JPH052279B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention supports a fuel assembly of a pressure tube type nuclear reactor, and is connected to a pressure tube at a position where fuel is loaded into the pressure tube to shield radiation from the fuel. and a shielding seal plug for sealing an end opening of a pressure pipe.

[Conventional technology]

As is well known, in a pressure tube reactor, a shielding seal plug is used to form a pressure boundary for the primary cooling water sealed in the pressure tube when a fuel assembly is loaded, and to shield radiation. .

Next, the conventional structure of such a shielding seal plug is shown in FIG. In the figure, 1 is the pressure pipe on the core side, 2 is the fuel assembly loaded in the pressure pipe, and 3 is the fuel assembly loaded in the pressure pipe.
is a shielding seal plug, and the shielding seal plug 3 is roughly divided into a shielding body 6 equipped with a collector joint 4 and a pick-up head 5 on the top that are connected to the fuel assembly 2, and a connecting pipe 7 at the rear of the shielding body 6. It is constructed as an assembly with a seal plug 8 which is integrally connected via a.

Here, the shielding body 6 is a solid cylindrical body made of steel,
This shields radiation leaking from the fuel assembly 2 to the outside of the core. On the other hand, the seal plug 8 includes a ball-type latch mechanism 9 that is coupled to the pressure tube 1 at the loading position into the pressure tube, and a seal mechanism 10 that tightly contacts the wall of the pressure tube 1 and seals the end opening of the pressure tube. As is well known, the latch mechanism 9 and seal mechanism 10 are opened and closed by a grab mechanism of the fuel exchange machine connected to the seal plug 8 during fuel exchange. In particular, the sealing mechanism 10 consists of a metal sealing member and a movable sealing dome provided at the tip of the sealing plug that receives a spring bias and presses the sealing member against the wall surface of the pressure pipe. The structure is such that the seal dome is relatively moved in the axial direction against the biasing spring by a grab operation, and the sealing member is retreated from the pressure pipe wall. Note that the lower end of a connecting pipe 7 that connects the above-mentioned shielding body 6 is bolted to the upper surface of the shield dome.

[Problem that the invention seeks to solve]

By the way, in the conventional shielding seal plug structure in which the shielding body 6 and the seal plug 8 are directly connected to the rigid body via the connecting pipe 7 as described above, when loading and removing the shielding seal plug, the following procedure is performed. Problems may arise. That is, the fuel assembly 2 often sticks to the pressure pipe 1 while being loaded in the pressure pipe or during loading. Moreover, if the shielding seal plug is pushed and loaded and the seal mechanism is opened and closed by the grab operation of the fuel exchanger connected to the seal plug 8 while this stick is still occurring, the pushing force applied to the seal plug 8 from the grab mechanism side or the sealing A large operating force that pushes up the shield dome to operate the mechanism 10 is directly applied to the fuel assembly 2 in the stuck state via the connecting pipe 7 and the shield 6, and as a result, the fuel assembly 2 exceeds the allowable load. Excessive load may cause damage or breakage.

An object of the present invention is to provide a configuration in which even if a stick occurs between a fuel assembly and a pressure pipe, a seal plug can be reliably attached and detached without applying an excessive load to the fuel assembly. This provides a shielding seal plug structure designed to protect the body.

[Means for solving problems]

In order to solve the above-mentioned problems, according to the present invention, a shield is provided with a coupling joint for connecting to a fuel assembly at the top, and a shield is connected to a pressure pipe at a loading position into a pressure pipe of a reactor core, and is connected to a pipe end opening. In the shielding seal plug, which is a connecting assembly with a seal plug that seals a The seal plug is constructed so that the axial movement operation force applied to the seal plug is absorbed by compressive deformation of the spring member.

[Effect]

With the above configuration, even if a stick occurs between the fuel assembly connected to the shielding seal plug and the pressure pipe when loading or removing the shielding seal plug, the sealing mechanism is applied to the sealing plug from the fuel exchanger side. The movement operation force is absorbed by the compressive deformation of the spring member interposed between the shield and the seal plug, which allows the seal plug to be inserted to the specified loading position in the pressure pipe without applying an excessive load to the fuel assembly, and the seal is sealed. The shielding seal plug can be attached and detached by operating the mechanism without any hindrance.

