Integrated nuclear reactor

Abstract

Several claimed embodiments of an integrated nuclear reactor relate to nuclear engineering and can be used in reactor systems using several different types of liquid coolants with high boiling points, such as liquid metals, molten salts, and the like. The structural features of the claimed embodiments of the invention, which utilize a spiral heat exchanger segmented along a secondary coolant circuit, provide an improvement in cost-performance by reducing the reactor's metal consumption; efficiently utilizing the reactor's internal volume; improving safety in the event of a leak in the heat exchanger's piping; and providing the ability to remove residual heat after shield plugs are removed before fuel is discharged.

Description

Technical Field

[0001] Both claimed embodiments of the invention relate to nuclear technology and can be used in reactors with different types of heat transfer fluids with a high boiling point, such as liquid metals, molten salts, etc. Background Art

[0002] Prior art discloses a nuclear power plant according to Russian Patent No. 2313143, with a priority date of June 20, 2006, comprising a reactor having a liquid metal reactor activator or its alloy placed below the level of a free heat carrier, an active zone, steam generators (SGs), circulation equipment, such as an axial pump, and a blanket gas system. The design and operating principle of a nuclear power plant analogous to the claimed invention are as follows. Several steam generators and pumps are installed below the level of the free heat carrier in an annular duct above the reactor core. The inner diameter of the annular duct is larger than the outer diameter of the core. The steam generator inlet is connected to the heat carrier volume above the core. The steam generator outlet is connected to the pump inlet suction chamber within the annular duct. The pump pressure chamber is connected to the nuclear power plant core via a downcomer region. The nuclear power plant operates as follows. The heat released during the fission of heavy nuclei heats the heat carrier in the reactor core. The heated heat carrier enters the volume above the furnace core through the operation of the pump. The heat carrier leaves this section and enters the several inlet sections of the several steam generator sections, flushing the several steam generator tubes below the free heat carrier level and transferring heat to the working medium circuit. The heat carrier leaves the outlet sections of the several steam generators and enters the suction chamber of the pump. The pump transfers energy to the heat carrier flow, which is consumed to overcome the hydraulic resistance of the downcomer area and the furnace core, and to increase the free heat carrier level in the inlet suction chamber of the several steam generators, which is equal to the hydraulic resistance of the inlet section of the several steam generators toward the suction nozzle of the pump. The cooled heat carrier flow leaves the pressure chamber of the pump and enters the furnace core through the downcomer area. A disadvantage of this solution is the low reliability of the power plant, which becomes apparent in the event of a failure of one of the several pumps connected in parallel to the common downcomer duct, because a large amount of the returning heat carrier flow will pass through the shut-down pump, which will significantly reduce the flow rate of the heat carrier flow through the furnace core and require a significant reduction in the reactor power.Furthermore, in the event of a failure of one of the SG sections due to loss of containment in one of the tubes and SG shutdown, a hot heat carrier flow will pass through the SG section that has been shut down by the secondary circuit. When mixed with the cold heat carrier flow exiting the still-operating SG section, this hot heat carrier flow will cause large temperature fluctuations of the heat carrier reaching the core, thereby degrading the performance of the core due to thermal cycle fatigue of the core's structural materials. This solution also has the disadvantage that it is impossible to remove excess heat during the fuel change operation if the shield plug, which is not shown in the drawings of this patent, is removed from the reactor during the fuel change operation. The shield plug is necessary to reduce the radiation dose in the upward direction when the heat carrier level can drop below the SG and heat dissipation stops.

