Solubility Of Uranium Research Articles

Thermodynamics, Solubility and the Separation of Uranium from Cerium in Molten In/3LiCl-2KCl System

The purpose of this work is to study the electrochemical behavior of uranium and cerium in fused In/3LiCl-2KCl system in the temperature range of 723–823 K by open-circuit potentiometry. The apparent electrode potential of Ce3+/Ce (U4+/U) couples and apparent standard potential of Ce-In (U-In) alloys vs AgCl/Ag reference electrode were established. The principal thermodynamic properties, activity and solubility of cerium and uranium were determined. The separation factor of uranium/cerium couple on liquid indium electrode was calculated. The experimental results have been shown that a lower temperature should be more effective for the separation uranium from cerium.

Uranyl speciation in sulfate-bearing hydrothermal solutions up to 250 °C

The speciation of uranyl in sulfate-bearing solutions at temperatures up to 250 °C has been investigated using in situ UV–Visible spectrophotometry. Formation constants for the reactions UO22++SO42-⟺UO2SO40 (logβ1= 3.38, 4.40, 5.44, 6.33, 7.74) and UO22++2SO42-⟺UO2SO422- (logβ2 = 4.10, 5.26, 6.83, 8.00, 9.70) were derived at 25, 100, 150, 200 and 250 °C respectively. These formation constants were fitted to the modified Ryzhenko–Bryzgalin (MRB) model to derive pK(298), A(zz/a) and B(zz/a) values for both complexes: 3.262, 2.212, −197.96 (UO2SO40) and 4.189, 3.21, −473.14 UO2SO422- respectively. Compared with values extrapolated using previously available data for 25, 70 and 75 °C, our new data suggest higher stability of UO2SO40 at temperatures above 150 °C and significantly lower stability of UO2SO422- at all temperatures above 25 °C. Molar absorbances of both sulfate species were also derived. At 25 °C we found our molar absorbance for UO2SO40 agreed well with those reported previously in the literature, however we report lower peak amplitudes for UO2SO422-. We also noted significant temperature-dependent red shifts in the molar absorbance of UO2SO40. We suggest that these shifts could be explained by changes in sulfate bonding behaviour around the uranyl ion – namely shifts in the distribution of complexes with sulfate bound in either a monodentate or bidentate configuration. Simple models calculated with our new data suggest that sulfate complexes may readily predominate over chloride complexes even in solutions containing upwards of 20 wt% chloride and only 100 ppm sulfate. In addition, moderate concentrations of sulfate (∼1 wt%) can increase the solubility of uranium by an order of magnitude. Thus we suggest that sulfate could play an important role in mobilising uranium in hydrothermal systems, and that the removal of sulfate via precipitation of sulfate minerals may act as a means of depositing uranium under oxidizing conditions. This in turn might explain the associations between sulfate minerals and uranium mineralisation occasionally seen in large uranium ore deposits such as Olympic Dam and MacArthur River.

Thermodynamic interpretation of uranium(IV/VI) solubility in the presence of α-isosaccharinic acid

The effect of α-isosaccharinic acid (ISA) on the solubility and redox of tetravalent and hexavalent uranium (U(IV), U(VI)) was investigated in the hydrogen ion concentration (pHc = −log [H+]) range of 6–13 and at total ISA concentration ([ISA]tot) = 10−4–10−1.2 mol/dm3 (M). The dependence of U(IV) solubility on pHc and [ISA]tot suggested the existence of U(OH)4(ISA)22− as a dominant species within the investigated pHc range of 6–12. For the U(VI)-ISA system, UO2(OH)3(ISA)23− was suggested as a dominant species at pHc 7–13. The formation constants of the U(IV)-ISA and U(VI)-ISA complexes were determined by least squares fitting of the solubility data. The solubility of U(IV) and U(VI) in the presence of ISA and its effect on the redox behavior were thermodynamically interpreted based on the obtained constants.

Solution equilibria of uranyl minerals: Role of the common groundwater ions calcium and carbonate.

