LiPb Flow Research Articles

Conceptual design of a PAV-based tritium extractor for the WCLL breeding blanket of the EU DEMO: Effects of surface-limited vs. diffusion-limited modeling

In order to close the fuel cycle, the EU DEMO will be equipped with a breeding blanket (BB) for the on-site tritium production. In the water cooled lithium lead (WCLL) BB concept, the tritium will be generated in the liquid PbLi from which it must then be extracted.The conceptual design of the tritium extraction and removal system for this BB concept is addressed here. It relies on the permeator against vacuum (PAV) technology, where the tritium dissolved in the PbLi is forced to cross a metal (Nb) membrane by pumping the vacuum on the secondary side. The proposed PAV geometrical configuration is based on the shell-and-tube concept, where the walls of the pipes in which the PbLi flows are the permeator membrane. The dimensioning of one permeator vessel for one of the PbLi loops is carried out here, adopting two different models for the tritium permeation: diffusion-limited (for the case of a non-contaminated membrane) and surface-limited (suitable for a contaminated Nb surface).The results show that in the case of a non-contaminated membrane it is possible to reach the target tritium extraction efficiency also at the PbLi nominal operating temperature, while in the case of a contaminated membrane the PbLi should be heated to enhance the permeation.

MHD effects of partition plates on thermofluid performance of Indian variant LLCB TBM for ITER

Abstract Liquid metal Lead-Lithium (PbLi) flow channels in Indian LLCB (lead lithium cooled ceramic breeder) Test Blanket Module consist of a sequence of parallel channels which are fed from a common inlet header. Thin radial-toroidal vertical plates known as partition plates at the central plane perpendicular to the applied magnetic field are primarily envisaged to enhance the mechanical strength of high aspect ratio electrically coupled parallel poloidal channels. In that case the partition plates are acting as an internal Hartmann wall and they have significant effects on velocity profile, pressure drop and heat transfer characteristics at ITER relevant applied magnetic field (B0 = 4 T). Three dimensional numerical simulation is performed in a model of full scale LLCB variant to study the effects of these partition plates on various flow field variables. Axial velocity near the thin partition wall and side wall jet structures are found to get significantly. Magneto-hydraulic pressure drop and redistribution of flow rates due to the presence of partition plates are assessed by comparing the results with no partition wall. Thermofluid simulation is carried out to obtain the temperature distribution of various structures for a given heat load profile based on neutronic estimation. The effects of buoyancy force on thermofluid flow profile in channels with high temperature gradient are also presented.

An integrated hydrogen isotopes transport model for the TRIEX-II facility

Abstract At ENEA Brasimone Research Centre, Italy, a new experimental facility named TRIEX-II ( Tri tium Ex traction) was designed and installed. Its aim is to characterize, in the range of operating conditions foreseen for the European Test Blanket System WCLL-TBS, several extraction technologies for hydrogen isotopes (Q2) solubilized in the flowing metallic LiPb alloy (15.7 at. % Li). One of these technologies is the packed column, an example of Gas/Liquid Contactors (GLCs). This paper proposes a multiscale modelling tool, combining different scales through two computational tools. The extraction column mock-up is described by a component-detail level model, developed in COMSOL Multiphysics, and integrated into a system level code of the whole TRIEX-II circuit, developed using MATLAB/Simulink. The integration is carried out by implementing the COMSOL component into an S-function of MATLAB/Simulink, preserving the process flow diagram of the loop. In this way, it was possible to quantify the Q2 concentrations and the permeation fluxes, and to evaluate the theoretical extraction efficiency. The LiPb flow field inside the extractor was also derived. Finally, a comparison with the experimental results was performed. The results suggest that this tool could be adapted for analyses of complex systems, at a multiscale level, in view of design improvements and safety studies for the tritium cycle of ITER.

