nuclear reactor

Abstract

To enable effective reactivity adjustment of a spherical fuel portion.SOLUTION: A nuclear reactor 11 is disclosed, comprising a fuel portion 1 with a spherical section, and a plurality of spherical control units 3 arranged around the spherical section, each having a neutron absorber 3a partially provided on an outer periphery thereof.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] This disclosure relates to a nuclear reactor.

Background Art

[0002] For example, Patent Document 1 discloses a nuclear reactor in which a control mechanism for controlling the reactivity of a fuel portion is arranged around the fuel portion.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In the nuclear reactor described in Patent Document 1, the fuel portion is formed in a columnar shape extending in the axial direction, and the surrounding control mechanism is formed in a cylindrical shape extending in the axial direction. The control mechanism is provided rotatably around the cylinder, and a neutron absorber provided on a part of the outer periphery is moved closer to or away from the fuel portion.

[0005] By the way, in the nuclear reactor described in Patent Document 1, since the fuel portion is formed in a columnar shape, the cylindrical control mechanism can be arranged along the axial direction at equal intervals with respect to any position on the outer periphery of the fuel portion. However, when the fuel portion has a spherical portion, in the case of the cylindrical control mechanism, the distance from the spherical portion of the fuel portion becomes large, and there is an ineffective region in the control of reactivity.

[0006] This disclosure solves the above - described problems, and an object thereof is to provide a nuclear reactor capable of effectively adjusting the reactivity with respect to a fuel portion having a spherical portion.

Means for Solving the Problems

[0007] To achieve the above-mentioned objectives, a reactor according to one aspect of the present disclosure includes a fuel section having a spherical portion, and a plurality of spherical control sections arranged around the spherical portion, with neutron absorbers provided on a portion of their outer circumference. [Effects of the Invention]

[0008] This disclosure enables effective adjustment of the reactivity for a fuel section having a spherical portion. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a schematic diagram of a nuclear power generation system using a reactor according to an embodiment. [Figure 2] Figure 2 is an axial cross-sectional view of the reactor according to the embodiment. [Figure 3] Figure 3 is a perspective view representing region S in Figure 2. [Figure 4] Figure 4 is an axial cross-sectional view of the reactor according to the embodiment. [Figure 5] Figure 5 is a perspective view showing an example of the drive mechanism of the control unit in the embodiment. [Figure 6] Figure 6 is an axial cross-sectional view of another example of the reactor of the embodiment. [Modes for carrying out the invention]

[0010] Embodiments relating to this disclosure will be described in detail below with reference to the drawings. However, the present invention is not limited by these embodiments. Furthermore, some of the components in the embodiments described below are substituted or substantially identical to those easily substituted by those skilled in the art.

[0011] Figure 1 is a schematic diagram of a nuclear power generation system using a reactor according to an embodiment.

[0012] As shown in Figure 1, the nuclear power generation system 50 includes a reactor vessel 51, a heat exchanger 52, a heat conduction section 53, a refrigerant circulation means 54, a turbine 55, a generator 56, a cooler 57, and a compressor 58.

[0013] The reactor vessel 51 has a reactor 11(12) according to an embodiment described later. The reactor vessel 51 houses the reactor 11(12) inside. The reactor vessel 51 houses the reactor 11(12) in a sealed state. The reactor vessel 51 is provided with an opening and closing part, such as a lid, so that the reactor 11(12) placed inside can be stored in or removed. The reactor vessel 51 can maintain a sealed state even when a nuclear fission reaction occurs in the reactor 11(12) and the inside becomes hot and high-pressure. The reactor vessel 51 is made of a material that has neutron shielding properties.

[0014] The heat exchanger 52 performs heat exchange with the reactor 11(12). In this embodiment, the heat exchanger 52 recovers heat from the reactor 11(12) via a cooling medium in a heat conduction section 53 located in the reactor 11(12). The heat conduction section 53 shown in Figure 1 is a schematic representation of the heat conduction section 4 of the reactor 11(12), which will be described later.

