Conceptual Design of a Lunar Regolith ClusteredReactor System

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Conceptual Design of a Lunar Regolith
Clustered-Reactor System
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Conceptual Design of a LRCS

• John Darrell BessJohn.Bess_at_inl.gov
• University of UtahCenter for Space Nuclear
  ResearchFebruary 14, 2008

Space Technology and ApplicationsInternational
Forum (STAIF 2008)
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Project Luna Succendo

• Preliminary development of a fast-fission,
  heatpipe-cooled, nuclear reactor that is modular,
  safe, reliable, and can be optimized for
  lunar-base power demand as well as implemented,
  and later evolved, using in situ lunar-regolith
  resources.

Preliminary development of a fast-fission,
heatpipe-cooled, nuclear reactor that is modular,
safe, reliable, and can be optimized for
lunar-base power demand as well as implemented,
and later evolved, using in situ lunar-regolith
resources.
lunar-regolith blanket rock, the layer of
loose,heterogeneous material scattered across
the lunar surface
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Supporting Objectives

• Neutronics analysis with Monte Carlo criticality
  code comparison
• MCNP5 and KENO-VI
• Launch accident characterization analyses
• Sensitivity studies regarding physical lunar
  emplacement
• Uncertainties analysis of variations in lunar
  regolith composition

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Lunar Surface Power

• Sustained human and robotic presence
• Life-support systems
• Communications
• Transportation
• Scientific missions
• Development of innovative spacetechnologies
  andknowledge
• Lunar colonization and in situ resourcemining
  and manufacturing

Eventual development of tourism,
commercialization, and a lunar society ( M )
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Fast-Fission, Heatpipe-Cooled Reactor

• Fast-Fission
• Dense, compact cores
• High fissile loading
• Liquid salt/metal coolant
• Actinide transmutation
• Deeper fuel burnup
• Low corrosion
• Intrinsic safety
• Transient stability

• Heatpipe-Cooling
• High heat transfer rate
• Latent heat
• Faster than conduction
• Wick structure
• Heat source/sink
• Inherent stability

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Power Conversion

• Potassium Boiler
• Stirling Engines
• Optimal for 40 kWe
• Developing 5 kWe free-piston, space convertor for
  NASA

• Heatpipe Radiator
• Redundancy in design
• Fin failure
• Loop failure
• Carbon armor

Heater Head Assembly
Displacer Drive Assembly
Alternator Assembly
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Defining the Reactor

• Additional Components
• Instrumentation and control
• Power management and distribution
• Connection to grid
• Axial shielding and/or reflector
• Lunar regolith shielding
• Lunar regolith reflectors

• lt100 kWt per subunit
• At least 10-yr power lifetime per subunit
• UO2 fuel pellets
• 93 U-235
• 95 TD
• SS-316 cladding
• Sodium (Na) heatpipes
• Distributed core design

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LEGO Reactor Subunit Core

• SS-316 monolithic, hexagonal core
• 2.94-cm (1.16) Pitch
• 23.8-cm (9.37) D
• 43 heatpipes
• 84 fuel pins
• 1.64-cm (0.64) OD

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The Concern for Launch Safety

• Subunit must remain subcritical (keff lt 0.985)
• Prior to launch
• During launch
• Upon accidental impact
• When submerged in moderator and/or reflector
  material
• When immersed in fire
• i.e. Always

• Current methods for maintaining a subcritical
  reactor
• Poison control rods or drums
• Removable beryllium reflectors
• Incorporated spectral shift absorbers (Re, B4C,
  Gd2O3)
• Fuel reactor in-orbit (or on the lunar surface)

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Launch Accident Analyses
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Computational and Data Biases
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gt7 r
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Lunar Regolith Composition
Engineering, Construction and Operations in Space
IV,American Society of Chemical Engineering, pp.
857-866, 1994.
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Rock-Melt Drilling

• Also known as Subterrene or Subselene drilling
• High temperature application with heat pipes to
  melt rock
• Melted material is forced into porous rock
• Results in a glassy finish with no debris
• 4-9 kWth power requirement

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Tri-Cluster, Base-Case Scenario

• JSC-1 composition
• Bulk density 1.8 g/cc
• Melt density 3.1 g/cc
• 2-m drilled depth
• Trace elements and volatiles were not included

• Tri-unit cluster
• Placed with centerline distances of 64 cm
• keff 1
• 24-cm inner diameter of hole
• 37-cm outer diameter of melt

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Tri-Cluster, Base-Case Scenario
Subunits placed 64 cm apart in JSC-1 (keff1)
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Emplacement Code Comparison
Regolith Fill1.6 0.22.50
sk lt 0.2Dkcodes 0.5 0.2
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Iron Variation Comparison
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Lunar Regolith Variation
Global Elemental Maps of the Moon The Lunar
Prospector Gamma-Ray Spectrometer, D.J.
Lawrence, et al., Science, 4, September 1998.
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Conclusions

• A modular, fast-fission, heatpipe-cooled, lunar
  regolith clustered-reactor system has been
  developed
• Some analyses of launch accident scenarios
  demonstrate favorably
• Need additional code comparison analyses for
  accident validation
• Awaiting upcoming code and data library releases

