JP6109580B2 - Molten core holding device and reactor containment vessel provided with the same - Google Patents

Description

  The present invention relates to a molten core holding device and a nuclear reactor containment vessel provided with the same.

  In a nuclear power plant, when an accident such as loss of coolant (LOCA) occurs in which the coolant in the reactor pressure vessel stored inside the reactor containment vessel flows out for some reason, an emergency core cooling system, etc. To cool the core in the reactor pressure vessel. However, although the probability is very low, when the emergency core cooling system does not operate, the core in the reactor pressure vessel melts without being sufficiently cooled, and the core melt (molten core) becomes the reactor pressure. There is a possibility of falling from the vessel into the containment vessel. As a countermeasure for such a severe accident, a technique described in Patent Document 1 has been proposed.

  In the technique described in Patent Document 1, the bottom surface of the lower dry well at the lower part of the reactor pressure vessel is constituted by an isolation metal plate, and the position of the isolation metal plate is lower than the level of pool water in the suppression chamber around the lower dry well. In this position, the lower part of the isolation metal plate communicates with the suppression chamber to fill the pool water, and the isolation metal plate receives and cools the core melt dropped from the reactor pressure vessel.

Japanese Patent Laid-Open No. 5-341081

  In the technique described in Patent Document 1 described above, since the core melt is cooled only by the flat plate-like isolation metal plate cooled by the pool water below the isolation metal plate, the amount of heat of the core melt is large. May not sufficiently cool the core melt, and may melt through the isolation metal plate.

  The present invention has been made to solve the above-described problems, and its purpose is to effectively cool the core melt in the event of a severe accident such as core melting, and to melt the core. It is an object of the present invention to provide a molten core holding device capable of preventing the diffusion of radioactive materials generated from an object to the outside, and a reactor containment vessel equipped with the same.

In order to solve the above problems, for example, the configuration described in the claims is adopted.
The present application includes a plurality of means for solving the above-described problems. To give an example, a molten core holding device that is installed below the reactor pressure vessel and receives all the core melt falling from the reactor pressure vessel. And it is comprised by the plate-shaped member without an opening part formed in uneven | corrugated shape in cross section by having several hollows in which an upper surface becomes a recessed part and a lower surface becomes a convex part, and cooling water contacts at least one surface A cooling plate is provided.

According to the present invention, since the cooling plate is formed in a concavo-convex shape in cross section, in the unlikely event that a severe accident occurs in which the core melt falls from the reactor pressure vessel, the heat transfer area of the cooling plate is increased. Thus, the core melt can be effectively cooled. As a result, it is possible to prevent the radioactive material generated from the core melt from diffusing to the outside.
Problems, configurations, and effects other than those described above will be clarified by the following description of embodiments.

It is a schematic longitudinal cross-sectional view which shows 1st Embodiment of the nuclear reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is a longitudinal cross-sectional view of the cut surface different from FIG. 1 which expands and shows a part of 1st Embodiment of the nuclear reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is a top view which shows the cooling plate which comprises 1st Embodiment of the fusion core holding | maintenance apparatus of this invention. It is explanatory drawing which shows the cooling state of the cooling plate when operating the blast valve in 1st Embodiment of the fusion core holding | maintenance apparatus of this invention and a nuclear reactor containment vessel provided with the same. It is explanatory drawing which shows the cooling state of the core melt in 1st Embodiment of the fusion core holding | maintenance apparatus of this invention and a nuclear reactor containment vessel provided with the same. It is explanatory drawing which shows the cooling state of the core melt in case the cooling water is not stored in the pedestal space in 1st Embodiment of the fusion core holding | maintenance apparatus of this invention and a nuclear reactor containment vessel provided with the same. It is explanatory drawing which shows the cooling state of the core melt in case the blasting valve in 1st Embodiment of the molten core holding | maintenance apparatus of this invention and a nuclear reactor containment vessel does not operate | move. It is a longitudinal cross-sectional view which expands and shows a part of 2nd Embodiment of the reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is a schematic longitudinal cross-sectional view which shows 3rd Embodiment of the nuclear reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is explanatory drawing which shows the cooling state of the core melt in 3rd Embodiment of the fusion core holding | maintenance apparatus of this invention, and a nuclear reactor containment vessel provided with the same. It is a longitudinal cross-sectional view which expands and shows a part of 4th Embodiment of the nuclear reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is explanatory drawing which shows the erosion state of the pedestal bed by the core melt in 4th Embodiment of the fusion core holding | maintenance apparatus of this invention and a nuclear reactor containment vessel provided with the same. It is a longitudinal cross-sectional view which expands and shows a part of 5th Embodiment of the nuclear reactor containment vessel provided with the fusion core holding | maintenance apparatus of this invention. It is sectional drawing which shows another example of the cooling plate which comprises the 1st thru | or 5th embodiment of the fusion core holding | maintenance apparatus of this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a molten core holding device of the present invention and a reactor containment vessel provided with the same will be described below with reference to the drawings.
[First Embodiment]
1 to 3 show a first embodiment of a melting core holding device of the present invention and a reactor containment vessel equipped with the same, and FIG. 1 shows a reactor storing equipped with a melting core holding device of the present invention. FIG. 2 is a schematic longitudinal sectional view showing a first embodiment of the vessel, and FIG. 2 is an enlarged view of a part of the first embodiment of the reactor containment vessel equipped with the melting core holding device of the present invention. FIG. 3 is a plan view showing a cooling plate constituting the first embodiment of the melting core holding device of the present invention.

