JPH0797143B2 - Union of fuel bundles and casters - Google Patents

Description

The present invention relates to a combination of a fuel bundle supporting a fuel rod of a nuclear reactor and a caster, and more particularly to a fuel capable of preventing breakage during fuel handling. Regarding a combination of a bundle and casters.

(Prior Art) In general, a large number of fuel assemblies are housed in the core of a nuclear reactor, and each fuel assembly is configured by housing a large number of fuel rods in a channel box.

Each fuel rod contains uranium oxide or plutonium oxide as a nuclear fuel contained in a closed cladding tube made of a zirconium alloy material. The large number of fuel rods are arranged in a lattice in a channel box and are supported by a plurality of fuel rod spacers provided in the axial direction of the fuel rods. The fuel rod spacer restrains the horizontal vibration of each fuel rod and secures the flow path of the coolant.

When designing such a fuel rod spacer, it is necessary to properly maintain the fuel rod spacing, have a fuel rod thermal expansion margin, facilitate assembly of the fuel rod bundle, and make contact with the fuel rod. Surface minimization, minimizing reactor coolant flow variations and limits, maximizing thermal limits, minimizing neutron absorption derived, operating reactor conditions To maintain sufficient mechanical strength to withstand the above.

Various fuel rod spacers have been proposed and used in the past to satisfy these design requirements. The fuel rod spacer shown in Japanese Utility Model Publication No. 48-27360 is known as one of the representative ones. This fuel rod spacer
As shown in FIGS. 3 and 4, 20 is a bar 22 and a divider in a spacer outer frame 21 formed in a substantially square shape.
23 are arranged in a lattice form to form a plurality of fuel rod passages 24, and a rectangular spring 26 is arranged at each intersection of the bars 22. Spacer outer frame 21, bar 22 and divider
23 is a material with a small neutron absorption cross section (zirconium, etc.)
Formed in. Only the rectangular spring 26 is made of a material having a high strength but a large neutron absorption cross section, and the amount thereof is minimized, which is considered to be preferable from the viewpoint of neutron economy.

Recently, various fuel rod spacers have been proposed to further improve the pressure loss reduction and the fuel assembly limit output increase in the fuel rod spacers. A typical example thereof is shown in JP-A-59-65287.
As shown in FIGS. 5 to 8, the fuel rod spacer 10 includes a spacer outer frame 11 formed in a substantially square shape, and the upper surface of the spacer outer frame 11 serves as a guide when the channel box is mounted. A plurality of lead-in tabs 12 and a plurality of flow tabs 13 for improving the thermal-hydraulic characteristics are provided. Further, the fuel rod passage 14 is formed by arranging a large number of cylindrical cells 15 having a substantially circular cross section (see FIG. 7) or a substantially octagon (see FIG. 8) in the spacer outer frame 11. A spring 16 is arranged between adjacent cells 15.

The fuel rod spacer 10 having the independent cell structure as described above
Suppresses a large change in the flow of the coolant passing through the spacer portion, especially by avoiding the blockage of the coolant flow path by the spacer constituent member or by limiting the vertical change of the cross-sectional shape of the cell 15. ing. as a result,
It is possible to reduce the pressure loss in the spacer portion and at the same time increase the limit output of the fuel rod.

By the way, such a fuel assembly is constructed by mounting a channel box from above onto a fuel bundle composed of a large number of fuel rods and fuel rod spacers supporting the fuel rods.

When mounting the channel box from above the fuel bundle, the spacer outer frame projects to the outside of the fuel rod,
It is conceivable that the lower surface of the channel box and the upper surface of the spacer outer frame interfere with each other, which makes it difficult to mount the channel box or the fuel rod spacer may be damaged.

In such a case, according to the fuel rod spacer 10 having the lead-in tabs 12 shown in FIGS. 5 to 8, since the lead-in tabs 12 serve as guides when the channel box is mounted, the lower surface of the channel box and the fuel rod spacer 10 are provided.
And will not interfere.

(Problems to be solved by the invention) After removing the channel box, the spent fuel assembly is mounted in a caster (not shown) for transporting spent fuel and transported to a reprocessing plant. It

Here, a fuel bundle (not shown) consisting of a number of fuel rods with the channel box removed and fuel rod spacers
Are mounted from above the casters through an upper lattice plate (not shown).

In this case, the fuel rod spacer 10 with the lead-in tab 12
Even if the above is used, the upper lattice plate and the lower surface of the spacer outer frame 11 protruding outward of the fuel rod interfere with each other. For this reason, it becomes difficult to mount the caster on the casters, or in some cases, the total weight of the fuel bundle is added to a part of the spacer outer frame 11 of the fuel rod spacer, or the fuel rod spacer 10 is damaged by the impact at the time of interference. It may happen.

The present invention has been made in consideration of such points,
An object of the present invention is to provide a combination of a fuel bundle and casters, which can enhance safety without damaging when the fuel bundle is mounted in the casters.

