Nuclear reactor emergency shutdown device, nuclear reactor, and method of controlling the same

Abstract

To provide a nuclear reactor emergency shutdown device, a nuclear reactor, and a method of controlling the nuclear reactor, which enable appropriate emergency shutdown of the nuclear reactor and simplification of the device.SOLUTION: There is provided a nuclear reactor emergency shutdown device comprising: a storage container; a passage connecting the storage container and an inside of a nuclear reactor; and a neutron absorber stored in the storage container in a solid state and designed such that a rise in temperature of the nuclear reactor to a preset temperature causes at least a portion thereof to melt and flow into the nuclear reactor through the passage.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a nuclear reactor emergency shutdown device, a nuclear reactor, and a method for controlling a nuclear reactor. [Background technology]

[0002] A nuclear power generation system has a nuclear reactor that stores nuclear fuel. In the nuclear power generation system, a nuclear reaction occurs in the nuclear fuel in the reactor, and the generated heat is extracted to the outside to heat a cooling medium. The heated cooling medium drives a turbine to rotate, thereby generating electricity using a generator. An example of such a nuclear power generation system is described in Patent Document 1. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-128323 Summary of the Invention [Problem to be solved by the invention]

[0004] Nuclear reactors are equipped with emergency shutdown devices. In conventional nuclear reactors, the nuclear fuel is in a ring shape, and the emergency shutdown device supplies neutron absorbing material from a shielded passage into the inside of the nuclear fuel. In this case, the neutron absorbing material is a solid, such as a sphere, and when the temperature of the reactor rises to a threshold temperature, a valve is opened and the neutron absorbing material is supplied from the shielded passage into the inside of the nuclear fuel. This requires a mechanism for opening and closing the valve, which poses a problem of making the reactor structure complicated.

[0005] The present disclosure is intended to solve the above-mentioned problems, and aims to provide a reactor emergency shutdown device, a nuclear reactor, and a method for controlling a nuclear reactor that can properly bring a nuclear reactor into emergency shutdown and simplify the device. [Means for solving the problem]

[0006] In order to achieve the above-mentioned object, the reactor emergency shutdown device of the present disclosure comprises a storage container, a passageway connecting the storage container with the interior of the reactor, and a neutron absorber that is stored in a solid state in the storage container and that melts at least partially when the temperature of the reactor rises and reaches a predetermined temperature, flows, and is supplied to the interior of the reactor through the passageway.

[0007] The nuclear reactor disclosed herein also includes a core formed by arranging a plurality of fuel blocks in a ring shape, a storage section disposed in a gap between the plurality of fuel blocks, and the reactor emergency shutdown device capable of supplying the neutron absorber of the storage container to the storage section.

[0008] The reactor control method disclosed herein also includes the steps of maintaining a neutron absorber in a solid state in a storage container, and, when the temperature of the reactor core rises and reaches a predetermined temperature, melting at least a portion of the neutron absorber, causing it to flow and be supplied to the reactor core through a passage. [Effects of the Invention]

[0009] According to the nuclear reactor emergency shutdown device, nuclear reactor, and nuclear reactor control method of the present disclosure, it is possible to properly bring the nuclear reactor into emergency shutdown and to simplify the device. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a schematic diagram showing a nuclear power generation system according to the first embodiment. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the reactor unit of the first embodiment. [Figure 3] FIG. 3 is a vertical cross-sectional view of a reactor unit showing the reactor emergency shutdown device of the first embodiment. [Figure 4] FIG. 4 is a horizontal cross-sectional view of a nuclear reactor. [Figure 5] FIG. 5 is a vertical cross-sectional view of a nuclear reactor showing the operating state of the nuclear reactor emergency shutdown device. [Figure 6]FIG. 6 is a vertical cross-sectional view of a reactor unit showing a reactor emergency shutdown device according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0012] [First embodiment] <Nuclear power generation system> FIG. 1 is a schematic diagram showing a nuclear power generation system according to the first embodiment.

[0013] As shown in FIG. 1, the nuclear power generation system 100 includes a reactor unit 101, a coolant circulation path 102, a turbine 103, a compressor 104, a generator 105, a heat exchanger 106, and a cooler 107.

[0014] The reactor unit 101 has a reactor vessel 111, a reactor 112, and a heat conduction section 113. The reactor vessel 111 houses the reactor 112 inside. The reactor vessel 111 houses the reactor 112 in a sealed state. The reactor vessel 111 is provided with an opening and closing section, such as a lid, so that the reactor 112 placed inside can be stored or removed. The reactor vessel 111 can maintain a sealed state even when a nuclear reaction occurs in the reactor 112 and the inside becomes hot and high pressure. The reactor vessel 111 is made of a material with thermal insulation properties.

