Abstract :

Spectroscopic actinide speciation, providing fundamental molecular scale information under varying conditions, is requisite to performance assessment of nuclear repositories, optimizing development of partitioning strategies and transmutation fuels. Actinide speciation aids understanding processes determinant in the behavior of actinides released into the environment. This, in turn, determines transport properties (mobilization/immobilization), reactivity, bio-availability and, hence, potential risk. Partitioning may be used to isolate long-lived radionuclides from nuclear fuel reprocessing waste for later transmutation to shorter lived nuclides or for their conditioning and immobilization in special matrices for disposal. In this presentation, examples of the application of X-ray and laser techniques for actinide speciation in these fields are presented. Examples will include studies of the formation of aqueous actinide-containing colloids, including structural characterization, identification of sorbed actinide species on mineral surfaces, and the comparison of coordination structures for trivalent actinide cations complexed with partitioning extractants to those of their lanthanide counterparts.