JPS6341516B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a nuclear reactor fuel inlet/output guide device suitable for use in a sodium cooled fast reactor.

The above nuclear reactor is equipped with a fuel inlet/outlet guide device as a means for forming a fuel delivery/transfer passageway between the reactor and fuel handling equipment, such as a fuel inlet/outlet machine. This guide device needs to have a sufficient earthquake resistance function in addition to the ability to maintain the airtightness of the inert cover gas sealed in the reactor vessel and the radiation shielding function. Of these, the seismic function is particularly important, not only for its seismic strength, but also for the possibility of an earthquake occurring while it is connected to fuel handling equipment.
It is desired that the displacement caused by earthquake shaking can be effectively absorbed midway through the fuel handling equipment without directly propagating it to the fuel handling equipment.

On the other hand, a conventional fuel inlet/outlet guide device of this type is constructed as shown in FIG. 1 or FIG. 2. In other words, Fig. 1 is what is called a self-supporting type, and in the figure, 1 is the reactor vessel, 2 is the upper plug of the reactor vessel 1, and inside the reactor vessel are sodium and primary coolants. Filled with inert cover gas. Reference numeral 3 indicates a fuel inlet/outlet machine that runs along a rail above the reactor vessel 1, and 4 indicates a door valve attached to the lower end of the fuel storage coffin 5. The fuel inlet/outlet guide device 6 includes a fuel guide tube 7 that communicates with the inside of the reactor vessel and is installed on the upper shield plug 2, a door valve 8 installed at the top of the guide tube 7, and an outer circumference of the guide tube 7. It consists of a radiation shielding body 9 which is a heavy object that is surrounded and integrally connected, and these assemblies are attached to the mounting bolts 1.
0, it is firmly fixed and installed on the upper surface of the shield plug 2. The guide device 6 having such a configuration has a rigid structure as a whole, and the shaking displacement of the reactor vessel 1 due to an earthquake propagates directly to the top door valve 8 of the guide device 6. For this reason, if the fuel inlet/outlet machine 3 is connected during an earthquake, a relative displacement will occur between the two, which may cause damage to the fuel handling equipment. For this reason, it was necessary to provide a special follow-up mechanism on the fuel inlet/outlet device 3 side to absorb the relative displacement with the guide device 6 described above. Furthermore, since the displacement of the reactor vessel side due to earthquake shaking is transmitted to the entire guide device 6, it is dangerous to support the guide device 6, for example, on a structure on the building side. It is necessary to have high seismic strength. As a result, sufficient mechanical strength is required on the reactor vessel side in order to support the large moment load, etc. that acts on the guide device 6 during an earthquake, and the reactor vessel and the shield plug become larger accordingly.

On the other hand, in order to prevent the displacement caused by an earthquake from propagating directly to the door valve 8, a guide pipe 7 is installed as shown in FIG.
is divided into upper and lower parts and separated from each other, and the upper divided body is supported by the building-side structure 11, and the upper and lower divided bodies of the guide pipe 7 are connected with each other with a bellows 12, and the relative displacement that occurs during an earthquake is absorbed by the bellows 12. Although such a bellows type is also known, this bellows 12 has a drawback in terms of durability as an airtight boundary component for cover gas, and sufficient reliability cannot be obtained. Moreover, maintenance and replacement of the bellows 12 requires extensive work, resulting in poor maintainability.

This invention has been made in view of the above points, and its purpose is to eliminate the drawbacks of conventional devices and provide a highly reliable device with excellent earthquake resistance, especially as a fuel guide device connected to fuel handling equipment. It is in.

The present invention will be described in detail below based on illustrated embodiments.
In FIG. 3, a guide tube 7 constituting the guide device 6
The shield body 9 is not integrated as in conventional devices, but is constructed as separate and independent parts, and is installed and supported individually. That is, with respect to the guide tube 7 which rises above the shield plug 2 of the furnace vessel 1, the shield body 9 is installed at a gap g over the entire area between the guide tube 7 and the guide tube 7. The shield body 9 is made up of upper and lower divided bodies 9A and 9B that are separated from each other, and the upper divided body 9A is attached to the building structure 11, and the lower divided body 9B is attached to the shield plug 2 of the reactor vessel 1 with bolts 10, respectively. It is fixedly supported through. Furthermore, the top of the guide tube 7 is attached to the building side structure 11 with a shaft sealing O-ring 1.
3. The shaft seal is supported so as to be slidable in the vertical direction via a shaft seal mechanism 15 consisting of a shaft seal casing 14, and the door valve 8 is located above the shaft seal mechanism 15.
Furthermore, the wall thickness of the guide tube 7 is not as thick as on the left, and it is designed and manufactured to have a flexible structure with relatively low bending stress when subjected to a lateral load or a couple load due to an earthquake or the like.