[0015] The reactor 112 stores nuclear fuel. The reactor 112 causes a nuclear reaction in the nuclear fuel, generating heat. The heat conduction unit 113 extracts the heat generated in the reactor 112 to the outside. Details of the reactor vessel 111, the reactor 112, and the heat conduction unit 113 will be described later.

[0016] The coolant circulation path 102 is a path for circulating the coolant. The coolant circulation path 102 connects the reactor unit 101 to the turbine 103, heat exchanger 106, cooler 107, compressor 104, and heat exchanger 106 in this order in the flow direction of the coolant, and is then connected back to the reactor unit 101. The high-temperature coolant extracted from the reactor unit 101 flows through the coolant circulation path 102, passes through the turbine 103, heat exchanger 106, cooler 107, compressor 104, and heat exchanger 106 in this order, and returns to the reactor unit 101.

[0017] The turbine 103 and the compressor 104 are connected by a connecting shaft 108 and are rotatable integrally. The compressor 104 is connected to a generator 105 by a connecting shaft 109, and the driving torque of the turbine 103 and the compressor 104 is transmitted to the generator 105. The turbine 103 is driven to rotate by the cooling medium heated by the reactor unit 101 and transmits the driving torque to the compressor 104. The compressor 104 is driven to rotate by the driving torque transmitted from the turbine 103 via the connecting shaft 108, and compresses the cooling medium cooled by the cooler 107. The generator 105 is driven by the driving torque transmitted from the compressor 104 via the connecting shaft 109 to generate electricity.

[0018] The heat exchanger 106 exchanges heat between the cooling medium that has been heated by the reactor unit 101 and then driven the turbine 103 and the cooling medium that has driven the compressor 104 .

[0019] The cooler 107 cools the cooling medium that has been heat exchanged by the heat exchanger 106 after driving the turbine 103. The cooler 107 cools the cooling medium by exchanging heat between the cooling medium flowing through the cooling medium circulation path 102 and a secondary cooling medium.

[0020] Heat generated by the reaction of nuclear fuel in the reactor 112 is extracted via the heat conduction unit 113. That is, the heat conduction unit 113 heats the cooling medium using the heat from the reactor 112 and causes the high-temperature cooling medium to flow through the cooling medium circulation path 102. The cooling medium flowing through the cooling medium circulation path 102 is supplied to the turbine 103.

[0021] The turbine 103 is driven to rotate by the cooling medium flowing through the cooling medium circulation path 102, and transmits the driving rotation force to the compressor 104. The cooling medium that has driven the turbine 103 flows through the heat exchanger 106 to the cooler 107 and is cooled. The cooling medium cooled by the cooler 107 is supplied to the compressor 104. The compressor 104 is driven to rotate by the driving rotation force transmitted from the turbine 103 via the connecting shaft 108, and compresses the cooling medium supplied from the cooler 107.

[0022] At this time, the generator 105 is driven by the driving torque transmitted from the compressor 104 via the connecting shaft 109 to generate electricity.

[0023] The cooling medium that has driven the compressor 104 is supplied to the heat exchanger 106. The heat exchanger 106 exchanges heat between the cooling medium that has driven the turbine 103 and the cooling medium that has driven the compressor 104. That is, the heat exchanger 106 heats the low-temperature cooling medium that has driven the compressor 104 with the high-temperature cooling medium that has driven the turbine 103.

[0024] The cooling medium heated by the heat exchanger 106 is then returned to the reactor 112 .

[0025] The nuclear power generation system 100 extracts heat from a nuclear reactor 112 using a cooling medium through a heat conduction section 113, drives a turbine 103 with the high-temperature, high-pressure cooling medium, and generates electricity using a generator 105.

[0026] <Reactor Unit> FIG. 2 is a vertical cross-sectional view showing the reactor unit of the first embodiment, FIG. 3 is a vertical cross-sectional view of the reactor unit showing the reactor emergency shutdown device of the first embodiment, and FIG. 4 is a horizontal cross-sectional view showing the reactor.

[0027] 2 to 4, the reactor unit 101 has a reactor vessel 111, a reactor 112, and a heat conduction section 113. The reactor 112 is housed inside the reactor vessel 111, and is provided with the heat conduction section 113. The heat conduction section 113 extracts heat generated in the reactor 112 to the outside.

[0028] <Reactor> The reactor 112 has a core 11, a reflector section 12, a heat conductor (heat conduction section 113) 13, a reactivity control device 14, and an emergency stop device 15. The reactor 112 has a cylindrical shape and is arranged vertically. That is, the central axis O of the reactor 112 is arranged along the vertical direction.

