Blade Guide

Abstract

To provide a blade guide which can be surely inserted in a reactor core where fuel is being exchanged, and correct inclination of a self-standing control rod in a fully inserted state.SOLUTION: A blade guide comprises: two control rod guide parts which are diagonally arranged across an intersection of a control rod in a cross section in a cross shape, and whose top ends are coupled by a coupling part. The blade guide is for correcting inclination of a control rod in a fully inserted state in a reactor core where fuel is being exchanged. The control rod guide part is a short structure, and a top end part side face is formed with a top guide knob part which interferes with a top guide for supporting the blade guide in the fuel cell and supports the blade guide in a vertical direction.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a blade guide, and more particularly to a blade guide suitable for correcting the inclination of a control rod when fuel is loaded into a nuclear reactor. [Background technology]

[0002] Patent Document 1 describes a centering device as an example of a blade guide that centers a reactor's control rod so that it stands upright in the center of the fuel cell, prevents interference between the fuel assembly and the control rod during fuel loading, and facilitates fuel loading operations.

[0003] This patent describes a centering device that includes a cross member having a lifting handle, two support blocks disposed below and along the length of the cross member and secured to the cross member, each support block having an outwardly projecting shoulder portion extending beyond the end of the adjacent cross member, and a cruciform blade depending downwardly from each support block, each of the cruciform blades having an angled lower end that facilitates downward entry of the cruciform blades into the cells of the four fuel assemblies of the core, including the control rods of the cruciform blades. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 4-252999 Summary of the Invention [Problem to be solved by the invention]

[0005] In general, in a boiling water reactor (BWR), the tasks performed when the reactor is shut down between the previous and next operating cycles include (1) removal of spent fuel that had a high burnup at the end of the previous operating cycle and will not be used in the next operating cycle, and temporarily removed fuel that is not spent fuel but needs to be removed for the convenience of work inside the reactor, (2) loading the same number of new fuel and temporarily removed fuel as the spent fuel and moving the fuel to arrange for the fuel for the next cycle, and (3) inspection and replacement of equipment to ensure that the reactor internals can perform as expected in the next cycle.

[0006] A fuel handling machine (FHM) is used to remove fuel assemblies from the reactor core, load them into the reactor core, and move fuel within the reactor. The fuel assemblies removed from the reactor core and those to be loaded into the reactor core are stored in the spent fuel pool (SFP).

[0007] A control rod (CR) is a mechanism that controls the start and stop of a nuclear reactor, as well as the adjustment of output power during operation, by absorbing neutrons. Control rods have a cross-shaped cross section and are inserted into the gaps between fuel cells consisting of four adjacent fuel assemblies. When the reactor is shut down, the control rods in the reactor core are inserted into all fuel cells except for the fuel cell (empty cell) from which all fuel assemblies have been removed.

[0008] Since the control rods are held upright by the interference of adjacent fuel assemblies, there is a risk that they may tip over if three or more fuel assemblies are removed from the fuel cell. To prevent the control rods from tipping over when replacing fuel assemblies, the fuel cell into which the control rods are inserted must have at least two fuel assemblies loaded diagonally inside the fuel cell (in a checkerboard pattern), or the fuel cell must have diagonal blade guides to prevent the control rods from tipping over.

[0009] Therefore, the procedure for emptying a fuel cell with four fuel assemblies is as follows: first, removing two fuel assemblies diagonally; second, installing blade guides diagonally across the fuel cell; and third, removing the remaining two fuel assemblies. After the above steps, the procedure for moving the blade guides from the empty cell is as follows: fourth, removing the control rods; fifth, moving the blade guides. Finally, the procedure for loading fuel assemblies into the empty cell is as follows: sixth, installing blade guides diagonally across the fuel cell; seventh, inserting control rods; eighth, loading two fuel assemblies diagonally; ninth, moving the blade guides; and tenth, loading the remaining two fuel assemblies.