Understanding the factors that govern aqueous solubility of uranyl minerals is important for predicting uranium mobility in groundwater and for designing effective remediation strategies. The uranyl-containing minerals metaschoepite [UO3∙(2H2O)] and uranophane [Ca(UO2)2(SiO3OH)2·5H2O] were synthesized and evaluated in batch solubility experiments conducted in the presence of common groundwater ions: calcium, bicarbonate/carbonate, and dissolved silica. Solid-phase characterization revealed the expected structural and thermogravimetric properties of metaschoepite and uranophane. Metaschoepite solubility in carbonate-free water followed a u-shaped pH dependency with minimum solubility near pH 8.5; uranium concentrations at pH ≳ 8.5 were approximately equivalent to the reference value for safe drinking water established by the EPA (30 μg/L). With increasing bicarbonate/carbonate concentration (1 mM - 50 mM) the solubility of metaschoepite increased, presumably due to the formation of uranyl-carbonate complexes. However, the experimental concentrations of uranium were lower than concentrations predicted from accepted complexation constants. For uranophane, equilibrium uranium concentrations were < 75 μg/L at typical groundwater concentrations of calcium and dissolved silica (pH > 7). The diversity of uranyl minerals that possibly form in the presence of common groundwater species: Ca-Mg-Na-K-Si-bicarbonate/carbonate-sulfate-chloride, has not been fully explored with respect to understanding potential mineral transformations and impacts on uranium solubility and mobility.

Microwave vitrification of uranium-contaminated soil for nuclear test site and chemical stability

In early days, nuclear tests had left plenty of radionuclide-contaminated soil over the world and disposal of which is vital to human health. In this work, vitrification technology was employed to achieve the immobilization of radionuclide. It was demonstrated that three kinds of simulated uranium contaminated soil for nuclear test site (Gray desert soil, Saline-alkali soil and Aeolian sandy soil) could be successfully vitrified within 30 min without any additional components via microwave sintering. All the uranium contaminated soil became amorphous at 1300 °C. Uranium was considered to be surrounded by aluminium silicate glass network structure, and three kinds of 50000 μg/g uranium concentration sintered soil samples presented reliable chemical durability. In addition, the ultimate solubility of uranium and chemical stability of different sintered soil samples were affected by the content of their components.

Thermodynamics of rare earth elements and uranium in gallium based quaternary metallic alloys

Thermodynamic properties of rare earth elements (Y, La, Nd) and uranium were experimentally determined in a number of quaternary alloys at 573–1073 K. Gallium based eutectic mixtures (Ga–Al, Ga–In and Ga–Zn) were chosen as the solvents. The systems studied were La–U–Ga–Al, La–U–Ga–In, La–U–Ga–Zn, La–Nd–Ga–In and La–Y–Ga–In. Activity of the metals in the alloys were determined employing the electromotive force measurements method with the electrolytes based on the ternary LiCl–KCl–CsCl eutectic containing chlorides of the elements studied. Solubility of uranium and lanthanum in La–U–Ga–In and La–U–Ga–Al alloys was determined from the chemical analysis of the saturated alloys, and activity coefficients were calculated from the difference of the temperature dependencies of activity and solubility. Composition of the intermetallic compounds formed in the alloys was assessed using X-ray diffraction analysis. The results obtained for the quaternary systems were compared with the corresponding ternary and binary systems.

Solubility of U(VI) in chloride solutions. III. The stable oxides/hydroxides in MgCl2 systems: Pitzer activity model for the system UO22+–Na+–K+–Mg2+–H+–OH−–Cl−–H2O(l)

We have developed new chemical, thermodynamic and activity models for the system UO22+–Na+–K+–Mg2+–H+–OH−–Cl−–H2O(l) within the Pitzer approach. The new thermodynamic model is based on previously reported data treated within the SIT approach for NaCl and KCl systems, as well as on new experimental data determined in this work for the MgCl2 system.The solubility of uranium(VI) was studied in 0.01–5.15 mol·kgw−1 MgCl2 solutions at pHm = 4.1–9.7 (with pHm = −log [H+]). Experiments were performed under Ar atmosphere at T = (22 ± 2) °C. In all investigated systems, the solubility of U(VI) is controlled by metaschoepite, UO3·2H2O(cr). In contrast to previously investigated NaCl and KCl systems, no ternary Mg–U(VI)–OH(s) solid phases formed in alkaline MgCl2 solutions within the timeframe of this study (≤ 200 days). A very significant increase in the solubility (up to 3 log10-units) is observed in acidic to near-neutral pHm conditions when increasing MgCl2 concentration from 0.01 to 5.15 mol·kgw−1, which reflects the strong ion interaction processes taking place in concentrated MgCl2 brines.The solubility of UO3·2H2O(cr) in the investigated NaCl, KCl and MgCl2 solutions is well described with the solubility and hydrolysis constants recommended by Altmaier et al., (2017) and NEA–TDB, and a Pitzer activity model derived in the present work. The latter model considers experimental data reported in the present study and available in the literature for NaCl, KCl and MgCl2 systems (solubility, potentiometric and spectroscopic data), in combination with well-stablished estimation methods and correlations with SIT coefficients.Chemical, thermodynamic and Pitzer activity models provided in this work for the system UO22+–Na+–K+–Mg2+–H+–OH−–Cl−–H2O(l) accurately describe all evaluated datasets, and represent an adequate tool for the calculation of U(VI) solubility and aqueous speciation in a variety of geochemical conditions including concentrated brine systems of relevance in salt-based repositories for nuclear waste disposal.

