Nuclear reactor and method for controlling a nuclear reactor

Abstract

To improve, in a nuclear reactor and a method for controlling the nuclear reactor, the efficiency of the nuclear reactor.SOLUTION: A nuclear reactor includes: a core composed of nuclear fuel; and a reactivity control device having a control unit provided with a neutron reflecting unit arranged outside the core and configured to reflect neutrons, and a neutron absorbing unit for absorbing neutrons. The neutron reflecting unit is disposed opposite to the outside of the core, and the neutron absorbing unit is movable between a first position not opposite to the core and a second position located between the core and the neutron reflecting unit.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a nuclear reactor and a method for controlling a nuclear reactor. [Background Art]

[0002] A nuclear power generation system includes a nuclear reactor that stores nuclear fuel. In the nuclear power generation system, a nuclear reaction is caused by the nuclear fuel in the nuclear reactor, the generated heat is extracted to the outside, and a coolant is heated. The heated coolant drives and rotates a turbine, whereby power is generated by a generator. Examples of such nuclear power generation systems include those described in Patent Documents 1 and 2. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Unexamined Patent Publication No. 2022-63014 [Patent Document 2] Japanese Unexamined Patent Publication No. 2022-61791 [Summary of the Invention] [Problem to be Solved by the Invention]

[0004] A nuclear reactor is provided with a reactivity control device. In a conventional nuclear reactor, nuclear fuel has a circular shape, and as the reactivity control device, a plurality of control units are provided outside the nuclear fuel. The control unit has a circular shape, is rotatably supported, and is provided with a neutron absorbing part at a portion in the circumferential direction. When the control unit rotates and the neutron absorbing part approaches the nuclear fuel, the reactivity of the nuclear fuel decreases, and when the neutron absorbing part moves away from the nuclear fuel, the reactivity of the nuclear fuel increases. In this case, when the neutron absorbing part of the control unit moves away from the nuclear fuel, although the reactivity of the nuclear fuel increases, there is a problem that some neutrons leak, resulting in a decrease in efficiency.

[0005] The present disclosure solves the above-described problem, and an object thereof is to provide a nuclear reactor and a control method for a nuclear reactor that improve efficiency in the nuclear reactor. [Means for solving the problem]

[0006] To achieve the above objectives, the reactor of the present disclosure comprises a core composed of nuclear fuel, and a reactivity control device having a control unit located outside the core and equipped with a neutron reflector that reflects neutrons and a neutron absorber that absorbs neutrons, wherein the neutron reflector is located facing the outside of the core, and the neutron absorber is movable between a first position not facing the core and a second position located between the core and the neutron reflector.

[0007] Furthermore, the reactor control method of this disclosure relates to a reactor in which a control unit having a neutron reflector and a neutron absorber facing the outside of a reactor core made of nuclear fuel is arranged, and the control unit controls the reactivity of the reactor core by moving the neutron absorber between a first position not facing the reactor core and a second position located between the reactor core and the neutron reflector. [Effects of the Invention]

[0008] The reactor and method of this disclosure can improve the efficiency of the reactor. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram representing the nuclear power generation system of this embodiment. [Figure 2] Figure 2 is a longitudinal cross-sectional view showing the reactor of this embodiment. [Figure 3] Figure 3 is a horizontal cross-sectional view representing a nuclear reactor. [Figure 4] Figure 4 is a schematic diagram showing the details of the control unit. [Figure 5] Figure 5 is a schematic diagram illustrating the operation of the control unit. [Modes for carrying out the invention]

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. However, these embodiments do not limit the present disclosure, and where there are multiple embodiments, they may be combinations of these embodiments. Furthermore, the components in the embodiments include those readily conceivable by those skilled in the art, those that are substantially identical, and those that are equivalent.

[0011] <Nuclear power generation system> Figure 1 is a schematic diagram representing the nuclear power generation system of this embodiment.

[0012] As shown in Figure 1, the nuclear power generation system 100 includes a reactor unit 101, a heat exchanger 102, a refrigerant circulation path 103, a turbine 104, a generator 105, a cooler 106, and a compressor 107.

[0013] The reactor unit 101 includes 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 / closing section, such as a lid, so that the reactor 112 located inside can be housed in or removed. The reactor vessel 111 can maintain its 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 that has neutron shielding properties.

