JP2002040192A - Fuel assembly container - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a fuel assembly container which ensures a full criticality safety for a large number of spent fuel assemblies, having stiffness and satisfactory containing efficiency and being low cost. SOLUTION: In the middle of a cylindrical metal vessel 17, a first 9 body super-cell 20, constituted by combining a plurality of metal square pipes in a plurality of lines and rows, is arranged and a neutron absorber charging plate 23 are arranged surrounding the 4 sides of the first 9 body super-cell 20. Outside the neutron absorber charging plat 23, a second 9 body super-cell 24 with a similar structure to the first 9 body super-cell 20 is arranged into a cross shape, and in the spaces 25 in the 4 corner parts formed facing the outer side of the 9 body super-cell 24, fuel cells 19 consisting of a plurality of metal square pipes 18 are embedded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly storage device, and more particularly to a fuel assembly storage device configured to efficiently store a large number of spent fuel assemblies while ensuring sufficient criticality safety. Related to the device.

[0002]

2. Description of the Related Art Spent fuel assemblies used in a nuclear reactor are cooled in a reactor facility for a certain period of time, then stored in a transport container (hereinafter referred to as a transport cask) and transported to a reprocessing plant. Either they are reprocessed or stored in a transportation cask, a transportation and storage cask, etc., and transported to an interim storage facility, where they are cooled for a long time and then reprocessed or finally disposed of.

In such a case, it is desirable that a large number of spent fuel assemblies (hereinafter, referred to as spent fuel) can be stored in the transport cask. The reasons for this are that we want to reduce the number of expensive casks used, that if the number of casks is large, the number of transportations will increase, and the possibility of accidents will increase. It can be easily understood.

However, if a large amount of spent fuel is stored in a fuel assembly storage device (hereinafter, referred to as a storage device or a fuel container) such as a cask having a certain size, heat removal or radiation is performed during a short cooling period. The shielding problem is particularly important,
It is known that as the cooling period lengthens, their importance decreases, and rather critical safety becomes more important.

[0005] In recent years, the reprocessing operation tends to be delayed from the initial plan, and accordingly, the cooling period of spent fuel has become longer. In such a case, a fuel container capable of storing more spent fuel in the limited space as described above while ensuring sufficient criticality safety is expected.

Therefore, stainless steel (hereinafter, referred to as a structural material)
SUS) to which boron (B) is added (BS)
The neutron absorption rate is increased by using US material) to ensure criticality safety (performance that guarantees never to become critical).

[0007] There is no significant difference in mechanical properties and processing from SUS containing no B when the B addition ratio in B-SUS is about 0.5 to 0.7%, but the B addition ratio is lower than the initial enrichment of the fuel. It is necessary to increase the value as the temperature rises, and the addition of B (for example, 1%) which greatly exceeds 0.5% has already been required.

[0008] When the B addition ratio is increased, the B-SUS material becomes hard and brittle, and the strength against impact force becomes insufficient, and processing becomes difficult. The use of concentrated boron obtained by enriching boron 10 (B10) greatly reduces such a problem, but results in a very expensive material.

[0009] From such a background, sufficient mechanical strength can be ensured at low cost, and more spent fuel can be stored in the limited space as described above, while ensuring sufficient criticality safety as described above. There is a need for a fuel assembly storage device that can.

Hereinafter, a specific description will be given of an example in which a fuel assembly of a boiling water reactor (BWR) is stored in a storage device. 26 (a) and (b) show BWR fuel assembly 1
26 (a) schematically shows a fuel bundle of the fuel assembly 1, and FIG. 26 (b) shows an upper portion of the fuel assembly 1. That is, as shown in FIG. 26A, a large number of fuel rods 6 are bundled using an upper tie plate 3 integrated with the handle 2, a lower tie plate 4, and a fuel spacer 5 formed in a lattice. The fuel bundle (which may be simply called a bundle) 7 is integrated.

The bundle 7 is housed inside the channel box 8 as shown in FIG. 26B, and the fuel assembly 1 is constituted as a whole. A channel fastener (sometimes simply referred to as a fastener) 9 is attached to integrate the channel box 8 and the bundle 7, and a pad 10 is attached to an upper outer surface of the channel box 8.

The pad 10 and the fastener 9 attached to the channel box 8 are used to secure a space for inserting and removing a control rod (not shown) in the nuclear reactor. Therefore, the fastener 9 has two functions. At the center of the fuel bundle 7, two water rods 11 are arranged together with the fuel rod 6 as shown in FIG. Figure 27 shows the fuel cell divider
The state in which the fuel assembly 1 is inserted (also referred to as loading) into the fuel cell 12 formed in the fuel cell 13 is shown in an enlarged cross-sectional view.

[0013] Since the fuel assembly of today's pressurized water reactor (PWR) is not equipped with a channel box, the fuel assembly and the fuel bundle are the same in the PWR fuel assembly.

As shown in FIG. 27, the fuel cell 12 is normally SUS partitioned in a cross-cut pattern by vertical and horizontal strips.
And a fuel cell partition frame 13. Fuel assembly 1
When is placed in water, the water rod 11 is filled with water, and the neutron multiplication factor is increased.

Since the fastener 9 and the pad 10 are attached to the outer periphery of the channel box 8, a relatively large gap 14 is formed, which is a major factor in reducing the number of storage units of the fuel assembly 1, and When water invades, there is a possibility that the water becomes a neutron moderator and increases the neutron multiplication factor of the fuel storage device (reduces the criticality safety). In the conventional fuel assembly storage device, B is added to the SUS fuel cell partition frame 13 as necessary, thereby suppressing an increase in the neutron effective multiplication factor.

