Status of ITER Neutronicsand CAD/MCNP
Development
Mohamed Sawanfor UW-Madison Team
Paul Wilson, Tim Tautges (SNL),Greg Sviatoslavsky, Brian Kiedrowski
FusionTechnologyInstitute
ITER TBM MeetingUCLA
May 10-11 2006
M. Sawan ITER TBM MeetingMay 10-11, 2006
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• ITER first magnetic fusion facilitywhich:
– will produce significant fusion power– requires nuclear licensing
• According to French regulation ITER– will be classified as a nuclear Installation
called “Installation Nucléaire de Base”(INB) due to the expected tritiuminventory and waste generation during thelifetime of ITER
• The aim of ITER Organization is to:– construct and operate such first-of-a-kind
nuclear installation satisfying the demandsand interests of the user community and offunding partners
Neutronic Analysis Service for ITER
M. Sawan ITER TBM MeetingMay 10-11, 2006
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• Extensive neutronics calculations and analyses in ITER are required to– ensure that existing, modified, or proposed structure, system, or component
designs will meet technical and functional requirements– demonstrate capability of safe operation– assess maintaining, repairing, replacing or modifying components– provide required baseline for access, repository and waste management of
components
• Neutronics calculations and analyses shall conform to the ITERManagement and Quality Program (MQP) that establishes the overallframework for the execution of the ITER Project
• This implies the availability of:– Adequate modelling tools which would reduce turnaround time between CAD-
based design and design changes and analysis.– Well documented QA procedures for neutronic work.– Database system
Role of Neutronic Analyses in ITER
M. Sawan ITER TBM MeetingMay 10-11, 2006
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US Neutronics Support Areas:Global model, diagnostics, TBM, FW/shield
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Previous Work on CAD Interfacewith 3D Neutronics
• Translation-based approaches– Tsige-Tamirat et al., FZK– Manson, Raytheon– Van Riper, White Rock Science– Wu et al., Hefei, China+ Speed– Setup effort
• Direct CAD evaluation– Franke et. al, SNL+ Setup effort– Speed
M. Sawan ITER TBM MeetingMay 10-11, 2006
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CAD-Based MCNP(X)• Use Common Geometry Module (CGM) to
interface MCNPX directly to CAD & othergeometry data– Previous efforts found CAD-based ray
tracing to be too slow (20-50x)– Implement ray-tracing approximations in CGM to reduce
calls to exact CAD function
• Benefits:– Dramatically reduce turnaround time
from CAD-based design changes– No translation to MC geometry representation
• Removes limitation on surface types• Improves robustness by using same engine for CAD and MCNP
– Can handle 3D models not supported in MCNP
CGMCAD Voxels
MCNPX
MCNPXNative
Geometry (Other)
M. Sawan ITER TBM MeetingMay 10-11, 2006
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MCNPX/CGM Example ARIES CompactStellerator
• High-degree NURBS geometry from curves/surfacesfit to Fourier series
IB
OB
θT
IB OB
θT
M. Sawan ITER TBM MeetingMay 10-11, 2006
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CPU Time vs. MCNPX
• MCNPX – original code• BB – Axis-oriented bounding box• OBB – Oriented bounding box
• Sorted BB – Grid-sorted BB• Dist limit – transport distance-limited• Facet-only: No ACIS ray intersection
– (less accurate, MUCH faster)
3cyls
0
10
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60
MCNPX
BB
Sor
t BB
Sor
t BB, d
ist lm
t
Sor
t OBB
Sor
t OBB, d
ist lm
t
OBB, F
acet
-only
Tim
e F
ac
tor
Cobalt
0
5
10
15
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MCNPX
BB
Sor
t BB
Sor
t BB, d
ist lm
t
Sor
t OBB
Sor
t OBB, d
ist lm
t
OBB, F
acet
-only
Tim
e F
ac
tor
4.3 3.0!
23.5 12.3!
+
M. Sawan ITER TBM MeetingMay 10-11, 2006
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CAD PROCESSINGCAD PROCESSINGCATIA
file
CATIA STEPfile
CUBIT
ACISfile
MCNPX/CGM
translation
data preparation:
model &analysis
“imprint” surfaces “merge” mating
surfaces
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Imprint & Merge ProcessImprint & Merge Process
Volume A
Volume B
Volume A
Volume B
1. PRIOR to Imprint, top of Volume Bmade up of one surface
2. Following IMPRINT, top of Volume Bmade up of three surfaces
3. Following MERGE, top of Volume B made up of twosurfaces plus one surface shared with Volume A
M. Sawan ITER TBM MeetingMay 10-11, 2006
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CAD Issues Requiring CAD Issues Requiring ““RepairRepair””
• Overlapping Volumes (i.e.: clashes)• Mating surfaces not contacting• Slight “Misalignment”
– Imprint generates ultra thin surfaces– Doesn’t always require repair
Complex Surface Definition
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Examples of Typical CAD IssuesExamples of Typical CAD Issuesand Typical Repairsand Typical Repairs
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Action - Volumes trimmed to contact only
Overlapping VolumesOverlapping VolumesIssue – Overlapping Volumes
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Action – Edit geometry toestablish proper contact
Mating Surfaces Not ContactingMating Surfaces Not Contacting
Issue – No Contact
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Action – Edit geometry to correct misalignment
MisalignmentMisalignmentIssue – misalignment … … causes imprint difficulty
and therefore no merge
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Action – MAY require recreating volume
Edges cross at this point
Action – MAY require recreating volume
Issue – Slight Edge Misalignment
MisalignmentMisalignment
Edges cross at this point
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Complex Surface DefinitionComplex Surface Definition
Action – Recreategeometry and/or“Unify” neighboringvolumes into a singlevolume.
