1. Nuclear Engineering Department Massachusetts Institute of Technology M artian S urface R eactor Group Martian Surface Reactor Group December 3, 2004

2. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 2 Motivation for Mars “We need to see and examine and touch for ourselves” “…and create a new generation of innovators and pioneers.”

3. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 3 Motivation for MSR

4. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 4 Nuclear Physics/Engineering 101

5. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 5 Nuclear Physics/Engineering 101

6. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 6 Goals Litmus Test –Works on Moon and Mars –100 kWe –5 EFPY –Obeys Environmental Regulations –Safe Extent-To-Which Test –Small Mass and Size –Controllable –Launchable/Accident Safe –High Reliability and Limited Maintenance –Scalability

7. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 7 MSR Components Core –Nuclear Components, Heat Power Conversion Unit –Electricity, Heat Exchange Radiator –Waste Heat Rejection Shielding –Radiation Protection

8. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 8 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

9. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 9 Proposed Mission Architecture HabitatReactor

10. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 10 CORE

11. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 11 Core - Design Concept Design criteria: –100 kWe reactor on one rocket –5 EFPY –Low mass –Safely Launchable –Maintenance Free and Reliable

12. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 12 Core - Design Choices Fast Spectrum, High Temp Ceramic Fuel – Uranium Nitride, 33.1 w / o enriched Lithium Heatpipe Coolant Tantalum Burnable Poison Hafnium Core Vessel External Control By Drums Zr 3 Si 2 Reflector material TaB 2 Control material Fuel Pin Elements in tricusp configuration

13. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 13 Heatpipe Fuel Pin Tricusp Material Core - Pin Geometry Fuel pins are the same size as the heat pipes and arranged in tricusp design.

14. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 14 Core – Design Advantages UN fuel, Ta poison, Re Clad/Structure high melting point, heat transfer, neutronics performance, and limited corrosion Heat pipes no pumps, excellent heat transfer, reduce system mass. Li working fluid operates at high temperatures necessary for power conversion unit (1800 K)

15. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 15 Core – Reactivity Control Reflector controls neutron leakage Control drums add little mass to the system and offer high reliability due to few moving parts Radial Reflector Control Drum Reflector and Core Top-Down View Reflect or Core Fuel Pin Fuel Reflector Zr 3 Si 2 Reflector Total Mass: 2654kg 42 cm 88 cm 10 cm Reflector

16. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 16 Core - Smear Composition

17. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 17 Core - Power Peaking

18. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 18 Operation over Lifetime BOL k eff : 0.975 – 1.027 EOL k eff : 0.989 – 1.044 = 0.052 = 0.055

19. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 19 Launch Accident Analysis Worst Case Scenarios: –Oceanic splashdown assuming Non-deformed core All heat pipes breached and flooded –Dispersion of all 235 U inventory in atmosphere

20. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 20 Launch Accident Results Reflectors StowedReflectors Detached WaterK eff =0.97081±0.00092K eff =0.95343±0.00109 Wet SandK eff =0.97387±0.00095K eff =0.96458±0.00099 Total dispersion of 235 U inventory (104 kg) will increase natural background radiation by 0.024% Inadvertent criticality will not occur in any conceivable splashdown scenario

21. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 21 Core Summary UN fuel, Re clad/structure, Ta poison, Hf vessel, Zr 3 Si 2 reflector Low burn, 5+ EFPY at 1 MW th, ~100 kW e, Autonomous control by rotating drums over entire lifetime Flat temperature profile at 1800K Subcritical for worst-case accident scenario

22. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 22 Future Work Investigate further the feasibility of plate fuel element design Optimize tricusp core configuration Examine long-term effects of high radiation environment on chosen materials

23. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 23 PCU

24. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 24 PCU – Mission Statement Goals: –Remove thermal energy from the core –Produce at least 100kWe –Deliver remaining thermal energy to the radiator –Convert electricity to a transmittable form Components: –Heat Removal from Core –Power Conversion/Transmission System –Heat Exchanger/Interface with Radiator

25. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 25 PCU – Design Choices Heat Transfer from Core –Heat Pipes Power Conversion System –Cesium Thermionics Power Transmission –DC-to-AC conversion –22 AWG Cu wire transmission bus Heat Exchanger to Radiator –Annular Heat Pipes

26. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 26 PCU – Heat Extraction from Core Heat Pipes from Core: –127 heat pipes –1 meter long –1 cm diameter –Rh wall & wick –400 mesh wick –0.5mm annulus for liquid –Li working fluid is Pressurized to boil @ 1800K

27. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 27 PCU – Heat Pipes (2) Possible Limits to Flow –Entrainment –Sonic Limit –Boiling –Freezing –Capillary Capillary force limits flow:

28. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 28 PCU - Thermionics Thermionic Power Conversion Unit –Mass: 240 kg –Efficiency: 10%+ 1.2MWt -> 125kWe –Power density: 10W/cm 2 –Surface area per heat pipe: 100 cm 2

29. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 29 PCU – Thermionics Design

30. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 30 PCU - Thermionics Issues & Solutions –Creep @ high temp Set spacing at 5 mm Used ceramic spacers –Cs -> Ba conversion due to fast neutron flux 0.01% conversion expected over lifetime –Collector back current T E = 1800K, T C = 950K

31. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 31 PCU – Power Transmission –D-to-A converter: 25 x 5kVA units 360kg total Small –Transmission Lines: AC transmission 25 x 22 AWG Cu wire bus 500kg/km total 83.5:1 Transformers increase voltage to 10,000V –1,385kg total for conversion/transmission system

32. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 32 PCU – Heat Exchanger to Radiator Heat Pipe Heat Exchanger

33. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 33 PCU – Failure Analysis Very robust system –Large design margins in all components –Failure of multiple parts still allows for ~90% power generation & full heat extraction from core No possibility of single-point failure –Each component has at least 25 separate, redundant pieces Maximum power loss due to one failure – 4% Maximum cooling loss due to one failure – 0.79%

34. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 34 PCU – Future Work Improving Thermionic Efficiency Material studies in high radiation environment Scalability to 200kWe and up Using ISRU as thermal heat sink

35. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 35 Radiator

36. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 36 Objective Design a radiator to dissipate excess heat from a nuclear power plant located on the surface of the Moon or Mars.

37. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 37 Goals Small mass and area Minimal control requirement Maximum accident safety High reliability

38. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 38 Decision Methodology Past Concepts –SP-100 –SAFE-400 –SNAP-2 –SNAP-10A –Helium-fed –Liquid Droplet –Liquid Sheet

39. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 39 Component Design Heat pipes –Carbon-Carbon shell –Nb-1Zr wick –Potassium fluid Panel –Carbon-Carbon composite –SiC coating

40. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 40 Structural Design Dimensions –Height 3 m –Diameter 4.8 m –Area 39 m 2 Mass –Panel 200 kg –Heat pipes 60 kg –Supports 46 kg

41. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 41 Support Supports –Titanium –8 radial beams –3 circular strips

42. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 42 Analysis Models –Isothermal –Linear Condenser Comparative Area –Moon 39 m 2 –Mars 38.6 m 2

43. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 43 Future Analysis of transients Model heat pipe operation Conditions at landing site Manufacturing

44. Nuclear Engineering Department Massachusetts Institute of Technology M artian S urface R eactor Group Shielding

45. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 45 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

46. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 46 Shielding - Constraints Weight limited by landing module (~2 MT) Temperature limited by material properties (1800K) Courtesy of Jet Propulsion Laboratory

47. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 47 Shielding - Design Choices Neutron shielding Gamma shielding boron carbide (B 4 C) shell (yellow) Tungsten (W) shell (gray) 40 cm12 cm Total mass is 1.97 MT Separate reactor from habitat –Dose rate decreases as 1/r 2 for r >> 50cm - For r ~ 50 cm, dose rate decreases as 1/r

48. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 48 Shielding - Dose w/o shielding Near core, dose rates can be very high Most important component is gamma radiation

49. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 49 Shielding - Neutrons MaterialReason for Rejection Z > 5Inefficient neutron slowing; too heavy H2OH2OToo heavy LiToo reactive LiHMelting point of 953 K BBrittle; would not tolerate launch well B 4 CAlPossible; heavy, needs comparison w/ other options

50. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 50 Shielding - Neutrons (2) MaterialMaximum thickness for 1 MT shield (cm) Dose Rate at shielding edge (mrem/hr) Dose rate at 10 m (mrem/hr) UnshieldedN/A2.40*10 7 26.8*10 3 Boral (B 4 CAl)20.31.24*10 5 323.2 Borated Graphite (BC) 22.74.28*10 4 111.1 Boron Carbide (B 4 C) 21.13.57*10 4 92.9

51. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 51 Shielding - Neutrons (3) One disadvantage: boron will be consumed

52. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 52 Shielding - Gammas MaterialReason for Rejection Z < 72 Too small density and/or mass attenuation coefficient Z > 83 Unstable nuclei Pb, Bi Possible, but have low melting points Re, Ir Difficult to obtain in large quantities Os Reactive Hf, Ta Smaller mass attenuation coefficients than alternatives

53. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 53 Shielding - Gammas (2) MaterialMaximum thickness for 3 MT shield (cm) Dose rate at 90 cm (mrem/hr) UnshieldedN/A2.51*10 6 Pb17.1594.66 Bi19.4599.88 W10.6480.00

54. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 54 Shielding - Gammas (3) Depending on mission parameters, exclusion zone can be implemented

55. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 55 Shielding - Design Two pieces, each covering 40º of reactor radial surface Two layers: 40 cm B 4 C (yellow) on inside, 12 cm W (gray) outside Scalable –@ 200 kW(e) mass is 2.19 metric tons –@ 50 kW(e), mass is 1.78 metric tons

56. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 56 Shielding - Design (2) For mission parameters, pieces of shield will move –Moves once to align shield with habitat –May move again to protect crew who need to enter otherwise unshielded zones

57. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 57 Shielding - Alternative Designs Three layer shield –W (thick layer) inside, B 4 C middle, W (thin layer) outside –Thin W layer will stop secondary radiation in B 4 C shield –Putting thick W layer inside reduces overall mass

58. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 58 Shielding -Alternative Designs (2) -The Moon and Mars have very similar attenuation coefficients for surface material -Would require moving 32 metric tons of rock before reactor is started

59. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 59 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.

60. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 60 MSR Assembly Sketch Breathtaking Figures Goes Here

61. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 61 MSR Mass Bottom Line: ~80g/We

62. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 62 MSR Cost Rhenium Procurement and Manufacture Nitrogen-15 Enrichment Halfnium Procurement

63. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 63 Mass Reduction Move reactor 2km away from people –Gain 500kg from extra transmission lines –Loose almost 2MT of shielding Use ISRU plant as a thermal sink –Gain mass of heat pipes to transport heat to ISRU (depends on the distance of reactor from plant) –Loose 360kg of Radiator Mass Bottom Line: ~60g/We

64. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 64 MRS Design Advantages Robustness Safety Redundancy Scalability

65. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 65 MSR Mission Plan Build and Launch –Prove Technology on Earth Earth Orbit Testing –Post Launch Diagnostics Lunar / Martian Landing and Testing –Post Landing Diagnostics Startup Shutdown

66. Nuclear Engineering Department Massachusetts Institute of Technology MSR Group, 12/3/2004 Slide 66 MSR Group Expanding Frontiers with Nuclear Technology “The fascination generated by further exploration will inspire…and create a new generation of innovators and pioneers.” ~President George W. Bush