JP2017111089A - Reactor containment and its drain sump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reactor containment capable of maintaining a function to prevent core meltdown matter from intruding into a drain sump even a severe accident occurs, and a drain sump thereof.SOLUTION: The reactor containment includes: a drain sump 7 which is disposed in the bottom to collect and discharge leaked water, which has an opening in the upper part thereof; a lid member 10 which is formed of a heat resistant material 12 containing at least a ceramic material and a structure member 11 covering the heat resistant material 12; and coupling means 13 and 14 for combining the lid members 10 with each other. A plurality of lid members 10 combined with the coupling means 13 and 14 covers the opening of the drain sump 7 from the top.SELECTED DRAWING: Figure 2

Description

  Embodiments of the present invention relate to a drain sump for collecting and draining leaked water generated inside, and a reactor containment vessel having a drain sump.

  When a severe accident occurs in the nuclear reactor, molten corium produced by the core melting spreads on the floor of the reactor containment vessel and enters the drain sump and accumulates. Since molten corium deposited in a narrow space such as a drain sump is difficult to cool, the reactor containment vessel may be damaged by the heat generated by the molten corium. In order to prevent such a situation, the drain sump is covered with a heat-resistant sump cover so that molten corium does not enter the drain sump.

Japanese Patent No. 5306074

  The molten corium (core melt) from which the nuclear fuel pellets have melted is hot. Therefore, it is preferable that the material of the sump cover (lid member) that covers the drain sump of the reactor containment vessel is ceramic that can withstand high temperatures. However, ceramics have low impact resistance, and if a worker accidentally drops a tool (falling object) etc. on the sump cover during maintenance inside the reactor containment vessel, the sump cover It may break. In addition, since a sintered body such as ceramics easily permeates water, the water collected in the drain sump penetrates into the inside of the sump cover. If severe accident occurs in such a state and molten corium contacts the sump cover, the water that has penetrated the sump cover will explosively evaporate due to the high heat of the molten corium, and the sump cover will break and scatter and melt. There is a problem that the infiltration prevention function of corium cannot be maintained.

  Embodiments of the present invention have been made in view of such circumstances, and provide a reactor containment vessel capable of maintaining the function of preventing the intrusion of core melt into a drain sump even when a severe accident occurs, and a drain sump thereof. Objective.

  A reactor containment vessel according to an embodiment of the present invention includes a drain sump that is provided at the bottom and has an opening at the top for collecting and draining water leakage, a heat-resistant material containing at least a ceramic material, and a structural material that covers the heat-resistant material. It comprises a formed lid member and a combination means for combining the lid members with each other, wherein the opening of the drain sump is covered from above by a plurality of the cover members combined by the combination means. .

  A drain sump for a reactor containment vessel according to an embodiment of the present invention is provided at the bottom of the reactor containment vessel and has an opening at the top, for collecting and draining water leakage generated inside the reactor containment vessel A drain sump, comprising: a lid member formed of a heat-resistant material containing at least a ceramic material and a structural material covering the heat-resistant material; and a combination means for combining the lid members with each other, and a plurality of combinations combined by the combination means The lid member is arranged so as to cover the opening from above.

  The embodiment of the present invention can maintain the function of preventing the core melt from entering the drain sump even when a severe accident occurs.

Sectional drawing which shows a nuclear reactor containment vessel. The perspective view which shows the state which looked at the cover member of 1st Embodiment from diagonally upward. The perspective view which shows the state which looked at the cover member of 1st Embodiment from diagonally downward. Sectional drawing which shows the cover member of 1st Embodiment. The figure which shows the state which piled up the cover member of 1st Embodiment. The figure which shows the state which covered the drain sump with the cover member of 1st Embodiment. The perspective view which shows the cover member of 2nd Embodiment. Sectional drawing which shows the cover member of 2nd Embodiment. The figure which shows the state which covered the drain sump with the cover member of 2nd Embodiment. The perspective view which shows the cover member of 3rd Embodiment. The top view which shows the state which combined the cover member of 3rd Embodiment. The figure which shows the state which covered the drain sump with the cover member of 3rd Embodiment. The perspective view which shows the cover member of 4th Embodiment. The figure which shows the state which covered the drain sump with the cover member of 4th Embodiment. The perspective view which shows the cover member of 5th Embodiment. The top view which shows the cover member of 5th Embodiment. The top view which shows the state which combined the cover member of 5th Embodiment. The figure which shows a state when combining the cover member of 5th Embodiment. The figure which shows the state which covered the drain sump with the cover member of 5th Embodiment.

(First embodiment)
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. As shown in FIG. 1, in a boiling water reactor (BWR) which is an example of a nuclear power plant, a reactor core 2 is provided inside a reactor pressure vessel 1. The reactor pressure vessel 1 is a vessel in which upper and lower openings of a cylindrical body are closed with upper and lower lids having a substantially hemispherical shape. The upper lid is also called an upper mirror, and the lower lid is also called a lower mirror. The reactor pressure vessel 1 is a container for the reactor core 2 and is a stainless steel structure that circulates cooling water and the like between the outside and withstands high temperature and pressure inside. The reactor pressure vessel 1 also has a function of blocking the radioactive material and radiation generated in the core 2 from the outside so as not to leak.