  The present embodiment is intended for a reactor containment vessel of an improved boiling water reactor (ABWR). In FIG. 1, a reactor containment vessel 1 of an improved boiling water reactor (ABWR) is made of reinforced concrete lined with a steel liner 2.

  In the reactor containment vessel 1, a reactor pressure vessel 4 containing a reactor core 3 that holds the fuel for the reactor is stored. The reactor pressure vessel 4 is supported by a substantially cylindrical pedestal 5 erected on the base portion 1 a of the reactor containment vessel 1. A diaphragm floor 6 is bridged between the side wall 1 b of the reactor containment vessel 1 and the pedestal 5.

  The inside of the containment vessel 1 includes an upper dry well 7 surrounding the reactor pressure vessel 4, a pedestal space 8 (lower dry well) formed below the reactor pressure vessel 4 inside the pedestal 5, and the pedestal 5. And a suppression chamber 9 and the like surrounding the outer peripheral surface. The suppression chamber 9 has pool water 10. The upper dry well 7, the pedestal space 8 and the suppression chamber 9 are partitioned by a diaphragm floor 6. The upper dry well 7 and the suppression chamber 9 communicate with each other via a vent pipe 11.

  When the reactor pressure vessel 4 or cooling system piping (not shown) is partially damaged for some reason and the steam is discharged into the upper dry well 7, the vent pipe 11 removes the steam from the upper dry well 7. To the suppression chamber 9. The steam guided to the suppression chamber 9 is condensed in the pool water 10 of the suppression chamber 9 and the pressure increase in the reactor containment vessel 1 is suppressed.

  The reactor containment vessel 1 is provided with a reactor emergency cooling system (ECCS) and a reactor isolation cooling system (RCIC) not shown. The reactor emergency cooling system and the reactor isolation cooling system cool the fuel in the reactor pressure vessel 4 by its automatic startup when a loss of coolant accident (LOCA) or a reactor isolation event occurs. is there.

  A melting core holding device 20 is installed below the pedestal space 8 below the reactor pressure vessel 4. The molten core holding device 20 receives the core melt D when a severe accident occurs in which the core 3 melts and the core melt D (molten core) falls from the reactor pressure vessel 4 into the pedestal space 8. It is.

  Next, details of the above-described first embodiment of the melting core holding device of the present invention will be described with reference to FIGS. 2 and 3, the same reference numerals as those shown in FIG. 1 denote the same parts, and detailed description thereof will be omitted.

  In FIG. 2, the melting core holding device 20 is installed inside the pedestal 5 in a state of being spaced upward from the base portion 1 a of the reactor containment vessel 1. The molten core holding device 20 includes a cooling plate 21 and a sacrificial layer 22 that covers the upper surface of the cooling plate 21.

  For example, as shown in FIGS. 2 and 3, the cooling plate 21 is formed in a substantially disk shape in plan view, and has a plurality of depressions whose bottom surface is convex. That is, the cooling plate 21 is formed in a concave-convex shape in cross section, and a plurality of concave portions 21a and a plurality of convex portions 21b are provided on the upper surface and the lower surface of the cooling plate 21, respectively. The cooling plate 21 is made of a metal material having a high thermal conductivity such as SUS.

  The sacrificial layer 22 is formed of a material having a melting point higher than that of the cooling plate 21 such as concrete or metal oxide. The sacrificial layer 22 is for preventing damage to the cooling plate 21 due to the heat of the core melt D when the core melt D falls from the reactor pressure vessel 4 onto the molten core holding device 20.

  A cooling water storage space 30 capable of storing cooling water is provided below the cooling plate 21 of the melting core holding device 20. The cooling water stored in the cooling water storage space 30 contacts the lower surface of the cooling plate 21 to cool the cooling plate 21, and cools the core melt D falling on the molten core holding device 20 through the cooling plate 21. To do.

  A lower water injection line 31 extends from the suppression chamber 9 to the cooling water storage space 30. A blast valve 32 is provided in the lower water injection line 31. The lower water injection line 31 supplies the pool water 10 (cooling water) of the suppression chamber 9 to the cooling water storage space 30 by opening the blast valve 32 when it detects signs of damage to the reactor pressure vessel 4. To do.

  An upper water injection line 33 extends from the suppression chamber 9 to the pedestal space 8 on the upper side of the melting core holding device 20. A melt valve 34 is provided in the upper water injection line 33. When the core melt D falls from the reactor pressure vessel 4 into the pedestal space 8, the upper water injection line 33 opens the melt valve 34 by the heat of the core melt D, so that the pool water of the suppression chamber 9 10 (cooling water) is supplied onto the molten core holding device 20.