[0010] A self-supporting control rod is a control rod that stands on its own in an empty cell without being supported by fuel assemblies or blade guides. In general, a self-supporting control rod has a structure in which the control rod is supported by an upper grid plate and stands on its own in an empty cell, so that the handle at the top end of the control rod is extended so that the top end of the control rod interferes with the upper grid plate when fully inserted.

[0011] When using independent control rods, the procedure for emptying a fuel cell containing four fuel assemblies is simply to remove the four fuel assemblies, and there is no need to move the blade guides from the empty cell.

[0012] Therefore, when using independent control rods, the procedure for emptying a fuel cell containing four fuel assemblies is simplified compared to when using conventional control rods, as the steps of installing the blade guide, withdrawing the control rod, and moving the blade guide are omitted.

[0013] When using self-supporting control rods, there is a concern that when loading fuel on the side of the tilted control rod in an empty cell, the control rod and the fuel assembly may interfere with each other, making it impossible to load the fuel assembly, due to the inclination of the control rod in the empty cell.

[0014] Therefore, before loading the fuel assemblies, a procedure is required to install blade guides diagonally across the fuel cell and correct the inclination of the control rod. In other words, when using self-supporting control rods, the procedure for loading fuel into an empty cell after the above procedure (the process of removing four fuel assemblies) is the second process of installing blade guides diagonally across the fuel cell to correct the inclination of the control rod, the third process of loading two fuel assemblies diagonally, the fourth process of moving the blade guides, and the fifth process of loading the remaining two fuel assemblies.

[0015] Therefore, when using self-supporting control rods, the step of inserting the control rods is omitted from the procedure of loading four fuel assemblies into an empty cell, simplifying the work compared to when using conventional control rods.

[0016] A typical blade guide has a length approximately equal to the entire length of the fuel assembly in order to prevent the control rod from falling over throughout the entire range of the control rod from the fully inserted state to the fully withdrawn state.

[0017] The autonomous control rod remains fully inserted throughout all processes, including removal of the fuel assembly from the reactor core, loading of the fuel assembly into the reactor core, and movement of the fuel assembly within the reactor.

[0018] Therefore, the blade guides used for the self-supporting control rods only need to have a length sufficient to correct the inclination of the control rod in the fully inserted state, and therefore can be shorter in length than typical blade guides.

[0019] That is, in the state shown in Fig. 2 (where the blade guide 1 is not inserted until its tip reaches the fuel support bracket) described later, the inclination of the control rod 2 in the fully inserted state can be corrected, so the length of the blade guide 1 shown in Fig. 2 is sufficient. The length of the blade guide 1 in Fig. 2 is shorter than that of a general blade guide.

[0020] When the length of the blade guide is shortened, the travel time for moving the blade guide, the space required for storing the blade guide, the materials required for manufacturing the blade guide, etc. are reduced.

[0021] A normal blade guide is seated on the fuel support bracket in the same way as a fuel assembly and is supported vertically. However, if the length of the blade guide is shortened, the tip of the blade guide does not reach the fuel support bracket, so it is necessary to support the blade guide vertically in a different way than a normal blade guide.

[0022] The fuel assemblies and the blade guides are moved between the fuel pool and the reactor core by a refueling machine. When the operation of the refueling machine is automated and the operation of moving the fuel assemblies or the blade guides by the refueling machine is also automated, it becomes necessary to automatically check the gripping state of the fuel assemblies or the blade guides by the refueling machine.

[0023] A normal blade guide has the same weight as a fuel assembly, and a fuel exchange machine capable of automating operations has a function of detecting the grip of a fuel assembly or a normal blade guide by a weight sensor.

[0024] If the length of the blade guide is shortened, the weight of the blade guide will decrease, and it is possible that the weight sensor of the fuel exchange machine will not be able to detect its grip.

[0025] Normally, blade guides are inserted into fuel cells with fully removed control rods, but when inserting a blade guide into a fuel cell with a fully inserted control rod to correct the inclination of the control rod, it is possible that the blade guide cannot be inserted due to interference between the blade guide and the control rod.

[0026] However, Patent Document 1 does not disclose any solution to the problem that occurs when inserting a blade guide into a fuel cell with a control rod fully inserted in order to correct the inclination of the control rod.

