JP5377064B2 - Core melt holding device and nuclear power plant - Google Patents

Description

  The present invention relates to a core melt holding device and a nuclear power plant using the same.

  In a water-cooled nuclear reactor, if cooling water is lost due to the stoppage of water supply to the reactor pressure vessel or the breakage of piping connected to the reactor pressure vessel, the reactor water level falls and the reactor core is exposed and cooled. It may become insufficient. Assuming such a case, the reactor is automatically shut down in response to a water level lowering signal, and the core is submerged and cooled by injecting coolant using an emergency core cooling system (ECCS), and a core melting accident is performed. It is designed to prevent it. However, although the probability is very low, it can be assumed that the emergency core cooling device does not operate and water injection devices for other cores cannot be used. In such a case, the core is exposed due to a decrease in the reactor water level, and sufficient cooling is not performed, and the fuel rod temperature rises due to decay heat that continues to occur after the reactor shuts down, eventually leading to core melting. It is possible.

  When such a situation occurs, the hot core melt (corium) melts into the lower part of the reactor pressure vessel, and further melts through the reactor pressure vessel lower mirror and falls onto the floor in the containment vessel. . Corium heats the concrete stretched on the containment floor, reacts with the concrete when the contact surface becomes hot, generates a large amount of noncondensable gases such as carbon dioxide and hydrogen, and melts and erodes the concrete. The generated non-condensable gas increases the pressure in the containment vessel and may damage the reactor containment vessel. Moreover, the containment vessel boundary may be damaged or the containment vessel structural strength may be reduced due to the melt erosion of concrete. As a result, if the reaction between corium and concrete continues, the containment vessel is damaged, and there is a possibility that radioactive materials in the containment vessel are released to the external environment.

  In order to suppress the reaction between corium and concrete, it is necessary to cool corium and cool the temperature of the contact surface with the concrete at the bottom of the corium to below the erosion temperature or prevent direct contact between corium and concrete. The erosion temperature of general concrete is 1500K or less. Therefore, various countermeasures have been proposed in case the core melt falls. A typical measure is called a core catcher. The core catcher is a facility that collects the fallen core melt with a heat-resistant material and cools the core melt in combination with water injection means.

  Even if cooling water is poured onto the top surface of the core melt that has fallen to the reactor containment floor, if the amount of heat removal at the bottom of the core melt is small, the temperature at the bottom of the core melt will be maintained high due to decay heat. Containment floor may not be able to stop concrete erosion. Therefore, there is a method of cooling the core melt from the bottom surface.

  When cooling by boiling water on the upper surface of the corium by pouring water into the corium, if the corium deposition thickness is thick, the corium bottom cannot be sufficiently cooled. Therefore, it is necessary to increase the floor area and to reduce the corium deposition thickness to a thickness that can be cooled.

However, it is difficult to secure a sufficiently large floor area in designing the containment vessel structure. For example, the decay heat of typical corium is about 1% of the rated heat output, and in the case of a furnace with a rated heat output of 4000 MW, the calorific value is about 40 MW. The boiling heat transfer amount on the upper surface varies depending on the state of the upper surface of the corium, but a heat flux of about 0.4 MW / m ² is assumed as the smaller value. Therefore, when heat generation of about 40 MW is removed only by heat transfer on the top surface of the corium, a floor area of about 100 m ² (circular diameter of 11.3 m) is required. Considering the conventional containment vessel structure, it has been difficult to secure this area.

  On the other hand, there is a method of removing heat from the bottom surface by providing a cooling water flow path below the corium deposition floor surface and guiding the cooling water. In the case of such a structure, it is essential to prevent the cooling water flow path from being melted and eroded and damaged by high-temperature corium. Therefore, there is a method of relaxing melting and thermal expansion due to high-temperature corium by using a high-melting-point tile in a portion in contact with corium (see, for example, Patent Document 1).

JP2005-189043

  When a tile made of a high melting point material is used for a portion in contact with corium, the temperature suddenly rises from about 100 ° C. to about 2000 ° C. when the corium is dropped. The tile may be damaged. In addition, a cooling water flow path is provided below the high melting point material, and the tile of the high melting point material is cooled from below by the cooling water, so the temperature difference between the upper side and the lower side of the tile of the high melting point material is extremely high. Become bigger. Due to the thermal stress generated by the temperature difference between the upper and lower sides of this high melting point material, the tiles of the high melting point material are deformed and the gaps between the tiles become large. The melting point material tile can be damaged.

  Therefore, the present invention aims to suppress the thermal shock caused by a rapid temperature rise when the core melt falls and the damage of the cooling water flow path due to the thermal stress caused by the temperature difference generated between the core melt and the cooling flow path. .

