Integrated Simulation Capabilities for Analysis of Experiments in the Versatile Test Reactor

iii Table of Contents . iv List of Figures . v List of Tables . vi Acronyms . vii 1 Introduction . 1 2 Background . 2 2.1 Versatile Test Reactor Program . 2 2.2 SAS4A/SASSYS-1 . 3 2.3 SAM . 4 3 Features and Capabilities . 6 4 Coupling Implementation . 7 4.1 Coupling Interfaces . 7 SAS4A/SASSYS-1 Interface . 7 SAM Interface . 8 4.2 Iteration and Convergence Schemes . 8 Iteration and Data Transfer Schemes . 8 Quasi-Newton Coupling Algorithm . 9 Numerical Instability Prevention . 11 5 Steady-State Verification . 14 6 Demonstration for VTR Test Vehicle . 19 6.1 System Code Models. 19 SAS4A/SASSYS-1 Model (VTR) . 19 SAM Model (Cartridge Loop) . 20 6.2 Steady State Results . 23 6.3 Transient Results . 26 Unprotected Loss of Heat Sink . 26 Unprotected Transient Overpower . 27 Unprotected Station Blackout . 29 7 Summary and Path Forward . 31 8 Acknowledgements . 32 References . 33 Integrated Simulation Capabilities for Analysis of Experiments in the Versatile Test Reactor October 31, 2019 ANL/NSE-19/39 v LIST OF FIGURES Figure 2.1: Cartridge Loop Conceptual Design [4] . 3 Figure 4.1: Definition of the Coupling Boundary Interface and Boundary Condition Options . 8 Figure 4.2: Coupled and Internal Program Flow Diagram . 9 Figure 4.3: Communicating Solution Convergence with the (a) Boundary Conditions (left),or (b) Independently (right) . 11 Figure 5.1: Comparison of SAS-SAM Coupled Results for Coolant Temperatures with Analytical Solution. 15 Figure 5.2: Comparison of SAS-SAM Coupled Results for Wall Heat Flux with Analytical Solution. 16 Figure 5.3: Coolant Heat Transfer Coefficients Calculated in SAS4A/SASSYS-1. 17 Figure 5.4: Comparison of SAS-SAM Coupled Results for ∆Tw with Analytical Solution . 18 Figure 6.1: Schematic of VTR Core (left) and a Test Assembly with a Test Cartridge Loop (right) . 20 Figure 6.2: Representation of the Two Structure Nodes NSI and NSO with an Argon Buffer in the SAS4A/SASSYS-1 Model . 20 Figure 6.3: Two-dimensional Representation of the SAM Cartridge Model . 21 Figure 6.4: Power and Flow Distributions in the SAS4A/SASSYS-1 Channels . 24 Figure 6.5: Ratio of Power to Flow in the SAS4A/SASSYS-1 Channels . 24 Figure 6.6: Steady State Coolant Temperatures in the Fuel and Test Channels . 25 Figure 6.7: Test Vehicle Coolant Velocity (left) and Temperature Distribution (right) . 26 Figure 6.8: ULOHS Power and Flow (left), and Reactivity Feedbacks (right) . 27 Figure 6.9: ULOHS VTR Coolant Temperatures (left) and Test Vehicle Temperatures (right) . 27 Figure 6.10: UTOP Power and Flow (left), and Reactivity Feedbacks (right) . 28 Figure 6.11: UTOP VTR Coolant Temperatures (left) and Test Vehicle Temperatures (right) . 29 Figure 6.12: USBO Power and Flow (left), and Reactivity Feedbacks (right) . 29 Figure 6.13: USBO VTR Coolant Temperatures (left) and Test Vehicle Temperatures (right) . 30 Integrated Simulation Capabilities for Analysis of Experiments in the Versatile Test Reactor October 31, 2019 ANL/NSE-19/39 vi LIST OF TABLES Table 6.1 Dimensions of the Cartridge Loop Fuel Assembly . 22 Table 6.2 Dimensions of the Cartridge Loop . 23 Integrated Simulation Capabilities for Analysis of Experiments in the Versatile Test Reactor October 31, 2019 ANL/NSE-19/39 vii ACRONYMS CRBR Clinch River Breeder Reactor CRDL Control Rod Driveline FFTF Fast Flux Test Facility FHR Fluoride-cooled High-temperature Reactor IFR Integral Fast Reactor IPC Interprocess Communication KAERI Korean Atomic Energy Research Institute LDRD Laboratory Directed Research and Development LFR Lead-cooled Fast Reactor LOF Loss of Flow M&S Modeling and Simulation MSR Molten Salt Reactor NEAC Nuclear Energy Advisory Committee PGSFR Prototype Gen-IV Sodium-cooled Fast Reactor SAM System Analysis Module SFR Sodium-cooled Fast Reactor TOP Transient Overpower ULOHS Unprotected Loss of Heat Sink USBO Unprotected Station Blackout UTOP Unprotected Transient Overpower VTR Versatile Test Reactor Integrated Simulation Capabilities for Analysis of Experiments in the Versatile Test Reactor October 31, 2019 ANL/NSE-19/39 1 1 Introduction The Versatile Test Reactor (VTR) program, a key DOE initiative, seeks to develop a domestic fast-neutron irradiation and testing capability that meets a variety of advanced nuclear energy needs. As there is currently significant diversity in the advanced reactor R&D technology scope (e.g. liquid-metal, molten-salt, and gas coolants, as well as novel fuel forms), there is a need for the capability to mechanistically analyze the coupled behavior of VTR with a variety of experiments and vehicles which may be utilized in VTR. With the intent of closing this modeling and simulation (M&S) gap, a capabilities development effort has been undertaken to develop a flexible and integrated system simulation capability that is necessary for the mechanistic, coupled M&S of VTR and its test vehicles. This integrated capability enables broad exploration of the potential capabilities of the test reactor by providing VTR designers with the tools necessary to achieve a range of operating conditions and experiment designers with the ability to utilize the entire capability range of the test reactor. Specifically, this effort focuses on extension of SAS4A/SASSYS-1 [1], the system-level liquidmetal safety analysis software developed and maintained by Argonne, to enable coupling with any external code or model representing a test vehicle. This effort also includes extension of SAM (System Analysis Module) [2], also developed and maintained by Argonne, to enable coupling with other system-level codes at a new interface. Here SAM will be utilized to model VTR test vehicles such as sodium or molten salt test capsules and support demon