[0027] Furthermore, when performing work involving the movement of fuel assemblies and the actuation of control rods, in order to prevent the reactor core from becoming critical, it is necessary to evaluate the subcriticality during the work in advance and create a work plan to ensure that a certain level of subcriticality or higher is always maintained.

[0028] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a blade guide that can be reliably inserted into a reactor core during refueling and can correct the inclination of an independent control rod in a fully inserted state. [Means for solving the problem]

[0029] In order to achieve the above object, the blade guide of the present invention is a blade guide that includes two control rod guide parts that are arranged diagonally across an intersection of a cross-sectionally cruciform control rod and have upper ends connected by a connecting part, and that corrects the inclination of a control rod in a fully inserted state in a nuclear reactor core during refueling, The control rod guide portion has a short structure, and an upper lattice plate gripping portion is provided on the upper end side thereof, which interferes with an upper lattice plate for supporting the blade guide in the fuel cell and supports the blade guide in the vertical direction. And, the upper grid plate gripping portion protrudes toward the adjacent fuel cell beyond the upper grid plate so as not to interfere with fuel movement in the adjacent fuel cell and movement of the blade guide, and the length in the upper grid plate direction is limited so as not to contact the fuel movement in the adjacent fuel cell and the blade guide, and the upper grid plate gripping portion is provided only on a side surface of one of the control rod guide portions; The upper grid plate gripping portion is formed in a wedge shape so that the blade guide is supported at a central position within the fuel cell by its own weight. It is characterized by: Effect of the Invention

[0030] According to the present invention, in a nuclear reactor core during refueling, the blade guide can be reliably inserted and the inclination of a self-supporting control rod in a fully inserted state can be corrected. [Brief description of the drawings]

[0031] [Figure 1] 1 is a schematic diagram showing a nuclear power plant in which a blade guide according to a first embodiment of the present invention is adopted; [Diagram 2] 1 is a perspective view showing a schematic configuration of a blade guide according to a first embodiment of the present invention; [Diagram 3] FIG. 2 shows a reactor core undergoing refueling, with blade guides, control rods, and fuel assemblies arranged in fuel cells separated by an upper grid plate. [Figure 4]FIG. 2 is a diagram showing a state in which the first embodiment of the blade guide of the present invention is gripped by a tube of a crane that constitutes a fuel exchange machine. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] The blade guide of the present invention will be described below based on the illustrated embodiment, in which the same reference numerals are used for the same components in each drawing. EXAMPLES

[0033] FIG. 1 shows a schematic configuration of a nuclear power plant 15 in which a first embodiment of a blade guide 1 of the present invention is adopted. The nuclear power plant 15 includes a fuel pool 16 and a nuclear reactor core 17.

[0034] 2 shows a schematic configuration of a first embodiment of the blade guide 1 of the present invention, in which the blade guide 1 of this embodiment is composed of a control rod guide portion 10, a handle portion 12, a blade guide connecting portion 13, and an upper grid plate gripping portion 14, and shows a state in which this blade guide 1 is inserted into the upper end portion of a control rod 2 having a cross-shaped cross section. The lower end of the control rod guide portion 10 is referred to as a tip portion 11 of the control rod guide portion.

[0035] FIG. 3 shows a reactor core 17 undergoing refueling, in which a blade guide 1, a control rod 2 having a cross-shaped cross section, and a fuel assembly 3 are arranged in a fuel cell 7 separated by an upper grid plate 4.

[0036] FIG. 4 shows the blade guide 1 being gripped by a tube 5 of a crane that constitutes the refueling machine.

[0037] First, a nuclear power plant 15 in which a first embodiment of a blade guide 1 of the present invention is adopted will be described with reference to FIG.

[0038] The reactor core 17 is a facility for bringing the fuel assemblies 3 to a critical state and generating energy through nuclear fission reactions, and when the reactor is shut down between operations, the fuel assemblies 3 in the reactor core 17 must be replaced and rearranged.

