Overview of GNEP Fast Reactor Simulation Program
Andrew Siegel, ANL
Work sponsored by U.S. Department of Energy Office of Nuclear Energy, Science & Technology
2GNEP Fast Reactor Meeting, ANL
Outline
Background/Approach
Overview of 2007 progress
3GNEP Fast Reactor Meeting, ANL
Outline
Background/Approach
4GNEP Fast Reactor Meeting, ANL
Motivating issues for simulation program
Predictive models are the backbone of reactor design/analysis
– Core, overall plant design
– Fuel performance
– Integrated safety assessment
– Certification
Question: Do existing tools/models meet GNEP needs?
If not, what improvements are needed?
How should these improvements be prioritized?
5GNEP Fast Reactor Meeting, ANL
State of Existing tools: short version
Most were first developed in 70’s and 80’s
– Targeted improvements through more recent programs (e.g. IFR)
Models based on assumptions about both computing power and solvers that are no longer true
– 1.E8 FLOPS Cray-1 (late 1970’s)
– 1.E15 FLOPS BG/P, Cray (2008)
Thus, easy to identify “shortcomings”
– Coarse discretizations/geometries underpinned by models based on experimentally measured correlations. e.g.
• Subchannel models with rod bundle heat transfer correlations• Homogenized geometries with few-group transport
Key question, though
– To what extent will improvements result in superior design, enhanced safety, quicker certification, etc?
6GNEP Fast Reactor Meeting, ANL
Current Fast Reactor Physics and Safety Analysis Code Suite
7GNEP Fast Reactor Meeting, ANL
Modeling improvements for GNEP
Four classes of needs for GNEP– Reduction of uncertainties for more optimal design– Improved efficiency of use via better software engineering – Detailed study of localized phenomena– Numerical experiments complement traditional experiments
Specific examples– More accurate predictions of peak subassembly temperature
• Reduction of “hot channel factors”– Much more seamless integration of tools
• Major increases in efficiency– Reduction of modeling uncertainties for flux calculations
• Used in fuel cycle analysis, heating calculation, reactivity coefficient calculation, control rod worth and shutdown margin evaluation, etc.
– Understanding of detailed localized phenomena• E.g. thermal striping in upper plenum, pipe flow, etc.
– Empirical correlations for low breeding ratio designs (grid spacers, etc.)– Parameterization of wire-induced cross flow
8GNEP Fast Reactor Meeting, ANL
Outline
Background/Approach
Overview of 2007 progress
9GNEP Fast Reactor Meeting, ANL
GNEP Fast Reactor Simulation Program 2007
Two simultaneous goals
– Develop general advanced capability• Begin develop general advanced modeling for each physical
process/enabling technology– Heat Transfer, neutron transport, structural mechanics– Framework: Meshing/geometry, visualization/analysis, solvers,
coupling, data archiving– Small coupling demonstration
• Ultimately, use for safety, optimized design, etc.
– Early application of new codes to study specific issues• Predictions with lower uncertainties• See previous slide
10GNEP Fast Reactor Meeting, ANL
07 Work Package Structure
Advanced Thermal Modeling
Advanced Neutronics Modeling
Code Framework Design
Advanced Structural Mechanics
ANL, LANL
ANL, ORNL, LANL, INL
LLNL
ANL, LLNL
11GNEP Fast Reactor Meeting, ANL
Overview of thermal hydraulics modeling goals
Fischer talk
Code
– Version 1. multi-resolution T-H (Nek)• DNS, LES: multi-pin -> several subassembly• RANS: Many subassemblies -> full core• Improved subchannel: Full core• Coupled to other modules• Usable by designers: “validated”, documented
Problems
– Quantify effect of wire wrap on mixing in rod bundle geometry
– Predictions of thermal striping at core outlet in upper plenum
– Identify subassembly hot-spots (reduce hot channel factors)
– Lowering uncertainties of assembly outlet temperature predictions
12GNEP Fast Reactor Meeting, ANL
LES of 7 Pin Configuration
Time-averaged axial (top) and transverse (bottom) velocity distributions.
