Distribution of Neptunium between TBP and Some Mineral Acids

Abstract

Abstract Neptunium-239 is used as the tracer for studies on solvent extraction behaviors of neptunium in the following system: 1. Nitric acid solution and TBP. 2. Hydrochloric acid solution and TBP. 3. Sulfuric acid solution and TBP. 4. Perchloric acid solution and TBP. Kd values are measured by combinations of scrubbing techniques and chemical treatments. In nitric, hydrochloric and sulfuric systems, neptunium gives three kinds of Kd, distribution ratio which could be assigned to oxidation states of (IV), (V) and (VI). On the other hand, in the perchloric system neptunium does not show Kd value which should be assigned to the oxidation state (IV). Some of these results are compared with those of uranium, plutonium and other elements. In the nitric system, neptunium (VI) shows an acid dependence of Kd value similar to those of uranium (VI) and plutonium (VI). Kd values of neptunium (IV) and plutonium (IV) vary in almost the same way against the acid concentration of nitric acid. There is also a strong similarity between acid dependences of uranium (VI) and neptunium (VI) in the hydrochloric system. Behavior of neptunium (V) are compared with those of protactinium. Finally a simple method for isolation of neptunium from irradiated uranyl salt is stated.