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Fabrication and Testing of Full-Length Single-Cell Externally Fueled Converters for Thermionic Reactors

Description: The preceding paper described designs and analyses of thermionic reactors employing full-core-length single-cell converters with their heated emitters located on the outside of their internally cooled collectors, and it presented results of detailed parametric analyses which illustrate the benefits of this unconventional design. The present paper describes the fabrication and testing of full-length prototypical converters, both unfueled and fueled, and presents parametric results of electrically heated tests. The unfueled converter tests demonstrated the practicality of operating such long converters without shorting across a 0.3-mm interelectrode gap. They produced a measured peak output of 751 watts(e) from a single diode and a peak efficiency of 15.4%. The fueled converter tests measured the parametric performance of prototypic UO(subscript 2)-fueled converters designed for subsequent in-pile testing. They employed revolver-shaped tungsten elements with a central emitter hole surrounded by six fuel chambers. The full-length converters were heated by a water-cooled RF-induction coil inside an ion-pumped vacuum chamber. This required development of high-vacuum coaxial RF feedthroughs. In-pile test rules required multiple containment of the UO (subscript 2)-fuel, which complicated the fabrication of the test article and required successful development of techniques for welding tungsten and other refractory components. The test measured a peak power output of 530 watts(e) or 7.1 watts/cm (superscript 2) at an efficiency of 11.5%. There are three copies in the file. Cross-Reference a copy FSC-ESD-217-94-529 in the ESD files with a CID #8574.
Date: June 1, 1994
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Design Modifications for Increasing the BOM and EOM Power Output and Reducing the Size and Mass of RTG for the Pluto Mission

Description: A companion paper analyzed the effect on source modules for three specific fuel options, and compared the predicted power output with JPL's latest goals for the Pluto Fast Flyby (PFF) mission. The results showed that a 5-module RTG cannot fully meet JPL's goals with any of the available fuels; and that a 6-module RTG more than meets those goals with Russian fuel, almost meets them with U.S. (Cassini-type) fuel, but still falls far short of meeting them with the depleted fuel from the aged (1982) Galileo spare RTG. The inadequacy of the aged fuel was disappointing,because heat source modules made from it already exist, and their use in PFF could result in substantial cost savings. The present paper describes additional analyses which showed that a six-module RTG with the aged fuel can meet JPL's stipulated power margin with a relatively simple design modification, that a second design modification makes it possible to recover all of the mass and size penalty for going from five to six heat source modules, and that a third modification could raise the EOM power margin to 16%. There are four copies in the file. Cross Reference ESD Files FSC-ESD-217-94-531 (CID #8572)
Date: June 1, 1994
Creator: Schock, Alfred; Or, Chuen T & Kumar, Vasanth
Partner: UNT Libraries Government Documents Department

Design Modifications for Increasing the BOm and EOM Power Output and Reducing the Size and Mass of RTG for the Pluto Mission

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. A companion paper analyzed the effect on source modules for three specific fuel options, and compared the predicted power output with JPL's latest goals for the Pluto Fast Flyby (PFF) mission. The results showed that a 5-module RTG cannot fully meet JPL's goals with any of the available fuels; and that a 6-module RTG more than meets those goals with Russian fuel, almost meets them with U.S. (Cassini-type) fuel, but still falls far short of meeting them with the depleted fuel from the aged (1982) Galileo spare RTG. The inadequacy of the aged fuel was disappointing,because heat source modules made from it already exist, and their use in PFF could result in substantial cost savings. The present paper describes additional analyses which showed that a six-module RTG with the aged fuel can meet JPL's stipulated power margin with a relatively simple design modification, that a second design modification makes it possible to recover all of the mass and size penalty for going from five to six heat source modules, and that a third modification could raise the EOM power margin to 16%.
Date: August 1, 1994
Creator: Schock, Alfred; Or, Chuen T & Kumar, Vasanth
Partner: UNT Libraries Government Documents Department

