RU2224328C2 - Thermal emission reactor-converter of packaged circuit - Google Patents

Abstract

FIELD: thermal emission method of energy conversion in nuclear power engineering and space technology. SUBSTANCE: thermal emission reactor-converter is intended for use in space power installations. Proposed thermal emission reactor has two or more energy-generating packages in the form of sealed case provided with branch pipes for inlet and outlet of heat transfer agent. Energy-generating assemblies cooled by heat transfer agent with active part and collectors for distribution and collection of heat transfer agent placed close to faces of packages are positioned inside case. Part of heat tube of melting system of heat transfer agent is installed in center of each energy- generating package uniaxially with thermal emission assemblies. Evaporation zone of heat tube is placed in heat transfer agent opposite to active part of energy- generating assembly. Outer diameter of evaporation zone of heat tube can be equal to outer diameter of active part of energy-generating assembly. Body of heat tube can be made of same materials as external case of active part of energy-generating assembly. EFFECT: increased operational safety of thermal emission reactor in space, simplified technique of multiple planned starts-up and shut-downs of thermal emission reactor in process of its long-term operation. 2 cl, 2 dwg

Description

 The invention relates to a thermionic method of converting thermal energy into electrical, nuclear and space energy and can be used to create primarily space nuclear power plants.

 The thermionic reactor-converter (TRP) of a space nuclear power plant (NPP) can be based on thermal, intermediate, and fast neutrons. TRP on thermal (and intermediate) neutrons due to the presence in the core of the moderator can only be created up to electric powers of not more than 100 ... 150 kW and a relatively low resource. TRPs with fast neutrons can be created at powers from 100 ... 150 kW to a megawatt level.

 Known TRP on thermal neutrons of the space nuclear power plant "Topaz" [1]. It contains an active zone (AZ), consisting of a moderator and thermionic electric power generating assemblies (EGS), usually called thermionic electric power generating channels (EHC), a reflector in which the controls are in the form of rotary drums. EHS from the outside are cooled by a heat carrier in the form of a eutectic NaK alloy.

 Such a TRP successfully worked out in space, generating an electric power of about 5 kW for about a year.

 However, in order to launch TRP in space, the coolant must be preheated in ground conditions by several hundred degrees and the TRP should be launched within no more than three hours after the launch from the Earth of a rocket from a nuclear power plant with TRP. In such a TRP, there is no system for melting the coolant, therefore, multiple start-up is impossible. The emergency cooling down of the TRP is also not ensured.

 Known TRP on fast neutrons according to the patent [2]. It contains AZ, recruited from EHS and booster fuel elements equipped with a system for removing gaseous fission fragments. Such a TRP has a relatively small volume of AZ, and, consequently, a small mass of radiation protection. However, ground-based testing of such a TRP requires a large amount of work, since the bulk of the tests to verify technical solutions and development of reliability indicators should be performed during nuclear power tests of TRP or even nuclear power plants with TRP. The emergency cooling down of the TRP is also not ensured.

 Known TRP patent [3]. It contains an AZ composed of EGCs and booster fuel elements, which are compactly placed in an additional sealed enclosure equipped with an autonomous cooling system. Such a TRP has a relatively small volume of the core and, therefore, a small mass of radiation protection. However, ground-based testing of such a TRP requires a large amount of work, since the bulk of the tests to verify technical solutions and development of reliability indicators should be performed during nuclear power tests of TRP or even nuclear power plants with TRP. The emergency cooling down of the TRP is also not ensured.

 Closest to the invention in technical essence is the TRP of a packet (modular) fast neutron scheme for high-power space nuclear power plants, proposed in [4]. TRP contains AZ, recruited from hydraulically independent power generating packages (EGP), consisting of a housing inside which thermionic EHS is placed. Each EGP in the TRP has an independent cooling system in the form of an autonomous lithium circuit with coolant collectors located at the ends, having nozzles for entering and leaving the coolant. The controls in the form of rotary drums are located in the side reflector of the TRP.

 Such a TRP can also have a relatively low mass and is designed for electric power from 100 ... 150 kW to several megawatts. The modular construction of TRP significantly simplifies experimental testing, since the bulk of the tests to verify technical solutions and develop reliability indicators can be performed with bench-based nuclear-free testing of EGP with electric heating. The introduction of modular (from EGP) construction simplifies the assembly of TRP, since it is assembled from a limited number of EGP.

