INVESTIGATIONS OF CARBIDES AS CATHODES FOR THERMIONIC SPACE REACTORS. Quarterly Progress Report for the Period Ending November 30, 1962
Two exploratory runs of less than 24-hr duration were carried out on a nominal 90UC --10ZrC sample under a cesium pressure of about 1.6 torr in an all- metal cell to gain preliminary information on the rate of vaporization. There was uncertainty in the pyrometric reading of the surface temperature of the sample in cesium vapor. The life-test cell used for determining emission stability of UC-- ZrC was designed and the first cell is about 75% completed. In addition two cell operating stations and their associated electronic instrumentation are being assembled and a high-vacuum station for outgassing the cell was set up. The effect of density on the rate of vaporization and electron emission of UC- ZrC in vacuum was studied. Measurements were completed on four nominal 90UC -10ZrC samples and two nominal 30UC--70ZrC samples of various densities. The low-density samples (86 to 92.5% theoretical density) emit about the same but the emission is definitely higher than that of samples of 97.5% theoretical density. The difference, however, decreases as temperature is increased. Measurements were completed on three nominal 90UC-- 10ZrC samples of various densities (86 to 97.5% theoreticai density) and were started on a nominal 30UC --70ZrC sample of 92.5% theoretical density. The rate of vaporization increased as the density of the sample was decreased. An all-metal cell was designed and is now being fabricated. This cell will make it possible to study the rate of vaporization of UC- ZrC in cesium plus cesium halide vapor at high temperatures. A thermionic emission microscope suitable for the study of the controlling factors for the emission of carbide cathodes is being fabricated. A high-temperature furnace is being fabricated which can be used together with an Instron Universal Tester to study the rupture strength of carbides by the four- point loading method. Essential features of the design of the carbide capsuie were firmed up and pertinent thermal and neutronic calcuiations needed for specifying fuel loading were made. Thermal cycling of the essential parts of the capsuie and thermal mock-up of the capsule were carried out in the laboratory. Vacuum emission and its variation with thermal history were measured on a hotpressed nominal UMoC/sub 2/ sample. Diffusion between UC and Ir, Re, and W- 26Re alloy was studied at 1800 deg C. Liquidphase formation was observed at the UC- Ir interface, and reaction layers and products were detected at the UC-- Re and the UC-(W-26Re) interfaces. The compatibility of UC with tungsten formed by the thermochemical decomposition of WF/sub 6/ in hydrogen is being studied at 2073 deg K by monitoring the vacuum emission of the tungsten deposited around a UC wafer. Preparation of submicron-size UZrC powder by hydriding U-- Zr alloy foils followed by carburization in CH/sub 4/ is under investigation. Cold- pressing and sintering of UC-ZrC bodies were studied; single-phase materials (86 to 93% dense) of 30 to 90 mol% UC were consistently obtained by using - 325 mesh powder prepared by grinding the arcmelted UC-- ZrC buttons. UC- ZrC bodies of UC concentration graded from 90 mol% at one end to 30 mol% UC at the other end were successfully prepared. Tungsten formed by thermochemical decomposition of volatile tungsten compounds is being studied as the emitter and clad for carbide fuels. A vacuum hos press was assembled for the hotpressing of carbide samples under clean conditions. (auth)
- Research Organization:
- General Atomic Div., General Dynamics Corp., San Diego, Calif.
- DOE Contract Number:
- NAS 3-2532
- NSA Number:
- NSA-17-016516
- OSTI ID:
- 4746564
- Report Number(s):
- GA-3866
- Resource Relation:
- Other Information: Orig. Receipt Date: 31-DEC-63
- Country of Publication:
- United States
- Language:
- English
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INVESTIGATIONS OF CARBIDES AS CATHODES FOR THERMIONIC SPACE REACTORS. Quarterly Progress Report for Period Ending November 30, 1961
INVESTIGATIONS OF CARBIDES AS CATHODES FOR THERMIONIC SPACE REACTORS. Quarterly Progress Report No. 3, December 1, 1961 through February 28, 1962
Related Subjects
CAPSULES
CARBIDES
CESIUM
CESIUM COMPOUNDS
CHEMICAL REACTIONS
DECOMPOSITION
DENSITY
DIFFUSION
EMISSION
EVAPORATION
FABRICATION
FUEL CANS
FURNACES
GENERATORS
GRAIN SIZE
HALIDES
HEAT TREATMENTS
HEATING
HIGH TEMPERATURE
IRIDIUM
LAYERS
LIQUIDS
MATERIALS TESTING
MEASURED VALUES
MICROSCOPY
MOLYBDENUM CARBIDES
POWDERS
PREPARATION
PROPULSION
QUANTITY RATIO
REACTION KINETICS
RHENIUM
RHENIUM ALLOYS
SINTERED MATERIALS
SINTERING
SPACE
STABILITY
SURFACES
TENSILE PROPERTIES
THERMAL CYCLING
THERMIONICS
TUNGSTEN
TUNGSTEN ALLOYS
TUNGSTEN COMPOUNDS
TUNGSTEN FLUORIDES
URANIUM ALLOYS
URANIUM CARBIDES
VACUUM
VAPORS
NESDPS Office of Nuclear Energy Space and Defense Power Systems