Theoretical Study of Plutonium(IV) Complexes Formed within the PUREX Process: A Proposal of a Plutonium Surrogate in Fire Conditions

Šulka, Martin; Cantrel, Laurent; Vallet, Valérie

doi:10.1021/jp507684f

Cited by 30 publications

(30 citation statements)

References 47 publications

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“…Lastly, concerning the ∆G hyd values, the Ce IV estimate is found to be in between Np IV and Pu IV , still closer to the latter with a difference of 8 kcal mol −1 . Such a level of similarities between hydrated Ce IV and Pu IV have been also reported from QM and experimental studies [42,43].…”

Section: Resultssupporting

confidence: 72%

Properties of the tetravalent actinide series in aqueous phase from a microscopic simulation self-consistent engine

Acher

Masella

Vallet

et al. 2020

Phys. Chem. Chem. Phys.

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In the context of nuclear fuel recycling and environmental issues, the understanding of the properties of radio-elements with various approaches remains a challenge regarding their dangerousness. Moreover, experimentally, it is imperative to work at sufficiently high concentrations to reach the sensitivities of the analysis tools, which often leads to precipitation for some of them, and stabilizing of specific oxidation states of some actinides remains a challenge, thus making it difficult to extract general trends across the actinide series. Complementary to experiments, modelling can be used to unbiasedly probe the actinide's properties in aquatic environment and offers a predictive tool. We report the first molecular dynamics simulations based on homogeneously built force fields for the whole series of the tetravalent actinides in aqueous phase from Th IV to Bk IV and including Pu IV . The force fields used to model the interactions among the constituents include polarization and charge donation microscopic effects. They are built from an automated iterative quantum ab initio based engine, the core element of a future machine learning procedure devoted to generate accurate force fields. The comparison of our simulated hydrated actinide properties to available experimental data show the model robustness and the relevance of our parameter assignment engine. Moreover our simulated structural, dynamical and hydration free energy data show that, apart from Am IV and Cm IV , the actinides properties change progressively along the series. arXiv:1907.07906v2 [physics.chem-ph]

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Section: Resultssupporting

confidence: 72%

Properties of the tetravalent actinide series in aqueous phase from a microscopic simulation self-consistent engine

Acher

Masella

Vallet

et al. 2020

Phys. Chem. Chem. Phys.

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“…[15][16][17][18][19] The chemical behavior of An(IV) was found highly consistent across the series, as commonly observed for f-elements (lanthanides (Ln) (4f) and An (5f)) in the same oxidation state, and are thus often considered as chemical analogues (e.g. [20][21][22][23][24][25] ).…”

Section: Introductionmentioning

confidence: 79%

“…30 Ce(IV) is often presented as a relevant analogue of An(IV). 22,24,25 As Ce is not radioactive, experimental studies can be more easily conducted with Ce(IV) than with An(IV), which could improve our scientific knowledge on An(IV) environmental chemistry. Therefore, prediction of Ce aqueous speciation is of great interest for different research fields.…”

Section: Introductionmentioning

confidence: 99%

Aqueous chemistry of Ce(iv): estimations using actinide analogues

et al. 2017

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The prediction of cerium (Ce) aqueous speciation is relevant in many research fields. Indeed, Ce compounds are used for many industrial applications, which may require the control of Ce aqueous chemistry for their synthesis. The aquatic geochemistry of Ce is also of interest. Due to its growing industrial use and its release into the environment, Ce is now considered as an emerging contaminant. Cerium is also used as a proxy of (paleo)redox conditions due to the Ce(iv)/Ce(iii) redox transition. Finally, Ce(iv) is often presented as a relevant analogue of tetravalent actinides (An(iv)). In the present study, quantum chemical calculations were conducted to highlight the similarities between the structures of Ce(iv) and tetravalent actinide (An(iv); An = Th, Pa, U, Np, Pu) aqua-ions, especially Pu(iv). The current knowledge of An(iv) hydrolysis, solubility and colloid formation in water was briefly reviewed but important discrepancies were observed in the available data for Ce(iv). Therefore, new estimations of the hydrolysis constants of Ce(iv) and the solubility of Ce(iv)-(hydr)oxides are proposed, by analogy with Pu(iv). By plotting pH-Eh (Pourbaix) diagrams, we showed that the pH values corresponding to the onset of Ce(iv) species formation (i.e. Ce(iv)-(hydr)oxide or dissolved Ce(iv)) agreed with various experimental results. Although further experimental studies are required to obtain a more accurate thermodynamic database, the present work might yet help to predict more accurately the Ce chemical behavior in aqueous solution.

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“…To make a selection of surrogate candidates, their behavior should be similar in all oxidation states. Considering for example the gaseous state, the volatility of Pu(VI), which still remains an open issue, should be addressed specifically because some of the candidates (Th, Ce) [1] cannot extend their oxidation degree up to VI. An alternative to surrogates is the development of a predictive model which includes all relevant physical and chemical transformations of plutonium containing substances.…”

Section: Introductionmentioning

confidence: 99%

Accurate Predictions of Volatile Plutonium Thermodynamic Properties

et al. 2019

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Having the ability to predict the nature and amounts of plutonium emissions in industrial accidents, such as in solvent fires at PUREX nuclear reprocessing facilities, is a key concern of nuclear safety agencies. In accident conditions and in the presence of oxygen and water vapor, plutonium is expected to form three major volatile species PuO2, PuO3, and PuO2(OH)2, for which the thermodynamic data necessary for predictions (enthalpies of formation and heat capacities) presently shows either large uncertainties or is lacking. In this work we aim to alleviate such shortcomings by obtaining the aforementioned data via relativistic correlated electronic structure calculations employing the Multi-State Complete Active Space with Second-Order Perturbation Theory (MS-CASPT2) with state-interaction RASSI spin-orbit coupling approach, which is able to describe the multireference character of the ground-state wavefunctions of PuO3 and PuO2(OH2). We benchmark this approach by comparing it to relativistic coupled cluster calculations for the ground, ionized and excited states of PuO2. Our results allow us to predict enthalpies of formation ∆ f H − • (298.15 K) of PuO2, PuO3 and PuO2(OH)2 to be (−449.5 ± 8.3) kJ mol −1 , (−553.2 ± 27.3) kJ mol −1 , and (−1012.6 ± 38.0) kJ mol −1 , respectively, which confirm the predominance of plutonium dioxide, but also reveal the existence of plutonium trioxide in gaseous phase under oxidative condition, though the partial pressures of PuO3 and PuO2(OH)2 are nonetheless always rather low under wet atmosphere. Our calculations also permit us to reassess prior results for PuO2, establishing the ground state of the PuO2 molecule is mainly of 5 Σ + g character, as well as to confirm the experimental value for the adiabatic ionization energy of PuO2.

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Theoretical Study of Plutonium(IV) Complexes Formed within the PUREX Process: A Proposal of a Plutonium Surrogate in Fire Conditions

Cited by 30 publications

References 47 publications

Properties of the tetravalent actinide series in aqueous phase from a microscopic simulation self-consistent engine

Properties of the tetravalent actinide series in aqueous phase from a microscopic simulation self-consistent engine

Aqueous chemistry of Ce(iv): estimations using actinide analogues

Accurate Predictions of Volatile Plutonium Thermodynamic Properties

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