Lead-bismuth Eutectic Research Articles

Cladding fatigue analysis under frequent beam trips for China initiative Accelerator Driven System

China initiative Accelerator Driven System (CiADS) is a 10 MW lead–bismuth eutectic (LBE) cooled subcritical reactor, which is designed to demonstrate the engineering feasibility of the ADS concept. An elaborated methodology was developed to deal with the nonlinear mechanical behaviors of fuels under transients. Based on this methodology, the fuel mechanical module was accomplished and coupled with the neutron dynamics module and thermo-hydraulics module in the extended BELLA code. The cladding mechanical simulation under frequent beam trips for CiADS was carried out using BELLA, and fatigue analysis based on the experimental data was discussed. Combined with the CiADS beam-trip transients, it is concluded that the tolerance of the CiADS cladding to beam trips is between 1000 and 11,000 cycles.

Lead-bismuth eutectic corrosion behavior of NbMoVCr refractory multi-principal element alloys coating synthesized by magnetron sputtering

Nanocrystalline NbMoVCr refractory multi-principal element alloys coatings are fabricated by magnetron sputtering technology to improve lead-bismuth eutectic (LBE) corrosion resistance of structural materials, and their corrosion behavior in oxygen-saturated liquid LBE at 600 and 650 °C has been investigated. The coatings exhibit good phase structural stability even at 650 °C exposure. Moreover, the coatings show promising LBE corrosion resistance with parabolic oxidation rate constant 3–5 orders of magnitude lower than other candidate steels (such as 316 L, HT9, T91, SIMP, CLAM, etc.) which is due to the formation of protective (CrV)2O3 solid solution layer. The oxidation process of the coating is mainly dominated by kinetic factors, including diffusion driving force (related to LBE solubility) and diffusion energy barrier (related to atomic radius). By the way, at the grain boundaries with much lower oxygen potential, thermodynamic factors dominate the oxidation process, and V with the highest oxygen activity shows evidence of selective oxidation.

Kobellite homologues from the Boliden Au–Cu–(As) deposit, Sweden: jigsaw patterning via nanoscale intergrowths in chessboard structures

Abstract Sulfosalt assemblages in a specimen from the Boliden Au–Cu–(As) deposit in northern Sweden, comprise micrometre to nanometre scale intergrowths of Se-rich izoklakeite and tintinaite with average formulae and calculated homologue number (N) given as: (Cu1.88Fe0.18)2.06(Pb22.92Ag1.47Cd0.01Zn0.01)24.41(Sb13.12Bi8.69)21.8(S50.19Se6.43Te0.12)56.73,N = 3.83, and (Cu1.31Fe0.74)2.05(Pb10.58Ag0.18Cd0.05Zn0.02)10.83(Sb10.2Bi5.23)15.43(S32.22Se2.46)34.7, N = 2.05, respectively. Tintinaite coexists with (Bi, Se)-rich jamesonite. High-angle annular dark field scanning transmission electron microscopy (HAADF STEM) imaging reveals chessboard structures comprising PbS and SnS modules with the number of atoms in the octahedral (M) sites counted as: n1 = 18 and n2 = 8 for tintinaite and n1 = 30 and n2 = 16 for izoklakeite. The homologue number can be calculated using the formula: N = (n1/6)–1 and N = n2/4 for PbS and SnS modules giving NTti = 2 and NIz = 4. A new N = 3 homologue, defined by n = 12 and n = 24 SnS and PbS modules, respectively, is identified as single or double units within areas with intergrowths between kobellite and izoklakeite. HAADF STEM imaging also reveals features attributable to lone electron pair micelles within the Sb-rich kobellite homologues. Atomic-resolution EDS STEM chemical mapping of Pb–Bi–Sb-sulfosalts shows a correlation with crystal structural modularity. The maps also highlight sites in the SnS modules of tintinaite in which Sb > Bi. Coherent nanoscale intergrowths between tintinaite and izoklakeite define jigsaw patterns evolving from chessboard structures and are considered to have formed during co-crystallisation of the two phases. Displacement textures and crosscutting veinlets (a few nm in width) are interpreted as evidence for superimposed syn-metamorphic deformation and are associated with the redistribution of Bi and Se. Imaging and mapping using HAADF STEM techniques is well suited to characterisation of Pb–Sb–Bi-sulfosalt phases, offering largely untapped potential to unravel the evolution of chessboard structures with applications across mineralogy but also extending into allied fields.