[0015] The refrigerant circulation means 54 is a path for circulating the refrigerant, and is connected to a heat exchanger 52, a turbine 55, a cooler 57, and a compressor 58. The refrigerant flowing through the refrigerant circulation means 54 flows in the order of heat exchanger 52, turbine 55, cooler 57, and compressor 58, and the refrigerant that has passed through the compressor 58 is supplied to the heat exchanger 52. Therefore, the heat exchanger 52 performs heat exchange between the cooling medium of the heat conduction section 53 and the refrigerant flowing through the refrigerant circulation means 54.

[0016] The turbine 55 receives the refrigerant that has passed through the heat exchanger 52. The turbine 55 is rotated by the energy of the heated refrigerant. In other words, the turbine 55 absorbs energy from the refrigerant by converting the energy of the refrigerant into rotational energy.

[0017] The generator 56 is connected to the turbine 55 and rotates together with the turbine 55. The generator 56 generates electricity by rotating together with the turbine 55.

[0018] The cooler 57 cools the refrigerant that has passed through the turbine 55. The cooler 57 is a condenser or the like when the refrigerant is temporarily liquefied by a chiller or the like.

[0019] The compressor 58 is a pump that pressurizes the refrigerant.

[0020] The nuclear power generation system 50 transfers the heat generated by the reaction of the nuclear fuel in the nuclear reactor 11 (12) to the heat exchanger 52 through the heat conduction part 53. In the heat exchanger 52, the nuclear power generation system 50 heats the refrigerant flowing through the refrigerant circulation means 54 with the heat of the heat conduction part 53. That is, the refrigerant absorbs heat in the heat exchanger 52. Thereby, the heat generated in the nuclear reactor 11 (12) is recovered by the refrigerant. The refrigerant is compressed by the compressor 58 and then heated when passing through the heat exchanger 52, and rotates the turbine 55 with the compressed and heated energy. The refrigerant is then cooled to the reference state by the cooler 57 and supplied to the compressor 58 again.

[0021] As described above, the nuclear power generation system 50 transfers the heat taken out from the nuclear reactor 11 (12) to the refrigerant that becomes the medium for rotating the turbine 55. Thereby, the nuclear reactor 11 (12) and the refrigerant that becomes the medium for rotating the turbine 55 can be isolated, and the risk of contamination of the medium for rotating the turbine 55 can be reduced.

[0022] FIG. 2 is an axial sectional view of the nuclear reactor of the embodiment. FIG. 3 is a perspective view showing the region S in FIG. 2. FIG. 4 is an axial sectional view of the nuclear reactor of the embodiment. FIG. 5 is a perspective view showing an example of the drive mechanism of the control unit of the embodiment.

[0023] As shown in FIGS. 2 to 5, the nuclear reactor 11 includes a fuel section (core) 1, a shielding section 2, a control section 3, a heat conduction section 4, a control rod 5, and a drive mechanism 6.

[0024] As shown in Figures 2 to 4, the fuel section 1 is composed of a plurality of plate-shaped fuel layers 1A. In Embodiment 1, the fuel layers 1A are formed in a disc shape. A plurality of fuel layers 1A are provided and arranged so that their plate surfaces face each other. In this embodiment, the direction in which these plurality of fuel layers 1A are arranged with their plate surfaces facing each other is called the axial direction. Each fuel layer 1A is arranged so that its circular center is aligned with the central axis CL in the axial direction, and its diameter gradually increases from one end and decreases from the center to the other end. Therefore, the fuel section 1 as a whole is formed in a spherical shape. Thus, the fuel section 1 has a spherical part which is part of the sphere.

[0025] Each fuel layer 1A is provided with a circular nuclear fuel section 1Aa in the center, as shown in Figure 3, which is a cross-section of a portion of region S in Figure 2, and a covering section 1Ab that covers the outer circumference of each nuclear fuel section 1Aa. The nuclear fuel section 1Aa consists of numerous pellet-shaped nuclear fuels 1Aaa supported by a support 1Aab. The nuclear fuel 1Aaa can be, for example, uranium dioxide (UO2), a nuclear fuel material, and the support 1Aab can be, for example, graphene as a moderator. Graphene has a structure in which hexagonal lattices made of carbon atoms and their bonds are continuous, and by making the direction of continuous hexagonal lattices the direction of heat transfer, the heat transfer efficiency can be improved. The covering section 1Ab can be, for example, chromium (Cr) to protect the nuclear fuel sections 1Aa. Each fuel layer 1A may be formed as a single circular shape, or it may be formed as a circular shape by a combination of multiple fan shapes such as region S.

