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INVENTION
Patent of the Russian Federation RU2070751
LOADING DEVICE FOR TESTS
THERMO-EMISSION ELECTRO-GENERATING ASSEMBLIES
The name of the inventor: Averyanov AN; Sinyavsky V.V.
The name of the patent holder: SP Korolev Rocket and Space Corporation Energia
Address for correspondence:
Date of commencement of the patent: 1994.06.16
Purpose: thermionic energy conversion. SUMMARY OF THE INVENTION: in order to avoid the formation of an additional source of cesium vapor (a "false" thermostat) in the cesium channel, the gas-adjusting gap near the boundary of the active part of the generating assembly is made profiled.
DESCRIPTION OF THE INVENTION
The invention relates to a thermionic method for converting thermal energy into electrical and reactor thermal physics and can be used in laboratory and reactor studies of thermionic energy converters (TEC), thermionic and other fuel elements.
Reactor tests of fuel elements, including thermionic power generating assemblies (EGS), are an important stage in the development of the reactor and power plant. Such tests are carried out in research nuclear reactors (NR) using special loop devices (PU), often called loop channels (PCs).
Known PCs for reactor tests EGS (Design and testing of thermoemission fuel elements, V. V. Sinyavsky et al. Atomizdat, 1981, pp. 24-28). The main purpose of the PC is to provide conditions close to the operating conditions for EGS tests (for heat generation, electrode temperatures, cesium vapor pressures, etc.). From this point of view, the following characteristic systems can be distinguished in the PC: provision of energy release, heat removal and thermal control; Providing parameters of the interelectrode environment; Output of electrical energy; Control and measurement of EGS characteristics and PC systems.
As a prototype, we will take a specific PU for testing the EGS of the Topaz reactor in the core of the first nuclear power plant (ibid., Pp. 27-28, Fig. 2.10).
The PU consists of a housing inside which a heat-sink system (CTC), cooled by the heat-carrier (water) of the reactor, is placed, with the possibility of installing EGS inside it. The STS, in turn, contains a thermal control system, which is a small gap (a fraction of a millimeter) that can be evacuated or filled with gas (a mixture of gases). The collector temperature is controlled by changing the gas pressure or the gas component ratio in this gap. The current terminals are isolated from the mass and are discharged from the cesium space through vacuum dense metal-ceramic assemblies. The reliability of the operation of such assemblies is enhanced by creating a safety fore-vacuum or high-vacuum cavity around them from the outside. The temperature regime of the PU units is maintained either by means of special built-in electric heaters or by radiation heat release in the materials of these assemblies.
The weakest node of such a PC is the portion of the heat-sink system near the boundary of the active (heat-producing) part of the EGS and its current lead. This is due to the fact that in this place there is a sharp change in the density of the heat flux passing through the gas gap of the STS, and, consequently, the temperature drop on it, other things being equal, proportional to the passing heat flux. This difference is especially significant in the tests of energy-intensive EGS. Since the STS is cooled by the coolant (water) of the reactor at approximately the same temperature along the entire PU, a significant difference in the temperature difference at the gas gap of the STS leads to a sharp decrease in the temperature of the inner wall of the cesium channel near the boundary of the active part of the EGS of the current lead. As a result, a section of the path may appear with a temperature below the temperature of the cesium vapor source. The result is known - the formation of a "false" thermostat with the inability to continue normal test modes. Such a case is considered in detail in V.V. Sinyavsky "Methods for determining the characteristics of thermionic fuel elements", M. Energoatomizdat, 1990, p. 144.145, Fig. 5-I. Therefore, in designing the PU, the task is not to allow the temperature of the path to drop below the temperature of the cesium vapor source.
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A PU is proposed comprising a housing in which a cesium vapor source is located, a cesium path and a coolant cooled by the research reactor of the STS, configured to house the test EGS with the current leads inside it, and there is a gap inside the STS filled with a gas or a mixture of gases, characterized in that the gap It is made profiled, and the width of the gap is chosen by the relation In the figure, the PU scheme is shown. It contains a body 1 inside which a cesium vapor source 2, a cesium channel 3 and a STS 4 are located. Inside the STS, EGS 5, consisting of separate EGE 6, each containing a fuel-emitting unit 7, a manifold 8 and a commutation bridge 9 EGS has a collector insulation 10 common to all EGEs and a cover 11. The extreme EGE has current leads 12 and 13, one of which is electrically insulated from the cover 11, passes inside the cesium channel 3 and through a special seal-out terminal 14 is withdrawn from the cesium channel 3 into the containment cavity 15 The STS 4 has a gap 16 that can be evacuated or filled with a gas, for example helium, of different pressures (or a mixture of gases). This gap 16, which is located along the EGS 5 and its current leads 12 and 13, is configured opposite the current leads 12 and 13 (gap portions 17 and 18, respectively). Outside, STS 5 is cooled by water of 19 reactors. The loop device is also equipped with systems for evacuation, gas supply, measurement of parameters, and others, which are not shown in the drawing. |
DEVICE WORKS AS FOLLOWING
After installing the PU with EGS 5 in the cell of the research reactor, its power is raised to the required level. In the interelectrode gaps 20 EGS 5, cesium vapor is supplied from the cesium vapor source 2 at an operating pressure whose saturation temperature is T cs .
