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A Transient Simulation Test Rig for Heat Pipe Cooled Space Nuclear Reactors. Adam Wheeler, Andrew Klein Department of Nuclear Engineering & Radiation Health Physics Oregon State University February 25, 2013. Outline. Introduction Reference design Variations from the Reference Design
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A Transient Simulation Test Rig for Heat Pipe Cooled Space Nuclear Reactors Adam Wheeler, Andrew Klein Department of Nuclear Engineering & Radiation Health Physics Oregon State University February 25, 2013
Outline • Introduction • Reference design • Variations from the Reference Design • Modeling programs • SolidWorks • STELLA • Models • Goals • Assumptions • Results from analysis • Discussion of results • Conclusion and future work • References
Introduction • Objective: Develop and analyze a test facility based on a 1 to 10kWe heat-pipe cooled space nuclear reactor • Goals: • Design a feasible test facility • Predict steady state performance • Predict transient responses • Method: Use a lumped parameter model and a 3D CAD simulation program for analysis
Reference Design • Reference system is a 1 to 10kWe reactor module • Developed by a collaboration between NASA Glenn and Marshall Research Centers and Los Alamos National Laboratory
Variations from the Reference Design Original Design • 1000K sodium heat pipes in core • 8 to 16 heat pipes from core to power convertors • Pin or plate fuel interface to heat pipes • Direct energy conversion via Stirling engines or Thermoelectrics • Cone-shaped radiator array Test Facility • 600K water heat pipes in core simulator • 8 heat pipes between core & power convertor simulators • Stainless steel cylinder interface to heat pipes • Power conversion thermal absorption simulator • Cylindrical radiator array
Modeling Programs SolidWorks • Used for 3D rendering and various types of simulations • Flow Simulation package allows for heat and fluid flow in a time dependent simulation • Lacks computational stability and speed but can give very detailed results STELLA • Object oriented flow based system • Great for modeling the transfer of some item (heat, chemicals, water, population, etc.) to another location through time • Lacks accuracy and detail but is very versatile and fast (STELLA can be made more accurate but quickly reaches a diminishing return in effort and time which makes more complex CFD programs more attractive)
Limits to the System • Upper bounds: • 700K in the heat pipes from the core to the ECS • 550K in the radiator array heat pipes • 1600K in the stainless steel cylinders • Lower bounds: • 600K in the heat pipes from the core to the ECS • 450K in the radiator array heat pipes
SolidWorksModel Boundary Conditions • To simulate the affects of convection, a direct heat sink boundary condition was applied which simplified the model • A heat source was placed in the core simulator’s heater rods • To model the heat pipes, a custom material with very high conductance at the heat pipe’s operating temperatures was used along with the heat pipe operator in Flow Simulation • Radiation transfer boundary conditions were placed on the outer surfaces of the model ECS
Stella Model Assumptions • Axial heat transfer is negligible in comparison to radial heat transfer • Heat transfer to and from sinks and sources can be done with 1D radial methods • Adiabatic boundary conditions assumed for outer edges of the system
Stella Model Energy Conversion Simulator Cross-section Core Simulator Cross-section
STELLA Model • STELLA model uses three basic components • Convertor • Used to control flow and system variables • Reservoir • Points for collecting the heat passing through system • Bidirectional flow • Forces directional flow between Reservoirs and • Controlled by connections between Convertors and Reservoirs
STELLA Model • The whole thing:
STELLA Results: One HP Lost Increasing Time
Discussion of Results • STELLA results: • System is fast in responding to heat transients • Temperature changes as a result of heat pipe losses are less then 100K • SolidWorksresults: • Reasonably agree with the STELLA time and temperature results, and show in greater detail the temperature differences across the system
Conclusion and Future Work • The computational models gave a decent result that can be used for future analysis • Future work: • Increasing accuracy in STELLA model • Exact design specifications • Cost of actually building the facility • Gravity scaling • Finding a functional variable heat absorption method
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