  In order to achieve the above-mentioned object, the present invention provides a core melt holding device provided in a lower space of a reactor pressure vessel, and a water supply vessel connected to a water supply channel extending from an open end that opens to the lower space; A cooling flow path forming body that includes an upper lid on which a protrusion is formed and forms a cooling flow path that extends from the water supply container to the cooling flow path opening that opens to the lower space on the back side of the protrusion of the upper lid. And a heat-resistant layer that includes a heat-resistant element supported by the protrusion on the upper surface of the upper lid and covers the upper surface of the upper lid.

  Further, the present invention is provided in a nuclear power plant in a reactor pressure vessel that houses a reactor, a containment vessel that houses the reactor pressure vessel, and a lower space of the reactor pressure vessel inside the containment vessel. A water supply container connected to a water supply flow path extending from an open end that opens to the lower space, and an upper lid on which a projection is formed, and the lower portion of the upper lid is raised from the water supply container to the back side of the projection. A cooling flow path forming body that forms a cooling flow path that extends to a cooling flow path opening that opens into the space, a heat resistant layer that includes a heat resistant element supported by the protrusion on the upper surface of the upper lid and covers the upper surface of the upper lid, And a core melt holding device.

  According to the present invention, the possibility of breakage of the cooling water flow path due to thermal shock due to a rapid temperature rise at the time of falling corium and thermal stress due to a temperature difference generated between corium and the cooling flow path is reduced.

It is the sectional elevation which expanded the II section of Drawing 3 in a 1st embodiment of the core melt maintenance device concerning the present invention. It is an elevation sectional view of a containment vessel which stored a 1st embodiment of a core melt maintenance device concerning the present invention. It is an elevational sectional view of the vicinity of the first embodiment of the core melt holding device according to the present invention. It is a top view in a 1st embodiment of a core melt maintenance device concerning the present invention. It is a partially expanded sectional view in 2nd Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 3rd Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 4th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 5th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 6th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 7th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a partially expanded sectional view in 8th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is a one part perspective view in 9th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention. It is an elevation sectional view in a 10th embodiment of a core melt maintenance device concerning the present invention. It is a one part perspective view in 11th Embodiment of the core melt holding | maintenance apparatus which concerns on this invention.

  An embodiment of a core melt holding device according to the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same or similar structure, and the overlapping description is abbreviate | omitted.

[First Embodiment]
FIG. 2 is an elevational sectional view of a containment vessel containing the first embodiment of the core melt holding device according to the present invention.

  The core 40 is formed inside the reactor pressure vessel 1. The reactor pressure vessel 1 is provided inside the containment vessel 2. The containment vessel 2 has a pedestal floor 41 and a cylindrical pedestal side wall 42 extending upward from the pedestal floor 41.

  The reactor pressure vessel 1 is supported by a pressure vessel support portion 44 provided on the pedestal side wall 42 via a support skirt 43. The space surrounded by the pedestal floor 41 and the pedestal side wall 42 below the reactor pressure vessel 1 is called a lower dry well 7. That is, the reactor pressure vessel 1 is provided above the lower dry well 7. A suppression pool 4 is formed inside the storage container 2 so as to surround the outer peripheral surface of the pedestal side wall 42.

  The core melt holding device 9 is provided on the pedestal floor 41 inside the lower dry well 7. A sump bed 8 is provided between the core melt holding device 41 and the reactor pressure vessel 1.

  Further, the storage container 2 has a water tank 5. A water injection pipe 14 extends from the water tank 5 to the core melt holding device 9. A water injection valve 60 is provided in the middle of the water injection pipe 14. Further, the storage container 2 has a storage container cooler 6. The containment vessel cooler 6 has a pipe extending from the end opened to the dry well to the water tank 5 through a heat exchanger submerged in water. The containment vessel cooler 6 is a static containment vessel cooling facility, a dry well cooler, or the like.

  FIG. 3 is an elevational sectional view of the vicinity of the core melt holding device in the present embodiment. FIG. 4 is a top view of the core melt holding device in the present embodiment. FIG. 3 shows a state in which the core melt 13 has dropped onto the core melt holding device 9 and is supplied from the water tank 5 to the core melt holding device 9.

  The core melt holding device 9 has a water supply container 10. The water supply container 10 is arrange | positioned at the center of the pedestal floor 41 enclosed by the pedestal side wall 42, for example. A water injection pipe 14 extending from the water tank 5 to the core melt holding device 9 is connected to the water supply container 10.

  The core melt holding device 9 has a cooling flow path assembly 50. The cooling flow path assembly 50 has a plurality of cooling flow path forming bodies 51. Each cooling flow path forming body 51 is formed in a fan shape. The plurality of cooling flow path forming bodies 51 are densely arranged in the circumferential direction around the water supply container 10. Therefore, the upper surface of the cooling channel assembly 50 has a shape obtained by cutting off the top of the conical surface rising from the center toward the outer periphery.

