Tracer studies neptunium

Since 1958, more than 20 nuclides of actinides ranging from neptunium to einsteinium were identified and prepared for tracer studies. From neutron-irradiated uranium samples 2 9Np was adjusted to the pentavalent state and separated by TBP extraction from perchloric acid media. Plutonium-239 was separated by TBP extraction from nitric acid solution followed by anion exchange in a system of Dowex-1 resin and nitric acid. Neptunium-237 was separated from a spent fuel solution of JRR-1 (Japan Research Reactor -1) using anion exchange and TBP extraction. The TBP extraction in the hydrochloric acid medium is a simple and effective technique to purify neptunium from plutonium contamination. On the other hand, both anion exchange and solvent extraction with HDEHP could be used to separate tracer scale plutonium from irradiated neptunium targets. 

Although the existence of a volatile higher fluoride of plutonium had been surmised from tracer experiments, positive evidence of the existence of PuF6 was obtained by Florin (31) who first prepared the compound. An investigation of the preparation and properties of PuF6 was also conducted by Mandleberg et al. (58). but in recent years the compound has been most intensively studied by Weinstock and his collaborators. Plutonium hexafluoride can be prepared by a variety of procedures similar to those used for the preparation of uranium hexafluoride. The most widely used method consists in the fluorination of plutonium tetrafluoride with elemental fluorine. Whereas uranium hexafluoride can be prepared by the analogous reaction at 300°, and neptunium hexafluoride at 500°, the preparation of plutonium hexafluoride by this reaction appears to require a... 

The discovery of the transuranium elements and the study of their properties, especially the chemical properties, furnished a tremendous amount of additional evidence of just the type needed to clarify this problem. It is in the transuranium elements that the really definitive chemical properties, from the standpoint of placing the heaviest elements in the periodic table, first appear. The first conclusive evidence that the 5f shell undergoes filling in this heavy region came from the tracer chemical observations of McMillan and Abelson (1940) on element 93, neptunium. Upon their discovery of neptunium, the first transuranium element, McMillan and Abelson were... 

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