 However, for the launch of the TRP in space, the coolant both in the TRP and in the cooling system must be pre-melted and heated several tens or hundreds of degrees above the freezing temperature of the coolant. This can be done, for example, using electric heaters powered by an external source of electricity, such as batteries. If it is necessary to repeatedly scheduled shutdown and restart the TRP, a special program for freezing the coolant must also be provided, which then ensures the scheduled start of the TRP. This is done by slow reduction according to the special program of thermal power of the TRP. However, situations are possible when an emergency, almost instantaneous shutdown of the TRP is performed. In this case, an emergency cooling down of the TRP is necessary. In the absence of a special emergency cooling system for the operating TRP due to the residual heat in the core, the fuel bundles will melt in the EHS and the solidified monolith of the alloy of fissile material with refractory metals will form in at least each of the EGPs (and possibly in the entire core). This task is especially relevant for TRP with a large core volume, high power and long life. This can lead to a change in the reactivity of TRP for the worse from a safety point of view. In addition, in a collision with space "debris" such a monolith upon falling to Earth will not burn in the atmosphere, but will fall to Earth, which is extremely undesirable from the point of view of ensuring the radiation safety of the Earth's population.

 The objective of the invention is to increase the safety of the operation of the TRP in space while simplifying the processes of multiple scheduled launches and shutdowns of the TRP during continuous operation.

 This problem is solved in the TRP of a batch scheme containing at least two EGPs in the form of a sealed enclosure equipped with nozzles for entering and leaving the coolant, with thermoemissive EGSs with an active part and coolant distribution and collection collectors located at the ends of the EGPs located inside the enclosure, in which, in the center of each EGP, coaxially with the thermionic EHS, a part of the heat pipe of the heat transfer system is installed, and the evaporation zone of the heat pipe is placed in the heat carrier opposite to a active part of the EHS. The outer size of the evaporation zone of the heat pipe can be chosen equal to the outer size of the active part of the EHS, and the body of the heat pipe can be made of the same material as the body of the EHS.

 Figure 1 and 2 explain the essence of the proposed TRP batch (modular) scheme.

 Figure 1 shows a transverse section of the TRP, and figure 2 is a longitudinal section of the EGP.

 The TRP contains an EGP 1 and a side reflector 2, in which the TRP controls are placed in the form of rotary cylinders 3 with neutron-absorbing plates 4. The EGP includes a sealed housing 5, inside of which are thermionic EHS 6, the outer cases 7 of which are cooled by a heat carrier 8, for example, a eutectic alloy NaK or Li. Inside the buildings 7 EHS 6 placed in series connected power generating elements (EGE) 9, forming the active part 10, and the elements of the end reflectors 11 and 12, in which the current leads 13 and 14. The active parts 10 of all EHS 6 of all EHP 1 form the active zone TRP, which is surrounded by a side reflector 2 and elements of the end reflectors 11 and 12.

 Above and below the active part 10 of the EHS 6, respectively, are the collector 15 of the distribution of the coolant 8 and the collector 16 for collecting the coolant 8. The supply of coolant in the EHP 1 is through the pipe 17 connected to the manifold 15, and the outlet through the pipe 18 connected to the collector 16.

 The current outputs 13 and 14 through the hermetic inputs 17 and 18 are led into the switching chambers 19 and 20, where the EHS 6 is switched, for example, serial-parallel, to obtain the required voltage and current of each EHP 1. From the switching chamber 20, two current outputs 22 go through the hermetic terminals 21, which allow for further switching of the EHP outside the body 5 of the EHP 1.

 In the center of each EGP 1 coaxially with the thermionic EHS 6, a part of the heat pipe 23 of the heat transfer melting system is installed, the evaporation zone 24 of the heat pipe 23 is located in the heat carrier 8 opposite the active part 10 of the EHS 6. The adiabatic zone 25 of the heat pipe is partially located in the collector 16, partially in the switching chamber 20 and partially outside the housing 5 of the EHP 1. The outer size (diameter) d of the evaporation zone 24 of the heat pipe is chosen equal to the outer size (diameter) D of the active part 10 of the EHS 6, and the housing 26 of the heat pipe 23 is made of the same mat rial that EGS 7 and the housing 6, inside the heat pipe 23 along its entire length the capillary structure 27 is installed.

 TRP packet scheme works as follows.

 In the initial state, the rotary cylinders 3 located in the reflector 2 are in the position of the absorbing plates 4 to the core with the EGP 1. Therefore, the TRP is not critical and in this state it is launched into space as part of the nuclear power plant. When this coolant 8 in the TRP can be both in liquid (molten) and solid (frozen) state.

