LIST OF FIGURES

Figure 1-1 Composite Axial TFE Power Profile 1-5
Figure 1-2 Data From FC-l on Peak Power Vs. Core Location 1-7
Figure 1-3 Relative Power Distribution (Local Power/Core Average Power) 1-8
Figure 1-4 Relative Power Vs. U-235 Loading 1-9
Figure 1-5 Individual Cell Cesium Optimums 1-13

Figure 2-1 High Pressure Helium Flow Data 2-15
Figure 2-2 Flow in Glass Tube at Low Pressures 2-16
Figure 2-3 Port Flow at Low Helium Pressures 2-17
Figure 2-4 Port Flow at Low Xenon Pressures 2-18
Figure 2-5 Cesium Flow Rate Data 2-21
Figure 2-6 Cesium Distribution in Port and Exit Tube Section After Hot Flow Test 2-23
Figure 2-7 Microstructures of the Tungsten Cladding of a Carbide Fueled Prototype Emitter after Biaxial Creep Tests at 2000°K and 60 psi Helium Pressure for 2000 hours and 120 psi Helium Pressure for 1000 hours. 2-27
Figure 2-8 ER Sampling Cells 2-29
Figure 2-9 Liquid Nitrogen Trapped WF₆ Sampling System 2-30
Figure 2-10 Typical Infrared Absorption Curve 2-31
Figure 2-11 Scanning Electron Photomicrograph of a Fractured Y₂O₃-6% La₂O₃ Surface at 2000X 2-35
Figure 2-12 Scanning Electron Photomicrograph of a Fractured Y₂O₃-10% Ho₂O₃ Surface at 100X 2-36
Figure 2-13 Photomicrograph of a Cross-Section of Multilayer Y₂O₃ -(Y₂O₃ + Nb) Ceramic-to-Metal seal at l00X before Autoclave Densification. 2-38
Figure 2-14 Photomicrograph of a Cross-Section of Multilayer Al₂O₃ -(Al₂O₃ + Nb) Ceramic-to-Metal Seal at l00X Before Autoclave Densification 2-39
Figure 2-15 Scanning Electron Micrograph at 10,000X of a Fractured Surface of an Al₂O₃ -30%W Cermet after a 2-Hour, 1473°K Thermal Treatment 2-42

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Figure 2-16 Scanning Electron Photomicrograph at 5000X of a Fractured Surface of an Al₂O₃-12% Pr₂O₃ Sample 2-43
Figure 2-17 Log of Resistivity Versus Time for Selected Trilayer Samples 2-45
Figure 2-18 Scanning Electron Micrograph at 2000X of a Fracture Ceramic Surface of a Graded Nb-A1₂O₃-Nb Trilayer after a 1073° K, 1514 hr test with and without a 10 VDC Potential Across the Trilayer 2-46
Figure 2-19 Scanning Electron Micrograph at 2000X of a Fractured Ceramic Surface of a TECO Al₂O₃-30% Nb Cermet with and without a 10 VDC Potential Across the Trilayer 2-47
Figure 2-20 Scanning Electron Micrograph at l000X of a Fractured Ceramic Surface of an Nb-Y₂O₃-Nb Graded Trilayer with and without a 10 VDC Potential Across the Trilayer 2-48
Figure 2-21 (a) Bright Field and (b) Polarized Light Photo- micrographs of a Cross-Section of a Mach 3 Plasma Sprayed Alumina Coating at 250X 2-49
Figure 2-22 Scanning Electron Photomicrographs at 2000X of a Plasma Sprayed Alumina Surface (a) Before and (b) After Sealing the Surface with Sputtered Al₂O₃ 2-51
Figure 2-23 Scanning Electron Micrographs at 5000X of Sputtered Alumina Applied to a Substrate Heated to (a) 425°K and (b) 750°K 2-52
Figure 2-24 Transmission Electron Micrograph at 19,720X of an Amorphous, Sputter Coated A1₂0₃ Coating (a) Before and (b) After a 2 hour, 1473°K Thermal Soak 2-53
Figure 2-25 Compression Test, Ceramic-to-Metal Seals Before and After Sputter Coating with Al₂O₃ 2-56
Figure 2-26 Scale Layout of Emitter In FC-3 2-68
Figure 2-27 Capsule Temperatures 2-69
Figure 2-28 Fuel Clad Thermal Analysis for FC-3 Capsule 2-70
Figure 2-29 Fuel Design for Cell No. 1 of FC-4 Capsule 2-73
Figure 2-30 Fuel Design for Cell No. 2 of FC-4 Capsule 2-74
Figure 2-31 Fuel Design for Cell No. 3 of FC-4 Capsule 2-75

