Advanced Neutronics: PHISICS project
C. Rabiti, Y. Wang, G. Palmiotti, A. Epiney, A. Alfonsi, H. Hiruta, J. Cogliati, T. Grimmett
What is PHISICS?
Parallel and Highly Innovative Simulation for INL Code System
• PHISICS was started two years ago• The idea behind the project is to provide state of the art
simulation capability to reactor physics designers
Key features are
Modeling flexibilityHardware/software flexibilityLong term maintainabilityUncertainty analysis
Focuses
Neutronic designFluxes, burn up, fuel cycleCore feedback to system codes
PHISICS & RELAP5 !?!?
• PHISCS was born under one constrain:
increasing accuracy should not come at the expense of user time
• How?– Take advantage of parallel computing available to
the average user– Introduce a more complete representation of the
physical phenomena
These are the reasons why we believe PHISICS is a good candidate to move RELAP5 forward
PHISICS Structure• Modular infrastructure to ensure easy upgrade of
components and maintenance. No deep interdependence of modules
Kernel
Interface Kernel
Interface
Data Type
Data Type
Data Type
Data Type
Inpu
t
Inpu
t
Driver
PHISICS-RELAP5: Coupling
RELAP 5:Plant and TH
XS-MIXER
INSTANT
Tf, Tc, ρc,…
XS
Power
BatemanSolver
Flux
Nuclide Densities
Fission Power
Time DriverDecay heat
XS Source
Following the arrow clockwise, the loop reproduces an operator split approach
Overview of the Components
• INSTANT: Transport/Diffusion Solver
• MRTAU: Bateman Solver
• Adjoint Perturbation Theory Module
• Time Dependent Driver
INSTANTIntelligent Nodal and Semistrucured Treatment for Advanced
Neutron Transport
• INSTANT is in continuous development to extend its capability
• Code is designed to take full advantage of middle to large cluster (10~1000 processors)
• Code is designed to focus on method adaptation while also mesh adaptation will be possible
INSTANT: General Features• Boundary condition
– Reflective (exact) Vacuum Periodic• Number of energy group: unlimited (memory)• Anisotropic order of the scattering: up to P33• Number of thermal groups (up-scattering): unlimited• Problem type:
– fundamental mode, forward and adjoint– Source, forward and adjoint
• Outer iteration: power iteration scheme accelerated with Chebyshev
• Inner iteration acceleration: diffusion partitioning
INSTANT: Nodal Mesh/Geometry
• INSTANT has the capability to treat (with a nodal approach) the following geometry/mesh capability
• 2/3D Cartesian• 2D triangular, Z extruded• 2D hexagonal, Z extruded
Takeda 1 Benchmark (Rod In)
PN order Keff
1 (diffusion) 0.93238
3 0.96117
5 0.96214
7 0.96230
Takeda 1 Benchmark (Rod In)
MHTGR 2D Triangular Geometry
Unstructured Mesh
• C5G7
INSTANT: Inner Iteration Algorithms
• INSTANT has 3 different inner iteration schemes:
• The Krylov space based solvers (CG, and GMRES), since based on a residual formulation, are suitable for multi-physics coupling using Jacobian Free Newton Krylov methods
Multi-color by axial layers
Conjugate Gradient
Generalized Minimal RESidual
• Speed• Memory
• Scalability
Parallel Implementation of INSTNAT
Number of processors
Total computing time (s)
Speed up
1 35.70 1.00
2 17.98 1.99
3 11.11 3.21
4 8.39 4.26
6 5.93 6.02
9 4.03 8.86
• 36x36 cells with quadratic shape functions used to discretize the problem• Computing time on a single desktop with P9
SN-PN Coupling• One of the middle term goals of
INSTANT is to provide the capability to use different algorithms and mesh structures in the same geometry
• The theoretical developments needed are under development in cooperation with Texas A&M University
• Implementation in the code will start in FY12
Perturbation ModuleThe tasks of the perturbation module are
• Compute the uncertainty due to cross section in– Keff– Reactivity feedbacks– Reaction rates
• Requirements– Classical perturbation theory (adjoint in fundamental
mode)– Generalized Perturbation Theory (source adjoint in critical
problems)– Cross section manipulation tools– Perturbation integral computation
Adjoint Capability
• The adjoint solution has been already implemented in INSTANT and a perturbation module is under development
• the perturbation module will provide sensitivity analysis of input parameters (cross sections) toward several figure of merit:
• Keff• Power peak • Control rod worth• Reaction rates• Etc.
Unstructured Mesh Adjoint
MRTAU: Deacy/Depletion
Multi-Reactor Transmutation Analysis Utility• This module solves the Bateman equation• Two solution methodologies are available
– Arbitrary order of Taylor development– Arbitrary Chebyshev Rational Approximation
Method order (CRAM)• CRAM is the default methodology• Comparison of CRAM and Taylor have been
performed to confirm the correct implementation of algorithms
MRTAU Test Case
• MOX (10% NpPu/HM, 50 MWD/kg) directly recycled from spent UO2 (4.2% 235U/U, 50 MWD/kg, 5 years decay storage
• CRAM 14th order• Taylor 2nd order• Depletion Burn-Up Sequence
– 100 days cool down– 100 days core– 100 days cool down
• Reference CRAM at 3000 time step (TS)• Results for few representative isotopes
100 Days Error (%)Out of range
200 Days Error (%)Out of range
300 Days Error (%)Out of range
MRTAU remarks
• The two implemented algorithms offers the needed flexibility to model either burn up and decay
• Study are on going to assess best trade of between computational time and accuracy for transient analysis using different methodologies and orders of accuracy
Time Driver
• The module is at the design stage• The algorithm is based on the same scheme
implemented in ERANOS/KIN3D• Adaptation of the original algorithms are under
study to increase speed for very short time step
• We promised it by the end of September
ConclusionPHISICS will bring a new set of capabilities to RELAP5• Pre depletion of the core• Multi group in energy• Cross section tabulation• More flexibility in the neutronic mesh• Transport• Exact decay heat and isotopic tracking
Our goal is to deliver higher accuracy without impacting usability and computational time
Seeking Your Input
Please let us know….• what more you would like to add from the
neutronics standpoint
• Why you think what we are doing is or is not beneficial to your work
Question?