Chemical consequences of nuclear transmutations in minerals. II. Behavior of 234U and 238U during incongruent dissolution of natural phosphate and silicate

The behavior of 234U and 238U during incongruent dissolution of minerals of pegmatite origin (orthite, monazite, xenotime) is studied. The relative content of U(IV) and U(VI) in the resulting extracts and the relative 234U/238U alpha-activity ratio in each of the oxidation states are determined. The difference in the behavior of U isotopes in phosphate and silicate minerals is found. The observed isotope effects are explained on the basis of a multiphase mineral structural model. The conclusion is made that fractionation of U isotopes in nature (Cherdyntsev-Chalov effect) includes a redistribution of 234U between various components of the mineral system or rock as one of the steps