Precise isotopic analysis of uranium in picomole and subpicomole quantities

Chen, J. H.; Wasserburg, G. J.

doi:10.1021/ac00236a027

Cited by 147 publications

(24 citation statements)

References 22 publications

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“…High precision 238 U/ 235 U measurements were obtained using a double spike approach, which corrects for instrumental mass bias during analysis and any isotopic fractionation induced by sample preparation steps (Chen and Wasserburg, 1981;Stirling et al, 2005;Weyer et al, 2008). The U double spike solution contained 233 U and 236 U (prepared in-house from 233 U and 236 U spikes) with a calibrated 233 U/ 236 U ratio of 0.46275 ± 0.00001).…”

Section: Double Spike Methodsmentioning

confidence: 99%

Low temperature equilibrium isotope fractionation and isotope exchange kinetics between U(IV) and U(VI)

Wang

Lundstrom

2015

Geochimica et Cosmochimica Acta

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Measurements of the uranium (U) isotope ratio 238 U/ 235 U provide an emerging redox proxy in environmental and paleoredox studies, but many key parameters concerning U isotope fractionation are still poorly constrained. Here we report the equilibrium isotopic fractionation between dissolved U(IV) and dissolved U(VI), and rates of isotope exchange between solid-phase U(IV) and dissolved U(VI). We conducted one experiment at high concentration [35 mM U(IV) and 32 mM U(VI)] and low pH (0.2) in hydrochloric acid media at room temperature to determine the equilibrium isotopic fractionation between dissolved U(IV) and dissolved U(VI). Isotopic equilibrium was reached in about 19 days under such experimental conditions. The equilibrium isotope fractionation was determined to be 1.64 ± 0.16&, with U(IV) being enriched in 238 U relative to U(VI). Applicability of the determined equilibrium fractionation is discussed.We also conducted a set of experiments to determine isotopic exchange rates between dissolved U(VI) and nanouraninite U(IV) under conditions closer to those in natural system, with lower concentrations and neutral pH. The exchange rate was found to conform to the rate law R = k[U(VI)] adsorbed , in which R is the isotopic exchange rate (lM day À1 ); k is the rate constant determined to be 0.21 day À1 ; and [U(VI)] adsorbed is the concentration of U(VI) adsorbed to nanouraninite (lM).Our results, combined with consideration of the variables controlling U(VI)-U(IV) contact in natural settings, indicate that the timescale for significant isotope equilibration varies depending on environmental conditions, mostly uranium concentrations. In natural uncontaminated sediments with low uranium concentrations, equilibration is expected to occur on a timescale of hundreds to thousands of years. In contrast, in U-contaminated aquifers with high U concentrations, significant equilibration could occur on timescales of weeks to years.

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Section: Double Spike Methodsmentioning

confidence: 99%

Low temperature equilibrium isotope fractionation and isotope exchange kinetics between U(IV) and U(VI)

Wang

Lundstrom

2015

Geochimica et Cosmochimica Acta

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“…There is, of course, some basic uncertainty in the estimated nucleosynthetic yield of these nuclei. The study by Chen & Wasserburg [157] [158] gave an upper limit of ( 247 Cm/ 235 U) ESS < 2 × 10 −3 . A new report by Stirling et al using more precise techniques on bulk meteorites but with very limited U/Nd elemental fractionation for chondrites, gives a bound of 1.0 × 10 −4 [159].…”