[0039] The fuel pool 16 is a facility for mainly storing and cooling the spent fuel assemblies 3, and the fuel assemblies 3 and the blade guides 1 before use are also stored in the fuel pool 16.

[0040] In a nuclear power plant 15, the blade guide 1 and the fuel assembly 3 are present in a reactor core 17 or a fuel pool 16 (as shown in FIG. 1). The blade guide 1 and the fuel assembly 3 are moved between the reactor core 17 and the fuel pool 16, or within the reactor core 17, by being held by a tube 5 of a crane constituting a fuel exchange machine.

[0041] The reactor core 17 is configured by loading four fuel assemblies 3 in a grid pattern, two by two, vertically and horizontally as shown in Fig. 3, by an upper grid plate 4, and dividing and arranging them in a number of fuel cells 7. In addition to a maximum of four fuel assemblies 3, each fuel cell 7 also contains one cross-shaped control rod 2 inserted between the four fuel assemblies 3, and one fuel support bracket 6 that supports the underside of the fuel assembly 3. A maximum of one blade guide 1 (one blade guide 1 shown in Fig. 2) is inserted into each fuel cell 7.

[0042] In addition, unless otherwise specified, the cross-shaped cross-sectional control rod 2 in this embodiment is a self-supporting control rod that will not tip over due to interference with the upper grid plate 4 when fully inserted, even in a fuel cell 7 that does not have a blade guide 1 or a fuel assembly 3.

[0043] Next, an example of the structure of the blade guide 1 of this embodiment will be described with reference to FIG.

[0044] As shown in Fig. 2, the blade guide 1 of this embodiment has two control rod guide portions 10a and 10b connected by a blade guide connecting portion 13. The two control rod guide portions 10a and 10b of the blade guide 1 support the control rod 2 having a cross-shaped cross section in the horizontal direction, and correct any inclination of the control rod 2 having a cross-shaped cross section.

[0045] The tip of the control rod guide parts 10a and 10b is formed with an acute-angled control rod guide part tip 11. This control rod guide part tip 11 raises the inclined control rod 2, which has a cross-shaped cross section, vertically and guides it into the gap between the two control rod guide parts 10a and 10b.

[0046] A handle portion 12 is attached to the upper portion of the blade guide 1 by a crane pipe 5 constituting the fuel exchange machine for moving the blade guide 1 within the reactor or the fuel pool 16. The crane pipe 5 constituting the fuel exchange machine grips the blade guide 1 by the handle portion 12 and moves the blade guide 1 to a designated position within the reactor or the fuel pool 16.

[0047] In addition, the control rod guide sections 10a and 10b have upper grid plate gripping sections 14 attached to their upper end sides. These upper grid plate gripping sections 14 interfere with the upper surface of the upper grid plate 4, thereby supporting the blade guide 1 in the vertical direction and preventing it from falling downward from the upper grid plate 4.

[0048] Furthermore, the upper grid plate gripping portion 14 is wedge-shaped so that the blade guide 1 is supported at the center position within the fuel cell 7 by its own weight.

[0049] In order to prevent the cross-sectional control rod 2 from being scratched due to interference with the blade guide 1, it is advisable to use a flexible material (e.g., resin) for the entire blade guide 1 or for the tip 11 and end of the control rod guide portion which is expected to interfere with the cross-sectional control rod 2.

[0050] In the blade guide 1 of this embodiment, the control rod guide portions 10a and 10b are shorter than in the conventional case, and therefore the control rod guide portion tips 11 do not come into contact with the fuel support fittings 6, and therefore the blade guide 1 can be supported vertically by the upper grid plate gripping portions 14 in a manner different from that of normal blade guides. Also, the blade guide 1 of this embodiment is held horizontally by the side surfaces of the control rod guide portions 10a and 10b interfering with the side surface of the upper grid plate 4, thereby preventing the fuel cell 7 from shifting or rotating from its center position.

[0051] Next, the function of the blade guide 1 of this embodiment will be described with reference to FIG.