  The weight of the reactor pressure vessel 1 is supported by a support skirt near the lower end of the trunk. Furthermore, a large number of brackets are attached to the inner surface of the reactor pressure vessel 1 and are lined with stainless steel or nickel alloy. In addition to the reactor core 2 and the support structure for supporting the reactor core 2, the reactor pressure vessel 1 contains reactor internal structures such as a flow path for circulating cooling water and related devices. ing.

  A reactor containment vessel 4 for housing the reactor pressure vessel 1 is also provided. The reactor containment vessel 4 is formed using concrete or the like and has sufficient strength. The reactor containment vessel 4 is a structure for forming a barrier against the release of radioactive material while serving as a pressure barrier when a severe accident occurs. Further, inside the reactor containment vessel 4, there is provided a pressure suppression chamber for condensing the steam released from the reactor pressure vessel 1 with water to prevent the pressure from rising.

  Furthermore, a space is provided below the reactor pressure vessel 1 in which various devices for driving the control rod are provided. At the time of maintenance of the nuclear power plant, an operator can work under the reactor pressure vessel 1. A water injection line 5 for injecting cooling water into the reactor containment vessel 4 in an emergency is provided.

  In addition, the water leakage generated from various pipes provided inside the reactor containment vessel 4 is collected and drained on the floor 6 at the bottom of the reactor containment vessel 4 at a position below the reactor pressure vessel 1. A drain sump 7 is provided. The drain sump 7 is formed as a drainage groove having a groove shape opened upward. Further, the drain sump 7 is provided with a water level gauge or the like and has a function of detecting water leakage. Further, the drain sump 7 is provided with a drainage device for draining the collected water to the outside of the reactor containment vessel 4.

  Furthermore, various safety measures are taken in nuclear power plants. For example, when the supply of cooling water to the reactor pressure vessel 1 is stopped or the cooling water is lost due to the breakage of the piping connected to the reactor pressure vessel 1, the water level inside the reactor pressure vessel 1 decreases. However, the core 2 is exposed and cooling becomes insufficient. In such a case, the nuclear reactor is automatically shut down in response to a water level lowering signal. Further, the core is submerged and cooled by injecting cooling water by an emergency core cooling system (ECCS) to prevent a core melting accident.

  However, although the probability is very low, it may be assumed that the emergency core cooling device does not operate and the water injection device to other cores 2 cannot be used. For example, a situation in which the supply of cooling water to the reactor pressure vessel 1 is stopped due to the loss of an external power source or an emergency power source due to factors such as an earthquake disaster. In such a situation, the water level inside the reactor pressure vessel 1 is lowered, so that the core 2 is exposed and cooling is not performed. Then, it is conceivable that the fuel rod temperature rises due to decay heat that continues to be generated even after the reactor is shut down, leading to melting of the core 2.

  When such a severe accident occurs, the high-temperature core melt melts into the lower part of the reactor pressure vessel 1, and further melts and penetrates the bottom 3 (lower mirror) of the reactor pressure vessel 1. It falls on the floor surface 6 inside the container 4. Such a core melt heats the concrete constituting the floor surface 6 of the reactor containment vessel 4. When the contact surface with which the core melt comes into contact is at a high temperature, the core melt reacts with the concrete to generate a large amount of non-condensable gases such as carbon dioxide and hydrogen, and melt and erode the concrete.

  The generated non-condensable gas increases the pressure inside the reactor containment vessel 4 and may damage the reactor containment vessel 4. Moreover, there is a possibility that the boundary of the reactor containment vessel 4 may be damaged or the structural strength of the reactor containment vessel 4 may be reduced due to melt erosion of concrete.

  Then, the reactor containment vessel 4 is damaged, and there is a risk that radioactive materials inside the reactor containment vessel 4 are released to the outside. In particular, if the core melt enters the drain sump 7 located in the lower part of the reactor containment vessel 4, the ratio of the area of the upper surface of the core melt to the volume of the core melt becomes small. Even if water is poured into the lower part of the reactor containment vessel 4, the temperature of the core melt inside the drain sump 7 does not decrease, and there is a risk that the melt erosion of the concrete will continue. Therefore, in the present embodiment, a lid member 10 that covers the upper opening of the drain sump 7 is provided in order to prevent the core melt from entering the drain sump 7 when a severe accident occurs.

  The lid member 10 of the first embodiment will be described with reference to FIGS. 2 to 6. As shown in FIG. 2, the lid member 10 according to the first embodiment is a rectangular parallelepiped configured as a hexahedron in which all surfaces are rectangular. Adjacent surfaces of the lid member 10 intersect at right angles. It is possible to cover the opening of the drain sump 7 by providing a plurality of lid members 10 having the same shape in a block shape and combining the lid members 10 with each other (see FIG. 6).

  The structural material 11 constituting the outer surface of the lid member 10 is made of a metal material such as stainless steel. Note that the entire surface of the structural member 11 may be subjected to a rust prevention treatment by performing a treatment such as painting, plating, and oil application. The structural material 11 forms a box body in which the edges of the six plate members are welded to each other. Further, a heat-resistant material 12 is provided inside the structural material 11. This heat-resistant material 12 forms a rectangular parallelepiped and is formed of a material such as metal oxide ceramics having heat resistance. In addition, you may form the heat-resistant material 12 using ceramics other than a metal oxide.

