WO2018021044A1

WO2018021044A1 - Boiling-water reactor reactor-core

Info

Publication number: WO2018021044A1
Application number: PCT/JP2017/025514
Authority: WO
Inventors: 清志藤本; 志郎高橋
Original assignee: 日立Ｇｅニュークリア・エナジー株式会社
Priority date: 2016-07-28
Filing date: 2017-07-13
Publication date: 2018-02-01
Also published as: JP2018017609A; JP6752072B2

Abstract

Provided is a boiling-water reactor reactor-core capable of improving the work efficiency of periodic inspection, fuel replacement and so on while preventing fuel from floating up during the operation. In a boiling-water reactor reactor-core 21, fuel assemblies 1 are closely arranged in a triangular lattice arrangement, and a control rod 11, which has a Y-shaped horizontal cross section, is interposed at the center point among three fuel assemblies (1a-1c). The fuel assemblies 1 are disposed such that long sides (71a-71c) of the upper surfaces of handles (7a-7c) provided to the three fuel assemblies (1a-1c) that surround the control rod 11 having the Y-shaped horizontal cross section face the center of the control rod 11 having the Y-shaped horizontal cross section. The fuel assemblies 1 are provided with a fuel floating preventing member 31 that is disposed above the upper surfaces of the handles and helps prevent the fuel assemblies from floating upward.

Description

Boiling water reactor core

The present invention relates to a core of a boiling water reactor, and in particular, a plurality of fuel assemblies are densely arranged in a triangular lattice arrangement, and a horizontal cross section is Y between three adjacent fuel assemblies. The core of a boiling water reactor in which a control rod of a V shape is inserted.

A light water breeder reactor has been developed in which fuel assemblies are densely loaded in a triangular lattice arrangement in the core. For example, according to Patent Document 1, the lateral movement of the fuel assembly is prevented by a tab and a plate spring provided between the fuel assembly loaded in the light water breeder reactor and the core upper support plate, and An arrangement is described which ensures gap retention and control rod insertion. Further, Patent Document 1 discloses a configuration in which a hold down spring is provided between a fuel assembly and a core upper support plate to prevent floating of the fuel assembly.
Moreover, although it is a pressurized water reactor, in order to prevent floating of a fuel assembly, the structure which distribute | arranges a leaf spring to the upper surface four sides of a fuel assembly upper nozzle is described in patent document 2. FIG.
Also, in a pressurized water reactor, the method of inserting control rods and the place to insert control rods are different from those of boiling water reactors and the control rods are inserted into the center of the fuel assembly from the top, so it is unnecessary when inserting control rods The handle for moving the fuel assembly is removed.

JP-A-8-220276 JP-A-8-36078

However, in the configuration described in Patent Document 1, the core upper support plate is installed at the core upper portion, and the core upper support plate and the fuel assembly having a horizontal cross section hexagonal shape are supported by the upper support mechanism (hold down spring). , To prevent fuel lift. Since the upper core support plate requires a space for installing the upper support mechanism with respect to each fuel assembly, the coolant flow path provided in the upper core support plate is smaller than the size of the fuel assembly having a horizontal cross section hexagonal shape. It is getting smaller. In order to reduce the burden of equipment on the coolant circulation pump of the reactor, it is necessary to reduce the pressure loss in the core upper support plate, and for that purpose, it is necessary to secure a wide coolant flow path. Although the fuel is prevented from floating by using the hold down spring as the upper support mechanism, it is necessary to install the hold down spring for a plurality of fuel assemblies, which makes installation difficult.
Further, in the configuration described in Patent Document 2, since the control rod is inserted from above into the center of the fuel assembly during reactor operation, the handle for moving the fuel assembly is removed. . Therefore, at the time of refueling, it is necessary to attach the handle, and it is not possible to improve the efficiency of the refueling operation.
Therefore, the present invention provides a core of a boiling water reactor capable of improving work efficiency such as periodic inspection or refueling while preventing fuel floating during operation.

In order to solve the above problems, according to the present invention, a boiling water atom in which fuel assemblies are densely arranged in a triangular lattice arrangement, and control rods with a horizontal cross section Y-shape are inserted at the center of three fuel assemblies. In the core of a furnace, the fuel assembly has a long side or a short side of an upper surface of a handle provided on three fuel assemblies surrounding the control rod having a horizontal cross-section Y-shape, the horizontal cross-section Y-shape The fuel rod is provided with a fuel lift preventing member which is disposed to face the center of the control rod and is disposed above the upper surface of the handle to suppress the upward lift of the fuel assembly.

ADVANTAGE OF THE INVENTION According to this invention, it becomes possible to provide the core of the boiling water reactor which can improve operation | work efficiency, such as a regular test | inspection or refueling, preventing the floating of the fuel at the time of operation | use.
Problems, configurations, and effects other than those described above will be apparent from the description of the embodiments below.

FIG. 3 is a partial plan view of the core showing the arrangement relationship between the fuel lifting prevention member and the fuel assembly of the first embodiment according to one embodiment of the present invention. FIG. 2 is a partial plan view of the core with the fuel floating prevention member removed in FIG. 1; It is a longitudinal cross-sectional view of a boiling water reactor concerning one embodiment of the present invention. It is a longitudinal cross-sectional view of the fuel assembly with which the core of a boiling water reactor shown in FIG. 3 is loaded. FIG. 5 is a partial plan view of the core showing the arrangement of the densely arranged fuel assemblies and control rods; FIG. 3 is a sectional view taken along the line AA of FIG. 2 and is a partial side view of the upper part of the three fuel assemblies. It is a partial top view of the fuel floating prevention member shown in FIG. They are a partial plan view which shows the positional relationship of the grating | lattice member and handle which comprise the fuel floating prevention member shown in FIG. 1, and the BB cross section arrow line view. They are a partial plan view which shows the positional relationship of the grating | lattice member and handle which comprise the fuel floating prevention member shown in FIG. 1, and its CC cross-section arrow line view. It is a figure which is the vicinity of a shroud head, and shows the state which installed the fuel floating prevention member shown in FIG. It is the partial top view of the fuel floating prevention member of Example 2 which concerns on the other Example of this invention, and the DD cross section arrow line view. FIG. 12 is a partial plan view showing a positional relationship between a grid member and a handle that constitute the fuel floating prevention member shown in FIG. 11 and a sectional view taken along the line E-E. FIG. 12 is a partial plan view showing a positional relationship between a grid member and a handle constituting the fuel floating prevention member shown in FIG. 11 and a sectional view taken along the line F-F. It is a fragmentary top view of a core showing arrangement relationship with a fuel floating prevention member and a fuel assembly of Example 3 concerning other examples of the present invention. FIG. 15 is a sectional view taken along the line GG in FIG. 14 and showing the positional relationship between the fuel floating prevention member and the upper portion of the fuel assembly. They are a partial plan view of the fuel floating prevention member of Example 4 which concerns on the other Example of this invention, the HH cross section arrow line view, and an II cross section arrow line view. It is a fragmentary top view of a core showing arrangement relation with a fuel floating prevention member and a fuel assembly of Example 5 concerning other examples of the present invention. FIG. 18 is a partial plan view showing a positional relationship between a grid member and a handle constituting the fuel floating prevention member shown in FIG. 17 and a JJ sectional arrow view thereof. FIG. 18 is a partial plan view showing a positional relationship between a grid member and a handle that constitute the fuel floating prevention member shown in FIG. 17 and a K-K cross sectional arrow view thereof. It is a fragmentary top view of a core showing arrangement relationship with a fuel floating prevention member and a fuel assembly of Example 6 concerning other examples of the present invention.

