Drive mechanism, control rod drive device and nuclear reactor

Abstract

To ensure good driving performance.SOLUTION: A drive mechanism 5 is provided, comprising a movably provided single rack gear 5A, a first pinion gear 5B configured to engage with the rack gear 5A to transmit driving force, and a second pinion gear 5C configured to engage with the rack gear 5A to transmit the driving force.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present disclosure relates to a drive mechanism, a control rod drive, 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 the control rods, thereby controlling the reactor power. The control rods are inserted and removed from the reactor core by the control rod drive mechanism (CRDM).

[0003] As a control rod drive device for a pressurized water reactor, for example, a magnetic jack drive mechanism shown in Patent Document 1 is generally applied. The magnetic jack uses electromagnetic force to move a latch that intermittently grips the control rod drive shaft (hereinafter simply referred to as the drive shaft) to drive the drive shaft in the axial direction, and is housed in a cylindrical control rod drive housing. The control rod drive housing is composed of a drive shaft housing that houses the drive shaft, and a latch housing that supports an electromagnetic coil on the outside and houses a latch inside. This drive mechanism is arranged outside the reactor vessel, and the lower end of the latch housing is connected to a nozzle that penetrates the inside and outside of the reactor vessel lid and is welded.

[0004] For example, US Pat. No. 5,999,333 shows a modular reactor in which the core, upper internals, steam generators, pressurizer, and primary loop circulating pump inlets and outlets are contained within the same reactor vessel, with the entire control rod drive mechanism located immersed in the coolant inside the reactor vessel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-123276 [Patent Document 2] Patent No. 6422189 Summary of the Invention [Problem to be solved by the invention]

[0006] Incidentally, in the drive mechanism arranged outside the reactor vessel, since it is connected to the nozzle stub that penetrates the lid, the welded part of the nozzle stub forms the pressure boundary of the primary coolant. Therefore, the soundness of the welded part must be always ensured. In the unlikely event that the welded part breaks, there is a risk that the primary coolant will leak, or that the control rod and the drive shaft will be thrown out of the reactor vessel by the pressure difference between the inside and outside of the reactor vessel as a thrust. Therefore, the design must be made assuming these accidents. On the other hand, when the entire control rod drive device is arranged inside the reactor vessel, the drive mechanism must be made compact, but it is difficult to ensure sufficient drive performance in terms of strength. Moreover, when the entire control rod drive device is arranged inside the reactor vessel, it is arranged immersed in the coolant, so lubricating oil cannot be used in the drive mechanism from the viewpoint of preventing the leakage of lubricating oil into the coolant, and it is also difficult to ensure sufficient drive performance here.

[0007] The present disclosure is devised to solve the above-mentioned problems, and has an object to provide a drive mechanism, a control rod drive device, and a nuclear reactor that can ensure drive performance. [Means for solving the problem]

[0008] In order to achieve the above-mentioned objective, a drive mechanism according to one embodiment of the present disclosure includes a single rack gear that is movably mounted, a first pinion gear that meshes with the rack gear to transmit a driving force, and a second pinion gear that meshes with the rack gear to transmit a driving force.

[0009] In order to achieve the above-mentioned object, a control rod drive device according to one embodiment 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 and removed from the core is connected.

[0010] 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. Effect of the Invention

[0011] According to the present disclosure, driving performance can be ensured. [Brief description of the drawings]

[0012] [Figure 1] FIG. 1 is a schematic diagram showing a nuclear reactor according to an embodiment. [Diagram 2] FIG. 2 is a schematic side view showing a control rod drive mechanism according to the embodiment. [Diagram 3] FIG. 3 is a partially enlarged cross-sectional view showing a control rod drive mechanism according to 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. [Diagram 5] FIG. 5 is a schematic cross-sectional view showing a drive mechanism of the embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional plan view showing a drive mechanism according to the embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional side view showing a part of the drive mechanism of the embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional side view showing a part of the drive mechanism of the embodiment. [Figure 9] FIG. 9 is a schematic diagram showing a drive mechanism of the embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the drawings. Note that the present invention is not limited to these embodiments. In addition, the components in the following embodiments include those that are replaceable and easy for a person skilled in the art, or those that are substantially the same.

[0014] FIG. 1 is a schematic diagram showing a nuclear reactor according to an embodiment.

