JP2831225B2 - Liquid metal cooled reactor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid metal-cooled nuclear reactor having inherent safety against an abnormal temperature rise of a coolant, and more particularly, to a liquid level with a rise in coolant temperature. The present invention relates to a reactor of the type in which a reactor power adjusting rod is directly inserted deep into a core by the action of a float using a rise.

[0002]

2. Description of the Related Art A nuclear power plant has a thermometer, a flow meter,
Various instruments such as a neutron detector are installed, and the operating status of the plant is constantly monitored. If an abnormality occurs and the signals of these instruments exceed a certain set level, the control circuit is activated, control rods and safety rods are inserted into the core, and the reactor is shut down. For example, if the main circulation pump stops due to an accident such as a power failure, the system immediately switches to a diesel-driven pony motor, but the flow rate decreases. Upon detecting this, a control rod or a safety rod is inserted. For example, in the case of a safety rod, it is held in a state of being suspended by an electromagnet, the power to the electromagnet is cut off by the above-mentioned signal, and a configuration is adopted in which the safety rod is inserted into the core by its own weight or by using the pressure of the compressed gas together. ing.

[0003]

However, in the prior art, there always exists a process mediated by an electric circuit. Therefore, if the cable is broken, short-circuited, or the connectors become loose due to poor quality or aging, the process from signal detection to insertion of control rods and safety rods may cause defects, or control gas leakage may occur. Therefore, there is no danger that the furnace will not be stopped even if an abnormality is detected. Therefore, measures such as multiplexing the furnace stop mechanism are taken in addition to performing sufficient periodic inspections, and the system is complicated.

[0004] It is an object of the present invention to provide a liquid metal-cooled nuclear reactor that can add inherent safety to the reactor, enhance safety and reduce the psychological burden on operators.

[0005]

According to the present invention, a reactor core is supported by a reactor internal structure inside a reactor vessel, and a low-temperature liquid metal coolant flows from an inlet pipe and is heated through the reactor core. It is premised on a liquid metal-cooled reactor that flows out of the outlet pipe and has a free liquid level inside. In order to achieve the above object, in the present invention, a liquid surface area limiting mechanism for narrowing the coolant level is provided at the upper part of the reactor vessel, and a float floating on the level and a vertical movement of the float are provided. A reactor power adjustment rod that performs insertion and withdrawal operations with respect to the core is provided, which is characterized by this point.

The above-mentioned liquid surface area limiting mechanism has, for example, a structure in which an inner cylindrical portion, an outer cylindrical portion, and an annular bottom portion closing between the lower edges thereof are integrated with each other, and the integrated structure is formed from the upper part of the furnace vessel. It is inserted so that the coolant is guided inside the inner cylinder. Also, a plurality of adjustment rod supports are suspended from the annular float to penetrate the internal structure of the reactor, and an adjustment rod receiver is attached to the adjustment rod support, and the reactor power adjustment rod is supported by the adjustment rod receiver. Then, it is preferable to insert and withdraw the reactor power adjusting rod from the lower part of the core.

[0007]

[Function] Liquid metal has a high saturation temperature even in the atmosphere (for example, about 881 ° C for sodium), and in a reactor using it as a coolant, some abnormalities occur in the cooling system and output system, causing the coolant temperature to rise. Even hard to boil. However, the free liquid level of the reactor rises due to the volume expansion of the coolant accompanying the high temperature of the liquid metal. The liquid surface area limiting mechanism has a function of increasing the liquid level change due to the volume expansion of the liquid metal to improve the sensitivity. As the liquid level of the coolant rises, the float floating on it also rises. Raising the float drives an adjustment rod connected thereto and inserts the adjustment rod into the core. This suppresses reactor reactions. That is,
This means that a unique nuclear reaction suppression mechanism utilizing physical phenomena is provided without an intermediate system such as an electronic circuit.

[0008]

FIG. 1 is a structural view showing an embodiment of a liquid metal cooled nuclear reactor according to the present invention, and FIG. 2 is a sectional view taken along the line AA 'of FIG. A reactor internal structure 12 is provided below the inside of the reactor vessel 10, and a core support plate 13 is provided above the reactor internal structure 12.
Is supported. A coolant inlet pipe 16 is connected to the lower side of the reactor vessel 10, and an outlet pipe 1 is connected to the upper side.
8 is connected, the low-temperature liquid metal coolant flows in through the inlet pipe 16, is heated through the core 14, becomes hot, and flows out through the outlet pipe 18. A core upper mechanism 20 is located above the core 14, and penetrates a shielding plug 22 that closes an upper opening of the reactor vessel 10. Core upper mechanism 20
Incorporates a control rod drive mechanism 24 and the like.

In the present invention, a liquid surface area limiting mechanism 30 for narrowing the coolant level is provided above the inside of the reactor vessel 10.
In this embodiment, the liquid surface area limiting mechanism 30 is
And an outer cylinder portion 34, and an annular bottom portion 36 closing the lower edge thereof are integrally formed. The structure is inserted through the upper opening of the reactor vessel 10, and the liquid level 40 is normally set in the inner cylinder. It is supported so as to be located at an intermediate portion of the portion 32. The inner cylinder portion 32 is much larger than the above-described upper core mechanism 20, and therefore has an annular clearance with a certain width between the two.