First, FIG. 3 shows a longitudinal sectional view of a boiling water reactor according to an embodiment of the present invention. Although FIG. 3 shows a resource-renewable boiling water reactor (RBWR) as an example, it is not limited thereto. For example, an advanced boiling water reactor (Advanced Boiling Water Reactor: ABWR), a recirculation pump, and cooling water as a moderator through the reactor pressure vessel and flowing it back to the downcomer in the reactor pressure vessel. High economy that eliminates the need for the recirculation pump in BWR and the internal pump in ABWR by using the normal boiling water reactor (BWR) that circulates the cooling water in the tank or the natural circulation system of the cooling water by chimney The present invention is similarly applicable to other reactors such as the Economic Simplified Boiling Water Reactor (ESBWR). That is, as long as it is a boiling water reactor, the configuration of the present invention described below can be applied to any configuration.

As shown in FIG. 3, in the resource recycling type boiling water reactor (RBWR), a cylindrical core shroud 24 is provided in the reactor pressure vessel 20, and a plurality of fuel assemblies are provided in the core shroud 24. The reactor core 21 loaded with is installed. Further, the axial upper end portion of the cylindrical core shroud 24 is covered with a shroud head 25 and disposed above the steam / water separator 27 and the steam / water separator 27 extending upward above the shroud head 25. A steam dryer 28 is provided. An annular downcomer 26 is formed between the reactor pressure vessel 20 and the core shroud 24. An internal pump 14 is disposed in the downcomer 26.

Cooling water discharged from the internal pump 14 is supplied to the core 21 through the lower plenum 30. The cooling water is heated as it passes through the core 21 to form a gas-liquid two-phase flow including water and steam. The gas-water separator 27 separates the gas-liquid two-phase flow into steam and water. The separated steam is further dehumidified by the steam dryer 28 and led to the main steam piping 29a. The moisture-removed steam is directed to a steam turbine (not shown) to rotate the steam turbine. A generator coupled to the steam turbine rotates to generate electrical power. The steam discharged from the steam turbine is condensed into water by a condenser (not shown). The condensed water is supplied as cooling water into the reactor pressure vessel 20 by the water supply pipe 29b. The water separated by the steam separator 27 and the steam dryer 28 falls and reaches the downcomer 26 as cooling water.

In addition, in order to control the nuclear reaction of the fuel assembly in the lower plenum 30 of the reactor pressure vessel 20, a control rod capable of inserting control rods having a plurality of Y-shaped horizontal sections (cross sections) into the core 21 A control rod drive mechanism is provided in a control rod drive mechanism housing provided with a guide pipe and installed below the bottom of the reactor pressure vessel 20, and the control rod is connected to the control rod drive mechanism. Here, the control rod having a Y-shaped horizontal cross section (cross section) has three wings extending outward from the tie rod (or center post) located at the center, and each wing is a neutron absorbing material It has a plurality of neutron absorbing rods filled with B ₄ C. These three wings are arranged at intervals of 120 degrees around the tie rods (or center posts). Then, among a plurality of fuel assemblies densely loaded in the core 21 in the form of a triangular lattice, a control rod having a Y-shaped horizontal cross section (cross section) is formed between three fuel assemblies adjacent to each other. Is inserted.

The core 21 is supported by a core support plate 22, and a plurality of fuel assemblies, for example, about 700 fuel assemblies are loaded in the core 21. Further, as shown in FIG. 3, a fuel floating prevention member 31 is provided above the handle provided at the upper portion of the fuel assembly to suppress the floating of the fuel assembly to the upper side.

FIG. 4 is a longitudinal sectional view of a fuel assembly loaded in the core of the resource reuse type boiling water reactor (RBWR) shown in FIG. As shown in FIG. 4, the fuel assembly 1 includes a plurality of fuel rods 2, an upper tie plate 3, a lower tie plate 4, a plurality of fuel spacers 6, a channel box 5, and a handle 7. The handle 7 is provided to be held by a crane or the like when loading the fuel assembly 1 into the core 21 or replacing the fuel assembly 1. Further, the fuel rod 2 is filled with a plurality of fuel pellets (not shown) in a sealed cladding tube (not shown).
The lower tie plate 4 supports the lower end of each fuel rod 2, and the upper tie plate 3 holds the upper end of each fuel rod 2. The lower part of the lower tie plate 4 constituting the fuel assembly 1 is fitted in the three upper openings 9 provided in the fuel support fitting 8 arranged to penetrate the core support plate 22 in the lower part of the fuel assembly 1. Be supported. A control rod moving opening 10 is provided at the center of the fuel support 8 so that the horizontal cross section (horizontal cross section) of the control rod can be moved up and down.

As shown in FIG. 4, an elastic body 33 is disposed between the upper surface of the handle 7 provided on the top of the fuel assembly 1 and the grid member 32 disposed above the handle 7. In other words, a part of the upper surface of the handle 7 is in contact with the lower surface of the grid member 32 via the elastic body 33. Thus, even if the fuel assembly 1 is displaced so as to float upward in the axial direction, the above-described displacement of the floating is suppressed by the elastic body 33 and the lattice member 32. That is, the floating of the fuel assembly 1 is prevented. The elastic body 33 intervenes between the upper surface of the handle 7 provided on the upper portion of the fuel assembly 1 and the lower surface of the grid member 32 to damage the fuel assembly 1 having the grid member 32 and / or the handle 7. As a result, the floating of the fuel assembly 1 can be well prevented.
The axial upper end surface of the elastic body 33 is fixed to the lower surface of the lattice member 32 to form a fuel floating prevention member 31. In this case, the axial direction lower end surface (the surface on the opposite side of the lower surface of the grid member 32 of the elastic body 33) of the elastic body 33 constituting the fuel floating prevention member 31 is fixed to the handle 7 constituting the fuel assembly 1. Without contact. Note that, instead of this configuration, the axial direction lower end surface of the elastic body 33 may be fixed to a part of the upper surface of the handle 7 constituting the fuel assembly 1. In this case, the elastic member 33 fixed to a part of the upper surface of the handle 7 cooperates with the lattice member 32 to constitute the fuel floating prevention member 31. As described above, in the core of the resource reuse type boiling water reactor (RBWR) according to the present embodiment, the upper grid plate and the upper portion disclosed in the above-mentioned Patent Document 1 by including the fuel floating preventing member 31. There is no need for the upper support mechanism for connecting the grid plate and the upper tie plate.

FIG. 5 is a partial plan view of the core 21 showing the arrangement of the densely arranged fuel assemblies 1 and the control rods 11. As shown in FIG. 5, each fuel assembly 1 is densely arranged by bundling a plurality of fuel rods in a triangular lattice in a channel box 5 having a horizontal cross section (cross section) having a hexagonal shape. Further, a control rod 11 having a Y-shaped horizontal cross section (cross section) is disposed between three fuel assemblies which are disposed adjacent to each other in the form of a triangular lattice. A resource-recycling boiling water reactor (RBWR) is a boiling water reactor (BWR) in which the volume ratio of water to fuel is reduced by densely loading a plurality of fuel assemblies 1 into a core 21 as described above. ). Resource recycling type boiling water reactor (RBWR) has a plutonium breeding ratio higher than that of conventional boiling water reactor (BWR), and the generation and consumption of fissile plutonium during reactor operation Can be approximately the same, and the growth ratio can be about 1.0.

Here, the nuclear reactor is operated by nuclear fission of fuel in the fuel assembly 1, but the proportion of uranium-235 to undergo nuclear fission decreases with the passage of operation time, so the fuel is systematically replaced with new one There is a need to. At the time of refueling, it is necessary to insert a control rod 11 having a Y-shaped horizontal cross section (cross section) to prevent reactor criticality, and at the time of refueling, a control rod 11 having a Y cross section (horizontal cross section) And it is rational to refuel in the combination of three fuel assemblies 1 in which the horizontal cross section (cross section) of the Y-shaped control rod and the adjacent fuel assembly 1 are adjacent. As described above, the handle 7 is provided at the upper part of the fuel assembly 1 for moving the fuel assembly, so that refueling can be performed without changing the arrangement of the handle 7 at the time of reactor operation. Is desirable.