[0029] <Reactor Core> As shown in FIGS. 2 and 4 , the core 11 is formed to have an overall polygonal prism shape (a hexagonal prism shape in this embodiment) centered on the central axis O. The core 11 has a plurality of fuel blocks 21 (six in this embodiment). Note that, although six or more fuel blocks 21 are preferred, the number is not limited. The fuel blocks 21 are nuclear fuel and have the same shape. The core 11 has a plurality of fuel blocks 21 arranged in the circumferential direction, forming a ring shape that is long in the axial direction (the direction along the central axis O). That is, the core 11 has a polygonal (hexagonal) outer shape, and the plurality of fuel blocks 21 each have a triangular outer shape. However, the shape of the core 11 is not limited to a hexagonal shape and may be a polygonal or circular shape.

[0030] The core 11 has a first space 22 in the center where the central axis O is located. The first space 22 has a cylindrical shape. The core 11 also has a plurality of (six in this embodiment) second spaces (gaps) 23a, 23b provided between the plurality of fuel blocks 21. The second spaces 23a, 23b each have the same rectangular parallelepiped shape. The second spaces 23a and the second spaces 23b may have the same shape or different shapes. The second spaces 23a, 23b are arranged radially from the outer periphery of the first space 22. That is, the second spaces 23a, 23b are arranged along the radial direction of the core 11 and are long in the axial and radial directions (directions perpendicular to the central axis O) and short in the circumferential direction (width direction).

[0031] Although not shown, the core 11 (fuel block 21) includes nuclear fuel (radioactive material) and a support body. The support body is disposed throughout the core 11. The support body has a plurality of holes formed along the axial direction. The holes have, for example, a cylindrical shape. The support body may include a moderator. Examples of the moderator that can be used include graphene, graphite, etc. The nuclear fuel body is disposed in the holes of the support body. The nuclear fuel body has a cylindrical shape corresponding to the shape of the holes of the support body. The nuclear fuel body may have a rod shape that is continuous in the axial direction, or a pellet shape that is discontinuous in the axial direction. The nuclear fuel body may use uranium (e.g., uranium-235), plutonium (e.g., plutonium-239, plutonium-241), thorium, etc. as a fissionable material.

[0032] <Reflector part> The reflector section 12 is arranged to surround the reactor core 11. The reflector section 12 is made up of reflector blocks such as graphite and metal blocks, and prevents radiation from leaking to the outside by reflecting radiation (neutrons) emitted from the nuclear fuel that makes up the reactor core 11. The reflector section 12 is sometimes called a reflector depending on the neutron scattering and neutron absorption capabilities of the material used.

[0033] The reflector section 12 has a body 31, a bottom 32, and a lid 33. The body 31 is cylindrical and disposed radially outside the core 11. That is, the body 31 surrounds and covers the outer periphery of the core 11. The bottom 32 is disk-shaped and disposed on one axial side of the body 31. That is, the bottom 32 covers and closes the lower part of the core 11. The lid 33 is disk-shaped and disposed on the other axial side of the body 31. That is, the lid 33 covers and closes the upper part of the core 11. When the reflector section 12 accommodates the core 11 inside, it is preferable to fill the sealed interior with an inert gas such as nitriding gas in order to prevent oxidation inside.

[0034] <Thermal conductor> The thermal conductor 13 constitutes the thermal conduction section 113. That is, the thermal conductor 13 conducts heat generated in the reactor core 11 to the heat transfer tubes 41. The thermal conductor 13 is arranged so as to penetrate the reactor core 11 in the axial direction. One longitudinal end of the thermal conductor 13 penetrates the lid section 33 of the reflector section 12 and extends to the outside. The thermal conductor 13 conducts heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 to the outside of the reflector section 12.

[0035] The thermal conductor 13 has, for example, a heat transfer tube 41. The heat transfer tube 41 is filled with a cooling medium (for example, carbon dioxide) and allows the cooling medium to flow. The heat transfer tube 41 is, for example, U-shaped and is arranged inside the reactor core 11, with one end and the other end penetrating the reflector part 12 (lid part 33) and extending to the outside. The cooling medium is supplied from one end of the heat transfer tube 41, flows inside the reactor core 11, and is then discharged to the outside from the other end of the heat transfer tube 41. At this time, the cooling medium is heated by the heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 and extracts the heat to the outside.

[0036] The core 11 (fuel block 21) may be configured by stacking a plurality of plate-shaped fuel plates in the axial direction. The reflector section 12 may be configured by stacking a plurality of plate-shaped shield plates in the axial direction. In this case, a ring-shaped shield plate is arranged on the outer periphery of the ring-shaped fuel plate. A plurality of ring-shaped fuel plates and shield plates are then arranged in the plate thickness direction.

