Engineering Aspects of an Actinide/Lanthanide Separation Concept Based on the Oxidation of Americium

The separation of Am from the lanthanides and curium is a key step in proposed advanced fuel cycle scenarios. The partitioning and transmutation of Am desirable to minimize the long-term heat load of material interred in a future high-level waste repository. A separation amenable to process scale-up remains elusive. Given only subtle chemistry differences within and between the ions of the trivalent actinide and lanthanide series this separation is challenging ; however, higher oxidation states of americium can be prepared using sodium bismuthate and separated via solvent extraction using diamylamylphosphonate (DAAP) extraction.  Among the other trivalent metals only Ce is also oxidized and extracted. Due to the long-term instability of Am(VI), the loaded organic phase was readily selectively stripped to partition the actinide to a new acidic aqueous phase.  Scale-up of such a separation concept provides an additional challenge. Filtration of the solid sodium bismuthate is necessary prior to extraction. Kinetic issues with the oxidized Am require very rapid separation after oxidation. Further complicating the process is the presence of Ce(IV) which is highly corrosive to stainless steel and results in the generation of elements that reduce the Am.  Engineering scale-up research, including cross-flow filtration development and the evaluation of potential equipment material of construction, will be presented. Additionally, the development and testing of a “hot” engineering-scale test bed will be detailed.