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SNAP I POWER CONVERSION SYSTEM MATERIALS DEVELOPMENT. Period covered: February 1, 1957 to June 30, 1959

Description: Investigations of materials for use in connection with the SNAP I mercury Rankine cycle power conversion system are discussed. Test programs are outlined and results are tabulated for each candidate material. Several nonmetallic materials and processing procedures were developed which enabled uncooled high-performance electric machinery to operate at 550 deg F in mercury vapor. (J.R.D.)
Date: June 20, 1960
Creator: Hambor, V.F. & Owens, J.J.
Partner: UNT Libraries Government Documents Department

HIGH-TEMPERATURE VAPOR-FILLED THERMIONIC CONVERTER. Quarterly Technical Progress Report for the Period October 1-December 31, 1962

Description: Cell F was operated at power for 484 hours. Cell F is the first cell in which the expected current emission density was observed from a carbide emitter in an engineered thermionic generator. Short-circuit currents of 120 amp were observed from the emitter in the cell. A maximum power output of 50 watts (5 w/ sq cm) was obtained at an emitter temperature of 2440 deg K. During steady state operation power was in the range from 10 to 30 watts. The cell was not optimized for maximum power. The contact potential in the cell agrees with that expected from a low work function carbide emitter and a fully cesiated collector. For a nominal contact potential of 1 volt and a short-circuit current of 120 amp, the optimum power should have been 120 watts, assuming no transport defects in the cell. Actually the maximum power output corresponding to a short-circuit current of 120 amp was more nearly 40 watts, indicating transport defects in the cell. (auth)
Date: January 1, 1963
Creator: Godsin, W.
Partner: UNT Libraries Government Documents Department

CORE TRANSFER FUNCTION MODELS FOR SNAP SYSTEM KINETICS

Description: A distributed parameter transfer function is developed for SNAP type reactor cores. The coolant may be either boiling, non-boiling, or both. In the boiling case the Bankoff model is used to find the spatial distribution of voids. The transfer functions obtained are not simple polynomials. However, they are readily analyzed for stabilily using the 7090 program TRAFIC, which uses a Nyquist diagram approach. Some general conclusions resulting from these calculations are included. (auth)
Date: April 29, 1963
Creator: Johnson, R. L.
Partner: UNT Libraries Government Documents Department

NUCLEAR FUEL (OXIDE) CLAD THERMIONIC CONVERTERS. Quarterly Technical Progress Report, May 1 through July 31, 1963

Description: Fabrication of the components for the FDM-1 converter and its back-up device was completed. The FDM-1 converter was assembled, and preparations for testing were completed. Performance testing was initiated, and a total of 330 hours of operation above 1000 deg K in a cesium environment were logged. The peak emitter temperature reached was 2000 deg K with a thermionic output of nearly 2 watts/cm/sup 2/. Indications of a cesium leak were observed, and the device was shut down for examination. A 500-hour thermal endurance test of the clad fuel pellets was performed. A post-test examination was conducted, and no diffusion of UO/sub 2/ into the cladding was observed. A thermal conductivity test specimen was exposed to a temperature of 1550 deg C for 500 hours with the result that some intergranular diffusion was noted. The post-test examination of the vacuum emission test pellet was also completed. The design of the advanced double-diode thermionic converter utilizing the results of prior efforts was initiated. (auth)
Date: August 15, 1963
Partner: UNT Libraries Government Documents Department

SNAP I Mercury Boiler Development, January 1957 to June 1959

Description: The mercury-boiler development program was undertaken to develop a system that would utilize the heat of radioisotope decay to boil and superheat mercury vapor for use with a small turbine-generator package. Through the use of a Rankine cycle, the mercury vapor can be provided continuously to power a turbine-driven alternator and produce electricity for extended periods of time. This mercury boiler and the related power-conversion system was planned for a satellite that would orbit the earth. This system design and development program was designated as SNAP-I. Development of the mercury boiler is described and a chronological description of the various mercury-boiler concepts is presented. The applicable results of an extensive literature survey of mercury are included. The mercury-boiler experimental-test-program description provides complete coverage of each experimental boiler and its relation to the system design of that period. A summary of all mercury boilers and their final disposition is also given. (auth)
Date: June 1, 1960
Creator: Jicha, J. & Keenan, J. J.
Partner: UNT Libraries Government Documents Department

SNAP I Radioisotope-Fueled Turboelectric Power Conversion System Summary, January 1957 to June 1959

Description: The SNAP I development program was initiated to develop a 500-watt turboelectric power conversion system for space applications, Superheated mercury vapor was used as the heat conversion working fluid. The conversion system was to obtain thermal energy from the decay of a radioisotope fuel such as Ce/sup 144/ . Each of the major components and systems is summarized with respect to initial design objectives, development progress to the point of program termination, results obtained from tests and, where indicated, future growth potential. Reference is made to 10 other reports which describe, in detail, the major components of this power generating system. Also included is a bibliography of documented reports that are related to the power conversion system design criteria or system integration into a flight vehicle. (auth)
Date: June 1, 1960
Creator: Dick, P. J.
Partner: UNT Libraries Government Documents Department

Emission Characteristics of Tantalum, Tungsten, Rhenium, and Iridium in Plasma Diodes

Description: Experimental determinations of the ionic and electronic emission characteristics of tantalum, tungsten, rhenium, and iridium cathodes in vapor thermionic converters are compared. It is shown that tantalum provides superior thermal ionization qualities at high pressure compared with tungsten, rhenium, and iridium. High electronic current densities may be obtained from cesium on rhenium and cesium on iridium at much lower cesium vapor pressures than for tantalum or tungsten. (auth)
Date: April 1, 1962
Creator: Gust, W. H.
Partner: UNT Libraries Government Documents Department