[0003] The prior art also discloses a nuclear reactor with a liquid metal heat carrier, equipped with at least one compact heat exchanger, specifically a steam generator arranged vertically in an annular chamber between the reactor vessel and a coaxial annular hub, with the furnace core and the hot heat carrier chamber of the main circuit located in the bottom section of the steam generator (WO 2009 / 024854), which is also an analogue of the claimed invention. The heat exchanger has a plurality of heat exchange tubes in the form of flat spirals, one above the other. A circulating pump is located within the heat exchanger (steam generator). The hot heat carrier is supplied from below to the pump inlet and then moves upward in the heat exchanger through the pump tubes, entering the heat exchanger tube bundle in a radial direction away from the heat exchanger axis and towards the periphery of the heat exchanger. Furthermore, the nozzles connecting the hot chamber of the furnace core to the pump inlet have guides for improving the fluid dynamics of the heat carrier flow and mechanical dampers for isolating the heat carrier from flowing into the heat exchanger in the event of an emergency shutdown of the pump when the heat carrier flow is reversed.

[0004] The prototype of the invention according to both claimed embodiments comprises a nuclear reactor having a similar arrangement of equipment in the reactor vessel as in the previous patent, a similar design of the heat exchanger (steam generator), and the same heat carrier circulation pattern in the primary and secondary circuits (WO 2018 / 007961), as shown in the drawings of the patent. This nuclear reactor lacks a hydraulic unit for balancing the velocity field and for moving the mechanical baffles in the pipe connecting the hot chamber of the furnace core to the pump inlet, and has other design differences that do not affect the selection of the nuclear reactor according to patent WO 2018 / 007961 as the prototype of the claimed invention.

[0005] This reactor has several disadvantages. The upper part of the pump, where the pump impeller and bearings are located, is washed by the hot heat transfer medium from the primary circuit. This complicates the design of a pump with a long service life because the corrosion and erosion resistance of the pump impeller material decreases with increasing heat transfer medium temperature. A further disadvantage of the prototype is that, in the event of a leak in the steam generator pipes, the egress of steam from the heat transfer medium to the reactor's gas chamber is hindered by the reactor's design features, as the heat transfer medium flows downward upon exiting the steam generator, carrying steam bubbles with it. Furthermore, the number of pumps in the prototype always equals the number of heat exchangers, which may not be optimal and leads to a deterioration in technical and economic performance. Due to the prototype's design features, if a fuel drain operation requires the removal of the shield plug from the reactor prior to the fuel drain operation, cooling the furnace core during the fuel drain operation is impossible, resulting in a reduced heat transfer medium level in the reactor and a potential interruption of the circulation circuit. One of the main drawbacks of the prototype, which makes it impossible to manufacture a nuclear reactor with the least possible metal consumption and better technical and economic characteristics, is the inefficient use by the heat exchanger (steam generator) of the inter-containment space between the reactor vessel and the coaxial annular hub. Summary of the Invention

[0006] The task that the claimed group of inventions aims to solve is to improve the design of a nuclear reactor in order to reduce metal consumption and improve technical and economic characteristics, its reliability and safety.

[0007] The general technical results achieved by the implementation of the two claimed embodiments include, in particular, improved technical and economic characteristics through a reduction in the metal consumption of the reactor. The reduction in metal consumption is achieved by efficient use of the reactor's internal space when the heat exchanger (steam generator) is placed in the annular space between the reactor vessel and the coaxial hub; better safety in the event of a leak in the heat exchanger (steam generator) tubes when heavy liquid metals (lead, lead-bismuth) are used as the heat carrier through the heat carrier flow circuit, in which case the direction of the heat carrier velocity vector in the heat exchanger (steam generator) is aligned with the direction of the velocity vector of the rising steam bubbles, thereby ensuring their efficient gravity separation into the gas chamber at the free heat carrier level; and the ability to remove excess heat for a period of time after the removal of the shield plug before fuel discharge, if the fuel discharge process provides for the removal of the shield plug before fuel discharge (which results in a reduction in the heat carrier level in the reactor and an interruption of the circulation circuit).

[0008] The essence of the invention claimed according to the first form is as follows.

