Track 1: Emerging Technologies in Space

Track 2: Mission Concepts and Logistics

Track 3: Space Nuclear Policy

Track 4: Space Reactors

Track 5: Radioisotope Power Systems

Track 6: Energy Conversion Technology and Development

Paper and Podium Presentation

AuthorsTitle
1S. B. Rawlins, D. L. Dale ThomasA PROPOSED SOLUTION TO ADDRESS NUCLEAR THERMAL PROPULSION FUEL EMBRITTLEMENT AND CRYOGENIC HYDROGEN REQUIREMENTS
2D. NikitaevAIR AND SPACE THERMAL ROCKET ENGINE WITH TURBOJET (ASTRET)
3T. Cwik, W. Zimmerman, M. SmithAN ARCHITECTURE FOR A NUCLEAR POWERED CRYOBOT TO ACCESS THE OCEANS OF ICY WORLDS
4A. AustinAN EXPLORATION OF MISSION CONCEPTS THAT COULD UTILIZE SMALL RPS
6G. RomanoskiAN INVESTIGATION OF THE RHEOLOGICAL BEHAVIOR OF PHENOLIC RESINS CONSIDERED FOR PRODUCTION OF CARBON BONDED CARBON FIBER INSULATION
7R. M. Wham, R. Steve Owens, J. H. Miler, S. PierceAUTOMATION OF NEPTUNIUM OXIDE–ALUMINUM TARGET FABRICATION
8D. K. Bond, B. Goddard, S. Bilbao Y. Leon, R. C. Singleterry, Jr.COMPARING THE EFFECTIVENESS OF POLYMER AND COMPOSITE MATERIALS TO ALUMINUM FOR EXTENDED DEEP SPACE TRAVEL
10C. WangCONCEPTUAL DESIGN OF A MICRO NUCLEAR REACTOR POWER SOURCE FOR MULTI-APPLICAITON
11J. N. Easley, C. DenbrockCONSIDERATIONS FOR CLOSED-LOOP BRAYTON POWER CYCLE FOR NUCLEAR THERMAL ROCKET WITH DECAY HEAT
12L. Carasik, M. Eades, V. PatelDECAY HEAT STUDIES TO REDUCE ACTIVE COOLING TIME OF A NUCLEAR THERMAL PROPULSION SYSTEM
13J. McduffeeDESIGN AND ANALYSIS OF A NPO2 TARGET FOR THE PRODUCTION OF PU238
14J. Hong, K. Son, J. Kim, J. KimDESIGN OF ETG FOR LOW ORBIT TEST OF THE KOREA LAUNCH VEHICLE
15C. DailyDESIGN OPTIMIZATION STUDIES FOR NPO2 TARGETS IRRADIATED IN THE HIGH FLUX ISOTOPE REACTOR
16Z. Li, M. Lang, J. Sun, L. ShiDEVELOPMENT OF A SYSTEM ANALYSIS CODE FOR NUCLEAR THERMAL ROCKET ENGINE
17A. P. ShivprasadDEVELOPMENT OF SINTERED YTTRIUM DIHYDRIDE COMPACTS FOR NUCLEAR REACTOR MODERATOR APPLICATIONS
18A.DEVELOPMENT OF THE PLUTONIUM MODELING AND ASSESSMENT (PUMA) SIMULATION THROUGH THE COUPLING OF EXPERIMENTS AND MOLECULAR DYNAMICS
19S. OritiDYNAMIC RPS PATH TO FLIGHT
20J. Locke, B. LalEMERGENCE OF A COMMERCIAL SPACE NUCLEAR ENTERPRISE
21C. E. Whiting, D. P. Kramer, C. D. BarklayEMPIRICAL POWER PREDCITION FOR MMRTG F1
22N. GallegoEVALUATION OF ALTERNATIVE FIBERS TO REPLACE NARC-RAYON FOR THE PRODUCTION OF CBCF
23S. JuddEXPERIMENTALLY VERIFYING THE EFFECTIVENESS OF FUELED CONTROL DRUMS
24M. A. WhiteFLEXURE ISOTOPE STIRLING CONVERTOR (FISC) DEVELOPMENT PROGRESS
25M. StewartFUEL ELEMENT TO MODERATOR ELEMENT HEAT TRANSFER ANALYSIS
26B. Makenas, D. WootanHANFORD'S ROLE IN SPACE POWER
27S. WhalenHIGH PERFORMANCE LIGHTWEIGHT MATERIALS MADE BY SHEAR ASSISTED PROCESSING AND EXTRUSION (SHAPE)
28X. Chunyang, X. JiachunHISTORY AND CHALLENGES OF SPACE NUCLEAR REACTOR POWER SYSTEMS
29T. G. Duffin, K. M. Benensky, S. J. Zinkle, M. W. BarnesHOT HYDROGEN TESTING AND MICROSTRUCTURAL CHARACTERIZATION OF MOLYBDENUM CERMETS FOR NUCLEAR THERMAL PROPULSION
30B. TaylorHYBRID FUEL COUPLING IN A PULSED Z-PINCH ROCKET ENGINE
31J. TeagueIMPACT TEMPERATURE DETERMINATION FOR GPHS SAFETY TESTING
32J. F. Zakrajsek, T. Sutliff, J. Hamley, C. Sandifer, P. Mccallum, T. Bishop, M. MccuneIMPLEMENTATION OF CROSS-AGENCY NUCLEAR APPLICATIONS
33P. MccallumIMPROVING THE NUCLEAR LAUNCH APPROVAL PROCESS; PROGRESS AND PLANS
34D. Chandler, M. W. Crowell, K. E. RoystonINCREASED PLUTONIUM-238 PRODUCTION VIA HIGH FLUX ISOTOPE REACTOR PERMANENT BERYLLIUM REFLECTOR REDESIGN
35K. G. Myhre, M. E. Woods, A. J. Unger, P. D. Benny, D. E. Benker, E. D. Collins, L. H. Delmau, D. W. Depaoli, F. D. Riley, R. M. WhamINITIAL TESTING OF MEDIATED ELECTROCHEMICAL OXIDATION FOR INCLUSION IN THE PLUTONIUM-238 PRODUCTION PROGRAM
36J. Zillinger, B. Segel, K. Benensky, D. Tucker, M. BarnesINVESTIGATION OF PRODUCTION PARAMETER EFFECTS ON SPARK PLASMA SINTERED MOLYBDENUM CERMET WAFERS FOR NUCLEAR THERMAL PROPULSION APPLICATIONS
37D. Lonnie JohnsonJOHNSON THERMO-ELECTROCHEMICAL CONVERTER (JTEC) AS A HEAT TO ELECTRIC GENERATOR FOR NUCLEAR POWER SYSTEMS
38P. McclureKILOPOWER - MAXIMUM CREDIBLE DOSE FOR A CRITICALITY ACCIDENT
39P. McclureKILOPOWER - MAXIMUM CREDIBLE FISSIONS FOR A CRITICALITY ACCIDENT
40D. I. PostonKILOPOWER REACTORS FOR POTENTIAL SPACE EXPLORATION MISSIONS
41C. Russell JoynerLEU NTP ENGINE SYSTEM TRADES AND MISSION OPTIONS
42C. J. Romnes, D. E. Chavez, B. J. Martinez, N. M. Osterhaus, W. R. Ford, R. LenardLOW ENRICHED URANIUM NUCLEAR THERMAL ROCKET DESIGN INSPIRED BY THE SPACE NUCLEAR THERMAL PROPULSION PROJECT
43B. SondelskiMASS OPTIMIZATION OF POWER SYSTEM FOR SPACE APPLICATIONS
44S. Wilson, S. OritiMATURATION OF DYNAMIC POWER CONVERTORS FOR RADIOISOTOPE POWER SYSTEMS
45W. Carpenter, K. Benensky, M. Barnes, D. Dennis TuckerMICROSTRUCTURAL EVOLUTION OF HIGH DENSITY W-CERMETS EXPOSED TO FLOWING HYDROGEN AT TEMPERATURES EXCEEDING 2000 K
46D. KramerMIXED ALUMINA/CERIA COMPOSITIONS AS AN ENHANCED CERAMIC PROCESSING SURROGATE FOR RPS FUEL PELLETS
47L. HawkinsMODELING HELIUM AND OXYGEN BEHAVIOR OF A PLUTONIA PELLET IN AN MMRTG
48A. Denig, M. EadesMONTE CARLO-INFORMED DECAY HEAT MODEL FOR CERMET LEU-NTP SYSTEMS
49D. KramerNUCLEAR HEAT SOURCE CONSIDERATIONS FOR AN ICY MOON EXPLORATION SUBSURFACE PROBE
50K. KowalNUCLEAR LAUNCH APPROVAL: OPTIONS FOR CRITERIA
51S. S. VossNUCLEAR SECURITY CONSIDERATIONS FOR SPACE NUCLEAR POWER: A REVIEW OF PAST PROGRAMS WITH RECOMMENDATIONS FOR FUTURE CRITERIA
52J. Rader, M. B. R. Smith, M. Scott Greenwood, T. Jay HarrisonNUCLEAR THERMAL PROPULSION DYNAMIC MODELING WITH MODELICA
53D. SikorskiNUCLEAR THERMAL ROCKET CONTROL
54R. S. Raju, J. E. FosterOVERVIEW AND FUTURE OF OPEN CYCLE GAS-CORE NUCLEAR ROCKET
55R. HowardOVERVIEW OF THE PLUTONIUM-238 SUPPLY PROGRAM’S CERMET PRODUCTION TARGET
56Y. JiPARAMETRIC STUDY ON THERMAL HYDRAULICS CHARACTERISTICS OF A PARTICLE BED REACTOR FOR NUCLEAR THERMAL PROPULSION
57F. Anne CarverPARTICLE SIZE ANALYSIS OF CERIUM DIOXIDE SURROGATE MATERIALS AS A SIMULANT FOR PLUTONIUM-238 DIOXIDE FUELS PROCESSING
58T. WinklePASSIVE AND ACTIVE COOLING ANALYSIS FOR DECAY HEAT OF NUCLEAR THERMAL PROPULSION SYSTEMS
59J. RockPATH TO A NEXT GENERATION RADIOISOTOPE THERMOELECTRIC GENERATOR (RTG)
60S. V. Howieson, J. Behrens, K. M. KowalPOTENTIAL LAUNCH APPROVAL PROCESS FOR COMMERCIAL SPACE NUCLEAR SYSTEMS
61D. DepaoliPROCESS DEVELOPMENT FOR PLUTONIUM-238 PRODUCTION AT OAK RIDGE NATIONAL LABORATORY
62R. Miller, B. Friske, K. R. Veach, JrQUALIFICATION OF SPECIAL PROCESSES USING A GRADED APPROACH FOR THE LIGHT-WEIGHT RADIOISOTOPE HEATER UNIT METALLIC COMPONENT PRODUCTION AT OAK RIDGE NATIONAL LABORATORY
63G. Bruder, F. RitzertRADIOISOTOPE POWER GENERATION WITH THERMOACOUSTIC POWER SYSTEM (TAPS) TECHNOLOGY
64T. J. SutliffRADIOISOTOPE POWER SYSTEMS - AN INTERAGENCY PROGRAM STATUS
65K. Rex Veach, Jr.RE-ESTABLISHMENT OF LIGHT-WEIGHT RADIOISOTOPE HEATER UNIT PLATINUM-30% RHODIUM ALLOY COMPONENTS PRODUCTION AT OAK RIDGE NATIONAL LABORATORY
66A. Camp, A. Klein, P. Mcclure, P. Mccallum, S. VossRECOMMENDATIONS FOR THE NUCLEAR SAFETY AND LAUNCH APPROVAL PROCESS FOR FISSION REACTORS
67D. I. PostonRESULTS OF THE KRUSTY NUCLEAR SYSTEM TEST
68D. I. PostonRESULTS OF THE KRUSTY WARM CRITICAL EXPERIMENTS
69N. D. Gaffin, S. J. Zinkle, K. M. BenenskyREVIEW OF IRRADIATION HARDENING AND EMBRITTLEMENT EFFECTS IN REFRACTORY METALS RELEVANT TO NUCLEAR THERMAL PROPULSION APPLICATIONS
70M. KrecickiSENSITIVITY STUDIES OF THE TUNGSTEN VECTOR ON THE PERFORMANCE OF A LEU NTP ENGINE
72J. Stephen Herring, S. Mackwell, C. Pestak, K. HilserSMALL MODULAR FISSION REACTORS FOR SPACE APPLICATIONS: ENABLING AN AFFORDABLE, COMMERCIALLY DEVELOPED POWER ARCHITECTURE FOR THE MOON AND BEYOND
73V. PatelSNRE EIGENVALUE UNCERTAINTY QUANTIFICATION FROM NUCLEAR DATA SOURCES
74J. R. CasaniSPACE FISSION POWER: NASA’S BEST BET TO CONTINUE TO EXPLORE THE OUTER SOLAR SYSTEM
75D. Wootan, B. MakenasSPACE POWER TESTING IN THE FAST FLUX TEST FACILITY
76J. Collins, J. Gary Wood, J. Stanley, W. OttingSUNPOWER ROBUST STIRLING CONVERTOR (SRSC) PROJECT OVERVIEW
77C. G. MorrisonTEMPERATURE AND POWER SPECIFIC MASS SCALING FOR LEU CLOSED-CYCLE BRAYTON SYSTEMS FOR SPACE SURFACE POWER AND NUCLEAR ELECTRIC PROPULSION
78K. Kazemzadeh, J. MccoyTHE DEVELOPMENT, PROTOTYPING AND TESTING OF A SHOCK TOLERANT MILLI-WATT RADIOISOTOPE POWER SYSTEM
79M. J. Eades, M. Reed, C. G. Morrison, W. Deason, S. Judd, V. Patel, P. VenneriTHE PYLON: COMMERCIAL LEU NUCLEAR FISSION POWER FOR LUNAR, MARTIAN, AND DEEP SPACE APPLICATIONS
80R. C. O\\'BrienTHE SIRIUS-1 NUCLEAR THERMAL PROPULSION FUELS TRANSIENT TEST SERIES IN THE IDAHO NATIONAL LABORATORY TREAT REACTOR
81D. Plachta, X. Wang, J. HartwigTHERMAL MODEL OF A ZERO BOIL OFF SYSTEM FOR THE NUCLEAR THERMAL PROPULSION SYSTEM
83X. LiuTHERMAL-HYDRAULIC DESIGN FEATURES OF A MICRO NUCLEAR REACTOR POWER SOURCE APPLIED FOR MULTI-PURPOSE
84A. AueronTRADES ON DENSIFIED PROPELLANT FOR NUCLEAR THERMAL PROPULSION
86J. J. Breedlove, T. M. Conboy, M. V. ZagarolaTURBO-BRAYTON CONVERTER FOR RADIOISOTOPE POWER SYSTEMS
87M. F. Chaiken, M. A. GibsonUPDATE ON RADIATION TESTING FOR SPACE FISSION POWER SYSTEMS

