RU2638647C2 - Mixing and spacer grids of nuclear reactor fuel assembly (versions) - Google Patents

Abstract

FIELD: electricity-producing industry.

SUBSTANCE: invention relates to the constructions of the spacer and mixing grids of the nuclear power reactors fuel assembly. The grid construction provides for availability of the rim and the stack of the intercrossing plates in the shape of lines that are linked to each other and to the rim at crossing areas and that form the field of nests for the fuel elements and the fuel assembly supporting elements sinking, at least some nests are hexagonal made. The construction also provides for the availability of the triangular nests for the heat carrier passage that are adjacent to the hexagonal nests. On the triangular nests ends there are mixing laminar deflectors that are turned towards the triangular nests. The nests' field is designed as the full metal matrix of the comb type with the rounded openings in the cross-section for the supporting elements sinking, with the hexagonal section openings for the fuel elements sinking, with the triangular section openings for the heat carrier passage. Along with this, the mixing deflectors are implemented on the end of one of the triangular opening facets with the tilt inward the triangular opening.

EFFECT: nuclear power reactor fuel assembly grids design simplification.

4 cl, 10 dwg

Description

The invention relates to nuclear technology, in particular to the designs of spacer and mixing grids of fuel assemblies (FAs) of nuclear power reactors.

In the design of fuel assemblies, the main nodes are a bunch of fuel elements (fuel elements), a head and a shank.

The fuel rods are usually fixed in the base plate of the shank and have the possibility of temperature and radiation expansion along the fuel assemblies; in this case, the fuel rods are spaced apart due to their elastic springing and fixing in the cells of the spacing grids (DR) located along the length of the fuel assembly.

In order to achieve equalization of the enthalpy in the reactor core between less loaded and more loaded areas in the fuel assembly designs, devices for mixing the coolant are used - mixing grids (PR) with deflectors for turbulence of the coolant flow located along the length of the fuel assembly.

A known design of a mixing and spacing grid designed for the fuel assembly of a nuclear reactor, which has a flow control structure consisting of tape elements with a device for turbulent flow, into which a spacing device consisting of cells in which fuel elements are fixed (patent EP 0795177 B1, G21C 3/322, 08.25.99).

The flow control structure (mixing lattice) contains a set of tape elements (plates) arranged crosswise, at the ends of which deflectors are made to turbulence the coolant flow; while the plates are mounted on the rim of the mixing lattice. Inside the mixing lattice, a cell field is installed for spacing the fuel rods and mounted on the rim of the mixing lattice.

A known design of the spacer and mixing lattice, designed for the fuel assembly of a nuclear reactor, which contains a girdle rim and three groups of mutually intersecting and parallel to each other in each group of bands equipped with slots at the intersection, while the strip is fixed to the rim. When the stripes intersect, cells are formed in the form of a hexagonal figure with concave faces alternating through one to span fuel rods, as well as adjacent trihedral cells in the form of a convex triangle and trihedral cells in the form of a regular equilateral triangle, on one of whose faces deflectors are made - trapezoidal scapula forms intended for mixing the coolant (patent RU 2249865 C1, G21C 3/34, 3/352, 09.09.2003).

A known design of a hexagonal spacer lattice for a fuel assembly of a nuclear reactor, which consists of curly cells interconnected by spot welding, a central cell for attaching the DR to the central fuel assembly tube and rim. To ensure the fixation of the fuel rods in the DR cells at the points of contact with the fuel rod, protrusions were made to the center of the cell (A.Ya. Kramerov. Questions of designing nuclear reactors. - M .: Atomizdat, 1971).

A known design of a hexagonal spacer lattice for a fuel assembly of a nuclear reactor, containing groups of mutually intersecting parallel plates arranged in one tier and forming hexagonal cells for placing fuel rods located on a regular triangular grid, and triangular cells located between hexagonal (patent RU 2518058 C1, G21C 3/00, 06/10/2014).

The closest analogue of the claimed invention (mixing lattice variant) is a mixing lattice design designed for a fuel assembly of a nuclear reactor, which contains a rim and a set of mutually intersecting plates in the form of strips connected to each other and with the rim at the intersections forming the field of cells for placing fuel elements and supporting elements of the fuel assembly, at least part of which is made hexagonal, and adjacent to the hexagonal cells of the trihedral cells for the passage of heat rer, which are made at the ends bent toward the trihedral cells mixing plate deflectors (Patent RU 2,383,954 C1, G21C 3/32, 10.03.2010).

