Core catcher

Abstract

The present invention relates to a core catcher which can improve cooling performance. The core catcher, according to the present invention, comprises: a main body container formed to accommodate a molten core material which has descended from the nuclear reactor pressure vessel and having sloped surfaces, which correspond to each other, in the lower part thereof; and a lower structure spaced apart from the lower part of the main body container to form a cooling channel therebetween and having a coolant inlet for supplying the coolant to the cooling channel along the central part of the lower structure, wherein the bottom surface of the main body container is formed in a wavy shape so as to increase the contact surface area with the coolant.

Description

Core Catcher

[0001] The present invention relates to a core catcher, and more particularly, to a core catcher capable of improving cooling performance.

[0002] Typically, in the event of a major accident at a nuclear power plant, core melt may be released into the lower part of the reactor through a damaged part of the reactor pressure vessel, which may cause radioactive materials to leak outside, resulting in casualties and serious environmental pollution.

[0003] To respond to a major accident at a nuclear power plant, a core catcher is installed to contain and cool the molten core.

[0004] FIG. 4 and FIG. 5 are drawings for explaining a conventional core catcher. The conventional core catcher includes a main body container (100) that accommodates core melt (10) and a lower structure (200) installed at the lower portion of the main body container (100).

[0005] An unillustrated support is placed between the main body container (100) and the lower structure (200), so that the main body container (100) can be supported on the lower structure (200), and a first cooling path (502) is formed between the lower structure (200) and the main body container (100) while maintaining a certain distance therebetween, through which cooling water can flow.

[0006] The main body container (100) is formed with a lower slope (102) in the shape of an inverted roof, and a border wall (104) extending upward from an end of the lower slope (102). The lower slope (102) and the border wall (104) constituting the main body container (100) are formed in opposite directions, so that the lower slope (102) has a V-shape with an obtuse cross-section.

[0007] The lower structure (200) is composed of an upper inclined surface (202) and a border wall surface (204) extending upward from an end of the upper inclined surface (202).

[0008] A pressure-maintaining structure (20) filled with cooling water is positioned at a distance from the outside of the lower structure (200), so that a second cooling passage (504) is formed between the lower structure (200) and the pressure-maintaining structure (20).

[0009] And, the cooling channels (502)(504) are connected to the reloading water tank (30) in the reactor building and the supply pipe (32) so that cooling water is supplied to the first cooling channel (502) formed between the lower structure (200) and the main body container (100) and the second cooling channel (504) formed between the lower structure (200) and the pressure maintenance structure (20).

[0010] A core catcher like this can cool the core molten material (10) contained in the main body container (100) by allowing coolant to flow through the cooling channels (502)(504) in the event of a major accident at a nuclear power plant.

[0011] However, in the case of the conventional core catcher, when the coolant is cooled, the part relatively close to the core melt (10) easily evaporates, generating a large amount of bubbles, and thus the cooling efficiency of the core melt (10) is reduced due to these bubbles.

[0012] In addition, since there are multiple cooling channels (502)(504) at the cooling water entry point, the cooling water circulation flow is not initially formed as intended.

[0013] In addition, since the height of the edge wall (104) of the main body container (100) constituting the core catcher structure and the edge wall (204) of the lower structure (200) are the same, there is a risk of a steam explosion due to overflowing of the edge wall (104) of the main body container (100) at the initial stage of cooling water supply.

[0014] Therefore, a method is needed to improve the cooling performance of the core catcher center by increasing the contact area between the coolant and the core catcher structure, create a coolant circulation flow, and prevent the coolant from coming into direct contact with the core melt (10) at the initial stage of cooling.

[0015] Meanwhile, it is necessary to prepare for the case where the core catcher structure collapses and becomes unable to function due to the impact of an extreme disaster, and it is also necessary to secure an extra cooling water source in addition to the reloading water tank (30) in the reactor building.

[0016] The present invention has been proposed to solve the conventional problems as described above, and an object of the present invention is to provide a core catcher configured to improve cooling performance.

[0017] The core catcher proposed by the present invention comprises a main body container formed to receive core melt dropped from a reactor pressure vessel and having a lower portion having inclined surfaces corresponding to each other; a lower structure installed while maintaining a gap with the lower portion of the main body container to form a cooling channel and having a cooling water inlet formed along the center portion thereof to supply cooling water to the cooling channel;

[0018] The lower surface of the above main body container provides a core catcher formed in a wave shape to increase the contact area of ​​the coolant.

[0019] The cooling path formed between the main body container and the lower structure is structured so that the cross-sectional area is large in the central part of the main body container so that the cooling flow rate increases, and the cross-sectional area gradually decreases as it goes toward the edge of the main body container.

[0020] A border wall is formed at each end of the edge of the main body container and the lower structure, and the border wall of the main body container is formed higher than the border wall of the lower structure.

[0021] The cooling water introduced through the cooling water inlet is configured to pass through the cooling passage, then return through the circulation passage in the space between the outer surface of the lower structure and the inner surface of the pressure-maintaining structure, and then return to the cooling water inlet.

