The separation of plutonium from irradiated nuclear fuel was originally developed in the nuclear weapons programmes of the 1940s and 1950s. Since nuclear weapons require plutonium of high fissile (239Pu) content, irradiation times in production reactors were short and burnups were low, no more than a few hundred MWd tonne 1. In these feed materials, the fission product loadings were therefore also low, and the content of higher actinides was small, so that they presented a much less severe challenge to separations technology than modern, high burnup fuels from civil reactors. In addition, little attention was paid to waste management in early weapons’ production programmes.

All large scale separations depend on the diverse redox chemistry which characterises the mid-actinides (see Table 3). In the media of interest for separations, the substantial chemical differences (for example in solubility in aqueous or non-aqueous solvents, or in affinity for a complexant) between the linear dioxo “actinyl” ions, MO2+/2+ formed by oxidation states v and vi, and the ‘‘simple’’ M3+/4+ ions formed by lower oxidation states generally provide the basis of useful separations. Solvent extraction processes, which are the mainstay of current technology, often exploit the differing affinity of different actinide species for selective complexants, usually O-donor ligands. The following examples are not an exhaustive description but serve to illustrate the diversity of processes which have been explored or used, and of the waste streams which can be produced.