JP2024175507A - Nuclear reactor and method for controlling nuclear reactor - Google Patents

Abstract

A nuclear reactor and a method for controlling the nuclear reactor are provided to improve efficiency in the nuclear reactor.
[Solution] The system comprises a core composed of nuclear fuel, and a reactivity control device having a control unit arranged outside the core and provided with a neutron reflecting unit that reflects neutrons and a neutron absorbing unit that absorbs neutrons, wherein the neutron reflecting unit is arranged facing the outside of the core, and the neutron absorbing unit is movable between a first position not facing the core and a second position located between the core and the neutron reflecting unit.
[Selected figure] Figure 3

Description

The present disclosure relates to a nuclear reactor and a method for controlling the nuclear reactor.

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 reactor using the nuclear fuel, and the generated heat is taken out to the outside to heat a refrigerant. The heated refrigerant drives a turbine to rotate, which generates electricity using a generator. Examples of such nuclear power generation systems are described in Patent Documents 1 and 2.

JP 2022-63014 A JP 2022-61791 A

The nuclear reactor is provided with a reactivity control device. In conventional nuclear reactors, the nuclear fuel is circular, and multiple control units are provided on the outside of the nuclear fuel as a reactivity control device. The control unit is supported in a circular shape so that it can rotate freely, and a neutron absorbing unit is provided on one side of the circumference. As the control unit rotates and the neutron absorbing unit approaches the nuclear fuel, the reactivity of the nuclear fuel decreases, and as the neutron absorbing unit moves away from the nuclear fuel, the reactivity of the nuclear fuel increases. In this case, when the neutron absorbing unit of the control unit moves away from the nuclear fuel, the reactivity of the nuclear fuel increases, but there is an issue that some neutrons leak out, reducing efficiency.

The present disclosure aims to solve the above-mentioned problems and provide a nuclear reactor and a method for controlling the reactor that improves the efficiency of the nuclear reactor.

To achieve the above object, the nuclear reactor disclosed herein comprises a core composed of nuclear fuel, and a reactivity control device having a control unit disposed outside the core and provided with a neutron reflector that reflects neutrons and a neutron absorber that absorbs neutrons, the neutron reflector being disposed facing the outside of the core, and the neutron absorber being movable between a first position not facing the core and a second position located between the core and the neutron reflector.

The disclosed method of controlling a nuclear reactor includes a control unit having a neutron reflector and a neutron absorber facing the outside of a core made of nuclear fuel, and the control unit controls the reactivity of the core by moving the neutron absorber between a first position not facing the core and a second position located between the core and the neutron reflector.

The reactor and method disclosed herein can improve the efficiency of the reactor.

FIG. 1 is a schematic diagram showing a nuclear power generation system according to the present embodiment. FIG. 2 is a vertical cross-sectional view showing the nuclear reactor of this embodiment. FIG. 3 is a horizontal cross-sectional view of a nuclear reactor. FIG. 4 is a schematic diagram showing the details of the control unit. FIG. 5 is a schematic diagram showing the operation of the control unit.

Below, a preferred embodiment of the present disclosure will be described in detail 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 various embodiments. Furthermore, the components in the embodiments include those that a person skilled in the art would easily imagine, those that are substantially the same, and those that are within the so-called equivalent range.

<Nuclear power generation system>
FIG. 1 is a schematic diagram showing a nuclear power generation system according to the present embodiment.

As shown in FIG. 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.

The reactor unit 101 has a reactor vessel 111, a reactor 112, and a heat conductive 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, for example a lid, so that the reactor 112 placed inside can be stored or removed. The reactor vessel 111 can maintain a sealed state even if a nuclear reaction occurs in the reactor 112 and the inside becomes hot and high pressure. The reactor vessel 111 is formed from a material that has neutron radiation shielding properties.

The reactor 112 stores nuclear fuel. The reactor 112 causes a nuclear reaction in the nuclear fuel, generating heat. The thermal conduction section 113 transfers the heat generated in the reactor 112 to the heat exchanger 102. Details of the reactor 112 and the thermal conduction section 113 will be described later.

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 thermal conduction section 113 that constitutes the reactor unit 101.

The refrigerant circulation path 103 is a path that circulates the refrigerant. The refrigerant circulation path 103 connects the heat exchanger 102, the turbine 104, the cooler 106, and the 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 passes through the compressor 107 returns to the heat exchanger 102. The heat exchanger 102 exchanges heat between the heat conductive portion 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 conductive portion 113, and the heat conductive portion 113 is cooled by the refrigerant.