[0009] An integrated nuclear reactor having a circulating heat carrier with a high boiling point comprises a core having an inlet chamber and an outlet chamber at the top and bottom, a shield plug, and a heat exchanger located below the level of the heat carrier. The heat exchanger is located in an annular space between the hub and a separation shell within the reactor vessel. The core, the inlet and outlet chambers, and the shield plugs are located in the hub. The separation shell forms a downpipe and separates the downward flow of cold heat carrier from the upward flow of hot heat carrier. The heat exchanger is a coil heat exchanger segmented along the secondary loop heat carrier so that the pipes of the heat exchanger sections are grouped in the secondary loop heat carrier inlet and outlet chambers on the pipes at the top of the reactor. The bottom of the heat exchanger is located above several windows in the hub, and the hot heat carrier flows from the outlet chamber of the core through the windows to the heat exchanger inlet. The cold heat carrier from the top of the heat exchanger enters an annular delay tank having a heat carrier level lower than the top of the reactor from which the heat carrier enters the annular downcomer and then flows into the inlet chamber of the furnace core. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 The design of an integrated nuclear reactor corresponding to the first form is shown.

[0011] Figure 2 The design of an integrated nuclear reactor corresponding to the second form is shown.

[0012] Figure 3A portion of a nuclear reactor is shown, detailing several openings in the bulkhead covering the top of the annular downcomer.

[0013] Figure 4 A section of the nuclear reactor is shown, detailing the design of the annular downcomer. DETAILED DESCRIPTION

[0014] Figure 1 The design of an integrated nuclear reactor corresponding to the first form is presented, which applies the principle of natural circulation of the main heat carrier circuit.

[0015] like Figure 1As shown, the integrated nuclear reactor comprises a vessel 1, a reactor core 2 with an outlet chamber 3 and an inlet chamber 4 above and below, a shield plug 5, and a heat exchanger 6 (steam generator). The claimed technical result is achieved by the fact that an annular space 7 between a hub 8 containing the reactor core 2, the outlet chamber 3 and the inlet chamber 4, and the shield plug 5, and a separator shell 9, which separates the downward heat carrier flow through an annular downcomer 10 between the reactor vessel 1 and the separator shell 9 from the hot, upward heat carrier flow, contains a coil heat exchanger (steam generator) 6 segmented along a secondary heat carrier circuit, with its axis coinciding with the axis of the reactor vessel 1. The heat carrier circulates by gravity convection. The hot heat carrier is supplied from the outlet of the reactor core 2 to the inlet of the heat exchanger 6 through several windows 11 in the hub 8. The bottom of the heat exchanger 6 is located above the windows 11. The annular space 7 also has several radiation shielding units 12, which reduce the neutron radiation dose on the reactor vessel 1 to an acceptable value and reduce the induced radioactivity of the secondary loop heat carrier to an acceptable value. The downcomer annular pipe 10 is connected to the annular delay tank 13 from above, below the level of the heat carrier 14. The dynamic pressure of the natural circulation is created by the difference between the density of the heat carrier in the cold downcomer annular pipe 10, where the heat carrier temperature is constant with respect to height, and the density of the heat carrier at the mid-level of the upward flow, where the temperature is first increased due to the heating of the heat carrier in the furnace core 2. Downstream is a section between the heat carrier outlet of the furnace core 2 and the inlet into the heat exchanger 6, with a uniform heat carrier temperature equal to the temperature at the outlet of the furnace core 2. Further downstream is a section in the heat exchanger where the temperature drops to the temperature of the heat carrier at the inlet of the furnace core 2. The cold heat carrier leaves the heat exchanger 6 directly into an annular delay tank 13 with a heat carrier level 14, above which there is an inert gas at a slight overpressure. From the annular delay tank 13, the heat carrier passes through the top edge of the separation shell 9 into the descending annular duct 10 and then into the inlet chamber 4 of the furnace core 2, thus closing the natural circulation loop. The heat exchanger 6 is segmented along the secondary heat carrier circuit so that the pipes of the heat exchanger sections 15 are grouped in the inlet cavity 16 and outlet cavity 17 of the secondary heat carrier circuit on the pipes 18 on the reactor top 19, so that in the event of a shutdown, the valves of one of the sections 15 of the heat exchanger 6 whose pipes have lost their containment body, maintain a uniform temperature distribution of the heat carrier at the heat exchanger outlet.To this end, pipes from several different coiling rows are arranged radially in each inlet and outlet chamber of the secondary heat carrier circuit. This prevents any significant temperature fluctuations of the heat carrier from reaching the furnace core 2 when hot and cold heat carriers mix, improving the survivability of the reactor. If the shield plug 5 needs to be removed for fuel discharge operation and the heat carrier level drops below the level at which the heat carrier overflows through the separation shell 9, in order to cool the furnace core 2 during the fuel discharge operation, the separation shell 9 has several windows 20 located at corresponding heights below the heat carrier level after the shield plug 5 is removed. During normal operation, several bypass valves 21 in the descending annular duct 10 are closed. Several actuators 22 on the reactor top 19 assist in opening the several bypass valves 21, thereby closing the natural circulation loop and removing excess heat through the portion of the heat exchanger 6 below the heat carrier level in the reactor after the shield plug 5 is removed during the fuel discharge operation.

