RU2238598C2 - Space-based double-mode nuclear power unit of transport-and-power module - Google Patents

Abstract

FIELD: nuclear power and space engineering; space power and motive installations.

SUBSTANCE: proposed double-mode nuclear power unit designed to solve two problems of delivering spacecraft to orbit followed by power supply to spacecraft equipment has thermionic converter reactor incorporating core and side reflector that accommodates operating elements of protection and control system. Thermionic converter reactor functions to supply with power transport-mode loads at rated power level and continuously running loads at reduced power level. Reactor core has two groups of fuel assemblies built of power-generating elements and rated at different service periods. First group incorporates assemblies of power-generating elements whose service period is equal to or longer than operating time of transport-mode loads and second group, of those whose service period is equal to or longer than total operating time of transport- and continuous-power-mode loads. Power-generating elements of second-group assemblies have reduced amount of fissionable material compared with those of first group. Assemblies of first group are disposed in peripheral part of core at side reflector and those of second group, in central part of core.

EFFECT: enhanced operating reliability and service period of nuclear power unit in both modes due to effective operation of protection and control system components.

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Description

The invention relates to space and nuclear technology and can be used to create space power and propulsion systems.

Currently, the most likely area of application for space nuclear power plants (NPPs) is to use them to solve two interrelated tasks: to deliver spacecraft (SC), and above all information, to the orbit of operation, mainly geostationary (GSO), and the subsequent long within 10-15 years of power supply of spacecraft equipment. Thus, the nuclear power plant will provide a solution to space problems sufficiently prepared for technical implementation. A resource of 10-15 years is essential to ensure competitiveness in relation to solar photovoltaic converters.

Such a space complex, designed both for launching a spacecraft into a working orbit, and for the subsequent long-term power supply of its equipment, is called a transport and energy module (TEM).

Known space nuclear power plant with thermionic converter reactor (TRP) "Topaz" [1]. It contains TRP on thermal neutrons, radiation protection, a cooling system with a coolant in the form of a eutectic alloy NaK, a control system and a supporting structure. TRP contains an active zone (A3), consisting of a moderator and thermionic power generating assemblies (EGS), usually called thermionic power generating channels (EGC), a reflector in which the controls are in the form of rotary drums.

Such a nuclear power plant with TRP successfully worked out in space, generating an electric power of about 5 kW for about a year to power the spacecraft equipment. However, this nuclear power plant cannot be used as a dual-purpose (dual-mode) installation for powering not only the spacecraft equipment, but also the electric propulsion system (ERP), both because of the low level of electric power and because of the relatively low resource.

Known space nuclear power plant with TRP as an electric power source for electric propulsion systems for transport operations to deliver the Martian expeditionary complex to Mars and return the expedition to Earth [2]. It contains TRP on fast neutrons with a slowing reflector, the active zone of which is composed of highly efficient EGCs; radiation protection; combined reactor control system; cooling system TRP of the circulation circuit with lithium coolant and a radiator-cooler based on heat pipes, made in the form of hydraulically independent modules. The electric power of such a nuclear power plant is from 2.5 to 15 MW (depending on the expedition scheme) and the resource is 12000 hours.

Such a nuclear power plant is capable of providing power to the electric propulsion system for delivery to Mars of an expeditionary complex weighing approximately 150 tons and returning to the Earth a return ship to Earth weighing 10 tons with a total expedition time of no more than 1.5 years. However, such a nuclear power plant, designed for high specific characteristics and relatively low resource, cannot be used for long-term power supply of spacecraft equipment.

A known dual-mode space nuclear power plant proposed in [3]. It is intended for two-purpose use as part of a nuclear energy propulsion unit (NED) or TEM: for powering the electric propulsion system and carrying out transport operations (mainly for delivering spacecraft to energy-intensive orbits, for example, geostationary) and for subsequent long-term power supply of onboard payload equipment of spacecraft, mainly information . The dual-mode space nuclear power plant contains a TRP with an active zone as a heat source and simultaneously a heat energy converter directly into electric energy (to provide electric power to transport mode consumers), an additional heat to electric converter located outside the TRP (for long-term supply of spacecraft payload consumers with electric power), a system cooling of TRP and an additional converter in the form of a circulation circuit with a refrigerator-emitter pumping a triad, pipelines and a device that switches the flow of coolant to an additional converter. As an additional converter, a thermoelectric converter of thermal energy into electrical energy can be used; thermionic converter of thermal energy into electric; electric machine generator based on steam or gas engines operating on the Rankine, Brighton or Stirling cycle; regenerative electrochemical generator. As a system for removing the untransformed heat of the thermodynamic cycle of the additional converter, the main CI can be used, as well as an additional refrigerator emitter.

