Abstract:
2,6-dipicolinic acid (DPA, expressed as H
2C) is expected to strip plutonium from high plutonium-retention waste organic solvent in the Purex process for spent fuel reprocessing. In order to separate the plutonium and uranium in the DPA stripping solution and recover the plutonium, the static adsorption experiment was conducted to investigate the adsorption performance of DPA-Pu(Ⅳ)/U(Ⅵ) complex on the strongly basic anion exchange resin DOWEX 1. The influence of DPA concentration, acidity, temperature and the main radiolysis products on the adsorption of plutonium and uranium by DOWEX 1 resin was studied, and the single crystal of DPA-U(Ⅳ)/U(Ⅵ) complex was obtained. By comparing the spectrum of the complex crystal and that of resin adsorbing with metal ions, the complex species adsorbed on resin of Pu(Ⅳ) (instead by U(Ⅳ)) and U(Ⅵ) were determined. The thermodynamic data of the adsorption reaction were obtained by temperature variation experiments. Adsorption experiment results show that DOWEX 1 resin can simultaneously adsorb plutonium and uranium under low acid conditions (0.1 mol/L HNO
3), and under high acid conditions (8 mol/L HNO
3) only plutonium but not uranium. Based on the above results, a practical plutonium stripping process is proposed that is plutonium and uranium adsorption on column at low acid, complex species transformation on column at high acid for uranium removal, and plutonium desorption from column at low acid. The process was validated by experiment, in which the plutonium recovery rate is 96%, and the uranium decontamination factor is about 2.8×10
3.