Amides and diamides as promising extractants in the back end of the nuclear fuel cycle: an overview

An overview of the work carried out on the development of amides/diamides as alternate extractants in the back end of fuel cycle has been given. Whereas a straight chain amide, viz. N,N-dihexyl octanamide (DHOA) is a promising alternate to tri-n-butyl phosphate (TBP) in the reprocessing of irradiated uranium-based fuels, a branched chain amide, viz. N,N-di(2-ethylhexyl) isobutyramide (D2EHIBA) has been found suitable for the selective recovery of U-233 from irradiated Th. DHOA has been found to extract Pu more efficiently than TBP under uranium loading conditions. On the other hand, significant improvement in the separation of U-233 from Th and fission products has been achieved by employing 0.5 M D2EHIBA in n-dodecane as compared to that of 5% TBP (the THOREX solvent). Stripping behaviour of U for DHOA and D2EHIBA is better than that of TBP. N,N',N,N',-dimethyl dibutyl tetradecyl malonamide (DMDBTDMA) has been evaluated for the partitioning of minor actinides (MA) from high-level nuclear waste with large uranium content (similar to20g/l). Designed amide ligands, viz. D2EHIBA showed improved separation of the desired actinide constituents like Pu (mainly Pu-239) and U-233 over the fission products and the major matrix elements like U and Th. (C) 2003 Elsevier B.V. All rights reserved.