[0015] The nuclear reactor 100 shown in FIG. 1 is a pressurized water reactor used in a pressurized water nuclear power plant. In the pressurized water nuclear power plant, in the nuclear reactor 100, after heating light water, which is the primary coolant, the high-temperature primary coolant is sent to a steam generator (not shown). Then, in the steam generator, the nuclear power plant evaporates the secondary coolant by heat-exchanging the high-temperature primary coolant with the secondary coolant, and drives a generator by sending the steam of the evaporated secondary coolant to a turbine, thereby generating electricity. Further, the high-temperature primary coolant flowing into the steam generator is cooled by heat-exchanging with the secondary coolant and returned to the nuclear reactor 100 to be heated to a high temperature again. On the other hand, the steam of the secondary coolant used for power generation in the turbine is cooled in a condenser and returned to a liquid state, and then returned to the steam generator via a feedwater pipe to become steam again by heat-exchanging with the primary coolant.

[0016] The reactor 100 has a reactor vessel 101 which is a pressure vessel. The reactor vessel 101 has a reactor vessel lid 101B fixed to a reactor vessel main body 101A by a number of stud bolts and nuts. The reactor vessel main body 101A is provided with an outlet nozzle 101Aa which sends the primary coolant to a steam generator, and an inlet nozzle 101Ab which returns the primary coolant cooled by heat exchange with the secondary coolant in the steam generator. A control rod drive mechanism 1 and a fuel assembly 102 are housed inside the reactor vessel 101. The control rod drive mechanism 1 is arranged on the upper side inside the reactor vessel 101, as will be described later in detail. The fuel assembly 102 is a nuclear fuel material and is arranged in a core 103 arranged on the lower side inside the reactor vessel 101. Although not shown, the fuel assembly 102 is configured to be elongated vertically by bundling a number of fuel rods in a lattice shape by a support grid. A large number of the fuel assemblies 102 are arranged in a standing state with their upper ends facing upward and their lower ends facing downward with respect to the core 103. In addition, the core 103 has control rods 104 arranged inside. The control rods 104 are inserted from the upper side into the many fuel assemblies 102 and can be inserted and removed. The control rods 104 are made of a control material that absorbs neutrons, and by being inserted into the fuel assemblies 102, they can absorb neutrons accompanying the nuclear fission reaction of the nuclear fuel material of the fuel assemblies 102 and control the fuel assemblies 102 not to reach a critical state. On the other hand, by being removed from the inside of the fuel assemblies 102, the control rods 104 can increase the number of neutrons in the reactor 100 and increase the reaction from criticality to the rated output. In addition, a large number of control rod guide tubes 105 that guide the raising and lowering of the control rods 104 are arranged inside the reactor vessel 101 between the core 103 and the control rod drive mechanism 1.

[0017] 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 cross-sectional view showing a drive mechanism of an embodiment. FIG. 6 is a schematic plan cross-sectional view showing a drive mechanism of an embodiment. FIG. 7 is a schematic side cross-sectional view showing a part of a drive mechanism of an embodiment. FIG. 8 is a schematic side cross-sectional view showing a part of a drive mechanism of an embodiment. FIG. 9 is a schematic view showing a drive mechanism of an embodiment.

[0018] 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 to control 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 gear mechanism 4, a drive mechanism 5, a drive shaft 6, and a biasing means 7.

[0019] 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.

[0020] The rotor 2A is provided to extend in the vertical direction on a central axis CL that extends in the vertical direction. The vertical direction in 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 with respect to a case 11 that houses the drive motor 2, the electromagnetic clutch 3, the reduction mechanism 4, and the drive mechanism 5. The rotor 2A is formed of a magnetic material. The rotor 2A has salient poles 2Aa. The salient poles 2Aa are protrusions that extend radially inward away from the central axis CL on the rotor 2A, and 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.

[0021] 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, face the rotor 2A, and are provided at intervals 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). Further, in the stator 2B, the electromagnetic coil 2C is constituted by an inorganic insulating cable 8 shown in FIG. 4.

[0022] The inorganic insulating cable 8 has a metal sheath 8b surrounding the core wire 8a and is filled with an inorganic insulator 8c such as magnesium oxide between the core wire 8a and the metal sheath 8b, and is also referred to as a MI cable (Mineral Insulated Cable). In the present embodiment, the inorganic insulating cable 8 is formed of, for example, Inconel 690 (registered trademark), in which the metal sheath 8b is a heat- and corrosion-resistant alloy excellent in heat resistance and corrosion resistance.

[0023] In this drive motor 2, the salient pole 2Aa of the rotor 2A is attracted to the core portion 2Ba around which the electromagnetic coil 2C is wound by the attractive force of the magnetic field generated by passing an electric current through the electromagnetic coil 2C of the stator 2B, and the rotor 2A rotates around the central axis CL. That is, the drive motor 2 constitutes a reluctance motor that rotates a 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 without using a permanent magnet.

[0024] 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.

[0025] 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 as the rotor 2A of the drive motor 2 rotates. The first magnetic pole 3A has an adsorption portion 3Aa that protrudes radially outward at the lower end in the axial direction and has a flat lower end surface.

