JPH10170687A - Used nuclear fuel storage rack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To densely store used fuels, prevent generation of high thermal stress, and facilitate the replacement by mutually and adjacently juxtaposing plural vertical housing cells in a shroud erected on a bottom plate. SOLUTION: A shroud 17 is erected by surrounding a porous part 11a formed in a central part of a bottom plate 11, and slender square cylindrical housing cells 19 are adjacently juxtaposed in it without connecting them to each other. Used fuels are put one by one in the respective cells 19, and since a storage rack 10 exists in pool water, water in the cells 19 rises by being heated by decay heat, and the pool water circulates by being sucked in the cells 19 through a lower space and the porous part 11a of the bottom plate 11. Since neutrons coming out of the used fuels are decelerated by the pool water and are also absorbed by walls of the cells 19, critical reaction is not caused. Though the cells 19 themselves also thermally expand by a rise in a water temperature in the cells 19, since the cells 19 are not fixed to each other, thermal expansion is not restrained, and therefore, excessive thermal stress is not caused.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a spent nuclear fuel storage rack for storing so-called spent nuclear fuel in water.

[0002]

2. Description of the Related Art A so-called spent fuel, which has undergone a predetermined combustion in a nuclear reactor of a nuclear power plant, continuously emits radiation and decay heat. It is stored in a storage rack placed in the water of a storage pit or a cooling pit attached to the place (Japanese Utility Model Publication No. 5-7598, Japanese Patent Application Laid-Open No. H05-5598).
No. 281395). The structure of such a rack will be described briefly. In FIG. 4, an elongated box-shaped storage cell 3 is inserted into a support plate 1 in which rectangular holes are formed at predetermined intervals in a horizontal direction to form a rack. Although not shown, the spent fuel to be stored has an outer shape with a rectangular cross section, and the inner cross section of the storage cell 3 is also rectangular. By the way, the mutual interval between the storage cells 3 is determined so as to achieve the subcritical condition. However, recently, due to various circumstances, it is required to store as much spent fuel as possible in the storage pit of the power plant. For this purpose, it has been proposed to use a material having a large neutron absorption capacity or a material having a large plate thickness as a constituent material of the storage cell, and to join the storage cells 5 to each other by welding 7 as shown in FIG.

[0003]

However, in the structure in which the storage cells are supported by a plate or the like as described above, there is a limit in shortening the interval between the storage cells, and even if the plate is replaced with a combined structure, the structure is reduced. Becomes too complicated. Further, when the storage cells are welded to each other, the thermal expansion of the storage cells due to decay heat is restrained, which causes a problem in structural strength. In addition, when the storage racks are sequentially replaced with storage racks capable of densely storing spent fuel, it is preferable from the standpoint of radiation shielding that the replacement be performed while the storage pits are filled with water. The present invention has been made in view of the above-described circumstances, and provides a spent nuclear fuel storage rack that can store spent fuel densely, does not generate high thermal stress due to decay heat, and is easy to replace. Make it an issue.

[0004]

According to the present invention, there is provided a spent nuclear fuel storage rack comprising: a horizontal bottom plate having a porous portion at a central portion; A vertical shroud standing upright on the bottom plate and having a rectangular flat cross section, a plurality of vertical storage cells arranged side by side in the shroud, and a bottom plate located outside the shroud And a mounting bolt that is disposed below the peripheral portion and that is attached to the mounting portion and penetrates the peripheral portion. When connecting the gantry and the bottom plate not to the outside of the shroud as described above, but to maximize the storage capacity by enlarging the shroud fully, align the mounting bolts with the vertical storage cell at the outermost peripheral position and install the mounting bolt You may arrange | position and penetrate in the periphery part of a bottom plate, and may be made to screw with a gantry.

