Drive mechanism, control rod drive device and nuclear reactor

Abstract

To reliably and easily disassemble and assemble a rack gear and a pinion gear.SOLUTION: A drive mechanism 5 includes: a rack gear 5A; a pinion gear 5B that meshes with the rack gear 5A; a positioning member 5D fixed to a portion of the rack gear 5A where no rack teeth 5Ab is located; and multiple contact members 5E provided along the rotational direction of the pinion gear 5B. When at least one of the rack gear 5A or the pinion gear 5B is moved in the relative movement direction when the rack gear 5A and the pinion gear 5B are engaged, the rotational position of a pinion tooth 5Bb of the pinion gear 5B is determined by the contact between the positioning member 5D and the contact member 5E as the meshing position with the rack tooth 5Ab of the rack gear 5A.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present disclosure relates to a drive mechanism, a control rod drive device, and a nuclear reactor. [Background technology]

[0002] In a pressurized water reactor (PWR), the number of neutrons generated in the reactor core is adjusted by absorbing them with control rods, thereby controlling the reactor power. The control rods are inserted and removed from the core by a control rod drive mechanism (CRDM).

[0003] BACKGROUND ART As a control rod drive device for a pressurized water reactor, for example, a rack and pinion drive mechanism disclosed in Patent Document 1 is known. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2022-023345 Summary of the Invention [Problem to be solved by the invention]

[0005] In a rack and pinion drive mechanism such as that shown in Patent Document 1, when the rack gear and pinion gear are disassembled and reassembled during maintenance, there is a risk that they will not mesh with each other if the rotation angle of the pinion gear is misaligned with respect to the rack gear.If this drive mechanism is applied to a control rod drive device, it is difficult to manage the meshing of all of the drive mechanisms that drive the many control rods, and since maintenance is performed in a radiation area, it is desirable to reduce the intervention of workers.

[0006] The present disclosure is devised to solve the above-mentioned problems, and aims to provide a drive mechanism, a control rod drive device, and a nuclear reactor that enable reliable and easy disassembly and assembly of a rack gear and a pinion gear. [Means for solving the problem]

[0007] In order to achieve the above-mentioned object, a drive mechanism according to one aspect of the present disclosure includes a rack gear, a pinion gear that meshes with the rack gear, a positioning member fixed to a portion of the rack gear that does not have rack teeth, and a plurality of abutment members provided along the rotational direction of the pinion gear, wherein when at least one of the rack gear or the pinion gear is moved in the direction of relative movement when the rack gear and the pinion gear mesh, the positioning member abuts against the abutment member, causing the rotational position of the pinion teeth of the pinion gear to mesh with the rack teeth of the rack gear.

[0008] In order to achieve the above-mentioned object, a control rod drive device according to one aspect of the present disclosure includes the above-mentioned drive mechanism and a drive shaft to which a control rod that can be raised and lowered by the drive mechanism and can be inserted into and removed from the reactor core is connected.

[0009] In order to achieve the above-mentioned object, a nuclear reactor according to one aspect of the present disclosure includes the above-mentioned control rod drive mechanism, a reactor core controlled by the control rod drive mechanism, and a reactor vessel in which the control rod drive mechanism and the reactor core are disposed. [Effects of the Invention]

[0010] According to the present disclosure, the rack gear and the pinion gear can be reliably and easily disassembled and assembled. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a schematic diagram showing a nuclear reactor according to an embodiment. [Figure 2] FIG. 2 is a schematic side view showing a control rod drive mechanism according to the embodiment. [Figure 3]FIG. 3 is a partially enlarged cross-sectional view showing the control rod drive mechanism of the embodiment. [Figure 4] FIG. 4 is a schematic perspective view showing a cable of an electromagnetic coil in a control rod drive mechanism according to the embodiment. [Figure 5] FIG. 5 is a schematic perspective view showing a drive mechanism according to the embodiment. [Figure 6] FIG. 6 is a schematic diagram showing the basic operation of the driving mechanism of the embodiment. [Figure 7] FIG. 7 is a schematic diagram showing the basic operation of the driving mechanism of the embodiment. [Figure 8] FIG. 8 is a schematic diagram showing the basic operation of the driving mechanism of the embodiment. [Figure 9] FIG. 9 is a schematic diagram showing the operation of the driving mechanism of the embodiment. [Figure 10] FIG. 10 is a schematic diagram showing the operation of the driving mechanism of the embodiment. [Figure 11] FIG. 11 is a schematic diagram showing the operation of the driving mechanism of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Note that the present invention is not limited to these embodiments. Furthermore, the components in the following embodiments include those that are easily replaceable by those skilled in the art, or those that are substantially identical.

[0013] FIG. 1 is a schematic diagram showing a nuclear reactor according to an embodiment.

[0014] The nuclear reactor 100 shown in FIG. 1 is a pressurized water reactor used in pressurized water nuclear power plants. In pressurized water nuclear power plants, the reactor 100 heats light water, which serves as a primary coolant, and then sends the high-temperature primary coolant to a steam generator (not shown). In the steam generator, the high-temperature primary coolant is evaporated by heat exchange with a secondary coolant, and the evaporated secondary coolant steam is sent to a turbine to drive a generator, thereby generating electricity. The high-temperature primary coolant that flows into the steam generator is cooled by heat exchange with the secondary coolant, returned to the reactor 100, and heated to a high temperature again. Meanwhile, the secondary coolant steam used in the turbine to generate power is cooled in a condenser, returned to a liquid state, and returned to the steam generator via a condenser pipe, where it exchanges heat with the primary coolant and becomes steam again.

