THERMIONIC DOUBLE-DIODE PROGRAM.
Final technical rept., 1 Nov 62-30 Nov 63,
MARTIN CO BALTIMORE MD
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Results of an extensive Martin-sponsored research and development program were utilized to evolve the design of a fueled, double-diode thermionic module for out-of-pile testing in a program sponsored by Air Force Systems Command. Two modules, each consisting of two diodes of cylindrical configuration connected electrically in series within a single sheath and utilizing a common cesium reservoir, were fabricated and tested. The emitters were the molybdenum claddings of the UO2-Mo cermet bushings used to represent the nuclear fuel in the module. The two modules were tested for cumulative periods of 330 and 715 hours, respectively, at emitter temperatures between 1500 and 2000 C, and at a spacing of 17 to 18 mils. Output power densities of l.5 to 6 watts per sq cm were produced under the above conditions. Upon completion of the testing, each of the modules was disassembled and examined. Eight UO2-Mo cermet fuel pellets clad with molybdenum were fabricated for study of materials compatibility problems. Dimensional stability, thermal conductivity, electrical resistivity, UO2 diffusion, and thermionic emission were investigated. An improved fueled thermionic double diode for out-of-pile testing adaptable to in-pile operation was designed. Author