KR101404954B1 - Method Of Nuclear Corium Cooling Using Liquid Metal Layer, And Nuclear Corium Cooling System Using The Same - Google Patents

Abstract

A reactor core melt cooling system according to the present invention includes: a reactor vessel including a core melt; A reactor cavity having the reactor vessel therein; And a liquid metal layer disposed at the bottom of the reactor cavity, wherein the reactor core is cooled by the liquid metal layer when the core melt leaks from the reactor vessel to the reactor cavity, And is configured to be blocked by a metal layer.

Description

TECHNICAL FIELD [0001] The present invention relates to a method of cooling a core melt using a liquid metal layer and a cooling system using the same,

The present invention relates to a method for cooling a core melt using a liquid metal layer and a reactor cooling system using the same. More particularly, the present invention relates to a reactor cooling system using a liquid metal layer, The present invention relates to a method of cooling a core melt using a liquid metal layer and a reactor cooling system using the liquid metal layer, which can solve the problem of continuous leakage of radioactive material due to exposure of a radioactive material to a containment vessel.

Reactors are seriously damaged due to serious damage to the reactor core when reactor safety cooling or reaction control is not properly performed due to malfunction of various safety equipment designed according to the stability evaluation. The major phenomena of such serious accidents are hydrogen generation and explosion due to the oxidation of nuclear fuel cladding materials, melting of nuclear fuel and the behavior of fused nuclear fuel in reactor vessel, reactor vessel damage, steam explosion, direct heating of reactor building (Reactor Containment Building) Concrete reaction and containment building overpressure. In particular, the phenomenon that directly affects the total damage level of serious accidents is damage of containment building which occurs mainly after the reactor vessel is broken. Many phenomena of such serious accidents are very uncertain and complicated, and it is difficult to analyze and manage serious accidents.

In recent years, the reactor outer wall cooling technology, which prevents the reactor vessel from being damaged by removing the decay heat generated from the core melt inside the reactor vessel by submerging the outer wall of the reactor vessel in case of a serious accident, As a result, many overseas light water reactors tend to incorporate these reactor exterior wall cooling technologies into consideration. An example is the reactor exterior wall cooling method in the new light water reactor AP1000 of Westinghouse, USA, shown in FIG.

According to this method, when a serious accident occurs in which the core of the reactor is melted and the core melt 125 is generated, the cooling water is injected into the reactor cavity 140 so as to flow from the bottom of the reactor cavity 140 to the primary pipe 150) The space up to the junction is filled with cooling water to submerge the outer wall of the reactor. When the cooling water is filled in the reactor cavity 140, the cooling water inlet 134 under the heat shield 130 is opened by the pressure of the filled cooling water, and the cooling water flows into the heat shield 130 through the cooling water inlet 134, Is discharged to the reactor cavity (140) through the cooling water outlet (135) located above the heat shield (130) along the outer wall of the reactor vessel (120) by natural convection.

In other words, the cooling water continuously circulates in the order of the reactor cavity 140, the cooling water inlet 134, the inside of the heat shield 130, the cooling water outlet 135, and the reactor cavity 140 in order to cool the outer wall of the reactor .

This method of cooling the outer wall of the reactor by the co-immersion of the reactor has been adopted as a method of cooling the outer wall of the reactor in most of the light water reactors both domestically and abroad. In addition, water is generally used as the cooling water in consideration of cost and ease of acquisition.

However, when water is used as the cooling water, the reactor core melt 125 flows through the reactor vessel 120 to the reactor cavity 140, or the reactor core melt 125 is heated by the heat shield 130 and the reactor core When the water in the reactor 140 is evaporated and the outer wall of the reactor is covered with the vapor film, a critical heat flux phenomenon occurs and the heat removal capability is limited, thereby damaging the reactor and eventually causing the core melt to leak out.

These outflows of core water content are caused by vapor explosion caused by meeting hot coolant with cool water when the core melt is leaked out of the core, MCCI phenomenon caused by meeting with concrete, and radioactive material is exposed to the containment vessel, There has been a problem in that it occurs continuously.