  Each cooling flow path forming body 51 is hollow, and a cooling flow path 11 extending while radially extending from the central portion of the cooling flow path assembly 50 to the outer peripheral portion is formed. An end of the cooling flow path 11 on the center side of the cooling flow path assembly 50 is connected to the water supply container 10. The end of the cooling channel 11 opposite to the water supply container 10 rises in the vertical direction at the outer periphery of the cooling channel assembly 50 and opens to the lower dry well 7. Therefore, the upper surface of the cooling channel 11 is an inclined heat transfer surface 52 that rises from the center toward the outer periphery.

  A water supply channel 15 is formed between the cooling channel assembly 50 and the pedestal side wall 42. The water supply channel 15 extends from the opening opened to the lower dry well 7 to the water supply container 10.

  FIG. 1 is an enlarged cross-sectional view of the core melt holding device according to the present embodiment, taken along the line II in FIG.

  The heat-resistant layer 12 is formed on the upper surface of the upper lid 19 of the cooling channel 11, that is, on the surface opposite to the inclined heat transfer surface 52 of the cooling channel 11. The heat-resistant layer 12 covers the entire upper surface of the cooling channel assembly 50, the wall surface facing the center of the outer peripheral portion, and the entire upper surface of the water supply container 10.

  A plurality of protrusions 18 are provided on the upper surface of the upper lid 19 of the cooling channel 11. The heat-resistant element that forms the heat-resistant layer 12 is supported by the protrusion 18.

  The heat-resistant elements forming the heat-resistant layer 12 include a heat-resistant material storage body 17 and a small heat-resistant material storage body 20 that are approximately the same size as the interval between the protrusions 18. The heat-resistant material storage body 17 is disposed between the protrusions 18. The small heat-resistant material storage body 20 is disposed between the heat-resistant material storage bodies 17, that is, on the protrusions 18. Concrete 21 may be laid on the upper surface of the heat-resistant element.

  The heat-resistant material storage body 17 and the small heat-resistant material storage body 20 are obtained by filling a granular heat-resistant material 16 into a metal or ceramic box-shaped container, for example. Instead of the box-shaped container, for example, a bag-shaped container formed of fibers of a high melting point material such as zirconia felt or alumina felt or normal fibers may be used.

  Instead of the small heat-resistant material storage body 20, fibers of a high melting point material may be packed between the heat-resistant material storage bodies 17. Alternatively, an amorphous refractory called a ramming material that generates glassy or crystalline material between particles by heating can also be used.

  The granular heat-resistant material 16 is formed by granulating a high melting point substance. The melting point of the high melting point material is preferably as high as possible.

  When the core melting accident occurs and the core melt 13 penetrates the reactor pressure vessel lower head 3, the core melt 13 falls on the concrete 21 in the core melt holding device 9. When breakage of the lower head 3 of the reactor pressure vessel 1 is detected, a detection signal, that is, a signal of the lower head temperature high or the pedestal ambient temperature high is output. When this detection signal is generated, the water injection valve 60 provided in the middle of the water injection pipe 14 is opened.

  When the water injection valve 60 is opened, the cooling water stored in the water tank 5 is supplied to the water supply container 10 through the water injection pipe 14 due to gravity drop. After the initial water injection is completed in this way, the water overflowing to the upper surface of the core melt holding device 9 passes through the water supply channel 15 to the water supply container 10 by natural circulation caused by boiling in the cooling channel 11. Supplied.

  Vapor generated by cooling the core melt 13 is condensed by the containment vessel cooler 6 at the upper part of the containment vessel 2. The condensed water returns to the water tank 5. Thus, cooling of the core melt 13 is continued by natural circulation of water.

  Water is supplied to the water supply container 10 immediately after the core melt 13 is dropped, and cooling water is supplied to the cooling flow path 11. The heat of the hot core melt 13 is transferred to the concrete 21 and the heat-resistant element, and further transferred to water through the upper surface of the cooling channel 11, that is, the inclined heat transfer surface 52.

  Immediately after the core melt 13 falls, the concrete 21 melts. Solidification on the lower surface of the core melt 13 is promoted by heat required for melting the concrete 21. As a result, the thermal conditions in the heat resistant layer 12 are relaxed. Moreover, since the shape of the heat-resistant material used for the heat-resistant layer 12 is granular, damage due to thermal shock is suppressed.

  When alumina cement having a high melting point is used as the concrete 21 covering the heat-resistant element, the thermal conditions in the heat-resistant layer can be further relaxed. Further, by reinforcing the concrete 21 with a fibrous structure, the possibility of breakage due to thermal shock during rapid heating when the core melt 13 falls is reduced.

