Liquid Metal Blanket Research Articles

Effect of electromagnetic coupling on MHD flow in the manifold of fusion liquid metal blanket

In fusion liquid metal (LM) blanket, magnetohydrodynamics (MHD) effects will dominate the flow patterns and the heat transfer characteristics of the liquid metal flow. Manifold is a key component in LM blanket in charge of distributing or collecting the liquid metal coolant. In this region, the complex three dimensional MHD phenomena will be occurred, and the velocity, pressure and flow rate distributions may be dramatically influenced. One important aspect is the electromagnetic coupling effect resulting from an exchange of electric currents between two neighboring fluid domains that can lead to modifications of flow distribution and pressure drop compared to that in electrical separated channels. Understanding the electromagnetic coupling effect in manifold is necessary to optimize the liquid metal blanket design.In this work, a numerical study was carried out to investigate the effect of electromagnetic coupling on MHD flow in a manifold region. The typical manifold geometry in LM blanket was considered, a rectangular supply duct entering a rectangular expansion area, finally feeding into 3 rectangular parallel channels. This paper investigated the effect of electromagnetic coupling on MHD flow in a manifold region. Different electromagnetic coupling modes with different combinations of electrical conductivity of walls were studied numerically. The flow distribution and pressure drop of these modes have been evaluated.

O29 Marqueurs métaboliques de la malabsorption protéique dans un modèle de miniporc insuffisant pancréatique

We propose a new activity on verification and validation (V&V) of MHD codes presently employed by the fusion community as a predictive capability tool for liquid metal cooling applications, such as liquid metal blankets. The important steps in the development of MHD codes starting from the 1970s are outlined first and then basic MHD codes, which are currently in use by designers of liquid breeder blankets, are reviewed. A benchmark database of five problems has been proposed to cover a wide range of MHD flows from laminar fully developed to turbulent flows, which are of interest for fusion applications: (A) 2D fully developed laminar steady MHD flow, (B) 3D laminar, steady developing MHD flow in a non-uniform magnetic field, (C) quasi-two-dimensional MHD turbulent flow, (D) 3D turbulent MHD flow, and (E) MHD flow with heat transfer (buoyant convection). Finally, we introduce important details of the proposed activities, such as basic V&V rules and schedule. The main goal of the present paper is to help in establishing an efficient V&V framework and to initiate benchmarking among interested parties. The comparison results computed by the codes against analytical solutions and trusted experimental and numerical data as well as code-to-code comparisons will be presented and analyzed in companion paper/papers.

Direct numerical simulation of turbulent liquid metal flow entering a magnetic field

This paper presents direct numerical simulations (DNS) of fully developed turbulent liquid-metal flow in a circular duct entering a magnetic field. The case of a magnetohydrodynamic flow leaving a strong magnetic field has been extensively studied experimentally and numerically owing to its similarity to typical flow configurations appearing in liquid metal blankets of nuclear fusion reactors. Although also relevant to the design of fusion reactor blankets, the flow entering the fringing field of a magnet remains unexplored because its high intricacy precludes any simplification of the governing equations. Indeed, the complexity of the magnetohydrodynamic–turbulence interaction can only be analysed by direct numerical simulations or experiments. With that purpose, this paper addresses the case of a fully developed turbulent flow (Reτ≈520) entering low, intermediate and strong magnetic fields under electrically insulating and poorly conducting walls by means of three-dimensional direct numerical simulations. Purely hydrodynamic computations (without the effect of the magnetic field) reveal an excellent agreement against previous experimental and numerical results. Current MHD results provide a very detailed information of the turbulence decay and reveal new three-dimensional features related to liquid-metal flow entering strong increasing magnetic fields, such as flow instabilities due to the effect of the Lorentz forces within the fringing region at high Ha numbers.

Numerical investigation of liquid metal magnetohydrodynamic flow in multilayer flow channel inserts

In the high temperature liquid metal blanket of fusion-based hydrogen production reactor (named FDS-III), there is a remarkable feature that the multilayer flow channel inserts (MFCI) as function component are put into the breeding zone. The low thermal conductivity of MFCI can prevent the internal PbLi's heat conduct to the outside. So the outlet temperature can achieve high temperature around 1000°C for high efficient production of hydrogen. However, the flow of liquid metal meandering through the MFCI will cause complex magnetohydrodynamic (MHD) effect under the strong fusion magnetic field. Liquid metal MHD effect is a key issue which should be concerned in high temperature breeder blanket (HTL). In this work, a numerical study was carried out to investigate the MHD effect of liquid metal PbLi in the MFCI. The MHD flows with typical modified geometry of the HTL MFCI were considered. The characteristics of flow and induced current fields were analyzed, and the pressure drop was evaluated. It also can be seen that the conductivity of the MFCI will have great impact on liquid metal flow's current and velocity distributions.