Korean Registered Patent No. 10-0549862 (2006. 01. 31)

SUMMARY OF THE INVENTION The present invention has been made in order to solve the above-mentioned problems, and an object of the present invention is to provide a method and a device for preventing the leakage of a core melt, The present invention provides a method for cooling a core melt using a liquid metal layer and a reactor cooling system using the liquid metal layer, which can solve the problem that the radioactive material is exposed to the containment vessel and the outflow of the radioactive material continuously occurs.

According to an aspect of the present invention, there is provided a reactor core melt cooling system including: a reactor vessel including a core melt; A reactor cavity having the reactor vessel therein; And a liquid metal layer disposed at the bottom of the reactor cavity, wherein the reactor core is cooled by the liquid metal layer when the core melt leaks from the reactor vessel to the reactor cavity, And is configured to be blocked by a metal layer.

Wherein the liquid metal storage tank is located above the reactor cavity so that upon occurrence of a leakage of the core melt, the liquid metal is forced into the reactor by gravity, And is configured to be provided inside the cavity.

The liquid metal storage tank includes a heating device for maintaining the liquid metal in a liquid state.

Alternatively, the liquid metal layer may already be present in the reactor cavity bottom, regardless of the leakage of the core melt.

Here, the density of the liquid metal constituting the liquid metal layer is lower than the density of the core melt, whereby the core melt leaking onto the liquid metal layer is arranged to be repositioned below the liquid metal layer.

With this density-based relocation arrangement, the heat removed from the core melt is transferred to the liquid metal layer relocated on the core melt and then finally transferred to the circulating cooling water provided on the liquid metal layer.

And a coolant separator installed inside the reactor cavity to avoid direct contact between the coolant and the core melt and direct contact between the core melt and the liquid metal layer.

The cooling water is provided in a space between the cooling water separator and the outer wall of the reactor cavity to the top or lower of the cooling water separator.

The cooling water may rise up to a level exceeding the height of the cooling water separator and contact the entire upper surface of the liquid metal layer as the core melt is leaked. Alternatively, the cooling water may be further supplied to the space, The cooling water may rise to a level exceeding the height of the cooling water separator and the cooling water may thereby be brought into contact with the entire upper surface of the liquid metal layer.

Alternatively, the cooling water is initially placed in the reactor cavity to provide a cooling system without the supply of external water.

According to another aspect of the present invention, there is provided a method of cooling a core of a reactor core by using a liquid metal layer provided at a bottom of the reactor core to cool the core core melt through the liquid metal layer, And to block the radioactivity from the core melt by the liquid metal layer.

According to the cooling method of the core melt using the liquid metal layer and the reactor cooling system using the liquid metal layer according to the present invention, the possibility of the steam explosion occurring when the core melt heated to about 2800 degrees and the cold cooling water meet is eliminated, To minimize the occurrence of MCCI phenomenon, and to suppress the leakage of the radioactive material from the core melt.

In addition, since the piping and IRWST facilities for filling the existing cooling water can be used as they are, it is possible to apply the present invention to a new power source as well as a new power source without additional cost.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic configuration example of a reactor core melt cooling system according to the present invention,
FIG. 2 is a conceptual diagram of a reactor core melt cooling system according to the present invention, showing a configuration of a position of a liquid metal layer in a power plant,
FIG. 3 is a conceptual view illustrating a reactor core melt cooling scenario according to the present invention in the event of external leakage of core melt;
Figs. 4A to 4D are exemplary configuration diagrams of Fig. 3,
Figure 5 is another exemplary configuration of Figure 3,
FIG. 6 is a view for explaining a general nuclear reactor outer wall cooling method according to the related art.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms and words used in the present specification and claims should not be construed in a conventional or dictionary sense, and the inventor should appropriately define the concept of the term to describe its invention in the best possible way It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, at the time of the present application, It should be understood that there may be water and variations.

