Methods of Redox Control and Measurement in Molten NaCl-CaCl<sub>2</sub>-UCl<sub>3</sub>

Newton, Matthew; Hamilton, D. Ethan; Simpson, Michael F.

doi:10.1149/09810.0019ecst

Cited by 7 publications

(4 citation statements)

References 5 publications

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“…First, open-circuit potential (OCP) measurements were performed after the salt melted for about 10 h, as shown in Figure 3a. A stable OCP value can be observed as a function of time with a steady state being reached after about 10,000 s. This long equilibrium process is relatively common in molten salt systems, as also reported by Newton et al 15 A stable OCP value of ∼0 V is expected since both W and Pt are relatively inert in the salt. The initial transient of OCP may be due to the homogenization and equilibrium process of the molten salt solution at the beginning of the experiment since the LiCl−KCl−EuCl 3 salt mixture before the melt was made by just simply stirring the LiCl, KCl, and EuCl 3 salt powders in the crucible.…”

Section: Materials Preparations and Corrosionsupporting

confidence: 78%

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

et al. 2022

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Corrosion sensing is essential to monitor and safeguard materials’ health in molten salts. The present study developed a three-electrode-array minisensor for high-temperature molten salt corrosion monitoring. By using the developed sensor, the impurity-driven corrosion of T91 by a fission product, europium, in the LiCl–KCl eutectic molten salt has been studied. The developed minisensor was validated to be an ideal probe for in situ corrosion monitoring in the high-temperature molten salt via the comparisons on concentrations of the dissolved corrosion products detected using this device and inductively coupled plasma mass spectroscopy. To analyze the large volume of data measured using the minisensor during in situ corrosion experiments, an algorithm has been developed to achieve the high-throughput data analysis. The well-designed minisensor can be potentially used for high-throughput corrosion experiments. Combined with the developed algorithm for high-throughput analysis, this study provided a platform to explore the application of electrochemical sensors for the in situ corrosion monitoring of materials in high-throughput molten-salt corrosion experiments.

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Section: Materials Preparations and Corrosionsupporting

confidence: 78%

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

et al. 2022

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“…This reaction with a more thermochemically stable metal would then be dominant in absorbing excess chemical potential and would thereby limit the corrosion that the MSR system may experience. The discrete constant rates of sodium additions are shown in Figure 11 In both fluoride and chloride systems, the possibility of over-reducing the salt as seen in the blue circle marked lines in Figures 10, 11 can be a valid concern depending on the choice of reducing metal or redox control method that is used (Zhang et al, 2018;Newton et al, 2020).…”

Section: Chloride Fuel Salt Analysismentioning

confidence: 99%

Depletion-driven thermochemistry of molten salt reactors: review, method, and analysis

et al. 2023

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Molten salt reactors (MSRs) are innovative advanced nuclear reactors that utilize nuclear fuel by dissolving it in a high-temperature liquid salt. This unique feature differentiates MSRs from other types of reactors and allows for enhanced safety and economic performance. The liquid fuel also entails several multiphysics effects that can complicate reactor design and operation. One primary effect termed here as depletion-driven thermochemistry is a driving force in altering the multiphysics behavior of the reactor. Essentially, depletion-driven thermochemistry is the effect that fuel depletion has on changing the chemical redox potential of the fuel salt over time. As the fuel is consumed, the redox potential shifts toward a more oxidizing state. Without active control, the changing chemistry due to depletion increases corrosion thereby limiting reactor component lifetimes. Additionally, the changing redox potential of the fuel salt alters the vapor pressures of chemical species dissolved in the fuel salt. Changing vapor pressures of species in the fuel salt is an important parameter to understand when off-gassing volatile species during normal reactor operation, and for source term characterization during accident scenario transients. The present work represents a fundamental step toward modeling and coupling the driving physics (i.e., neutronics and chemistry) involved in altering the redox potential in an MSR. Here, the neutronic code Griffin models the depletion of the fuel-salt system, while the chemical equilibrium code Thermochimica calculates the thermochemical state of the isotopic inventory, using the Molten Salt Thermodynamic Database - Thermochemical (MSTDB-TC). These two codes are tightly coupled to predict the impact of fuel depletion in altering the chemistry in MSR systems. Redox potential control methods are discussed and can be modeled using this multiphysics approach. The vapor pressures of chemical species that could be extracted to an off-gas system, as determined by the reactor’s thermochemical state, are examined. The neutronics-chemistry coupling developed in this work is expected to have potential application for analyzing corrosion, source term evolution, and material safeguards in MSR systems. Lastly, suggestions for areas of further improvements of the models to expand these capabilities by incorporating other coupled physics effects is provided.

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“…Electrochemical techniques are proposed for that task. For example, the redox potential of salt could be monitored and controlled to mitigate the effects of impurities and to measure the efficacy of salt-cleaning procedures, − but the redox potential is affected by all impurities in the mixture. While electrochemical techniques are element specific, , they are relatively low-resolution methods that produce broad element-specific peaks that overlap in multicomponent solutions .…”

Section: Introductionmentioning

confidence: 99%

In-Situ Analysis of Corrosion Products in Molten Salt: X-ray Absorption Reveals Both Ionic and Metallic Species

et al. 2023

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Understanding and controlling the chemical processes between molten salts and alloys is vital for the safe operation of molten-salt nuclear reactors. Corrosion processes in molten salts are highly dependent on the redox potential of the solution that changes with the presence of fission and corrosion processes, and as such, reactor designers develop electrochemical methods to monitor the salt. However, electrochemical techniques rely on the deconvolution of broad peaks, a process that may be imprecise in the presence of multiple species that emerge during reactor operation. Here, we describe in situ measurements of the concentration and chemical state of corrosion products in molten FLiNaK (eutectic mixture of LiF–NaK–KF) by high-resolution X-ray absorption spectroscopy. We placed a NiCr foil in molten FLiNaK and found the presence of both Ni2+ ions and metallic Ni in the melt, which we attribute to the foil disintegration due to Cr dealloying.

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Methods of Redox Control and Measurement in Molten NaCl-CaCl₂-UCl₃

Cited by 7 publications

References 5 publications

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

Depletion-driven thermochemistry of molten salt reactors: review, method, and analysis

In-Situ Analysis of Corrosion Products in Molten Salt: X-ray Absorption Reveals Both Ionic and Metallic Species

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Methods of Redox Control and Measurement in Molten NaCl-CaCl2-UCl3

Cited by 7 publications

References 5 publications

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

In Situ Corrosion Monitoring of the T91 Alloy in a Molten Chloride Salt Using a Miniaturized Electrochemical Probe for High-Throughput Applications

Depletion-driven thermochemistry of molten salt reactors: review, method, and analysis

In-Situ Analysis of Corrosion Products in Molten Salt: X-ray Absorption Reveals Both Ionic and Metallic Species

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Methods of Redox Control and Measurement in Molten NaCl-CaCl₂-UCl₃