 In a radiation-safe orbit, for example, with an altitude of 800 km, the TRP is launched. To do this, automatically, on command from the Earth (or the control system of a nuclear power plant or spacecraft), the rotary cylinders 3 are rotated so that the plates 4 extend from the core with the EGP 1. First, the TRP is brought to an intermediate, relatively small level of thermal power. The reaction of fission of the fuel material in the EGE 9 of the active part 10 of the EHS 6 begins with the release of heat. The generated heat is removed from the outer surface of the EHS 6 housings 7 to the coolant 8 which was not pumped at the initial moment, for example, the NaK or Li eutectic alloy. When this coolant 8 is heated, and if it was solid, it melts and then heats above the melting point. After some time, the entire coolant 8 in each of the EGP 1 TRP will be melted and slightly heated. Since the evaporation zone 24 of the heat pipe 23 is located in the same coolant, heat conduction from the heated coolant 8 through the housing 26 will be transferred to the evaporation zone 24 of the heat pipe 23. Due to the supply of heat from the capillary structure 27 of the evaporation zone 24 of the heat pipe, evaporation will occur a working fluid, the vapor of which, having passed the adiabatic zone 25, is condensed in the evaporation zone (not shown) of the heat pipe laid along the mains with the coolant of the cooling system (not shown). Thereby, the coolant outside the TRP will be heated and melted. After that, the coolant circulation is turned on and the TRP is cooled by the circulating coolant 8. The coolant 8 is supplied to the EGP 1 through the pipe 17, then through the transfer manifold 15 it enters the active part 10, cooling the outer shells 7 of the EHS 6. The coolant heated in the active part 10 into the collection manifold 16, and from it through the pipe 18 enters the cooling system (not shown). The arrows show the movement of the coolant 8 in the EGP 1 in the nominal operating mode of the TRP of the batch circuit.

 After reaching the working level of thermal power, a working fluid (cesium vapor) is supplied to the EHS 6 and they begin to generate electricity. EHS 6 are equipped with current outputs 13 and 14, with which inside the housing 5 EHP 1 EHS 6 are switched in parallel, sequentially or parallel-sequentially. Switching is carried out in the switching chambers 19 and 20, from the latter, with the help of current outputs 22 isolated from the housing, the electric power enters the external switching devices (not shown) and consumers, including for supplying pumps that provide coolant circulation (not shown). The heat of the thermodynamic cycle, which was not converted to EHS 6, is removed by the heat carrier 8, as described above, and then, using the cooling system, it is discharged into space by radiation in a nuclear power refrigerator (emitter) (not shown).

 After the end of the planned work cycle, the TRP is stopped. For this, the thermal power of the TRP is gradually reduced by a decrease in the electric power generated by the EHS 6. After reaching a certain intermediate reduced level of thermal power, the generation of electricity in EGS 6, and therefore in EGP 1 and in the whole TRP, stops. Accordingly, the circulation of the heat carrier 8 in the EGP 1 stops due to lack of power supply. However, the cooling of the EGP 1 does not stop, since the active part 10 of the EGS 6 released in the fuel material of the EGE 9 is carried out by heat conduction through the as yet molten coolant 8 to the evaporation zone 24 of the heat pipe 23 Due to the supply of heat from the capillary structure 27 of the evaporation zone 24 of the heat pipe, the working fluid will evaporate, the vapor of which, passing through the adiabatic zone 25, will condense in the evaporation zone of the heat pipe s laid along the mains with a coolant cooling system (not shown). Thus, heat will be released into space.

 Subsequently, the TRP is suppressed by turning the rotary cylinders 3 placed in the reflector 2 to the position with absorbing plates 4 to the core with EGP 1. The TRP becomes non-critical, its neutron power is zero. However, the thermal power is not equal to zero, since there is residual heat in the fuel cores of the EGE 9. This heat, similar to the heat conduction considered above, is delivered to the evaporation zone 24 of the heat pipe 23 and is discharged into space using it. Gradually, the residual heat becomes lesser, the temperature of the coolant 8 in the EGP 1 decreases to at some point it freezes.

 The restart of the TRP is carried out similarly to the first launch described above.

