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.