FIG. 28 is a cross-sectional view of a portion of the fuel assembly storage device for storing spent fuel, ie, a metal container 15, in which a large number of fuel cells 12 are arranged in a grid pattern by fuel cell partition frames 13. ing. In the metal container 15 for BWR fuel assemblies currently in practical use, 52 can be stored, but in FIG. 28, the number of fuel cells 12 is increased to 69 as an example that is more dimensionally allowable.

[0017]

As more efficient transportation and intermediate storage of spent fuel is required more and more, a corresponding fuel assembly storage device is required. FIG. 29 shows a case where the drawing is made as an example in the case where the number of fuel cells is further increased to 76.

However, since the conventional metal container 15 shown by a broken line cannot be accommodated, an enlarged metal container 16 having a larger diameter as shown by a solid line is required. If the diameter of the metal container is increased, the shield constituting the outer periphery and the shock absorber at the time of falling cannot be used at all, which is not practical. Against this background, dense storage of fuel assemblies is required.

The present invention has been made to satisfy such a demand, and an object of the present invention is to provide a metal square tube for housing a fuel assembly, typically stainless steel, and boron (a neutron absorbing material). By reducing the number of B-SUS tubes to which B) is added or the rate of addition of B, the cost of the structural material can be reduced, B can be effectively used for neutron absorption at a low cost, and at a high density. It is an object of the present invention to provide a fuel assembly storage device capable of storing spent fuel and new fuel, particularly a metal container (basket) for directly storing a fuel assembly. Here, the fuel assembly storage device is a fuel transport container,
It targets transport and storage containers, but does not cover radiation shields that form the outer periphery of these containers.

[0020]

According to a first aspect of the present invention, a plurality of metal square tubes are provided in a cylindrical metal container, and a plurality of metal square tubes are provided in at least a part of the plurality of metal square tubes. A supercell made by integrally fixing metal square tubes is arranged,
At least some of the metal square tubes of the supercell include a neutron absorbing material.

According to the present invention, the metal square tube containing no neutron absorbing material mainly shares the strength by being integrally joined as a whole, and the metal square tube containing the neutron absorbing material is used to increase the neutron absorption. Since the function of suppressing the magnification is shared, manufacturability, strength and subcriticality can be achieved at the same time. These characteristics are particularly important requirements for densely packed fuel assemblies.

According to a second aspect of the present invention, in the metal square tube containing the neutron absorber, an absorber metal plate containing the neutron absorber is attached to at least a part of the metal square tube. And

According to the present invention, the metal square tube containing no neutron absorbing material for housing the fuel assembly and the second metal square tube mounted with the absorbing metal plate containing the neutron absorbing material are integrally formed. To improve strength and
The structure which does not apply a force to an absorber metal plate can be made.

According to a third aspect of the present invention, a plurality of metal square tubes are provided in a cylindrical metal container, and a plurality of metal square tubes are attached to at least a part of the plurality of metal square tubes. A supercell integrally fixed is provided, wherein the supercell is formed by interposing a plate-like neutron absorbing material between one metal square tube and the other metal square tube. . According to the present invention, the same operation and effect as those of the second aspect can be obtained.

According to a fourth aspect of the present invention, the metal square tube is made of stainless steel, and the neutron absorbing material has a boron content of 0.7.
% Or less. According to the present invention, stainless steel having a boron content of about 0.7% or less can be easily manufactured and processed by conventional techniques, and has no problem in strength and brittleness. This content may be reduced depending on the amount of fissile material contained in the fuel assembly.

According to a fifth aspect of the present invention, the metal square tube has a thick metal square tube portion and a thin metal square tube portion having substantially the same outer shape but different inner shapes. It is characterized in that boron, which is a neutron absorbing material, is added at about 0.7% or less to a thick-walled stainless steel pipe forming a square pipe section made of a metal.

According to the present invention, the absolute amount of boron addition is ensured by adding boron as a neutron absorbing material to stainless steel in a concentration range that can ensure sufficient workability and strength, and increasing the thickness. , Manufacturability, strength and subcriticality can be simultaneously achieved. These characteristics are particularly important requirements for densely packed fuel assemblies.

According to a sixth aspect of the present invention, a supercell connecting member for connecting a plurality of supercells assembled by bundling the plurality of metal square tubes so as not to protrude from the outer surface of the supercell cross-sectional width excluding the connecting member portion. It is characterized by comprising.

According to the present invention, the area of the supercell connecting member occupying the cross section of the metal container (basket) can be limited to a minimum, so that the number of fuel assemblies that can be accommodated in the metal container is reduced to a minimum. Can be suppressed.

According to a seventh aspect of the present invention, in the connecting portion,
What protrudes from the outer surface of the supercell cross-sectional width is different in a horizontal surface of the supercell, and is configured to have a different axial height from another coupling member provided on a side surface of another adjacent supercell. It is characterized by becoming.

According to the present invention, when it is required to further increase the strength of the supercell, the square tube connecting member is arranged so as to surround the supercell. At this time, the mounting axis of the square tube connecting member is set by the side surface of the supercell. Since the directional height is made different and the area occupying the cross section of the metal container (basket) is limited to a minimum, a decrease in the number of fuel assemblies that can be stored in the metal container can be minimized.

