Lithium-lead Alloy Research Articles

Pre-conceptual design and proof of principle assessments of self-cooled Toroidally symmetric lead-lithium (TSLL) blanket

A new self-cooled liquid metal blanket concept called TSLL (Toroidally Symmetric Lead-Lithium) blanket is proposed and assessed, including analysis for magnetohydrodynamic (MHD) flows, structural analysis, and heat transfer and neutronics assessments using the ARC reactor with demountable magnets designed by the Commonwealth Fusion Systems (CFS) as a testbed. The proposed blanket utilizes lead-lithium (PbLi) alloy as breeder/coolant and reduced activation ferritic/martensitic (RAFM) steel as structural material. A special feature of the new concept is the toroidally symmetric flow in the blanket integrated first wall and the breeding zone to reduce the MHD pressure drop, while using anchor links to strengthen the first wall construction. Provided analysis suggests acceptable MHD pressure drop, required mechanical integrity and high tritium breeding ratio of ∼ 1.64. As a result of these assessments, the new blanket concept can be recommended for more detailed studies as a promising blanket candidate for implementation in future fusion devices.

Garnet-type lithium sensors for the monitoring and control of Pb-Li alloys in tritium breeding modules

During the EU-DEMO conceptualization, eutectic Pb-Li was considered as the prime candidate liquid breeding material. Nonetheless, the conversion of lithium into tritium through the breeding reaction will result in a decrease in the lithium concentration within the alloy. Then, the monitoring of the lithium concentration in Pb-Li alloys is critical for the optimal Tritium Breeding Blanket (TBB) performance, as lithium affects dissolution of structural materials, tritium inventory and extraction rates. Garnet-like ceramics possess desirable properties for their use in lithium sensors, like high lithium-ion conductivity, good chemical stability, low thermal expansion coefficient, and great mechanical strength. For these reasons, electrochemical sensors based on garnet-type ceramics offer advantages for measuring lithium in molten Pb-Li alloys, such as high selectivity and fast response. This work presents the development of lithium sensors based on the garnet-type ceramic Li6BaLa2Ta2O12. The material was characterized by XRD and SEM, exhibiting good crystallinity and a homogeneous microstructure. The sensors were evaluated in a potentiometric configuration in molten Pb-Li alloys with lithium concentrations ranging from 3 to 35 at% Li. Potentiometric measurements were used to obtain correlations that allow the determination of the lithium activity in the lead–lithium alloys studied.

Development of lead lithium (Pb-16Li) alloy production system and characterization of the produced alloy

A lead lithium (Pb-16Li) production facility of capacity ∼75 kg has been developed at Institute for Plasma Research (IPR). Pb-16Li ingots were produced from an in-house developed Pb-16Li production system using the MHD stirring technique. The produced ingots were characterized analytically and microstructurally to determine the composition as well as to verify the homogeneity. Inductive Coupled Plasma-Optical Emission Spectrocopy (ICP-OES) analysis result shows the eutectic Li composition of 0.59±0.04 wt% which suggests the formation of Pb-16Li eutectic. To further confirm the eutectic formation, the eutectic temperature of the produced ingots had been determined by the Differential Scanning Calorimetry (DSC) and Pb-16Li solidification curve. The DSC analysis results and the solidification curve of the Pb-16Li samples indicate the melting temperature in the range of 235–238 °C which is similar to the Pb-16Li eutectic temperature ∼235 °C as reported in the literature and hence confirm the formation of Pb-16Li eutectic. A total of ∼750 kg of Pb-16Li ingots were produced from the system, and the produced Pb-16Li is being used as a process fluid in the various experimental systems at IPR.

Hydrogen Transport Model in Eutectic PbLi for Data Evaluation in an Absorption-Desorption Experimental Facility