[0016] The technical results achieved by implementing the invention according to the second form claimed include, in addition to the above, enabling the nuclear reactor to operate at a reduced capacity in the event of failure of at least one heat exchanger section; improved reliability of pumps and equipment on top of the reactor, such as the CPS mechanism, through heat carrier circulation in the reactor, in which cold heat carrier is supplied to the annular delay tank with a free heat carrier level; and optimal conditions for gravity separation of steam bubbles in the event of an SG tube leak, since the velocity vectors of the heat carrier flow and rising steam bubbles are upward.

[0017] The essence of the invention claimed according to the second form is as follows.

[0018] An integrated nuclear reactor comprises a heat carrier having a high boiling point, a core having inlet and outlet chambers above and below, a shield plug, and a heat exchanger located below the level of the heat carrier in an annular space between the core, the inlet and outlet chambers, and the shield plug, and a separator shell within the reactor vessel, the separator shell forming an annular downcomer that separates the downward flow of cold heat carrier from the upward flow of hot heat carrier, and a circulation device, such as at least one circulation pump. The heat exchanger is a coil heat exchanger segmented along the secondary loop heat carrier so that the pipes of the heat exchanger sections are grouped in the secondary loop heat carrier inlet and outlet chambers on the pipes at the reactor top. The bottom of the heat exchanger is above several windows in the hub, through which the hot heat carrier flows from the outlet chamber to the heat exchanger inlet, and the cold heat carrier from the top of the heat exchanger enters the annular delay tank, which has a heat carrier level below the reactor top. A vertical circulation pump is arranged in the reactor vessel so that the heat carrier is supplied to the pump impeller suction port directly from the annular delay tank from below the heat carrier level through several windows in the pump shell and a pump pipe connected to the top of the reactor, and a pump discharge pipe is connected to the annular downcomer through several windows in the separation shell or partition, through the separation shell, or through the partition covering the top of the annular downcomer.

[0019] Figure 2 A design of the integrated nuclear reactor corresponding to the second form is shown, wherein the heat carrier is circulated by the pump or pumps.

[0020] Figure 3 A portion of the claimed reactor is shown, detailing several openings in a baffle covering the top of the annular downcomer.

[0021] Figure 4 A portion of the claimed reactor is shown, showing in detail the design of the annular downcomer, the number of baffles corresponding to the number of pumps in the reactor.

