JPS6039594A - Storage rack for used fuel - 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, in which the fuel removed from the reactor is stored and cooled, and its decay heat is removed. That's what I do.

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, and usually cells partitioned by boron-containing A-state stainless steel are connected vertically and horizontally. It is configured.

1 and 2 show a partially vertical front view and a plan view of a conventional spent fuel storage rack, in which a large number of cells 30 are mounted on a base 20 formed on the bottom surface of a fuel storage pool 10. A spent fuel storage rack consisting of
Each cell stores spent fuel F.

As shown in FIG. 2, the cell 30 includes a cell 31 formed by rectangular cylinders 40 that are planted on the base 20 with one pitch shifted in the vertical and horizontal directions, and a cell 31 formed between these rectangular cylinders 40. There are three types of cells: 3303 types of cells formed by closing one side of the outermost rectangular cylinder 40 with a vertical plate 41;

The rectangular cylinder 40 described above is made of a metal material with high radiation shielding ability, such as boron-containing stainless steel, so that a sufficiently subcritical state can be maintained even when the fuel is stored in close proximity. In this case, in order to assemble four adjacent rectangular tubes 40 by welding and form cells 32 and 33 between them, the four corners of the rectangular tubes 40 must be welded. The deformation becomes large and direct welding is difficult. For this reason, cells 32 and 33 of a predetermined size are formed by inserting angles 42 into the corners of the adjacent rectangular cylinders 40 and the vertical plates 41, and fixing them by welding while adjusting.

[Problems with the Background Art] However, providing the angle 42 in the cell 32, 33 reduces the inner diameter of the cell 32, 33 by the thickness of the angle, so the inner diameter must be increased by the thickness of the angle 42. Interference with fuel F must be avoided.

Therefore, the fuel storage pitch must be widened by the thickness of the angle 42, resulting in a reduction in fuel storage density, which has the disadvantage of lowering the storage density.

[Objective of the Invention J The present invention has been made in view of the above-mentioned circumstances in the background art, and it is possible to produce a plurality of fuels of the same size by directly connecting a plurality of boron-added austenite plates to steel moon rectangular plates. It is an object of the present invention to provide a spent fuel storage rack that can increase the fuel storage density by connecting storage cells.

[Summary of the Invention] The spent fuel storage rack of the present invention includes a plurality of right-angled plates having L-shaped cross sections arranged adjacent to each other on a base having a coolant flow path fixed to the bottom of the storage pool. , and are constructed by directly fixing the cells by welding to form a plurality of cells.

[Embodiment of the Invention] A spent fuel storage rack according to an embodiment of the present invention will be described below with reference to the drawings.

FIG. 3 is a partially longitudinal front view of the spent fuel storage rack, and FIG. 4 is a plan view thereof.

In these figures, large plates 5o and 51 are planted on two adjacent sides near the periphery on a base 20 formed in one section of the fuel storage pool 10, and their intersections 52 are welded to form a right angle. It is assembled into a shape. 50 of these large plates,
51 includes a large number of rectangular plates 60 (60a and 60b, which will be described later), each having a cross-sectional shape.

60c) are placed and sequentially welded to form a large number of self-0
form.

As shown in FIG. 5, the right-angled plate 60 is formed into an L-shape by bending or welding a plate at right angles. As the material of this right-angled plate 6o, austenitic stainless steel to which 1% or less of boron, which has a high radiation shielding ability, is added is used.

Generally, austenitic stainless steel contains 3 boron.
It can be added up to % R%, but if the boron content exceeds 20 to 5 oppm, polide, which is a compound of chromium and boron, appears, and if it exceeds 1100 ppm, eutectic (F
e, Cr) 2 B is formed. Although the crystal grains are made finer by the addition of boron, the solid solution strengthening of boron itself is not so significant, and the dispersion strengthening of polide causes hardening. Therefore, when 3% by weight of boron is added, the elongation drops to a few percent. The elongation of austenitic stainless steel is 4
Since it is 0% or more, the elongation of austenitic stainless steel with 3% by weight of boron added is about 1/10 of that without the addition, 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 is possible, and weldability does not deteriorate so much.