Lightning Talk

AuthorsTitle
1M. HoutsA VERSATILE NUCLEAR THERMAL PROPULSION (NTP) SYSTEM
2B. Skidmore, H. A. Quintana, A. J. Parkison, L. B. Davenhall, K. D. AbneyAM-241 OXIDE PRODUCTION AT LOS ALAMOS NATIONAL LABORATORY
4W. Kowalski, V. ClarkASSESSMENT OF MISSION-CENTRIC TECHNICAL CRITERIA FOR SAFE AND SUSTAINABLE SPACE NUCLEAR LICENSING
5D. BealeBERYLLIUM OXIDE AS A SOLID CORE NUCLEAR REACTOR ENGINE MODERATOR
6L.BETAVOLTAICS FROM COTS: POWER FOR YEARS
7J. KatalenichCONCEPTUAL DESIGN OF A HIGH POWER DENSITY HEAT SOURCE MODULE
8A. Gonzalez, W. CulbrethDECAY HEAT CAPTURE FOR ADDITIONAL NUCLEAR THERMAL ROCKET THRUST
9S. Powers, C. Powers, S. Cendro, D. Ochoa-Cota, B. KretschmerDEVELOPMENT CAMPAIGN OF AN ADDITIVELY MANUFACTURED, INDUCTIVELY HEATED MODEL OF A SOLID-CORE NUCLEAR THERMAL ROCKET ENGINE
10R. HowardDEVELOPMENT OF ROBUST AND RELIABLE EXPERIMENTS TO QUALIFY NUCLEAR THERMAL PROPULSION ENGINE FUELS AND COMPONENTS
12D. CheikhENHANCED THERMOELECTRIC PERFORMANCE OF RARE-EARTH TELLURIDE COMPOUNDS VIA BAND STRUCTURE ENGINEERING
13A. J. Rau, W. J. WaltersFISSION MATRIX NEUTRONICS CALCULATIONS WITH TEMPERATURE FEEDBACK IN A NUCLEAR THERMAL PROPULSION CORE
14S. Kumar Mishra, A. Pente, A. Kumar, C. Prakash Kaushik, B. DikshitGRAPHENE SUPERLATTICE BASED THERMOELEMENT FOR RADIOISOTOPE THERMOELECTRIC GENERATOR
15A. LoHEAVY ION THERMIONIC ENERGY CONVERSION (HITEC): A DESIGN STUDY
16C. PerezIMPROVING POWER FACTOR AND MECHANICAL PROPERTIES OF YB14MGSB11 FOR APPLICATION IN A RADIOISOTOPE THERMAL GENERATOR.
17P. R. Rubiolo, M. Tano Retamales, V. Ghetta, N. Capellan, J. Giraud, J. Blanco, S. DavidMOLTEN SALT REACTORS FOR NUCLEAR ELECTRIC PROPULSION
18C. B. Reynolds, J. F. Horton, C. R. Joyner Ii, T. KokanNTP LUNAR DESIGN REFERENCE MISSIONS
19J. KatalenichOBSERVATIONS OF AGING 238PUO2 MICROSPHERES
20G. MarcantelOPTIMIZATION OF PLUTONIUM-238 PRODUCTION IN THE ADVANCED TEST REACTOR FOR RADIOISOTOPE THERMOELECTRIC GENERATORS IN DEEP SPACE EXPLORATION APPLICATIONS
21J. NavarroORNL-INL DATA DRIVEN OPTIMIZATION PRODUCTION AND HARVESTING TOOL
22H. Honglei, X. Jiachun, H. GuPERFORMANCE ANALYSIS OF NUCLEAR THERMAL PROPULSION REACTOR USING DRIVER FUEL ELEMENT
23C. BryanPOTENTIAL IMPROVEMENTS TO 237NP TARGETS AT THE HIGH FLUX ISOTOPE REACTOR
24C. Painter, C. Lavender, J. VineetPROCESS DEVELOPMENTS IN FABRICATING U-10MO PLATE FUEL
25K. BenenskyRECENT FY18/FY19 NTP MATERIALS DEVELOPMENT ACTIVITIES AT NASA MARSHALL SPACE FLIGHT CENTER
26M. B. R. SmithTHE RADIOISOTOPE POWER SYSTEM DOSE ESTIMATION TOOL (RPS-DET) 2019 DEVELOPMENT UPDATE
27M. EadesVERSATILE NTP CORE DESIGN
28H. Longmire, J. Henkel, P. Hoppe, A. MooreY-12 FABRICATION OF KRUSTY ALLOY COMPONENTS

Paper and Podium Presentation

A PROPOSED SOLUTION TO ADDRESS NUCLEAR THERMAL PROPULSION FUEL EMBRITTLEMENT AND CRYOGENIC HYDROGEN REQUIREMENTS

S. B. Rawlins, D. L. Dale Thomas samathebrea@gmail.com
This paper introduces the concept of a minimally intrusive power generation system that may be applied to a nuclear thermal propulsion (NTP) engine. Most bimodal or dual-mode NTP designs are optimized for maximum electrical power generation but require significant changes to the reactors configuration. This greatly diminishes their usefulness to modern NTP programs that focus on affordability and expediency. Nevertheless, the benefits of successfully generating additional power from the reactor, especially while it is not in use, include reducing the total system mass by several metric tons, avoiding fuel embrittlement concerns, and assisting with cryogenic hydrogen propellant storage. Thus, a system designed for fewest reactor modifications rather than greatest power generation could provide the right compromise between theoretical and practical design efficiency. This paper outlines the relevant design requirements for such a system before listing several candidate solutions.
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AIR AND SPACE THERMAL ROCKET ENGINE WITH TURBOJET (ASTRET)

D. Nikitaev nikitaev@unlv.nevada.edu
NTP relies on the high temperatures of fission to heat a propellant to produce thrust and may be applied to both jet and rocket engines. These types of engines were explored by projects NERVA and NEPA; however, the materials of that time were too heavy for aerospace vehicles. Today, materials such as high entropy alloys allow for such technologies to succeed, and a merging of the NEPA and NERVA designs resulted in ASTRET. Multiphysics modeling and a parametric study have shown that delivering a 70-ton payload into orbit by a single-stage spaceplane is not only possible, but cheaper than current launch vehicles after incurring the initial research costs. A spaceplane utilizing two ASTRET engines requires 2,500,000 liters of hydrogen propellant with a heavy gaseous seed such as krypton. The added molecular weight of the seed allows for a smaller propellant tank, an increase in the overall change in velocity, and a decrease in the fluid\'s specific heat capacity at the expense of some of the specific impulse. The temperatures inside ASTRET have been kept at modest levels and are below the maximum ratings of the selected materials. In the lower atmosphere (<25km), ASTRET uses a closed nuclear cycle which limits the radiation coming out of the nozzle and may be declared safe by the regulatory environment. This study was part of an undergraduate senior design project and more work must be done, including CFD modelling and verification of calculations, to declare that this engine has real world application.
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AN ARCHITECTURE FOR A NUCLEAR POWERED CRYOBOT TO ACCESS THE OCEANS OF ICY WORLDS

T. Cwik, W. Zimmerman, M. Smith cwik@jpl.nasa.gov
The icy moon oceans beckon with ingredients that potentially may harbor extant life. Beginning with the Galileo and Cassini missions, measurements have revealed the presence of global oceans under the icy crust of several moons of Jupiter and Saturn. Among those moons, Europa and Enceladus have their ocean in contact with the rocky core, providing an environment similar to the conditions existing on the terrestrial sea-floor where life has developed at hydrothermal vents. A detailed trade space study was conducted to develop a technology architecture defining a system that would access an icy moons ocean. This paper outlines the architecture with specific consideration to the power source necessary to drive the system.
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AN EXPLORATION OF MISSION CONCEPTS THAT COULD UTILIZE SMALL RPS

A. Austin alexander.austin@jpl.nasa.gov
The NASA Radioisotope Power Systems (RPS) Program Mission Analysis Team at the Jet Propulsion Laboratory (JPL) requested a JPL Innovation Foundry Architecture Team (A-Team) study to assess mission pull for small RPS (1 mWe - 40 We) in order to inform the RPS Program Office on what future power system developments should be focused on. The A-Team is JPLs concurrent engineering design team for science definition and early mission concept development, targeting concept maturation levels of 1 through 3. The requested small RPS study was tasked to identify the architecture space of potential small RPS missions, and suggest power levels that could enable or enhance potential future small spacecraft missions. This paper describes the collaborative engineering processes that the A-Team and Mission Analysis Team used to reach results quickly and the findings to inform the RPS Program about mission concept power requirements on RPS for small missions.
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AN INVESTIGATION OF THE RHEOLOGICAL BEHAVIOR OF PHENOLIC RESINS CONSIDERED FOR PRODUCTION OF CARBON BONDED CARBON FIBER INSULATION

G. Romanoski romanoskigr@ornl.gov
Carbon Bonded Carbon Fiber Insulation is made from chopped and carbonized rayon fibers bonded by carbonized phenolic resin. The rheological behavior of several resins was investigated to determine if alternative resins would be more effective in forming carbon-bond precursors.
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AUTOMATION OF NEPTUNIUM OXIDE–ALUMINUM TARGET FABRICATION

R. M. Wham, R. Steve Owens, J. H. Miler, S. Pierce whamrm@ornl.gov
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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COMPARING THE EFFECTIVENESS OF POLYMER AND COMPOSITE MATERIALS TO ALUMINUM FOR EXTENDED DEEP SPACE TRAVEL

D. K. Bond, B. Goddard, S. Bilbao Y. Leon, R. C. Singleterry, Jr. bonddk@vcu.edu
Since the last Apollo mission in 1972 there have been no manned missions into deep space. There are many causes, both political and scientific, but to successfully extend manned missions towards Mars, radiation protection must be in place to shield astronauts from the two primary sources of space radiation: GCRs and SPEs. The research evaluates the shielding capabilities of various polymer and composite materials comparing them to liquid hydrogen and aluminum. Each material is evaluated at 18 thicknesses ranging from 0.01 to 1000 g/cm3 and for the number of nucleons per volume, contained within each material. This research also includes an analysis of the effect of hydrogen storage used within carbon based materials, the effectiveness of Lunar and Martian Regolith as shielding materials, and quantify the effect of using materials containing neutron absorbers: 6Li and 10B.
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CONCEPTUAL DESIGN OF A MICRO NUCLEAR REACTOR POWER SOURCE FOR MULTI-APPLICAITON

C. Wang chlwang@mail.xjtu.edu.cn
  Micro HPR power source is featured with lower noise level, higher power output, longer lifetime than conventional power sources. It could be applied for the energy system of space or undersea vehicles. The HPR power source is considered as an ideal candidate for the space and underwater reactor concept. In this paper, a 120kWe lithium HPR power source applied for multiple use is neutronics designed. Uranium nitride fuel with 70% enrichment and lithium heat pipe are adopted in the reactor core. Tungsten and water are used as shields on both sides of the core. The reactivity is controlled by 6 control drums with B4C neutron absorbers. Monte Carlo code MCNP is used to obtain kinetics parameters, the power distribution, shield analysis, reactivity coefficient and core criticality safety. A code MCORE coupling MCNP and ORIGEN is used to analysis the fuel depletion characteristics of the designed reactor core. A 14-year once-through fuel cycle is adopted according to optimization analysis. Overall, the designed core parameters preliminary satisfy the safety requirements and the rector is neutronics safe. This work provides reference to the design and application of the micro nuclear power source.
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CONSIDERATIONS FOR CLOSED-LOOP BRAYTON POWER CYCLE FOR NUCLEAR THERMAL ROCKET WITH DECAY HEAT