  In addition, all the parts of the heat-resistant material 12 do not need to be comprised with ceramics. For example, a part of the heat-resistant material 12 may be made of ceramics, and the other part may be made of a material other than ceramics. Furthermore, the structure may not be such that one heat-resistant material 12 is provided inside one structural material 11. For example, a plurality of plate-like heat-resistant materials 12 may be provided in the vertical direction in a single structural material 11.

  As shown in FIGS. 2 and 3, convex portions 13 (engaging portions) are provided at four corners of the upper surface of the lid member 10 of the first embodiment, and two side surfaces of the four side surfaces of the lid member 10 are provided. Convex portions 13 (engaging portions) are also provided at the four corners. These convex portions 13 protrude perpendicularly to the surface on which each is provided. For example, the convex portion 13 on the upper surface of the lid member 10 projects upward, and the convex portion 13 on the side surface of the lid member 10 projects laterally.

  Furthermore, the four corners of the lower surface of the lid member 10 are provided with concave portions 14 (engaged portions) with which the convex portions 13 on the upper surface of the other lid member 10 are engaged. Moreover, the recessed part 14 (engaged part) with which the convex part 13 of the side surface of the other lid member 10 is engaged is provided also in each of the four corners of two side surfaces of the four side surfaces of the lid member 10. Thus, in the lid member 10, the convex portions 13 are provided on three adjacent surfaces among the six surfaces, and the surfaces other than the surfaces on which the convex portions 13 are provided, that is, the convex portions 13 are provided. Concave portions 14 are provided on three surfaces opposite to the surface.

  As shown in FIG. 4, the lid member 10 includes a neutron absorber 15 that absorbs neutron beams generated by a nuclear reaction. The neutron absorber 15 is made of a material such as boron carbide (B4C: boron carbide). In this embodiment, a powdered neutron absorber 15 is filled between the structural material 11 and the heat-resistant material 12.

  Further, all six surfaces of the lid member 10 are surfaces constituted by the structural material 11. That is, the heat-resistant material 12 and the neutron absorber 15 are covered with the structural material 11. The convex portion 13 and the concave portion 14 are portions integrated with the structural material 11. In particular, the inner surface of the recess 14 is also a portion covered with the structural material 11. As described above, the heat-resistant material 12 and the neutron absorbent 15 are covered with the structural material 11, so that external water does not penetrate into the heat-resistant material 12 and the neutron absorbent 15. In the present embodiment, not only the upper and side surfaces of the lid member 10 but also the lower surface of the lid member 10 is formed of the structural material 11, so that the heat-resistant material 12 and neutrons can be obtained even when the water level flowing through the drain sump 7 is increased. The absorbent 15 is prevented from getting wet. Further, the structural material 11 prevents the neutron absorber 15 from leaking out.

  As shown in FIG. 5, when a plurality of lid members 10 are stacked on the floor surface 6, the four convex portions 13 on the upper surface of the lower lid member 10 are formed on the lower surface of the lid member 10 stacked on the upper side. The four recesses 14 are engaged. When the lid members 10 are arranged side by side, the four convex portions 13 on the side surface of one lid member 10 are engaged with the four concave portions 14 on the side surfaces of the other lid member 10.

  In addition, the depth dimension of the recessed part 14 is formed slightly smaller than the protruding dimension of the projecting part 13. Therefore, when a plurality of lid members 10 are combined, a gap through which water can pass is formed between the surfaces of the lid members 10. When the opening of the drain sump 7 is closed with a plurality of lid members 10, water leakage generated inside the reactor containment vessel 4 can pass through the gap between the lid members 10 and enter the drain sump 7. Yes.

  As shown in FIG. 6, when the openings of the drain sump 7 are covered with a plurality of lid members 10, they can be stacked with their side surfaces separated from each other. For example, the drain sump 7 can be covered with the lid member 10 stacked in three stages of an upper stage, a middle stage, and a lower stage. In this case, first, the lower lid member 10 is installed on the floor surface 6 in the vicinity of the drain sump 7. Then, two middle lid members 10 whose side surfaces are separated from each other are stacked on the upper surface of the lower lid member 10. Of the four convex portions 13 on the upper surface of the lower lid member 10, the concave portions 14 on the lower surface of one middle lid member 10 are engaged with the two convex portions 13, and the other two convex portions 13 have The recess 14 on the lower surface of the other middle lid member 10 is engaged.

  Then, the upper lid member 10 is stacked on the upper surface of the two middle lid members 10. Further, the convex portion 13 on the upper surface of the two middle lid members 10 is engaged with the concave portion 14 on the lower surface of the upper lid member 10. In other words, the upper two lid members 10 are held by the upper lid member 10 so as not to be separated from each other. That is, the convex portion 13 and the concave portion 14 constitute a separation preventing means. Furthermore, by engaging the concave portion 14 on the lower surface of the other upper lid member 10 with the convex portion 13 on the free end side of the upper surface of the lid member 10, the installation area of the lid member 10 can be expanded. In this way, by stacking the plurality of lid members 10 with their side surfaces separated from each other, water flowing from above can easily enter the drain sump 7. Furthermore, since the convex part 13 and the recessed part 14 of each cover member 10 are mutually engaged, even if an earthquake etc. generate | occur | produces and external force is added to the cover member 10, the state which the cover members 10 were combined can be maintained. . The convex part 13 and the concave part 14 can be combined to arrange or stack the lid members 10. In the first embodiment, the convex portion 13 and the concave portion 14 constitute a combination means.