In addition, a conventional boiling water type atom in which a plurality of fuel rods are arranged in a square grid shape in a channel box having a rectangular horizontal cross section (cross section) and a plurality of fuel assemblies are loaded in a square grid shape in a core With respect to the reactor, in the resource recycling type boiling water reactor (RBWR), the number of fuel rods per fuel assembly can be increased. However, because the weight per fuel rod is reduced, the weight of the entire fuel assembly is reduced as compared to a conventional boiling water reactor. Further, in the resource reuse type boiling water reactor (RBWR), the pipe diameter of the cladding of the fuel rods densely arranged in the form of a triangular lattice in the fuel assembly 1 is reduced. Therefore, assuming that the fuel spacer 6 is axially separated at a distance similar to that of the conventional boiling water reactor and the fuel rods are supported, the central fuel between the support portions of the fuel spacers 6 is used. It is expected that the amount of horizontal displacement of the rod 2 will be large and contact with other fuel rods 2 will occur. Therefore, as shown in FIG. 4 described above, the installation distance in the axial direction of the fuel spacer 6 is narrowed compared to the case of the conventional boiling water reactor.
Narrowing the installation interval of the fuel spacer 6 means that the number of the installed fuel spacers 6 increases, and the pressure loss to the cooling water flowing upward in the fuel assembly 1 increases, and the fuel assembly 1 At the same time, the fluid force acting to lift axially upward also increases. If the fuel assembly 1 floats upward in the axial direction, the lower tie plate 4 may be disengaged from the insertion portion of the fuel support 8 and contact with other structures, possibly causing damage to the fuel assembly 1. Are concerned. Therefore, as shown in FIG. 3 and FIG. 4, providing the fuel floating prevention member 31 in the axial direction of the fuel assembly 1 has technical significance. Although the case where the fuel floating prevention member 31 is comprised with the lattice member 32 and the elastic body 33 is demonstrated as an example below, it is not restricted to this, The fuel floating prevention member 31 is comprised only with the lattice member 32, This fuel floating up Needless to say, the elastic body 33 may be disposed between the preventing member 31 and the upper surface of the handle 7 of the fuel assembly 1.
Hereinafter, an embodiment of the present invention will be described in detail focusing on the fuel floating prevention member 31 with reference to the drawings.

FIG. 1 is a partial plan view of a core showing an arrangement relationship between a fuel lifting prevention member 31 and a fuel assembly 1 according to a first embodiment of the present invention, and FIG. 2 is a view showing the fuel lifting in FIG. FIG. 7 is a partial plan view of the core with the prevention member 31 removed. As described above, in the resource recycling type boiling water reactor (RBWR), for example, about 700 fuel assemblies 1 are loaded in the core 21 (FIG. 3). In FIG. 1 and FIG. 2, ten fuel assemblies 1 out of a plurality of fuel assemblies 1 loaded in the core 21 and three fuel assemblies (for example, fuel assemblies) disposed apart from each other A control rod 11 (indicated by a dotted line in FIG. 1) having a Y-shaped horizontal section (cross section) disposed between the bodies 1a to 1c) is shown as an example. As shown in FIG. 5, in each fuel assembly 1, a plurality of fuel rods are densely arranged in a triangular lattice by bundling a plurality of fuel rods in a channel box 5 having a hexagonal horizontal cross section (cross section). Further, a control rod 11 having a Y-shaped horizontal cross section (cross section) is disposed between three fuel assemblies which are disposed adjacent to each other in the form of a triangular lattice. The control rod 11 having a Y-shaped horizontal cross section (cross section) includes three wings arranged at an interval of 120 degrees from one another.

As shown in FIG. 1, a lattice member 32 constituting the fuel floating prevention member 31 disposed above the plurality of fuel assemblies 1 has a shape in which triangular lattices are two-dimensionally connected. In other words, the grid member 32 constituting the fuel lift prevention member 31 has a repeated pattern of triangular grids. For example, the lattice member 32a intersects with the long side 71a of the upper surface of the handle 7a constituting the fuel assembly 1a, and the lattice member 32b intersects the long side 71b of the upper surface of the handle 7b constituting the fuel assembly 1b. A grid member 32 is disposed to intersect the long side 71c of the upper surface of the handle 7c constituting the fuel assembly 1c. A horizontal cross section (cross section) is formed between the fuel assembly 1a, the fuel assembly 1b, and the fuel assembly 1c, which are three fuel assemblies arranged adjacent to each other in a triangular lattice. A Y-shaped control rod 11 is disposed, and a connection portion between the grid member 32a, the grid member 32b, and the grid member 32c is a tie rod (or center) having a horizontal cross section (cross section) at the center of the control rod 11 It is located almost directly above the post) (not shown). The grid member 32a intersects with the long side 71a of the upper surface of the handle 7a (a side defining both side surfaces along the longitudinal direction of the handle 7a) so that the intersecting position is the substantially central portion of the long side 71a. It is. Similarly, the grid member 32b intersects with the long side 71b of the upper surface of the handle 7b (side defining both side surfaces along the longitudinal direction of the handle 7b) so as to intersect substantially at the center of the long side 71b. It is a department. The grid member 32c intersects with the long side 71c on the upper surface of the handle 7c (a side defining both side surfaces along the longitudinal direction of the handle 7c) so as to be substantially orthogonal to it. It is.

The above-mentioned relationship is similarly applied to the three fuel assemblies 1 adjacent to each other in the form of a triangular lattice and the lattice members 32 disposed above the three fuel assemblies 1. . As described above, by arranging the grid members 32 constituting the fuel floating prevention member 31 so as to intersect the long side of the handle 7 constituting the fuel assembly 1, the cooling water above the respective fuel assemblies 1 (cooling It is possible to secure a flow path of cooling water (coolant) having a wide area without blocking the flow path of the material) by the grid member 32. In addition, it is also possible to suppress an increase in pressure loss for the cooling water flowing upward through the fuel assembly 1.

Further, as shown in FIG. 2, the long side 71a of the upper surface of the handle 7a constituting the fuel assembly 1a, the long side 71b of the upper surface of the handle 7b constituting the fuel assembly 1b, and the handle 7c constituting the fuel assembly 1c The three fuel assemblies 1a to 1c are arranged such that the long side 71c of the upper surface is directed to the tie rod (or center post) (not shown) which is the center of the Y-shaped control rod 11 in the horizontal cross section (horizontal cross section). The core 21 is loaded. Such an arrangement relationship is based on the fact that the horizontal cross section (cross section) between the three fuel assemblies and the three fuel assemblies 1 arranged in a triangular lattice adjacent to each other is Y-shaped. The same applies to the case where the control rod 11 is disposed. Thus, the handles 7a to 7c of the three fuel assemblies 1a to 1c closely arranged in the form of a triangular lattice adjacent to each other so that the horizontal cross section (cross section) surrounds the Y-shaped control rod 11 Since all the long sides 71a to 71c on the top face are directed to the tie rod (or center post) which is the center of the Y-shaped control rod 11, the handle during reactor operation The periodic inspection or the fuel replacement can be performed without changing the arrangement of 7a to 7c, and the workability can be improved.

On the other hand, as shown in FIGS. 1 and 2, the short side 72a of the upper surface of the handle 7a constituting the fuel assembly 1a (the side defining both end portions in the longitudinal direction of the handle 7a) and the fuel assembly 1b Short side 72b of the upper surface of the handle 7b (side defining both ends in the longitudinal direction of the handle 7b) and short side 71c of the upper surface of the handle 7c constituting the fuel assembly 1c (both ends of the handle 7c in the longitudinal direction Side does not intersect with any grid member 32, and the horizontal cross section (cross section) is directed to a tie rod (or center post) (not shown) which is the center of the Y-shaped control rod 11. It is distributed without. The same applies to the handles 7 constituting the other fuel assemblies 1.

