Pb 17Li Research Articles

Ab initio study of longitudinal and transverse dynamics, including fast sound, in molten UO2 and liquid Li–Pb alloys

The disparity between the masses of the two components in a binary liquid system can lead to the appearance of a peculiar phenomenon named “fast sound,” which was identified for the first time in Li4Pb several decades ago and later observed in other Li based alloys. However, the exact characteristics and nature of this phenomenon and the reasons behind its appearance have not totally been identified yet. In this work, we analyze the longitudinal and transverse current correlation functions of UO2, Li4Pb, and Li0.17Pb0.83, as obtained from ab initio molecular dynamics simulations. We find that fast sound appears to occur in the two former systems but not in the latter. Additionally, we discuss some of the properties of the liquid mixtures that may be related to the appearance (or absence) of the phenomenon, such as the composition, the polyhedral structure of the melt, and the type of bonding in the system.

Solubility of Bi in Li–Pb Eutectic Alloy Between 508 and 623 K

Liquid lithium–lead (Li–Pb) eutectic alloy is one of the candidate liquid tritium breeding materials of fusion blanket and it contains bismuth (Bi) as an initial impurity or transmutation product from lead. The saturated solubility of Bi, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> (wt.ppm), in Li–Pb was measured in the temperature range from 508 to 623 K. The measured results were plotted on the graph with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$S$ </tex-math></inline-formula> (wt.ppm) versus 1/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$T$ </tex-math></inline-formula> . From these plots, a positive temperature dependence, where the solubility decreases as the temperature is lowered, is confirmed. The equation of the solubility of Bi in Li–Pb was obtained, too. In addition, the dissolution enthalpy of Bi in Li–Pb, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta H_{\mathrm {sol}}$ </tex-math></inline-formula> , was quantified from this equation. The precipitation morphology of Bi in Li–Pb was also investigated. X-ray diffraction was used to analyze the precipitates collected from the surface of the liquid phase. As a result, the peak pattern of Li3Bi was found from the precipitate. Moreover, the amount of polonium produced when the cold trap is introduced to a Li–Pb loop of a fusion reactor was predicted from the solubility obtained in this study.

Corrosion behavior and mechanism of CLAM and 316L steels in flowing Pb–17Li alloy under magnetic field

The liquid lead-lithium (Pb–17Li) blanket has many applications in fusion reactors due to its good tritium breeding performance, high heat transfer efficiency and safety. The compatibility of liquid Pb–17Li alloy with the structural material of blanket under magnetic field is one of the concerns. In this study, corrosion experiments China low activation martensitic (CLAM) steel and 316L steel were carried out in a forced convection Pb–17Li loop under 1.0 T magnetic field at 480 °C for 1000 h. The corrosion results on 316L steel showed the characteristic with a superficial porous layer resulted from selective leaching of high-soluble alloy elements and subsequent phase transformation from austenitic matrix to ferritic phase. Then the porous layers were eroded by high-velocity jet fluid. The main corrosion mechanism of CLAM steel was selective dissolution-base corrosion attack on the microstructure boundary regions and exclusively on high residual stress areas. CLAM steel performed a better corrosion resistance than that of 316L steel. The high Ni dissolution rate and the erosion of corroded layers are the main causes for the severe corrosion of 316L steel.

Submicron-thick yttria-stabilized zirconia coating as an advanced tritium permeation barrier

Tritium permeation through structural materials is one of the critical issues in a fusion reactor from the viewpoints of an efficient fuel cycle and radiological safety. Ceramic coatings have been studied as tritium permeation barriers (TPBs) and shown sufficient reduction of hydrogen isotope permeation. In high thermal efficiency liquid blanket concepts, however, not only tritium permeation but also corrosion of the structural materials by liquid tritium breeders such as lithium–lead (Li–Pb) is a serious concern. This study focuses on the fabrication of two kinds of yttria-stabilized zirconia (YSZ) coatings by metal organic decomposition and characterization through several tests such as deuterium permeation and static Li–Pb exposure. The 4 mol%-Y2O3-containing YSZ coating of less than 100 nm in thickness showed three orders of magnitude lower deuterium permeation flux than uncoated substrate after crystallization and grain growth, and the high permeation reduction performance maintained through the thermal cycle tests. The 10 mol%-Y2O3-containing YSZ coating sample showed a high permeation flux due to the defects formed during the permeation measurement. Both coatings showed compatibility with Li–Pb. A phase transformation was confirmed in the 4 mol%-Y2O3-containing YSZ coating after bending tests, suggesting that the coating sample achieved a self-repairing property. These results indicate that the 4 mol%-Y2O3-containing YSZ coating would apply to the TPB.