2 is a conceptual diagram of a reactor core melt cooling system according to the present invention, showing a configuration of a position of a liquid metal layer in a power plant, and Fig. 3 is a schematic view showing a core molten metal cooling system Fig. 4 is a schematic view showing the nuclear reactor cooling system according to the present invention, Fig. 4 is a schematic view of Fig. 3, Fig. 5 is a schematic view of another embodiment of Fig. 3, Fig. 3 is a view for explaining a general nuclear reactor outer wall cooling method according to the present invention.

Basic cooling system structure

A reactor core melt cooling system using a liquid metal layer is described as an example.

1, the system according to the present invention includes a heat shield 20 surrounding the outer wall of the reactor vessel at a predetermined distance from the reactor vessel 10, and a heat shield 20 surrounding the heat shield 20 and the reactor vessel 10, And a reactor cavity 30 in which the reactor core 30 is disposed.

Here, as shown in FIG. 2, a liquid metal layer is additionally provided at the reactor cavity bottom, which removes the core melt at about 2800 degrees by direct contact with the reactor core melt leaking from the reactor core, The heat removed by the liquid metal layer is configured to be transferred to the circulating cooling water and finally removed. That is, when the core melt is leaked from the reactor vessel to the reactor cavity, it is cooled by the liquid metal layer while blocking the radioactivity from the core melt by the liquid metal layer.

This liquid metal is stored in a separate liquid metal storage tank (50). As shown in FIG. 1, the liquid metal storage tank 50 is installed above the reactor cavity 30. The reason for this is that the liquid metal is supplied to the inside of the reactor cavity 30 by gravity. By adopting the gravity-based addition strategy, which is the passive stabilization system, it is possible to operate even in the case of a power loss accident of the power plant. Of course, it is also possible to force transfer through a pump or the like.

Although not shown, the liquid metal storage tank 50 is provided with a heating device to maintain the liquid metal in a liquid state.

The liquid metal layer can be provided at the bottom of the reactor cavity 30 in two ways, the first being provided only at the core melt leakage accident, or alternatively, the liquid metal layer can be provided to the core melt 30 It may already be provided in the reactor cavity bottom without the

Gallium, or alloys thereof, which may be applied to the present invention. The gallium material itself, which is a liquid metal, corresponds to what is known to those skilled in the art, and therefore, a detailed description thereof will be omitted.

However, although not limited to a specific material, the density of the liquid metal constituting at least the liquid metal layer must be lower than the density of the core melt, which will be described with reference to Fig.

First, as shown in FIG. 3, when an external leakage accident occurs in the core melt, the core melt falls on the liquid metal layer provided in the lower portion of the reactor cavity.

Thereafter, the core melt leaking onto the liquid metal layer due to the density difference between the core melt and the liquid metal layer is relocated under the liquid metal layer.

With this density-based relocation arrangement, the heat removed from the core melt is transferred to the liquid metal layer relocated on the core melt and then finally transferred to the circulating cooling water provided on the liquid metal layer.

The cooling system for the outer wall of the reactor generally includes a water storage tank 40 for storing cooling water therein and a water storage tank 40 having one end connected to the water storage tank 40 and the other end connected to the lower portion of the reactor cavity 30 or the heat shield 20 Cooling water injection pipes 60 and 61 connected to each other to form a passage through which the cooling water of the water storage tank 40 is injected into the reactor cavity 30 or the heat shield 20, 50 and the other end of which communicates with the inner space of the reactor cavity 30 to form a moving path of the liquid metal.

The system further includes cooling water injection valves 80 and 81 provided in the cooling water injection pipes 60 and 61 for interrupting the flow of the cooling water injected into the reactor cavity 30 or the heat shield 20, , A liquid metal injection valve (90) provided in the liquid metal injection pipe (70) for interrupting the injection flow of the liquid metal, and a coolant supply pipe (60) composed of the water storage tank (40) And at least one pump (100) provided in the system and pumping the cooling water.

As shown in FIG. 1, the reactor outer wall cooling system includes a water storage tank 40, a cooling water injection pipe 60, a liquid metal storage tank 60, A tank 50, a liquid metal injection pipe 70, and a coolant pump 100.

