JPS61137097A - Spent fuel storage rack - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a spent fuel storage rack for storing fuel taken out from a nuclear reactor.

[Technical Background of the Invention] Generally, in a nuclear power plant, a spent fuel storage rack is installed at the bottom of a fuel storage pool, and the fuel removed from the reactor is stored in this rack and cooled, and its decay heat is removed. I try to do that.

In such a spent fuel storage rack, in order to increase the amount of fuel stored, it is necessary to interpose a metal material with a high radiation shielding ability between the stored fuel. For this reason, rectangular cylindrical cells are usually formed using boron-containing austenitic stainless steel, and a large number of these cells are arranged in a checkered pattern to form a spent fuel storage rack. .

10 and 11 show a partially vertical front view and a plan view of a conventional spent fuel storage rack. A spent fuel storage rack is installed, and spent fuel F is stored in each cell.

As shown in FIG. 3, the cell 3 includes a cell 3a formed by rectangular cylinders 4 that are planted on the base 2 so as to be offset by one pitch in the vertical and horizontal directions, and a cell 3a formed between these rectangular cylinders. 3I of the cell 3C formed by closing one side between the cell 3b and the outermost rectangular cylinder 4 with the vertical plate 5.
There is category i.

The rectangular cylinder 4 is made of a metal material with a high radiation velocity H ability, such as poron-containing stainless steel, so that it can maintain a sufficiently subcritical state even when the fuel is stored in close proximity. In order to assemble the four rectangular cylinders 4 by welding, it is necessary to weld the four corners of the rectangular cylinders 4 together, which results in large welding deformation and makes direct welding difficult.

For this reason, angles 6 are inserted into the corners of the adjacent rectangular cylinders 4 and the vertical plates 5, and fixed by welding while adjusting the spacing, thereby forming cells 3b13C of a predetermined size.

[Problems with back M technology] However, when angles 6 are provided in cells 3b and 3C, the inner diameters of cells 3b and 3c become smaller by the thickness of the angles 6, so the inner diameters are increased by the thickness of angles 6. Therefore, interference with fuel F must be avoided. Therefore, the fuel storage pitch must be widened by the thickness of the angle 6. Further, since these cells 3b13c have a large welding deformation, a large margin of inner diameter must be taken in order to insert fuel, resulting in a disadvantage that the fuel storage density is reduced.

Furthermore, since the rectangular cylinder body 4 is welded and restrained via the angle 6, the rigidity of the entire rack tends to be insufficient, and if an overload is applied during an earthquake, the spent fuel storage rack When mounting the fuel storage boule 1 on a rack, excessive force is applied to the bolt 7 and its base material, so these parts have to be severely reinforced.

[Object of the Invention] The present invention has been made in view of the above-mentioned circumstances in the background art, and by directly connecting a plurality of rectangular cylinders made of boron-added austenitic steel material in the vertical and horizontal directions, it is possible to save fuel! It is an object of the present invention to provide a spent fuel storage rack in which the stiffness of the spent fuel storage rack is increased, the rigidity of the entire spent fuel storage rack is prevented from decreasing, and the earthquake resistance is improved.

[Summary of the Invention] The spent fuel storage rack of the present invention consists of a rectangular tube made of austenite I stainless steel material to which 1% or less boron has been added, on a base having a cooling material passage fixed to the bottom of the fuel storage pool. It is characterized in that the bodies are closely arranged adjacent to each other, cells are formed only within the square cylinder body, and fuel is stored in these cells.

[Embodiments of the invention] Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partially longitudinal front view of a spent fuel storage rack of the present invention, and FIG. 2 is a plan view thereof.

In these figures, on a base 20 formed as a part of the fuel storage boule 10, rectangular cylinders 3o are arranged closely in the vertical and horizontal directions and welded one after another to form a large number of cells 40.

As shown in FIG. 3, the rectangular tube body 30 is made by abutting a pair of U-shaped channels 31 made by bending plate materials at right angles into a prismatic shape, and joining the butts together at a welded portion 32. I-shaped acid formation or bending a plate material into a round tube shape, welding between the side edges, and then forming it into a square tube. As shown in FIG. 1, the upper part of the rectangular cylinder 30 is chamfered 33 to facilitate insertion of the fuel F.

As the material for these rectangular cylinders 30, austenitic stainless steel to which 1% or less of boron, which has a large radiation shielding ability, is added is used.

Generally, 3W boron is added to austenitic stainless steel.
Addition of up to 1% will result in lumps, but if the boron content is 2.
When it exceeds 0 to 50 pDl, polide, which is a compound of chromium and boron, appears, and when it exceeds 100(] , the solid solution strengthening of boron itself is not so remarkable, and the dispersion strengthening of polide causes hardening.For this reason, when 3% by weight of boron is added, the elongation increases by a few%.
It falls to a certain extent.

Since the elongation of austenitic stainless steel is 40% or more, the elongation of austenitic stainless steel with 3mff1% boron added is about 1/1 of that of one without additives.
10, making bending very difficult.