THE SNAP II POWER CONVERSION SYSTEM TOPICAL REPORT NO. 12. BOILER DEVELOPMENT

Description: The SNAP II boilers which were designed are summarized. As shown by test results from the three boilers which were tested, a continuous progress in design was achieved. These designs were based on test data from both the SNAP I and SNAP II programs. As the quantity of data increased, physical models describing the heat transfer process were developed. These physical models provide the necessary correlation parameters which permit the extension of existing data to advanced design. Preliminary test sections were designed on the assumption that an allvapor nmodel which ignores the presence of the liquid phase during forced convection boiling could be used to describe the process quantitatively. The conventional Dittus-Boelter equation was applied with the increase in the vapor flow along the tube being ascribed to liquid evaporation. The assumption led to a design that fell short by about an order of magnitude since the exit qualities were only in the range of 10%, far less than required for complete vaporization. As a result, a revision in the concept of the mechanics of boiling was found necessary and a theoretical analysis was formulated, based on a dry wall'' or dropwise'' type boiling phenomenon. The test results of the preliminary test sections and the SNAP I boiler were plotted on the basis of dry-wall boiling parameters containing the area mean temperature difference and mass velocity. A conservative design curve was established and used to design the thirteen tube boiler. The design was found by test to be conservative, and the measured performance and the degree of conservatism were found to be within the expected spread in earlier test data. Dropwise boiling pictures the heat transfer as occurring directly from the wall to the drop through a film created by the vapor being ejected from the underside of the drop. ...
Date: July 17, 1961
Creator: Gido, R.G.; Koestel, A.; Haller, H.C.; Huber, D.D. & Deibel, D.L.
Partner: UNT Libraries Government Documents Department

Emission Characteristics of Tantalum, Tungsten, Rhenium, and Iridium in Plasma Diodes

Description: Experimental determinations of the ionic and electronic emission characteristics of Ta, W, Re, and lr cathodes in vapor thermionic converters are compared. It is shown that Ta provides superior thermal ionization qualities at high pressure compared with W, Re, and Lr. High electronic current densities may be obtained from Cs on Re and Cs on Ir at much lower Cs vapor pressures than from Ta or W. An over-all efficiency of 19% was achieved with a Re cathode at 2440 deg K. (auth)
Date: March 15, 1962
Creator: Gust, W. H.
Partner: UNT Libraries Government Documents Department

CHARACTERISTICS OF A THERMIONIC CONVERTER WITH A HIGH-TEMPERATURE COLLECTOR

Description: Current-voltage characteristics of a cesium-on-tantalum thermionic converter with a collector temperature comparable to that of the emitter were obtained for a variety of electrode temperatures and cesium vapor pressures. The results show that for emitter temperatures in excess of 2000 deg K, power outputs of a few watts per square centimeter can be obtained when the ratio of collector temperature to emitter temperature is as high as 0.75 to 0.80, which is the required range for best performance of a radiation-cooled Carnot engine, and that at temperature ratios above 0.80 the power output is insensitive to changes in electrode spacing for ratios of spacing to electron mean free path greater than 100 at a cesium vapor pressure of 5 torr. (auth)
Date: January 15, 1963
Creator: Blue, E. & Ingold, J.H.
Partner: UNT Libraries Government Documents Department

RADIOISOTOPE FUELED AUXILIARY POWER UNIT. Quarterly Progress Report No. 6, April 1958-July 1958

Description: A modular concept has evolved which permits testing of SNAP-1 as an attachable unit. Integrity testing of fuel elements in simulated pad aborts is reported. The adequacy of a full-scale boiler mockup in vaporizing mercury at the design point was tested; a new boiler coil designed to prevent slugging was tested. The sintering properties of CeO/sub 2/ were further investigated. Dynamic mercury corrosion testing of Croloy 5 Si and Croloy 5 Ti is reported. Static lead tests of CeO/sub 2/ pellets, brazed joints, and flame sprayed coatings continued. Testing of the power conversion system turbine, centrifugal pumps, controls, radial gap alternator, bearings, and steels is described. Design of a facility for testing the APU module is under way. A conceptual design of SNAP-3 was delineated. (N.W.R.)
Date: October 31, 1963
Partner: UNT Libraries Government Documents Department

RF OSCILLATIONS AND POWER OUTPUT IN ALKALINE THERMIONIC CONVERTERS

Description: Experiments were made using a potassium plasma cell with a Ta emitter and a Ag-plated Cu collector. The r-f frequencies, rms voltages, power output, and other quantities were measured under various conditions of emitter temperature, potassium vapor pressure, and d-c and r-f loads. Ion and electron densities were calculated and compared with the oscillations occurring. (D.L.C.)
Date: April 1, 1962
Creator: Richards, H.K.
Partner: UNT Libraries Government Documents Department

SNAP II POWER CONVERSION SYSTEM TOPICAL REPORT NO. 8, MERCURY CONDESING RESEARCH STUDIES

Description: Experimental results are summarized for investigations on the condenser fluid mechanics of mercury under zerogravity, two-phase conditions. Conditions required for interfacial stability in tubes were determined as a function of tube diameters. Correlated two-phase pressure drop data are presented as functions of tube inlet Reynolds number and vapor specific volume. Flow regime stability was studied under zero-gravity and 2.55-gravity conditions and at various Reynolds numbers. the effect of noncondensable gas on flow performance in mercury forced convection condensers was evaluated. (D.L.C.)
Date: May 31, 1961
Creator: Kiraly, R.J. & Koestel, A.
Partner: UNT Libraries Government Documents Department