J. N. Easley, C. Denbrock jne87@msstate.edu | denbrock@umich.edu
A nuclear thermal rocket (NTR) is an example of a broader class of nuclear thermal propulsion (NTP) technologies. In future years, the nuclear thermal rocket will be a viable option for Mars and deep-space missions because of its high specific impulse (Isp) and efficient power conversion systems. One issue associated with NTP is cooling the reactor during post-thrust operations while in transit. One solution would be to incorporate a Brayton power cycle into the engine. The benefits of this are two-fold. Firstly, incorporating a power cycle would provide power to the habitat module without the need for solar panels (which become much less viable the farther out into space a spacecraft travels). Secondly, the Brayton cycle would act as a coolant system for the nuclear reactor during post-thrust operations and would eliminate the need to power down the reactor completely. Nuclear decay heat from the reactor could provide power for a time, but once the energy from decay heat drops below the energy needed to run the power cycle, the nuclear reactor can provide the additional energy needed to keep thermal power input into the cycle constant. This paper aims to investigate the benefits of incorporating a Brayton power cycle into the nuclear thermal rocket as well as model the reactor power input needed during this post-thrust transitional period.
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DECAY HEAT STUDIES TO REDUCE ACTIVE COOLING TIME OF A NUCLEAR THERMAL PROPULSION SYSTEM

L. Carasik, M. Eades, V. Patel l.carasik@usnc.com
Decay heating occurs within an Nuclear Thermal Propulsion (NTP) system after reactor shutdown due to fission products decaying and producing heat within the reactor. The decay heat is large enough during this period to cause the NTP system components to heat up past their temperature limits without sufficient cooling. If the temperature limits are surpassed, the NTP system could be damaged including the reactor core components. This is mitigated by the usage of both active and passive cooling stages after the NTP system shuts down. The active stage requires the expenditure of reactor coolant (also the propellant of the NTP) to cool the system. This coolant/propellant is contained within the NTP system and the more coolant/propellant needed translates to the higher mass and cost requirement of the NTP system. This motivates an effort to reduce the active cooling stage that in turn reduces system mass and costs. In this work, two design parameters are investigated for potential reduction of the active cooling stage length. These investigations are done by modeling a simplified NTP system using TRICORDER and it was found that the active cooling stage can be reduced by using high emissivity radiator coatings and the addition of radiator fins.
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DESIGN AND ANALYSIS OF A NPO2 TARGET FOR THE PRODUCTION OF PU238

J. Mcduffee mcduffeej@ornl.gov
Current production of Pu-238 at Oak Ridge National Laboratory uses NpO2aluminum cermet pellets as the feed material. The advantage of cermet is that its thermal conductivity is much higher than that of the oxide alone, which greatly reduces pellet temperatures. However, the melting point of the material is quite low due to the aluminum in the matrix, and the recovery of the Pu-238 results in substantial radioactive liquid waste. There is potentially both a significant production gain and a reduction in post-irradiation processing cost and waste associated with using a pure NpO2 pellet. This work describes ongoing efforts to design a NpO2 pellet to maximize production of Pu-238 in the High Flux Isotope Reactor.
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DESIGN OF ETG FOR LOW ORBIT TEST OF THE KOREA LAUNCH VEHICLE

J. Hong, K. Son, J. Kim, J. Kim jthong@kaeri.re.kr
Korea Aerospace Research Institute will launch a satellite for a low-orbit test of the Korea Launch Vehicle in 2021. An electrically heated thermoelectric generator (ETG) with mass of 850 g will be one of its payloads. To assure the design heritage and the reliability of the ETG in the space environment, a small ETG will be tested at the top of the satellite for more than a year. In this study, an ETG with 10 W of heat input was designed through simulations such as heat transfer analysis, modal analysis, thermoelectric analysis, and structural analysis. In addition, a mockup was fabricated and basic performance tests were carried out.
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DESIGN OPTIMIZATION STUDIES FOR NPO2 TARGETS IRRADIATED IN THE HIGH FLUX ISOTOPE REACTOR

C. Daily dailycr@ornl.gov
Efforts to re-establish a domestic 238Pu production capability in support of National Aeronautics and Space Administration (NASA) mission objectives are ongoing throughout the US Department of Energy (DOE) complex. Design and optimization studies of 237Np-bearing targets are underway at Oak Ridge National Laboratory (ORNL). It is anticipated that targets will be irradiated in ORNLs High Flux Isotope Reactor (HFIR) and in the Advanced Test Reactor at Idaho National Laboratory. A variety of target materials, containments, arrangements, and irradiation histories have been analyzed, and the results indicate that a sufficient quantity of 238Pu can be produced in HFIR to fulfill NASAs current mission objectives. This paper focuses on the design and optimization of new target configurations containing pellets that are (1) 92% 2% of the theoretical density (TD) of NpO2, (2) loaded into pins of cladding materials that can be handled as solid waste following post-irradiation 238Pu recovery operations, (3)irradiated in various vertical experiment facility (VXF) locations in the HFIR permanent beryllium reflector, and (4) rotated within and/or moved to another VXF location following each HFIR operational cycle to maximize 238Pu production and minimize peak heat generation rates.
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DEVELOPMENT OF A SYSTEM ANALYSIS CODE FOR NUCLEAR THERMAL ROCKET ENGINE

Z. Li, M. Lang, J. Sun, L. Shi lizeguang@mail.tsinghua.edu.cn
A new system analysis code for nuclear thermal rocket engine (NTRE) is developed, which can perform the whole NTRE system simulation. In this paper, the models of hydrogen physical property and system balance calculation used in the analysis code are briefly introduced to show the basic idea of the code. Then system simulations have been done on the three cycle schemes for 100 kN thrust, and the detailed working parameters of each cycle has been obtained. On the basis of these results, the comparison is done among the three cycles.
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DEVELOPMENT OF SINTERED YTTRIUM DIHYDRIDE COMPACTS FOR NUCLEAR REACTOR MODERATOR APPLICATIONS

A. P. Shivprasad aps@lanl.gov
High-density compacts of yttrium dihydride were synthesized using powder metallurgy and exhibited densities greater than 90% of the theoretical density. Compacts were then examined for phase purity using X-ray diffraction and elastic properties using resonant ultrasound spectroscopy. Results showed that sintered material was made up of approximately 1% yttrium trihydride and the rest yttrium dihydride. Youngs, bulk, and shear moduli were all lower than reported in literature and were attributed to internal porosity. Modulus values were clearly observed to vary as functions of density, while Poissons ratio was calculated as 0.221 0.003 and was independent of density. This work represents a novel achievement in demonstrating the feasibility of powder processing techniques to yield high-density yttrium dihydride compacts.
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DEVELOPMENT OF THE PLUTONIUM MODELING AND ASSESSMENT (PUMA) SIMULATION THROUGH THE COUPLING OF EXPERIMENTS AND MOLECULAR DYNAMICS

A. ajparkison@lanl.gov
A finite element computer simulation has been developed at the Los Alamos National Laboratory (LANL) to simulate the production process of 238PuO2 heat source pellets. This simulation, the Plutonium Modeling and Assessment (PUMA) code, is built upon the MOOSE framework. It was developed through an extensive experimental campaign using surrogates and validated for use in the PuO2 system through molecular dynamics simulations. The PUMA code is currently being used at LANL to understand and improve upon the current fabrication process.
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DYNAMIC RPS PATH TO FLIGHT

S. Oriti salvatore.m.oriti@nasa.gov
NASA Glenn Research Center has been pursuing the development of dynamic power conversion for several decades. Candidate NASA missions involve mutli-year travel to far away destinations, or to extreme environments where sunlight does not exist. Human-base mission studies also show that power needs would be beyond the capabilities of solar energy conversion, and instead would require nuclear reactor energy sources, for which the thermal energy must be converted to electricity. Dynamic power conversion technology has developed sufficiently to make a sound engineering argument that it is suitable for these NASA missions. Dynamic conversion power sources have yet to be flown in space, and thus suffer a disadvantage owing to their lack of heritage data on flight missions. One of the largest obstacles for adoption is the uncertainty in reliability of a device with moving parts. However, significant progress has been made toward demonstrating the technology capable in all relevant environments, with the necessary long life. Another hurdle for adoption is the lack of mission, which would drive specific requirements, and provide a solid timeline for technology development endpoint. Until a mission is identified, an alternative approach is necessary to advance a dynamic power conversion system towards flight.
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EMERGENCE OF A COMMERCIAL SPACE NUCLEAR ENTERPRISE

J. Locke, B. Lal jlocke@ida.org
Space nuclear systems have historically been developed and operated solely by the government. Private entities have always played a role in developing and launching nuclear payloads, but the Federal government drove of development and operation of such systems with the private sector playing the role of a contractor. However, recent years have seen growing private sector interest in leading the development, launch, and use of nuclear technologies for space applications. This growth follows similar trends toward commercialization in the broader space sector. This paper summarizes research that included a survey of the literature and interviews with 12 companies related to the space nuclear industry. The paper presents a definition of commercial space activities, develops a model for space nuclear systems, and then explores the status of commercial space nuclear activities in the United States. Ultimately we assess that the private sector is interested in expanding their role in the space nuclear enterprise, but requires, among other changes, regulatory revision to become fully commercial.
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EMPIRICAL POWER PREDCITION FOR MMRTG F1

C. E. Whiting, D. P. Kramer, C. D. Barklay chris.whiting@udri.udayton.edu
Power predictions for the MMRTG are, in part, based off of early performance data for the MMRTG F1 unit, currently on Mars. Now that F1 has been in operation for over half of its design life, a detailed analysis of its performance can be obtained. In this paper, a power degradation curve was made using the F1 telemetry data. Upon analysis of the data, it was determined that the power degradation does not obey first-order kinetics, and a much higher order rate equation was derived. This empirical degradation curve and rate equation can then be used to predict the performance of F1 for the remaining 7 years of its design life. These empirical predictions indicate that at the end of design life, F1 will be producing 75.2 We. This is a 25% increase in power over earlier predictions. A conservative estimate for future MMRTG performance indicates that the minimum power at the end of design life is 72.8 We. This is a 32% increase in power over earlier predictions. Communicating this improvement in the power prediction is important so that future science missions can plan to appropriately make use of the power that MMRTG will provide. In addition, it may be useful to communicate to the community the fact that the power degradation of MMRTG is steadily decreasing with time. Using a fixed annual power degradation value will not accurately describe the behavior of the MMRTG power.
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EVALUATION OF ALTERNATIVE FIBERS TO REPLACE NARC-RAYON FOR THE PRODUCTION OF CBCF

N. Gallego gallegonc@ornl.gov
A unique Carbon Bonded Carbon Fiber (CBCF) insulation was developed to provide thermal protection to the isotopic fuel in Radioisotope Power Systems. The microstructure of CBCF is comprised of chopped and carbonized rayon fibers bonded at intersections by carbonized phenolic resin. Production of CBCF insulation at ORNL has been sustained for the past three decades by a single lot of rayon purchased from North American Rayon Corporation (NARC) of Elizabethton, TN in 1987. NARC ceased operations in 1996. Although ORNL has a seven-to-ten-year supply of rayon at the current rate of consumption, an effort has been initiated to identify a new source to meet long-range needs. A summary of findings from the ongoing search for a fiber to replace NARC rayon for production of CBCF is presented.
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EXPERIMENTALLY VERIFYING THE EFFECTIVENESS OF FUELED CONTROL DRUMS

S. Judd s.judd@usnc.com
Water submersion criticality is a known problem in all current LEU Nuclear Thermal Propulsion core designs. This paper concerns a new control drum design that has the required control authority to shutdown cores even when submerged in water. It then describes the design, process, and results of a low-cost experiment used to test the feasibility and functionality of this new design.
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FLEXURE ISOTOPE STIRLING CONVERTOR (FISC) DEVELOPMENT PROGRESS

M. A. White maury.white@amsc.com
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field. The AMSC Stirling development team (formerly Infinia Corporation) is developing an advanced Stirling convertor, designated as the Flexure Isotope Stirling Convertor (FISC), for high efficiency Radioisotope Power Systems (RPS). After a successful Phase I FISC design, a Phase II fabrication and test contract with NASA Glenn Research Center (GRC) is about 30% complete at this writing in late 2018. Two FISC demonstration units will be thoroughly evaluated in Phase 2, then delivered to GRC for a wide range of Phase 3 performance assessments and flight qualification tests. FISC is a direct derivative of Infinias Technology Demonstration Convertor (TDC) and Stirling Radioisotope Generator (SRG) development contract with DOE/GRC between the mid-1990s and 2005. All four TDC units assigned to long-term testing at GRC demonstrated exceptional life and reliability in excess of 12 years with no maintenance or degradation. FISC uses the same basic topology as the already robust TDC. Some changes were required to address significantly higher operating temperature environments, and additional changes will further improve design margins, robustness and efficiency.
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FUEL ELEMENT TO MODERATOR ELEMENT HEAT TRANSFER ANALYSIS

