JP2002257978A - Spent fuel storage rack and manufacturing method for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the manufacturing time greatly and improve the economical efficiency greatly by omitting a strip shaped grid plate and the welding of the strip shaped grid plate, realizing strong assembly, omitting trouble in welding operation, and simplifying operation between narrow grids. SOLUTION: A strip shaped grid plate 11 is formed of a plate material of an approximately same width as that of a fuel assembly, and includes a plurality of hook shaped projection parts 14 and recessed parts 15 which can be engaged with them formed on both side edges along a width direction of the plate material. A flat grid plate 12 is formed of a plate material of an approximately same width as of a multiple of the width of the fuel assembly, and includes a plurality of slits 16 for inserting the strip shaped grid plate 11 at an approximately same interval as the width of the fuel assembly. An intersecting point of both grid plates are integrated into one body by combining the strip shaped grid plate 11 and the flat grid plate 12 in a grid shape and locking the hook shaped projection parts 14 and the recessed part 15.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spent fuel storage rack for storing spent fuel assemblies taken out of a nuclear reactor in a fuel pool and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, in a nuclear power plant,
The spent fuel removed from the reactor core after the reactor has been operated for a certain period of time is stored and stored in a spent fuel storage rack previously installed in the spent fuel storage pool until reprocessing, and cooled. To remove the decay heat of spent fuel.

[0003] In recent years, there has been a demand to increase the storage capacity by effectively utilizing the space in the spent fuel storage pool.
In order to respond to this, a material with a large neutron absorption capacity is interposed between the stored fuels to keep the subcriticality between the fuels and narrow the interval between the stored fuels. There has been proposed a spent fuel storage rack that can increase the density by using it as a strength member.

As such a spent fuel storage rack, a so-called grid-like structure is used in which boron-added stainless steel having excellent neutron absorption capacity and good structural strength is used, and one of these is interposed between stored fuels. Is known (for example, JP-A-2000-25853).
No. 8, etc.).

A conventional example of a spent fuel storage rack satisfying such conditions will be described. In this spent fuel storage rack, a strip-shaped grid plate provided with protrusions and a flat grid plate provided with slits are combined in a grid shape, and their intersections are combined to form a fuel storage cell. Things.

FIG. 4 shows such a spent fuel storage rack 1.
5 is a plan view of FIG. 5, and FIG.
FIG. 3 is an explanatory view showing a state where the first and the flat lattice plates 12 are combined.

As shown in FIG. 5, the strip-shaped lattice plate 11 is provided with a projection 14 and a recess 15 on the back surface thereof.
The flat lattice plate 12 is provided with slits 16 corresponding to the projections 14 of the rectangular lattice plate 11. At the time of manufacture, the protrusions 14 of the strip-shaped lattice plate 11 are inserted through the slits 16 of the plate-shaped lattice plate 12 and fitted into the recesses 15 on the back surface of the adjacent strip-shaped lattice plate 11 to be combined in a lattice shape. That is, the spent fuel storage rack 10 is composed of a plurality of strip-shaped grid plates 11 and flat grid plates 12, which are combined in a grid shape and fitted and fixed to each other, and a plurality of square-shaped fuel storage cells are arranged side by side as shown in FIG. 13 is formed.

The fuel storage cell 13 is integrally mounted on a base 3 provided on the bottom surface of the spent fuel storage pool (not shown in FIG. 4) with bolts and nuts. The plurality of fuel assemblies 7 are connected to the fuel storage cells 1
3, which are individually inserted into the seat 3 on the base 3 (not shown).
Is fitted and supported.

FIG. 6 is an enlarged vertical sectional view taken along the line BB of FIG. As shown in FIG. 6, the strip-shaped grid plate 11 is provided with a plurality of protrusions 14 at one end along the width direction, and further, the adjacent strip-shaped grid is provided at the opposite edge. A recess 15 is formed to fit with the projection 14 of the plate 11. Each of the strip-like lattice plates 11 is set to have a length corresponding to the axial length of the fuel assembly 7 and a width corresponding to the width of one fuel storage cell 13.

