Microscale characterization of uranium(VI) silicate solids and associated neptunium(V)
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Matthew Douglas
Summary
The uranium(VI) silicate phases uranophane, Ca[(UO2)(SiO3OH)]2·5H2O, and sodium boltwoodite, Na[(UO2)(SiO3OH)]·1.5H2O, were synthesized in the presence of small, variable quantities (0.5–2.0 mol % relative to U) of pentavalent neptunium (Np(V), as NpO2+), to investigate the nature of its association with these U(VI) solid phases. Solids were characterized by X-ray powder diffraction (XRD), gamma spectrometry (GS), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDS), and transmission electron microscopy (TEM) with electron energy-loss spectroscopy (EELS). Neptunium concentration was determined in the bulk solid phases by GS and was found to range from 780–15800 μg/g. In some cases, Np distributions between the aqueous and solid phases were monitored, and 78–97% of the initial Np was associated with the isolated solid. Characterization of individual crystallites by TEM/EELS suggests the Np is associated with the U(VI) phase. No discrete Np phases, such as Np oxides, were observed. Because the U(VI) silicates are believed to be important solubility-controlling solids on a geologic timescale, these results suggest that the partitioning of the minor actinides to these solids must be considered when assessing the performance of a waste repository for spent nuclear fuel.
© by Oldenbourg Wissenschaftsverlag, München
Articles in the same Issue
- Radiochemical separation of actinides from environmental samples for determination with DF-ICP-MS and alpha spectrometry
- A comparative evaluation of 238Pu determination in NIST-SRM-947-Pu by alpha spectrometry and thermal ionization mass spectrometry
- Microscale characterization of uranium(VI) silicate solids and associated neptunium(V)
- Diffusion and sorption of U(VI) in compacted bentonite studied by a capillary method
- Crystal structure of new uranyl oxalates (NH4)2[UO2(C2O4)2· H2O]·2H2O and (NH4)2-x(N2H5)x[(UO2)2(C2O4)3]·3H2O (x=0 and x=1). Comparison with other uranyl oxalates
- Extraction of U(VI) with unsymmetrical N-methyl-N-decylalkylamide in toluene
- The effect of water treatment on the presence of particle-bound 210Po and 210Pb in groundwater
- On the transport and speciation of ruthenium in high temperature oxidising conditions
- Speciation of Tc(IV) in chloride solutions by capillary electrophoresis
Articles in the same Issue
- Radiochemical separation of actinides from environmental samples for determination with DF-ICP-MS and alpha spectrometry
- A comparative evaluation of 238Pu determination in NIST-SRM-947-Pu by alpha spectrometry and thermal ionization mass spectrometry
- Microscale characterization of uranium(VI) silicate solids and associated neptunium(V)
- Diffusion and sorption of U(VI) in compacted bentonite studied by a capillary method
- Crystal structure of new uranyl oxalates (NH4)2[UO2(C2O4)2· H2O]·2H2O and (NH4)2-x(N2H5)x[(UO2)2(C2O4)3]·3H2O (x=0 and x=1). Comparison with other uranyl oxalates
- Extraction of U(VI) with unsymmetrical N-methyl-N-decylalkylamide in toluene
- The effect of water treatment on the presence of particle-bound 210Po and 210Pb in groundwater
- On the transport and speciation of ruthenium in high temperature oxidising conditions
- Speciation of Tc(IV) in chloride solutions by capillary electrophoresis
