DEVICE FOR TRAPPING DEBRIS IN A NUCLEAR FUEL ASSEMBLY

Abstract

The invention relates to a device for trapping debris in a fuel assembly of a nuclear reactor, which is mounted in the bottom nozzle of the fuel assembly. The device consists of two interconnected plate-type filter elements arranged one above the other and having channels for the passage of a coolant. In the lower filter element, the channels are inclined toward the axis of the fuel assembly, and in the upper filter element, the channels are parallel to the axis of the fuel assembly. The channels can be produced, in particular, by waterjet cutting to form slots in the field of a filter element plate, the slots being separated lengthwise by vertical ribs and widthwise by crosspieces. The vertical ribs and the crosspieces between the channels of each of the filter elements have roundings formed thereon, and a gap is provided between the vertical ribs and crosspieces formed in the plates of different filter elements. The technical result is the possibility of intercepting and trapping debris of any size contained in a coolant loop, without reducing the flow cross section for the coolant.

Claims

1. A device for trapping debris in a fuel assembly of a nuclear reactor, which is mounted in the bottom nozzle of the fuel assembly, the device consisting of two interconnected plate-type filter elements arranged one above the other and having channels for a coolant passage having a length and a width, wherein the channels in the lower filter element are inclined toward the axis of the fuel assembly, and the channels in the upper filter element are parallel to the axis of the fuel assembly, characterized in that the channels for the coolant passage are formed as slots in the area of a filter element plate, the slots being separated lengthwise by vertical ribs and widthwise by crosspieces, wherein roundings are formed on the vertical ribs and on the crosspieces between the channels for the coolant passage of each of the filter elements, and a gap is provided between the vertical ribs and the crosspieces formed in the plates of different filter elements.

2. The device according to claim 1, wherein the roundings of the vertical ribs and of the crosspieces are provided on the side of the gap.

3. The device according to claim 1, wherein the crosspieces of the upper and lower filter elements are offset with respect to one another.

4. The device according to claim 1, wherein the crosspieces of the upper filter element are inclined toward the axis of the fuel assembly in a direction opposite to the incline of the channels of the lower filter element.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0017] The essence of the invention is illustrated by the drawings.

[0018] FIG. 1 shows a perspective view of the fuel assembly of a nuclear reactor with the device for trapping debris according to the present invention: [0019] a) WWER fuel assembly; [0020] b) PWR fuel assembly.

[0021] FIG. 2 shows a cross-section of the device for trapping debris in a fuel assembly.

[0022] FIG. 3 shows a fragment of the device for trapping debris in a fuel assembly: [0023] a)with the rounding on the vertical ribs and on the crosspieces between the channels; [0024] b)with offset crosspieces of the upper and lower filter elements; [0025] c)with the crosspieces of the upper filter element inclined toward the axis of the fuel assembly.

[0026] Device (1) for trapping debris in a nuclear fuel assembly (2) is mounted in the bottom nozzle (3) of the fuel assembly (2) and comprises two interconnected plate-type filter elements as a plate (4) wherein channels (5) for a coolant passage are made parallel to the axis of the fuel assembly (2), and a plate (6) with channels (7) inclined toward the axis of the fuel assembly (2). The channels are separated lengthwise along the plates (4,6) by vertical ribs (8) and widthwise by crosspieces (9). The length of the channels is defined by a pitch between the vertical ribs (8), and width of the channels (5,7) is defined by a pitch and location of the crosspieces (9). Roundings (10) are formed on the vertical ribs (8) and the crosspieces (9). The crosspieces (9) of the upper filter element (4) can be made with an inclination to the fuel assembly axis in the direction opposite to the direction of the inclination of the channels (7) of the plate (6).

BEST EMBODIMENT OF THE INVENTION

[0027] The device for trapping debris in a fuel assembly of a nuclear reactor operates in the following way.

[0028] The device (1) is made of two interconnected plates (4,6) arranged one above the other, wherein slots forming the channels (5,7) are made, for example, using waterjet cutting method. The slots are separated lengthwise by vertical ribs (8) and widthwise by crosspieces (9). Channels (5) of the upper plate (4) are parallel to the axis of the fuel assembly (2), and channels (7) of the lower plate (6) are inclined toward the axis of the fuel assembly (2). Roundings (10) can be formed on the vertical ribs (8) of the channels and on the crosspieces (9). A gap (not shown) is provided between the vertical ribs (8) and crosspieces (9) of the different plates. The device made in such a way is mounted in the bottom nozzle of the fuel assembly (2). During operation of the fuel assembly in the nuclear reactor the coolant flow containing debris enters an inlet of the fuel assembly (2). Particles that can cause fretting wear of the fuel elements claddings, are mainly wire fragments of various sizes. When moving in the coolant flow these particles are oriented with their long side along the current lines, that is, along the lines of less resistance. Thus, the particles move with their long axis parallel to the fuel assembly axis. When interacting with the inclined channels the particles are oriented parallel to the channels and fall into the gap between the ribs (8) and crosspieces (9) of different plates (4,6) of the trapping device. Roundings (10) provided on the ribs (8) and crosspieces (9) reduce formation of the vortices after the crosspieces, which aids in reducing the coefficient of hydraulic resistance. Making the filter elements from single plates further increases reliability of both the device and the fuel assembly in general. Inclination of the crosspieces (9) of the upper filter element (4) toward the fuel assembly axis improves filtering capacity by allowing the filter to trap debris with smaller linear dimensions.

[0029] At the end of the operation the fuel assembly (2) is unloaded from the reactor, and the debris trapped by the trapping device (1) are also removed with the fuel assembly (2).

INDUSTRIAL APPLICABILITY

[0030] Thus, the device for trapping debris in a fuel assembly of a nuclear reactor increases reliability of the fuel assemblies during their long-term operation in a nuclear reactor, reduces the coefficient of hydraulic resistance, and reduces the labor intensity of manufacturing the device.