Natural analogue approaches to prediction of long-term behaviour of Ca2UO5∙2-3H2O X-phase: case study from Tulul Al Hammam site, Jordan

E. V. Sokol, S. N. Kokh, H. N. Khoury, Yu V. Seryotkin, S. V. Goryainov, S. A. Novikova, I. A. Sokol

Research output: Contribution to journalArticlepeer-review

3 Citations (Scopus)

Abstract

The Tulul Al Hammam area in central Jordan is an advantageous natural analogue site to study long-term U(VI) retention in ~ 1 Ma old U-bearing combustion metamorphic marbles with clinker-like mineralogy exposed to prolonged supergene alteration for at least ~ 100 kyr. The marbles contain abundant grains of high-temperature (ca. 800–850 °C) primary double Ca-U(VI) oxides (mainly Ca3UO6 and CaUO4), which are commonly replaced by hydrated calcium uranates with various impurities (Si, Fe, Al and F). A more hydrous natural analogue of X-phase (Ca2UO5·2-3H2O) occurs as a predominant secondary U compound after primary Ca-U(VI) oxides. The phase was studied by single-crystal XRD, SEM/EDX and electron microprobe (EPMA) analyses and Raman spectroscopy. It is a non-crystalline phase with a specific finger-like microtexture consisting of thin (no wider than 1–2 μm) lamellar particles. Its Raman spectrum shows a single strong band at 706–713 cm−1, sometimes coexisting with up to three weak diffuse bands (ν ~ 390, ~ 540 and 1355–1400 cm−1). The find of the natural X-phase (Ca2UO5·2-3H2O) is evidence of its long-term stability in a natural environment. It proves explicitly that the compound Ca2UO5·nH2O is a solubility-limiting phase in aged cements. The results have implications for geological disposal of radioactive wastes.

Original languageEnglish
Article number512
Number of pages14
JournalArabian Journal of Geosciences
Volume10
Issue number23
DOIs
Publication statusPublished - 1 Dec 2017

Keywords

  • Cement
  • Central Jordan
  • Long-term U retention
  • Natural analogue site
  • Radwaste management
  • X-phase CaUO·2-3HO
  • URANIUM
  • CD
  • NORTHERN JORDAN
  • IMMOBILIZATION
  • X-phase Ca2UO5 center dot 2-3H(2)O
  • ORIGIN
  • HOT PARTICLES
  • ZN
  • SPECTROSCOPY
  • MAQARIN AREA
  • CEMENT PORE WATERS

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