[0022] like Figure 2As shown, the integrated nuclear reactor comprises a vessel 1, a core 2 having an outlet chamber 3 and an inlet chamber 4 above and below the core 2, a shield plug 5, a heat exchanger 6 (steam generator), and (several) circulating pumps 23. The claimed technical result is achieved by the fact that an annular space 7 between a hub 8 containing the reactor core 2, the outlet chamber 3 and the inlet chamber 4, and the shield plug 5, and a separation shell 9 forming an annular downcomer 10 and separating the downward heat carrier flow passing through the annular downcomer 10 between the reactor vessel 1 and the separation shell 9, contains a coil heat exchanger 6 segmented along a secondary heat carrier circuit, the axis of which coincides with the axis of the reactor vessel 1. Hot heat carrier is supplied from the outlet of the core 2 to the inlet of the heat exchanger 6 through several windows 11 in the hub 8. The bottom of the heat exchanger 6 is above the windows 11. The annular space 7 below the heat exchanger contains several radiation shielding units 12, which reduce the neutron radiation dose to the reactor vessel and the induced activity of the secondary circuit heat carrier to an acceptable value. The cold heat carrier leaves the heat exchanger 6 and enters an annular delay tank 13 with a heat carrier level 14. The inert gas, at the required overpressure, ensures the required anti-cavitation pressure head on the pump impeller. The heat exchanger 6 is segmented along the secondary circuit, with the pipes of several sections 15 grouped in the inlet and outlet cavities 16 and 17 of the secondary heat carrier circuit on pipes 18 at the reactor top 19. In the event of a shutdown, valves in one of the sections 15 of the heat exchanger 6, whose pipes have lost their containment, maintain a uniform temperature distribution of the heat carrier at the outlet of the heat exchanger 6. To this end, pipes from several different coil rows are arranged radially in each inlet and outlet chamber of the secondary heat carrier circuit. When the hot and cold heat carriers are mixed when the valves close one of the heat exchanger sections, this prevents any significant temperature pulsations of the heat carrier from reaching the furnace core 2, improving the survivability of the reactor. Several pumps 23 are mounted vertically on the pipe 24, on the reactor top 19, above the heat exchanger 6. The heat carrier is supplied to the pump suction directly from the annular delay tank 13 from below the heat carrier level 14 through several windows in the pipe 25 and in the housing 26 of the pump connected to the reactor top 19. The pressure pipes 27 of the several pumps 23 pass through the windows in the separation shell 9 or the partition 28, respectively, through the separation shell or the partition 28 covering the top of the annular downcomer 10 between the reactor vessel 1 and the separation shell 9 (see Figure 3 ) is connected to the inlet chamber 4 of the furnace core 2 of the reactor. The partition 28 is below the heat carrier level 14 in the annular delay tank 13. The partition 28 has an opening 29 (see Figure 3) is used to release gas when the reactor is filled with the heat carrier or steam bubbles in the event of a leak in the heat exchanger (steam generator) 6 tube. The pressure pipes 27 of several pumps 23 are connected to the annular downcomer 10 through the side separation shell 9 or through the top partition 28.

[0023] In addition, the annular downcomer 10 can be provided with a plurality of longitudinal partitions 30 (see FIG. Figure 4 ) According to the inlet chamber 4 (see Figure 2 ) is divided into several equal sections.

[0024] A required number of check valves 31 can also be arranged in the annular downcomer 10, and if one or more pumps are shut off, the corresponding parts of the check valves are closed by a reverse pressure drop (see Figure 2 ).

[0025] Instead of the check valve, a valve 32 with several actuators can be arranged in the annular downcomer 10 at the reactor top 19, depending on the number of pumps 23 present, to isolate the heat carrier backflow from the operating pump towards the pressure pipe 27 of the shut-off pump. There is no strict requirement for the tightness of the seal when the valve is closed, which facilitates reliable movement when closing (see Figure 2 ).

[0026] As in the first form of the claimed invention, if the fuel discharge operation requires the removal of the shield plug 5 and the heat carrier level drops to the point where the heat carrier from the annular delay groove 13 is supplied to the duct 25 and the windows in the pump housing 26 (see FIG. Figure 2 ), in order to cool the furnace core 2 during the fuel discharge operation, the window 20 can be arranged at an appropriate height in the separation shell 10 below the level of the heat carrier after the shield plug is removed (see Figure 1 ), which are closed during normal operation by several bypass valves 21 in the annular downcomer, and the several bypass valves 21 have actuators 22 on the top of the reactor 19 to assist in opening the several bypass valves, thereby ensuring that after the shield plug is removed during the fuel discharge operation, the natural circulation loop is closed and the residual heat is removed by the heat exchanger in the section below the level of the heat carrier.