〔Example〕

FIG. 1 shows the structure of a shielding seal plug according to an embodiment of the present invention, and the same members corresponding to FIG. 2 are given the same reference numerals. That is, according to the present invention, a spring member indicated by reference numeral 11 is installed and interposed in the connecting portion between the shielding body 6 and the connecting pipe 7 of the seal plug 8 connected to the rear end thereof. As a concrete structure for this purpose, a concave groove 12 is formed in the lower end surface of the shielding body 6 to serve as a receiving seat for the connecting tube 7, and the tip of the connecting tube 7 is inserted and coupled here so as to be slidable in the axial direction within the groove. Here, the spring member 11 is compressed and interposed between the tip of the connecting pipe 7 and the bottom of the groove 12. Note that 13 is a retaining flange for the connecting pipe. Further, the spring member 11
A coil spring or a disc spring is used, and is assembled in a compressed state so that the weight of the upper shield 6 and fuel assembly 2 can be sufficiently supported by the compression spring force in the assembled state. Therefore, in a normal fuel exchange operation, the spring member 11 is not compressed and deformed more than the assembled state due to these weights, and the assembled dimensions of the shielding seal plug as a whole are maintained at specified dimensions.

On the other hand, in the process of loading the shielding seal plug 3 into the pressure pipe 1 together with the fuel assembly 2 during fuel exchange, the fuel assembly 2 and pressure pipe 1 unexpectedly come together just before the seal plug 3 reaches the specified loading position. If a stick occurs between the two, the upward force of the seal mechanism 10 applied to the seal plug 3 from the grab mechanism side of the fuel exchanger is absorbed by the compressive deformation of the spring member 11, and the fuel assembly is removed via the shield 6. The fuel assembly can be safely protected by preventing excessive load from being applied to the body 2. Furthermore, in this case as well, the seal plug 3 has a movable stroke in the axial direction corresponding to the compressive deformation of the spring member 11 described above, so the seal plug 8 is pushed to a predetermined loading position and the ball latch mechanism 9 is connected to the pressure pipe. 1, and in this loading position, the sealing mechanism 10 can be operated without any trouble to reliably seal between the pressure pipe 1 and the pressure pipe 1.

Also, even if a stick occurs between the pressure pipe 1 and the fuel assembly 2 when fuel is loaded in the pressure pipe,
Due to the intervention of the spring member 11, the sealing mechanism 10 of the seal plug 8 can be moved and operated without any hindrance by the grab operation of the fuel exchanger without applying an excessive load to the fuel assembly 2 as in the case of loading the pressure pipe 1.
The shielding seal plug 3 can be pulled out from the pressure pipe 1 together with the fuel assembly 2 by breaking the seal between the fuel assembly 2 and the fuel assembly 2.

〔Effect of the invention〕

As described above, according to the present invention, there is provided a shield equipped with a coupling joint for connecting to the fuel assembly at the top, and a seal that connects to the pressure pipe at the loading position into the pressure pipe of the reactor core and seals the pipe end opening. In a shielding seal plug that is a connecting assembly with a plug, a spring member is interposed in the connecting portion between the shielding body and the seal plug, and the spring member is applied to the seal plug from the fuel exchange machine side when the shielding seal plug is attached or detached. By absorbing the axial movement operating force through compressive deformation of the spring member, even if a stick occurs between the pressure pipe and the fuel assembly during fuel exchange, the fuel assembly will not be damaged. The shielding seal plug can be reliably attached and detached by a grab operation of the fuel exchanger without applying an excessive load, thereby preventing damage to the fuel assembly and ensuring safety.

[Brief explanation of the drawing]

FIG. 1 is a structural diagram of a shielding seal plug according to an embodiment of the present invention showing the state of loading into a pressure pipe, and FIG. 2 is a structural diagram of a conventional shielding seal plug corresponding to FIG. 1. In each figure, 1...pressure pipe, 2...fuel assembly, 3...shielding seal plug, 4...collection joint, 5...pick up head, 6...shielding body, 7...connecting pipe, 8... ... Seal plug, 9 ... Ball latch mechanism, 10 ... Seal mechanism, 11 ... Spring member, 1
2... Concave groove.

Claims (1)

[Scope of Claims] 1. Connection between a shielding body equipped with a coupling joint for connecting to a fuel assembly at the top and a sealing plug that is coupled to a pressure tube at a loading position into the pressure tube of the reactor core to seal the tube end opening. In a shielding seal plug that is an assembly, a spring member is interposed in the connecting portion between the shielding body and the seal plug, and a spring member is provided to prevent axial movement applied to the seal plug from the fuel exchange machine side when the shielding seal plug is attached or removed. A shielding seal plug for a pressure tube nuclear reactor, characterized in that the operating force is absorbed by compressive deformation of the spring member. 2. In the shielding seal plug according to claim 1, a concave groove is formed on the lower end surface of the shield, and the concave groove serves as a receiving seat for the connecting portion, and the connecting pipe on the seal plug side can slide into the concave groove. 1. A shielding seal plug for a pressure tube nuclear reactor, characterized in that the plug is inserted into and connected to the connecting pipe, and a spring member is compressed and interposed between the end face of the connecting pipe and the bottom of the concave groove.