title: Non- identical thermochemical behavior of234U-and238U- isotopes in metamict britholite.
abstract: A radiochemical analysis of the valence state of uranium isotopes in minerals involves isolation of the U(IV) and U(VI) valence forms and determination of the radioactivity of the234U and238U isotopes in each fraction. If the nuclear decay of the uranium in the minerals is accompanied by a redox process, the distribution of the234U isotope in the U(IV) and U(VI) forms will differ from that of the238U isotope: oxidation leads to enrichment of the U(VI) fraction with the radiogenic234U isotope; reduction facilitates enrichment of the U(IV) fraction with234U. If the mineral is heated to 600-700°C before the radiochemical analysis, then an equilibrium activity ratio (AR) for both valences. The question arises: What are the processes that bring this about? The authors of this research studied changes of the AR in the U(IV) and U(VI) fractions after isochronous thermal annealing.
authors: St-Petersburg State University, University Embankment, 7-9, 199034, Russian Federation. Electronic address: skriplev85@mail.ru.
authors: Mikhail I
authors: MI
authors: Skriplev
authors: St-Petersburg State University, University Embankment, 7-9, 199034, Russian Federation.
authors: Roman V
authors: RV
authors: Bogdanov
authors: St-Petersburg State University, University Embankment, 7-9, 199034, Russian Federation.
authors: Lawrence R
authors: LR
authors: Schwink
keywords: Alpha-decay; Britholite; Metamict minerals; Natural analogues; Thermochemistry; Uranium isotopes