Such a nuclear power plant is able to provide power to the electric propulsion system for delivery to the orbit of operation and the subsequent long-term power supply of the spacecraft equipment. However, the use of these converters as an energy source for long-term power supply requires higher values of the upper temperature of the thermodynamic cycle, and, consequently, a high operating temperature of the structural materials of the circuit. High temperatures of the structural material reduce reliability and limit the life of the nuclear power plant. In addition, the presence of the second cascade reduces the lower temperature of the thermodynamic cycle, which leads to an increase in the surface of the refrigerator-emitter, and therefore the mass of the nuclear power plant.

Known space dual-mode nuclear power plants, described in [4]. It is intended for dual-purpose use as part of a nuclear power reactor (TEM), namely: for powering an electric propulsion system and carrying out transport operations (for example, for delivering spacecraft to a GSO) and for subsequent long-term power supply of onboard equipment of a payload of spacecraft, mainly information.

The space nuclear power plant contains TRP on fast neutrons with a slowing reflector; radiation protection; combined reactor control system; circulation cooling system TRP, consisting of pipelines with lithium coolant, an electromagnetic pump with a refrigerator-emitter based on heat pipes, made in the form of hydraulically independent modules. The TRP active zone was recruited from EHS, the hardened doped tungsten single crystal being used as emitter shells of it. The electric power of the nuclear power plant in the transport mode is 100-150 kW with a resource of up to 1.5 years; the power of a nuclear power plant in the power supply mode of the spacecraft equipment is 10–40 kW with the claimed resource of up to 10 years. Both operating modes of the nuclear power plant are provided due to the operation of the TRP in two modes: at the nominal (transport) mode with the maximum power level and in the mode of reduced thermal and, therefore, electric power.

However, the creation of such a dual-mode nuclear power plant with a long operating mode is associated with significant difficulties and, above all, with the need to create a dual-mode EHS for a long life. Typically, the EHS is created for only one operating mode, when its parameters, including the geometric dimensions and the number of EGE in the EHS, can be selected optimal for this mode. The operation of the EHS in any other mode in terms of thermal power will not be optimal, the temperature fields in one of the modes will be substantially uneven, which in principle casts doubt on the possibility of creating an EHS that could operate for a long time in two significantly different modes. In addition, the current – voltage characteristics of the EHS as an autonomous energy source are “soft”, i.e. operating current and voltage depend on thermal power, so each mode will have its own operating voltage, which will complicate the operation of such a nuclear power plant. The long-term TRP resource will require the creation of a new methodology for testing the EHS during loop reactor tests at a shortened time base.

Closest to the invention in technical essence is the space dual-mode nuclear power unit of the transport and energy module, proposed in [5]. It contains TRP as a source of electricity for consumers of a transport mode with a nominal power level and consumers of a long-term power supply mode with a reduced power level. TRP consists of an active zone formed from EHS, and a reflector in which the working bodies of the control and protection system (CPS) are located in the form of rotary drums (cylinders) from a material that slows down neutrons, such as beryllium, and overlays from a material that absorbs neutrons, for example, boron. The active zone is formed from EGE assemblies with an emitter shell, inside which fissile material is placed, and the EHS switching system is equipped with current leads. The TRP core is composed of two groups of EGE assemblies with different work resources. In this case, the first group is recruited from the EGS with a service life equal to or more than the operating hours of the consumers of the transport mode, and the second group is recruited from the EHS with a resource equal to or more than the sum of the working hours of the consumers of the transport mode and consumers of the long-term power supply mode, each of the EHS groups is equipped with own switching system of EHS with independent current outputs. The EGE of the assemblies of the second group contain a lower amount of fissile material relative to the EGE of the first group, for example, the volume fraction of fissile material inside the emitter shell of the EGE of the assemblies of the first group can be equal to 70-85%, and in the EGE of assemblies of the second group it can not exceed 50%.

Moreover, as follows from the description of the invention [5] on page 9, the assembly of the first group, i.e. with a high content of fissile material, are located in the central part of the active zone, and assemblies of the second group with a reduced amount of fissile material are located on the periphery of the active zone.