M. Stewart Mark.E.Stewart@nasa.gov
This paper concerns an issue in Nuclear Thermal Propulsion (NTP) reactor design, namely, the heat flow between Fuel Elements (FE) and Moderator Elements (ME) in a reactor. This question is important as this heat flow is used to drive the propellant turbopumps, and must be properly matched for successful operation of relevant rocket reactors. The current NASA GCD NTP design requires insight into this issue. This heat flow is more complex than simple conduction. This paper aims to quantify the relevant effects through 1-D heat equation analysis and ANSYS 2-D thermal simulations.
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HANFORD'S ROLE IN SPACE POWER

B. Makenas, D. Wootan David.wootan@pnnl.gov
Hanford\'s role in early space reactor development and testing ranged from thermo-electric and thermionic power systems, SP-100 test reactor fuels testing, the design and fabrication of the SP-100 ground engineering system test, thermal propulsion testing for the Multi-MW reactor, and the proposed Jupiter Icy Moons Orbiter (JIMO) reactor.
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HIGH PERFORMANCE LIGHTWEIGHT MATERIALS MADE BY SHEAR ASSISTED PROCESSING AND EXTRUSION (SHAPE)

S. Whalen Scott.whalen@pnnl.gov
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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HISTORY AND CHALLENGES OF SPACE NUCLEAR REACTOR POWER SYSTEMS

X. Chunyang, X. Jiachun timberarch@163.com
Nuclear reactors are anticipated to power manned mission to Mars and other prospective deep space endeavors in the future and lots of attempts have been made in the U.S. and Russia since 1950s. This paper aims to present a retrospective review of the history of space nuclear reactor power systems from technology and non-technology perspectives and to put forward reflections on opportunities for future developments.
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HOT HYDROGEN TESTING AND MICROSTRUCTURAL CHARACTERIZATION OF MOLYBDENUM CERMETS FOR NUCLEAR THERMAL PROPULSION

T. G. Duffin, K. M. Benensky, S. J. Zinkle, M. W. Barnes tduffin2@vols.utk.edu
Nuclear thermal propulsion is capable of high specific impulse as well as high thrust and is the leading candidate propulsion technology for a crewed Mars mission. In this study, molybdenum ceramic metallic fuels were produced via spark plasma sintering and tested at 2000 K, 2250 K and 2500 K in flowing hydrogen in both thermal cycling and steady-state conditions. Tested samples were evaluated for mass loss and their microstructure was characterized. Mass loss was greater for thermally cycled samples than for those at steady-state and increased with both temperature and ceramic volume loading. Intense damage was observed in the ceramic particles in specific regions for the 2000 K tests that had higher frequency under thermal cycling.
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HYBRID FUEL COUPLING IN A PULSED Z-PINCH ROCKET ENGINE

B. Taylor brian.d.taylor@nasa.gov
The work presented here sought to explore a portion of the parameter space of a hybrid nuclear fuel in regards to ignition and burn by analyzing the effect of initial geometry and thermodynamic conditions. The authors performed 0D power balance and 1D burn wave calculations to determine temperature progression and energy production for defined initial conditions. Geometries examined are representative of concept fuels for a Pulsed Fission-Fusion (PuFF) engine. This work focuses on lithium deuteride and uranium 235 for the fuel since these are seen as leading candidates for PuFF. Presented below is a power balance illustrating a reduction in the energy and density required to breakeven of hybrid fuels in comparison with fusion fuels. Also the impact of fusion and fissile fuel quantities upon initial energies is presented. One can see that the initial energy required to breakeven in a hybrid cylindrical nuclear fuel decreases with decreasing fissile liner thickness, decreasing fusion fuel core radius, and increasing compression ratio of the fusion fuel.
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IMPACT TEMPERATURE DETERMINATION FOR GPHS SAFETY TESTING

J. Teague mulford@lanl.gov
Impact Testing of General Purpose Heat Sources (GPHS) is done to benchmark extensive safety calculations quantifying launch safety. Efforts to conduct an impact test at the extreme low end of the temperature range for launch highlights uncertainties in determining the GPHS clad temperature during impact tests. Direct measurement of clad temperatures in the impact configuration are described, and the effect of emissivity of the various components indicated. Calculation of the experimental clad impact temperature using the ANSYS thermal transport model indicates that the clad temperature at impact was outside the relevant range for launch safety modelling of GPHS behavior.
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IMPLEMENTATION OF CROSS-AGENCY NUCLEAR APPLICATIONS

J. F. Zakrajsek, T. Sutliff, J. Hamley, C. Sandifer, P. Mccallum, T. Bishop, M. Mccune june.f.zakrajsek@nasa.gov
The Radioisotope Power System (RPS) Program was established in 2009 to manage RPS investments for NASA to ensure the availability of RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible. The RPS Program is a multi-centerand multi-agencyprogram. NASA is in partnership with the Department of Energy (DOE) Office of Nuclear Energy to provide technologically robust nuclear power system solutions to robotic spacecraft and exploration missions. During the last decade, the RPS Program and DOE have supported missions, developed technologies and initiated new power system developments. These technical areas, as all technical areas, have challenges and standard engineering solutions; however, clearing the path to enable the technical work requires agreements to be established. This paper describes a process by which two governmental agencies have established a successful basis to accomplish the needed work.
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IMPROVING THE NUCLEAR LAUNCH APPROVAL PROCESS; PROGRESS AND PLANS

P. Mccallum peter.w.mccallum@nasa.gov
Launches involving radioisotope power systems (RPS) or radioisotope heater units (RHUs) must comply with a number of different statutory, regulatory, and administrative requirements. While some of these are well defined, others have been carried out on the basis of past practice rather than a set of formal standards. In addition, some of the requirements reference outdated standards and are in need of updates. The overall process is also time consuming and expensive. This paper describes efforts by NASA, the Department of Energy (DOE) and others to make improvements to the process while maintaining safety and environmental protection.or full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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INCREASED PLUTONIUM-238 PRODUCTION VIA HIGH FLUX ISOTOPE REACTOR PERMANENT BERYLLIUM REFLECTOR REDESIGN

D. Chandler, M. W. Crowell, K. E. Royston chandlerd@ornl.gov
Irradiation of 237Np-bearing targets in the permanent beryllium reflector (PBR) of Oak Ridge National Laboratorys (ORNL) High Flux Isotope Reactor (HFIR) results in high-purity 238Pu that can be used as a reliable power source for deep space and planetary National Aeronautics and Space Administration missions. However, HFIRs 238Pu production capability is constrained by the available irradiation volume in its PBR. In preparation for the HFIR beryllium change-out in 2023, ORNL staff have redesigned the PBR to include six additional irradiation sites, be more versatile with respect to irradiation and scattering experiments, and enhance its thermal-structural performance. The new PBR design offers large potential increases in annual 238Pu production at ORNL.
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INITIAL TESTING OF MEDIATED ELECTROCHEMICAL OXIDATION FOR INCLUSION IN THE PLUTONIUM-238 PRODUCTION PROGRAM

K. G. Myhre, M. E. Woods, A. J. Unger, P. D. Benny, D. E. Benker, E. D. Collins, L. H. Delmau, D. W. Depaoli, F. D. Riley, R. M. Wham myhrekg@ornl.gov
Oak Ridge National Laboratory is currently restarting the United States capability to produce kilogram quantities of 238 Pu annually for space power applications. This involves the purification of 238 Pu from neutron-irradiated 237 Np targets. Plutonium oxide is produced at various points during the radiochemical processing of these irradiated 237 Np targets, including as a final product for shipment to Los Alamos National Laboratory. Dissolution of the plutonium oxide product material is required to obtain an isotopic assay and impurity analysis of the product material. An electrochemical method that produces highly oxidizing ions in solution is currently being investigated as a rapid method for dissolving these plutonium oxide samples.
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INVESTIGATION OF PRODUCTION PARAMETER EFFECTS ON SPARK PLASMA SINTERED MOLYBDENUM CERMET WAFERS FOR NUCLEAR THERMAL PROPULSION APPLICATIONS

J. Zillinger, B. Segel, K. Benensky, D. Tucker, M. Barnes zill0470@vandals.uidaho.edu | rns59@case.edu
This study focused on nuclear fuel fabrication using powder blending and spark plasma sintering (SPS) of Mo-ZrO2 surrogate ceramic-metal (cermet) fuels. The study consisted of two co-projects: a powder blending/distribution study and an SPS parameter optimization study. The powder blending study focused on optimization of the powder processing parameters in order to fabricate high density cermets with uniformly distributed dispersed ceramic microstructures. The SPS parameter optimization study focused on the impact of sintering parameters (temperature, dwell time, and pressure) on the microstructural properties of a cermet (density/porosity, grain structure, and hardness). In the powder blending and distribution study, addition of 0.1 wt% and 0.5 wt% binder resulted in complete coverage and even distribution of large, spherical ZrO2 particles with Mo powder for batches of 50 vol% and 60 vol% ceramic loading respectively. When optimizing SPS parameters, fuel density (decreased porosity) was directly related to increase in sintering temperature, pressure, and time. Grain diameter and material hardness were observed to increase with temperature and pressure as well, indicating grain growth during the sintering process. Optimal sintering parameters suggested from this study, for Mo-ZrO2 cermets with 60 vol% ceramic loading, were found to be at a temperature of 1400C, at 50 MPa uniaxial pressure, for at least 5 minutes dwell time.
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JOHNSON THERMO-ELECTROCHEMICAL CONVERTER (JTEC) AS A HEAT TO ELECTRIC GENERATOR FOR NUCLEAR POWER SYSTEMS

D. Lonnie Johnson bprokes@johnsonrd.com
The Johnson-Thermo-Electrochemical Converter (JTEC) is a solid state heat engine that has the potential for achieving energy conversion efficiency levels as high 30 to 40% net, 70 to 80% of Carnot. Over the past five decades, conventional thermoelectric converters (Seebeck) have only achieved efficiency levels less than 15% of Carnot (6% net). As a more efficiency replacement for conventional converter technology, JTEC will provide NASA an attractive alternative for addressing the ever present need to minimize the amount of mass that must be delivered to space using expensive launch vehicles. A laboratory proof of concept demonstration has been successfully completed and an initial application analyses has been performed to understand the technology and its potential impacts at maturity. Johnson Research in collaboration with John Hopkins Applied Physics Laboratory are starting a program under the Radioisotope Power Systems Program to further explore the concept and advance the technology.
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KILOPOWER - MAXIMUM CREDIBLE DOSE FOR A CRITICALITY ACCIDENT

P. Mcclure pmcclure@lanl.gov
Inadvertent criticality is one end state for a space reactor launch accident. If a criticality were to occur, then consequences of this event must be estimated. This paper uses an estimate for the number fissions combined with estimates of release from historic space reactor criticality tests to estimate the dose to receptors at 100 m and 1000 m.
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KILOPOWER - MAXIMUM CREDIBLE FISSIONS FOR A CRITICALITY ACCIDENT

P. Mcclure pmcclure@lanl.gov
Inadvertent criticality is one end state for a space reactor launch accident. If a criticality were to occur, then consequences of this event must be estimated. The first step in estimating consequences is to estimate the source term, which is a function of the number of fissions that have occurred during the criticality. This paper presents a bounding estimate for the number of fissions for a Kilopower space reactor criticality accident based upon values for all historic criticality accidents to date.
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KILOPOWER REACTORS FOR POTENTIAL SPACE EXPLORATION MISSIONS

D. I. Poston poston@lanl.gov
Fission systems can expand our capability to explore space by orders of magnitude. This paper presents variations of the Kilopower concept, which could provide robust, long-lived power from 1 to 10 kWe for space exploration missions. The small, simple reactor design uses existing technology and lends itself to quick and affordable development. The simplicity in design, operation and development led to the success of the Demonstration Using Flattop Fissions (DUFF) and Kilowatt Reactor Using Stirling TechnologY (KRUSTY) tests. Conceptual designs and masses are presented for 1-kWe space science mission, 10-kWe NEP missions, a 1-kWe lunar demo mission and a 10-kWe Mars ISRU demo mission.
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LEU NTP ENGINE SYSTEM TRADES AND MISSION OPTIONS

