JPH0131158B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an improvement in a nuclear reactor in which a liquid metal is used as a coolant and a reactor core is suspended and supported within the coolant in a reactor vessel.

[Technical background of the invention]

Nuclear reactors, such as fast breeder reactors, generally use liquid metal, typically liquid metal sodium, as a coolant and are operated at higher temperatures than light water reactors. In such fast breeder reactors, in order to prevent the reactor main vessel, core equipment, piping, etc. from being damaged by thermal stress when starting or stopping reactor operation, the walls of these components are usually A method is used to reduce the thickness.

In addition, in order to make the overall structure of such a fast breeder reactor simple, a nuclear reactor that eliminates piping as much as possible, that is, a reactor that exchanges heat between the primary coolant and the secondary coolant. A so-called tank-type nuclear reactor structure is being considered, in which a primary heat exchanger and a coolant circulation pump are installed within the main reactor vessel.

In this tank-type nuclear reactor, for example, as shown in FIG. 1, the upper opening in the figure of the reactor main vessel 1 is closed with a roof slab 2, and the interior includes a reactor core 3, a core upper mechanism 4, a primary heat exchanger 5, , a coolant circulation pump 6 and a coolant 7. core 3
is housed at the lower end in the figure of a core support member 8 suspended from the roof slab 2, and the core upper mechanism 4 is supported by a rotary plug 9 rotatably provided above the core support member 8. has been done. The reactor main vessel 1 is suspended in the reactor room 11 via a ring gutter 10, and a safety vessel 12 is provided outside the reactor main vessel 1 so as to cover the reactor main vessel 1. It is being

By adopting such a tank-type nuclear reactor structure, piping for the primary heat exchange system and coolant circulation system can be eliminated.

[Problems with background technology]

However, even in a nuclear reactor that employs such a tank-type reactor structure, the following problems are expected. That is, the reactor core support member 8 is formed to be relatively thin in terms of thermal stress, and is supported by the roof slab 2 and attached to the reactor main vessel 1 in order to absorb a large amount of thermal expansion due to the increase in size. It has a cantilevered structure suspended inside. The core 3, which is a heavy object, is supported at the lower end of the core support member 8. Therefore, when shock or vibration input is applied from the outside, the vibrations of the reactor main vessel 1, the vibrations of the coolant 7, and the bending deformation of the roof slab combine to cause the core support member 8 to bend in the vertical and horizontal directions. It exhibits a complicated deformation mode, and there is a possibility that the core support member 8 and a part of the reactor core 3 may be damaged due to an increase in local stress due to the deformation, so some kind of countermeasure is desired.

Therefore, in order to solve this problem, an annular body is fitted to the outer periphery of the lower end of the core support member 8.
It is conceivable to fix this annular body to the inner surface of the reactor main vessel 1 with a support member, but in this case, the reactor main vessel 1 and the reactor core 3 will be coupled to each other in the event of an earthquake, etc., resulting in a complicated There is a risk of movement.

Furthermore, when mechanically connecting the reactor core and the reactor main vessel 1 using a support member, the support member is formed into a so-called mortar shape in order to absorb the thermal expansion of the support member, and the core support It is necessary to connect the outer periphery of the lower end of the member 8 and the annular body attached to the outer periphery of the lower end so as to be movable in the vertical direction. However, in an earthquake, there is not only horizontal motion but also vertical motion, so in such a structure, since there is no vertical restraint other than the roof slab, the core support member 8 and the reactor core 3 are subject to large vertical vibrations. there's a possibility that.

In this way, if the reactor core exhibits complex coupled behavior of horizontal motion and vertical motion, it could have a significant impact on the health of the entire reactor.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and its purpose is to improve the horizontal and vertical alignment between the vessel and the reactor core during an earthquake, etc., without complicating the entire structure. It is an object of the present invention to provide a nuclear reactor that can quickly suppress relative displacement without affecting other components, thereby improving the health of the entire reactor during earthquakes and the like.

[Summary of the Invention] The present invention provides a nuclear reactor in which a liquid metal is used as a coolant and a reactor core is suspended and supported in the coolant in a main reactor vessel. It is characterized in that it is covered with a container through a gap, and this container is fixed to the reactor container with a fixing member.

〔Effect of the invention〕

In the present invention, a container is provided to cover the side and bottom surfaces of the core, and a fluid gap filled with coolant is formed between the container and the core. Therefore, when an impact input is applied to the reactor and the core moves relative to the reactor main vessel, there will be a relative displacement between the vessel fixed to the reactor main vessel and the reactor core. This results in a local pressure difference across the fluid gap. Therefore, the core is pushed back by a force that offsets this pressure difference.