In the water storage tank 40, cooling water (water) for cooling the outer wall of the reactor vessel 10 is stored in the middle-large-and-large gasification reactor in which the core is melted. refueling water storage tank (IRWST)) is used as the water storage tank (40), a cooling system can be constructed by using existing facilities without additional water storage facilities.

One end of the cooling water injection pipes 60 and 61 may be connected to the water storage tank 40 and the other end may be connected to a lower portion of the reactor cavity 30 or a lower portion of the heat shield 20.

The cooling water pump 100 is provided on the path of the cooling water injection pipes 60 and 61 to forcibly pump the cooling water stored in the water storage tank 40 to supply cooling water.

In this way, the water tank 40, the cooling water injection pipes 60 and 61, the cooling water pump 100, the liquid metal storage tank 50 and the liquid metal injection pipe 70 are connected to the inside of the reactor cavity 30 or the heat shield 20 The cooling water of the water storage tank 40 is supplied to the cooling water injection pipe 60 and the cooling water is supplied to the cooling water injection pipe 60. In this case, And injects the liquid metal 51 coolant into the bottom of the reactor cavity 30 through the liquid metal injection pipe 70 to form a liquid metal layer and cool the core melt.

A cooling water injection valve 81 is provided at an outlet side of the cooling water pump 100 in the path of the cooling water injection pipes 60 and 61 to intercept the flow of cooling water supplied through the cooling water injection pipes 60 and 61, A cooling water injection valve 80 is also provided on the outlet side of the cooling water supply pipe 60 to control the flow of cooling water supplied from the water storage tank 40 to the cooling water injection pipes 60 and 61.

In addition, a liquid metal injection valve 90 is provided in the path of the liquid metal injection pipe 70 to interrupt the flow of the liquid metal 51 injected through the liquid metal injection pipe 70.

On the other hand, the position and / or the arrangement of the respective components shown in Fig. 1 are only illustratively shown for the sake of understanding. For example, the liquid metal storage tank 50 may be located anywhere in the containment building 1 It should be noted that

FIGS. 4a to 4d illustrate a nuclear reactor core cooling scenario according to an exemplary embodiment of the present invention in the event of external leakage of core melt.

The cooling system of the reactor core melt according to the present embodiment further includes a cooling water separator 21 installed inside the reactor cavity 30 as shown in FIG. In this embodiment according to FIG. 4, the cooling water separator 21 is retained by the outer side wall of the reactor cavity 30.

1 and 5, the shape of the cooling water separator 21 is maintained by the bottom surface of the reactor cavity 30, and in view of the necessity of providing additional cooling water along with leakage of the core melt, And the basic operation principle is the same.

The coolant separator 21 is provided to avoid direct contact between the cooling water and the core melt and to induce direct contact between the core melt and the liquid metal layer, thereby eliminating the possibility of a steam explosion in which the heated core melt and cold cooling water meet can do.

According to the shape of the cooling water separator, a cooling system is provided according to the following two cases in which the initial cooling water is supplied and the cooling water is not supplied. For reference, two cases are also shown in the drawings. In the first case, if there are complicated structures and pipes that are difficult to modify in the reactor cavity, the cooling water separator is installed at the bottom and the cooling water separator is installed at the bottom.

4A, in order to avoid direct contact of the cooling water from the upper part provided in the space between the cooling water separator 21 and the outer wall of the reactor cavity 30 according to the accident scenario, with the core melt, And separated from the center by a coolant separator (see FIG. 4B).

The total water level gradually increases as the core melt leaks (see FIG. 4C), and the cooling water supplied from the outside as shown in FIG. 4D exceeds the height of the top of the cooling water separator 21, And comes into contact with the entire upper surface of the metal layer.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It is to be understood that various changes and modifications may be made without departing from the scope of the appended claims.

