PNNL

Abstract

The complexation of Pu(IV) with fluoride at elevated temperatures was studied by solvent extraction technique. A solution of NaBrO3 was used as holding oxidant to maintain the oxidation state of plutonium throughout the experiments. The distribution ratio of Pu(IV) between the organic and aqueous phases was found to decrease as the concentrations of fluoride were increased. Stability constants of the 1:1 and 1:2 Pu(IV)-F- complexes, dominant in the aqueous phase under the experimental conditions, were calculated from the effect of fluoride ions on the distribution ratio. The thermodynamic parameters, including enthalpy and entropy of complexation between Pu(IV) and fluoride at 25 degrees C - 55 degrees C were calculated from the stability constants at different temperatures by using the Van’t Hoff equation.