Thirty-Plus Years of Solvent Extraction Development for Minor Actinide Separations in Europe

Recycling used nuclear fuel contributes significantly to the sustainability of nuclear energy production. The well-established PUREX process to separate uranium and plutonium is pivotal to this recycling, minimizing the need for uranium mining and milling. Additionally separating and recycling the minor actinides — most notably americium — further contributes to this goal: By reducing the long-term decay heat of the final waste to be disposed of in a deep geologic repository, its volume is utilized more efficiently. Internationally, efforts are underway to develop novel solvent extraction processes to separate americium from used nuclear fuels. For more than thirty years, collaborative European research programs have dealt with the development of solvent extraction systems and flowsheets. Initially, a suite of three consecutive processes (An(III)/Ln(III) co-extraction, An(III)-Ln(III) separation, and Am(III)-Cm(III) separation) was required to obtain an americium product. This was later reduced to two and finally only one process, directly extracting americium from the PUREX raffinate solution. Alternatively, processes to co-separate neptunium, plutonium, americium, and curium were also developed, addressing the so-called homogeneous recycling strategy. This paper summarizes the progress made in past and current EURATOM programs on actinides separations, focusing on the development of new extractants and flowsheet trials. Without steady funding and a highly motivated and collaborative team this progress certainly would not have been achieved.