[0026] The shielding section 2 surrounds the spherical fuel section 1. The shielding section 2 is made of, for example, graphite and functions as a reflector that reflects radiation (neutrons) irradiated from the nuclear fuel 1Aaa of the fuel section 1, thereby preventing radiation leakage to the outside covering the fuel section 1. As shown in Figures 2 to 4, the shielding section 2 is composed of multiple plate-shaped shielding layers 2A. Each shielding layer 2A is positioned with its circular center aligned with the central axis CL in the axial direction, and its diameter gradually increases from one end and decreases from the center to the other end. Therefore, the shielding section 2 as a whole is formed in a spherical shape to cover the periphery of the fuel section 1. In this way, the shielding section 2 is arranged along the outer shape of the fuel section 1 and has a spherical portion. Furthermore, as shown in Figure 3, which is a cross-section of a part of region S in Figure 2, the main shielding layer 2A is formed in a fan-shaped form that covers the periphery of the fuel layer 1A along its outer circumference. The shielding section 2 houses the fuel section 1 inside a sealed interior, with each shielding layer 2A. To prevent oxidation inside the fuel section 1, it is preferable to fill the sealed interior with an inert gas, such as a nitride gas.

[0027] The control unit 3 is located radially outside the fuel layer 1A and is positioned in the shielding section 2. In Embodiment 1, the control unit 3 is formed in a spherical shape, as shown in Figures 2, 4, and 5. As shown in Figure 2, multiple control units (12 in the embodiment) are arranged around the fuel section 1 in a circumferential direction with the central axis CL as the center, and these multiple units are arranged at equal intervals. Furthermore, as shown in Figure 4, multiple control units 3 are arranged in the axial direction along the central axis CL, following the shape of the spherical portion of the fuel section 1, and these multiple units are arranged at equal intervals from the outer circumference of the fuel section 1. The shielding section 2 that supports this control unit 3 is composed of plate-shaped shielding layers 2A, as described above. As shown in Figure 3, the shielding layer 2A has support holes 2Aa into which the spherical control unit 3 is inserted. The support holes 2Aa are formed in the shape of through holes, depressions, grooves, etc., so that when multiple shielding layers 2A are arranged in a line in the axial direction, they form a sphere, and the spherical control unit 3 is inserted therein. Therefore, the control unit 3 is inserted into the support hole 2Aa and supported by the shielding layer 2A being arranged in the axial direction.

[0028] The control unit 3 has a neutron absorber 3a provided on a part of its spherical outer circumference. The neutron absorber 3a can be made of, for example, boron carbide (B4C). The control unit 3 also has a reflector 3b provided on a part of its spherical outer circumference where the neutron absorber 3a is not provided. The reflector 3b reflects radiation (neutrons) irradiated from the nuclear fuel 1Aaa of the fuel unit 1, and can be made of, for example, graphite.

[0029] The control unit 3 is rotatably supported within the support hole 2Aa in the shielding section 2. As the control unit 3 rotates, the neutron absorber 3a moves closer to or further away from the outer circumference of the fuel section 1. When the neutron absorber 3a moves closer to the fuel section 1, the reactivity of the fuel section 1 decreases, and when the neutron absorber 3a moves further away from the fuel section 1, the reactivity of the fuel section 1 increases. In this way, the control unit 3 can control the reactivity of the fuel section 1, which is the reactor core, and thus control the core temperature of the fuel section 1 by moving the neutron absorber 3a closer to or further away from the fuel section 1. The core temperature is the average core temperature taken outside the shielding section 2 by the heat conduction section 4. Also, as the neutron absorber 3a moves further away from the rotating control unit 3, the reflector 3b moves closer to the outer circumference of the fuel section 1. The reflector 3b moving closer to the fuel section 1 prevents radiation leakage to the outside. In this embodiment, the control unit 3 has a neutron absorber 3a provided in one half of its spherical shape, and a reflector 3b provided in the other half of its spherical shape.

