Yafei Wang

• Ph.D. in Nuclear Engineering
• Associate Professor at Shanghai Jiao Tong University

The use of Bi electrode for the electrochemical separation of Sr and Cs is a promising method for separating radioactive nuclides. Because both the active electrode and molten salt system are in liquid form, the electrochemical reactions involve various physical changes, making the process complex and interdependent. By integrating the diffusion, e...

Analogous to the aqueous solution where the pH of the solvent affects its multiple behaviors, the optical acidity-basicity of molten salts also greatly influences their thermophysical and thermochemical properties. In the study, we develop ion probes to quantitatively determine the acidity-basicity scale of molten NaCl-xAlCl3 (x = 1.5-2.1) salt usi...

The electrorefining of spent nuclear fuels is a key step to recover uranium and transuranium on separated cathodes. However, the electrolyte salts become contaminated with fission products after batches of electrorefining, and therefore the two unit processes for the drawdown of actinide and lanthanide are suggested before treatment of the contamin...

The structure and dynamic properties of Cs in the mixed system of LiCl-KCl molten salt and a liquid metal (Bi and Pb) electrode are investigated through first-principles molecular dynamics simulation. It is found that the dynamic properties of different ions in molten salt could be significantly affected when the liquid metal electrode is coupled a...

The present study developed a finite element model to study the electrodeposition process of Ce(III) from LiCl–KCl eutectic molten salt for pyroprocessing of spent nuclear fuel. The input parameters for the model were extracted experimentally through electrochemical testing, including cyclic voltammetry, open circuit potential, linear polarization,...

In the study, we report an in situ corrosion and mass transport monitoring method developed using a radionuclide tracing technique for the corrosion study of 316L stainless steel (316L SS) in a NaCl–MgCl2 eutectic molten salt natural circulation loop. This method involves cyclotron irradiation of a small tube section with 16 MeV protons, later weld...

In the study, we report an in situ corrosion and mass transport monitoring method developed using a radionuclide tracing technique for the corrosion study of 316L stainless steel (316L SS) in a NaCl-MgCl 2 eutectic molten salt natural circulation loop. This novel method involved cyclotron irradiation of a small tube section with 16 MeV protons, lat...

Electrochemistry has been used for decades to study materials' degradation in situ in corrosive environments, whether it is in room-temperature chemically aggressive solutions containing halide ions or in high-temperature oxidizing media such as pressurized water, liquid metals, or molten salts. Thus, following the recent surge in high-throughput t...

ASME Sec(III) Div(5) code-certified structural alloys for Molten (halide) Salt Reactors (MSRs) such as 800H, SS316, and IN617 have significant Cr content. This makes them readily-degradable in molten halide salts due to the thermodynamic favorability of soluble chromium halide formation. It is therefore imperative to discover alloys with corrosion...

Insufficient availability of molten salt corrosion‐resistant alloys severely limits the fruition of a variety of promising molten salt technologies that could otherwise have significant societal impacts. To accelerate alloy development for molten salt applications and develop fundamental understanding of corrosion in these environments, here an int...

The design of corrosion-resistant high entropy alloys (CR-HEAs) is challenging due to the alloys' virtually astrological composition space. To facilitate this, efficient and reliable high-throughput exploratory approaches are needed. Toward this end, the current work reports a first-principles-based approach exploiting the correlations between work...

Insufficient availability of molten salt corrosion-resistant alloys severely limits the fruition of a variety of promising molten salt technologies that could otherwise have significant societal impacts. To accelerate alloy development for molten salt applications and develop fundamental understanding of corrosion in these environments, here we pre...

Structural material corrosion is a significant concern for the development of molten salt-cooled reactors (MSR) and redox control was proposed to mitigate the corrosion. This study presents an efficient approach to identify the partial pressure of F2 gas for fluorine driven corrosion, the concentration ratios of UF4/UF3 and ZrF4/ZrF2, and the parti...

This work studied the electrochemical behavior of iodide in molten LiF-NaF-KF mixture and the separation of iodide from the molten salt at 973 K using a graphite working electrode. The cyclic voltammetry (CV) and chronoamperometry (CA) measurements indicated an anodic passivation layer was formed on the graphite electrode in this melt and the layer...

The electrochemical behavior of La2O3 was investigated in LiF-NaF-KF (FLiNaK, 46.5-11.5-42.0 mol %) eutectic at 700°C. In the electrochemical tests, two kinds of working electrodes, i.e., tungsten and graphite, were utilized. The present study showed that La³⁺ ions can be deposited in the form of La metal on a tungsten cathode or LaC2 on a graphite...