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Figure 2-32 Typical Example Illustrating Cracks in the Cladding of 6F1 Emitters. (Emitter No. 4, 2X) 2-78
Figure 2-33 Longitudinal Cross Section of No. 1 Emitter of TFE 6F1 (5X) 2-80
Figure 2-34 Longitudinal Cross Section of No. 3 Emitter of TFE 6F1 (5X) 2-81
Figure 2-35 Typical Macroscopic View of Fuel-Cladding Interaction Layer (Emitter No. 1, 30X) 2-82
Figure 2-36 Typical Microscopic View of Fuel-Cladding Interaction Layer (Emitter No. 3, 75X) 2-83
Figure 2-37 Typical Fuel Microstructures in TFE, 6F1 (Emitter No. 2, 100X), Showing High Degree of Porosity 2-84
Figure 2-38 Fuel Material Near Cladding of the Bottom of Emitter No. 1 of TFE 6F1, Showing Absence of Segregation of Tungsten-Containing Phase (150X) 2-85
Figure 2-39 Grain Growth in Fluoride Tungsten and Porosities at Grain Boundary of Tungsten Cladding of Emitter No. 2 of TFE 6F1, 75X 2-87
Figure 2-40 Grain Boundary Cracking in Tungsten Cladding of Emitter No. 2 of TFE 6F1, 100X 2-87
Figure 2-41 Al₂O₃ Support for Bellville Washer of Emitter No. 2 of TFE 6F1. Note Part of the Disc Disintegrated into Individual Grains. 200X 2-88
Figure 2-42 Interaction Layer Between Al₂O₃ Disc in Figure 2-41 and Tantalum Holder 2-88
Figure 2-43 Collector-Trilayer Structures in TFE 6F1. Note Gap Between Al₂O₃ Layer and the Nb Outer Sheath. 30X 2-89
Figure 2-44 Intercell Region Above Emitter No. 2 of TFE 6F1. Note Dark Region Around Fission Product Venting Orifice and Crack in A1₂O₃ Layer at Bottom of Convolution of Insulator skirt (2X) 2-91
Figure 2-45 Surfaces of Nb-l Zr Sheath Surrounding the Fission Product Venting Orifices of Emitter No. 2 (2X) 2-91

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Figure 2-46 Typical Example of Cross Section of the A1₂O₃ Fission Product Venting Tube (Emitter No. 1, 5X) 2-92
Figure 2-47 Weld Joint Between Tantalum Transition of Emitter No. 2 and Niobium Collector of Emitter No. 1. Note White Phase on the Niobium Side of the Weld (100X) 2-94
Figure 2-48 Weld Joint Between Tantalum and Niobium Skirt of Insulator in Emitter No. 2. Note White Phase Around the Weld (75X) 2-94
Figure 2-49 Niobium Convolution of Insulator Skirt of Emitter No. 2. Note White Phase Grew in from the Cesium Side Toward the Plasma-Sprayed Al₂O₃ Layer Side (75X) 2-95
Figure 2-50 Tantalum to Tungsten Diffusion Bond in Emitter No. 2 Note Kirkendell Voids on Tantalum Side of the Interface (100X) 2-95
Figure 2-51 Macroscopic Appearance of Emitter No. 5 in TFE 6F2 (2X) 2-98
Figure 2-52 Al₂O₃ Layer in the Intercell Region Above Emitter No. 2 in 6F2. Note Dark Region Around Fission Product Venting Orifice (2X) 2-99
Figure 2-53 Nb-1Zr Sheath Surface Facing the Al₂O₃ Insulation Layer of the Intercell Region Shown in Figure 2-52. Note Dark Deposit (2X) 2-100
Figure 2-54 Al₂O₃ Support for the Bellville Washer of Emitter No. 5 of 6F2. Note Cracks. (2X) 2-101