Further, when a granular heat-resistant material is mixed as an aggregate of the concrete 21 covering the heat-resistant element, the concrete 21 also has an effect as a heat-resistant material. When hematite (Fe ₂ O ₃ ) is mixed as the aggregate of the concrete 21 covering the heat-resistant element, the chemical reaction between the concrete 21 and the core melt 13 can be suppressed.

  After the cooling water is supplied to the cooling channel 11, due to the temperature difference between the core melt 13 and the cooling water, a rapid temperature gradient is generated in the granular heat-resistant material having a low thermal conductivity, and thermal expansion occurs. However, when a granular heat-resistant material is used, there is a gap between the heat-resistant materials, so that it is possible to prevent damage to the heat-resistant material and the cooling channel due to thermal expansion.

  When the concrete 21 covering the heat-resistant element is completely melted and the core melt 13 comes into contact with the heat-resistant material storage body 17, a part of the core melt 13 slightly enters the voids of the granular heat-resistant material 16. However, since the temperature of the core melt 13 at this time is substantially equal to the melting point, the core melt 13 that has entered the gap is instantly solidified by the heat deprived by the granular heat-resistant material, thereby closing the gap. By using a material having a high melting point such as alumina, magnesia, or zirconia as the granular heat-resistant material 16, melting of the granular heat-resistant material 16 can be suppressed.

  Furthermore, since the heat-resistant layer 12 is cooled by the cooling water flowing through the cooling channel 11, the core melt 13 can be maintained in a solidified state.

  As the granular heat-resistant material 16, an amorphous refractory material called a ramming material in which a glassy or crystalline material is generated between particles by heating may be used. In this case, when the core melt 13 is heated, the gaps between the granular heat-resistant materials are filled with glassy or crystalline materials, and the refractories are bonded to each other. As a result, the possibility that the core melt 13 enters the granular heat-resistant material is reduced.

  By holding the core melt 13 with the granular high melting point material, the heat-resistant material is damaged by thermal shock and thermal stress, and the core melt holding device 9 can be prevented from being damaged due to the temperature of the cooling channel 11 rising. .

[Second Embodiment]
FIG. 5 is a partially enlarged sectional view of the core melt holding device according to the second embodiment of the present invention.

  In the present embodiment, the heat-resistant layer 12 includes a heat-resistant material storage body 17 formed in a rectangular parallelepiped and a heat-resistant material storage body 22 formed with a protrusion on the lower surface. The granular heat resistant material 16 is accommodated in any of the heat resistant material accommodating bodies 17 and 22.

  The heat-resistant material storage body 17 formed in a rectangular parallelepiped is supported by the protrusion 18 of the upper lid 19 of the cooling channel 11. A gap corresponding to the size of the protrusion 18 is formed between the heat-resistant material storage bodies 17 formed in these rectangular parallelepipeds. In this gap, a protrusion of the heat-resistant material storage body 22 having a protrusion formed on the lower surface is fitted. Furthermore, a gap is also formed between the heat-resistant material storage bodies 22 on which the protrusions are formed. The protruding portion of the heat-resistant material storage body 22 is fitted into this gap. In this way, the heat-resistant material storage body 22 formed with the protrusions is laminated on the heat-resistant material storage body 17 formed in a rectangular parallelepiped.

  As described above, the heat-resistant material storage bodies 17 and 22 are formed into a multi-layered structure so that the core melt 13 (see FIG. 3) is physically dropped without laying concrete on the top. The shift between the heat-resistant material storage bodies 17 and 22 due to a general impact is suppressed.

  Moreover, you may adhere | attach the fitting part of the heat-resistant material accommodating bodies 17 and 22 using a low melting-point adhesive agent, cement, or an indefinite shape refractory. Thereby, the shift | offset | difference with respect to the heat-resistant material accommodating bodies 17 and 22 is further suppressed.

  By making the heat-resistant material storage bodies 17 and 22 into a multi-layer using a mutual fitting structure, damage to the heat-resistant material due to thermal shock and thermal stress is suppressed. As a result, it is possible to suppress damage to the core melt holding device due to an increase in the temperature of the cooling channel 11.

[Third Embodiment]
FIG. 6 is a partially enlarged sectional view in the third embodiment of the core melt holding device according to the present invention.

  The heat resistant layer 12 of the present embodiment includes a heat resistant block 23. The heat-resistant block 23 is formed into a block shape by, for example, pressing and fixing an irregular refractory and then heating only the block surface. Each heat-resistant block 23 is supported by a protrusion 18 provided on the upper lid 19 of the cooling channel 11.

  Each heat-resistant block 23 includes, for example, an inclined surface that is shorter than between adjacent projections 18 and has the same inclination as the inclined surface of the upper lid 19, and extends from the inclined portion toward the horizontal center of the core melt holding device. A pair of horizontal surfaces opposed in the vertical direction are formed. The heat resistant blocks 23 are installed in combination such that the upper horizontal surface of the heat resistant material block 23 partially overlaps the lower horizontal surface of the adjacent heat resistant material block.