In the gap 16,17 and 18, gas is supplied at a pressure P g . In the fuel of the node 7, heat is generated, part of which is converted to electricity, and the unreformed part (90%) enters the collector 8 and then passes through the gap 16, is discharged to the heat carrier 19. As a result of the temperature drop at the gap 16, the collector temperature T ci T cs . Through sections 17 and 18 of the gap along the current leads, the heat flux is much less (than the generation of heat due to the fission of uranium nuclei). However, due to the profiling of the gap in sections 17 and 18 and here the temperature of the path inside which cesium vapor is located is higher than T cs .
Let us consider a system of heat balance equations for the PU region near the boundary of the fuel-generating part of the EGS and the current lead.
For radial heat transfer, the gaseous heat release density in the g (Z) current lead will be the same (with some error), in the gap between the current lead and the supporting tube (g 1 ), in the supporting tube (g 2 ), in the helium gap that we need (G 3 ), in the PC case (g 4 ) and in the section of the housing the cooling coolant (g 5 value g (Z) is defined as
Q (z) = q j + q U (2)
Where g j is the Joule heat dissipation,
Q U heat release from g-capture in the material of the current lead.
With a small margin of error
G (Z) = g 1 = g 2 = g 3 = g 4 = g 5 . (3)
Given that we are not interested in the temperature difference between the current lead and the supporting tube and the main temperature difference will be in the gas-adjustable gap, we rewrite equation (3) in the form
G (Z) g 3
or 
Assuming the temperature of the body T to equal the temperature of the cooling coolant T c , and the value of T micsn as the minimum admissible value of the saturation temperature of cesium vapor at the corresponding pressure from (4), we obtain (1).
As information confirming the effectiveness and technical feasibility of the proposed solution, consider a typical PU for EGS tests at a current of 100 A, with an efficiency of about 10% at a cooling water temperature of 40 ° C and an operating pressure of a cesium vapor of 4-6 mm Hg. Corresponding to T cs» 360 ° C. A 6 mm diameter wire with a wall thickness of 1.5 mm is made of niobium, U - heating in which is 188 W / m. At a current of 100 A, the total line power will be 425 W / m.
Let's consider 3 variants of gas filling of an adjusting backlash: helium, a mix helium-nitrogen (50% on 50%) and air. The following values are respectively obtained:
D not / r no. І 2,63; 
D air / r no. І 0,28.
For the latter case, at r no. 12 mm we will have d air 3,36 mm. In the case of a smaller gap, condensation of cesium vapor on the inner wall of the carrier tube is possible with the formation of an additional source of cesium vapor (a "false" thermostat).
Thus, the proposed PU allows reliable tests of EGS by eliminating the possibility of forming a "false" thermostat in the cesium path near the boundary of the active part of the EGS, where, for design and technological reasons, it is usually impossible to install electric heaters of this section of the tract.
CLAIM
A loop device for testing thermionic power generating assemblies comprising a housing in which a source of cesium vapor is placed, a cesium path and a heat dissipation system cooled by the heat transfer medium of the research reactor, configured to house a test thermoemission assembly inside it with the current leads, the heat-sink system comprising an annular gap filled with gas Or a mixture of gases, characterized in that the gap is made profiled, and the width of the gap opposite the current leads is selected from the relation 
Where d (Z) is the width of the annular gap filled with gas, in the section Z, m;
D n.t. internal diameter of the cesium channel, m; 
The minimum permissible temperature of the inner wall of the cesium tract, K;
T in the temperature of the coolant, K;
Q (z) the linear heat dissipation inside the cesium channel in the section Z, W / m;
L g coefficient of thermal conductivity, gas, W / m H degree.
print version
Date of publication 05.04.2007gg
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