Figure 3-1 Fuel Pellet Designs for TFE 2F4 3-3
Figure 3-2 UO₂ Fuel Press 3-9
Figure 3-3 TFE 2LF2 New Features 3-11
Figure 3-4 2LF2 Insulator Seal 3-13
Figure 3-5 In-Core Testing from July 1971 to January 1973 3-35
Figure 3-6 Performance History of Oxide Fueled Devices 3-39
Figure 3-7 Performance History of Carbide Fueled Devices 3-40

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Figure 3-8 Thermionic Performance Comparison 3-43
Figure 3-9 Diametral Increase Versus Burnup 3-51
Figure 3-10 Diametral Increase Versus Burnup 3-53
Figure 3-11 Emitter Distortion in TFE 1F1 During the Life Test 3-55
Figure 3-12 Emitter Distortion in TFE 6F3 Emitters During the Life Test 3-56
Figure 3-13 Emitter Distortion in TFE 6F3 at 8062 Hours 3-57
Figure 3-14 Cesium Discharge Lifetest Histories 3-66
Figure 3-15 Cesium Discharge Lifetest Histories 3-67
Figure 3-16 LT-1A Discharge IV Characteristics 3-68
Figure 3-17 Post-Operational Apperance of LT-1A 3-69
Figure 3-18 Post-Operational Apperance of LT-2A 3-70
Figure 3-19 Post-Operational Apperance of LT-2B 3-71

Figure 4-1 Reactor Elevation View 4-7
Figure 4-2 Reactor Plan View 4-8
Figure 4-3 Arrangement of Components for F Series Cells 4-9
Figure 4-4 Thermionic Fuel Element 4-10
Figure 4-5 Calculational Model 4-21
Figure 4-6 Relative Power and Fuel Density Distribution 4-23
Figure 4-7 Rq Geometry for an Explicit TFE in the Electric Propulsion Reactor 4-26
Figure 4-8 Comparison of Relative Power in a TFE Adjacent to the Reflector from an RZ Calculation and a Rq Calculation 4-28
Figure 4-9 Contour Plot of Relative Power in a TFE Adjacent to the Reflector 4-29
Figure 4-10 Geometry of ZrH-TFE Lattice of Moderated 240 Kwe Reactor 4-34
Figure 4-11 Driver Fuel Element Arrangement 4-36
Figure 4-12 NEP Reactor Thermionic Fuel Element 4-42

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Figure 4-13 TFE Connection for 120 kWe NEP Reactor 4-43
Figure 4-14 TFE Stem Assembly Layout 4-44
Figure 4-15 Bottom TFE Connection 4-45
Figure 4-16 Configurational Layout of NEP Reactor 4-46
Figure 4-17 Reflector Axial Expansion Versus Temperature 4-51
Figure 4-18 Reflector Lateral Expansion Versus Temperature 4-52
Figure 4-19 Bellville Spring Design 4-53
Figure 4-20 Temperature Distribution in Reflector 4-55
Figure 4-21 Temperature Distribution in Reflector 4-56
Figure 4-22 Temperature Distribution in Reflector 4-57
Figure 4-23 Temperature Distribution in Reflector 4-58
Figure 4-24 Reflector Element Weight 4-60
Figure 4-25 Control Rod Deceleration Snubber 4-62
Figure 4-26 Snubber Energy Absorption Vs. Travel 4-63
Figure 4-27 Control Rod Snubber Pressure Vs. Displacement 4-64

