Presentation on theme: "Tritium Transport in Multi-Region Lead-Lithium Liquid Metal Blankets"— Presentation transcript:
1 Tritium Transport in Multi-Region Lead-Lithium Liquid Metal Blankets Presented byAlice YingMaterials taken fromDr. Hongjie Zhang’s Ph. D. ThesisNov th, 20142nd EU-US DCLL WorkshopUniversity of California, Los AngelesEdward K. Rice Room
2 FNST Blanket CAD- Geometry Tritium transport modeling development at UCLA is guided by the construction of a virtual integrated simulation predictive capabilityNeutronics Radiation damage ratesThermo-fluidStructure/thermo-mechanicsSpecies (e.g. T, HT) transportElectro-magneticsMHDSpecial moduleRadioactivityTransmutationSafetyFNST Blanket CAD- GeometryMesh servicesAdaptive mesh/mesh refinementVisualizationData translators: InterpolationTime step control & concurrent exe-cution of multiple simulationsAnalyzer and AdaptorSynchronizerConsistency ControllerWrapperTopology optimizerSituation Analysis (Constraints)Meta-level ModelsBase Level Computational SimulatorsSpatial, DynamicsData from Multiple-effect testing facility, TBM, FNSFValidation/VerificationDatabase/Constitutive equations
3 Tritium Transport Modeling and Simulation Approach There is not yet a “single” code powerful enough to solve all the physics involved.Multi-step processesCompute flow and temperature fields accounting coupled effects such as buoyancy effect on MHD velocity profileSolve tritium transport modelsMulti-solver/simulation platformsUser functions are written to solve interface mass transfer, source terms, other effects. Advanced mesh generation scheme with prism layers can be inserted to provide fine grid resolution in the boundary layer.Utilized parallel solver and capability of CAD model import.MHD SolverNeutronicsCodeExperimental DatabaseThermofluid CodeData MappingMass Transfer SolverUser FunctionsInterface mass transferMulti-material and domainsHelium bubblesChemical compositionsMHD velocityTemperatureVelocityTritium generation rateTransport properties
4 General equation for a dissolved species (from TMAP ) Ignore tritium radioactive decay in PbLiHalf-life of tritium: 12.3y, rate of 5.5% per yearGenerated tritium atoms are transferred to the extraction system, they stay in the blanket only for a short time.Trap effects from defects/irradiation in the structure are not included. Traps resulting from helium bubbles in PbLi blankets are treated separately (add-on).1 G. R. Longhurst, “TMAP7 User Manual”, Idaho National Engineering and Environmental Laboratory Bechtel BWXT Idaho, LLC, 2004
5 Coupling through Material Interfaces Coupling at the LM/FS interfaceSievert’s law and impose continuity of partial pressures, leading to the concentration discontinuities at interfacesContinuity of fluxesBoundaries and boundary labels for the modeled systemCoupling at the LM/FCI interfaceCoupling at the FS/HC interfaceDissociation and recombination
6 Numerical Codes: MHD solver HiMAG -- Finite volume method, Structured grids, UCLAStream -- Finite volume method, Structured grids, Cradle Japan (can also solve temperature in the case of mixed convection)Primary Mass transfer solver, Sc/Tetra -- Finite volume method, Unstructured grids, Cradle JapanBuild and solve the proper tritium transport equations in Sc/TetraSolve non-MHD flow and temperature fields.Handle the blankets geometry complexity.Write and build our own user functions (in c++) into the mass transfer solver considering the factors: (1) multiple domains, (2) coupling through the material interfaces, (3) temperature-dependent transport properties, and (4) space-dependent tritium source terms.COMSOL is used for cross checking and methodology evaluationData MappingMapping the MHD data into the Sc/Tetra solver using the user-defined function.
