Nuclear Engineering Department Massachusetts Institute of Technology M artian S urface R eactor Group Nuclear Reactors for The Moon and Mars Tyler Ellis Michael Short Martian Surface Reactor Group November 14, 2004

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 2 MSR Motivation

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 3 Nuclear Physics/Engineering 101

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 4 Nuclear Physics/Engineering 101

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 5 Proposed Mission Architecture HabitatReactor

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 7 MSR Components Core –Nuclear Components, Heat Power Conversion Unit –Electricity, Heat Exchange Radiator –Waste Heat Rejection Shielding –Radiation Protection

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 8 CORE

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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 Zr 3 Si 2 Reflector material TaB 2 Control material

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 12 Core - Design Specifications (2) Fuel pins are the same size as heatpipes and arranged in tricusp design Heatpipe Fuel Pin Tricusp Material

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 13 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 Reflector Core Fuel Pin Fuel Reflector Zr 3 Si 2 Reflector Total Mass: 1892kg 37 cm 99cm 10cm Radial Reflector Control Drum Reflector and Core Top-Down View

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 14 Core - Future Work Perform U 235 enrichment versus system mass analysis Investigate further the feasibility of plate fuel element design Develop comprehensive safety analysis for launch accidents

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 15 PCU

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 18 PCU – Design Specifications Heat Pipes from Core: –1 meter long –1 cm diameter –100 heat pipes –Molybdenum Pipes –Lithium Fluid Boiling STP: 1615K Pressurized to 1800K CORE

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 19 PCU - Design Specifications (2) Thermionic Power Conversion Unit –Mass: 250 kg –Efficiency: 10%+ 1MWt -> 100kWe –Power density: 10W/cm 2 –Surface area per heat pipe: 100 cm 2

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 20 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 Reactor

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 21 PCU - Decision Specifications (4) Heat Pipe Heat Exchanger

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 23 Radiator

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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.

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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 Unfolds on surface Packed for launch Panels radiate to environment Core PCU Radiator

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 28 Radiator - Future Work Mechanical design of radiator panels Mathematical modeling

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 29 Shielding

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 30 Shielding - Design Concept Dose rate on Moon & Mars is ~14 times higher than on Earth Goal: –Reduce dose rate to between mrem/hr Neutrons and gamma rays emitted, requiring two different modes of attenuation

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 31 Shielding - Design Choices Neutron shielding Gamma shielding B 4 C shell Tungsten shadow shield Separate reactor from habitat –Dose rate decreases as 1/r 2 for r >> 50cm Use lunar or Martian surface material for further radiation attenuation

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 32 Shielding - Constraints Weight limited by landing module (~3 MT) Temperature limited by material properties (1800K) Courtesy of Jet Propulsion Laboratory

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 33 Shielding - Geometry Cylindrical shell to attenuate neutrons to target dose within < 50 m Shadow shield may be more appropriate depending on mission parameters B 4 C will be stable up to 2100K Hydrogenous materials are not viable

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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.

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 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

Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 11/14/2004 Slide 36 MSR Group Expanding Frontiers with Nuclear Technology Tyler Michael