According to the invention of claim 8, the neutron absorbing material is not contained in the cylindrical metal container at all, or the neutron absorbing material is contained within a range that does not impair strength and workability even if the neutron absorbing material is contained. A first metal square tube to be mounted and a second metal square tube mounted on one side of an absorber metal plate having a neutron absorber content increased to such an extent that the mechanical strength is not hindered. And the four second metal square tubes are arranged in a cross shape such that a space formed by facing the absorber metal plate mounting surfaces is substantially the same as the inner surface of the metal square tubes, The first metal square tube is arranged in each of the four corner spaces, and a supercell in which a total of eight metal square tubes are integrally fixed is arranged at least in a part of the metal container. And

According to the present invention, of the eight metal square tubes which do not contain or contain a small amount of neutron absorbers and which have good workability and sufficient strength, four neutron absorbers each contain a large amount of neutron absorbers on one side. The absorber metal plate is fixed by welding or the like, and one fuel assembly surrounded by the absorber metal plate is disposed at the center. Therefore, all eight metal square tubes fixed integrally secure sufficient strength, and the absorber metal plate containing many neutron absorbers does not require complicated processing,
Also, since it does not require mechanical strength, it is used exclusively for suppressing neutron multiplication factor.

That is, according to the present invention, it is possible to achieve both mechanical strength and criticality security by separating functions. The effect of suppressing the neutron multiplication factor can be significantly improved in combination with the effect of claim 10 described later.

According to a ninth aspect of the present invention, the neutron absorbing material is not contained in the cylindrical metal container at all, or the neutron absorbing material is contained within a range that does not impair strength and workability even if the neutron absorbing material is contained. A first metal square tube to be mounted and a second metal square tube mounted on one side of an absorber metal plate having a neutron absorber content increased to such an extent that the mechanical strength is not hindered. A nine-body supercell, which secures the strength by surrounding and fixing one of the second metal square tubes with eight first metal square tubes, is disposed at least in a part of the metal container. It is characterized by becoming.

According to the present invention, as in the case of the eighth aspect, the neutron multiplication factor is suppressed at one center and the strength is secured by eight metal square tubes on the outer periphery. The effect of suppressing the neutron multiplication factor can be significantly improved in combination with the effect described in claim 10 described below.

According to a tenth aspect of the present invention, most of the storage sections for storing a large number of fuel assemblies are formed by combining supercells in which a plurality of metal square tubes are integrated. It is characterized in that the fuel assembly is arranged so as to be surrounded by a neutron absorbing material filling plate filled with a neutron absorbing material in a range of at least half of the entire length from the handle side when the fuel assembly is stored.

According to the present invention, the neutron absorbing plate is disposed at least in a portion where the concentration of fissile material is high in the axial length of the fuel assembly, as described above. Thus, the effect of suppressing the neutron multiplication factor can be significantly improved.

According to the eleventh aspect of the present invention, there is provided a nine-body supercell capable of storing nine fuel assemblies in a 3 × 3 array in a cylindrical metal container, one in the center of a cross and four in the front, rear, left and right directions. 5 in total
A neutron absorbing material-filled plate filled with a neutron absorbing material is disposed between the central nine-body supercell and the front, rear, left and right nine-body supercells, and further sandwiched by the adjacent supercells on the outer periphery. It is characterized in that a metal square tube is arranged in the space. According to the present invention, not only the five supercells but also a large number of metal square tubes for storing the fuel assemblies are arranged, so that a larger number of fuel assemblies can be stored.

A twelfth aspect of the present invention is characterized in that the neutron absorbing material-filled plate is formed by filling boron carbide powder in a flat stainless steel container. According to the present invention, it is possible to manufacture a neutron absorbing plate which is simple in structure and manufacture and can be filled with a large amount of boron carbide powder as a neutron absorbing material.

Also, since the cross section of the metal square tube is limited to a size that can be stored only after the channel box constituting the outer periphery of the fuel assembly is removed, there is no channel box. Can increase.

Further, by limiting the height of the metal square tube for storing the fuel assembly to a height that does not interfere with the fastener for fixing the channel box constituting the outer periphery of the fuel assembly, the cross section of the fastener is reduced. The space occupied can be saved.

Further, the metal square tube containing the fuel assembly containing or mounted with the neutron absorbing material contains the neutron absorbing material in at least a half of the entire length from the handle side. Alternatively, the neutron multiplication factor can be effectively suppressed by mounting.

[0044]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a fuel assembly storage device according to the present invention will be described with reference to FIGS. FIG. 1 is a plan view partially showing a cross section of a fuel assembly storage device according to the present embodiment, FIG. 2 is an enlarged plan view showing a nine-body supercell in FIG. 1, and FIG. 3 is a metal square in FIG. FIG. 4 is a perspective view showing only the upper part of a state in which the fuel assembly is inserted into the fuel cell formed in the tube. FIG. 4 is a cross-sectional view showing, in an enlarged manner, the metal square tube and the fuel assembly inserted in the fuel cell in FIG. FIG.

In FIG. 1, reference numeral 17 denotes a substantially cylindrical and long metal container, and 69 metal squares for housing 69 fuel assemblies in the metal container 17 along the longitudinal direction. Tube 18
Are arranged substantially in a checkered pattern, and 69 fuel cells 19 are arranged.