[0015] The reactor 100 has a reactor vessel 101, which is a pressure vessel. The reactor vessel 101 includes a reactor vessel main body 101A and a reactor vessel lid 101B fixed thereto by a plurality of stud bolts and nuts. The reactor vessel lid 101B is positioned and fixed to the reactor vessel main body 101A by positioning pins 101Ac formed on the opening edge of the reactor vessel main body 101A. The reactor vessel main body 101A is provided with an outlet nozzle 101Aa that sends primary coolant to a steam generator and an inlet nozzle 101Ab through which the primary coolant cooled by heat exchange with secondary coolant in the steam generator is returned. A control rod drive mechanism 1 and fuel assemblies 102 are housed inside the reactor vessel 101. The control rod drive mechanism 1, details of which will be described later, is located in the upper part of the reactor vessel 101. The fuel assemblies 102 are nuclear fuel material and are located in a core 103 located in the lower part of the reactor vessel 101. Although not shown, the fuel assemblies 102 are configured vertically in a long grid-like manner, with many fuel rods bundled together by support grids. Many of these fuel assemblies 102 are arranged in a state where they stand upright in the core 103, with their upper ends facing upward and their lower ends facing downward. Control rods 104 are also arranged inside the core 103. The control rods 104 are inserted into the many fuel assemblies 102 from above and are removable. The control rods 104 are made of a control material that absorbs neutrons. By inserting them into the fuel assemblies 102, they can absorb neutrons associated with the nuclear fission reaction of the nuclear fuel material in the fuel assemblies 102 and prevent the reactor from going critical. On the other hand, by removing the control rods 104 from the inside of the fuel assemblies 102, they can increase the number of neutrons in the reactor 100 and increase the reaction from criticality to rated power. Furthermore, inside the reactor vessel 101, between the reactor core 103 and the control rod drive mechanism 1, a large number of control rod guide tubes 105 for guiding the control rods 104 as they move up and down are arranged.

[0016] Fig. 2 is a schematic side view showing a control rod drive mechanism of an embodiment. Fig. 3 is a partially enlarged cross-sectional view showing a control rod drive mechanism of an embodiment. Fig. 4 is a schematic perspective view showing a cable of an electromagnetic coil in a control rod drive mechanism of an embodiment. Fig. 5 is a schematic perspective view showing a drive mechanism of an embodiment.

[0017] As described above, the control rod drive mechanism 1 is housed inside the reactor vessel 101. The control rod drive mechanism 1 moves the control rod 104 in the vertical direction, thereby controlling the insertion and removal of the control rod 104 into and from the fuel assembly 102. The control rod drive mechanism 1 has a drive motor (drive unit) 2, an electromagnetic clutch 3, a reduction mechanism 4, a drive mechanism 5, a drive shaft 6, and a biasing means 7.

[0018] As shown in Fig. 2, the drive motor 2 is disposed on the upper side of the control rod drive mechanism 1. As shown in Fig. 3, the drive motor 2 has a rotor 2A and a stator 2B.

[0019] The rotor 2A is provided to extend in the vertical direction on a central axis CL that also extends in the vertical direction. The vertical direction along which the central axis CL extends is also referred to as the axial direction. The rotor 2A is provided to be rotatable about the central axis CL relative to a case 11 that houses the drive motor 2 and the electromagnetic clutch 3. The rotor 2A is made of a magnetic material. The rotor 2A has salient poles 2Aa. The salient poles 2Aa are protrusions that extend radially inward and away from the central axis CL on the rotor 2A, and multiple salient poles 2Aa are provided at intervals in the circumferential direction around the central axis CL. In addition, the rotor 2A is formed with a hollow portion 2Ab consisting of a through hole that penetrates in the axial direction on the central axis CL.

[0020] The stator 2B is formed in a cylindrical shape centered on the central axis CL so as to surround the rotor 2A. The stator 2B is made of a magnetic material. The stator 2B has a plurality of core portions 2Ba that extend radially inward toward the central axis CL and face the rotor 2A, and are spaced apart in the circumferential direction around the central axis CL. In the stator 2B, an electromagnetic coil 2C is wound around each core portion 2Ba via an insulating material (not shown). Furthermore, the electromagnetic coil 2C of the stator 2B is formed of an inorganic insulated cable 8 shown in FIG. 4.

[0021] 4, the inorganic insulated cable 8 is also called an MI cable (Mineral Insulated Cable), and has a core wire 8a surrounded by a metal sheath 8b, with an inorganic insulator 8c such as magnesium oxide filled between the core wire 8a and the metal sheath 8b. In this embodiment, the inorganic insulated cable 8 has the metal sheath 8b made of a heat-resistant and corrosion-resistant alloy, such as Inconel 690 (registered trademark), which has excellent heat resistance and corrosion resistance.

[0022] In this drive motor 2, the magnetic field generated by passing a current through the electromagnetic coil 2C of the stator 2B attracts the salient poles 2Aa of the rotor 2A to the core 2Ba around which the electromagnetic coil 2C is wound, causing the rotor 2A to rotate around the central axis CL. In other words, the drive motor 2 does not use permanent magnets, but constitutes a reluctance motor in which the rotor 2A made of a magnetic material is rotated by the magnetic field generated in the electromagnetic coil 2C of the stator 2B.

[0023] As shown in FIG. 3, the electromagnetic clutch 3 has a first magnetic pole 3A, a second magnetic pole 3B, and an electromagnetic coil 3C.

[0024] The first magnetic pole 3A is made of a magnetic material and is fixed to the rotor 2A of the drive motor 2. Therefore, the first magnetic pole 3A rotates in conjunction with the rotation of the rotor 2A of the drive motor 2. The first magnetic pole 3A has an attraction portion 3Aa formed at its lower axial end that protrudes radially outward and has a flat lower end surface.

[0025] The second magnetic pole 3B is made of a magnetic material, can be magnetically attracted to the first magnetic pole 3A, and is provided so as to be movable in the axial direction relative to the case 11. The second magnetic pole 3B is also provided so as to be rotatable about the central axis CL relative to the case 11. The second magnetic pole 3B has an attraction portion 3Ba at its upper axial end that protrudes radially outward and has a flat upper end surface. The attraction portion 3Ba is provided so that its upper end surface faces the lower end surface of the attraction portion 3Aa of the first magnetic pole 3A. The lower end of the second magnetic pole 3B is connected to the reduction mechanism 4.

