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Nuclear Engineering Department
Massachusetts Institute of Technology
Lunar Surface Reactor Group
Progress Report 2Decisions and Models
Lunar Surface Reactor Group
October 25, 2004
LSR Group, 10/25/2004Slide 2
Nuclear Engineering Department
Massachusetts Institute of Technology
Overview – Schedule
• Original schedule: – November 3rd completion date for all models and
decisions.– November 15th finished. Except report
• Revised Schedule– November 3rd completion date for all models and
decisions.– Finish November 22nd.
LSR Group, 10/25/2004Slide 3
Nuclear Engineering Department
Massachusetts Institute of Technology
CORE
LSR Group, 10/25/2004Slide 4
Nuclear Engineering Department
Massachusetts Institute of Technology
Core - Current Status
• Decisions made:
– Zr3Si2 reflector material
– Pin fuel elements
• Decisions to be made this week:
– Heat pipe coolant
– Bounds of operating temperature
– Bounds of geometry
LSR Group, 10/25/2004Slide 5
Nuclear Engineering Department
Massachusetts Institute of Technology
Core - Schedule
Memo - Method of Reflection 27-Oct
Memo - Structural Materials 28-Oct
Deliver - Bounds for Geometry (Shielding) 1-Nov
Memo - Bounds for Geometry (mass) 1-Nov
Deliver - Core Thermo-hydraulics (PCU) 1-Nov
Memo - Control Mechanisms 3-Nov
Memo - Core Thermo-hydraulics 3-Nov
Memo - Preliminary Model 3-Nov
LSR Group, 10/25/2004Slide 6
Nuclear Engineering Department
Massachusetts Institute of Technology
Core - Schedule Post Nov. 3rd
• Accident analysis
– Launch accidents
– Feedback coefficients
– Power transients
• Spatial Model
• Report
LSR Group, 10/25/2004Slide 7
Nuclear Engineering Department
Massachusetts Institute of Technology
PCU
LSR Group, 10/25/2004Slide 8
Nuclear Engineering Department
Massachusetts Institute of Technology
PCU – Current Status
• Decision: Thermionics– Inlet temperature 1800K– Outlet Temperature 950K
• Progress– Thermionic model
• inlet/outlet temperature vs. efficiency– Balance between decent radiator size and generated power
– Heat Pipe model• Heat pipe configuration to ensure 100kWe at appropriate
temperature• Issues to be resolved
– Power Transmission• DC-to-AC conversion?
– Heat Exchanger– ISRU
• Needs– 1800K Core Temperature verification
LSR Group, 10/25/2004Slide 9
Nuclear Engineering Department
Massachusetts Institute of Technology
PCU – Decision Methodology
Brayton Sterling Thermionics
Small Mass and Size (Cost) - 1.35
Actual PCU 2 1 3
Outlet Temperature 3 3 3
Peripheral Systems (i.e. Heat Exchangers, A to D converter) 1 1 1
Launchable/Accident Safe - 1.13
Robust to forces of launch 1 2 3
Fits in rocket 3 3 3
Controllable - 1.14 2 2 2
High Reliability and Limited Maintenance - 1.00
Moving Parts 1 2 3
Radiation Resistant 2 3 1
Single Point Failure 1 2 3
Proven System 2 2 2
Inlet Temperature 3 3 1
Total 23.77 26.55 28.51
LSR Group, 10/25/2004Slide 10
Nuclear Engineering Department
Massachusetts Institute of Technology
PCU - Schedule
Deliverables:Memo - PCU OptionsMemo - PCU TypeDeliver - Output Temperatures Approximation, RadiatorDeliver - Preliminary Lunar Analysis of PCU,
Radiator/ CoreMemo - Scaling OptionsMemo - Scalability Analysis for Mars (Radiator, Core) Memo - Detailed Design; Piping, Vessel, Materials
(Lunar, Mars)
Will meet Nov. 3Finished (1st Draft) Post Nov. 3
LSR Group, 10/25/2004Slide 11
Nuclear Engineering Department
Massachusetts Institute of Technology
Radiator
LSR Group, 10/25/2004Slide 12
Nuclear Engineering Department
Massachusetts Institute of Technology
Radiator – Current Status
• Research of thermal properties of lunar and Martian environments.
• Programming of model for thermal calculations.
• Tabulation of the thermal and mechanical properties of structural and functional materials.
• Compilation of all potential radiator concepts.
LSR Group, 10/25/2004Slide 13
Nuclear Engineering Department
Massachusetts Institute of Technology
Radiator - Schedule
• Application of mission-specific design restrictions to list of radiator concepts. Oct. 27th
• Choice of materials and general structural design. Oct. 29th
• Modeling of radiator concepts. Nov 3rd.
LSR Group, 10/25/2004Slide 14
Nuclear Engineering Department
Massachusetts Institute of Technology
Shielding
LSR Group, 10/25/2004Slide 15
Nuclear Engineering Department
Massachusetts Institute of Technology
Shielding – Current Status
• Gamma and neutron spectrum still unknown so have the following contingencies: (UPDATE 10/24: first spectrum estimate available)
– Neutron flux < ~7*105 neutrons/cm2•sec and thermal• Neglect neutron shielding because reactor dose is less than GCR
dose– Neutron flux > ~7*105 neutrons/cm2•sec but thermal
• Use boron-10– Neutron flux > ~7*105 neutrons/cm2•sec but fast
• Use neutron absorbing metal hydride (e.g. LiH, BH3)– Gamma shielding
• Use lead unless neutron shield is too heavy– If neutron shield is too heavy, use cadmium for neutron and gamma
attenuation
• If neutron/gamma shield too heavy, use surface– (Moon: silicon oxides, Mars: iron oxides; both have similar macroscopic
gamma interaction cross sections)
LSR Group, 10/25/2004Slide 16
Nuclear Engineering Department
Massachusetts Institute of Technology
Shielding – Schedule
• Choose geometry– Ideally, use hemispheric shell– If too heavy, use cylindrical shell and leave axial side
unshielded– If both too heavy, bury core– If burying core is unfeasible for other engineering
conditions, use cylindrical shell with “exclusion zone”• Choose material based on above considerations in light
of newly available spectrum• After above decisions, perform analysis with core group
for shield’s impact on reflection and leakage characteristics (may occur after 11/3)
LSR Group, 10/25/2004Slide 17
Nuclear Engineering Department
Massachusetts Institute of Technology
LSR GroupExpanding Frontiers with Nuclear Technology
The End