[0014] The reactor 112 stores nuclear fuel. The reactor 112 generates heat by causing a nuclear reaction with the nuclear fuel. The heat conduction unit 113 transfers the heat generated in the reactor 112 to the heat exchanger 102. Details of the reactor 112 and the heat conduction unit 113 will be described later.

[0015] The heat exchanger 102 exchanges heat with the reactor 112 that constitutes the reactor unit 101. The heat exchanger 102 recovers heat from the reactor 112 via the heat conduction section 113 that constitutes the reactor unit 101.

[0016] The refrigerant circulation path 103 is a path for circulating refrigerant. The refrigerant circulation path 103 connects a heat exchanger 102, a turbine 104, a cooler 106 and a compressor 107. The refrigerant flowing through the refrigerant circulation path 103 flows in the order of the heat exchanger 102, the turbine 104, the cooler 106 and the compressor 107, and the refrigerant that has passed through the compressor 107 can return to the heat exchanger 102. The heat exchanger 102 performs heat exchange between a heat conduction part 113 and the refrigerant flowing through the refrigerant circulation path 103. That is, the refrigerant flowing through the refrigerant circulation path 103 is heated by the heat conduction part 113, and the heat conduction part 113 is cooled by the refrigerant.

[0017] The turbine 104 is supplied with refrigerant that has passed through the heat exchanger 102. The turbine 104 rotates by the energy of the heated refrigerant. The turbine 104 converts the energy of the refrigerant into rotational energy and absorbs energy from the refrigerant.

[0018] A generator 105 is coaxially connected to the turbine 104. The generator 105 rotates integrally with the turbine 104. The generator 105 generates power by rotating via the rotational force of the turbine 104.

[0019] The cooler 106 cools the refrigerant that has passed through the turbine 104. The cooler 106 is a condenser or the like when temporarily liquefying a chiller or refrigerant.

[0020] The compressor 107 compresses the refrigerant that has passed through the cooler 106. The compressor 107 functions as a pump that pressurizes the refrigerant.

[0021] Heat generated by the nuclear fuel reaction in a nuclear reactor 112 is transferred to the heat exchanger 102 via the heat conduction part 113. The refrigerant flowing through the refrigerant circulation path 103 is compressed by the compressor 107 and then supplied to the heat exchanger 102. The heat exchanger 102 heats the refrigerant flowing through the refrigerant circulation path 103 by the heat of the heat conduction part 113. In other words, the refrigerant absorbs heat via the heat exchanger 102 and is increased in temperature, whereby the heat generated in the nuclear reactor 112 is recovered by the refrigerant.

[0022] The turbine 104 is supplied with refrigerant that has been compressed by the compressor 107 and heated by the heat exchanger 102. The turbine 104 rotates using the supplied refrigerant, driving the generator 105, which then generates electricity. The refrigerant that has rotated the turbine 104 is cooled to a reference temperature in the cooler 106 before being supplied to the compressor 58.

[0023] The nuclear power generation system 100 transfers heat extracted from the reactor 112 to a refrigerant via a heat conduction unit 113, and uses the high-temperature, high-pressure refrigerant to drive a turbine 104, thereby generating electricity with a generator 105. As a result, the reactor 112 and the refrigerant, which is the medium that drives the turbine 104, can be isolated, and the risk of radioactive contamination of the medium that drives the turbine 104 can be reduced.

[0024] <Reactor> Figure 2 is a vertical cross-sectional view representing the reactor of this embodiment, and Figure 3 is a horizontal cross-sectional view representing the reactor.

[0025] As shown in Figures 2 and 3, the reactor unit 101 includes a reactor vessel 111, a reactor 112, and a heat conduction section 113. The reactor 112 is housed inside the reactor vessel 111, and the heat conduction section 113 is provided therein. The heat conduction section 113 extracts the heat generated in the reactor 112 to the outside.

[0026] The reactor 112 comprises a core 11, a shielding section 12, a heat conductor (heat conduction section 113) 13, and a reactivity control device 14. The reactor 112 is cylindrical in shape and arranged vertically. That is, the reactor 112 has its central axis O aligned vertically.