[0026] The first magnetic pole 3A and the second magnetic pole 3B are formed with a hollow portion 3D consisting of a through hole that penetrates in the axial direction on the central axis CL. The hollow portion 3D is formed with an inner diameter equivalent to that of the hollow portion 2Ab formed in the rotor 2A of the drive motor 2 and communicates with the hollow portion 2Ab.

[0027] The electromagnetic coil 3C is fixed to the case 11 and is provided so as to generate a magnetic field in the axial direction of the first magnetic pole 3A and the second magnetic pole 3B. The electromagnetic coil 3C is made up of an inorganic insulated cable 8 shown in FIG.

[0028] When a current flows through the electromagnetic coil 3C of the electromagnetic clutch 3, a magnetic field is generated in the axial direction, which acts on the attracting portion 3Aa of the first magnetic pole 3A and the attracting portion 3Ba of the second magnetic pole 3B. When the magnetic field acts on the attracting portion 3Aa and the attracting portion 3Ba, an attractive force is generated between them, and the second magnetic pole 3B is attracted to and attracted to the first magnetic pole 3A. When the second magnetic pole 3B is attracted to the first magnetic pole 3A, the rotation of the drive motor 2 is transmitted to the reduction mechanism 4 and the drive mechanism 5 via the first magnetic pole 3A and the second magnetic pole 3B. On the other hand, when a current is not flowing through the electromagnetic coil 3C of the electromagnetic clutch 3, the magnetic field does not act on the attracting portion 3Aa of the first magnetic pole 3A and the attracting portion 3Ba of the second magnetic pole 3B, and the attraction between the first magnetic pole 3A and the second magnetic pole 3B is released. When the attraction between the first magnetic pole 3A and the second magnetic pole 3B is released, the rotation of the drive motor 2 is no longer transmitted to the speed reduction mechanism 4 and the drive mechanism 5, and the speed reduction mechanism 4 and the drive mechanism 5 become free to rotate.

[0029] The reduction mechanism 4 is disposed between the electromagnetic clutch 3 and the drive mechanism 5. The rotation about the central axis CL of the drive motor 2 is transmitted to the reduction mechanism 4 via the electromagnetic clutch 3, and the reduction mechanism 4 transmits this rotation to the drive mechanism 5 while reducing the rotation speed. Although not shown in the figure, the reduction mechanism 4 is configured by, for example, multiple reduction units, each made up of a planetary gear mechanism, stacked in the axial direction. With this configuration, the reduction mechanism 4 has a hollow portion that penetrates in the axial direction at its center. The hollow portion consists of a through-hole that penetrates in the axial direction on the central axis CL, and is formed with an inner diameter equivalent to that of the hollow portion 3D formed in the electromagnetic clutch 3, and communicates with the hollow portion 3D.

[0030] With the electromagnetic clutch 3 in an attracted state, the drive mechanism 5 is driven by the drive motor 2 to raise and lower the drive shaft 6. As shown in FIG. 5, the drive mechanism 5 has a rack gear 5A, a pinion gear 5B, a guide portion 5C, a positioning member 5D, and a contact member 5E.

[0031] The rack gear 5A is formed to extend continuously and linearly in the vertical direction (axial direction) so as to be inserted into the hollow portions 2Ab and 3D. The rack gear 5A has a large number of rack teeth 5Ab formed on the plate surface of a rack body 5Aa formed in the shape of a long plate, along the vertical direction of the rack gear. In the rack gear 5A of this embodiment, the rack teeth 5Ab are formed on one plate surface. The rack teeth 5Ab are not provided on the upper portion of the rack body 5Aa. The rack gear 5A is provided so as to be able to move up and down in the axial direction by a guide portion 5C (first guide portion 5CA). The lower end of the rack gear 5A is connected to the drive shaft 6.

[0032] The pinion gear 5B has pinion teeth 5Bb formed along the outer circumferential surface of a disk-shaped pinion body 5Ba. The pinion gear 5B has the pinion body 5Ba fixed to a rotation shaft 5Bc extending in a direction perpendicular to the central axis CL. The rotation of the drive motor 2 is transmitted to the pinion gear 5B via an electromagnetic clutch 3 and a reduction mechanism 4. In this embodiment, the reduction mechanism 4 is connected to the rotation shaft 5Bc via an axis conversion mechanism (not shown) for transmitting the rotation to the rotation shaft 5Bc perpendicular to the central axis CL, since the rotation about the central axis CL of the drive motor 2 is transmitted to the reduction mechanism 4. The pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab of the rack gear 5A. Therefore, when the rotation of the drive motor 2 is transmitted to the pinion gear 5B, the rack gear 5A moves up and down along the axial direction. The pinion gear 5B is provided so as to be movable up and down in the axial direction by a guide portion 5C (second guide portion 5CB). In Fig. 5, the pinion gear 5B is shown moved to a position above the position where it meshes with the rack gear 5A.

[0033] The guide portion 5C has a first guide portion 5CA that guides the vertical movement of the rack gear 5A, and a second guide portion 5CB that guides the vertical movement of the pinion gear 5B.

[0034] The first guide portion 5CA has a slider 5CAa and a slide rail 5CAb. The slider 5CAa does not have rack teeth 5Ab and is fixed to each of the opposing plate surfaces of the rack body 5Aa of the rack gear 5A. The slide rail 5CAb is formed to extend continuously linearly in the up-down direction (axial direction) parallel to the rack gear 5A. The slide rail 5CAb is fixed to the reactor vessel body 101A of the reactor vessel 101. The slide rail 5CAb is assembled to the slider 5CAa so that the slider 5CAa can move up and down in the axial direction. Therefore, the first guide portion 5CA guides the rack gear 5A to which the slider 5CAa is fixed so that the rack gear 5A can move up and down in the axial direction via the slide rail 5CAb. Furthermore, the first guide portion 5CA maintains the meshing distance of the rack gear 5A meshing with the pinion gear 5B by restricting movement of the slider 5CAa in directions other than the axial direction using the slide rail 5CAb.

