CN201111965Y - PWR fuel assembly upper nozzle - Google Patents

Abstract

The utility model relates to the field of nuclear fuel elements, in particular to an upper pipe seat of a pressurized water reactor fuel assembly. The compression spring device of the utility model is arranged between the upper grid plate and the upper frame plate, and only the upper end of the pressure rod protrudes from the through hole provided on the upper frame plate, because the part of the spring device above the upper pipe seat is simplified , saving space, so the compression spring device can be evenly distributed at the four corners of the upper pipe seat, so that the fuel assembly is evenly stressed and the safety performance is improved. At the same time, positioning pin holes are arranged symmetrically at the four corners, so that the installation of the PWR fuel assembly is more flexible and convenient.

Description

PWR fuel assembly upper nozzle

technical field

The utility model relates to the field of nuclear fuel elements, in particular to an upper pipe seat of a pressurized water reactor fuel assembly.

Background technique

The PWR fuel assembly is the core component of the PWR, where heat is generated, and its design is related to the safety, reliability and economy of the PWR.

A compression spring device is arranged in the upper pipe seat of the PWR fuel assembly. The compression spring in the compression spring device is pressed down by the reactor compression part, so that the fuel assembly bears sufficient axial pressure to prevent the fuel assembly from moving due to the upward hydraulic action of the coolant. In addition, when the reactor is running, because the fuel assembly is fixed between the upper and lower plates of the core, and the thermal expansion and radiation growth of the fuel assembly and the internal components are different, the compression spring device on the fuel assembly also plays a role in compensating Function, so that the fuel assembly has more growth space, so that the bending deformation of the assembly is properly controlled. The existing PWR fuel assembly upper nozzle generally uses four sets of leaf springs, which occupy a relatively large space and can only be fixed above the two diagonal corners of the upper nozzle. Due to the non-uniform arrangement, the fuel assembly is not stressed. Uniform, bending damage may occur. In addition, the existing PWR fuel assembly upper pipe seat is provided with positioning pin holes at diagonal positions, and the installation direction is limited.

Contents of the invention

The purpose of the utility model is to provide a pressurized water reactor fuel assembly upper nozzle which can make the fuel assembly bear uniform force and have higher safety performance.

The utility model is realized in the following way: an upper pipe seat of a pressurized water reactor fuel assembly, which includes an upper grid plate, an upper frame plate arranged above the upper grid plate, and a compression joint between the upper grid plate and the upper frame plate The spring device, the compression spring device includes a compression rod, a compression spring is sheathed outside the compression rod, and a compression cap is provided through the compression rod above the compression spring. The lower end of the frame plate, the upper end of the pressure rod stretches out from the through hole provided on the upper frame plate, and the lower end of the pressure rod 8 stretches into the established through hole of the upper grid plate 4 .

In the utility model, the compression spring device is arranged between the upper grid plate and the upper frame plate, and only the upper end of the pressure rod protrudes from the through hole provided on the upper frame plate, since the spring device on the top of the upper pipe seat is simplified. part, saving space, so the compression spring device can be evenly distributed at the four corners of the upper pipe seat, so that the fuel assembly is evenly stressed, and the safety performance is improved. At the same time, positioning pin holes are arranged symmetrically at the four corners, so that the installation of the PWR fuel assembly is more flexible and convenient.

Description of drawings

Fig. 1 is the front view of the upper nozzle of a kind of pressurized water reactor fuel assembly provided by the utility model;

Fig. 2 is the top view of the upper nozzle of a kind of pressurized water reactor fuel assembly provided by the utility model;

Fig. 3 is the schematic diagram during the work of a kind of pressurized water reactor fuel assembly upper nozzle provided by the utility model;

Among the figure: 1 positioning pin hole, 2 upper frame plate, 3 compression spring device, 4 upper grid plate, 5 pressure cap, 6 pin, 7 compression spring, 8 pressure bar.

Detailed ways

As shown in Figures 1 to 2, a PWR fuel assembly upper nozzle includes an upper grille 4, an upper frame plate 2 above the upper grille 4, and an upper grille 4 and an upper frame plate 2 A compression spring device 3 is arranged between them, and the compression spring device 3 includes a compression rod 8, and a compression spring 7 is sleeved on the outside of the compression rod 8. The compression rod 8 includes two sections with different rotation diameters, the upper end section is thick, and the lower end section is thinner. . Above the compression spring 7, a compression cap 5 is installed through the compression rod 8, the compression cap 5 is fixed on the compression rod by a pin, and the compression cap 5 is close to the lower end of the upper frame plate 2 under the action of the compression spring 7 , the upper end of the pressure rod 8 stretches out from the through hole provided on the upper frame plate 2, and the lower end of the pressure rod 8 extends into the through hole provided by the upper grid plate 4. The four corners of the upper frame plate 2 are respectively provided with positioning pin holes 1 .

The installation process of compression spring device 3 of the present utility model is as follows:

Put the pressure cap 5 and the compression spring 7 between the upper grid plate 4 and the upper frame plate 2. At this time, the compression spring 7 should be compressed for a certain distance to generate a certain pre-tightening force; put the pressure rod 8 to reach a certain Position, pressure rod 8 and pressure cap 5 are equipped with a pin hole drilled; pin 6 is put into the drilled pin hole, and locked by spot welding.

The working principle of the utility model is: after these parts of the compression spring device 3 are assembled according to the above procedures, since the compression spring 7 is designed with a certain pre-tightening force, the compression spring device 3 will be fixed at the required position when there is no external force. position. When the upper end of the pressure rod 8 is subjected to a downward force greater than the pre-tightening force of the compression spring, as shown in Figure 3, the pressure rod 8 can move downward along the through holes of the upper frame plate 2 and the upper grid plate 4; After the force is applied, the compression spring device resets under the action of the spring force.

When running in the reactor, the reactor pressing parts are directly pressed on multiple sets of pressing spring devices 3 evenly distributed in the fuel assembly upper nozzle, that is, pressing on the top of each pressing rod 8 . Multiple sets of pressing spring devices 3 evenly transmit the pressure of the pressing parts to the stressed parts of the fuel assembly. The pressure on the compression spring device 3 in the working state should not only prevent the fuel assembly from moving due to the upward hydraulic action of the coolant, but also effectively control the bending deformation of the fuel assembly caused by thermal expansion and radiation growth, so that the fuel assembly can Maintain normal working condition.

The four corners of the upper frame plate 2 of the utility model are respectively provided with positioning pin holes 1, the fuel assembly can be loaded into the core at any angle, so that the fuel assembly can be loaded into the core at different angles in each cycle, so that the assembly Burnup is more even.

Claims (2)

1. a fuel assembly upper nozzle of a pressurized water reactor, it comprises an upper grille (4), an upper frame plate (2) that is located on the upper grille (4), is characterized in that: on the described upper grille (4) and the upper frame plate (2) are provided with a compression spring device (3), the compression spring device (3) includes a compression rod (8), and a compression spring (7) is sleeved on the outside of the compression rod (8) ), above the compression spring (7), a compression cap (5) is provided through the compression rod (8), and the compression cap (5) is close to the upper frame plate (2) under the action of the compression spring (7) ), the upper end of the pressure rod (8) stretches out from the through hole provided with the upper frame plate (2), and the lower end of the pressure rod (8) stretches into the through hole of the upper grid plate (4). 2. The upper nozzle of a PWR fuel assembly according to claim 1, characterized in that: positioning pin holes (1) are respectively provided at the four corners of the upper frame plate (2).

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