Study on the performance of hydrogen isotopes permeation sensor in liquid Li–Pb

Liquid Li–Pb alloy is served as neutron multiplier, tritium breeder, and coolant in Dual Coolant Lithium–Lead (DCLL) breeding blankets. In order to monitor the tritium transport continuously and measure the tritium production rate accurately, the concentration of hydrogen isotopes in liquid breeder is an essential factor for tritium measurement. The hydrogen isotopes permeation-based capsule seems to be the most reliable sensor and is simple from the fabrication point of view. To verify the stability and repeatability of hydrogen isotopes concentration measured by permeation capsule in Li–Pb, a system based on a Nb-capsule and a quadrupole mass spectrometry was devised. The sensor would be applied to determine the variation rate of total pressure while a quadrupole mass spectrometry to measure partial pressure values of different hydrogen isotopes. The response time of the sensor is less than 100 s in liquid Li–Pb alloy and the growth rate of pressure has good repeatability in dynamic mode. Besides, calculations based on numerical simulation of the hydrogen isotopes sensor are presented.

Inclusion of the Coulomb Interaction in the Embedded-Atom Model: Lithium–Lead System

A scheme is proposed for the incorporation of a screened Coulomb interaction into an embedded-atom model, which allows one to describe two- and multicomponent solutions with strong component interaction by the molecular dynamics method. The effective particle charges satisfy the electroneutrality condition and are determined via minimization of the total energy. The potentials of the pure components and fitted cross pair potentials are used in the calculations, with allowance for the electronic contributions to energy and pressure. For pairs of 1–2 in Li–Pb solutions (1 is for Li, and 2 is for Pb), a pair potential of the form 8–4 is proposed. Calculations were performed for several Li–Pb melts at zero pressure and temperatures up to 1000 K, as well as for a Li17Pb83 solution under shock compression at temperatures up to 25 000 K and pressures up to 470 MPa. The thermodynamic properties of the Li17Pb83 solution are presented in tabular form. The diffusion and structural properties of this and other solutions, the Gruneisen coefficients, and the Hugoniot adiabat are also calculated.

Investigation of alumina film formed over aluminized RAFM steel by plasma assisted heat treatment

Reduced Activation Ferritic Martensitic (RAFM) steel is currently under intense consideration as a structural material for the blanket applications in fusion reactor. The concept of blanket module utilizes both solid i.e. Li2TiO3 and liquid breeder material, i.e. Eutectic Pb-17Li operating at 320–480 °C. The critical issues like liquid metal corrosion of RAFM steel, tritium permeation into RAFM steel and magneto hydrodynamic drag generation due to flowing Pb–17Li is already reported. αAl2O3 + FeAl coatings have been found promising to mitigate these challenges & reported with a substrate of P91 steels. However, coatings with hot dipping process on RAFM are scarcely reported as RAFM steel is in under development. Hence, an experimental investigation is done to examine the effects of heat treatments to form FeAl with a top layer of Al2O3. In-RAFM steel (9Cr-1.4W-0.06Ta) samples were hot dipped in a molten bath of 93%Al & 7%Si at 730 °C. These hot dipped samples were subjected to various heat treatments in 3 different routes. In the 1st route, normalizing heat treatment has been carried out at 980 °C for 30 min followed by thermal tempering in a muffle furnace at 760 °C for 90 min. 2nd route consists of plasma tempering along with normalizing in which O2 was used at low pressure (5 mbar) at 760 °C/90 min with pulsed DC at −520 V. Whereas in the third route, to form α-Al2O3, plasma assisted heat treatments were conducted directly without normalizing up to 24 h. The transformations of these phases have been analyzed through X-ray diffraction. Moreover, to confirm Al2O3 coatings, its thickness as well as the case depth of diffused FeAl, cross-sections of coated samples were investigated by mapping through SEM equipped with energy dispersive x-rays. Among these heat treatments, α-Al2O3 + FeAl formation with a thickness of ∼60–70 μm was observed in route 2. Route 1 resulted in to the formation of θ-Al2O3 + FeAl while route 3 indicated less diffusion of Al in to the substrate with defects.