Effect of contact resistance on liquid metal MHD flows through circular pipes

Effect of contact resistance on magnetohydrodynamic (MHD) laminar flows through circular pipes are investigated by numerical simulations. A numerical method is proposed to investigate this issue. This method is that the induced magnetic field is individually calculated through two different governing equations in the liquid and the solid domains, special boundary conditions are given considering effects of the contact resistance. This method is validated by comparing with analytical solution and another numerical method. Numerical results of the velocity distribution and the MHD pressure drop affected by the contact resistance through circular pipes are given. It is shown that the contact resistance has a significant impact on the MHD pressure drop under the conditions of the fusion liquid metal blanket , and normally, the big contact resistance as a result of poor wetting can cause the MHD pressure drop to be several times lower than no contact resistance case. In addition, non-uniform contact resistance will cause the jet instability in the Robert layer and form a larger jet near the area of contact resistance. In the end, numerical results are compared with experimental results which include the effect of non-uniform contact resistance on the velocity distribution; it is indicated that numerical results are in good agreement with experimental results and validates that the larger velocity jet will be caused by the non-uniform contact resistance from experimental results.

Magneto-convective flows in electrically and thermally coupled channels

A liquid metal blanket concept using a PbLi alloy as breeder material and helium as coolant is one of the proposed designs that will be tested in the experimental fusion reactor ITER. In order to finalize the design of the helium cooled lead lithium (HCLL) blanket, studies are still required to fully understand the behavior of the electrically conducting breeder under the influence of the intense magnetic field that confines the fusion plasma. Liquid metal HCLL blanket flows are expected to be mainly driven by buoyancy forces caused by non-isothermal operating conditions due to neutron volumetric heating, since only a weak forced flow is required for tritium extraction. The present numerical study aims at clarifying the influence of electromagnetic and thermal coupling of neighboring fluid domains on magneto-convective flows in geometries relevant for the HCLL blanket concept. Velocity and temperature distributions are discussed for various volumetric heat sources.

Effect of a magnetic field on stability and transitions in liquid breeder flows in a blanket

We review previous studies on instabilities and transitions in magnetohydrodynamic flows in a special context of liquid-metal blanket applications. In the past, possible transitions in blanket flows were mostly attributed to instabilities in the Hartmann layers. More recent studies show, however, that the side layers can experience instabilities at sufficiently lower Reynolds numbers. This suggests that in the blanket flows, the appearance of turbulence can most likely be related to the side rather than Hartmann layers. Various factors that may affect stability in blanket flows have been discussed. In particular, buoyancy forces can result in potentially unstable inflectional velocity profiles. First computational results, illustrating possibility of instabilities and quasi-two-dimensional turbulence in vertical mixed-convection flows heated volumetrically are presented.

Methodology for forming multilayer structures of the liquid metal blanket for a thermonuclear reactor

The requirements for the multilayer structure of the flow duct wall of the lithium blanket for the thermonuclear reactor are considered. The choice of the design for the multilayer wall of the flow duct in the blanket is justified. The theoretical and technological aspects of adhesive contact and diffusion welding of the metal-ceramic structure are discussed. The experimental results obtained while forming and analyzing the properties of the experimental models of the multilayer wall are presented.

Adhesion-diffusion formation of a multilayer wall for the liquid metal flow channel of a fusion reactor blanket

A technique for calculating the adhesion-diffusion formation of a multilayer metal-ceramic structure is presented. The development of this technique is dictated by requirements imposed on the wall of the liquid metal flow channel of a fusion reactor blanket. The parameters of the adhesion-diffusion process (pressure, temperature, hold-up time, and the physical properties of materials) are related to the strength characteristics of the resulting composite (incompleteness of the adhesion contact, adhesion energy, and energy and strength of cohesion). Results are illustrated by calculating the formation parameters of the multilayer metal-ceramic structure and its strength as applied to the fusion reactor liquid-metal blanket.