• Tri-cluster emplacement has been characterized
  with both codes
• Iron composition confirmed as dominant
  constituent in regolith
• Further thermodynamic and heat transfer analyses
  necessary to develop final coupled-reactor design

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Lunar Power Supply
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Space Reactor Heritage

• U.S. has launched one SNAP-10A reactor
• Russia has launched over 30 space reactor systems
• Various concepts have been developed over the
  past 50 yrs
• SP-100
• Mars Surface Reactor (MSR)
• Sectored Compact Reactor (SCoRe)
• Safe and Affordable Fission Engine (SAFE)
• Space Nuclear Steam Electric Energy (SUSEE)
• Space Power Annular Reactor System (SPARS)
• Submersion Subcritical Safe Space (S4) Reactor
• Affordable Fission Surface Power System (AFSPS)
• Heatpipe Operated Mars/Moon Exploration Reactor
  (HOMER)

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The Stagnant Cycleof Space Technology
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The One-Size-Fits-All Reactor

• Inexpensive
• Extremely low mass
• Available now
• Continuous power in range of kW MW
• Directly scalable to higher power levels
• Functions under various gravitational and
  environmental conditions

• Functions on any lunar or planetary surface
• Highly reliable with graceful performance
  degradation
• Can support human and robotic missions
• 3-20 yr lifetime without maintenance
• Completely testable on Earth

• Inexpensive
• Extremely low mass
• Available now
• Continuous power in range of kW MW
• Directly scalable to higher power levels
• Functions under various gravitational and
  environmental conditions

• Functions on any lunar or planetary surface
• Highly reliable with graceful performance
  degradation
• Can support human and robotic missions
• 3-20 yr lifetime without maintenance
• Completely testable on Earth

• Inexpensive
• Extremely low mass
• Available now
• Continuous power in range of kW MW
• Directly scalable to higher power levels
• Functions under various gravitational and
  environmental conditions

• Functions on any lunar or planetary surface
• Highly reliable with graceful performance
  degradation
• Can support human and robotic missions
• 3-20 yr lifetime without maintenance
• Completely testable on Earth
• Proliferation resistant

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Lunar Regions of Interest

• Lunar Poles
• H2O?
• Solar extremes
• Imbrium Region
• K, Fe, Ti, Th
• Equatorial Regions
• He-3
• Lunar geology
• Far Side of Moon
• Solar wind and volatiles
• Space telescopes

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Average Atomic Compositions of Lunar Regolith
Samples
G. HEIKEN, D. VANIMAN, and B.M. FRENCH, Lunar
Sourcebook A Users Guide to the Moon,
Cambridge University Press, (1991).
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Average Atomic Compositions of Lunar Regolith
Basalts
G. HEIKEN, D. VANIMAN, and B.M. FRENCH, Lunar
Sourcebook A Users Guide to the Moon,
Cambridge University Press, (1991).
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Average Atomic Compositions of Lunar Regolith
Breccias
G. HEIKEN, D. VANIMAN, and B.M. FRENCH, Lunar
Sourcebook A Users Guide to the Moon,
Cambridge University Press, (1991).
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Average Trace Elements
G. HEIKEN, D. VANIMAN, and B.M. FRENCH, Lunar
Sourcebook A Users Guide to the Moon,
Cambridge University Press, (1991).
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Maximum Trace Elements
G. HEIKEN, D. VANIMAN, and B.M. FRENCH, Lunar
Sourcebook A Users Guide to the Moon,
Cambridge University Press, (1991).
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Regolith Sample Sites
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Lunar ExplorationPast, Present, Future

• Ranger Program
• Lunar Impact
• Lunar Orbiter Program
• Sightseeing
• Surveyor Program
• Soft Landing
• Apollo Program
• Human Spaceflight
• Luna (Lunik) Programme
• Russian Missions
• Lunar Prospector
• And Many More

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Technological Assumptions

• Deployable using existing or proposed launch
  vehicles
• Robotic or human assembly capabilities
• Rock-melt drilling
• Microwave sintering
• Use control, power, radiator, and transmission
  systems already developed

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Launch Vehicles
Faring Limits10.5-m H, 7.5-m D
Faring Limitslt13.8-m H, lt5-m D

• Current (7-9 mT)
• Delta IV Heavy
• Atlas V Heavy Launch Vehicle (HLV)

• Proposed (20-21 mT)
• NASAs Exploration System Architecture Study
  (ESAS)

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Stirling Engines

• External combustion piston engine
• 25 efficiency
• 12.5 kWe units
• Developing 50 kWe units
• Operate by repeated heating and cooling of a
  sealed gas

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Microwave Sintering

• Effective and efficient heating and sintering of
  ceramic objects
• Fine Fe-metal dust particles
• Reduces local lunar dust
• Lunar Lawn mower

Microwave Sintering of Lunar Soil Properties,
Theory, and PracticeL.A. Taylor and T.T. Meek,
J Aero Eng, 18( 3) 188-196 July 2005.
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Primary Subunit Dimensions

• 49-cm (19) fueled height
• 106-cm (42) heatpipe extension from core
• 170-cm (67) primary subunit length