The closest analogue of the claimed invention (a spacer grid variant) is a spacer grid construction comprising a rim and curly cells interconnected along mating surfaces, and mounting surfaces for connecting curly cells are made on mating surfaces (patent RU 2256960 C1, G21C 3/34, 21/00, 07/20/2005).

The disadvantage of these design solutions is:

- the complexity of the design of PR and DR, which is due to the presence of a large number of component elements (plates or cells) of various configurations and the need for their connection by welding or soldering;

- the need to create and use for the manufacture of components of PR and DR a large number of special equipment and for the assembly and connection of these elements of special equipment.

The present invention is the creation of an improved mixing (distance) lattice, which is fixed on the supporting structural elements of the bundle of the fuel assembly.

As a result of solving this problem, it is possible to obtain new technical and technological results, consisting in the possibility of reducing the level of complexity of the design of PR and DR, and therefore the possibility of introducing high-performance and more efficient technological cycles of manufacturing PR and DR.

These technical results are achieved by design options:

- mixing lattice (option 1);

- distance grid (option 2).

The mixing lattice of the fuel assembly of a nuclear reactor (option 1) contains a rim and a set of mutually intersecting plates in the form of strips connected to each other and to the rim at the intersections, forming a field of cells for driving fuel elements and supporting elements of the fuel assembly, at least some of which are made hexagonal , and adjacent to the hexagonal cells of the trihedral cells for the passage of the coolant, at the ends of which are made bent towards the trihedral cells mixing plate deflectors, according to and Upon acquiring the cell field, it is made in the form of an all-metal matrix of a honeycomb type with rounded holes in the cross section for driving support elements, with hexagonal holes for fuel rods, with triangular holes for coolant passage, and mixing deflectors are made at the end of one of the faces of a triangular hole with a slope inside the trihedral hole.

The spacer grid of the fuel assembly of a nuclear reactor (option 2) contains a rim and a set of cells connected to each other and to the rim along mating surfaces arranged in a hexagonal pattern and forming a field of cells for the passage of fuel rods and supporting elements of the fuel assembly having each hexagonal shape with thrust elements for a fuel rod formed by bulges on the edges of the cell inside it, according to the invention, the cell field is made in the form of an all-metal matrix of a honeycomb type with figured holes in pepper section for sinking the reference elements with holes figure hexagonal profile for the penetration of fuel rods with holes made on the walls of the abutment elements for the fuel element bulges into the holes and spaced 120 degrees apart.

A distinctive feature of the present invention is that the field of PR or DR cells is formed by a combination of jumpers of an all-metal matrix, continuously passing into each other and creating a given cross-sectional configuration of cells of various profiles.

This technical solution allows you to apply for the manufacture of PR and DR high-performance and waste-free method of layer-by-layer application of source material using modern 3D-printers; this eliminates the need for the manufacture of a large number of component parts PR and DR and their connection by welding or soldering.

The rim of the mixing and spacing grids is a shell, inside which there is a cell field in the form of an all-metal matrix, connected to the rim by welding or soldering; it is advisable to increase the manufacturability of manufacturing mixing and spacing grids, the rim is made of six separate sectors.

Alternatively, the cell field and the rim of the mixing and spacing grids can be made together in the form of an all-metal matrix of a honeycomb type.

The proposed technical solution is illustrated graphically.

In FIG. 1 is a schematic diagram of the PR of the existing structure; FIG. 1a shows a fragment of a field of PR cells made of a set of intersecting plates.

In FIG. 2 shows the PR of the proposed design (option 1), FIG. 2a shows a fragment of an all-metal matrix of a field of PR cells; in FIG. 2b shows a fragment of an all-metal PR with a jointly made field of cells and a rim.

In FIG. 3 is a schematic diagram of the DR of the existing structure; FIG. Figure 3a shows a fragment of the field of DR cells made of a set of cells made from blank tubes.

In FIG. 4 shows the DR of the proposed design (option 2), FIG. 4a shows a fragment of an all-metal matrix of a field of DR cells and a cross-section BB of a thrust element for a fuel element, FIG. 4b shows a fragment of an all-metal DR with a joint field of cells and a rim.

Information confirming the possibility of carrying out the invention

Option 1

The mixing lattice (PR) (see Fig. 2) contains a hexagonal rim 1, inside of which there is an all-metal matrix 2 of the field of PR cells connected to the faces of the rim by welding or soldering.

