Core catcher

Abstract

The present invention relates to a core catcher configured to facilitate the flow of cooling water and improve cooling performance. The core catcher of the present invention comprises: a main body container formed to accommodate a core melt dropped from a nuclear reactor pressure container and having the bottom formed of inclined surfaces corresponding to each other; a lower structure installed to be spaced apart from the bottom of the main body container to form a cooling flow path and having a cooling water inlet for supplying cooling water to the cooling flow path along the center thereof; a plurality of supports installed to maintain a space between the main body container and the lower structure; and cross-flow / down-flow isolation partition walls installed at respective longitudinal ends of the cooling flow path to reduce irregular cross-flow and down-flow of the cooling water flowing through the cooling flow path.

Description

Core Catcher

[0001] The present invention relates to a core catcher, and more particularly, to a core catcher capable of facilitating the flow of coolant and 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, causing radioactive materials to leak outside, potentially causing 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 core melt.

[0004] The core catcher includes a main body container that receives the core molten material, and a lower structure that is arranged with a space between the lower surface of the main body container and the space therebetween to form a cooling path through which coolant can flow.

[0005] Figures 8 and 9 are drawings showing the lower structure constituting a conventional core catcher. The core catcher is formed by extending one side in the transverse direction, and the lower structure is formed by an inclined bottom surface and a border wall surface extending upward from the end of the bottom surface.

[0006] These substructures are arranged with two members facing each other, and a plurality of supports are arranged at intervals on the upper portion thereof, and a main body container is supported on the upper portion thereof, thereby forming a cooling path through which cooling water can flow between the substructure and the main body container.

[0007] However, in the case of conventional core catchers, due to reasons such as the shape of the cooling channel and the heat flux distribution within the core catcher, cross-flow of the cooling water and downward flow at the long-axis end may occur in a wide area of ​​the cooling channel, which may locally cause cooling water stagnation and high-foaming areas due to accumulation of intermediate gases.

[0008] Therefore, the degree and period of this phenomenon are highly variable, which may cause instability in the coolant flow through the cooling channel and local deterioration or uncertainty in cooling performance.

[0009] In addition, as shown in Fig. 9, irregular downward and cross-flows of coolant may occur locally between the rim wall of the main body container and the rim wall of the lower structure, which may cause instability in coolant flow and local deterioration or uncertainty in cooling performance.

[0010] And when supplying coolant to the cooling channel, the coolant inflow is only through a single connection point, so the coolant inflow is concentrated in one place, which may cause overall coolant flow obstruction and cooling performance imbalance due to the influence of the degree of subcooling of the inflow coolant, etc., and the coolant inflow part forms an open flow path in the longitudinal direction, which causes flow instability and reduced cooling performance due to the cross-flow of the coolant.

[0011] 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 facilitate the flow of coolant and improve cooling performance.

[0012] 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 formed to maintain 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; a plurality of supports installed to maintain a space between the main body container and the lower structure; and cross-flow / downflow isolation bulkheads installed at each of the longitudinal ends of the cooling channel to reduce irregular cross-flow and downward flow of cooling water flowing in the cooling channel.

[0013] One or more slit supports having a plurality of gaps formed between the main body container and the lower structure may be provided.

[0014] The cooling water supplied through the cooling channel formed between the main body container and the lower structure is configured to be supplied while being distributed to multiple locations through the cooling water distribution pipe.

[0015] The outlet of the above cooling water distribution pipe is formed so that cooling water can be discharged between the supports, and a plurality of baffles are formed in the cooling water inlet of the lower structure to suppress the cross flow of cooling water supplied to the cooling channel.

[0016] The cooling water introduced into the cooling water inlet is configured to pass through the cooling path between the main body container and the lower structure, pass through the space between the rim wall of the main body container and the rim wall of the lower structure, and then move through the precipitation portion of 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 and be circulated, and the precipitation portion is provided at least one at each longitudinal end of the core catcher.

[0017] The core catcher according to the present invention is provided with cross-flow / downflow isolation baffles at both ends between the main body container and the lower structure, and a slit support is provided along the between the main body container and the lower structure, thereby reducing the occurrence of cross-flow and downflow that may occur in the cooling flow path, thereby preventing a decrease in cooling performance.

