Preparation of Trace Single Oxidation State Plutonium Solutions

The trace levels of single oxidation state plutonium(Pu(Ⅳ,Ⅴ,Ⅵ)) solution was prepared, and the stability was monitored over time. The oxidation state distribution of the solution was analyzed by solvent extraction methods, in which Pu(Ⅳ) was extracted with TTA and Pu(Ⅳ+Ⅵ) was separated by HDEHP. The Pu(Ⅳ) solution is prepared by heating the solution until dryness in 1 mol/L HNO₃ repeatedly, and Pu(Ⅵ) solution is obtained by keeping Pu(Ⅳ) in 0.5-1 mol/L HNO₃-0.1 mmol/L KMnO₄ system for 24 h. Pu(Ⅵ) is reduced automatically to Pu(Ⅴ) in the dark for 5 d. All of these single plutonium solutions could not keep steady in pH=3.0, 0.01 mol/L NaCl system. Consequently, single oxidation state plutonium solutions need to be prepared freshly for each experiment.