JPS63284491A - Spacer for fuel rod - Google Patents

Abstract

PURPOSE:To prevent failure by projecting plural guide plates for loading spent fuel casks to an outside frame of spacers having an approximately square shape so as to incline from the rear face of said frame toward the inside thereof and providing notched parts having tapers to corner parts. CONSTITUTION:A spent fuel assembly is loaded in the form of a fuel bundle consisting of many pieces of fuel rods and fuel rod spacers through an upper grating plate into the spent fuel transport cask after a channel box is removed. The guide plates 17A for loading the spent fuel transport casks are projected to the rear faces of the outer frame 11A of the spacers and the notches 19 are provided on the corner parts and, therefore, the guide plates 17A enter the upper grating plate first, then the guide plates 17A play the role of the guide at the time of loading. The interference of the corner parts with the upper grating plate is prevented by the notches 19 in the corner parts and the spacers 10A are passed throughly through the upper grating plate. The failure of the fuel rod spacers is, therefore, obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel rod spacer that supports fuel rods of a nuclear reactor, and more particularly to a fuel rod spacer that can prevent damage during fuel handling.

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

Each fuel rod contains nuclear fuel, uranium oxide or plutonium oxide, contained within a sealed cladding tube made of zirconium alloy material. Supported by multiple fuels mentioned above. With this fuel rod spacer.

Each fuel rod is restrained from horizontal vibration and a coolant flow path is secured.

When designing such a fuel rod spacer, considerations must be made to maintain appropriate fuel rod spacing, allow for fuel rod thermal expansion, facilitate assembly of fuel rod bundles, and reduce contact with fuel rods. minimize surface area, minimize reactor coolant flow changes and restrictions, maximize thermal limits, minimize derived neutron absorption, and reactor conditions during operation. These include maintaining sufficient mechanical strength to withstand the

Various fuel rod spacers have been proposed and used to meet these design requirements. As one of the typical examples, a fuel rod spacer disclosed in Japanese Utility Model Publication No. 48-27360 is known. As shown in FIGS. 5 and 6, this fuel rod spacer 20 has bars 22 and dividers 23 disposed in a lattice shape within a spacer outer frame 21 formed in a substantially square shape to accommodate a plurality of fuel rods. A passage 24 is formed, and square springs 26 are disposed at each intersection of the bars 22. spacer outer frame 21,
The bar 22 and the divider 23 are made of a material with a small neutron absorption cross section (such as zirconium). Only the rectangular spring 26 is formed using a material that has high strength but a large neutron absorption cross section, and is preferred from the viewpoint of neutron economy because its overall view is minimized.

Recently, various fuel rod spacers have been proposed to further improve the reduction of pressure loss in the fuel rod spacers and the increase in the critical output of the fuel assembly. A typical example thereof is shown in Japanese Patent Application Laid-Open No. 59-65287. As shown in FIGS. 7 to 10, this fuel rod spacer 10 includes a spacer outer frame 11 formed in a substantially square shape.
On the upper surface of the spacer outer frame 11, a plurality of lead-in tabs 12 that serve as guides when the channel box is attached, and a plurality of flow tabs 13 for improving thermal hydraulic properties are provided. Further, a fuel rod passage 14 is formed by arranging a large number of cylindrical cells 15 having a substantially circular cross-sectional shape (see FIG. 9) or a substantially hexagonal shape (see FIG. 10) in the spacer outer frame 11, A spring 16 is disposed between adjacent cells 15.

Fuel rod spacer 1 consisting of an independent cell structure in this way
0 suppresses large changes in the flow of coolant passing through the spacer section, particularly by avoiding blockage of the coolant flow section by spacer components or by limiting vertical changes in the cross-sectional shape of the cells 15. are doing. As a result, the pressure loss at the spacer portion can be reduced, and at the same time, the limit output of the fuel rod can be increased.

Incidentally, such a fuel assembly is constructed by attaching a channel box from above to a fuel bundle consisting of a large number of fuel rods and fuel rod spacers that support the fuel rods.