[0018] In addition, the cooling water supplied to the cooling water inlet is supplied while being distributed to multiple locations through the cooling water distribution pipe, thereby eliminating the transverse flow instability of the cooling water that may occur in the cooling path.

[0019] In addition, a precipitation part is provided at each of the longitudinal ends of the core catcher, so that sufficient cooling water is supplied to both longitudinal ends of the core catcher separated from the cooling channel, thereby preventing a decrease in cooling efficiency.

[0020] Figure 1 is a schematic diagram of a core catcher according to the present invention viewed from the side and front.

[0021] Figure 2 is a perspective view of the main parts of the core catcher according to the present invention.

[0022] Figure 3 is a cross-sectional view of a core catcher according to the present invention.

[0023] FIG. 4 is a drawing for explaining a bulkhead provided in a core catcher according to the present invention.

[0024] FIG. 5 is a drawing for explaining a slit support provided in a core catcher according to the present invention.

[0025] Figure 6 is a drawing for explaining a cooling water supply unit provided in a core catcher according to the present invention.

[0026] FIG. 7 is a drawing for explaining a baffle provided in a cooling water inlet of a core catcher according to the present invention.

[0027] Figures 8 and 9 are drawings for explaining the flow state of coolant flowing through a cooling channel in a core catcher of a conventional technology.

[0028] Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the attached drawings.

[0029] FIG. 1 is a schematic diagram of a core catcher according to the present invention, FIG. 2 and FIG. 3 are perspective views and cross-sectional views of main parts of a core catcher according to the present invention, and FIG. 4 to FIG. 7 show drawings for explaining main parts provided in a core catcher according to the present invention.

[0030] A core catcher is installed in the lower cavity of a reactor pressure vessel to receive and cool the core melt (10) that falls 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-maintaining structure (20) of the reactor building.

[0031] A core catcher according to one embodiment of the present invention includes a main body container (100), a lower structure (200), and a support (300).

[0032] 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).

[0033] 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.

[0034] 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).

[0035] A plurality of supports (300) are arranged to maintain a gap between the lower structure (200) and the main body container (100), so that the main body container (100) is supported by the lower structure (200), and a cooling path (400) is formed as a single integrated space while maintaining a constant gap between the lower structure (200) and the main body container (100).

[0036] Additionally, a ditch-shaped cooling water inlet (402) is formed along the central portion of the lower structure (200) so as to supply cooling water to the cooling channel (400).

[0037] A pressure-maintaining structure (200) is positioned at a distance from the outside of the lower structure (200), and accordingly, a precipitation portion (404) communicating with a cooling channel (400) is formed between the lower structure (200) and the pressure-maintaining structure (20), so that cooling water can flow.

[0038] The inside of the pressure-retaining structure (20) is filled with cooling water, and in the event of a major accident at a nuclear power plant, cooling water supplied from the in-containment reload tank (IRWST) (30) can be supplied to the cooling water inlet (402) through the cooling water supply line (40), and accordingly, the cooling water supplied to the cooling water inlet (402) passes through the cooling channel (400) 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 moves downward through the downwelling portion (404) of the space between the outer surface of the lower structure (200) and the inner surface of the pressure-retaining structure (20) and returns to the cooling water inlet (402), thereby performing a cooling effect through a co-current natural circulation.

[0039] At this time, due to reasons such as heat flux distribution within the core catcher, cross-flow of the cooling water occurs in a wide area of ​​the cooling channel (400) and downward flow occurs at the longitudinal end of the long axis of the core catcher, which may cause localized flow stagnation and high-foaming areas of the cooling water. Therefore, to resolve this, as shown in FIG. 4, a yellow flow / downward flow isolation partition (406) is installed at each of the longitudinal ends of the cooling channel (400).

[0040] By using this cross-flow / downflow isolation baffle (406), irregular cross-flow and downward flow of the cooling water flowing in the cooling channel (400) at the longitudinal end of the core catcher can be reduced, thereby eliminating the flow instability of the cooling water flowing in the cooling channel (400).

