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Nuclear Reactors for The Moon and Mars

Nuclear Reactors for The Moon and Mars. Tyler Ellis Michael Short Martian Surface Reactor Group November 14, 2004. MSR Motivation. Nuclear Physics/Engineering 101. Nuclear Physics/Engineering 101. Habitat. Reactor. Proposed Mission Architecture. MSR Mission.

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Nuclear Reactors for The Moon and Mars

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  1. Nuclear Reactors for The Moon and Mars Tyler Ellis Michael Short Martian Surface Reactor Group November 14, 2004

  2. MSR Motivation

  3. Nuclear Physics/Engineering 101

  4. Nuclear Physics/Engineering 101

  5. Habitat Reactor Proposed Mission Architecture

  6. MSR Mission • Nuclear Power for the Martian Surface • Test on Lunar Surface • Design characteristics of MSR • Safe and Reliable • Light and Compact • Launchable and Accident Resistant • Environmentally Friendly

  7. MSR Components • Core • Nuclear Components, Heat • Power Conversion Unit • Electricity, Heat Exchange • Radiator • Waste Heat Rejection • Shielding • Radiation Protection

  8. CORE

  9. Core - Design Concept • Develop a 100 kWe reactor with a 5 full-power-year lifetime • Evaluation of options were based on design criteria: • Low mass • Launchability • Safety • High Reliability

  10. Core - Design Choices • Fast Spectrum • Ceramic Fuel – Uranium Nitride, 35 w/o enriched • Tantalum Burnable Poison • Liquid Lithium Heatpipe Coolant • Fuel Pin Elements in tricusp configuration • External control using drums • Zr3Si2 Reflector material • TaB2 Control material

  11. Core - Design Specifications • UN fuel and Ta poison were chosen for heat transfer, neutronics performance, and limited corrosion • Heatpipes eliminate the need for pumps, have excellent heat transfer, and reduce system mass. • Li working fluid operates at high temperatures necessary for power conversion unit, 1800K

  12. Fuel Pin Heatpipe Tricusp Material Core - Design Specifications (2) • Fuel pins are the same size as heatpipes and arranged in tricusp design

  13. 99cm Reflector and Core Top-Down View Reflector Control Drum Reflector 37 cm Core Fuel Fuel Pin Zr3Si2 Reflector Total Mass: 1892kg 10cm Radial Reflector Core - Design Specifications (3) • Reflector controls neutron leakage • Control drums add little mass to the system and offer high reliability due to few moving parts

  14. Core - Future Work • Perform U235 enrichment versus system mass analysis • Investigate further the feasibility of plate fuel element design • Develop comprehensive safety analysis for launch accidents

  15. PCU

  16. PCU – Design Concept Goals: • Remove thermal energy from the core • Produce at least 100kWe • Deliver remaining thermal energy to the radiator Components: • Heat Removal from Core • Power Conversion System • Power Transmission System • Heat Exchanger/Interface with Radiator

  17. PCU – Design Choices • Heat Transfer from Core • Heat Pipes • Power Conversion System • Cesium Thermionics • Power Transmission • DC-to-AC conversion • OOOO gauge Cu wire transmission • Heat Exchanger to Radiator • Annular Heat Pipes

  18. PCU – Design Specifications • Heat Pipes from Core: • 1 meter long • 1 cm diameter • 100 heat pipes • Molybdenum Pipes • Lithium Fluid • Boiling point @ STP: 1615K • Pressurized to boil @ 1800K CORE

  19. PCU - Design Specifications (2) • Thermionic Power Conversion Unit • Mass: 250 kg • Efficiency: 10%+ • 1MWt -> 100kWe • Power density: 10W/cm2 • Surface area per heat pipe: 100 cm2

  20. Reactor PCU - Design Specifications (3) • Power Transmission • D-to-A converter: • 20 x 5000VA units • 300kg total • Small • Transmission Lines: • AC transmission • OOOO gauge Cu wire • 1kg/m

  21. PCU - Decision Specifications (4) • Heat Pipe Heat Exchanger

  22. PCU – Future Work • Improving Thermionic Efficiency • Material behavior in high radiation environment • Heat pipe failure analysis • Scalability to 200kWe • Using ISRU as thermal heat sink

  23. Radiator

  24. Radiator – Design Concept • Need a radiator to dissipate excess heat from a nuclear power plant located on the surface of the Moon or Mars.

  25. Radiator – Design Choices • Evolved from previous designs for space fission systems: • SNAP-2/10A • SAFE-400 • SP-100 • Transfers heat from PCU to heat pipes • Radiates thermal energy into space via large panels

  26. Radiator – Design Choices (2) • Heat pipes send heat to large radiator panels through vaporization of fluid • Heat conducted to panels at the condensing end of the heat pipes • High-emissivity panels use radiation to reject heat to space

  27. Radiator – Design Specifications • Nb-Zr heat pipes with carbon radiator panels • Panels folded vertically next to reactor during transit • For operation panels lay parallel to surface Core PCU Unfolds on surface Panels radiate to environment Radiator Packed for launch

  28. Radiator - Future Work • Mechanical design of radiator panels • Mathematical modeling

  29. Shielding

  30. Shielding - Design Concept • Dose rate on Moon & Mars is ~14 times higher than on Earth • Goal: • Reduce dose rate to between 0.6 - 5.7 mrem/hr • Neutrons and gamma rays emitted, requiring two different modes of attenuation

  31. Shielding - Design Choices Neutron shielding Gamma shielding B4C shell Tungsten shadow shield • Separate reactor from habitat • Dose rate decreases as 1/r2 for r >> 50cm • Use lunar or Martian surface material for further radiation attenuation

  32. Shielding - Constraints • Weight limited by landing module (~3 MT) • Temperature limited by material properties (1800K) Courtesy of Jet Propulsion Laboratory

  33. Shielding - Geometry • Cylindrical shell to attenuate neutrons to target dose within < 50 m • Shadow shield may be more appropriate depending on mission parameters • B4C will be stable up to 2100K • Hydrogenous materials are not viable

  34. Shielding - Future Work • Shielding using extraterrestrial surface material: • On moon, select craters that are navigable and of appropriate size • Incorporate precision landing capability • On Mars, specify a burial technique as craters are less prevalent • Specify geometry dependent upon mission parameters • Shielding modularity, adaptability, etc.

  35. Reactor Mass Breakdown Core: 2.7 MT PCU: 2.05 MT Radiator: 1.5MT Shield: 2 MT ___________________ Total Mass of Reactor – 8.25 Metric Tons Well Below Lander Limit of 15 MT

  36. MSR GroupExpanding Frontiers with Nuclear TechnologyTyler Ellis tyler9@mit.eduMichael Short hereiam@mit.edu

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