[0052] As shown in Figure 3, when a fuel assembly 3 is loaded into a fuel cell 7 separated by an upper grid plate 4, in a cell in which a cross-shaped control rod 2 is inserted in an offset manner, such as in fuel cell 7a in the upper right of Figure 3, there is a concern that the fuel assembly 3 and the cross-shaped control rod 2 may interfere with each other, making it impossible to load the fuel assembly 3.

[0053] Therefore, as shown in the fuel cell 7b at the lower right of FIG. 3, the blade guide 1 is inserted into the fuel cell 7b, and the control rod 2, which has a cross-shaped cross section, is corrected so as to be positioned in the center of the fuel cell 7b.

[0054] The driving force for inserting the blade guide 1 into the fuel cell 7 and for correcting the cross-sectionally shaped control rod 2 to the center of the fuel cell 7 by the blade guide 1 is the weight of the blade guide 1. Therefore, the blade guide 1 has a weight necessary to achieve the required driving force.

[0055] Moreover, in the blade guide 1 of this embodiment, the upper grid plate gripping portion 14 contacts the upper surface of the upper grid plate 4 to support the upper grid plate 4 in the vertical direction. The upper grid plate gripping portion 14 protrudes into the adjacent fuel cells 7a, 7b, 7c, 7d so as not to impede the movement of the fuel assemblies 3 and the blade guide 1 in the adjacent fuel cells 7a, 7b, 7c, 7d, and has a structure in which the length in the upper grid plate 4 direction is limited so as not to contact the fuel assemblies 3 or the blade guide 1 in the adjacent fuel cells 7a, 7b, 7c, 7d, and is provided only on one surface of one control rod guide portion 10a or 10b.

[0056] When loading a fuel assembly 3 into a fuel cell 7c in which a blade guide 1 and a control rod 2 with a cross-shaped cross section are inserted, such as the fuel cell 7c in the lower left of Figure 3, the handle portion 12 and the blade guide connecting portion 13 have a structure with limited thickness so that the fuel assembly 3 and the blade guide 1 do not interfere with each other.

[0057] In a fuel cell 7 in which two or more fuel assemblies 3 are loaded diagonally, such as the fuel cell 7d in the upper left of Figure 3, the control rod 2 with a cross-shaped cross section is corrected to the center position of the fuel cell 7d due to interference with the fuel assemblies 3 and without support by the blade guide 1.

[0058] Finally, a method for moving the blade guide 1 of this embodiment within the reactor or the fuel pool 16 will be described with reference to FIG.

[0059] The blade guide 1 of this embodiment is moved by the crane tube 5 constituting the refueling machine from the fuel pool 16 to the fuel cell 7 in the reactor, from the fuel cell 7 in the reactor to another different fuel cell, and from the fuel cell 7 in the reactor to the fuel pool 16. When automating the operation of the refueling machine and streamlining the movement of the fuel assembly 3 or the blade guide 1 by the crane tube 5 constituting the refueling machine, it becomes necessary to automatically confirm the gripping state of the blade guide 1 by the crane tube 5 constituting the refueling machine.

[0060] Generally, a fuel exchange machine capable of automating the operation has a function of detecting the grip of the fuel assembly 3 by a weight sensor. To enable detection of the grip by the tube 5 of the crane constituting the fuel exchange machine, the blade guide 1 has solid column-shaped control rod guide parts 10a and 10b with acute tips and has the same weight as the fuel assembly 3.

[0061] According to this embodiment, the blade guide 1 can be reliably inserted into the reactor core 17 during refueling, and the inclination of the self-supporting control rod in the fully inserted state can be corrected. In addition, the time required to move the blade guide 1, the space required to store the blade guide 1, the materials required to manufacture the blade guide 1, etc. are reduced.

[0062] The present invention is not limited to the above-mentioned embodiment, and various modifications and applications are possible. The above-mentioned embodiment has been described in detail to explain the present invention in an easily understandable manner, and the present invention is not necessarily limited to having all of the configurations described.

