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The corrosion behavior of iron with vacancies in a liquid lead‐bismuth eutectic environment is simulated by molecular dynamics with embedded‐atom model potential at 700–1073 K. The vacancy is substituted into Fe crystal with the percentage of 0%, 0.2%, 0.4%, 1.0%, and 2.0% to investigate the effect of the vacancy on the corrosion behavior of iron. By evaluating the time‐dependences of penetration depths and the number of penetrating Pb and Bi atoms and also observing the trajectory of a penetrating Bi atom, we concluded that temperature and vacancy will enhance the corrosion behavior of iron in liquid lead‐bismuth, and the corrosivity of Bi atom is larger than that of Pb atom. The result is supported by the calculated substitutional energies of each Pb or Bi atom with a Fe atom or vacancy, which are in the order of EvacBi

Investigations on entropy generation and thermal irreversibility analysis are conducted for liquid lead-bismuth eutectic (LBE) in an annular pipe. To find better performance in convective heat transfer, the computational fluid dynamics (CFD) code based on the finite volume method (FVM) is adopted to solve this problem. The elevated temperature LBE flows in the annular pipe, and four types of heat flux, including constant, linear increase and decrease, and parabolic distributions are imposed at the inside wall of the annular pipe. The investigations are conducted for the specific average heat input of 200 kW/m2, and the different Peclet number Pe is set from 1200 to 3200. The SST k-ω turbulent model and Cheng-Tak Prt model are adopted. The mesh independence validation and models verification are also conducted and the maximum Nu error is 5.43% compared with previous experimental correlations. The results from the local and system scales, respectively, including volumetric dimensionless entropy generation, Ns, Be, and Ep, are discussed. The results indicate that the viscous friction and heat transfer caused by entropy generation can be found in the viscous sub-layer and buffer layer respectively. Heat transfer is the primary factor that leads to irreversible losses. Besides, the results show that the best thermodynamic performance occurs under parabolic distributed heat flux in the research scope. [ABSTRACT FROM AUTHOR]

Liquid lead-bismuth eutectic corrosion and the deposition of corrosion particles can lead to surface roughening of rod bundles, which impacts the convective heat transfer characteristics of the rod bundles. In this study, the Kays turbulent Prandtl number model and the SST k ‐ ω turbulence model were validated using the existing models. Then, the validated model was used to simulate the convective heat transfer in different rough rod bundles. Based on the numerical simulation results, a new Nusselt number correlation for liquid lead-bismuth eutectic within the rough rod bundle was developed. The applicable range of the new correlation is P/D = 1.1–1.5, Pe = 400–4000, and ε / D e = 0.0015–0.009. The error between the Nusselt number obtained from the correlation and the numerical simulation results is within 20 %. [ABSTRACT FROM AUTHOR]

Austenitic stainless steel is a promising candidate structural material for direct contact components with lead‑bismuth eutectic (LBE) in lead-cooled fast reactor (LFR). However, the preferential dissolution of Ni from austenitic steels at low oxygen concentrations will lead to the precipitation of Ni-containing phases in the low-temperature parts of reactors, which has a risk of pipe clogging. In this paper, three samples, comprising one extracted from a corrosion tank after prolonged operation and two prepared, respectively, by quenching in liquid nitrogen and cooling in the furnace, were obtained to investigate the effect of cooling rate on the precipitation characteristics and growth mechanism of Bi 3 Ni that forms by the reaction of dissolved Ni and Bi in LBE. The results showed that rod-like Bi 3 Ni was found in all three Ni-containing LBE samples. As the cooling rate increased, the width of Bi 3 Ni decreased. The Bi 3 Ni in all three samples displayed a pseudo-hexagonal prismatic shape and had a typical faceted growth character; the cooling rate had no effect on the morphology of them. The crystallographic analysis showed that the growth axis of Bi 3 Ni was in the 〈010〉 direction, and the prism planes were composed of {001} and {101}. In addition, the precipitation of Bi 3 Ni inevitably increased the content of Pb 7 Bi 3 , which would in turn enhance the volumetric expansion of solid LBE samples. For the growth mechanism, Bi 3 Ni phases were controlled by the screw dislocation mechanism, with the step growth rate of the dislocation core being greater than that of the outer edges. Given the low cooling rate and low Ni content in the LBE coolant of reactors, the precipitation of Bi 3 Ni with a rod-like morphology seems to be inevitable. • Three Ni-containing LBE samples were prepared with different cooling rates. • Regardless of the cooling rate, Bi 3 Ni in all three samples displayed a pseudo-hexagonal prismatic shape. • The Bi 3 Ni grew along the <010> direction, and the prism planes were composed of {001} and {101}. • Considering the low cooling rate and low Ni content, the precipitation of rod-like Bi 3 Ni seems to be inevitable. [ABSTRACT FROM AUTHOR]

