Mass Dependence of Uranium Isotope Effects in the U(IV)−U(VI) Exchange Reaction

Isotope separation of 233 U by anion exchange chromatography based on the U(IV)−U(VI) exchange is studied. After long-distance migration, 233 U enrichment is observed at the rear band boundary. To examine the isotope effects of 233 U, 234 U, and 238 U, three-isotope plots of local enrichment factors are constructed for the isotopes contained in sample fractions of the eluted uranium band. The results clearly show an anomalous mass dependence for 233 U. We previously reported that the even-mass nuclides 232 U, 234 U, 236 U, and 238 U show a regular mass-dependence in their isotope separation behaviors, while 235 U does not fall on the same line. The isotope effects of the odd-mass nuclides 233 U and 235 U deviate from the linear mass dependence observed among the even-mass nuclides. The isotope effects observed in chemical exchange are shown to be closely related to the isotope shifts in the atomic spectra of uranium isotopes.