[0027] <Core> The reactor core 11 is formed to have a polygonal prism shape (a hexagonal prism shape in this embodiment) around a central axis O. The reactor core 11 has a plurality of fuel blocks 21 (six in this embodiment). The fuel blocks 21 are nuclear fuel and have the same shape. The reactor core 11 forms a long ring in the axial direction (direction along the central axis O) as the plurality of fuel blocks 21 are arranged along the circumferential direction. That is, the reactor core 11 has a polygonal shape (hexagonal shape) on its outer surface, and the plurality of fuel blocks 21 have a triangular shape on their outer surface. However, the shape of the reactor core 11 is not limited to a hexagonal shape, and may be a polygonal shape or a circle.

[0028] The reactor core 11 has a first space 22 in the center where the central axis O is located. The first space 22 is cylindrical in shape. The reactor core 11 also has a plurality of (six in this embodiment) second spaces 23 between a plurality of fuel blocks 21. The plurality of second spaces 23 are rectangular parallelepipeds and each has the same shape. The plurality of second spaces 23 are arranged radially from the outer circumference of the first space 22. That is, the second spaces 23 are arranged along the radial direction of the reactor 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). However, the reactor core 11 is not limited to being composed of a plurality of fuel blocks 21 with second spaces 23, but may also be a single rectangular tube or cylindrical shape without second spaces 23. Furthermore, the reactor core 11 is not limited to a cylindrical shape having the first space 22, but may also be a prismatic or cylindrical shape without the first space 22.

[0029] The reactor core 11 (fuel block 21), although not shown in the diagram, includes nuclear fuel (radioactive material) and a support structure. The support structure is arranged throughout the entire area of ​​the reactor core 11. The support structure has multiple holes along its axial direction. The holes are, for example, cylindrical in shape. The support structure may include a moderator. For example, graphene or graphite can be used as the moderator. The nuclear fuel is placed in the holes of the support structure. The nuclear fuel corresponds to the shape of the holes in the support structure and is cylindrical in shape. The nuclear fuel may be in the shape of a continuous rod along the axial direction or in the shape of a discontinuous pellet along the axial direction. The nuclear fuel can be made of fissile material such as uranium (e.g., uranium-235), plutonium (e.g., plutonium-239, 241), or thorium.

[0030] <Shielding area> The shielding section 12 is positioned to surround the reactor core 11. The shielding section 12 consists of a metal block and suppresses the leakage of radiation to the outside by reflecting radiation (neutrons) emitted from the nuclear fuel constituting the reactor core 11. Depending on the neutron scattering and neutron absorption capabilities of the materials used, the shielding section 12 may be called a reflector.

[0031] The shielding section 12 has a body 31, a bottom 32, and a lid 33. The body 31 is cylindrical and is positioned radially outside the core 11. That is, the body 31 covers the outer circumference of the core 11. The bottom 32 is disc-shaped and is positioned on one side of the body 31 in the axial direction. That is, the bottom 32 covers the lower part of the core 11. The lid 33 is disc-shaped and is positioned on the other side of the body 31 in the axial direction. That is, the lid 33 covers the upper part of the core 11. When housing the core 11 inside the shielding section 12, it is preferable to fill the sealed interior with an inert gas, such as nitride gas, to prevent oxidation inside.

[0032] <Thermal Conductor> The heat conductor 13 constitutes the heat conduction section 113. That is, the heat conductor 13 conducts the heat generated in the reactor core 11 to the heat exchanger 102 (see Figure 1). The heat conductor 13 is positioned to penetrate the reactor core 11 in the axial direction. One end of the heat conductor 13 in the longitudinal direction extends to the outside, penetrating the cover 33 of the shielding section 12. The heat conductor 13 transmits the heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 to the outside of the shielding section 12.

[0033] The heat conductor 13 includes, for example, heat transfer tubes 41. The heat transfer tubes 41 are filled with a coolant (for example, carbon dioxide) and the coolant is fluid. The heat transfer tubes 41 are, for example, U-shaped and are placed inside the reactor core 11, with one end and the other end extending to the outside through the shielding portion 12 (lid portion 33). The coolant is supplied from one end of the heat transfer tubes 41, flows inside the reactor core 11, and is then discharged to the outside from the other end of the heat transfer tubes 41. At this time, the coolant is heated by the heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11, and the heat is released to the outside.