Thermocline sensible heat storage (SHS) systems are usually utilized in parabolic trough solar power systems. Liquid lead–bismuth eutectic (LBE) is a potential heat transfer medium for SHS systems, but its influences on the performances of SHS systems are rarely studied. In this study, a simulation model of thermocline SHS tank using liquid LBE as the heat transfer fluid is established, and the influences of initial cold and hot LBE temperatures on the operation and mechanical performances of the tank are estimated. The results reveal that when the liquid LBE is used as the heat transfer fluid, the SHS tank can operate stably. The initial cold LEB temperature has almost no influence on both the total heat storage and heat release durations of the tank, while the initial hot LBE temperature has proportional relationships with the total heat storage and heat release durations. The heat storage performance as well as the heat release behavior of the tank can be improved by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature. The peak maximum mechanical stress of the tank can be decreased by increasing the initial cold LBE temperature, or by decreasing the initial hot LBE temperature.

• For the solid-phase oxygen control LBE system, numerical simulations are performed for the 1:1 scale 3D UPBEAT loop. • Simulation results are in general agreement with experimental results at about 350℃ and empirical correlations at 500℃. • The mass transfer coefficient increases with the temperature and it reaches its maximum at about 475℃. The Venturi-type solid-phase oxygen control system with a bypass mass exchanger is widely regarded as an effective approach to keep the oxygen concentration in the LBE under reasonable ranges to reduce the corrosion. In this work, numerical simulations of the particle–fluid mass transfer of the oxygen concentration in LBE are performed for the 1:1 scale 3D UPBEAT loop under various conditions. The discrete element method is applied to generate the geometry of the packing of the PbO spheres. The velocity profile and oxygen concentration governing equations are solved by using the SST turbulence model. At the same temperature, the oxygen mass transfer coefficient increases monotonically with the flow rate. At the same mass flow rate, the mass transfer coefficient increases with the temperature, reaching a maximum at about 475 °C. It provides guidance for future research in the design and optimization of oxygen control systems under high temperature in lead–bismuth nuclear reactors. [ABSTRACT FROM AUTHOR]

• The PCHE features a combined channel structure. • The combined channel design enhances the heat transfer capacity. • The effects on the heat transfer characteristics are investigated. • Typical heat transfer correlations are suggested. The Printed Circuit Heat Exchanger (PCHE) plays a critical role in the supercritical carbon dioxide (sCO 2) power generation systems, directly impacting the efficiency of the Brayton cycle. In this study, A comparative analysis was conducted to assess the flow and heat transfer characteristics of liquid lead–bismuth eutectic and sCO 2 in the combined channel PCHE, as well as in the straight channel and zigzag channel PCHEs. The results indicate that the combined channel configuration of the PCHE offers improvements in heat transfer performance without significantly increasing the resistance of liquid LBE. Additionally, this study analyzes the influence of fluid velocity, pressure, temperature, buoyancy forces and thermal acceleration on the heat transfer characteristics of the combined channel. Finally, the numerical calculation results are evaluated using typical heat transfer correlation equations from the literature to assess their applicability. [ABSTRACT FROM AUTHOR]

The corrosion behavior was investigated in a static environment of liquid Pb-Bi eutectic (LBE) saturated with 10−6 wt.% oxygen at 500°C and 600 °C. The investigation focused on 15-15Ti and 15-15Ti-Y austenitic stainless steel specimens, exposing them for up to 5000 h. Additionally, both steel types were analysed after exposure to liquid Pb 40 Bi 60 alloy with 10−6 wt.% oxygen concentration at 600 °C for 2000 h. The main objective was to investigate the structure and composition of oxide layers formed during corrosion, with specific attention to the role of yttrium (Y) in influencing corrosion behavior. The addition of Y resulted in promoting denser spinel oxide layer formation, which exhibited enhanced properties in reducing outward cation diffusion, inward oxygen diffusion, and PbBi penetration into the steels. [ABSTRACT FROM AUTHOR]

