FI82781B - KLUVET BRAENSLE-ELEMENT FOER KAERNREAKTOR, ISYNNERHET FOER KOKVATTENREAKTOR. - Google Patents

Description

1 82781

A split fuel element of a nuclear reactor, especially a boiling water reactor

The invention relates to a fuel element for a nuclear reactor, in particular a boiling water reactor, which has a rectangular or hexagonal cross-section and in which fuel rods are arranged so as to form a grid in which slots running perpendicular to the width of the cross-section are arranged.

In the fuel element known from DE-A-3 215 363, slits are formed by projections directed into the housing. They extend along the entire length of the fuel element, as shown in particular in Figure 7.

The object of the invention is to provide a fuel element which achieves a higher energy output than a previously known fuel element. For this purpose, according to the invention, the slots are arranged in such a way that the slots extend over the upper part of the length of the fuel elements and the space delimiting the slots in the longitudinal direction contains fuel rods which are somewhat shorter than the fuel rods between the slots.

In the invention, in the use of the fuel element, only additional water is fed to the upper part from outside the bypass line, which acts as a retarder. In this way, the lack of a retarder is compensated for at those points where, especially in boiling water reactors, less deceleration occurs due to evaporation inside the fuel element. The invention is preferably implemented so that the gap extends over the entire cross-section 30 and almost half the height of the fuel element.

. ···. The shorter fuel rods may preferably be located in a support which closes the gap from the center of the fuel element and which extends from one side of the edge of the fuel element to the other. This bracket provides the necessary attachment to the shorter fuel rods. In addition, the structure of the fuel element can thus be made 2 82781 stiffer. This is especially the case if the support is metallurgically attached to the plates defining the gap as its walls. It is further recommended to provide a spacer in the wall so that the thin-walled slit-deflecting plates can be kept at the correct distance from each other.

The invention will be described in more detail by describing one embodiment thereof with the aid of the accompanying drawing. In it, Figure 1 shows a fuel element-10 according to the invention in a perspective view.

Figures 2, 3 and 4 show details of the invention in three mutually perpendicular sections.

The fuel element shown in Figure 1 belongs to a boiling water reactor with a capacity of e.g. 1300 MW. It has a foot part 2 by means of which it is fastened to a lower support plate (not shown) and an end part 3 which is fitted to the upper inner lattice. In Figure 1, invisible fuel rods extending between the base portion 2 and the end portion 3 are enclosed in a fuel element housing 5 which directs flow 20 through the fuel element when the fuel element is in use in a vertical position and flows through it from bottom to top.

The fuel element 1 according to the invention has its upper part 7, which extends halfway along the length of the fuel element 25, provided with a water gap 8, which instead of one row of fuel rods extends transversely through the entire cross-sectional area of the square fuel element. In this way, a further retarder can be provided in the area where the deceleration is reduced due to the steam content 30 in the fuel element in the boiling water reactor.

As can be seen from Fig. 2, a support 10 is arranged transversely to the lower part of the slot 8, passing through the fuel element, with bores 11 which receive shorter fuel rods 12. The fuel rods 12 are practically shorter than normal by the height of the gap 8.

II

3,72781 fuel rods 13 extending over the entire length of the fuel element 1, e.g. 4 m. The length of the rods 12 is e.g.

1.9 m.

As shown in Fig. 4, the gap 8 extends through the entire square cross-section of the fuel-5 material element 1, i.e. from one side of the housing 5 to the opposite side. The walls delimiting the gap 8 are two flat sheet metal plates 14 running parallel to each other at a distance corresponding to the diameter of the fuel rod and connected by a support 10 metallurgically in one piece, as can be seen in Figure 3. A spacer 15 is arranged in the middle of the fuel element, which improves the strength.

Claims (5)

A fuel element for a nuclear reactor, in particular a boiling water reactor, which has a square or hexagonal cross-section and is arranged with fuel rods so as to form a grid arranged perpendicular to the edge of the cross-section across the width of the fuel rods. the slots (8) are located at the top of the fuel element (1) and the space bounded longitudinally by the slots (8) includes fuel rods (12) which are somewhat shorter than the fuel rods (13) between the slots (8). ). Fuel element according to Claim 1, characterized in that the gap (8) extends over the entire cross-section and almost half the height of the fuel element (1). Fuel element according to Claim 1 or 2, characterized in that the shorter fuel rods (12) are arranged in a support (10) which closes the gap (8) at the center of the fuel element and which extends from one side of the edge of the fuel element to the second page. Fuel element according to Claim 3, characterized in that the support (10) is metallurgically attached to the plates (14) which delimit the gap (8) in the walls. 4,82781 Fuel element according to Claim 4, characterized in that 30 spacers (15) are arranged between the walls. li 5 82781