RU2461086C2 - Spacer grid of fuel assembly - Google Patents

Abstract

FIELD: power industry.

SUBSTANCE: spacer grid consists of shaped cells with bulges; shaped cells have at least one interface zone throughout the height, and at least one spacing zone with bulges. Cells are connected to each other on edges of interface zone and have a gap in spacing zone.

EFFECT: forces appearing in the described spacer grid at contact of fuel element with spacer bulges have no effect on adjacent cells of the grid at formation of a beam.

3 cl, 10 dwg

Description

Technical field

The invention relates to nuclear energy, and more specifically to fuel assemblies (FAs) for nuclear reactors with water under pressure.

State of the art

Known spacer grid with nodes connecting the fuel element to the cell (RU 2127000, G21C 3/34). This lattice consists of cells in the form of adjacent polyhedrons equipped with internal protrusions, of which the workers are located in the center of three adjacent faces and have a height greater than others - safety belts located at the edges, as well as with notches located along the working protrusions along both sides of them.

A disadvantage of the aforementioned device is the increased stiffness of the internal working protrusions, weakened by notches in the nodes of the connection of the elements of the fuel with cells. In the conditions of the VVER-1000 reactor core, cell surfaces that come into contact with the fuel elements under the influence of hydraulic, thermal and radiation loads in the reactor gradually relax. This leads to a weakening of the interference fit of the fuel elements in the spacer grids, the appearance of gaps and, as a result, damage to the claddings of the fuel elements.

Known spacer grid (patent RU 2256960, G21C 3/34, G21C 21/00). The spacer grid contains shaped cells interconnected along mating surfaces on which mounting pads are made to connect the shaped cells. The initial cells are obtained by stamping from pipes whose wall thickness differs from batch to batch. To account for this factor, repeated stamping is performed to perform installation sites with calibration of their outer surface. Double stamping increases the complexity of manufacturing, which is a disadvantage of this design.

The closest analogue is the spacer grid according to patent RU 2127000, G21C 3/34, which is taken as a prototype.

Disclosure of invention

The aim of the invention is to improve the conditions for assembling a bundle of fuel rods, to improve the thermomechanical behavior of the fuel assembly during operation, including under seismic effects.

The objective of the invention is to increase the rigidity of the spacer lattice from lateral loads, reducing the loads on the fuel elements.

The technical result of the invention is the creation of a spacer grid, in which the forces arising from the contact of a fuel rod with spacer gears do not affect adjacent cells of the spacer grid during beam formation.

This goal is achieved in that the spacer grid, consisting of curly cells (1) interconnected according to the invention, has a distinctive feature, consisting in the fact that each cell (1) in height has at least one mating zone and, as at least one distance zone (5), in which the beetles (2) are located, while the connection of adjacent cells (1) with each other is made along the faces (6) of the interface zone (4), and in the distance zone adjacent cells have a gap.

Alternatively, the distance zone and the interface can be adjacent to different ends of the cells.

Alternatively, each cell has two or more two distance zones with beetles (2) located between the mating zones.

This solution makes it possible to ensure the operation of the cell – cladding of the fuel rod pair in the elastic region, and the tightness decreases in comparison with the standard design, which reduces the effort when equipping the fuel assembly bundle and eliminates the possibility of nadira formation on the polished surface of the fuel cladding, as well as stamping each distance section ( zone of beetles), as well as the site of the connection of the cells with each other in their size.

A brief description of the drawings.

