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Integrated Multi-physics Simulation and Ceramic Breeder Blanket R&D
Alice YingUCLA
With contributions from FNST members
FNST MeetingAugust 18-20, 2009
UCLA
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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
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Integrated multi-physics Simulation Objectives
• Integrated multi-physics simulation is necessary to model real-world situations, explore design options, and guide R&DA 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 accuracyBecause 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 DEMOCompiles data and knowledge base derived from many fusion R&Ds in out-of-pile facilities and fission reactorsProvides 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
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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. T2) transport
Electro-magnetics
Data Management: Interpolation Neutral format
MHD
Coupled effect
Special module
Database/Constitutive equations
RadioactivityTransmutation
Time step control for transient analysis
PartitioningParallelism
Safety
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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 maturitySample analysis codes and mesh requirements in ISPC
Physics Analysis code Mesh specification
Neutronics MCNP Particle in cell (PIC)
Attila Unstructured tetrahedral mesh (node based)
Electro-magnetics
OPERA(Cubit)
Unstructured tetrahedral (Hex-) mesh (node based)
ANSYS Unstructured 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)
MHD HIMAG Unstructured 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)
Safety RELAP5-3DMELOCR
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
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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
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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
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Initial Results on the Assessment of FCI Thermal Conductivity Requirement
TBM condition DEMO condition
He-inlet (Input) 350oC 350oC
He-outlet (Calculated) 400.6oC 413.1oC
T (He) 50.6oC 63.1oC
PbLi-inlet (Input) 360oC 450oC
PbLi-Outlet (Calculated) 393oC 472.84oC
T (PbLi) 33oC 22.84oC
Heat Generation W Removal (W)(ITER condition)
Removal (W)(DEMO condition)
Be 312080.5
FS 132571
PbLi 342795 387230 272390
FCI 53527.5
Total 841974 850192 850180
He 462962 577790
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
0
5
10
15
20
0 5 10 15 20 25 30 35 40
FSLiPbSiC
Pow
er D
ensi
ty (
W/c
m3 )
Radial Distance from FW (cm)
Radial Distribution of Power Density in DCLL TBM Components
Neutron Wall Loading 0.78 MW/m2
LL
SiC FS
Interpolated 1-D Heating profiles used in analysis
10TBM
DEMO
FCI k = 1 W/mK
Temperatures at Mid-plane He
He
PbLi
PbLi
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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
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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
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Two Boundary Conditions Needed at the Fluid/Structure Interfaces
GAP elementGAP element
Boundary 2_1Boundary 2_1 Boundary 1_2Boundary 1_2
C2C2
Face iFace iFace jFace j
Prism elementPrism element
C1C1
Fluid Solid
1K. Kizu, A. Pisarev, T. Tanabe, Co-permeation of deuterium and hydrogen through Pd, J. of Nuclear Materials, 289(2001) 291-302
1E-4 1E-3 0.01 0.1 1 101E-8
1E-7
1E-6
1E-5
1E-4
1E-3
J(D
2)/m
ol m
-2 s
-1
P(D2) (Pa)
Calculated 825K Measured 825K Sctetra Calculated 865K Measured 865K
1E-3 0.01 0.1 11E-8
1E-7
1E-6
1E-5
1E-4
1E-3
Sur
face
flux
/ m
ol m
-2 s
-1
Effective deuterium pressure (Pa)
Calculated H2 flux
Calculated D2 flux
Calculated HD flux Measured H
2 flux
Measured D2 flux
Measured HD flux
Initial COMSOL/SCTetra results compared with existing data1
T2T
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
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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
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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 oC
High creep (thermal and irradiation) deformation region
Plot showing how forces propagate through pebble contacts
orthorhombic packing obtained numerically
Example: Pebble bed thermomechanics
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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
Loading pressure (MPa)Ave
rag
eco
nta
ctfo
rce
s(N
)
0 2 4 6 8 100
10
20
30
DEM results
y = 3.413 x
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.