EXTRACTION OF TRANSURANIC ELEMENTS WITH A DIHEXYL-N,N-DIETHYLCARBAMOYLMETHYL PHOSPHONATE TRIBUTYL-PHOSPHATE SYSTEM - INITIAL INVESTIGATIONS

An extractant system, 0.75 ($) under bar M DHDECMP and 1 ($) under bar M TBP in an aliphatic hydrocarbon diluent, was evaluated for selectiv ely removing transuranic elements (TRUs) from acidic waste streams. Th is evaluation involved six parts: 1) Investigating the tendency to for m third phases as a function of HNO3 concentration. 2) Measuring the d istribution coefficients for the radioactive waste components UO22+, A m3+ and Pu4+ as a function of aqueous nitrate concentration. 3) Measur ing the distribution coefficients for the important, nonradioactive wa ste components HNO3, Fe3+, Zr4+, and Bi3+ as a function of aqueous nit rate concentration. 4) Qualitatively determining the impact of potenti al feed additives such as fluoride ion and oxalate ion upon these disb rituion values. 5) Qualitatively evaluating the tendency to form inter facial crud upon contact with acidified solutions containing high meta l (Zr4+) loadings. 6) Investigating extractant pretreatment to remove trace orgaophosphorus impurities which affect metal distribution value s at low acid concentrations. The results of this evaluation are discu ssed along with theiry consequences with respect to developing a flows heet for processing wastes stored at the U.S. Department of Energy's H anford site.