Martian surface reactor group december 3 2004
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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


Proposed mission architecture

Habitat

Reactor

Proposed Mission Architecture



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


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