Of the 69 fuel cells 19, nine fuel cells 19 formed by arranging three square rows of metal square tubes 18 shown by a bold line frame at the center portion were replaced with first nine-body supercells 20. Called. The first nine-body supercell 20 is formed by welding the metal square tubes 18 of the fuel cells a to h, k as shown in an enlarged plan view in FIG.
The connecting member 22 is welded to each corner and attached to each corner.

A neutron absorbing material filling plate 23 is disposed outside the four sides of the first nine-body supercell 20. The neutron absorbing material filling plate 23 is made by integrating a pair of thin metal plates such as stainless steel with a neutron absorbing material such as boron carbide (B ₄ C).

The first 9
A second nine-body supercell 24 having a structure similar to that of the body supercell 20 is provided. Five sets are arranged.
In each of the four corner spaces 25 formed by the side surfaces of the second nine-body supercells 24 facing each other, six metal square tubes 18 are provided to constitute the fuel cells 19. Of the six fuel cells, four of the fuel cells surrounded by dotted lines near the corners are made of metal square tubes 18 in two rows and two in substantially the same manner as the nine-body supercell.
Row combination welding is performed to form a four-body supercell. By disposing the four-body supercell, the strength can be ensured.

According to the present embodiment, a cylindrical metal container
In configuring a fuel assembly storage device having 69 fuel cells 19 with 69 metal square tubes 18 in 17, a first 9-body supercell 20 is provided at the center of a metal container 17, A neutron absorbing material-filled plate 23 is provided outside the four sides of the first nine-body supercell 20, and a second nine-body supercell 24 is provided outside the neutron absorbing material-filled plate 23 in a substantially cross shape. That is, nine metal square tubes 18 are arranged in four corner spaces 25 formed between the side surfaces of the respective second nine-body supercells, and six fuel cells 19 are provided.

Therefore, the first nine-body supercell 20 suppresses the neutron multiplication factor, and the neutron multiplication factor with the neutron absorption effect of the neutron absorbing material-filled plate 23 can greatly reduce the neutron multiplication factor. it can.

As shown in FIG. 2, the first nine-body supercell 20 is composed of upper and lower fuel cells a to h and a fuel cell k at the center. It is made of an absorber-added metal square tube 26 to which a neutron absorber is added. A connecting member 22 is welded 21 to each of the corners of the fuel cells a, c, e, and g, and the connecting members 22 at the four corners are supercell cross-sectional widths w excluding the connecting member 22.
1 are fixed to a width w2 (equal in this example) so as not to protrude from the outer surface.

In the four sets of second nine-body supercells 24 shown in FIG.
Like the body supercell 20, it is constituted by a square tube 26 made of a metal with an absorbing material.

FIG. 3 shows one metal square tube 18 shown in FIG.
FIG. 3 is a perspective view of an example in which the fuel assembly 1 with the channel box 8 mounted therein is inserted, that is, loaded, and only the upper portion is shown, that is, inside the fuel cell 19. As shown in FIG. 3, the metal square tube 18 can be shortened so that the channel fastener 9 and the pad 10 do not interfere with the upper portion of the metal square tube 18.
In addition, a cut may be provided in the metal square tube 18 to make it easier to insert the fuel assembly 1.

As shown in FIG. 4, when the metal square tube 18 and the channel box 8 are viewed from above (in a direction perpendicular to the axis) (excluding the handle portion), the channel fastener 9 and the pad
10 appears to overlap with the meat portion of the metal square tube 18 as shown by the two-dot chain line. Therefore, the useless gap shown in FIG. 27 in the cross-sectional direction of the metal square tube 18 by the fastener 9 and the pad 10 is used.
14 can be deleted.

Further, since the fastener 9 occupies a more wasteful space than the pad 10, it is effective even if the fastener 9 escapes. As a means to achieve this,
For example, before loading the fuel assembly 1 on the metal square tube 18,
A spring-free bolt that protrudes out of the channel box 8 that functions to secure the control rod insertion space when loading the core (a bolt that fastens from the top of the fuel bundle that has only the function of simply fixing the fuel bundle and the channel box 8). It is also possible to take a means of exchanging with.

Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 5 corresponds to FIG.
3, the same parts as those in FIG. 3 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted. That is, in the present embodiment, a metal plate having a high neutron absorber addition rate is provided on one side surface of the metal square tube 18.
27 is fixed by welding.

According to the present embodiment, since the forming process of the absorbent metal plate 27 is not easy, the flat plate-shaped one is simply welded and fixed to the metal square tube 18, so that there is a slight Even if the absorbent moves, there is no problem in the absorption characteristics, and there is no need to have a strength corresponding to an external force, so that there is an effect that the production becomes easy.

FIG. 6 shows another example of FIG.
That is, in this example, a window 28 is opened in the metal square tube 18, and an absorbing metal plate 27 is fitted into the window 28 and fixed by welding or the like. In this configuration example, it can be used as the absorber-added metal square tube 26 for the fuel cell k shown in FIG.

Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 7 corresponds to FIG. 2, and the same parts as those in FIG. 2 are denoted by the same reference numerals, and the description of the overlapping parts will be omitted. Portions of each metal square tube 18 which are blacked out at corners and the like are fixing portions formed by welding 21. Fuel cells b, d,
The g and h metal square tubes 18 are the square tubes to which the absorbing material metal plates 27 shown in FIG. 5 are fixed, and the metal square tubes 18 of the fuel cells a to g are welded 21 at all corners. be able to.