[0030] The rotation of the control unit 3 is driven by the drive mechanism 6. As shown in Figure 5, the drive mechanism 6 is configured such that, for example, in the control unit 3, an operating rod is provided protruding from the outside of the center of the reflector 3b side, with the center O forming each half of the control unit 3 where the neutron absorber 3a and reflector 3b are provided as a reference. The drive mechanism 6 can move the neutron absorber 3a and reflector 3b of the control unit 3 in three dimensions by rotating this operating rod around it as shown by arrow A, or around the center O as shown by arrow B. The operating rod is actuated by, for example, a motor or gear. The arrangement of the drive mechanism 6 is not limited to the above, as long as it can move the neutron absorber 3a and reflector 3b of the control unit 3 in three dimensions. The drive mechanism 6 is biased to rotate so that the neutron absorber 3a of the control unit 3 approaches the circumferential surface of the fuel section 1, and is configured so that if the connection with the control unit 3 is severed by a clutch mechanism or the like, the neutron absorber 3a will automatically move closer to the outer circumference of the fuel section 1. Therefore, the drive mechanism 6 can, for example, automatically move the neutron absorber 3a closer to the circumferential surface of the fuel section 1 in the event of an emergency where the temperature of the fuel section 1 exceeds a set temperature, thereby reducing the reactivity of the fuel section 1. The drive mechanism 6 can also drive individual control units 3. Therefore, the reactor 11 can perform fine-tuned reactivity control at various points in the fuel section 1 by being able to drive individual control units 3.

[0031] The heat conduction section 4 includes a heat conduction support section 4a and a cooling tube 4b. The heat conduction support section 4a surrounds the spherical shielding section 2. The heat conduction support section 4a transmits the heat generated by the nuclear fission reaction of the nuclear fuel in the fuel section 1 to the outside of the shielding section 2 by solid heat conduction. The heat conduction support section 4a can be made of, for example, titanium, nickel, copper, or graphite. Graphite, in particular, can be made of graphene. Although not shown, the heat conduction support section 4a may be composed of multiple plate-shaped heat conduction support layers, similar to the shielding section 2. Each heat conduction support layer is positioned axially with its circular center aligned with the central axis CL, and its diameter gradually increases from one end and decreases from the center to the other end. Therefore, the heat conduction support section 4a as a whole is formed in a spherical shape to surround the fuel section 1. In this way, the heat conduction support section 4a is positioned along the outer shape of the fuel section 1 and has a spherical portion. The cooling tubes 4b are supported by the heat conduction support section 4a and circulate a cooling medium. The cooling medium can be, for example, carbon dioxide (CO2). The cooling medium is not limited to gases; any fluid including liquids is acceptable. Multiple cooling tubes 4b are arranged with one end serving as the cooling medium supply side and the other end serving as the cooling medium discharge side, with their intermediate sections following a trajectory along the spherical heat conduction support section 4a. Multiple cooling tubes 4b form a ring shape with their supply and discharge ends connected outside the reactor 11, leading to the heat exchanger 52 of the nuclear power generation system 50. The supply ends and discharge ends of multiple cooling tubes 4b may be combined into one. Thus, the heat conduction section 4, via the heat conduction support section 4a, transmits the heat generated by the nuclear fission reaction of the nuclear fuel in the fuel section 1 to the outside of the shielding section 2 by solid heat conduction, and recovers this heat in the heat exchanger 52 of the nuclear power generation system 50 via the cooling medium circulating in the cooling tubes 4b.

[0032] The control rod 5 is provided in a way that it can be inserted into and removed from a through-hole 5a that penetrates the fuel section 1 in the axial direction. In this embodiment, the control rod 5 is provided in a way that it can be inserted into and removed from a through-hole 5a formed on the central axis CL. The control rod 5 is made of a neutron absorber. For example, boron carbide (B4C) can be used as the neutron absorber. The control rod 5 is provided so that it can move axially, be inserted into the through-hole in the fuel section 1, or be withdrawn from the through-hole 5a in the fuel section 1, thereby moving closer to or further away from the fuel section 1, which is the reactor core. When the control rod 5 is inserted into the fuel section 1, the reactivity of the fuel section 1 decreases, and when the control rod 5 is withdrawn from the fuel section 1, the reactivity of the fuel section 1 increases. In this way, the control rod 5 can control the reactivity of the fuel section 1 and the core temperature of the fuel section 1 by inserting or withdrawing the neutron absorber into or from the fuel section 1 by sliding the neutron absorber. The control rod 5 has a drive unit (not shown) that drives its sliding movement. The drive unit is biased to move so that the control rod 5 is inserted into the through hole of the fuel section 1, and automatically inserts the control rod 5 into the fuel section 1 if the connection with the control rod 5 is severed by a clutch mechanism or the like. For example, in an emergency when the temperature of the fuel section 1 exceeds a set temperature, the control rod 5 can be automatically inserted into the fuel section 1 to reduce the responsiveness of the fuel section 1.