[0034] The reactor core 11 has a first space 22 in its center, that is, inside the six fuel blocks 21, and six second spaces 23 in the circumferential gaps between the six fuel blocks 21. It is preferable that a large number of heat transfer tubes 41 are arranged in the first spaces 22 and the second spaces 23. In addition, the heat transfer tubes 41 may be arranged not only in the first spaces 22 and the second spaces 23, but also circumferentially at intervals on the outside of the multiple fuel blocks 21. That is, multiple heat transfer tubes 41 may be arranged to surround each fuel block 21. Furthermore, the heat conductor 13 may be provided, for example, as a solid heat conductor, so as to penetrate the multiple fuel blocks 21 in the axial direction.

[0035] The reactor core 11 (fuel block 21) may be constructed by stacking multiple plate-shaped fuel plates in the axial direction. The shielding section 12 may also be constructed by stacking multiple plate-shaped shielding plates in the axial direction. In this case, ring-shaped shielding plates are arranged on the outer circumference of ring-shaped fuel plates. Multiple ring-shaped fuel plates and shielding plates are then arranged in the thickness direction.

[0036] Furthermore, the heat conduction section 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 shielding plates and the ring-shaped heat conduction plates are alternately stacked in the thickness direction. The heat conduction plates have an outer diameter larger than the outer diameter of the shielding plates and extract the heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 radially outward. For example, titanium, nickel, copper, and graphite can be used for the heat conduction plates. Graphene can be used in particular. Graphene has a structure in which a continuous hexagonal lattice made of carbon atoms and their bonds is formed, and by making the direction of the continuous hexagonal lattice the direction of heat transfer, the heat transfer efficiency can be improved.

[0037] <Reactivity control device> The reactivity control device 14 is located in the shielding section 12. The reactivity control device 14 is positioned to surround the reactor core 11. The reactivity control device 14 has a plurality of (six in this embodiment) control units 51. However, the number of control units 51 is not limited. The plurality of control units 51 are arranged outside the reactor core 11, spaced circumferentially (preferably at equal intervals). The plurality of control units 51 are arranged facing each other on the outside of the plurality of fuel blocks 21 that constitute the reactor core 11.

[0038] The control unit 51 is arranged along the axial direction of the reactor core 11. The control unit 51 has approximately the same length as the reactor core 11. The control unit 51 has a neutron reflector 52 and a neutron absorber 53. The neutron reflector 52 is arranged facing the outside of the plurality of fuel blocks 21 that constitute the reactor core 11. The neutron absorber 53 is movable between a first position that does not face the reactor core 11 (fuel block 21) and a second position located between the reactor core 11 (fuel block 21) and the neutron reflector 52. The neutron reflector 52 can be made of beryllium oxide (BeO). However, the neutron reflector 52 is not limited to beryllium oxide; for example, (NgO) can also be used. For example, the neutron absorber 53 can be made of boron carbide (B4C). Here, the neutron reflector 52 has higher neutron reflection performance than the neutron absorber 53 and the shielding unit 12. The neutron absorption section 53 has higher neutron absorption performance than the neutron reflection section 52 and the shielding section 12.

[0039] The control unit 51 controls the movement of the neutron absorbing unit 53, which switches the member facing the reactor core 11 (fuel block 21) between the neutron reflecting unit 52 and the neutron absorbing unit 53. That is, when the neutron absorbing unit 53 is in the first position, the neutron reflecting unit 52 faces the reactor core 11 (fuel block 21), and when the neutron absorbing unit 53 is in the second position, the neutron absorbing unit 53 faces the reactor core 11 (fuel block 21).

[0040] The neutron reflector 52 is fixed to the shielding section 12 so as to face the outside of the reactor core 11 (fuel block 21). On the other hand, the neutron absorber 53 is movably supported on the shielding section 12. A connecting section 54 is connected to one end of the neutron absorber 53 in the axial direction. The connecting section 54 penetrates the cover section 33 of the shielding section 12, with one end connected to one end of the neutron absorber 53 and the other end extending to the outside of the shielding section 12. The drive unit 55 is located outside the reactor 112. The other ends of the multiple connecting sections 54 are connected to the drive unit 55. The drive unit 55 can move the multiple neutron absorber sections 53 via the multiple connecting sections 54.

[0041] The reactivity control device 14 includes a control device 56. The control device 56 is connected to the drive unit 55. The control device 56 can control the movement positions of the multiple neutron absorption units 53 by driving and controlling the drive unit 55. The control device 56 is, for example, a computer, and is implemented by a processing unit including a microprocessor such as a CPU (Central Processing Unit).