After assembling the metal square tubes 18 of the fuel cells a to g by welding 21, the metal square tubes 18 of the fuel cells h are finally inserted into the predetermined positions (h) indicated by the two-dot chain lines to obtain the metal. Square tube
Weld 18 outer corners. Welders have been developed for welding narrow and narrow spaces, and the inner corners can also be welded by using such a welder.

According to the present embodiment, the metal square tube 18 of the fuel cell h is provided with the absorber metal plate 27 on one side surface, and the absorber metal plate 27 is provided at the position indicated by the two-dot chain line. By
It is possible to adopt a configuration in which the absorbing metal plates 27 are arranged on the four sides of the inner surface of the fuel cell k at the center, and the metal square tube of the fuel cell k can be omitted.

FIG. 8 is a plan view for explaining the first embodiment from the viewpoint of securing the overall mechanical strength. That is, in FIG. 8, the portion indicated by a bold line in the metal container 17 is a portion particularly intended to maintain the strength, and the five 9-body supercells 20 and 24 each have an outer periphery that contributes particularly to securing the strength. Will be arranged.

The nine-body supercells 20 and 24 are fixed to each other by the connecting member 22 shown in FIGS. 2 and 7, and are fixed to the metal container 17 on the outer periphery. As shown by the bold line in the four corner spaces 25, a portion composed of four fuel cells in a four-body supercell shape is also arranged so as to contribute to maintaining strength.

As shown in FIG. 2 and FIG.
May not be w2 = w1, but w2 may be greater than w1. For example, when strength is further improved. In such a case, the connecting member 22 is fixed to the side surface of the supercell so as to pass the metal container 17.
At this time, by changing the position (height) of the orthogonal coupling member 22 in the mounting axis direction, it is possible to reduce waste of space due to spatial interference in the horizontal direction.

Next, a fourth embodiment of the present invention will be described with reference to FIG. FIG. 9 is an exploded view for explaining the fourth embodiment of the present invention, in which the left side from the center line along the IX-IX direction in FIG.
The lower part is basically the same as that of FIG. 1, but it is natural that the structure is different between the side where the fuel assembly is inserted and the side where the fuel assembly is received.

When storing the spent fuel assembly with the channel box mounted, it is assumed that a slight bending will occur due to irradiation. It is desirable to increase the inside cross-sectional area of the metal square tube 18.

Therefore, in the present embodiment, the upper portion of the metal square tube 18 is formed by the thick portion 18a, and the lower portion is formed by the thin portion 18b. The connecting member 22 is fixed intermittently in the axial direction. Instead of being intermittent, the whole may be joined by an integral joining member 22, and in the case of intermittent, a structure in which the strength needs to be increased may be arranged densely. Absorbent filling plate 23
Is provided with a gap between the supercells using the coupling member 22, and is inserted into the gap. It may be easily fixed by welding or the like if necessary, but is not expected as a strength member.

FIGS. 10 to 20 are examples showing conceptually plan views of various supercell structures applied in the first embodiment. The detailed description of these embodiments is similar to that of FIGS.

The embodiment shown in FIG. 10 is the first example in which the neutron absorber is not added.
Metal square tube 18 and second metal square tube with neutron absorber
This is a two-body supercell 29 formed by fixing 26 in pairs. The embodiment shown in FIG. 11 is a four-body supercell 30 constituted by combining two cells diagonally.

The embodiment shown in FIG. 12 and the embodiment shown in FIG. 13 are obtained by alternately combining the first metal square tubes 18 and the second metal square tubes 26.
Third and fourth structures configured to accommodate the fuel assembly in the body
This is an example of the nine-body supercells 31 and 32 shown in FIG. FIG. 12 and FIG.
The first metal square tube 18 and the second metal square tube 26 can be arranged in a zigzag pattern by combining them.

The embodiment shown in FIGS. 14 to 16 is also an embodiment of a nine-body supercell. In the embodiment shown in FIG. 14, a long plate-shaped neutron is placed between upper and lower metal square tubes 18, 18 arranged in three rows. This is an example in which the absorbing plate 34 is inserted over the entire length, and the embodiment of FIG. 15 shows an example in which the long flat neutron absorbing plate 34 is sandwiched only between two metal square tubes 18.

In the embodiment shown in FIG. 16, thick-walled square tubes 37 and thin-walled square tubes 38 are alternately arranged, and a thin-walled neutron absorbing plate 39 and a thick-walled neutron absorbing plate 40 are arranged therebetween and integrally fixed. This is an example in which a nine-body supercell is configured. The neutron absorbing plates 39 and 40 have a thick wall surrounding the central square tube, and other thin walls.

According to this configuration, the absorption capacity is high at the central portion in common with the embodiments of FIGS. 2 and 7, and the central supercell is particularly effective when the absorbent filling plate is arranged as shown in FIG. is there. That is, the neutron multiplication factor can be effectively suppressed between the center and the outer periphery.

FIGS. 17 to 20 show an embodiment of a 16-body supercell. FIG. 17 shows a first 16-body supercell 41 in which 16 metal square tubes 18 are arranged in 4 rows and 4 columns. In this example, two long flat neutron absorbing plates 34 are sandwiched between upper and lower metal square tubes 18 arranged in a row. FIG. 18 shows a second 16-body supercell 42 to which the concept of the embodiment shown in FIGS. 14 and 17 is applied.
This is an example in which a long plate-like neutron absorbing plate 34 is sandwiched between 18.