[0022] A check valve is provided in the above circulation path to ensure that the coolant flows only toward the coolant inlet.

[0023] The above-mentioned substructure is composed of a sacrificial material capable of absorbing thermal shock for core melting and preventing reaction with concrete even if the main body container is damaged.

[0024] The above cooling path is configured so that cooling water can be supplied through a supply pipe connected to a reload water tank, and a passive condensing cooling water tank is connected to the supply pipe through a connecting pipe so that additional cooling water can be supplied, and a three-way valve and a check valve are provided in the connecting pipe.

[0025] The core catcher according to the present invention can expand the contact area of ​​the coolant by forming the lower bottom surface of the main body container in a wave shape, and further, the cooling flow path formed between the main body container and the lower structure has a large cross-sectional area in the central portion where the coolant flows in and gradually decreases in cross-sectional area toward the edge, so that the flow rate and velocity of the coolant act differently depending on the portion of the core catcher, thereby improving the cooling efficiency.

[0026] In addition, the rim wall of the main body container is formed higher than the rim wall of the lower structure, thereby preventing the coolant flowing along the cooling channel from overflowing into the core melt in the early stage of cooling, thereby preventing a steam explosion.

[0027] Figure 1 is a cross-sectional perspective view of the main part of the core catcher according to the present invention.

[0028] Figure 2 is a configuration diagram of a core catcher according to the present invention.

[0029] Figure 3 is a drawing for explaining the introduction of cooling water in a core catcher according to the present invention.

[0030] Figure 4 is a cross-sectional perspective view of the main part of a core catcher of a conventional technique.

[0031] Figure 5 is a configuration diagram of a core catcher of the prior art.

[0032] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0033] Fig. 1 is a cross-sectional perspective view of the main part of a core catcher according to the present invention, Fig. 2 is a configuration diagram of a core catcher according to the present invention, and Fig. 3 is a drawing for explaining the introduction of cooling water in a core catcher according to the present invention.

[0034] A core catcher may be installed in the lower cavity of a reactor pressure vessel to receive and cool the core melt (10) falling from the reactor pressure vessel in the event of a major accident at a nuclear power plant, thereby preventing mutual reaction between the core melt (10) and the pressure-retaining structure (20) of the reactor building.

[0035] A core catcher according to one embodiment of the present invention includes a main body container (100) and a lower structure (200).

[0036] The main body container (100) includes a lower slope (102) formed in the shape of an inverted roof, and a border wall (104) extending upward from an end of the lower slope (102).

[0037] The lower slope (102) and the edge wall (104) constituting the main body container (100) are formed in opposite directions, so that the lower slope (102) has a V-shape with an obtuse cross-section.

[0038] The lower structure (200) includes an upper inclined surface (202) and a border wall surface (204) extending upward from an end of the upper inclined surface (202).

[0039] A plurality of supports (not shown) are arranged between the lower structure (200) and the main body container (100), so that the main body container (100) is supported with a gap between the lower structure (200), and a cooling path (300) formed as an integrated space is formed between the lower structure (200) and the main body container (100).

[0040] Additionally, a ditch-shaped cooling water inlet (302) is formed along the central portion of the lower structure (200) to supply cooling water to the cooling channel (300).

[0041] A pressure-maintaining structure (20) is positioned at a distance from the outside of the lower structure (200), and accordingly, a circulation path (304) connected to a cooling path (300) is formed between the lower structure (200) and the pressure-maintaining structure (20), so that cooling water can circulate.

[0042] A check valve (306) (308) is installed in the circulation path (304) so ​​that the cooling water in the circulation path (304) can only flow toward the cooling water inlet (302).

[0043] In addition, the core catcher according to the present invention is configured such that the bottom surface of the lower slope (102) of the main body container (100) is formed in a wave shape (106) to increase the contact area of ​​the coolant. With this structure, the contact area of ​​the coolant flowing in the cooling channel (300) is expanded accordingly, thereby increasing the cooling efficiency.

[0044] The cooling passage (300) formed between the main body container (100) and the lower structure (200) is formed by widening the gap between the lower structures (200) toward the center of the main body container (100) so that the amount of cooling fluid flowing in increases, and is structured so that the gap between the lower structures (200) becomes narrower toward the edge of the main body container (100).

[0045] Accordingly, the central part of the main body container (100) where a lot of core melt (10) is accumulated and is thick can have a large cooling flow rate and a slow flow rate, and as it goes toward the edge of the main body container (100), the cooling flow rate relatively decreases and the flow rate increases, so that the cooling efficiency of the central part of the main body container (100) where the amount of core melt (10) is large can be increased. For this reason, it is possible to prevent evaporation from easily occurring in the part where the accumulated amount of core melt (10) is large, thereby preventing a large amount of bubbles from being generated, thereby preventing the cooling efficiency of the core melt (10) from decreasing due to bubbles.

[0046] In addition, the core catcher according to the present invention has a rim wall surface (104) of the main body container (100) formed higher than the rim wall surface (204) of the lower structure (200), so that when supplying coolant, the coolant can be prevented from initially overflowing the rim wall surface (104) of the main body container (100), thereby preventing the risk of a steam explosion caused by this.

