JPS6238392A - Fuel spacer - 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 [Field of Application of the Invention] The present invention relates to a fuel spacer for a fuel assembly used in a nuclear reactor.

[Background of the invention]

As an independent cell type fuel spacer for a fuel assembly used in a nuclear reactor, for example, Fig. 2A of Japanese Patent Application Laid-open No. 59-65287 and No. 1 of Japanese Patent Publication No. 55-38638 are examples.
A fuel spacer with the structure shown in the figure has been proposed.

FIG. 22 shows a fuel spacer proposed in the above-mentioned Japanese Patent Laid-Open No. 59-65287. This fuel spacer 1 is formed by arranging a large number of cylindrical members (independent cells) 3 into which fuel rods 6 are inserted in a lattice pattern, and joining adjacent cylindrical members by welding them together at welds Ws. The outer periphery of a bundle of cylindrical members is surrounded by a band-shaped side band 2, and the contact points (welded portions W2) with the cylindrical members are welded together. Note that 4 and 5 in FIG. 22 are
These are springs and protrusions of the cylindrical member for supporting each fuel rod 6 (in FIG. 22 and the figures described below, the nuclear reactant loaded in the fuel rod is not shown).

As shown in FIGS. 23 and 24, the cylindrical surface of the cylindrical member 3 has a C-shaped notch 7A for supporting the spring 4, and notches for forming the protrusion 5 (FIGS. 23 and 24). (notches not shown) are provided in each case.

The spring 4 used in the present fuel spacer 1 is a continuous loop type spring formed from one circular ring. When attaching the spring 4 to the cylindrical member 3, first, the spring member on one side of the spring 4 is inserted into the cylindrical member 3 through the C-shaped notch 7A of the cylindrical member 3. Rotate C
The protruding piece 8A formed by the letter-shaped notch 7A is inserted from one entrance of the loop-shaped spring 4 (that is, the protruding piece 8
Cover A with spring 4). Next, the vertical direction of another cylindrical member 3 is reversed to that of the cylindrical member with which the spring 4 is engaged (so that the notch 7A looks U-shaped), and this cylindrical member 3 is By rotating, the protruding piece 8A is inserted from the other entrance of the spring 4, and with the spring members of each side of the spring 4 protruding into the cylindrical member, the upper and lower parts of the cylindrical members are joined by welding, and the spring 4 is hold.

FIG. 25 is an enlarged view of a part of the fuel spacer 3 shown in FIG. 22. 26 and 27 are a 5sz-81x cross-sectional view and a Sss Sls cross-sectional view of FIG. 25, respectively, showing the spring 4 of the fuel rod 6 and the cylindrical member when the fuel rod 6 is inserted into the cylindrical member 3. The state of support by the protrusion 5 is shown.

Among the symbols in these figures, 4A represents a convex portion provided at the center in the longitudinal direction of the spring 4, and 4B represents a convex portion provided at the upper and lower portions of the spring 4. Further, numeral 9 represents a notch for forming a protrusion 5 protruding inside the cylindrical member 3, and other reference numerals refer to the above-mentioned FIG. 22. 23rd
It is the same as FIG.

The independent cell fuel spacer with the structure described above has higher structural strength than the lattice-type fuel spacer that has been applied to fuel assemblies for boiling water reactors. This is intended to reduce pressure loss and improve neutron economy. It has also been experimentally confirmed that this fuel spacer improves the thermal limit of the fuel rod. However, as shown in FIG. 26, the independent cell fuel spacer described so far has a structure in which two protruding pieces 8A of the cylindrical member 3 pass through the spring 4. The gap between the spring and the spring 4 and the gap between the upper and lower convex portions 4B of the spring and the fuel rod 6 are, for example, a lattice-type fuel spacer (Japanese Unexamined Patent Application Publication No. 1983-1973) having a continuous loop-shaped spring similar to the present fuel spacer 1. (Refer to Publication No. 63589, in this fuel spacer, one grid member passes through the spring)
It is smaller than that by at least the thickness of the protruding piece 8A. For this reason, the independent cell fuel spacer exerts a predetermined spring force within an extremely limited space, and when inserting a fuel rod (when assembling a fuel assembly) or during an earthquake, the spring 4 In order to design the spring 4 so that it does not lose its function as an elastic body due to damage or plastic deformation even when a large load is applied, it is necessary to consider what kind of problems the spring 4 may have during fuel rod insertion (M standing) or during an earthquake. It is necessary to understand in advance whether there is a possibility that such problems may occur, and to design the system to prevent such problems from occurring.

Figure 28, Figure 29, Figure 30, Figure 31, Figure 32,
FIGS. 33 and 34 each illustrate a problem that may occur when inserting the fuel rod 6 into the cylindrical member 3 of the fuel spacer when assembling the fuel assembly. In these figures, 6A represents the tube part of the fuel rod 6, 6C represents the lower end plug, and 6B represents the weld bead at the lower part of the fuel rod, and the other symbols refer to the above-mentioned FIG. This is the same as in FIG. 23, etc.

FIG. 28 shows a case where the weld bead 6B of the fuel rod interferes with the convex part 4B on the upper part of the spring when the fuel rod 6 is inserted into the cylindrical member 3, and FIG. Figure 5
14-814 sectional view.

In this case, the tube portion 6A of the fuel rod is in contact with the projection 5 on the upper side of the cylindrical member, as can be seen from FIG.

The inside of the spring 4 is in contact with the cylindrical member 3, so if you try to forcefully insert the fuel rod, the protrusion 4B on the upper part of the spring and its vicinity may be plastically deformed, or the protrusion 5 of the cylindrical member or the fuel rod tube may be deformed. 6A etc. may be damaged.

FIG. 30 shows a case where the weld bead portion 6B interferes with the convex portion 4A at the center of the spring when the fuel rod is inserted.
FIG. 31 is a sectional view 815-8L11 of FIG. 30. In this case as well, if an attempt is made to insert more fuel rods, the same problem as in the case of FIG. 28 will occur.

FIG. 32 shows a case where the weld bead 6B of the fuel rod interferes with the protrusion 5 on the lower side of the cylindrical member.
3 is a cross-sectional view of the 81B SIB in FIG. 32, and FIG. 34 is a broken side view taken along the line ■-■ in FIG. 33. In this case, as shown in these figures, the inside of the spring comes into contact with the protruding piece 8A of the cylindrical member at and near the center of the spring,
Since the outer side is in contact with the pipe portion 6A of the fuel rod, the fuel rod 6
When trying to insert the spring further, not only the protrusion 5 on the lower side of the cylindrical member but also the protrusion 4A in the center of the spring and its vicinity and the protrusion 4
The fuel rod tube portion 6A that is in contact with the fuel rod A will also suffer damage such as plastic deformation.

Figure 35 shows that the fuel rods 6 move in the direction of the spring 4 (in the direction of the arrow As in the figure) under the load (acceleration) in the cross-sectional direction of the fuel assembly during earthquakes, transportation, handling, etc. ,
FIG. 36 is a sectional view taken along line 817-817 in FIG. 35, showing a state in which the inside of the spring near the center of the spring is in contact with the protruding piece 8A of the cylindrical member. In this case, the convex portion 4A at the center of the spring is plastically deformed and the tube portion 6 of the fuel rod is
Since the fuel rod A also receives a reaction force equivalent to the force of the fuel rod 6 pushing the spring 4 only at the contact portion with the spring, a large stress is also generated in the tube portion 6A.