  Concrete 21 is laid on the upper side of the heat-resistant layer 12. Alternatively, a low melting point adhesive or cement may be introduced into a gap formed between adjacent heat resistant blocks 23 to bond the heat resistant blocks 23 together.

  In such a core melt holding device, the core melt 13 is once held by the concrete 21, whereby damage to the heat-resistant layer 12 due to thermal shock can be suppressed. Further, by adopting a structure in which a large number of heat-resistant blocks 23 are installed by the protrusions 18, gaps are formed between the heat-resistant material blocks. For this reason, when the temperature of the heat-resistant block 23 rises due to heat transfer from the core melt 13 and thermal expansion occurs, the thermal stress generated by absorbing the thermal expansion can be reduced. As a result, damage to the heat resistant block 23 can be suppressed.

  Further, even when the concrete 21 is completely melted, the core melt 13 is in direct contact with the heat-resistant blocks 23, and the core melt 13 enters the gaps between the heat-resistant blocks 23, it is possible to solidify near the entrance of the gaps. High nature. Therefore, it can suppress that the core melt 13 reaches | attains the upper cover 19 of the cooling flow path 11 in a liquid state.

[Fourth Embodiment]
FIG. 7 is a partially enlarged sectional view in the fourth embodiment of the core melt holding device according to the present invention.

  In the core melt holding device of the present embodiment, the second and higher heat-resistant blocks 24 are laminated instead of the concrete 21 (see FIG. 6) in the third embodiment. The heat-resistant block 24 for the second and higher layers has, for example, a shape in which two plates are arranged while being shifted in the radial direction of the core melt holding device. The heat-resistant blocks 24 for the second and higher layers adjacent to each other are arranged so as to partially overlap each other.

  The heat-resistant block 24 for the second and higher layers is formed into a block shape, for example, by pressing and hardening an amorphous refractory, and then heating only the block surface, like the heat-resistant block 23 of the first layer. Further, a low melting point adhesive or cement may be introduced into the gap between the heat-resistant blocks 24 for the second and higher layers to bond them.

  In such a core melt holding device, the core melt 13 is sequentially deposited from the bottom near the center of the core melt holding device 9. For this reason, the heat-resistant blocks 23 and 24 are pressed down by the deposited core melt 13 sequentially from the bottom near the center of the core melt holding device. As a result, the lifting of the heat resistant blocks 23 and 24 is suppressed.

  In addition, since concrete is not laid on the upper surface of the heat-resistant layer 12, the heat-resistant block 24 for the second and higher layers located at the top is highly likely to be damaged by thermal shock. However, since the heat-resistant blocks 23 and 24 have a multi-layer structure, heat transfer to the lower heat-resistant block is mitigated by the heat capacity of the damaged second-layer or higher heat-resistant block 24. As a result, the heat resistant blocks 23 and 24 of all layers are prevented from being damaged.

  By adopting a structure in which a large number of heat-resistant material blocks 23 and 24 are installed by the protrusions 18, there are gaps between the heat-resistant material blocks. For this reason, when the temperature of the heat-resistant blocks 23 and 24 rises due to heat transfer from the core melt 13 and thermal expansion occurs, the gap absorbs the thermal expansion and reduces the generated thermal stress. As a result, damage to the heat resistant blocks 23 and 24 is suppressed.

  In the present embodiment, since the adjacent heat-resistant blocks 23 and 24 are partially overlapped, the gap between the heat-resistant blocks 23 and 24 is plural times from the upper surface of the heat-resistant layer 12 to the upper lid 19. It will be bent. Therefore, even if the fallen core melt 13 is in direct contact with the heat-resistant block 24 for the second and higher layers, and the core melt 13 penetrates into such a gap, it is solidified near the entrance of the gap and cooled in a liquid state. Reaching the upper lid of the flow path is suppressed.

  As described above, in the present embodiment, the heat resistant layer 12 is damaged by the thermal shock and the thermal stress, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel rising.

[Fifth Embodiment]
FIG. 8 is a partially enlarged sectional view in the fifth embodiment of the core melt holding device according to the present invention.

  In the core melt holding device of the present embodiment, the heat-resistant layer 12 is formed by arranging polygonal column heat-resistant bodies 29 formed of a heat-resistant material on the upper cover 19 of the cooling channel 11. The polygonal column heat-resistant body 29 is supported by the protrusions 18 formed on the upper lid 19. As the polygonal column heat-resistant body 29, for example, a block-shaped one formed by pressing only the block surface after pressing and fixing an irregular refractory can be used. Concrete 21 is laid on the upper surface of the heat-resistant layer 12.