However, in the TRP, as in any other reactor, there is a radial non-uniformity of the neutron flux density and, accordingly, the heat release density, with the flux density being maximum in the central part of the core and minimal at its periphery at the side reflector (where the working bodies of the CPS are located at the TPP) . This leads to two undesirable consequences, namely: uneven heating of the coolant along the EHS and a decrease in the efficiency of the working bodies of the CPS located in the lateral slow-down reflector. The second circumstance is especially important. This is due to the fact that the influence of a change in the position of the absorbing pads of the CPS working bodies extends mainly to the distribution of the neutron flux at the reflector, i.e. in the peripheral part of the TRP core. If the bulk of the fissile material is located in the central part of the active zone, a loss of controllability of the TRP or the necessity of introducing additional working bodies of the CPS to the central part of the active zone is possible, which can significantly complicate the design of the TRP.

The technical result achieved by using the invention is to increase the reliability of the nuclear power plant in two modes that differ significantly in electrical power and resource by increasing the efficiency of the working bodies of the CPS located in the side reflector.

The specified technical result is achieved in the space dual-mode nuclear power plant of the transport and energy module containing a TRP with an active zone and a side reflector with CPS working bodies located in it as an electric power source for consumers in the transport mode with a nominal power level and consumers in a long-term power supply mode with a low power level, and the core is composed of two groups of EGE assemblies with different work resources, while the first group is recruited from EGE assemblies with a work resource, p or more than the operating hours of the consumers of the transport regime, and the second group is recruited from EGE assemblies with a resource equal to or more than the sum of the operating hours of the consumers of the transport regime and consumers of the long-term power supply regime, and the EGE of the assemblies of the second group contain a lower amount of fissile material relative to the EGE of the first group, where the assemblies of the EGE of the first group are located in the peripheral part of the active zone near the side reflector, and the assemblies of the second group with a reduced amount of fissile material are in the central the second part of the core.

Figure 1 shows a diagram of a space dual-mode nuclear power plant transport-energy module; figure 2 is a cross section of the TRP; figure 3 and 4 are structural diagrams of the EGE of the first and second groups of assemblies, respectively; figure 5 - distribution of the neutron flux along the radius of the active zone, demonstrating the effectiveness of the proposed technical solution.

The dual-mode space nuclear power plant TEM contains a TRP 1, a circulation cooling system 2 with an electromagnetic pump 3 and a radiator-radiator 4. The TRP contains a housing 5 and an active zone (A3) recruited from EGE assemblies of two groups, the first group being formed by assemblies 6, which are placed on the periphery of A3 (Fig. 1 and Fig. 2), and the second group of assemblies 7 (in Fig. 1 and Fig. 2 they are placed in the center of A3 inside the conditional dashed line). Each of the groups of EGE assemblies is equipped with its own switching system 8 and 9, respectively, of assemblies 6 of the first group and assemblies 7 of the second group with independent current outputs 11 and 10.

The TRP includes a reflector 12, which contains the executive controls (CPS) of the TRP in the form of rotary cylinders 13 with neutron-absorbing pads 14.

The first and second groups of assemblies are equipped with channels 15 and 16, respectively, for supplying cesium vapor and removing gaseous fission products (GPA) of uranium.

Thus, the core is composed of 2 groups of EGE assemblies, and the first group is composed of EHS 6 with EGE with high specific characteristics, but with a relatively low service life equal to or more than the operating time of consumers of transport mode (ERE), usually 0 , 5 ... 1.5 years. The second group is composed of EHS 7 with EGE with reduced specific characteristics, but with a resource equal to the total resource of the NPP, i.e. equal to or more than the sum of the operating hours of consumers of the transport mode (ERDU) and consumers of the long-term power supply mode (spacecraft equipment).

Assemblies 6 (FIG. 3) and 7 (FIG. 4) contain an EGE with an emitter shell 17, inside which fissile material 18 is placed, and a collector 19. The collector insulation 20 and the housing 21 common to all EGE assemblies will be cooled externally ( drawings not shown), for example, eutectic alloy NaK or Li. The gap between the cylindrical part of the emitter shell 17 and the collector 19 is the interelectrode gap 22 of the thermionic converter, which is filled with cesium vapor under operating conditions. The EGE of the assemblies of at least the second group are equipped with a gas outlet device, made, for example, in the form of a tube 23 with a nozzle 24. Fissile material 18 occupies an incomplete volume inside the emitter shell 17, part of this volume forms a central gas cavity (CHP), which - due to the different content of fissile material is different for the EGE assemblies of the first and second groups (Fig.3 and Fig.4, respectively).