  One lid member 10 is formed to have a size and weight that can be carried by an operator. Therefore, it can be easily carried into the existing reactor containment vessel 4. Further, the lid member 10 can be installed without changing existing facilities such as the floor surface 6 and the wall surface of the reactor containment vessel 4. Moreover, when performing a periodic inspection etc., it is possible to easily remove the lid member 10 covering the opening of the drain sump 7.

  In the present embodiment, the surface of the heat-resistant material 12 made of metal oxide ceramics is covered with a structural material 11 made of stainless steel having higher toughness than the heat-resistant material 12, so that the lid having impact resistance is provided. The member 10 can be used. Therefore, even if an operator accidentally drops a tool (falling object) or the like onto the lid member 10 during maintenance, the lid member 10 is not broken. Further, even if an earthquake or the like occurs and an impact or the like is applied to the lid member 10, the heat-resistant material 12 is not cracked or broken.

  Further, when a severe accident occurs, even if the core melt comes into contact with the lid member 10 and the structural material 11 is melted, it is possible to prevent the accumulated heat resistant material 12 from entering the drain sump 7. When the core material melts and the structural material 11 is melted, the neutron absorber 15 inside the lid member 10 is mixed into the core melt, so that a nuclear reaction (chain reaction of nuclear materials). Can be suppressed. Furthermore, when the core melt melts the structural material 11, the structural material 11 is deprived of heat, so that the core melt is cooled and solidified, and the core melt does not fall to the bottom of the drain sump 7.

  Further, since the heat-resistant material 12 is covered with the structural material 11 and is maintained in a state in which water does not penetrate into the heat-resistant material 12, the heat-resistant material 12 is maintained even when the high-temperature core melt contacts the heat-resistant material 12. Since the steam explosion does not occur inside the heat-resistant material 12 and the shape of the heat-resistant material 12 is maintained, the function of preventing the core melt from entering the drain sump 7 can be maintained.

  In the present embodiment, the lid member 10 is formed as a rectangular parallelepiped (hexahedron), but the lid member 10 may be formed as a hexahedron with a partly inclined surface. For example, the lid member 10 may be shaped like a parallelepiped.

  In the present embodiment, the combination means is constituted by the convex portion 13 and the concave portion 14, but the combination means may be constituted by other means. For example, it is good also as a structure which fixes a magnet to each surface of the cover member 10, and mutually connects the cover members 10 with magnetic force. Moreover, when combining each cover member 10, you may adhere | attach the cover members 10 using an adhesive agent.

(Second Embodiment)
Next, the lid member 20 of the second embodiment will be described with reference to FIGS. As shown in FIG. 7, the lid member 20 of the second embodiment is a rectangular parallelepiped configured as a hexahedron. The structural member 21 constituting the outer surface of the block-shaped lid member 20 is formed from a metal material such as stainless steel. Furthermore, a heat-resistant material 22 made of a material such as metal oxide ceramics is provided inside the structural material 21. The lid member 20 has a through hole 24 that is linearly penetrated from the upper surface to the lower surface. The through hole 24 is provided at a position displaced from the center position of the lid member 20. The through hole 24 may be provided at the center position of the lid member 20.

  As shown in FIG. 8, a powdered neutron absorber 25 is filled between the structural material 21 and the heat-resistant material 22. Further, the heat resistant material 22 is provided with a through hole 26 penetrating in the vertical direction. By covering the inner surface of the through hole 26 with the structural material 21, the aforementioned through hole 24 is formed. As described above, the heat-resistant material 22 and the neutron absorbent 25 are covered with the structural material 21, so that external water does not penetrate into the heat-resistant material 22 and the neutron absorbent 25.

  As shown in FIG. 9, when covering the opening of the drain sump 7 with a plurality of lid members 20, first, the fixing portion 27 is formed by making a hole in the floor surface 6 in the vicinity of the drain sump 7. A support rod 28 is fixed to the fixing portion 27. The support bar 28 extends in the vertical direction.

  The through hole 24 of the lid member 20 is a circular hole, and the support bar 28 is a cylindrical member. The support rod 28 has a diameter smaller than that of the through hole 24 of the lid member 20. The lid member 20 is installed in a state where the support rod 28 is inserted into the through hole 24. In the second embodiment, the plurality of lid members 20 are stacked by inserting the through holes 24 into the upper ends of the support bars 28. In the second embodiment, the combination means is configured by the through hole 24 and the support rod 28. When the opening of the drain sump 7 is closed with a plurality of lid members 20, water leakage generated inside the reactor containment vessel 4 can pass through the gap between the lid members 20 and enter the drain sump 7. Yes. Moreover, you may form the unevenness | corrugation for forming the clearance gap through which water can pass in the side surface of the cover member 20. As shown in FIG.

  The length of the support bar 28 is longer than the vertical dimension of the lid member 20. Therefore, the plurality of lid members 20 can be stacked in the vertical direction by the respective support bars 28. The lid member 20 thus stacked can maintain the stacked state even when an external force such as an earthquake is applied. In this example, the three-stage lid member 20 is stacked in the vertical direction, but the opening of the drain sump 7 may be covered by the single-stage lid member 20 without stacking the lid member 20 in the vertical direction.

