JP2017187370A - Nuclear reactor containment and molten reactor core receiving device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent or suppress reaction between debris of a molten reactor core and a pedestal floor from progressing in a case that a core meltdown accident occurs.SOLUTION: According to an embodiment, a nuclear reactor containment 13 has: a cylindrical pedestal wall 16 for supporting a nuclear reactor pressure containment 12; a pedestal floor 18 surrounded with the pedestal wall 16, positioned below the nuclear reactor pressure containment 12, and constituting a bottom part of the nuclear reactor containment 13; and a molten reactor core receiving part 26 arranged above the pedestal floor 18. The molten reactor core receiving part 26 is made of a material having a higher melting point, higher heat resistance, and low reactivity than a material constituting the pedestal floor 18. The molten reactor core receiving part 26 causes, when a meltdown is happening, a flow of a molten reactor core to branch off before reaching the pedestal floor 18, and absorbs heat of the molten reactor core so as to lower the temperature of the molten reactor core.SELECTED DRAWING: Figure 1

Description

  Embodiments described herein relate generally to a nuclear reactor containment vessel and a melting core receiving device provided with means for responding to a core melting accident.

  In the nuclear reactor, if some accident event causes a situation such as pipe loss or loss of coolant in the reactor pressure vessel due to damage to the reactor pressure vessel itself, or loss of heat removal function generated in the core, As the fuel in the core melts, the high-temperature molten fuel (molten core, debris) may flow downward from the core.

  When this happens, debris accumulates on the bottom of the pressure vessel. As the state continues, the bottom of the reactor pressure vessel is damaged and flows into the reactor containment vessel. The spilled debris heats the reactor containment concrete and causes a debris-concrete reaction. In this reaction, when concrete is heated to a high temperature, a large amount of non-condensable gases such as carbon dioxide and hydrogen are generated and the concrete is melted and eroded. Generation of a large amount of non-condensable gas may increase the pressure in the reactor containment vessel and lead to damage to the reactor containment vessel. On the other hand, when a signal for melting the core is transmitted, water is injected into the pedestal at the bottom of the reactor containment vessel, and there is also a system for suppressing the erosion. However, when the reactor containment vessel is damaged, a large amount of radioactive material is released to the outside environment.

  In order to avoid the above situation, the following measures have been proposed.

  For example, in order to suppress the debris-concrete reaction caused by debris flowing into the containment vessel, a proposal has been made to promote the cooling of the debris by installing a holding device (core catcher) for receiving the falling debris and providing a cooling means. Yes.

  Further, as a method for suppressing the debris-concrete reaction in the pedestal, a method for suppressing erosion by forming the wall surface and floor surface of the pedestal region with concrete having coarse aggregate is known.

JP 2008-139023 A Japanese Patent No. 4580855

  In any known technique for installing the core catcher, it is not considered that debris is deposited in a thinly dispersed state on the core catcher in any case where the debris flows out of the core of the nuclear reactor. In addition, when a large amount of debris flows out in a short time, there is a problem that the debris may reach the bottom of the pressure vessel over the wall of the core catcher.

  Moreover, in the said well-known technique using the concrete which has a coarse aggregate in the wall surface and floor surface of a pedestal area | region, a debris-concrete reaction is suppressed by the composition of concrete. However, when collective debris accumulates in one place, there is a problem that the concrete debris reaction may proceed due to the progress of concrete heating.

  The embodiment of the present invention has been made in view of the above circumstances, and prevents the progress of the reaction between the debris and the pedestal bed by the molten core when a core melting accident occurs and the debris falls into the pedestal space. Or to suppress.

  A reactor containment vessel according to an embodiment of the present invention is a reactor containment vessel that houses a reactor pressure vessel that houses a core, and includes a cylindrical pedestal wall that supports the reactor pressure vessel, and the pedestal wall A pedestal floor that is positioned below the reactor pressure vessel and that constitutes the bottom of the reactor containment vessel, and is disposed above the pedestal floor and is higher than the material that constitutes the pedestal floor. A melting core receiving portion made of a material having a melting point, high heat resistance, and low reactivity, and the melting core receiving portion has a melting core formed by melting the core below the reactor pressure vessel. When the molten core falls, before the molten core reaches the pedestal bed, the flow of the molten core is branched into a plurality of parts, the heat of the molten core is absorbed, and before the molten core reaches the pedestal bed Of the melting core It is intended to reduce the degree, characterized by.