[0037] Furthermore, the heat conduction unit 113 may be provided by stacking multiple plate-shaped heat conduction plates in the axial direction. In this case, the ring-shaped fuel plates and shield plates are alternately stacked in the plate thickness direction with the ring-shaped heat conduction plates. The heat conduction plates have an outer diameter larger than that of the shield plates, and extract heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 radially outward. The heat conduction plates may be made of, for example, titanium, nickel, copper, or graphite. Graphene, in particular, may be used as graphite. Graphene has a structure consisting of a continuous hexagonal lattice made of carbon atoms and their bonds. By aligning the direction of heat transfer along the continuous hexagonal lattice, heat transfer efficiency can be improved.

[0038] <Reactivity Control Device> The reactivity control device 14 is disposed in the reflector section 12. The reactivity control device 14 is disposed so as to surround the periphery of the reactor core 11. The reactivity control device 14 has a plurality of control drums (control sections) 51 (12 in this embodiment). However, the number of control drums 51 is not limited. The plurality of control drums 51 are disposed outside the reactor core 11 at intervals (preferably at equal intervals) in the circumferential direction. The plurality of control drums 51 are disposed facing the outside of the plurality of fuel blocks 21 that constitute the reactor core 11.

[0039] The control drum 51 has a cylindrical shape and is arranged along the axial direction of the core 11. The control drum 51 has approximately the same length as the core 11. The control drum 51 is rotatably supported by the reflector section 12. A connecting section 52 is connected to one axial end of the control drum 51. The connecting section 52 penetrates the lid section 33 of the reflector section 12, with one end connected to one end of the control drum 51 and the other end extending outside the reflector section 12. The drive section 53 is arranged outside the reactor 112. The other ends of the multiple connecters 52 are connected to the drive section 53. The drive section 53 can rotate the multiple control drums 51 via the multiple connecters 52.

[0040] The control drum 51 has a drum main body 54 and a neutron absorbing section 55. The control drum 51 is configured such that the neutron absorbing section 55 is provided on a portion of the drum main body 54 in the circumferential direction. The drum main body 54 can be made of, for example, graphene, and the neutron absorbing section 55 can be made of, for example, boron carbide (B4C). As the control drum 51 rotates, the circumferential position of the neutron absorbing section 55 relative to the drum main body 54 changes. That is, as the control drum 51 rotates, the neutron absorbing section 55 can move closer to or away from the reactor core 11. When the neutron absorbing section 55 approaches the reactor core 11, the reactivity of the nuclear fuel constituting the reactor core 11 decreases, and when the neutron absorbing section 55 moves away from the reactor core 11, the reactivity of the nuclear fuel increases. The reactivity control device 14 rotates the multiple control drums 51 to move the neutron absorbing section 55 toward or away from the core 11, thereby controlling the reactivity of the nuclear fuel in the core 11 and the temperature of the core 11. Here, the temperature of the core 11 is the average core temperature that is taken out to the outside of the reflector section 12 by the thermal conductor 13.

[0041] The reactivity control device 14 has a control device 56. The control device 56 is connected to a drive unit 53. The control device 56 can control the rotational positions of the multiple control drums 51 by driving and controlling the drive unit 53. The control device 56 is, for example, a computer, and is realized by an arithmetic processing device including a microprocessor such as a CPU (Central Processing Unit). The control device 56 can acquire the temperature of the core 11. The control device 56 controls the rotational positions of the multiple control drums 51 that constitute the reactivity control device 14, and moves the neutron absorbing unit 55 away from the core 11. This increases the reactivity of the core 11, and the reactor 112 starts operating. Meanwhile, the control device 56 controls the rotational position of the control drum 51, and moves the neutron absorbing unit 55 closer to the core 11. This decreases the reactivity of the core 11, and the reactor 112 stops operating.

[0042] <Emergency stop device> As shown in FIGS. 3 and 4, when the temperature of the core 11 rises and reaches a predetermined temperature during operation of the reactor 112, the emergency shutdown device 15 is activated to shut down the reactor 112.

[0043] The reactor 112 has a housing section 70. The housing section 70 is disposed in a gap between the plurality of fuel blocks 21 that constitute the reactor core 11. The emergency stop device 15 is disposed vertically above the reactor 112, and is capable of supplying a neutron absorber 83, which will be described later, to the housing section 70 from the outside.

[0044] The accommodation section 70 has a first accommodation section 71 and a second accommodation section 72. However, the accommodation section 70 is not limited to the first accommodation section 71 and the second accommodation section 72, and may be provided, for example, on the surface side of the core 11 and the reflector section 12. The first accommodation section 71 is disposed inside the cylindrical core 11, i.e., in the gap at the center. The first accommodation section 71 has a hollow cylindrical shape and is disposed axially at the center of the core 11. Note that the first accommodation section 71 is not limited to a hollow cylindrical shape and may have any shape, such as a rectangular prism shape. The first accommodation section 71 has approximately the same length as the core 11. The second accommodation section 72 is disposed radially from the first accommodation section 71 toward the gaps between the multiple fuel blocks 21. The second accommodation section 72 has a hollow rectangular parallelepiped shape and is disposed in the gaps between the multiple circumferentially adjacent fuel blocks 21. The second accommodation section 72 has approximately the same length as the core 11.