On the other hand, the flat lattice plate 12 is
And a length corresponding to the axial length of the fuel storage cells 13
And a plurality of slits into which the projections 14 of the strip-shaped lattice plate 11 are inserted at every one-cell pitch of the fuel storage cells 13. 16.

The plurality of strip-shaped grid plates 11 and the flat grid plates 12 are arranged so as to intersect at right angles with each other in the plane of the spent fuel storage rack 10 so as to intersect at right angles.
The projections 14 of the strip-shaped lattice plate 11 are inserted into the slits 16 of the rectangular lattice plate 11.
Spent fuel storage rack 1 with fitting and fixing recesses 15
0 is formed.

Then, the strip-shaped grid plates 11 are welded to each other, and the strip-shaped grid plates 11 and the flat grid plates 12 are firmly fixed to each other to form a plurality of fuel storage cells 13 arranged side by side.

FIG. 7 is a sectional view taken along line CC of FIG. 6, and FIG. 8 is a sectional view taken along line DD of FIG. As shown in FIG. 7, the rectangular grid plate 11 and the flat grid plate 12
(The intersection on the concave portion 15 side) is welded as a welded portion 17 and firmly fixed to each other. Similarly, as shown in FIG. 8, at the portion where the slit 16 and the projection 14 are located, the joint between the projection 14 of the strip-shaped grid plate 11 and the recess 15 of the adjacent strip-shaped grid plate 11 is further welded. It is welded as the part 17 to firmly fix the strip-shaped lattice plates 11 to each other.

As described above, in manufacturing the spent fuel storage rack 10, one flat lattice plate 12
A plurality of strip-shaped lattice plates 1
1 are arranged at right angles so that the concave portions 15 face each other, and the end side surface of the abutted strip-shaped grid plate 11 and the flat grid plate 12 are fixed by welding to perform the first-stage assembly.

Next, the flat grid plate 12 is placed on the projections 14 of the first grid plate 11 so that the slits 16 of the second flat grid plate 12 are located on the protruding portions 14 thereof. Of the second flat plate-like lattice plate 12
And the projection 14 is projected from the slit 16.

Thereafter, the second-stage strip-shaped lattice plate 11 is disposed so that the recess 15 thereof is fitted with the projection 14 projecting from the slit 16, and the projection of the first-stage strip-shaped lattice plate 11 is welded. Part 14 and second-stage flat lattice plates 12 and 2
The stepped strip-shaped lattice plate 11 is connected to the recess 15. After that, the flat grid plate 12 and the strip grid plates 11 are sequentially stacked in the same procedure to manufacture the spent fuel storage rack 10.

[0017]

However, in the spent fuel storage rack described above, the strip-shaped grid plates 11 and the strip-shaped grid plates 11 and the flat-plate grid plates 12 are welded to each other so as to be firmly connected to each other. Since a plurality of fuel storage cells 13 arranged side by side are fixed to each other, it takes a lot of time and labor to perform the welding operation, and it becomes necessary to use a special jig and tool because the welding operation is performed between narrow grids. There is a problem with economy.

Further, all of the boron-added stainless steel used as the material of the strip-shaped lattice plate 11 and the plate-shaped lattice plate 12 is made of boron-added stainless steel. It has material properties that make welding difficult.

The present invention has been made in view of the above-mentioned circumstances, and eliminates a strip-shaped grid plate as a constituent element and a welded portion between the strip-shaped grid plate and the flat-plate grid plate, thereby greatly reducing the manufacturing time. It is an object of the present invention to provide a spent fuel storage rack that can be reduced in cost and improve economy, and a method of manufacturing the same.

It is another object of the present invention to provide a spent fuel storage rack having a high neutron absorption capacity.