Anomalous electronic behaviour of disordered alloy systems

In the present work the concept of complex formation has been incorporated in the structure of well known Faber–Ziman formula for the purpose of studying the composition dependence of electrical resistivities of liquid alloy systems which possess anomalous nature and also exhibit large deviation from metallic behaviour around specific composition. Within the framework of complex formation model the thermodynamic properties of the systems have been calculated. The study reveals that the anomalous electronic behaviour of liquid Li–Pb, Na–Pb, Li–Sn and Na–Sn can be attributed to the preferential ordering of unlike atoms.

Faradaically selective membrane for liquid metal displacement batteries

In the realm of stationary energy storage, a plurality of candidate chemistries continues to vie for acceptance, among them the Na–NiCl2 displacement battery, which has eluded widespread adoption owing to the fragility of the β″-Al2O3 membrane. Here we report a porous electronically conductive membrane, which achieves chemical selectivity by preferred faradaic reaction instead of by regulated ionic conduction. Fitted with a porous membrane of TiN, a displacement cell comprising a liquid Pb positive electrode, a liquid Li–Pb negative electrode and a molten-salt electrolyte of PbCl2 dissolved in LiCl–KCl eutectic was cycled at a current density of 150 mA cm−2 at a temperature of 410 °C and exhibited a coulombic efficiency of 92% and a round-trip energy efficiency of 71%. As an indication of industrial scalability, we show comparable performance in a cell fitted with a faradaic membrane fashioned out of porous metal. Molten-salt batteries such as Na–NiCl2 are promising candidates for grid storage, but suffer from fragility of ion-selective ceramic membranes. Here the authors report the operation of a Li–Pb||PbCl2 battery fitted with a robust TiN mesh membrane that functions by protective faradaic reaction.

The kinetics process of a Pb(ii)/Pb(0) couple and selective fabrication of Li-Pb alloys in LiCl-KCl melts.

The electrode reaction of Pb(ii) and co-reduction of Li(i) and Pb(ii) were investigated on a tungsten electrode in LiCl–KCl eutectic melts by a range of electrochemical techniques. From cyclic voltammetry and square wave voltammetry measurements, the reduction of Pb(ii) was found to be a one-step diffusion-controlled reversible process with the exchange of 2 electrons. The diffusion coefficients of Pb(ii) were computed, and they obey the Arrhenius law. Using the linear polarization technique, the kinetic parameters, such as exchange current intensity (j0), standard rate constant (k0) and charge transfer resistance (Rct) for the Pb(ii)/Pb(0) couple on a tungsten electrode were studied at different temperatures, and the activation energy is 27.32 kJ mol−1, smaller than the one for diffusion of Pb(ii), which further confirmed that the reduction of Pb(ii) was controlled by diffusion. A depolarisation effect for Li(i) reduction was observed from the results of cyclic voltammetry, square wave voltammetry and chronopotentiometry due to the formation of Li–Pb alloys by co-reduction of Li(i) and Pb(ii). Furthermore, five Li–Pb intermetallic compounds, LiPb, Li8Pb3, Li3Pb, Li10Pb3 and Li17Pb4 characterized by scanning electronic microscopy and X-ray diffraction, were selectively prepared by potentiostatic electrolysis on a tungsten electrode and galvanostatic electrolysis on a liquid Pb electrode, respectively.

Evaluation of Pb–17Li compatibility of ODS Fe-12Cr-5Al alloys

The Dual Coolant Lead Lithium (DCLL: eutectic Pb–17Li and He) blanket concept requires improved Pb–17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3+ZrO2 (125YZ), (3) Y2O3+HfO2 (125YH), and (4) Y2O3+TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb–17Li for 1000 h at 700 °C. Alloys showed promising compatibility with Pb–17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (∼1 at.%) in Al content beneath the oxide scale was observed in all four ODS alloys, which extended 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb–17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

Thermodynamic optimization of the Li–Pb system aided by first-principles calculations

The Li–Pb system was optimized using CALPHAD (CALculation of PHAse Diagram) method. The enthalpies of formation of eight intermetallic compounds Li4Pb (Li22Pb5), Li7Pb2, Li10Pb3, Li3Pb, Li8Pb3, Li5Pb2, αLiPb and βLiPb at 0 K were calculated from first-principles calculations with DFT + GGA approximations. The liquid phase was treated as (Li,Li0.8Pb0.2,Pb) using an associated solution model because a short-range-order phenomenon was proven to exist in liquid. The solution phases fcc and bcc were described as (Li,Pb) with a simple substitutional model. The intermetallic compounds Li4Pb, Li3Pb and Li5Pb2 were treated as stoichiometric compounds. With certain solubility ranges, the intermetallic compounds Li7Pb2, αLiPb and βLiPb were modeled as Li7(Li,Pb)2, (Li,Pb)(Li,Pb) and (Li,Pb)(Li,Pb) using the two-sublattice model. A set of self-consistent thermodynamic parameters in the Li–Pb system was obtained in the present work.