Thermofluid MHD studies in a model of Indian LLCB TBM at high magnetic field relevant to ITER

Numerical simulation of 3D MHD flow in a full scale variant of India propose Lead-Lithium cooled Ceramic Breeder (LLCB) Test Blanket Module(TBM) for ITER program has been carried out at high Hartmann number (Ha=17,845). The model geometry takes into account the integrated First wall (FW) which is provisioned with internal helium cooling channels for dual cooling purpose. The MHD effects on steady state velocity profile, modification of wall electric potential distribution due to electrical coupling of parallel channels has been analysed. Flow rate distribution in electrically coupled parallel channels has been obtained for a fixed PbLi flow rate in the common inlet header. Steady state thermofluid analysis has been performed using user defined heat density data obtained from neutronic estimation in similar variant. Prediction of thermal hot spots in various structural walls and sharing of heat load by coupled PbLi and First wall helium cooling circuit is presented.

Effect of magnetic field on corrosion behavior of Indian reduced activation ferritic/martensitic steel in liquid Pb–Li

In the present study, the effect of a magnetic field on the corrosion of Indian reduced-activation ferritic/martensitic steel (IN RAFMS) in flowing lead–lithium eutectic (Pb–Li) has been studied in an electromagnetic-pump-driven loop (EMPPIL-M). The loop was operated for 2800 h at an average flow velocity of 1.5 m s−1 with a 0.5 T magnetic field over the IN RAFMS samples. The corrosion rate in the presence of a magnetic field at a temperature of 773 K was found to be 1.3 times higher than that observed in the absence of a magnetic field. Non-uniform corrosion, resulting in the formation of distinct surface features, was observed over the surface of the sample located inside the magnetic field. Pb–Li attack in the presence of a magnetic field was not only confined to the prior austenite and martensitic lath boundaries (as in the absence of magnetic field), but also occurred in the intra-lath regions resulting in the formation of substructures. The development of electric potential over metallic samples and significant gradients in Pb–Li flow due to the magnetohydrodynamic effect played a major role in the formation of surface features and accelerating the corrosion rate within the magnetic field. On the other hand, the increase in the depletion of iron from the steel matrix observed in the presence of the magnetic field was a result of its direct interaction with the field parameters.

DEMO WCLL breeding zone cooling system design: Analysis and discussion

The Water-Cooled Lithium-Lead (WCLL) Breeding Blanket (BB) is a key component in charge of ensuring Tritium self-sufficiency, shielding the Vacuum Vessel and removing the generated power of DEMO reactor. The last function is fulfilled by two independent cooling systems: First Wall (FW) that removes the plasma heat flux and Breeding Zone (BZ) that removes the deposited power of charged particle and neutron. Several layouts of BZ coolant system have been investigated in order to identify a configuration that guarantee Eurofer temperature below the limit (823 K) and good thermal-hydraulic performances (i.e. water outlet temperature 601 K). A research activity is conducted to study and compare four configurations, which rely on different arrangement of the stiffening plates (i.e. toroidal-poloidal and radial-poloidal), orientation of the cooling pipes (i.e. horizontal, vertical) and PbLi flow path. The analysis is performed using a CFD codes, thus a 3D finite volume model of each configuration is developed, adopting the commercial ANSYS CFX code. The objective is to compare the BZ cooling system layouts, identifying and discussing advantages and key issues from the thermal-hydraulic point of view, also considering feedbacks from MHD and neutronic analyses. The research activity aims at laying the groundwork for the finalization of the WCLL blanket design, pointing out relevant thermal-hydraulic aspects.

Activity and decay heat calculations for the European DEMO WCLL breeder blanket module including activated LiPb flow

This paper presents the analyses performed within the SAE (Safety and Environment) project of EUROfusion/PPPT aimed at providing up-to-date estimates of the activity inventories and the decay heat generation in the WCLL. Detailed evaluation of the WCLL PPPT reactor concept based on the generic Multi-Module-Segment (MMS) model was performed by calculating the decay heat and activity inventories for the WCLL central inboard/outboard blanket modules (DEMO 2015 baseline, MMS design). Following, the estimation of radial distribution of decay heat and activity in breeder blanket module material mixture is presented. And finally, the preliminary approach to evaluate Li flow inside the breeder zone is presented in this paper. Additional calculations were performed to identify dominant nuclides after the irradiation.

