JPH01304385A - Fuel assembly - Google Patents

Abstract

PURPOSE:To allow the movement of the assembly in parallel to the next row by mounting channel fasteners to the respective positions of corner posts. CONSTITUTION:Screw holes 32 for fixing the channel fasteners are inscribed to each of 4 pieces of the corner posts 31 of an upper tie plate 30 and a channel box 33 which are the important part of the assembly. Clips 34 are disposed to all the four corners at the top end of the channel box 33 and fixing holes 36 of the channel fasteners are provided to the respective clips. Channels spacers 35 are provided to all the uppermost ends of the four side faces. The channel fasteners can be fixed to the prescribed position of the assembly even if the assembly is moved in parallel to the next in the reactor core with the assembly constituted in such a manner. Since the channel spacers 35 are always coincident in position with the channel spacers 35 of the next assembly opposite thereto and, the spacing between the channel boxes 33 can be assured. The bending of the assembly is, therefore, easily corrected by moving the assembly to the prescribed position of the core.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a fuel assembly loaded into the core of a boiling water nuclear reactor.

(Prior Art) A conventional fuel assembly is constructed as shown in FIG. 5, and a plurality of fuel rods 2 and a water rod F 3 are housed in a rectangular cylindrical channel box 1.

The fuel rods 2 and water rods 3 are bundled into a bundle by a plurality of spacers 4 arranged in multiple stages in the axial direction, and the spacing between them is maintained, and their lower ends are connected to a lower end plug 7. The fuel pan I is assembled into the fuel pan I-kuru 15 by supporting the lower tie plate 5 via the lower tie plate 5 and supporting the upper end thereof to the two-part tie plate 6 via the upper end plug 8, respectively.

A rectangular cylindrical channel box 1 is fitted around the outer periphery of the fuel bundle 15 configured in this way, and a fuel assembly 21 is assembled.
It is assembled in.

The upper tiebrae 1-6 is constructed as shown in the front view of FIG. 6, and has a plurality of boss portions 10 having fitting holes 9 into which the two-part end plugs 8 of the fuel rods 2 and water rods 3 are fitted. to clothe As shown in the plan view of FIG. 7, the boss portions 1o are connected by webs 11 and arranged in a lattice pattern, and a corner post 12 is provided upright at each corner of the boss portions 1o.
A screw hole 14 for fixing the channel box 1 is threaded in one of the corner posts l-12a. A gate-shaped handle portion 13 is erected inside the corner post 2.

The channel box 1 is composed of a box body 16, a clip 17, and a channel spacer 18, as shown in FIGS.
~12. , 12a, and are installed at two diagonal positions on the upper end of the box body 16, and one clip 17a is provided with a fixing hole 19 for fixing to the corner post 12a. In addition, the channel spacer 18
are provided on three sides of the box body 16 on two sides that are in contact with the control rod, in order to ensure a distance between adjacent channel boxes across the control bar.

The channel box 1 and fuel bundle 15 configured as described above are installed at corner posts 1- at the four corners of the upper tie brake 1-6.
The threaded hole 14 in one tapped hole corner post 1.2a of 12 and the clip 17a of channel box 1
It is fixed by fitting the channel fastener 20 in alignment with the fixing hole. The channel fasteners 20 play the role of inserting each channel fastener 20 of the four pairs of fuel assemblies 21 into each other and fixing the fuel assemblies 2I upright in a normal position when fuel is loaded.

On the other hand, the channel box 1 deforms during use. The main deformations are expansion due to the pressure flowing through the channel box 1 during cooling and bending due to the difference in irradiation growth due to neutron irradiation. This curve is such that the surface with a large amount of neutron irradiation becomes convex. Therefore, near the outer periphery of the core, the core curves in a convex manner toward the center of the core. If this deformation becomes large, there is a risk that it will interfere with the control rod and interfere with insertion and withdrawal of the control rod.

(Problems to be Solved by the Invention) As described above, the curve of the outer periphery of the core becomes convex toward the center of the core. Therefore, if we consider one outermost cell consisting of one control rod and four fuel assemblies, the channel box of the outermost fuel assembly is bent toward the control rod, and the channel box of the outermost fuel assembly is bent toward the center of the core with the control rods in between. The channel boxes of the fuel assemblies in the second row from the outermost periphery of the control rods are bent in the direction away from the control rods. Therefore, if the bend in the channel box of the outermost fuel assembly becomes large and there is a concern that it may interfere with the control rods, if you move it parallel to the second row from the outermost circumference, this time it will conversely move further away from the control rods. As it bends, the problem disappears.

However, current fuel assemblies have only one screw hole for fixing screwed into corner post 1 of the upper tie plate, and only one of the channel box clips has a fixing hole. , the mounting position of the channel fastener is structurally limited. For this reason, when a fuel assembly is moved in parallel to an adjacent fuel assembly, it is impossible to match the position of the channel fastener of the moved fuel assembly with the opposing channel fastener of the adjacent fuel assembly. In addition, since the channel spacers are provided only on the two sides of the box body, when the fuel assemblies are moved parallel to each other in the same manner as above, the channel spacers of the opposing adjacent fuel assemblies are Unable to match. In other words, in conventional fuel assemblies,
It is structured so that it cannot move in parallel and can only move to point-symmetric positions. Therefore, when the channel box is used for a long period of time, there is a problem in that there are very limited methods for correcting the bends by moving the fuel assembly.