  In the second embodiment, the through hole 24 of the lid member 20 has a circular shape and the support bar 28 has a cylindrical shape, but the through hole 24 of the lid member 20 has a square shape and is supported by the support rod 28. The rod 28 may have a prismatic shape. Since the support rod 28 has a prism shape, the lid member 20 can be prevented from rotating.

  Thus, the lid member 20 can be stably provided on the floor surface 6 or the wall surface of the reactor containment vessel 4 by the support rod 28. Further, since the support rod 28 penetrating the through hole 24 of one lid member 20 can be inserted into the through hole 24 of the other lid member 20, a plurality of lid members 20 can be combined by one support rod 28. Can be supported.

  In addition, since the heat-resistant material 22 is covered with the structural material 21 and is maintained in a state in which water does not permeate the heat-resistant material 22, the heat-resistant material 22 is maintained even when the high-temperature core melt contacts the heat-resistant material 22. Since no steam explosion occurs in the interior of the refractory and the shape of the heat-resistant material 22 is maintained, the function of preventing the core melt from entering the drain sump 7 can be maintained. Moreover, the nuclear reaction can be suppressed by the lid member 20 having the neutron absorber 25.

  In addition, although the recessed part 33 is provided in the corner | angular part of the four corners of the structural material 31, and the cylinder member 34 is provided in one corner | angular part, it is good also as another form. For example, a configuration in which the concave portion 33 is provided at two corners of the four corners of the structural member 31 and the cylindrical member 34 is provided at the two corners may be employed. Further, the concave portion 33 and the cylindrical member 34 may not be provided at the four corners of the structural material 31. For example, you may make it provide the recessed part 33 and the cylindrical member 34 in each center position of the four sides of the structural material 31. FIG.

(Third embodiment)
Next, the lid member 30 of the third embodiment will be described with reference to FIGS. 10 to 12. As shown in FIG. 10, the lid member 30 of the third embodiment is a plate-like member having a predetermined thickness, and has a substantially hexahedral block shape. The structural member 31 constituting the outer surface of the lid member 30 is made of a metal material such as stainless steel. Furthermore, a heat-resistant material 32 made of a material such as metal oxide ceramics is provided inside the structural material 31. A powdered neutron absorber is filled between the structural material 31 and the heat-resistant material 32.

  Further, the structural member 31 forms a substantially square box in plan view, and is formed with a recess 33 in which the corners of the four corners are cut out in a curved shape. That is, the recess 33 is provided on the outer peripheral surface of the structural material 31. In addition, the corners of the four corners of the heat-resistant material 32 inside the structural material 31 are provided with recesses that are cut out in a curved shape.

  In addition, a cylindrical member 34 having a cylindrical shape is provided at one corner of the four corners of the structural material 31 cut out. The cylindrical member 34 is formed of a metal material such as stainless steel and has a through hole 35 (hole portion) penetrating in the vertical direction. Moreover, the cylindrical member 34 is being fixed to the corner | angular part of the structural material 31 by welding. Thus, the cylindrical member 34 and the recessed part 33 are provided along the outer peripheral surface of the lid member 30. Therefore, as shown in FIG. 11, when a plurality of lid members 30 are arranged in a plane, the outer peripheral surfaces of the lid members 30 come into contact with each other, and the cylindrical member 34 of one lid member 30 The lid member 30 is engaged with the recess 33.

  Further, in the plan view of the lid member 30, the curvature of the curved recess 33 is the same as the curvature of the outer periphery of the cylindrical member 34. Further, the outer periphery of the cylindrical member 34 can be surrounded by the recesses 33 of the three lid members 30. Therefore, when the cylindrical member 34 of one lid member 30 is engaged with the recess 33 of the surrounding lid member 30, the lid members 30 can be arranged closely.

  As shown in FIG. 12, when covering the opening of the drain sump 7 with a plurality of lid members 30, first, the fixing portion 37 is formed by drilling holes in the floor surface 6 near the drain sump 7 and the bottom of the drain sump 7. . A support bar 38 is fixed to the fixing portion 37. The support bar 38 extends in the vertical direction. Note that a holding member 39 that holds the lid member 30 is fixed to a portion of the support bar 38 that is erected from the fixing portion 37 at the bottom of the drain sump 7 at the same height as the floor surface 6.

  The through hole 35 of the cylindrical member 34 is a circular hole, and the support bar 38 is a cylindrical member. The diameter of the support bar 38 is smaller than the diameter of the through hole 35 of the cylindrical member 34. The lid member 30 is installed in a state where the support bar 38 is inserted into the through hole 35 of the cylindrical member 34. In the third embodiment, the plurality of lid members 30 are stacked by inserting the through holes 35 into the upper ends of the support bars 38. In the third embodiment, the combination means is constituted by the through hole 35 and the support rod 38. When the opening of the drain sump 7 is closed with a plurality of lid members 30, water leakage generated inside the reactor containment vessel 4 can pass through the gap between the lid members 30 and enter the drain sump 7. Yes. Further, unevenness for forming a gap through which water can pass may be formed on the side surface of the lid member 30.