6 is a sectional view taken along the line AA in FIG. 2 and is a partial side view of the upper part of the three fuel assemblies 1a to 1c. As shown in FIG. 6, handles 7a, 7b, and 7c are provided above the three fuel assemblies 1a to 1c to allow the fuel assemblies to be suspended by a crane for movement. Further, as described above, each fuel assembly 1a to 1c has a configuration in which a plurality of fuel rods are bundled in a triangular lattice and densely arranged in the channel box 5 having a horizontal cross section (cross section) in a hexagonal shape. The channel box 5 has six side surfaces extending in the axial direction. Among the six side surfaces, the horizontal cross section (cross section) is disposed at a distance of 120 from each other centering on a tie rod (or center post) (not shown) constituting the Y-shaped control rod 11. Among the three wings, the fuel assembly contact prevention pads 13 are provided near the upper end portions of the four side faces except the two side faces of the channel box 5 facing the two wings. . On the other hand, control rod contact prevention pads 12 are provided in the vicinity of the upper portions of the side surfaces of the two surfaces of the channel box 5 facing the two wings. In FIG. 6, a state in which one wing constituting the control rod 11 having a Y-shaped horizontal cross section (cross section) is disposed between the fuel assembly 1b and the fuel assembly 1c disposed adjacent to each other Is shown.

FIG. 6 shows a state in which the control rod 11 having a Y-shaped horizontal cross section (cross section) is inserted to the top. Further, as shown in FIG. 2, the surfaces other than the side surfaces of the channel box 5 on the side where the control rod 11 with a Y-shaped horizontal cross section (cross section) is inserted are the channels of other adjacent fuel assemblies 1. The fuel assembly 1b has a gap between the fuel assembly 1b and two adjacent fuel assemblies into which control rods 11 having a Y-shaped horizontal cross section (cross section) are inserted. It is clearly narrower than the gap between the side surface of the channel box 5 and the side surface of the channel box 5 of the fuel assembly 1c. Therefore, as shown in FIG. 6, the thickness of the control rod contact prevention pad 12 is larger than the thickness of the fuel assembly contact prevention pad 13, and the control rod contact prevention pad 12 and the fuel provided on these fuel assemblies 1b When the control rod contact prevention pads 12 provided on the assembly 1c abut on each other, the insertion path of the control rod 11 having a Y-shaped horizontal cross section (cross section) is secured.

FIG. 7 is a partial plan view of the fuel lift preventing member 31 shown in FIG. 1, and FIG. 8 is a partial plan showing the positional relationship between the grid member 32 and the handle 7 constituting the fuel lift preventing member 31 shown in FIG. FIG. 9 is a partial plan view showing the positional relationship between the handle member 7 and the grid member 32 constituting the fuel floating prevention member 31 shown in FIG. 1 and FIG. FIG.

As shown in FIG. 7, the planar shape of the lattice member 32 constituting the fuel floating prevention member 31 is a combination of the lattice member 32a, the lattice member 32b and the lattice member 32c in a triangular lattice shape, and each lattice member The grid members 32a, the grid members 32b, and the grid members 32c are disposed above the handles 7a, the handles 7b, and the handles 7c as described above. Also, as described in FIG. 1, the grid member 32a is on the long side 71a of the top surface of the handle 7a, the grid member 32b is on the long side 71b of the top surface of the handle 7b, and the grid member 32c is on the long side 71c of the handle 7c. By arranging the grid members 32 constituting the fuel lift-up preventing member 31 to intersect with each other, the fuel lift-off preventing member 31 can be realized with a simple and simple structure by the grid member 32 having a repeated pattern of triangular grids. .
The grid member 32, the control rod contact preventing pad 12, and the fuel assembly contact preventing pad 13 which constitute the fuel lift preventing member 31 are made of, for example, stainless steel.

The upper view of FIG. 8 is a portion in a state of being rotated 90 degrees clockwise or counterclockwise in the arrangement relationship between the fuel assembly 1a shown in FIG. 1 and the grid member 32a constituting the fuel floating prevention member 31. FIG. 8 is a plan view, and the lower view of FIG. 8 is a sectional view taken along the line BB in the upper view. As shown in the upper drawing of FIG. 8, the grid members 32a intersect so as to be substantially orthogonal to the long side of the top surface of the handle 7a.
Further, the upper drawing of FIG. 9 shows the arrangement relationship between the fuel assembly 1a shown in FIG. 1 and the lattice member 32a constituting the fuel floating prevention member 31, and the lower drawing of FIG. It is C section arrow line view. As shown in the lower side of FIG. 8 and the lower side of FIG. 9, the axial upper end surface of the elastic body 33 is fixed to the lower surface of the lattice member 32a, and the fuel floating prevention member 31 is configured. In this case, the axial direction lower end surface (the surface on the opposite side of the lower surface of the grid member 32a of the elastic member 33) of the elastic body 33 constituting the fuel floating prevention member 31 is fixed to the handle 7a constituting the fuel assembly 1a. Without contact. In the present embodiment, the case where a coil spring is used as the elastic body 33 is shown as an example. As shown in the lower part of FIG. 9, a part of the upper surface of the handle 7a constituting the fuel assembly 1a is biased by the coil spring as the elastic member 33 in contact with the fuel assembly 1a. It is pressed by a certain pressing force. Even if the fluid force acts to lift the fuel assembly 1a upward in the axial direction by pressure loss to the cooling water, the fuel lift preventing member 31 and / or Or, the fuel assembly 1a can be prevented from being damaged.

The elastic body 33 is not limited to a coil spring, and a leaf spring or a bamboo spring may be used. Moreover, although the case where one coiled spring is used as the elastic body 33 is shown as an example in FIG.8 and FIG.9, the number of objects of the coiled spring as the elastic body 33 to install is not restricted to this, Two or more The coil spring may be installed. Further, in the present embodiment, one end (the upper end portion in the axial direction) of the coil spring as the elastic body 33 is fixed to the lower surface of the grid member 32a, but the present invention is not limited thereto. For example, one end (axially lower end) of the coil spring as the elastic body 33 is fixed to the upper surface of the handle 7a constituting the fuel assembly 1a, and the other end of the coil spring is not fixed to the lower surface of the grid member 32a. , And may be in contact with each other.
However, considering that the coil spring as the elastic body 33 is immersed in the cooling water (coolant) in the reactor pressure vessel 20 for a long time, one end of the coil spring as the elastic body 33 is on the upper surface of the handle 7a. It is desirable to fix and replace the coil assembly as the elastic member 33 together with the fuel assembly 1a at the time of refueling or the like.

FIG. 10 shows the vicinity of the shroud head 25 in which the fuel floating prevention member 31 shown in FIG. 1 is installed. FIG. 10 is a side view of the upper portion of the core 21 in the reactor pressure vessel 20. As shown in FIG. The core 21 has an annular (ring-like) core support frame 23 on the side of the outermost periphery of the fuel assembly 1 densely arranged in a triangular lattice, that is, the side of the outermost fuel assembly 1. The inner side surface (inner peripheral surface) of the core support frame 23 is shaped to have unevenness so as to match the shape of the outermost fuel assembly 1 (the channel box 5 having a hexagonal cross section). The outer surface (outer peripheral surface) of the core support frame 23 has substantially the same shape and size as the inner surface (inner peripheral surface) of the cylindrical core shroud 24. The core support frame 23 is fixed to a support (not shown) provided on the inner surface (inner peripheral surface) of the core shroud 24. As shown in FIG. 10, the fuel floating prevention member 31 is disposed above the handle 7 constituting the fuel assembly 1 densely arranged in the form of a triangular lattice. The outermost periphery of the fuel floating prevention member 31 is supported by the core support frame 23.
Thus, the fuel floating prevention member 31 is fixed in both the horizontal direction and the vertical direction (axial direction) in the core 21. In the present embodiment, a configuration in which the fuel floating prevention member 31 is supported by the core support frame 23 is shown as an example, but the present invention is not limited to this configuration. For example, a support member may be provided on the inner side surface (inner peripheral surface) of the core shroud 24, and the outermost periphery of the fuel floating prevention member 31 may be fixed by the support member.