The determination of the transport parameters of the hydrogen isotopes in the eutectic lead-lithium (PbLi) alloy represents a key issue for the design of the different breeding blanket systems that are being developed based on this liquid metal. This is the case for the dual-coolant lithium-lead blanket where the values of the Sieverts’ constant and diffusivity will delimit the magnitude and the kinetics of the induced tritium flux produced by the breeding blanket toward the circuit of He for the refrigeration of the structures. In addition, the design (sizing and efficiency) of future tritium extraction systems of the breeding alloy or the He coolant purification system will be defined on the basis of these transport parameters. Taking into account the current literature, there exists a very wide band (even more than three orders of magnitude) in the experimental results for the Sieverts’ constant obtained by different research groups using different experimental techniques. This dispersion band in terms of solubility is not acceptable from the point of view of the design of a breeding blanket for a fusion reactor. With the aim of reducing this dispersion of results, the Absorption-Desorption facility available at the University of the Basque Country (UPV/EHU) has been upgraded and new samples of high quality PbLi will be measured in the near future in collaboration with CIEMAT. In this work, a complete theoretical model is described for the interaction between isotopes of hydrogen and the eutectic PbLi sample considering the particular boundary conditions for the absorption and desorption processes. This model has been specifically developed for the upgraded Absorption-Desorption facility available at the UPV/EHU, according to the new configuration of the experimental chamber made of glass and quartz and the geometry of the crucible made of tungsten that is designed to hold the PbLi sample. Three different phases are described (loading, pumping, and release) together with the boundary conditions that have been taken into account in each one. This way, different mathematical expressions for the concentration profile of the isotopes of hydrogen through the PbLi sample are posed for each phase so that the experimental measurements to be carried out in the upgraded Absorption-Desorption facility will be fitted to them, and as a result, the transport parameters will be obtained.

Concept design of a facility to determine helium solubility in Pb-16Li

The design of an experimental setup to determine helium solubility in liquid metals, such as the eutectic Pb-16Li alloy is presented. The apparatus design is based on the concept of saturation–desorption. The lead–lithium alloy is saturated by helium through its surface as well as by bubbling the helium directly into the liquid, which also aids the liquid mixing. Once the helium saturated solution is obtained, part of the liquid is transferred into a second vessel where the dissolved helium is desorbed into a deep vacuum. The transferred portion of the liquid is weighed, and the amount of helium in the gas phase is determined from the total pressure increase as well as by residual gas analysis via a quadrupole mass spectrometer.

Study into the physical chemistry and technology of alkali liquid metal coolants for nuclear and thermonuclear power plants

It is shown that, as the result of developing alkali liquid metal coolants, including sodium, eutectic sodium-potassium alloy, lithium and cesium, the scientific basis has been established for their application in nuclear power. The paper presents data from investigations of thermophysical, neutronic and physicochemical properties and characteristics of various alkali liquid metal coolants, the content of solid-phase and dissolved impurities in coolants, mass transport of impurities in circulation circuits with alkali liquid metal coolants, development of systems for removal of impurities, and control of the content of impurities in alkali liquid metal coolants. Alkali liquid metal coolants are considered as a part of a system that includes a structural material in contact with the coolant, and a gas space that compensates for the thermal expansion of the coolant. The state of the system is defined by the physicochemical properties of the system’s components. And the coolant and the structural materials also represent subsystems consisting of a base material, a coolant and impurities contained both in the material and in the coolant. It has been shown that each alkali liquid metal coolant has its own set of impurities that define its technology. It depends on the physicochemical properties of the solution of the structural material impurities and components in the coolant. Objectives have been formulated for investigating further alkali liquid metal coolants, as stemming from the need to improve the efficiency, environmental friendliness, reliability and safety, and for extending the life of nuclear power plants in operation or under design. Alkali liquid metals are promising candidate materials for being used in thermonuclear power not only as the coolant but also as the tritium breeding medium. These include, first of all, lithium and its eutectic alloy with lead (17 at. % of lithium). The possibility for using lithium or a lithium-lead alloy as a coolant in the blanket of the international thermonuclear power reactor is compared.

Experimental setup for study of mechanical performance of materials in liquid Pb-16Li and first results

Dual Coolant Lithium Lead (DCLL) Breeding Blanket, which is using the eutectic lead-lithium alloy (Pb-16Li) as tritium breeder, neutron moderator and coolant, is being developed in the frame of the EUROfusion project. Flow channel inserts (FCI) are insulating components embedded along the Pb-16Li channels inside the DCLL breeding blanket modules developed to minimize the magnetohydrodynamic pressure drop and heat losses. There is an effort to modify the originally designed steel-ceramic-steel layered structure of FCI by eliminating the steel protective layer leading to simple steel-ceramic structure. In this arrangement, the ceramic is directly exposed to liquid Pb-16Li. Demanding operating conditions of the DCLL blanket, in particular elevated temperatures, may give a rise to thermomechanical stresses leading to component failure. Therefore, the assessment of mechanical behaviour of the material in direct contact with Pb-16Li is of primary interest.To study the mechanical properties of the material exposed to corrosive environment of Pb-16Li at elevated temperatures, a dedicated experimental setup was designed. Three-point flexural test is adopted to evaluate the flexural stress-strain material response. Since the experimental procedure is performed in liquid Pb-16Li at high temperatures with an inert atmosphere, the mechanical test takes place in an isolated testing chamber filled with molten Pb-16Li transferred from the melting chamber prior the mechanical test. A specificity of the presented facility is its capability of material testing of three samples within one testing procedure in Pb-16Li at temperatures up to 650 °C.

Design of the CIEMAT Corrosion Loop for Liquid Metal Experiments

The main components of a liquid breeder blanket in a fusion power reactor are lead lithium alloy (PbLi) and the steel structure in which the liquid is enclosed (EUROFER). Several compatibility tests have shown that structural materials always suffer from corrosion attacks. The governing mechanism can be attributed to the dissolution of the steel by the liquid breeder and is strongly related to the PbLi chemistry, velocity profile, and temperature. A new facility, CiCLo-C (CIEMAT Corrosion Loop, Internally Coated), is dedicated to the study of corrosion in materials under the severe breeding blanket condition. An effort was made to design an experimental facility with a specific test section able to work at quite ambitious operation parameters: up to 550 °C and a 1 m/s flow of PbLi. Furthermore, an innovative tantalum coating was introduced in the whole loop to avoid impurities coming from the pipeline, which can disturb the measurements, and to better preserve the installation.

First Principles Study on the Dissolution Corrosion Behavior of RAFM Steel in the Liquid PbLi

Liquid Lead-Lithium (PbLi) alloys are promising functional material which can act as both neutron multiplier and tritium breeder in liquid blanket of fusion reactors, however, their corrosion behavior on RAFM steel is still a challenge. In this work, the dissolution, diffusion, bonding and charging behavior of steel alloy elements in liquid PbLi were investigated by using the first principles molecular dynamics simulations. The dissolution order of the main alloy elements of RAFM steel dissolved into the liquid PbLi was Cr>Fe>V>Mn>Ta>W>C. O atom tend to bond with Li atom in liquid PbLi and the O dissolution energy had negative value of -3.84 eV. The binding energies of Y-O, Ti-O, Al-O, Si-O, Zr-O, Ta-C, V-C, Ta-N and V-N pairs within liquid PbLi at temperature 500°C show that related oxides/carbides/nitrides in RAFM steel do not likely to decompose and may not affect their dissolution corrosion behavior. These data can provide indispensable information for understanding the dissolution corrosion behavior of advanced RAFM steel in liquid PbLi.

Core size effects of laser fusion subcritical research reactor for fusion engineering research

A multi-purpose high repetition laser facility, the so-called Japan establishment for power-laser community harvest (J-EPoCH) is proposed as a next generation laser facility. J-EPoCH will operate at the maximum rate of 100 Hz. The omnidirectional 12 laser beams with 8 kJ would yield ∼1013 neutrons with a large high aspect ratio target. As one of the applications of J-EPoCH, a laser fusion subcritical research reactor has been conceptually designed based on existing technologies. Moreover, a variety of fusion engineering studies: energy conversion, tritium breeding, neutron irradiation effects, etc, can be conducted. The feasibility of the subcritical research reactor is considered in terms of neutron-thermal (n-t) conversion and tritium breeding. Lead–lithium alloy (Li17Pb83) and boron carbide (B4C) have the potential to be studied for preliminary fusion power generation. The subcritical reactor will generate 21.4 W and 20.0 W of the thermal fusion power with the Li17Pb83 and the B4C layers of the thickness of 80 cm, respectively at 1 Hz operation. The Li17Pb83 layer of a 5 mm thickness will achieve the temperature rise of 0.203 mK per shot. The thermal fusion energy is detectable with conventional measurement techniques. The core with the Li17Pb83 layer thickness of 100 cm will yield more than one tritium from a deuterium–tritium fusion neutron. However, laser windows reduce the efficiency of n-t conversion and tritium yield.

Lithium sensors based on Li6La3Ta1.5Y0.5O12 and Li6BaLa2Ta2O12 garnet electrolytes for molten lead alloys

The development of effective breeding blankets is crucial to the success of future fusion reactors. One of the main liquid breeding candidates is molten eutectic Pb-Li. In this environment, it is essential to control lithium concentration and dosage to keep the adequate composition in the melt. In this frame, on-line and on-board lithium monitoring tools, which can operate under extreme conditions, are required. Electrochemical sensors based on lithium conducting solid electrolytes (Li6La3Ta1.5Y0.5O12 and Li6BaLa2Ta2O12) were designed and tested. These potentiometric sensors were used to measure the Open Circuit Potential (OCP) in molten lead-lithium alloys with different lithium concentrations. Measurements were performed at 400 °C, 500 °C, and 600 °C. Experimental OCP values were in good agreement with those calculated with the Nernst equation. OCP values showed a linear relationship versus the logarithm of the lithium activities, fulfilling the Nernst equation.

Thermodynamic Description of Liquid Lithium–Lead Alloys

Thermodynamic Description of Liquid Lithium–Lead Alloys

Numerical investigation on the MHD flow characteristics of eutectic lead-lithium alloy in a U-turn duct with different aspect ratios of the connecting channel

In the design and development of liquid breeder blankets, a number of duct geometries are considered, such as the multiple channel, U-turn duct and T-shaped duct. In the presence of the magnetic field, the motion of electrically-conducting liquid metal leads to Megnetohydrodynamic phenomena, as results of the liquid metal flow profile changes inside the flow channels and additional pressure drop of liquid breeder blankets. A three-dimensional liquid-metal (LM) magnetohydrodynamic (MHD) flows in a U-turn duct with large aspect ratio of the duct cross-section of the connecting channel and in a U-turn conduit with manifold in the connecting region is studied, respectively. Here, the effects of the electrical conductivity of the separating wall in the manifold and different Hartmann numbers on the flow features are considered. Since the 3-D currents are induced due to the complicated geometrical flow path, the electrical conductivity of the separating wall plays a key role in the distribution of mass flow rate among the parallel ducts in manifold. Thus, in the present study, the distribution of the mass flow rate is analyzed for different electrical conductivity of the structural walls. Furthermore, since the aim of the optimal design of liquid-metal blanket is to achieve a proper velocity distribution and reduce the pressure drop caused by the flow opposing Lorentz force, the investigation of the effect of the duct geometry on the pressure distribution in this study is significant.

Design development and testing of mutual inductance type level sensor for molten lead-lithium alloy

Continuous level measurement of molten Pb-Li in various Pb-Li containing tanks is a challenge owing to the high operating temperature of molten Pb-Li and its corrosive nature. A mutual inductance type level sensor has been designed and developed for molten Pb-Li applications, based on knowledge and experience gained form the development of similar level sensor for liquid sodium system. Appropriate temperature compensation technique has been implemented to compensate for the temperature effects on Pb-Li electrical conductivity for the operating temperature range. The testing of level sensor has been performed in solid Aluminium as well as Stainless Steel blocks, followed by molten Pb-Li at 300 °C. In all the cases, the temperature compensated output of MI probe has been found to exhibit adequate sensitivity and vary linearly with the change in level of the conducting medium. In the case of molten Pb-Li at 300 °C, the testing was carried out in reference to a conductivity level switch, and the accuracy was found to be within 2% of full scale.

Prediction of PbLi fluid flow and temperature field in a thermal convection loop for qualification of fusion materials

Two modeling tools, a thermohydraulics code and a computational model in COMSOL Multiphysics, have been developed, tested and then applied to the analysis of fluid flow and heat transfer in a thermal convection loop (TCL). Such a device has recently been used to experimentally evaluate corrosion compatibility of APMT (Fe–21Cr–5Al–3Mo) steel with high-temperature molten eutectic lead-lithium (PbLi) alloy at Oak Ridge National Lab, TN, USA. The 1-D thermohydraulics code allows for rapid calculations of the loop parameters as a function of the applied heat flux. The supplemental COMSOL finite-element computations provide detailed 3-D velocity and temperature field data but are much more time consuming. Both modelling tools demonstrate an excellent agreement in the computed circulation velocity as well as maximum and minimum temperatures. The performed TCL analysis focuses on flow development in the “hot” and “cold” legs, formation of Dean vortices in corner regions, blocking effect of the immersed samples, and radiative and convective cooling effects under the experiment-relevant conditions for Prandtl number Pr=0.015, Grashof numbers Gr∼107, and Reynolds numbersRe∼104.

Physical Background, Computations and Practical Issues of the Magnetohydrodynamic Pressure Drop in a Fusion Liquid Metal Blanket

In blankets of a fusion power reactor, liquid metal (LM) breeders, such as pure lithium or lead-lithium alloy, circulate in complex shape blanket conduits for power conversion and tritium breeding in the presence of a strong plasma-confining magnetic field. The interaction of the magnetic field with induced electric currents in the breeder results in various magnetohydrodynamic (MHD) effects on the flow. Of them, high MHD pressure losses in the LM breeder flows is one of the most important feasibility issues. To design new feasible LM breeding blankets or to improve the existing blanket concepts and designs, one needs to identify and characterize sources of high MHD pressure drop, to understand the underlying physics of MHD flows and to eventually define ways of mitigating high MHD pressure drop in the entire blanket and its sub-components. This article is a comprehensive review of earlier and recent studies of MHD pressure drop in LM blankets with a special focus on: (1) physics of LM MHD flows in typical blanket configurations, (2) development and testing of computational tools for LM MHD flows, (3) practical aspects associated with pumping of a conducting liquid breeder through a strong magnetic field, and (4) approaches to mitigation of the MHD pressure drop in a LM blanket.

