A method for treating in one cycle an aqueous solution resulting from a dissolution of a spent nuclear fuel in nitric acid, the aqueous solution comprising uranium(VI), plutonium(IV), americium(III), curium(III) and fission and activation products including ruthenium and technetium, the cycle comprising:
- a) a co-extraction of uranium(VI) and plutonium(IV) from the aqueous solution, the co-extraction comprising at least one contacting, in an extractor, of the aqueous solution with an organic solution S1 comprising a monoamide or a mixture of monoamides in an organic diluent, followed by a separation of the aqueous and organic solutions from each other, the monoamide(s) being of formula (I):
- wherein:
- n=1, 2 or 3;
- R1 is a straight or branched chain alkyl group comprising from 4 to 12 carbon atoms;
- and
- R2 is a straight or branched chain alkyl or alkoxy group, the chain of which is optionally interrupted one or more times by an oxygen atom and the total number of carbon atoms and, if applicable, of oxygen atoms is between 3 and 10;
- b) a decontamination of the organic solution issued from a) with respect to americium(III), curium(III) and fission and activation 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 and aqueous solutions from each other;
- c) a partitioning of the uranium(VI) and plutonium(IV) present in the organic solution issued from b) into an aqueous solution comprising either plutonium(IV) without uranium(VI), or a mixture of plutonium(IV) and uranium(VI), and an organic solution comprising uranium(VI) without plutonium(IV), the partitioning comprising:
- c1) a stripping of plutonium, in the +IV oxidation state, and of a fraction of the uranium(VI) from the organic solution issued from 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 and aqueous solutions from each other;
- c2) a re-extraction of all or part of the uranium(VI) fraction present in the aqueous solution issued from c1), the re-extraction comprising at least one contacting, in an extractor, of the aqueous solution with an organic solution S2 comprising the monoamide or the mixture of monoamides in the organic diluent, followed by a separation of the aqueous and organic solutions from each other;
- d) a decontamination of the organic solution issued from c1) with respect to technetium, the decontamination comprising:
- d1) a stripping of technetium, in the +IV oxidation state, from the organic solution issued 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 the +VII oxidation state to the +IV oxidation state, followed by a separation of the organic and aqueous solutions from each other;
- d2) a re-extraction of the uranium(VI) fraction present in the aqueous solution issued from d1), the re-extraction comprising at least one contacting, in an extractor, of the aqueous solution with an organic solution S3 comprising the monoamide or the mixture of monoamides in the organic diluent, followed by a separation of the aqueous and organic solutions from each other;
- e) a stripping of uranium(VI) from the organic solution issued from d1), the stripping comprising at least one contacting, in an extractor, of the organic solution with an aqueous solution comprising at most 0.05 mol/L of nitric acid, followed by a separation of the organic and aqueous solutions from each other;
- and
- f) optionally, a regeneration of the organic solution issued from e);
- whereby a first and a second aqueous solution decontaminated with respect americium(III), curium(III) and fission and activation products are obtained, the first aqueous solution comprising either plutonium(IV) without uranium(VI), or a mixture of plutonium(IV) and uranium(VI), and the second aqueous solution comprising uranium(VI) without plutonium(IV).