  Further, the molten core receiving apparatus according to the embodiment of the present invention includes a pedestal floor that is surrounded by a cylindrical pedestal wall that supports the reactor pressure vessel and forms the bottom of the reactor containment vessel below the reactor pressure vessel. A melting core receiving device disposed above the pedestal bed, which is made of a material having a high melting point, high heat resistance and low reactivity compared to the material constituting the pedestal bed, and forming a gap between them in the horizontal direction And when the molten core formed by melting the reactor core in the reactor pressure vessel falls below the reactor pressure vessel. In addition, before the molten core reaches the pedestal bed, the flow of the molten core is branched into a plurality of parts, the heat of the molten core is absorbed, and the molten core before the molten core reaches the pedestal bed. To lower the temperature of Sometimes, and it said.

  According to the embodiment of the present invention, when a core melting accident occurs and debris falls into the pedestal space, it is possible to prevent or suppress the progress of the reaction between the debris and the pedestal floor caused by the molten core.

1 is a schematic sectional elevation showing an entire reactor containment vessel according to a first embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning a 1st embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning a 2nd embodiment of the present invention. It is an elevational sectional view around the pedestal space showing a situation where the molten core has dropped into the pedestal space in the reactor containment vessel according to the third embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space with the reactor containment vessel concerning a 4th embodiment of the present invention. It is sectional drawing which expands and shows one of the lump of FIG. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning a 5th embodiment of the present invention. It is an elevational sectional view around a pedestal space showing a situation immediately after the occurrence of a core melting accident in a reactor containment vessel according to a sixth embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning the 6th embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning a 7th embodiment of the present invention. It is an elevation sectional view of the circumference of a pedestal space which shows the situation where the fusion core fell to the pedestal space by the reactor containment vessel concerning the 8th embodiment of the present invention. It is an elevational sectional view around the pedestal space showing a situation in which the molten core has dropped into the pedestal space in the reactor containment vessel according to the ninth embodiment of the present invention.

  Hereinafter, embodiments of a reactor containment vessel and a melting core receiving apparatus according to the present invention will be described with reference to the drawings. Here, the same or similar parts are denoted by common reference numerals, and redundant description is omitted.

[First Embodiment]
FIG. 1 is a schematic vertical sectional view showing the entire reactor containment vessel according to the first embodiment of the present invention. FIG. 2 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the first embodiment of the present invention.

  Here, a boiling water reactor will be described as an example. The core 11 is accommodated in the reactor pressure vessel 12, and the reactor pressure vessel 12 is accommodated in the reactor containment vessel 13. The reactor containment vessel 13 is divided into a dry well 14 and a wet well 15, and the reactor pressure vessel 12 is arranged in the dry well 14.

  A cylindrical pedestal wall 16 is disposed in the lower portion of the dry well 14, and the reactor pressure vessel 12 is supported by the pedestal wall 16 via a vessel support (not shown). A pedestal floor 18 is formed at the bottom of a space (pedestal space) 17 surrounded by the pedestal wall 16. The pedestal wall 16 and the pedestal floor 18 are made of concrete.

  The wet well 15 is disposed so as to surround the pedestal wall 16, and a pressure suppression pool 19 is formed in the wet well 15. A vent pipe 20 extends from the dry well 14 into the pressure suppression pool 19. At the time of an accident, the vapor in the dry well 14 flows into the pressure suppression pool 19 through the vent pipe 20 and condenses, so that the pressure increase in the reactor containment vessel 13 is suppressed.

  In order to supply the water of the pressure suppression pool 19 to the pedestal space 17 at the time of an accident, the emergency cooling water supply piping 21 is connected to the pressure suppression pool 19, and the emergency cooling water supply valve 22 is arrange | positioned in the middle.

  Assuming a core melting accident, the molten core receiving portion (melting) for receiving the molten core 25 before the molten core 25 (see FIG. 2) that has dropped through the bottom of the reactor pressure vessel 12 reaches the pedestal bed 18. A core receiving device 26 is arranged on the pedestal floor 18.