According to the present embodiment, it is possible to provide a core of a boiling water reactor capable of improving the working efficiency of periodic inspection or refueling while preventing fuel floating during operation.
Further, according to the present embodiment, the long sides of the upper surfaces of the handles of the three fuel assemblies closely arranged in the form of a triangular lattice adjacent to each other so as to surround the Y-shaped control rods are Y-shaped. Since the control rod is disposed to be directed to the center of the control rod, periodic inspection or refueling can be performed without changing the arrangement of the handle at the time of reactor operation, and the workability can be improved.
Furthermore, according to the present embodiment, the long sides of the upper surfaces of the handles of the three fuel assemblies closely arranged in the form of a triangular lattice adjacent to each other so as to surround the Y-shaped control rods are intersected. By arranging the grid member having the repeated pattern shape of the triangular grid, the fuel floating prevention member can be realized with a simple and simple structure.
Further, according to the present embodiment, by arranging an elastic member such as a spring on a grid member having a repeated pattern of triangular grids to constitute a fuel floating prevention member, it is preferable to lift the fuel assembly upward in the axial direction. It is possible to prevent

FIG. 11 is a partial plan view of a fuel lifting prevention member of a second embodiment according to another embodiment of the present invention, and a sectional view taken along the line DD of FIG. The present embodiment is different from the first embodiment in that a groove or a recess which can be fitted to a handle constituting the fuel assembly is provided on the lower surface of the lattice member constituting the fuel lifting prevention member. The other configuration is the same as that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

The left view of FIG. 11 has the same plan configuration of the grid member 32 constituting the fuel lift prevention member 31 as the grid member 32a, the grid member 32b, and the grid member similar to the configuration shown in FIG. 7 in the first embodiment described above. Each of the

grid members

32a, 32b, and 32c, as described above, includes the handle 7a of the fuel assembly 1a and the handle 7b of the fuel assembly 1b, as described above. It is disposed above the handle 7c of the fuel assembly 1c. Also, as described in FIG. 1, the grid member 32a is on the long side 71a of the top surface of the handle 7a, the grid member 32b is on the long side 71b of the top surface of the handle 7b, and the grid member 32c is on the long side 71c of the handle 7c. A grid member 32 constituting the fuel lift prevention member 31 is disposed to intersect.

The right view of FIG. 11 is a sectional view taken along the line DD in the left view. As shown in the right figure, a groove 34 (or a recess) is provided on the lower surface of the lattice member 32a constituting the fuel lift prevention member 31 at a position intersecting the upper surface of the handle 7 of the fuel assembly 1.
12 is a partial plan view showing the positional relationship between the grid member 32a and the handle 7a constituting the fuel floating prevention member 31 shown in FIG. 11, and its EE cross section arrow view, and FIG. They are a partial plan view which shows the positional relationship of the grid member 32a which comprises the fuel floating prevention member 31 shown to, and a handle, and the FF cross section arrow directional view.

The upper view of FIG. 12 is a partial view of the fuel assembly 1a shown in FIG. 1 and the grid member 32a of the fuel lift preventing member 31 rotated 90 degrees clockwise or counterclockwise. FIG. 12 is a plan view, and the lower part of FIG. 12 is a sectional view taken along the line E-E in the upper view. As shown in the upper view of FIG. 12, the grid members 32a intersect so as to be substantially orthogonal to the long side of the upper surface of the handle 7a. Further, as shown in the lower part of FIG. 12, the grid member 32a has a groove 34 (or a recess) obtained by forming a substantially trapezoidal notch on the lower surface. Further, as shown in the lower part of FIG. 13, the groove 34 (or the recess) is continuous in the width direction (short side direction) of the grid member 32 a.
In other words, the grid member 32 a includes the groove 34 (or the recess) continuous in the width direction. The bottom of the groove 34 (or the recess), that is, the portion closest to the top surface of the grid member 32a in the lower part of FIG. 12, is flattened and one end of a coil spring as an elastic body 33 is fixed. The short side of the upper surface of the handle 7a is held so that the opening width of the groove 34 (or recess) gradually expands toward the handle 7a side from the bottom of the groove 34 (or recess) to which one end of the coil spring is fixed. It has slopes on both sides. Thus, since the groove 34 (or the recess) provided on the lower surface of the lattice member 32a has an inclined surface, the lattice member 32a can be easily positioned with respect to the handle 7a constituting the fuel assembly 1a. More specifically, the grid member 32 constituting the fuel lifting prevention member 31 having a repeated grid pattern of triangular grid is disposed above the plurality of fuel assemblies 1 densely loaded in the core 21 in the form of triangular grid. As shown in FIG. 10 described above, when fixed to the core support frame 23, the groove 34 (or the recess) provided on the lower surface of the lattice member 32 has an inclined surface. The groove 34 (or the recess) can be fitted on the upper surface of the handle 7 in a self-aligned manner through the inclined surface with respect to 7, and positioning of the grid member 32 with respect to the handle 7 constituting the fuel assembly 1 Becomes easy.

Further, as shown in the lower side of FIG. 12 and the lower side of FIG. 13, the groove 34 (or the recess) provided on the lower surface of the lattice member 32a is engaged with the handle 7a constituting the fuel assembly 1a. Here, temporarily, displacement in the A direction indicated by a white arrow in the upper drawing of FIG. 12, that is, vibration or external force along the long side direction (longitudinal direction) of the grid member 32a is applied to the fuel assembly 1a Assume that the As shown in the lower part of FIG. 12, one of the two side surfaces along the longitudinal direction of the handle 7a abuts on the inclined surface of the groove 34 (or the recess) provided on the lower surface of the grid member 32a. The displacement of the fuel assembly 1a in the A direction is restricted. In other words, the groove 34 (or the recess) provided on the lower surface of the grid member 32 a has a function as a displacement restricting portion that restricts the displacement of the fuel assembly 1. The function as the displacement restricting portion is the displacement of the fuel assembly 1b and the fuel assembly 1c also in the displacement in the B direction and the C direction indicated by white arrows in the left view of FIG. A groove 34 (or a recess) provided on the lower surface of the grid member 32 b and the grid member 32 c regulates the movement. As described above, the groove 34 (or the recess) provided on the lower surface of the grid member 32 functions as a displacement restricting portion of the fuel assembly 1, whereby the control rod contact preventing pad 12 shown in FIG. Also, it is not necessary to provide the fuel assembly contact prevention pad 13 on the side surface of the channel box 5 constituting the fuel assembly 1. In other words, the groove 34 (or the recess) provided on the lower surface of the grid member 32 functions as a displacement restricting portion of the fuel assembly 1 to make the gap between the fuel assemblies 1 disposed adjacent to each other It becomes possible to secure a gap as an insertion path of the control rod 11 of horizontal cross section (cross section) Y-shape.

The opening width of the groove 34 (or the recess) provided on the lower surface of the grid member 32 may be larger than the width (short side) of the upper surface of the handle 7 to be fitted, and the opening width may be set appropriately.

According to the present embodiment, in addition to the effects of the first embodiment, the positioning of the grid member constituting the fuel floating prevention member with respect to the handle constituting the fuel assembly is facilitated.
Further, according to the present embodiment, since the lower surface of the grid member constituting the fuel lift prevention member has a groove (or a recess) which can be fitted to the handle constituting the fuel assembly, the fuel assembly can be displaced. It becomes possible to regulate.