The coolant in the cooling system 2 is circulated by a pumping device 3, usually made in the form of an electromagnetic pump. The heat that has not been converted into a TRP is discharged by radiation into space from the surface of the refrigerator-emitter 4, made, for example, on the basis of heat pipes.

It is equipped with terminals 10 and 11 for the removal of generated electricity to consumers or the power distribution system (not shown in FIGS. 1 and 2).

Space dual-mode nuclear power plant operates as follows.

In the initial state, the rotary cylinders 13 TRP are in position with absorbing pads 14 to A3. Therefore, TRP 1 is not critical and in this state the space nuclear power plant is launched into space. In a radiation-safe orbit, for example, 800 km high, a nuclear power plant is launched. To do this, automatically, on command of the Earth or the control system of the nuclear power plant (or spacecraft), the rotation of the rotary cylinders 13 is carried out so that the pads 14 depart from A3. The reaction of dividing the fuel material (fissile material 18) inside the emitter shells 17 of the EGE of assemblies 6 and 7 begins. The heat released in assemblies 6 and 7 is removed from A3 by the heat transfer medium 25 of cooling system 2 pumped into CI 4. In CI 4, heat is discharged radiation into outer space. The coolant cooled in 4 enters the pump 3, which, having created a pressure, pumps the coolant 25 through the active zone of the TRP 1, cooling assemblies 6 and 7.

After reaching the operating level of thermal power of the nominal mode, interelectrode gaps 22 of the EEG of assemblies 6 and 7 are supplied through channels 15 and 16, respectively, with a working fluid (cesium vapor) and assemblies 6 and 7 begin to generate electricity. Electricity generated by both groups of assemblies 6 and 7, using isolated current leads 10 and 11 is transferred to the consumer of the transport mode. The unconverted heat of the thermodynamic cycle of assemblies 6 and 7 is removed by the coolant 25 similarly to that considered in the start-up mode and then discharged into space by radiation in CI 4. The flow rate and heating of the coolant can be chosen optimal to obtain the required electric power of the transport mode of operation, when the generated electricity is consumed for power ERDU. Moreover, in the generator mode, the EGE assemblies of both groups work.

After the operation of the nuclear power plant in the transport mode, for example, after the spacecraft is delivered with the help of the electric propulsion system to the orbit of the spacecraft’s functioning, for example, geostationary, the nuclear power plant must be switched to the second mode of operation, providing consumers with the long-term power supply of the spacecraft equipment at a reduced power level, but with a significantly longer resource (10 ... 15 years). To do this, the first group of assemblies 6, which have consumed their planned resource equal to the operating time of the nuclear power plant in transport mode, are disabled, for example, by removing cesium vapor from the MEZ 22 EGE of assemblies 6 (assemblies of the first group) through channel 15 or using current outputs 10. After of this assembly, the first group 6 does not work as electricity generating devices, but as ordinary fuel elements, i.e. sources of heat which is removed by the heat carrier 25.

EGE of assemblies of the second group during operation in transport mode consumed only part of their design resource (0.5 ... 1.5 years with a resource of 15 years or more) and can continue to work as power generating devices. Through current leads 11, electricity generated only by assemblies 7, i.e. less power than in transport mode is supplied to consumers of the long-term power supply of spacecraft equipment. The heat released in the EGE of the assemblies 6, operating as a fuel rod, and the non-converted heat of the thermodynamic cycle in the EGE of the assemblies 7 are removed by the coolant 25 of the cooling system 2, which then enters the CI 4, where the heat is released by radiation into outer space. The coolant cooled in CI 4 enters the pump 3, which, having created a pressure, pumps the coolant 25 into the active zone of the TRP 1.

The service life of assemblies 6 of the EEG of the first group (Fig. 3) as a heat source is significantly higher than the source of electricity, since in this case such main reasons for limiting the EHS resource as swelling of fissile material 18 with deformation of the emitter shell 17 to short-circuit the electrodes and electric a breakdown of collector insulation 20 will not affect the ability of the EGE of assemblies 6 to function as a conventional fuel element (fuel element) of a nuclear reactor.