  In the melting core receiving portion 26, a plurality of masses 27 are arranged in the horizontal direction and the vertical direction, and a small gap is formed between the masses 27 adjacent to each other. Each lump 27 is made of a material having a high melting point, high heat resistance, and low reactivity compared to the concrete constituting the pedestal floor 18. As such a material, for example, a metal such as tungsten, molybdenum, or copper, or a metal oxide such as beryllium oxide can be considered.

  The shape of each mass 27 may be any shape as long as it allows a gap through which the molten core 25 can pass when in contact with each other, such as a sphere or a cylinder, or an irregular shape. .

  In this embodiment, when a core melting accident occurs, the emergency cooling water supply valve 22 is opened, and the water in the pressure suppression pool 19 is supplied to the pedestal space 17 through the emergency cooling water supply pipe 21. Thereby, as shown in FIG. 2, the periphery of the melting core receiving part 26 in the pedestal space 17 is filled with water.

  On the other hand, it is assumed that the molten core 25 is formed by melting the core, and the molten core 25 falls downward from the bottom of the reactor pressure vessel 12. In that case, as shown in FIG. 2, the molten core 25 reaches the molten core receiving portion 26 before reaching the pedestal bed 18.

  The molten core 25 is cooled by water in the pedestal space 17. Further, when the molten core 25 flows down through the gaps between the adjacent masses 27, the molten core 25 branches and flows, and each mass 27 absorbs the heat of the molten core 25, so that the molten core 25 becomes the pedestal bed 18. Before reaching the temperature, the temperature of the melting core 25 decreases. Thereby, the chemical reaction between the concrete which comprises the pedestal floor 18 and the molten core 25 can be suppressed or prevented.

  As a configuration for supplying cooling water to the pedestal space 17 at the time of a core melting accident, in the above description, the emergency cooling water supply pipe 21 and the emergency cooling water supply valve 22 are used to supply the water in the pressure suppression pool 19 to the pedestal space 17. To supply. Instead of such a configuration, a cooling water pool (not shown) different from the pressure suppression pool 19 is provided inside or outside the reactor containment vessel 13, and the cooling water pool is stored in the pedestal space 17 in the event of a core melting accident. You may make it supply to.

[Second Embodiment]
FIG. 3 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the second embodiment of the present invention.

  In the second embodiment, the melting core receiving part (melting core receiving device) 26 includes a plurality of masses 27 arranged on the pedestal floor 18 and a plurality of masses 27 inside the pedestal wall 16. And a cylindrical partition plate 30 surrounding the outer periphery in the horizontal direction. The upper part of the cylindrical partition plate 30 is open. An annular space 31 is formed between the pedestal wall 16 and the cylindrical partition plate 30. A plurality of partition plate through holes 33 are formed on the side wall of the cylindrical partition plate 30.

  An upper plate 32 that extends horizontally so as to cover the upper side of the plurality of masses 27 inside the cylindrical partition plate 30 is disposed. The upper plate 32 is fixed to the cylindrical partition plate 30, and a plurality of upper plate through holes 35 are formed in the upper plate 32.

  The lump 27, the cylindrical partition plate 30, and the upper plate 32 are all made of a material having a high melting point, high heat resistance, and low reactivity compared to the concrete constituting the pedestal floor 18.

  In the example illustrated in FIG. 3, each of the plurality of masses 27 has a spherical shape or a cylindrical shape having substantially the same diameter. In addition, a plurality of depressions 34 are formed in the pedestal floor 18 that is in direct contact with the lump 27, and the lump 27 enters the depression 34 of the pedestal floor 18 so that the lump 27 is placed on the pedestal floor 18. The movement is suppressed.

  Further, the movement of the mass 27 is also suppressed by arranging the upper plate 32 above the plurality of masses 27.

  In this embodiment, when a core melting accident occurs, the periphery of the molten core receiving portion 26 in the pedestal space 17 is filled with water, as in the first embodiment.

  The molten core 25 is cooled by water in the pedestal space 17. Further, the melting core 25 falls down from the bottom of the reactor pressure vessel 12 and hits the upper surface of the upper plate 32 before contacting the plurality of masses 27, and the plurality of upper plate through-holes 35 of the upper plate 32 are formed. pass. Thereafter, the molten core 25 flows downward while branching into the gaps between the plurality of masses 27. In this case, the upper plate 32 and the mass 27 absorb the heat of the molten core 25, and the temperature of the molten core 25 is lowered before the molten core 25 reaches the pedestal bed 18. Thereby, the chemical reaction between the concrete which comprises the pedestal floor 18 and the molten core 25 can be suppressed or prevented.