[0035] The second guide portion 5CB has a support rail 5CBa. The support rail 5CBa is formed to extend continuously and linearly in the up-down direction (axial direction) parallel to the rack gear 5A. A pair of support rails 5CBa are provided to sandwich the rotation shaft 5Bc of the pinion gear 5B. The pair of support rails 5CBa are provided at both ends of the rotation shaft 5Bc that penetrates the pinion gear 5B. Therefore, the second guide portion 5CB guides the pinion gear 5B via the support rails 5CBa so that it can move up and down in the axial direction. Furthermore, the second guide portion 5CB maintains the meshing distance of the pinion gear 5B meshing with the rack gear 5A by restricting movement of the pinion gear 5B in any direction other than the axial direction using the support rails 5CBa.

[0036] In this way, the guide portion 5C guides the vertical movement of the rack gear 5A and the pinion gear 5B, and maintains the positional relationship between the rack gear 5A and the pinion gear 5B so as to maintain an meshing distance E (see FIG. 9(a)) between the rack teeth 5Ab of the rack gear 5A and the pinion teeth 5Bb of the pinion gear 5B. Here, the meshing distance E between the rack gear 5A and the pinion gear 5B is, for example, the distance between the rack body 5Aa of the rack gear 5A and the pinion body 5Ba of the pinion gear 5B as shown in FIG. 9(a) so that the rack teeth 5Ab and the pinion teeth 5Bb mesh with each other so that the rotation of the pinion gear 5B is transmitted to the rack gear 5A, and preferably is the distance such that the contact points of the rack teeth 5Ab and the pinion teeth 5Bb are on a common tangent.

[0037] The positioning member 5D is attached to the rack gear 5A. The positioning member 5D is rod-shaped, with a base end 5Da fixed above the rack body 5Aa, which is the portion not having the rack teeth 5Ab, and a tip end 5Db extending toward the pinion gear 5B. The tip end 5Db of the positioning member 5D is connected to the base end 5Da via a shaft 5Dc, and is formed so as to bend in the vertical direction in which the rack gear 5A and the pinion gear 5B move up and down (see FIG. 8(b)). The positioning member 5D is biased by an elastic force such as a spring so that the tip end 5Db bends relative to the base end 5Da when an external force is applied and returns to a straight horizontal position when the external force is removed. The positioning member 5D has a length such that when the rack gear 5A and the pinion gear 5B are in the meshing interval E relationship, the tip of the tip portion 5Db does not reach the rotation center S of the rotation shaft 5Bc of the pinion gear 5B.

[0038] The abutment member 5E is provided on the pinion gear 5B. The abutment member 5E is fixed to the pinion body 5Ba and formed in a rod shape extending parallel to the direction of extension of the rotation center S of the rotation shaft 5Bc. A plurality of abutment members 5E (eight in this embodiment) are provided at equal intervals along the rotation direction of the pinion gear 5B, centered on the rotation shaft 5Bc. If the number of abutment members 5E is B and the number of pinion teeth 5Bb is A, then A > B, A and B are natural numbers, and the relationship B × α = A is satisfied, where α is a natural number. The abutment member 5E moves up and down together with the pinion gear 5B and rotates around the rotation shaft 5Bc together with the pinion gear 5B. The abutment member 5E is provided so as to be able to abut against the tip end 5Db of the positioning member 5D within the range in which the positioning member 5D extends when the pinion gear 5B moves up and down. Because the positioning member 5D is provided in a portion of the rack gear 5A that does not have rack teeth 5Ab, the abutting member 5E abuts against the positioning member 5D in the portion that does not have rack teeth 5Ab. When the rack gear 5A and the pinion gear 5B are in the relationship of meshing interval E, the positioning member 5D has a length such that the tip of the tip portion 5Db does not reach the rotation center S of the rotation shaft 5Bc of the pinion gear 5B. Therefore, the abutting member 5E, which is located closer to the rack gear 5A than the rotation center S, abuts against the tip portion 5Db of the positioning member 5D. When the abutting member 5E abuts against the positioning member 5D, the pinion gear 5B rotates around the rotation shaft 5Bc.

[0039] The drive shaft 6 is connected to the lower end of the rack gear 5A of the drive mechanism 5 and, as shown in FIG. 2, is inserted into the control rod guide tube 105. The drive shaft 6 may be configured as a rack gear 5A. Therefore, the drive shaft 6 is provided so as to be able to move up and down in the axial direction on the central axis CL relative to the case 11. During the up and down movement, the drive shaft 6 is inserted through a hollow portion 3D formed in the first magnetic pole 3A and the second magnetic pole 3B of the electromagnetic clutch 3, a hollow portion 2Ab formed in the rotor 2A, and a hollow portion of the reduction mechanism 4. The drive shaft 6, which is connected to the rack gear 5A or configured as the rack gear 5A, moves up and down in the vertical direction by the drive mechanism 5 and the control rod drive device 1. The control rod 104 is connected to the lower end of the drive shaft 6.

[0040] Therefore, when the electromagnetic clutch 3 is attracted and the transmission of driving force from the drive motor 2 is connected, the drive mechanism 5 and the control rod drive device 1 receive rotation in one direction from the drive motor 2, causing the drive shaft 6 (control rod 104) to rise. When the electromagnetic clutch 3 is attracted and the transmission of driving force from the drive motor 2 is connected, the drive mechanism 5 and the control rod drive device 1 receive rotation in the other direction from the drive motor 2, causing the drive shaft 6 (control rod 104) to fall. When the electromagnetic clutch 3 is attracted and the drive mechanism 5 and the drive motor 2 are connected, the drive mechanism 5 and the control rod drive device 1 hold the drive shaft 6 (control rod 104) at a predetermined raised or lowered position when the drive motor 2 is not driven. Furthermore, when the electromagnetic clutch 3 is released from attraction and the transmission of driving force from the drive motor 2 is cut off, the drive mechanism 5 and the control rod drive device 1 are free to rotate, allowing the drive shaft 6 to descend freely and the control rod 104 to fall freely together with the drive shaft 6. Therefore, by disengaging the electromagnetic clutch 3, the scram action of the control rod 104 falling freely is compensated for, and the control rod 104 is inserted into the fuel assembly 102, suppressing the nuclear fission reaction of the nuclear fuel material in the fuel assembly 102 and preventing it from reaching a critical state.

[0041] As shown in Fig. 2 , in this embodiment, the biasing means 7 is provided in the control rod guide tube 105. The biasing means 7 is provided inside the control rod guide tube 105 and constitutes a compression spring that constantly biases the drive shaft 6 inserted through this control rod guide tube 105 downward toward the core 103. The biasing means 7, which is a compression spring, is provided such that its upper end is caught in the engagement portion 105a at the upper end inside the control rod guide tube 105 and its lower end is caught in the engagement portion 6a of the drive shaft 6 inside the control rod guide tube 105. Therefore, when the electromagnetic clutch 3 is released from attraction and the transmission of driving force from the drive motor 2 is cut off, the biasing means 7 assists the free downward movement of the drive shaft 6 and assists the free fall of the control rod 104 together with the drive shaft 6. When the electromagnetic clutch 3 is in the released state, a load is generated due to the meshing of the reduction mechanism 4 and the drive mechanism 5, but the biasing means 7 resists this load and assists the free descent of the drive shaft 6, thereby assisting the free fall of the control rod 104 together with the drive shaft 6. In the case of a nuclear reactor for a ship, the action of the biasing means 7 functions to reliably insert the control rod 104 into the fuel assembly 102 even in the event of the reactor (hull) tilting, swaying, or capsizing.

[0042] The operation of the drive mechanism 5 will now be described.

[0043] The basic operation of the drive mechanism 5 is shown in Figures 6, 7, and 8. In Figures 6 to 8, the positioning member 5D (rack gear 5A) is fixed, and the abutting member 5E (pinion gear 5B) is guided by the guide portion 5C and descends as shown by arrow D.

[0044] In the basic operation shown in FIG. 6, when the positioning member 5E abuts against the positioning member 5D below a reference line L that is perpendicular to the rotation axis 5Bc and passes through the rotation center S of the rotation axis 5Bc and the center of the abutting member 5E, as shown in FIG. 6(a), a force M is generated in the normal direction of the abutting member 5E at the contact point between the positioning member 5D and the abutting member 5E. Because the abutting member 5E abuts against the positioning member 5D below the reference line L, the force M acts to lift the abutting member 5E upward. As a result, a moment R that rotates the abutting member 5E clockwise around the rotation axis 5Bc in FIG. 6(a) is generated in the abutting member 5E. Then, as shown in FIG. 6(b), the abutting member 5E rotates clockwise together with the pinion gear 5B, as if pushed up by the positioning member 5D. As a result of this further clockwise rotation, the abutting member 5E moves above the rotation center S of the rotation axis 5Bc. Eventually, as shown in FIG. 6(c), the contact member 5E reaches a position beyond the length of the positioning member 5D, separates from the tip of the positioning member 5D, and continues to descend, but stops rotating together with the pinion gear 5B.

[0045] In the basic operation shown in Fig. 7, when the positional relationship is such that the abutting member 5E abuts on the positioning member 5D above the reference line L as shown in Fig. 7(a), the force M acts to lower the abutting member 5E because the abutting member 5E abuts on the positioning member 5D above the reference line L. As a result, a moment R is generated in the abutting member 5E, causing it to rotate counterclockwise in Fig. 7(a) around the rotation axis 5Bc. Then, as shown in Fig. 7(a), the abutting member 5E rotates counterclockwise together with the pinion gear 5B, being pushed down by the positioning member 5D. Eventually, as shown in Fig. 7(b), the abutting member 5E reaches a position where the length of the positioning member 5D does not reach the tip of the positioning member 5D, and it separates from the tip of the positioning member 5D and continues to descend, but stops rotating together with the pinion gear 5B.

[0046] In the basic operation shown in FIG. 8, when the abutting member 5E abuts against the positioning member 5D on the reference line L as shown in FIG. 8(a), the force M is along the reference line L and does not act to move the abutting member 5E up or down. Therefore, no moment R is generated in the abutting member 5E to rotate about the rotation axis 5Bc. Then, the abutting member 5E descends together with the pinion gear 5B, and the tip 5Db of the positioning member 5D is bent downward (in the direction of arrow K in FIG. 8(b)), as shown in FIG. 8(b). Then, the abutting member 5E abuts against the positioning member 5D above the reference line L, and a moment R is generated in the abutting member 5E to rotate counterclockwise around the rotation axis 5Bc in FIG. 8(b). Then, the abutting member 5E rotates counterclockwise together with the pinion gear 5B, being pushed down by the positioning member 5D, as shown in FIG. 8(b). 8(c), the contact member 5E reaches a position beyond the reach of the positioning member 5D, separates from the tip of the positioning member 5D, and continues to descend, but stops rotating together with the pinion gear 5B. Meanwhile, the positioning member 5D returns to a linear shape due to its elastic force.

[0047] The operation of the drive mechanism 5 is shown in Figures 9, 10 and 11. In Figures 9 to 11, the rack gear 5A is fixed, and the pinion gear 5B is guided downward by the guide portion 5C in the same manner as in the basic operation.

[0048] In the operation shown in Fig. 9, when the pinion gear 5B descends, one of the contact members 5E comes into contact with the positioning member 5D of the rack gear 5A. The operation shown in Fig. 9 corresponds to the case where the contact member 5E comes into contact with the positioning member 5D below the reference line L, as in the basic operation shown in Fig. 6. Therefore, as shown in Fig. 9(a), the pinion gear 5B rotates clockwise around the rotation axis 5Bc due to the generation of moment R. Thereafter, as shown in Figs. 9(b) and 9(c), the pinion gear 5B further descends and rotates further clockwise. Eventually, the pinion gear 5B reaches a position where the contact member 5E is no longer within the length of the positioning member 5D, and then separates from the tip of the positioning member 5D. The pinion gear 5B continues to descend, but then stops rotating. The rotation angle position at which the rotation of the pinion gear 5B stops, i.e., the rotation angle position of the abutting member 5E' that has reached a position beyond the reach of the positioning member 5D, is the rotation angle position at which the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab of the rack gear 5A as the pinion gear 5B further descends. The rotation angle position at which the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab of the rack gear 5A can be set by the abutting member 5E being positioned in a positional relationship that matches the rotation angle of the pinion teeth 5Bb while satisfying the relationship of

[0038] with respect to the number of teeth of the pinion teeth 5Bb, the meshing interval E between the rack teeth 5Ab of the rack gear 5A and the pinion teeth 5Bb of the pinion gear 5B that is maintained by the guide portion 5C, and the length of the positioning member 5D.