The Effects of Edge Dislocations on The Corrosion Behavior of Pure Iron in Liquid Lead-Bismuth Eutectic: A Molecular Dynamics Study

The effect of liquid lead–bismuth eutectic (LBE) on the corrosion evolution of iron-based materials with varying densities of edge dislocation defects was studied. Molecular dynamics simulations were conducted at temperatures ranging from 823 K to 1173 K, and the process of penetration of Pb and Bi atoms at the dislocation core was analyzed. The results indicated that Fe atoms near the dislocation core have the lowest substitution energy (−4.79 eV/atom), making them more likely to be replaced by Pb and Bi atoms. Moreover, it was found that the increase in dislocation density did not result in a high penetration depth of LBE atoms, attributed to the interaction of dislocations. These findings provide crucial insights into the LBE corrosion mechanism in iron-based materials with dislocation defects.

LES of the upper plenum of the liquid metal fast reactor under the forced flow conditions

A Large Eddy Simulation (LES) of the upper plenum of the E-SCAPE (European SCAled Pool Experiment) facility under the normal operations has been conducted to gain deeper insights into the thermal hydraulics phenomena in liquid metal fast reactors (LMFRs). The results unravel the overall flow features in the upper plenum, the thermal instability in the above core structure region and the impact of the jets from the barrel holes on the large flow circulation and thermal mixing.The above core structure region is represented using a homogeneous porous model. It is shown that during the normal operations, most of the hot stream of the lead bismuth eutectic (LBE) from the core center rises to the top and disperses from the upper barrel holes. Conversely, the cold LBE spread out from the lower barrel holes. Mixing between the two streams only affect the fluids leaving from the middle heights demonstrating limited mixing. These jets help to create a large circulation in the upper plenum region which prevents any thermal stratification. At the interface between the hotter and colder streams, there are unsteady large-scale structures resulting in a mixing layer in the thermal field. This strong mixing is not conventional turbulence and potentially cannot be captured by Reynolds Averaged Navier Stokes average (RANS) modelling.The flow in the upper plenum is dominated by the influences of the different types of jets, which include some free jets issued horizontally or angled upwards and some jets impinging onto the structures in the plenum. The jets overall behave similar to ‘standard’ jets, though significant interactions between the top and bottom jets and the background circulations have strong influences at later stages of the jets, typically after four jet diameters leading to the jets not reaching self-similarity. In addition, the turbulence that is observed in the upper plenum is largely generated by the jet flows and hence the distribution of turbulence is very non-uniform. Away from the jets, turbulence is minimal with the mixing largely driven by the large-scale circulation.

Irradiation-decelerated corrosion behavior of CrN/TiSiN multilayer coating in liquid Pb–Bi eutectic alloy

CrN/TiSiN multilayer coatings deposited at 316 L substrate were selected to explore the effects of irradiation on LBE (Liquid Pb–Bi eutectic alloy) corrosion. The as-deposited and irradiated coatings were exposed in LBE. After exposure, all CrN/TiSiN coatings presented oxidation accompanied with PbBi penetration. Irradiated coatings revealed better corrosion resistance with thinner oxide layer and smaller penetration thickness. The largest decrement of 39 % in oxidation thickness was observed in CrN/TiSiN deposited with Ti80Si20 under 150 V. The irradiation-decelerated LBE corrosion could be attributed to the rapidly formed protective oxide layer resulting from the irradiation defects which accelerated nucleation and diffusion process during oxides formation. The decelerated effect was relatively weak in coatings deposited with a bias voltage under 100 V, in which the decrement is under 10 %. The enhanced corrosion resistance was attributed to the quickly formed dense and continuous chromium oxide which rapidly formed due to the irradiation induced defects and acted as diffusion barrier to slow down LBE penetration.

