JPS6266194A - Nuclear fuel aggregate - 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 [Technical Field of the Invention] The present invention relates to a nuclear fuel assembly disposed in the core of a nuclear reactor.

[Technological forward leaning of the invention and its problems] Generally, the nuclear fuel assembly placed in the core of a nuclear reactor is
As shown in the figure, a plurality of fuel rods 1 containing nuclear fuel material are shown.
A fuel rod bundle 5 is inserted into a hollow cylindrical channel box 6, and the fuel rod bundle 5 is held at equal intervals by spacers 2 and held at the top and bottom by an upper tie plate 3 and lower tie plates 1 to 4. 5 and the channel box 6 are fixed by fixing bolts 8 of channel fasteners 7.

FIGS. 6 and 7 show the channel fastener 7 of such a nuclear fuel assembly and the fixing part between the fuel rod bundle 5 and the channel box 6. spring 10,
The fixing bolt 8 is inserted into the through hole provided in the clip 12 of the channel box 6, and is inserted into the post 13 of the upper tie plate 3.
The channel box 6 and the upper tie plate 3 of the fuel rod bundle 5 are fixed by being screwed into the screw hole 14 provided in the upper tie plate 3 of the fuel rod bundle 5. Further, the leaf spring 10 of the channel fastener 7 has a function of maintaining an appropriate distance between adjacent nuclear fuel assemblies by its elastic force.

The installation of the channel fasteners 7 (and the fixing of the channel box 6 and the upper tie plate 3 of the fuel rod bundle 5) is done in the atmosphere for new fuel, but for nuclear fuel once loaded into the reactor core. When removing and storing the channel box 6 of the assembly, this is done remotely under water as shown in Figure 8. In such operations, the nuclear fuel assembly is removed from the spent fuel storage. The channel box 6 is held in the channel attachment/detachment device 15 in the pool, and the fixing bolt 8 of the channel fastener 7 is operated using the long wrench 16 to attach/detach the channel box 6. For example, when attaching the channel box 6, as shown in FIG. As shown in the figure, first cover the fuel rod bundle 5 with the channel box 6 (A), then align the fixing bolt 8 of the channel fastener 7 with the screw hole 14 of the upper tie plate 3 (B), and rotate the fixing bolt 8. Avoid and fix it (C).

However, such work requires a high level of skill and time to handle small parts in underwater remote work, especially the positioning of the fixing bolt 8 with respect to the screw hole 14,
Moving the removed channel fastener 7 to the storage location,
It takes time to move from the storage location to the installation location. In addition, since this is underwater remote work, the channel fastener 7
It is difficult to install at position f (f), and there is a possibility that the installation will be in poor condition. Figure 10 shows an example of such installation in poor condition. A gap may occur between the outer wall of the channel box 6 and the guard 10 of the channel fastener 7. When such a gap occurs, the reaction force F of the nuclear fuel assembly adjacent to the leaf spring 9 acts, Due to the buffer between the guard 10 and the reactor internals 17, an upward force T acts on the guard 10, and an excessive load is applied to the fixing bolt 8, which may cause damage.If such damage occurs, During reactor operation, phenomena such as tilting of the fuel or floating of the channel box 6 occur, which may impede the insertion of control rods or change the thermo-hydraulic characteristics of the reactor core, which may affect the health of the reactor. There is a possibility of damage.

On the other hand, in recent years, it has become common to use the channel box 6 for a longer period than the fuel life, so the frequency of such work has increased significantly.
At iKW's nuclear reactors, approximately 200 channel boxes 6 are installed and removed every year. Therefore, there is a problem that the time required for the work and the burden on the workers increases, and there is a problem that the installation of the channel fastener 7 increases the risk that the integrity of the reactor will be impaired due to the occurrence of a defective condition.

[Purpose of the Invention] The present invention has been made in response to the above-mentioned conventional circumstances, and enables the channel box to be easily and accurately attached and detached in a short time even during underwater remote work, thereby reducing the burden on workers. The objective is to provide a nuclear fuel assembly that can reduce the amount of energy used, reduce working time, and improve the health of the reactor.