The object of the present invention has been made in consideration of the above-mentioned circumstances, and is to provide a fuel assembly that can be moved in parallel to an adjacent row.

[Structure of the invention]

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an upper tiebrae 1- that supports a plurality of fuel rods and water rods tied together in a bundle via an upper end plug. , a handle post and four corner posts are set upright, and a clip and a channel spacer are attached to a channel box that surrounds the plurality of bundled fuel rods and water rond via channel fasteners. In the fuel assembly that has been prepared, thread holes for fixing the channel fasteners in each of the four corner posts 1 to 1, place the clips on all four corners of the upper end of the channel box, and attach the channel fasteners to each clip. The present invention provides a fuel assembly characterized in that the fuel assembly is provided with a fixing hole and the channel spacer is provided at the uppermost end of all four sides.

(Function) In a fuel assembly configured in this way, the channel fastener can be fixed at a predetermined position on the fuel assembly even when moved parallel to each other in the core, Since the position always matches the channel spacer of the fuel assembly, the distance between the channel boxes that sandwich the control rods can be secured. Therefore, the bend can be easily corrected by moving the fuel assembly to a predetermined position in the reactor core.

(Example) Hereinafter, an upper tie plate and a channel box showing the main parts of a fuel assembly according to an example of the present invention will be described with reference to FIGS. 1 to 4. In FIGS. 1 to 4, the same parts as in FIGS. 5 to 9 are designated by the same reference numerals, and explanations of the configurations of these parts will be omitted.

In FIGS. 1 and 2, the corner posts 31 disposed at the four corners of the upper tie plate 30 are thicker than the conventional corner posts 1- which have no tapped holes, and have a channel at the upper end. A tapped hole 32 for fixing the fastener 20 is threaded.

In FIGS. 3 and 4, the channel box 33
is equipped with clips 34 at the four ends of the upper end, and each clip 3
4 is provided with a fixing hole 36 for fixing it to the tie plate 1-corner post 1-31 through the channel fastener 20. Additionally, channel spacers 35 are provided on the four sides of the box body 16. The channel spacer 35 is installed at the extreme end of the box body 16, in order to prevent interference with the upper grid plate that supports the fuel assembly 21 above in the reactor core. 21
The channel spacers 35 are located at the center of each side of the box body 16 so that the positions of the channel spacers 35 always match.

Therefore, according to the configuration described in item 1, the channel fastener 20
can be fixed at any position, the fuel assembly 2] can be moved parallel to the adjacent position within the reactor core, and even in this case, the position of the channel spacer 35 of the channel box 33 is the same as that of the opposing channel box. This corresponds to the position of the channel spacer 35 of No. 33, and it is possible to ensure the spacing between the channel boxes that sandwich the control rods.

〔Effect of the invention〕

As described above, according to the fuel assembly according to the present invention, the channel fasteners can be attached to each position on the corner post 1, so the fuel assembly can be moved in parallel in a line within the reactor core. Since channel spacers are provided on all four sides, it is possible to secure the distance between the channel boxes that sandwich the control rod hair, making it possible to use the channel boxes for a longer period of time, which was previously limited due to deformation. .

[Brief explanation of the drawing]

Fig. 1 shows the main parts of a fuel assembly according to an embodiment of the present invention - a front view with a part of the two-part tie plate cut away;
The figure is a plan view of a partial tiebrae 1~ shown in Figure 1.
FIG. 3 is a plan view of a channel box showing essential parts of a fuel assembly according to an embodiment of the present invention, FIG. 4 is a front view of the channel box shown in FIG. 3, and FIG. 5 is a conventional fuel assembly. 6 is a partially cutaway front view of the two-part tiebrae 1- shown in FIG. 5; FIG. 7 is a plan view of the upper tiebrae 1- shown in FIG. 6; 8 is a plan view of the channel box shown in FIG. 5, and FIG. 9 is a front view of the channel box shown in FIG. 8. 2 Fuel rod 3 Water rod 1 20 Channel fastener 30 Upper tiebrae 1 to 31 Corner post 3
2 Tapered hole 33 Channel box 34
・Clip 35 ・Channel base 36 ・Fixed hole agent Patent attorney Noriyuki Ken Yudo Ken Daishimaru

Claims (1)

[Claims] A handle post and four corner posts are erected on an upper tie plate that supports a plurality of fuel rods and water rods tied together in a bundle via an upper end plug, In a fuel assembly including a clip and a channel spacer in a channel box that surrounds the fuel rods and water rods via channel fasteners, screw holes for fixing the channel fasteners are threaded in each of the four corner posts. A fuel assembly characterized in that the clips are arranged at all four ends of the upper end of the channel box, each clip is provided with a fixing hole for a channel fastener, and the channel spacer is provided at the uppermost end of all four sides. body.