FIG. 14 is a partial plan view of the core showing the arrangement relationship between the fuel lift prevention member and the fuel assembly of Example 3 according to another example of the present invention, and FIG. 15 is a GG cross section of FIG. It is an arrow view, Comprising: It is a figure which shows the positional relationship of a fuel floating prevention member and the upper part of a fuel assembly. In this embodiment, of the grid members constituting the fuel lift prevention member, the fuel assemblies are displaced toward the Y-shaped control rod side on the lower surface of the grid members arranged to intersect with the fuel assembly handle. The second embodiment differs from the first embodiment in that a fuel assembly displacement restricting portion for restricting the pressure is provided. The other configuration is the same as that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in FIG. 14, of the lattice members 32 constituting the fuel lift-up preventing member 31, the lattice members 32a are arranged to intersect the long sides of the upper surface of the handle 7a constituting the fuel assembly 1a, and Are arranged to intersect with the long side of the upper surface of the handle 7b constituting the fuel assembly 1b.
As shown in FIG. 15, the axial direction upper end surface of the coil spring as the elastic body 33 is fixed to the lower surface of the lattice member 32a, and the fuel floating prevention member 31 is configured. In this case, the axial direction lower end surface (surface of the elastic member 33 opposite to the lower surface of the grid member 32a) of the coil spring as the elastic member 33 constituting the fuel floating prevention member 31 is a handle constituting the fuel assembly 1a. It is in contact without being fixed to 7a. Further, the axial direction upper end surface of the coil spring as the elastic body 33 is fixed to the lower surface of the lattice member 32c, and the fuel floating prevention member 31 is configured. In this case, the axial direction lower end surface of the coil spring as the elastic body 33 constituting the fuel floating prevention member 31 (the surface on the opposite side to the lower surface of the lattice member 32c of the elastic body 33) is a handle constituting the fuel assembly 1c. It is in contact without being fixed to 7ca.
In the lower surface of the grid member 32a, in the area from the vicinity of the position where the coil spring as the elastic body 33 is fixed to the Y-shaped control rod 11, there is provided a protrusion projecting toward the fuel assembly 1a. Further, in the lower surface of the grid member 32c, in the area from the vicinity of the position where the coil spring as the elastic body 33 is fixed to the Y-shaped control rod 11, there is provided a protrusion projecting toward the fuel assembly 1c.
The convex portion provided on the lower surface of the lattice member 32a and the convex portion provided on the lower surface of the lattice member 32c are continuous through the connection portion of the lattice member 32a and the lattice member 32c, and the fuel assembly displacement regulating portion 35 Configure The connection between the

grid members

32a and 32c is located directly above the tie rod (or center post) (not shown) which is the center of the Y-shaped control rod 11. Further, as shown in FIG. 15, of the fuel assembly displacement restricting portions 35 provided on the lower surface of the lattice member 32a and the lattice member 32c, the end surface on the lattice member 32a side is the fuel assembly 1a from the lower surface of the lattice member 32a. It has an inclined surface which is relatively steeply inclined toward the center of the Y-shaped control rod 11 as it goes to the side. In the fuel assembly displacement restricting portion 35, the end face on the grid member 32c side is relatively toward the center of the Y-shaped control rod 11 as it goes from the lower surface of the grid member 32c to the fuel assembly 1c side. It has a steeply inclined slope.

Here, the displacement in the A direction and the C direction indicated by the outlined arrows in FIGS. 14 and 15, that is, the center of the Y-shaped control rod 11 along the long side direction (longitudinal direction) of the grid member 32a. Horizontal vibration or external force toward the side is applied to the fuel assembly 1a, and the horizontal direction toward the center of the Y-shaped control rod 11 along the long side direction (longitudinal direction) of the grid member 32c. It is assumed that vibration or external force is applied to the fuel assembly 1c. In this case, as shown in FIG. 15, of the two side surfaces along the longitudinal direction of the handle 7a constituting the fuel assembly 1a, the side surface on the center side of the Y-shaped control rod 11 is the fuel assembly displacement restricting portion It abuts on the inclined surface which is one end face of 35, and the displacement of the fuel assembly 1a in the A direction is restricted. Further, of the two side surfaces along the longitudinal direction of the handle 7c constituting the fuel assembly 1c, the side surface on the center side of the Y-shaped control rod 11 is inclined at the other end surface of the fuel assembly displacement restricting portion 35. It abuts on the surface, and the displacement of the fuel assembly 1c in the C direction is restricted. As a result, it is possible to secure a gap formed between the fuel assembly 1a and the fuel assembly 1c, that is, a gap as an insertion path for the control rod 11 with a horizontal cross section (cross section) of Y-shape. Therefore, in the present embodiment, it is not necessary to provide the control rod contact prevention pad 12 shown in FIG. 6 in the first embodiment on the side surface of the channel box 5 constituting the fuel assembly 1.

According to the present embodiment, in addition to the effects of the first embodiment, the fuel assembly displacement restricting portion is provided on the lower surface of the lattice member constituting the fuel lift preventing member, so that the Y-shaped control rod side of the fuel assembly It is possible to regulate the displacement of the

FIG. 16 is a partial plan view of a fuel floating prevention member according to a fourth embodiment of the present invention, and a sectional view taken along the line HH and a sectional view taken along the line I-I. In the present embodiment, of the lattice members constituting the fuel lift prevention member, the shape of the lower surface of the lattice member in the area other than the area intersecting with the handle decreases in width toward the lower side (the fuel assembly side). This embodiment differs from the first embodiment in that the vertical cross-sectional shape is configured to be thin. The other configuration is the same as that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in the upper drawing of FIG. 16, among the lattice members 32 constituting the fuel lift prevention member 31, the lattice members 32a are arranged to intersect the long side of the upper surface of the handle 7a constituting the fuel assembly 1a, The grid member 32b is disposed to intersect the long side of the top surface of the handle 7b constituting the fuel assembly 1b, and the grid member 32c is disposed to intersect the long side of the top surface of the handle 7c constituting the fuel assembly 1c.

As shown in the lower left view of FIG. 16, the HH cross-sectional shape of the grid member 32a in the upper view forms a square shape. The position of the HH cross section corresponds to a position intersecting the long side of the upper surface of the handle 7a constituting the fuel assembly 1a. On the other hand, as shown in the lower right drawing of FIG. 16, the I-I cross-sectional shape of the grid member 32a in the upper drawing has a smaller width as the shape on the lower side goes downward (the fuel assembly side), ie, vertical cross-sectional shape Has a narrowing shape. The position of the I-I cross section corresponds to a position not intersecting the long side of the upper surface of the handle 7a constituting the fuel assembly 1a. That is, in the region intersecting with the handle 7 constituting the fuel assembly 1, the lattice member 32 constituting the fuel lift-up preventing member 31 of the present embodiment has a rectangular shape in vertical cross section to provide elasticity not shown. The end of the coil spring as the body 33 is shaped so as to be easily fixed, and the vertical cross-sectional shape in the area not intersecting with the handle 7 decreases in width toward the lower side (fuel assembly side) on the lower side, that is, vertical By making the cross-sectional shape thin, pressure loss to cooling water (coolant) flowing upward through the fuel assembly 1 is reduced.
In other words, the fluid flowing out from the upper outlet of the fuel assembly 1 (cooling water) in the region other than the region intersecting the handle 7 that constitutes the fuel assembly 1 among the grid members 32 that constitute the fuel floating prevention member 31 Can collide with the grid member 32, the fluid force received by the grid member 32 can be reduced. As a result, it is possible to improve the soundness of the fuel floating prevention member 31.

According to the present embodiment, in addition to the effects of the first embodiment, it is possible to reduce the fluid force received by the fuel lift preventing member due to the collision of the fluid as the cooling water, and improve the soundness of the fuel lift preventing member. Become.

