Recovery of Uranium, Plutonium, and Neptunium from High-Level Waste Solutions prior to Actinide Partitioning

AbstractThe prior removal of uranium along with plutonium and neptunium from high-level waste (HLW) can simplify the subsequent actinide partitioning steps. In this context, extraction and stripping behavior of uranium, plutonium, and neptunium was investigated employing 1.1-M solutions of tri-n-butyl phosphate (TBP) and N,N-dihexyl octanamide (DHOA) dissolved in n-dodecane as extractants in the presence of 6 g/L U relevant to pressurized heavy-water reactor (PHWR) high-level waste (HLW) conditions. Reductants such as acetohydroxamic acid (AHA) and hydroxyurea (HU) were evaluated for selective stripping of plutonium and neptunium over uranium from the loaded organic phases. These studies indicated the possibility of quantitative recovery of U(VI), Pu(IV), and Np(IV) from HLW solution employing either DHOA or TBP as extractant. Integration of this step in the minor actinide partitioning simplifies the treatment of HLW with the specially designed extractants like octyl(phenyl)- N, N-diisobutyl carbamoyl methyl phosphine oxide (CMPO), N, N, N′, N′-tetraoctyl diglycolamide (TODGA), and N, N, N′, N′-tetra(2-ethylhexyl) diglycolamide (TEHDGA).