The cell field (see Fig. 2, 2a) contains fragments of a hexagonal structure of hexagonal cells 3 for free passage of fuel rods and adjacent trihedral cells 4. On one of the faces of the trihedral cells there are plate deflectors 5, preferably trapezoidal, bent inside the cell 4. Cell 6 for the passage of the supporting structural elements of the fuel assembly is made in the shape of a curly circle.

The rim 1 is a shell (see Fig. 2) having six faces. The rim can be made of six separate sector plates.

As an option (see Fig. 2b), the PR can be made in the form of an all-metal matrix with a single field of cells 7 and a rim 8.

Option 2

The distance grid (DR) (see Fig. 4) contains a hexagonal rim 9, inside of which there is an all-metal matrix 10 of the field of DR cells connected to the faces of the rim by welding or soldering.

The cell field (see Figs. 4, 4a) contains fragments of a hexagonal structure from figured holes 11 in cross section for driving support elements, holes 12 of a figured six-sided hexagonal profile for driving fuel elements with thrust elements 13 for fuel elements made on the walls of the holes with bulges inside the hole and located 120 degrees apart.

The rim 9 is a shell (see Fig. 4) having six faces. The rim can be made of six separate sector plates.

Alternatively (see Fig. 4b), the DR can be made in the form of an all-metal matrix with a single field of cells 14 and a rim 15.

The proposed DR and PR installed in the fuel assemblies work as follows:

In a fuel assembly, the main functional structural element is a bundle of fuel elements. The fuel rods are fixed in the cells 12 of the spacer grids (DR) located along the length of the fuel assemblies by means of thrust elements 13. The DRs are connected to structural support elements, for example, duct pipes passing in the cells 11 of the DR, by welding, forming a frame.

In order to more efficiently mix the coolant and improve heat removal from the surface of the claddings of fuel rods in the spans between the DRs, PRs are installed that are fixed in the fuel assembly frame, for example, by welding the PR to the supporting elements passing in cells 6 of the PR; while the fuel rods freely pass through the cells 3 PR. The coolant passes through the free space of the cells 3, cooling the fuel rods, as well as through the trihedral cells 4; at the same time, in the cells 4, the coolant is deflected by the deflectors 5 and mixes with the coolant from the neighboring cells 3 at the outlet from the PR, thereby equalizing the enthalpy between neighboring regions of the coolant passing through the fuel assembly.

The implementation of the proposed technical solution allows us to simplify the design of PR and DR, reduce the number of components and the necessary equipment for their manufacture to a minimum, sharply reduce the cost of manufacturing PR and DR.

The manufacture of this design can be carried out using a high-performance and waste-free innovative method of layer-by-layer deposition of metal material using modern 3D printers using additive technology.

First, a dose of powder material is sprayed onto a special platform. According to the coordinates obtained from the computer model, with the help of an electron beam gun or laser, they begin to affect the surface of the powder; this generates enough heat to melt the metal. Then the process is repeated in layers.

Claims (4)

1. The mixing lattice of the fuel assembly of a nuclear reactor, containing a rim and a set of mutually intersecting plates in the form of strips connected to each other and to the rim at the intersection, forming a field of cells for driving fuel elements and supporting elements of the fuel assembly, at least some of which are made hexagonal, and adjacent to the hexagonal cells of the trihedral cells for the passage of the coolant, at the ends of which are made bent towards the trihedral cells mixing plate deflectors, characterized in that the cell field is made in the form of an all-metal matrix of a honeycomb type with rounded holes in the cross section for driving support elements, with hexagonal holes for fuel elements, with triangular holes for coolant passage, the mixing deflectors being made at the end of one of the faces of the triangular hole with tilt into the trihedral hole. 2. The mixing lattice according to claim 1, characterized in that the cell field and the rim are made together in the form of an all-metal matrix of a honeycomb type. 3. A spacer grid of a fuel assembly of a nuclear reactor containing a rim and a set of cells connected to each other and to the rim along mating surfaces arranged in a hexagonal pattern and forming a field of cells for driving fuel elements and supporting elements of a fuel assembly having each hexagonal shape with thrust elements for fuel elements formed by bulges on the edges of the cell inside it, characterized in that the field of cells is made in the form of an all-metal matrix of a honeycomb type with figured holes across This section is for driving support elements, with holes of a figured hexagonal profile for driving fuel elements with stop elements for fuel elements made on the walls of the holes, bulges inside the hole and located 120 degrees apart. 4. The spacer grid according to claim 3, characterized in that the cell field and the rim are made together in the form of an all-metal matrix of a honeycomb type.

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