JPH0131157B2 - - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an improvement in a nuclear reactor in which the reactor core is suspended in a fluid coolant within 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.

By the way, fast breeder reactors can be broadly divided into loop type and tank type. In the case of a loop type, the coolant heated inside the reactor is circulated through thin-walled piping (primary system) to a heat exchanger room located in a separate room, and then returned to the reactor. There is. However, in such a loop-type reactor, the coolant itself inside the reactor circulates over a wide range within the building through piping.
In particular, for large-scale nuclear reactors, there are points that need to be reconsidered from the viewpoint of construction costs and safety.

Therefore, in order to solve this problem, we have developed a nuclear reactor that eliminates piping as much as possible, that is, a primary heat exchanger 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 material circulation pump is installed inside 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.

A core support member 8 is suspended from the roof slab 2 . The lower end of the core support member 8 in the figure is fitted into the center hole of a conical support 9 made of an annular body fixed to the center of the inner surface of the side wall of the reactor main vessel 1. This prevents the parts from moving horizontally. core 3
is housed in the lower end of the core support member 8 in the figure, and the core upper mechanism 4 is housed in the lower end of the core support member 8 in the figure.
It is supported by a rotary plug 10 which is rotatably provided above. The reactor main vessel 1 is suspended in the reactor room 12 via a ring gutter 11, and a safety vessel 13 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 an external impact input or vibration input is applied, the core support member 8 exhibits a complicated deformation mode in the vertical and horizontal directions in combination with the vibrations of the reactor main vessel 1 and the coolant 7. , there is a possibility that part of the core support member 8 or the core 3 may be damaged due to local stress due to the deformation or an increase in response acceleration.

Therefore, as mentioned above, conventional nuclear reactors have a structure in which the lower end of the core support member 8 is horizontally supported by the conical support 9. However, in the event of an earthquake, etc., the reactor main vessel 1 There is a possibility that the reactor core 3 may be coupled with each other and exhibit complicated movements. Furthermore, when mechanically connecting the reactor core and the reactor main vessel 1 in this way using a support member, in order to absorb vertical thermal expansion of the support member in particular, the outer periphery of the lower end of the core support member 8 and , it is necessary to connect the conical support 9 fitted to the outer periphery of this lower end portion so as to be movable in the vertical direction. Furthermore, since an earthquake causes not only horizontal motion but also vertical motion, 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. At this time,
A relative displacement occurs between the core support member 8 and the conical support 9.

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 these circumstances, and its purpose is to reduce the influence of vibrations in the reactor core on other components during earthquakes, etc., without complicating the overall structure. Another object of the present invention is to provide a nuclear reactor that can quickly attenuate vibrations and thereby improve 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 reactor vessel, in which a cylinder is provided between the outside of a side wall of the reactor core and the side wall. A fluid gap having the shape of a shape is provided and an auxiliary cylinder is disposed therein, hydrodynamic resistors are provided at both ends of the fluid gap, and the auxiliary cylinder is fixed to the reactor vessel by a fixing member. It is said that

〔Effect of the invention〕

According to the present invention, when a vibration input is applied to a nuclear reactor and the reactor core causes a relative movement with respect to the reactor main vessel, that is, when a cylindrical body fixed to the reactor main vessel and the reactor core If a relative displacement occurs in
The coolant in the fluid gap produces circumferential and axial flow. In this case, hydrodynamic resistors are provided at both ends of the fluid gap, so
Axial flow of coolant encounters greater resistance and creates a greater pressure differential across the fluid gap. Therefore, the reactor core receives a force that offsets this pressure difference, that is, a fluid reaction force, and the amplitude of vibration is suppressed.

Furthermore, the vibrational energy in the reactor core generated by the vibration input is dissipated by the flow friction of the coolant flowing in the fluid gap, as described above. In other words, since the resistors are provided at both ends of the fluid gap, the coolant in the gap effectively acts as a buffer, making it possible to quickly suppress vibrations in the core.

In addition, the outer surface of the side wall of the reactor core is connected to the reactor main vessel via the coolant in the fluid gap, so compared to the case where the reactor core and the reactor main vessel are mechanically connected, , there is a relatively loose coupling relationship. Therefore, it is possible to prevent the occurrence of complex deformation modes expected due to coupled vibration. In addition, according to the present invention, an effective vibration damping effect is exhibited not only in the horizontal direction but also in the vertical direction, so that the health of the entire furnace can be improved in the event of an earthquake.

Further, in the present invention, since the reactor core and the auxiliary cylinder are arranged in a non-contact state, there is sufficient margin for the gap against thermal deformation of the reactor core. Moreover, in this case, the above-mentioned effects can be achieved with only a very simple configuration in which the core portion is covered with the auxiliary cylinder. Therefore, there is no possibility of complicating the whole system.

[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.

The difference in FIG. 2 from FIG. 1 is that an auxiliary cylinder 16 for core resting is externally mounted on the core accommodating portion of the core support member 8 in a non-contact manner. That is, the core support member 8 is made of, for example, a thin-walled cylindrical body with a bottom, and has a structure in which the core 3 can be installed inside and below. The auxiliary cylinder 16 is coaxially arranged so as to cover the side surface of the core housing portion of the core support member 8 from the outside without contact, and forms a cylindrical fluid gap 17 along the inner surface, and a conical annular body. It is supported by the reactor main vessel 1 via a support plate 19 consisting of. Note that the auxiliary cylinder 16 is provided with a hole 20 on the side surface, and a pipe 21 communicating the reactor core 3 and the circulation pump 6 is passed through the hole 20 without contact.