  In this embodiment, the water in the pedestal space 17 descends the annular space 31 and flows into the cylindrical partition plate 30 through the plurality of partition plate through holes 33 of the cylindrical partition plate 30. Then, the water inside the cylindrical partition plate 30 rises while cooling the lump 27, the upper plate 32 and the melting core 25, and passes through the upper plate through hole 35 of the upper plate 32 to the upper side. Thus, natural convection of water is promoted by the presence of the cylindrical partition plate 30, and cooling of the molten core 25 is promoted.

  When the core melting accident occurs and the molten core 25 reaches the upper surface of the upper plate 32, the upper plate 32 is expected to be destroyed by melting or the like. It is expected that the molten core 25 flows to a position where the molten core 25 contacts the plurality of masses 27. Therefore, as a modification of the second embodiment, a configuration in which the upper plate through hole 35 is not provided in advance is also possible.

[Third Embodiment]
FIG. 4 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the third embodiment of the present invention.

  This third embodiment is a modification of the second embodiment. In the third embodiment, there are two pieces corresponding to the upper plate 32 of the second embodiment, and these are arranged at intervals in the vertical direction. Here, the upper upper plate is referred to as an upper upper plate 32a, and the lower upper plate is referred to as a lower upper plate 32b. A plurality of upper plate through holes 35 are formed in each of the upper upper plate 32a and the lower upper plate 32b.

  A plurality of partition plate through-holes 33 are formed at a position between the lower upper plate 32b and the upper upper plate 32a and below the lower upper plate 32b.

  The configuration other than the above is the same as that of the second embodiment.

  In the third embodiment, when a core melting accident occurs, the periphery of the molten core receiving portion 26 in the pedestal space 17 is filled with water, as in the second embodiment.

  When the melting core 25 falls downward from the bottom of the reactor pressure vessel 12, the melting core 25 first hits the upper upper plate 32a and passes through the upper plate through holes 35 of the upper upper plate 32a. Thereafter, the melting core 25 flows downward while branching the gaps between the plurality of lumps 27 between the upper upper plate 32a and the lower upper plate 32b. Thereafter, the melting core 25 hits the lower upper plate 32b and passes through the plurality of upper plate through holes 35 of the lower upper plate 32b. Thereafter, the melting core 25 flows downward while branching the gaps between the plurality of masses 27 below the lower upper plate 32b. Thereafter, the molten core 25 reaches the pedestal bed 18.

  As described above, in the third embodiment, the molten core 25 dropped through the reactor pressure vessel 10 is formed on the upper upper plate 32a and the lower upper plate 32b before reaching the pedestal floor 18. It passes through the upper plate through-hole 35 and passes between thicker layers of the plurality of masses 27 as compared to the second embodiment. Therefore, it is expected that the temperature of the molten core 25 when the molten core 25 reaches the pedestal bed 18 is further lowered as compared with the second embodiment.

  At this time, the water in the pedestal space 17 descends the annular space 31 and is formed between the lower upper plate 32b and the upper upper plate 32a and at positions below the lower upper plate 32b. Flows into the inside of the cylindrical partition plate 30 through the partition plate through hole 33. The water inside the cylindrical partition plate 30 rises while cooling the mass 27, the lower upper plate 32 b, the upper upper plate 32 a, and the melting core 25.

  When the core melting accident occurs and the melting core 25 reaches the upper surface of the upper upper plate 32a, it is expected that the upper upper plate 32a is destroyed by melting or the like. Similarly, when the melting core 25 reaches the upper surface of the lower upper plate 32b, the lower upper plate 32b is expected to be destroyed by melting or the like. Therefore, for the same reason as described as a modification in the description of the second embodiment, the upper plate through hole 35 is not provided in advance as a modification of the third embodiment. Is possible.

  Furthermore, in the third embodiment, the upper upper plate 32a and the lower upper plate 32b are provided to form a two-stage structure, but three or more stages are also possible.

[Fourth Embodiment]
FIG. 5 is an elevational sectional view around the pedestal space showing a situation where the molten core has dropped into the pedestal space in the reactor containment vessel according to the fourth embodiment of the present invention. 6 is an enlarged cross-sectional view showing one of the blocks shown in FIG.