Corrosion kinetics of T91 steel under low oxygen conditions (10−7 wt% O) in lead-bismuth eutectic at 500 °C

Among the advanced reactor designs of the fourth generation, the Lead-cooled Fast Reactor (LFR) stands out as one of six distinct types. The corrosion caused by the liquid Lead-Bismuth Eutectic (LBE) on structural materials is recognized as a significant obstacle hindering the development of LFR. The corrosion kinetics of T91 steel in static LBE with 10−7 wt% oxygen at 500 ºC is analyzed in this study. The formed oxide scale consists of an outer (Fe, Cr)3O4 layer with a Fe-Cr spinel structure and an inner internal oxidation zone (IOZ). The thickness evolution of the oxide layers follows a parabolic rule, with rate constants determined for different layers. The dissolution rate of metals into the LBE decreases over time, indicating diminishing the concentration gradient of Fe across the oxide layer-LBE interface. The observed deviations from expected norms may be attributed to dynamic flow conditions and non-isothermal loop experiments, which accelerate Fe diffusion into LBE.

Electrochemical method for determining the solubility of impurities in lead-bismuth eutectic using molten salt electrolytes

Traditional physical methods for measuring solubility were often affected by viscosity, density, and surface tension. In this study, we selected appropriate electrolytes to determine the solubility of impurities in the lead-bismuth circuit at reactor operating temperatures using electrochemical methods. Taking the measurement of the solubility of impurity Ce in liquid Bi as an example, we demonstrated that electrochemical methods can accurately determine its solubility in the LiCl-KCl molten salt. Furthermore, the successful measurement of other impurities such as La, Ce, U, and Mn in lead-bismuth eutectic (LBE) using the designed system has confirmed the universality of this method.

Comparison between DNS and RANS approaches for liquid metal flows around a square rod bundle

The thermal-hydraulic characteristics of liquid metal flows around rod bundles are of great interest for the research and design of fourth generation nuclear reactors. Currently, a large research effort is aimed at the development of accurate numerical models for low Prandtl number fluid flows, since the data available in the literature are quite scarce. Direct Numerical Simulation (DNS) is undoubtedly the most accurate approach, but its large requirements of computational resources and time make it less practical than other simplified methods such as the Reynolds-Average Navier Stokes (RANS) approach. The present paper provides a comparison between numerical results of a flow of liquid Lead-Bismuth Eutectic (LBE) at Pr=0.031 around four vertical cylindrical rods arranged in a square lattice, obtained by DNS and RANS. Several turbulence models are considered, including the standard k−ε, k−ω SST, and two Reynolds stress models, namely the ones by Launder, Reece and Rodi (LRR), and Speziale, Sarkar and Gatski (SSG). The accuracy of these models is assessed by comparing the mean Nusselt number, the pressure drop, and local field distributions with those obtained by DNS.

Corrosion behavior of δ-ferrite in AISI 316 austenitic stainless steel exposed to oxygen-saturated lead‑bismuth eutectic at 550 °C

δ-ferrite is usually found in the 300 series austenitic stainless steels (ASS), but the role of δ-ferrite on corrosion behaviors exposed to oxygen-controlled lead–bismuth eutectic (LBE) has not yet been elucidated. The corrosion behaviors of AISI 316 ASS containing δ-ferrite in the oxygen-saturated static LBE at 550 °C were studied in terms of their solution-treated and accelerated-aging treated conditions. The δ-ferrite and decomposed δ-ferrite exhibit the superior resistance to oxidation attack compared to the austenite, and the δ-ferrite possesses a better corrosion resistance than the decomposed δ-ferrite. Compared with the austenite, the higher diffusivities of Cr and Si in δ-ferrite cause a reduction in the critical concentration required for the formation of chromium oxide and Si-rich oxide. A mixture of Cr2O3 oxide and Fe-Cr-Si spinel oxide developed on the surface of δ-ferrite can effectively impede the metal transfer, leading to the superior resistance to oxidation attack. The retained δ-ferrite and M23C6 carbides in the decomposed δ-ferrite oxidizes independently into FeCr2O4 and Cr2O3 oxides, respectively. The presence of Cr2O3 scale around the retained δ-ferrite decreases its oxidation rate, resulting in the non-uniform oxide phenomenon.