[0021]

In order to solve the above-mentioned problems, according to the first aspect of the present invention, a plurality of fuel storage cells for storing spent fuel assemblies are formed by a plurality of strip-shaped lattice plates and a flat plate. A spent fuel storage rack formed by a lattice-like combination with a lattice plate, wherein the strip-like lattice plate is made of a plate having substantially the same width as the width of the fuel assembly, and the width direction of the plate is A plurality of hook-shaped protrusions and a recess in which these can be locked, and the flat grid plate is made of a plate material having a width substantially equal to a multiple of a width of the fuel assembly. The plate material has a plurality of slits through which the rectangular grid plate can be inserted at substantially the same interval as the width of the fuel assembly, and the rectangular grid plate and the flat grid plate are combined in a grid, and The hook By locking the parts and recesses, provides a spent fuel storage rack, characterized in that integrated the intersection of the two grid plates.

According to the second aspect of the present invention, in the spent fuel storage rack according to the first aspect, the outermost flat lattice plate is made of stainless steel to which boron is not added, while the outermost flat lattice plate is other than the outermost circumference. The grid plate and the strip-shaped grid plates are provided with a spent fuel storage rack, which is made of stainless steel to which boron is added.

According to the third aspect of the present invention, in the spent fuel storage rack according to the first aspect, the outermost outermost flat lattice plate is compared with the other outermost flat lattice plates and strip-shaped lattice plates. Provided is a spent fuel storage rack which is made of stainless steel to which a small amount of addition is made or stainless steel to which concentrated boron is added.

In the invention according to claim 4, claims 1 to 3
In the spent fuel storage rack according to any one of the above, the material of the flat grid plate and the strip grid plate other than the outermost periphery is replaced with stainless steel, and is constituted by a metal material that absorbs neutrons such as hafnium. To provide a spent fuel storage rack.

In the invention according to claim 5, a plurality of fuel storage cells for storing used fuel assemblies are formed by a combination of a plurality of strip-shaped grid plates and a flat grid plate. A method of manufacturing a storage rack, comprising, as the strip-shaped lattice plate, a plate member having a width substantially equal to the width of the fuel assembly, and a plurality of hook-like projections on both side edges along the width direction of the plate member. While the one having a concave portion with which these can be applied is applied, the flat lattice plate is constituted by a plate material having a width substantially the same as a multiple of the width of the fuel assembly, and the plate material is formed of the fuel assembly. Applying a slit having a plurality of slits through which the strip-shaped lattice plate can be inserted at substantially the same interval as the width, the hook-shaped projections of the strip-shaped lattice plate are connected to the slits of the plate-shaped lattice plate and adjacent strip-shaped lattice plates. of Assembling in a grid insert in part,
A method for manufacturing a spent fuel storage rack is provided, wherein the intersections are integrated by non-welding and the procedure is repeated to assemble the spent fuel storage rack.

According to a sixth aspect of the present invention, in the method for manufacturing a spent fuel storage rack according to the fifth aspect, stainless steel to which boron is not added, and material other than the outermost circumference are used as the material of the outermost flat grid plate. While stainless steel or boron-enriched stainless steel containing less boron is used as compared to the flat grid plate and the strip grid plate, boron is used as the material of the flat grid plate and the strip grid plate other than the outermost periphery. A method for manufacturing a spent fuel storage rack, characterized in that a metal material that absorbs neutrons, such as stainless steel or hafnium, to which iron is added is applied.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. Note that the same components as those of the above-described conventional technology are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 is a plan view of a spent fuel storage rack 10 according to the present embodiment, and FIG. 2 is a combination of a strip-shaped grid plate 11 and a flat grid plate 12 of the spent fuel storage rack 10 according to the present embodiment. FIG.

As shown in FIGS. 1 and 2, the spent fuel storage rack 10 according to the present embodiment is configured such that the hook-shaped projections 14 of a plurality of long rectangular strips 11 are connected to the flat grid 1.
2 is inserted into the slit 16 provided in the second rectangular plate 11 and fitted into the concave portion 15 on the rear surface of the adjacent strip-shaped lattice plate 11 so as to be combined in a lattice shape. 13, the fuel storage cell 13 is integrally mounted on the base 3.