When installing the channel box from above the fuel bundle, the spacer outer frame protrudes outward from the fuel rods, so
The lower surface of the channel box and the upper surface of the outer frame of the spacer may interfere with each other, making it difficult to mount the channel box, and in some cases, the fuel rod spacer may be damaged.

In such a case, according to the fuel rod spacer 10 having the lead-in tab 12 shown in FIG. 7 to FIG. There will be less interference between

(Problem to be solved by the invention) After the channel box is removed, the spent fuel assembly is placed in a cask (not shown) for transporting spent fuel and transported to a reprocessing plant. Ru.

Here, a fuel bundle (not shown) consisting of a number of fuel rods and fuel rod spacers with channel boxes removed.
is installed from above the spent fuel transport cask through an upper grate plate (not shown) of the spent fuel transport cask.

In this case, even if the fuel rod spacer 10 having the lead-in tabs 12 on the upper side is used, the upper grid plate and the lower surface of the spacer outer frame 11 protruding outward from the fuel rods will interfere with each other. Attachment may become difficult, and in some cases, the entire weight of the fuel bundle may be applied to a portion of the spacer outer frame 11 of the fuel rod spacer, or the fuel rod spacer 10 may be damaged by the impact upon interference.

Furthermore, even when a lead-in tab is provided on the lower surface of the spacer, there is a risk that the four corner portions of the lower surface of the spacer may interfere with the spent fuel transport cask.

The present invention has been made in consideration of these points,
An object of the present invention is to provide a fuel rod spacer that can enhance safety without being damaged when a fuel bundle is installed in a cask.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a plurality of loading guide plates that are inclined inward from the lower surface of the spacer outer frame in a substantially square shape, and that are provided at four corners of the lower surface. This is a fuel rod spacer characterized by having a notch part having an inclination.

(Function) When installing a fuel bundle into a spent fuel transportation cask, the loading guide plate first enters the upper grate plate of the cask, and then this loading guide plate plays the role of a guide.
The fuel rod spacer can be smoothly passed through the upper grid plate of the spent fuel transport cask.

Further, even if there is a deviation in the relative angle between the fuel assembly and the spent fuel transport cask during loading, the slanted cuts at the four corners of the lower surface allow the fuel assembly to be passed smoothly into the upper lattice plate.

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

FIGS. 1 and 2 are diagrams showing an embodiment of a fuel rod spacer according to the present invention. In Figures 1 and 2,
The fuel rod spacer IOA is equipped with a spacer outer frame 11A formed in a substantially square shape, and on the upper surface of this spacer outer frame 11A, there is a lead in tab 12A that serves as a guide when installing a channel box, and a lead in tab 12A that serves as a guide when installing a channel box. A plurality of blow tabs 13A are each provided. Further, within the spacer outer frame 11A, a large number of cylindrical cells 15 having a substantially circular cross-sectional shape are arranged to form a fuel rod passage 14. Further, a spring 16 is arranged between adjacent cells 15 to press and support the fuel rods 18.

Furthermore, a plurality of guide plates 17A for spent fuel transport cask groups are provided on the lower surface of the spacer outer frame 11A, projecting downward, for example, seven guide plates for each side of the spacer outer frame 11A. Since 8×8 fuel rods 18 are housed in the spacer outer frame 11A, one guide plate 17 for the spent fuel transport cask group is provided between each fuel rod 18. Further, the guide plate 17A for the spent fuel transport cask group is inclined inward of the spacer outer frame 11A, and the tip of the guide plate 17A for the spent fuel transport cask group enters inside the outer surface of the fuel rod 18. I'm here.

The four corner portions of the lower surface of the spacer are provided with cut portions 19 that slope upward.

FIGS. 3 and 4 also show another embodiment of the fuel rod spacer according to the present invention. This fuel rod spacer has bars 22 and dividers 23 in a lattice, respectively, within a spacer outer frame 21A formed in a substantially square shape. A plurality of fuel passages 2 are arranged in a shape.
4 is formed, and a square spring 26 is arranged at each intersection of the bars 22.

A plurality of lead-in tabs 27A are provided on the upper surface of the spacer outer frame 21A to serve as guides when the channel box is attached. Furthermore, a plurality of guide plates 28A for spent fuel transport casks are protruded downward from the bottom surface, for example, three guide plates for each cask group! and,
The four corner portions 3o are provided with sloped cuts at the corner portions of the spacer outer frame 21A so as to slope from the lower surface toward the upper surface.

