JPH03160398A - Spacer for fuel assembly of nuclear reactor - Google Patents

Abstract

PURPOSE:To improve posturing stability by providing a contacting support part of which width is wider than a position of an engaging part at a protrudent part side of a rigid support of a clip shaped spring member, and also by making the spring member be contacted to and supported by a sidewall, by the contacting support part. CONSTITUTION:At a center part of a protrusion part of a rigid support, a large width contacting support part 11 extending sideward, is monolithicly formed. This contacting support part 11 contacts to a surface of a grid plate 4 at both side end parts, at least, by clipping function of the attached clip, and consequently the supporting part 11 gives two points supporting of which width are wider then contact parts 19 of both ends. Accordingly, in this case, when lateral force works to the clip shaped spring member 16, tilting of the member is well prevented by a large width two points supporting of the aforementioned contacting support part 11.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a spacer for a nuclear reactor fuel assembly that holds rod-like elements such as fuel rods bundled in a square lattice arrangement with mutual spacing. It is.

[Prior Art] For example, in a fuel assembly loaded into a boiling water reactor (BWR), rod-shaped elements including a required number of fuel rods and wood pipes are arranged in a square array, and their lower ends are connected through end plugs. Attached to the upper and lower tie plates, spacers made of a lattice of thin strips are placed at predetermined intervals at multiple locations at intermediate height positions.
Generally, the spacing between the rod-like elements is maintained at a predetermined interval, and the outer periphery is covered with a rectangular cylindrical channel box.

A required number of such fuel assemblies are installed upright on the seat of the reactor core structure, and during reactor operation, coolant is pumped through the lower orifice of the seat and moved upward between the fuel rods of each fuel assembly. The reaction heat of the fuel rods is used to boil the coolant and extract the heat to the outside, while also removing heat from the fuel assembly.

Conventionally, in such fuel assemblies, the side walls of a plurality of rod-like element insertion cells formed by a latticework of strips have been used as spacers to maintain the arrangement interval of rod-like elements such as fuel rods at a predetermined value. back-to-back elastic bars each protruding toward the center of the cell and adjacent cells to support the rod-like element substantially in its radial direction;
It is known that a clip type spring member having rigid support protrusions on both sides is engaged and clamped to the side wall.

FIG. 10 is a schematic plan view showing a conventional spacer equipped with this type of clip-type spring member, and FIG. 10a is an enlarged longitudinal cross-sectional view of the clip-type spring member 6.
An enlarged perspective view of the rigid support protrusion side is shown in FIG.

That is, as shown in FIG. 10, the spacer 3 is constructed by welding a lattice plate 4 made of a plurality of strips, surrounding the four circumferences of the lattice plate 4 with similar slightly thicker strips 9, and assembling it into a square lattice shape. Inside, a plurality of cells 2 are formed by the lattice structure, and a fuel rod 1 is inserted into each cell 2, and a large space for 9 cells is provided in the center with a large diameter. A water channel 5 is inserted therethrough. A clip-type spring member 6 is attached to the four sides of each cell 2 so as to engage with the grid plate 4 on the side wall of the cell, as shown in FIG. 10a, and one side of the clip has an elastic support projection. The other side of the section 7 is made of an Inconel spring band plate formed into a clip shape as a rigid support protrusion 8, and is engaged with the grid plate 4 of the cell side wall on both sides. The width dimension of the clip-type spring member 6 is determined in relation to its material and plate thickness so that the elastic support protrusion 7 has a required elastic modulus, and the rigidity of the rigid support protrusion 8 is determined as shown in the figure. The required rigidity is obtained by using a double-crested or triple-crested shape.

Here, for one cell 2, elastic support protrusions 7 are formed on two opposing sides by clip-type spring members 6 on four sides.
The attachment direction of each clip-type spring member 6 is determined so that the rigid supporting projections 8 and 8 face each other, and the fuel 48 1 or water channel 5 is supported with an appropriate pressing force between these opposing projections 7.8. It is supposed to be done.

[Problems to be Solved by the Invention] Spacers for fuel assemblies in BWRs are installed at about seven locations in the axial direction of the fuel assembly in order to keep the spacing between fuel rods constant. It is necessary to configure the system to minimize pressure loss. For this reason, in addition to reducing the thickness of the lattice plates that make up the spacer, measures are generally taken to increase the cross-sectional area of the flow passages by reducing the diameter of the fuel rods. In this case, since the distance between the fuel rods and the grid plate becomes large, each projection 7 is used as a clip-type spring member as shown in FIG. 10c.
．． 8 with a larger protrusion height must be used. When clip-type spring members with a large protrusion height are used in this way, if the holding force of the fuel rods loosens due to a decrease in the spring force of each spring member in the furnace during use,
When a horizontal 1f1 impact load is applied to the fuel rods in the assembly during an earthquake or when transporting the assembly, the clip-type spring member on the cell side wall along the load application direction tilts in the load application direction and supports the fuel rods. There has been a problem in that contact with the rod-like elements held by the fuel rods may become unstable, resulting in insufficient support, especially for fuel rods having a relatively large mass. Additionally, when assembling a fuel assembly, if the clip-type spring member is unstable and tends to tilt as described above when inserting the fuel rod into the cell, it may cause damage when it comes into contact with the end plug of the fuel rod. There was also a risk that the clip-type spring member would be deformed or damaged.