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

The generator 105 is connected coaxially to the turbine 104. The generator 105 rotates together with the turbine 104. The generator 105 generates electricity by rotating due to the rotational force of the turbine 104.

The cooler 106 cools the refrigerant that has passed through the turbine 104. The cooler 106 may be a chiller or a condenser if the refrigerant is temporarily liquefied.

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

The heat generated by the reaction of the nuclear fuel in the reactor 112 is transferred to the heat exchanger 102 via the heat conduction section 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 with the heat of the heat conduction section 113. In other words, the refrigerant absorbs heat and is heated by the heat exchanger 102, and the heat generated in the reactor 112 is recovered by the refrigerant.

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 is driven to rotate by the supplied refrigerant, which drives the generator 105, which then generates electricity. The refrigerant that rotates the turbine 104 is cooled to a reference temperature by the cooler 106, and then supplied to the compressor 58.

The nuclear power generation system 100 transfers heat extracted from the reactor 112 to the refrigerant through the heat conduction section 113, and the high-temperature, high-pressure refrigerant drives the turbine 104 to generate electricity through the generator 105. This makes it possible to isolate the reactor 112 from the refrigerant that serves as the medium for driving and rotating the turbine 104, thereby reducing the risk of radioactive contamination of the medium for driving and rotating the turbine 104.

<Nuclear Reactor>
FIG. 2 is a vertical sectional view showing the nuclear reactor of this embodiment, and FIG. 3 is a horizontal sectional view showing the nuclear reactor.

As shown in Figures 2 and 3, 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 a heat conduction section 113. The heat conduction section 113 extracts heat generated in the reactor 112 to the outside.

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

<Reactor Core>
The core 11 is formed to have a polygonal prism shape (hexagonal prism shape in this embodiment) centered on the central axis O as a whole. The 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 core 11 forms a ring shape that is long in the axial direction (direction along the central axis O) by arranging the plurality of fuel blocks 21 in the circumferential direction. That is, the core 11 has a polygonal (hexagonal) outer shape, and the plurality of fuel blocks 21 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.

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 23 between the plurality of fuel blocks 21. The plurality of second spaces 23 have a rectangular parallelepiped shape and each have the same shape. The plurality of second spaces 23 are arranged radially from the outer periphery of the first space 22. That is, the second space 23 is arranged along the radial direction of the core 11, and has a shape that is long in the axial direction and radial direction (direction perpendicular to the central axis O) and short in the circumferential direction (width direction). However, the core 11 is not limited to one having the second space 23 and composed of a plurality of fuel blocks 21, and may have an integral square tube shape or cylindrical shape without the second space 23. Furthermore, the core 11 is not limited to a cylindrical shape having the first space 22, but may be a prismatic or cylindrical shape without the first space 22.

Although not shown, the core 11 (fuel block 21) includes nuclear fuel (radioactive material) and a support. The support is disposed throughout the core 11. The support is provided with a plurality of holes along the axial direction. The holes are, for example, cylindrical. The support may include a moderator. For example, graphene, graphite, etc. can be used as the moderator. The nuclear fuel is disposed in the hole of the support. The nuclear fuel corresponds to the shape of the hole of the support and is cylindrical. The nuclear fuel may be a rod shape that is continuous in the axial direction, or may be a pellet shape that is discontinuous in the axial direction. The nuclear fuel may be uranium (e.g., uranium 235), plutonium (e.g., plutonium 239, 241), thorium, etc., as a fissile material.

<Shielding part>
The shielding part 12 is disposed so as to cover the periphery of the reactor core 11. The shielding part 12 is made of a metal block, and suppresses leakage of radiation to the outside by reflecting radiation (neutrons) irradiated from the nuclear fuel that constitutes the reactor core 11. The shielding part 12 is sometimes called a reflector depending on the neutron scattering and neutron absorption capabilities of the material used.

The shielding part 12 has a body 31, a bottom part 32, and a lid part 33. The body 31 has a cylindrical shape and is disposed radially outside the core 11. That is, the body 31 covers the outer periphery of the core 11 so as to surround it. The bottom part 32 has a disk shape and is disposed on one side of the body 31 in the axial direction. That is, the bottom part 32 covers the lower part of the core 11 so as to block it. The lid part 33 has a disk shape and is disposed on the other side of the body 31 in the axial direction. That is, the lid part 33 covers the upper part of the core 11 so as to block it. When the shielding part 12 contains 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.

