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Integrated Multi-physics Simulation of Nuclear Components as an Essential Element in

Developing Predictive Capabilities for DEMO

A Cross Cutting Research Thrust for the Themes: Fusion Power and Plasma Material Interface

ReNeW Workshop March 2-4, 2009

UCLA

A. Ying, M. Abdou, S. Smolentsev, R. Munipalli, D. Youchison, P. Wilson, M. Sawan, B. Merrill

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Introductory Remarks• Predicting the performance of a plasma chamber nuclear component

at present 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.

• Because of the complex geometry of the fusion system, these codes should be run in 3D with a true geometric representation in order to achieve high quality prediction. – Maintaining consistency in the geometric representation among the

codes is challenging.

• Using the output from a code as an input to the other code currently involves lots of human effort, and machine time. – It is a source of error.

• The proposed research thrust is to remedy this deficiency, whilegiving a more realistic prediction of the phenomena and performances that occur in a fusion nuclear environment.

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Integrated multi-physics simulation is necessary to model real-world situations, explore design options, and guide R&D

FW

Top Plate

SiC

Grid Plate Assy

Bottom Plate

Back Plate Assy

How will flow distribution be affected by the radiative heat flux, or downstream conditions?

Should the electrical conductivity of SiC FCI be tailored along the flow direction to control natural convection and MHD pressure loss?

How much heat will leak from Pb-17Li into the helium coolant? What is the actual Pb-17Li outlet temperature?

Pb-17Li flow streamlines inside a FCI duct (U contour/U,V vector)

How much tritium will be built-up in this recirculation zone?

DCLL Blanket Details and MHD Flow Features:Sharp gradients, extreme sensitivity to geometry,

Strong coupling across flow/heat/structures

Will structural deformations of FCI have a huge impact on MHD effects?

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Example: Detailed DAG-MCNP 3-D neutronics analysis of TBM integrated with the surrounding water cooled frame and representation of exact source and other in-vessel components:

– yields total tritium production in the TBM that is 45% lower than the 1-D estimate

– yields total nuclear heating in the TBM that is 35% lower than the 1-D estimate of 0.574 MW

Mid-plane tritium production rate

Mid-plane nuclear heating (gamma: left; neutron: right)

Y2 plane nuclear heating (gamma: left; neutron: right)

Careful representation of a geometrically complex fusion component is essential to predict performance to a reasonable level of accuracy

DCLL TBM

PbLi Volume

W/cc

W/ccg/cc.s

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Integrated multi-physics Simulation Predictive Capability (ISPC)

• 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

NeutronicsRadiation damage rates

Thermo-fluid

Structure/thermo-mechanics

Species (e.g. T2)transport

Electro-magnetics

Data Management: InterpolationNeutral format

MHD

Coupled effect

Special module

Database/Constitutive equations

RadioactivityTransmutation

Time step control for transient analysis

PartitioningParallelism

Safety

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Radiativeheat flux

Pb-Li flow FCI

Helium-cooled structure

Utilizing a combination of fusion specific research codes and off-the-shelf third party software

Liquid metal flow in DCLL blanket channels

MHD velocity profile in the ducts computed using HIMAG

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

System representation codeRELAP5-3DMELOCR

Safety

Unstructured second order mesh (node based)

COMSOLSpecies transport

Unstructured second order Hex/Tet mesh (node based)

ANSYS/ABAQUS

Structural analysis

Unstructured hybrid mesh (cell based)

HIMAGMHD

Unstructured hybrid mesh (cell based)

Fluent(Gambit)

Unstructured hybrid mesh (node based)

SC/Tetra & CFdesign

CFD/ Thermo-fluids

Unstructured Hex/Tet mesh (node based and edge based formulations)

ANSYS

Unstructured tetrahedral (Hex-) mesh (node based)

OPERA(Cubit)

Electro-magnetics

Unstructured tetrahedral mesh (node based)

Attila

Particle in cell (PIC)MCNPNeutronics

Mesh specificationAnalysis codePhysics

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Fusion Research provides material database, constitutive equations, and special modules for ISPC

Discrete element simulation of pebble bed provides contact forces at critical pebble/pebble contact areas- eliminating potential design flaws

FEM simulation needs to integrate with a Thermo-fluid code to account accurate temperature boundary conditionsNeeds incorporating fusion specific constitutive equations into user function of structural code. E.g.:

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

σε )/105.21exp(104.1 32.

Txx −− −=

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The computational meshes, even through are derived from a common CAD model, for different physical analysis have different requirements. The transfer of information between disciplines across various computational meshes has to be accurate and satisfies physical conservation laws.

CAD Model

MHD meshFine mesh resolution in the Hartmann layers

Stress analysis mesh

No discretizationin the fluid domain

∑∑

∑∑=

=

nodes Solidfaces Fluid

nodes Solidfaces Fluid

,

solidfluid

solidfluid

MM

FFvv

vv

• Conservation of forces and moments have to be ensured while translation between computational meshes

Coupling across Physical Disciplines and Data Interpolation

• Total heat deposition qcomputed from a neutronicssolver going into a fluids solver must be conserved (in each material)

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An effort has begun to develop this integrated multi-physics simulation tool for ITER FW/Shield and TBM Designs

CFD & Heat Transfer

Neutron Source Modeling

Radiation TransportDetailed distribution of nuclear heating

Large orthogonal regular grids in MCNP (~26M voxels)

Large unstructured hybrid mesh in CFD (~15M elements)

Based on MOAB infrastructure (KD tree for MCNP mesh, interpolation to centroid or vertices of CFD cells)

Example: Integrated ITER FW Neutronics and CFD/Thermal Analysis

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ISPC – an effective mechanism to integrate results of ongoing R&D and continuously evolve to Validated Predictive Capability for DEMO

Ultimate Goal: Validated Predictive Capability for DEMO

ISPCSingle- and Multiple-effect Experiments

Material DatabaseConstitutive Correlations/

Models

TBM Design and Data Interpretation

ITER TBMFNF/CTF test data

ValidationInitial Benchmark

FNF/CTF Chamber Design

• 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

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A Research Thrust ISPC provides a most effective, cost- and time-saving approach to develop predictive

capability for DEMO

• To structure the advancement of fusion energy research • To document systematically data, knowledge base, and validation

cases (necessary for QA) for DEMO – preserve investments • To maintain fusion nuclear science and technology research a

cutting edge venture – virtual reality • To provide a natural interface for Fusion Simulation Project (FSP)

through an accurate prediction of the plasma facing surface temperature, enabling realistic characterization of plasma shotsvis-à-vis to its surroundings

It is essential that such a Research Thrust be recommended by ReNeW

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Summary• The ISPC represents a paradigm shift in the manner in which

multidisciplinary simulations are performed.– From the outset, the emphasis will be on multi-physics

integration rather than separate threads of model development that might eventually come together at some point in the future.

• We strongly recommend a new Research Thrust aimed at developing Integrated multi-physics Simulation Predictive Capability (ISPC) for Fusion Nuclear Components. – This will allow faster and more effective approach toward

developing Validated/Verified Predictive Capability for DEMO. – In the near term, ISPC will be an important tool for:

• reducing design uncertainties • facilitating the understand of the experimental results• providing a fully integrated, high-fidelity simulation for performance

prediction of FNF/CTF fusion plasma chamber systems – Results from these near-term experiments facilities will also help

validate the ISPC for eventual use in DEMO.