Recent progress in the extraction chemistry of actinide ions

For over 40 years now, actinide scientists worldwide have maintained and sustained a high level of activity and interest in the chemistry and technology of actinide element liquid-liquid extraction systems, but the thrust and scope of this activity has changed. Two to three decades ago large teams of chemists and chemical engineers in a few countries strove to develop the essential elements of processes (e.g. PUREX, THOREX, BUTEX etc.) for reprocessing irradiated nuclear fuel. Today, much smaller groups of investigators scattered around the globe are pursuing challenging actinide element extraction chemistry and systems of particular interest to them. Examples of these latter activities include 1. continued studies of selected PUREX process features (e.g., neptunium chemistry, modeling of plutonium and uranium extraction and separation, etc.); 2. consideration of certain aliphatic amides as a replacement for TBP in PUREX-type processes; 3. investigation of nitrogen and sulfur-based compounds to effect liquid-liquid extraction separation of trivalent actinides and lanthanides, synthesis and application of bifunctional organophosphorus reagents for removal of all TRU elements from nuclear waste solutions; various synergistic extraction systems etc. This paper highlights the objectives and status of these modernday actinide extraction studies and also attempts to project the near-future thrust and direction of investigations of actinide liquid-liquid extraction systems. (orig.)