[0049] The operation shown in Fig. 10 corresponds to the case where the contact member 5E contacts the positioning member 5D above the reference line L, as in the basic operation shown in Fig. 7. Therefore, as shown in Fig. 10(a), the pinion gear 5B rotates counterclockwise around the rotation axis 5Bc due to the generation of moment R. Then, as shown in Fig. 10(a), the pinion gear 5B stops rotating because the contact member 5E reaches a position where the length of the positioning member 5D does not reach the pinion gear 5B and moves away from the tip of the positioning member 5D, as shown in Fig. 7(b). Then, the pinion gear 5B further descends, and the contact member 5E' (see Fig. 10(b)) next to the contact member 5E that first moved away from the tip of the positioning member 5D contacts the positioning member 5D. Then, the pinion gear 5B assumes a position where the abutment member 5E' is in the same position as in Figure 9(b), and continues through (c) and (d) to become the abutment member 5E' in Figure 9, and as it descends further, it reaches a rotational angle position where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab of the rack gear 5A.

[0050] The operation shown in Fig. 11 corresponds to the case where the contact member 5E contacts the positioning member 5D at the reference line L, as in the basic operation shown in Fig. 8. Therefore, as shown in Fig. 11(b), the pinion gear 5B rotates counterclockwise around the rotation axis 5Bc due to the generation of moment R. Then, as shown in Fig. 11(c), the pinion gear 5B stops rotating because the contact member 5E reaches a position where the length of the positioning member 5D does not reach the pinion gear 5B and moves away from the tip of the positioning member 5D, as shown in Fig. 8(c). Then, the pinion gear 5B further descends, and the contact member 5E' next to the contact member 5E that first moved away from the tip of the positioning member 5D contacts the positioning member 5D. Then, the pinion gear 5B becomes the contact member 5E' of the operation shown in FIG. 9, and as it further descends, it reaches a rotational angle position where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab of the rack gear 5A.

[0051] In the drive mechanism 5 of the above-described embodiment, the rack gear 5A is fixed in its vertical movement and the pinion gear 5B is lowered. However, this is not limited to this. For example, even if the rack gear 5A is raised while the pinion gear 5B is fixed in its vertical movement, the pinion gear 5B will be positioned at a rotational angle where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab. Also, even if the configuration is turned upside down and the rack gear 5A is fixed in its vertical movement and the pinion gear 5B is lowered, or even if the rack gear 5A is raised while the pinion gear 5B is fixed in its vertical movement, the pinion gear 5B will be positioned at a rotational angle where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab. Also, even if both the pinion gear 5B and the rack gear 5A are raised or lowered so that they approach each other, the pinion gear 5B will be positioned at a rotational angle where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab. Furthermore, for example, the movement direction of the rack gear 5A and pinion gear 5B is not limited to vertical movement, and movement in any other direction will similarly result in a rotation angle position where the pinion teeth 5Bb of the pinion gear 5B mesh with the rack teeth 5Ab.

[0052] Here, in the reactor 100 of the embodiment, in the reactor vessel 101, the rack gear 5A is provided in the reactor vessel main body 101A, and at least the pinion gear 5B is provided in the reactor vessel lid 101B, and at least the pinion gear 5B is configured to be detachable from the reactor vessel main body 101A together with the reactor vessel lid 101B. Therefore, in the reactor 100 of the embodiment, the pinion gear 5B can be detached from the rack gear 5A when the reactor vessel lid 101B is detached from the reactor vessel main body 101A, and the pinion gear 5B can be attached to the rack gear 5A when the reactor vessel lid 101B is attached to the reactor vessel main body 101A. In the reactor 100 of the embodiment, the pinion gear 5B of the drive mechanism 5 (control rod drive device 1) can be disassembled and assembled together with the reactor vessel lid 101B.

[0053] Here, the guide unit 5C includes a positioning pin 101Ac formed on the edge of the opening of the reactor vessel body 101A in the reactor 100. The positioning pin 101Ac guides the assembly of the reactor vessel lid 101B to the reactor vessel body 101A and aligns the reactor vessel lid 101B to the reactor vessel body 101A. Meanwhile, a first guide unit 5CA of the guide unit 5C guides the pinion gear 5B and aligns the pinion gear 5B to the rack gear 5A. The pinion gear 5B is provided on the reactor vessel lid 101B. Therefore, when the positioning pin 101Ac is used to align the reactor vessel lid 101B to the reactor vessel body 101A, the first guide unit 5CA can align the pinion gear 5B to the rack gear 5A in multiple control rod drive devices 1. With this configuration, simply by assembling reactor vessel lid 101B to reactor vessel main body 101A, the meshing positions of pinion gears 5B and rack gears 5A of the multiple control rod drive mechanisms 1 can be properly aligned and fitted together.

[0054] In this way, the drive mechanism 5 of the embodiment includes a rack gear 5A, a pinion gear 5B that meshes with the rack gear 5A, a positioning member 5D fixed to a portion of the rack gear 5A that does not have rack teeth 5Ab, and a plurality of abutment members 5E provided along the rotational direction of the pinion gear 5B. When at least one of the rack gear 5A or the pinion gear 5B is moved in the direction of relative movement when the rack gear 5A and the pinion gear 5B mesh, the positioning member 5D abuts against the abutment member 5E, causing the rotational position of the pinion teeth 5Bb of the pinion gear 5B to become a meshing position with the rack teeth 5Ab of the rack gear 5A.