• Fe, Cr, and a mixture of Fe and Cr were added to liquid LBE at 1173 K and cooled with liquid nitrogen to study their precipitation characteristics. • There were three morphologies of precipitates: faceted dendrite, polyhedron (cube, octahedron, and hopper), and seaweed dendrite. • The solid-liquid interface structure and growth mechanism of precipitates were discussed. • The study provides an important reference for the impurity filtering process in the lead-cooled fast reactor (LFR) and the accelerator driven sub-critical (ADS) system. The compatibility of structural steels with liquid lead-bismuth eutectic (LBE) restricts the development of the lead-cooled fast reactor (LFR) and the accelerator driven sub-critical (ADS) system. During the reactor operation, alloying elements in steel can dissolve into LBE. The dissolved alloying elements could precipitate in cold parts of the reactor due to the decrease in solubility, which can cause pipe clogging and worsen heat transfer. Therefore, it is necessary to study their precipitation characteristics to provide a reference for the filtration process. In this paper, Fe, Cr, and a mixture of Fe and Cr were added to liquid LBE at 1173 K and quenched in liquid nitrogen to study their precipitation characteristics. The scanning electron microscope (SEM) and field-emission scanning electron microscope (FESEM) were used to analyze the morphology, and the phase structure was identified by an X-ray diffractometer. The chemical compositions of precipitates were analyzed by an energy dispersive spectrometer (EDS, Esprit Compact, Bruker) and an electron probe microanalyzer (EPMA, EPMA-8050 G, Shimadzu). The solid-liquid interface structure and growth mechanism of precipitates were also discussed. The difference in growth mechanisms resulted in various morphologies for the precipitates. There were three morphologies of precipitates: faceted dendrite, polyhedron (cube, octahedron, and hopper), and seaweed dendrite. All the precipitates in LBE have a faceted growth character except the seaweed dendrites, irrespective of their morphology. The growth of Fe, Cr, and Cr-Fe faceted dendrites originated from continuous growth followed by lateral growth. On the contrary, the cubic and octahedral precipitates were controlled by the spiral growth mechanism, and the growth mechanism of hopper crystals was two-dimensional nucleation. The formation of seaweed dendrites was caused by a strong local undercooling of nonfaceted dendrites. [ABSTRACT FROM AUTHOR]

• A mass exchanger was designed to develop solid phase oxygen control technology. • The dissolution rates of PbO at various conditions were obtained. • The control of the oxygen concentration was achieved in the LBE loop. The precise control of dissolved oxygen in lead–bismuth eutectic (LBE) reactors is very important. Solid phase oxygen control is a promising solution for regulating dissolved oxygen in the LBE. In order to better develop solid phase control technology, we designed a bypass mass exchanger holding PbO pellets. The dissolved oxygen in the LBE loop was controlled by PbO mass exchanger (PbO MX) technology. PbO MX is composed of a packed bed charging bucket, PbO ceramic pellets and bypass. The oxygen concentration in LBE under different conditions was measured using electrochemical oxygen sensors. The dissolution rate of PbO at different temperatures and flow rates were obtained. The effect of LBE flow rate and temperature parameters on the oxygen supply performance was obtained from the experimental results. The high-precision control of the dissolved oxygen concentration was achieved in the LBE loop. [ABSTRACT FROM AUTHOR]