Relatively easy countermeasures for the problems mentioned above include, for example, reducing the outer diameter of the fuel rods to ensure space for deformation of the springs, or leaving the outer diameter of the fuel rods unchanged. Another possible method is to lower the height of a protrusion provided on the cylindrical member and intentionally make the fuel rod eccentric toward the protrusion with respect to the cylindrical member. However, if the former method (reducing the outer diameter of the fuel rod) inevitably reduces the amount of nuclear reactant that can be loaded into the fuel rod, it is necessary to increase the enrichment to maintain the fission reaction. This is not desirable from the viewpoint of fuel cycle cost. On the other hand, if the latter method (the fuel rods are eccentrically moved toward the protrusion side) is used, there will be a portion where the fuel rod spacing becomes narrow, which is not preferable from both a nuclear and thermal-hydraulic point of view. Furthermore, in this case, the gap between the fuel rod and the cylindrical member becomes smaller near the protrusion, so the flow of coolant in this area deteriorates, and corrosion products contained in the coolant cause damage to this area. There is also a risk that the gap will be blocked and the fuel rods will be thermally damaged. In addition, as another countermeasure, the height of the convex portion 4A at the center of the spring 4 (dimension hz in FIG. 37) may be lowered to avoid the problems shown in FIGS. 30, 32, and 35. There is a method to prevent this from occurring, and to reduce the height of the upper and lower convex portions 4B of the spring 4 and to reduce the dimension h2) in Fig. 37.
Another possible method is to prevent the occurrence of the problem shown in the figure. However, the stress generated in the spring 4 due to deformation when inserting the fuel rod 6 into the cylindrical member 3 is generally largest at the center of the spring, and the convex portion 4A at the center of the spring also serves to keep the stress low. Therefore, from the viewpoint of the mechanical soundness of the spring 4, it is not preferable to reduce the height hl of the convex portion 4A at the center of the spring. Furthermore, if the height hl of the convex part 4A at the center of the spring is reduced, the gap between the spring 4 and the fuel rod 6 will become narrower near the convex part 4A, and the flow of coolant will deteriorate. I don't like it in terms of aspects either. on the other hand,
Lowering the height of the upper and lower convex portions 4B of the spring is effective against the problem shown in FIG. 28, but it is not preferable for the problem shown in FIG. 35 because it actually aggravates the problem. In this way, the spring 4 is designed to maintain a very delicate balance.
If you focus on only one defect and change the shape easily,
Changing the shape of the spring is not a very desirable method as it may exacerbate other problems or cause new problems.

For the reasons mentioned above, it can be said that the independent cell spacer with the structure described so far has a very narrow allowable range of applicable fuel rod outer diameters and is a fuel spacer with an extremely small degree of freedom in design. .

Therefore, when applying this fuel spacer to fuel assemblies currently in use, it is necessary to take drastic measures to prevent new problems from occurring due to design changes.

[Purpose of the invention]

The purpose of the present invention is to provide a suitable method for maintaining the soundness of the springs constituting the fuel spacer even when a large load is applied to the springs constituting the fuel spacer, such as when assembling a fuel assembly or during an earthquake. It is an object of the present invention to provide a fuel spacer which has a much wider allowable range of applicable fuel rod outer diameters than conventional ones and whose members are easy to manufacture and assemble.

[Summary of the invention]

The problems that are of concern with the independent cell type fuel spacers that have been discussed so far are mainly the structure of the independent cell that supports the continuous loop spring, and the combination of the independent cell and the inserted fuel rod (large diameter). This is due to However, as a countermeasure to this problem, if the outer diameter of the applied fuel rod is made smaller or the height of the protrusion for fuel healing support of the independent cell (cylindrical member) is lowered, the effect This is not a practical countermeasure because a new problem arises that has a surplus that offsets the above. Furthermore, the shape of the spring is also unfavorable for the reasons mentioned above.

Therefore, in the present invention, the shapes of the independent cells and springs and the method of holding the springs are basically the same as those of the fuel spacers described above, and the spacer on which the springs deform is made larger.

In the fuel spacer of the present invention, the first method is to make the notch in the wall surface of the independent cell E-shaped so that the protruding piece that holds the spring is separated in the axial direction of the independent cell. The space between the protrusions is used as a passage space when the central part of the spring is pushed toward the adjacent independent cell by the fuel rod, and the spring comes into contact with the independent cell and plastic deformation occurs, and the fuel rod and independent cell It has a structure that prevents it from being damaged.

In addition, as a second method, the shape of the above-mentioned notch is C
The flat part of the protrusion is placed outside the independent cell so that most of the protrusion formed by the notch is flat and the center of the plate thickness of the protrusion is separated from the center of the independent cell by half the fuel pitch. Even if the independent cells of the protruding pieces are brought into contact with each other with their notches facing each other in the axial length of the independent cells of the protruding pieces, and the lengths along the axial direction of the independent cells are opposite to each other, the protruding pieces do not interfere with each other. Alternatively, by setting the length so that the gap between the protrusions along the independent cell axis direction is comparable to that of the first method, a structure is obtained in which the same effect as the first method can be obtained.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 to 8.