C. Russell Joyner claude.joyner-ii@rocket.com
The future of human exploration missions to Mars are dependent on solutions to the technology challenges being worked by NASA and industry. One of the key architecture technologies involves propulsion that can transport the human crew from Earth orbit to other planets and back to Earth with the lowest risk to crew and the mission. Nuclear Thermal Propulsion (NTP) is a proven technology that provides the performance required to enable benefits in greater payload mass, shorter transit time, wider launch windows, and rapid mission aborts due to its high specific impulse (Isp). Aerojet Rocketdyne (AR) has stayed engaged for several decades in working NTP engine systems and has worked with NASA recently to perform an extensive study on using Low Enriched Uranium (LEU) NTP engine systems for a Mars campaign involving crewed missions from the 2030s through the 2050s. The impacts of the NTP engine system on the Mars transfer vehicle (MTV) configuration have been assessed via several trade studies since 2016, including thrust size, number of engine systems, liquid hydrogen stage size, reaction control system sizing, propellant losses, NASA Space Launch System (SLS) payload fairing (PLF) size impact, and aggregation orbit. AR study activity in 2018 included examining NTP stages derived from Mars crew mission elements to deliver extremely large cargo via multiple launches or directly off the NASA Space Launch System (SLS). This paper provides an update on the results of the on-going engine system and mission trade studies.
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LOW ENRICHED URANIUM NUCLEAR THERMAL ROCKET DESIGN INSPIRED BY THE SPACE NUCLEAR THERMAL PROPULSION PROJECT

C. J. Romnes, D. E. Chavez, B. J. Martinez, N. M. Osterhaus, W. R. Ford, R. Lenard gemini.carly@gmail.com
The development of a low enriched, nuclear thermal rocket (NTR) has become a necessity for more effective deep space travel. An NTR provides a significantly higher specific impulse (I sp ) than chemical rockets. Starting in the 1960s the United States began the Nuclear Engine for Rocket Vehicle Applications (NERVA) program. The overall design of the NTR described in this paper, INsTAR, incorporates many elements from the NERVA prototypes. While many NERVA engines incorporated a high enriched uranium fuel, the low enriched uranium fuel concepts have proven to be feasible. The overall design objective was to develop a full core design for an NTR that addresses the problems found in the Space Nuclear Thermal Propulsion Project core and improves upon the I sp and thrust to weight ratio observed during the project. The core design is characterized with respect to neutronics, thermal hydraulics, and propulsive performance. A critical component of the design was the study of materials utilized in the core and their compatibilities at high operating temperatures.
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MASS OPTIMIZATION OF POWER SYSTEM FOR SPACE APPLICATIONS

B. Sondelski sondelski@wisc.edu
A Brayton cycle coupled to a direct cooled nuclear reactor is being designed and optimized for a space surface power application. Robust models for the various Brayton cycle components were developed and integrated. Separately, a nuclear reactor model which provides an optimized reactor mass for given flow conditions was developed. Then mass correlations for the size of the recuperative heat exchanger and radiator panel, along with the reactor mass model, were integrated with the cycle model, and an optimization algorithm was developed to find the least massive power system. The optimization routine is being used to explore the effects of turbine inlet temperature, cycle pressures, and other various cycle parameters on the full system mass.
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MATURATION OF DYNAMIC POWER CONVERTORS FOR RADIOISOTOPE POWER SYSTEMS

S. Wilson, S. Oriti scott.d.wilson@nasa.gov
Dynamic Radioisotope Power Systems (DRPS) are being developed by NASAs Radioisotope Power Systems (RPS) Program in collaboration with the U.S. Department of Energy (DOE) for space science and exploration missions. A development effort is currently underway to mature dynamic power convertors for infusion into a potential future flight generator. This convertor maturation effort was formulated by the RPS Program at NASA Headquarters and utilizes expertise from agencys technology and mission centers to support requirements development and technology assessments. The effort is being executed by Glenn Research Centers (GRC) DRPS Project and the Thermal Energy Conversion Branch. The Dynamic Power Convertor (DPC) contracts consist of three phases to enable design, fabrication, and independent assessment of prototypes after delivery to the government. The contracts are intended to gather data on candidate dynamic conversion technologies to fill knowledge gaps, support assessments of dynamic conversion technologies, and elicit generator requirements. The 110-watt Stirling Radioisotope Generator (SRG-110) and Advanced Stirling Radioisotope Generator (ASRG) flight development projects provided Stirling convertor demonstration units and engineering models to verify and validate convertors against performance specifications and mission requirements. These units utilize temperature resistant materials and non-contacting bearings to demonstrate wear-free, long-life operation. This maturation effort builds on past lessons-learned and new requirements focused on demonstrating convertor robustness to critical environments meant to stress key aspects of each convertor within the margins of the design. This effort seeks to realize the full potential of dynamic power conversion technologies for NASAs space science and exploration missions.
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MICROSTRUCTURAL EVOLUTION OF HIGH DENSITY W-CERMETS EXPOSED TO FLOWING HYDROGEN AT TEMPERATURES EXCEEDING 2000 K

W. Carpenter, K. Benensky, M. Barnes, D. Dennis Tucker william.carpenter@mines.sdsmt.edu
Nuclear thermal propulsion (NTP) shows promising potential for crewed space exploration by enabling high specific impulse and thrust. The development of NTP systems presents unique fuel material challenges due to requirements for high operating temperatures, exceeding 2500 K, and chemical compatibility with a hydrogen propellant (coolant) during operation. NASA has been investigating ceramic-metal (cermet) fuels due to their high temperature capability and hydrogen compatibility of the refractory metal matrix. For this study, subscale tungsten (W) cermet specimens, with 60 vol% zirconia surrogate (ZrO2), were consolidated via spark plasma sintering (SPS). Sintered samples were tested at 2000C for 60 minutes and 2500?C for 5 minutes in flowing H2. After testing, as produced and tested specimens were cross sectioned for microstructural examination using optical microscopy, scanning electron microscopy, and microhardness in order to understand the stability of the bulk cermet microstructure under the different conditions. While the specimens retained structural integrity throughout testing with minimal mass loss, the microstructural investigation revealed hydrogen attack and migration of ZrO2 particles. Overall, the W matrix showed minimal grain growth and embrittlement as a result of testing.
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MIXED ALUMINA/CERIA COMPOSITIONS AS AN ENHANCED CERAMIC PROCESSING SURROGATE FOR RPS FUEL PELLETS

D. Kramer daniel.kramer@udri.udayton.edu
Due to various safety and other considerations, the U.S. currently employs plutonium-238in the form of 238PuO2 ceramic pellets as the fuel source in its current RPS (Radioisotope Power System) design. It is anticipated that a future European RPS design will also utilize a ceramic fuel form, such as 241AmO2-x. Understanding the processing characteristics of the selected ceramic fuel form is one technical subject common to both efforts. While it would be ideal to perform RPS fuel processing experiments with the actual heat source radioisotope, due to radiological, cost, materials availability, and other considerations the employment of a non-hazardous and non-radioactive surrogate material could greatly ease this field of study. Identifying a cold surrogate material, that as closely as possible mimics the processing characteristics of the selected radioisotope, will enhance future development studies in support of both European and U.S. RPS activities. This paper centers on the recent application of mixed alumina/ceria compositions as an enhanced ceramic processing surrogate in support of both respective RPS programs.
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MODELING HELIUM AND OXYGEN BEHAVIOR OF A PLUTONIA PELLET IN AN MMRTG

L. Hawkins lhawk1124@yahoo.com
The PuO2 pellets in the Multi-mission Radioisotope Thermoelectric Generator (MMRTG) were studied to understand the thermal, chemical and diffusion properties of the internally produced gases, to mitigate material interactions during the mission. Helium gas, produced from the alpha decay of the plutonium, and oxygen ions, produced by the reduction reaction of the PuO2, were modeled in COMSOL to demonstrate the behavior as the gases escape from the pellet. Helium and oxygen ions were produced by internal reactions which diffused through the grains. The thermal model produced an approximately 92 K temperature gradient from the centerline of the pellet to the surface. The physical properties of both elements were temperature dependent, and models were made for each depending on the rate of diffusion and permeation. The helium model of the open porosity demonstrated a higher pressure in the center, with a pressure gradient of approximately 0.065 Pa to the surface. The oxygen model showed the difference between two sizes of grains in the pellet, taking approximately 0.07 s to diffuse to the grain boundary for a 10 ?m grain and approximately 1.65 s for a 50 ?m grain. However, inaccuracies of this model resulted from the use of the diffusion coefficient of oxygen gas, and not that of an oxygen ion. A more accurate model can be produced with the correct diffusion coefficient.
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MONTE CARLO-INFORMED DECAY HEAT MODEL FOR CERMET LEU-NTP SYSTEMS

A. Denig, M. Eades andrewdenig@hotmail.com
Two methodologies for performing decay heat analysis with Monte Carlo simulations were developed and implemented on a representative nuclear thermal rocket (NTR) design. This paper presents the underlying theory, discusses the methodology, and states the key results. This work investigated the importance of utilizing a time-dependent Q-value for fission in NTRs due to its short burn time. Two approaches for deriving the Q-value were taken: one based on deconvolving the fission rate from the power to yield the rate of fission energy deposition, and the other based on the convergence of the fission product decay power during a long burn. The fission product decay power method produces results closer to theoretical values, as it captures more of the underlying physics occurring during burnup such as fission product transmutation. The calculated Q-values were employed to derive decay power profiles which were compared to the Emrich1 model. According to these new models, the Emrich model underestimates the amount of hydrogen required for decay heat cooling by as much as 23.3%.
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NUCLEAR HEAT SOURCE CONSIDERATIONS FOR AN ICY MOON EXPLORATION SUBSURFACE PROBE

D. Kramer daniel.kramer@udri.udayton.edu
RTG powered spacecraft have enabled the identification of several icy moons within the solar system which may contain sub-surface oceans of water below a thick ice cap up to tens of kilometers. Inserting a probe into one of these oceans may assist in determining whether Earth is the only place in the solar system where life forms have existed. One concept discussed in the literature is to employ plutonium-238 as a heat source within a probe to melt through the moons ice shell to the liquid ocean. This would then allow the investigation of the ocean environment. This paper discusses considerations for helping to identify potential radioisotope heat source for an icy moon probe, such as: thermal power output, half-life, future availability, etc. Additionally, a first-order analysis infers that two radioisotopes (curium-244 and uranium-232) exhibit a number of the characteristics likely required for a future ocean probe to one of the icy moons. The analysis suggests that compared to the mass of plutonium-238 required, 244Cm could require 75% less mass and 232U would require 88% less mass, while still yielding a similar thermal output. In addition to these options, consideration is given to polonium radioisotopes (Po-208 in particular) as a potential alternative. The authors highly recognize that the selection of any new radioisotope heat source material will require extensive; radiological considerations, realistic evaluation of obtainability, cost factors, and launch safety considerations.
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NUCLEAR LAUNCH APPROVAL: OPTIONS FOR CRITERIA

K. Kowal kkowal@ida.org
Space nuclear systems can be a key source of power and propulsion for many space exploration and science missions. The viability of space nuclear applications would benefit from a regulatory regime that is clear, cost effective, timely, and able to integrate safety into the entire lifecycle of a space nuclear system. Criteria for the safety of launching nuclear systems would inform the approval process and provide further accountability to the public that safety is being sufficiently considered. A framework is described, which can inform criteria for the nuclear launch approval process, and is focused on leveraging the established processes used by other agencies for transportation and use of nuclear materials on Earth to inform the development of a clear, transparent and predictable launch approval process for space nuclear systems. Findings include the potential for a multi-tiered approach to nuclear launch approval that is based on the material being launched, the system that contains the material, and a comparison to previously launched systems.
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NUCLEAR SECURITY CONSIDERATIONS FOR SPACE NUCLEAR POWER: A REVIEW OF PAST PROGRAMS WITH RECOMMENDATIONS FOR FUTURE CRITERIA

S. S. Voss svoss@gnnallc.com
Nuclear security plays an integral role in the design and mission planning for the proposed use of high enriched uranium (HEU) in small, compact power systems for space. Nuclear security issues have taken on great importance within the United States (US) and internationally since the early 1990s with the end of the Soviet Union resulting in excess weapons usable nuclear materials (NM) and the rise of international terrorism. As a result, US leadership has made nuclear security and the reduction in the use of weapons-usable materials a high national priority. For some missions, the use of HEU in space nuclear reactors and rockets may be enabling for future space missions. I examine whether or not the use of HEU can be justified based upon US Presidential policy. I also examine the unique challenge that space nuclear reactors present in establishing safety and security requirements. A review of past US and Russian nuclear security and safety guidelines for space nuclear power provides insights into what has worked in the past and how it may be applied in the future.
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NUCLEAR THERMAL PROPULSION DYNAMIC MODELING WITH MODELICA

J. Rader, M. B. R. Smith, M. Scott Greenwood, T. Jay Harrison smithmb@ornl.gov
Oak Ridge National Laboratory (ORNL) is participating in the nuclear thermal propulsion (NTP) research and development effort supported by the National Aeronautics and Space Administration (NASA). This effort involves collaboration between multiple research groups that represent various government agencies and industry partners. ORNL has developed a Modelica-based modeling package for dynamic system modeling of nuclear reactors called the Transient Simulation Framework of Reconfigurable Models (TRANSFORM). While this software has been successfully demonstrated in simulations of traditional pressurized-water reactors, boiling-water reactors, liquid-metal reactors, and molten-salt reactors, it has also been adapted for nontraditional use in modeling hybrid energy systems and in tritium transport. This versatility is being applied to the current NTP project, where specific modules within TRANSFORM are being developed for and applied to transient modeling of the NASA NTP design. This paper presents the current state of the ORNL-NTP model, the utility of TRANSFORM methodologies in NTP transient simulations, the ability to develop NTP-specific modules, and proposed future work for the model.
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NUCLEAR THERMAL ROCKET CONTROL