  The pedestal 5 is provided with a communication hole 35 that allows the cooling water storage space 30 on the lower surface side of the cooling plate 21 and the pedestal space 8 on the upper surface side of the cooling plate 21 to communicate with each other. The opening 35 a on the pedestal space 8 side of the communication hole 35 is provided at a high position with a margin with respect to the deposition height when it is assumed that the core melt D has accumulated on the molten core holding device 20. .

  The communication hole 35 can supply the cooling water supplied from the lower water injection line 31 to the cooling water storage space 30 to the pedestal space 8 on the upper side of the melting core holding device 20, and can be supplied from the upper water injection line 33 to the melt holding device 20. The cooling water supplied to can be supplied to the cooling water storage space 30.

  The pedestal 5 is provided with a steam discharge hole 36 that allows the cooling water storage space 30 and the upper dry well 7 to communicate with each other. When the core melt D deposited on the molten core holding device 20 is cooled by the cooling water stored in the cooling water storage space 30, the steam discharge hole 36 allows the steam generated in the cooling water storage space 30 to be It is discharged to the well 7.

Next, the operation at the time of a severe accident in the first embodiment of the molten core holding device of the present invention and the reactor containment vessel provided with the same will be described with reference to FIGS. 2 and 4 to 7.
FIG. 4 is an explanatory view showing the cooling state of the cooling plate when the blast valve in the first embodiment of the melting core holding device of the present invention and the reactor containment vessel equipped therewith is shown, and FIG. 5 shows the present invention. FIG. 6 is an explanatory view showing the cooling state of the core melt in the first embodiment of the molten core holding device and the reactor containment vessel equipped therewith, FIG. 6 is the molten core holding device of the present invention and the nuclear reactor equipped therewith Explanatory drawing which shows the cooling state of the core melt when the cooling water is not stored in the pedestal space in the first embodiment of the containment vessel, FIG. 7 is the molten core holding device of the present invention and the atom equipped therewith It is explanatory drawing which shows the cooling state of a core melt in case the blasting valve in 1st Embodiment of a reactor containment vessel does not operate | move. 4 to 7, the same reference numerals as those shown in FIGS. 1 to 3 are the same parts, and detailed description thereof is omitted.

  When a loss of coolant accident (LOCA) or reactor isolation event occurs due to pipe breakage, etc., a reactor emergency cooling system (not shown) provided in the reactor containment vessel 1 shown in FIG. 2 and reactor isolation cooling The core 3 built in the reactor pressure vessel 4 is cooled by a system (not shown). However, if the cooling function of these cooling systems is lost at the same time, the water level in the reactor pressure vessel 4 is lowered, the fuel in the core 3 is overheated and melted by decay heat, and the core is lost. It can be envisaged that the melt D will penetrate the bottom of the reactor pressure vessel 4.

  When such signs of damage to the reactor pressure vessel 4 are detected from the water level in the reactor pressure vessel 4, the time of the water injection interruption, etc., the blast valve 32 provided in the lower water injection line 31 is opened, and the suppression chamber 9 The pool water 10 (cooling water) is supplied to a cooling water storage space 30 provided below the melting core holding device 20.

  The cooling water supplied to the cooling water storage space 30 floods the cooling water storage space 30 and cools the cooling plate 21 of the molten core holding device 20 as shown in FIG. Thereafter, the cooling water overflows from the opening 35 a of the communication hole 35, flows into the pedestal space 8 on the upper side of the melting core holding device 20, and is stored on the upper side of the melting core holding device 20.

  With respect to the flow rate of the cooling water supplied from the lower water injection line 31 to the cooling water storage space 30, the cooling water storage space 30 can be submerged within the time when the core melt D is assumed to fall into the molten core holding device 20. It is determined as follows. Thus, the cooling plate 21 of the molten core holding device 20 is reliably cooled by this cooling water before the core melt D falls on the molten core holding device 20.

  As the accident event progresses, when the core melt D penetrates the bottom of the reactor pressure vessel 4, the core melt D falls onto the sacrificial layer 22 of the molten core holding device 20 and accumulates.

  As shown in FIG. 5, the core melt D melts the sacrificial layer 22 of the melting core holding device 20 and reaches the cooling plate 21 of the melting core holding device 20. The bottom of the core melt D spreads on the cooling plate 21 so as to be dispersed in the respective recesses 21 a on the upper surface of the cooling plate 21. Thus, since a part of the bottom of the core melt D is dispersed and spreads in the respective recesses 21a of the cooling plate 21, the core melt D does not accumulate in a large mountain shape, and the core melt D may be recritical. Is reduced.

  The core melt D deposited on the melting core holding device 20 is cooled from the upper surface by the cooling water stored on the upper side of the melting core holding device 20. Further, the cooling water stored in the cooling water storage space 30 is cooled from the lower surface via the cooling plate 21. Since the cooling plate 21 is formed in a concavo-convex shape when viewed in cross section, the heat transfer area of the cooling plate 21 is increased from that of a flat plate, and the cooling capacity is improved.