 However, situations are possible when during TRP operation at any power level the TRP emergency stops the paths of almost instantly turning the rotary cylinders 3 located in the reflector 2 to the position of the absorbing plates 4 to the core with EGP 1. The TRP becomes non-critical, its neutron power is zero, Generation of electricity in the EGS 6 does not occur, and therefore, the circulation of the coolant in the EGP 1 also stops. However, the thermal power is not equal to zero, since there is residual heat in the fuel sulfur echnikah EGE 9. In this case, you need an emergency cooling TRP. In the absence of a special emergency cooldown system for the operating TRP due to residual heat generation in the core, the fuel will melt in EGE 9, EHS 6 and subsequent formation, at least in each of the EGP 1, and possibly in the entire active zone of the TRP, solidified monolith alloy fissile material with refractory metals. This task is especially relevant for TRP with a large core volume, high power and long life. This can lead to a change in the reactivity of TRP for the worse from a safety point of view. In addition, in a collision with space "debris" such a monolith upon falling to Earth will not burn in the atmosphere, but will fall to Earth, which is extremely undesirable from the point of view of ensuring the radiation safety of the Earth's population.

 However, the presence of the evaporation zone 24 of the heat pipe 23 in the coolant 8 in the center of each EGP 1 prevents this situation, which is dangerous from the radiation point of view, since it automatically cools each EGP 1 in the TRP of the batch circuit. At the same time, no additional systems and devices for emergency cooling of the TRP are required. No additional sources of electricity are required, as the cooldown is provided without the cost of electricity. The generated heat, similarly to the thermal conductivity discussed above, is delivered to the evaporation zone 24 of the heat pipe 23 and is discharged into space with its help. Gradually, the residual heat becomes smaller, the temperature of the coolant 8 in the EGP 1 decreases and at some point it freezes.

 The placement of the evaporation zone 24 of the heat pipe 23 in the coolant 8 provides the best thermal contact during heat transfer by heat conductivity from the EHS 6 to the housing 26 of the evaporation zone 24 of the heat pipe. The location of the evaporation zone 24 of the heat pipe in the center of the EHP 1 opposite and coaxially active part 10 of the EHC 6 provides the best conditions for heat removal with a minimum temperature difference from all the EHC 6 with non-circulating coolant 8.

 The choice of the outer size (diameter d) of the evaporation zone 24 of the heat pipe, which is equal to the outer size (diameter D) of the active part 10 of the EHS 6, provides the same coolant speeds and, therefore, the conditions of heat removal both in the peripheral EHS and in the EHS located next to heat pipe evaporation zone.

 The implementation of the housing 26 of the heat pipe from the same material as the housing 7 of the active part 10 of the thermionic EHS, for example, from a niobium alloy, ensures the absence of mass transfer processes of dissimilar materials in the circulating coolant.

 Thus, the placement in the coolant in the center of each EHP opposite the active part and coaxially with the thermionic EHS parts of the heat pipe of the melting system of the coolant simplifies the processes of multiple scheduled starts and shutdowns of TRP during long-term operation and increases the safety of operation of TRP in space, including in emergency situations , due to the provision of automatic, without the cost of electricity, cooldown of the reactor.

Sources of information
1. Kuznetsov V.A., Gryaznov G.M., Artyukhov G.Ya. et al. Development and creation of a thermal emission nuclear power plant "Topaz". - Atomic energy "1974. T.36, issue 6. S.450-454.

 2. Patent RU 207638S C1, MKI H 01 J 45/00. Thermionic converter reactor. Publ. 03/27/97. Bull. 9.

 3. Patent RU 2086036 C1, MKI H 01 J 45/00. Thermionic converter reactor. Publ. 07/27/97. Bill. 21.

 4. Patent RU 2168794 C1, MKI H 01 J 45/00. Thermionic reactor-converter of a batch circuit. Publ. 06/10/2001. Bull. 16.

Claims (3)

1. The thermionic emission reactor-converter of the batch circuit, containing at least two power generating packages in the form of a sealed enclosure, equipped with nozzles for entering and leaving the coolant, with the coolant coolant located inside the enclosure, thermionic power generating assemblies with the active part, distribution and collection collectors of the coolant located at the ends of the package, characterized in that in the center of each power generation package coaxially with thermionic power generation assemblies installed portion of the heat pipe coolant system melting, and vaporization zone of the heat pipe is placed in the coolant opposite the active part of the power generating assemblies. 2. The thermionic emission reactor-converter of the batch circuit according to claim 1, characterized in that the outer diameter of the evaporation zone of the heat pipe is chosen equal to the outer diameter of the active part of the thermionic power generating assembly. 3. The thermionic emission reactor-converter of the batch circuit according to claim 1, characterized in that the casing of the heat pipe is made of the same material as the outer casing of the active part of the thermionic power generating assembly.

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