Hydrothermal formation of heavy rare earth element (HREE)–xenotime deposits at 100 °C in a sedimentary basin

Abstract Most rare earth element deposits form from magmatic fluids, but there have also been discoveries of heavy rare earth element (HREE)–enriched hydrothermal xenotime deposits within sedimentary basins. As xenotime is notoriously insoluble, the question arises as to whether these lesser-known deposits form at typical basin temperatures or by influx of much hotter magmatic-hydrothermal fluids. The Browns Range District in northern Western Australia hosts deposits of xenotime that are enriched in HREEs and also uranium. The ore bodies consist of fault-controlled hydrothermal quartz-xenotime breccias that crosscut Archean basement rocks and overlying Paleoproterozoic sandstones. Analyses of fluid inclusions show that the xenotime precipitated at remarkably low temperatures, between 100 and 120 °C, in response to decompression boiling. The inclusions contain high excess concentrations of yttrium (10−3 mol/kg), REEs (1–7 × 10−5 mol/kg), and uranium (4 × 10−5 mol/kg) in equilibrium with xenotime at these low temperatures, showing that availability of phosphate limited the amount of xenotime precipitated. The analyses further identify SO42– and Cl– as the ligands that facilitated the elevated REE and uranium solubilities. These findings establish that significant REE transport and deposition is feasible at basin temperatures, and hence they raise the potential of unconformity settings for REE exploration. Moreover, the aqueous metal contents support a genetic link between this type of ore fluid and world-class Proterozoic unconformity-related uranium deposits elsewhere.

Solubility and ion-irradiation effects of uranium in Nd2Zr2O7 pyrochlore

Nd2Zr2O7 pyrochlore with higher physicochemical and radiation stability has been considered as a host matrix for actinide immobilization of high level radioactive wastes. Uranium is a constituent and the decay-daughter product of high level radioactive wastes. It is necessary to study the solubility and ion-irradiation effect of uranium in Nd2Zr2O7 pyrochlore. The solubility of U is studied by the A site substitution in the pyrochlore structure. A series of uranium-doped zirconate pyrochlore compositions is prepared by the sol-gel-spray pyrolysis-high temperature sintering method. The structures of immobilization are studied by using X-ray diffraction (XRD) and Raman spectroscopy. The XRD and Raman spectroscopy studies reveal that the solubility limit of uranium in Nd2Zr2O7 is estimated at 10 at%. The lattice parameter of pyrochlore decreases with U content increasing, which is due to lower ionic radius of U. The immobilization structure changes from order pyrochlore to disorder structure. Further addition of U content leads to the separation of U3O8 phase in the immobilization. The U ions with high valance may be substituted at A or B site in Nd2Zr2O7 pyrochlore, which results in the A–O and B–O bond destruction. In order to keep the balance of charge, extra O ions should enter into the vacancy site, the structure of pyrochlore maybe transforms into a disorder structure. The radiation resistance of immobilization is investigated by ion-beam irradiation with 2 MeV Kr15+ ions at room temperature. The Nd2Zr2O7 and Nd1.9U0.1Zr2O7 are irradiated at doses of 1 dpa and 3 dpa, respectively. Analyses of the XRD and Raman spectroscopy data show that the Nd2Zr2O7 pyrochlore remains full pyrochlore structure even at a higher irradiation dose, which suggests that the Nd2Zr2O7 exhibits higher radiation resistance as potential immobilization. In contrast, the Nd1.9U0.1Zr2O7 immobilization shows the weaker radiation resistance, the pyrochlore structure completely transforms into a disorder fluorite structure. The A–O and B–O bonds of Nd1.9U0.1Zr2O7 pyrochlore structure are easy to destroy under ion irradiation conditions due to the disorder of pyrochlore. At the same time, the excess O ions are rearranged in U-rich pyrochlore after irradiation. Bond destruction and ion rearrangement of pyrochlore structure result in the full disorder fluorite structure. The actinides-doped pyrochlore structure is modified due to the change in physicochemical propertyof actinide, which results in the reductionof the solubility limit and radiation resistance.