  Thus, the core melt D is effectively cooled by increasing the heat transfer area of the cooling plate 21 and cooling the core melt D from both the upper and lower surfaces. For this reason, the molten core holding device 20 is prevented from being damaged.

  When the core melt D is cooled by the cooling water stored in the cooling water storage space 30, the cooling water boils and steam is generated in the cooling water storage space 30. The steam is discharged to the upper dry well 7 through the steam discharge hole 36 or to the pedestal space 8 through the communication hole 35.

  As described above, when a sign of damage to the reactor pressure vessel 4 is detected, the blast valve 32 is opened and cooling water is supplied to the cooling water storage space 30. As shown in FIG. It may be assumed that the core melt D falls into the molten core holding device 20 before water overflows from the opening 35 a of the communication hole 35.

  In this case, since the cooling water is not stored in the upper pedestal space 8 of the melting core holding device 20, the core melt D deposited on the melting core holding device 20 is not cooled from the upper surface, and the cooling water storage space. Only the lower surface is cooled by the cooling water stored in 30.

  For this reason, the temperature in the pedestal space 8 is increased by the heat of the core melt D, and the melting valve 34 provided in the upper water injection line 33 is opened. When the melting valve 34 is opened, the pool water 10 (cooling water) of the suppression chamber 9 is supplied to the pedestal space 8 on the upper side of the melting core holding device 20 through the upper water injection line 33, and the core melt is supplied by this cooling water. D is cooled from the top.

  Thus, even when the core melt D falls into the molten core holding device 20 in the state where the cooling water is not stored in the pedestal space 8 on the upper side of the melting core holding device 20, the core melt D is surely provided. Cooling from both the upper and lower surfaces prevents the molten core holding device 20 from being damaged.

  Further, as shown in FIG. 7, it may be assumed that the core melt D falls into the molten core holding device 20 without the blast valve 32 provided in the lower water injection line 31 being operated for some reason.

  In this case, the melting valve 34 provided in the upper water injection line 33 is opened by the heat of the core melt D, and the cooling water is supplied to the upper pedestal space 8 of the molten core holding device 20 through the upper water injection line 33. The core melt D is cooled from the upper surface by this cooling water.

  Thereafter, the cooling water reaches the opening 35 a of the communication hole 35 and flows into the cooling water storage space 30 through the communication hole 35. The cooling plate 21 of the molten core holding device 20 is cooled by this cooling water, and the core melt D is also cooled from the lower surface via the cooling plate 21.

  The cooling plate 21 is protected from the heat of the core melt D by the sacrificial layer 22 until the cooling water flows from the pedestal space 8 into the cooling water storage space 30 and cools the cooling plate 21. For this reason, damage to the cooling plate 21 is prevented.

  Thus, even when the blast valve 32 provided in the lower water injection line 31 does not operate and the core melt D falls to the molten core holding device 20, the core melt D is reliably cooled from both the upper and lower surfaces and melted. Damage to the core holding device 20 is prevented.

  As described above, according to the first embodiment of the molten core holding device of the present invention and the nuclear reactor containment vessel provided with the same, the cooling plate 21 is formed in a concavo-convex shape in cross section. In the unlikely event that a severe accident such as dropping from the reactor pressure vessel 4 occurs, the heat transfer area of the cooling plate 21 can be increased to effectively cool the core melt D. As a result, the radioactive material generated from the core melt D can be prevented from diffusing to the outside.

  In addition, since the cooling plate 21 is formed in a concavo-convex shape when viewed in cross section, the bottom of the core melt D that has dropped onto the cooling plate 21 spreads and spreads in the respective recesses 21 a on the top surface of the cooling plate 21. The possibility of recriticality can be reduced.

  Furthermore, according to the present embodiment, since the communication hole 35 that connects the cooling water storage space 30 below the cooling plate 21 and the pedestal space 8 above the cooling plate 21 is provided, the cooling water communicates. The coolant 35 can flow into the cooling water storage space 30 and the pedestal space 8 above the cooling plate 21 through the holes 35, and the core melt D can be reliably cooled from both the upper and lower surfaces.

  Further, according to the present embodiment, the opening 35 a on the pedestal space 8 side of the communication hole 35 is provided at a position higher than the deposition height when it is assumed that the core melt D has accumulated on the molten core holding device 20. Therefore, it becomes possible to cool the core melt D while being submerged. For this reason, the core melt D can be reliably cooled from the upper surface.

  Furthermore, according to the present embodiment, since the lower water injection line 31 provided with the blast valve 32 is provided in the cooling water storage space 30, when a sign of damage to the reactor pressure vessel 4 is detected, the cooling water storage is performed. The cooling plate 21 can be cooled in advance by supplying cooling water to the space 30.

  Further, according to the present embodiment, since the upper water injection line 33 provided with the melting valve 34 is provided in the pedestal space 8 on the upper side of the melting core holding device 20, the cooling water from the lower water injection line 31 is stored in the cooling water. Even when the water cannot be supplied to the space 30, the cooling water can be supplied to the cooling water storage space 30.

