d1) a stripping of technetium, in oxidation state +IV, from the organic solution resulting from c1), the stripping comprising at least one contacting, in an extractor, of the organic solution with an aqueous solution comprising from 0.1 mol/L to 3 mol/L of nitric acid and at least one reducing agent capable of reducing technetium from oxidation state +VII to oxidation state +IV, followed by a separation of the organic solution from the organic solution;
• d2) an extraction of the uranium fraction contained in the aqueous solution resulting from d1), the extraction comprising at least one contacting, in an extractor, of the aqueous solution with an organic solution identical to the organic solution of a), followed by a separation of the aqueous solution from the organic solution;
• e) a stripping of uranium from the organic solution resulting from d1), the stripping comprising at least one contacting, in an extractor, of the organic solution with an aqueous solution comprising no more than 0.05 mol/L of nitric acid, followed by a separation of the organic solution from the organic solution;
• and
• f) a regeneration of the organic solution resulting from step e);
• whereby a first and a second aqueous solution are obtained, decontaminated with respect to americium, curium and fission products including technetium, the first aqueous solution comprising either plutonium without uranium, or a mixture of plutonium and uranium, and the second aqueous solution comprising uranium without plutonium.