MIXER-SETTLER RUNS TO STUDY URANIUM(IV) AS A REDUCTANT IN URANIUM/PLUTONIUM SEPARATION

Mixer-settler runs were carried out to study the use of hydrazine-stabilized uranium(IV) nitrate solutions to reduce plutonium in the uranium-plutonium separation in TBP processes. Concentration profiles for nitric acid, uranium(VI), uranium(IV), and plutonium were determined, and material balances and decontamination factors were calculated. Some relevant partition coefficients were measured. Information was also obtained on the kinetics of the uranium(IV)--plutonium(IV) reaction, of the aerial oxidation of uranium(IV) at low acidities in the TBP phase, and of reoxidation of plutonium(III) in the aqueous phase at acidities above 2.5 M. It was shown that the Wall mixer-settler used only operated at about 50% stage efficiency under the conditions of the runs. The implications of the results for flowsheet design were indicated. (auth)