Changes in chemical composition of TixAl1−xN coatings immersed in oxygen-saturated Lead–Bismuth Eutectic at low and moderate temperatures (250 °C ≤ T ≤ 410 °C)

Lead–Bismuth Eutectic (LBE) will serve as a liquid metal coolant in accelerator-driven systems, posing a corrosive threat to exposed materials. To address this challenge, TixAl1-xN coatings (0.38 ≤ x ≤ 0.58) were applied onto AISI 316 L austenitic stainless steel using the reactive bipolar magnetron sputtering technique. These coated samples underwent immersion in static oxygen-saturated LBE at temperatures of 250 °C and 360 °C for durations of 500 h and 1000 h, and at 410 °C for 500 h. XPS depth profiles revealed minimal oxidation at 250 °C even after 1000 h. However, at 360 °C, a mixed oxide layer of (Ti, Al)Ox was formed on the coating's surface. Exposure to LBE at 410 °C for 500 h led to the creation of an oxide bilayer comprising TiO2 (outer sublayer) and (Ti, Al)Ox depleted of Ti (inner sublayer). A model is proposed to illustrate the oxidation mechanism.

Synergism of Al and Si occurs on corrosion of Ti3Al1−xSixC2 MAX in the static Pb-Bi eutectic at 550 ºC

MAX phase ceramics attract increased attention for lead-cooled fast reactors due to their promising compatibility with lead-bismuth eutectic (LBE). This work systematically investigates the corrosion behaviors of five Ti3Al1−xSixC2 MAXs with Al/Si complex A component in static LBE at 550 ºC up to 3000 h. Based on the lattice structure, mechanical properties, surface morphologies, and elemental composition during corrosion, a synergism of Al and Si during oxidation and diffusion is found, which contributes to a continuous and well-attached Al2O3 layer with improved LBE corrosion resistance. Therefore, the multi-element design will bring a broad space for the applications of MAX ceramics.

New insight of the enhanced oxidation resistance of T91 steel in 450 °C liquid lead-bismuth eutectic by adding Al and Si element

The study investigated the oxidation behavior of T91 steel modified with Al (T91-Al) and Si (T91-Si) in lead-bismuth eutectic (LBE) at 450 °C under oxygen-saturated conditions (10−7–10−8 wt.%) and oxygen-controlled conditions (3.2 × 10−4 wt.%). Advanced characterization techniques were employed to understand the thermodynamic and kinetic mechanisms of enhanced oxidation properties of the modified T91 steel. The results indicate that the oxidation resistance of the materials follows this order: T91 < T91-Al < T91-Si. Noteworthy, the oxidation resistance of T91-Si material exhibited minimal correlation with dissolved oxygen. Under oxygen-controlled conditions, the oxide film of T91 and T91-Al was attacked and broken by LBE, with the former eventually peeling off. In contrast, both materials showed significant oxide film thickening, except T91-Si under oxygen-saturated conditions. The addition of Al improved the quality of the inner oxide film on T91-Al by generating Al2O3, thereby slowing down the diffusion of Fe from the matrix and enhancing oxidation resistance. Conversely, Si actively participated in the oxidation process of T91-Si, slowing down the diffusion of Fe, and facilitating the diffusion of Cr, thereby strengthening the oxide film protection. Consequently, the oxide thickness of T91-Si material was only 24 % of T91 and 35 % of T91-Al under saturated oxygen conditions.

