Lifetime changes in the characteristics of thermionic converters

The substantiation of the lifetime stability of the emission properties of electrodes and electric characteristics of the electricity-generating channel (EGC) and element (EGE) of a space thermionic nuclear power system for an operating period of 5–10 or more years is examined. The basic reasons for the changes in the emission properties of EGE/EGC electrodes and a Topaz type reactor-converter are analyzed on the basis of test data and data from experimental simulation of the working processes in the interelectrode medium. A scheme is proposed for the working process occurring in the interelectrode medium of the EGE; the scheme is based on the Topaz materials and technology. The stability of the emission characteristics of electrodes with respect to possible changes during prolonged operation is analyzed for the most advanced designs of space nuclear power systems. The changes in time and the corresponding changes in the output electrical characteristics are estimated. 36 references. State Science Center of the Russian Federation—A. I. Leipunskii Physics and Power-Engineering Institute. Translated from Atomnaya énergiya, Vol. 89, No. 1, pp. 57–67, July, 2000.     

Databank for the current-voltage characteristics of thermionic converters

Investigations of thermionic converters, supporting design investigations and developments in space nuclear power systems, are being conducted in the Laboratory of Studies of Fundamental Problems of Conversion of Various Forms of Energy at the State Science Center of the Russian Federation—Physics and Power-Engineering Institute. As a result, a great deal of experimental data has been accumulated in the form of the current-voltage characteristics of arc operating regimes with different electrode materials. The databank stores the experimental data in electronic form. At present it contains the results of 17 experiments. For data handling convernience, a program for viewing the entire digital information has been developed. The results of a search can be printed out. The data control apparatus makes it possible to select the data required by the user. A current version of the databank is discussed as an example. 6 figures. 1 table, 13 references. State Science Center of the Russian Federation—A. I. Leipunskii Physics and Power-Engineering Institute. Translated from Atomnaya énergiya, Vol. 89, No. 1, pp. 71–74, July, 2000.     

Efficient binary sources of working-body vapor for thermionic converters

Scientific and Industrial Association SFTI, Republic of Georgia. Translated from Atomnaya Énergiya, Vol. 75, No. 6, pp. 430-435, December, 1993.     

Efficient ternary sources of working-body vapors for thermionic converters

Scientific and Industrial Association SFTI, Republic of Georgia. Translated from Atomnaya énergiya, Vol. 76, No. 5, pp. 401–406, May, 1994.     

Limiting thermionic energy conversion characteristics

The limiting current–voltage characteristics, electronic efficiency, and the efficiency taking account of the radiative heat losses from the emitter for a diode thermionic energy converter operating in the regime of a low-voltage arc discharge are calculated. It is shown that for low-temperature energy converters (emitter temperature 1300–1600 K, current density 2–4 A/cm²) the efficiency does not exceed 20% even at low collector temperature – half the emitter temperature. The requirements for the work function of the electrodes that must be satisfied to obtain the limiting characteristics are determined. The relations and computational results obtained can be used to develop advanced thermionic power-generation facilities.     

Adsorption and emission features of collectors of thermionic energy converters in the case of mass transfer in the interelectrode gap

Translated from Atomnaya Énergiya, Vol. 69, No. 3, pp. 196–197, September, 1990.     

Identification of the factors determining thermionic energy converter efficiency

A method of using the experimental current–voltage characteristics to perform diagnostics on the parameters of a thermionic energy converter in the arc regime without setting up special experiments and perturbing actual processes was developed. The current–voltage characteristics measured in a wide range of the collector temperatures make it possible to determine the main physical parameters responsible for the efficiency of the energy conversion process: the electron temperature in the plasma near the collector, the heat of evaporation of the electrons from the emitter, the heat of condensation of the electrons on the collector, and the effective work function of the collector.     

Surface requirements for electrostatic direct energy converters

There are two major electrostatic direct energy converter concepts which will be discussed from the point of view of the surfaces. One is the Venetian blind concept and the other is the periodic electrostatic focusing concept. They are both of the direct collector type. Fluxes of D⁺, T⁺, He⁺⁺, electrons, and X-rays are given. Design consideration due to thermionic emission, secondary electron emission, and radiation cooling are discussed. A detailed discussion is devoted to breakdown physics, the voltages and electric field strengths that can be employed, and how surface deterioration may affect voltage holding due to He⁺⁺ bombardment blistering.     

Investigation of the characteristics of thermionic converters with a Mo (110) single-crystal collector with Ion-implanted oxygen

Institute of Nuclear Reactors, Russian Scientific Center "Kurchatovskii Institut." Translated from Atomnaya énergiya, Vol. 76, No. 2, pp. 151–152, February, 1994.     

Study of thermionic energy converter with electromagnetic regulation of working substance pressure

Conclusion A method is proposed for electromagnetic regulation of the size and composition of the working substance vapor fed into the interelectrode gap of a TEC. It is been demonstrated that this method can be used to increase the output electrical parameters and operating efficiency of thermionic converters. Experimental studies were conducted on TECs with cesium and cesium-oxygen vapor source with electromagnetic regulation of the size and stoichiometric composition of the mixture fed into the TEC interelectrode gap. The studies showed that in cesium-oxygen TECs magnetic regulation allows the maximum electrical power of the converter to be raised further, probably because of the more optimal stoichiometric composition of the mixture. A cesium-barium vapor source with magnetic regulation of the stoichiometric composition of the mixture is proposed. Russian Research Center “Kurchatov Institute,” and Sukhumi Physicotechnical Institute, Republic of Georgia. Translated from Atomnaya énergiya, Vol. 85, No. 2, pp. 107–111, August, 1998.     

Control strategy optimization for energy efficiency and harmonic mitigation in multi-series converters

To provide electrical power for the Research System of Superconducting Magnets (RSSMs) including the background field superconducting magnet and the tested superconducting objects, the high power phase-controlled converter will be used to develop the power supply system. However, because of its inner nonlinear feature, the current harmonics and the reactive power are injected into the AC power supply system. To improve the quality of the power supply system for RSSMs, an improved synchronous control strategy is suggested for the superconducting magnet power supply system, which comprises four series-connected six-pulse converters fed by a phase-shifting transformer, respectively. According to the proposed control strategy, the basic unit is two 12-pulse converters and the control method will be changed in terms of load fluctuations which are represented by the per unit value of converter output voltage. As a result, harmonic is greatly reduced but the power factor is also high.