Section: Estimates Of the Ism Inventory Of Short-lived Nucleimentioning

confidence: 99%

Short-lived nuclei in the early Solar System: Possible AGB sources

et al. 2006

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The abundances of short-lived radionuclides in the early solar system (ESS) are reviewed, as well as the methodology used in determining them. These results are compared with the inventory estimated for a uniform galactic production model. It is shown that, to within a factor of two, the observed abundances of 238 U, 235 U, 232 Th, 244 Pu, 182 Hf, 146 Sm, and 53 Mn are roughly compatible with long-term galactic nucleosynthesis. 129 I is an exception, with an ESS inventory much lower than expected from uniform production. The isotopes 107 Pd, 60 Fe, 41 Ca, 36 Cl, 26 Al, and 10 Be require late addition to the protosolar nebula. 10 Be is the product of energetic particle irradiation of the solar system as most probably is 36 Cl. Both of these nuclei appear to be present when 26 Al is absent. A late injection by a supernova (SN) cannot be responsible for most of the short-lived nuclei without excessively producing 53 Mn; it can however be the source of 53 Mn itself and possibly of 60 Fe. If a late SN injection is responsible for these two nuclei, then there remains the problem of the origin of 107 Pd and several other isotopes. Emphasis is given to an AGB star as a source of many of the nuclei, including 60 Fe; this possibility is explored with a new generation of stellar models. It is shown that if the dilution factor (i.e. the ratio of the contaminating mass to the solar parental cloud mass) is f 0 ∼ 4×10 −3 , a reasonable representation for many nuclei is obtained; this requires that ( 60 Fe/ 56 Fe) ESS ∼ 10 −7 to 2×10 −6 . The nuclei produced by an AGB source do not include 53 Mn, 10 Be or 36 Cl if it is very abundant. The role of irradiation is discussed with regard to 26 Al, 36 Cl and 41 Ca, and the estimates of bulk solar abundances of these isotopes are commented on. The conflict between various scenarios is emphasized as well as the current absence of an astrophysically plausible global interpretation for all the existing data. Examination of abundances for the actinides indicates that a quiescent interval of ∼ 10 8 years is required for actinide group production. This is needed in order to explain the data on 244 Pu and the new bounds on 247 Cm. Because this quiescent interval is not compatible with the 182 Hf data, a separate type of r-process event is needed for at least the actinides, distinct from the two types that have previously been identified. The apparent coincidence of the 129 I and trans-actinide time scales suggests that the last heavy r contribution was from an r-process that produced very heavy nuclei but without fission recycling so that the yields at Ba and below (including I) were governed by fission.

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“…Figure 1 shows Thermal Ionisation Mass Spectrometry (TIMS) is the technique of choice for actinides measurements in nuclear sample when high accuracy is needed [8][9][10]. This method advanced analytical capacities with per-mil-level precision [11,12] and the latest generation of these instruments allows isotope measurements with precision of several ppm level [13,14]. In recent years, inductively coupled plasma source mass spectrometers equipped with multi collectors (MC-ICPMS) can attain isotope ratio precision ≤ 0.01% [15][16][17].…”

Section: Introductionmentioning

confidence: 99%

Accurate determination of Curium and Californium isotopic ratios by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 248Cm samples for transmutation studies

Gourgiotis,

Isnard,

Aubert

et al. 2010

International Journal of Mass Spectrometry

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46The French Atomic Energy Commission has carried out several experiments including the 47 mini-INCA (INcineration of Actinides) project for the study of minor-actinide transmutation 48 processes in high intensity thermal neutron fluxes, in view of proposing solutions to reduce 49 the radiotoxicity of long-lived nuclear wastes. In this context, a Cm sample enriched in 248 Cm 50 (~97 %) was irradiated in thermal neutron flux at the High Flux Reactor (HFR) of the Laue-51Langevin Institute (ILL). This work describes a quadrupole ICP-MS (ICP-QMS) analytical 52 procedure for precise and accurate isotopic composition determination of Cm before sample 53 irradiation and of Cm and Cf after sample irradiation. The factors that affect the accuracy and 54 reproducibility of isotopic ratio measurements by ICP-QMS, such as peak centre correction, 55 detector dead time, mass bias, abundance sensitivity and hydrides formation, instrumental 56 background, and memory blank were carefully evaluated and corrected. Uncertainties of the 57 isotopic ratios, taking into account internal precision of isotope ratio measurements, peak 58 tailing, and hydrides formations ranged from 0.3% to 1.3%. This uncertainties range is quite 59 acceptable for the nuclear data to be used in transmutation studies.

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Precise isotopic analysis of uranium in picomole and subpicomole quantities

Cited by 147 publications

References 22 publications

Low temperature equilibrium isotope fractionation and isotope exchange kinetics between U(IV) and U(VI)

Low temperature equilibrium isotope fractionation and isotope exchange kinetics between U(IV) and U(VI)

Short-lived nuclei in the early Solar System: Possible AGB sources

Accurate determination of Curium and Californium isotopic ratios by inductively coupled plasma quadrupole mass spectrometry (ICP-QMS) in 248Cm samples for transmutation studies

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