[0045] The first containment section 71 is disposed in a gap in the center of the core 11, and the second containment section 72 is disposed in a gap between adjacent fuel blocks 21. A plurality of second containment sections 72 (three in this embodiment) are provided. The one first containment section 71 and the three second containment sections 72 are connected to one another. The first containment section 71 and the second containment section 72 are formed of a material with low neutron absorption performance. That is, the first containment section 71 and the second containment section 72 are formed of a material with neutron absorption performance at least lower than that of the neutron absorber 83. The first containment section 71 and the second containment section 72 are formed of a material, such as graphite, whose structural viability can be confirmed under high temperature and high pressure.

[0046] The core 11 has a first space 22 provided in the center, that is, inside the six fuel blocks 21. The first accommodation section 71 is arranged in the first space 22. The core 11 has six second spaces 23a, 23b provided in the circumferential gaps between the six fuel blocks 21. The three second spaces 23a and the three second spaces 23b are arranged alternately in the circumferential direction of the core 11. The three second accommodation sections 72 are arranged in one of the three second spaces 23a. In the other three second spaces 23b, a large number of heat transfer tubes 41 constituting the thermal conductor 13 are arranged.

[0047] That is, the second accommodation sections 72 arranged in the second space section 23a and the large number of heat transfer tubes 41 arranged in the second space section 23b are arranged alternately in the circumferential direction of the core 11. Note that the heat transfer tubes 41 are arranged not only in the second space section 23b but also in the plurality of cutouts formed to communicate with the second space section 23a. The heat transfer tubes 41 are also arranged at intervals in the circumferential direction outside the plurality of fuel blocks 21. That is, the plurality of heat transfer tubes 41 are arranged so as to surround the periphery of each fuel block 21.

[0048] The emergency stop device 15 has a storage container 81, a passage 82, and a neutron absorber 83. The storage container 81 is disposed above the reactor 112. Note that the storage container 81 is not limited to being disposed above the reactor 112, but may be disposed to the side of the reactor 112. The storage container 81 has a hollow cylindrical shape and stores a large number of neutron absorbers 83 therein. However, the shape of the storage container 81 is not limited. The passage 82 connects the storage container 81 to the accommodation unit 70. Multiple passages 82 (three in this embodiment) are provided and connect the storage container 81 to different positions in the accommodation unit 70. Here, the three passages 82 axially penetrate the lid 33 and connect the storage container 81 to the three second accommodation units 72. Note that the number of passages 82 is not limited to three. Also, a passage connecting the storage container 81 to the first accommodation unit 71 may be provided.

[0049] The neutron absorber 83 is stored in the storage vessel 81. When stored in the storage vessel 81, the neutron absorber 83 is maintained in a solid state at room temperature or at a temperature corresponding to the normal operating temperature of the reactor 112. On the other hand, when stored in the storage vessel 81, when the reactor 112 enters an emergency operating state and the temperature of the core 11 rises and reaches a predetermined temperature (e.g., 800°C), at least a portion of the neutron absorber 83 melts and becomes fluid. When melted, the neutron absorber 83 becomes fluid and flows down from the storage vessel 81 into the passage 82 due to its own weight. The neutron absorber 83 is then supplied from the storage vessel 81 through the passage 82 into the interior of the reactor 112.

[0050] The neutron absorber 83 is made of a material with higher neutron absorption performance than the containment section 70. The neutron absorber 83 includes multiple granules and a connector. The multiple granules constituting the neutron absorber 83 are, for example, spherical and have neutron absorption capabilities. The granules may be made of, for example, boron carbide (B4C). The spherical granules have an outer diameter smaller than the inner diameter of the passage 82, the inner diameter of the first containment section 71, and the width of the second containment section 72. In other words, the granules can be supplied from the containment vessel 81 through the passage 82 to the inside of the first containment section 71 and the second containment section 72. The connector is maintained in a solid state at room temperature or at a temperature during normal operation of the reactor 112. When the reactor 112 enters an emergency operation state and the temperature of the core 11 reaches a predetermined temperature, it melts and becomes fluid. The connector connects the multiple granules in both a solid and fluid state. The connector is made of a material that melts at a predetermined temperature or higher, such as a metal or alloy, such as iron, silver, lead, or copper, or a resin.