[0063] For example, in the above embodiment, the use in combination with an autonomous control rod has been described as an example, but the control rods that the blade guide of the present invention targets are not limited to autonomous control rods, and can also be applied to other types of control rods by appropriately reviewing the procedures.

[0064] Furthermore, the blade guide of the present invention is not limited to being used to completely replace normal blade guides, but can be used in combination with normal blade guides. That is, in a nuclear reactor core in which normal control rods and independent control rods are mixed, it is possible to apply normal blade guides to fuel cells in which normal control rods are used, and to apply the blade guide of the present invention to fuel cells in which independent control rods are used. Even in the case of fuel cells in which normal control rods are used, the blade guide of the present invention can be applied instead of the normal blade guide to empty cells in which the procedures of pulling out the control rods and moving the blade guides can be omitted. [Explanation of symbols]

[0065] 1...blade guide, 2...cross-sectional control rod, 3...fuel assembly, 4...upper lattice plate, 5...crane tube that constitutes the fuel exchange machine, 6...fuel support bracket, 7, 7a, 7b, 7c, 7d...fuel cell, 10, 10a, 10b...control rod guide portion, 11...tip of control rod guide portion, 12...handle portion, 13...blade guide connection portion, 14...upper lattice plate gripping portion, 15...nuclear power plant, 16...fuel pool, 17...reactor core.

Claims

1. A blade guide comprising two control rod guide sections arranged diagonally across an intersection of a cross-sectionally shaped control rod and connected at the upper end by a connecting section, for correcting the inclination of a control rod in a fully inserted state in a nuclear reactor core during refueling, the control rod guide portion has a short structure, and an upper lattice plate gripping portion is provided on the side surface of the upper end portion thereof, the upper lattice plate gripping portion interfering with an upper lattice plate for supporting the blade guide in the fuel cell and supporting the blade guide in the vertical direction; the upper grid plate gripping portion protrudes toward the adjacent fuel cell beyond the upper grid plate so as not to interfere with fuel movement in the adjacent fuel cell and movement of the blade guide, and the length in the upper grid plate direction is limited so as not to contact the fuel movement in the adjacent fuel cell and the blade guide, and the upper grid plate gripping portion is provided only on a side surface of one of the control rod guide portions; A blade guide, wherein the upper grid plate gripping portion is formed in a wedge shape so that the blade guide is supported at a central position within the fuel cell by its own weight.

2. 2. The blade guide of claim 1, A blade guide, characterized in that a tip of the control rod guide portion is formed at a tip of the control rod guide portion having an acute angle.

3. 3. A blade guide according to claim 1 or 2, A handle portion is attached to the upper portion of the blade guide for moving it within a reactor or a fuel pool by a fuel exchange machine, and the fuel exchange machine grasps the blade guide with the handle portion and moves the blade guide to a designated position within the reactor or the fuel pool.

4. 2. The blade guide of claim 1, a blade guide for inserting the blade guide into the fuel cell into which the cross-shaped control rod is inserted in an offset state, the blade guide being inserted into the fuel cell into which the cross-shaped control rod is inserted in an offset state, and correcting the cross-shaped control rod so that it is positioned in the center of the fuel cell.

5. 5. The blade guide of claim 4, A blade guide characterized in that the driving force for inserting the blade guide into the fuel cell and for correcting the control rod, which has a cross section, to the center of the fuel cell by the blade guide is the weight of the blade guide itself.

6. 4. The blade guide of claim 3, using the refueling machine to move the blade guide from the fuel pool to the fuel cell in the reactor, to move the blade guide from the fuel cell in the reactor to another different fuel cell, and to move the blade guide from the fuel cell in the reactor to the fuel pool; The control rod guide portion is formed into a solid, columnar shape with a sharp tip so that its weight is within a range that enables the fuel exchange machine to detect the grip of the blade guide, or so that it has a weight that generates the driving force necessary to correct the inclination of the control rod, which has a cross-shaped cross section.

7. A blade guide according to any one of claims 1 to 6, A blade guide, characterized in that the entire blade guide or the tip and end portions of the control rod guide portion are made of a flexible material.

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