[Structure of Invention]

(Means for Solving Problems) According to the present invention, a fuel rod spacer having a substantially square spacer outer frame, a plurality of fuel rods arranged in a square lattice in the fuel rod spacer, and an upper lattice plate are provided. In a combination of a fuel bundle including casters for transporting spent fuel and casters, a plurality of mounting guide plates are provided so as to incline from the lower surface of the spacer outer frame to the inner side of the spacer outer frame, and the mounting guide plates are mounted. Is a combination of a fuel bundle and casters, characterized in that at least one protrusion is provided on one side of the outer frame of the spacer.

(Working) When mounting the fuel bundle in the caster for transporting spent fuel, the mounting guide plate first enters the upper grid plate of the caster, and then this mounting guide plate plays the role of a guide. The spacer can be smoothly passed through the upper lattice plate.

Embodiments Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are views showing an embodiment of a combination of a fuel bundle and casters according to the present invention. 1 and 2, the fuel rod spacer 10 is provided with a spacer outer frame 11 formed in a substantially square shape, and the upper surface of the spacer outer frame 11 has a lead-in tab 12 which serves as a guide when the channel box is mounted, and A plurality of flow tabs 13 are provided for the purpose of improving the thermal hydraulic characteristics. Further, in the outer spacer frame 11, a large number of tubular cells 15 having a substantially circular transverse cross section are arranged, and a fuel rod passage 14 is formed. Further, a spring 16 for pressing and supporting the fuel rod 18 is arranged between the adjacent cells 15.

Further, a plurality of mounting guide plates 17 are provided downwardly on the lower surface of the spacer outer frame 11, for example, seven each for each side of the spacer outer frame 11. Since 8 × 8 fuel rods 18 are stored in the spacer outer frame 11, the mounting guide plate 17 is a fuel rod.
One will be provided between 18 of each other. Further, the mounting guide plate 17 is inclined inward of the spacer outer frame 11, and the tip of the mounting guide plate 17 is located inside the outer surface of the fuel rod 18.

Next, the operation of this embodiment having such a configuration will be described.

After removing the channel box, the spent fuel assembly becomes a fuel bundle consisting of a large number of fuel rods and fuel rod spacers, and an upper lattice plate is provided in a caster (not shown) for transporting spent fuel. Be installed through.

At the time of this mounting, since the mounting guide plate 17 is projectingly provided on the lower surface of the spacer outer frame 11, first, the mounting guide plate 17 enters the upper lattice plate, and then the mounting guide plate 17 serves as a guide. As a result, the fuel rod spacer 10 smoothly passes through the upper lattice plate.

As described above, according to the present embodiment, the mounting guide plate 17 serves as a guide and the fuel rod spacers 10 pass through the upper lattice plate smoothly. Therefore, when mounting the fuel bundle in the casters, the spacer outer frame 11 There is no interference between the lower surface and the upper lattice plate. Further, since seven mounting guide plates 17 are provided on each side of the spacer outer frame 11, the spacer outer frame 11 and the upper grid plate are aligned with each other.
This is easily done by means of 17, which allows the fuel bundle to be mounted in the caster in a well-balanced manner.

In this embodiment, seven mounting guide plates 17 are provided on each side of the outer frame 11, but the number of mounting guide plates 17 is increased by increasing the strength of the mounting guide plates 17. Can be reduced.

〔The invention's effect〕

According to the present invention, when the fuel bundle is mounted in the caster for transporting the spent fuel, the mounting guide plate protruding from the lower surface of the spacer outer frame serves as a guide, and thus the lower surface of the spacer outer frame and the upper portion of the spacer outer frame are There is no interference with the lattice plate. Therefore, the fuel rod spacer is not damaged,
The integrity and safety of the fuel rod spacer can be ensured.

[Brief description of drawings]

1 and 2 are views showing an embodiment of a combination of a fuel bundle and casters according to the present invention. FIG. 1 is its plan view, FIG. 2 is its side view, FIG. 3 and FIG. FIG. 4 is a view showing a conventional fuel rod spacer in which a fuel rod passage is formed by a bar and a divider, FIGS. 5 and 6 are views showing a conventional fuel rod spacer in which a fuel rod passage is formed by a cell, and FIG. Is a view showing a conventional cylindrical cell, and FIG. 8 is a view showing a conventional cylindrical cell. 10 …… Fuel rod spacer, 11 …… Spacer outer frame, 12 Lead-in tab, 13 …… Flow tab, 15 …… Cell, 16 …… Spring, 17 …… Mounting guide plate, 18 …… Fuel rod.

Claims (1)

[Claims] 1. A fuel rod spacer having a substantially square spacer outer frame, a plurality of fuel rods arranged in a square lattice in the fuel rod spacer, and a spent fuel transport caster having an upper lattice plate. In the combination of the fuel bundle and the caster, a plurality of mounting guide plates are provided so as to project from the lower surface of the spacer outer frame inwardly of the spacer outer frame, and the mounting guide plates are at least 1 per side of the spacer outer frame. A combination of a fuel bundle and casters, which is characterized by protruding three.