[0005]

Embodiments of the present invention will be described below with reference to the accompanying drawings. First, referring to FIG. 1, a horizontal bottom plate 11 is fixed by a mounting bolt 15 on a gantry 13 fixed to the bottom of a storage pool (not shown). The porous portion 11a formed at the center of the bottom plate 11 is separated from the bottom surface of the pool for this reason, and an inflow space (not shown) for pool water is formed at the bottom. An enclosing plate 17 having a rectangular flat cross section is erected around the porous portion 11a, and elongated rectangular tubular storage cells 19 are arranged side by side with each other. The storage cell 19 has an inner surface facing the outer surface of the spent fuel at a narrow interval, and accepts the spent fuel stably, but is made of a modified stainless steel having a neutron absorption capacity larger than that of normal stainless steel. And satisfies the subcritical conditions. The storage cells 19 arranged in rows and columns are not connected to each other, and have a hanging hole 17a for lifting at the upper end of the surrounding plate 17 above the upper end. . The height of the surrounding plate 17 may be reduced, and the suspension plate 118 having holes as shown in FIG. 2 may be joined by welding. In addition, in FIG.
Is a short shroud.

In the storage rack 10 configured as described above, the spent fuel is put into each storage cell 19 one by one. The storage rack 10 is in the pool water, so the water in the storage cell 19 is heated by the decay heat and rises. For this reason, the pool water is sucked into the storage cell 19 through the space below the bottom plate 11 and the porous portion 11a, and the pool water is appropriately cooled, and circulates as described above. Neutrons emitted from the spent fuel are decelerated by the pool water and further absorbed by the wall of the storage cell 19, so that no critical reaction occurs.
Although the temperature of the water in the storage cell 19 rises, the temperature of the storage cell 19 itself increases, and the storage cell 19 is not fixed to each other. Therefore, the thermal expansion is not restricted, and an excessive thermal stress occurs. Absent. In the above-described embodiment, the mounting bolt 15 for fixing the bottom plate 11 to the gantry 13 is provided outside the enclosing plate 17, but as shown in FIG. 3, it is located inside the enclosing plate 217 that is fully enlarged. The mounting bolt 115 may be arranged on the outer peripheral portion of the bottom plate 111 and screwed to the mount 113 as described above. At this time, the mounting bolt 115 is
The storage cell is disposed at the center of the storage cell so that the storage cell can be tightened from above. In this way, the long tightening tool can be passed through the storage cell to access the mounting bolts 115 and tighten and loosen them.

[0007]

As described above, according to the present invention, since the storage cells are provided adjacent to each other without being connected to each other, the spent fuel can be stored at a high density and the decay heat can be reduced. The generation of excessive thermal stress due to the above is prevented. In addition, the mounting bolts are aligned with the storage cells when outside or inside the shroud, so that handling tools can be accessed from above the storage rack, and mounting and dismounting can be performed in storage pools or pits. Can be carried out with water in the container.

[Brief description of the drawings]

FIG. 1 is a partially cutaway perspective view showing the entire structure of an embodiment of the present invention.

FIG. 2 is a partial perspective view showing a partially modified portion of the embodiment.

FIG. 3 is a partial perspective view showing a partially modified portion of the embodiment.

FIG. 4 is a partially cutaway perspective view of a conventional device.

FIG. 5 is a partially cutaway perspective view of another conventional device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Storage rack 11 Bottom plate 11a Porous part 13 Stand 15 Mounting bolt 17 Shroud plate 17a Hanging hole 19 Storage cell 111 Bottom plate 113 Stand 115 Mounting bolt 117 Shroud plate 217 Shroud plate

Claims (2)

[Claims] 1. A horizontal bottom plate having a porous portion at a central portion thereof,
A vertical enclosing plate having a rectangular flat cross section and standing on the bottom plate surrounding the perforated portion; a plurality of vertical storage cells arranged side by side in the enclosing plate; A spent nuclear fuel storage rack, comprising: a rack disposed below a peripheral portion of a bottom plate located outside a plate; and a mounting bolt penetrating the peripheral portion and screwing to the rack. 2. A horizontal bottom plate having a perforated portion, a vertical surrounding plate standing upright on the bottom plate surrounding the perforated portion and having a rectangular flat cross section, and adjacent to each other in the surrounding plate. A plurality of vertical storage cells arranged side by side, a pedestal disposed below a bottom plate located below the storage cells adjacent to the inner side surface of the enclosure plate, and arranged in alignment with the vertical storage cells And a mounting bolt which penetrates the bottom plate and is screwed to the gantry.