Further, the guide plates 28A for the spent fuel transport cask group are provided between every other fuel rod, and the tips of the guide plates 28A are inserted inside the outer surfaces of the fuel rods.

Next, regarding the operation of this embodiment having such a configuration,
The present invention will be explained using FIGS. 1 and 2.

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 is loaded into a spent fuel transport cask (not shown) through the upper grid plate. be done.

For this loading, a guide plate 17A for the spent fuel transport cask group is provided protruding from the lower surface of the spacer outer frame 11A, and a corner cutout 19 is provided.
First, the spent fuel transport cask group loading guide plate 17A enters the upper lattice plate, and then this loading guide plate 17A
The corner cutouts 19 serve as guides, and the fuel rod spacers IOA smoothly pass through the upper lattice plate without the corner portions interfering with the upper lattice plate.

According to this embodiment, the spent fuel transport cask loading guide plate 17A and the corner cutouts 19 serve as guides, and the fuel rod spacers 10A smoothly pass through the upper lattice plate, so that the fuel bundle is When loading spent fuel into the spent fuel transport casters, there is no interference between the lower surface of the spacer outer frame 11A and the upper grid plate, and the spent fuel transport cask loading guide plate 17A is attached to one side of the spacer outer frame llA. Since the spacer outer frame 11A and the upper lattice plate are provided with seven protruding pieces, alignment between the spacer outer frame 11A and the upper grid plate can be easily performed by the spent fuel transport cask loading guide plate 17A, so that the fuel bundle can be loaded into the cask in a well-balanced manner. Even if there is a deviation in the relative angle between the spent fuel transport cask and the fuel bundle, the corner cutouts 19 serve as a guide, and the spent fuel can be loaded into the cask with balance.

In addition, although this example shows an example in which seven spent fuel transport cask loading guide plates 17A are protruded from each side of the outer frame 11A, the strength of the spent fuel transport cask loading guide plates 17A is increased. By doing so, the number of spent fuel transport cask loading guide plates 17A can also be reduced.

The invention example shown in FIGS. 3 and 4 also includes a spent fuel transport cask loading guide plate 28/A and a corner cutout 29.
The action is as explained using FIGS. 1 and 2 above.

[Effects of the Invention] According to the present invention, when loading a fuel bundle into a spent fuel transportation cask, the spent fuel transportation cask loading guide plate and the bottom corner portion protrude from the lower surface of the outer frame of the spacer. Since the slanted notch provided in the spacer serves as a guide, there is no interference between the spacer and the upper lattice plate.

Therefore, the fuel rod spacers will not be damaged.

The integrity and safety of the fuel rod spacer can be ensured.

[Brief explanation of the drawing]

FIG. 1 is a plan view of the fuel rod spacer of the present invention, FIG. 2 is a partially cutaway side view of the fuel rod spacer of the present invention, FIG. 3 is a plan view of the fuel rod spacer of the present invention, and FIG. The figure is a side view of the fuel spacer of the present invention. Fig. 5 is a plan view of a conventional fuel rod spacer, Fig. 6 is a side view of a conventional fuel rod spacer, Fig. 7 is a plan view of a conventional fuel rod spacer, and Fig. 8 is a side view of a conventional fuel rod spacer. Figure 9 is a perspective view of a conventional fuel rod spacer cell.
The θ diagram is a plan view of a cell of a conventional fuel rod spacer. 10A... Fuel rod spacer 11A... Spacer outer frame 12A... Lead in tab 13A... Flow tab 15... Cell 16... Spring 17A... Spent fuel transport cask loading guide plate 1
8...Fuel rod 19...Corner cutout 28A...Spent fuel transport cask loading guide plate 2
9... Corner cut Ixl Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] A plurality of guide plates for loading the spent fuel transportation cask are provided protruding from the lower surface of the spacer outer frame in a substantially square shape, tilting inward from the spacer outer frame, and the cut portions have slopes at four corners of the lower surface. A fuel rod spacer characterized by having: