RU2510538C1 - Fuel assembly of nuclear reactor - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: invention refers to fuel assembly elements of a nuclear reactor of VVER-440 type and is aimed at providing a possibility of increasing power and energy generation of VVER-440 fuel assemblies. The fuel assembly of the nuclear reactor includes a top nozzle, a bottom nozzle attaching their cover to a bundle of fuel elements, which is arranged in a frame. The frame includes spacer grids with hexagonal rims, which are connected by means of a central pipe. On each of the spacer grids, which are arranged in the upper part of the frame, on the upper edge of each face of the rim between two corner fuel elements on each of the ends of the face, as well as between a middle fuel element of a peripheral row and fuel elements adjacent to it there are diverting elements in the form of plates bent from the rim at an acute angle and projecting to the space between the above fuel elements.

EFFECT: improving efficiency of heat carrier temperature equalisation across the fuel assembly cross section.

Description

The invention relates to nuclear energy, and in particular, to elements of a fuel assembly (FA) of a VVER-440 type nuclear reactor.

The design of the VVER-440 fuel assemblies (see Kirillov P.L., Yuryev Yu.S., Bobkov V.P. Handbook of Thermohydraulic Calculations (nuclear reactors, heat exchangers, steam generators). M: Energoatomizdat, 1990, p. 317) [1] the main structural units are a bunch of fuel elements (fuel elements), spacer grids (DR), mounted on the central pipe, head, shank and a cover connecting them. The fuel rods are fixed in the upper, spacing and lower support grids.

At present, the factor limiting the increase in the power of VVER-440 fuel assemblies is the non-uniformity of the temperature of the coolant over the cross section of the fuel assemblies, and calculations show that the highest temperature of the coolant occurs in the region of the 2-3rd fuel rods from the beam periphery in the upper part of the fuel assembly.

Known fuel assemblies of a VVER-1000 type nuclear reactor containing fuel elements (fuel rods), a head and a shank mounted on a power frame including a DR with rims, while on each edge of the rim faces of each DR there are fenders in the form of petals, inclined at a certain angle to the axis of the fuel assembly, in order to ensure the unobtrusiveness of the DR of neighboring fuel assemblies during overloading and mixing of the coolant in order to equalize the temperature of the coolant along the cross section of the fuel assembly (RU 2163036 C2, publ. 02.10.2001). Moreover, the rims of the DR are made of components that are overlapped by welded joints, and spot-welded to the DR cells.

The disadvantages of the known fuel assemblies are the increased hydraulic resistance of the DR caused by the presence of chippers along the entire length of all edges of the rims of all DRs, low mixing efficiency in the presence of multidirectional chippers on the upper and lower edges of the rim at the same time, the complexity of making connections of the components of the rims.

The objective of the invention is to provide the possibility of increasing the power and power generation of fuel assemblies VVER-440.

The technical result of the invention is to increase the efficiency of balancing the temperature of the coolant along the cross section of the fuel assembly.

The technical result is achieved in that in a fuel assembly of a nuclear reactor containing a head, a shank connecting their case and a bundle of fuel rods, placed in a frame including spacing grids with hexagonal rims connected by a central pipe, according to the invention, on each of the spacing grids located in the upper parts of the frame, on the upper edge of each face of the rim between two angular fuel rods at each end of the face, and also between the middle along the face and neighboring fuel rods of the peripheral row deflecting elements in the form of plates bent from the rim at an angle of 5 ... 15 ° and protruding into the space between these fuel rods are filled.

In addition, the rims of the spacer grids are preferably made of zirconium alloy using laser cutting.

Figure 1 shows a General view of the fuel assemblies VVER-440.

Figure 2 - proposed DR, top view.

Figure 3 - face of the DR.

Figure 4 is a cross section of the face of the DR.

Figure 5 is a photo of the rim face.

The fuel assembly of a nuclear reactor contains a head 1, a shank 2 and a cover and a power frame connecting them, including the upper and lower support grids 3 and 4 and spacer grids (DR) 5 and a central pipe (CT). A beam of fuel elements (fuel rods 6) is fixed in the power frame. (see figure 1). The fuel rods 6 are mounted in the DR 5 and the lower support grid 4 (HP).

On each of the DR 5 located in the upper part of the frame (from four to ten DR, for example), on the upper edge of each face 7 of the rim 8 of the DR between two corner cells for fuel rods 9, 10 and 11, 12 at each end of the face 7, as well as between the middle 13 along the edge 7 and adjacent cells for the fuel elements 14 and 15 of the peripheral row, deflecting elements 16 are made (Fig. 3).

The deflecting elements 16 are made in the form of plates with a length of 4 ... 5 mm, bent from the rim 8 at an acute angle and protruding into the space between these fuel rods (figure 4).

The angle between the deflecting element 16 and the plane, which is a continuation of the plane of the outer surface of the face 7 of the rim 8, is preferably selected from the interval of 5-20 °. At smaller angles, the efficiency of mixing the coolant decreases, and at large angles, the hydraulic resistance of the DR increases.

The presence of deflecting elements 16 is not on all DR 5, but only on DR in the upper part of the frame does not lead to a significant increase in the hydraulic resistance of the fuel assembly. Also, this is facilitated by the location of these elements only on the upper edge of the rims 7 and not along the entire length of the rim 8, and where there are the most heat-stressed fuel rods - in the corner zones and in the middle zone of each rim 7.

In addition, the absence of similar multidirectional deflecting elements on the lower edge of the rims increases the effect of equalizing the temperature of the coolant along the cross section of the fuel assembly due to the direction of the peripheral cooler coolant from the case to the warmer center. Multidirectional deflecting elements on the lower edge of the rim do not give such an effect, because part of them is on the lower edge of the rims, on the contrary, directs the coolant from the center to the periphery of the fuel assembly.

The shape of the rim 7 with the deflecting elements 16 with high accuracy can be performed using high-performance laser cutting technology.

Claims (3)

1. A fuel assembly of a nuclear reactor comprising a head, a shank connecting their case and a bundle of fuel rods, placed in a frame including spacer grids with hexagonal rims connected by a central pipe, characterized in that on each of the spacer grids located in the upper part of the skeleton, on the upper edge of each face of the rim between the two angular fuel rods at each end of the face, as well as between the middle along the face and adjacent fuel rods of the peripheral row, deflecting elements are made in the form of a layer Bent from the rim at an acute angle and projecting into the space between said fuel rods. 2. The fuel assembly according to claim 1, characterized in that the plates are bent from the rim at an angle of 5-20 °. 3. The fuel assembly according to claim 1, characterized in that the rims of the spacer grids are made of zirconium alloy using laser cutting.

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