  Furthermore, according to the present embodiment, since the sacrificial layer 22 is provided on the upper surface of the cooling plate 21, the core melt D is held in the molten core before the cooling plate 21 is cooled by the cooling water in the cooling water storage space 30. Even when falling on the apparatus 20, the cooling plate 21 is protected from the heat of the core melt D by the sacrificial layer 22, and damage to the cooling plate 21 can be prevented.

[Second Embodiment]
Next, a second embodiment of the melting core holding device of the present invention and a reactor containment vessel equipped with the same will be described with reference to FIG.
FIG. 8 is an enlarged longitudinal sectional view showing a part of the second embodiment of the reactor containment vessel equipped with the melting core holding device of the present invention. In FIG. 8, the same reference numerals as those shown in FIGS. 1 to 7 are the same parts, and detailed description thereof is omitted.

  The second embodiment of the molten core holding device of the present invention and the reactor containment vessel shown in FIG. 8 are configured in substantially the same manner as the first embodiment, but the cooling water storage space 30 is provided with the second embodiment. By storing the cooling water in advance, a difference is that the sacrificial layer 22 that covers the lower water injection line 31 provided with the blast valve 32 and the cooling plate 21 is unnecessary.

  The cooling water storage space 30 on the lower side of the melting core holding device 40 is in a state of being submerged in advance with cooling water. For this reason, the cooling plate 21 of the melting core holding device 40 is cooled in advance with cooling water.

Next, the operation at the time of a severe accident in the second embodiment of the melting core holding device of the present invention and the reactor containment vessel provided with the same will be described with reference to FIG.
The core melt D penetrating through the bottom of the reactor pressure vessel 4 shown in FIG. 8 falls on the cooling plate 21 of the molten core holding device 40 and accumulates. Similar to the first embodiment, the bottom of the core melt D spreads on the cooling plate 21 so as to be dispersed in the respective recesses 21a on the upper surface of the cooling plate 21.

  At this time, since the lower surface of the cooling plate 21 is cooled by the cooling water stored in advance in the cooling water storage space 30, the lower surface of the core melt D is immediately cooled by heat transfer with the cooling water via the cooling plate 21. Is done. For this reason, the temperature of the lower surface of the core melt D is lowered, and the cooling plate 21 is prevented from being damaged. Further, since the cooling plate 21 is cooled in advance by the cooling water, the cooling plate 21 is protected from the heat of the core melt D until the cooling plate 21 is cooled by the cooling water in the cooling water storage space 30. A sacrificial layer is also unnecessary.

  Since the core melt D deposited on the molten core holding device 40 is not cooled from the upper surface side, the melting valve 34 provided in the upper water injection line 33 is opened by the heat of the core melt D, and the upper water injection line 33 is opened. Then, cooling water is supplied to the pedestal space 8 on the upper side of the melting core holding device 40. The core melt D is cooled from the upper surface by this cooling water.

  Thereafter, the cooling water reaches the opening 35 a of the communication hole 35 and flows into the cooling water storage space 30 through the communication hole 35. For this reason, even if the cooling water in the cooling water storage space 30 partially boils, the flooded state of the cooling water storage space 30 is maintained, and the core melt D is reliably cooled from the lower surface.

  Thus, the core melt D is effectively cooled by increasing the heat transfer area of the cooling plate 21 and cooling the core melt D from both the upper and lower surfaces.

  According to the second embodiment of the molten core holding device of the present invention and the reactor containment vessel provided therewith, since the cooling water is stored in the cooling water storage space 30 in advance, a blast valve 32 is provided. In addition, the sacrificial layer 22 that covers the lower water injection line 31 and the cooling plate 21 is not necessary, and the same effects as those of the first embodiment described above can be obtained with a small configuration.

[Third Embodiment]
Next, a third embodiment of the melting core holding device of the present invention and a reactor containment vessel equipped with the same will be described with reference to FIG.
FIG. 9 is a schematic longitudinal sectional view showing a third embodiment of a reactor containment vessel equipped with the melting core holding device of the present invention. In FIG. 9, the same reference numerals as those shown in FIGS. 1 to 8 are the same parts, and detailed description thereof is omitted.

  The third embodiment of the containment vessel equipped with the fusion core holding apparatus of the present invention is the one in which the second embodiment is directed to the containment vessel of an improved boiling water reactor (ABWR). However, the difference is that it is intended for a MARK-II type reactor containment vessel. Further, in the third embodiment of the melting core holding device of the present invention, the cooling plate 21 constituting the second embodiment is a flat plate having a plurality of depressions, whereas the cooling plate 71 Is mainly different in that a flat plate having a plurality of depressions is bent at the center to form a V-shaped cross-sectional view.

  The MARK-II type reactor containment vessel 51 shown in FIG. 9 is made of steel. The reactor containment vessel 51 is entirely surrounded by a concrete shielding wall 52.

  In the reactor containment vessel 51, a reactor pressure vessel 54 containing a core 53 is stored. The reactor pressure vessel 54 is supported by a substantially cylindrical pedestal 55 erected on the bottom of the reactor containment vessel 51. A diaphragm floor 56 is bridged between the side wall of the reactor containment vessel 51 and the pedestal 55. A pedestal floor 62 made of concrete is provided at a substantially center in the vertical direction inside the pedestal 55.

