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