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Basic Analyses

• Coolant void effects nonexistent
• Na, K, NaK coolant neutronically interchangeable
• Subunit rotation insignificant
• Trace Elements
• Ave 0.4-0.8 Dr
• Max 2.7-3.0 Dr

• Doppler effect slightly negative due to small
  quantities of U-238 in fuel
• Moderator effect slightly positive
• Geometrically delayed neutrons
• Lunar surface acts as large thermal sink

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Subunit Emplacement

• Basic centerline placement
• 37 to 100 cm distances between all three units
• Void, water, or loose regolith fill (r1.3 g/cc)
  around reactor and heatpipes
• X-, Y-, and Z-deviations of single subunit

• Drilled hole radius
• 12 to 21 cm
• Melt radius predicted by the following
  equation
• Avoided melt interaction between holes

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Effects of Tri-Cluster Emplacement
1.7 0.22.70
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Rock-Melt Reflector Worth

4 - 57.15
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X-Deviation of a Single Subunit
No significant change in reactivity in the Y or Z
directions
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Effect of Drilled Hole Radius
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Variability of the Lunar Regolith

• Bulk density 1.2 1.92 g/cc
• Melt density 2.6 3.6 g/cc
• Compositional analysis of major constituents of
  samples from various Apollo and Luna missions

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Variations in the Bulk and Melt Densities of the
Lunar Regolith
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Variation in Regolith Iron
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Variation in Regolith Titanium
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Variation in Regolith Aluminum
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Variation in Regolith Oxygen
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30 kWe Hexagonal Cluster

• Similar hole and regolith characteristics as
  tri-cluster arrangement
• Average trace element composition included
• Subunits placed 60-cm apart
• 10-cm diameter, interstitial B4C control rods to
  determine controllability of complete reactor
  system

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Effects of Hexagonal Emplacement
sk lt 0.2Dkfill 0.5 0.2
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Estimated Mass of Single Subunit
Each subunit contains 88 kg HEU. Maximum
shielding mass would not increase total mass
above 1 metric ton.
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Specific Mass Comparison
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Physical Dimensions
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Coupling Analysis

• Averys coupling coefficients
• Coefficients determined between all units in the
  hexagonal cluster
• Adjacent kij 0.11210.0025
• 2-Away kij 0.13740.0026
• Cross-Cluster kij 0.14110.0025
• Infinite coupling kij 0.14960.0025
• Reactor system is very loosely coupled

Tightly coupled systems typically have kij values
in the thousandths decimal place.
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Drafting Board ? Launch Pad

• Thorough thermodynamic and heat transfer analysis
• Ground testing
• Confirmation of final design for flight testing
• Safety and security measures

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Linearly Coupled Subunits
60-cm apart
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Extended Tri-Cluster Coupling
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Averys Coupling Coefficients

• DEFINITIONS
• For a system of N coupled reactors
• kij is the expectation that a neutron from
  reactor i causes a fission in reactor j
• Si is the total system neutron source
• kex is the excess reactivity of the system
• Di is the measure of subcriticality of a reactor

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Averys Coupling Coefficients
i
j
k
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Coupling the LEGO Reactor
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Uniqueness of the Reactor Design

• Lunar regolith functions as both shielding and
  reflector material
• Reactor subunits are subcritical in design
• Potential for unlimited reactor lifetime and
  power level
• Modularity

• Decreased neutron fluence reduced material
  damage
• Reduced thermal loads
• Failure of single subunit does not cause complete
  reactor failure
• Versatility in placement of new reactor systems
• Potential for Lunar evolution of design (in situ)

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LEGO Reactor Evolution

• Fuels Development
• Nitride Fuels
• U-233, Cm-245/-244
• Reactor Control
• B4C Tri-Shades
• Axial Reflectors/Shielding
• Be or BeO
• Hydride Material

• Cladding Development
• Refractory Metals
• Tungsten-Cermet
• Waste-Heat Rejection
• Liquid Droplet Radiators
• Regolith Heat Sink
• Thermophotovoltaics

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Potential Applications

• Non-Lunar, Extraterrestrial Surfaces
• Mars, Mercury, Moons, Asteroids
• Symbiosis with Lunar Manufacturing
• Thorium Breeding

• Irradiation Research and Development
• Neutron Flux-Trap
• Radioisotope Breeding
• Component Testing
• Regolith Analyses
• Terrestrial Develop of Modular Reactors for Rural
  and Developing Areas

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Lunar Power Expansion
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Conclusions

• A modular, fast-fission, heatpipe-cooled, lunar
  regolith clustered-reactor system was developed
• Uncertainties in regolith composition and
  emplacement has been characterized
• Narrow, deep holes
• Iron composition
• Subterrene lining
• Non-nuclear reactor component studies needed to
  develop axial reflector and/or shielding

• Launch accident scenarios demonstrate favorably
  yet need additional code comparison analyses
• Awaiting next code and data library releases
• Preliminary mass and volume estimates are
  favorable for a lunar reactor design
• Technological advancements will produce more
  competitive design
• Further thermodynamic and heat transfer analyses
  necessary to develop final LEGO reactor design

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