Numerical Simulation of Heat Transfer Characteristics between Liquid Lithium Lead and Oil

The liquid LiPb experimental loop is an essential device for studying the compatibility of LiPb with structural materials of the fusion reactor. The heat exchanger is one of the most important devices of the LiPb loop, which is used to control the temperature distribution and study the LiPb flow characteristics in the working condition of the LiPb loop. Based on the heat transfer theory, the liquid LiPb experimental loop cooler is designed at first, which is a tube-type countercurrent heat exchanger with YD-300 heat-conducting oil as the coolant. Numerical simulation analysis was carried out to verify the feasibility of the design scheme under the design condition and the normal operation by using the FLUENT software. The results show that the theoretical design parameters are in good agreement with the numerical simulation results and the average concentration deviation is less than 2%. Furthermore, the average volume temperature and film temperature of heat conducting oil under different working conditions are lower than 310℃ and 375℃ respectively, which indicates that the cooling effect of the LiPb fluid can be realized and the design scheme of the cooler is reasonable.

Engineering design and development of lead lithium loop for thermo-fluid MHD studies

In the frame of the design and development of Liquid breeder blankets, a number of R & D activities are in progress in the area of liquid metal technology development. In presence of strong plasma confining toroidal magnetic field, motion of electrically conducting liquid metal leads to Magneto Hydro Dynamic (MHD) phenomena, as a consequence of which liquid metal flow profile changes inside the flow channels of liquid breeder blankets and additional pressure drop occurs due to the flow opposing Lorentz force (J × B). For the design and development of liquid breeder blankets, 3D MHD flow needs to be studied for various flow configurations as present in the liquid breeder blankets. A lead lithium (Pb-Li) MHD loop is being developed at IPR to perform MHD experiments for Pb-Li flow in various flow geometry such as U-bend, transition zones, circular pipes, sudden expansion and contraction, etc. The test mock ups will be placed in a uniform magnetic field up to 1.4 T, produced by a C-shaped Iron core electromagnet with a pole gap of 370 mm. Both Isothermal and thermo-fluid MHD experiments are being planned for MHD database generation and code validation.

Magnetohydrodynamic and thermal analysis of PbLi flows in poloidal channels with flow channel insert for the EU-DCLL blanket

Magnetohydrodynamic (MHD) processes are known to be critically important for the dual coolant lithium lead (DCLL) breeding blanket (BB) concept. In order to minimize the MHD pressure drop in the European DCLL blanket design, the liquid metal breeder (PbLi) is decoupled electrically from the ferritic–martensitic structure (EUROFER) using insulating ceramic-based flow channel inserts (FCIs). The impact of the FCI on the velocity profile and the pressure drop in the DCLL front poloidal channels is studied. Two-dimensional momentum and induction equations for fully developed flows are solved numerically using the ANSYS-Fluent simulation platform under DCLL-relevant conditions (, ). Velocity and pressure drop in the PbLi flows have been computed first for a channel without FCI and then for three possible alumina-based FCI design: two types of sandwich FCI and one naked FCI. In order to analyze thermal effects in the blanket, the obtained velocity profiles are used as inputs to solve the 3D energy equation. The computations of the temperature distribution in the DCLL poloidal front channel with a prototypical exponentially varying heat generation profile are obtained using convective boundary conditions. Results show the effect of the FCI and MHD phenomena on heat transfer.