  Since the polygonal column is strong against the axial thermal stress, the polygonal column is prevented from being damaged by the thermal stress caused by the temperature difference generated between the upper surface and the lower surface of the polygonal column heat-resistant body 29. For this reason, the heat-resistant layer 12 is damaged by the thermal stress generated by the fall of the core melt 13, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel 11 rising.

[Sixth Embodiment]
FIG. 9 is a partially enlarged sectional view in the sixth embodiment of the core melt holding device according to the present invention.

  The core melt holding device of the present embodiment uses an upper polygonal column heat-resistant body 30 instead of the concrete in the fifth embodiment. There are a plurality of upper polygonal column heat-resistant bodies 30, which are arranged so as to be stacked on a polygonal column heat-resistant body 29 arranged on the upper lid 19.

  Even in such a core melt holding device, as in the fifth embodiment, the heat-resistant layer 12 is damaged by the thermal stress caused by the fall of the core melt 13, and the temperature of the cooling channel 11 rises. This prevents the core melt holding device 9 from being damaged. In addition, since no concrete is used, time and labor required for laying concrete and drying are reduced.

[Seventh Embodiment]
FIG. 10 is a partially enlarged sectional view in the seventh embodiment of the core melt holding device according to the present invention.

  In the core melt holding device of the present embodiment, the cooling channel 11 is formed with a channel 25 extending in the vertical direction at the outer edge. For this reason. Corresponding to the discontinuous corners from the inclined part to the vertical part of the cooling channel 11, discontinuous corners are also formed between the upper lid 19 and the channel wall 28 of the vertical part.

  At the discontinuous corners between the upper lid 19 and the flow passage walls 28 in the vertical part, corner heat-resistant materials 26 are arranged according to the shape. Further, a vertical portion heat-resistant material 27 is fitted to the upper end of the corner portion heat-resistant material 26 on the vertical portion side. A plurality of vertical portion heat-resistant materials 27 are stacked along the flow path wall 28 in the vertical portion. Further, the corner heat-resistant material 26 and the vertical heat-resistant material 27 may be bonded to each other using a low melting point adhesive or cement.

  As described above, since the heat-resistant layer 12 is fitted to the portion along the flow path wall 28 in the vertical portion, it is possible to reduce places that are structurally constrained. Therefore, thermal stress can be relieved by releasing upward the thermal expansion accompanying the temperature rise of the heat-resistant material. As a result, the heat resistant material is damaged by the thermal stress, and the core melt holding device 9 can be prevented from being damaged due to the temperature of the cooling channel 11 rising.

[Eighth Embodiment]
FIG. 11 is a partially enlarged sectional view in the eighth embodiment of the core melt holding device according to the present invention.

  In the core melt holding device 9 of the present embodiment, the prism stopper 35 and the cylinder stopper 36 are attached to the upper lid 19 of the cooling channel 11. For example, the cylindrical stopper 36 is provided at a position near the center of the upper cover 19 of the cooling flow path 11 of the core melt holding device 9, and the prism stopper 35 is provided on the outer peripheral side.

  As a heat-resistant element supported by the prism stopper 35, a prismatic heat-resistant material 37 is disposed. In addition, as a heat-resistant element supported by the column stopper 36, a column heat-resistant material 38 is disposed.

  The prismatic heat-resistant material 37 is formed in a shape that can be fitted to the prismatic stopper 35. The heat-resistant material 38 for a cylinder is formed in a shape that can be fitted to the cylinder stopper 36. However, the prismatic heat-resistant material 37 is formed in a shape that cannot be fitted to the cylindrical stopper 36. Moreover, the heat-resistant material for a cylinder 38 is formed in a shape that cannot be fitted to the prismatic stopper 35.

  In this way, the shape of the protrusion provided on the upper surface of the upper lid 19 is changed depending on the position, and the shape of the heat-resistant element to be disposed at each position can be fitted to the shape of the protrusion at each position. Even if you try to install a heat-resistant element in a place where it is not installed, it cannot be fitted with the protrusion and cannot be installed. For this reason, it becomes easy to arrange | position each heat-resistant element in a predetermined position, and the error of arrangement | positioning reduces.

  Here, two types of stoppers are arranged at different positions in the radial direction, but three or more types of stoppers may be used. Moreover, you may change the magnitude | size of a stopper.

  As described above, the heat resistant material and the stopper have a structure corresponding to the installation location, so that a discontinuous surface due to an installation error is hardly generated. For this reason, the heat-resistant material is damaged by the thermal stress when the core melt 13 is dropped, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel rising.

[Ninth Embodiment]
FIG. 12 is a partial perspective view of the ninth embodiment of the core melt holding device according to the present invention.

