JPS608783A - Nuclear fuel element for nuclear reactor - 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 The present invention involves filling a cladding tube with a large number of fuel pellets,
The present invention relates to a nuclear fuel element for a nuclear reactor in which a plenum spring is interposed between the fuel pellet and the end plug, and particularly relates to improvements in the plenum spring portion thereof.

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

FIG. 1 is a longitudinal cross-sectional view of the conventional nuclear fuel element for a nuclear reactor, in which a large number of fuel pellets (J) are packed and stacked in a cladding tube (l), and end plugs (3) and an end plug (3) are provided at both ends of the cladding tube (l). da is attached. A plenum 5 is formed between the top end of the fuel pellet and the upper end plug 3 to accommodate the fission product gas, and the plenum 5 is provided with a plenum 5 for pressing the stacked fuel pellets and preventing their movement. A plenum spring 6 is provided. by the way,
A fuel pellet holding plate 7 is interposed between the plenum spring 6 and the fuel pellet in order to increase the pressing area of the spring on the fuel pellet λ and to apply a uniform load to the fuel pellet λ. The bullet retaining plate is welded in advance to one end of the plenum spring B in order to facilitate its insertion into the cladding tube l.

Therefore, the conventional nuclear fuel element for a nuclear reactor as described above is
When manufacturing it, it is necessary to weld the fuel pellet retainer plate to the plenum spring in advance, which requires special welding equipment and jigs and tools, which incurs equipment costs and consumables costs such as welding electrodes. There are other problems.

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 fuel pellet side end of the fuel pellet, and at least seven coils that contact the fuel pellet together with a plenum spring are screwed into the tightly wound portion.

Embodiments of the present invention will be described below with reference to FIGS. 1 to 7. Note that the same parts as in FIG. 1 are given the same reference numerals.

In FIG. 2, a bent end plug 3 and a holder are attached to both ends of the cladding tube/, and a large number of fuel pellets are filled and stacked inside the cladding tube/, and the top of the fuel pellet λ and A plenum spring 6 is interposed between the trap and the upper end stopper 3.

This structure is exactly the same as the conventional one, but in the present invention, a tightly wound portion G is formed at the fuel pellet side end (lower end) of the plenum spring base, and in this tightly wound portion S, As shown in FIG. 3, seven coils 9. Alternatively, as shown in FIG. 7, the coils 9 and 10 are concentrically screwed together to form the above-mentioned coils. , 10 are in the same plane as the lower surface of the plenum spring base.

Then, the lower surface of the plenum spring base contacts the fuel pellet unit with the disassembled coil at its lower end, and
The fuel pellet is pressed against a relatively wide area to prevent its movement.

In this way, in the present invention, a tightly wound portion is formed at the end of the plenum spring on the fuel pellet side, and a small number of coils (7 in total) are screwed into the tightly wound portion, and the ends of the coil and the plenum spring are connected to each other. Since the fuel pellets are held down by the end, 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. Moreover, it does not require special welding. No equipment is required, and manufacturing costs can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a conventional nuclear fuel element for a nuclear reactor, FIG. 2 is a vertical cross-sectional view of a nuclear fuel element for a nuclear reactor according to the present invention, and FIG. 3 is an enlarged cross-sectional view of the fuel pellet side end of a plenum spring. FIG. 7 is an enlarged sectional view showing the same part as FIG. 3 showing another embodiment of the present invention. l...cladding tube, co...fuel pellet, 3. 'I・
...End plug, Ri...Plenum, 6...Plenum link, Su...Tightly wound part, Wa, 10...Coil. Applicant's agent Kiyoshi Inomata 1A 82nd

Claims (1)

[Claims] In 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, the end of the plenum spring on the fuel pellet side forms a tightly wound portion. A nuclear fuel element for a nuclear reactor, characterized in that at least one coil that contacts a fuel pellet together with a plenum spring is screwed into the tightly wound portion thereof.