Figure 5-1 Sidethrust NEP Spacecraft and 120 kWe NEP Thermionic Reactor Power System 5-3
Figure 5-2 NEMO Power Plant 5-5
Figure 5-3 NEMO Power Plant Coolant Flow 5-7
Figure 5-4 NEMO Reactor Control 5-8
Figure 5-5 TRIOS Power Plant Evaluation 5-9
Figure 5-6 NEMO Shield Configuration 5-10
Figure 5-7 TRIOS Shield Configuration 5-11

Figure A-l TFE 6F2 Operating History A-17
Figure A-2 TFE 6F2 Operating History A-19
Figure A-3 TFE 6F2 Relative Performance History A-21
Figure A-4 TFE 6F2 IV Characteristics A-22

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Figure A-5 Neutron Radiographs of TFE 6F2 at 7685 Hours (0° ) A-23
Figure A-6 TFE 6F3 Operating History A-29
Figure A-7 TFE 6F3 Operating History A-31
Figure A-8 TFE 6F3 Relative Performance History A-33
Figure A-9 TFE 6F3 IV Characteristics A-34
Figure A-10 Neutron Radiographs of TFE 6F3 at 5106 Hours (120° ) A-35
Figure A-1l Neutron Radiographs of TFE 6F3 at 6683 Hours (120° ) A-36
Figure A-12 Neutron Radiographs of TFE 6F3 at 8062 Hours A-37
Figure A-13 Neutron Radiographs of TFE 6F3 at 8062 Hours A-38
Figure A-14 TFE 6F4 Operating History A-41
Figure A-15 TFE 6F4 Operating History A-42
Figure A-16 TFE 6F4 Relative Performance History A-43
Figure A-17 TFE 6F4 IV Characteristics A-44
Figure A-18 Neutron Radiographs of TFE 6F4 at 0 Hours A-45
Figure A-19 Neutron Radiographs of TFE 6F4 at 0 Hours A-46
Figure A-20 Neutron Radiographs of TFE 6F4 at 1577 Hours A-47
Figure A-21 Neutron Radiographs of TFE 6F4 at 1577 Hours A-48
Figure A-22 Neutron Radiographs of TFE 6F4 at 2956 Hours A-49
Figure A-23 Neutron Radiographs of TFE 6F4 at 2956 Hours A-50
Figure A-24 TFE 6F5 Operating History A-54
Figure A-25 TFE 6F5 Operating History A-55
Figure A-26 TFE 6F5 Relative Performance History A-56
Figure A-27 TFE 6F5 IV Characteristics A-57
Figure A-28 Neutron Radiographs of TFE 6F5 at 0 Hours A-58
Figure A-29 Neutron Radiographs of TFE 6F5 at 0 Hours A-59
Figure A-30 Neutron Radiographs of TFE 6F5 at 1379 Hours A-60
Figure A-31 Neutron Radiographs of TFE 6F5 at 1379 Hours A-61
Figure A-32 TFE 2F1 Operating History A-67
Figure A-33 TFE 2F1 Operating History A-69
Figure A-34 TFE 2F1 Relative Performance History A-71
Figure A-35 TFE 2F1 IV Characteristics A-72
Figure A-36 Neutron Radiographs of TFE 2F1 at 6444 Hours A-73