Design, Analysis, and Optimization of a Radioisotope Thermophotovoltaic (RTPV) Generator, and its Applicability to an Illustrative Space Mission

Description: Paper presented at the 45th Congress of the IAF in Jerusalem, Israel, October 1994. The paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator (RTPV), to complement similar studies of Radioisotope Thermoelectric Generators (RTGs) and Stirling Generators (RSGs) previously published by the authors. To focus the design effort, it was decided to direct it at a specific illustrative space mission, Pluto Fast Flyby (PFF). That mission, under study by the JPL, envisages a direct eight to nine-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a six-week post-encounter cruise.
Date: October 1, 1994
Creator: Schock, Alfred; Mukunda, Meera; Or, Chuen T; Kumar, Vasanth & Summers, G.
Partner: UNT Libraries Government Documents Department

Development and Use of the Galileo and Ulysses Power Sources

Description: Paper presented at the 45th Congress of the International Astronautical Federation, October 1994. The Galileo mission to Jupiter and the Ulysses mission to explore the polar regions of the Sun required a new power source: the general-purpose heat source radioisotope thermoelectric generator (GPHS-RTG), the most powerful RTG yet flow. Four flight-qualified GPHS-RTGs were fabricated with one that is being used on Ulysses, two that are being used on Galileo and one that was a common spare (and is now available for the Cassini mission to Saturn). In addition, and Engineering Unit and a Qualification Unit were fabricated to qualify the design for space through rigorous ground tests. This paper summarizes the ground testing and performance predictions showing that the GPHS-RTGs have met and will continue to meet or exceed the performance requirements of the ongoing Galileo and Ulysses missions. There are two copies in the file.
Date: October 1, 1994
Creator: Bennett, Gary L; Hemler, Richard J & Schock, Alfred
Partner: UNT Libraries Government Documents Department

Effect of Fuel and Design Options on RTG Performance versus PFF Power Demand

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. The present paper confines its attention to the relatively conservative option employing standard thermoelectric unicouples, since that may be the only one flight-ready for the projected PFF launch in 2001. There are four copies in the file; also a copy in the ESD files. Included in the file are two previous documents with the same title dated 4/18/1994.
Date: August 1, 1994
Creator: Schock, Alfred & Or, Chuen T
Partner: UNT Libraries Government Documents Department

Analysis, Optimization, and Assessment of Radioisotope Thermophotovoltaic System Design for an Illustrative Space Mission

Description: A companion paper presented at this conference described the design of a Radioisotope Thermophotovoltaic (RTPV) Generator for an illustrative space mission (Pluto Fast Flyby). It presented a detailed design of an integrated system consisting of a radioisotope heat source, a thermophotovoltaic converter, and an optimized heat rejection system. The present paper describes the thermal, electrical, and structural analyses which led to that optimized design, and compares the computed RTPV performance to that of a Radioisotope Thermoelectric Generator (RTG) designed for the same mission. RTPV's are of course much less mature than RTGs, but our results indicate that - when fully developed - they could result in a 60% reduction of the heat source's mass, cost, and fuel loading, a 50% reduction of generator mass, a tripling of the power system's specific power, and a quadrupling of its efficiency. The paper concludes by briefly summarizing the RTPV's current technology status and assessing its potential applicability for the PFF mission. For other power systems (e.g. RTGs), demonstrating their flight readiness for a long mission is a very time-consuming process to determine the long-term effect of temperature-induced degradation mechanisms. But for the case of the described RTPV design, the paper lists a number of factors, primarily its cold (0 to 10 degrees C) converter temperature, that may greatly reduce the need for long-term tests to demonstrate generator lifetime. In any event, our analytical results suggest that the RTPV generator, when developed by DOE and/or NASA, would be quite valuable not only for the Pluto mission but also for other future missions requiring small, long-lived, low mass generators. Another copy is in the Energy Systems files.
Date: June 28, 1994
Creator: Schock, Alfred; Mukunda, Meera & Summers, G.
Partner: UNT Libraries Government Documents Department