D. Sikorski dsikorsk@vols.utk.edu
This paper presents the historical methods of control of nuclear thermal rockets (NTR), with a focus on the state of the technology, with the most recent NTR control experience being the United States Rover program. Gaps in control technology are identified and next steps in developing controls for nuclear thermal rockets are proposed.
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OVERVIEW AND FUTURE OF OPEN CYCLE GAS-CORE NUCLEAR ROCKET

R. S. Raju, J. E. Foster ritzsr@umich.edu
Human exploration of entire solar system can be enabled if the gas core nuclear rocket concept is made feasible. The Gas-Core Nuclear Rocket has the potential to greatly reduce the trip time for a given mission as compared to chemical or electric propulsion systems. Operating at high temperature (104 105 K), the Gas-Core Nuclear Rocket achieve specific impulse (approaching 5000 s) and high thrust, essentially eclipsing conventional solid core nuclear thermal rockets. Challenges to the realization of this technology include 1) stably confining fissioning plasma, 2) preventing plasma erosion due to mixing and subsequent entrainment with hydrogen fuel, 3) optimizing heat transfer from the uranium plasma to the hydrogen fuel, and 4) protecting the nozzle from the high-temperature exhaust. In this review, past gas core nuclear technology development is surveyed along with a discussion of the current status of the technology.
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OVERVIEW OF THE PLUTONIUM-238 SUPPLY PROGRAM’S CERMET PRODUCTION TARGET

R. Howard howardrh@ornl.gov
The Plutonium-238 Supply Program is tasked with establishing a reliable domestic supply of Pu-238 to fuel radioisotope thermal generators and its role in supporting future space exploitation is crucial. In order to meet this need, researchers at the Oak Ridge National Laboratory developed a robust production target design that is used to irradiate neptunium/aluminum cermet pellets to transmute the feedstock into the usable Pu-238. This paper describes this target design, and the innovative design features employed to improve target fabrication and assembly.
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PARAMETRIC STUDY ON THERMAL HYDRAULICS CHARACTERISTICS OF A PARTICLE BED REACTOR FOR NUCLEAR THERMAL PROPULSION

Y. Ji jiyu1994joe11@163.com
Nuclear Thermal Propulsion (NTP) is regarded as a promising technology and selected as the leading candidate for the human exploration to Mars, as suggested in Design Reference Architecture 5.0 (DRA 5.0). For a long time, many novel NTP systems have been proposed, designed and tested, among which Nuclear Engine for Rocket Vehicle Application (NERVA) is the most famous one. In the NERVA program, enormous technologies were developed and some records were accomplished. Based on these achievements, a more excellent, compact and lightweight design, i.e., particle bed reactor (PBR) was proposed in the 1980s. In this paper, the thermal hydraulics characteristics of a proposed PBR are investigated. By assuming the characteristics are indifferent along the circumference, a two-dimensional steady-state analysis concerning the turbulent flows in PBR is performed using Computational Fluid Dynamics (CFD) tool. In addition, some further work investigates the effect of various aspects including flow direction, mass flow rate and the height of the nuclear reactor core on the internal flow and heat transfer processes within the reactor core. These findings may provide technical support for the subsequent design of PBR.
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PARTICLE SIZE ANALYSIS OF CERIUM DIOXIDE SURROGATE MATERIALS AS A SIMULANT FOR PLUTONIUM-238 DIOXIDE FUELS PROCESSING

F. Anne Carver fcarver@lanl.gov
Failure attributed to pellet cracking during fabrication of 238PuO2 pellets places a severe burden on production efforts through lost time, increased radiation dose due to product rework, and supplementary costs. Unfortunately, the difficulty in working with this material makes identification of root causes, and subsequent correction, infeasible on the production floor. Furthermore, the work presented here begins to experimentally investigate the behavior and variable sensitivity of the grog feedstock at the front end of the pellet production process using CeO2 surrogate material. This information is critical for establishing a baseline for the grog feedstock, one of the key variables in defining the performance of a 238PuO2 pellet during fabrication. Looking forward, this analysis lays the foundation for continued study and training using non-surrogate PuO2 materials.
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PASSIVE AND ACTIVE COOLING ANALYSIS FOR DECAY HEAT OF NUCLEAR THERMAL PROPULSION SYSTEMS

T. Winkle tristan.winkle@oregonstate.edu
Methods for decay heat removal are analyzed with the goal of reducing propellant consumption using TRansient Investigation COde for Reactor DEvelopments and Research (TRICORDER) tool developed by Ultra Safe Nuclear Corporation. TRICORDER is used to perform two-dimensional steady state conduction analysis to determine system radiative capabilities. 2-D results show significant reductions in cooldown time over legacy estimates. TRICORDER is also used to simulate three-dimensional transient active cooling through fuel and tie tube channels in order to evaluate hydrogen flow profiles. Legacy flow profiles are tested and deemed to be wasteful of hydrogen. Methods for reducing hydrogen consumption through more efficient flow profiles are discussed, and an example improved profile is simulated and commented upon.
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PATH TO A NEXT GENERATION RADIOISOTOPE THERMOELECTRIC GENERATOR (RTG)

J. Rock Jennifer.l.rock@nasa.gov
The Next Generation RTG Project (Next Gen RTGP) is one of three NASA-led projects commissioned by the Radioisotope Power Systems (RPS) Program. NASA HQ created the RPS Program in 2009 to ensure investments made in RPS technologies and systems would best meet future mission needs. As commissioned by the RPS Program, the main objective of the Next Gen RTGP is to mature an RPS technology and transition it to a new vacuum rated flight system design to ultimately allow DOE to fuel and deploy the Next Gen RTG for NASA mission needs for a non-atmosphere power solution. The Next Gen RTGP is offering system designers access to thermoelectric research previously conducted within the RPS Program as a potential energy conversion technology to meet that objective. The Next Gen RTGP works with DOE to provide system design contracts, and leverages an interagency partnership between the RPS Program and the DOE Office of Nuclear Energy to provide technically feasible power system solutions. The contracts are through Idaho National Laboratory (INL).
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POTENTIAL LAUNCH APPROVAL PROCESS FOR COMMERCIAL SPACE NUCLEAR SYSTEMS

S. V. Howieson, J. Behrens, K. M. Kowal showieso@ida.org
The current launch approval process for any space nuclear system has only been used for government launches, but there has been increasing interest by commercial entities to use space nuclear systems. To inform the identification of options to develop a launch approval process for commercial entities, we review the existing legal framework and launch approval process for government launches using nuclear systems and commercial launches with non-nuclear systems. We then discuss potential launch approval processes and implications for two different commercial space nuclear launch scenarios. We conclude by presenting the unresolved issues regarding commercial space nuclear launch approval, and recommend Congress establish a comprehensive approval framework.
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PROCESS DEVELOPMENT FOR PLUTONIUM-238 PRODUCTION AT OAK RIDGE NATIONAL LABORATORY

D. Depaoli depaolidw@ornl.gov
The third chemical processing campaign conducted at Oak Ridge National Laboratory with irradiated neptunium oxidealuminum cermet targets produced plutonium-238 oxide product meeting purity specifications for space power applications. This is a major step for the Plutonium?238 Supply Program toward reestablishing production. This summary highlights results to date and presents focus areas of current activities to improve process efficiency and to increase production rate.
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QUALIFICATION OF SPECIAL PROCESSES USING A GRADED APPROACH FOR THE LIGHT-WEIGHT RADIOISOTOPE HEATER UNIT METALLIC COMPONENT PRODUCTION AT OAK RIDGE NATIONAL LABORATORY

R. Miller, B. Friske, K. R. Veach, Jr millerrg@ornl.gov
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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RADIOISOTOPE POWER GENERATION WITH THERMOACOUSTIC POWER SYSTEM (TAPS) TECHNOLOGY

G. Bruder, F. Ritzert geoff.bruder@nirvana-es.com
Nirvana Energy Systems (NES) has pioneered and is commercializing an innovative ThermoAcoustic Power System (TAPS) based on technology developed by NASA and Xerox Palo Alto Research Center (PARC). The novel TAPS technology has no hot moving parts and incorporates well proven, reliable linear actuators in an engine based on the Stirling cycle. NES has designed, optimized, built and tested all sub-systems for reliability, ease of manufacturing and cost reduction over free-piston Stirling engines. The convertor is insensitive to radioisotope heat degradation, capable of 10+ years continuous operation, inexpensive to manufacture using well-established methods, and yields greater than 25% thermal to electrical efficiency all while being designed for a specific power greater than 30 We/kg. The NES Thermoacoustic Radioisotope Generator (TRG) represents the ultimate in remote power devices and is the next step toward reliable dynamic power conversion for space.
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RADIOISOTOPE POWER SYSTEMS - AN INTERAGENCY PROGRAM STATUS

T. J. Sutliff tsutliff@nasa.gov
Radioisotope power systems (RPS) have been in use in the United States for over 50 years. RPS-enabled NASA missions have utilized space nuclear power allowing them to explore planets, moons, and interstellar space. This exploration resulted in changes to our understanding of our Solar System and our place within it. In 2009, NASA HQ created a NASA program to ensure investments made in RPS technologies and systems would be best utilized by future missions. The RPS Program seeks to ensure the availability of RPS for the exploration of the solar system in environments where conventional solar or chemical power generation is impractical or impossible. The RPS Program, in partnership with the DOE Office of Nuclear Energy began, and continues to operate as an interagency partnership to provide technologically robust power system solutions to robotic spacecraft and exploration missions that otherwise would not be feasible. This paper provides a synopsis of current activities after a decade of formal interagency partnering.
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RE-ESTABLISHMENT OF LIGHT-WEIGHT RADIOISOTOPE HEATER UNIT PLATINUM-30% RHODIUM ALLOY COMPONENTS PRODUCTION AT OAK RIDGE NATIONAL LABORATORY

K. Rex Veach, Jr. rveach2662@gmail.com
During FY2018 the Oak Ridge National Laboratory (ORNL) Radioisotope Power Systems (RPS) Program completed re-establishment of capability to produce platinum-30% rhodium (Pt-30Rh) alloy components for the Light Weight Radioisotope Heater Unit (LWRHU) Program. These components were last produced at Mound Laboratory in the mid/late-1990s for the National Aeronautics and Space Administration (NASA) Cassini mission. The LWRHU Pt-30Rh Clad Body Subassembly and component fabrication operations are being performed in the iridium alloy Clad Vent Set (CVS) production area at ORNL. Existing equipment (furnaces, electron beam welders, presses, inspection, etc.) are being utilized along with new equipment (two lathes and laser marker) that were purchased for this work. ORNL purchased and qualified an initial quantity of starting materials (Pt powder, Pt-30Rh foil, sheet, and tubing). Equipment, tooling, and materials were procured/fabricated and qualified. Drawings and specifications were updated/modified/developed to the ORNL RPS Program format. Procedures were developed and qualified. All drawings, specifications, and procedures were reviewed/approved by the Idaho National Laboratory (INL) RPS Lead Lab Document Configuration Control Board (DCCB). The dimensional inspection operations and special processes (cleaning, heat treating, sintering, dye penetrant inspection, leak testing, and welding) were successfully qualified and documented. This paper will discuss the process of re-establishing LWRHU production at ORNL to provide for future NASA space exploration science mission needs10.
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RECOMMENDATIONS FOR THE NUCLEAR SAFETY AND LAUNCH APPROVAL PROCESS FOR FISSION REACTORS

A. Camp, A. Klein, P. Mcclure, P. Mccallum, S. Voss acamp32@comcast.net
NASAs Nuclear Power & Propulsion Technical Discipline Team has chartered a study of potential improvements to the nuclear safety and launch approval process. The study concurs with previous efforts that have identified excess duplication, complexity and uncertainty in the current approval process. With a focus on fission reactors, general design criteria and safety criteria are proposed that ensure public and environmental safety, while reducing the uncertainty and complexity in the review and approval process. These criteria take into account the long history of space reactor development and related government standards for nuclear safety. Also, recommendations are made for changes in organizational responsibilities to clarify roles and reduce duplication.
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RESULTS OF THE KRUSTY NUCLEAR SYSTEM TEST

D. I. Poston poston@lanl.gov
The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kWt Kilopower space reactor. This paper presents results from the KRUSTY nuclear system test, which operated the reactor power system at various temperatures and power levels for 28 consecutive hours. The testing showed that the system operated as expected, and that the reactor is highly tolerant of possible failure conditions and transients. The key feature demonstrated was the ability of the reactor to load-follow the demand of the power conversion system. The thermal power of the test ranged from 1.5 to 5.0 kWt, with a fuel temperature up to 880 C. Each 80-We-rated Stirling engine produced ~90 We at a component efficiency of ~35% and an overall system efficiency of ~25%.
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RESULTS OF THE KRUSTY WARM CRITICAL EXPERIMENTS

