RU67760U1 - KINDING LATTICE OF THE FUEL ASSEMBLY OF THE NUCLEAR REACTOR - Google Patents

Abstract

The utility model relates to nuclear technology, in particular, to the designs of spacing and mixing grids of fuel assemblies of nuclear power reactors.

In a mixing lattice of a fuel assembly of a nuclear reactor containing a rim and a set of intersecting plates with deflectors, a feature is that the set of plates connected to each other and to the rim at the intersections forms cells for the passage of the fuel elements and adjacent cells into which mixing deflectors are bent made in the form of plate deflecting elements.

The implementation of the proposed technical solution in the designs of fuel assemblies allows you to increase the power of reactor plants. 1 n.p., 10 ill.

Description

The technical field to which the utility model relates.

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

State of the art

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, which are a type of DR.

Known spacer grid containing the fixing fuel rods of the cell between which secondary channels are formed in which

two or more deflecting elements are installed, spaced in height, which turbulence and direct the flow of the coolant to the fuel elements (patent WO 9619811 A1, G21C 3/322, 06/27/96). The deflecting elements controlling the flow are made in the form of a tree, the trunk of which is made of a rectangular plate, and the branches of the guide vanes extend from the trunk at different height levels, providing mixing of the coolant flow. The disadvantage of this design is the possibility of touching the deflecting elements with the fuel rods at a height exceeding the height of the secondary channel, as well as the complexity of their manufacture and installation in the lattice.

The closest analogue of the claimed utility model is the 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, inside of which a spacing device consisting of cells in which the fuel rods 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 grid, a cell field is installed for spacing the fuel rods and fixed to

the rim of the mixing grid.

The disadvantage of this design solution is its increased hydraulic resistance to the flow of coolant, which does not allow its use in fuel assemblies with increased energy release.

SUMMARY OF THE INVENTION

The technical task of this utility model is to create an improved mixing lattice.

As a result of solving this problem, it is possible to obtain new technical results consisting in the possibility of efficiently mixing the coolant and improving heat removal from the surface of the fuel rod cladding, and therefore in the possibility of introducing improved fuel cycles for the operation of fuel assemblies with high fuel burnup and increased uneven energy release.

These technical results are achieved in that in the mixing lattice of the fuel assembly of a nuclear reactor containing a rim and a set of intersecting plates with deflectors, a feature is that a set of plates connected to each other and to the rim at the intersection points forms cells for the passage of fuel rods and adjacent they have cells, into which mixing deflectors made in the form of plate deflecting elements are bent.

A distinctive feature of this utility model is that plate deflectors made on the plates and designed to mix the flow of coolant at the outlet of the mixing

the gratings are bent inside the cells adjacent to the cells for the free passage of fuel rods, i.e. deflectors are located in the area that excludes contact with fuel rods.

The mixing lattice is made of a set of plates, which have grooves at the intersection points, allowing the plates to adhere to each other; in order to create structural rigidity, the end sections of the plates are connected by welding or soldering at the intersection of the plates, and the ends of the plates of the mixing grid by welding or soldering are fixed to the faces of the rim, forming a single structure.

The rim of the mixing lattice is a shell, inside of which are placed the plates of the mixing lattice.

It is advisable to increase the manufacturability of manufacturing a mixing grid, the rim is made of six separate sectors.

It is advisable to increase the turbulization of the coolant flow in the rim on each of its faces to perform deflectors bent inside the cells adjacent to the cells for the passage of the fuel rod.

It is advisable to perform deflectors trapezoidal in shape.

It is advisable in one rim below the mixing lattice, for spacing fuel rods, to establish a field of cells having a hexagonal shape with three supports for fuel rods in the form of bellows located 120 degrees apart, formed by stamping on the faces of the hexagon inside the cell; while the cells are interconnected and

with rim by welding or soldering.

It is advisable to improve the heat transfer between adjacent fuel assemblies on each face of the rim between the plates of the mixing lattice and the field of cells to make grooves for the passage of coolant.