According to the above configuration, even if relative displacement occurs in the horizontal and vertical directions between the reactor vessel 1 and the building side structure 11 due to earthquake shaking, the guide pipe 7 and the shield body 9 are separated by the gap g. Since they do not interfere with each other and the guide tube itself has a flexible structure, this displacement is absorbed by the bending deformation of the guide tube itself and the slide between it and the shaft sealing mechanism 15, and the displacement is absorbed by the guide tube itself and the shaft seal mechanism 15. Prevent the effects of displacement from occurring. Further, the radiation shielding body 9 is constructed as a separate and independent component separated from the guide tube 7, and it is possible to adopt a unique support structure without considering interference with the guide tube 7. That is, as shown in the illustrated example, the sheathing body 9 is divided into upper and lower divided bodies 9A and 9B, and the upper divided body 9A is supported on the building-side structure 11 to reduce the load of the sheathing body 9 applied to the reactor vessel side. Alternatively, the entire shield body 9 can be suspended and supported by the building-side structure 11. This allows the shield plug 2 on the furnace vessel side to
The heavy load on the shield body 9 and the large moment load during an earthquake can be greatly reduced, and the load burden on the reactor vessel 1 is reduced accordingly, ensuring higher safety in terms of mechanical strength. It is advantageous to be able to do so. Furthermore, by using a shaft sealing mechanism 15 that can employ an O-ring or the like as a sealing mechanism that absorbs the vertical displacement of the guide tube 7 and maintains the airtightness of the cover gas in the furnace, it is possible to improve the conventional structure shown in FIG. It has superior durability compared to conventional bellows, and the seal mechanism can be easily inspected and replaced, resulting in high reliability.

As described above, in a fuel inlet/output device, the present invention configures the fuel guide tube as a flexible structure, and separates the guide tube and the radiation shielding body surrounding the outer periphery of the guide tube from each other as independent parts, and also separates them from each other. Each is installed and supported independently with a gap across the entire area. Therefore, the displacement caused by earthquake shaking is absorbed by the guide tube itself, no relative displacement is exerted on the fuel handling equipment, there is no need for a displacement tracking mechanism such as a movable block, and the guide tube can absorb heavy objects independently of the guide tube. It is now possible to support part or all of the radiation shielding body on the building side structure, which greatly reduces the load on the reactor vessel, improving seismic performance and reliability. can be achieved.

[Brief explanation of drawings]

Figures 1 and 2 are cross-sectional views of the conventional device;
FIG. 3 is a sectional view of the structure of an embodiment of the present invention. 1...Furnace vessel, 2...Upper shield plug, 3
... Fuel handling machine, 6... Fuel inlet/outlet guide device, 7... Fuel guide pipe, 8... Door valve, 9...
... Radiation shield body, 9A, 9B... Divided body of shield body, 15... Shaft seal mechanism.

Claims (1)

[Scope of Claims] 1. A fuel inlet/outlet guide pipe that communicates with the inside of the reactor vessel and is installed to stand up from the upper shield plug of the reactor vessel toward the fuel handling equipment above, and the outer periphery of the guide pipe. In a nuclear reactor fuel inlet/output guide device comprising an enclosed radiation shield and a door valve combined at the top of the guide tube, the fuel guide tube is configured as a flexible structure, and the fuel guide tube and radiation shield are A fuel inlet/outlet guide device for a nuclear reactor, characterized in that the bodies are separated from each other and each is independently installed and supported with a gap between the inside and outside. 2. The fuel inlet/outlet guide device for a nuclear reactor according to claim 1, wherein the top of the guide tube is supported on a building side structure via a shaft sealing mechanism. 3. The fuel inlet/outlet guide device for a nuclear reactor according to claim 1, wherein at least a portion of the radiation shielding body is supported by a building side structure.