Thermionic Reactor Design Studies

Description: Paper presented at the 29th IECEC in Monterey, CA in August 1994. The present paper describes some of the author's conceptual designs and their rationale, and the special analytical techniques developed to analyze their (thermionic reactor) performance. The basic designs, first published in 1963, are based on single-cell converters, either double-ended diodes extending over the full height of the reactor core or single-ended diodes extending over half the core height. In that respect they are similar to the thermionic fuel elements employed in the Topaz-2 reactor subsequently developed in the Soviet Union, copies of which were recently imported by the U.S. As in the Topaz-2 case, electrically heated steady-state performance tests of the converters are possible before fueling.
Date: August 1, 1994
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Thermionic Reactor Design Studies

Description: During the 1960's and early 70's the author performed extensive design studies, analyses, and tests aimed at thermionic reactor concepts that differed significantly from those pursued by other investigators. Those studies, like most others under Atomic Energy Commission (AEC and DOE) and the National Aeronautics and Space Administration (NASA) sponsorship, were terminated in the early 1970's. Some of this work was previously published, but much of it was never made available in the open literature. U.S. interest in thermionic reactors resumed in the early 80's, and was greatly intensified by reports about Soviet ground and flight tests in the late 80's. This recent interest resulted in renewed U.S. thermionic reactor development programs, primarily under Department of Defense (DOD) and Department of Energy (DOE) sponsorship. Since most current investigators have not had an opportunity to study all of the author's previous work, a review of the highlights of that work may be of value to them. The present paper describes some of the author's conceptual designs and their rationale, and the special analytical techniques developed to analyze their performance. The basic designs, first published in 1963, are based on single-cell converters, either double-ended diodes extending over the full height of the reactor core or single-ended diodes extending over half the core height. In that respect they are similar to the thermionic fuel elements employed in the Topaz-2 reactor subsequently developed in the Soviet Union, copies of which were recently imported by the U.S. As in the Topaz-2 case, electrically heated steady-state performance tests of the converters are possible before fueling. Where the author's concepts differed from the later Topaz-2 design was in the relative location of the emitter and the collector. Placing the fueled emitter on the outside of the cylindrical diodes permits much higher axial conductances to reduce ohmic losses ...
Date: June 1, 1994
Creator: Schock, Alfred
Partner: UNT Libraries Government Documents Department

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Applicability to an Illustrative Space Mission

Description: The paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator (RTPV), to complement similar studies of Radioisotope Thermoelectric Generators (RTGs) and Stirling Generators (RSGs) previously published by the author. Instead of conducting a generic study, it was decided to focus the design effort by directing it at a specific illustrative space mission, Pluto Fast Flyby (PFF). That mission, under study by JPL, envisages a direct eight-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a post-encounter cruise lasting up to one year.
Date: February 14, 1994
Creator: Schock, A.; Mukunda, M.; Or, T.; Kumar, V. & Summers, G.
Partner: UNT Libraries Government Documents Department

Radioisotope Thermophotovoltaic (RTPV) Generator and Its Application to the Pluto Fast Flyby Mission