FIG. 19 shows a 4 × 4 16-body supercell, in which four sets of neutron absorbing plates 34 arranged in a cross shape in the gap between four square metal tubes 18 are assembled and integrated. This is an example of the third 16-body type supercell 43. FIG. 20 is an example in which the example in FIGS. 12 and 13 is extended to 4 × 4 fourth 16-body supercells 44.

FIGS. 21 to 25 collectively show fifth to ninth embodiments of the second to sixth fuel assembly storage devices 45 to 49 in which various supercells are arranged in a metal container 17. It is shown.

FIG. 21 is a plan view showing a fifth embodiment of the present invention in which a second fuel assembly storage device 45 is partially cross-sectionally shown. A total of 52 fuel cells 19 are provided in a total of 52 fuel cells 19. This is a second fuel assembly storage device 42 that can store each of the assemblies.

In this embodiment, the four supercells 30 shown in FIG. 11 are arranged in the same manner as in FIG.
Since two metal square tubes with an absorber added per supercell are used, the effect of suppressing the neutron multiplication factor is greater than in the case of FIGS. Further, the effect of suppressing the neutron multiplication factor is greater inside the metal container 17, so the outer supercell is arranged so as to exclude the outermost periphery.

Next, a sixth embodiment according to the present invention will be described with reference to FIG. The third fuel assembly storage device 46 shown in FIG. 22 can store 69 fuel assemblies similarly to the first embodiment shown in FIG. 1, and has five 9-unit supercells similarly arranged. The fuel assembly storage device is the same as that shown in FIG.
A body supercell 31 is arranged, and a second nine body supercell 24 is arranged around the third nine body supercell 31.

Since five metal square tubes with the addition of an absorbing material indicated by x are used in the central supercell 31, the effect of suppressing the neutron multiplication factor is much larger than in the case of FIG. 2 or FIG. The effect of suppressing the neutron multiplication factor is greater inside the container 17.

For this reason, in the outer supercell 24, the metal square tube with the addition of the absorbing material is eccentric to the center, so as to be adjacent to the non-absorbing material square tube in the central supercell 31, and the outermost periphery and the next layer. Is arranged to exclude.

In the four-body supercell 30 as well, one absorber-added square tube indicated by a cross is eccentrically arranged at the center. From such a background, the absorbent filling plate used in FIG. 1 is not used.

Next, a seventh embodiment according to the present invention will be described with reference to FIG. The fourth fuel assembly storage device 47 shown in FIG. 23 can store 69 fuel assemblies as in the embodiment of FIG. 1, and has a nine-body supercell 31 disposed at the center of the metal container 17, and The fuel assembly storage device is the same in that the absorbent filling plates 23 are arranged at four positions in the upper, lower, left and right directions.

Since five absorber-added square tubes indicated by X are used in the central supercell 31, the effect of suppressing the neutron multiplication factor is much larger than in the case of FIG. 2 or FIG. The packing plate 23 is shifted to the outer periphery by one layer as compared with the case of FIG. 1 and optimized so as to maximize the effect of suppressing the neutron multiplication factor.

Next, an eighth embodiment according to the present invention will be described with reference to FIG. In this embodiment, as shown in FIG. 24, 76 metal square tubes 18 are arranged in a metal container 17, and a fifth fuel assembly storage device 48 for storing 76 fuel assemblies is provided.
A 4 × 4 array of 16 supercells 41 is arranged at the center.

Since the 16-body supercell 41 incorporates eight absorber-added square tubes indicated by X, the effect of suppressing the neutron multiplication factor is large, and the more the inside of the metal container 17 is, the more the effect of suppressing the neutron multiplication factor is increased. Because of its large size, the absorber-added square tube is eccentric to the center on the outside, adjacent to the absorber-free square tube in the central supercell, and excluding the outermost periphery and the next layer. From such a background, the neutron absorbing material filling plate 23 used in FIG. 1 is not used.

Next, a ninth embodiment according to the present invention will be described with reference to FIG. This embodiment is a fuel assembly storage device 49 that arranges 76 metal square tubes 18 in a metal container 17 as shown in FIG. 25 and stores 76 fuel assemblies.
A four-body supercell 30 shown in FIG. 11 is arranged at the center of the metal container 17 in the same manner as in FIG.

Unlike the case of FIG. 11, in the case of storing 76 fuel assemblies in which a large number of fuel assemblies are arranged also on the outer periphery of the supercell,
Since the neutron multiplication factor cannot be sufficiently suppressed only by a total of 10 absorber-added square tubes at the center, the absorber-filled plates 23 are arranged in an L-shape at one position from the supercell 30 at each of the four corners. It is optimized to effectively suppress the neutron multiplication effect.

Although the fuel assembly storage device for effectively storing the fuel assemblies of the boiling water reactor (BWR) has been described above, the same configuration is naturally applied to the pressurized water reactor (PWR).
In many cases, the present invention can also be applied to a fuel assembly storage device that effectively stores the above fuel assemblies. However, in many cases, it is more difficult to suppress the neutron multiplication effect when storing the fuel assembly of the pressurized water reactor, so a metal square tube or absorber with more neutron absorber is added. It is necessary to adopt a filling plate.

[0090]

According to the present invention, a large number of metal square tubes containing a fuel assembly are arranged in a metal container, and the first metal square tube containing no neutron absorbing material and the neutron absorbing material are used. The second metal square tube containing the metal tube, or the second metal square tube with the absorber metal plate attached thereto, or the metal plate with a significantly increased neutron absorber content is integrally fixed to increase the strength. A supercell is constructed by improving it.