7 User defined function to apply tritium transfer boundary conditions at LM/FS or FCI structure interface has been built into Sc/Tetra thermo-fluid codeStiff-spring methodEnsured flux continuity while obeying Sieviet law at the PbLi/Solid interface
8 Code validationCasesValidated with co-permeation of Deuterium and Hydrogen through Pd from experiments by K. Kizu, A. Pisarev, T. Tanabe, J. of Nuclear Materials, (2001)Validated with US-JA TITAN experiment of tritium/hydrogen permeation through α-Fe/PbLi sample, collaborated between INL and the University of Tokyo.Validated with in-reactor tritium release experiment from lithium-lead with tritium generation source term, conducted in the fast neutron reactor “YAYOI” of the University of TokyoValidated with analytical solution of mass transfer in a absorption- convection-permeation problem
9 Validation of UCLA Code: Transient H transport modeling through a-Fe/PbLi system Experimental data generated through US-JA TITAN collaborationsRecombinationLocal chemical equilibriumSieverts’ lawConvective fluxDownstream-side ArUpstream-side H2Experimental Set-upKr= recombination coefficientKs= solubilityK= equilibrium partition coefficientH2 concentration CH2,down in Ar purge gasModeling Methodology3D Mass transfer equations are solved using both COMSOL and SC/Tetra.Species equilibrium, recombination flux and Sieverts’ Law at interfaces are computed using C++ user functionReferences:Data provided by Satoshi FukadaP. FAUVET and J. SANNIER, “HYDROGEN BEHAVIOUR IN LIQUID 17Li83Pb ALLOY”, Journal of Nuclear Materials (1988) 516 5l9F. Reiter, “Solubility and diffusivity of hydrogen isotopes in liquid Pb-17Li”, Fusion Engineering and Design 14 (1991)
10 Cases studied and results Buoyancy effect on tritium transport in PbLi MHD flows with permeable wallTritium transport in a DCLL-type poloidal duct with FCI and PESTritium transport in a DCLL U-shaped flowTritium transport in HCLL configuration and comparison with DCLL caseHelium bubble effectsCritical yet interesting tritium transport features can only be revealed/seen through sophisticated, multi-physics simulations
11 Tritium Transport in the Buoyancy Affected PbLi MHD flows Coupled MHD flow and heat transfer analysisgXBDownward flowxyRe=1E4Gr=1E8Ha=400Buoyancy induced reversed flowVelocity Profile (m/s)High tritium concentrationTritium concentration (mol/m3)DownwardUpwardUsing analyzed parameters
12 Tritium transport in a DCLL duct with PES slot Behind FWFCI and PES affect tritium transfer behavior and permeation rate through-changing the local MHD velocity distribution, which in turn affects tritium diffusion and convection.providing a path for tritium to migrate though PES and interact between the core and the gap.PES at back wall2a=0.06m, 2b=0.06m, RAFS wall 0.002m, FCI 0.002m, PES 0.003m, Gap 0.002mFront wallRich phenomena !Color scheme:Purple: T diffusive flux,Black: velocity,Rainbow: T concentrationDCLL duct with PES1.8 T used in the analysisColor scheme: tritium concentrationPbLi flowPES- pressure equalization slot
13 PES locations affect tritium transport in a DCLL-type poloidal duct Tritium concentration profile
14 Tritium permeation rate vs. FCI electric conductivity Ha, FCI conductivity effects on Tritium transport in a DCLL-type poloidal ductTritium Losses for Three PES ConfigurationsNo PESPES in the wall // BPES in the wall ⊥ Bgeneration (mol/s)1.406e-81.410e-81.412e-8permeation (mol/s)1.76e-101.99e-101.87e-10Losses1.25%1.42%1.32%If a PES is on the wall parallel to the magnetic field, tritium loss rate increases by 15% because the velocity is reduced near the front wall.Tritium permeation rate vs. FCI electric conductivityAs the FCI electric conductivity decreases, the effect of electromagnetic coupling between the flow in the gap and the bulk flow reduces;Thus the velocity in the gap drops and tritium permeation rate increases;Over the range of reference electric conductivity of the FCI from 5 to 500 Ω-1m-1, tritium permeation rate decreased by about 46%.Tritium losses for three PES configurations as Ha changes
15 By flowing PbLi in DCLL for heat removal results in a lower tritium partial pressure and permeation compared with HCLLHCLL BU AnalyzedFlow and tritium near the turn-around region next to FW1.8 T used in the analysisMass flow rate: 0.33 kg/sCaseAverage PbLi velocity in channelTotal tritium generation indomainTritium exit from outletIntegrated permeation to coolant% loss due to permeationDCLL duct7 cm/s 1.409e-8 mol/s 1.387e-8 mol/s 2e-10 mol/s 1.8HCLL BU (2)0.8 mm/s 2.494e-8 mol/s 2.063e-8 mol/s 4.308e-9 mol/s 17
