Tiiermionic converter

947,281. Thermionic converters. GENERAL DYNAMICS CORPORATION. Oct. 5, 1962 [Oct. 20, 1961], No. 37870/62. Heading H1D In a " plasma thermocouple using e.g. caesium vapour, a further work-functionreducing gas, e.g. hydrogen, is controllably released into the envelope during operation to reduce the anode work-function from about 1.8 volts to 1 volt, i.e. the converter efficiency (expressed as voltage output over ¸ maximum potential level) is increased from about 45% to 70%. As described, the converter operates in a nuclear reactor and comprises a nuclear fuel material/cathode 26 surrounded by an anode container 14 mounted on ceramic insulators 16, 18 and-housed in a nuclear fuel-can 10. The fuel material/cathode may be uranium dioxide encased in an electron emitter such as tantalum, or uranium carbide or a uranium carbide - zirconium carbide mixture which itself acts as the electron emitter, in addition to providing the necessary heat for electron emission. At the base of the converter two reservoirs 44, 46 contain respectively caesium, and a hydrogen releasing material such as zirconium hydride, uranium hydride or calcium hydride. The hydride container 46 is isolated from the converter by a sheet of e.g. palladium or tantalum 54 which -becomes permeable to hydrogen at operating temperature but is opaque to larger molecules, e.g. caesium. The hydrogen concentration is controlled by heating coils 52 surrounding the hydride container 46. The permeable sheet 54 may rely on the converter heat or be provided with heating means 64. Operating figures quoted.-Anode temperature 0-1000‹ C., e.g. 300‹ C.; cathode temperature 1000-2000‹ C.; caesium concentration 10-6 to about 1 mm. Hg, e.g. 10-5 mm. Hg; hydrogen concentration to result in back currents of 5 to 15% of the cathode current, e.g. 10%; cathode current 1 amp. per square centimeter.