JPS6335951B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear fuel element for a nuclear reactor in which a cladding tube is filled with a large number of fuel pellets and a plenum spring is interposed between the fuel pellets and an end plug. Regarding improvement of the spring part.

In general, a nuclear fuel element for a nuclear reactor is often used in which a large number of fuel pellets are filled and stacked in a cladding tube.

FIG. 1 is a longitudinal sectional view of the conventional nuclear fuel element for a nuclear reactor, in which a large number of fuel pellets 2 are filled and stacked in a cladding tube 1, and end plugs 3 and 4 are provided at both ends of the cladding tube 1, respectively. is installed. A plenum 5 is formed between the top end of the fuel pellet 2 and the upper end plug 3 to accommodate the fission product gas, and the plenum 5 presses the stacked fuel pellets 2 to prevent their movement. A plenum spring 6 is provided to prevent this. Incidentally, a fuel pellet holding plate 7 is interposed between the plenum spring 6 and the fuel pellet 2 in order to increase the pressing area of the spring against the fuel pellet 2 and to apply a uniform load. Furthermore, the fuel pellet presser plate is welded to one end of the plenum spring 6 in advance in order to facilitate its insertion into the cladding tube 1.

Therefore, when manufacturing conventional nuclear fuel elements for nuclear reactors as described above, it is necessary to weld the fuel pellet holding plate to the plenum spring in advance, which requires special welding equipment, jigs, and other equipment. However, there are problems such as the cost of equipment and consumables such as welding electrodes.

In view of these points, the present invention aims to obtain a nuclear fuel element for a nuclear reactor that does not require welding work etc. for the plenum spring and can reduce manufacturing costs. A tightly wound portion is formed at the end of the fuel pellet on the side of the fuel pellet, and within the tightly wound portion, there is at least one portion that contacts the fuel pellet together with a plenum spring.
It is characterized by having several coils screwed together.

Embodiments of the present invention will be described below with reference to FIGS. 2 to 4. Note that the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 2, end plugs 3 and 4 are attached to both ends of a cladding tube 1, and a large number of fuel pellets 2 are filled and stacked inside the cladding tube 1.
Furthermore, a plenum spring 6 is interposed between the top of the fuel pellet 2 and the upper end plug 3. This configuration is exactly the same as the conventional one, but
In the present invention, a tightly wound portion 8 is formed at the fuel pellet side end (lower end) of the plenum spring 6, and one coil 9, as shown in FIG. 3, is formed in this tightly wound portion 8. Alternatively, as shown in FIG. 4, two coils 9 and 10 are screwed concentrically,
The lower end surfaces of the coils 9 and 10 are arranged in the same plane as the lower surface of the plenum spring 6.

The lower surface of the plenum spring 6, together with the coil 9 etc. screwed onto its lower end, comes into contact with the fuel pellet 2, and presses the fuel pellet 2 over a relatively wide area to prevent its movement.

As described above, in the present invention, a tightly wound portion is formed at the end of the plenum spring on the fuel pellet side, at least one coil is screwed into the tightly wound portion, and the end of this coil and the end of the plenum spring are formed. Since the fuel pellets are held down by the plenum spring, there is no need to weld the pellet holding plate to the plenum spring as in the conventional case, and the installation is extremely simple as it is only necessary to screw the coil in. No equipment is required, and manufacturing costs can be significantly reduced.

[Brief explanation of the drawing]

Figure 1 is a vertical cross-sectional view of a conventional nuclear reactor fuel element.
FIG. 2 is a longitudinal sectional view of a nuclear fuel element for a nuclear reactor according to the present invention, FIG. 3 is an enlarged sectional view of the end of a plenum spring on the fuel pellet side, and FIG. 4 is a third diagram showing another embodiment of the present invention. It is an enlarged sectional view showing the same part. 1...Claying tube, 2...Fuel pellets, 3, 4...
...End plug, 5...Plenum, 6...Plenum spring, 8...Tightly wound portion, 9, 10...Coil.

Claims (1)

[Claims] 1 Fill the cladding tube with a large number of fuel pellets,
In a nuclear fuel element for a nuclear reactor in which a plenum spring is interposed between the fuel pellet and the end plug, a tightly wound portion is formed at the end of the plenum spring on the fuel pellet side, and the fuel is inserted together with the plenum spring into the tightly wound portion. 1. A nuclear fuel element for a nuclear reactor, characterized in that at least one coil is threaded onto the pellet.