JPS5841390A - Nuclear 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 The present invention relates to a nuclear reactor fuel storage rack for storing nuclear fuel assemblies used in nuclear power plants.

At nuclear power plants, spent fuel taken out of the reactor core is stored in a spent fuel pool temporarily installed inside the reactor building until it is transported to a reprocessing plant for reprocessing. Stored in inland water. In recent years, it has become necessary to store large amounts of spent fuel due to delays in spent fuel reprocessing.5 Therefore, the space in the spent fuel pool (hereinafter referred to as the pool) can be used effectively to reduce the interval between stored fuels. Improvements have been made to shorten the . A nuclear reactor fuel storage rack (hereinafter referred to as a rack) based on this improvement is referred to as a high-density rack. The rack needs to have a structure in which the stored fuel does not reach criticality due to mutual influence, so a neutron absorbing material is inserted between the fuels. Considering the ease of assembly, racks are manufactured by assembling prefabricated square tubes made of strength members and neutron absorbing materials by welding or bolting.

As such a conventional neutron absorbing material, there is Boral (trade name), which is made by diffusing boron carbide aluminum containing boron, which has good neutron absorbing properties, and further coating it with aluminum. However, since Polar has poor corrosion resistance, it is safe to seal it tightly to prevent it from coming into contact with the water in the spent fuel pool.

FIG. 1 shows an example of this type of high-density rack, in which a rectangular tube 1 is integrated with reinforcing members 2, 3, 4, and a base 5. Figure 2 is a cross-sectional view of a rectangular tube using Boral, Figure 3
The figure is a plan view, and the square tube has an outer tube 6, an inner tube 7, a boral 8,
It consists of spacers 9 and 1o.

In this structure, in order to seal the Boral 8, the rectangular tube is made up of an inner tube 7 and an outer tube 6 made of stainless steel, the Boral 8'f: is inserted into the gap created between them, and the upper and lower ends of the rectangular tube are sealed and welded. The disadvantage is that it is very time-consuming. In particular, the manufacturing precision of the inner cylinder 7 and outer cylinder 6 must be made strict, and the seal welding at the upper and lower ends of the rectangular cylinder must be performed with great care to ensure the integrity of the neutron absorbing material Boral. There is.

Furthermore, it has been proposed to use stainless steel containing Bk for neutron absorption, but in this case, the strength of the stainless steel containing B decreases due to neutron irradiation and the weldability is poor, so it is not suitable for manufacturing racks.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the above-mentioned drawbacks of the prior art and to provide a fuel storage rack for a nuclear reactor that is easy to manufacture and has a simple structure.

The present invention focuses on the fact that the corrosion resistance of amorphous alloys improves when they contain Cr, and that amorphous alloys are usually thin at several tens of μm and have excellent workability. The above objective was achieved by using a neutron absorbing material to which an element with high neutron absorption ability was added.

That is, the present invention uses B as a neutron absorbing material.

Sm, Gd, Eu, DY, Rh, Cd, In, Er.

)(f) An amorphous alloy of stainless steel containing one or more elements selected from f and r is used.

The present invention will be described below based on embodiments shown in the accompanying drawings.

In FIGS. 4 and 5, a neutron absorbing material 12 made of an amorphous alloy is fixed to a rectangular cylindrical strength member 11. As shown in FIG. Since the neutron absorbing material 12 made of an amorphous alloy may be crystallized by heating, it is necessary to avoid fixing it to the strength member 11 by welding or the like.

In this embodiment, a rivet 13 is welded in advance to a rectangular cylindrical strength member 11, a neutron absorbing material 12 made of an amorphous alloy is fully wrapped around the outer peripheral surface of this strength member, and then a rivet 13 is welded to a rectangular cylindrical strength member 11.
3 is deformed and fixed using a hammer or the like. Note that since the neutron absorbing material 12 made of an amorphous alloy is thin and deformable at several tens of micrometers, the hole into which the rivet 13 is inserted can be easily made by punching. The fuel rack according to the present invention is constructed by assembling the obtained rectangular tubes as shown in FIG.

In the present invention, the neutron absorbing material is obtained by adding B to the composition of stainless steel, melting it, and making it amorphous by spraying the molten metal onto a roll rotating at high speed. Therefore, it is essential that the amorphous alloy contains Cr1 or C'' and NI, and also contains elements with high neutron absorption ability.These elements with high neutron absorption ability include B, Sm, Gd, Eu, Dy, Rh, Cd, In
.

Selected from Br, Hf and Jr. One or more of these elements are contained in the amorphous alloy.

It is desirable that the Cr content in the amorphous alloy is 12% or more. When the Cr content is less than 12%, the corrosion resistance of the amorphous alloy decreases. On the other hand, if the Cr content is too high,
When B is used as an element with high neutron absorption ability, the amount of B added for making it amorphous becomes small, making it difficult to use an amorphous alloy as a neutron absorbing material, so it should be kept at 13% or less. Good. Taking B as an example, the amount of addition of an element having a high neutron absorption ability in the amorphous alloy is preferably 4 to 8 weight. The desired neutron absorption effect is exhibited depending on the content of B, and if the content is outside this range, it becomes difficult to make the material amorphous.

Example A stainless steel alloy having the composition shown in Table 1 was made amorphous,
This is formed into a rectangular cylinder as shown in Figs. 4 and 5,
When maintained in contact with water in the spent fuel pool, the corrosion resistance was good as shown in Table 1.

As described above, according to the present invention, the amorphous alloy has excellent corrosion resistance and is sound even when in contact with water in the spent fuel pool. Moreover, since only one type of rectangular tube is required without providing an outer tube and sealing the gap therebetween, manufacturing is easy and the structure is simple. In addition, the storage density of the rectangular tube is improved because it can be reinforced with only one type of rectangular tube and the neutron absorbing material made of an amorphous alloy is extremely thin.

[Brief explanation of drawings]

Figure 1 is a front view of a conventional nuclear reactor fuel storage rank;
The figure is a longitudinal cross-sectional view of a conventional rectangular tube, FIG. 3 is a cross-sectional view of a conventional rectangular tube, FIG. 4 is a cross-sectional view showing an example of a rectangular tube in the present invention, and FIG. 5 is a cross-sectional view of a rectangular tube in the present invention. It is a longitudinal cross-sectional view showing an example.

Claims (1)

[Claims] 1. A rectangular tube formed by a neutron absorbing material and a strength member for holding the same as a holding member for holding a plurality of fuel assemblies in an upright alignment at predetermined intervals. The neutron absorbing material used in the nuclear reactor fuel storage rack is B, Bm, Gd, or Eu. Dy, Rh, Cd, In, Er, Hf! 1. A fuel storage rack for a nuclear reactor, characterized in that it is an amorphous alloy of stainless steel containing one or more elements selected from Ir and Ir.