Issue – definition ofneighboring complexsurfaces differ slightly,preventing surfacesfrom merging
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Complex Surfaces & MisalignmentComplex Surfaces & MisalignmentIssue – Misalignment
along curvedsurfaces
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Distribution of Repair EffortsDistribution of Repair Efforts
40%40%MisalignmentMisalignment
50% Complex50% ComplexSurfaceSurfaceDefinitionDefinition
10% Overlapping Volumes10% Overlapping Volumes& Non-contact& Non-contact
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Improving the ProcessImproving the Process
➤Direct Link to CATIA (or appropriate modeler)data – eliminating possible translation issues
➤Work with original ITER data – simplificationprocess may have introduced errors
➤Tighten design process to minimize “designer-introduced” issues
➤Leverage prior work via configuration control -allowing future model revisions to address onlythose area that have changed
M. Sawan ITER TBM MeetingMay 10-11, 2006
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MCNP(X)-CGMDevelopment Plan & Progress
• Upgrade to newest versions of MCNP(X)• Upgrade to MCNPX v2.5.0 complete
– MCNP compatibility enhancement• Forced collision variance reduction• Reflecting boundary conditions• Surface flux tally
– Features added• Elimination of fatal errors from cell and surface definitions• Elimination of surface definitions entirely• Ability to define reflecting boundary conditions in CAD geometry
file
M. Sawan ITER TBM MeetingMay 10-11, 2006
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MCNP(X) Compatibility
• Geometry– Cell volume/Surface areas – functional– Boundary conditions
• Specular reflection – functional• White reflection – functional• Periodic – near term
– Lattice/universe – long term• Source
– Fixed source – functional– Fission source – testing– Surface source write/read – long term
M. Sawan ITER TBM MeetingMay 10-11, 2006
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MCNP(X) Compatibility
• Variance Reduction– Cell importance – functional– Exponential transform – functional– Forced collision – functional– Weight windows (cell-based) – testing– Weight windows (mesh-based) – functional– Detector tallies - functional
M. Sawan ITER TBM MeetingMay 10-11, 2006
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MCNP(X) Compatibility
• Tallies– Surface current (type 1) – functional
• Cosine bins – functional (directional ambiguity)– Surface flux (type 2) – functional– Cell flux (type 4,6,7) – functional– Pulse height (type 8) – testing– Point detector (type 5) – functional– Mesh tallies – functional in MCNPX
• Note: MCNP and MCNPX have different mesh tally implementations– Cell flagging – functional– Surface flagging – functional– Multipliers – functional– Segmenting – long term ??
M. Sawan ITER TBM MeetingMay 10-11, 2006
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CGM-related Enhancements
• CAD/Cubit definition of materials – near term
• CAD/Cubit definition of tallies – long term
• Further geometry-based performanceenhancements
M. Sawan ITER TBM MeetingMay 10-11, 2006
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ITER Model
• “Simplified” ITERbenchmark model
• 40° toroidalsegment
• Source definedon 40x40 R-Z grid
• 774 volumes• 18116 surfaces
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Source Characterization
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Neutron Wall Loading
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Neutron Wall LoadingNormalization = 1.97 x 1019 n/s in 40o segment
0.00
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0.80
0 250 500 750 1000 1250 1500 1750
Poloidal Distance (cm)
Ne
utr
on
Wa
ll L
oa
din
g (
MW
/m2)
O/BI/B
M. Sawan ITER TBM MeetingMay 10-11, 2006
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F2: Surface flux tally
F4: Cell flux tally
F2: Surface flux tally
F4: Cell flux tally
Divertor Tallies
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Radial flux profile behind dummy port plug
Tally spheres behindport plug
M. Sawan ITER TBM MeetingMay 10-11, 2006
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Nuclear heating in IB Leg of TF Coil
Preliminary19 calculations of 2.6Mparticles (36 hours)2.2 kW total
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7
Nuclear Heating (kW)
TOP
BOTTOM
M. Sawan ITER TBM MeetingMay 10-11, 2006
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International meeting on ITER neutronics willbe held in Madison July 24-26, 2006
• Review progress of the various CAD/MCNP approachesbeing developed by the various ITER Participant Teams
–The results of the ITER benchmark exercise will be presented anddiscussed
–Determine advantage/shortcomings of various approaches and theprospect for application to ITER analyses
• Check the status of ongoing validation of the code ATTILAagainst results of fusion experiments and its evaluation ingeneral as a tool to complement MCNP calculations
• Discuss QA procedures for neutronics analyses beingdeveloped and implemented in ITER
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