Description: The limited supply of relatively long-half-life isotopes having a reasonably high power density and the low conversion efficiencies obtainable with thermoelectric devices have so far limited the power output of isotope-fueled sources of electric power to several tens of watts. In addition, the high cost of the available isotopes results in a very large expense for isotope-fueled generators producing several hundred watts. It appears that a small, minimumweight, conduction-cooled reactor is an attractive alternate to the isotope-fueled power supplies in the 200-w size range. The proposed reactor is a small, high-density fast core of U/sup 233/ surrounded by a beryllium reflector. This approach, generally speaking, gives a reactor that is more compact and of lighter weight than can be obtained with a moderated system having a softer neutron spectrum. In the reactor design, the path of heat flow is from the core to the inner reflector and then to the thermoelements in close contact with the inner reflector. The reject heat flowing from the thermoelement cold junctions enters the outer pontion of the reflector, which acts as the heat sink and conducts the reject heat to the large, circular, tapered-fin radiator which is attached to the reflector. Survey physics calculations for various reactor systems fueled with U/sup 235/, U/sup 233/, and Pu/sup 239/ are reported. Some limits imposed on the system design by the thermoelectric generator are discussed, and the problem of radiator design for the space environment is treated in some detail. No attempt is made to present a detailed final design of the power supply; rather, the report is restricted to a general delineation of the limits imposed by various parameters and a resulting final conclusion as to the performance limits of small conduction-cooled reactors in this size range. (auth)
Date: March 1, 1963
Creator: MacFarlane, D. R.
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