Spectroscopic Speciation Studies on the Actinide Lanthanide SEParation Process (ALSEP)

摘要

Separation of the minor actinides is a critical component to the management and storage of used nuclear fuel. Transmutation of the minor actinides is a viable option for reducing the volume and radiotoxicity of spent nuclear fuel waste.1 The minor actinide americium is the most significant contributor to the radiotoxicity of the resultant used nuclear fuel after 300 years if uranium, plutonium and neptunium are removed. Due to the chemical similarities of the actinides and lanthanides, separating americium from the fission product lanthanides is challenging. Liquid-liquid separation processes that exploit the electronic structure differences between the actinides and lanthanides separate these ions by employing hard bases to bind the lanthanides and soft bases to selectively bind the actinides. The Actinide Lanthanide SEParation (ALSEP) process,2 a liquid-liquid extraction system which employs 2-ethylhexylphosphonic acid mono-2-ethylhexyl ester (HEH[EHP]) and N,N,N',N'-tetra(2-ethylhexyl)diglycolamide (T2EHDGA) in one organic phase, has shown great efficiency and promise for selective recovery of trivalent actinides such as americium, although the stripping step of ALSEP suffers from slow kinetics2. In this work, we begin the process of understanding the chemical mechanisms of ALSEP by investigating metal-complex speciation.