FIG. 17 is a partial plan view of the core showing the arrangement relationship between the fuel uplift preventing member and the fuel assembly of a fifth embodiment according to another embodiment of the present invention. The present embodiment is different from the first embodiment in that each of the lattice members constituting the fuel floating prevention member has a lattice expanding member extending corresponding to the upper surface of the handle constituting each fuel assembly. The other configuration is the same as that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in FIG. 17, among the lattice members 32 constituting the fuel floating prevention member 31, the lattice members 32a arranged to intersect the long side of the upper surface of the handle 7a constituting the fuel assembly 1a are the upper surfaces of the handle 7a. At a position intersecting the long side, a lattice expanding member 36a is extended corresponding to the upper surface of the handle 7a. As shown in FIG. 17, the area of the plane of the lattice expanding member 36a is equal to or larger than the area of the upper surface of the handle 7a. The grid member 32a and the grid expanding member 36a are orthogonal to each other. Further, a grid member 32b arranged to intersect the long side of the upper surface of the handle 7b constituting the fuel assembly 1b extends at a position intersecting the long side of the upper surface of the handle 7b in correspondence with the upper surface of the handle 7b. It has a lattice expanding member 36b. The area of the plane of the lattice expanding member 36b is equal to or larger than the area of the upper surface of the handle 7b, and the lattice member 32b and the lattice expanding member 36b are orthogonal to each other. Similarly, a grid member 32c arranged to intersect the long side of the upper surface of the handle 7c constituting the fuel assembly 1c extends in a position corresponding to the upper surface of the handle 7c at a position intersecting the long side of the upper surface of the handle 7c. Grating expanding member 36c. The area of the plane of the lattice expanding member 36c is equal to or larger than the area of the upper surface of the handle 7c, and the lattice member 32c and the lattice expanding member 36c are orthogonal to each other.

18 is a partial plan view showing the positional relationship between the lattice member 32a, the lattice expanding member 36a and the handle 7a constituting the fuel floating prevention member 31 shown in FIG. 17 and its JJ cross section arrow view; 17 is a partial plan view showing a positional relationship between a grid member 32a, a lattice expanding member 36a, and a handle 7a constituting the fuel floating prevention member 31 shown in FIG. 17, and its K-K cross section arrow view.
The upper view of FIG. 18 is a portion in a state of being rotated 90 degrees clockwise or counterclockwise in the arrangement relationship between the fuel assembly 1a shown in FIG. 17 and the lattice member 32a constituting the fuel floating prevention member 31. FIG. 18 is a plan view, and the lower part of FIG. 18 is a sectional view taken along the line JJ in the upper view. As shown in the upper part of FIG. 18, the lattice expanding member 36a has the same length and the same width as the upper surface of the handle 7a constituting the fuel assembly 1a. One end of a coil spring as the elastic body 33 is fixed to the lower surface of the lattice expanding member 36a, and one end of the coil spring as the elastic body 33 is in contact with the handle 7a without being fixed.

The upper view of FIG. 19 is the same as the arrangement relationship between the fuel assembly 1a shown in FIG. 17 and the lattice member 32a and the lattice expanding member 36a, and the lower view of FIG. . As shown in the lower part of FIG. 19, coil springs as two elastic bodies 33 are provided on the lower surface of the lattice expanding member 36 a so as to be mutually separated along the longitudinal direction and to be fixed at one end. The other ends of the coil springs as the two elastic bodies 33 are in contact with the upper surface of the handle 7a without being fixed. Thus, floating of the fuel assembly 1a in the axial direction can be prevented by the lattice expanding member 36a on the entire top surface of the handle 7a. Incidentally, as shown in the lower part of FIG. 19, by providing the lattice expanding member 36a, it becomes possible to arrange a plurality of coil springs as the elastic body 33, and a load on the coil spring (elastic body 33) per one It is also possible to reduce the

According to this embodiment, in addition to the effects of the first embodiment, by providing the lattice expanding members to the respective lattice members constituting the fuel floating prevention member, floating of the fuel assembly can be more effectively prevented.
Moreover, according to the present embodiment, the load on the elastic body disposed to prevent damage to the fuel floating prevention member and / or the fuel assembly can be reduced, and the life of the elastic body can be prolonged. It becomes.

FIG. 20 is a partial plan view of the core showing the arrangement relationship between the fuel uplift preventing member and the fuel assembly of a sixth embodiment according to another embodiment of the present invention. In this embodiment, the short sides of the upper surface of the handle constituting the fuel assembly (the sides defining the longitudinal ends of the handle) are directed to the tie rod (or center post) which is the center of the Y-shaped control rod. The embodiment differs from the first embodiment in that the assembly is loaded in the core, and the grid members constituting the fuel floating prevention member are arranged such that the connection portions of the plurality of grid members intersect the long side of the upper surface of the handle. The other configuration is the same as that of the first embodiment. The same components as those of the first embodiment are denoted by the same reference numerals, and the description thereof will not be repeated.

As shown in FIG. 20, control of a Y-shaped horizontal cross section (cross section) between the fuel assembly 1a, the fuel assembly 1b, and the fuel assembly 1c closely arranged in the form of a triangular lattice adjacent to each other A bar 11 is arranged. Short side 72a of the upper surface of the handle 7a constituting the fuel assembly 1a (side defining both side surfaces along the longitudinal direction of the handle 7a), short side 72b of the upper surface of the handle 7b constituting the fuel assembly 1b (long side of the handle 7b Y-shaped control is a side that defines both sides along the direction, and a short side 72c of the top surface of the handle 7c that constitutes the fuel assembly 1c (a side that defines the two sides along the longitudinal direction of the handle 7c) It is arranged to be directed to a tie rod (or center post) (not shown) which is the center of the rod 11. Such an arrangement relationship is such that Y-shaped control rods 11 are disposed between the three other fuel assemblies disposed adjacent to each other in a triangular lattice and the three fuel assemblies 1. The same is true for cases. Thus, the handles 7a to 7c of the three fuel assemblies 1a to 1c closely arranged in the form of a triangular lattice adjacent to each other so that the horizontal cross section (cross section) surrounds the Y-shaped control rod 11 Since all the short sides 72a to 72c of the top face are directed to the tie rod (or center post) which is the center of the Y-shaped control rod 11, the handle during reactor operation The periodic inspection or the fuel replacement can be performed without changing the arrangement of 7a to 7c, and the workability can be improved.

Moreover, as shown in FIG. 20, the lattice member 32 which comprises the fuel floating prevention member 31 is provided with the repeating pattern shape of a triangular lattice. For example, the grid member 32 disposed above the handle 7a of the fuel assembly 1a has a long side so as to be substantially orthogonal to the long side 71a of the upper surface of the handle 7a (a side defining both side surfaces along the longitudinal direction of the handle 7a) A grid member 32a disposed substantially at the center of 71a, a grid member 32d intersecting at a predetermined inclination angle with the long side 71a at a substantially center of the long side 71a, and a length substantially at the center of the long side 71a The grid member 32e intersects the side 71a at a predetermined inclination angle. In other words, the connection portion of the grid member 32a, the grid member 32d, and the grid member 32e is located above the substantially central portion of the long side 71a. A coil spring (not shown) as an elastic body 33 having one end fixed to the lower surface of the connecting portion of the

grid members

32a, 32d and 32e and the other end abutting without being fixed to the upper surface of the handle 7a Is provided.

The above-mentioned relationship is similarly applied to the three fuel assemblies 1 adjacent to each other in the form of a triangular lattice and the lattice members 32 disposed above the three fuel assemblies 1. . As described above, each fuel assembly 1 is prevented from rising at the connection portion of the three lattice members, so that the soundness of the fuel floating prevention member 31 configured by the lattice members 32 is improved.

In addition, the shape of the lower surface of the connection portion of the three grid members may be the same as that of the first embodiment (FIGS. 8 and 9) or the second embodiment (FIGS. 12 and 13) described above. The lattice expanding member (FIGS. 17 to 19) shown in the fifth embodiment may be provided. Furthermore, in the grid member, the shape of the lower surface of the region other than the connection portion may be the shape shown in the above-described fourth embodiment (lower right view in FIG. 16).

