Processing of the nuclear spent fuels

Recycling of nuclear spent fuels aiming to prepare MOx (mixed oxide (U,Pu)O-2) fuels became since a few years a mature industry in France and in the world. This recycling requires chemical processing of the spent fuels in view of the separation of plutonium and uranium, valuable for their potential energy content, from the nuclear wastes i.e. fission products and minor actinides (neptunium,, americium and curium). The chemical process employed world wide for nuclear fuel reprocessing is the so-called PUREX process based on hydrometallurgical operations. After dissolution of the spent fuel with a concentrated nitric acid solution , the required separations are performed by liquid-liquid extraction using an organic solvent made of a mixture of tri-n-butylphosphate are diluted in aliphatic hydrocarbons. To master the implementation of these complex industrial operations, which involve redox, acido-basic, complexation and immiscible phase distribution reactions, the concepts of the analytical chemistry of solutions, for which professor Bernard Tremillon became famous, were found highly successful. The dissolution of nuclear spent fuels and the separations by liquid-liquid extraction will be presented in this article as examples. Analytical chemistry of solutions is also used today as a conceptual framework for the design of complementary separation methods of nuclear wastes, as in the case of neptunium, within the 30 December 1991 law.