Similarly to the right-angled plate 60, the radish 50.51 is also made of austenitic stainless steel to which 1% or less of boron is added.

In the present invention, the large plate 50, 51 with good dimensional accuracy and the right-angled plate 60 with good dimensional accuracy are directly welded, and the right-angled plate 60
Since the cells are directly connected to each other to form a self-container, and only two corners need to be welded to form each cell, it is possible to construct a self-container with low welding distortion and high dimensional accuracy.

As shown in FIG. 6(A), the right-angled plate 60 includes a right-angled plate 60a with both ends chamfered 61, a right-angled plate 60b with one end chamfered 61 as shown in FIG. ), a right-angled plate 6 with no chamfers on both ends
Welding accuracy can be further improved by using three types of 0C and welding the chamfered portion 61 and the bent portion 62 of the right-angled plate 60 in appropriate combinations. When assembling this, first, the right-angled plate 60a is set near the intersection 52 of the large plate 50 and the large plate 51, and its two chamfered portions 61 are welded to the radish 50.51, and then the right-angled plate 60
a and 60b are suitably combined and welded in sequence, and finally, a right-angled plate 600 is welded and assembled at the opposing points of intersection of the radish 50 and 51, thereby forming each self 0.

7 and 8 show details of the base 20 described above, and the base 20 is composed of an upper plate 21, a side plate 22, and a base plate 23. As shown in FIG. The upper plate 21 has a transparent round hole 24 for placing the lower part of the fuel F, and
The rectangular plate 60 is positioned and welded so that its center 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 each of the side plates 22 is provided with cooling holes 25 through which cooling water for cooling the fuel passes.

The base plate 23 connects the spent fuel storage rack to the fuel storage pool 1.
This is for installation at the bottom of the fuel storage pool 10.
It is fixed to a foundation bolt 11 protruding from the bottom with a nut 12, and is also fixed to a side plate 22 by welding.

[Effects of the Invention] As described above, in the spent fuel storage rack of the present invention, the boron-added A-stenite steel rectangular plates and large plates with good dimensional accuracy are assembled by directly welding, so that each cell can be formed easily. In order to do this, only two corners need to be welded, the number of welding points can be reduced to half of the conventional size, and the inner dimensions of each cell can be assembled with high precision.

Therefore, since each cell can be formed with dimensions slightly larger than the fuel, the inner dimensions of each cell can be reduced, and the pitch of each cell can also be reduced, so the fuel storage density can be increased by the amount of the pitch reduction. Can be done.

[Brief explanation of drawings]

FIG. 1 is a partially longitudinal front view of a conventional spent fuel storage rack, FIG. 2 is a plan view thereof, and FIG. 3 is a partially longitudinal front view showing an embodiment of the spent fuel storage rack of the present invention. Fig. 4 is a plan view thereof, Fig. 5 is a perspective view of the right-angled plate, Fig. 6 (A),
(B) and (C) are respectively plan views of the right-angled plate, FIG. 7 is a vertical sectional view showing details of the base, and FIG. 8 is a plan view of the upper plate. 10...Fuel storage pool 20...
......Base 5o, 51...Large plate 60.60a, 60b, 60C.=Right angle plate 70.
・・・・・・・・・・・・Cell F・・・・・・・・・・・・Fuel Agent Patent Attorney Nori Chika Kensuke (1 idiot) Figure 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) A large number of right-angled plates with L-shaped cross sections are arranged adjacent to each other on a base fixed to the bottom of the storage pool and has a coolant flow path, and the plates are fixed at right angles by welding. A spent fuel storage rack characterized by forming cells. (2) The spent fuel storage rack according to claim 1, wherein the right-angled plates are made of austenitic stainless steel material to which 1% or less of boron is added.