  A heat-resistant material holding plate 31 having a width in the vertical direction is placed on the upper surface of the upper lid 19 of the cooling flow path forming body 51 of the present embodiment. Since the cooling flow path forming bodies 51 are densely arranged in the circumferential direction centering on the water supply container 10, the heat-resistant material holding plate 31 draws a circle centering on the water supply container as a whole. A plurality of heat-resistant material holding plates 31 are provided on the upper lid of each cooling flow path forming body 51, and the plurality of circles drawn by the heat-resistant material holding plates 31 draw concentric circles.

  Each heat-resistant material holding plate 31 is formed of a high melting point material. Further, the heat-resistant material holding plate 31 forming one circle has a structure in which a plurality of members are fitted via the heat-resistant material holding plate fitting portion 32.

  Between the concentric circles drawn by the heat-resistant material holding plate 31, for example, a heat-resistant element such as the heat-resistant material container (see FIG. 1) of the first embodiment is arranged, and a heat-resistant layer is formed. That is, the heat-resistant material holding plate 31 supports the heat-resistant element.

  In such a core melt holding device 9, since the heat-resistant material holding plate 31 is drawn as a circle as a whole, it does not slide down along the slope of the upper lid 19 at a predetermined height from the water supply container 10. Therefore, it is not necessary to join the heat-resistant material holding plate 31 to the upper lid 19, and the difference in thermal expansion between the upper lid 19 of the cooling channel 11 and the heat-resistant material is that the heat-resistant material holding plate 31 is different from the upper lid 19 of the cooling channel 11. It is absorbed by moving relatively. As a result, the possibility that the heat-resistant material is damaged by thermal stress is suppressed.

  Further, since it is not necessary to join a heat-resistant material or a heat-resistant material stopper to the upper lid 19 of the cooling channel 11, discontinuous portions of the upper lid 19 are reduced. Therefore, stress concentration occurring at discontinuous portions is suppressed.

  As described above, in the present embodiment, the heat-resistant material is damaged by the thermal stress, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel rising.

[Tenth embodiment]
FIG. 13 is an elevational sectional view of the tenth embodiment of the core melt holding device according to the present invention.

  In the present embodiment, the molded amorphous refractory material 33 is spread on the upper surface of the upper lid 19 to form a heat resistant layer. These irregular refractory materials 33 are integrally formed on the upper surface of the upper lid 19.

  For example, a small amorphous refractory material 33 is molded in a factory or the like and is carried into the storage container 2 (see FIG. 2). The loaded amorphous refractory material 33 can be combined by heating inside the containment vessel 2. Further, when a core melt holding device is formed by combining a plurality of cooling flow path forming bodies 51, an indefinite refractory is laid in advance on the upper surface of each cooling flow path forming body 51, and the containment vessel 2. You may couple | bond by heating etc. after carrying in to. Further, concrete may be laid on the upper surface of the molded amorphous refractory.

  In such a core melt holding device, since the amorphous refractory material 33 is molded and used, there is no clear seam. For this reason, it becomes difficult for the core melt 13 to penetrate into the heat-resistant layer. Further, since voids exist between the particles of the amorphous refractory, thermal stress due to thermal expansion can be relaxed by the voids.

  As described above, in the present embodiment, the heat-resistant material is damaged by the thermal stress, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel rising.

[Eleventh embodiment]
FIG. 14 is a partial perspective view of the eleventh embodiment of the core melt holding device according to the present invention.

  In the present embodiment, the heat-resistant element is a heat-resistant material storage body 34 that is integrally molded with an amorphous heat-resistant material. The heat-resistant material storage body 34 covers the upper surface of the upper lid 19 of the cooling channel 11. The outer peripheral portion of the heat-resistant material storage body 34 may be joined to other than the cooling flow path forming body 51. Further, a plurality of the joined heat-resistant material storage bodies 34 may be stacked. Concrete may be laid on the upper surface of the heat-resistant material container 34.

  In such a core melt holding device, since the heat-resistant material storage body 34 is bonded in advance before construction on site, construction on site can be simplified. Moreover, the shift | offset | difference of the heat-resistant material storage body 34 by the load of the core melt 13 is suppressed, and possibility that the core melt 13 will penetrate | invade to the upper cover 19 part of the cooling flow path 11 is reduced.

  In this way, the heat-resistant material is damaged by the thermal stress, and the core melt holding device is prevented from being damaged due to the temperature of the cooling channel rising.

[Other embodiments]
The above description is merely an example, and the present invention is not limited to the above-described embodiments, and can be implemented in various forms. Moreover, it can also implement combining the characteristic of each embodiment.