[0041] And, in order to supply sufficient recirculation flow rate between the edge wall (104) of the main body container (100) at both ends in the longitudinal direction separated from the cooling path (400) by the isolation bulkhead (406) and the edge wall (204) of the lower structure (200), one or more precipitation parts (404) may be provided at each of the transverse (long-axis) ends of the core catcher (see Fig. 1).

[0042] FIG. 5 is a structure for reducing irregular cross-flow and downward flow of local cooling water that may occur between the edge wall (104) of the main body container (100) and the edge wall (204) of the lower structure (200). To this end, one or more slit supports (408) are provided between the main body container (100) and the lower structure (200).

[0043] The slit support (408) is installed separately from the scattered support (300) and can be installed between the support (300).

[0044] The slit support (408) can be formed to support the main body container (100), and a plurality of gaps (410) are formed in the slit support (408) to allow cooling water to flow.

[0045] These slit supports (408) reduce the flow area for the longitudinal (transverse) coolant flow (crossflow) of the core catcher and increase the flow resistance, thereby reducing the crossflow momentum. In this way, when the crossflow between the regions of the cooling channel (400) separated by the slit supports (408) is reduced, the accumulation (concentration) of steam that may occur locally in the cooling channel (400) is alleviated, thereby reducing the occurrence of downward flow.

[0046] The size of the gap (410) formed in the slit support (408) is preferably formed to a size suitable for maintaining a stable natural convection abnormal flow through pressure equilibrium of the cooling water flowing in the cooling channel (400). The shape of the gap (410) is shown as being rectangular in this embodiment, but may be formed in various shapes such as a slit, circle, or oval.

[0047] In addition, the core catcher of the present invention provides a structure to prevent transverse flow instability of the cooling water that may occur throughout the cooling channel (400) as shown in FIG. 6.

[0048] To this end, when supplying the cooling water from the reload tank (30), which is the supply unit, to the cooling water inlet (402) through the cooling water supply pipe (40), the cooling water supply pipe (40) can be configured to be supplied in a distributed manner to multiple locations by connecting the cooling water distribution pipe (412).

[0049] The end of the cooling water distribution pipe (412) is positioned between the supports (300) so that cooling water can be supplied evenly distributed over the entire surface of the cooling path (400) between the supports (300).

[0050] In addition, the core catcher of the present invention has a plurality of partition walls (414) formed in the lower structure (200) to suppress the cross flow of cooling water supplied to the cooling channel (400) as shown in FIG. 7.

[0051] Due to this bulkhead (414), when supplying coolant to the cooling channel (400), it is possible to suppress transverse (long-axis) flow rate vibration that may occur within the coolant inlet (402).

[0052] 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 accommodate the core melt that has fallen from the reactor pressure vessel and having a lower portion with inclined surfaces corresponding to each other; A lower structure having a cooling water inlet formed along the center of the lower part of the main body container to form a cooling channel while maintaining a gap therebetween; and supplying cooling water to the cooling channel; A plurality of supports installed to maintain space between the main body container and the lower structure; A cross-flow / downflow isolation bulkhead installed at each of the longitudinal ends of the cooling channel to reduce irregular cross-flow and downward flow of the cooling water flowing through the cooling channel; Core catcher containing .

2. In claim 1, A core catcher provided with one or more slit supports having a plurality of gaps formed between the main body container and the lower structure.

3. In claim 1, A core catcher configured so that the cooling water supplied through the cooling channel formed between the main body container and the lower structure is distributed to multiple locations through the cooling water distribution pipe.

4. In claim 3, The outlet of the above cooling water distribution pipe is a core catcher configured to allow cooling water to be discharged between the supports.

5. In claim 1, A core catcher having multiple baffles formed in the cooling water inlet of the above-mentioned lower structure to suppress the cross flow of cooling water supplied to the cooling channel.

6. In claim 1, The cooling water flowing into the cooling water inlet is made to pass through the cooling path between the main body container and the lower structure, pass through the space between the rim wall of the main body container and the rim wall of the lower structure, and then move through the precipitation part of 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 so that it can be circulated. The above-mentioned precipitation unit is a core catcher provided at least once at each longitudinal end of the core catcher.

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