Monte Carlo simulation of the corrosion of irradiated simplified nuclear waste glasses

Jan, Amreen; Delaye, Jean‐Marc; Gin, Stéṕhane; Kerisit, Sebastien N.

doi:10.1016/j.jnoncrysol.2019.05.025

Cited by 15 publications

(14 citation statements)

References 41 publications

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“…that irrespective of the glass composition an increase in the concentration of 3coordinated boron leads to an increase in the rate of leaching. 32 These results are also supported by experimental studies of leaching of sodium borosilicate glasses as a function of boron content in the glass (from 0 to 75 mol % B 2 O 3 ). 39 The experimentally measured normalized release rates of Na, Si, and B adjusted for pH 9 as presented in Table 2 of ref 39 are plotted in Figure S2 as a function of the percentage of 3coordinated boron atoms measured using NMR spectroscopy.…”

Section: Discussionsupporting

confidence: 58%

“…Therefore, radiation damage should directly play a role at this stage of leaching because it introduces dangling and strained bonds into the network, thereby facilitating the process of leaching either by directly reducing the number of the bonds that need to be hydrolyzed or by facilitating the interaction of water with the strained bonds and other preexisting defects. Radiation damage can also broaden the ring distribution , and thereby directly affect the diffusion barriers for water molecules . More specifically for the case of the ISG glass and its simple and complex counterparts, the effects of ion irradiation have been extensively studied using both experimental approaches and atomistic simulations. − ,,,,, All these studies have shown that ion irradiation causes network depolymerization and transformation of 4-coordinated boron into 3-coordinated boron.…”

Section: Discussionmentioning

confidence: 99%

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New Insights about the Importance of the Alteration Layer/Glass Interface

et al. 2020

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This work addresses the impact of radiation damage on the leaching of international simple glass (ISG). Pristine and specimens irradiated with multi-energy Au ions were leached for 82 days at 90 o C in pure water and pH 9 and regularly sampled. Samples leached for 13 and 58 days were characterized using transmission electron microscopy (TEM) to study the microstructure(s) of the alteration layers formed from the radiation-damaged and pristine glasses. Furthermore, a sample altered for 82 days was immersed in water enriched in isotopically tagged water molecules (H2 18 O) to study and compare the mobility and reactivity of water at room temperature in the alteration layers formed on these glasses. The studies revealed that radiation damage diminished the chemical durability of the ISG glass since the beginning of the leaching experiment. Concomitantly, the formation of a non-porous alteration layer of about 237 nm after 13 days of leaching evolving into the formation of a nanoporous alteration layer of about 570 nm after 58 days of leaching was observed in the irradiated glasses. In contrast, a non-porous altered layer of about 138 nm only developed in the non-irradiated specimen altered for 58 days. Using energy-filtered transmission electron microscopy, the altered layers in all the cases were found to be depleted in boron, in agreement with the time of flight secondary ion mass spectroscopy studies. Despite pore formation, similar behaviour in the 18 O - 16 O exchanges (with respect to the uncertainties) was observed in the major part of the alteration layers whether formed from the irradiated or pristine ISG, leading to the conclusion that the greater alterability of the radiationdamaged ISG may not be due to the porosity. However, isotopic exchanges also revealed a significantly higher reactivity of water in the alteration-layer/glass interface for the irradiated glass. While these studies provide important insights about the role of porosity and radiation damages, they also highlight the complex nature of glass dissolution and suggest that studies directed at alteration-layer/glass interface are needed to better understand and explain the mechanisms controlling the glass dissolution in the residual alteration rate regime.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

New Insights about the Importance of the Alteration Layer/Glass Interface

et al. 2020

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“… − On an experimental basis, many instrumental techniques have been devised to study the effects of water on glasses, such as X-ray photoelectron spectroscopy (XPS), , Fourier transform infrared (FTIR) spectroscopy, , secondary ion mass spectrometry (SIMS), , transmission electron microscopy (TEM), atom probe tomography (APT), − spectroscopic ellipsometry (SE), NMR spectroscopy, , and inductively coupled plasma atomic emission spectrometry (ICP-AES) . In addition to these experimental techniques, different atomistic simulation techniques have demonstrated their success in describing the glass–water interface, such as ab initio molecular dynamics (AIMD), classical molecular dynamics (MD), and Monte Carlo (MC) simulations. − …”

