Thermodynamic evaluation and optimization of the (NaF+AlF3+CaF2+BeF2+Al2O3+BeO) system

Robelin, Christian; Chartrand, Patrice

doi:10.1016/j.jct.2012.09.005

Cited by 14 publications

(15 citation statements)

References 36 publications

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“…Such measurements are important since the diffusion coefficients provide an information on the individual dynamics of the ions, complementing the viscosity or electrical conductivity measurements which inform about the collective dynamics of the macroscopic system. During the past decade, these experimental efforts have been accompanied by the development of simulation tools adapted to the study of molten fluorides and chlorides, namely density functional theory 26 , thermodynamic modeling [27][28][29] and molecular dynamics (MD) 30,31 . Among those, the latter has proven to be efficient for the study of the structure and dynamics of the system at the microscopic scale, allowing the interpretation of ex-perimental results [32][33][34] and the prediction of quantities that hitherto remained unknown 29 .…”

Section: Introductionmentioning

confidence: 99%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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The transport properties of molten LiF-YF 3 mixtures have been studied by pulsed field gradient nuclear magnetic resonance spectroscopy, potentiometric experiments, and molecular dynamics simulations. The calculated diffusion coefficients and electric conductivities compare very well with the measurements across a wide composition range. We then extract static (radial distribution functions, coordination numbers distributions) and dynamic (cage correlation functions) quantities from the simulations. Then, we discuss the interplay between the microscopic structure of the molten salts and their dynamic properties. It is often considered that variations in the diffusion coefficient of the anions are mainly driven by the evolution of its coordination with the metallic ion (Y 3+ here). We compare this system with fluorozirconate melts and demonstrate that the coordination number is a poor indicator of the evolution of the diffusion coefficient. Instead, we propose to use the ionic bonds lifetime. We show that the weak Y-F ionic bonds in LiF-YF 3 do not induce the expected tendency of the fluoride diffusion coefficient to converge toward the one of yttrium cation when the content in YF 3 increases. Implications on the validity of the Nernst-Einstein relation for estimating the electrical conductivity are discussed.

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Section: Introductionmentioning

confidence: 99%

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Levesque¹,

Sarou‐Kanian²,

Salanne³

et al. 2013

The Journal of Chemical Physics

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“…Despite its practicality, structural features, such as molecular species and network formation, are not accounted for. However, structural features may be imposed on the model, for example by explicitly introducing ions with different coordinations [40,41]. In this formalism, a set of two anions and two cations makes up a quadruplet, taken to be the basic unit in the liquid solution, and the excess parameters to be optimised are those related to the following second-nearest neighbour (SNN) exchange reaction:…”

Section: Liquid Solutionmentioning

confidence: 99%

Thermodynamic Description of the ACl-ThCl4 (A = Li, Na, K) Systems

Flores

Rooijakkers

Konings

et al. 2021

Thermo

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The ACl-ThCl4 (A = Li, Na, K) systems could be of relevance to the nuclear industry in the near future. A thermodynamic investigation of the three binary systems is presented herein. The excess Gibbs energy of the liquid solutions is described using the quasi-chemical formalism in the quadruplet approximation. The phase diagram optimisations are based on the experimental data available in the literature. The thermodynamic stability of the liquid solutions increases in the order Li < Na < K, in agreement with idealised interactions and structural models.

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“…A later effort on the NaF-BeF2 pseudo-binary by Robelin and Chartrand [25] endeavored to extend the application of the MQM with variable coordination numbers by adopting two endmembers for BeF2, which they identified as BeIVF2, the four-coordinated beryllium with fluorine, and the dimer Be2F4. These yielded still better agreement with the observed higher BeF2-content phase equilibria by allowing compositions to be computed with coordination numbers intermediate between the monomer and dimer determined by the ratio of these endmembers.…”

Section: Coordination Numbers and Mqm Generationmentioning

confidence: 99%

“…Figure2. Overlaid phase diagrams based on melt models for NaF-BeF2 using[25] and not using[24] multiple endmembers for BeF2. The selected experimental data points are those of Roy, et al[26] and Novoselova[27].…”

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confidence: 99%

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Developing Practical Models of Complex Salts for Molten Salt Reactors

Besmann¹,

Schorne-Pinto²

2021

Preprint

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olten salt reactors (MSRs) utilize salts as coolant or as the fuel and coolant together with fissile isotopes dissolved in the salt. It is necessary to therefore understand the behavior of the salts to effectively design, operate, and regulate such reactors, and thus there is a need for thermodynamic models for the salt systems. Molten salts, however, are difficult to represent as they exhibit short range order that is dependent on both composition and temperature. A widely useful approach is the modified quasichemical model in the quadruplet approximation that provides for consideration of first and second nearest neighbor coordination and interactions. Its use in the CALPHAD ap-proach to system modeling requires fitting parameters using standard thermodynamic data such as phase equilibria, heat capacity, and others. Shortcoming of the model is its inability to directly vary coordination numbers with composition or temperature. Another issue is the difficulty in fitting model parameters using regression methods without already having very good initial values. The proposed paper will discuss these issues and note some practical methods for the effective genera-tion of useful models.

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Thermodynamic evaluation and optimization of the (NaF+AlF3+CaF2+BeF2+Al2O3+BeO) system

Cited by 14 publications

References 36 publications

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Structure and dynamics in yttrium-based molten rare earth alkali fluorides

Thermodynamic Description of the ACl-ThCl4 (A = Li, Na, K) Systems

Developing Practical Models of Complex Salts for Molten Salt Reactors

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