[0026] The second magnetic pole 3B is made of a magnetic material, can be magnetically attached 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 end in the axial direction 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.

[0027] The first magnetic pole 3A and the second magnetic pole 3B are formed with a hollow portion 3D consisting of a through hole penetrating in the axial direction on the central axis CL. The hollow portion 3D is formed with an inner diameter equal to that of the hollow portion 2Ab formed in the rotor 2A of the drive motor 2 and communicates with the hollow portion 2Ab.

[0028] 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 formed of an inorganic insulated cable 8 shown in FIG.

[0029] In this electromagnetic clutch 3, when a current flows through the electromagnetic coil 3C, a magnetic field is generated in the axial direction, which acts on the attraction portion 3Aa of the first magnetic pole 3A and the attraction portion 3Ba of the second magnetic pole 3B. When the magnetic field acts on the attraction portion 3Aa and the attraction portion 3Ba, an attraction force is generated between them, and the second magnetic pole 3B is attracted 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 no current flows through the electromagnetic coil 3C, the magnetic field does not act on the attraction portion 3Aa of the first magnetic pole 3A and the attraction 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 reduction mechanism 4 and the drive mechanism 5, and the reduction mechanism 4 and the drive mechanism 5 become free to rotate.

[0030] The reduction mechanism 4 is disposed between the electromagnetic clutch 3 and the drive mechanism 5. The reduction mechanism 4 receives the rotation of the drive motor 2 via the electromagnetic clutch 3, and transmits the rotation to the drive mechanism 5 while reducing the speed. As shown in FIG. 5, the reduction mechanism 4 includes, for example, a first reduction section 4A, a second reduction section 4B, and a third reduction section 4C, which are made up of a planetary gear mechanism, stacked in the axial direction. Due to this configuration, the reduction mechanism 4 has a hollow section 4D penetrating in the axial direction at its center. The hollow section 4D is formed as a through hole penetrating in the axial direction on the central axis CL, and is formed with an inner diameter equivalent to that of the hollow section 3D formed in the electromagnetic clutch 3, and communicates with the hollow section 3D.

[0031] 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 to Fig. 9, the drive mechanism 5 is provided inside a case 11, and has a rack gear 5A, a first pinion gear 5B, a second pinion gear 5C, a differential mechanism (differential gear) 5D, a first output shaft 5E, a second output shaft 5F, a first transmission gear group 5G, and a second transmission gear group 5H.

[0032] The rack gear 5A is formed as a single unit and extends continuously and linearly in the vertical direction (axial direction) so as to be inserted into the above-mentioned hollow portions 2Ab, 3D, and 4D. The rack gear 5A has a plate surface formed in a long plate shape, on which a large number of meshing teeth 5Aa are formed along the extending direction. In the embodiment, the rack gear 5A has the meshing teeth 5Aa formed on one plate surface. The rack gear 5A is supported inside the case 11 so as to be movable in the vertical direction. The lower end of the rack gear 5A is connected to the drive shaft 6.

[0033] The first pinion gear 5B has meshing teeth 5Ba formed on a cylindrical peripheral surface. The meshing teeth 5Ba of the first pinion gear 5B mesh with the meshing teeth 5Aa of the rack gear 5A. The first pinion gear 5B is fixed to a shaft 5Bb extending in a horizontal direction perpendicular to a central axis CL along the up-down direction (axial direction). The first pinion gear 5B is rotatably provided by the shaft 5Bb being rotatably supported inside the case 11 by a bearing 5Bc.

[0034] The second pinion gear 5C has meshing teeth 5Ca formed on a cylindrical peripheral surface. The meshing teeth 5Ca of the second pinion gear 5C mesh with the meshing teeth 5Aa of the rack gear 5A. The meshing teeth 5Ca of the second pinion gear 5C have the same pitch module as the meshing teeth 5Ba of the first pinion gear 5B. The second pinion gear 5C is fixed to a shaft 5Cb extending in a horizontal direction perpendicular to the central axis CL along the vertical direction (axial direction). The second pinion gear 5C is rotatably provided by the shaft 5Cb being rotatably supported inside the case 11 by a bearing 5Cc.

[0035] The differential mechanism 5D has a gear case 5Da, a small gear 5Db, a first output gear 5Dc, and a second output gear 5Dd.

[0036] The gear case 5Da is rotatably supported inside the case 11 by a bearing 5De, and is thereby rotatably provided around the central axis CL. The gear case 5Da is connected to the reduction gear mechanism 4, and rotates when the rotation of the drive motor 2 is transmitted thereto.

