Experimental Speciation of Plutonium(IV) in Natural Seawater

Dumas, Thomas; Guigue, Mireille; Moisy, Philippe; Colina-Ruiz, Roberto; León, J.; Matara-aho, Minja; Solari, Pier Lorenzo; Monfort, Marguerite; Moulin, Christophe; Beccia, Maria Rosa; Auwer, Christophe Den

doi:10.1002/slct.201702762

Cited by 7 publications

(6 citation statements)

References 20 publications

(19 reference statements)

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“…However, the number of Pu atoms reduces as PuO 2 moves away from a bulk material into a nanoparticulate form because of the Pu atoms near the surface having fewer Pu neighbors (Figure S6). , This effect is well demonstrated for PuO 2 nanoparticles recently by Micheau et al, 2020, which demonstrated that EXAFS can significantly underestimate the particle size when compared to small angle X-ray scattering measurements. Therefore, because of these effects, this value only represents a lower limit on the proportion of PuO 2 in the sample.…”

Section: Resultssupporting

confidence: 65%

“…Note that we refer to the x-axis of the FT as r, and pair distances as R. The first of the two peaks was successfully modeled as 6(2) Pu-Fe scatterers at 3.39(1) Å with an elevated Debye Waller factor (σ 2 ; pair-distance distribution variance) of 0.021(4) Å fewer Pu neighbors, thereby reducing the average coordination number in a particle. 66,70 If we assume that the PuO2 nanoparticles are on average 4 nm, as the TEM analysis of G-FHS-3000 and G-FHS-1000 indicates, this would correspond to an average of 10 Pu-Pu scatterers (Figure SI 3). 71 Using this assumption we can estimate that approximately 30% of all Pu in FH-S-3000 is present as PuO2 with the remainder existing as an inner sphere complex with the ferrihydrite.…”

Section: Ferrihydritementioning

confidence: 99%

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Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Balboni

Smith

Moreau

et al. 2020

ACS Earth Space Chem.

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Understanding interactions between plutonium and iron (oxy)hydroxide minerals is necessary to gain a predictive understanding of plutonium environmental mobility and ensuring long-term performance of nuclear waste repositories. Plutonium sorption and desorption reactions with mineral surfaces, formation of PuO2 nanoparticles, and coprecipitation processes are all likely important processes under a range of geochemical conditions. We investigated plutonium fate during the formation of ferrihydrite and its subsequent recrystallization to goethite. Ferrihydrite was synthesized with varying quantities of Pu(IV) following either a sorption or coprecipitation process; the ferrihydrite was then aged hydrothermally to yield goethite. The synthesized materials were characterized via extended x-ray absorption fine structure spectroscopy, transmission electron microscopy, and acid leaching to elucidate the nature of plutonium association with ferrihydrite and goethite. In samples prepared following the sorption method, plutonium was identified in two different forms: a PuO2 precipitate and a surface sorbed plutonium complex. For the samples prepared via coprecipitation the data demonstrate that no PuO2 formation occurs in the ferrihydrite precursor and in the goethite experiments where plutonium concentration is ≤ 1000 ppm (mg Kg -1 ). In these coprecipitation experiments plutonium extended x-ray absorption fine structure data indicate the plutonium is strongly bound to the minerals either via formation of a strong inner sphere complex, or via an incorporation process. In the coprecipitation experiments, PuO2 formation only occurs at the highest plutonium concentration (3000 ppm), suggesting that during ferrihydrite recrystallization part of the plutonium can be remobilized to form PuO2 nanoparticles if the plutonium concentration is sufficiently elevated. In a series of acid leaching 11/16/21 3 experiments, less plutonium was removed from the goethite surface when formed via the coprecipitation process compared to the sorption process. Collectively, our results demonstrate that the nature of plutonium associated with the precursor ferrihydrite (adsorbed versus coprecipitated) will have a direct impact on the association of plutonium with its recrystallization product (goethite). Furthermore, the data illustrate that some properties of plutonium association with the precursor ferrihydrite are retained through recrystallization process to goethite. These findings show that plutonium strongly associates to iron (oxy)hydroxides formed through coprecipitation processes and in these materials plutonium can be strongly retained by the iron minerals.

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Section: Resultssupporting

confidence: 65%

Section: Ferrihydritementioning

confidence: 99%

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Balboni

Smith

Moreau

et al. 2020

ACS Earth Space Chem.