Trapping and thermal diffusion for energetic deuterium implanted into SiC

During ITER and DEMO reactor operation Li–Pb blanket flow channel inserts made from SiC will be exposed to both radiation and tritium. Absorption, desorption, and tritium diffusion are expected to occur and will strongly depend on the irradiation conditions; temperature, and neutron and gamma fluxes. Reaction bonded (RB) SiC samples were deuterium implanted at both room temperature and 450°C at different implantation energies and the corresponding TSD spectrum was obtained for each implantation energy. After implantation the samples were subjected to SIMS analysis. The TSD spectra obtained for all the samples implanted at different energies are very similar and characterized by a prominent deuterium desorption occurring at temperatures between 450 and 1000°C with a maximum that exhibits a clear trend to shift toward higher temperature as either implantation energy or implantation temperature increase. SIMS analysis before heating the deuterium implanted samples indicates that the implanted deuterium has a tendency to become bonded to Si rather than to C. The SIMS analysis shows that once heated up to 1000°C only part of the implanted deuterium was thermally released. The temperature shift observed when increasing the deuterium implantation energy and, hence, penetration, implies a deuterium diffusivity value at 700°C of about 8.5×10−17m2/s.

Volumetric properties of near-eutectic liquid Li–Pb alloys

The density and the thermal expansion of liquid lithium–lead alloys with Pb content of 83.0 and 84.3 at. % was measured using gamma-ray attenuation technique over the temperature range from liquidus to 1000 K. The density change during solid–liquid phase transition was directly measured for the first time for Li15.7Pb84.3 alloy. A comparison of the obtained results with literature data has been carried out.

Evaluation of thermal conductivity for liquid lead lithium alloys at various Li concentrations based on measurement and evaluation of density, thermal diffusivity and specific heat of alloys

The thermophysical properties of lead lithium alloy (Pb–Li) are essential for the design of liquid Pb–Li blanket system. The purpose of the present study is to make clear the density, the thermal diffusivity and the heat conductivity of the alloys as functions of temperature and Li concentration. The densities of the solid alloys were measured by means of the Archimedean method. The densities of the alloys at 300K as a function of Li concentration (0at%<χLi<28at%) were obtained in the equation as ρ(300K)[g/cm3]=−6.02×10−2×χLi+11.3. The density of the liquid alloys was formulated as functions of temperature and Li concentration (0at%<χLi<30at%), and expressed in the equation as ρ[g/cm3]=(9.00×10−6×T−7.01×10−2)×χLi+11.4−1.19×10−3T. The thermal diffusivity of Pb, Pb–5Li, Pb–11Li and Pb–17Li were measured by means of laser flash method. The thermal diffusivity of Pb–17Li was obtained in the equation as αPb–17Li[cm2/s]=3.46×10−4T+1.05×10−1 for the temperature range between 573K and 773K. The thermal conductivity of the Pb–17Li at the temperature of 773K was newly obtained and expressed in the equation as λ[W/mK]=4.47×10−2χLi2−0.08χLi+14.9. The dependence of Li concentration on the thermal diffusivities of the alloys was larger at higher temperature. The temperature dependence of the thermal conductivities of the alloys was larger when the Li concentration in the alloys was higher.

Characteristics of nickel and iron diffusion in molten lead–17lithium alloy

Diffusion characteristics of transition metals – nickel (Ni) and iron (Fe) diffusion in the molten lead–17lithium (Pb–17Li) were investigated experimentally under the argon atmosphere in the temperature range from 300°C to 600°C by using the long capillary method. The axial concentration distributions of Ni and Fe in Pb–17Li specimens were measured by ICP-MS, and the diffusion coefficients of Ni and Fe were determined based on the Fick's second law. The Arrhenius correlations of diffusion coefficient of Ni and Fe were obtained as DNi=7.37×10−5exp (−4.66×103/RT) (300°C≤T≤450°C) [cm2/s], DFe=3.21×10−4exp (−2.64×104/RT) (450°C≤T≤600°C) [cm2/s]. It is found that the diffusion coefficient of Ni is one order magnitude bigger than that of Fe in Pb–17Li. The diffusion coefficient of Fe in Pb–17Li was approximately in the same order as that in lead–bismuth eutectic reported by authors.