[0037] The small gear 5Db is disposed inside the gear case 5Da. The small gear 5Db is made of a bevel gear and has meshing teeth 5Dba formed on its outer periphery. The small gear 5Db is fixed to a shaft 5Df extending in the horizontal direction. The small gear 5Db is rotatably provided by the shaft 5Df being rotatably supported on the gear case 5Da by a bearing 5Dg. A plurality of identical small gears 5Db (two in the embodiment) may be disposed inside the gear case 5Da. The plurality of small gears 5Db are disposed so that the rotational axes of the shaft 5Df intersect at the central axis CL.

[0038] The first output gear 5Dc is disposed inside the gear case 5Da. The first output gear 5Dc is a hollow bevel gear with a hole in the center, and meshing teeth 5Dca are formed on the outer periphery. The first output gear 5Dc is rotatably supported inside the gear case 5Da by the bearing 5Dh, and is provided rotatably around the central axis CL. The meshing teeth 5Dca of the first output gear 5Dc mesh with the meshing teeth 5Dba of the small gear 5Db.

[0039] The second output gear 5Dd is disposed inside the gear case 5Da. The second output gear 5Dd is a hollow bevel gear with a hole in the center, and meshing teeth 5Dda are formed on the outer periphery. The meshing teeth 5Dda of the second output gear 5Dd have the same pitch module as the meshing teeth 5Dca of the first output gear 5Dc. The second output gear 5Dd is rotatably supported inside the gear case 5Da by the bearing 5Di, and is provided rotatably around the central axis CL. The second output gear 5Dd faces the first output gear 5Dc in the vertical direction, and the meshing teeth 5Dda mesh with the meshing teeth 5Dba of the small gear 5Db.

[0040] The first output shaft 5E is formed in a cylindrical shape extending in the vertical direction. The first output shaft 5E is rotatably supported inside the case 11 by a bearing 5Ea, and is thereby rotatably provided around the central axis CL. The upper end of the first output shaft 5E is coupled to the first output gear 5Dc of the differential mechanism 5D.

[0041] The second output shaft 5F is formed in a cylindrical shape extending in the vertical direction. The second output shaft 5F is inserted into the cylinder of the first output shaft 5E and rotatably supported inside the first output shaft 5E by a bearing 5Fa, so that the second output shaft 5F is rotatably provided around the central axis CL. That is, the second output shaft 5F is configured to penetrate the first output shaft 5E on the same axis, and is provided to be rotatable relative to each other. The second output shaft 5F also has a hollow portion 5Fb that penetrates the center in the axial direction due to the cylindrical shape. The hollow portion 5Fb is formed to have an inner diameter equal to that of the hollow portion 4D formed in the reduction mechanism 4, and communicates with the hollow portion 4D. Therefore, the rack gear 5A of the drive mechanism 5 is inserted into the hollow portion 5Fb. The upper end of the second output shaft 5F is connected to the second output gear 5Dd of the differential mechanism 5D.

[0042] The first output shaft 5E and the second output shaft 5F are configured to penetrate on the same axis as described above, and are therefore both formed to extend below the differential mechanism 5D along the axial direction.

[0043] The first transmission gear group 5G has an output gear 5Ga, a bevel transmission gear 5Gb, and a spur transmission gear 5Gc.

[0044] The output gear 5Ga is connected to a lower end of the first output shaft 5E. The output gear 5Ga is made of a hollow bevel gear having a hole in the center, and has meshing teeth 5Gaa formed on its outer periphery.

[0045] The bevel gear 5Gb is a bevel gear and has meshing teeth 5Gba formed on its outer periphery. The meshing teeth 5Gba of the bevel gear 5Gb mesh with the meshing teeth 5Gaa of the output gear 5Ga. The bevel gear 5Gb is fixed to a shaft 5Gd extending along the horizontal direction. The bevel gear 5Gb is rotatably provided by the shaft 5Gd being rotatably supported inside the case 11 by a bearing 5Ge.

[0046] The spur transmission gear 5Gc has meshing teeth 5Gca formed on the outer periphery of the disk shape. A plurality of spur transmission gears 5Gc are provided, and the meshing teeth 5Gca are meshed with each other and provided continuously. In the driving mechanism 5 of the embodiment, three spur transmission gears 5Gc are provided. The first spur transmission gear 5Gc is fixed to the shaft 5Gd together with the bevel transmission gear 5Gb, and is rotatably provided by the bearing 5Ge. The second spur transmission gear 5Gc is fixed to the shaft 5Gf extending in the horizontal direction. The second spur transmission gear 5Gc is rotatably provided by the shaft 5Gf being rotatably supported inside the case 11 by the bearing 5Gg. The third spur transmission gear 5Gc is fixed to the shaft 5Bb together with the first pinion gear 5B, and is rotatably provided by the bearing 5Bc.

