Method for separating uranium (VI) from actinides(IV) and/or actinides (VI) and its uses

A method for reprocessing an irradiated nuclear fuel comprising:

• i) co-extracting uranium(VI), plutonium(IV) and neptunium(VI) from a first aqueous acidic phase resulting from the dissolution of said nuclear fuel in an acid, by bringing said aqueous acidic phase in contact with an organic phase which is immiscible with water and which contains an extractant, and then by separating said first aqueous phase from said organic phase;
• ii) back-extracting plutonium (III) from the organic phase resulting from step i) without back-extracting uranium and neptunium by bringing said organic phase in contact with a second aqueous acidic phase which contains uranium(IV) as a reducing agent capable of reducing plutonium(IV) into plutonium(III), and then by separating said organic phase and said second aqueous phase;
• iii) oxidizing uranium(IV) and neptunium(IV) present in the organic phase resulting from step ii) into uranium(VI) and neptunium(VI);
• which process further comprises the step of separating uranium(VI) from the neptunium(VI) present in the organic phase resulting from step iii), by
• a) bringing said organic phase in contact with a third aqueous acidic phase containing at least one lacunary heteropolyanion and a reducing agent capable of reducing neptunium(VI) without reducing uranium(VI), for stripping neptunium from said organic phase without stripping uranium;
• and
• b) separating the organic phase resulting from step a) from the aqueous phase resulting from step a) and thereby separating said uranium from neptunium.

A method for reprocessing an irradiated nuclear fuel comprising:

• i) co-extracting uranium(VI), plutonium(IV) and neptunium(VI) from a first aqueous acidic phase resulting from the dissolution of said nuclear fuel in an acid, by bringing said aqueous acidic phase in contact with an organic phase which is immiscible with water and which contains an extractant, and then by separating said first aqueous phase from said organic phase;
• ii) back-extracting plutonium in the oxidation state (III) and neptunium in the oxidation state (V) from the organic phase resulting from step i) without back-extracting uranium by bringing said organic phase in contact with a second aqueous acidic phase which contains a reducing agent capable of reducing plutonium(IV) into plutonium(III) and neptunium (VI) into neptunium(V), and then by separating said organic phase and said second aqueous phase;
• which process further comprises the step of separating uranium(VI) present in the organic phase resulting from step ii) from traces of plutonium and neptunium which have not been back-extracted from the organic phase at step ii), by
• a) bringing said organic phase in contact with a third aqueous acidic phase containing at least one lacunary heteropolyanion, for stripping plutonium and uranium from said organic phase without stripping uranium;
• and
• b) separating the organic phase resulting from step a) from the aqueous phase resulting from step a) and thereby separating said uranium from neptunium.