1. Nuclear Engineering Department Massachusetts Institute of Technology L unar S urface R eactor Group Progress Report 2 Decisions and Models Lunar Surface Reactor Group October 25, 2004

2. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 2 Overview – Schedule Original schedule: –November 3 rd completion date for all models and decisions. –November 15 th finished. Except report Revised Schedule –November 3 rd completion date for all models and decisions. –Finish November 22 nd.

3. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 3 CORE

4. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 4 Core - Current Status Decisions made: –Zr 3 Si 2 reflector material –Pin fuel elements Decisions to be made this week: –Heat pipe coolant –Bounds of operating temperature –Bounds of geometry

5. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 5 Core - Schedule Memo - Method of Reflection27-Oct Memo - Structural Materials28-Oct Deliver - Bounds for Geometry (Shielding)1-Nov Memo - Bounds for Geometry (mass)1-Nov Deliver - Core Thermo-hydraulics (PCU)1-Nov Memo - Control Mechanisms3-Nov Memo - Core Thermo-hydraulics3-Nov Memo - Preliminary Model3-Nov

6. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 6 Core - Schedule Post Nov. 3rd Accident analysis –Launch accidents –Feedback coefficients –Power transients Spatial Model Report

7. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 7 PCU

8. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 8 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

9. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 9 PCU – Decision Methodology BraytonSterlingThermionics Small Mass and Size (Cost) - 1.35 Actual PCU213 Outlet Temperature333 Peripheral Systems (i.e. Heat Exchangers, A to D converter)111 Launchable/Accident Safe - 1.13 Robust to forces of launch123 Fits in rocket333 Controllable - 1.14222 High Reliability and Limited Maintenance - 1.00 Moving Parts123 Radiation Resistant231 Single Point Failure123 Proven System222 Inlet Temperature331 Total23.7726.5528.51

10. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 10 PCU - Schedule Deliverables: Memo - PCU Options Memo - PCU Type Deliver - Output Temperatures Approximation, Radiator Deliver - Preliminary Lunar Analysis of PCU, Radiator/ Core Memo - Scaling Options Memo - Scalability Analysis for Mars (Radiator, Core) Memo - Detailed Design; Piping, Vessel, Materials (Lunar, Mars) Will meet Nov. 3Finished (1 st Draft)Post Nov. 3

11. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 11 Radiator

12. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 12 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.

13. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 13 Radiator - Schedule Application of mission-specific design restrictions to list of radiator concepts. Oct. 27 th Choice of materials and general structural design. Oct. 29 th Modeling of radiator concepts. Nov 3 rd.

14. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 14 Shielding

15. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 15 Shielding – Current Status Gamma and neutron spectrum still unknown so have the following contingencies: (UPDATE 10/24: first spectrum estimate available) –Neutron flux < ~7*10 5 neutrons/cm 2 sec and thermal Neglect neutron shielding because reactor dose is less than GCR dose –Neutron flux > ~7*10 5 neutrons/cm 2 sec but thermal Use boron-10 –Neutron flux > ~7*10 5 neutrons/cm 2 sec but fast Use neutron absorbing metal hydride (e.g. LiH, BH 3 ) –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)

16. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 16 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)

17. Nuclear Engineering Department Massachusetts Institute of Technology LSR Group, 10/25/2004 Slide 17 LSR Group Expanding Frontiers with Nuclear Technology The End