Simplified method for the preparation of micro samples for the simultaneous isotopic analysis of uranium and plutonium

A basic anion resin is employed to selectively adsorb plutonium and uranium from 8 M HNO₃ solutions containing dissolved spent reactor fuels. After a few beads of the resin are equilibrated with the solution, a single bead is used for establishing the isotopic composition of plutonium and uranium. The resin bead separation essentially removes all possible isobaric interference from such elements as americium and curium and at the same time eliminates most fission product contamination in the mass spectrometer. Small aliquots of dissolver solution that contain 10^-6g of U and 10^-8 g of Pu are adequate for preparing about ten resin beads. By employing a single-focusing, tandem-magnet-type mass spectrometer, equipped with pulse counting for ion detection, simultaneous plutonium and uranium assays are obtained. The quantity of each element per bead may be as low as 10^-9 to 10^-10g. The technique of isotope dilution can be coupled with the ion exchange bead separation and used effectively for measuring the total quantity of U and Pu. The technique possesses advantages such as: reduced radiation hazards from the infinitely smaller samples, thus less shielding and transport cost for sample handling; greatly simplified chemical preparations that eliminate fission products and actinide isobaric interferences; and the minor isotopes are more precisely established. (author)