  Further, the length of the support bar 38 erected from the fixed portion 37 of the floor surface 6 is formed longer than the vertical dimension of the lid member 30. Further, in the support bar 38 erected from the fixed part 37 at the bottom of the drain sump 7, the length from the holding member 39 to the upper end part of the support bar 38 is longer than the vertical dimension of the lid member 30. Therefore, the plurality of lid members 30 can be stacked in the vertical direction by the respective support bars 38. The lid members 30 stacked in this way can maintain the stacked state even when an external force such as an earthquake is applied. In this example, the three-stage lid member 30 is stacked in the vertical direction, but the opening of the drain sump 7 may be covered by the single-stage lid member 30 without stacking the lid member 30 in the vertical direction.

  Further, the edge of the lid member 30 that is not supported by the support bar 38 is placed on the floor surface 6 near the drain sump 7. Further, the concave portion 33 on the edge not supported by the support bar 38 is engaged with the cylindrical member 34 of the other lid member 30 so that the lid member 30 is not rotated in the horizontal direction.

  In the third embodiment, the through hole 35 of the cylindrical member 34 has a circular shape and the support bar 38 has a cylindrical shape, but the through hole 35 of the cylindrical member 34 has a rectangular shape and is supported. The rod 38 may have a prismatic shape. Since the support bar 38 has a prismatic shape, the lid member 30 can be prevented from rotating. Further, in this example, the cylindrical member 34 is formed in a cylindrical shape, but the cylindrical member 34 may be formed in a rectangular cylindrical shape.

  Further, since the heat-resistant material 32 is covered with the structural material 31 and is maintained in a state where water does not permeate the heat-resistant material 32, the heat-resistant material 32 is maintained even when the high-temperature core melt contacts the heat-resistant material 32. Since the steam explosion does not occur inside and the shape of the heat-resistant material 32 is maintained, the function of preventing the core melt from entering the drain sump 7 can be maintained. Moreover, nuclear reaction can be suppressed because the cover member 30 has a neutron absorber.

(Fourth embodiment)
Next, the lid member 40 of the fourth embodiment will be described with reference to FIGS. 13 to 14. As shown in FIG. 13, the lid member 40 of the fourth embodiment has a substantially hexahedral block shape. The structural member 41 constituting the outer surface of the lid member 40 is formed from a metal material such as stainless steel. Furthermore, a heat-resistant material 42 made of a material such as metal oxide ceramics is provided inside the structural material 41. A powdered neutron absorber is filled between the structural material 41 and the heat-resistant material 42.

  The structural member 41 forms a substantially rectangular box as viewed from the side, and is formed with recesses 43 whose corners at the four corners are cut out in a curved shape. That is, in the structural material 41, the recess 43 is provided on the outer peripheral surface including the upper surface and the lower surface. Note that the corners at the four corners of the heat-resistant material 42 inside the structural material 41 are also provided with recesses that are cut out in a curved shape.

  A cylindrical member 44 having a cylindrical shape is provided at one of the four corners of the cutout of the structural member 41. The cylindrical member 44 is formed of a metal material such as stainless steel and has a through hole 45 (hole portion) penetrating in the horizontal direction. Moreover, the cylinder member 44 is being fixed to the corner | angular part of the structural material 41 by welding. Thus, the cylindrical member 44 and the recessed part 43 are provided along the outer peripheral surface of the lid member 40. Therefore, as shown in FIG. 14, when a plurality of lid members 40 are arranged in a plane, the side surfaces of the lid members 40 are in contact with each other, and the cylindrical member 44 of one lid member 40 is adjacent to each other. The lid member 40 is engaged with the recess 43.

  Further, in the side view of the lid member 40, the curvature of the curved recess 43 is the same as the curvature of the outer periphery of the cylindrical member 44. Therefore, when the cylindrical member 44 of one lid member 40 is engaged with the recess 43 of another adjacent lid member 40, the lid members 40 can be arranged closely.

  As shown in FIG. 14, when covering the opening of the drain sump 7 with a plurality of lid members 40, first, a support bar 47 extending in the horizontal direction is inserted into the through hole 45 of the cylindrical member 44. Then, the end portion of the support rod 47 is fixed to the floor surface 6 near the drain sump 7 or the like. The support bar 47 is installed in a direction in which the longitudinal direction is perpendicular to the extending direction of the drain sump 7. Furthermore, although not shown in this example, a plurality of frame members for fixing the support rod 47 may be bridged over the drain sump 7. Further, by supporting the support bar 47 on these frame members, the longitudinal direction thereof may be set in the same direction as the extending direction of the drain sump 7.

  Further, the through hole 45 of the cylindrical member 44 is a circular hole, and the support bar 47 is a cylindrical member. Note that the diameter of the support rod 47 is smaller than the diameter of the through hole 45 of the cylindrical member 44. The lid member 40 is installed in a state where the support rod 47 is inserted into the through hole 45 of the cylindrical member 44. In the third embodiment, the combination means is configured by the through hole 45 and the support rod 47. When the opening of the drain sump 7 is closed with a plurality of lid members 40, water leakage generated inside the reactor containment vessel 4 can pass through the gap between the lid members 40 and enter the drain sump 7. Yes. Further, unevenness for forming a gap through which water can pass may be formed on the side surface of the lid member 40.