[0047] And the substructure (200) can be made of a sacrificial material that can absorb thermal shock for the core melt (10) and prevent reaction with the substructure (200) made of concrete even if the main body container (100) is damaged and loses its function.

[0048] The core catcher as described above is filled with cooling water inside the pressure maintenance structure (20), and in the event of a major accident at a nuclear power plant, cooling water supplied from the reload water tank (IRWST) (30) within the containment building is supplied to the cooling water inlet (302) through the supply pipe (32).

[0049] Accordingly, the cooling water supplied to the cooling water inlet (302) passes through the cooling path (300) between the main body container (100) and the lower structure (200), passes between the edge wall surface (102) of the main body container (100) and the edge wall surface (202) of the lower structure (200), and then circulates through the circulation path (304) of the space between the outer surface of the lower structure (200) and the inner surface of the pressure-maintaining structure (20) to return to the cooling water inlet (302) and cool.

[0050] When supplying cooling water in the initial stage of the cooling action, the edge wall (104) of the main body container (100) is formed higher than the edge wall (206) of the lower structure (200), thereby preventing the cooling water from overflowing the edge wall (104) of the main body container (100), thereby preventing the risk of a steam explosion.

[0051] And when performing a cooling action, the bottom surface of the lower slope (102) of the main body container (100) is formed in a wave shape (106), thereby increasing the contact area of ​​the cooling water, thereby improving the cooling efficiency.

[0052] In addition, the cooling channel (300) has a large cross-sectional area toward the center of the main body container (100) and gradually decreases in cross-sectional area toward the edge of the main body container (100), so that the central part of the main body container (100) where a lot of core melt (10) has accumulated has a large amount of cooling flow and a slow flow rate, and as it goes toward the edge of the main body container (100), the cooling flow rate relatively decreases and the flow rate increases, so that the cooling efficiency of the central part of the main body container (100) where the amount of core melt (10) is large is greatly increased.

[0053] In this way, the cooling water supplied from the reload water tank (IRWST) (30) in the containment building is supplied to the cooling water inlet (302) through the supply pipe (32), and the cooling water flows through the cooling path (300) and then returns through the circulation path (304) to circulate and cool the core molten material (10). At this time, when the cooling water inventory of the reload water tank (30) is insufficient, the passive condensation cooling water tank (40) is connected to the connecting pipe (42) as shown in FIGS. 2 and 3 so that cooling water can be supplied separately, and this connecting pipe (42) is connected to the supply pipe (32).

[0054] A three-way valve (44) is connected to one end of the connecting pipe (42), and a check valve (46) is connected to the other end, so that the cooling water of the passive condensing cooling water tank (40) can only flow toward the supply pipe (32), and the cooling water of the supply pipe (32) is prevented from flowing toward the connecting pipe (42).

[0055] The passive condensation cooling water tank (40) is installed much higher than the location of the reload water tank (30) inside the reactor building, so that additional cooling water can be supplied by the water head difference due to gravity.

[0056] Although the preferred embodiments of the present invention have been described above for illustrative purposes, they are not limited thereto, and various modifications may be made within the scope of the claims, the detailed description of the invention, and the attached drawings.

Claims

1. A main body container formed to receive the core molten material that has fallen from the reactor pressure vessel and having a lower portion with inclined surfaces corresponding to each other; A lower structure formed with a cooling water inlet that supplies cooling water to the cooling water path along the center of the lower part of the main body container and is installed while maintaining a gap therebetween to form a cooling path; Including, The lower surface of the above main body container is a core catcher formed in a wave shape to increase the contact area with the coolant.

2. In claim 1, A core catcher having a structure in which the cooling path formed between the main body container and the lower structure has a large cross-sectional area in the central part of the main body container so that the amount of cooling flow increases, and the cross-sectional area gradually decreases as it goes toward the edge of the main body container.

3. In claim 1, A core catcher in which a border wall surface is formed at each end of the edge of the main body container and the lower structure, and the border wall surface of the main body container is formed higher than the border wall surface of the lower structure.

4. In claim 1, A core catcher configured so that the coolant introduced through the above coolant inlet passes through the cooling path, returns through the circulation path in the space between the outer surface of the lower structure and the inner surface of the pressure-maintaining structure, and then returns to the coolant inlet.

5. In claim 4, The above circulation path is provided with a core catcher with a check valve to ensure that the coolant flows only toward the coolant inlet.

6. In claim 1, The above-mentioned substructure is a core catcher made of a sacrificial material capable of absorbing thermal shock for core melting and preventing reaction with concrete even if the above-mentioned main body container is damaged.

7. In claim 1, The above cooling path is configured so that cooling water can be supplied through a supply line connected to a reload water tank, and a core catcher configured so that a passive condensing cooling water tank is connected to the supply line through a connecting line so that cooling water can be additionally supplied.

8. In claim 7, A core catcher provided with a three-way valve and a check valve in the above connecting pipe.

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