[0033] Therefore, in the embodiment, the reactor 11 can extract the heat generated by the nuclear fission reaction of the nuclear fuel in the fuel section 1 to the outside through the heat conduction section 4. The heat extracted to the outside is then transferred to the coolant, which rotates the turbine 55. Furthermore, in the embodiment, the reactor 11 has a spherical section in the fuel section 1, which is the core of the reactor. This allows for a small surface area relative to the volume in the spherical section, minimizing the amount of neutrons leaking from the fuel section 1 and improving the economic efficiency of neutrons.

[0034] Figure 6 is an axial cross-sectional view of another example of the reactor of the embodiment.

[0035] The reactor 12 shown in Figure 6 differs from the reactor 11 in that, while the reactor 11 is formed in a spherical shape as a whole, the reactor 12 has a configuration in which a part of the reactor is not spherical but has a spherical section. In the description of this reactor 12, the same reference numerals are used for parts equivalent to those of the reactor 11, and explanations of parts other than those that differ are omitted.

[0036] The reactor 12 specifically includes a fuel section (core) 1, a shielding section 2, a control unit 3, a heat conduction section 4, control rods 5, and a drive mechanism 6. The fuel section 1, shielding section 2, and heat conduction section 4 are formed in a cylindrical shape including hemispherical spherical sections Q at both ends. The control unit 3 is formed in a spherical shape, similar to the reactor 11, and is supported by the shielding section 2. Multiple control units 3 are arranged around the fuel section 1 in a circumferential direction around a central axis CL, and are arranged at equal intervals (see Figure 2). As shown in Figure 6, multiple control units 3 are arranged in the axial direction along the central axis CL, along the shape of the fuel section 1 including the spherical section Q, from the outer circumference of the fuel section 1, and are arranged at equal intervals. The control unit 3 is driven by a drive mechanism 6 (see Figure 5). The control rods 5 are provided in the fuel section 1 so as to be removable from through holes 5a that penetrate the central axis CL.

[0037] In the reactor 12, the hemispherical portions at both ends of the cylindrical shape were described as spherical portions Q, but this is not the only example. For example, although not explicitly shown in the figure, a reactor having spherical portions includes those in which the fuel section 1, shielding section 2, and heat conduction section 4 are formed in an elliptical shape, or a long sphere or flattened ellipse shape like a rugby ball, in the cross-section shown in Figure 6, with a portion forming spherical portions Q. That is, the spherical portions Q include shapes such that, when viewed in an axial cross-section as shown in Figure 6, the diameter at at least one end of the fuel section 1 is smallest, and it gradually increases toward the center in the axial direction. The control units 3 are arranged in multiples at equal intervals from the outer circumference of the fuel section 1 in the axial direction along the central axis CL, following the shape including the spherical portions Q of the fuel section 1, and multiple units are arranged at equal intervals.

[0038] Incidentally, in the reactors 11 and 12 described above, the shielding section 2 may be configured as a space provided between the fuel section 1 and the heat conduction section 4. In this case, the heat conduction support section 4a of the heat conduction section 4 seals and covers the area around the fuel section 1, and the sealed structure of the shielding section 2, which forms a space, may be filled with an inert gas such as nitride gas. Also, in the case of a shielding section 2 that forms a space, the control unit 3 is arranged within that space.

[0039] Thus, the reactors 11 and 12 of the embodiment include a fuel section 1 having a spherical portion, and a spherical control section 3 arranged in a plurality along the spherical portion, with a neutron absorber 3a provided on a part of its outer circumference.