The base 3 is integrally mounted on the bottom surface of a spent fuel storage pool (not shown in FIG. 1) with bolts and nuts (not shown). Are individually inserted into the fuel storage cells 13 and fitted and supported in seat holes (not shown) on the base 3.

FIG. 3 is an enlarged vertical sectional view taken along line AA of FIG. As shown in FIG.
Reference numeral 1 denotes a length corresponding to the axial length of the fuel assembly 7 and a width corresponding to the width of one cell of the fuel storage cell 13, and a plurality of hook-like projections 14 are provided along both side edges thereof. The hook-shaped projection 14 is provided at a position where the installation height at one end surface and the installation height at the opposite end surface are different from each other. That is, the hook-shaped projection 14 has a tip hook 14a projecting downward in FIG.

On the other hand, the flat lattice plate 12 is
And a length corresponding to the axial length of the fuel storage cells 13
Have a width corresponding to the width of the spent fuel storage rack 10 in which the hook-shaped projections 14 of the strip-shaped lattice plate 11 are inserted at a pitch of one cell of the fuel storage cells 13. Has a slit 16. The width of the slit 16 of the flat lattice plate 12 is set to a width that allows the hook-shaped projection 14 of the rectangular lattice plate 11 to be inserted.

Since the tips of the hook-shaped projections 14 of the strip-shaped lattice plate 11 are inserted into the lower ends of the slits 16 of the plate-shaped lattice plate 12, the lattice plates are connected to each other without welding.

The plurality of flat grid plates 12 and strip grid plates 11 are arranged so as to intersect at right angles with each other on the plane of the spent fuel storage rack 10, and are inserted into the slits 16 of the flat grid plate 12. The hook-shaped projections 14 of the plate-like lattice plate 11 are inserted through and fitted into the recesses 15 on the back surface of the adjacent plate-like lattice plate 11, thereby connecting the plate-like lattice plate 12 and the plate-like lattice plate 11 to each other, The storage cell 13 is configured. As shown in FIG. 3, the vertical width a of the concave portion 15 on the back surface of the strip-shaped lattice plate 11 is larger than the vertical height of the hook-shaped projection 14 including the tip hooked portion 14a. Recess 1
After being inserted into the fuel cell 5, it is possible to move in the axial direction of the fuel assembly (vertical direction in FIG. 3), and by this movement, the tip hook 14 a is inserted into the slit 16 of the flat lattice plate 12. In the state, it can relatively move downward in the recess 15,
As a result, the plate-like lattice plate 12 is sandwiched by the tip hooks 14a.

The material of the outermost strip-shaped lattice plate 11 is stainless steel to which boron is not added.
Stripe grid plate 11 and flat grid plate 12 other than the outermost periphery
Is a stainless steel to which boron is added.

Thus, a plurality of fuel storage cells 13 arranged in parallel are formed. In this case, the outermost flat lattice plate 1 is formed.
The two are firmly connected to each other by welding. When the fuel storage cells 13 are formed, the hook-shaped projections 14 of the strip-shaped grid plate 11 are located on both side edges and at different heights. And the hook-shaped projections 14 can be inserted into the slits 16 having different heights of the flat lattice plate 12 without interfering with each other.

The width of the slit 16 of the flat grid plate 12 is set to a width that allows the hook-shaped projection 14 of the strip grid plate 11 to be inserted.
Since the tips of the 4 are inserted into the lower ends of the slits 16 of the flat grid plate 12, the grid plates can be connected to each other without welding.

According to this structure, the outermost strip-shaped lattice plate 11 and the plate-shaped lattice plate 12 are made of stainless steel to which boron is not added. Sufficient in strength, the outermost grid plate maintains the strength of the entire spent fuel storage rack against earthquake loads,
Both boron-added stainless steel and stainless steel contribute to the absorption of neutrons from spent fuel.