FIG. 1 shows a protruding piece 8B for holding one cylindrical member 3 (independent cell) constituting a fuel spacer and a spring 4 (not shown in this figure) and a notch 7B for forming the protruding piece 8B. FIG. 2 is a sectional view taken along line 5s-8□ in FIG. 1. FIG. 3 also shows the two cylindrical members 3 and the cylindrical member 3 with the fuel rods 6 inserted therein.
FIG. 4 is a cross-sectional view taken along line 82-8z in FIG. 3. FIG. In addition, the fourth
The figure and the figures described below do not show nuclear reactants loaded in the fuel rods.

The cylindrical surface of the cylindrical member 3 is provided with a spring 4 as shown in FIG.
8-shaped notch 7 for forming a protruding piece 8B that holds the
B is provided. Further, the cylindrical member 3 includes fuel rods 6
Two protrusions 5 are provided on the top and bottom of the cylindrical member to support the cylindrical member. 1. It is formed to protrude inside a cylindrical member. Spring 4
As shown in FIG. 3, this is a continuous loop type spring having convex portions 4A and 4B provided at the center and upper and lower portions of the surface facing the fuel rods 6.

When attaching the spring 4 to the two cylindrical members 3, first insert the spring member on one side of the spring 4 into the figure-eight notch 7-B, ? After passing, the cylindrical member 3 is rotated so that the protruding piece 8B of the cylindrical member enters the spring 4. Next, the vertical direction of the other cylindrical member 3 is reversed to that of the cylindrical member with which the spring 4 is engaged so that the notch 7B looks Y-shaped, and then the protruding piece 8B is already attached to the other cylinder. Insert the member into the spring 4 from the entrance opposite to the spring entrance into which the protruding piece 8B was inserted. Finally, the relative angle between the two cylindrical members is adjusted so that the center of the protrusion 5 of one cylindrical member is inclined by a predetermined angle with respect to the straight line connecting the centers of the cylindrical members, and the cylindrical members are welded at the weld zone W1. and hold the spring 4.

Note that the fuel spacer of this embodiment has a band-like member (side band) surrounding the outer periphery of a bundle of a large number of cylindrical members 3 to which springs 4 having the structure described above are attached. and a band-shaped member are joined by each weld, and the overall structure is the same as that of the fuel spacer 1 shown in FIG. 12 described above.

As shown in FIGS. 5 and 6 (FIG. 6 is a sectional view of Sa-8B in FIG. 5), according to this embodiment, the fuel rods 6 are inserted into the cylindrical member 3 when assembling the fuel assembly. The central part of the spring (the convex part 4A and its vicinity) is inserted into the fuel rod by the lower end plug welding bead part 6A, which has a larger outer diameter than the fuel rod tube part 6B.
Even when the cylindrical member is pushed toward the adjacent cylindrical member, the center gap Z1 in the cylinder height direction of the figure-eight notch 7B of the cylindrical member
can be used as a passage space for the spring 4, so that it is possible to prevent the spring 4 from losing its function as an elastic body due to excessive deformation, and from damaging the fuel rod 6 or the protrusion 5 of the cylindrical member. can. However, according to this embodiment, the seventh
As shown in FIG.

Even when a large acceleration is applied in the cross-sectional direction of the fuel assembly such as during an earthquake, during transportation, or during handling, and the fuel e6 moves in the direction of contact with the spring 4 (in the direction of arrow As in the figure), the center of the spring 4 (the convex portion 4A and its vicinity) can pass through the above-mentioned spatial space Z1, so that plastic deformation of the spring 4 can be prevented.

Furthermore, in this case, as the fuel rod 6 moves toward the spring 4, the fuel rod 6 contacts not only the central convex portion 4A of the spring 4 but also the upper and lower convex portions 4B by a predetermined amount of movement. Therefore, the reaction force that the fuel rod 6 receives from the spring 4 can be dispersed, and excessive stress can be prevented from being generated in the fuel rod 6.