10: Reactor vessel
20: Thermal Shield
21: Cooling water separator
30: Reactor joint
40: Water tank
50: Liquid metal storage tank
60, 61: 1st and 2nd cooling water injection piping
70: Liquid metal injection piping
80,81: Cooling water injection valve
90: Liquid metal injection valve
100: pump
110: Steam generator

Claims (20)

A reactor core melt cooling system,
A reactor vessel containing a core melt therein;
A reactor cavity having the reactor vessel therein; And
A liquid metal layer disposed at the bottom of the reactor cavity;
, ≪ / RTI >
Wherein the liquid metal layer is cooled by the liquid metal layer when the core melt is leaked from the reactor vessel to the reactor cavity, and is blocked by the liquid metal layer from the core melt,
Wherein the density of the liquid metal constituting the liquid metal layer is lower than the density of the core melt so that the core melt leaking onto the liquid metal layer is relocated below the liquid metal layer. .
The method according to claim 1,
Wherein the liquid metal storage tank is located above the reactor cavity so that upon occurrence of a leakage of the core melt, the liquid metal is forced into the reactor by gravity, And the cooling water is supplied to the inside of the cavity.
3. The method of claim 2,
Wherein the liquid metal storage tank comprises a heating device for maintaining the liquid metal in a liquid state.
The method according to claim 1,
Wherein the liquid metal layer is already provided in the reactor cavity bottom regardless of leakage of the core melt.
delete The method according to claim 1,
Wherein the heat removed from the core melt is transferred to the liquid metal layer relocated on the core melt and then finally transferred to the circulating cooling water provided on the liquid metal layer.
The method according to claim 6,
And a coolant separator installed inside the reactor cavity to avoid direct contact between the coolant and the core melt and direct contact between the core melt and the liquid metal layer.
8. The method of claim 7,
Wherein the cooling water is provided in a space between the cooling water separator and an outer wall of the reactor cavity up to a height of the top or lower of the cooling water separator.
9. The method of claim 8,
And the cooling water is raised to a level exceeding the height of the cooling water separator as the core melt is leaked, thereby contacting the entire upper surface of the liquid metal layer.
9. The method of claim 8,
The coolant is further supplied to the space as the core melt is leaked so that the coolant rises to a level exceeding the height of the coolant separator so that the coolant is in contact with the entire upper surface of the liquid metal layer Reactor core melt cooling system.
A method for cooling a reactor core melt,
Wherein the liquid metal layer provided in the reactor cavity bottom is used to block the radioactivity from the core melt by the liquid metal layer while being cooled by the liquid metal layer when the reactor core melt leaks from the reactor vessel to the reactor cavity,
Wherein the density of the liquid metal constituting the liquid metal layer is lower than the density of the core melt so that the core melt leaking onto the liquid metal layer is rearranged below the liquid metal layer . 12. The method of claim 11,
Wherein the liquid metal storage tank is located above the reactor cavity so that upon occurrence of a leakage of the core melt, the liquid metal is forced into the reactor by gravity, Wherein the cooling water is supplied to the inside of the cavity.
13. The method of claim 12,
Wherein the liquid metal storage tank is heated to maintain the liquid metal in a liquid state.
12. The method of claim 11,
Wherein said liquid metal layer is already provided in said reactor cavity bottom regardless of a leakage of core melt.
delete 12. The method of claim 11,
Wherein the heat removed from the core melt is transferred to the liquid metal layer repositioned on the core melt and then finally transferred to the circulating cooling water provided on the liquid metal layer.
17. The method of claim 16,
Wherein a cooling water separator is provided in the reactor cavity to avoid direct contact between the cooling water and the core melt and direct contact between the core melt and the liquid metal layer.
18. The method of claim 17,
Wherein the cooling water is provided in a space between the cooling water separator and an outer wall of the reactor cavity up to a height of the top or lower of the cooling water separator.
19. The method of claim 18,
Wherein the cooling water is raised to a level exceeding a height of the cooling water separator as the core melt is leaked to contact the entire upper surface of the liquid metal layer.
19. The method of claim 18,
The coolant is further supplied to the space as the core melt is leaked so that the coolant rises to a level exceeding the height of the coolant separator so that the coolant is in contact with the entire upper surface of the liquid metal layer Cooling method of reactor core melt.

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