[0042] <Department Head> Figure 4 is a schematic diagram showing the details of the control unit, and Figure 5 is a schematic diagram showing the operation of the control unit.

[0043] As shown in Figure 4, the reactivity control device 14 has a plurality of control units 51. The control units 51 are located outside the reactor core 11, facing the radially outer planar portion 21a of the triangular-shaped fuel block 21. Specifically, the control unit 51 has a neutron reflector 52 and a neutron absorber 53. The neutron reflector 52 is positioned facing the planar portion 21a of the fuel block 21. The neutron absorber 53 is movable between a first position that does not face the planar portion 21a of the fuel block 21 and a second position located between the planar portion 21a of the fuel block 21 and the neutron reflector 52.

[0044] The neutron reflector 52 is positioned with a predetermined gap between it and the planar portion 21a of the fuel block 21. The neutron reflector 52 has a triangular shape and includes one planar portion 52a facing the planar portion 21a of the fuel block 21, and two planar portions 52b and 52c that do not face the planar portion 21a of the fuel block 21. The control unit 51 is provided with a rail 61 that guides the neutron absorber 53 to move freely between a first position and a second position. The rail 61 is positioned in a straight line from the position (gap) where the planar portions 21a and 52a face each other between the fuel block 21 and the neutron reflector 52, to the position where the planar portions 52b of adjacent neutron reflectors 52 face each other in the circumferential direction. The rails 61, for example, form a pair, with the lower rail provided at the bottom 32 of the shielding section 12 and the upper rail provided at the cover 33 of the shielding section 12.

[0045] The neutron absorbing section 53 is supported so as to be movable along the rail 61. That is, the neutron absorbing section 53 is supported so as to be movable between a first position and a second position by the rail 61. Here, the first position of the neutron absorbing section 53 is the position where the neutron absorbing section 53 faces the planar portion 52b of the neutron reflecting section 52. When the neutron absorbing section 53 is in the first position, it is hidden behind the neutron reflecting section 52 and does not face the reactor core 11 (fuel block 21). On the other hand, as shown in Figure 5, the second position of the neutron absorbing section 53 is the position where the neutron absorbing section 53 faces the planar portion 21a of the fuel block 21 and the planar portion 52a of the neutron reflecting section 52. When the neutron absorbing section 53 is in the second position, the neutron absorbing section 53 faces the reactor core 11 (fuel block 21), while the neutron reflecting section 52 is hidden behind the neutron absorbing section 53 and does not directly face the reactor core 11 (fuel block 21).

[0046] The reactivity control device 14 can adjust the position of the neutron absorption section 53 relative to the reactor core 11. The neutron reflector 52 is triangular in shape, and the neutron absorption section 53 is flat. That is, the thickness of the neutron reflector 52 is greater than the thickness of the neutron absorption section 53. However, the neutron reflector 52 is not limited to a triangular shape; it may also be flat like the neutron absorption section 53. Even if the neutron reflector 52 is flat, it is preferable that its thickness is greater than the thickness of the neutron absorption section 53.

[0047] As shown in Figure 4, when the neutron absorber 53 is in a first position, hidden by the neutron reflector 52 and not facing the fuel block 21, the neutron reflector 52 faces the fuel block 21. In this case, neutrons emitted outward from the fuel block 21 are reflected back to the fuel block 21 by the neutron reflector 52 and contribute to nuclear fission. Therefore, the reactivity of the nuclear fuel constituting the reactor core 11 increases. On the other hand, as shown in Figure 5, when the neutron absorber 53 is in a second position, between the fuel block 21 and the neutron reflector 52 and facing the fuel block 21, the neutron reflector 52 does not directly face the fuel block 21. In this case, neutrons emitted outward from the fuel block 21 are absorbed by the neutron absorber 53 and not returned to the fuel block 21, and do not contribute to nuclear fission. Therefore, the reactivity of the nuclear fuel constituting the reactor core 11 decreases.

[0048] The reactivity control device 14 can control the reactivity of the nuclear fuel in the reactor core 11 and thus control the temperature of the reactor core 11 by moving the neutron absorption unit 53 that constitutes the control unit 51, thereby increasing or decreasing the area in which the neutron reflector 52 faces the reactor core 11. Here, the temperature of the reactor core 11 is the average core temperature taken out to the outside of the shielding unit 12 by the heat conductor 13.