16 Tritium transport in a DCLL U-shaped flow The reference DCLL design: Three U-shaped duct flow with FCI and FS walls connected through inlet/outlet with manifoldsThe analyzed DCLL central U-shape channel as representative of the three channelsThe inlet manifold design will determine the fraction of PbLi liquid flow in the gap. (There was no communication between the core and the gap in this U- shaped duct.)The resulting effect on the tritium permeation may be important.Two cases analysis was carried out:The gap inlet velocity = the core inlet velocityThe gap inlet velocity = 10% of the core inlet velocity
17 Velocity in the Gap between FCI and the Structural Wall Affects Tritium Transport in DCLL Tritium concentrations (mol/m3) at mid-planes of a U-shaped DCLL channel for different gap inlet velocityBackvelocity (m/s)U-shaped ductTritium generation, inventory and permeation with a change of the gap inlet velocityDCLL U-shaped ChannelThe gap inlet velocity = the core inlet velocityThe gap inlet velocity = 10% of the core inlet velocityTritium generation rate (mol/s)9.72e-8Tritium inventory (mol)2.64e-63.57e-6T exit rate from outlet (mol/s)9.60e-89.44e-8T permeation rate (mol/s)1.16e-92.81e-9Losses percentage (%)1.2%2.9%
18 Regarding He bubble: Initial Progress of the Effect of Helium Bubble on Tritium Transport in PbLi Mix-Convection MHD FlowCoupled PbLi Mix-Convection MHD Flow with Multi-SpeciesHe nano-bubbles represented as a passive scalar carried by PbLi flowTritium absorption within bubbles is captured using the species equilibrium model.CT_LMCT2_bubbleCbubblesgXBDownward flowxyExample CaseRe=1E5 Gr=1E8 Ha=400Downward flowUniform He-nano-bubbles generate rate at 1e11(1/m3s)Bubble size r = 20nmNo bubble agglomerationResults show that the amount of absorbed T in He-bubbles is low and it may have no significant effect on atomic T concentration.
19 Tritium concentration maps for three different scenarios of size and number of bubbles attached to the wallM-shaped velocity profile and the concentration of tritium trapped inside bubblesU0= 0.07 m/s DCLL like velocityMore on He-bubblesA higher velocity provides a lower bubble concentration and a lower amount of tritium trapped inside the bubbles.Over the range of mean velocity from 0.7 mm/s to 0.07 m/s, the He bubble concentrations dropped by two orders of magnitude from 1.4e6 to 1.4e4, and the amount of tritium trapped in the bubbles decreased by about 6 orders of magnitude from 9.0e17 to 9.6e11.ScenarioAverage permeation flux (mol/m2/s)Ratio between the tritium permeation rate across the bubble and the total (%)Tritium partial pressure in bubble (Pa)15.3e-111.9e-11.37e-525.7e-112.5e-21.00e-535.54e-116.3e-21.04e-5
20 Summary Recommendations We now have a 3D computational predictive capability for analyzing tritium transport phenomena affected by multi-physics and geometric featuresThrough this capability,Identified the effect of the design features and material uncertainties on tritium transport and permeationQuantified the difference of tritium inventory and permeation rate between DCLL and HCLL blanket conceptsTo provide guidance on the PbLi blanket designs to comply with tritium control requirements with regard to the reduction in tritium permeationRecommendationsSurface effect: Oxidized and clean wall surfaces have different surface properties (e.g., adsorption, desorption, and recombination constants). Thus tritium permeation could be affected by the surface conditions. The proposed model is capable of accounting for such phenomena through the use of sticking coefficients. However, data is needed.He bubble effects- The amount of tritium trapped into helium bubbles is insignificant at low tritium partial pressure regime such as in DCLL concepts. However, at high tritium partial pressure, which occurs in a HCLL concept, the amount of tritium trapped into helium bubbles is markedly high. Further modeling and analyses are necessary to evaluate the impact of helium bubbles especially for the low PbLi velocity blankets. (can be a problem for tritium removal if not removed.)The current solubility data results in a ~ 80% difference in permeation rate. Dedicated experimental campaigns aimed at obtaining more reliable material properties are needed.
21 Backup -- MHD velocity profile MHD velocity profile obtained by using Stream code for a duct flowFCI with PES flow field comparisons between Stream and Ming-Jiu Ni’s solutionComparison between analytical and numerical solutions. The agreement is quite good in the core, while in the side layer the computed velocity is slight lower than Hunt’s solution.