[0051] The neutron absorbers 83 are maintained in a solid state when the reactor 112 is in a temperature range from room temperature to normal operation, and remain stored in the storage vessel 81. At this time, the neutron absorbers 83 are not supplied to the first containment section 71 and the second containment section 72, and the reactivity of the nuclear fuel in the core 11 increases. On the other hand, when the reactor 112 reaches a predetermined temperature in an emergency operation state, the neutron absorbers 83 melt and flow, and are supplied from the storage vessel 81 through the passage 82 to the first containment section 71 and the second containment section 72 and filled therein. At this time, the reactivity of the nuclear fuel in the core 11 decreases.

[0052] It should be noted that the neutron absorber 83 is not limited to this configuration. The neutron absorber 83 may have any configuration as long as it can be stored in the storage container 81, partially melted at a predetermined temperature, and supplied to the storage section 70 through the passage 82.

[0053] <Nuclear reactor control method> FIG. 5 is a vertical cross-sectional view of a nuclear reactor showing the operating state of the nuclear reactor emergency shutdown device.

[0054] 1, 2, and 4, in the nuclear reactor 112, the control device 56 controls the rotational positions of the multiple control drums 51 that make up the reactivity control device 14 in accordance with the temperature of the reactor core 11. That is, by rotating the control drum 51, the neutron absorbing section 55 is moved away from the reactor core 11 to increase the reactivity of the reactor core 11, or by moving the neutron absorbing section 55 closer to the reactor core 11 to decrease the reactivity of the reactor core 11. Heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 is extracted to the outside of the reflector section 12 by the thermal conductor 13 (heat transfer tubes 41). The heat extracted to the outside of the reflector section 2 is transferred to the cooling medium by the heat transfer tubes 41, and the cooling medium rotates the turbine 103, causing the generator 105 to generate electricity.

[0055] 3 and 4, during operation of the reactor 112, the temperature of the core 11 is below a predetermined temperature, and therefore the emergency shutdown device 15 is in an inactive state. That is, the neutron absorber 83 is maintained in a solid state and remains stored in the storage vessel 81, and is not supplied to the first storage section 71 or the second storage section 72.

[0056] On the other hand, when the reactor 112 enters an emergency operation state, the temperature of the core 11 rises. Then, when the temperature of the core 11 reaches a predetermined temperature, the emergency stop device 15 is activated. That is, as shown in FIGS. 3 and 5, the heat of the core 11 is transferred to the neutron absorber 83 of the containment vessel 81 through the passage 82, and the neutron absorber 83 melts. Then, the molten neutron absorber 83 becomes fluid and flows through each passage 82 into the first containment section 71 and the second containment section 72, where it is supplied and filled. In addition, the control device 56 rotates the control drum 51 to bring the neutron absorber 55 closer to the core 11.

[0057] As a result, the core 11 has the first accommodation section 71 filled with neutron absorbers 83 located inside, the second accommodation sections 72 filled with neutron absorbers 83 located between the fuel blocks 21, and the neutron absorber 55 of the control drum 51 located outside. As a result, the reactivity of the nuclear fuel in the core 11 decreases, and the reactor 112 is brought to an emergency shutdown. After the reactor 112 is brought to an emergency shutdown, when the temperature of the core 11 drops below a predetermined temperature, the neutron absorbers 83 begin to solidify and return to a solid state.

[0058] [Second embodiment] 6 is a vertical cross-sectional view of a reactor unit showing a reactor emergency shutdown device according to the second embodiment. Note that members having the same functions as those in the first embodiment described above are given the same reference numerals and detailed descriptions thereof will be omitted.

[0059] As shown in Fig. 6, the reactor unit 101A has a reactor vessel 111, a reactor 112A, and a heat conduction section 113 (see Fig. 2). The reactor 112A is housed inside the reactor vessel 111, and is provided with the heat conduction section 113. The heat conduction section 113 extracts heat generated in the reactor 112A to the outside.

[0060] <Reactor> The reactor 112A includes a core 11, a reflector section 12, a thermal conductor (thermal conduction section 113) 13 (see FIG. 2), a reactivity control device 14, and an emergency stop device 15A. The reactor 112 has a cylindrical shape and is arranged horizontally. That is, the reactor 112A is arranged with its central axis O aligned horizontally.

[0061] In the reactor unit 101A, the reactor vessel 111 and the heat conduction section 113 have almost the same configuration as in the first embodiment, and therefore their explanations are omitted. In the reactor 112A, the core 11, the reflector section 12, the heat conductor 13, and the reactivity control device 14 have almost the same configuration as in the first embodiment, and therefore their explanations are omitted.

[0062] The emergency shutdown device 15A is activated when the temperature of the core 11 rises and reaches a predetermined temperature during operation of the reactor 112A, and shuts down the reactor 112A.

[0063] The reactor 112A has a storage section 70. The storage section 70 is arranged in a gap between the multiple fuel blocks 21 that make up the reactor core 11. The emergency stop device 15A is arranged vertically above the reactor 112A and is capable of supplying a neutron absorber 83A (described later) to the storage section 70 from the outside. The storage section 70 has a first storage section 71 and a second storage section 72.