This invention was made in view of the above-mentioned problems, and it improves the posture stability of the clip-type spring member in a spacer equipped with the clip-type spring member, and improves the stability during use in a furnace and during transportation. Provided is a spacer for a nuclear reactor fuel assembly that improves the holding performance of a rod-shaped element inside and maintains a stable posture of a clip-type spring member when inserting a rod-shaped element during fuel assembly assembly to prevent deformation or damage. The purpose is to

[Means for Solving the Problems] In the spacer for a nuclear reactor fuel assembly according to the invention as set forth in claim 1, rod-shaped elements such as fuel rods are held in a state where they are bundled in a square lattice arrangement with spaces between them. A spacer for a nuclear reactor fuel assembly, wherein back-to-back spacers are provided on the side walls of a plurality of rod-like element insertion cells, each protruding toward the center of the cell and adjacent cells in order to support the rod-like elements substantially in the radial direction thereof. A clip type spring member having elastic/rigid support protrusions on both sides is engaged and clamped, wherein a contact support part wider than the engaging portion is provided on the rigid support protrusion side of the clip type spring member. In addition to providing
The above-mentioned problem is solved by making the contact support part contact and support the side wall.

Further, in the spacer for a nuclear reactor fuel assembly according to the invention as set forth in claim 2, in addition to the above-mentioned configuration, the contact support portion is engaged with the side wall to further improve posture stability. .

[Function] In the spacer for a nuclear reactor fuel assembly according to the invention described in claim 1, the spacer for a nuclear reactor fuel assembly holds rod-shaped elements such as fuel rods in a state where they are bundled in a square lattice arrangement with mutual spacing. Among the body spacers, in particular, on the side walls of the plurality of rod-like element insertion cells, back-to-back elastic bands protrude toward the center of each of the cells and adjacent cells in order to support the rod-like elements substantially in the radial direction. A clip-type spring member having rigid support protrusions on both sides is engaged and clamped, wherein the clip-type spring member has a contact support part wider than the engaging portion on the side of the rigid support protrusion. At the same time, the clip-type spring member is brought into contact with and supported by the side wall by the contact support portion.
The lateral posture stability of the clip-type spring member is improved by the wide contact support portion.

Further, a spacer for a nuclear reactor fuel assembly according to claim 2. Furthermore, since the contact support portion is engaged with the side wall, even if a lateral force is applied to the clip-type spring member, it does not cause lateral displacement with respect to the side wall, and the holding stability of the rod-shaped element is further improved. It will improve.

In the invention of this application, the wide contact holding part is provided only on the rigid support protrusion side, so that the plate width on the elastic support protrusion side can be designed to any desired dimension as in the conventional case, and its spring coefficient It is possible to maintain the same degree of freedom in design as before.

[Example] An example of the spacer for a nuclear reactor fuel assembly according to the present invention will be described below with reference to the drawings.

FIG. 1 shows a first embodiment, and the lattice plate 4 constituting the cell side wall is the same as that in FIG. The clip-type spring member 16 of this embodiment is formed by integrally molding an elastic support protrusion 17 located on the back side of the grid plate 4 and a rigid support protrusion l8 located on the front side in the drawing.
A wide contact support portion l1 projecting laterally is integrally formed in the center portion on the side of the rigid support protrusion. This contact support part 11 contacts the surface of the lattice plate 4 at least at both ends thereof in the attached state by the supporting action of the clip, and provides two-point support wider than the contact parts 19 at both ends. . Therefore, in this embodiment, when a force is applied to the clip-type spring member 16 in the lateral direction, its tilting is prevented by the wide two-point support of the contact support portion l1.

FIG. 2 shows a second embodiment, in which a clip-type spring member 26 is integrally provided with a wide contact support portion 22 at one end thereof on the rigid support protrusion 28 side.

FIG. 3 shows a third embodiment, in which a clip-type spring member 36 is integrally provided with wide contact support portions 31 and 32 at two locations, one in the center and one end on the rigid support protrusion 38 side. ing.

FIG. 4 shows a fourth embodiment, in which a clip-type spring member 46 has three wide contact support portions 41, 42.4 at the center and both ends on the rigid support protrusion 48 side.
It has 3 in one.