D. I. Poston poston@lanl.gov
The Kilowatt Reactor Using Stirling TechnologY (KRUSTY) was a prototypic nuclear-powered test of a 5-kWt Kilopower space reactor. This paper presents results from the KRUSTY critical experiments, which were completed prior to the final system test. The first set of criticals were cold or zero-power criticals; i.e. the core was not heated by fission power. These were followed by three warm criticals, where fission power heated the core to 200, 300 and 450 C respectively. These criticals provided the data and confidence required to proceed with the KRUSTY nuclear system test. The criticals also provided valuable data for the benchmarking of codes applicable to all nuclear systems. Overall, the results of the KRUSTY criticals, cold and warm, matched extremely well with the pre-test predictions
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REVIEW OF IRRADIATION HARDENING AND EMBRITTLEMENT EFFECTS IN REFRACTORY METALS RELEVANT TO NUCLEAR THERMAL PROPULSION APPLICATIONS

N. D. Gaffin, S. J. Zinkle, K. M. Benensky ngaffin@vols.utk.edu
Nuclear thermal propulsion (NTP) is advantageous for future crewed interplanetary missions because of its capability for high specific impulse, thrust, large abort windows, and good cargo capacity. A fuel under consideration for use in NTP systems is a ceramic metallic (cermet) consisting of fissile fuel particles, such as uranium dioxide (UO2) or uranium nitride (UN), suspended in a structural refractory metal matrix, such as molybdenum (Mo) or tungsten (W). When structural materials are irradiated at low temperatures (below ~0.35 times the melting point) to low doses (0.001 to 0.1 displacements per atom), irradiation hardening and embrittlement may occur. This phenomenon increases the yield strength of materials, but also causes a decline in ductility and an increase in the ductile to brittle transition temperature (DBTT). During operation, large temperature gradients are present throughout the core, causing regions of the fuel element to operate at relatively low temperatures and receive neutron doses conducive to irradiation hardening. A comprehensive literature review was conducted to determine the effects of low-fluence neutron irradiation of pure and alloyed Mo and W. Irradiation hardening occurs in Mo and W up to 1070 and 1100 K respectively, with significant changes in the mechanical properties even at very low neutron doses. The reviewed literature relevant to NTP applications are summarized, knowledge gaps identified, and implications of mechanical property evolution on fuel performance and operating margins discussed.
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SENSITIVITY STUDIES OF THE TUNGSTEN VECTOR ON THE PERFORMANCE OF A LEU NTP ENGINE

M. Krecicki mkrecicki@gatech.edu
This paper explores the sensitivity of the criticality to the tungsten vector for a nuclear thermal propulsion (NTP) core, utilizing low enriched uranium (LEU) fuel. Tungsten ceramic metal composite (cermet) fuel is required due to the extremely high temperatures achieved in the core. However, tungsten has a non-negligible thermal neutron absorption cross section. This requires the tungsten to be enriched to contain mostly 184W to maintain a critical configuration. The results of this study show that the core favors a harder spectrum, as expected, to reduce the parasitic absorption in tungsten. In addition, inaccurate tungsten vector definition (or relatively high manufacturing tolerances) can have a detrimental effect on the prediction of criticality, i.e., above 1,000 pcms.
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SMALL MODULAR FISSION REACTORS FOR SPACE APPLICATIONS: ENABLING AN AFFORDABLE, COMMERCIALLY DEVELOPED POWER ARCHITECTURE FOR THE MOON AND BEYOND

J. Stephen Herring, S. Mackwell, C. Pestak, K. Hilser jherring@usra.edu
More capable robotic exploration, ISRU, and sustained human presence will require electrical power in the 40 kW to 150 kW range that is continuously available throughout the entire day/night cycles of the planetary body being explored. In the case of the Moon, a power plant capable of meeting this need would form the basis for establishing commercial electrical utility services on the lunar surface. Such services will jump-start the exploration, resource mapping, commercial exploitation, and colonization of the Moon by a broad mix of public and private users that include space agencies, industries, adventurers, and entrepreneurs. To address the challenges and opportunities of establishing in-space commercial electrical utilities, Universities Space Research Association (USRA) recently began an internal research and development (IRAD) project to perform a concept study of a new small modular fission reactor (SMFR) targeted for use on the Moon.
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SNRE EIGENVALUE UNCERTAINTY QUANTIFICATION FROM NUCLEAR DATA SOURCES

V. Patel v.patel@usnc.com
Nuclear thermal propulsion designs include large margins for manufacturing, thermal, and neutronic uncertainties. In the past these uncertainties could be better understood through rapid design and experimental measurements. With shifts to more effort on computational designs and larger computing power available, uncertainties can be quantified using computational means. New nuclear thermal propulsion designs use monte-carlo analysis where well established deterministic uncertainty quantification techniques are not valid. This paper describes a total monte-carlo method that can be applied to determine sensitivities and uncertainties to neutron multiplication factors, neutron spectrum, and burnup from many sources including geometrical, material, and nuclear data. Focus is placed on comparing the Small Nuclear Rocket Engine eigenvalue uncertainty found to the iterated fission probability method.
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SPACE FISSION POWER: NASA’S BEST BET TO CONTINUE TO EXPLORE THE OUTER SOLAR SYSTEM

J. R. Casani John.R.Casani@jpl.nasa.gov
Implementation of balanced, cost-efficient programs to develop power technologies would enable future Voyager- and Cassini-class missions at the outermost planets; open up subsurface missions at Europa, Enceladus, and Titan; and facilitate orbiter and lander missions at Neptune and Triton. A rebalancing of the NASA power technology portfolio could establish the option of using fission power in space. The timing is right for the development of a small nuclear reactor design (such as KRUSTY) that can provide power for multi-year robotic missions and serve as a pathfinder and risk reduction strategy for the larger needs of future human exploration space power systems. *
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SPACE POWER TESTING IN THE FAST FLUX TEST FACILITY

D. Wootan, B. Makenas David.wootan@pnnl.gov
Westinghouse Hanford Company (WHC) was deeply involved in the development of a 100-kilowatt electric reactor for space, called SP-100, funded jointly by the National Aeronautics and Space Administration, the Department of Energy, and the Department of Defense, specifically the Strategic Defense Initiative Office. The SP-100 program was initiated in 1983 for the development of a compact nuclear reactor capable of producing electrical power in the range of 10 to 1000 kilowatt electric. This was a national program with contributions by the Jet Propulsion Laboratory, Los Alamos National Laboratory, Oak Ridge National Laboratory, the General Electric Company, Westinghouse Hanford Company, and a number of industrial suppliers. The mission of the program was to develop technology to support construction of a flight prototype in the mid-1990\'s. .
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SUNPOWER ROBUST STIRLING CONVERTOR (SRSC) PROJECT OVERVIEW

J. Collins, J. Gary Wood, J. Stanley, W. Otting josh.collins@ametek.com
In October 2017, the team of Sunpower and Aerojet Rocketdyne were awarded of a development contract by NASA GRC under NASAs ROSES 2016 Announcement of Opportunity. The contract is in support of the Radioisotope Power Source (RPS) offices goal of developing a robust, dynamic RPS for potential future flight missions. Sunpowers proposed design the Sunpower Robust Stirling Convertor (SRSC) implements robustness improvements identified in the point of departure, high performance free-piston Stirling convertor design the Advanced Stirling Convertor Engineering Unit (ASC-E3). New, key requirements for potential RPS missions have been added to project, and the expectation is the convertor produced in this contract will enable a 250W to 500W generator. Based on a modular design, the SRSC is predicted to enable a range of generators with variable levels of redundancy from 250W to 500W. This paper will focus on Phase II of the SRSC project, present the SRSC predicted performance, and highlight design improvements made to increase robustness while maintaining high performance and specific power.
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TEMPERATURE AND POWER SPECIFIC MASS SCALING FOR LEU CLOSED-CYCLE BRAYTON SYSTEMS FOR SPACE SURFACE POWER AND NUCLEAR ELECTRIC PROPULSION

C. G. Morrison c.morrison@usnc.com
The specific mass (or mass per unit power) is a fundamental performance metric in space power systems. For surface power, a low specific mass reduces launch costs and lander size. For nuclear electric propulsion, a low specific mass enables fast transit with within the solar system. Studies on specific mass have typically focused on point designs and have not adequately explored the design space and scaling of specific mass. Previous research by the author has studied closed cycle Brayton power conversion and has shown that specific mass is a strong function of temperature and power. This paper continues this research and explores the design space for radiatively-cooled closed nuclear Brayton systems with an emphasis on temperature and power. The resulting analyses show the scaling laws for specific mass.
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THE DEVELOPMENT, PROTOTYPING AND TESTING OF A SHOCK TOLERANT MILLI-WATT RADIOISOTOPE POWER SYSTEM

K. Kazemzadeh, J. Mccoy k.kazemzadeh@hi-z.com
Hi-Z Technology, Inc. has recently built, developed and tested a new milliwatt radioisotope power system (mW-RPS) after more than a decade of dormancy. Using a single 1.1Wt radioisotope heater unit (RHU), it will provide steady electric power of about 35 mW at 5 volts while also providing heat to the surrounding system components. Recent work has improved and validated the impact tolerance of the device. Development continues toward flight readiness.
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THE PYLON: COMMERCIAL LEU NUCLEAR FISSION POWER FOR LUNAR, MARTIAN, AND DEEP SPACE APPLICATIONS

M. J. Eades, M. Reed, C. G. Morrison, W. Deason, S. Judd, V. Patel, P. Venneri m.eades@usnc.com
USNC-Space is a wholly U.S. owned and operated company that was spun out of USNC to commercialize nuclear technology for space applications. USNC is a commercial company developing a terrestrial gas-cooled micro-modular reactor (MMR) for off-grid and rugged locations on Earth. The Pylon is a low-enriched uranium (LEU) fission reactor system utilizing the core technology of the MMR to provide electrical power and heat in locations such as the Moon, Mars, and open space. The reactor was designed to provides 1 MWth for a period of 10 years at temperatures of 1150 K. A direct-cycle Brayton power conversion system was baselined for power conversion. For Lunar and space applications a radiator was used for heat rejection, while a convective design was used for the Mars concept. The Pylon was designed to have a mass under 5,000 kg and to be able to provide hundreds of kWth for ISRU operations at heat rejection temperatures and high-quality process heat at temperatures as high as 1150 K.
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THE SIRIUS-1 NUCLEAR THERMAL PROPULSION FUELS TRANSIENT TEST SERIES IN THE IDAHO NATIONAL LABORATORY TREAT REACTOR

R. C. O\\'Brien Robert.Obrien@inl.gov
Nuclear Thermal Propulsion (NTP) fuels and component materials are subjected to extreme temperature transients through nuclear heating to NTP system from space cold to operational temperatures. Methodology for transient testing conceptual NTP fuels is presented in addition to the capsule design for static testing under the SIRIUS-1 series at the Idaho National Laboratory Transient Reactor Test (TREAT) reactor.
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THERMAL MODEL OF A ZERO BOIL OFF SYSTEM FOR THE NUCLEAR THERMAL PROPULSION SYSTEM

D. Plachta, X. Wang, J. Hartwig jason.w.hartwig@nasa.gov
NASA is currently developing an updated concept for a nuclear thermal propulsion (NTP) system. To enable this concept, efficient thermal insulation and cryocooler heat exchanger systems are required to eliminate boil-off of propellant. This paper presents the results of a thermal model used to assess the feasibility of using active cooling with a tube-on-tank heat exchanger configuration for the inline tank of the NTP system. Results show that: (1) cryocooler working fluid temperature and mass flow rate can be adjusted to achieve zero boil off (ZBO) with broad area cooling, (2) over-sizing the cryocooler lift directly translates into a reduction in tank pressure, and (3) broad area cooling may still maintain ZBO despite the reduced heat transfer between tank wall and propellant that is expected in reduced gravity.
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THERMAL-HYDRAULIC DESIGN FEATURES OF A MICRO NUCLEAR REACTOR POWER SOURCE APPLIED FOR MULTI-PURPOSE

X. Liu lx1181605510@163.com
Micro heat pipe cooled reactor power source (HRP) could be applied for space or underwater vehicles and it meets the future demands of them, safer structure, longer operating time, fewer mechanical moving parts than conventional power devices. In this paper, a 50kWe potassium heat pipe cooled reactor power source system is proposed. The reactor core is featured with Uranium nitride fuel and potassium heat pipes. Tungsten and water are used as shields and the reactivity is controlled by control drums. The thermoelectric generator (TEG) consists of thermoelectric conversion units and water cooler. The thermoelectric conversion units convert thermal energy to electric energy through the high-performance thermoelectric material. A code applied for designing and analyzing the rector power system is developed. It consists of multi-channel rector core model, heat pipe model using thermal resistance network, thermoelectric conversion and thermal conductivity model. Then tthe steady-state calculations are also conducted. It is concluded that the preliminary design of HPR design is reasonable and reliable. The designed residual heat removal system has sufficient safety margin to release the decay heat of the reactor. This work provides reference to the design of heat pipe cooled micro nuclear power source.
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TRADES ON DENSIFIED PROPELLANT FOR NUCLEAR THERMAL PROPULSION