[0064] The emergency stop device 15A has a storage container 81A, a passage 82A, and a neutron absorber 83A. The storage container 81A is disposed above the reactor 112A. Multiple storage containers 81A (two in this embodiment) are disposed above the reactor 112A with an axial gap between them. The position, shape, and number of storage containers 81A are not limited. The passage 82A penetrates the body 31 in the radial direction and connects each storage container 81A to the accommodation unit 70. One passage 82A is provided for each storage container 81A, but the number is not limited. The passage 82A connects the storage container 81A to different positions in the accommodation unit 70.

[0065] The neutron absorber 83A is stored in the storage vessel 81A. When stored in the storage vessel 81A, the neutron absorber 83A is maintained in a solid state at a temperature ranging from room temperature to the temperature of the reactor 112A in normal operation. On the other hand, when stored in the storage vessel 81A, when the reactor 112A enters an emergency operation state and the temperature of the core 11 rises, at least a portion of the neutron absorber 83A melts and becomes fluid when it reaches a predetermined temperature. When melted, the neutron absorber 83A becomes fluid and flows down from the storage vessel 81A into the passage 82A due to its own weight. Then, the neutron absorber 83A is supplied from the storage vessel 81A through the passage 82A into the reactor 112A. The neutron absorber 83A is similar to the neutron absorber 83 of the first embodiment.

[0066] The neutron absorber 83A is maintained in a solid state when the reactor 112A is in a temperature range from room temperature to normal operation, and remains stored in the storage vessel 81A. At this time, the neutron absorber 83A is not supplied to the first containment section 71 and the second containment section 72, and the reactivity of the nuclear fuel in the core 11 increases. On the other hand, when the reactor 112A reaches a predetermined temperature in an emergency operation state, the neutron absorber 83A melts and flows, and is supplied from the storage vessel 81A through the passage 82A to the first containment section 71 and the second containment section 72 and filled therein. At this time, the reactivity of the nuclear fuel in the core 11 decreases.

[0067] [Effects of this embodiment] The reactor emergency shutdown device of the first embodiment comprises a storage container 81, 81A, a passage 82, 82A connecting the storage container 81, 81A with the interior of the reactor 112, 112A, and a neutron absorber 83, 83A that is stored in a solid state in the storage container 81, 81A and that melts at least a portion of when the temperature of the reactor 112, 112A rises and reaches a predetermined temperature, and flows and is supplied to the interior of the reactor 112, 112A through the passage 82, 82A.

[0068] According to the reactor of the first aspect, the neutron absorbers 83, 83A are stored in a solid state in the storage vessels 81, 81A, and when the temperature of the reactors 112, 112A reaches a predetermined temperature, at least a portion of the neutron absorbers 83, 83A melts and is supplied into the reactors 112, 112A through the passages 82, 82A. This allows the reactor 112 to be properly brought to an emergency shutdown. Furthermore, valves for opening and closing the passages 82, 82A and the like are no longer necessary, allowing the reactor 112 to be simplified.

[0069] The reactor emergency shutdown device according to the second aspect is the reactor emergency shutdown device according to the first aspect, further comprising: a storage vessel 81, 81A disposed vertically above the reactor 112, 112A; a passage 82, 82A disposed along the vertical direction, with an upper end communicating with the storage vessel 81, 81A and a lower end communicating with the core 11 of the reactor 112, 112A. This allows the neutron absorbers 83, 83A of the storage vessel 81, 81A to be appropriately supplied to the core 11 through the passage 82, 82A by their own weight.

[0070] The reactor emergency shutdown device according to the third aspect is the reactor emergency shutdown device according to the first or second aspect, and further includes a reactor 112, 112A having a core 11 configured by arranging a plurality of fuel blocks 21 in an annular shape, and a storage section 70 arranged in a gap between the plurality of fuel blocks 21, and a passage 82, 82A has a lower end portion communicated with the storage section 70. This allows the neutron absorber 83, 83A to be appropriately supplied to the reactor core 11 by the passage 82, 82A.

[0071] The reactor emergency shutdown device according to the fourth aspect is the reactor emergency shutdown device according to the third aspect, further comprising: a first container 71 disposed in a gap at the center of the core 11; and a plurality of second containers 72 disposed in circumferential gaps among the plurality of fuel blocks; and the passages 82, 82A have lower ends connected to the second container 72. This allows neutron absorbers 83, 83A to be appropriately supplied to the gap at the center of the core 11 and the circumferential gaps among the plurality of fuel blocks 21 in the event of an emergency in the reactor 112, 112A.