Description: This paper describes the results of a DOE-sponsored design study of a radioisotope thermophotovoltaic generator. Instead of conducting a generic study, it was decided to focus the design by directing it at a specific space mission, Pluto Fast Flyby (PFF). That mission, under study by JPL, envisages a direct eight-year flight to Pluto (the only unexplored planet in the solar system), followed by comprehensive mapping, surface composition, and atmospheric structure measurements during a brief flyby of the planet and its moon Charon, and transmission of the recorded science data to Earth during a one-year post-encounter cruise. Because of Pluto's long distance from the sun (30-50 A.U.) and the mission's large energy demand, JPL has baselined the use of a radioisotope power system for the PFF spacecraft. The chief advantage of Radioisotope Thermophotovoltaic (RTPV) power systems over current Radioisotope Thermoelectric Generators (RTGs) is their much higher conversion efficiency, which greatly reduces the mass and cost of the required radioisotope heat source. Those attributes are particularly important for the PFF mission, which - like all NASA missions under current consideration - is severely mass- and cost-limited. The paper describes the design of the radioisotope heat source, the thermophotovoltaic converter, and the heat rejection system; and presents the results of the thermal, electrical, and structural analysis and the design optimization of the integrated RTPV system. It briefly summarizes the RTPV system's current technology status, and lists a number of factors that my greatly reduce the need for long-term tests to demonstrate generator lifetime. Our analytical results show very substantial performance improvements over an RTG designed for the same mission, and suggest that the RTPV generator, when developed by DOE and/or NASA, would be quite valuable not only for the PFF mission but also for other future missions requiring small, long-lived, low-mass generators. There ...
Date: January 16, 1994
Creator: Schock, Alfred; Mukunda, Meera; Or, Chuen T; Kumar, Vasanth & Summers, G.
Partner: UNT Libraries Government Documents Department

Superconducting thermoelectric generator

Description: Thermoelectricity is produced by applying a temperature differential to dissimilar electrically conducting or semiconducting materials, thereby producing a voltage that is proportional to the temperature difference. Thermoelectric generators use this effect to directly convert heat into electricity; however, presently-known generators have low efficiencies due to the production of high currents which in turn cause large resistive heating losses. Some thermoelectric generators operate at efficiencies between 4% and 7% in the 800{degrees} to 1200{degrees}C range. According to its major aspects and bradly stated, the present invention is an apparatus and method for producing electricity from heat. In particular, the invention is a thermoelectric generator that juxtaposes a superconducting material and a semiconducting material - so that the superconducting and the semiconducting materials touch - to convert heat energy into electrical energy without resistive losses in the temperature range below the critical temperature of the superconducting material. Preferably, an array of superconducting material is encased in one of several possible configurations within a second material having a high thermal conductivity, preferably a semiconductor, to form a thermoelectric generator.
Date: January 1, 1994
Creator: Metzger, J.D. & El-Genk, M.S.
Partner: UNT Libraries Government Documents Department

Insulator coating for high temperature alloys method for producing insulator coating for high temperature alloys

Description: A method for fabricating an electrically insulating coating on a surface is disclosed comprising coating the surface with a metal, and reacting the metal coated surface with a nonmetal so as to create a film on the metal-coated surface. Alternatively, the invention provides for a method for producing a noncorrosive, electrically insulating coating on a surface saturated with a nonmetal comprising supplying a molten fluid, dissolving a metal in the molten fluid to create a mixture, and contacting the mixture with the saturated surface. Lastly, the invention provides an electrically insulative coating comprising an underlying structural substrate coated with an oxide or nitride compound. This invention has applications to breeding blankets for fusion reactors as well as to alkali metal thermal to electric converters.
Date: December 31, 1994
Creator: Park, J.H.
Partner: UNT Libraries Government Documents Department

Impact of the use of low or medium enriched uranium on the masses of space nuclear reactor power systems

Description: The design process for determining the mass increase for the substitution of low-enriched uranium (LEU) for high-enriched uranium (HEU) in space nuclear reactor systems is an optimization process which must simultaneously consider several variables. This process becomes more complex whenever the reactor core operates on an in-core thermionic power conversion, in which the fissioning of the nuclear fuel is used to directly heat thermionic emitters, with the subsequent elimination of external power conversion equipment. The increased complexity of the optimization process for this type of system is reflected in the work reported herein, where considerably more information has been developed for the moderated in-core thermionic reactors.
Date: December 1, 1994
Partner: UNT Libraries Government Documents Department

