Journal of Nuclear Fuel Cycle and Waste Technology

The interaction of U(VI) (hexavalent uranium) species with natural organic matter (NOM) in KURT (KAERI Underground Research Tunnel) groundwater is investigated using a laser spectroscopic technique. The luminescence spectra of the NOM are observed in the ultraviolet and blue wavelength regions by irradiating a laser beam at 266 nm in groundwater. The luminescence spectra of U(VI) species in groundwater containing uranium concentrations of 0.034-0.788 mg·L-1 are measured in the green-colored wavelength region. The luminescence characteristics (peak wavelengths and lifetime) of U(VI) in the groundwater agree well with those of Ca2UO2(CO3)3(aq) in a standard solution prepared in a laboratory. The luminescence intensities of U(VI) in the groundwater are weaker than those of Ca2UO2(CO3)3(aq) in the standard solution at the same uranium concentrations. The luminescence intensities of Ca2UO2(CO3)3(aq) in the standard solution mixed with the groundwater are also weaker than those of Ca2UO2(CO3)3(aq) in the standard solution at the same uranium concentrations. These results can be ascribed to calcium-U(VI)-carbonate species interacting with NOM and forming non-radiative U(VI) complexes in groundwater.

Keywords

Groundwater,Natural organic matter,Uranium-carbonate species,Laser spectroscopy,Luminescence