[0072] The reactor emergency shutdown device according to the fifth aspect is the reactor emergency shutdown device according to the third or fourth aspect, and further includes a plurality of passages 82, 82A, which communicate with different positions in the accommodation unit 70. As a result, even if the passage 82, 82A is blocked, the neutron absorber 83, 83A can be appropriately supplied to the accommodation unit 70 through any one of the passages 82, 82A.

[0073] A reactor emergency shutdown device according to a sixth aspect is a reactor emergency shutdown device according to any one of the first to fifth aspects, and further includes a neutron absorber 83, 83A having a plurality of granular bodies having a neutron absorbing function and capable of passing through the passages 82, 82A, and a connector connecting the plurality of granular bodies made of a material that is solid at room temperature and becomes fluid at a predetermined temperature or higher. Thus, by connecting the plurality of granular bodies having a neutron absorbing function with the connector, the granular bodies can easily transition between a solid state and a liquid state.

[0074] The nuclear reactor according to the seventh aspect includes a core 11 configured by arranging a plurality of fuel blocks in an annular shape, a storage section 70 arranged in a gap between the plurality of fuel blocks, and emergency stop devices (reactor emergency stop devices) 15, 15A capable of supplying neutron absorbers 83, 83A of storage containers 81, 81A to the storage section 70. This allows the nuclear reactor 112 to be properly brought to an emergency shutdown, and also simplifies the nuclear reactor 112.

[0075] The method for controlling a nuclear reactor according to the eighth aspect includes the steps of maintaining neutron absorbers 83, 83A in a solid state in storage vessels 81, 81A, and, when the temperature of the core of the nuclear reactor 112, 112A rises and reaches a predetermined temperature, melting at least a part of the neutron absorbers 83, 83A, flowing, and being supplied to the nuclear core 11 through passages 82, 82A. This allows the nuclear reactor 112 to be properly brought to an emergency shutdown, and also simplifies the nuclear reactor 112. [Explanation of symbols]

[0076] 11 Reactor Core 12 Reflector section 13 Thermal Conductors 14 Reactivity Control Device 15,15A emergency stop device (reactor emergency stop device) 21 Fuel Block 22 First space part 23a, 23b Second space (gap) 31 Torso 32 Bottom 33 Lid 41 Heat transfer tube 51 Control drum 52 Connecting part 53 Drive unit 54 Drum body 55 Neutron absorber 56 Control device 70 Storage section 71 First storage section 72 Second storage section 81,81A Storage container Passages 82 and 82A 83,83A Neutron absorber 100 Nuclear Power Systems 101,101A Reactor Unit 102 Coolant circulation path 103 Turbine 104 Compressor 105 Generator 106 Heat exchanger 107 Cooler 108,109 Connecting shaft 111 Reactor Vessel 112,112A reactor 113 Heat Conduction Section

Claims

1. A storage container; a passageway communicating the storage vessel with the interior of the reactor; a neutron absorber that is stored in a solid state in the storage container and that melts at least a portion of when the temperature of the reactor rises and reaches a predetermined temperature, and flows and is supplied into the reactor through the passage; A reactor emergency shutdown device equipped with:

2. the storage vessel is disposed vertically above the reactor, the passage is disposed along the vertical direction, and an upper end of the passage is connected to the storage vessel and a lower end of the passage is connected to the core of the reactor. The nuclear reactor emergency shutdown device according to claim 1.

3. the reactor has a core formed by arranging a plurality of fuel blocks in an annular manner, and a storage section disposed in a gap between the plurality of fuel blocks, and a lower end of the passage is in communication with the storage section; 3. The nuclear reactor emergency shutdown device according to claim 2.

4. the accommodation portion includes a first accommodation portion disposed in a gap at the center of the core and a plurality of second accommodation portions disposed in circumferential gaps among the plurality of fuel blocks, and a lower end of the passage is connected to the second accommodation portion. The nuclear reactor emergency shutdown device according to claim 3.

5. The passages are provided in plurality and communicate with different positions of the storage section. The nuclear reactor emergency shutdown device according to claim 3.

6. The neutron absorber includes a plurality of granular bodies having a neutron absorbing function and capable of passing through the passage, and a connector that connects the plurality of granular bodies and is made of a material that is solid at room temperature and becomes fluid at the predetermined temperature or higher. The nuclear reactor emergency shutdown device according to claim 1.

7. a reactor core configured by arranging a plurality of fuel blocks in an annular manner; a receiving portion disposed in a gap between the plurality of fuel blocks; the reactor emergency shutdown device according to claim 1, which is capable of supplying the neutron absorber of the storage container to the storage section; A nuclear reactor equipped with:

8. maintaining the neutron absorber in a solid state in a containment vessel; When the temperature of the reactor core rises and reaches a predetermined temperature, at least a portion of the neutron absorber melts, flows, and is supplied to the reactor core through a passage; A method for controlling a nuclear reactor comprising:

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