  The length of the support bar 47 is longer than the left and right dimensions of the lid member 40. For this reason, the plurality of lid members 40 can be supported by the support rods 47 in the left-right direction. The lid member 40 thus supported can maintain a stacked state even when an external force such as an earthquake is applied. In this example, the cylindrical member 44 is provided and installed on the lower side of the lid member 40, but the cylindrical member 44 may be provided and installed on the upper side of the lid member 40. That is, the lid member 40 in FIG. 14 may be installed in an inverted state.

  Further, the edge of the lid member 40 on the side not supported by the support rod 47 is engaged with the cylindrical member 44 of the other lid member 40 so that the lid member 40 is not rotated in the vertical direction. Yes.

  In the fourth embodiment, the through hole 45 of the cylindrical member 44 has a circular shape and the support bar 47 has a cylindrical shape, but the through hole 45 of the cylindrical member 44 has a rectangular shape and is supported. The rod 47 may have a prismatic shape. Since the support rod 47 has a prismatic shape, the lid member 40 can be prevented from rotating.

  In addition, since the heat-resistant material 42 is covered with the structural material 41 and is maintained in a state where water does not permeate the heat-resistant material 42, the heat-resistant material 42 even if the high-temperature core melt contacts the heat-resistant material 42. Since the steam explosion does not occur inside the heat-resistant material 42 and the shape of the heat-resistant material 42 is maintained, the function of preventing the core melt from entering the drain sump 7 can be maintained. Moreover, nuclear reaction can be suppressed because the cover member 40 has a neutron absorber.

  In addition, although the recessed part 43 is provided in the corner | angular part of the four corners of the structural material 41, and the cylinder member 44 is provided in one corner | angular part, it is good also as another form. For example, a configuration in which the concave portions 43 are provided at two corners of the four corners of the structural member 41 and the cylindrical member 44 is provided at the two corners may be employed. Further, the concave portion 43 and the cylindrical member 44 may not be provided at the four corners of the structural member 41. For example, the concave portion 43 and the cylindrical member 44 may be provided at each central position on the four sides of the structural member 41.

(Fifth embodiment)
Next, the lid member 50 of the fifth embodiment will be described with reference to FIGS. 15 to 19. As shown in FIG. 15, the lid member 50 of the fifth embodiment has two structural members 51 stacked one above the other. Each structural member 51 has a hexahedral block shape forming a substantially square box in plan view. These structural members 51 are formed from a metal material such as stainless steel. Further, a heat-resistant material 52 made of a material such as metal oxide ceramics is provided inside each structural material 51. A powdered neutron absorber is filled between the structural material 51 and the heat-resistant material 52.

  As shown in FIG. 16, the upper and lower structural members 51 are provided displaced in the horizontal direction. In this example, the upper and lower structural members 51 are displaced in the horizontal direction so that one corner of the upper structural member 51 is disposed at the center position of the lower structural member 51 in plan view. A welded portion 53 is provided in which contact surfaces between the lower surface of the upper structural member 51 and the upper surface of the lower structural member 51 are welded to each other. That is, a step (stepped portion) is formed by the upper, lower, and side surfaces of the upper and lower structural members 51.

  As shown in FIG. 18, when the openings of the drain sump 7 are covered with a plurality of lid members 50, first, the structure above the other lid member 50 is formed on the upper surface of the structural material 51 below the one lid member 50. The lower surface of the material 51 is placed. In this way, the side surfaces of the upper structural material 51 and the side surfaces of the lower structural material 51 are brought into contact with each other in the lid members 50. That is, when the plurality of lid members 50 are combined in the horizontal direction, the lid members 50 are closely arranged by engaging the steps of one lid member 50 with the steps of the other lid member 50. be able to. When the opening of the drain sump 7 is closed with a plurality of lid members 50, water leakage generated inside the reactor containment vessel 4 can pass through the gap between the lid members 50 and enter the drain sump 7. Yes. Further, irregularities for forming a gap through which water can pass may be formed on the side surface of the lid member 50.

  As shown in FIGS. 17 and 19, when the plurality of lid members 50 are arranged in a plane, the upper structural member 51 covers the space between the lower structural members 51. In addition, since the heat-resistant material 52 is provided inside each structural material 51 (see FIG. 16), when the plurality of lid members 50 are arranged in a plane, a space between the heat-resistant materials 52 below is provided. An upper heat-resistant material 52 is covered. Therefore, even if the core melt melts the structural material 51 when a severe accident occurs, the upper heat-resistant material 52 closes the gap between the lower heat-resistant materials 52, so that the core melt is prevented from entering the drain sump 7. it can.

  In addition, since the heat-resistant material 52 is covered with the structural material 51 and is maintained in a state in which water does not permeate the heat-resistant material 52, the heat-resistant material 52 even if the high-temperature core melt contacts the heat-resistant material 52. Since no steam explosion occurs inside and the shape of the heat-resistant material 52 is maintained, the function of preventing the core melt from entering the drain sump 7 can be maintained. Moreover, nuclear reaction can be suppressed because the cover member 50 has a neutron absorber.

  A plurality of frame members for supporting the plurality of lid members 50 may be bridged over the drain sump 7. Further, a support bar extending upward from the bottom surface of the drain sump 7 may be provided, and the lid member 50 may be supported on the upper end portion of the support bar.