FIG. 5 shows a fifth embodiment. In this example, the clip-type spring member 56 has a wide width on the entire rigid support protrusion 48 side to provide large rigidity, and at the same time, the center portion and both ends thereof are wide. The three contact portions are contact support portions 51, 52, and 53 that are wider than the elastic support protrusion 57.

FIG. 6 shows a sixth embodiment, which constitutes a modification of the first embodiment, that is, an embodiment of the invention according to claim 2. The clip-type spring member 66 in this example includes:
A wide contact support portion 61 extending laterally is integrally formed in the center of the 68 rigid support protrusions, and the lattice plate 4
includes an engaging portion 63 that receives both ends of the contact support portion 61.
is press-molded to further ensure the lateral tilting prevention effect of the contact support portion 61 of the clip-type spring member 66.

FIG. 7 shows a seventh embodiment, in which a wide contact support portion 71 projecting laterally is integrally formed at the center of a rigid support protrusion 78 of a clip-type spring member 76, and a lattice plate 4 is press-molded with a bag-shaped engagement portion 73 that receives both ends of the contact support portion 71.

FIG. 8 shows an eighth embodiment, in which a wide contact support portion 81 extending laterally is integrally molded at the center of a rigid support protrusion 88 of a clip-type spring member 86, and both ends of the contact support portion 81 are integrally formed. It is bent toward the lattice plate 4, and slit-like holes 84 for receiving and engaging the bent portions at both ends of the contact support portion 81 are punched into the lattice plate 4.

9a and 9b show a ninth embodiment, in which a wide contact support portion 91 projecting laterally is integrally formed at the center of a rigid support protrusion 98 of a clip-type spring member 96. At the same time, a convex portion 95 is provided at the center thereof and protrudes toward the grid plate 4 side, and a small hole 96 for receiving and engaging the convex portion 95 is bored in the grating plate 4, and these convex portions 9
5 and the small hole 96, the position of the clip-type spring member 96 does not shift.

The above embodiments are merely some examples of the present invention, and it goes without saying that the present invention can be modified in various other ways.

[Effects of the Invention] As described above, according to the present invention, the stability of the mounting posture and the holding stability of the rod-shaped element can be improved while maintaining the degree of freedom in designing the elastic support protrusion of the clip-type spring member. This can be achieved without adding a large protrusion as a spacer that would create resistance to the coolant flow path.

[Brief explanation of the drawing]

FIG. 1 is an enlarged perspective view showing the main parts of the first embodiment of the invention, FIG. 2 is an enlarged perspective view showing the main parts of the second embodiment, and FIG. 3 shows the main parts of the third embodiment. FIG. 4 is an enlarged perspective view showing the main parts of the fourth embodiment. FIG. 5 is an enlarged perspective view showing the main parts of the fifth embodiment. FIG. 6 is an enlarged perspective view showing the main parts of the sixth embodiment. FIG. 7 is an enlarged perspective view showing the main parts of the seventh embodiment. FIG. 8 is an enlarged perspective view showing the main parts of the eighth embodiment.
The figure is an enlarged perspective view showing the main part of the ninth embodiment, Figure 9b is a sectional view taken along the line A-A in Figure 9a, Figure 10 is a schematic plan view showing an example of the subameter, and Figure 10a is An enlarged vertical sectional view of a clip-type spring member portion in a conventional spacer, FIG. FIG. 3 is an enlarged vertical cross-sectional view of a clip-type spring member portion of the spacer. (Explanation of symbols of main parts) 3... Spacer, 4... Grid plate, +1.22.
3+, 32, 41, 42, 43, 51, 52, 53, 6
1,71,81.91...contact support part, 16,26,
36, 46, 56, 66, 76, 86.96...Clip type spring member, 17, 27, 37, 47, 57
, 67, 77, 87.97... elastic support protrusion, 18
,28,38,48,58,68,711,H,98・
...Rigidity support protrusion, 63.73...Engagement part, 84.
...Slit hole, 95...Protrusion, 96...Small hole.

Claims (1)

[Scope of Claims] 1. A spacer for a nuclear reactor fuel assembly that holds rod-like elements such as fuel rods bundled in a square lattice arrangement with mutual spacing, the spacer comprising a side wall of a plurality of rod-like element insertion cells. and engaging clip-type spring members having back-to-back elastic/rigid support protrusions on both sides that respectively protrude toward the center of the cell and adjacent cells in order to support the rod-like element substantially in its radial direction. The clip type spring member has a contact support portion wider than the engagement portion on the rigid support protrusion side, and is supported in contact with the side wall by the contact support portion. A spacer for nuclear reactor fuel assemblies featuring: 2. The spacer for a nuclear fuel assembly according to claim 1, wherein the contact support portion is engaged with the side wall.