Study of hydrogen recovery from Li-Pb using packed tower

Extraction of hydrogen from a Li-Pb flow to inert Ar one using a random packed tower is experimentally investigated for development of a more efficient tritium recovery system of DEMO fusion reactors. A small-scale tower of 57.2 mm in diameter and 300 mm in height packed with SS304 Raschig rings is supplied with two counter-current flows, which one is liquid Li-Pb absorbing hydrogen of 5.06 kPa in equilibrium pressure from the top of the tower and another is Ar gas from the bottom. Overall mass-transfer rates are experimentally determined as a function of Li-Pb flow rates and Ar gas ones at constant temperature of 673 K. Overall mass-transfer capacity coefficients are determined by fitting a transfer equation of hydrogen in a random packed tower to experimental variations of its concentration in gas under given conditions of the space velocity of liquid or gas, and the values of the mass-transfer capacity coefficient increase with Li-Pb flow rates almost linearly. The hydrogen recovery ratios between the top and bottom of the tower were almost independent of the Li-Pb flow rate, and its values were between 20% and 30%.

Corrosion–erosion and mass transfer dynamic behaviors of reduced activation ferritic/martensitic steel in a nonisothermal Pb-17Li system

Corrosion tests were performed to study corrosion–erosion behaviors of reduced activation ferritic/martensitic steel JLF-1 and mass transfer behaviors of metal elements in a nonisothermal Pb-17Li flow. The tests were performed using isothermal and nonisothermal mixing pots at approximately 773 K for up to 1000 h. The test results indicate that the steel surface corroded according to the dissolution of steel compositions (i.e., Fe and Cr) in the flowing Pb-17Li. The corroded surface then revealed a granular structure with small pebble-shaped protrusions. The protrusions were formed by preferential corrosion along the boundaries of microstructures on the steel surface. Small-scale corrosion-erosion was caused by the removal of the small protrusions from the steel surface in flowing Pb-17Li. There was also large-scale corrosion–erosion according to the destruction of the steel surface after the surface was deeply corroded. Metal elements, such as Fe, Cr and Ni, were dissolved from the steel in the flowing Pb-17Li. They were transferred to a low-temperature region with the Pb-17Li flow and finally precipitated as round-shaped particles on metal wires installed in the low-temperature region of the mixing pot.

Numerical and experimental MHD studies of Lead-Lithium liquid metal flows in multichannel test-section at high magnetic fields

Numerical simulation and experiments have been performed at high magnetic fields (1–3T) to study the MHD assisted molten Lead-Lithium (PbLi) flow in a model test-section which has typical features of multiple parallel channel flows as foreseen in various blanket module of ITER. The characteristics Hartmann number of the presented case study is up to 1557 which is relevant to typical fusion blanket conditions. Symbols B0, a, σ, μ in the definition of Hartmann number are strength of the applied magnetic field, characteristic length scale which is half the channel width parallel to the magnetic field, electrical conductivity and dynamic viscosity of PbLi respectively. Flow distribution in two electrically coupled parallel channels that are fed from a common inlet manifold has been analyzed by measuring the side wall potential difference data of individual channels and by numerical simulation. Both the results of numerical prediction and measured flowrate indicate unequal distribution in parallel channels and the variation is a function of the total flowrate and applied magnetic field strength. Also 3-D currents generated due to the complex geometrical flow path play a key role in distribution of the flow among the parallel channels. A similarity coefficient (K) is proposed for quantitative estimation of the similarity between numerical and corresponding experiment data of wall potential distribution. The measured pressure drop in the test-section is analyzed for different flow conditions to verify the applicability of laminar flow model.

The effect of wall flow velocity on compatibility of high-purity SiC materials with liquid Pb-Li alloy by rotating disc testing for 3000 h up to 900 °C