Effects of hydrated lime on radionuclides stabilization of Hanford tank residual waste

Chemical stabilization of tank residual waste is part of a Hanford Site tank closure strategy to reduce overall risk levels to human health and the environment. In this study, a set of column leaching experiments using tank C-104 residual waste were conducted to evaluate the leachability of uranium (U) and technetium (Tc) where grout and hydrated lime were applied as chemical stabilizing agents. The experiments were designed to simulate future scenarios where meteoric water infiltrates through the vadose zones into the interior of the tank filled with layers of grout or hydrated lime, and then contacts the residual waste. Effluent concentrations of U and Tc were monitored and compared among three different packing columns (waste only, waste + grout, and waste + grout + hydrated lime). Geochemical modeling of the effluent compositions was conducted to determine saturation indices of uranium solid phases that could control the solubility of uranium. The results indicate that addition of hydrated lime strongly stabilized the uranium through transforming uranium to a highly insoluble calcium uranate (CaUO4) or similar phase, whereas no significant stabilization effect of grout or hydrated lime was observed on Tc leachability. The result implies that hydrated lime could be a great candidate for stabilizing Hanford tank residual wastes where uranium is one of the main concerns.

Solubility of U(VI) in chloride solutions. I. The stable oxides/hydroxides in NaCl systems, solubility products, hydrolysis constants and SIT coefficients

The solubility of uranium(VI) is studied at T=(22±2)°C in carbonate-free 0.03–5.61mol·kgw−1 NaCl solutions at pHm=4–14.5 (pHm=−log [H+]). The solid phases metaschoepite UO3·2H2O(cr) and sodium uranate Na2U2O7·H2O(cr) (or NaUO2O(OH)(cr)) are characterized by XRD, SEM–EDS, thermogravimetry and quantitative chemical analysis. UO3·2H2O(cr) controls the solubility of U(VI) in acidic to near neutral pH conditions regardless of NaCl concentration. Na2U2O7·H2O(cr) forms in alkaline systems and is stable at pHm≥7 over the complete range of NaCl concentrations investigated.The solubility of UO3·2H2O(cr) at pHm<7 in NaCl solutions is very well described with the hydrolysis constants recommended by the NEA–TDB, a set of SIT coefficients evaluated in the present study and a solubility product of log*K°s,0{UO3·2H2O(cr)}=(5.35±0.13). Titration experiments and UV–vis absorption spectra of saturated solutions at pHm=4–5 in dilute to concentrated NaCl solutions confirm the speciation calculated in the present study and show the predominance of the trinuclear hydroxide complex (UO2)3(OH)42+ at high chloride concentrations. Solubility data obtained at 7≤pHm≤14.5 with Na2U2O7·H2O(cr) and in solutions equilibrated simultaneously with Na2U2O7·H2O(cr) and UO3·2H2O(cr) yield a solubility product of log*K°s,0{0.5 Na2U2O7·H2O(cr)}=(12.2±0.2) and the formation constants of the anionic hydrolysis species UO2(OH)3− (log*β°(1,3)=−(20.7±0.4)) and UO2(OH)42− (log*β°(1,4)=−(31.9±0.2)). SIT coefficients for these species are derived based on the solubility data obtained in dilute to concentrated NaCl systems.The chemical, thermodynamic and SIT activity models provided in this work for the system UVI–Na+–H+–Cl−–OH−–H2O(l) represent an accurate and robust tool for the calculation of U(VI) solubility and aqueous speciation in a variety of geochemical conditions relevant in the context of nuclear waste disposal.