A. Aueron ala0018@uah.edu
Nuclear Thermal Propulsion is an enabling technology for expanding both manned and unmanned spaceflight capability. For most efficient use of propellant by mass it must use cryogenic hydrogen, but its mass density is low compared to other propellant options. This results in large propellant tanks which can be heavy and absorb more heat from the space environment than smaller propellant tanks. Hydrogens density can be increased by storing it at lower temperatures, but such densification is usually discussed in the context of launch vehicles or other Earth applications. This paper explores trades on in space liquid hydrogen propellant storage that result from densified liquid hydrogen. It was found that during spacecraft coast storing close to the freezing point results in a small reduction of required active cooling power compared to storing near the boiling point. During burns when the Nuclear Thermal Propulsion emits neutrons and gamma rays increased liquid hydrogen density increases the amount of heat absorbed from the radiation per unit area and depth of hydrogen, but the higher density allows for more favorable tank geometries that reduce net heating.
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TURBO-BRAYTON CONVERTER FOR RADIOISOTOPE POWER SYSTEMS

J. J. Breedlove, T. M. Conboy, M. V. Zagarola jfb@creare.com
Creare has teamed with Aerojet Rocketdyne, Sest Incorporated (Sest), and the University of New Mexico Institute for Space and Nuclear Power Studies (UNM-ISNPS) to develop a turbo-Brayton power converter for future NASA missions that use radioisotope heat sources. NASA has considered the closed Brayton cycle attractive for space since the 1960s, and Creare has developed miniature Brayton technology for over 40 years. Key characteristics include high specific power, high efficiency, long-life operation without wear, undetectable vibration, and flexible packaging. Detailed design results indicate a 300 W e -class converter with a turbine inlet temperature of 730C will have a thermal-to-electric conversion efficiency of nearly 25% and a specific power greater than 20 W e /kg.
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UPDATE ON RADIATION TESTING FOR SPACE FISSION POWER SYSTEMS

M. F. Chaiken, M. A. Gibson max.f.chaiken@nasa.gov
Radiation effects on materials and electronics is a major topic that needs to be addressed for the advancement of Kilopower fission reactor power systems. The Kilopower project team has taken steps towards developing a standardized radiation environment qualification test plan for components and materials. Candidate nuclear reactor facilities for both low fluence electronics and high fluence materials irradiations have been identified and approached. Collaborations are being pursued with both NASA and external experts to ensure that the results of the qualification testing are appropriate and relevant to nuclear fission power flight systems.
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A VERSATILE NUCLEAR THERMAL PROPULSION (NTP) SYSTEM

M. Houts michael.houts@nasa.gov
For full papers, please enter your abstract here (250 words or less). For lightning talks, ignore this field.
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AM-241 OXIDE PRODUCTION AT LOS ALAMOS NATIONAL LABORATORY

B. Skidmore, H. A. Quintana, A. J. Parkison, L. B. Davenhall, K. D. Abney bes@lanl.gov
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ASSESSMENT OF MISSION-CENTRIC TECHNICAL CRITERIA FOR SAFE AND SUSTAINABLE SPACE NUCLEAR LICENSING

W. Kowalski, V. Clark william@atomosnuclear.com
The policy of the United States for nuclear power sources in space is to ensure that there is no undue risk of release of radioactive material. Using the historic SP-100 space nuclear reactor power system technology program, we reviewed safety requirements encompassing spacecraft and mission design to assess deviation from and additional specificity needed to create a modern, commercial perspective to safety with regard to nuclear power systems in space. We found that spacecraft and operational design criteria yield a more sustainable safety process than a reactor-focused approach.
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BERYLLIUM OXIDE AS A SOLID CORE NUCLEAR REACTOR ENGINE MODERATOR

D. Beale danimarie24@outlook.com
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BETAVOLTAICS FROM COTS: POWER FOR YEARS

L. lance.hubbard@pnnl.gov
Overwhelmingly, betavoltaics (BV) long-lasting power opens a broad range of applications which are not currently available. The birth of very low power electronics has opened up a market for the wide and accepted use of BVs (US Patent: US9887018). Todays low-power electronics are feeding the internet of things revolution. We propose to develop a low-power demonstration to support basic science studies in efficiency, component damage, and manufacturing processing of betavoltaic devices. Beta particle impacts have the potential to damage the metal contact region of the betavoltaic device. Beta particles impact in the region where power is extracted from the semiconductor, this electron-hole pairs made by the beta can promote the formation of metal alloys at the extraction point which leads to lost power generation. The formation of intermetallic contact alloys by beta impacts is not well known and can lead to device inoperability. The formation of beta-induced alloys at the contacts of the betavoltaic needs to be understood for the next generation of semiconductors. This work will seek to understand the formation of intermetallic regions at the contacts, as well as propose possible mitigation strategies. A better understanding of contact intermetallic formation from betavoltaics will set PNNL up as a world leader in this field and lead to development of PNNL based betavoltaic power for mission-critical sensor platforms.
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CONCEPTUAL DESIGN OF A HIGH POWER DENSITY HEAT SOURCE MODULE

J. Katalenich jakatale@gmail.com
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DECAY HEAT CAPTURE FOR ADDITIONAL NUCLEAR THERMAL ROCKET THRUST

A. Gonzalez, W. Culbreth aimeegonz53@yahoo.com
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DEVELOPMENT CAMPAIGN OF AN ADDITIVELY MANUFACTURED, INDUCTIVELY HEATED MODEL OF A SOLID-CORE NUCLEAR THERMAL ROCKET ENGINE

S. Powers, C. Powers, S. Cendro, D. Ochoa-Cota, B. Kretschmer scpowers@usc.edu
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DEVELOPMENT OF ROBUST AND RELIABLE EXPERIMENTS TO QUALIFY NUCLEAR THERMAL PROPULSION ENGINE FUELS AND COMPONENTS

R. Howard howardrh@ornl.gov
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ENHANCED THERMOELECTRIC PERFORMANCE OF RARE-EARTH TELLURIDE COMPOUNDS VIA BAND STRUCTURE ENGINEERING

D. Cheikh Dean.A.Cheikh@jpl.nasa.gov
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FISSION MATRIX NEUTRONICS CALCULATIONS WITH TEMPERATURE FEEDBACK IN A NUCLEAR THERMAL PROPULSION CORE

A. J. Rau, W. J. Walters wjw24@psu.edu
n/a
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GRAPHENE SUPERLATTICE BASED THERMOELEMENT FOR RADIOISOTOPE THERMOELECTRIC GENERATOR

S. Kumar Mishra, A. Pente, A. Kumar, C. Prakash Kaushik, B. Dikshit shaktimishra15@gmail.com
In the present days RTGs; major limitation is the lower conversion efficiency of segmented thermoelectric unicouple; which necessiates the development of technically suitable thermoelement with enhanced efficiency. The maximum conversion of thermal to electrical energy of the present day thermoelement is limited to 15 % only. This is attributed to its lower Seebeck coefficient and figure-of-merit. Graphene superlattice heterostructures based thermoelement is being studied to increase the conversion efficiencies significantly and seems to be promising candidate for replacement of the existing lower efficient thermoelement. This is possible by applying different electric potential on the top metallic gate electrodes periodically patterned over the h-BN encapsulated graphene superlattice which is deposited on a SiO2 substrate backed by a doped Si substrate acting as a back gate. The maximum Seebeck coefficient can be tuned by varying the gate electrodes potential. Initially the gate voltage is supplied from an external source and later switched over to Seebeck potential after reaching a stable voltage range. Transfer matrix approach was followed for theoretical calculations of the Seebeck coefficient. This also describes the feasibility of graphene superlattice element based RTGs followed by evaluation of its overall efficiency under the similar conditions with respect to temperature & surface area of heat source. Due to higher efficiency, this gives the possibility for an alternative radioisotope like easily available radio nuclides Am-241 and Sr-90 as compared to Pu-238; which is used in todays RTGs. This can be achieved without compromising with the power output & payload.  
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HEAVY ION THERMIONIC ENERGY CONVERSION (HITEC): A DESIGN STUDY

A. Lo loaustin09@berkeley.edu
The cesium vapor diode is the only demonstrable power producing thermionic energy conversion (TEC) device deployed in space to date. It remains a promising candidate for nuclear space power applications given its high power density and simplistic design. In the current state of the art, emission electrons ionize the Cs vapor which conducts the electrons across the interelectrode gap, losing 50% of their energy in the process. This fundamental physics drawback constrains a TECs design (interelectrode gap, wgap<0.5mm) and limits operating efficiencies (5.5%, TOPAZ reactor). The author proposes an alternative plasma ignition source for in-core nuclear reactor TECs: heavy ions from fissioning a cladless nuclear fuel element. This concept was explored briefly by General Motors and the Office of Naval Research in the 1960s and yielded promising results, yet was never pursued further by either group. This plasma ignition scheme would simultaneously enhance device efficiency (>30%) and relax design constraints (wgap>5mm) by raising the plasma Teand allowing for noble gas electron conduction instead of Cesium. LBNLs Nuclear Data Group is collecting dE/dx data in plasma targets of various compositions and ionizations using the 88-inch cyclotron as a source of low energy (~1MeV/nucleon), high charge-state heavy ions.This data will benchmark Michigan State Universitys Plasma Theory and Simulation Group PIC code to verify its applicability Heavy Ion Thermionic Energy Converter (HITEC) reactor design.This graduate work is being carried out in collaboration with Argonne National Laboratory, Michigan State University, and University of California Berkeley.
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IMPROVING POWER FACTOR AND MECHANICAL PROPERTIES OF YB14MGSB11 FOR APPLICATION IN A RADIOISOTOPE THERMAL GENERATOR.

C. Perez cpe@ucdavis.edu
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MOLTEN SALT REACTORS FOR NUCLEAR ELECTRIC PROPULSION

P. R. Rubiolo, M. Tano Retamales, V. Ghetta, N. Capellan, J. Giraud, J. Blanco, S. David pablo.rubiolo@lpsc.in2p3.fr
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NTP LUNAR DESIGN REFERENCE MISSIONS

C. B. Reynolds, J. F. Horton, C. R. Joyner Ii, T. Kokan Christopher.Reynolds@rocket.com
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OBSERVATIONS OF AGING 238PUO2 MICROSPHERES

J. Katalenich jakatale@gmail.com
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OPTIMIZATION OF PLUTONIUM-238 PRODUCTION IN THE ADVANCED TEST REACTOR FOR RADIOISOTOPE THERMOELECTRIC GENERATORS IN DEEP SPACE EXPLORATION APPLICATIONS

G. Marcantel gracemarcantel16@gmail.com
Plutonium production for use in Radioisotope Thermoelectric Generators (RTGs) is becoming increasingly important in the United States due to several reasons. The plutonium stockpile originally purchased from the USSR has steadily decreased due to utilization in RTGs and the degrading quality of the specific plutonium isotope of interest in the stockpile: plutonium-238. With a half-life of 87.7 years, the quality has decreased since it was originally purchased just after the Cold War. The United States is aiming to produce high-quality 238Pu and become independent in space fuel production in the process. The high-quality plutonium combined with the currently available low-quality plutonium will produce usable fuel for future space explorations like the Mars 2020 expedition. This paper details the new models / methodologies investigated by Center for Space Nuclear Research (CSNR) to optimize 238Pu production in the Advanced Test Reactor (ATR). Increasing the 238Pu production at ATR will supplement the current production at the High Flux Isotope Reactor (HFIR) at Oak Ridge National Labs in Tennessee to achieve the national goal of 1.5 2.0 kg 238Pu per year.
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ORNL-INL DATA DRIVEN OPTIMIZATION PRODUCTION AND HARVESTING TOOL

J. Navarro navarroj@ornl.gov
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PERFORMANCE ANALYSIS OF NUCLEAR THERMAL PROPULSION REACTOR USING DRIVER FUEL ELEMENT

H. Honglei, X. Jiachun, H. Gu huohl09@163.com
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POTENTIAL IMPROVEMENTS TO 237NP TARGETS AT THE HIGH FLUX ISOTOPE REACTOR

C. Bryan bryancd@ornl.gov
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PROCESS DEVELOPMENTS IN FABRICATING U-10MO PLATE FUEL

C. Painter, C. Lavender, J. Vineet Chad.Painter@pnnl.gov
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RECENT FY18/FY19 NTP MATERIALS DEVELOPMENT ACTIVITIES AT NASA MARSHALL SPACE FLIGHT CENTER

K. Benensky kelsabenensky@gmail.com
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THE RADIOISOTOPE POWER SYSTEM DOSE ESTIMATION TOOL (RPS-DET) 2019 DEVELOPMENT UPDATE

M. B. R. Smith smithmb@ornl.gov
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VERSATILE NTP CORE DESIGN

M. Eades m.eades@usnc.com
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Y-12 FABRICATION OF KRUSTY ALLOY COMPONENTS

H. Longmire, J. Henkel, P. Hoppe, A. Moore hollie.longmire@cns.doe.gov
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