The impact of hydrogen valence on its bonding and transport in molten fluoride salts

Lam, Stephen T.; Li, Qingjie; Mailoa, Jonathan P.; Forsberg, Charles W.; Ballinger, R. G.; Li, Ju

doi:10.1039/d0ta10576g

“…The peak value of F-Be-F is located at 108 o , which represents a BeF2 tetrahedral configuration, and the Be-F-Be represents corner-sharing tetrahedra with a median angle of 127 o . These observations agree with our previous study [9], where the detailed analysis was performed on the local and extended structures in Flibe, and Be-F4 tetrahedral chains were observed with up to 4 Be atom centers. As shown in Figure 7b), the three-body interactions are accurately modeled by the NN (--), with the angular distributions almost exactly overlapping the AIMD (-) results in every species combination.…”

Section: Local Structure Of Flibesupporting

confidence: 93%

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

Lam

¹

,

Li²,

Ballinger³

et al. 2021

Preprint

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Lithium-based molten salts have attracted significant attention due to their applications in energy storage, advanced fission reactors and fusion devices. Lithium fluorides and particularly 66.6%LiF-33.3¾F2 (Flibe) are of considerable interest in nuclear systems, as they show an excellent combination of desirable heat-transfer and neutron-absorption characteristics. For nuclear salts, the range of possible local structures, compositions, and thermodynamic conditions presents significant challenges in atomistic modeling. In this work, we demonstrate that atom-centered neural network interatomic potentials (NNIP) provide a fast and accurate method for performing molecular dynamics of molten salts. For LiF, these potentials are able to accurately model dimer interactions, crystalline solids under deformation, semi-crystalline LiF near the melting point and liquid LiF at high temperatures. For Flibe, NNIPs accurately predicts the structures and dynamics at normal operating conditions, high temperature-pressure conditions, and in the crystalline solid phase. Furthermore, we show that NNIP-based molecular dynamics of molten salts are scalable to reach long timescales (e.g., nanosecond) and large system sizes (e.g., 105 atoms), while maintaining ab initio accuracy and providing more than three orders of magnitude of computational speedup for calculating structure and transport properties.

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“…As shown, semi-crystalline contains large localized atomic displacements while maintaining a partially ordered structure, while liquid configurations are highly disordered. The disorder of the liquid state is confirmed by calculation of radial distribution functions in previous work [9].…”

Section: Solid-to-liquid Phases Of Lifsupporting

confidence: 71%

“…All calculations were performed using the Perdew-Burke-Ernzerhof (PBE) generalized gradient approximation (GGA) exchange-correlation functional and projectoraugmented wave (PAW) potentials for the nucleus and core electrons (Li_sv, Be, and F). These simulation protocols were previously validated for a variety of fluoride salts to produce accurate predictions for a variety of chemical and physical properties [9].…”

Section: Ab Initio Data Generationmentioning

confidence: 99%

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

Lam

¹

,

Li²,

Ballinger³

et al. 2021

Preprint

Self Cite

0

View full text Add to dashboard Cite

Lithium-based molten salts have attracted significant attention due to their applications in energy storage, advanced fission reactors and fusion devices. Lithium fluorides and particularly 66.6%LiF-33.3¾F2 (Flibe) are of considerable interest in nuclear systems, as they show an excellent combination of desirable heat-transfer and neutron-absorption characteristics. For nuclear salts, the range of possible local structures, compositions, and thermodynamic conditions presents significant challenges in atomistic modeling. In this work, we demonstrate that atom-centered neural network interatomic potentials (NNIP) provide a fast and accurate method for performing molecular dynamics of molten salts. For LiF, these potentials are able to accurately model dimer interactions, crystalline solids under deformation, semi-crystalline LiF near the melting point and liquid LiF at high temperatures. For Flibe, NNIPs accurately predicts the structures and dynamics at normal operating conditions, high temperature-pressure conditions, and in the crystalline solid phase. Furthermore, we show that NNIP-based molecular dynamics of molten salts are scalable to reach long timescales (e.g., nanosecond) and large system sizes (e.g., 105 atoms), while maintaining ab initio accuracy and providing more than three orders of magnitude of computational speedup for calculating structure and transport properties.

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“…Recently, Lam et al used computational methods based on first principles to elucidate tritium chemistry and transport properties in molten fluoride salts [48]. Their results agree with the Henry's coefficient data below in that 3 H + has a higher solubility than 3 H 0 in FLiBe.…”

Section: Tritiummentioning

confidence: 65%

Thermochemical Modeling in Molten Fluoride Salts for Radionuclide Speciation

Shahbazi

¹

,

Bucknor

²

,

Thomas

³

et al. 2021

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An important aspect of the licensing process for nuclear reactors is providing a reasonable assurance of safety to the general public. This includes modeling potential radionuclide releases from the reactor during normal operations and accident scenarios, which is known as the reactor's source term. A new class of advanced (non-LWR) reactors are being developed which use molten salts as the coolant fluid. Because the molten salt coolant represents a credited barrier for radionuclide transport between the fuel and the environment, a necessary aspect of mechanistic source term (MST) analysis for the KP-FHR is modeling the thermochemistry of molten salts. Provided here is a review of the theory of the thermodynamic principles governing multicomponent phase equilibria, the background of molten salt thermochemistry research, and a summary of the thermochemical data relevant to the KP-FHR coolant salt, Li2BeF4, commonly referred to as "FLiBe". A review of literature is followed by a brief introduction to methods that can be used to model the thermochemical behavior of molten salt mixtures. The methodology outlined is based on the use of a commercial thermodynamic modeling software called FactSage, which is one of only a few available softwares based on the modified quasichemical model (MQM), which is the recommended solution model for molten salts.

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The impact of hydrogen valence on its bonding and transport in molten fluoride salts

Abstract: In molten fluoride salt systems, the chemistry and transport of hydrogen are coupled to its valence state, which controls the balance of tritium leakage and corrosion.

Cited by 28 publications

References 53 publications

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

Modeling LiF and FLiBe Molten Salts with Robust Neural Network Interatomic Potentials

Thermochemical Modeling in Molten Fluoride Salts for Radionuclide Speciation

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