<Thermal conductor>
The thermal conductor 13 constitutes the thermal conduction section 113. That is, the thermal conductor 13 conducts heat generated in the core 11 to the heat exchanger 102 (see FIG. 1 ). The thermal conductor 13 is arranged so as to penetrate the core 11 in the axial direction. One longitudinal end of the thermal conductor 13 penetrates the lid 33 of the shielding section 12 and extends to the outside. The thermal conductor 13 conducts heat generated by the nuclear reaction of the nuclear fuel in the core 11 to the outside of the shielding section 12.

The thermal conductor 13 has, for example, a heat transfer tube 41. The heat transfer tube 41 is filled with a refrigerant (for example, carbon dioxide) and the refrigerant can flow. The heat transfer tube 41 has, for example, a U-shape and is disposed inside the reactor core 11, with one end and the other end penetrating the shielding part 12 (lid part 33) and extending to the outside. The refrigerant is supplied from one end of the heat transfer tube 41, flows inside the reactor core 11, and is discharged to the outside from the other end of the heat transfer tube 41. At this time, the refrigerant is heated by the heat generated by the nuclear reaction of the nuclear fuel in the reactor core 11, and takes the heat out to the outside.

The core 11 has a first space 22 provided in the center, that is, inside the six fuel blocks 21, and six second spaces 23 provided 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 space 22 and the second space 23. The heat transfer tubes 41 may be arranged not only in the first space 22 and the second space 23, but also outside the multiple fuel blocks 21 at intervals in the circumferential direction. In other words, the multiple heat transfer tubes 41 may be arranged so as to surround each fuel block 21. Furthermore, the heat conductor 13 may be provided, for example, as a solid heat conducting member, so as to penetrate the multiple fuel blocks 21 in the axial direction.

The core 11 (fuel block 21) may be configured by stacking multiple plate-shaped fuel plates in the axial direction. The shielding section 12 may be configured by stacking multiple plate-shaped shielding plates in the axial direction. In this case, a ring-shaped shielding plate is arranged on the outer periphery of the ring-shaped fuel plate. Then, multiple ring-shaped fuel plates and shielding plates are arranged in the plate thickness direction.

Furthermore, the heat conducting section 113 may be provided by stacking a number of plate-shaped heat conducting plates in the axial direction. In this case, the ring-shaped fuel plates and shielding plates are alternately stacked in the plate thickness direction with the ring-shaped heat conducting plates. The heat conducting plates have an outer diameter larger than that of the shielding plates, and extract the heat generated by the nuclear reaction of the nuclear fuel in the core 11 radially outward. The heat conducting plates may be made of, for example, titanium, nickel, copper, or graphite. As graphite, graphene may be used in particular. Graphene has a structure in which a hexagonal lattice made of carbon atoms and their bonds is continuous, and by making the direction of the continuous hexagonal lattice the direction of heat transfer, the heat transfer efficiency can be improved.

<Reactivity control device>
The reactivity control device 14 is disposed in the shielding portion 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 units 51 (six in this embodiment). However, the number of control units 51 is not limited. The plurality of control units 51 are disposed outside the reactor core 11 at intervals (preferably at equal intervals) in the circumferential direction. The plurality of control units 51 are disposed facing the outside of the plurality of fuel blocks 21 that constitute the reactor core 11.

The control unit 51 is disposed along the axial direction of the core 11. The control unit 51 has a length substantially equal to that of the core 11. The control unit 51 has a neutron reflecting unit 52 and a neutron absorbing unit 53. The neutron reflecting unit 52 is disposed facing the outside of the multiple fuel blocks 21 constituting the core 11. The neutron absorbing unit 53 is movable between a first position not facing the core 11 (fuel block 21) and a second position located between the core 11 (fuel block 21) and the neutron reflecting unit 52. The neutron reflecting unit 52 may be made of beryllium oxide (BeO). However, the neutron reflecting unit 52 is not limited to beryllium oxide, and may be made of, for example, NgO. The neutron absorbing unit 53 may be made of, for example, boron carbide (B ₄ C). Here, the neutron reflecting portion 52 has higher neutron reflection performance than the neutron absorbing portion 53 and the shielding portion 12. The neutron absorbing portion 53 has higher neutron absorption performance than the neutron reflecting portion 52 and the shielding portion 12.

