Status of ITER Neutronics and CAD/MCNP …2006/05/11 · Status of ITER Neutronics and CAD/MCNP...

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


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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


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US Neutronics Support Areas:Global model, diagnostics, TBM, FW/shield


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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


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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)


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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


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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

20

30

40

50

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

20

25

30

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!

+


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CAD PROCESSINGCAD PROCESSINGCATIA

file

CATIA STEPfile

CUBIT

ACISfile

MCNPX/CGM

translation

data preparation:

model &analysis

“imprint” surfaces “merge” mating

surfaces


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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


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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


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Examples of Typical CAD IssuesExamples of Typical CAD Issuesand Typical Repairsand Typical Repairs


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Action - Volumes trimmed to contact only

Overlapping VolumesOverlapping VolumesIssue – Overlapping Volumes


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Action – Edit geometry toestablish proper contact

Mating Surfaces Not ContactingMating Surfaces Not Contacting

Issue – No Contact


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Action – Edit geometry to correct misalignment

MisalignmentMisalignmentIssue – misalignment … … causes imprint difficulty

and therefore no merge


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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


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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


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Complex Surfaces & MisalignmentComplex Surfaces & MisalignmentIssue – Misalignment

along curvedsurfaces


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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


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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


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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


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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


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• Variance Reduction– Cell importance – functional– Exponential transform – functional– Forced collision – functional– Weight windows (cell-based) – testing– Weight windows (mesh-based) – functional– Detector tallies - functional


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• 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 ??


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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


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ITER Model

• “Simplified” ITERbenchmark model

• 40° toroidalsegment

• Source definedon 40x40 R-Z grid

• 774 volumes• 18116 surfaces


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Source Characterization


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Neutron Wall Loading


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Neutron Wall LoadingNormalization = 1.97 x 1019 n/s in 40o segment

0.00

0.10

0.20

0.30

0.40

0.50

0.60

0.70

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


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F2: Surface flux tally

F4: Cell flux tally

F2: Surface flux tally

F4: Cell flux tally

Divertor Tallies


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Radial flux profile behind dummy port plug

Tally spheres behindport plug


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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


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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

Status of ITER Neutronics and CAD/MCNP …2006/05/11 · Status of ITER Neutronics and CAD/MCNP...

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