  The fourth embodiment is a modification of the third embodiment, in which cavities 40 are formed in the respective masses 27 and openings 41 of the cavities 40 are formed.

  The configuration other than the above is the same as that of the third embodiment.

  According to the fourth embodiment, when the lump 27 is heated by the heat of the molten core 25 at the time of the core melting accident, the air in the cavity 40 is ejected and cracked in the molten core 25 that is solidifying. Can be generated. The cooling water flows along the cracks, whereby the cooling of the molten core 25 can be promoted. The cooling of the molten core 25 can also be promoted by the molten core 25 flowing into the cavity 40.

  As a modification of the fourth embodiment, it is also possible to form the cavities 40 in the respective masses 27 and not form the openings 41 of the cavities 40 in advance. Even in that case, when the lump 27 is heated by the heat of the melting core 25, a part of the lump 27 is melted or broken to form an opening, and the opening 41 is formed in advance. Similar effects can be obtained.

  In the example shown in FIG. 5, it seems that the cavities 40 are formed in all the plurality of lumps 27, but the cavities 40 are formed in a part of the plurality of lumps 27, and the cavities 40 are formed in the other lumps 27. A configuration in which is not formed is also possible.

[Fifth Embodiment]
FIG. 7 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the fifth embodiment of the present invention.

  The fifth embodiment is a modification of the fourth embodiment, in which cavities 40 are formed in the respective masses 27, and water is enclosed in the cavities 40. The opening 41 (FIG. 6) is not formed.

  Other configurations are the same as those in the fourth embodiment.

  According to the fifth embodiment, when the lump 27 is heated by the heat of the melting core 25 at the time of the core melting accident, a part of the lump 27 is melted or broken, and the water in the cavity 40 is discharged. It is possible to generate cracks in the molten core 25 that is ejected and solidified. The cooling water flows along the cracks, whereby the cooling of the molten core 25 can be promoted. The cooling of the molten core 25 can also be promoted by the molten core 25 flowing into the cavity 40.

  In the example shown in FIG. 7, it seems that the cavities 40 are formed in all the masses 27 and water is sealed in all the cavities 40, but this embodiment is not limited to such a configuration. That is, a configuration in which the cavity 40 is formed in a part of the plurality of lumps 27 and the cavity 40 is not formed in the other lumps 27 is possible, and water is sealed in a part of the plurality of cavities 40. In addition, a configuration in which water is not sealed in the other cavity 40 is also possible.

[Sixth Embodiment]
FIG. 8 is an elevational sectional view around the pedestal space showing a situation immediately after the occurrence of a core melting accident in a reactor containment vessel according to the sixth embodiment of the present invention. FIG. 9 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the sixth embodiment.

  The sixth embodiment is a modification of the first embodiment. In the sixth embodiment, a storage box 50 is attached to the pedestal wall 16, and a plurality of masses 27 of the molten core receiving portion 26 are stored in the storage box 50 during normal operation of the nuclear reactor. Yes. A storage box opening / closing device 51 is attached to the storage box 50. The storage box opening / closing device 51 is closed during normal operation of the reactor and is configured to open immediately after the occurrence of a core melting accident. When the storage box opening / closing device 51 is opened, the plurality of masses 27 stored in the storage box 50 are discharged into the pedestal space 17.

  In the sixth embodiment, the lump 27 preferably has a shape that is easy to roll, for example, a spherical shape.

  The configuration other than the above is the same as that of the first embodiment.

  In this sixth embodiment, when a core melting accident occurs, the emergency cooling water supply valve 22 (FIG. 1) is opened, and the water in the pressure suppression pool 19 is supplied to the pedestal space 17 through the emergency cooling water supply pipe 21. Is done. Thereby, the vicinity of the pedestal floor 18 in the pedestal space 17 is filled with water. Further, the storage box opening / closing device 51 is opened, and a plurality of masses 27 of the melting core receiving part 26 come out of the storage box 50 and fall and accumulate on the pedestal floor 18 in the pedestal space 17.

  Thereafter, when the molten core 25 falls downward from the bottom of the reactor pressure vessel 12, the molten core 25 is a mass of the molten core receiving portion 26 before reaching the pedestal floor 18, as shown in FIG. 27, each mass 27 absorbs the heat of the molten core 25, and the temperature of the molten core 25 decreases before the molten core 25 reaches the pedestal bed 18.

