[en] Efficient nuclear reactor thermionic converter units are described which can be constructed at low cost and assembled in a reactor which requires a minimum of fuel. Each converter unit utilizes an emitter rod with a fluted exterior, several fuel passages located in the bulges that are formed in the rod between the flutes, and a collector receiving passage formed through the center of the rod. An array of rods is closely packed in an interfitting arrangement, with the bulges of the rods received in the recesses formed between the bulges of other rods, thereby closely packing the nuclear fuel. The rods are constructed of a mixture of tungsten and thorium oxide to provide high power output, high efficiency, high strength, and good machinability

[en] A thermionic converter unit for use in a nuclear reactor to generate current, which can be constructed at low cost and which efficiently utilizes the nuclear fuel, is described. The reactor utilizes an array of thermionic emitters whose peripheries are fluted so that a bulge of one emitter interfits the depression of another to permit compact mounting, each emitter having several fuel passages located in the bulged portions for holding nuclear fuel and having a central collector passage for holding a thermionic collector. The emitters are constructed of rods of tungsten containing a small amount of thorium oxide, the thorium oxide not only improving the machinability of the tungsten but making it an efficient emitter. 5 claims, 3 figures

[en] A nuclear fuel cell is described for use in a thermionic nuclear reactor in which a small conduit extends from the outside surface of the emitter to the center of the fuel mass of the emitter body to permit escape of volatile and gaseous fission products collected in the center thereof by virtue of molecular migration of the gases to the hotter region of the fuel

[en] This paper deals with processes of the first filling of the TFE interelectrode spaces of the TOPAZ-2 nuclear power system, which are performed at the stage of checkout testing. Given a data and their discussion. copyright 1996 American Institute of Physics

[en] The paper presents an overview of a thermionic power generating channels development results and test loop channels for space nuclear power plants in the first generation of AM (Atom Mirnyj) reactor

[en] An algorithm of a simple grapho-analytical method for determining optimum fuel element length distribution along the axis of a multi-element thermionic fuel assembly is described. The method is useful for solving problems of geometric profiling in the presence of several nonuniformities and any kind of limitations on lifetime, reliability, performance and other properties of the fuel assemblies. The method is based of the Volt-thermal diagrams. Presented results of practical utilization of the method are presented and prove its usefulness

[en] An in-core thermionic reactor was selected by GA as the energy source for the SP-100 space nuclear power system. The conventional power subsystems of heat source, heat transport, and power conversion are combined in one component; the thermionic fuel element (TFE) which is also the basic component of the thermionic reactor. The reactor and TFE designs are described and the results of nuclear, thermal, and electrical analyses are given. The reactor was shown to meet the demanding SP-100 requirements and to be scalable into the megawatt power range

[en] The irradiation procedure followed to study the possible swelling of UO₂ in a thermionic converter fuel element is presented. No swelling was observed. It is thus proved that UO₂ remains a very interesting fuel element for thermionic conversion

[en] The theoretical analysis of fuel element cladding deformation under working temperatures during small thermal cycles, when the cladding material remains elastic and a firm bond, obtained in the process of radial mass transfer of the fuel, is kept between the fuel rod and the cladding, is performed. It is shown that nonlinear dependence of the cladding material upon stress in asymmetry of the cycle regarding heating and cooling rates leads to resulting positive or negative deformation depending on the asymmetry type. Increase of the cladding diameter takes place, when a mean heating rate exceeds a cooling rate (V_n/V_c > 1) and in the case of tungsten cladding and uranium dioxide fuel rod can achieve 1% per 10³ h

[en] A two-dimensional transient model is developed to simulate steady-state and transient operations of single-cell thermionic fuel elements (TFEs). Model predictions are in good agreement with published data to within 4.5 and 5.5% for fission and electrically heated TFEs of the TOPAZ-II type, respectively. In addition, the results of a transient analysis simulating the startup of an electrically heated TFE, following a step function increase in thermal power, are in presented and discussed