A A
A A
Snapshot of axial velocity
13GNEP Fast Reactor Meeting, ANL
Reactor Core TH Plan – desktop strategy
Empirical subchannel codes:
• Very fast – capable of whole core at pin level (400,000 pins)
• Past practice:– Empirical, based on experimental data– Serial– Complex input decks
• Current effort:– Empirical, data from experiment and
from LES simulations– Parallel– Input based on same mesh framework
as detailed TH/neutronics
217 pin velocity distribution from Nek5000 subchannel analysis
14GNEP Fast Reactor Meeting, ANL
Status of 07 work
Fischer talk
– Development of Nek code
– Design of reactor core mesh/geometry
– Analysis of 7-pin and 19-pin LES
– 217-pin (single assembly) Large Eddy Simulations
– Analysis of upper plenum thermal striping, comparison with CHAD
– Star-CD inter-comparisons using RANS
– Coupling with neutron transport
– Comparison with COBRA
– IAEA international benchmark on transient coolant behavior in the outlet plenum of Monju based on measurements made during a plant trip test performed in December 1995
Open issues: Validation cases, computer time, transient coupling …
15GNEP Fast Reactor Meeting, ANL
Yang talk
Code
– Version 0 of UNIC (Unstructured Deterministic Neutron Transport)• General geometry capability using unstructured finite elements• First order form solution using method of characteristics• Second order form solution using even-parity flux formulation• Parallel capability for scaling to thousands of processors• Adjoint capability for sensitivity and uncertainty analysis• X-section generation
Calculations
– An ABR full subassembly with fine structure geometrical description for coupling with thermal-hydraulics calculation
– A whole ABR configuration with pin-by-pin description
Summary of Neutronics 07 work scope
16GNEP Fast Reactor Meeting, ANL
Four benchmark problems are being analyzed– All require P7 or S8 angular order– 33, 100, and 230 groups are planned
30º symmetry core with homogenized assemblies– ~40,000 spatial DOF
• ~100 processors 120º periodic core with homogenized
assemblies– ~400,000 spatial DOF
• ~500 processors 30º symmetry core with homogenized pin
cells– 1.7 million spatial DOF
• ~1000 processors Single assembly with explicit geometry
– 2.2+ million spatial DOF • ~5000 processors
ABTR Whole-Core Calculations
Barrel ID = 2.27 m
Equivalent core OD = 1.31 m
Inner Core (24) Outer Core (30)Fuel Test (6)
Primary Control (7)
SecondaryControl (3)
Reflector (78)
Shield (48)
P
T
T
P
T
P
S
S
T
P
T
T
T
P
S
P
T
T
P
Material Test (3)
17GNEP Fast Reactor Meeting, ANL
Structural mechanics
Ferencz talk
Code
– Adaptation/application of LLNL Diablo code
– Integrating/coupling with other physics modules
Calculations
– Core restraint
– Calculate structural response reliably to evaluate the reactivity effects during both long-term irradiation and transient conditions.
18GNEP Fast Reactor Meeting, ANL
Framework Design
Goals
– Develop/implement overall (lightweight) software architecture
– Visualization/Analysis (Bradley talk)• Use/Develop Visit (LLNL)
– Parallel solver library• Use/develop PETSc
– Mesh generation• Use CUBIT from Sandia
– High-performance i/o • Use hdf5 and pNetCFD
– Coupling/runtime meshing• Use/Develop MOAB
– Testing framework• Custom, just beginning development (on critical path)
– Repository management• Use svn + informal policing (need to improve)
neutrontransport fuel
thermohydraulics
Structuralmechanics
balance of plant
Coupling
Visualization
Mesh generation
High-performance i/o
Ultra-scalable solvers
Components•formalized interfaces•encapsulate physics•follow strict design rules•unit tests
Framework•provide services to components•Defines module structure•domain of CS
•MC•MOL•Direct
Uncertainty
Geometry
Enabling technologies
19GNEP Fast Reactor Meeting, ANL
Frameworks, cont.