  The inside of the reactor containment vessel 51 includes a dry well 57 that surrounds the reactor pressure vessel 54 above the diaphragm floor 56, a pedestal space 58 that is surrounded by the pedestal 55 and the pedestal floor 62 below the reactor pressure vessel 54, and It consists of a suppression chamber 59 formed below the diaphragm floor 56 and the pedestal floor 62. The suppression chamber 59 has pool water 60.

  The suppression chamber 59 formed on the lower side of the diaphragm floor 56 and the suppression chamber 59 formed on the lower side of the pedestal floor 62 communicate with each other through a through hole 55 a provided in the pedestal 55. The through-hole 55a allows the pool water of the suppression chamber 59 below the diaphragm floor 56 and the suppression chamber 59 below the pedestal floor 62 to flow into each other.

  The dry well 57 and the suppression chamber 59 are communicated with each other via a vent pipe 61 supported on the diaphragm floor 56.

  A molten core holding device 70 is installed in the pool water 60 of the suppression chamber 59 below the pedestal floor 62 below the reactor pressure vessel 54. When the molten core holding device 70 receives the molten core D that has fallen from the reactor pressure vessel 54, the molten core holding device 70 is at a low position so that the molten core D does not come out on the surface of the pool water 60. is set up.

  The melting core holding device 70 includes a cooling plate 71 having a plurality of depressions having a substantially V shape in cross section and a convex bottom surface. That is, the cooling plate 71 is formed in a substantially V shape and an uneven shape in cross section, and a plurality of concave portions 71 a and a plurality of convex portions 71 b are provided on the upper surface and the lower surface of the cooling plate 71, respectively. The cooling plate 71 is cooled with its upper and lower surfaces contacting the pool water 60.

  A communication hole 73 is provided in the outer peripheral portion of the cooling plate 71 to communicate the space on the lower surface side of the cooling plate 71 as the cooling water storage space 80 and the space on the upper surface side of the cooling plate 71. The communication hole 73 allows the pool water 60 of the suppression chamber 59 to flow into the upper and lower spaces of the cooling plate 71.

Next, the action at the time of a severe accident in 3rd Embodiment of the fusion core holding | maintenance apparatus of this invention mentioned above and a nuclear reactor containment vessel is demonstrated using FIG.
FIG. 10 is an explanatory diagram showing a cooling state of the core melt in the third embodiment of the melting core holding device of the present invention and the reactor containment vessel equipped with the same. In FIG. 10, the same reference numerals as those shown in FIGS. 1 to 9 are the same parts, and detailed description thereof is omitted.

  In FIG. 10, the core melt D penetrating the bottom of the reactor pressure vessel 54 falls and accumulates on the pedestal bed 62. The core melt D erodes and penetrates the pedestal bed 62 by the heat, and falls and accumulates on the molten core holding device 70.

  The bottom of the core melt D is deposited on the cooling plate 71 so as to be dispersed in the respective recesses 71a on the upper surface of the cooling plate 71, as in the second embodiment. Further, the core melt D is deposited in a slightly biased direction toward the center of the cooling plate 71 because the cooling plate 71 is formed in a substantially V shape in cross section. For this reason, obstruction | occlusion of the communicating hole 73 provided in the outer peripheral part of the cooling plate 71 by the core melt D is suppressed.

  The upper surface of the core melt D is directly cooled by the pool water 60 (cooling water) of the suppression chamber 59, and the lower surface is cooled by the pool water 60 via the cooling plate 71.

  When the core melt D is cooled by the pool water 60 on the upper side of the molten core holding device 70, the pool water 60 boils and the amount of water decreases, but the pool water 60 on the lower side of the molten core holding device 70 It is supplied to the upper side of the molten core holding device 70 through the communication hole 73 of the cooling plate 71. For this reason, the core melt D is reliably cooled from the upper and lower surfaces by the pool water 60 of the suppression chamber 59, and damage to the molten core holding device 70 is prevented.

  According to the third embodiment of the molten core holding device of the present invention and the reactor containment vessel provided therewith, even when the MARK-II type reactor containment vessel is the target, The same effect as in the embodiment can be obtained.

  In addition, according to the present embodiment, since the communication hole 73 that connects the space on the lower surface side of the cooling plate 71 as the cooling water storage space 80 and the space on the upper surface side of the cooling plate 71 is provided, the cooling water communicates. It can flow into the space on both upper and lower sides of the cooling plate 71 through the hole 35, and the core melt D can be reliably cooled from both the upper and lower surfaces.

  Furthermore, according to the present embodiment, when the molten core holding device 70 receives the core melt D, the molten core holding device 70 is installed at a low position where the core melt D does not come out on the surface of the pool water 60. As a result, the core melt D can be cooled in a submerged state. For this reason, the core melt D can be reliably cooled from the upper surface.

