Change in the properties of the electrodes of thermionic single-element EGC at the initial stage of operation

Koryukin, V. A.

doi:10.1007/bf02673515

Cited by 3 publications

(2 citation statements)

References 2 publications

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“…The evaluations of the effect of fission products on the output power of EGC with oxide fuel for the example of barium neglected tungsten mass transfer from the emitter to the collector [1, 2]. An EGC with oxide fuel is a continuously operating source of oxygen capable of maintaining the oxygen pressure in the interelectrode gap at 10 -5 -10 -4 Pa [11,15]. The presence of oxygen on the surface of a tungsten emitter results in the formation of volatile oxides (WO, WO 2 , WO 3 ) and thereby substantially higher tungsten evaporation as compared with sublimation [1,9].…”

Section: Effect Of Simultaneous Cesium and Barium Adsorption On Egc Omentioning

confidence: 99%

Effect of fission products on the output power of thermionic egc with communicating and separated fuel-element cavities and an interelectrode gap

2011

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The behavior of fission products in electricity-generating channels with communicating and separated fuelelement cavities and an interelectrode gap (IEG) is examined in application to a secondary-loop channel and a space nuclear power facility. Thermodynamic and kinetic computational studies of the behavior of gaseous and volatile fission products in the IEG and vacuum-cesium system are performed. Their effect on the output electrical power of thermionic EGCs with communicating and separated fuel-element cavities and IEGs is evaluated, taking barium as an example. The results can be used to determine the optimal design and further optimize EGCs by performing tests in the secondary-loop channel and with facility implementations.Different factors affect the serviceability of a multielement electricity generating channel (EGC) with oxide nuclear fuel and with separated, partially separated, or communicating fuel element cavities and an interelectrode gas (IEG) and, in particular, the change of the output characteristics of the electricity generating elements [1, 2]. One such factor is the presence of fission products and cesium activation on electrode surfaces. The amount and effect of the fission products and activation in the IEG on the output characteristics of an individual channel and the thermionic converter reactor as a whole depend on their concentration in the cesium gas of the cesium-vacuum system, more accurately, at the entrance into the IEG. In turn, the concentration of the fission products in the cesium gas of the cesium-vacuum system depends on how cesium vapor is fed into the IEG and the geometric characteristics and temperature of the system [3]. In this connection, there is definite interest in modeling the concentration of fission products along the IEG and in the channels of the cesium-vacuum system and to make a comparative evaluation of the effect of the fission products, specifically, barium on the output electric power of the thermionic EGC with communicating and separated fuel-element cavities and an IEG. The present article is devoted to examining these questions for typical EGC schemes [3].Thermodynamic Calculations of the Phase Composition of Volatile Fission Products in the Fuel Cavity, IEG, and Cesium-Vacuum System. In a multielement EGC with communicating channels, the gaseous and volatile fission products Br, I, Kr, Xe, Rb, Cs, Sr, Ba, Te, and Se and their compounds formed in the fuel cavity of a fuel element are extracted into the IEG. They do not condense in the trap or gas-extraction channel, but flow into the IEG and then into the cesium-vacuum system. Thermodynamic calculations using the ASTRA-4 program of the partial pressure of the gas-phase components above oxide fuel (UO 2-x ) with sub-stoichiometric composition in a fuel cavity with cesium vapor pressure from 133 to 227 Pa and

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Section: Effect Of Simultaneous Cesium and Barium Adsorption On Egc Omentioning

confidence: 99%

Effect of fission products on the output power of thermionic egc with communicating and separated fuel-element cavities and an interelectrode gap

2011

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“…In this case, the EGC core is a continually operating and controllable source of oxygen, capable of maintaining the oxygen pressure in the interelectrode gap at the level 10 -5 −10 -4 Pa [7], when the vacuum work function of a cylindrical tungsten emitter with (110) and (112) faces on the emission surface is well known to approach the more efficient rhenium, whose use is inadmissible in space nuclear power systems with reactors operating on thermal and intermediate energy neutrons.…”

mentioning

confidence: 99%

Analysis of physicochemical processes in multicomponent electricity generating channels with communicating fuel-element and interelectrode gaps

2008

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The behavior of the main components of uranium dioxide, gaseous impurities, and fission products and the transfer of emitter material to a collector under conditions where the fuel-element and interelectrode gaps of a multicomponent electricity generating channel (EGC) communicate with one another are examined. The results of in-reactor experimental investigations of the temperature zones of condensation of fission products, using uranium dioxide based model fuel, and circuit tests of EGC are presented. It is shown that fission product settling on the collector is negligible; tungsten transfer from the emitter onto the collector can counterbalance this effect.A multicomponent electricity generating channel (EGC) with communicating fuel element and interelectrode cavities gives the most acceptable mass/size characteristics of a converter reactor in a built-in space nuclear power system as a result of fewer structural materials in the core and a smaller spacing between serially connected electricity generating components. The relative simplicity of such a construction also makes it technologically more adaptable, and the presence of the working body of the interelectrode gap (cesium) in the fuel element cavity retards mass transfer and simultaneously limits the emission of uranium dioxide and simplifies the gas removal system through which fission products are removed from the fuel elements. The problematic task in such a structural arrangement of the EGC is limiting the flow of impurity elements as well as the main components and fission products of oxide fuel through the gas removal system into the interelectrode gap.The gas medium in the interelectrode gap is formed, just as in the case of separate cavities, by the residual technological gases and technological gases adsorbed on the electrode surfaces, by the products of activation of cesium and fission of fuel, which pass through the emitter shell, as well as hydrogen flowing from the zirconium hydride moderator. These processes change the adsorption, emission, and radiative properties of the electrodes, and taken together they can degrade the electric power output of the EGC.Technical solutions involving the reactor and thermionic converter have now been developed to ensure stable operation of EGC:• the flow of hydrogen into the interelectrode gap is limited to pressures 10 -3 -10 -4 Pa by introducing diffusion barriers along the path to the EGC and sinks in front of these barriers; at higher pressures, the oxide ceramic of the spacers is reduced and at lower pressures the role of hydrogen in the reduction of tungsten oxides deposited on the collector is decreased, which decreases the density and results in weak adhesion followed by separation of the oxide layer when the thickness reaches about 30 µm [1, 2];

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Corrosion behavior and deuterium permeability of aluminide coating in high-temperature carbon dioxide atmosphere

Dong

Jiang

Zhong

et al. 2022

Surface and Coatings Technology

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Change in the properties of the electrodes of thermionic single-element EGC at the initial stage of operation

Cited by 3 publications

References 2 publications

Effect of fission products on the output power of thermionic egc with communicating and separated fuel-element cavities and an interelectrode gap

Effect of fission products on the output power of thermionic egc with communicating and separated fuel-element cavities and an interelectrode gap

Analysis of physicochemical processes in multicomponent electricity generating channels with communicating fuel-element and interelectrode gaps

Corrosion behavior and deuterium permeability of aluminide coating in high-temperature carbon dioxide atmosphere

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