[0047] That is, in the first transmission gear group 5G, the output gear 5Ga rotates together with the first output shaft 5E, and this rotation is transmitted to the first pinion gear 5B via each spur transmission gear 5Gc. In this manner, the first output shaft 5E engages with the first pinion gear 5B via the first transmission gear group 5G.

[0048] The second transmission gear group 5H has an output gear 5Ha, a bevel transmission gear 5Hb, and a spur transmission gear 5Hc.

[0049] The output gear 5Ha is connected to the lower end of the second output shaft 5F. The output gear 5Ha is a hollow bevel gear with a hole in the center, and meshing teeth 5Haa are formed on the outer periphery. In the configuration example of the embodiment, the meshing teeth 5Haa of the output gear 5Ha have the same pitch module as the meshing teeth 5Gaa of the output gear 5Ga.

[0050] The bevel gear 5Hb is a bevel gear, and has meshing teeth 5Hba formed on its outer periphery. The meshing teeth 5Hba of the bevel gear 5Hb mesh with the meshing teeth 5Haa of the output gear 5Ha. In the configuration example of the embodiment, the meshing teeth 5Hba of the bevel gear 5Hb have the same pitch module as the meshing teeth 5Gba of the bevel gear 5Gb. The bevel gear 5Hb is fixed to a shaft 5Hd extending along the horizontal direction. The bevel gear 5Hb is rotatably provided by the shaft 5Hd being rotatably supported inside the case 11 by the bearing 5He.

[0051] The spur transmission gear 5Hc has meshing teeth 5Hca formed on the outer periphery of the disk shape. A plurality of spur transmission gears 5Hc are provided, and the meshing teeth 5Hca are continuously provided by meshing with each other. In the configuration example of the embodiment, the meshing teeth 5Hca of the spur transmission gear 5Hc are the same pitch module as the meshing teeth 5Gca of the spur transmission gear 5Gc. In the driving mechanism 5 of the embodiment, three spur transmission gears 5Hc are provided. The first spur transmission gear 5Hc is fixed to the shaft 5Hd together with the bevel transmission gear 5Hb, and is rotatably provided by the bearing 5He. The second spur transmission gear 5Hc is fixed to the shaft 5Hf extending in the horizontal direction. The second spur transmission gear 5Hc is rotatably provided by the shaft 5Hf being rotatably supported inside the case 11 by the bearing 5Hg. The third spur transmission gear 5Hc is fixed to the shaft 5Cb together with the second pinion gear 5C and is rotatably mounted by a bearing 5Cc.

[0052] That is, in the second transmission gear group 5H, the output gear 5Ha rotates together with the second output shaft 5F, and this rotation is transmitted to the second pinion gear 5C via each spur transmission gear 5Hc. In this manner, the second output shaft 5F engages with the second pinion gear 5C via the second transmission gear group 5H.

[0053] The operation of the drive mechanism 5 will be described. As shown in FIG. 9, in the drive mechanism 5, when the electromagnetic clutch 3 is in an attracted state, the rotation of the drive motor 2 is transmitted to the gear case 5Da of the differential mechanism 5D. Here, the gear case 5Da rotates in the R1 direction. Then, as the gear case 5Da rotates, the first output shaft 5E rotates in the R1 direction due to the meshing between the small gear 5Db and the first output gear 5Dc. At the same time, as the gear case 5Da rotates, the second output shaft 5F rotates in the R1 direction due to the meshing between the small gear 5Db and the second output gear 5Dd.

[0054] When the first output shaft 5E rotates in the R1 direction, the first transmission gear group 5G rotates in the R2 direction through the output gear 5Ga connected to the first output shaft 5E, and then the second spur transmission gear 5Gc rotates in the R3 direction, and the third spur transmission gear 5Gc rotates in the R4 direction. Accordingly, the first pinion gear 5B rotates in the R4 direction, and the rack gear 5A moves upward in the S1 direction.

[0055] On the other hand, when the second output shaft 5F rotates in the R1 direction, the bevel transmission gear 5Hb and the first spur transmission gear 5Hc of the second transmission gear group 5H rotate in the R5 direction via the output gear 5Ha connected to the second output shaft 5F, and then the second spur transmission gear 5Hc rotates in the R6 direction and the third spur transmission gear 5Hc rotates in the R7 direction. Accordingly, the second pinion gear 5C rotates in the R7 direction and the rack gear 5A moves upward in the S1 direction.

[0056] In addition, when the rotation of the drive motor 2 is transmitted to the gear case 5Da of the differential mechanism 5D in the direction opposite to the R1 direction, the first pinion gear 5B rotates in the direction opposite to the R4 direction and the second pinion gear 5C rotates in the direction opposite to the R7 direction, causing the rack gear 5A to move downward, which is the direction opposite to the S1 direction.

[0057] In this manner, in the drive mechanism 5, the first pinion gear 5B and the second pinion gear 5C cooperate to move the rack gear 5A in the vertical direction.