[0049] In other words, as shown in Figures 2 and 3, the control device 56 can obtain the temperature of the reactor core 11. The control device 56 controls the position of the neutron absorption units 53, which constitute the plurality of control units 51, by moving them away from the reactor core 11 and facing the neutron reflector units 52 toward the reactor core 11. As a result, the reactivity of the reactor core 11 increases, and the reactor 112 starts operation. On the other hand, the control device 56 controls the position of the neutron absorption units 53, which constitute the plurality of control units 51, by moving them closer to the reactor core 11 and not facing the neutron reflector units 52 toward the reactor core 11. As a result, the reactivity of the reactor core 11 decreases, and the reactor 112 stops operation.

[0050] <Methods for controlling nuclear reactors> As shown in Figures 1, 2, and 3, in the reactor 112, the control device 56 controls the movement position of the neutron absorber 53 in the multiple control units 51 that make up the reactivity control device 14 according to the temperature of the reactor core 11. That is, the neutron absorber 53 is moved so that the neutron reflector 52 faces the reactor core 11 to increase the reactivity of the reactor core 11, or the neutron absorber 53 faces the reactor core 11 to decrease the reactivity of the reactor core 11. Specifically, the neutron absorber 53 is moved to a first position so that the neutron reflector 52 faces the fuel block 21, and the neutron absorber 53 does not face the fuel block 21. Then, neutrons emitted from the fuel block 21 are reflected by the neutron reflector 52 and returned to the fuel block 21. As a result, external leakage of neutrons emitted from the fuel block 21 is suppressed, and the generated neutrons can be effectively utilized to contribute to nuclear fission.

[0051] The heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11 is removed to the outside of the shielding section 12 by the heat conductor 13 (heat transfer tube 41). The heat removed to the outside of the shielding section 2 is transferred to the coolant by the heat exchanger 102, the coolant rotates the turbine 104, and the generator 105 generates electricity.

[0052] [Effects of this embodiment] The reactor according to the first embodiment comprises a reactor core 11 made of nuclear fuel, and a reactivity control device 14 having a control unit 51 which is provided with a neutron reflector 52 that reflects neutrons and a neutron absorber 53 that absorbs neutrons, located outside the reactor core 11, wherein the neutron reflector 52 is located facing the outside of the reactor core 11, and the neutron absorber 53 is movable between a first position not facing the reactor core 11 and a second position located between the reactor core, the neutron reflector 52.

[0053] According to the reactor of the first embodiment, during operation of the reactor 112, the control unit 51 moves the neutron absorption unit 53 to a first position so that the neutron reflector 52 faces the reactor core 11. As a result, neutrons emitted from the nuclear fuel in the reactor core 11 are reflected by the neutron reflector 52 and returned to the reactor core 11. Therefore, external leakage of neutrons generated in the reactor core 11 is suppressed, the generated neutrons can be effectively utilized, and the efficiency of the reactor 112 can be improved.

[0054] The reactor according to the second embodiment is the reactor according to the first embodiment, further, the first position is a position in which the neutron absorbing section 53 is hidden by the neutron reflecting section 52 and does not face the reactor core 11. This makes it possible to effectively reduce the influence of the neutron reflecting section 52 on the reactor core 11 when the neutron reflecting section 52 is located at the first position.

[0055] The reactor according to the third embodiment is a reactor according to the first or second embodiment, further comprising a core 11 with a polygonal shape, and neutron reflectors 52 positioned opposite a plurality of planar portions 21a of the polygonal core 11. This allows neutrons emitted radially outward from the nuclear fuel in the core 11 to be appropriately reflected back to the core 11 by the neutron reflectors 52.

[0056] The reactor according to the fourth embodiment is a reactor according to the third embodiment, further comprising multiple neutron reflectors 52 arranged opposite to multiple planar sections 21a of the polygonal core 11, and multiple neutron absorbers 53 provided corresponding to the multiple neutron reflectors 52. This makes it possible to effectively arrange the neutron reflectors 52 and neutron absorbers 53 for each planar section 21a of the core 11.