The service life of assemblies 7 of EGE of the second group as an electric power source is significantly higher than that of EGE of the first group, since special measures have been taken to increase the resource of EGE and assemblies 7 as a whole in the generator mode by reducing the volume fraction of fissile material 18 inside the emitter shell 17 (Fig. .4), for example, to less than 50%, i.e. reduced relative to the EGE assemblies 6 of the first group, in which the volume fraction of fissile material can be 70 ... 85%, a decrease in specific heat loads and a decrease in the swelling rate of fissile material 18 are achieved.

Placing the EGE assemblies of the first group (with a high content of fissile material) in the peripheral part of the active zone near the side reflector, where the working bodies (rotary drums) of the CPS are located, leads to a redistribution of the neutron flux density over the cross section of the active zone, namely: a relative increase in flux density in peripheral part A3 and a relative decrease in flux density in the central part, where the EGE assemblies of the second group with a low content of fissile material are located. Figure 5 shows a qualitative picture of the distribution of the neutron flux density f (r) over section A3 of the TRP for three cases: 1) when A3 is assembled from EGE assemblies of only one group, for example, the first (curve "a"), 2) when A3 is drawn from two groups of assemblies, with the assemblies of the EGE of the first group (with a high content of fissile material) located in the central part of A3, and the assemblies of the second group (with a low content of fissile material) in the peripheral part of A3, i.e. as in the prototype (curve "b"), 3) when A3 is also composed of the same two groups of assemblies, however, the EGE assemblies of the first group (with a high content of fissile material) are located in the peripheral part of A3, and the assemblies of the second group (with a low content of fissile substances) - in the central part of A3, i.e. as proposed in this technical solution (curve "c"). Comparison of curves “b” and “c” shows that the proposed technical solution due to the redistribution of the relative neutron flux over section A3 makes it possible to increase the efficiency of the CPS bodies, whose working bodies are located in the side reflector of the TRP, and thereby increase the controllability and safety of the operation of the TRP of the space dual-mode Nuclear power plant.

The use of the considered tools is estimated to create a long-life assembly of 7 EGE of the second group for a dual-mode nuclear power plant TEM. The necessary decrease in the volume fraction of the fissile isotope in the active zone of the TRP 1 can be compensated by a corresponding increase in the volume of the active zone.

After working out the full resource in both modes of operation, the TRP is turned off and the TEM nuclear power plant ceases to work.

Thus, the present invention provides the possibility of operation of a space nuclear power plant TEM in two modes that differ significantly in electrical power and resource with an increase in operating life at a reduced power level with an increase in operational reliability due to an increase in the efficiency of CPS bodies. At the same time, a more uniform heating of the coolant in the TRP core, and, consequently, less intense work of the hull and other loaded elements of the TRP and the nuclear power plant as a whole, is achieved, which also increases the reliability of the nuclear power plant.

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.Vol. 6, issue 6. S. 450-454.

2. Ageev V.P. and others. An energy propulsion unit based on a thermionic nuclear electric propulsion system for the Martian expeditionary complex. Scientific tech. Sat Issue 1 (134) of the RD and the EU. Ed. NIITP. 1992.S. 25-33.

3. Patent RU 2140675. Space dual-mode nuclear power plant.

4. Sukhov Yu.I., Sinyavsky V.V. Overview of the work of RSC Energia named after SP Korolev on thermionic nuclear power plants of high power for space applications. Scientific tech. Sat Rkt. Proceedings of RSC Energia named after SP Korolev. Series 12: Ed. RSC Energia, Kaliningrad Mosk. region, 1995. Issue 3-4: Space thermionic emission nuclear power plants and large-scale electric propulsion systems. Part 1.P. 20-24.

5. Patent RU 2187854. Space dual-mode nuclear power installation of the transport and energy module.

Claims (1)

A dual-mode space nuclear power plant of a transport and energy module containing a thermionic reactor with a core and a side reflector with control and protection system working bodies placed therein as an electric power source for consumers in the transport mode with a nominal power level and consumers in the long-term power supply mode with low power level, and the core is composed of two groups of assemblies of power generating elements with different resources and work, while the first group is recruited from assemblies of power generating elements with a service life equal to or more than the operating hours of consumers of the transport mode, and the second group is recruited from assemblies of power generating elements with a resource equal to or more than the sum of the working hours of consumers of the transport mode and consumers of the long-term power supply mode moreover, the power generating elements of the assemblies of the second group contain a reduced amount of fissile material relative to the power generating elements of the assemblies of the first group Twa, characterized in that the power generating assembly elements of the first group are arranged in the peripheral part of the core at a lateral reflector, and the power generating assembly elements of the second group are arranged in the central part of the core.

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