Hydrodynamic resistors 23 and 24, which will be described below, are provided at both ends of the cylindrical fluid gap 17. That is, the upper resistor 23 provided above the fluid gap 17 in the drawing
A support member side upper resistance member 25 consisting of a flange protruding from the intermediate portion of the core support member 8 and a projecting circumferential wall extending downward in the figure from the intermediate position of the flange, and this resistance member. 25 through a predetermined gap, the upper end of the auxiliary cylinder 16 extends outward in the figure, and further extends in the axial direction. on the other hand,
The lower resistor 24 includes a support member side lower resistance member 27 whose lower end edge in the drawing of the core support member 8 extends downward, and an auxiliary cylinder that fits into the resistance member 27 through a predetermined gap. The lower end of the body 16 in the figure extends inward in the radial direction, and is further comprised of a cylindrical lower resistance member 28 which is folded back in the axial direction.

Suppose now that a horizontal impact input is applied to the nuclear reactor according to the present embodiment configured as described above, and horizontal vibrations are generated in the reactor core 3 relative to the reactor main vessel 1. In this case, the core accommodating portion of the core support member 8 that supports the core 3 is displaced in the radial direction with respect to the auxiliary cylinder 16. As a result, in the fluid gap 17, the coolant flows in the circumferential direction and in the axial direction.
Because of the provision of the resistor, the axial flow of the coolant is significantly inhibited, resulting in a larger pressure difference inside the fluid gap 17 than would be the case without the resistor. As a result, the core 3 receives a force in a direction that cancels out this pressure difference, and the amplitude of vibration is suppressed.

In addition, the vibration energy of the core 3 generated by the vibration input of the reactor is caused by the flow friction of the coolant flowing in the fluid gap, especially between the resistors 23 and 24.
It is quickly absorbed by the flow friction of the fluid passing through it.

On the other hand, when the reactor core 3 vibrates in a direction perpendicular to the reactor main vessel 1, the coolant in the fluid gap 17 primarily flows in the axial direction. In this case, large flow friction is generated by the resistors 23 and 24 in the same way as the horizontal vibration, and the vibration of the core 3 is quickly suppressed as described above.

As described above, according to this embodiment, the auxiliary cylinder 16 is externally mounted on the core housing portion of the core support member 8 via the fluid gap 17, and a resistance member is provided in a portion of the core support member 8 and the auxiliary cylinder 16. Although it has an extremely simple structure, the coolant used for cooling the core 3 is effectively used as a buffer material.
It is possible to suppress vibrations in the reactor core during earthquakes, etc., and the vibration damping effect is extremely high in all directions. In this case, the core support member 8 and the auxiliary cylinder 16 are in a non-contact state, and the support member 19 that supports the auxiliary cylinder 16 is formed in an annular shape. Since the deformation of the core support members 8 and 8 due to thermal expansion all exhibit the same tendency, excessive stress due to thermal expansion will not act on these members. Therefore, the reactor core 3 is always stably supported by the roof slab 2, and the safety of the nuclear reactor can be made extremely high.

In addition, as described above, the core support member 8 and the auxiliary cylinder 1
6 is in a non-contact relationship, so the reactor core and the reactor main vessel do not receive any direct load and are loosely connected. Therefore, it is possible to prevent the occurrence of complicated deformation modes due to impact input.

It should be noted that the present invention is not limited to the above-mentioned embodiment, and for example, the shape of the upper resistor 23 may be configured as shown in FIGS. 3a to 3d. Further, the shape of the lower resistor 24 may also be configured as shown in FIGS. 4a to 4d. In these, as shown in FIGS. 3d and 4d,
The most effective core vibration damping effect can be obtained by using resistors with a multistage stacked structure.

[Brief explanation of drawings]

FIG. 1 is a schematic longitudinal sectional view showing a conventional tank-type nuclear reactor, FIG. 2 is a schematic longitudinal sectional view showing a tank-type nuclear reactor according to an embodiment of the present invention, and FIGS. 3 a to d 4A to 4D are partial sectional views showing modified examples of the upper resistor, and FIGS. 4A to 4D are partial sectional views showing modified examples of the lower resistor. 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... Conical support,
10... Rotating plug, 11... Ring gutter, 1
2...Reactor room, 13...Safety container, 16...Auxiliary cylinder, 17...Fluid gap, 19...Support plate, 23...Upper resistor, 24...Lower resistor,
25... Upper resistance member on the support member side, 26... Upper resistance member on the cylinder side, 27... Lower resistance member on the support member side, 28... Lower resistance member on the cylinder side.

Claims (1)

[Claims] 1. In a nuclear reactor in which a reactor core is housed in the lower part of a core support member suspended in liquid coolant in a reactor vessel, there is a space between the outer circumferential surface of the lower part of the core support member and the outer circumferential surface of the lower part. an auxiliary cylinder provided with a cylindrical fluid gap; a member that fixes the auxiliary cylinder to the reactor vessel; and a member that fixes the auxiliary cylinder to the reactor vessel; 1. A nuclear reactor, comprising: a hydrodynamic resistor provided at one position.