Experimental Base of an Innovation S-Channel to Reduce MHD Pressure Drop

Consequent on MHD geometry sensibility phenomena was measured in an accident case; the more detail experiments have been conducted at the liquid metal experimental loop upgrade facility (LMEL-U). The experimental results indicate that MHD pressure drop can be greatly reduced in the special designed ducts. Base on the experimental data, an innovation channel concept (tentatively called as the secondary flow channel, short in “S-channel”) is addressed as a reducing MHD pressure drop channel for the application of a liquid metal blanket system in fusion reactor. It may be a dawn for solving MHD pressure drop key issue of liquid metal blanket system.

Stressed state of the electrical insulation barrier in the wall structure of a thermonuclear reactor liquid-metal blanket

A technique for analytic determination of normal and tangential stresses in the three-layer structure of a multilayer wall of a flow-through part of thermonuclear reactor liquid-metal blanket is developed. The results of computational analysis of the influence of elastic properties of materials and geometric parameters of the layers on their stressed state are considered.

Thermo-Fluid Simulation in a Liquid Metal Blanket with Three-Surface-Multi-Layered Channel

A thermo-fluid simulation was conducted to clarify heat transfer properties and then to show a design window of the first wall of a Li/V blanket with three-surface-multi-coated channels. Channel dimensions were treated as parameters and their effects on the heat transfer properties and the design window were discussed in the various heat flux of 0.8 to 1.2 MW/m2. In the simulation, the magnetic field of 1 and 10T was assumed in order to investigate how the velocity profiles affect the heat transfer performance. The MHD flow was supposed to be two-dimensional-fully-developed laminar flow. Three-dimensional heat-transfer simulation was conducted with assumption of one-side heating by the constant heat flux on the first wall by using the flow field obtained by the 2D flow analysis. It was found that effects of the flow distributions were small on the heat transfer. The channel height, however, affects the heat transfer characteristics so much and the design window is shown to be limited to relatively small channel dimensions due to the induced stress in the first wall.

Simulation of MHD Flows in Liquid Metal Blanket with Flow Channel Insert

A direct simulation of 3D liquid metal flow in the DCLL (Dual Coolant Lead Lithium) blanket is conducted to study the distribution of pressure and velocity influenced by different material properties of FCI (Flow Channel Insert). A consistent and conservative scheme and projection method on a collocated mesh (Ni et al., J Comp Phys 227 (2007)174-204 and 227 (2007) 205-228) are employed to solve the incompressible Navier-Stokes equations with the Lorentz force included based on an electrical potential formula. As an illustration, three blanket flows have been considered: liquid metal flow in a channel without FCI, with a silicon carbide FCI and with a FCI made of conductive material. It is shown that liquid metal flows in blanket with FCI are 3D developing flows. It is verified that: MHD pressure drop can be reduced by using silicon carbide FCI; PES (Pressure Equilibrium Slot) can balance the pressure difference between two sides of FCI near the slot but the pressure difference is still very large far away from PES; conductive FCI cannot reduce MHD pressure drop. Due to the leakage of current circuit across the slot, with PES opened at one side, a strong reversed velocity is observed in PES. The comparison of velocity distribution between numerical simulation and experiment from LEVI (Xu et al., ISFNT-9, 2009) is conducted. The difference shows that further experimental and numerical analysis is needed.

Effects of Radial Variation of the Magnetic Field on the Pressure Distribution in the European Liquid-Metal Blanket Concept

Liquid-metal flows in the European helium cooled lead lithium blanket are strongly affected by the intensity and the distribution of the externally applied magnetic field required for plasma confinement. An experimental campaign has been performed to investigate the pressure distribution of magnetohydrodynamic flows in a scaled model of a liquid-metal blanket module.A variety of experiments has been carried out to asses the influence of flow rates and of the strength and non-uniformity of the magnetic field on the pressure distribution in the test-section. The magnetic field available in the laboratory is characterized by a large zone of uniform magnitude and gradients at the entrance and the exit. The mock-up has been located at various positions along the magnet axis to reproduce operating conditions in which the toroidal field varies in radial direction, i.e. it changes from the back plate to the first wall. Measurements show that the magnitude of the total pressure drop in the mock-up is significantly influenced by the strength of the local magnetic field at the manifolds, while gradients across the breeder units have minor effects. This study confirms the critical role of manifolds in determining the total pressure drop in the blanket.