The boron-added stainless steel used as a material for the strip frame plate 11 and the flat lattice plate 12 other than the outermost periphery is not welded because the weldability decreases as the added boron amount increases. It is arranged only inside and serves as a neutron absorber. For this reason, the strip-shaped lattice plate 11 and the plate-shaped lattice plate 12 in which boron-added stainless steel having a larger amount of boron than the boron-added stainless steel used in the conventional spent fuel storage rack is disposed inside.
By reducing the plate thickness by applying the above material, it is possible to realize the spent fuel storage rack 10 having a higher density and a sufficient shielding effect.

Further, by eliminating the welding of the boron-added stainless steel, difficult operations in manufacturing the spent fuel storage rack 10 are reduced, and the manufacturing cost is significantly reduced. Regarding that stainless steel is inferior in neutron absorption capacity to boron-added stainless steel, only stainless steel is used on the outermost flat lattice plate, and the outermost of the spent fuel storage rack is used. The two flat lattice plates and the spent fuel storage rack are located between the spent fuel stored in the Since a certain gap is present, the problem of subcriticality can be complemented.

In the future, even if higher neutron absorption capacity is required for the material of the spent fuel storage rack due to the higher burnup of the fuel, the material of the outermost flat lattice plate 12 is relatively doped with boron. If you use low volume stainless steel,
For stainless steel with a large amount of added boron other than the outermost circumference,
Since the impact value and elongation value are good, there is an advantage in structural strength, and the subcriticality of spent fuel is also effective by adding boron to stainless steel.

In the spent fuel storage rack having the above-mentioned structure, boron-added stainless steel is used for each lattice plate other than the outermost periphery. However, enriched boron-added stainless steel or hafnium may be used. it can.

Further, by using stainless steel to which inexpensive boron is not added or stainless steel to which relatively little boron is added to each of the outermost lattice plates, the total price of the spent fuel storage rack can be reduced. Can be expected.

Therefore, according to the present embodiment, the outermost flat lattice plate made of stainless steel to which boron is not added or stainless steel to which relatively little boron is added with respect to an earthquake load has sufficient structural strength. In addition to having a rectangular grid plate and a flat grid plate other than the outermost periphery, they are joined together without welding, so that they can sufficiently withstand vibration during earthquakes, reducing welding work that is difficult in manufacturing and reducing manufacturing costs. Significant cost reduction is realized.

Further, the present invention is applied to a material for a strip-shaped lattice plate and a plate-shaped lattice plate in which boron-added stainless steel having a larger amount of boron than that used for a conventional spent fuel storage rack is disposed inside. By reducing the plate thickness, a spent fuel storage rack having a higher denseness and a sufficient shielding effect can be realized.

On the other hand, the outermost lattice plate made of stainless steel to which boron is not added or stainless steel to which boron is added in a relatively small amount is stored at the outermost side of one spent fuel storage rack. Between the spent fuel stored on the outermost side of the other spent fuel storage rack facing the other spent fuel, there is a certain distance between the two flat lattice plates and the spent fuel storage rack. Since the gap is present, the problem of subcriticality can be complemented.

Further, by using stainless steel to which inexpensive boron is not added or stainless steel to which a relatively small amount of boron is added to each outermost lattice plate, the price of the spent fuel storage rack as a whole is low. Therefore, the effect that the economic efficiency is improved can be obtained.

[0048]

As described above, according to the spent fuel storage rack and the method for manufacturing the same according to the present invention, it is possible to realize a robust assembly by omitting welding of the strip-shaped grid plate and the strip-shaped grid plate. As a result, the time required for the welding work can be reduced, the work between narrow grids can be facilitated, and the like, so that the manufacturing time can be greatly reduced and the cost can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a plan view showing an example of a spent fuel storage rack according to an embodiment of the present invention.