The lead-lithium (Pb-Li) alloy is considered as a coolant and a tritium breeder for fusion reactor blanket systems. One of the critical requirements in realization of the systems is the compatibility of silicon carbide (SiC) and its composites, as structural and/or functional materials of the blanket, with liquid Pb-Li flow at high temperatures. This study aims to clarify the corrosion process of high-purity SiC materials under flow condition of liquid Pb-Li for 3000 h at 700 and 900 °C, respectively, by using the rotating disc corrosion equipment. Furthermore, the effect of wall flow velocity on the compatibility was specifically evaluated. For that purpose the decrease rate (about 32–37%) of the wall flow velocity on disc type’s sample by the dragging effect by fluidic viscosity was first calculated by numerical analysis of the rotating flow condition. The wall flow velocity dependence on the reaction layer’s thickness was then evaluated for both high purity SiC and SiC/SiC composites. The test results show that the formation process of the surface reaction layer mainly depends on both the time required for the chemical reaction and the wall flow velocity in the initial stage but the reaction layer thickness tended to approach to the constant regardless of the wall flow velocity with increasing exposed time. In short, no accelerated corrosion was found for about 3000 h. It was also found that there was no significant difference of the temperatures between 700 and 900 °C. Finally the key corrosion mechanism, i.e., the reaction of oxide impurities, e.g., Li2O, in liquid Pb-Li with the Si-oxide layer over SiC, was identified.

MHD pressure drop measurement of PbLi flow in double-bended pipe

The design of liquid metal cooling system for the liquid blanket concepts in magnetic fusion reactor requires the magnetohydrodynamics (MHD) friction loss coefficients for various pipes including pipes and bents to estimate the pressure drop of the whole blanket. The aim of this study is to reveal the MHD pressure drop of PbLi flow in a double-bended pipe. The experiments were conducted in the Oroshhi-2 loop having a super conducting magnet of 3T at NIFS in Japan. In this paper, the MHD pressure drops of the pipe under the magnetic field of 0.5T–3.0T, the ranges of Reynolds number (Re) of 2000–200,000 and Hartmann number (Ha) of 106–640 at the upstream, double-bended and downstream regions were measured. As the results, all the MHD friction loss coefficients in three regions were well correlated with the interaction parameter (Na = Ha2/Re) in the range of 0.1 < N < 100. Finally, the correlation equations of MHD friction loss coefficient against the interaction parameters at the upstream, double-bended and downstream regions of the pipe were obtained. Moreover, it was briefly discussed on the implementation to the liquid metal cooling system design for fusion reactor.

MHD thermohydraulics analysis and supporting R&D for DCLL blanket in the FNSF

A Fusion Nuclear Science Facility (FNSF) has been recognized in the fusion community as a necessary facility to resolve the critical technology issues of in-vessel components prior to the construction of a DEMO reactor (Abdou et al., 1996) [1]. Among these components, development of a reliable, low-cost and safe blanket system that provides self-sufficient tritium breeding and efficient conversion of the extracted fusion energy to electricity, while meeting all material, design and configuration limitations is among the most important but still challenging goals. In the recent FNSF study in the US (Kesel et al., 2015) [2], a Dual-Coolant Lead-Lithium (DCLL) blanket has been selected as the main breeding blanket concept. This paper summarizes the most important details of the proposed DCLL blanket design, presents the MHD thermohydraulic analysis for the PbLi flows in the blanket conduits and introduces supporting R&D studies, which are presently ongoing at UCLA. We also discuss the required pre-FNSF R&D in the area of MHD Thermofluids to support the further work on the DCLL blanket design & analysis and its integration into the fusion facility.

Ultrasonic Doppler Velocimetry Experiment of Lead-Lithium Flow with Oroshhi-2 Loop

The lead-lithium eutectic alloy (PbLi) is a promising coolant for nuclear fusion reactors. Although PbLi flow and heat transfer in a nuclear fusion reactor condition needs to be comprehended, no velocity profile measurement techniques have been developed yet. Since PbLi is a high-temperature liquid metal, ultrasonic Doppler velocimetry (UDV) is a promising method. In the present study, we investigated a UDV measurement in a high-purity PbLi forced convection loop environment. In summary, naturally contained oxide particles as flow tracers could differ by PbLi purity, and this difference could influence UDV measurability.