[0027] The nuclear reactor design as described herein increases the hydraulic resistance to the return heat carrier flow or completely blocks it when one or more pumps are shut down and enables the reactor to operate at a reduced capacity.

Claims

1. An integrated nuclear reactor having a circulating heat carrier with a high boiling point, the nuclear reactor comprising: a furnace core having an outlet chamber above the furnace core and an inlet chamber below the furnace core; a shield plug; and a heat exchanger located below the level of the heat carrier, characterized in that: The heat exchanger is coaxially located with the furnace core in an annular space between a hub and a separator shell in the reactor vessel; the furnace core, the inlet chamber, the outlet chamber and the shield plug are located in the hub; The separation shell forms an annular downcomer and separates the cold heat carrier flowing downward from the hot heat carrier flowing upward; the heat exchanger is a coil heat exchanger, and its coil row is divided into multiple sections along the secondary loop heat carrier, so that the pipes of several heat exchanger sections are grouped and connected to several inlet chambers and outlet chambers arranged at the top of the reactor for the secondary loop heat carrier to circulate; the bottom of the heat exchanger is located above several windows in the hub, so that the hot heat carrier discharged from the outlet chamber of the furnace core enters the heat exchanger through the several windows, and after the heat carrier undergoes heat exchange through the coil row, it is discharged from the top of the heat exchanger as a cold heat carrier and enters the annular delay tank, wherein the annular delay tank has a heat carrier level lower than the heat carrier level at the top of the reactor when the cold heat carrier enters the annular downcomer, and the cold heat carrier then flows into the inlet chamber of the furnace core to complete the cycle.

2. An integrated nuclear reactor having a heat carrier having a high boiling point, the nuclear reactor comprising: a furnace core having an outlet chamber above the furnace core and an inlet chamber below the furnace core; a shielding plug disposed below the level of the heat carrier; at least one circulation pump disposed within the reactor vessel; and a heat exchanger, characterized in that: The heat exchanger is coaxially arranged with the furnace core in an annular space between a hub and a separation shell in the reactor container, the furnace core, the inlet chamber, the outlet chamber and the shielding plug are placed in the hub, the separation shell forms an annular downcomer and separates the cold heat carrier flowing downward from the hot heat carrier flowing upward, and the heat exchanger is a coil heat exchanger, the coil row of which is divided into multiple sections along the secondary loop heat carrier, so that the pipes of several heat exchanger sections are grouped and connected to several inlet chambers and outlet chambers arranged at the top of the reactor for the secondary loop heat carrier to circulate; the bottom of the heat exchanger is located above several windows in the hub. , so that the hot heat carrier flows from the outlet chamber of the furnace core into the heat exchanger through the several windows; after the heat carrier undergoes heat exchange through the coil row, it is discharged from the top of the heat exchanger as a cold heat carrier and enters the annular delay tank, wherein the annular delay tank has a heat carrier level lower than the top of the reactor, and the circulation pump is arranged in the reactor container, so that the heat carrier is directly introduced from the annular delay tank from below the heat carrier level through the several windows in the pump housing and the pump pipe connected to the top of the reactor into the suction port of the circulation pump, and the pressure pipe of the circulation pump is connected to the annular downcomer via the separation shell or partition.

3. The reactor according to claim 2, wherein: The annular downcomer is divided into equal sections by a plurality of longitudinal partitions between the reactor vessel and the separation shell according to the number of circulation pumps in the reactor, and all parts of the annular downcomer meet at the inlet chamber of the furnace core.

4. The reactor according to claim 2, wherein: Several check valves are located in the annular downcomer.

5. The reactor according to claim 2, wherein: Several valves with actuators arranged on top of the reactor are located in the annular downcomer according to the number of the circulation pumps.

6. The reactor according to claim 1 or 2, wherein: The separation shell has a window with bypass valves, the bypass valves are located in the annular downcomer, and the actuators of the bypass valves are arranged on the top of the reactor.

7. The reactor according to claim 1 or 2, wherein: A plurality of radiation shielding units are located in the annular space.

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