Effect analysis of oxide layer on thermal hydraulic characteristics of LBE cooled reactor

For Lead-Bismuth Eutectic (LBE) alloy cooled reactor, oxidation corrosion is very important and would affect the thermal hydraulic characteristics of the reactor. In this paper, based on LETHAC code developed by Xi’an Jiaotong University (XJTU) for system level thermal hydraulic analysis LBE reactor, a simulation module for oxidation corrosion is developed and added. The influence of oxidation layer on the heat transfer characteristics of the reactor is conducted. Based on LESMOR reactor designed by XJTU, a simulation calculation is carried out under the long-term operation conditions of the reactor considering the growth of oxidation layer. The distribution of the oxide layer in the reactor, the change of temperature appreciation caused by the oxide layer over time and the distribution in the reactor are obtained. The presence of oxide layer will affect the fluid temperature and wall temperature of reactor. The longer the run time, the greater the impact. This paper could provide solid analysis methodology reference for the design of LBE reactor.

Nano-scale corrosion mechanism of T91 steel in static lead-bismuth eutectic: A combined APT, EBSD, and STEM investigation

T91 steel is a candidate material for structural components in lead-bismuth-eutectic (LBE) cooled systems, for example fast reactors and solar power plants [1]. However, the corrosion mechanisms of T91 in LBE remain poorly understood. In this study, we have analysed the static corrosion of T91 in liquid LBE using a range of characterisation techniques at increasingly smaller scales. A unique pattern of liquid metal intrusion was observed that does not appear to correlate with the grain boundary network. Upon closer inspection, electron backscatter diffraction (EBSD) reveals a change in the morphology of grains at the LBE-exposed surface, suggesting a local phase transition. Energy dispersive X-ray (EDX) maps show that Cr is depleted in the T91 material near the LBE interface. Furthermore, we observed the dissolution of all Cr-enriched precipitates in this region. Although the corrosion is conducted in an oxygen deficient environment, both scanning transmission electron microscopy (STEM) and atom probe tomography (APT) reveal a thin surface oxide layer (presumably wüstite) at the LBE-steel interface. Using electron energy loss spectroscopy (EELS) in the STEM, as well as APT, the atomic scale elemental redistribution and 3D morphology of the corrosion interface is investigated. By combining results from these different techniques, several types of oxide phases and structures can be identified. Based on this detailed nano-scale information, we propose potential mechanisms of T91 corrosion in LBE.

Effect of Si addition on the microstructure and liquid lead-bismuth eutectic cavitation erosion behaviors of AlCrFeMoTi laser clade coatings

High entropy alloys exhibit high resistance to the lead-bismuth eutectic (LBE), making them promising candidate materials for protective coatings. However, improving their mechanical properties and resistance to cavitation erosion in flowing LBE environment remains a challenge. In this study, AlCrFeMoTi coatings were synthesized using laser cladding, and Si was added to enhance their resistance to cavitation erosion. The results showed that the AlCrFeMoTi coatings mainly contained FeMoTi and Fe-Cr phases. After the addition of Si, a single phase FeMoTi was formed. Moreover, Si increased the hardness of the coatings by 9.6%. After cavitation erosion in LBE at 500 ℃, cracks formed on the surface of the coatings and the main damage mechanism of the coating was lamellar spalling. The addition of Si inhibited crack propagation and reduced the erosion depth of the coatings by 43.5%. It can be attributed to the addition of Si makes the oxidation homogeneous and the strengthening of the single-phase.

Microstructure, Mechanical Properties, and Lead–Bismuth Eutectic Corrosion Behaviors of FeCrAlY-Al2O3 Nanoceramic Composite Coatings

Seven FeCrAlY-Al2O3 nanoceramic composite coatings are deposited on F/M steel via plasma spraying and laser remelting. A systematic investigation is conducted to examine the dependence of microstructure, mechanical properties, and lead–bismuth eutectic (LBE) corrosion resistance on the nano-Al2O3 addition and different Cr and Al contents. With the increase in Al content in FeCrAlY, gradual refinement of the coating grains occurs. The addition of nano-Al2O3 promotes the elemental segregation and precipitation of the second phase. The nano-Al2O3 notably enhances the mechanical properties of the coatings that are primarily attributed to second-phase and fine-grain strengthening. After LBE corrosion tests, intergranular corrosion morphology could be observed, where the contents of Cr and Al significantly influence the corrosion behavior of the coatings at varying temperatures.