The present study explored the electrochemical behaviors of CrF2 in FLiNaK molten salt at 873 K by the electrochemical techniques of cyclic voltammetry (CV) and chronopotentiometry (CP). It was confirmed that the disproportionation reaction of 3 C r F 2 ↔ 2 C r F 3 + C r would occur in FLiNaK molten salt. Considering both chromium trivalent and div...

It is found that lanthanum species can exist in the form of LaF6³⁻ in FLiNaK (46.5 LiF-11.5 NaF-42 KF, mol%) molten salt in previous studies. The understanding of transport and reaction kinetics parameters of LaF6³⁻ ions in FLiNaK molten salt is essential for the electrochemical separation of lanthanum from FLiNaK melt to achieve the coolant clean-...

Separation of the adjacent lanthanide (Ln) pair such as Sm-Eu from each other using chemical methods is difficult due to their similar chemical features. In the present work, electrochemical separation of Eu and Sm from each other were studied in molten LiCl-KCl-1 wt% EuCl3-1 wt% SmCl3 at 500 °C. By using a Cu reactive electrode, Sm was selectively...

Molten chloride salts can be corrosive to the structural alloys used in nuclear applications where they have been considered as advanced coolants and electrolytes. This paper investigates the corrosion of Alloy 709 and Inconel 718 in KCl-LiCl-EuCl3 molten salt. Europium is found to be very corrosive in chloride salts, which results in the rapid rel...

In the present study, the concentration-dependent activity and activity coefficients of K and Li in liquid bismuth at 973 K and 1023 K were determined by electromotive force measurement (emf) which was performed in an electrochemical cell: K (Li)-Bi (reference) || molten salt electrolyte || liquid Bi (working). Instead of simply mixing Bi and K or...

Separation of some active metal ions such as Ce3+, Eu3+, and La3+ from molten fluoride salt using electrochemical process is difficult. The currently available electrodeposition process assisted by the solid reactive electrode or liquid metal electrode faces challenges such as the isolation of the reactive electrode due to the formation of a compou...

Electrochemical studies of LaF 3 in molten FLiNaK salt were performed on inert working electrodes. An additional reduction reaction prior to the decomposition of FLiNaK melt was observed when LaF 3 was dissolved in and the reduction product was later recognized as lanthanum metal by SEM analysis. This phenomenon is very surprising and interesting c...

Modeling and simulation are effective tools for understanding the electrochemical processes in pyroprocessing as well as for predicting some fundamental data of actinides and fission products in molten salt. The present study first reviewed the available models, and then identified the potential mechanisms that influence the electrochemical process...

The thermodynamic behaviors of lanthanides in molten salt are significant for the pyroprocessing of spent nuclear fuel. In this study, the ternary phase diagram of LiCl-KCl-GdCl3 system was assessed by the CALPHAD method using two-sublattice model. The liquidus surfaces were calculated and plotted from 720 K to 1000 K. The solubility of GdCl3 from...

In the part I, The developed model by the present study was validated by available experimental data. In the second part of the study, the major electrochemical processes of pyroprocessing, including electrorefining, electrolysis of actinide and rare earth were investigated by the model to study their separation performance under different operatin...

Pyroprocessing is a method involving electrochemistry, thermodynamics, and transport theory. Driven by the current, nuclear materials redistribute between anode, electrolyte, and cathode to realize the desired separation. In the present study, a model for predicting the mass transport for the electrochemical process was developed. The model took in...

The activity coefficients of lanthanides in liquid bismuth at different concentrations and temperatures were calculated based on the assessed expression of Gibbs energy by the method of CALPHAD (CALculation of PHAse Diagrams). The temperature- and concentration-dependent correlations of the activity coefficients of eight lanthanides were developed...

The fluoride molten salt such as FLiNaK and FLiBe is one of the coolant candidates for the next generation nuclear reactor concepts, for example, the fluoride salt cooled high temperature reactor (FHR). For mitigating corrosion of structural materials in molten fluoride salt, the redox condition of the salts needs to be monitored and controlled. Th...

The binary systems of Bi-Pr, Bi-Ce, and Bi-Er were thermodynamically assessed by the CALPHAD method based on the available experimental data utilizing sub-regular model and the two-sublattice model. Enthalpies and entropies of formation of intermetallic compounds and enthalpies of mixing of liquid phase at different concentrations were calculated....

Thermodynamic properties of rare earth metals in LiCl-KCl molten salt electrolyte are crucial to the development of electrochemical separation for the treatment of used nuclear fuels. In the present study, activity coefficient, apparent potential, and diffusion coefficient of lanthanum, yttrium, scandium, and terbium in the molten salt (58 at% LiCl...