The control unit 51 switches the member facing the core 11 (fuel block 21) between the neutron reflecting unit 52 and the neutron absorbing unit 53 by moving the neutron absorbing unit 53. That is, when the neutron absorbing unit 53 is located in the first position, the neutron reflecting unit 52 faces the core 11 (fuel block 21), and when the neutron absorbing unit 53 is located in the second position, the neutron absorbing unit 53 faces the core 11 (fuel block 21).

The neutron reflecting section 52 is fixed to the shielding section 12 so as to face the outside of the core 11 (fuel block 21). On the other hand, the neutron absorbing section 53 is supported by the shielding section 12 so as to be freely movable. The neutron absorbing section 53 has one axial end connected to a connecting section 54. The connecting section 54 penetrates the lid section 33 of the shielding section 12, one end connected to one end of the neutron absorbing section 53, and the other end extending outside the shielding section 12. The driving section 55 is disposed outside the reactor 112. The other ends of the multiple connecting sections 54 are connected to the driving section 55. The driving section 55 is capable of moving the multiple neutron absorbing sections 53 via the multiple connecting sections 54.

The reactivity control device 14 has a control device 56. The control device 56 is connected to a drive unit 55. The control device 56 can control the movement positions of the multiple neutron absorbing units 53 by controlling the drive unit 55. 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).

<Control Unit>
FIG. 4 is a schematic diagram showing the details of the control unit, and FIG. 5 is a schematic diagram showing the operation of the control unit.

As shown in FIG. 4, the reactivity control device 14 has multiple control units 51. The control units 51 are arranged outside the core 11, facing the radially outer flat surface 21a of the triangular fuel block 21. Specifically, the control units 51 have a neutron reflector 52 and a neutron absorber 53. The neutron reflector 52 is arranged facing the flat surface 21a of the fuel block 21. The neutron absorber 53 is movable between a first position not facing the flat surface 21a of the fuel block 21, and a second position located between the flat surface 21a of the fuel block 21 and the neutron reflector 52.

The neutron reflector 52 is disposed with a predetermined gap from the flat surface 21a of the fuel block 21. The neutron reflector 52 has a triangular outer shape and has one flat surface 52a facing the flat surface 21a of the fuel block 21, and two flat surfaces 52b, 52c that do not face the flat surface 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 the first position and the second position. The rail 61 is disposed in a straight line from the position (gap) where the flat surface 21a and the flat surface 52a face each other between the fuel block 21 and the neutron reflector 52 to the position where the flat surfaces 52b of the circumferentially adjacent neutron reflectors 52 face each other. The rails 61 are, for example, a pair of upper and lower rails, with the lower rail provided on the bottom 32 of the shielding part 12 and the upper rail provided on the lid part 33 of the shielding part 12.

The neutron absorbing section 53 is supported so as to be freely movable along the rails 61. That is, the neutron absorbing section 53 is supported by the rails 61 so as to be freely movable between a first position and a second position. Here, the first position of the neutron absorbing section 53 is a position where the neutron absorbing section 53 faces the flat section 52b of the neutron reflecting section 52, and when the neutron absorbing section 53 is located at the first position, the neutron absorbing section 53 is hidden behind the neutron reflecting section 52 and does not face the core 11 (fuel block 21). On the other hand, as shown in FIG. 5, the second position of the neutron absorbing portion 53 is a position where the neutron absorbing portion 53 faces the flat portion 21a of the fuel block 21 and the flat portion 52a of the neutron reflecting portion 52. When the neutron absorbing portion 53 is located in the second position, the neutron absorbing portion 53 faces the core 11 (fuel block 21), and the neutron reflecting portion 52 is hidden behind the neutron absorbing portion 53 and does not directly face the core 11 (fuel block 21).

The reactivity control device 14 can adjust the position of the neutron absorbing section 53 relative to the core 11. The neutron reflecting section 52 has a triangular shape, and the neutron absorbing section 53 has a flat plate shape. That is, the thickness of the neutron reflecting section 52 is greater than the thickness of the neutron absorbing section 53. However, the neutron reflecting section 52 is not limited to a triangular shape, and may have a flat plate shape like the neutron absorbing section 53. Even if the neutron reflecting section 52 has a flat plate shape, it is preferable that the thickness of the neutron reflecting section 52 is greater than the thickness of the neutron absorbing section 53.