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Containment vessel, 3 ... Lower head, 4 ... Suppression pool, 5 ... Water tank, 6 ... Containment vessel cooler, 7 ... Lower dry well, 8 ... Sump bed, 9 ... Retain core melt Device: 10 ... Water supply container, 11 ... Cooling channel, 12 ... Heat-resistant layer, 13 ... Core melt, 14 ... Water injection pipe, 15 ... Water supply channel, 16 ... Granular heat-resistant material, 17 ... Heat-resistant material container, 18 ... Projection, 19 ... Upper lid, 20 ... Small heat-resistant material container, 21 ... Concrete, 22 ... Heat-resistant material container, 23 ... Heat-resistant block, 24 ... Heat-resistant block for second layer or more, 25 ... Channel, 26 ... For corner Heat-resistant material, 27 ... Heat-resistant material for vertical portion, 28 ... Flow path wall of vertical portion, 29 ... Polygonal heat-resistant body, 30 ... Polygon-shaped heat-resistant body for upper side, 31 ... Heat-resistant material holding plate, 32 ... Fitting of heat-resistant material holding plate Mating part, 33 ... irregular refractory material, 34 ... heat-resistant material container, 35 ... prismatic strike Par, 36 ... Cylinder stopper, 37 ... Heat-resistant material for prism, 38 ... Heat-resistant material for cylinder, 40 ... Core, 41 ... Pedestal floor, 42 ... Pedestal side wall, 43 ... Support skirt, 44 ... Pressure vessel support, 50 ... Cooling Channel assembly 51: Cooling channel formation body 52 ... Inclined heat transfer surface 60 ... Water injection valve

Claims (17)

In the core melt holding device provided in the lower space of the reactor pressure vessel,
A water supply container connected to a water supply flow path extending from an open end that opens to the lower space;
A cooling flow path forming body that includes an upper lid on which a protrusion is formed and forms a cooling flow path that extends from the water supply container to the cooling flow path opening that opens to the lower space on the back side of the protrusion of the upper lid. ,
A heat-resistant layer covering the upper surface of the upper lid with a heat-resistant element supported by the protrusion on the upper surface of the upper lid;
A core melt holding device characterized by comprising:   2. The core melt holding device according to claim 1, wherein the heat-resistant element includes a heat-resistant material container and a granular heat-resistant material housed in the heat-resistant material container.   3. The core melt holding device according to claim 2, wherein the granular refractory material includes an amorphous refractory that generates either glassy or crystalline between particles by heating. 4.   4. The core melt holding device according to claim 1, wherein the core melt holding device has any one of a fiber and an amorphous refractory packed between adjacent heat-resistant elements. 5.   The core heat-retaining device according to claim 1, wherein the heat-resistant layer includes concrete laid on an upper surface of the heat-resistant element.   The core melt holding device according to claim 5, wherein the concrete contains any of a fibrous structure, an aggregate formed of a granular heat-resistant material, and an aggregate formed of hematite. .   The core melt holding device according to any one of claims 1 to 6, wherein the heat resistant layer is formed by stacking the heat resistant elements in a plurality of layers.   The core melt holding device according to any one of claims 1 to 7, wherein the heat-resistant elements are blocks formed so as to be fitted to each other.   The core melt holding device according to any one of claims 1 to 8, wherein the heat-resistant element is a block formed into a polygonal column.   10. The core melt holding device according to claim 8, wherein the heat-resistant element is obtained by molding an amorphous refractory and heating a surface thereof. 11.   The core melt holding device according to any one of claims 1 to 10, wherein the heat-resistant element in contact with the upper lid is provided so that an upper surface thereof is horizontal.   12. The projection according to any one of claims 1 to 11, wherein the projection includes a plurality of types having different shapes, and the heat-resistant element is formed in a shape fitted to each of the projections. The core melt holding device according to claim 1.   The core melt holding device according to any one of claims 1 to 12, wherein the adjacent heat-resistant elements are joined to each other.   The cooling channel forming body has a wall surface that rises in the vertical direction, and has a wall surface heat-resistant element that is stacked on the opposite surface of the wall surface to the cooling channel and is fitted to the lower one. The core melt holding device according to any one of claims 1 to 13, characterized in that:   The core melt holding device according to any one of claims 1 to 14, wherein the protrusions are formed concentrically around the water supply container.   2. The core melt holding device according to claim 1, wherein all the heat-resistant elements are integrally formed of an irregular heat-resistant material. A reactor pressure vessel that houses the reactor; and
A containment vessel for housing the reactor pressure vessel;
A water supply container provided in a lower space of the reactor pressure vessel inside the containment vessel and connected to a water supply flow path extending from an opening end opened to the lower space, and an upper lid on which a protrusion is formed is provided. A cooling flow path forming body that forms a cooling flow path that extends to the cooling flow path opening that opens to the lower space while rising from the water supply container on the back side of the protrusion of the upper lid, and is supported by the protrusion on the upper surface of the upper lid A core melt holding device comprising: a heat-resistant layer that includes the heat-resistant element and covers the upper surface of the upper lid;
A nuclear power plant characterized by comprising:

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