Software design
– Begun development of standards documentation
– No work yet on Users Guide
– Only informal coding standards -- portability challenges
20GNEP Fast Reactor Meeting, ANL
UNIC
MOAB
XSection
Depletion
Nek
T c, T f,
c on th
q on n
q,
o
n th
Tc, Tf,
c on Lc (
th ) on L
c (n )
on L
c (n )
Driver
MaterialProperties
T c, T f
on L c
( th)
on
th
21GNEP Fast Reactor Meeting, ANL
Establishment of Software Process
Mihai Anitescu (MCS staff)– Applied mathematician– Uncertainty analysis
Alvaro Caceres (MCS post-doc):– Physics Ph.D., hpc software engineer– SHARP code architecture
Tom Fanning (NE Staff)– Reactor Safety– Improvements to SAS based on SHARP
Paul Fischer (MCS Staff)– CFD (higher order methods)– Nek development lead
Dinesh Kaushik (MCS staff)– Computational scientist– Parallel implementation of UNIC
James Lottes (MCS pre-doc)– Parallel algorithms for CFD– Nek development
Dave Pointer (NE Staff)– Fluid dynamics/heat transfer– Application/analysis of CFD tools
Christian Rabiti (NE staff)– Computational neutronics– UNIC development/verification
Barry Smith (MCS Staff)– Computational Mathematician– Optimized parallel solvers for UNIC
Mike Smith (NE staff)– Computational neutronics– UNIC development lead
Tim Tautges (MCS Staff)– Former CUBIT lead, adv. Meshing– Mesh generation, integration
Won-sik Yang (NE Staff)– Reactor design– Problem definition, validation, …
• Co-located code team • Weekly meeting• Shared code repo• Internal Wiki• Automated test suite• …
22GNEP Fast Reactor Meeting, ANL
Other collaborators
Carlos Pantano (UIUC)– Joint INCITE award– Subgrid-scale modeling of liquid
metals in fast reactor core
Elmer Lewis (Northwestern)– Advanced neutronics methods
Jean Ragusa (Texas A&M)– Joint NERI award– Advanced coupling methods
Informal “steering committee”– James Cahalan – Bob Hill– Hussein Khalil– Bob Rosner– Temitope Taiwo
23GNEP Fast Reactor Meeting, ANL
Integration challenges
Major challenges being worked on
– How to transition users from current to new tools
– How much work to invest in improvement/integration of existing tools vs modern capabilities
– How to integrate work done outside of ANL (e.g. SM) with main code suite
– How to overlay code with GNEP milestones
– How to handle fast transients in coupling framework
24GNEP Fast Reactor Meeting, ANL
Computing time
ANL GNEP dedicated small cluster (coming)
Director’s allocations on ANL BG/L and ORNL Cray
Must compete otherwise
– 1M hours: 2007 INCITE award “LES of Wire Wrapped Fuel Pins”
– 50M hours: 2008 INCITE neutronics proposal
– 20M hours: 2008 INCITE T-H proposal
25GNEP Fast Reactor Meeting, ANL
Incorporation of Legacy Modules
Codes such as SASIVa, Cobra IV, Relap, etc., are trusted and familiar tools for reactor designers.
All new codes will need to be benchmarked against these, as a starting baseline (in addition to validation against new experiments, etc.)
Moreover, these codes are often fast – e.g., < 10 seconds on a workstation for TH subchannel model of a 217-pin assembly vs. 4 hours on 100,000 processors for a first principles (LES) solution.
– (High fidelity simulations improved subchannel models)
SHARP will support legacy code interfaces to allow users and developers to:
– validate a given geometry/model against current tools, without changing the geometry definition
– focus on testing / debugging a single high-fidelity module while retaining coupled physics at low cost
26GNEP Fast Reactor Meeting, ANL
Extra Slides
27GNEP Fast Reactor Meeting, ANL
H
Fuel Pinand Wire
CornerSubchannel
EdgeSubchannel
InteriorSubchannel
Duct Wall
Fuel Pin D
P
Wire Wrap
Example: Hot Channel Factors