This effect is shown in Figure 5, which shows the relationship between the acceleration G in the cross-sectional direction that the fuel assembly receives during an earthquake, etc., and the pressure F that the fuel rod 6 receives from the spring 4 at that time. This is what is shown. In FIG. 9, Fl is the initial reaction force of the spring 4, and F2 is the reaction force of the spring when the fuel rod 6 contacts the upper and lower convex portions of the spring. Also, G1 is the acceleration when the force pushing the fuel rod 6 spring 4 and the reaction force of the spring 4 are balanced, and Gt is the acceleration when the fuel rod 6 contacts the upper and lower convex portions 4B of the spring. . In the case of a conventional fuel spacer, the fuel rod 6 always contacts only the central convex portion 4A of the spring and does not contact the upper and lower convex portions 4B (see Fig. 35), so that the acceleration G and the fuel rod are The relationship between the reaction force F received from the spring is as shown by the two-dot chain line (Pz~P2~P8~P4) in FIG. On the other hand, in the case of the fuel spacer of this embodiment, the solid line (Ps~P2~
P3 to Pa) and the dashed dotted line (Pg to P7).

From this figure, it is easy to see that by employing this embodiment, the reaction force that the fuel rod 6 receives from the spring 4 is significantly reduced, which is very effective in maintaining the mechanical integrity of the fuel rod. be understood.

FIG. 10 shows a second embodiment of the present invention,
FIG. 11 is a sectional view taken along line 5a-8a in FIG. 10. In the first embodiment described above, the notch made on the cylindrical surface of the cylindrical member to form the protruding piece that holds the spring is E-shaped, and the cross-sectional shape of the protruding piece remains arcuate. On the other hand, in this embodiment, the shape of the notch 7C made on one cylindrical surface is C-shaped, most of the formed protrusion 8C is made flat, and the center of the plate thickness of the protrusion 8C and the center of the cylindrical member are The difference is that the protruding piece 8C is made to protrude outside the cylindrical member so that the distance m from the cylindrical member is half the fuel pitch.

Figures 12 and 13 (Figure 13 is the 5o-
8a sectional view) uses the cylindrical member 3 of this example,
This figure shows a state in which a fuel rod 6 is inserted into a cylindrical member to which a spring 4 is attached in the same manner as in the first embodiment and whose upper and lower sides are welded together at a welded portion Wl between the cylindrical members.

In this case, the projecting pieces 8C are spaced apart from each other by a spatial space Zx (
(see Figure 10). In this example, the length of the formed protrusion 8C along the axial direction of the cylindrical member is such that even when the cylindrical members are combined, the two protrusions 8C do not interfere, and the end surfaces of the protrusions have almost no gap. Since they are set to face each other, the state is the same as when a single flat member passes through the spring 4. Therefore, according to this embodiment, compared to the conventional fuel spacer having a structure in which two protruding pieces pass through the spring 4 (see FIG. 30), the spring 4 is at least as thick as the plate thickness of one protruding piece. Since the space in which the fuel rods 4 can be deformed is increased, it is possible to prevent problems when inserting the fuel rods as shown in FIGS. 28, 30, and 32. In addition, in the case of this embodiment, if the height of the upper and lower convex portions 4B of the spring (dimension hz in FIG. 37) is made slightly larger than the height of the central convex portion (dimension h1) in FIG. 37,
Effects similar to those of the first embodiment can also be obtained during an earthquake.

A third embodiment of the present invention will be described with reference to FIGS. 14 to 17. In addition, Fig. 15.

It is a 5t-87 sectional view of FIG. 14. Figure 16 is.

Using the cylindrical member 3 shown in FIG. 14, a spring 4 is attached in the same manner as in the above-mentioned first and second embodiments, and the cylindrical members are joined together by welding the top and bottom at the welding part W1.
FIG. 17 is a sectional view taken along the line Ss-Ss of FIG. 16.

In this embodiment, a protruding piece 8D is formed in the cylindrical surface of the cylindrical member 3 by a C-shaped notch 7D, similar to the second embodiment described above.