[Summary of the Invention] That is, the present invention covers the outside of a fuel rod bundle whose upper part is supported by an upper tie plate with a hollow cylindrical channel box, and this channel box and the upper tie plate are connected to a channel fastener. In a nuclear fuel assembly fixed by a fixing bolt, the channel fastener is fixed to the channel box by a fixing means different from the fixing bolt, so that the channel box can be easily and accurately attached and detached in a short time. This system is designed to reduce the burden on workers, shorten work time, and improve the health of the reactor.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 and FIG. 2 show the main parts of a nuclear fuel assembly according to an embodiment of the present invention.
A leaf spring 20 for maintaining a predetermined distance between adjacent nuclear fuel assemblies, a guard 21 for protecting the end of the leaf spring 20, a channel box 22, and an upper tie plate 23. Fixed Pol I-2 for fixing
A channel fastener 26 consisting of a /I and a washer 25 is fixed to the upper end of the channel box 22. The channel box 22 is made of a zirconium alloy, and the guard 21 of the channel fastener 26 is fixed to the channel box 22.
Since it is made of stainless steel, it is difficult to weld it directly [therefore, a through hole is provided in the side wall of the channel box 22 and the guard 21, and the fixing pin 27 is inserted into this through hole to connect the fixing pin 27 and the cart. This is done by welding 21. The mounting portion of the fixing bolt 24 of the guard 21 has a sufficient length relative to the length of the fixing poles 1 to 24 so that the fixing poles I to 24 are kept vertically, and the fixing bolt 24 is The handle has been treated with a stopper, and the whole is constructed as one piece.

In the nuclear fuel assembly configured in this way, the channel box 22 is connected to the upper tie plate 2, as shown in FIG.
3, the channel fastener 26 is fixed in the predetermined position of the channel box 22, so the fixing bolt 24 is automatically inserted into the screw hole 28 of the upper tie plate 23.
(A), and then the channel box 22 and the upper tie plate 23 are fixed by rotating the fixing pole 24 to the fixing pole 1 (B).

In other words, in the nuclear fuel assembly of this embodiment, since the channel fastener 26 is fixed at a predetermined position of the channel box 22, when the channel box 22 and the upper tie plate 23 are attached and detached, the channel fastener 26 is removed from the attachment/detachment location. There is no need to move from the storage location to the attachment/detachment location or from the storage location to the attachment/detachment location, and the positioning of the fixing bolt 24 and the upper tie plate 23 is performed automatically, so the work can be done in a shorter time and easier than before. I can do it. Furthermore, the installation of the channel fastener 26 is free from defects.

FIG. 4 shows the main parts of a nuclear fuel assembly according to another embodiment of the present invention. In the nuclear fuel assembly of this embodiment, the clip 31 of the channel box 30 is constructed of a thick plate with screw holes. , fixing nut 32 to guard 33 and leaf spring 34
The channel box 30 and the channel fastener 36 are fixed by passing through and fixing to the screw hole of the clip 31. Note that the outer diameter of the fixing nut 32 is larger than the outer diameter of the fixing bolt 37.

In the nuclear fuel assembly configured in this way, the fixing nut 3
By rotating the fixed poles 1 to 37 while fixing the rotation of the upper tie plate 38 and the channel box 30 with a wrench, the upper tie plate 38 and the channel box 30 can be attached and detached in the same manner as in the nuclear fuel assembly of the previous embodiment. effect can be obtained. In addition, if the fixing bolt 37 etc. is damaged,
By rotating the fixed nuts 1 to 32, the channel fastener 36 can be removed from the channel box 30 and replaced.

[Effects of the Invention] As explained above, according to the nuclear fuel assembly of the present invention, since the channel box and the channel fastener are fixed by a fixing means different from the fixing bolt, the channel box can be easily attached and detached in a short time. , and can be performed accurately, reducing the burden on workers, shortening working time, and improving the health of the reactor.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing the main parts of a nuclear fuel assembly according to an embodiment of the present invention, FIG. 2 is a top view showing the main parts of the nuclear fuel assembly shown in FIG. 1, and FIG. 3 is the same as that shown in FIG. FIG. 4 is an explanatory diagram showing the procedure for installing the nuclear fuel assembly channel box shown in FIG.
Fig. 5 is a partially cutaway perspective view showing a conventional nuclear fuel assembly, Fig. 6 is a longitudinal sectional view showing the main parts of a conventional nuclear fuel assembly, and Fig. 7
The figure is a top view showing the main parts of the nuclear fuel assembly shown in Figure 6, Figure 8 is an explanatory diagram showing how the channel box is installed, and Figure 9 is a nuclear fuel assembly with a defective channel fastener installed. FIG. 10 is an explanatory view showing the procedure for installing a channel box in a conventional nuclear fuel assembly. 20...Flat spring 21...Guard 22...Channel box 23...
・・・・・・Upper tie plate 24・・・・・・・・・
To fixed pole 1 26......Channel fastener 27...
...Fixing pin Applicant Toshiba Corporation Patent attorney Sa Suyama - (A) (B) Figure 3 Figure 4 Figure 8

Claims (1)

[Claims] (1) Covering the outside of the fuel rod bundle whose upper part is supported by an upper tie plate with a hollow cylindrical channel box,
In this nuclear fuel assembly in which the channel box and the upper tie plate are fixed by fixing bolts of channel fasteners, the channel fastener is fixed to the channel box by a fixing means different from the fixing bolts. nuclear fuel assembly.