[0055] According to this drive mechanism 5, by moving at least one of the rack gear 5A and the pinion gear 5B using the positioning member 5D and the abutting member 5E, the rotational position of the pinion teeth 5Bb of the pinion gear 5B can be set to a position where the pinion teeth 5Bb mesh with the rack teeth 5Ab of the rack gear 5A. As a result, the drive mechanism 5 of this embodiment allows the rack gear 5A and the pinion gear 5B to be reliably and easily disassembled and assembled.

[0056] In the driving mechanism 5 of the embodiment, the positioning member 5D is configured to be bendable so that it can be restored by elastic force.

[0057] According to this drive mechanism 5, the positioning member 5D is configured to be bendable so that it can return to its original position by elastic force, and therefore, when the positioning member 5D comes into contact with the abutting member 5E, the positioning member 5D bends, which shifts the contact point between the abutting member 5E and the positioning member 5D, generating a rotation moment R of the pinion gear 5B and preventing excessive load from being applied to the positioning member 5D and the abutting member 5E. As a result, the drive mechanism 5 of this embodiment can smoothly rotate the pinion gear 5B and prevent damage to the members.

[0058] Furthermore, the drive mechanism 5 of the embodiment includes a guide portion 5C that maintains the meshing interval E between the rack gear 5A and the pinion gear 5B.

[0059] According to this drive mechanism 5, the meshing interval E between the rack gear 5A and the pinion gear 5B is maintained by the guide portion 5C, thereby ensuring the meshing accuracy between the rack gear 5A and the pinion gear 5B. As a result, the drive mechanism 5 of this embodiment allows the rack gear 5A and the pinion gear 5B to be reliably disassembled and assembled.

[0060] In the driving mechanism 5 of the embodiment, three or more contact members 5E are provided along the rotation direction of the pinion gear 5B.

[0061] According to this drive mechanism 5, it is possible to bring the positioning members 5D into contact with the contact members 5E at various rotational positions of the pinion gear 5B, thereby achieving smooth operation. For example, in the drive mechanism 5 of the embodiment, it is practical to provide six to eight contact members 5E along the rotational direction of the pinion gear 5B, which satisfies the relationship condition of

[0038] .

[0062] Moreover, the control rod drive device 1 of the embodiment includes the above-mentioned drive mechanism 5 and a drive shaft 6 to which a control rod 104 that can be moved up and down by the drive mechanism 5 and can be inserted into and removed from the reactor core 103 is connected.

[0063] According to this control rod drive device 1, since the drive mechanism 5 is included, the rack gear 5A and the pinion gear 5B for moving the control rod 104 up and down can be reliably and easily disassembled and assembled.

[0064] The control rod drive device 1 also includes a drive motor 2, a drive mechanism 5 driven by the drive motor 2, a drive shaft 6 that is capable of moving up and down by the drive mechanism 5 and to which a control rod 104 that can be inserted and removed into the core 103 is connected, and an electromagnetic clutch 3 that connects or disconnects the transmission of driving force from the drive motor 2 to the drive shaft 6, and all of the above components (drive motor 2, electromagnetic clutch 3, reduction mechanism 4, drive mechanism 5, drive shaft 6, electromagnetic clutch 3, core 103, control rod 104) are arranged inside the reactor vessel 101.

[0065] According to this control rod drive mechanism 1, the drive motor 2, electromagnetic clutch 3, reduction gear mechanism 4, drive mechanism 5, and drive shaft 6 are arranged inside the reactor vessel 101, and therefore there is no configuration for driving the control rod 104 outside the reactor vessel 101. That is, the control rod drive mechanism 1 of the embodiment does not require a nozzle that penetrates from the inside to the outside of the reactor vessel 101, and therefore, by applying the control rod drive mechanism 1 of the embodiment, there is no need to design the reactor vessel 101 assuming an accident in which the nozzle weld breaks. As a result, the control rod drive mechanism 1 of the embodiment can improve the safety of the reactor vessel 101.

[0066] Furthermore, in the control rod drive device 1 of the embodiment, the drive mechanism 5 is formed by meshing the pinion gear 5B with the rack gear 5A. The control rod drive device 1 of the embodiment drives the drive shaft 6 to move up and down by such simple meshing of the rack and pinion. As a result, the control rod drive device 1 of the embodiment can reliably drive the control rod 104 in high-temperature and underwater environments with a simple configuration that is less prone to malfunction.

[0067] Furthermore, in the control rod drive device 1 of the embodiment, the electromagnetic clutch 3 connects or disconnects the transmission of the driving force from the drive motor 2 to the drive shaft 6, and disconnecting the transmission of the driving force from the drive motor 2 to the drive shaft 6 allows the drive shaft 6 to freely descend, thereby allowing the control rod 104 to freely fall together with the drive shaft 6. Therefore, according to the control rod drive device 1 of the embodiment, by disconnecting the electromagnetic clutch 3, the control rod 104 falls freely and is inserted into the fuel assembly 102, thereby suppressing the nuclear fission reaction of the nuclear fuel material in the fuel assembly 102 and preventing it from reaching a critical state.

[0068] In the control rod drive device 1 of the embodiment, the drive motor 2 rotates the rotor 2A made of a magnetic material by the attractive force of the magnetic field generated in the electromagnetic coil 2C of the stator 2B.

[0069] According to this control rod drive mechanism 1, the drive motor 2 can be configured as a reluctance motor that does not use permanent magnets. Permanent magnets have low heat resistance and are difficult to use inside the reactor vessel 101, which can reach high temperatures of 350°C or more. As a result, the control rod drive mechanism 1 of this embodiment can be installed inside the high-temperature reactor vessel 101.

[0070] In the control rod drive device 1 of the embodiment, the cables of the electromagnetic coils 2C and 3C of the drive motor 2 and the electromagnetic clutch 3 are made of inorganic insulated cables 8.