However, in the second embodiment, the length of the protrusion along the axial direction of the cylindrical member is such that when the cylindrical members are combined, the end surfaces of the protrusion face each other with almost no gap (see Fig. 12). On the other hand, in this embodiment, the difference is that the length is set so that the gap between the end surfaces of the protruding pieces is the same as that in the first embodiment described above (see Fig. 3 and Fig. 16). .

Therefore, as can be seen from FIG. 16, in this embodiment, the state is the same as when a single flat member separated vertically passes through the spring 4, so that the spring 4 and the protruding piece 8D The gap is increased, and the space Z8 between the end faces of the protruding pieces can be used as a passage space for the center portion of the spring. As a result, the deformation space of the spring 4 is dramatically increased compared to the conventional one, and it is possible to obtain the same effects as the first and second embodiments, and even greater effects than these embodiments.

In addition, in the above description of the embodiment, only the case where the cross-sectional shape of the independent cells constituting the fuel spacer is circular, but it can also be applied when the cross-sectional shape of the independent cells is polygonal, such as octagonal or hexagonal. Applying the present invention.

Similar effects can be obtained. Each figure shown in FIG. 18 to FIG. 21 shows a square tube member 10 in which the first embodiment of the present invention is applied to an independent cell (square tube member 10) having an octagonal cross-sectional shape.
This figure shows a state in which a spring 4 is attached to this rectangular tube member 10, the rectangular tube members are connected by welding, and then a fuel rod 6 is inserted.

19 is a sectional view taken along line 5lI-5a in FIG. 18, and FIG. 21 is a sectional view taken along line 51o-8ta in FIG. This is the same as shown in . As can be seen from a comparison between FIG. 20 and FIG. 3, the support methods for the springs 4 and fuel rods 6 are the same in both cases, except for the different shapes of the independent cells. Therefore, it is easily understood from these figures that even when the cross-sectional shape of the independent cell is polygonal, it is fully possible to apply each of the embodiments of the present invention, and the above-mentioned effects can be obtained. Good morning.

〔Effect of the invention〕

According to the present invention, it is possible to secure a larger spring deformation space within a limited fuel rod gap than a fuel spacer with a conventional structure, and it can also be used when an extremely large load is applied to the spring, such as during an earthquake. Since the reaction force received from the fuel rod springs can be dispersed, from the perspective of ensuring the integrity of the springs and independent cells, it is not only possible to significantly widen the allowable range of applicable fuel rod outer diameters, but also to The integrity of the fuel rod itself can also be ensured. Furthermore, in the present invention,
There is no need to make any changes to the shape of the spring itself or the way it is held, and on the other hand, the processing that is applied to the independent cells is extremely partial and slight, and since only one type of independent cell is required, it is easy to assemble the fuel spacer. It is.