[Seventh Embodiment]
FIG. 10 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the seventh embodiment of the present invention.

  In this embodiment, a horizontally extending plate-like portion 60 is disposed as a melting core receiving portion above the pedestal floor 18 at a position spaced from the upper surface of the pedestal floor 18. The plate-like portion 60 is disposed so as to cover the pedestal floor 18 and has a protruding portion 61 that penetrates the pedestal wall 16 and extends outward in the horizontal direction of the pedestal space 17. The plate-like portion 60 is made of a material having a high melting point, high heat resistance, and low reactivity as compared with the concrete constituting the pedestal floor 18 and is porous in which a large number of through holes (not shown) are formed. For example, a sintered body.

  The configuration other than the above is the same as that of the first embodiment.

  In this embodiment, when a core melting accident occurs, the vicinity of the pedestal floor 18 and the plate-like portion 60 in the pedestal space 17 is filled with water, as in the first embodiment.

  The molten core 25 falls from the bottom of the reactor pressure vessel 12 into the lower pedestal space 17 and hits the upper surface of the plate-like portion 60. Thereafter, the melting core 25 gradually passes through the plate-like portion 60 through the many through holes of the plate-like portion 60 and then reaches the pedestal bed 18. The molten core 25 is cooled by the water in the pedestal space 17 and is cooled by the plate-like portion 60 while passing through the through hole of the plate-like portion 60. The heat of the plate-like portion 60 spreads in the horizontal direction and is also released to the outside of the pedestal wall 16 through the protruding portion 61.

  By using a porous material (for example, a sintered body) in which a large number of through holes are formed as the material of the plate-like portion 60, the heat transfer area where the molten core 25 and the plate-like portion 60 come into contact with each other increases, and the molten core. 25 heat is effectively transmitted to the plate-like portion 60.

  As a result, the temperature of the melting core 25 decreases before the melting core 25 reaches the pedestal bed 18, and the chemical reaction between the concrete constituting the pedestal bed 18 and the melting core 25 can be suppressed or prevented.

  In the above description, the plate-like portion 60 has the protruding portion 61 that penetrates the pedestal wall 16 and extends outward in the horizontal direction of the pedestal space 17. As a modified example of the seventh embodiment, the plate-like portion 60 may be configured not to have the protruding portion 61 extending through the pedestal wall 16. In that case, the heat in the plate-like portion 60 is not released to the outside of the pedestal wall 16 by heat conduction in the plate-like portion 60. However, since the molten core 25 is cooled by the cooling water in the pedestal space 17 while the molten core 25 is on the upper surface of the plate-like portion 60 and while passing through the through hole of the plate-like portion 60, the molten core 25 is Before reaching the pedestal bed 18, the temperature of the melting core 25 decreases.

[Eighth Embodiment]
FIG. 11 is an elevational sectional view around the pedestal space showing a situation where the molten core has dropped into the pedestal space in the reactor containment vessel according to the eighth embodiment of the present invention.

  The eighth embodiment is a modification of the seventh embodiment, and the plate-like portion 60 in the seventh embodiment includes an upper plate-like portion 60a and a lower plate-like portion 60b. Each of the upper plate-like portion 60a and the lower plate-like portion 60b extends in the horizontal direction, and is arranged at an interval in the vertical direction.

  Each of the upper plate-like portion 60 a and the lower plate-like portion 60 b has a protrusion 61 that penetrates the pedestal wall 16 and extends outward in the horizontal direction of the pedestal space 17. The upper plate-like portion 60a and the lower plate-like portion 60b are made of a material having a high melting point, high heat resistance, and low reactivity as compared with the concrete constituting the pedestal floor 18, and are porous in which a large number of through holes are formed. It is.

  Other configurations are the same as those in the seventh embodiment.

  In this embodiment, when a core melting accident occurs, the melting core 25 falls from the bottom of the reactor pressure vessel 12 into the lower pedestal space 17 and first hits the upper surface of the upper plate-like portion 60a. Thereafter, the melting core 25 gradually passes through the upper plate-like portion 60a through the through hole of the upper plate-like portion 60a, and then hits the upper surface of the lower plate-like portion 60b. Thereafter, the melting core 25 gradually passes through the lower plate-like portion 60b through the through hole of the lower plate-like portion 60b. Thereafter, the molten core 25 reaches the pedestal bed 18. The molten core 25 is cooled by the upper plate portion 60a and the lower plate portion 60b while passing through the through holes of the upper plate portion 60a and the lower plate portion 60b. The heat of the upper plate-like portion 60 a and the lower plate-like portion 60 b spreads in the horizontal direction and is released to the outside of the pedestal wall 16 through the protruding portion 61.