The supercell having the above structure is arranged at least in a part of the inside of a metal container, and a neutron absorbing material-filled plate is used in combination, if necessary, so that complicated processing or mechanical processing of a metal plate to which a neutron absorbing material is added can be performed. Self-holding of strength is not required, and sufficient mechanical strength can be obtained.

Further, a suitable arrangement of the neutron absorbing material and a large amount of the neutron absorbing material loaded by the neutron absorbing material filling plate can be easily obtained, the neutron multiplication effect can be easily and sufficiently suppressed, and the neutron multiplying effect can be easily and sufficiently reduced. A large amount of fuel assemblies can be safely stored per device.

[Brief description of the drawings]

FIG. 1 is a partial cross-sectional plan view for explaining a first embodiment of a fuel assembly storage device according to the present invention.

FIG. 2 shows a first ninth arrangement provided in the metal container in FIG.
The top view which shows a body supercell.

FIG. 3 is a perspective view showing only a state in which a boiling water fuel assembly is inserted into a metal square tube in FIG. 1;

FIG. 4 is an enlarged cross-sectional view showing a state in which the fuel assembly is inserted into a metal square tube in FIG. 3;

FIG. 5 is a perspective view for explaining a main part of a second embodiment of the present invention.

FIG. 6 is a perspective view for explaining another example in FIG. 5;

FIG. 7 is a plan view illustrating a supercell according to a third embodiment of the present invention.

FIG. 8 is a plan view for explaining the point of securing the overall strength in the first embodiment.

FIG. 9 is a view for explaining a fourth embodiment of the present invention, which is developed along the direction of the arrows IX-IX in FIG. 1, and a left side view from the center line is a longitudinal sectional view, and a right side view is a side view. FIG.

FIG. 10 is a plan view showing a two-body supercell applied to the embodiment of the present invention.

FIG. 11 is a plan view showing a four-body supercell applied to the embodiment of the present invention.

FIG. 12 is a plan view showing a third nine-body supercell applied to the embodiment of the present invention.

FIG. 13 is a plan view showing a fourth nine-body supercell applied to the embodiment of the present invention.

FIG. 14 is a plan view showing a fifth nine-body supercell applied to the embodiment of the present invention.

FIG. 15 is a plan view showing a sixth nine-body supercell applied to the embodiment of the present invention.

FIG. 16 is a plan view showing a seventh nine-body supercell applied to the embodiment of the present invention.

FIG. 17 is a plan view showing a first 16-body supercell applied to the embodiment of the present invention.

FIG. 18 is a plan view showing a second 16-body supercell applied to the embodiment of the present invention.

FIG. 19 is a plan view showing a third 16-body supercell applied to the embodiment of the present invention.

FIG. 20 is a plan view showing a fourth 16-body supercell applied to the embodiment of the present invention.

FIG. 21 is a plan view showing a fuel assembly storage device that stores 52 fuel assemblies each including five 4-body supercells according to the fifth embodiment of the present invention.

FIG. 22 shows a sixth embodiment of the present invention in which five 9-body supercells are arranged, and four 4-body supercells are further provided.
FIG. 4 is a plan view showing a fuel assembly storage device that stores 69 fuel assemblies arranged in a body.

FIG. 23 is a view showing a seventh embodiment of the present invention, in which a nine-body supercell is arranged at the center, and a fuel assembly housing 69 fuel assemblies in which neutron absorbing material-filled plates are further arranged at four locations. FIG. 2 is a plan view showing the device.

FIG. 24 In the eighth embodiment of the present invention, 16 large fuel assemblies of 4 × 4 array can be accommodated in the center.
FIG. 9 is a plan view showing a fuel assembly storage device for storing 76 fuel assemblies in which a 16-body supercell is arranged and a number of neutron absorbing material-containing metal square tubes are arranged adjacent thereto.

FIG. 25 is a ninth embodiment of the present invention, in which five four-body supercells are arranged in the center, and a neutron-filled plate separated by one layer is arranged in an L-shape in each of the four corner spaces. 76
FIG. 2 is a plan view showing a fuel assembly storage device for storing a body.

26A is a perspective view showing a fuel bundle for explaining the concept of a boiling water fuel assembly, and FIG. 26B is a perspective view showing only a state in which a channel box is attached to the fuel bundle shown in FIG. FIG.

FIG. 27 is a plan view partially showing a cross section of a main part in a state where a fuel assembly is stored in a conventional fuel assembly storage device.

FIG. 28 is a plan view partially showing a cross section of a conventional fuel assembly storage device that stores 69 fuel assemblies.

FIG. 29 is a plan view showing a case where 76 fuel assemblies are housed for explaining the problem to be solved by the invention and a partial cross section of a conventional fuel assembly housing apparatus.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Fuel assembly, 2 ... Handle, 3 ... Upper tie plate, 4 ... Lower tie plate, 5 ... Fuel spacer, 6 ... Fuel rod, 7 ... Fuel bundle, 8 ... Channel box, 9
… Channel fastener, 10… pad, 11… water rod, 12… fuel cell, 13 …… fuel cell partition frame, 14… relatively large gap, 15… fuel container, 16… expanded fuel container, 17… cylindrical metal Container, 18: metal square tube, 18a: thick part, 18b: thin part, 19: fuel cell, 20: first nine-body supercell, 21 ...
Welding, 22 joining member, 23 neutron absorbing material filled plate, 24 second 9-body supercell, 25 corner space, 26 absorbing metal square tube, 27 absorbing metal plate, 28 window 29 ... 2 body supercell, 30 ... 4 body supercell, 31 ... third 9 body supercell, 32 ... fourth body 9 supercell, 33 ... fifth 9 body supercell, 34 ... long plate-shaped neutron absorbing plate, 35…
Sixth nine-body supercell, 36 ... seventh nine-body supercell, 37 ... thick-walled square tube, 38 ... thin-walled square tube, 39 ... thin-walled neutron absorbing plate, 40 ... thick-walled neutron absorbing plate, 41 ... first 16 Body supercell, 42 ... second 16 body supercell, 43 ... third 16 body supercell, 44 ... fourth 16 body supercell, 45 ... second fuel assembly storage device, 46 ... third fuel assembly storage Equipment, 47
... Fourth fuel assembly storage device, 48 ... Fifth fuel assembly storage device, 49 ... Sixth fuel assembly storage device.