Section: Introductionmentioning

confidence: 99%

Leaching and Reactivity at the Sodium Aluminosilicate Glass–Water Interface: Insights from a ReaxFF Molecular Dynamics Study

et al. 2021

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In this study, we used ReaxFF reactive force field molecular dynamics (MD) simulations to investigate the dynamics associated with reactivity at the sodium aluminosilicate (NAS) glass−water interface. By combining van Hove correlation functions and visual analysis of individual trajectories, we found that when a Na + ion leaves its initial position at the glass surface under the effect of water, it can be replaced either by a H + ion or by another diffused Na + , resulting in a (Na + ⇌ H + ) ion exchange or (Na + ⇌ Na + ) ion exchange, respectively. These rearrangements at the NAS glass−water interface take place through many events such as the formation of oxygen-bearing functional groups (silanol Si(OH), germinal silanol Si(OH) 2 , and Al(OH)) and the agglomeration of Na + ions on the glass surface. The high affinity between water and Na + ions leads to two events, namely, the penetration of the water molecule into the first glass layer and the release of Na + ions into the bulk water. The release of sodium ions into bulk water takes place via several successive steps: (1) leaving their original position to an area more exposed to bulk water, (2) diffusion to the surface of the glass, (3) leaving the surface toward the solution, and (4) coming back to the glass surface. Statistical analysis shows that oxygen-bearing functional group formation occurs both by protonation of the nonbridging oxygen (NBO) site and by filling defects such as Si III , Al III , and Al IV by OH − resulting from the dissociation of water molecules, while in the bulk, they could be produced by the proton jumps between two adjacent NBO sites and dissociation of the water diffused in deep layers of glass. Germinal silanol groups (Si(OH) 2 ) are present in small amounts in the first layer of the glass after the protonation of two NBOs from a single Si IV . This process is accompanied by the conversion of Al III and Al IV units into Al V units and Si III units into Si IV units. By comparing the networks of Si and Al, we found that Al is more impacted by the occurrence of water molecules than Si, which is explained by an increase in the diffusion coefficient of Al compared with Si when these units become protonated (Si(OH) and Al(OH)).

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“…For example, Monte Carlo (MC) simulations have been used to simulate borosilicate glass corrosion using an ordered cristobalite network to represent the glass structure and a set of probabilities to represent the hydrolysis mechanisms. It has been shown that, as the alteration proceeds, a stationary state is reached, in which a protective layer enriched in silicon atoms forms between the pristine glass and solution after the removal of the soluble elements (B, Na + ). ,, However, the model structure does not simulate the disorder within the glass and the set of probabilities are empirical. In this context, Kerisit and Du recently developed a new approach (amorphous MC approach) in which glass structures generated from molecular dynamics simulations were used as starting points for MC simulations .…”

Section: Introductionmentioning

confidence: 99%

Atomic Insights into the Events Governing the Borosilicate Glass–Water Interface

et al. 2021

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An atomistic understanding of the mechanisms that govern the borosilicate glass−water interface is highly needed to obtain initial assessments of the phenomena occurring during the degradation of nuclear waste forms. To this end, we have simulated a structural model of sodium borosilicate glass using classical molecular dynamics (CMD) simulations followed by a Car−Parrinello ab initio molecular dynamics (AIMD) simulation and periodic density functional theory (DFT) calculations to study both the reactivity and water adsorption events on a sodium borosilicate glass. The obtained results revealed that: (i) Na + ions are directly involved in the first stages of the dissolution mechanism, namely, the penetration of water and the release of the most accessible sodium from the surface of the glass to the aqueous solution, (ii) due to the presence of a higher amount of sodium ions closer to B IV than B III units, the boron atom with the B III unit is more accessible to accommodate water molecules than the one with the B IV unit, and (iii) the attack of B III by a water molecule occurs by a phenomenon of nondissociative adsorption followed by dissociative adsorption where the adsorbed water dissociates by the presence of another nearby water molecule. An analysis of the electronic structure, based on maximally localized Wannier functions, shows that the nondissociative adsorption presents a noncovalent bond between one of the lone pairs of the water molecule and B III (B−OH 2 ) by an interatomic distance of 1.57 Å, whereas the dissociative adsorption of this water molecule showed a B−OH covalent bond by an interatomic distance of 1.49 Å. Water molecules are collectively adsorbed on a B adsorption site, which ultimately leads to terminal B−OH and silanol H−NBO formations. As B−OH is formed, the boron site begins to attract more water molecules, which can be considered an early stage of solvation of the glass around this site. By combining DFT approaches and Bader charge analysis, our calculation reports that the adsorption of a single water molecule onto a sodium-rich site exhibits higher total interaction energy than onto a pure boron atomic site. On the other hand, DFT revealed that the water molecule adsorbed on the sodium-rich site exhibits a higher elongation of the H−O W bond length of about 0.05 Å, indicating the high probability of water dissociation and favoring the formation of H−NBO precipitates.

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Monte Carlo simulation of the corrosion of irradiated simplified nuclear waste glasses

Cited by 15 publications

References 41 publications

New Insights about the Importance of the Alteration Layer/Glass Interface

New Insights about the Importance of the Alteration Layer/Glass Interface

Leaching and Reactivity at the Sodium Aluminosilicate Glass–Water Interface: Insights from a ReaxFF Molecular Dynamics Study

Atomic Insights into the Events Governing the Borosilicate Glass–Water Interface

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