Retardation of uranium and thorium by a cementitious backfill developed for radioactive waste disposal

The solubility of uranium and thorium has been measured under the conditions anticipated in a cementitious, geological disposal facility for low and intermediate level radioactive waste. Similar solubilities were obtained for thorium in all media, comprising NaOH, Ca(OH)2 and water equilibrated with a cement designed as repository backfill (NRVB, Nirex Reference Vault Backfill). In contrast, the solubility of U(VI) was one order of magnitude higher in NaOH than in the remaining solutions. The presence of cellulose degradation products (CDP) results in a comparable solubility increase for both elements. Extended X-ray Absorption Fine Structure (EXAFS) data suggest that the solubility-limiting phase for uranium corresponds to a becquerelite-type solid whereas thermodynamic modelling predicts a poorly crystalline, hydrated calcium uranate phase. The solubility-limiting phase for thorium was ThO2 of intermediate crystallinity. No breakthrough of either uranium or thorium was observed in diffusion experiments involving NRVB after three years. Nevertheless, backscattering electron microscopy and microfocus X-ray fluorescence confirmed that uranium had penetrated about 40 μm into the cement, implying active diffusion governed by slow dissolution-precipitation kinetics. Precise identification of the uranium solid proved difficult, displaying characteristics of both calcium uranate and becquerelite.

Biomineralization of U(VI) phosphate promoted by microbially-mediated phytate hydrolysis in contaminated soils

The bioreduction of uranium may immobilize a significant fraction of this toxic contaminant in reduced environments at circumneutral pH. In oxic and low pH environments, however, the low solubility of U(VI)-phosphate minerals also makes them good candidates for the immobilization of U(VI) in the solid phase. As inorganic phosphate is generally scarce in soils, the biomineralization of U(VI)-phosphate minerals via microbially-mediated organophosphate hydrolysis may represent the main immobilization process of uranium in these environments. In this study, contaminated sediments were incubated aerobically in two pH conditions to examine whether phytate, a naturally-occurring and abundant organophosphate in soils, could represent a potential phosphorous source to promote U(VI)-phosphate biomineralization by natural microbial communities. While phytate hydrolysis was not evident at pH 7.0, nearly complete hydrolysis was observed both with and without electron donor at pH 5.5, suggesting indigenous microorganisms express acidic phytases in these sediments. While the rate of hydrolysis of phytate generally increased in the presence of uranium, the net rate of inorganic phosphate production in solution was decreased and inositol phosphate intermediates were generated in contrast to similar incubations conducted without uranium. These findings suggest uranium stress enhanced the phytate-metabolism of the microbial community, while simultaneously inhibiting phosphatase production and/or activity by the indigenous population. Finally, phytate hydrolysis drastically decreased uranium solubility, likely due to formation of ternary sorption complexes, U(VI)-phytate precipitates, and U(VI)-phosphate minerals. Overall, the results of this study provide evidence for the ability of natural microbial communities to liberate phosphate from phytate in acidic sediments, possibly as a detoxification mechanism, and demonstrate the potential utility of phytate-promoted uranium immobilization in subsurface environments. These processes should be investigated in more detail with pure cultures isolated from these sediments.

First Principles Study of Uranium Solubility in Gd2Zr2O7 Pyrochlore

Ab initio calculation is performed to investigate the uranium solubility in different sites of Gd2Zr2O7 pyrochlore. The Gd2Zr2O7 maintains its pyrochlore structure at low uranium dopant levels, and the lattice constants of Gd2(Zr2−yUy)O7 and (Gd2−yUy)Zr2O7 are generally expressed as being linearly related to the uranium content y. Uranium is found to be a preferable substitute for the B-site gadolinium atoms in cation-disordered Gd2Zr2O7 (where gadolinium and zirconium atoms are swapped) over the A-site gadolinium atoms in ordered Gd2Zr2O7 due to the lower total energy of (Gd2−yZry)(Zr2−yUy)O7.

Thermodynamics of uranium in (Ga + Sn) eutectic alloy

Thermodynamic properties of uranium were studied in (U+Ga), (U+Sn) and (U+Ga+Sn) systems. Activity and activity coefficients of uranium were determined in alloys with tin and (gallium+tin) eutectic (0.135 Sn mass fraction) between T=(573 and 1073)K. Solubility of uranium in (Ga+Sn) eutectic and in pure Ga was measured between T=(298 and 1073)K. Activity coefficients, partial and excess thermodynamic functions of uranium in alloys with Ga, Sn and (Ga+Sn) eutectic were calculated.

Adsorption and desorption of uranium(VI) by Fe–Mn binary oxide in aqueous solutions

The adsorption and desorption behaviors of uranium(VI) by a synthetic Fe/Mn (mass ratio of 57:1) binary oxide (FMBO) has been investigated. The pseudo-second-order kinetic and the Dubinin–Radushkevich isotherm models showed.that the adsorption process involved chemical adsorption. The calculated thermodynamic parameters (ΔH°, ΔS°, ΔG°) indicated that the adsorption process of uranium(VI) onto FMBO was spontaneous and endothermic. The desorption experiments indicated that the high desorption rate of uranium(VI) from FMBO by organic acids would increase the total solubility of uranium (in the exchangeable form), which would in turn enhance bio-absorption of uranium from soil via phytoremediation.