[0058] Here, there are cases where one of the first pinion gear 5B and the second pinion gear 5C (for example, the first pinion gear 5B) meshes properly with the rack gear 5A, while the other (for example, the second pinion gear 5C) does not mesh sufficiently with the rack gear 5A due to backlash or the like. In such a case, in a drive mechanism that does not have a differential mechanism, the second pinion gear 5C, which is not sufficiently meshed with the rack gear 5A, cannot transmit the driving force to the rack gear 5A. Therefore, the driving force transmitted to the rack gear 5A is only from the first pinion gear 5B. In this case, the second pinion gear 5C does not share the load, and the strength of the first pinion gear 5B alone causes an overload, which may result in gear damage.

[0059] In this regard, when the drive mechanism 5 of the embodiment includes the differential mechanism 5D, if the drive motor 2 is driven in a state in which the second pinion gear 5C is not properly meshed due to backlash, the differential mechanism 5D causes the second pinion gear 5C to rotate until the backlash is eliminated and properly mesh with the rack gear 5A before the properly meshed first pinion gear 5B applies force to the rack gear 5A. After the second pinion gear 5C properly meshes, both pinion gears 5B and 5C share the force equally (=1 / 2 each) to drive the rack gear 5A. The differential mechanism 5D constantly performs such a function without distinguishing between the first pinion gear 5B and the second pinion gear 5C, so that both pinion gears 5B and 5C can always properly mesh with the rack gear 5A and share the force evenly. In this manner, the drive mechanism 5 of the embodiment transmits the drive forces of both the pinion gears 5B and 5C to the rack gear 5A by the differential mechanism 5D in a state in which the first pinion gear 5B and the second pinion gear 5C are smoothly and reliably meshed with the rack gear 5A. That is, the control rod drive device 1 of the embodiment can realize a high-output actuator by the drive mechanism 5.

[0060] The drive shaft 6 is connected to the lower end of the rack gear 5A of the drive mechanism 5, and is inserted into the control rod guide tube 105 as shown in FIG. 2. The drive shaft 6 may be configured as a rack gear 5A. Therefore, the drive shaft 6 is provided so as to be capable of moving up and down in the axial direction on the central axis CL relative to the case 11. During the upward and downward movement, the drive shaft 6 is inserted into a hollow portion 5Fb formed in the drive mechanism 5, a hollow portion 3D formed in the first magnetic pole 3A and the second magnetic pole 3B of the electromagnetic clutch 3, and a hollow portion 2Ab formed in the rotor 2A. The drive shaft 6 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.

[0061] Therefore, when the electromagnetic clutch 3 is attracted and the transmission of the driving force from the drive motor 2 is connected, the drive mechanism 5 and the control rod drive device 1 transmit rotation in one direction by the drive motor 2, and raise the drive shaft 6 (control rod 104). When the electromagnetic clutch 3 is attracted and the transmission of the driving force from the drive motor 2 is connected, the drive mechanism 5 and the control rod drive device 1 transmit rotation in the other direction by the drive motor 2, and lower the drive shaft 6 (control rod 104). 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 being driven. Furthermore, when the electromagnetic clutch 3 is in a released state 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 allowing 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 nuclear fission reaction of the nuclear fuel material of the fuel assembly 102 inserted inside the fuel assembly 102 is suppressed and controlled so as not to reach a critical state.

[0062] 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 into the 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 hooked on the engagement portion 105a at the upper end inside the control rod guide tube 105 and its lower end is hooked on the engagement portion 6a of the drive shaft 6 inside the control rod guide tube 105. Therefore, the biasing means 7 assists the free descent of the drive shaft 6 and assists the free fall of the control rod 104 together with the drive shaft 6 by cutting off the transmission of the driving force from the drive motor 2 in a state in which the electromagnetic clutch 3 is released from attraction. When the electromagnetic clutch 3 is in a 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 marine nuclear reactor, the action of the biasing means 7 has the function of reliably inserting the control rod 104 into the fuel assembly 102 even in the event of the reactor (hull) tilting, rocking, or capsizing.

[0063] Thus, the drive mechanism 5 of the embodiment includes a single movably mounted rack gear 5A, a first pinion gear 5B that meshes with the rack gear 5A to transmit a driving force, and a second pinion gear 5C that meshes with the rack gear 5A to transmit a driving force.

[0064] According to this drive mechanism 5, the driving force from the first pinion gear 5B and the second pinion gear 5C is added and transmitted to a single rack gear 5A, so that it is possible to maintain the driving transmission strength while achieving miniaturization and ensure driving performance. Moreover, according to this drive mechanism 5, the driving force is transmitted by dividing the load between the first pinion gear 5B and the second pinion gear 5C for the single rack gear 5A, so that the load applied to one gear can be reduced, and therefore it is possible to transmit the driving force in a low load transmission range where the gears do not seize even in a situation where lubricating oil cannot be used, and driving performance can be ensured.