As shown in FIG. 4, when the neutron absorbing section 53 is in a first position hidden by the neutron reflecting section 52 and not facing the fuel block 21, the neutron reflecting section 52 faces the fuel block 21. At this time, neutrons emitted from the fuel block 21 to the outside are reflected by the neutron reflecting section 52 and returned to the fuel block 21, contributing to nuclear fission. Therefore, the reactivity of the nuclear fuel constituting the core 11 increases. On the other hand, as shown in FIG. 5, when the neutron absorbing section 53 is in a second position facing the fuel block 21 between the fuel block 21 and the neutron reflecting section 52, the neutron reflecting section 52 does not directly face the fuel block 21. At this time, neutrons emitted from the fuel block 21 to the outside are absorbed by the neutron absorbing section 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 core 11 decreases.

The reactivity control device 14 can increase or decrease the area of the neutron reflecting part 52 facing the core 11 by moving the neutron absorbing part 53 constituting the control part 51, thereby controlling the reactivity of the nuclear fuel in the core 11 and controlling the temperature of the core 11. Here, the temperature of the core 11 is the average core temperature taken out to the outside of the shielding part 12 by the thermal conductor 13.

That is, as shown in FIG. 2 and FIG. 3, the control device 56 can acquire the temperature of the core 11. The control device 56 moves and controls the position of the neutron absorbing section 53 constituting the multiple control sections 51, moving the neutron absorbing section 53 away from the core 11 and making the neutron reflecting section 52 face the core 11. Then, the reactivity of the core 11 increases, and the reactor 112 starts operating. On the other hand, the control device 56 moves and controls the position of the neutron absorbing section 53 constituting the multiple control sections 51, moving the neutron absorbing section 53 closer to the core 11 and making the neutron reflecting section 52 not face the core 11. Then, the reactivity of the core 11 decreases, and the reactor 112 stops operating.

<Control method of nuclear reactor>
As shown in Fig. 1, Fig. 2 and Fig. 3, in the nuclear reactor 112, the control device 56 controls the moving position of the neutron absorbing part 53 in the multiple control parts 51 constituting the reactivity control device 14 according to the temperature of the core 11. That is, the neutron absorbing part 53 is moved to face the neutron reflecting part 52 to the core 11 to increase the reactivity of the core 11, or the neutron absorbing part 53 is faced to the core 11 to decrease the reactivity of the core 11. That is, the neutron absorbing part 53 is moved to a first position, and the neutron reflecting part 52 is positioned to face the fuel block 21, and the neutron absorbing part 53 is positioned not to face the fuel block 21. Then, the neutrons emitted from the fuel block 21 are reflected by the neutron reflecting part 52 and returned to the fuel block 21. Therefore, the external leakage of the neutrons emitted from the fuel block 21 is suppressed, and the generated neutrons can be effectively utilized to contribute to nuclear fission.

The heat generated by the nuclear reaction of the nuclear fuel in the core 11 is extracted to the outside of the shielding part 12 by the thermal conductor 13 (heat transfer tube 41). The heat extracted to the outside of the shielding part 2 is transferred to the coolant by the heat exchanger 102, and the coolant rotates the turbine 104, generating electricity with the generator 105.

[Effects of this embodiment]
The nuclear reactor of the first aspect comprises a core 11 composed of nuclear fuel, and a reactivity control device 14 having a control unit 51 arranged outside the core 11 and provided with a neutron reflecting unit 52 that reflects neutrons and a neutron absorbing unit 53 that absorbs neutrons, the neutron reflecting unit 52 being arranged facing the outside of the core 11, and the neutron absorbing unit 53 being movable between a first position not facing the core 11 and a second position located between the core and the neutron reflecting unit 52.

According to the reactor of the first aspect, when the reactor 112 is in operation, the control unit 51 moves the neutron absorbing unit 53 to the first position to make the neutron reflecting unit 52 face the core 11, so that neutrons emitted from the nuclear fuel in the core 11 are reflected by the neutron reflecting unit 52 and returned to the core 11. This prevents neutrons generated in the core 11 from leaking outside, and allows the generated neutrons to be used effectively, improving the efficiency of the reactor 112.