  Thereby, before the molten core 25 reaches the pedestal bed 18, the temperature of the molten core 25 is further lowered as compared with the seventh embodiment, and the chemical reaction between the concrete constituting the pedestal floor 18 and the molten core 25. Can be suppressed or prevented.

  In the above description, the plate-like portion 60 has two stages of the upper plate-like part 60a and the lower plate-like part 60b, but may have three or more stages.

[Ninth Embodiment]
FIG. 12 is an elevational sectional view around the pedestal space showing a situation where the molten core has fallen into the pedestal space in the reactor containment vessel according to the ninth embodiment of the present invention.

  The ninth embodiment is a modification of the seventh embodiment, and a cooler 70 is thermally connected to the protruding portion 61 of the plate-like portion 60 in the seventh embodiment. The cooler 70 is disposed outside the pedestal wall 16 and is configured to be cooled by cooling water introduced from outside the reactor containment vessel 13, for example.

  Other configurations are the same as those in the seventh embodiment.

  In the ninth embodiment, when a core melting accident occurs and the molten core 25 is on the plate-like portion 60 or passes through the through-hole of the plate-like portion 60, the heat of the molten core 25 is plate-like. It is transmitted to part 60. The plate-like portion 60 is cooled by the water in the pedestal space 17 and is cooled by the cooler 70 outside the pedestal wall 16 through the protruding portion 61.

  In the ninth embodiment, since the plate-like portion 60 is actively cooled by the cooler 70, the plate-like portion 60 is cooled more effectively than the seventh embodiment, and as a result, the molten core 25 cooling is promoted.

[Other Embodiments]
Various features of the embodiment described above can be combined.

  For example, the shape of the plurality of masses 27 of the first embodiment (FIGS. 1 and 2) may be a spherical shape as in the second embodiment (FIG. 3), or the fourth embodiment (FIG. 5, FIG. 5). It is good also as a shape which has a cavity like FIG. Furthermore, it is good also as a structure which enclosed water in the cavity like 5th Embodiment (FIG. 7).

  The cooler 70 of the ninth embodiment (FIG. 12) may be connected to each of the upper plate portion 60a and the lower plate portion 60b of the eighth embodiment (FIG. 11).

  Further, the material of the lump 27, the upper plate 32, the upper upper plate 32a, and the lower upper plate 32b in the first to sixth embodiments is the same as the material of the plate-like portion 60 in the seventh to ninth embodiments. In addition, a porous body (for example, a sintered body) in which a large number of through holes are formed may be used.

  As mentioned above, although some embodiment of this invention was described, these embodiment is shown as an example and is not intending limiting the range of invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 11 ... Core, 12 ... Reactor pressure vessel, 13 ... Reactor containment vessel, 14 ... Dry well, 15 ... Wet well, 16 ... Pedestal wall, 17 ... Pedestal space, 18 ... Pedestal floor, 19 ... Pressure suppression pool, 20 DESCRIPTION OF SYMBOLS ... Vent pipe, 21 ... Emergency cooling water supply piping, 22 ... Emergency cooling water supply valve, 25 ... Melting core, 26 ... Melting core receiving part (melting core receiving device), 27 ... Lump, 30 ... Cylindrical partition Plate 31, annular space 32, upper plate 32 a, upper upper plate 32 b, lower upper plate 33, partition plate through hole 34, recess 35, upper plate through hole 40, cavity 41, opening 50, storage box, 51 ... storage box opening / closing device, 60 ... plate-like part, 60a ... upper plate-like part, 60b ... lower plate-like part, 61 ... projecting part, 70 ... cooler

Claims (15)