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Masatoshi Kawashima 2-1 Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Hamakawasaki Plant (72) Inventor Kenichi Yoshioka No. 2, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa No. 1 Inside the Toshiba Hamakawasaki Plant (72) Inventor Hironori Kumano Mido No. 2-1, Ukishima-cho, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Hamakawasaki Plant (72) Inventor Ishiji Mitsashi 2-1 Hachikawa-Kawasaki Plant, Toshiba Corporation (72) Inventor Sadayoshi 8th Shin-Sugita-cho, Isogo-ku, Yokohama-shi, Kanagawa Pref.

Claims (12)

[Claims] 1. A plurality of metal square tubes are provided in a cylindrical metal container, and a plurality of metal square tubes are integrally fixed to at least a part of the plurality of metal square tubes. A fuel assembly storage device, comprising a supercell comprising: a plurality of metal square tubes of the supercell, wherein at least some of the metal square tubes include a neutron absorbing material. 2. The metal square tube containing a neutron absorber, wherein an absorber metal plate containing a neutron absorber is attached to at least a part of the metal square tube. The fuel assembly storage device according to any one of the preceding claims. 3. A plurality of metal square tubes are disposed in a cylindrical metal container, and the plurality of metal square tubes are integrally fixed to at least a part of the plurality of metal square tubes. Wherein the supercell has a flat neutron absorbing material interposed between one metallic square tube and the other metallic square tube. . 4. The fuel assembly storage device according to claim 3, wherein the metal square tube is made of stainless steel, and a neutron absorbing material has a boron content of 0.7% or less. 5. A thick metal square tube comprising a thick metal square tube portion and a thin metal square tube portion having substantially the same outer shape but different inner shapes. 4. The fuel assembly storage device according to claim 1, wherein boron as a neutron absorbing material is added to the thick stainless steel pipe forming the portion at about 0.7% or less. 6. A supercell connecting member for connecting a plurality of supercells assembled by bundling a plurality of metal square tubes so as not to protrude from the outer surface of the supercell cross-sectional width excluding the connecting member portion. 4. The fuel assembly storage device according to claim 1, wherein: 7. The connecting portion, which protrudes from the outer surface of the supercell cross-sectional width, differs in a horizontal surface of the supercell, and is different from another connecting member provided on a side surface of another adjacent supercell. 4. The fuel assembly storage device according to claim 1, wherein the fuel assembly storage device is configured to have different axial heights. 8. A first metal containing no neutron absorbing material in a cylindrical metal container or containing a neutron absorbing material within a range that does not impair strength and workability even if the neutron absorbing material is included. A second tube made of a metal tube having a neutron-absorbing material-enriched metal plate on one side attached to a side surface of the metal tube, the second metal tube having a neutron-absorbing material-enhanced concentration that does not impair mechanical strength; Are arranged in a cross so that the space formed by the mounting surfaces of the absorbing metal plates facing each other is substantially the same as the inner surface of the metal square tube. A fuel assembly comprising: a supercell in which the first metal square tube is arranged and a total of eight metal square tubes are integrally fixed; and a supercell is arranged in at least a part of the metal container. Storage device. 9. A first metal containing no neutron absorbing material in a cylindrical metal container or containing a neutron absorbing material within a range that does not impair strength and workability even if the neutron absorbing material is included. A second tube made of a metal tube having a neutron-absorbing material-enriched metal plate on one side attached to a side surface of the metal tube, the second metal tube having a neutron-absorbing material-enhanced concentration that does not impair mechanical strength; A metal square tube surrounded by eight first metal square tubes and secured to secure a nine-body supercell disposed at least in a part of the metal container. Fuel assembly storage device. 10. A storage unit for storing a large number of fuel assemblies is constituted by combining supercells in which a plurality of metal square tubes are integrated, and a supercell arranged in a central part is:
The fuel assembly is arranged so as to be surrounded by a neutron absorbing material filling plate filled with a neutron absorbing material in a range of at least a half of the entire length from the handle side when the fuel assembly is housed. The fuel assembly storage device according to claim 9. 11. A 3 × fuel assembly is placed in a cylindrical metal container.
A nine-body supercell that can hold nine bodies in three arrays is arranged in a cross shape, one in the center and four in front, rear, left and right, and a total of five bodies are arranged. A neutron-absorbing material-filled plate filled with a neutron-absorbing material, and a metal square tube disposed in a space between adjacent supercells on an adjacent outer periphery. 12. The fuel assembly storage device according to claim 10, wherein the neutron absorbing material-filled plate is formed by filling boron carbide powder particles in a flat stainless steel container.