Furthermore, the vibrational energy in the core generated by the impact input is dissipated by the flow friction of the coolant flowing in the fluid gap, as described above. In other words, the coolant forming the fluid gap effectively acts as a buffer, making it possible to quickly suppress vibrations in the core.

In addition, the side and bottom surfaces of the reactor core are connected to the reactor main vessel via the coolant in the fluid gap, compared to a case where the reactor core and the reactor main vessel are mechanically connected. This relationship makes it difficult for coupled vibration to occur between the two. Therefore, it is possible to prevent the occurrence of complex deformation modes that would be expected due to coupled vibrations, and as a result, the health of the entire furnace during earthquakes can be improved.

Moreover, in this case, the above-mentioned effects can be achieved with only a very simple configuration of covering the reactor core with a container. Therefore, it does not cause the overall complexity.

[Embodiments of the invention]

Hereinafter, one embodiment of the present invention will be described with reference to FIG. Note that in FIG. 2, the same parts as in FIG. 1 are given the same reference numerals, and explanations of the overlapping parts will be omitted.

2 differs from FIG. 1 in that a steady rest container 16 is provided to cover the core housing portion of the core support member 8. That is, the core support member 8 is made of, for example, a thin-walled cylinder with a bottom,
It has a structure that allows the reactor core 3 to be accommodated in the lower part of the interior. The container 16 is coaxially arranged so as to cover the side and bottom surfaces of the core housing portion of the core support member 8 from the outside without contact, and the fluid gap 1 is disposed along the inner surface of the container 16 .
7 and is supported by the reactor main vessel 1 via a support plate 19 formed in a so-called mortar shape. Note that the container 16 has a hole 20 on the side surface.
A core 3 and a circulation pump 6 are provided in this hole 20.
A pipe 21 communicating with the two is passed through without contact.

Suppose now that a horizontal impact input is applied to the nuclear reactor according to the present embodiment configured as described above, causing the reactor core 3 to vibrate in the horizontal direction relative to the reactor main vessel 1. In this case, the core housing portion of the core support member 8 that supports the core 3 is
A radial displacement occurs relative to the container 16. As a result, in the fluid gap 17, a pressure difference is created between the part where the gap is momentarily narrowed and the part where the gap is widened, and the core 3 is given a force in the direction that offsets this pressure difference, and the Move in the direction to reduce displacement.

Furthermore, the pressure difference in the fluid gap 17 caused by the displacement of the reactor core 3 with respect to the reactor main vessel 1 is as follows:
This causes the coolant present in the fluid gap 17 to flow within the fluid gap 17. Therefore, fluid friction occurs within the fluid gap 17, and the vibration energy applied to the core 3 is dissipated by this fluid friction. In other words, since the coolant 7 constituting the fluid gap 17 effectively acts as a buffer material, the vibrations of the core 3 are quickly suppressed.

On the other hand, even if the reactor core 3 vibrates in the vertical direction with respect to the reactor main vessel 1, an effective vibration damping action by the fluid gap 17 will similarly act on the reactor core 3.

As described above, according to the present embodiment, the cooling that is normally used for cooling the core 3 is achieved by an extremely simple structure in which the core accommodating portion of the core support member 8 is covered with the container 16 via the fluid gap 17. The material can be effectively used as a buffer material to suppress vibrations in the reactor core during earthquakes, etc., and its damping effect is extremely high against vibrations in any direction. In this case, the core support member 8 and the container 16 are in a non-contact state. Therefore, the container 16, the support plate 19 and the core support member 8
The deformation caused by thermal expansion can be absorbed by the gap portion, and no excessive stress is applied to these members. For this reason, the core 3 is connected to the roof slab 2.
The reactor can be stably supported at all times, making the reactor extremely safe.

Note that the present invention is not limited to the above-mentioned embodiments, and various modifications can be made without departing from the gist thereof.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view showing a conventional tank-type nuclear reactor, and FIG. 2 is a schematic vertical cross-sectional view showing a tank-type nuclear reactor according to an embodiment of the present invention. 1...Reactor main vessel, 2...Roof slab, 3
... Core, 4 ... Core upper mechanism, 5 ... Primary heat exchanger, 6 ... Coolant circulation pump, 7 ... Coolant,
8... Core support member, 9... Rotating plug, 10...
...Ring gutter, 11...Reactor room, 12...Safety vessel, 16...Container, 17...Fluid gap,
19...Support plate.

Claims (1)

[Claims] 1. In a nuclear reactor that uses liquid metal as a coolant and has a reactor core housed in the lower part of a core support member suspended in the coolant in the reactor vessel, the side and bottom surfaces of the lower part of the core support member are 1. A nuclear reactor comprising: a container provided to cover the reactor via a fluid gap; and a member for fixing the container to the reactor container.