A side view of an example independent cell, FIG. 2 shows the St of FIG.
3 is a broken side view showing a normal fuel rod support state in the first embodiment, and FIG. 4 is a sectional view of S in FIG. 3.
2-82 sectional view, FIG. 5 is a cutaway side view showing the fuel rod insertion state in the first embodiment, and FIG. 6 is the Ss in FIG.
Fig. 7 is a broken side view showing the fuel rod support state during an earthquake in the first embodiment, Fig. 8 is the S4 S4 cross section of Fig. 7, and Fig. 9 is a cross-sectional view of the fuel rod of the present invention. FIG. 3 is an explanatory diagram showing the relationship between the acceleration at the spacer during an earthquake and the reaction force that the fuel rod receives from the spring. Fig. 10 is a side view of an independent cell showing a second embodiment of the fuel spacer of the present invention, Fig. 11 is a sectional view from 85 to S5 in Fig. 10, and Fig. 12 is a fuel rod insertion in the second embodiment. FIG. 13 is a sectional view taken along line 5s-8a in FIG. 12, FIG. 14 is a side view of an independent cell showing the third embodiment of the fuel spacer of the present invention, and FIG. 87-87 sectional view in the figure, FIG. 16 is a broken side view showing the fuel rod insertion state in the third embodiment, FIG. 17 is a 5R-3a sectional view in FIG. 16, and FIG. 18 is a fuel rod of the present invention. A side view of an independent cell when the first embodiment of the spacer is applied to an independent cell with a hexagonal cross section, FIG. 19 is a sectional view taken along line 39-89 in FIG. 18, and FIG. 20 is a hexagonal independent cell type fuel spacer. 21 is a cross-sectional view of the S1a S section of FIG. 20, FIG. 22 is a plan view showing the structure of the fuel spacer of the present invention and the conventional fuel spacer, and FIG. FIG. 24 is a side view of an independent cell for a fuel spacer, FIG. 24 is a Sll-Sll sectional view of FIG. 23, FIG. 25 is a plan view showing the fuel rod support state in a conventional fuel spacer, and FIG. Sll-
812 sectional view, Figure 27 is 81s Sta in Figure 25
28, 30, and 32 are broken side views showing defects in the conventional fuel spacer when inserting fuel rods, and FIG. 29 is a sectional view of 814S14 in FIG. 28, and FIG. 31. is a 815-\S1s cross-sectional view in Fig. 30, Fig. 33 is a 5ze-8ta cross-section and side view in Fig. 32, Fig. 34 is a broken side view taken from the ■-■ arrow in Fig. 33, and Fig. 35 Figure 36: 8"-8" of Figure 4:418 is a broken side view showing the state of fuel rod support during an earthquake with a conventional fuel spacer.
Cross-sectional view - Fig. 37 Figure 1 is a cutaway side view showing how fuel rods are supported in a conventional fuel spacer.

1...Fuel spacer, 2...Side band, 3...
・Independent cell (cylindrical member), 4... Spring, 4A... Convex part at the center of the spring, 4B... Convex parts above and below the spring, 5...
Projection, 6...Fuel rod, 6A...Fuel rod tube part, 6B
... Lower end plug welding bead of fuel rod, 6C... Lower end plug of fuel rod, -7''A, 7B, 7G, 7D... Notch, 8A, 8B.

8G, 8D... Projection piece, 9... Notch, 10... Independent cell (square tube member with octagonal cross section), V/s... Weld between independent cells, Wz... Independent cell - Weld between side bands.

Z* + Zz * Zs...Spring passage space or ridge storage space.

Claims (1)

[Claims] 1. A large number of cylindrical members (independent cells) connected to each other;
A fuel spacer consisting of a spring and a band member surrounding the outer periphery of the bundle of cylindrical members and maintaining a distance between the elements in a nuclear reactor fuel assembly including a plurality of elongated elements,
The spring is a continuous loop-shaped spring that has an overall elliptical shape and has convex portions formed on the surface side at its longitudinal center, upper end, and lower end for supporting the element. The spring member on one side of the cylindrical member projects into one cylindrical member, and the spring member on the opposite side projects into a cylindrical member adjacent to the cylindrical member, and each spring has an E of the wall surface of one cylindrical member. supported by a protruding piece formed by a letter-shaped notch and a protruding piece having vertically opposite directions formed by an E-shaped notch on the wall surface of the cylindrical member adjacent to the cylindrical member, each A fuel spacer characterized in that the element is supported by a protrusion formed from the cylindrical member so as to protrude inside the cylindrical member and a spring member on one side of the spring. 2. The notch provided in the wall surface of the cylindrical member (independent cell) is C-shaped, and most of the protruding piece formed by this notch is flat, and the flat part of the protruding piece is a plate. The center of thickness is separated from the center of the cylindrical member by half the arrangement interval of the elements, and the length along the axial direction of the protruding cylindrical member is such that the upper and lower sides of one of the two cylindrical members are the same as the other. Even if the cylindrical member is brought into contact with the cylindrical member in a state where the notches face each other, the protruding pieces do not contact each other, or the gap between the protruding pieces along the axial direction of the cylindrical member is as described above. The fuel spacer according to claim 1, which is formed by an E-shaped notch and has a length comparable to the gap between the vertically separated projecting pieces. 3. The fuel spacer according to claim 1 or 2, wherein the independent cells into which the fuel rods are inserted have an overall octagonal cross-sectional shape. 4. The fuel spacer according to claim 1 or 2, wherein the independent cells into which the fuel rods are inserted have a generally hexagonal cross section.