CFD analysis of WCLL BB PbLi manifold

ENEA CR Brasimone has developed the new design of the Water Cooled Lithium Lead Breeding Blanket (WCLL BB). In the new design Breeding Zone (BZ) water coolant flows in radial-toroidal direction, and PbLi flows in radial-poloidal direction; a gap between the Back Plate (BP) and the BZ constitutes the PbLi inlet manifold. The paper presents the CFD analysis of the WCLL BB PbLi inlet manifold, performed by ANSYS CFX-15 code. The objective of the analysis is to investigate the PbLi flow paths in the manifold region and to optimize the mass flow rate distribution in the BZ of the module. A preliminary analytical analysis is performed to evaluate pressure drop at orifices and to select the diameter of the orifices. CFD simulations are performed with the selected geometries. The optimal geometric configuration is a compromise between the need to have low PbLi velocity, to limit MHD issues and Eurofer corrosion, and to preserve the structural capability of the stiffening plates to withstand the overpressure conditions. Results demonstrate that the layout of the manifold and the size of the orifices is suitable to uniformly distribute the PbLi in the BZ, fulfilling the fluid velocity constraints. Specific MHD analyses are required to evaluate more realistic flow paths and to demonstrate the feasibility of the design.

Tritium aspects of the fusion nuclear science facility

The Fusion Nuclear Science Facility (FNSF) is intended to bridge the technical gaps from ITER to DEMO, and provide a fully nuclear environment for the advancement of materials and blanket science, among other missions. Though smaller (∼500MW fusion power) than the envisioned DEMO, our FNSF design still seeks to test DEMO-relevant components and technologies, and to that end one of its goals is to achieve a tritium breeding ratio near one using a dual-cooled lead lithium (DCLL) blanket. We explore here the migration of bred tritium through in-vessel components and coolant loops, which is exacerbated by the relatively low solubility of tritium in PbLi and the high operating temperatures envisioned in later phases of operation. Some features inherent to the design of the DCLL help limit tritium losses, namely the relatively high PbLi flow rates; coupled with efficient tritium extraction, the DCLL potentially achieves low tritium permeation losses without the use of permeation barriers. We outline here the design of such an extraction system, and some of the materials challenges that must be met in order to realize it. The efficacy of these and other design features, such as coaxial piping, is demonstrated via a series of parameter studies. We also investigate the effect of parameter uncertainties, and find that the imprecise knowledge of the tritium solubility in PbLi in particular leads to very disparate estimates of tritium losses. Depending on the experimental value used, losses range from ∼0.05 to over 6g of tritium per year. The former is acceptable based on estimated environmental releases and resultant dose to members of the public; the latter exceeds regulatory limits

Compatibility of an FeCrAl alloy with flowing Pb-Li in a thermal convection loop

A mono-metallic thermal convection loop (TCL) fabricated from alloy APMT (Fe21Cr5Al3Mo) tubing and filled with 0.025 m long tensile specimens of the same alloy was operated continuously for 1000 h with commercially pure Pb-17 at.%Li (Pb-Li) at a peak temperature of 550 ± 1.5 °C and a temperature gradient of ∼116 °C. The resulting Pb-Li flow rate was ∼0.0067 m/s. A 1050 °C pre-oxidation treatment (to form an external alumina scale) given to most specimens exposed within the TCL decreased total mass loss by a factor of 3–30 compared to adjacent specimens that were not pre-oxidized. However, all specimens exposed above 500 °C lost mass suggesting that the alumina scale was not entirely stable in flowing Pb-Li at these temperatures. Post-exposure room temperature tensile tests indicated that the mechanical properties of APMT were substantially influenced by extended exposures in the range of 435–490 °C, which caused an increase in yield strength (∼65%) and a corresponding decrease in ductility associated with α′ embrittlement. Specimens annealed in argon at the same temperature exhibited identical changes without exposure to Pb-Li. Scanning transmission electron microscopy revealed Cr-clusters within the microstructure in specimens exposed in the low temperature regions (<490 °C) of the TCL, indicating the formation of α′ consistent with the mechanism of α′ embrittlement.