A reactor containment vessel for storing a reactor pressure vessel containing a core,
A cylindrical pedestal wall that supports the reactor pressure vessel;
A pedestal floor surrounded by the pedestal wall and positioned below the reactor pressure vessel and constituting the bottom of the reactor containment vessel;
A melting core receiving part that is disposed above the pedestal bed and is made of a material having a high melting point, high heat resistance, and low reactivity compared to the material constituting the pedestal bed;
Have
When the molten core formed by melting the core falls below the reactor pressure vessel, the molten core receiving part is configured to flow the molten core before the molten core reaches the pedestal bed. Branching into a plurality, absorbing the heat of the molten core, and lowering the temperature of the molten core before the molten core reaches the pedestal bed,
A reactor containment vessel characterized by The molten core receiving portion includes a plurality of masses, and the plurality of masses are arranged in a horizontal direction and a vertical direction with a gap formed between each other,
The reactor containment vessel according to claim 1. A plurality of indentations are formed in the pedestal floor to suppress movement of the plurality of masses;
The reactor containment vessel according to claim 2, wherein: Compared to the material constituting the pedestal floor, it is made of a material having a high melting point, high heat resistance, and low reactivity, and is arranged so as to spread horizontally above the plurality of masses to move the plurality of masses. Further having at least one upper plate to suppress,
The reactor containment vessel according to claim 2 or claim 3, wherein The at least one upper plate is
A lower upper plate made of a material having a high melting point, high heat resistance, and low reactivity compared to the material constituting the pedestal floor, and arranged so as to spread horizontally above the plurality of masses,
An upper upper plate made of a material having a high melting point, high heat resistance and low reactivity compared to the material constituting the pedestal floor, and disposed above the lower upper plate and spaced apart from the lower upper plate; ,
Including
A part of the plurality of masses is also disposed between the lower upper plate and the upper upper plate;
The reactor containment vessel according to claim 4.   The reactor containment vessel according to any one of claims 2 to 5, wherein a cavity is formed in at least a part of the plurality of masses.   The reactor containment vessel according to claim 6, wherein water is sealed in the cavity. It is arranged so as to surround the horizontal periphery of the melting core receiving part so as to limit the horizontal movement of the melting core receiving part, and forms an annular space between the inner side of the pedestal wall and the upper part is opened. And a cylindrical partition plate in which a plurality of partition plate through holes are formed,
An emergency cooling water supply device for supplying cooling water to the space above the pedestal floor under the reactor pressure vessel surrounded by the pedestal wall;
The reactor containment vessel according to any one of claims 1 to 7, further comprising: A storage box that is disposed above the pedestal floor and stores the molten core receiving part at a normal time;
A storage box opening and closing device that is disposed above the pedestal floor and can drop the molten core receiving part onto the pedestal floor when the molten core is generated;
The reactor containment vessel according to claim 1, further comprising:   10. The nuclear reactor according to claim 1, wherein the molten core receiving portion includes a porous material in which a large number of through-holes through which the molten core can pass is formed. Containment vessel.   The reactor containment vessel according to claim 10, wherein the melting core receiving portion includes a plate-like portion that extends horizontally over the pedestal floor above the pedestal floor.   The atom according to claim 11, wherein the molten core receiving portion includes a protruding portion that is thermally joined to the plate-like portion, extends through the pedestal wall, and extends to the outside of the pedestal wall. Containment vessel.   The reactor containment vessel according to claim 12, further comprising a cooler disposed outside the pedestal wall and thermally bonded to the protrusion. The plate-like portion is
A lower plate-like portion extending horizontally and covering the pedestal floor above the pedestal floor;
The upper plate-like portion that extends horizontally and covers the lower plate-like portion above the lower plate-like portion, and is arranged with an interval in the vertical direction from the lower plate-like portion,
The reactor containment vessel according to any one of claims 11 to 13, characterized by comprising: A melting core receiving device that is surrounded by a cylindrical pedestal wall that supports a reactor pressure vessel and is disposed above the pedestal bed that forms the bottom of the reactor containment vessel below the reactor pressure vessel,
Compared to the material constituting the pedestal floor, it is made of a material having a high melting point, high heat resistance, and low reactivity, and includes a plurality of masses arranged in the horizontal and vertical directions with a gap formed between them,
When the molten core formed by melting the core in the reactor pressure vessel falls below the reactor pressure vessel, the plurality of masses are formed before the molten core reaches the pedestal bed. Diverting the flow of the molten core into a plurality, absorbing the heat of the molten core, and lowering the temperature of the molten core before the molten core reaches the pedestal bed,
A melting core receiver.

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