FIG. 2 is an explanatory view showing a combined state of a rectangular grid plate and a flat grid plate in the embodiment of FIG. 1;

FIG. 3 is a sectional view taken along the line AA in FIG. 1;

FIG. 4 is a plan view showing a conventional spent fuel storage rack.

FIG. 5 is an explanatory view showing a state in which a strip-shaped grid plate and a flat grid plate are combined in a conventional example.

FIG. 6 is an enlarged vertical sectional view taken along line BB in FIG. 4;

FIG. 7 is a sectional view taken along the line CC in FIG. 6;

FIG. 8 is a sectional view taken along line DD in FIG. 6;

[Explanation of symbols]

 REFERENCE SIGNS LIST 3 base 7 fuel assembly 10 spent fuel storage rack 11 strip-shaped grid plate 12 flat grid plate 13 fuel storage cell 14 hook-shaped protrusion 14 a tip hook 15 recess 16 slit

Claims (6)

[The claims] 1. A spent fuel storage rack in which a plurality of fuel storage cells for storing used fuel assemblies are formed by a combination of a plurality of strip-shaped grid plates and a flat grid plate in a grid pattern. The strip-shaped lattice plate is formed of a plate having a width substantially the same as the width of the fuel assembly, and has a plurality of hook-shaped protrusions and a recess in which these can be locked on both side edges along the width direction of the plate. The flat grid plate is configured by a plate material having a width substantially equal to a multiple of the width of the fuel assembly, and the strip grid plate is provided on the plate material at substantially the same interval as the width of the fuel assembly. It has a plurality of slits that can be inserted, by combining these strip-shaped lattice plate and the plate-shaped lattice plate in a lattice shape, and by locking the hook-shaped protrusion and the concave portion, the intersection of the two lattice plates That we have integrated Characterized spent fuel storage rack. 2. The spent fuel storage rack according to claim 1, wherein the outermost flat plate grid plate is made of stainless steel to which boron is not added, while the other outermost plate grid plates and strip grids are provided. A spent fuel storage rack characterized in that the plate is made of boron-added stainless steel. 3. The spent fuel storage rack according to claim 1, wherein the outermost flat grid plate has a smaller amount of boron added than the outermost flat grid plate and the strip grid plate. Or a concentrated boron-added stainless steel. 4. The spent fuel storage rack according to claim 1, wherein the material of the flat grid plate and the strip grid plate other than the outermost periphery is replaced with stainless steel, and neutrons such as hafnium are removed. A spent fuel storage rack comprising a metal material to be absorbed. 5. A method for manufacturing a spent fuel storage rack, wherein a plurality of fuel storage cells for storing spent fuel assemblies are formed by a combination of a plurality of strip-shaped grid plates and a flat grid plate. In addition, the strip-shaped lattice plate is formed of a plate having substantially the same width as the width of the fuel assembly, and a plurality of hook-shaped protrusions may be engaged with both side edges along the width direction of the plate. While having a concave portion, the flat lattice plate is constituted by a plate material having a width substantially equal to a multiple of the width of the fuel assembly, and the plate material is provided at substantially the same interval as the width of the fuel assembly. A grid having a plurality of slits through which the strip-shaped lattice plate can be inserted is applied. In shape A method for manufacturing a spent fuel storage rack, comprising: assembling, integrating intersections thereof by non-welding, and repeating the procedure to assemble a spent fuel storage rack. 6. The method of manufacturing a spent fuel storage rack according to claim 5, wherein the outermost flat grid plate is made of stainless steel to which boron is not added, a flat grid plate other than the outermost grid, and a strip. While stainless steel containing less boron or enriched boron-added stainless steel is used as compared to the plate-like lattice plate, the material of the plate-like lattice plate and strip-like lattice plate other than the outermost periphery is stainless steel or boron-added stainless steel. A method for manufacturing a spent fuel storage rack, comprising applying a metal material that absorbs neutrons such as hafnium.