Further, according to the present invention, the liquid surface 4 of the liquid metal coolant is provided.
It has a float 42 floating at zero, and a reactor power adjusting rod 44 that inserts into and pulls out from the core 14 as the float 42 moves up and down. In this embodiment, the float 4
Reference numeral 2 denotes an annular shape located between the inner cylindrical portion 32 of the liquid surface area limiting mechanism 30 and the upper core mechanism 20, and two adjustment rod supports 46 are suspended from positions symmetrical with respect to the center. . Both adjusting rod supports 46 are provided in the grooves 1 of the core support plate 13.
It is guided so as to fit into 3a, and can be freely moved only in the vertical direction. Furnace structure 12
The adjusting rod receiver 48 is located above the adjusting rod receiver 48.
Are integrally fixed to the adjustment rod support 46.
Then, the reactor power adjusting rod 44 is placed on the adjusting rod receiver 48.
Is supported.

The reactor power adjusting rod 44 is provided in the upper core mechanism 2.
It is inserted from the adjustment rod entry / exit guide 26 that passes through zero. As with other control rods, the material of the reactor power adjustment rod 44 is B ₄ C
Neutron absorber, etc., and after being used for a certain period of time,
Pull out from the adjustment rod access guide 26 and replace it with a new one.

The installation of such a reactor vessel internal mechanism is as follows.
This can be done as follows. First, the reactor internal structure 12 is set in the reactor vessel 10. Next, the adjusting rod support 46 including the float 42 is inserted into the through hole of the furnace internal structure 12, and the divided core support plate 13 is placed on the furnace internal structure 12 with the adjustment rod support 46 interposed therebetween. Further, the core 14 is set on the core support plate 13. The liquid surface area limiting mechanism 30 is inserted and fixed to the upper part of the reactor vessel 10 as described above. Finally, core upper mechanism 2
0, the shield plug 22 and the like are attached.

The shape of the inner cylindrical portion 32 of the liquid surface area limiting mechanism 30 is determined by the size of the entire reactor vessel 10 and how much sensitivity of the liquid level change is given. Liquid sodium expands about 3% in volume when the temperature rises by 100 ° C. On the other hand, the volume change of the stainless steel during that time is about 0.2%. Thus, as a trial calculation, it is assumed that the lower part of the reactor vessel having an inner diameter of 4 m is filled with a 15 m-deep sodium. If this whole sodium is 500 ℃
As a result, the sodium volume increases by about 2.6 m ³ . Assuming that the liquid surface area limiting mechanism 30 covers 70% of the space cross-sectional area in the reactor vessel, the float 42 expands to about 42
cm rise. As a result, the reactor power adjusting rod 44 is inserted into the core 14 by about 42 cm.

When the temperature of the liquid metal coolant rises due to an abnormality in the reactor system, the liquid level rises due to the volume expansion of the liquid metal, and the float 42 moves upward accordingly. This movement of the float 42 causes the reactor power adjusting rod 44 to be inserted into the reactor core 14 without passing through an electric signal, thereby suppressing the nuclear reaction of the reactor. When the coolant temperature decreases, the position of the float 40 also decreases, the reactor power adjusting rod 44 is withdrawn from the core 14, and the nuclear reaction of the reactor approaches the rating. When the liquid level is below a certain set position, the adjusting rod receiver 48 comes into contact with the in-furnace structure 12,
The reactor power adjustment rod 44 is held at a fixed position.

Although the preferred embodiment of the present invention has been described in detail above, the present invention is not limited to such a configuration. As a liquid surface area limiting mechanism, a double cylindrical member is incorporated, but as a structure having only an inner cylindrical portion and an annular bottom portion, the outer periphery of the annular bottom portion is fixed to the inner wall of the reactor vessel without leakage. It may have a configuration or a structure in which the upper part of the reactor vessel itself is narrowed. A configuration in which the reactor power adjusting rod is hung from a float via a fulcrum is also possible.

[0016]

As described above, the present invention utilizes the fact that the volume expansion of the liquid metal used as a coolant is large, and considers the temperature rise due to an abnormality in the reactor system as an abnormal rise in the liquid level. Since the reactor power adjusting rod is inserted directly into the reactor core by the movement, it is possible to suppress the nuclear reaction of the reactor without using an electric signal. That is, a liquid metal-cooled reactor having a unique nuclear reaction suppression mechanism utilizing a physical phenomenon excluding the intermediate system can be obtained. This improves the inherent safety of the reactor and reduces the psychological burden on operators.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing one embodiment of a liquid metal cooled nuclear reactor according to the present invention.

FIG. 2 is a view taken in the direction of arrows AA ′ in FIG. 1;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reactor vessel 12 Reactor internals 14 Reactor core 16 Inlet piping 18 Outlet piping 30 Liquid surface area limiting mechanism 40 Liquid surface 42 Float 44 Reactor power adjusting rod 46 Adjusting rod support 48 Adjusting rod support

Claims (3)

(57) [Claims] 1. A reactor core is supported by an internal structure inside a reactor vessel, and a low-temperature liquid metal coolant flows in from an inlet pipe, is heated through the reactor core and flows out from an outlet pipe,
In a reactor of the type having a free liquid level inside, a liquid surface area limiting mechanism for narrowing the coolant level is provided at the top of the reactor vessel, and a float floating on the liquid level and a vertical movement of the float A liquid metal-cooled nuclear reactor, comprising: a reactor power adjusting rod that is inserted into and pulled out of the core. 2. A liquid surface area limiting mechanism comprising: an inner cylindrical portion and an outer cylindrical portion;
2. The reactor according to claim 1, wherein the reactor has an integrated structure with an annular bottom portion closing between lower edges thereof, and the coolant is guided inside the inner cylinder portion. 3. 3. A plurality of adjusting rod supports are suspended from an annular float so as to penetrate the reactor internals, and an adjusting rod receiver is attached to the adjusting rod supports, and the power of the reactor is adjusted by the adjusting rod receivers. The reactor according to claim 1 or 2, wherein the rod is supported, and the reactor power adjusting rod is inserted and withdrawn from a lower part of the core.