  In addition, according to the present embodiment, since the cooling plate 71 is formed in a substantially V shape in cross section, the core melt D is unlikely to accumulate on the outer periphery of the cooling plate 71, and the core melt D is Blocking the communication hole 73 provided in the outer peripheral portion can be suppressed.

[Fourth Embodiment]
Next, a fourth embodiment of the melting core holding device of the present invention and a reactor containment vessel equipped with the same will be described with reference to FIG.
FIG. 11 is an enlarged longitudinal sectional view showing a part of a fourth embodiment of a nuclear reactor containment vessel equipped with a melting core holding device of the present invention. In FIG. 11, the same reference numerals as those shown in FIGS. 1 to 10 are the same parts, and detailed description thereof is omitted.

  The fourth embodiment of the melting core holding device of the present invention and the reactor containment vessel provided with the same is configured in substantially the same manner as the third embodiment, but the inner periphery of the pedestal 55 is placed on the pedestal floor 62. The difference is that a protective member 63 that covers the surface is provided.

  In FIG. 11, the protection member 63 has an upper surface inclined downward from the outer peripheral side toward the center, a bottom portion 64 provided with an opening 64 a in the central portion, and a cylindrical wall portion extending upward from the outer peripheral portion of the bottom portion 64. 65. The protection member 63 is formed of a heat resistant material. The protection member 63 protects the pedestal 55 from the core melt D.

Next, the operation at the time of a severe accident in the fourth embodiment of the melting core holding device of the present invention and the reactor containment vessel provided therewith will be described with reference to FIG.
FIG. 12 is an explanatory view showing an eroded state of the pedestal bed by the core melt in the fourth embodiment of the melting core holding device of the present invention and the reactor containment vessel equipped with the same. In FIG. 12, the same reference numerals as those shown in FIGS. 1 to 11 are the same parts, and detailed description thereof is omitted.

  In FIG. 12, when the core melt D falls to the pedestal bed 62, the core melt D is held in the protective member 63. For this reason, the core melt D is not deposited so as to spread to the pedestal 55, and the pedestal 55 is protected from the core melt D.

  The core melt D held in the protection member 63 flows along the inclined surface 64b of the bottom 64 of the protection member 63 and flows from the opening 64a of the bottom 64 to the pedestal bed. This core melt D erodes through the pedestal floor 62 before it erodes the protective member 63 and falls onto the molten core holding device 70.

  This is because the protective member 63 is made of a heat-resistant material, whereas the pedestal floor 62 is made of concrete.

  As in the third embodiment, the core melt D dropped onto the molten core holding device 70 is reliably cooled from both the upper and lower surfaces by the pool water 60 of the suppression chamber 59 to prevent the molten core holding device 70 from being damaged. Is done.

  According to the fourth embodiment of the molten core holding device of the present invention and the reactor containment vessel provided with the same, the same effects as those of the third embodiment described above can be obtained.

  Further, according to the present embodiment, since the protective member 63 formed of a heat-resistant material is provided on the pedestal floor 62 so as to cover the inner peripheral surface of the pedestal 55, the pedestal 55 is eroded by the core melt D. The core melt D can be dropped onto the molten core holding device 70. For this reason, the structural strength of the pedestal 55 is maintained.

[Fifth Embodiment]
Next, a fifth embodiment of the melting core holding device of the present invention and a reactor containment vessel equipped with the same will be described with reference to FIG.
FIG. 13 is an enlarged longitudinal sectional view showing a part of a fifth embodiment of a nuclear reactor containment vessel equipped with a melting core holding device of the present invention. In FIG. 13, the same reference numerals as those shown in FIGS. 1 to 12 are the same parts, and detailed description thereof is omitted.

  In the fifth embodiment of the molten core holding device of the present invention and the reactor containment vessel shown in FIG. 13, the entire pedestal floor 62 in the fourth embodiment is made of concrete. In contrast, the central part of the pedestal floor 62 is replaced with a melting plug 62a formed of a material that is easier to melt than concrete.

  When the core melt D falls to the pedestal bed 62, the melt plug 62a is melted and penetrates before the pedestal bed 62 by the heat. For this reason, the core melt D quickly falls from the pedestal bed 62 onto the melt core holding device 70.

  According to the fifth embodiment of the molten core holding device of the present invention and the reactor containment vessel provided with the same, the same effects as those of the fourth embodiment described above can be obtained.

  Further, according to the present embodiment, since the central portion of the pedestal floor 62 is replaced with the melt plug 62a formed of a material that is easier to melt than concrete, the core melt D is transferred from the pedestal floor 62 onto the molten core holding device 70. It can be dropped quickly. Therefore, the portion of the pedestal floor 62 other than the melt plug 62a is not easily affected by the erosion caused by the core melt D, and the structural strength of the pedestal 55 is reliably maintained.

[Others]
In the first to fifth embodiments described above, the melting core holding device including the cooling plates 21 and 71 having a plurality of depressions having a convex bottom surface is shown as an example. The plates 21 and 71 may be formed in an uneven shape in cross section. For example, the melting core holding device can include a cooling plate 91 shown in FIG.