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“…This demonstrates that Pu complexes, likely in a carbonated [Pu(V)-(CO 3 ) n ] + form, are relatively mobile in CASW. Their transport is likely mainly colloid-facilitated, as demonstrated in previous work; − Pu(IV) has shown to be speciated as {PuO 2 }-type colloids in natural seawater …”

Section: Resultssupporting

confidence: 63%

“…Their transport is likely mainly colloid-facilitated, as demonstrated in previous work; 50−52 Pu(IV) has shown to be speciated as {PuO 2 }-type colloids in natural seawater. 53 Both the DGT KMS-1 and DGT Chelex-100 configurations captured Pu(IV) linearly as a function of time from SWS and CASW. Additionally, we demonstrated linear Pu(IV) uptake by DGT KMS-1 throughout a 15-day period in CASW with a close reproduction between c DGT and c 0 soln , endorsing DGT KMS-1 for marine Pu(IV + V) measures over this timescale.…”

Section: +mentioning

confidence: 96%

Novel DGT Configurations for the Assessment of Bioavailable Plutonium, Americium, and Uranium in Marine and Freshwater Environments

et al. 2021

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Plutonium, americium, and uranium contribute to the radioactive contamination of the environment and are risk factors for elevated radiation exposure via ingestion through food or water. Due to the significant environmental inventory of these radioelements, a sampling method to accurately monitor their bioavailable concentrations in natural waters is necessary, especially since physicochemical factors can cause significant temporal fluctuations in their waterborne concentrations. To this end, we engineered novel diffusive gradients in thin-film (DGT) configurations using resin gels, which are selective for UO 2 2+ , Pu(IV + V), and Am(III) among an excess of extraneous cations. In this work, we also report an improved synthesis of our in-house ion-imprinted polymer resin, which we used to manufacture a resin gel to capture Am(III). The effective diffusion coefficients of Pu, Am, and U in agarose cross-linked polyacrylamide were determined in freshwater and seawater simulants and in natural seawater, to calibrate these configurations for environmental deployments.

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“…The beamline is licenced to receive samples with radioisotope activities up to two million times their isotope-specific European exemption limits and complies with all legal requirements and safety precautions to avoid contaminating aerosol dissemination and guarantee the public dose rate outside the beamline. It has successfully shown its flexibility by accommodating a wide array of diverse sample environments during its years of operation (Be ´chade et al, 2012;Menut et al, 2015;Be ´chade et al, 2013;LLorens et al, 2014;Dumas et al, 2018;Bengio et al, 2020).…”

Section: Measurement By Synchrotron Radiation and Experimental Setupmentioning

confidence: 99%

Size and structure of hexanuclear plutonium oxo-hydroxo clusters in aqueous solution from synchrotron analysis

Dumas

Virot

Menut

et al. 2022

J Synchrotron Radiat

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The size and shape of a water-soluble hexanuclear plutonium cluster were probed by combining synchrotron small-angle X-ray scattering (SAXS) and extended X-ray absorption fine structure (EXAFS). A specific setup coupling both techniques and dedicated to radioactive samples on the MARS beamline endstation at Synchrotron SOLEIL is described. The plutonium hexanuclear cores are well stabilized by the 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid ligands and this allows a good evaluation of the setup to probe the very small plutonium core. The results show that, in spite of the constrained conditions required to avoid any risk of sample dispersion, the flux and the sample environment are optimized to obtain a very good signal-to-noise ratio, allowing the detection of small plutonium aggregates in an aqueous phase. The structure of the well defined hexanuclear cluster has been confirmed by EXAFS measurements in solution and correlated with SAXS data processing and modelling. An iterative comparison of classical fit models (Guinier or sphere form factor) with the experimental results allowed a better interpretation of the SAXS signal that will be relevant for future work under environmentally relevant conditions.

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Experimental Speciation of Plutonium(IV) in Natural Seawater

Cited by 7 publications

References 20 publications

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Transformation of Ferrihydrite to Goethite and the Fate of Plutonium

Novel DGT Configurations for the Assessment of Bioavailable Plutonium, Americium, and Uranium in Marine and Freshwater Environments

Size and structure of hexanuclear plutonium oxo-hydroxo clusters in aqueous solution from synchrotron analysis

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