1 Integrated Multi-physics Simulation and Ceramic Breeder Blanket R&D Alice Ying UCLA With contributions from FNST members FNST Meeting August 18-20, 2009 UCLA

2 Outline Status on Integrated Multi-physics Simulation –For both Liquid and Ceramic Breeder Blankets –Currently its development serves an Ad-Hoc Design Analysis Tool Ceramic Breeder Blanket R&D –Design Analysis (mainly for TBM) –R&D Mainly on the modeling development (small experiments planned aiming to provide data for code validation) –Pebble bed thermo-mechanics –Tritium permeation and purge gas conditions

3 Integrated multi-physics Simulation Objectives Integrated multi-physics simulation is necessary to model real-world situations, explore design options, and guide R&D A plasma chamber nuclear component in a fusion environment involves many technical disciplines and many computational codes such as: MCNP for neutronics, CFD/thermofluid codes for FW surface temperatures, and ANSYS for stress/deformation, etc. Careful representation of a geometrically complex fusion component is essential to predict performance to a reasonable level of accuracy Because of the complex geometry of the fusion system, these analyses should be performed in 3D with a true geometric representation in order to achieve high quality prediction. An effective mechanism to integrate results of ongoing R&D and continuously evolve to Validated Predictive Capability for DEMO Compiles data and knowledge base derived from many fusion R&Ds in out-of-pile facilities and fission reactors Provides high level of accuracy, reduces substantially risk and cost for the development of complex multi-dimensional system of the plasma chamber in-vessel components for DEMO and near term fusion devices

4 Integrated multi-physics Simulation Basis A platform to streamline plasma chamber component design Utilizing a CAD-based solid component model as the common element across physical disciplines The multi-physical phenomena occurring in a fusion nuclear chamber system are modeled centering on CAD Many interfaces must be designed to facilitate information transfer, execution control, and post-processing visualization Validation/Verification CAD- Geometry Mesh services Adaptive mesh/ mesh refinement Visualization Neutronics Radiation damage rates Thermo- fluid Structure/ thermo- mechanics Species (e.g. T 2 ) tran s port Electro- magnetics Data Management: Interpolation Neutral format MHD Coupled effect Special module Database/Constitutive equations Radioactivity Transmutation Time step control for transient analysis Partitioning Parallelism Safety

5 Utilizing a combination of fusion specific research codes and off-the-shelf third party software Example: MHD flows with heat transfer and natural convection computed using codes developed in the fusion community (such as HIMAG.) Traditional CFD/thermal analysis for non-conducting flows performed using off-the-shelf third party software – motivated by their speed and maturity Sample analysis codes and mesh requirements in ISPC Physics Analysis code Mesh specification NeutronicsMCNPParticle in cell (PIC) AttilaUnstructured tetrahedral mesh (node based) Electro- magnetics OPERA (Cubit) Unstructured tetrahedral (Hex-) mesh (node based) ANSYSUnstructured Hex/Tet mesh (node based and edge based formulations) CFD/ Thermo- fluids SC/Tetra & CFdesign Unstructured hybrid mesh (node based) Fluent (Gambit) Unstructured hybrid mesh (cell based) MHDHIMAGUnstructured hybrid mesh (cell based) Structural analysis ANSYS/ ABAQUS Unstructured second order Hex/Tet mesh (node based) Species transport COMSOL or others Unstructured second order mesh (node based) SafetyRELAP5-3D MELOCR System representation code DAG-MCNP (Sawan’s presentation) Assisted by CAD Translator such as MCAM TMAP-4 COMSOL Multi-physics Chemical modules Utilize analogy between mass and heat transport equations and extend CFD capability to solve mass transport equations with relevant BCs

6 Initial DCLL MCNP Neutronics Analysis Assisted by MCAM CAD Translator Integrated into ITER FEAT 20 degree Model CAD model Split CAD model and fill voids MCNP model Using MCNP parallel version with a shorter CPU running time

7 Initial DCLL MCNP Neutronics Results (MCAM method) Heating Rate (W/cc) and TBR Neutron Heating Gamma Heating Mid-Plane Neutron Heating Gamma Heating Neutron Heating Gamma Heating TBM Radial 1st Breeder layer TBM Toroidal Mid-plane

He inlet He outlet He Temperature He Velocity Helium circuit flow characteristics Visualization is an important element in the integrated multi-physics predictive capability simulation tool He velocity above the outlet near the front He velocity above the outlet near the back DCLL He Circuit Design Analysis