Origin of low lattice thermal conductivity in promising ternary PbmBi2S3+m (m = 1–10) thermoelectric materials

Ternary Pb-Bi-S compounds emerge as potential thermoelectric materials owing to low thermal conductivity, but the origin of their intrinsic low lattice thermal conductivities lacks further investigation. Herein, a series of ternary PbmBi2S3+m (m = 1–10) compounds are synthesized and their crystal structure evolutions with increasing m values are clearly unclosed. The room-temperature lattice thermal conductivities in PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9 can reach at 0.57, 0.56 and 0.80 W m−1 K−1, respectively, outperforming other ternary sulfur-based compounds. Theoretical calculations show that the low lattice thermal conductivities in PbmBi2S3+m (m = 1–10) mainly originate from soft phonon dispersion caused by strong lattice anharmonicity, and both asymmetric chemical bond and lone pair electrons (Pb 6s2 and Bi 6s2) can favorably block phonon propagation. Furthermore, the elastic measurements also confirm relatively low sound velocities and shear modulus, and the Grüneisen parameter (γ) calculated by sound velocities can reach at 1.67, 1.85 and 1.94 in PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9, respectively. Finally, the intrinsic low lattice thermal conductivities in PbmBi2S3+m (m = 1–10) contribute to promising thermoelectric performance, and the maximum ZT values of 0.47, 0.38 and 0.45 can be achieved in undoped PbBi2S4, Pb3Bi2S6 and Pb6Bi2S9, respectively.

Preparation of Cr-N coatings on 316H stainless steel via pack chromizing and gas nitriding, and their resistance to liquid metal corrosion in early stages

Liquid metal corrosion has become a critical issue in lead-cooled fast reactor when the steel encounters lead–bismuth eutectic (LBE). Although various coatings applied in LBE have garnered interest from many researchers, there are few reports on the compatibility of chrome carbide or chromium nitride coatings in LBE. Thus, Cr carbide and Cr-nitride coatings with thicknesses of 80 μm were prepared on 316H stainless steel (SS) to investigate the corrosion behavior in contact with static liquid LBE at 550 °C for 25, 76, and 207 h. These coatings were synthesized via pack chromizing and subsequent gas nitriding. The results showed that a distinct LBE penetration layer appeared on the surface of the as-received 316H SS after exposure to LBE. Pack-chromized coating and pack-chromized + gas nitride coating did not undergo obvious consumption in LBE in the early stages. Cracks in the pack-chromized coating promoted the preferential diffusion of oxygen and PbBi. The Cr in the pack-chromized + gas nitride coating slightly diffused outward to combine with oxygen to form Cr-oxide scale on the coating surface. These coatings act as a barrier to LBE corrosion, making the surface of the coating impermeable to LBE.

Experimental investigations on flow-induced vibration characteristics of fuel rod with an independent channel for small lead-based reactor

ABSTRACT The technology of nuclear reactors is evolving rapidly, driven by the pursuit of more powerful and efficient systems. The Small Lead-based Reactor (SLR) represents an advanced nuclear reactor design that holds great promise for delivering enhanced power and efficiency. In the context of the SLR’s fuel rod, the high-speed coolant flow within the reactor can induce vibration, potentially causing fretting wear and damage to the cladding. This study utilized the Burgreen correlation to establish an equivalence relationship between water and Lead-Bismuth Eutectic (LBE). An experiment was then conducted to simulate axial flow-induced vibration (FIV) of a simply supported fuel rod, employing an equivalent water loop. Flow-induced vibration characteristics in both the time and frequency domains were investigated at different flow speeds. The experimental results revealed a positive correlation between flow velocity and amplitude. The fuel rod exhibited low-frequency vibrations with a random pattern, registering frequencies around 14 Hz. These experimental findings can be leveraged to enhance the accuracy of numerical simulations for axial flow-induced vibration (FIV) of the fuel rod. Subsequently, the revised numerical model was applied to simulate FIV in the LBE environment using computational fluid dynamics (CFD), and the numerical results were found to be in agreement with the experimental data.