[0065] Moreover, the drive mechanism 5 of the embodiment includes a differential mechanism 5D that transmits the drive force of the drive motor (drive unit) 2 to each of the pinion gears 5B and 5C.

[0066] According to this drive mechanism 5, by including the differential mechanism 5D, each pinion gear 5B, 5C can be meshed smoothly and reliably with the rack gear 5A, and the load on both pinion gears 5B, 5C can be evenly distributed, and strength can be ensured. In order to realize a small nuclear reactor 100, it is desirable to place the control rod drive mechanism 1 inside the nuclear reactor vessel 101. In that case, there is a restriction that lubricating oil cannot be used, and it is ideal to design it so that the strength margin of the gear is large to distribute the force applied to the gear and that it can be used without lubrication. Increasing the strength margin means using a large gear, but since the control rod drive mechanism 1 needs to be placed inside the small nuclear reactor vessel 101, a large gear cannot be used. Therefore, although the force is distributed by using multiple small gears (two in the embodiment), it is necessary to distribute (share) the force reliably and evenly to the two gears. According to the drive mechanism 5, by including the differential mechanism 5D, it is possible to distribute (share) the force reliably and evenly to the two gears.

[0067] Here, the drive mechanism 5 of the embodiment is provided with a cylindrical frame (not shown) that is attached to the case 11 separately from the case 11 and can be removed from the case 11, and the first pinion gear 5B, the second pinion gear 5C, the differential mechanism 5D, the first output shaft 5E, the second output shaft 5F, the first transmission gear group 5G, and the second transmission gear group 5H, excluding the rack gear 5A, are supported by this frame. By configuring the drive mechanism 5 in this manner, during maintenance, the rack gear 5A can be left in the case 11 and the other components can be removed from the case 11, improving maintainability. During this maintenance, when the first pinion gear 5B, the second pinion gear 5C, the differential mechanism 5D, the first output shaft 5E, the second output shaft 5F, the first transmission gear group 5G, and the second transmission gear group 5H are returned to the case 11 and reassembled, a problem occurs in which the pinion gears 5B, 5C do not mesh sufficiently with the rack gear 5A. However, the drive mechanism 5 of this embodiment can eliminate this problem by using the differential mechanism 5D.

[0068] In addition, the drive mechanism 5 of the embodiment includes a first output shaft 5E that engages with the first pinion gear 5B and a second output shaft 5F that engages with the second pinion gear 5C, and is configured such that one of the first output shaft 5E and the second output shaft 5F penetrates the other on the same axis.

[0069] According to this drive mechanism 5, the first output shaft 5E and the second output shaft 5F are configured so that one penetrates the other on the same axis, so that the first output shaft 5E and the second output shaft 5F can be arranged to extend in the same direction. Therefore, in the drive mechanism 5 of the embodiment, the pinion gears 5B, 5C can be arranged to mesh with the rack gear 5A at positions close to each other, which contributes to miniaturization.

[0070] Moreover, the control rod drive device 1 of the embodiment includes a drive shaft 6 that is provided so as to be movable up and down by the drive mechanism 5 described above and to which a control rod 104 that can be inserted into and removed from the reactor core is connected.

[0071] According to this control rod drive device 1, the drive force is transmitted to the single rack gear 5A in the drive mechanism 5 by the first pinion gear 5B and the second pinion gear 5C, so that the drive performance of the drive shaft 6 (control rod 104) can be ensured. Also, according to this control rod drive device 1, by including the differential mechanism 5D, each pinion gear 5B, 5C is smoothly and reliably meshed with the rack gear 5A, and the drive shaft 6 (control rod 104) can be driven by the rotational forces of both pinion gears 5B, 5C. Also, according to this control rod drive device 1, one of the first output shaft 5E and the second output shaft 5F is configured to penetrate the other on the same axis, which contributes to miniaturization.

[0072] In addition, the control rod drive device 1 comprises a drive motor 2, a drive mechanism 5 driven by the drive motor 2, a drive shaft 6 which is capable of moving up and down by the drive mechanism 5 and to which a control rod 104 which can be inserted and removed from the core 103 is connected, and an electromagnetic clutch 3 which 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.

[0073] According to this control rod drive mechanism 1, the drive motor 2, the electromagnetic clutch 3, the reduction gear mechanism 4, the drive mechanism 5, and the 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 weld of the nozzle breaks. As a result, the safety of the reactor vessel 101 can be improved according to the control rod drive mechanism 1 of the embodiment.