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

The reactor according to the third aspect is the reactor according to the first or second aspect, and further, the core 11 has a polygonal outer shape, and the neutron reflecting section 52 is disposed opposite a plurality of flat sections 21a of the polygonal core 11. This allows neutrons emitted radially outward from the nuclear fuel in the core 11 to be appropriately reflected by the neutron reflecting section 52 and returned to the core 11.

The reactor according to the fourth aspect is the reactor according to the third aspect, and further includes a plurality of neutron reflecting sections 52 arranged opposite the plurality of planar sections 21a of the polygonal core 11, and a plurality of neutron absorbing sections 53 provided corresponding to the plurality of neutron reflecting sections 52. This allows the neutron reflecting sections 52 and neutron absorbing sections 53 to be effectively arranged for each planar section 21a of the core 11.

The reactor according to the fifth aspect is the reactor according to the second aspect, and further, the neutron absorbing section 53 is movable between the second position and the first position, which is hidden by the neutron reflecting section 52 adjacent to the second position in the circumferential direction of the core 11 and does not face the core 11. This makes it possible to easily ensure the movement path (rails 61) of the neutron absorbing section 53 and to simplify the configuration.

The reactor according to the sixth aspect is a reactor according to any one of the first to fifth aspects, and further includes rails 61 that guide the neutron absorbing section 53 to move freely between the first and second positions. This allows the neutron absorbing section 53 to be easily moved using the rails 61.

In the seventh aspect of the reactor control method, in a reactor 112 in which a control unit 51 having a neutron reflector 52 and a neutron absorber 53 facing the outside of a core 11 made of nuclear fuel is disposed, the control unit 51 controls the reactivity of the core 11 by moving the neutron absorber 53 between a first position not facing the core 11 and a second position located between the 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 to make the neutron reflector 52 face the core 11, so that neutrons emitted from the nuclear fuel in the core 11 are reflected by the neutron reflector 52 and returned to the core 11. Therefore, the external leakage of neutrons generated in the core 11 is suppressed, the generated neutrons can be effectively utilized, and the efficiency of the reactor 112 can be improved.

REFERENCE SIGNS LIST 11 Reactor core 12 Shielding section 13 Thermal conductor 14 Reactivity control device 21 Fuel block 22 First space section 23 Second space section 31 Body 32 Bottom section 33 Lid section 41 Heat transfer tube 51 Control section 52 Neutron reflecting section 53 Neutron absorbing section 54 Connection section 55 Drive section 56 Control device 100 Nuclear power generation system 101 Reactor unit 102 Heat exchanger 103 Coolant circulation path 104 Turbine 105 Generator 106 Cooler 107 Compressor 111 Reactor vessel 112 Reactor 113 Thermal conduction section

Claims (7)

a reactor core composed of nuclear fuel;
a reactivity control device having a control unit provided with a neutron reflector that is disposed outside the reactor core and that reflects neutrons and a neutron absorber that absorbs neutrons;
Equipped with
The neutron reflecting portion is disposed facing the outside of the reactor core,
The neutron absorbing unit is movable between a first position not facing the reactor core and a second position located between the reactor core and the neutron reflecting unit.
Nuclear reactor. 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.
2. The nuclear reactor of claim 1. The core has a polygonal outer shape, and the neutron reflecting portion is disposed opposite a plurality of planar portions of the polygonal core.
A nuclear reactor according to claim 1 or 2. The neutron reflecting portion is arranged in a plurality of positions facing a plurality of planar portions of the polygonal core, and the neutron absorbing portion is provided in a plurality of positions corresponding to the plurality of neutron reflecting portions.
4. The nuclear reactor of claim 3. The neutron absorbing unit is movable between the second position and the first position where the neutron absorbing unit is hidden by the neutron reflecting unit adjacent to the second position in the circumferential direction of the core and does not face the core.
5. The nuclear reactor of claim 4. A rail is provided to movably guide the neutron absorbing unit between the first position and the second position.
5. The nuclear reactor of claim 4. In a nuclear reactor, a control unit having a neutron reflector and a neutron absorber facing the outside of a core made of nuclear fuel is disposed,
the control unit controls the reactivity of the core by moving the neutron absorbing unit between a first position not facing the core and a second position located between the core and the neutron reflecting unit.
How to control a nuclear reactor.

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