The analysis of the valency state of plutonium by solvent extraction separation and alpha counting

Plutonium(VI) and plutonium (IV) in 1.5 mol/l nitric acid are extracted by 0.1 mol/l D2EHPA-5%TIOA-dimethyl benzene, while the plutonium (III)remains in the aqueous phase. Extracted Pu(IV) can be stripped by 0.1 mol/l oxalic acid while Pu(VI) is still in the organic phase. After sampling the separated plutonium species and making them into sources, alpha counting is carried out and the concentration of them are calculated. When the amount of plutonium in a source plate is as high as 1.5 μg, the relative standard deviation is +-4%. The relative deviation of this method from controlled-potential coulometry is about 2%