JPH0116075Y2 - - Google Patents

Description

[Detailed description of the invention] This invention is based on a seal plug that seals the opening of a pressure pipe in a pressure tube reactor to form a pressure boundary for the primary coolant, and a seal plug that is inserted into the pressure pipe together with a fuel assembly. Regarding the improvement of the assembly structure with Yahei plug.

As is well known, in the above-mentioned pressure tube reactor, a fuel assembly is inserted, together with upper and lower shield plugs, into a pressure tube containing a primary coolant.
In addition, a seal plug is attached to the opening of the pressure pipe that is opened for fuel exchange to form a pressure boundary for the primary coolant. During fuel exchange, the fuel assembly, shield plug, and seal plug are removed and loaded by remote control using a fuel exchange machine.

Next, a conventional assembly structure inside a pressure pipe is shown in FIG. In the figure, 1 indicates a large number of pressure pipes installed vertically in the reactor core, 2
3 is a fuel assembly, 3 is a lower seal plug, and 4 is a seal plug. The fuel assembly 2 and the shield plug 3 are integrally connected to each other via a collet joint, etc., and a ball latch mechanism 6 is attached to the shield plug via a connecting pipe 5, and the ball latch mechanism 6 is attached at the insertion position in the pressure pipe. The fuel assembly 2 and the seal plug 3 are connected to the pressure pipe 1 via this ball latch mechanism 6.
is supported by On the other hand, the seal plug 4, which is formed as a separate and independent component, has the sealing surface of the seal element attached to the plug body 7, which is attached to the pressure pipe 1.
The sealing mechanism 8 is in pressure contact with the inner wall of the pressure pipe 1 to form a pressure boundary, and the ball latch mechanism 9 is located behind the sealing mechanism 8 to support the sealing plug 4 on the pressure pipe 1.
Note that the ball latch mechanisms 6 and 9 and the seal mechanism 8
Attachment and detachment is performed by operating the actuator by operating the fuel exchanger's grab.

The fuel exchange operation in the conventional configuration described above is performed in the following order. First, a fuel exchanger (not shown) is connected to the lower open end 10 of the pressure pipe 1, and the seal plug 4 is grasped by a grab operation, the seal mechanism 8 and the ball latch mechanism 9 are removed, and the fuel exchanger is pulled out from the pressure pipe 1.
Next, operate the grab of the fuel exchanger again and pressure pipe 1.
Insert the flexible plug 3 into the housing, grasp the flexible plug 3, remove the ball latch mechanism 6, and remove the flexible plug
and pull out the fuel assembly 2 together. Thereafter, in the reverse procedure to the above, new fuel and the seal plug are loaded into the pressure pipe while still being connected together, and finally the seal plug is inserted.

In this way, in the conventional structure, the seal plug 4 is handled alone, the fuel assembly 2 and the seal plug 3 are handled as an integral unit by the grab of the fuel exchanger, and the ball latch mechanisms 9 and 6 are used, respectively.
It is supported by the pressure pipe 1 via. In such a configuration, the ball latch mechanism 9 of the seal plug 4 is located below the seal mechanism 8;
The ball latch mechanism 6 of the sealing plug 3 will naturally be located above the sealing plug 4. That is, one side 9 of the ball latch mechanism is located outside the primary cooler, and the other 6 is located inside the primary coolant pressure boundary.

On the other hand, in pressure tube reactors, over the course of long-term reactor operation, radioactive fine insoluble foreign matter (hereinafter referred to as "crud"), such as rust, has recently become more important than the core components. It has become clear that there is a phenomenon in which this elutes into the coolant, settles inside the pressure pipe, and accumulates at the bottom. For this reason, in the conventional structure described above, the ball latch mechanism 6 of the insulation plug 3 is exposed to the primary coolant.
The crud may intrude into the movable parts of the ball latch mechanism 6, causing the ball latch mechanism 6 to become inoperable during fuel exchange. Moreover, in the unlikely event that it becomes impossible to remove the plug 3 when changing the fuel,
This must be avoided at all costs, as it will seriously disrupt the reactor's operating schedule.

This idea was developed in consideration of the above points, and its purpose was to eliminate the possibility that the fuel exchange work would be obstructed by crud deposited in the lower part of the pressure pipe, and also to shorten the fuel exchange work time. It is an object of the present invention to provide a pressure pipe shield and seal plug assembly that can be used in a pressure pipe.

This purpose is achieved by eliminating the conventional ball latch mechanism of the seal plug and creating an assembly structure in which the seal plug is integrally connected to the tip of the seal plug, and the fuel assembly, The entire weight of the shield plug and seal plug is supported by the pressure pipe through the seal plug's locking support mechanism, such as a ball latch mechanism, and the fuel assembly, shield body, and seal plug are integrated as one body during fuel exchange. This is achieved by making it possible to load and unload the pressure pipe.

This invention will be explained below based on illustrated embodiments.

First, in FIG. 2, the seal plug 4 is equipped with a ball latch mechanism 9, which is a locking support mechanism, on its plug body 7, as in FIG. 1, and a seal mechanism 8 located in front of the ball latch mechanism.
A lower shield plug 3 is integrally connected to the distal end side of the seal plug 4 via a connecting pipe 5 with a connecting bolt 11, and the fuel assembly 2, the shield plug 3, and the seal are connected to each other by a connecting bolt 11. The entire weight of the plug 4 is supported by the pressure tube 1 via the ball latch mechanism 9.

Furthermore, in the applied example shown in FIG. 3, in addition to the structure shown in FIG.
The seal plug 3 is connected to the seal plug 4 via a collet joint 12 so as to enable disconnection between the seal plug 3 and the seal plug 4. This makes it possible to individually remove the seal plug 4 for maintenance and inspection after taking it out of the furnace.

Now, according to the embodiments shown in FIGS. 2 and 3, there is no locking support mechanism on the inside of the pipe with the seal mechanism 8 forming the pressure boundary of the primary coolant in the pressure pipe as a boundary, and the primary cooling There is no need to consider crud in the material. Moreover, since the ball latch mechanism 9, which is the only locking support mechanism, is located behind the seal mechanism 8, there is no fear of the crud entering the movable part, and normal operation is always guaranteed. In addition, when changing fuel, the fuel assembly 2, seal plug 3, and seal plug 4 can be removed and loaded with a single grab operation, making it possible to significantly shorten the work time compared to conventional methods. You can obtain practical benefits such as:

[Brief explanation of the drawing]

FIGS. 1 and 2 are sectional views of pressure pipe assembly structures based on the conventional and one embodiment of this invention, respectively, and FIG. 3 is a structural diagram showing the main parts of another embodiment of this invention. 1: Pressure pipe, 2: Fuel assembly, 3: Shiyahei plug, 4: Seal plug, 8: Seal mechanism, 9:
Ball latch mechanism as a locking support mechanism, 11:
Connection bolt, 12: Collet joint.

Claims (1)

[Scope of utility model registration request] A flexible plug inserted into the pressure pipe together with the fuel assembly, a sealing mechanism that presses the sealing surface against the inner wall of the pressure pipe to form a pressure boundary for the primary coolant, and a pressure disposed behind the sealing mechanism. A pressure pipe shield and seal plug assembly in a pressure tube type nuclear reactor, characterized in that the seal plug is integrally connected with a seal plug equipped with a locking support mechanism for supporting the pipe. Three-dimensional.