[0074] In the control rod drive mechanism 1 of the embodiment, the drive mechanism 5 is realized by meshing the pinion gears 5B, 5C with the rack gear 5A. The control rod drive mechanism 1 of the embodiment drives the lifting and lowering of the drive shaft 6 by such simple meshing of the rack and pinion. As a result, the control rod drive mechanism 1 of the embodiment can reliably drive the control rod 104 in a high-temperature and underwater environment with a simple configuration that is less prone to failure.

[0075] 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, and allows the control rod 104 together with the drive shaft 6 to freely fall. 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, so that the nuclear fission reaction of the nuclear fuel material in the fuel assembly 102 can be suppressed and controlled to prevent a critical state.

[0076] 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.

[0077] According to this control rod drive mechanism 1, the drive motor 2 can be configured as a reluctance motor that does not use a permanent magnet. 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, according to the control rod drive mechanism 1 of this embodiment, it is possible to realize installation inside the high-temperature reactor vessel 101.

[0078] In the control rod drive device 1 of the embodiment, the drive motor 2 and the electromagnetic clutch 3 have cables for the electromagnetic coils 2C, 3C made of an inorganic insulated cable 8.

[0079] According to this control rod drive device 1, by using the inorganic insulated cable 8, the functions of the electromagnetic coils 2C, 3C can be maintained even when water enters the inside of the stator 2B.

[0080] 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.

[0081] According to this control rod drive mechanism 1, by using a heat-resistant and corrosion-resistant alloy for the metal sheath 8b of the inorganic insulated cable 8, the heat resistance is improved and the functions of the electromagnetic coils 2C and 3C can be maintained in a high-temperature environment.

[0082] In the control rod drive mechanism 1 of the embodiment, hollow portions 2Ab, 3D, 5Fb are formed on the central axis CL of the rotor 2A of the drive motor 2, penetrating in the axial direction, and a drive shaft 6 is inserted into the hollow portions 2Ab, 3D, 5Fb.

[0083] According to this control rod drive device 1, since the drive shaft 6 is inserted into the hollow portions 2Ab, 3D, and 5Fb, the drive shaft 6 can be disposed on the central axis CL of the rotor 2A of the drive motor 2, and the device can be made compact.

[0084] Moreover, the control rod drive mechanism 1 of the embodiment has a biasing means 7 that constantly biases the drive shaft 6 toward the core 103 side.

[0085] According to this control rod drive device 1, when the electromagnetic clutch 3 is in a released state, a load that prevents free fall is generated by the reduction gear 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, according to the control rod drive device 1 of the embodiment, the nuclear fission reaction of the nuclear fuel material in the fuel assembly 102 can be reliably suppressed and safely controlled so as not to reach a critical state. In the case of a marine nuclear reactor, the action of the biasing means 7 has the function of reliably inserting the control rod 104 into the fuel assembly 102 even in the event of the reactor (hull) tilting, rocking, or capsizing.

[0086] Moreover, the nuclear reactor 100 of this 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.

[0087] According to this reactor vessel 101, the driving performance of the control rod drive mechanism 1 can be ensured, the safety of the reactor vessel 101 can be improved, the reactor vessel 101 can be made smaller, and the control rod 104 can be reliably driven in high temperature and underwater environments, thereby enabling safe control. [Explanation of symbols]

[0088] 1. Control rod drive mechanism 2 Drive motor (drive unit) 5. Driving mechanism 5A Rack Gear 5B First pinion gear 5C Second pinion gear 5D differential mechanism 5E First output shaft 5F 2nd output shaft 6 Drive shaft 100 reactor 101 Reactor vessel 103 Core 104 Control Rod

Claims

1. a single movably mounted rack gear; a first pinion gear that meshes with the rack gear and transmits a driving force; a second pinion gear that meshes with the rack gear and transmits a driving force; a differential mechanism that transmits a driving force of a driving unit to each of the pinion gears; a first output shaft engaged with the first pinion gear; a second output shaft engaged with the second pinion gear; Including, The differential mechanism includes a gear case that rotates around a central axis by the transmission of rotation of the drive unit, a plurality of small gears that are rotatably supported inside the gear case and rotate with the rotation of the gear case, a first output gear that meshes with each of the small gears inside the gear case and is rotatable around the central axis, and a second output gear that meshes with each of the small gears inside the gear case and is rotatable around the central axis, A drive mechanism comprising the first output shaft and the second output shaft, one of which penetrates the other on the same axis, the first output shaft connected to the first output gear, and the second output shaft connected to the second output gear.

2. A drive mechanism according to claim 1; a drive shaft that is capable of being raised and lowered by the drive mechanism and to which a control rod that can be inserted and removed from the reactor core is connected; A control rod drive mechanism comprising:

3. The control rod drive mechanism according to claim 2 ; 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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