Abstract The oxide-dispersion strengthened (ODS) ferritic steels have been considered as promising candidate structural materials for liquid lead-bismuth eutectic (LBE) cooled reactors, and the corrosion of the ODS steel in liquid LBE presents a critical challenge. In order to improve the corrosion resistance of the ODS steel, a type of Y-Si-O strengthened ODS steel was designed and fabricated. The grain structure and dispersed nanoparticles were carefully characterized by the scanning electron microscope (SEM), the transmission electron microscope (TEM), the high-resolution transmission electron microscope (HRTEM) and the atomic probe tomography (APT) methods. Y 2 Si 2 O 7 and Y 2 SiO 5 nanoparticles both with monoclinic cubic crystal structure were found to be dominated in the matrix. And the number density and average diameter of the distributed nanoparticles were counted to be 1.8 × 1024 m−3 and ∼6 nm, respectively. The three dimensions APT reconstruction revealed that the as-received ODS alloy contained a high number density of nanometer scale yttrium-, silicon-, vanadium-, and oxygen-enriched nano-particles Furthermore, the high temperature property and corrosion resistance of the ODS steel were evaluated preliminarily. The miniature specimen tensile tests performed at 550 °C showed satisfactory high tensile strength of the ODS steel. The corrosion resistance was significantly improved by the addition of silicon according to the test of 1000 h exposure to liquid LBE. Highlights • A type of nano Y-Si-O-strengthened 9Cr ODS steel was designed and fabricated. • Most of the Y-Si-O particles were monoclinic cubic Y 2 Si 2 O 7 and Y 2 SiO 5. • The steel had good tensile property at 550 °C and corrosion resistance in LBE. [ABSTRACT FROM AUTHOR]

For the proper design and operation of lead oxide mass exchanger (PbO MX), the dissolution kinetics of PbO in flowing liquid Lead-bismuth eutectic (LBE) needs to be determined. A computational fluid dynamics (CFD) method of the PbO MX was established. The solid-phase oxygen control part of the MX is PbO spheres packed bed, which is regarded as a porous media in the simulation calculation. The oxygen mass transfer process between PbO spheres packed bed and liquid LBE was simulated by a porous media model with the species transport model. The relationship between the dissolution rate of MX and the flow rate, temperature and initial oxygen concentration is predicted. The dissolution rate of PbO increases exponentially with increasing temperature of LBE. Besides, the dissolution rate of oxygen is positively correlated with the LBE flow velocity. In the specific oxygen concentration range, the MX inlet oxygen concentration has little effect on the dissolution rate. The smaller the porosity of PbO spheres packed bed has, the smaller the dissolution rate of oxygen is. Furthermore, when the porosity is constant, the dissolution rate of oxygen increases with the increase of the height of the packed bed of PbO spheres. • The porous media model is used to simulate the oxygen mass transfer of lead oxide mass exchanger (PbO MX). • The dissolution rate of PbO increases exponentially with increasing temperature of LBE. • The oxygen dissolution rate is proportional to the flow rate with other conditions fixed. • The small porosity leads to the decrease of the LBE velocity, causing a lower dissolution rate. [ABSTRACT FROM AUTHOR]

• The yttria-stabilized zirconia (YSZ) solid electrolyte oxygen sensor with LSCF (lanthanum strontium cobalt ferrite)/air reference electrode was investigated. • The performance of two LSCF/air reference electrode sensors was tested on a LBE dynamic loop. • This study demonstrates that the LSCF/air sensor can be used to monitor oxygen concentration in non-isothermal LBE systems. Oxygen sensors are the major part of the active oxygen control system (OCS) to be used in the liquid lead–bismuth eutectic (LBE) system. In this paper, the electromotive force (EMF) measured by yttria stabilized zirconia (YSZ) solid electrolyte sensor with LSCF (lanthanum strontium cobalt ferrite)/air reference electrode in static oxygen saturated LBE is used to obtain relationship between EMF and temperature. The EMF output by oxygen sensors is deterministic and predictable. At the same time, the performance of oxygen sensors in flow loop of liquid LBE were also studied. EMF output curves of oxygen sensors corresponding to the operation of consuming dissolved oxygen are given. It is proved that the LSCF/air sensor can be used to monitor oxygen concentration in non-isothermal LBE systems. [ABSTRACT FROM AUTHOR]

Abstract: An improved meshless numerical method (MPS-MAFL) is utilized to simulate single Taylor bubble rising in liquid LBE to study its hydrodynamic characteristics. The computational region is a circular tube in which the liquid is described using discretized particles by non-uniform grid scheme. The gas–liquid interface was approximately treated as a free surface boundary and nonslip conditions are applied to the tube wall. Several simulation results and corresponding analysis including Taylor bubble propagation procedure, velocity profile around bubble nose and in the wake region as well as in the falling film are presented. Some experimental results and CFD numerical simulations from other researchers are compared with the present study as validation. The simulation results agree well with both theoretical analysis and experimental results, which demonstrate the reasonable selection of model as well as the accuracy and reliability of moving particle method (MPS-MAFL). [Copyright &y& Elsevier]