Screening Investigations of Novel Nitrogen Donor Ligands

Doctoral thesis, 2005

With an increasing global demand for electricity, nuclear power plays an important role. The nuclear power industry is in different stages of development throughout the world. While some countries are just starting up their power plants others are looking at designing the next generation of nuclear power plants, and others are closing down their plants. Regardless of where in this stage of development one is, it is important to have a concept on how to take care of the spent nuclear fuel. Several options exist, such as the once-through cycle or reprocessing. Both these methods produce a residue that must be disposed of and isolated for a very long time. Transmutation of the spent nuclear fuel is a technique that may reduce the amount and the storage time of the spent nuclear fuel by converting the long lived radionuclides into short lived or stable nuclides. Successful transmutation must be accompanied with an effective separation, or partitioning, of the elements in the spent fuel since only a few elements are the target for transmutation. Solvent extraction is one of the preferred techniques for this partitioning. Special consideration is given to the separation of trivalent actinides and trivalent lanthanides in the waste since these groups of elements have similar chemical properties and hence may be difficult to separate.  This work is focused on the separation of actinides from lanthanides using novel nitrogen containing extracting reagents for solvent extraction. These nitrogen bearing reagents has been investigated using mainly solvent extraction techniques to find chemical and extraction properties for these reagents and to optimize the system in order to use these reagents in a future process. Methods for making screening test of these ligands are discussed where certain properties of the reagents are investigated, such as solubility, radiolytic and hydrolytic stablility and extraction capacity. The ligands were found to be able to specifically sepatare actinides from lanthanides. Further on, a model based on Hansen’s solubility parameter concept, which can predict the outcome of an extraction experiment is presented. The model was found to work quite well.