Thermoelectric material development. Final report

Description: A search was made for improved TE materials that could have higher efficiency than state-of-the-art SiGe alloys used in Radioisotope Thermoelectric Generators. A new family of materials having the skutterudite structure was identified (cubic space group Im3, formula (Fe, Co, Ni)As{sub 3}). Properties of n-type IrSb{sub 3}, CoSb{sub 3}, and their solid solutions were investigated. Pt, Te, Tl, and In were used as dopants. The thermal conductivity was reduced by about 70% for the solid solutions vs the binary compounds. A maximum ZT of about 0.36 was measured on Co-rich solid solutions which is 160% improved over that of the binary compounds.
Date: October 1, 1994
Creator: Vandersande, J.W.; Allevato, C. & Caillat, T.
Partner: UNT Libraries Government Documents Department

Calculational framework for safety analyses of non-reactor nuclear facilities

Description: A calculational framework for the consequences analysis of non-reactor nuclear facilities is presented. The analysis framework starts with accident scenarios which are developed through a traditional hazard analysis and continues with a probabilistic framework for the consequences analysis. The framework encourages the use of response continua derived from engineering judgment and traditional deterministic engineering analyses. The general approach consists of dividing the overall problem into a series of interrelated analysis cells and then devising Markov chain like probability transition matrices for each of the cells. An advantage of this division of the problem is that intermediate output (as probability state vectors) are generated at each calculational interface. The series of analyses when combined yield risk analysis output. The analysis approach is illustrated through application to two non-reactor nuclear analyses: the Ulysses Space Mission, and a hydrogen burn in the Hanford waste storage tanks.
Date: June 1, 1994
Creator: Coleman, J.R.
Partner: UNT Libraries Government Documents Department

Data processing unit and power system for the LANL REM instrument package. Final report

Description: The NEPSTP spacecraft needs highly reliable instrumentation to measure the nuclear reactor health and performance. These reactor measurements are essential for initial on-orbit phase operations and documentation of performance over time. Los Alamos National Laboratory (LANL), under the guidance of W. C. Feldman, principal investigator, has designed the Radiation Environment Monitoring (REM) package to meet these needs. The instrumentation package contains two neutron detectors, one gamma-ray detector, a data processing unit, and an instrument power system. The REM package is an integration of quick turn-around, state of the practice technology for detectors, data processors, and power systems. A significant portion of REM consists of subsystems with flight history. Southwest Research Institute (SwRI) has been tasked by LANL to design support electronics, including the Data Processing Unit (DPU) and Power System for REM. The goal for this project is to use technologies from current programs to speed up and simplify the design process. To meet these design goals, the authors use an open architecture VME bus for the DPU and derivatives of CASSINI power supplies for the instrument power system. To simplify integration and test activities, they incorporate a proven software development strategy and tool kits from outside vendors. The objective of this report is to illustrate easily incorporated system level designs for the DPU, power system and ground support electronics (GSE) in support of the important NEPSTP program.
Date: March 1, 1994
Creator: Lockhart, W.
Partner: UNT Libraries Government Documents Department

Radiological Impact of 1993 Operations at the Savannah River Site

Description: An offsite individual residing at the SRS boundary at the point of the maximum exposure (maximum individual) received a dose of 0.11 mrem from SRS atmospheric releases in 1993 (See Table 1 for a 5-yr history of doses). This dose was only 1.1% of the EPA public dose limit of 10 mrem/yr (DOE, 1990). Tritium oxide releases were responsible for 90% of the atmospheric dose. Ninety-nine percent of the atmospheric dose was accounted for with the inclusion of I-129, U-235, U-238, Pu-238 and Pu-239. The 50-mile population received a collective dose of 7.6 person-rem from 1993 atmospheric releases. Ninety-nine percent of this dose also resulted from the release of the same isotopes that dominated the maximum individual dose due to atmospheric releases. For both the individual and the population, atmospheric radiation dose was dominated by the inhalation and vegetation consumption pathways. The maximum dose received by an offsite individual as a result of SRS liquid releases in 1993 was 0.14 mrem (See Table 1 for a 5-yr history). This does was only 3.5% of the EPA limit for drinking water of 4 mrem/yr (DOE, 1990). This dose was dominated by Cs-137 accumulated in Savannah River fish and tritium in drinking water. More than 99% of the maximum individual dose from liquid releases resulted from tritium, Sr-90, Cs-137,and Pu-239. The population dose from liquid releases in 1993 was 1.5 person-rem. Again, tritium, Sr-90, Cs-137, and Pu-239 contributed more than 99% of this dose. The major exposure pathway to the population was drinking water. Radiation dose to the general public from operations at the Savannah River Site continued to be a very small fraction of the natural background dose. A resident of the CSRA receives about 300 mrem per year from background radiation. The population within 80 km of the SRS (620,000) ...
Date: October 28, 1994
Creator: Simpkins, A.A.
Partner: UNT Libraries Government Documents Department