[0071] According to this control rod drive device 1, by using the inorganic insulated cable 8, it is possible to maintain the function of the electromagnetic coils 2C, 3C even when the inside of the stator 2B is flooded with water.

[0072] In the control rod drive mechanism 1 of the embodiment, the inorganic insulated cable 8 has the metal sheath 8b made of a heat-resistant and corrosion-resistant alloy.

[0073] According to this control rod drive device 1, by using a heat-resistant and corrosion-resistant alloy for the metal sheath 8b of the inorganic insulated cable 8, heat resistance is improved and the function of the electromagnetic coils 2C and 3C can be maintained in a high-temperature environment.

[0074] In the control rod drive mechanism 1 of the embodiment, hollow portions 2Ab, 3D are formed on the central axis CL of the rotor 2A of the drive motor 2, penetrating in the axial direction, and the drive shaft 6 is inserted into the hollow portions 2Ab, 3D.

[0075] According to this control rod drive device 1, the drive shaft 6 is inserted into the hollow portions 2Ab and 3D, so that the drive shaft 6 can be arranged on the central axis CL of the rotor 2A of the drive motor 2, thereby enabling the device to be made more compact.

[0076] Furthermore, the control rod drive mechanism 1 of the embodiment has biasing means 7 that constantly biases the drive shaft 6 toward the reactor core 103 side.

[0077] According to this control rod drive device 1, when the electromagnetic clutch 3 is in a released state, a load that prevents the control rod 104 from freely falling is generated by the reduction mechanism 4 and the drive mechanism 5, but the biasing means 7 resists this load and assists the free descent of the drive shaft 6, thereby assisting the free fall of the control rod 104 together with the drive shaft 6. As a result, the control rod drive device 1 of this embodiment can reliably suppress the nuclear fission reaction of the nuclear fuel material in the fuel assembly 102 and safely control it so that it does not reach a critical state. In the case of a marine nuclear reactor, the action of the biasing means 7 functions to reliably insert the control rod 104 into the fuel assembly 102 even in the event of the reactor (hull) listing, rocking, or capsizing.

[0078] Moreover, the nuclear reactor 100 of the embodiment includes the above-mentioned control rod drive mechanism 1, a reactor core 103 controlled by the control rod drive mechanism 1, and a reactor vessel 101 in which the control rod drive mechanism 1 and the reactor core 103 are disposed.

[0079] According to this nuclear reactor 100, since it includes the control rod drive mechanism 1 having the above-described drive mechanism 5, it is possible to reliably and easily disassemble and assemble the rack gear 5A and the pinion gear 5B for moving the control rod 104 up and down. As a result, in the nuclear reactor 100 of this embodiment, maintenance of the control rod drive mechanism 1 can be safely performed even in a radiation area. Furthermore, according to this nuclear reactor 100, it is possible to ensure the drive performance of the control rod drive mechanism 1, improve the safety of the reactor vessel 101, reduce the size of the reactor vessel 101, and reliably drive the control rod 104 in high-temperature and underwater environments, thereby enabling safe control.

[0080] The present disclosure includes the following inventions. [Invention 1] Rack gear and a pinion gear that meshes with the rack gear; a positioning member fixed to a portion of the rack gear that does not have rack teeth; a plurality of abutment members provided along the rotation direction of the pinion gear; when at least one of the rack gear and the pinion gear is moved in a direction of relative movement when the rack gear and the pinion gear are meshed, the positioning member abuts against the abutting member, causing the rotational position of the pinion teeth of the pinion gear to be in mesh with the rack teeth of the rack gear. [Invention 2] The drive mechanism according to invention 1, wherein the positioning member is configured to be bendable so as to be able to return to its original position by elastic force. [Invention 3] 3. The drive mechanism according to claim 1, further comprising a guide portion that maintains a meshing gap between the rack gear and the pinion gear. [Invention 4] 4. The drive mechanism according to any one of the first to third aspects, wherein three or more of the contact members are provided along the rotation direction of the pinion gear. [Invention 5] A drive mechanism according to any one of inventions 1 to 4; a drive shaft that is capable of moving up and down by the drive mechanism and to which a control rod that can be inserted into and removed from the reactor core is connected; A control rod drive mechanism comprising: [Invention 6] A control rod drive mechanism according to claim 5; a reactor core controlled by the control rod drive mechanism; a reactor vessel in which the control rod drive mechanism and the reactor core are disposed; Including, nuclear reactors. [Explanation of symbols]

[0081] 1 Control rod drive mechanism 5 Drive mechanism 5A rack gear 5Ab rack teeth 5B pinion gear 5Bb pinion teeth 5C Information Department 5D positioning member 5E Contact member 6 drive shaft 100 reactor 101 Reactor vessel 103 Reactor Core 104 Control Rods

Claims

1. Rack gear and a pinion gear that meshes with the rack gear; a positioning member fixed to a portion of the rack gear that does not have rack teeth; a plurality of abutment members provided along the rotation direction of the pinion gear; when at least one of the rack gear and the pinion gear is moved in a direction of relative movement when the rack gear and the pinion gear are meshed, the positioning member abuts against the abutting member, causing the rotational position of the pinion teeth of the pinion gear to be in mesh with the rack teeth of the rack gear.

2. The drive mechanism according to claim 1 , wherein the positioning member is configured to be bendable so as to be able to return to its original position by elastic force.

3. 3. The drive mechanism according to claim 1, further comprising a guide portion that maintains an engagement gap between the rack gear and the pinion gear.

4. The drive mechanism according to claim 1 or 2, wherein three or more of the contact members are provided along the rotation direction of the pinion gear.

5. The drive mechanism according to claim 1; a drive shaft that is capable of moving up and down by the drive mechanism and to which a control rod that can be inserted into and removed from the reactor core is connected; A control rod drive mechanism comprising:

6. The control rod drive mechanism according to claim 5; a reactor core controlled by the control rod drive mechanism; a reactor vessel in which the control rod drive mechanism and the reactor core are disposed; Including, nuclear reactors.

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