Theoretical Investigation of Actinide Ligation in Aqueous and Organic Phase for Nuclear Waste Treatment

The generation of radioactive waste has a prominent negative
impact
on the use of nuclear energy due to potential health concerns and
cost of waste storage. This potential impact continues to rise as
the quantity of waste increases due to the increasing growth in energy
demand. One of the leading contributions to the radioactivity of this
waste is due to the presence of actinides. The removal of these actinides
by ligand-based solvent extraction methodologies provides an invaluable
process necessary for the promotion of nuclear energy. By evaluating
different ligands that are currently applied for actinide solvent
extractions, more effective ligands could be proposed and synthesized
for the successful separation of actinides from nuclear waste. Here,
density functional theory (DFT) calculations for a variety of ligands
and actinides are reported to explain the extraction process. Different
solvation and ligation effects were evaluated for the computation
of stability constants. The ratio of water and nitrate ligands in
the coordination environment of actinides (Ac­(III), Th­(IV), Am­(III),
and Cm­(III)) was first examined. Results from this step provided reliable
initial conditions for the extraction of these actinides in both the
aqueous (343HOPO) and the organic phase (BTBP). We also report a DFT
benchmarking study as well as a modified BTBP ligand performance evaluation.