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Martian Surface Reactor Group December 3, 2004. Motivation for Mars. “We need to see and examine and touch for ourselves” “…and create a new generation of innovators and pioneers.”. Motivation for MSR. Nuclear Physics/Engineering 101. Nuclear Physics/Engineering 101. Goals.

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motivation for mars
Motivation for Mars
  • “We need to see and examine and touch for ourselves”
  • “…and create a

new generation of

innovators and pioneers.”

goals
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
msr components
MSR Components
  • Core
    • Nuclear Components, Heat
  • Power Conversion Unit
    • Electricity, Heat Exchange
  • Radiator
    • Waste Heat Rejection
  • Shielding
    • Radiation Protection
msr mission
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
core design concept
Core - Design Concept
  • Design criteria:
    • 100 kWe reactor on one rocket
    • 5 EFPY
    • Low mass
    • Safely Launchable
    • Maintenance Free and Reliable
core design choices
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
  • Zr3Si2 Reflector material
  • TaB2 Control material
  • Fuel Pin Elements in tricusp configuration
core pin geometry

Fuel Pin

Heatpipe

Tricusp Material

Core - Pin Geometry
  • Fuel pins are the same size as the heat pipes and arranged in tricusp design.
core design advantages
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)
core reactivity control

88 cm

Fuel Pin

Reflector and Core Top-Down View

10 cm

Reflector

Control Drum

Reflector

42 cm

Fuel

Core

10 cm

Reflector

Zr3Si2 Reflector

Total Mass: 2654kg

Radial Reflector

Core – Reactivity Control
  • Reflector controls neutron leakage
  • Control drums add little mass to the system and offer high reliability due to few moving parts
operation over lifetime
Operation over Lifetime

BOL keff: 0.975 – 1.027

= 0.052

EOL keff: 0.989 – 1.044

= 0.055

launch accident analysis
Launch Accident Analysis
  • Worst Case Scenarios:
    • Oceanic splashdown assuming
      • Non-deformed core
      • All heat pipes breached and flooded
    • Dispersion of all 235U inventory in atmosphere
launch accident results
Launch Accident Results
  • Total dispersion of 235U inventory (104 kg) will increase natural background radiation by 0.024%
  • Inadvertent criticality will not occur in any conceivable splashdown scenario
core summary
Core Summary
  • UN fuel, Re clad/structure , Ta poison, Hf vessel, Zr3Si2 reflector
  • Low burn, 5+ EFPY at 1 MWth, ~100 kWe,
  • Autonomous control by rotating drums over entire lifetime
  • Flat temperature profile at 1800K
  • Subcritical for worst-case accident scenario
future work
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
pcu mission statement
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
pcu design choices
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
pcu heat extraction from core
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
pcu heat pipes 2
PCU – Heat Pipes (2)
  • Possible Limits to Flow
    • Entrainment
    • Sonic Limit
    • Boiling
    • Freezing
    • Capillary
  • Capillary force limits flow:
pcu thermionics
PCU - Thermionics
  • Thermionic Power Conversion Unit
    • Mass: 240 kg
    • Efficiency: 10%+
      • 1.2MWt -> 125kWe
    • Power density:

10W/cm2

    • Surface area

per heat pipe:

100 cm2

pcu thermionics issues solutions
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
    • TE = 1800K, TC = 950K
pcu power transmission
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
pcu heat exchanger to radiator
PCU – Heat Exchanger to Radiator
  • Heat Pipe Heat Exchanger
pcu failure analysis
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%
pcu future work
PCU – Future Work
  • Improving Thermionic Efficiency
  • Material studies in high radiation environment
  • Scalability to 200kWe and up
  • Using ISRU as thermal heat sink
objective
Objective
  • Design a radiator to dissipate excess heat from a nuclear power plant located on the surface of the Moon or Mars.
goals1
Goals
  • Small mass and area
  • Minimal control requirement
  • Maximum accident safety
  • High reliability
decision methodology
Decision Methodology
  • Past Concepts
    • SP-100
    • SAFE-400
    • SNAP-2
    • SNAP-10A
    • Helium-fed
    • Liquid Droplet
    • Liquid Sheet
component design
Component Design
  • Heat pipes
    • Carbon-Carbon shell
    • Nb-1Zr wick
    • Potassium fluid
  • Panel
    • Carbon-Carbon composite
    • SiC coating
structural design
Structural Design
  • Dimensions
    • Height 3 m
    • Diameter 4.8 m
    • Area 39 m2
  • Mass
    • Panel 200 kg
    • Heat pipes 60 kg
    • Supports 46 kg
support
Support
  • Supports
    • Titanium
    • 8 radial beams
    • 3 circular strips
analysis
Analysis
  • Models
    • Isothermal
    • Linear Condenser
  • Comparative Area
    • Moon 39 m2
    • Mars 38.6 m2
future
Future
  • Analysis of transients
  • Model heat pipe operation
  • Conditions at landing site
  • Manufacturing
shielding design concept
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
shielding constraints
Shielding - Constraints
  • Weight limited by landing module (~2 MT)
  • Temperature limited by material properties (1800K)

Courtesy of Jet Propulsion Laboratory

shielding design choices
Shielding - Design Choices

Neutron shielding Gamma shielding

boron carbide (B4C) shell (yellow) Tungsten (W) shell (gray)

40 cm 12 cm

  • Total mass is 1.97 MT
  • Separate reactor from habitat
    • Dose rate decreases as

1/r2 for r >> 50cm

- For r ~ 50 cm, dose rate decreases as 1/r

shielding dose w o shielding
Shielding - Dose w/o shielding
  • Near core, dose rates can be very high
  • Most important component is gamma radiation
shielding neutrons 3
Shielding - Neutrons (3)
  • One disadvantage: boron will be consumed
shielding gammas 3
Shielding - Gammas (3)
  • Depending on mission parameters, exclusion zone can be implemented
shielding design
Shielding - Design
  • Two pieces, each covering 40º of reactor radial surface
  • Two layers: 40 cm B4C (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
shielding design 2
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
shielding alternative designs
Shielding - Alternative Designs
  • Three layer shield
    • W (thick layer) inside, B4C middle, W (thin layer) outside
    • Thin W layer will stop secondary radiation in B4C shield
    • Putting thick W layer inside reduces overall mass
shielding alternative designs 2
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
shielding future work
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.
msr assembly sketch
MSR Assembly Sketch
  • Breathtaking Figures Goes Here
msr mass
MSR Mass

Bottom Line: ~80g/We

msr cost
MSR Cost
  • Rhenium Procurement and Manufacture
  • Nitrogen-15 Enrichment
  • Halfnium Procurement
mass reduction
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

mrs design advantages
MRS Design Advantages
  • Robustness
  • Safety
  • Redundancy
  • Scalability
msr mission plan
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
msr group expanding frontiers with nuclear technology
MSR GroupExpanding 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