9 Initial Results on the Assessment of FCI Thermal Conductivity Requirement TBM conditionDEMO condition He-inlet (Input)350 o C He-outlet (Calculated)400.6 o C413.1 o C  T (He) 50.6 o C63.1 o C PbLi-inlet (Input)360 o C450 o C PbLi-Outlet (Calculated)393 o C o C  T (PbLi) 33 o C22.84 o C HeatGeneration WRemoval (W) (ITER condition) Removal (W) (DEMO condition) Be FS PbLi FCI Total He Heat leak from FCI/PbLi to He 2.6%32% For FCI thermal conductivity = 1 W/mk How will MHD velocity profile change this requirement? (TBD) Recall PbLi has higher temperatures than He during DEMO operations Interpolated 1-D Heating profiles used in analysis

10 TBM DEMO FCI k = 1 W/mK Temperatures at Mid-plane He PbLi

11 Ceramic Breeder Blanket Design and R&D RAFS FW with He coolant channels He purge gas pipe Be pebbles Ceramic breeder pebbles Cooling plate HCCB TBM module (710  389  510 mm) He coolant manifolds for FW/Breeding zones  Adopt edge-on approach  Locate welds at the back (as much as possible)  Reduce the amount of Be at the back  Assemble the blanket from pre- fabricated breeder units Purge gas inlet Purge gas outlet A completely assembled breeding unit to be inserted into the structural box

12 Predictive capability development for tritium permeation estimation and purge gas flow design Accounting for flow, nuclear heating, and tritium production profiles - Velocity profile - Convection and conduction of heat (temperature profile) - Convection and diffusion of tritium - Isotopic swamping effect -Geometric complexity Approach – Using COMSOL Multi-physics for fluid flow, temperature, convection and diffusion mass transport Mathematical Models –Performed benchmark problems for code and problem set-up validation using literature data and TMAP4 –FEM method (not yet available for turbulent flow analysis) Extend a CFD/thermo-fluid code for mass transport analysis using user defined functions –Eliminate data mapping from CFD code to COMSOL –Accurate turbulent flow and heat transfer calculations

13 Two Boundary Conditions Needed at the Fluid/Structure Interfaces GAP element Boundary 2_1 Boundary 1_2 C2 Face i Face j Prism element C1 Fluid Solid 1 K. Kizu, A. Pisarev, T. Tanabe, Co-permeation of deuterium and hydrogen through Pd, J. of Nuclear Materials, 289(2001) Initial COMSOL/SCTetra results compared with existing data 1 T2T2 T 1.Apply Sieverts’ law to calculate equilibrium concentration at the solid face (surface) Discontinuity in the concentration profile at the interface 2.Continue diffusive flux at the normal direction of the interface Boundary Conditions

14 Capability to predict packed bed thermo-mechanics through-out its lifetime remains a key to the success of ceramic breeder blanket designs Issues: 3-D Temperature profiles Differential thermal stress Contact forces at contact Plastic/creep deformation Particle breakage Gap formation Much work remains to be done to establish such capability 14  Discrete element simulation of pebble bed provides contact forces at critical contact areas- eliminating potential design flaws Ceramic breeder Be pebbles FW panel with He channels Internal cooling plate Elastic/Plastic deformation region T < 600 o C High creep (thermal and irradiation) deformation region Plot showing how forces propagate through pebble contacts orthorhombic packing obtained numerically Example: Pebble bed thermomechanics

15 Pebble bed Thermomechanics Progress and Plan FEM creep contact model for single pebble has been constructed & simulated in an attempt to derive constitutive equations for use in DEM simulation (which otherwise can’t be obtained) More analysis is needed to give better constitutive equation (compared with experimental pebble deformation data) Plan: Conduct Creep Experiments on Pebble Bed (reconfirmation with Pebble Failure Map of correlation between single pebble failure and pebble bed loading pressure) & estimation of Stress State due to differential thermal expansion between pebble bed and the structural wall Pebble mechanical integrity at high temperatures under compressive loads (Li2TiO3) –experiments conducted at UCLA) Average force at contact under various applied loads (DEM simulation- UCLA) The forces exerted on the pebbles during the operation should be less than 15 N; or the pressure applied to the pebble bed from containing structural less than ~ 5 MPa.