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Figure A-37 Neutron Radiographs of TFE 2F1 at 8021 Hours A-74
Figure A-38 TFE 2F2 Operating History A-79
Figure A-39 TFE 2F2 Operating History A-81
Figure A-40 TFE 2F2 Relative Performance History A-83
Figure A-41 TFE 2F2 IV Characteristics A-84
Figure A-42 Neutron Radiographs of TFE 2F2 at 2618 Hours A-85
Figure A-43 Neutron Radiographs of TFE 2F2 at 4195 Hours A-86
Figure A-44 Neutron Radiographs of TFE 2F2 at 5574 Hours A-87
Figure A-45 TFE 2F3 Operating History A-91
Figure A-46 TFE 2F3 Operating History A-92
Figure A-47 TFE 2F3 Relative Performance History A-93
Figure A-48 TFE 2F3 IV Characteristics A-94
Figure A-49 Neutron Radiographs of TFE 2F3 at 0 Hours A-95
Figure A-50 Neutron Radiographs of TFE 2F3 at 1577 Hours A-96
Figure A-51 Neutron Radiographs of TFE 2F3 at 2956 Hours A-97
Figure A-52 TFE 1F1 Operating History A-101
Figure A-53 TFE 1F1 Operating History A-103
Figure A-54 TFE 1F1 Relative Performance History A-105
Figure A-55 TFE 1F1 IV Characteristics A-106
Figure A-56 TFE 1F1 Parasitic Discharge Test History A-107
Figure A-57 TFE 1F1 Parasitic Discharge IV Characteristics A-108
Figure A-58 Neutron Radiographs of TFE 1F1 A-109
Figure A-59 TFE 1F3 Operating History A-113
FigureA-60 1F3 Operating History A-114
Figure A-61 TFE 1F3 Relative Performance History A-115
Figure A-62 TFE 1F3 IV Characteristics A-116
FigureA-63 TFE 1F3 Parasitic Discharge Test History A-117
Figure A-64 TFE 1F3 Parasitic Discharge I-V Characteristics A-118
Figure A-65 Neutron Radiographs of TFE 1F3 at 3378 Hours A-119
Figure A-66 TFE 1F4 Operating History A-124
Figure A-67 TFE 1F4 Operating History A-125

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Figure A-68 TFE 1F4 Relative Performance History A-126
Figure A-69 TFE 1F4 IV Characteristics A-127
Figure A-70 TFE 1F4 IV Characteristics A-128
Figure A-7l TFE 1F4 Emitter Sheath Potential Test A-129
Figure A-72 TFE 1F4 Parasitic Discharge IV Characteristics A-131
Figure A-73 Neutron Radiographs of TFE 1F4 A-132
Figure A-74 Neutron Radiographs of TFE 1F4 A-133
Figure A-75 TFE 2E2 Operating History A-137
Figure A-76 TFE 2E2 Operating History A-139
Figure A-77 TFE 2E2 Relative Performance History A-141
Figure A-78 TFE 2E2 IV Characteristics A-142
Figure A-79 Neutron Radiographs of TFE 2E2 at 8228 Hours A-143
Figure A-80 Neutron Radiographs of TFE 2E2 at 9805 Hours A-144
Figure A-81 Neutron Radiographs of TFE 2E2 at 11084 Hours A-145
Figure A-82 Mark VIIA IC-D3 Operating History A-148
Figure A-83 Mark VIIA IC-D3 Operating History A-149
Figure A-84 Neutron Radiograph of IC-D3 A-150
Figure A-85 Mark VI IC-I6 Operating History A-153
Figure A-86 Mark VI IC-I6 Operating History A-155
Figure A-87 16 Relative Performance History A-157
Figure A-88 IC-I6 IV Characteristics A-158
Figure A-89 Neutron Radiographs of Mark VI IC-I6 A-159
Figure A-90 Neutron Radiographs of Mark VI IC-I6 A-160
Figure A-91 Neutron Radiographs of Mark VI IC-I6 A-161
Figure A-92 FC-3-l Operating History A-164
Figure A-93 FC-3-2 Operating History A-165
Figure A-94 FC-3-3 Operating History A-166
Figure A-95 FC-3-4 Operating History A-167
Figure A-96 Neutron Radiographs of FC-3 Top Emitters A-168

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Figure A-97 Neutron Radiographs of FC-3 Bottom Emitters A-169
Figure A-98 Neutron Radiographs of FC-3 Top Emitters A-170
Figure A-99 Neutron Radiographs of FC-3 Bottom Emitters A-171
Figure A-100 Mark VIIA OC-A4 Life Test History A-175
Figure A-101 Mark VIIA OC-A4 Life Test History A-176
Figure A-102 Mark VIIA OC-A4 A-177
Figure A-103 Mark VIIA OC-A4 Post-Test Appearance A-178
Figure A-104 Mark VIIA Post-Test Appearance A-179
Figure A-105 Mark VIIA OC-A4 Post-Operational Metallographic Examination A-180

Figure B-1 Program Milestones B-4
Figure B-2 Organization Chart B-7

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