Separation of actinide redox species with cation exchange chromatography and its application to the analysis of spent fuel leaching solutions

Separation methods on a Dionex CS10 cation exchange chromatography column have been investigated by on-line coupling of an ion chromatograph to an ICP-MS. In spent nuclear fuel, isobaric interferences of Am, Pu and U often hinder direct mass spectrometric measurements of these elements. Am and U could easily be separated as they exist in different oxidation states (Am3+ and UO22+). In order to separate Pu, Pu has been oxidised to PuO22+ with KMnO4. The oxidised Pu could so be eluted first, together with Np, well separated from the U and Am fraction. This separation method has been applied to the determination of the isotopic composition of Pu and to the estimation of the Am concentrations in leaching solutions. Furthermore, the separation method has been applied to perform a speciation between the reduced (Pu3+, Pu4+) and the oxidised ions (PuO2+, PuO22+) of Pu in a leaching solution. The change of the oxidation state composition could so be followed in a leaching solution in contact with air.