The invention is illustrated by drawings, on which:

Figure 1 - spacer grid with the location of the cells on a rectangular grid, bottom view;

Figure 2 - spacer grid with the location of the cells on a triangular grid. Bottom view;

Figure 3 is a longitudinal section of a cell of a spacer grid of a rectangular shape with the location of the spacing zones at opposite ends of the cells of the spacer grids;

Figure 4 is a longitudinal section of a cell of a spacer grid of a rectangular shape with the location of the spacing zone and the interface zone of the opposite ends of the cell;

Figure 5 is a longitudinal section of a cell of a spacer grid of a triangular shape with the location of the spacing zone and the conjugation zone at opposite ends of the cell;

6 is a longitudinal section of a cell of the spacer grid of a triangular shape with the location of the spacing zones at opposite ends of the cell;

7 - A fragment of a spacer grid of a rectangular shape with an inscribed element fuel (3), bottom view;

Fig. 8 is a fragment of a spacer grid of a triangular shape with an inscribed fuel element (3), bottom view;

Fig.9 is a longitudinal section of three rectangular cells with the location of the beetles on the faces of 5 zones of pairing (4);

Figure 10 - A longitudinal section of three rectangular cells with the location of the beetles on the faces (5) adjacent to the faces of the mating zones (4).

Embodiments of the invention.

A distance grid consisting of curly cells (1) interconnected and containing beetles (2) interacting with heat-generating elements (3) is made in such a way that each cell (1) has at least one mating zone in height ( 4) and at least one distance zone (5), in which the beetles (2) are located, while the connection of adjacent cells (1) with each other is made along the faces (6) of the conjugation zone (4), and in the distance zone cells have a gap.

Alternatively, the spacer grid is configured such that the spacing zone (5) with the beetles (2) and the mating zone (4) are located at opposite ends of the cells of the spacing grids.

Alternatively, the spacer grid is designed so that each cell has two or more two spacing zones (5).

The work of the spacer grid is as follows.

When installing fuel rods in the spacer beam of a fuel assembly bundle (3), first passes the mating zone (4) and then the spacing zone (5). This makes it possible to exclude the possibility of sticking a fuel rod into the ends of the cells with possible deviations of the end of the fuel rod. After the beam is assembled, each fuel rod is distanceed by its own group of pickles, the operation of which does not depend on the work of the pickles of adjacent cells, while the cells in the mating zone create a stiffening belt. This stiffness belt perceives lateral loads arising from neighboring fuel assemblies in all operating modes, including during transport and technological operations and during seismic influences, in which loads are practically not transferred to the fuel cladding. In this case, when assembling the beam due to the fact that the spacing zone practically does not affect the mating zone, the dimensions of the spacing grids will not change, i.e. This solution allows you to collect the bundles of fuel rods more accurately (with a lower tolerance).

For the variant when the pupples are located at opposite ends of the cells, the work of the spacer grid is carried out in a similar way, which significantly reduces the efforts to install the fuel rods into the bundle, and, accordingly, the thermomechanical forces from the temperature and radiation extensions of the bundle of fuel rods with the fuel assembly frame during normal operation.

The invention extends to any type of honeycomb spacer grids used in fuel assemblies of nuclear reactors.

Industrial applicability

The invention has industrial applicability for the active zones of domestic reactors of WWER type and the active zones of foreign PWRs. The invention can be used for any industrial heat exchange equipment containing heating elements formed into a bundle using spacer grids and washed with a coolant.

The present invention allows to protect fuel elements from hydrodynamic loads, to reduce the likelihood of fretting wear and to increase the stiffness of the beam of fuel elements, as well as to increase the accuracy of the positioning of fuel rods in the beam and reduce the tolerance on the size of the spacer grids.

Claims (3)

1. A spacer grid consisting of curly cells (1) interconnected and containing beetles (2), interacting with heat-generating elements (3), characterized in that each curly cell (1) has at least one zone in height pairing (4) and at least one distance zone (5), in which beetles (2) are located, while the connection of adjacent curly cells (1) to each other is made along the faces (6) of the pairing zone (4), and in the spacing zone (5) adjacent figured cells have a gap. 2. The spacer grid according to claim 1, characterized in that the spacing zone (5) with beetles (2) and the mating zone (4) are located at opposite ends of the figured cells of the spacing grids. 3. The spacer grid according to claim 1, characterized in that each curly cell has two or more two distance zones (5) and interface zones (4).

Images