Numerical investigation on the comparison of the MHD flow features of lithium and eutectic lead-lithium alloy in a conduit with four-parallel ducts

• The difference in the MHD (magnetohydrodynamics) flow characteristics between Lithium (Li) and eutectic lead-lithium (LiPb) is analyzed. • Commercial software CFX is used to investigate the LM MHD flows in a conduit with four-parallel ducts. • The effect of the local electric conductivity of the duct walls on the mass imbalance among the outlet ducts is investigated. • The mechanism governing the flow imbalance in the four-parallel ducts is discussed. • The pressure drop and mass flow rate in the case with Pb-17Li is larger than those in the case with pure Li. At present, the magnetohydrodynamic (MHD) flows of liquid-metal (LM) Pb-17Li and pure Li through a conduit with four-parallel ducts having partly different electrical conductivity are numerically analyzed. Here, the conduit system can cause counter flow and co-flow, which can be a good candidate for the design of duct flow in the liquid-metal blanket. Meanwhile, since lithium (Li) and eutectic lead-lithium (LiPb) are the promising liquid metal materials for a self-cooled blanket, the MHD flow characteristics of these two liquid metals become important and have to be taken into account during the design of a fusion liquid-metal blanket. The current study focuses on the electromagnetic features of the two liquid-metal flows, and considers the flow imbalance that is affected by different wall electrical conductivity in four-parallel ducts. The results present that the pressure drop and mass flow rate in the case with Pb-17Li is larger than those in the case with pure Li because of different properties of the liquid metals used therein. Furthermore, the influence of the local electrical conductivity of the structural walls on the flow imbalance among the outlet ducts is analyzed for the two different working fluids, and the mechanism governing the flow imbalance in the outlet ducts is discussed.

Code-to-Code Comparison for a PbLi Mixed-Convection MHD Flow

In “An Approach to Verification and Validation of MHD Codes for Fusion Applications” [S. Smolentsev et al., Fusion Eng. Des., Vol. 100, p. 65 (2015)], an effort for verification and validation of computer codes for liquid metal flows in a magnetic field for fusion cooling/breeding applications was initiated. The current study continues that effort. A group of experts in computational magnetohydrodynamics from several institutions in the United States and Europe performed a code-to-code comparison for the selected reference case of a mixed-convection buoyancy-opposed magnetohydrodynamic flow of eutectic lead-lithium (PbLi) alloy in a thin-wall conducting square duct at Hartmann number Ha = 220, Reynolds number Re = 3040, and Grashof number Gr = 2.88 × 107. As shown, the reference flow demonstrates a boundary layer separation in the heated region and formation of a reversed flow zone. The results of the comparison suggest that all five solvers predict well the key flow features but have moderate quantitative differences, in particular, in the location of the separation point. Also, two of the codes are more computationally dissipative, showing no velocity and temperature oscillations.

Volume and pressure of helium bubbles inside liquid Pb16Li. A molecular dynamics study

The behaviour of helium impurities inside metals has been well studied in the last 30 years, however, little attention has been devoted to helium atoms inside liquid metals. Here we have investigated the nucleation and coalescence processes of helium atoms inside liquid eutectic lithium–lead alloys using atomistic simulations. Several key findings regarding He bubbles inside liquid PbLi eutectic are presented. The radius versus the number of atoms has been calculated in the temperature range 600–1000 K. The trend can be fitted and likely extrapolated to larger bubbles (micrometer size). The value of thermal expansion of He bubbles is given as well and compared to the thermal expansion of bulk He. The pressure inside He bubbles has been calculated as a function of bubble size. Finally, the importance of accurate interatomic potentials for the He–metal interaction is discussed.

Structure Factor and Phonon Dispersion in Liquid Pb–Li Eutectic

Lead–lithium alloy in its eutectic form, i.e., Pb83Li17 is one of the most promising candidates for its application as liquid blanket in fusion reactor with its properties such as low melting point, high boiling point and appropriate absorption and activation cross section for neutrons. In the present paper, phonon frequencies and sound velocity of liquid Pb–Li eutectic are reported using theoretical formalism. Further, structural properties of Pb–Li eutectic are determined in a self-consistent way using temperature-dependent Debye–Waller factor-like term. The results suggest that the size effects have significant role in determining the elastic properties of Pb–Li eutectic, viz. sound velocity and phonon frequencies.