Magnetic field effect on the corrosion processes at the Eurofer–Pb–17Li flow interface

Structural and elemental analyses of the RAFM steel (EUROFER 97) interface with flowing Pb–17Li eutectic (velocity 5 cm/s at 550 °C, 1000 h) under the action of a strong magnetic field (B = 1.7 T) were performed using optical microscopy, SEM, confocal microscopy, precision micro-hardness methods, SIMS and point or line-scan EDX analyses. The results show that the magnetic field induces a faster crushing of martensite into the grains, a deeper dissolution of grain boundaries, an enhancement of the Fe and Cr mass transfer and a fast detachment of corrosion layers due to MHD effects.

Corrosion of steels in molten gallium (Ga), tin (Sn) and tin lithium alloy (Sn–20Li)

The compatibility of steels in liquid gallium (Ga), tin (Sn) and tin lithium alloy (Sn–20Li) was investigated by means of static corrosion tests. The corrosion tests were performed for reduced activation ferritic martensitic steel JLF-1 (JOYO-HEAT, Fe–9Cr–2W–0.1C) and austenitic steel SUS316 (Fe–18Cr–12Ni–2Mo). The test temperature was 873K, and the exposure time was 250 and 750h. The corrosion of these steels in liquid Ga, Sn and Sn–20Li alloy was commonly caused by the formation of a reaction layer and the dissolution of the steel elements into the melts. The reaction layer formed in liquid Ga was identified as Fe3Ga from the results of metallurgical analysis and the phase diagram. The growth rate of the reaction layer on the JLF-1 steel showed a parabolic rate law, and this trend indicated that the corrosion could be controlled by the diffusion process through the layer. The reaction layer formed in liquid Sn and Sn–20Li was identified as FeSn. The growth rate had a linear function with exposure time. The corrosion in Sn and Sn–20Li could be controlled by the interface reaction on the layer. The growth rate of the layer formed in liquid Sn and Sn–20Li was much slower than that in liquid Ga. The weight change of the JLF-1 specimen immersed in Sn–20Li for 750h was measured after the removal of the adherent Sn–20Li in a Li pool. The weight loss was 1.42×103g/m3, and this value was 1500 times larger than that tested in liquid lead lithium alloy (Pb–17Li) at the same conditions in the previous studies.

Corrosion of Indian RAFMS in Pb–17Li in a rotating disc corrosion test facility at 773 K

A rotating disc type corrosion test facility has been developed to study the compatibility of structural steels in lead–lithium eutectic at selected temperatures and flow velocities. The compatibility of an Indian Reduced Activation Ferritic–Martensitic Steel (IN RAFMS) disc rotating at 360 revolutions per minute (RPM) in Pb–17Li was studied at 773K after an exposure of 3000h. Results indicated that weight loss occurred at a rate of 1.02μg/cm2h for a total duration of 3000h. The corrosion mechanism was governed by dissolution of alloying elements from the sample surface and penetration of Pb–17Li into the IN RAFMS matrix. The microstructure of the parent material got altered up to a depth of 30μm from the exposed surface although effects of Pb–17Li penetration were noted up to 100μm. The depth of Pb–17Li attack increased with increase in linear flow velocities along the radial direction of the IN RAFMS disc.

Model improvements for tritium transport in DEMO fuel cycle

DEMO operation requires a large amount of tritium, which is directly produced inside the reactor by means of Li-based breeders. During its production, recovering and purification, tritium comes in contact with large surfaces of hot metallic walls, therefore it can permeate through the blanket cooling structure, reach the steam generator and finally the environment.The development of dedicated simulation tools able to predict tritium losses and inventories is necessary to verify the accomplishment of the accepted tritium environmental releases as well as to guarantee a correct machine operation.In this work, the FUS-TPC code is improved by including the possibility to operate in pulsed regime: results in terms of tritium inventory and losses for three pulsed scenarios are shown. Moreover, the development of a 1-D model considering the radial profile of the tritium generation is described. By referring to the inboard segment on the equatorial axis of the helium-cooled lithium–lead (HCLL) blanket, preliminary results of the 1-D model are illustrated: tritium partial pressure in Li–Pb and tritium permeation in the cooling and stiffening plates by assuming several permeation reduction factor (PRF) values. Future improvements will consider the application of the model to all segments of different blanket concepts.