According to the present embodiment, in addition to the effects of the first embodiment, since the fuel assembly is prevented from floating at the connection portion of the plurality of grid members constituting the fuel floating prevention member, the fuel floating prevention member It is possible to further improve the soundness.

In Examples 1 to 6 described above, although a resource recycling type boiling water reactor (RBWR) is shown as an example of a boiling water reactor, the present invention is not limited to this, and the horizontal cross section is not limited to this. If it is a core structure in which fuel assemblies having hexagonal channel boxes are densely loaded adjacent to each other in a triangular lattice, for example, an improved boiling water reactor (ABWR), highly economical simplified boiling It is equally applicable to a water reactor (ESBWR) or a conventional boiling water reactor (BWR) having a recirculation pump.

In addition, the boiling water nuclear reactor may be configured by combining the configurations shown in the above-mentioned Example 2 to Example 5 in any combination. For example, the groove 34 (or the recess) and the fuel assembly displacement restricting portion 35 may be provided on the lower surface of the lattice member 32 by combining the second embodiment and the third embodiment. Further, the second embodiment and the fourth embodiment are combined, and a groove 34 (or a recess) is provided on the lower surface of the grid member 32 in the area intersecting the handle, and the lower surface of the grid member 32 in the area other than the area intersecting the handle. The vertical cross-sectional shape may be configured to be thin. Further, all the configurations of the embodiment 2 to the embodiment 5 may be combined, that is, two or more embodiments of the embodiment 2 to the embodiment 5 may be arbitrarily combined.

The present invention is not limited to the embodiments described above, but includes various modifications.
For example, the embodiments described above are described in detail in order to explain the present invention in an easy-to-understand manner, and are not necessarily limited to those having all the configurations described.

1, 1a, 1b, 1c: fuel assembly, 2: fuel rod 3, upper tie plate 4, lower tie plate 5, channel box 6, fuel spacer , 7, 7a, 7b, 7c ... handle, 8 ... fuel support bracket, 9 ... top opening, 10 ... opening for control rod movement, 11 ... control rod, 12 · · · Control rod contact preventing pad 13, fuel assembly contact preventing pad 14, internal pump 20, reactor pressure vessel 21, core 22, core support plate 23,・・・ Core support frame, 24 ・・・ Core shroud, 25 ・・・ Shroud head, 26 ・・・ down link, 27 ・・・ Air-water separator, 28 ・・・ Steam dryer, 29a · · · Main steam Piping, 29b ··· Water supply piping, 30 · · · Lower plenum, 31 · · · Fuel

lifting preventing members

32, 32a, 32b, 32c, 32d, 32e: lattice members, 33: elastic bodies, 34: grooves, 35: fuel assembly displacement regulating portion, 36a, 36b, 36c, 36d, 36e ... lattice expanding members, 71a, 71b, 71c ... long sides, 72a, 72b, 72c ... short sides

Claims

A core of a boiling water nuclear reactor, in which fuel assemblies are densely arranged in a triangular lattice arrangement, and control rods with a horizontal cross section Y-shape are inserted at the centers of three fuel assemblies,
In the fuel assembly, the long side or the short side of the upper surface of the handle provided on the three fuel assemblies surrounding the control rod with the horizontal cross section Y-shape faces the center of the control rod with the horizontal cross section Y-shaped Arranged as
A core of a boiling water nuclear reactor, comprising: a fuel floating prevention member disposed above the upper surface of the handle and suppressing upward floating of the fuel assembly.
In a core of a boiling water reactor according to claim 1,
The core of a boiling water nuclear reactor, wherein the fuel lifting prevention member comprises a grid member having a repeating pattern shape of a triangular grid.
In a core of a boiling water reactor according to claim 2,
An elastic body is provided between the grid member intersecting the long side of the upper surface of the handle, and the upper surface of the handle, and the lower surface of the grid member where one end of the elastic body intersects the long side of the upper surface of the handle A core of a boiling water reactor, which is fixed to an upper surface of the handle.
In a core of a boiling water reactor according to claim 3,
The core of a boiling water reactor, wherein the elastic body is a coil spring, a leaf spring, or a bamboo spring, and presses the fuel assembly downward.
In a core of a boiling water reactor according to claim 3,
The lower surface of the grid member is provided with a groove or recess in a portion intersecting the long side of the upper surface of the handle, the opening width of the groove or recess is larger than the width of the upper surface of the handle, and the upper surface of the handle is A core of a boiling water reactor, which is fitted to the groove or the recess through the elastic body.
In a core of a boiling water reactor according to claim 3,
From the center side of the control rod of the horizontal cross section Y-shape to the center of the control rod of the horizontal cross section Y-shape from the center side of the control rod of the horizontal cross section Y shape in the lower surface of the grid member The region has a convex portion projecting toward the fuel assembly side, and the fuel assembly restricts the displacement toward the center of the control rod of the horizontal cross section Y shape by abutting the handle to the convex portion. A core of a boiling water reactor comprising an assembly displacement control unit.
In a core of a boiling water reactor according to claim 3,
A core of a boiling water reactor, wherein a vertical cross-sectional shape in a region other than a portion which is a lower surface of the grid member and intersects with a long side of an upper surface of the handle becomes thinner toward the fuel assembly.
In a core of a boiling water reactor according to claim 3,
The grid member has a grid expanding member extending corresponding to the long side of the upper surface of the handle at a portion intersecting the long side of the upper surface of the handle, and the lower surface of the grid expanding member and the upper surface of the handle A core of a boiling water reactor, wherein the elastic body is disposed therebetween.
In a core of a boiling water reactor according to claim 3,
A connection portion of a plurality of grid members forming a triangular grid is located above a substantially central portion of the upper surface of the handle, and between a lower surface of the connection portion of the plurality of grid members and a substantially central portion of the upper surface of the handle A core of a boiling water reactor, characterized in that the elastic body is disposed.
The core of the boiling water reactor according to any one of claims 5 to 7, wherein the grid member is a long side of the upper surface of the handle at a portion intersecting with the long side of the upper surface of the handle. A core of a boiling water reactor, comprising: a lattice expansion member extending corresponding to the elastic body disposed between the lower surface of the lattice expansion member and the upper surface of the handle.
In a core of a boiling water reactor according to claim 5 or 6,
A core of a boiling water reactor, wherein a vertical cross-sectional shape in a region other than a portion which is a lower surface of the grid member and intersects with a long side of an upper surface of the handle becomes thinner toward the fuel assembly.
In a core of a boiling water reactor according to claim 5,
From the center side of the control rod of the horizontal cross section Y-shape to the center of the control rod of the horizontal cross section Y-shape from the center side of the control rod of the horizontal cross section Y shape in the lower surface of the grid member The region has a convex portion projecting toward the fuel assembly side, and the fuel assembly restricts the displacement toward the center of the control rod of the horizontal cross section Y shape by abutting the handle to the convex portion. A core of a boiling water reactor comprising an assembly displacement control unit.
In a core of a boiling water reactor according to claim 12,
The grid member has a grid expanding member extending corresponding to the long side of the upper surface of the handle at a portion intersecting the long side of the upper surface of the handle, and the lower surface of the grid expanding member and the upper surface of the handle A core of a boiling water reactor, wherein the elastic body is disposed therebetween.
In a core of a boiling water reactor according to claim 13,
The grid member has a grid expanding member extending corresponding to the long side of the upper surface of the handle at a portion intersecting the long side of the upper surface of the handle, and the lower surface of the grid expanding member and the upper surface of the handle A core of a boiling water reactor, wherein the elastic body is disposed therebetween.
The core of the boiling water reactor according to any one of claims 5 to 8, wherein the outermost periphery of the fuel floating preventing member is loaded on the inner peripheral surface at the outermost periphery. The boiling water reactor is characterized in that it is fixed to a toroidal core support frame provided on the outer periphery of the core, or a support member provided on the inner peripheral surface of the cylindrical core shroud, having a shape compatible with the above. Core.