  FIG. 14 is a sectional view showing another example of the cooling plate constituting the first to fifth embodiments of the melting core holding device of the present invention. In FIG. 14, the same reference numerals as those shown in FIGS. 1 to 13 are the same parts, and detailed description thereof is omitted.

  In FIG. 14, the cooling plate 91 is formed in a cross-sectional wave shape. That is, a plurality of concave portions 91a and a plurality of convex portions 91b are provided on the upper surface and the lower surface of the cooling plate 71, respectively. As a result, the heat transfer area of the cooling plate 91 is increased from that of the flat plate like the cooling plates 21 and 71 described above, and the cooling capacity is improved. Further, when the core melt D falls from the reactor pressure vessels 4 and 54 onto the cooling plate 91, the bottom of the core melt D spreads so as to be dispersed in the respective recesses 91a on the upper surface of the cooling plate 91, and the core. The melt D does not accumulate in a large mountain shape.

  Thus, by forming the cooling plate 91 in a cross-sectional wave shape, the heat transfer area of the cooling plate 91 can be increased, and the possibility of recriticality of the core melt D can be reduced.

  In the first embodiment described above, an example of a configuration including the lower water injection line 31 provided with the blast valve 32 and the upper water injection line 33 provided with the melting valve 34 is shown. It is also possible to adopt a configuration including only the lower water injection line 31 provided with 32 and a configuration including only the upper water injection line 33 provided with the melting valve 34.

  The present invention is not limited to the first to fifth embodiments described above, and includes various modifications. The above-described embodiment has been described in detail for easy understanding of the present invention, and is not necessarily limited to the one having all the configurations described. For example, part of the configuration of one embodiment can be replaced with the configuration of another embodiment, and the configuration of another embodiment can be added to the configuration of one embodiment. Moreover, it is also possible to add, delete, or replace another configuration for a part of the configuration of each embodiment.

1, 51 Reactor containment vessel 4, 54 Reactor pressure vessel 5, 55 Pedestal 20, 40, 70 Melting core holding device 21, 71, 91 Cooling plate 30, 80 Cooling water storage space 31 Lower water injection line 32 Explosion valve 33 Upper water injection line 34 Melting valve 35, 73 Communication hole 62 Pedestal floor 62a Melting plug 63 Protective member D Core melt (melting core)

Claims (8)

A molten core holding device that is installed below the reactor pressure vessel and receives all the core melt falling from the reactor pressure vessel ,
Consists of a plate-like member without an opening formed in a concavo-convex shape in cross section by having a plurality of depressions whose upper surface is a concave portion and the lower surface is a convex portion, and includes a cooling plate with which cooling water contacts at least one surface A melting core holding device characterized by that. A reactor pressure vessel;
A pedestal that supports the reactor pressure vessel;
It has a cooling plate composed of a plate-like member having no opening formed in an uneven shape in cross section by having a plurality of depressions whose upper surface is a concave and the lower surface is a convex, and below the reactor pressure vessel A molten core holding device that receives all the core melt that is installed and falls from the reactor pressure vessel ;
A cooling water storage space provided on the lower surface side of the cooling plate so that cooling water can be stored; and
A reactor containment vessel comprising a communication hole that communicates the cooling water storage space and the space on the upper surface side of the cooling plate. The reactor containment vessel according to claim 2 ,
A reactor containment vessel further comprising a lower water injection line provided with a blast valve and capable of supplying cooling water to the cooling water storage space. The reactor containment vessel according to claim 3 ,
A reactor containment vessel, further comprising an upper water injection line provided with a melting valve and capable of supplying cooling water to the space on the upper surface side of the cooling plate. The reactor containment vessel according to claim 2 ,
A melting valve, and further comprising an upper water injection line capable of supplying cooling water to the space on the upper surface side of the cooling plate;
A reactor containment vessel in which cooling water is stored in the cooling water storage space in advance. A reactor pressure vessel with a built-in core,
A cylindrical pedestal that supports the reactor pressure vessel;
A pedestal floor provided inside the pedestal;
A pedestal floor having a cooling plate made of a plate-like member having a V-shape in cross-sectional view and having a plurality of depressions with a concave portion on the upper surface and a convex portion on the lower surface, and formed in an uneven shape in cross-sectional view A molten core holding device that is installed so as to hang over the inner wall of the pedestal and receives all the core melt falling from the pedestal floor ;
A cooling water storage space provided on the lower surface side of the cooling plate so that cooling water can be stored; and
Provided only in the outer peripheral portion of the cooling plate, comprising a communication hole that communicates the cooling water storage space and the space on the upper surface side of the cooling plate,
A reactor containment vessel in which cooling water is stored in advance in the cooling water storage space and the space on the upper surface side of the cooling plate. The reactor containment vessel according to claim 6 ,
A reactor containment vessel characterized in that a protective member for protecting the pedestal from a core melt falling on the pedestal floor is installed on the pedestal floor. The reactor containment vessel according to claim 7 ,
A reactor containment vessel, wherein a central portion of the pedestal bed is replaced with a melting plug formed of a material that is more easily melted than a material forming the pedestal bed.

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