[0057] The reactor according to the fifth embodiment is a reactor according to the second embodiment, further comprising a neutron absorber 53 that is movable between a second position and a first position that is hidden by a neutron reflector 52 adjacent to the circumferential direction of the core 11 relative to the second position and does not face the core 11. This makes it easy to secure a movement path (rail 61) for the neutron absorber 53 and simplifies the configuration.

[0058] The reactor according to the sixth embodiment is a reactor according to any one of the first to fifth embodiments, further provided with a rail 61 that guides the neutron absorbing section to move freely between a first position and a second position. This allows the neutron absorbing section 53 to be easily moved using the rail 61.

[0059] The seventh embodiment of the reactor control method involves a reactor 112 in which a control unit 51 having a neutron reflector 52 and a neutron absorber 53 facing the outside of a reactor core 11 made of nuclear fuel is arranged. The control unit 51 controls the reactivity of the reactor core 11 by moving the neutron absorber 53 between a first position that does not face the reactor core 11 and a second position located between the reactor core 11 and the neutron reflector 52. As a result, when the reactor 112 is in operation, the control unit 51 moves the neutron absorber 53 to the first position so that the neutron reflector 52 faces the reactor core 11, and neutrons emitted from the nuclear fuel in the reactor core 11 are reflected by the neutron reflector 52 and returned to the reactor core 11. Therefore, external leakage of neutrons generated in the reactor core 11 is suppressed, the generated neutrons can be effectively utilized, and the efficiency of the reactor 112 can be improved. [Explanation of Symbols]

[0060] 11 Core 12 Shielding section 13. Thermal Conductors 14. Reactivity control device 21 Fuel Block 22 First space part 23 Second space 31 Torso 32 Bottom 33 Lid 41 Heat transfer tubes 51 Control Unit 52 Neutron reflector 53 Neutron Absorption Section 54 Connecting part 55 Drive unit 56 Control device 100 Nuclear power generation systems 101 Reactor Unit 102 Heat exchanger 103 Refrigerant circulation path 104 Turbine 105 Generator 106 Cooler 107 Compressor 111 Reactor Vessel 112 Nuclear reactor 113 Heat conduction section

Claims

1. The reactor core is composed of nuclear fuel, A reactivity control device having a control unit that is positioned outside the reactor core and is provided with a neutron reflecting unit that reflects neutrons and a neutron absorbing unit that absorbs neutrons, Equipped with, The neutron reflector is positioned opposite the outside of the reactor core, The neutron absorbing section is movable between a first position not facing the reactor core and a second position located between the reactor core and the neutron reflecting section. The reactor core has a polygonal shape, and the neutron reflector is arranged opposite to a plurality of planar portions of the polygonal reactor core. The neutron reflecting sections are arranged in multiple locations opposite to the multiple planar sections of the polygonal reactor core, and the neutron absorbing sections are provided in multiple locations corresponding to the multiple neutron reflecting sections. The neutron absorbing portion is movable between the second position and the first position, which is hidden from the neutron reflecting portion adjacent to the second position in the circumferential direction of the core and does not face the core. nuclear reactor.

2. The reactor core is composed of nuclear fuel, A reactivity control device having a control unit that is positioned outside the reactor core and is provided with a neutron reflecting unit that reflects neutrons and a neutron absorbing unit that absorbs neutrons, Equipped with, The neutron reflector is positioned opposite the outside of the reactor core, The neutron absorbing section is movable between a first position not facing the reactor core and a second position located between the reactor core and the neutron reflecting section. The reactor core has a polygonal shape, and the neutron reflector is arranged opposite to a plurality of planar portions of the polygonal reactor core. The neutron reflecting sections are arranged in multiple locations opposite to the multiple planar sections of the polygonal reactor core, and the neutron absorbing sections are provided in multiple locations corresponding to the multiple neutron reflecting sections. A rail is provided to guide the neutron absorbing section so that it can move between the first position and the second position. nuclear reactor.

3. The first position is a position where the neutron absorbing portion is hidden by the neutron reflecting portion and does not face the reactor core. The reactor according to claim 1 or claim 2.

4. In the reactor according to claim 1 or claim 2, The control unit controls the reactivity of the reactor core by moving the neutron absorption unit between a first position not facing the reactor core and a second position located between the reactor core and the neutron reflector. A method for controlling a nuclear reactor.

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