Advanced Multi-Physics Modeling & Simulation Efforts for Fast Reactors J.W. Thomas Argonne National Laboratory IAEA Technical Meeting on Priorities in Modeling & Simulation in Fast Reactor Systems April 14-16, 2014
Acknowledgements Simulations in this presentation were performed by: Argonne National Laboratory E. Merzari E. Shemon C. Lee M.A. Smith A. Obabko R. Jain V. Mahadevan T. Tautges Lawrence Livermore Laboratory J. Solberg R. Ferencz R. Whitesides 2
Outline Background on SHARP SHARP Physics Modules Coupled Multi-Physics Demonstration Problems EBR-II Loss of Heat Sink Neutronics& Thermal-Hydraulics dynamically coupled Follow-up Structural Mechanics simulation Analysis of Radial Core Expansion Phenomenon Neutronics, Thermal-Hydraulics, Structural Mechanics dynamically coupled Conclusions and Future Work 3
Motivation Conventional tools simplify one field of physics in order to couple another Commercial CFD and FEA tools clearly lack integration with neutronics SHARP does multi-physics Without losing accuracy of each physics module Maintaining spatial resolution Solving practical engineering problems SHARP predictions of power profile in EBR-II transient 4
SHARP: Technology-Versatile Reactor Core Simulator Flexible multi-physics coupling to optimize performance Well-validated physics modules Trusted pedigree More mechanistic models Finer resolution Framework (MOAB) Variety of computing platforms 5 SHARP Reactor Core Simulator
SHARP Neutronics: PROTEUS Unstructured finite element mesh Efficient parallel algorithm (space & angle) Runs on a variety of platforms ranging from desktops to supercomputers Gordon Bell Prize supercomputing finalist PROTEUS Mesh of the Advanced Test Reactor 6
SHARP Thermal-Hydraulics: Nek5000 Spectral Element Discretization: High accuracy at lower cost Open Source Features Direct Numerical Simulation & Large Eddy Simulation of turbulent flows Conjugate heat transfer Low-Mach combustion Magnetohydrodynamics Moving mesh 2012 OECD/NEA blind benchmark Matis Scaling: 1999 Gordon Bell Prize 7
SHARP Structural Mechanics: Diablo Parallel implicit code with focused multi-physics capability Multiple contact algorithms Modular design simplifies extensions Material models Element kinematics Mechanics Formulations MacArthur-Maze Bridge Collapse due to tanker truck fire 8
SHARP Physics Module Features NEK5000& PROTEUS& DIABLO& 9
SHARP Multi-Physics Coupling SHARP framework tool CouPE drives the physics solvers PROTEUS and Nek5000 Diablo integration effort is underway For Pseudo Steady-State Transients, one global CouPE iteration includes PROTEUS: k eff and flux update at the current T/H condition Nek5000: Simulation for a fixed integration time CouPE Nek PROTEUS Diablo 10
Selective Homogenization Capability SHARP capable of detailed representation of core geometry, e.g. fuel pins, wire wraps, duct walls Prohibitively expensive for full core simulations PROTEUS and Diablo: Homogenize fuel pin geometry of select assemblies Nek5000 Options: 1. Channel-like model 2. Porous media representation 11
Objectives of Demonstration Problems The coupled demonstration effort is meant to ensure that the integrated SHARP suite is usable from the onset Demonstrate causality and reasonable feedback in coupled demonstrations for a variety of cases. Perform practical engineering problems using readily available computing resources Flexibility in resolution, coupling schemes, meshing choices No comparisons to experiments yet 12
Experimental Breeder Reactor II (EBR-II) Pseudo steady-state transient analysis of simplified loss-of-heat sink modeled with specified change in inlet temperature Single fuel assembly model of XX09 Dynamic coupling of neutronics(proteus) and thermal-hydraulics (Nek5000) Thermal expansion (Diablo) modeled with the final temperatures from Nek5000 Full core model Neutronics and thermal-hydraulics only Heterogeneous model of XX09 Other assemblies homogenized Nek5000 employs channel-like model Structural response of XX09 following coupled simulations XX09 13
Pseudo Steady-State Transient Loss of Heat Sink Simplified Loss of Heat Sink Transient Delayed temperature increase at the core T/H driven transient Inlet temperature a hyperbolic function of time Integral power is constant Coolant density feedback produces measurable causality EBR-II Core with Inlet Temperature Profile 14
XX09 Model Realistic Full assembly Neutronics Reflective boundary conditions Thermal-Hydraulics Inlet-Outlet boundary conditions Dirichletcondition for temperature on sides Simplistic turbulent modeling Structure Zero axial displacement at the bottom Temperature (Nek5000 I.C.) Power (PROTEUS I.C.) 15
XX09 Pseudo Steady-State Transient 1.0 0.999 As the temperature wave reaches the core, the feedback accelerates as expected (Doppler broadening). 0.998 0.997 16
17 XX09 Pseudo Steady-State Transient
XX09 Early Diablo Demonstration Structural feedback is a major component of feedback Assembly bowing affects the neutronicresponse of the reactor Final Nek5000 temperatures provided to Diablo to predict structural deformation due to thermal expansion 18
19 EBR-II Full core
EBR-II Full Core EBR-II full core simulation. Each assembly has a separate composition and mass flow rate. Run pseudo steady-state transients. 20
Core Thermal Expansion Phenomenon We rely on core thermal expansion as one of the primary reactivity feedback mechanisms for LMR safety. Core restraint system design mustdemonstrate that thermal expansion is a negativereactivity feedback mechanism ABTR ULOF transient simulation performed with SAS4A/SASSYS-1 21
Core Restraint System Top Load Pad (TLP) Restraint Ring Above Core Load Pad (ACLP) Restraint Ring Core Grid 22 Advanced Burner Test Reactor (ABTR) Inlet Plenum Structure Core Support Structure
Demonstration Models Interior of the ducts are homogenized Demonstrated flexibility to scale to higher fidelity if more resources are available. 23 7-Assembly Test Problem Ducts, load-pads and restraint rings explicitly represented. Full ABTR core composition 23
24 7-Assembly Test Problem
ABTR Core (in progress) ABTR full core power distribution ABTR full core velocity distribution [cm/s] 25ABTR full core mesh with core restraint rings
Conclusions and Future Work SHARP s capability to perform heterogeneous, continuum-scale simulations of reactors has been previously demonstrated for each physics module Now demonstrating capability to perform integral multi-physics simulations of engineering-scale problems on readily available commodity cluster compute platforms Flexibility to provide detailed resolution only where necessary Causality in the multi-physics feedback demonstrated Verification and validation to follow in future work Improving the process Include dynamic coupling with Diablo Automate the coupling process 26