Compatibility of SiCf/SiC composite exposed to liquid Pb–Li flow

SiCf/SiC composites are candidate structural and functional materials for fusion blankets, attractive for their potential application for higher temperature liquid metal blankets compared to the range possible for metallic materials. However, the experimental data on the long term compatibility of SiCf/SiC composites with high temperature liquid metal is inadequate. To acquire parametric data on the compatibility of NITE SiCf/SiC composites with a high temperature liquid metal stream, the corrosion behavior was examined in liquid Pb–Li using a rotating disk apparatus. The materials used in this study were exposed to relative flow velocity of ∼10–37cm/s at 900°C for 1000h. Oxidation layers were detected on the matrix and fiber near the surface exposed to liquid Pb–Li at 900°C for 1000h. Additional results for shorter exposure times and relationship to flow velocity are discussed.

Qualification of MHD effects in dual-coolant DEMO blanket and approaches to their modelling

Design refinements of vertical insulated banana-shaped liquid metal channels are being considered as a progress of conceptual design of dual-coolant liquid metal blankets (DEMO specifications). Among them: (a) optimised channel geometry and (b) improvements on flow channel inserts. Progress of channel conceptual design is conducted in parallel with underlying physics of MHD models in diverse aspects: (1) MHD models, (2) MHD turbulence, (3) LM buoyancy effects, (4) three-dimensional flows, and (5) LM/FCI/wall electrical and thermal coupling; in order to progress on common liquid metal flow characterisation, pressure drop and three-dimensional flows. The analyses are assumed as extension of those previous carried out for the DCLL blankets [1,2] for new design refinements. At the present stage of the conceptual design progress, a preliminary thermofluid MHD study is of crucial interest for further design improvements and future detailed modelling. The paper overviews the ongoing modelling studies, making model refinements explicit, and anticipates some modelling results.

Implementation of two-phase tritium models for helium bubbles in HCLL breeding blanket modules

Tritium self-sufficiency requirement of future DT fusion reactors involves large helium production rates in the breeding blankets; this might impact on the conceptual design of diverse fusion power reactor units, such as Liquid Metal (LM) blankets. Low solubility, long residence-times and high production rates create the conditions for Helium nucleation, which could mean effective T sinks in LM channels.A model for helium nano-bubble formation and tritium conjugate transport phenomena in liquid Pb17.5Li and EUROFER is proposed. In a first approximation, it has been considered that He bubbles can be represented as a passive scalar. The nucleation model is based on the classical theory and includes a simplified bubble growth model. The model captures the interaction of tritium with bubbles and tritium diffusion through walls.Results show the influence of helium cavitation on tritium inventory and the importance of simulating the system walls instead of imposing fixed boundary conditions.

Overview of Fusion Nuclear Technology Activities at SWIP

The fusion nuclear technology (FNT) activities at SWIP are overviewed, which are including the design and R&D of the helium-cooled solid breeder test blanket module (TBM), development of Liquid metal blanket technology, structure and function materials research for ITER shielding and test blanket, ITER shielding blanket material development and the joining technologies and the R&D for ITER gravity support.

Electrical insulation test of alumina coating fabricated by sol–gel method in molten PbLi pool

Development of electrical insulation coatings, which insulate an induced electric current from electrical conducting walls, is a key technology for the research and development of self-cooled liquid metal blanket including lead–lithium (PbLi) fusion blankets. As for magnetohydrodynamic (MHD) thermofluid study, an electrical insulation coating is extremely important from the viewpoint of the secure electrical insulating wall condition. The present study employs a sol–gel (SG) method to fabricate an Al 2O 3 coating, and discusses the feasibility of the SG coating as an electrical insulation coating for the PbLi through the electrical insulation test in the molten PbLi pool and the SEM with EDS analysis on the SG coating structure. The present study shows that the SG coating will be a potential electrical insulation coating for PbLi with both the operation time and the temperature limitation.

MHD thermofluid issues of liquid-metal blankets: Phenomena and advances

The major accomplishments in the MHD thermofluid area over the last few years are reviewed for liquid-metal blankets. After summarizing basic liquid-metal blanket concepts, such as self-cooled blankets and in particular those to be tested in ITER, namely the dual-coolant and the helium-cooled lead–lithium blanket modules, we consider the most important MHD phenomena and discuss their impact on heat and mass transfer during blanket operation with special emphasis placed on underlying flow physics. Among them are: MHD pressure drop, three-dimensional flows, MHD instability and turbulence, buoyancy-driven flows, electromagnetic coupling, and interfacial phenomena associated with hydrodynamic slip.