RU2594897C1 - Nuclear reactor fuel assembly - Google Patents

Abstract

FIELD: nuclear physics.

SUBSTANCE: invention relates to nuclear reactor fuel assemblies (FA). Fuel assembly includes fuel elements, arranged in rows in spacer grids with certain pitch to form hydraulic cells for coolant passage. Based on direction of flow of coolant area of negative enthalpy devices are installed, deflecting coolant flow from axial direction so that displacement vector of flow rate of coolant from one hydraulic cell to another, then, in area of positive enthalpy, devices are installed, made so that coolant flow swirls within each hydraulic cell.

EFFECT: technical result is reduction of maximum steam content and high margin before crisis of heat exchange during reactor operation.

1 cl, 3 dwg

Description

Technical field

The invention relates to nuclear energy, and more specifically to fuel assemblies of nuclear reactors with water under pressure.

State of the art

The energy release over the cross section of the fuel assembly of a nuclear reactor has significant irregularities. This leads to an uneven distribution of the parameters of the coolant and, accordingly, the reserves before the heat transfer crisis in the cells between the fuel elements. To align the parameters of the coolant along the cross section of the fuel assembly, mixing devices are used in the form of gratings with deflectors (blades) or inclined faces.

There is a method of increasing critical heat fluxes in fuel assemblies using a device (mixing lattice) for mixing the coolant along the cross section of the fuel assembly [Patent RU No. 2383954, filed September 15, 2008. G21C 3/32], including a lattice made of intersecting plates, forming at the intersection of hexagonal cells for placing fuel rods, equipped with deflectors (deflecting elements). The baffles are inclined in one circumferential direction around the hexagonal cell.

The fuel assembly with the known device for mixing the coolant has the disadvantage that the deflectors create a motion of the coolant around each fuel element, i.e. mixing of the coolant occurs only in the cells surrounding a particular fuel rod and, therefore, does not quite efficiently align the coolant enthalpy with the cross section of the fuel assembly. In addition, in the area of high vapor content of the coolant in fuel assemblies with increased energy release, as well as in modes with lower, relative to nominal, parameters of the coolant (pressure, mass velocity), this device is not effective. In this area it is necessary to apply gratings with high turbulizing properties.

Disclosure of invention

The aim of the invention is the provision of heat removal from the fuel elements of the fuel assemblies with increased energy release.

The objective of the invention is the creation of a fuel assembly having a scheme for intensifying heat transfer, providing sufficient reserves before the heat transfer crisis, both in the region of negative and in the region of positive relative enthalpy.

The technical result of the invention is to reduce the maximum vapor content (improving the operating conditions of the claddings of fuel elements) and increase the reserves before the crisis of heat transfer during operation of the switchgear.

Achieving the objective of the invention is to increase critical heat fluxes, is ensured by the fact that the fuel assemblies (1) of the nuclear reactor contain fuel elements (2) arranged in rows (3) in the spacer grids (4) of the fuel assembly (1), form hydraulic cells (5) for the passage of the coolant. What is new is that in the direction of flow of the coolant flow (6), devices (7) are installed that are designed to deflect the coolant flow (6) from the axial one so that the flow velocity vector (6) of the coolant is displaced from one hydraulic cell (6 ) in another, and then, in the region of positive enthalpy, devices (8) are installed, made so that the flow of flow (6) of the coolant within each hydraulic cell (5) swirls.

This is a scheme for organizing the flow of coolant when devices are used in the region of negative enthalpy that allow efficient mixing of the coolant (for example, to distill the coolant into adjacent cells), and in the region of positive enthalpy, devices with high turbulent properties (for example, ensuring swirling of the flow in each cell formed with fuel rods), will reduce the maximum vapor content (improving the operating conditions of the cladding of fuel rods) and increase reserves before the heat transfer crisis.

Brief Description of the Drawings

The invention is illustrated by drawings, on which:

FIG. 1 - fuel assembly with devices for mixing the coolant;

FIG. 2 is a diagram of horizontal velocity vectors when the heat carrier flow deviates (top view);

FIG. 3 is a diagram of velocity vectors when swirling a coolant flow in a cell.

Embodiments of the invention

In fuel assemblies (1) of a nuclear reactor containing fuel elements (2) located in rows (3) in the spacer grids (4) of the fuel assembly (1) and forming hydraulic cells (5) for the passage of the coolant in the direction of flow (6) of the coolant in the region of negative enthalpy, devices (7) are installed that deflect the coolant flow (6) from the axial one so that the flow velocity vector (6) of the coolant shifts from one hydraulic cell (5) to another, and then, in the positive enthalpy, installed devices (8), made so that there is a swirling flow (6) of the coolant within each hydraulic cell (5).

In a fuel assembly with such devices, an increase in critical heat fluxes in the core of a nuclear reactor is carried out as follows.

The coolant enters the fuel assembly (1) and is heated accordingly to the energy released in the fuel elements. Since the energy release over the cross section and height of the fuel assembly has significant unevenness, heating of the coolant also turns out to be uneven. In the region of negative enthalpy, to equalize the temperatures and vapor contents of the coolant in different cells and fuel assemblies, it deflects flows (6) in each cell (5) formed by fuel elements (2), providing them with movement to adjacent cells (5), which leads to the corresponding averaging over the cross section of the fuel assembly of temperatures and steam contents. In this case, the direction of movement of the flow is chosen so that the total resulting horizontal force from the flow of coolant to the elements of the fuel assembly was equal to zero. In the field of positive enthalpy, devices are used that turbulent the flow, increasing the intensity of heat removal from the surface of the fuel elements.

Thus, the proposed solution, namely the use of two sequential circuits - mixing with subsequent turbulization of the coolant flow, have significant novelty and technical efficiency.

The economic efficiency of the application of the invention is also determined by increasing the safety of a nuclear reactor by reducing the unevenness of the parameters of the coolant in the fuel assembly and the core and the possibility of increasing the power of the reactor by increasing the reserves to critical parameters of the coolant.

Claims (1)

 A fuel assembly (1) of a nuclear reactor containing fuel elements (2) arranged in rows (3) in the spacer grids (4) of the fuel assembly (1) forming hydraulic cells (5) for the passage of the coolant, characterized in that in the direction of flow (6) in the area of negative enthalpy, devices (7) are installed that deflect the flow (6) of the coolant from the axial in such a way that the flow velocity vector (6) of the coolant moves from one hydraulic cell (5) to another, and then to areas of positive enthalpy, devices (8) are installed, made so that there is a swirling flow (6) of the coolant within each hydraulic cell (5).

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