The proposed technical solution is illustrated graphically.

Figure 1 shows a schematic diagram of a PR, figure 2 shows a remote element A of a PR in figure 1, figure 3 shows a cross section bB in figure 2, figure 4 shows a PR with trapezoidal deflectors, Fig. 5 shows a hexagonal rim, Fig. 6 shows a rim with mixing deflectors, Fig. 7 shows a rim made of six sectors, Fig. 8 shows a PR with a cell field installed in a single rim for spacing fuel elements, in Fig. 9 a field of cells is shown; FIG. 10 shows a rim with grooves.

Information confirming the possibility of implementing the proposed technical solution

The mixing lattice (PR) (see Fig. 1) contains a hexagonal rim 1, inside of which are placed the plates 2 of the mixing lattice.

The plates 2 (see FIG. 2) of the mixing lattice form cells 3 for the free passage of the fuel elements and adjacent cells 4, into which the deflectors 5 are bent. The plates 2 (see FIG. 3) have grooves 6 at the intersection points allowing coupling plates with each other; while the end sections of the plates 2 at their intersections

connected by welding or soldering. It is advisable (see figure 4) deflectors 5 to perform a trapezoidal shape.

The ends of the plates 2 PR (see figure 2) are connected by welding or soldering with the faces of the rim 1.

The rim 1 is a shell (see figure 5) having six faces 7.

To increase turbulization of the coolant flow (see Fig. 6), mixing deflectors 5 can be made at the upper ends of the faces 7 of the rim.

To improve manufacturability (see Fig.7), the rim can be made of six separate sectors 8.

It is advisable (see Fig. 8) in one rim 1 below the plates 2 of the mixing lattice to establish for spacing the fuel element field of cells 9.

Cells 9 (see Fig. 9) may have a hexagonal shape with three supports 10 for fuel elements in the form of beams.

To improve heat transfer on each face 7 of the rim (see figure 10) can be made grooves 11.

The proposed PR installed in the fuel assembly works as follows:

In fuel assemblies, the main functional structural element is a fuel rod bundle, which is fixed in the cells of spacing grids (DR) located along the length of the fuel assembly; while DR are connected

between themselves by structural elements, for example, corner profiles, forming a frame.

In order to more efficiently mix the coolant and improve heat removal from the surface of the cladding of fuel elements in the spans between the DRs, PRs are installed that are fixed in the frame of the fuel assembly, for example, by welding the rims 1 to the corner profiles; 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 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.

Using the proposed design of the mixing lattice allows, due to changes in the size and number of deflectors, to regulate the hydraulic resistance of the PR and, depending on the location of the PR in the fuel assembly, equalize the enthalpy of various regions of the reactor core.

The implementation of the proposed technical solution in the designs of fuel assemblies allows you to increase the power of reactor plants.

The manufacture of this design can be carried out on known equipment using standard technologies.

Claims (6)

1. The mixing lattice of the fuel assembly of a nuclear reactor containing a rim and a set of intersecting plates with deflectors, characterized in that the set of plates connected to each other and to the rim at the intersection, forms cells for the passage of the fuel elements and adjacent cells into which mixing deflectors made in the form of plate deflecting elements. 2. The mixing grid according to claim 1, characterized in that the mixing deflectors are made of a trapezoidal shape. 3. The mixing grid according to claim 1, characterized in that on the faces of the rim are made mixing deflectors, bent inside the cells adjacent to the cells for the passage of the fuel rod. 4. The mixing grid according to claim 1, characterized in that the rim is made in the form of six separate sectors. 5. The mixing grid according to any one of claims 1 to 4, characterized in that in one rim below the mixing grid there is a field of cells having a hexagonal shape with three supports for fuel elements in the form of bellows located 120 degrees apart, formed by stamping on faces of the hexagon inside the cell; while the cells are interconnected and with the rim. 6. The mixing lattice according to claim 5, characterized in that a groove is made in the rim on each face located between the plates of the mixing lattice and the cell field.