Radioisotope thermoelectric generator transportation system subsystem 143 software development plan

Description: This plan describes the activities to be performed and the controls to be applied to the process of specifying, developing, and qualifying the data acquisition software for the Radioisotope Thermoelectric Generator (RTG) Transportation System Subsystem 143 Instrumentation and Data Acquisition System (IDAS). This plan will serve as a software quality assurance plan, a verification and validation (V and V) plan, and a configuration management plan.
Date: November 10, 1994
Creator: King, D.A.
Partner: UNT Libraries Government Documents Department

Water/sand flooded and immersed critical experiment and analysis performed in support of the TOPAZ-II Safety Program

Description: Presented is a brief description of the Narciss-M2 critical assemblies, which simulate accidental water/wet-sand immersion of the TOPAZ-II reactor as well as water-flooding of core cavities. Experimental results obtained from these critical assemblies, including experiments with several fuel elements removed from the core, are shown. These configurations with several extracted fuel elements simulate a proposed fuel-out anticriticality-device modification to the TOPAZ-II reactor. Preliminary computational analysis of these experiments using the Monte Carlo neutron-transport method is outlined. Nuclear criticality safety of the TOPAZ-II reactor with an incorporated anticriticality unit is demonstrated.
Date: November 1, 1994
Creator: Glushkov, E. S.; Ponomarev-Stepnoi, N. N.; Bubelev, V. G.; Garin, V. P.; Gomin, E. A.; Kompanietz, G. V. et al.
Partner: UNT Libraries Government Documents Department

Work plan for the fabrication of the radioisotope thermoelectric generator transportation system package mounting

Description: The Radioisotope Thermoelectric Generator (RTG) has available a dedicated system for the transportation of RTG payloads. The RTG Transportation System (System 100) is comprised of four systems; the Package (System 120), the Semi-trailer (System 140), the Gas Management (System 160), and the Facility Transport (System 180). This document provides guidelines on the fabrication, technical requirements, and quality assurance of the Package Mounting (Subsystem 145), part of System 140. The description follows the Development Control Requirements of WHC-CM-6-1, EP 2.4, Rev. 3.
Date: November 9, 1994
Creator: Satoh, J. A.
Partner: UNT Libraries Government Documents Department

Processing and properties of iridium alloys for space power applications

Description: Iridium alloys are used as fuel cladding in radioisotope thermoelectric generators due to their high-melting point, high- temperature strength, and oxidation and corrosion resistance. Although iridium has a face-centered cubic crystal structure, it undergoes a distinct ductile-to-brittle transition characteristic of many body-centered cubic metals. Improved ductility in the alloys is achieved through material purification and controlled alloy additions at the parts per million (ppm) level. A vacuum arc remelt operation produces a nearly defect-free casting, which is further processed to sheet products. A change in processing from drop castings of small arc-melted buttons to large arc-remelted ingots has substantially improved product yields. The effects of processing changes on alloy microstructure, sheet textures, oxidation effects, high-strain-rate ductility, and fabricability are discussed.
Date: December 31, 1994
Creator: Ohriner, E. K.
Partner: UNT Libraries Government Documents Department