Further, since the addition of boron tends to significantly lower the impact value, the amount of boron added is preferably 1% or less. If the amount of boron added is 1% or less, the impact value does not decrease so much, bending work is possible, and weldability does not deteriorate so much.

In the present invention, since the cell 40 is formed by directly connecting the rectangular cylinders 30 with good dimensional accuracy, it is possible to configure the cell 40 with small welding distortion and good dimensional accuracy.

Further, by directly connecting the rectangular cylinders 30 to each other, a decrease in the rigidity of the rectangular cylinders 30 can be prevented.

The rectangular tube bodies 30 are connected as shown in FIGS. 4 to 6.

First, as shown in FIG. 4, two rectangular cylinders 30a and 3Q
b are placed adjacent to each other, and the corner portions 34 are fixed by welding portions 35. Next, as shown in FIG.
Another rectangular cylindrical body 30c is placed adjacent to a, and the corner portions thereof are fixed by welding portions 36. Further, as shown in FIG. 6, another rectangular cylinder 30d is arranged adjacent to the side surface of the rectangular cylinders 30a and 30c, and a welded portion 3 is formed between the corner portions of the rectangular cylinders 30d.
Fixed by 7. Thereafter, the rectangular tube bodies 30 are sequentially welded and restrained in the same manner.

In addition, the connection of the rectangular cylinder 30 is performed using a reinforcing plate 5 as shown in FIG.
It is also possible to weld reinforcement through 0.

In this case, although the storage density is reduced by the thickness of the reinforcing plate 50, higher rigidity can be obtained by attaching reinforcing plates to the inside and outside of the rectangular cylinder 30.

FIGS. 8 and 9 show details of the base 20 described above, and the base 20 is composed of a plate 21, a side plate 22, and a base plate 23. The lower end of the fuel F is fitted into the upper plate 21! A round hole 24 for placing the cell 40 is transparently provided, and the rectangular cylinder 30 is positioned and welded so that the center of each cell 40 coincides with the center of each round hole 24.

The side plates 22 are for supporting the upper plate 21 and are welded to the upper plate, and the side plates 22 each have cooling holes 25 through which cooling water for cooling fuel passes. The rectangular cylinder 30 is welded 2 to the upper plate 21 using the chamfer 26 at the lower part.
7 has been done. The M separation plate 23 is for installing the spent fuel storage rack at the bottom of the fuel storage pool 10.
M foundation bolt 1 protruding from the bottom of the fuel storage pool 10
1 with a nut 12, and is also fixed to a side plate 22 with a welded portion 13.

[Effects of the Invention] As described above, in the spent fuel storage rack of the present invention, rectangular cylinders made of boron-added austenitic stainless steel with good dimensional accuracy are assembled by direct welding, and cells made only of rectangular cylinders are assembled. The inner dimensions of each cell can be precisely assembled to form the cell.

Therefore, since each cell can be formed with dimensions slightly thicker than the fuel, the inside of each cell can be made smaller, and the pitch of each cell can also be made smaller, so the fuel storage density can be increased by the reduction in pitch. be able to.

At the same time, by directly restraining the rectangular cylinder, the rigidity of the rack can be obtained, resonance with the building during an earthquake can be avoided, overload can be prevented, and earthquake resistance can be improved.

[Brief explanation of drawings]

The first factor is a partial vertical sectional view showing an embodiment of the spent fuel storage rack of the present invention, FIG. 2 is a plan view thereof, FIG. 3 is a plan view of a square cylinder, and FIGS. 4 to 6 are FIG. 7 is a plan view of a modification showing a method of connecting rectangular cylinders,
Fig. 8 is a vertical cross-sectional view showing details of the base, Fig. 9 is a plan view of the upper plate, Fig. 10 is a partial vertical cross-sectional view of a conventional spent fuel storage rack, and Fig. 11 is a plan view thereof. . 1.10・・・・・・Fuel storage pool 2.20・
...Base 3.3a, 3c, '40...Cell 4.30a to 30d...Square cylinder 5...
... Vertical plate 6 ... Angle 13.32.35.36.37 ... Welding part 21 ...
......Top Plate 22...Side Plate 23...Base plate 24...Round Hole 25... ...Cold part hole 26.33...Chamfer 31...Channel 34...Corner part 50...Reinforcement plate F・・・・・・・・・Fuel Agent Patent Attorney Sa Suyama - Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Figure 7 Figure 8 Figure 9 Figure 11 Figure ℃ figure

Claims (3)

[Claims] (1) On a base having a coolant flow path fixed to the bottom of the fuel storage pool, rectangular cylinders made of austenitic stainless steel material to which 1% or less boron has been added are arranged closely adjacent to each other in the vertical and horizontal directions. A spent fuel storage rack characterized by forming cells only inside cylinders and storing fuel within these cells. (2) The spent fuel storage rack according to claim 1, wherein adjacent rectangular cylindrical bodies are connected by welding their corner portions. (3) The spent fuel storage rack according to claim 1, wherein adjacent rectangular cylinders are welded and restrained via reinforcing plates.