TY - JOUR

T1 - Natural analogue approaches to prediction of long-term behaviour of Ca2UO5∙2-3H2O X-phase

T2 - case study from Tulul Al Hammam site, Jordan

AU - Sokol, E. V.

AU - Kokh, S. N.

AU - Khoury, H. N.

AU - Seryotkin, Yu V.

AU - Goryainov, S. V.

AU - Novikova, S. A.

AU - Sokol, I. A.

N1 - Publisher Copyright: © 2017, Saudi Society for Geosciences.

PY - 2017/12/1

Y1 - 2017/12/1

N2 - 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.

AB - 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.

KW - Cement

KW - Central Jordan

KW - Long-term U retention

KW - Natural analogue site

KW - Radwaste management

KW - X-phase CaUO·2-3HO

KW - URANIUM

KW - CD

KW - NORTHERN JORDAN

KW - IMMOBILIZATION

KW - X-phase Ca2UO5 center dot 2-3H(2)O

KW - ORIGIN

KW - HOT PARTICLES

KW - ZN

KW - SPECTROSCOPY

KW - MAQARIN AREA

KW - CEMENT PORE WATERS

UR - http://www.scopus.com/inward/record.url?scp=85036597692&partnerID=8YFLogxK

U2 - 10.1007/s12517-017-3305-5

DO - 10.1007/s12517-017-3305-5

M3 - Article

AN - SCOPUS:85036597692

VL - 10

JO - Arabian Journal of Geosciences

JF - Arabian Journal of Geosciences

SN - 1866-7511

IS - 23

M1 - 512

ER -