A dissymmetric RN,N-dialkylamides of formula (I) in which: R.sup.1 represents a linear C.sub.1 to C.sub.4 alkyl, R.sup.2 represents a linear C.sub.1 to C.sub.10 alkyl, and R.sup.3 represents a linear or branched C.sub.6 to C.sub.15 alkyl, where R.sup.3 is different from a n-octyl, n-decyl, n-dodecyl, 2-ethylhexyl and 2-ethyloctyl group when R.sup.1 represents a n-butyl group and R.sup.2 represents an ethyl group. A method for synthesising the N,N-dialkylamides, and uses of same for extracting uranium and/or plutonium from an aqueous acid solution or for fully or partially separating the uranium from the plutonium contained in an aqueous acid solution and a solution resulting from the dissolution of spent nuclear fuel in nitric acid. A method for treating an aqueous solution resulting from the dissolution of spent nuclear fuel in nitric acid, which allows the uranium and the plutonium contained in the solution to be extracted, separated and decontaminated in a single cycle.

A dissymmetric RN,N-dialkylamides of formula (I) in which: R.sup.1 represents a linear C.sub.1 to C.sub.4 alkyl, R.sup.2 represents a linear C.sub.1 to C.sub.10 alkyl, and R.sup.3 represents a linear or branched C.sub.6 to C.sub.15 alkyl, where R.sup.3 is different from a n-octyl, n-decyl, n-dodecyl, 2-ethylhexyl and 2-ethyloctyl group when R.sup.1 represents a n-butyl group and R.sup.2 represents an ethyl group. A method for synthesising the N,N-dialkylamides, and uses of same for extracting uranium and/or plutonium from an aqueous acid solution or for fully or partially separating the uranium from the plutonium contained in an aqueous acid solution and a solution resulting from the dissolution of spent nuclear fuel in nitric acid. A method for treating an aqueous solution resulting from the dissolution of spent nuclear fuel in nitric acid, which allows the uranium and the plutonium contained in the solution to be extracted, separated and decontaminated in a single cycle.

The use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

The use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

The-use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

The-use of carbamides as extractants for fully or partially separating uranium(VI) from plutonium(IV) in an aqueous solution obtained by dissolving a spent nuclear fuel in nitric acid, by method of liquid-liquid extraction, without carrying out any reduction of the plutonium(IV) to plutonium(III). The invention also relates to new carbamides. Uses are the processing of spent nuclear fuels based on uranium (especially uranium oxides—UOX) or uranium and plutonium (especially mixed uranium and plutonium oxides—MOX).

A method for treating retained plutonium in a waste organic phase of a plutonium uranium reduction extraction (PUREX) process is provided. The waste organic phase of the PUREX process contains an organic solvent and plutonium, and the method includes contacting the waste organic phase of the PUREX process with an aqueous back extraction solution containing 2,6-pyridinedicarboxylic acid for back extraction to obtain a plutonium back extraction product; and the plutonium in the back extraction solution may be loaded onto the column for adsorption, transformation and desorption by an anion exchange column, ultimately recovering plutonium in the back extraction solution.

A method for treating retained plutonium in a waste organic phase of a plutonium uranium reduction extraction (PUREX) process is provided. The waste organic phase of the PUREX process contains an organic solvent and plutonium, and the method includes contacting the waste organic phase of the PUREX process with an aqueous back extraction solution containing 2,6-pyridinedicarboxylic acid for back extraction to obtain a plutonium back extraction product; and the plutonium in the back extraction solution may be loaded onto the column for adsorption, transformation and desorption by an anion exchange column, ultimately recovering plutonium in the back extraction solution.

Reactor target assemblies are provided that can include a housing defining a perimeter of at least one volume and Np or Am spheres within the one volume. Reactor assemblies are provided that can include a reactor vessel and a bundle of target assemblies within the reactor vessel, at least one of the target assemblies comprising a housing defining a volume with Np or Am spheres being within the volume. Irradiation methods are also provided that can include irradiating Np or Am spheres within a nuclear reactor, then removing the irradiated spheres from the reactor and treating the irradiated spheres.

The present invention relates to a method for recovering plutonium from spent radioactive fuel. In one embodiment, the method comprises steps of extracting tetravalent plutonium from an aqueous solution of the spent radioactive fuel using a first organic solvent comprising tributyl phosphate; reducing tetravalent plutonium to trivalent plutonium by adding to an organic phase a second organic solvent comprising dimethylhydroxylamine; and stripping plutonium into the aqueous phase for recycling by adding an aqueous dilute acid solution into an organic phase. The method can significantly improve the efficiency of recovering plutonium from spent radioactive fuel compared with HAN stripping, and at the same time, can avoid the problems resulting from U(IV) reduction and extraction.