  Thus, in this embodiment, it has heat-resistant materials 12, 22, 32, 42, 52 made of a material such as ceramics, and all of the surfaces of the heat-resistant materials 12, 22, 32, 42, 52 are made of metal. Cover members 10 and 20 satisfying all of heat resistance, impact resistance, ease of installation, and water impermeability (water permeation prevention function) by being covered with structural members 11, 21, 31, 41 and 51 made of materials. , 30, 40, 50 can be formed.

  In the above-described embodiment, the structural materials 11, 21, 41, 51 are formed of a metal material such as stainless steel, but the structural material may be formed of other materials. For example, the structural material may be formed of a hard resin material. Furthermore, the structural material may be formed using fiber reinforced plastic (FRP) or the like. By using such a fiber reinforced plastic structural material, the core melt is deprived of heat as the heat of evaporation when the core melt melts and evaporates the structural material. The core melt does not fall to the bottom of the drain sump 7.

  Note that the above-described embodiments may be combined. For example, the lid members 20 may be connected to each other by providing the convex portions 13 and the concave portions 14 of the first embodiment on the upper surface, the lower surface, and the side surfaces of the lid member 20 of the second embodiment. Further, the through hole 24 of the second embodiment is formed with respect to the lid member 50 of the fifth embodiment, and the support bar is inserted into the through hole 24 to support the lid member 50 using the support bar. You may do it.

  According to the embodiment described above, by having a lid member formed of a heat-resistant material containing a ceramic material, a structural material that has a higher toughness than this heat-resistant material and covers the entire surface of the heat-resistant material, It can be prevented from being damaged even when impacted by falling objects, and by preventing water from penetrating into the heat-resistant material, it is possible to maintain the function of preventing the intrusion of the core melt even when severe accidents occur.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, replacements, changes, and combinations can be made without departing from the scope of the invention. These embodiments and their modifications are included in the scope and gist of the invention, and are also included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Reactor pressure vessel, 2 ... Core, 3 ... Bottom part, 4 ... Reactor containment vessel, 5 ... Water injection line, 6 ... Floor surface, 7 ... Drain sump, 10 ... Cover member, 11 ... Structural material, 12 ... Heat-resistant material , 13 ... convex part, 14 ... concave part, 15 ... neutron absorber, 20 ... lid member, 21 ... structural material, 22 ... heat-resistant material, 24 ... through hole, 25 ... neutron absorber, 26 ... through hole, 27 ... fixed , 28 ... support rod, 30 ... lid member, 31 ... structural material, 32 ... heat-resistant material, 33 ... recess, 34 ... cylindrical member, 35 ... through hole, 37 ... fixing part, 38 ... support rod, 39 ... holding member 40 ... Lid member, 41 ... Structural material, 42 ... Heat-resistant material, 43 ... Recess, 44 ... Tube member, 45 ... Through hole, 47 ... Support rod, 50 ... Lid member, 51 ... Structural material, 52 ... Heat-resistant material, 53 ... welded part.

Claims (8)

A drain sump that is provided at the bottom and has an opening at the top to collect and drain leaks;
A lid member formed of a heat-resistant material containing at least a ceramic material and a structural material covering the heat-resistant material;
A combination means for combining the lid members with each other;
With
A reactor containment vessel characterized in that the opening of the drain sump is covered from above by a plurality of lid members combined by the combination means.   2. The reactor containment vessel according to claim 1, wherein the structural material is made of a hard resin material or a metal material having a surface subjected to rust prevention treatment. The lid member has a block shape having at least six surfaces;
The union means is
Engaging portions provided on three adjacent surfaces of the six surfaces of the lid member;
An engaged portion provided on a surface opposite to the surface on which the engaging portion is provided and engaged with the engaging portion of another lid member;
The reactor containment vessel according to claim 1 or 2, characterized by comprising: The combination means consists of a through hole provided in the lid member,
2. The support member is provided on a floor surface or a wall surface of the reactor containment vessel, and the cover members can be combined by inserting the support rod into the through hole. The reactor containment vessel according to any one of claims 1 to 3. The union means is
A cylindrical member provided on the outer peripheral surface of the lid member and having a hole;
A concave portion provided on the outer peripheral surface opposite to the portion provided with the cylindrical member and engaged with the cylindrical member of the other lid member;
The reactor containment vessel according to any one of claims 1 to 4, characterized by comprising: The lid member has at least two upper and lower heat-resistant materials laminated,
The combination means comprises a step portion formed on the lid member by providing the heat-resistant materials displaced in the horizontal direction,
When the plurality of lid members are combined in the horizontal direction, the stepped portions of the one lid member are engaged with the stepped portions of the other lid member, so that the space between the lower heat-resistant materials is increased. The reactor containment vessel according to any one of claims 1 to 5, wherein the heat-resistant material is covered.   The nuclear reactor containment vessel according to claim 1, wherein the lid member includes a neutron absorber. A drain sump that is provided at the bottom of the reactor containment vessel and has an opening at the top, for collecting and draining water leaking inside the reactor containment vessel,
A lid member formed of a heat-resistant material containing at least a ceramic material and a structural material covering the heat-resistant material;
A combination means for combining the lid members with each other;
With
A drain sump for a nuclear reactor containment vessel, wherein the plurality of lid members combined by the combination means are arranged so as to cover the opening from above.

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