[0040] In this embodiment, the reactors 11 and 12 have a plurality of spherical control units 3 arranged around the fuel section 1 which has a spherical portion. Therefore, in the reactors 11 and 12 of this embodiment, the neutron absorbers 3a of each spherical control unit 3 can be positioned at a constant distance from the outer circumference of the fuel section 1. That is, in the reactors 11 and 12 of this embodiment, the control units 3 can be positioned in a region where the reactivity can be effectively controlled for any part of the outer circumference of the fuel section 1. As a result, according to the reactors 11 and 12 of this embodiment, effective adjustment of the reactivity for the fuel section 1 which has a spherical portion can be performed.

[0041] Furthermore, in the reactors 11 and 12 of the embodiment, the control unit 3 is provided with a neutron absorber 3a in one spherical half and a reflector 3b in the other half.

[0042] According to the reactors 11 and 12 of this embodiment, the reactivity can be adjusted by moving the neutron absorber 3a closer to or further away from the fuel section 1, while the leakage of radiation to the outside can be prevented by moving the reflector 3b closer to the fuel section 1.

[0043] Furthermore, the reactors 11 and 12 of the embodiment further include a drive mechanism 6 that moves the neutron absorber 3a of the control unit 3 closer to or further away from the fuel unit 1.

[0044] According to the reactors 11 and 12 of this embodiment, the drive mechanism 6 allows the spherical control unit 3 to change the orientation and position of the neutron absorber relative to the fuel unit 1 in three dimensions, thereby enabling fine control of the reactivity of the fuel unit 1.

[0045] Furthermore, in the reactors 11 and 12 of the embodiment, the control unit 3 is supported by a shielding unit 2 that surrounds the fuel unit 1 and shields it from radiation emitted from the fuel unit 1.

[0046] According to the reactors 11 and 12 of this embodiment, by placing the control unit 3 in the shielding unit 2, it is possible to shield from radiation irradiated from the fuel unit 1 while effectively adjusting the reactivity with respect to the fuel unit 1.

[0047] Furthermore, in the reactors 11 and 12 of the embodiment, the control unit 3 is supported within the space surrounding the fuel unit 1.

[0048] According to the reactors 11 and 12 of this embodiment, by arranging the control unit 3 in space, the degree of freedom of movement of the control unit 3 for three-dimensionally changing the orientation and position of the neutron absorber relative to the fuel unit 1 can be improved.

[0049] This disclosure encompasses the following inventions: [Invention 1] The spherical fuel section, A spherical control unit is provided, which is arranged in multiple locations around the aforementioned spherical portion and has a neutron absorber on a part of its outer circumference. A nuclear reactor, including one. [Invention 2] The reactor according to Invention 1, wherein the control unit is provided with the neutron absorber in one spherical half and the reflector in the other half. [Invention 3] The reactor according to invention 1 or 2, further comprising a drive mechanism for moving the neutron absorber of the control unit closer to or further away from the fuel unit. [Invention 4] The reactor according to any one of inventions 1 to 3, wherein the control unit is supported by a shielding unit that surrounds the fuel unit and shields it from radiation emitted from the fuel unit. [Invention 5] The reactor according to any one of inventions 1 to 3, wherein the control unit is supported within the space surrounding the fuel section. [Explanation of symbols]

[0050] 1 Fuel section 2 Shielding section 3. Control Unit 3a Neutron absorber 3b Reflector 6. Drive mechanism 11,12 nuclear reactor

Claims

1. The spherical fuel section, A spherical control unit is provided, which is arranged in multiple locations around the aforementioned spherical portion and has a neutron absorber on a part of its outer circumference. A drive mechanism for moving the spherical control unit in three dimensions so as to move the neutron absorber of the control unit closer to or further away from the fuel unit, Includes, The control unit is provided with a neutron absorber in one half of a spherical shape and a reflector in the other half. The center of the halves formed by the neutron absorber and the reflector is used as a reference, and an operating rod extends outward from the center of the reflector side. The drive mechanism moves the neutron absorber and reflector of the control unit in three dimensions by rotating the operating rod around it or around the center. nuclear reactor.

2. The reactor according to claim 1, wherein the control unit is supported by a shielding unit that surrounds the fuel unit and shields it from radiation emitted from the fuel unit.

3. The reactor according to claim 1, wherein the control unit is supported within the space surrounding the fuel section.

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