Effect of anthropogenic organic complexants on the solubility of Ni, Th, U(IV) and U(VI)

The influence of anthropogenic organic complexants (citrate, EDTA and DTPA from 0.005 to 0.1M) on the solubility of nickel(II), thorium(IV) and uranium (U(IV) and U(VI)) has been studied. Experiments were carried out in 95%-saturated Ca(OH)2 solutions, representing the high pH conditions anticipated in the near field of a cementitious intermediate level radioactive waste repository. Results showed that Ni(II) solubility increased by 2–4 orders of magnitude in the presence of EDTA and DTPA and from 3 to 4 orders of magnitude in the case of citrate. Citrate had the greatest effect on the solubility of Th(IV) and U(IV)/(VI). XRD and SEM analyses indicate that the precipitates are largely amorphous; only in the case of Ni(II), is there some evidence of incipient crystallinity, in the form of Ni(OH)2 (theophrastite). A study of the effect of calcium suggests that U(VI) and Ni(II) may form metal-citrate-OH complexes stabilised by Ca2+. Thermodynamic modelling underestimates the concentrations in solution in the presence of the ligands for all the elements considered here. Further investigation of the behaviour of organic ligands under hyperalkaline conditions is important because of the use of the thermodynamic constants in preparing the safety case for the geological disposal of radioactive wastes.

Thermodynamic properties of uranium in gallium–aluminium based alloys

Activity, activity coefficients and solubility of uranium was determined in gallium-aluminium alloys containing 1.6 (eutectic), 5 and 20 wt.% aluminium. Additionally, activity of uranium was determined in aluminium and Ga–Al alloys containing 0.014–20 wt.% Al. Experiments were performed up to 1073 K. Intermetallic compounds formed in the alloys were characterized by X-ray diffraction. Partial and excess thermodynamic functions of U in the studied alloys were calculated.

Thermodynamic properties of uranium in liquid gallium, indium and their alloys

Activity, activity coefficients and solubility of uranium was determined in gallium, indium and gallium–indium alloys containing 21.8 (eutectic), 40 and 70wt.% In. Activity was measured at 573–1073K employing the electromotive force method, and solubility between room temperature (or the alloy melting point) and 1073K employing direct physical measurements. Activity coefficients were obtained from the difference of experimentally determined temperature dependencies of uranium activity and solubility. Intermetallic compounds formed in the respective alloys were characterized using X-ray diffraction. Partial and excess thermodynamic functions of uranium in the studied alloys were calculated. Liquidus lines in U–Ga and U–In phase diagrams from the side rich in gallium or indium are proposed.

U在烧绿石Nd&lt;sub&gt;2&lt;/sub&gt;Zr&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;7&lt;/sub&gt;中的固化研究

以具有较强抗辐照和化学稳定性的锆基烧绿石Nd2Zr2O7为固化基材，针对锕系核素U进行固化研究。以硝酸盐作为原料，通过柠檬酸络合和喷雾热解的方法，在1200℃保温12 h成功制备了含U 10 mol%的烧绿石固化体。产物经X-射线粉末衍射、拉曼光谱进行表征，结果表明：U很好的包容到烧绿石固化体中，固化体保持单一的烧绿石结构；U离子半径小于Nd，导致固化体晶格常数减小；随着U成分的增加，固化体的烧绿石结构趋向于无序化。 The solubility of Uranium in pryochlore Nd2Zr2O7 has been studied using zirconate pyrochlores as potential material for use in the high level nuclear waste because of their chemical and radi- ation stabilities. Uranium-doped Pyrochlore Nd1.9U0.1Zr2O7 was synthesized at 1200˚C for 12 h by sol-spray pyrolysis method using nitrate and citrate acid as raw materials. The phase compositions of the products were characterized by powder XRD, SEM, Raman spectrum. The results reveal that Uranium has been incorporated in the lattice of Nd2Zr2O7, while maintaining the single pyrochlore structure. The lattice parameter decreases for Nd2Zr2O7 pyrochlore with increase in Uranium content because the effective ionic radius of U is less than that of Nd3+. With increasing Uranium content, the degree of crystal structural disorder increases.