Molten corium cooling device and nuclear facility

Abstract

To cool a molten corium flowing out of a reactor vessel at an early stage.SOLUTION: A molten corium cooling device, in which a structure installed on a foundation portion of a reactor containment vessel supports a reactor and which cools a molten corium falling from a lower portion of a reactor vessel, includes: a cavity provided in a hollow shape in the foundation portion; a water storage tank provided in the cavity and storing cooling water; a heat transfer member that receives the molten corium and transfers heat of the molten corium to the cooling water in the water storage tank; and a jet nozzle that jets the cooling water in the water storage tank above the heat transfer member.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a core melt cooling device and a nuclear power facility.

Background Art

[0002] A reactor containment vessel is erected on a solid ground such as rock, and a reactor is disposed inside. The reactor is supported by a concrete structure provided at the base of the reactor containment vessel. In nuclear power facilities, as a severe accident, an accident in which the core melt flows out of the reactor vessel is assumed. Since the core melt melts the lower part of the reactor vessel and falls downward, a cavity is provided below the reactor vessel, and the core melt is received by the cavity and cooled by cooling water. As such a nuclear power facility, for example, there is one described in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In conventional nuclear power facilities, when an accident occurs in which the core melt flows out of the reactor vessel, by operating a pump, cooling water is supplied to the core melt that has fallen into the cavity for cooling. However, when the power supply in the nuclear power facility is lost, the pump cannot be operated, and there is a risk that the core melt cannot be cooled early.

[0005] The present disclosure solves the above-described problems, and an object thereof is to provide a core melt cooling device and a nuclear power facility that enable early cooling of the core melt that has flowed out of the reactor vessel.

Means for Solving the Problems

[0006] The core melt cooling device of the present disclosure for achieving the above object is a core melt cooling device that supports a nuclear reactor by a structure installed at the base of a nuclear reactor containment vessel and cools the core melt that falls from the lower part of the nuclear reactor vessel. In the device, a cavity provided in a hollow shape in the base part, a water storage tank provided in the cavity for storing cooling water, a heat transfer member for receiving the core melt and transferring the heat of the core melt to the cooling water in the water storage tank, and a spray nozzle for spraying the cooling water in the water storage tank above the heat transfer member are provided.

[0007] In addition, the nuclear power facility of the present disclosure includes a nuclear reactor disposed inside the nuclear reactor containment vessel and the core melt cooling device.

Advantages of the Invention

[0008] According to the core melt cooling device and the nuclear power facility of the present disclosure, the core melt flowing out from the nuclear reactor vessel can be cooled early.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Embodiments for Carrying Out the Invention

[0010] Hereinafter, with reference to the drawings, preferred embodiments of the present disclosure will be described in detail. Note that the present disclosure is not limited by this embodiment, and when there are a plurality of embodiments, those configured by combining each embodiment are also included. In addition, the constituent elements in the embodiment include those that can be easily assumed by those skilled in the art, those that are substantially the same, and those within a so-called equivalent range.

[0011] <Nuclear facility> FIG. 1 is a schematic diagram showing the nuclear facility of the present embodiment.

[0012] As shown in FIG. 1, the nuclear facility 10 is applied to a nuclear power plant. The nuclear facility 10 of the present embodiment uses light water as a reactor coolant and a neutron moderator, forms high-temperature and high-pressure water that does not boil throughout the primary system, sends the high-temperature and high-pressure water to a steam generator to generate steam by heat exchange, and sends the steam to a turbine generator to generate electricity, and includes a pressurized water reactor (PWR). However, the reactor is not limited to a pressurized water reactor and can also be applied to other reactors such as a boiling water reactor (BWR).

[0013] The reactor containment vessel 11 is arranged on a solid ground G such as bedrock. The reactor containment vessel 11 includes a base portion 12 and a containment vessel main body 13. The base portion 12 is installed on the ground G, and the containment vessel main body 13 is erected on the base portion 12. The base portion 12 and the containment vessel main body 13 form an integral structure. The containment vessel main body 13 is provided with a structure 14 constructed by reinforced concrete or the like inside. The structure 14 is arranged inside the containment vessel main body 13 above the base portion 12.

[0014] The reactor 15 is arranged at the central portion of the reactor containment vessel 11. The structure 14 defines a cylindrical space portion 16 at the central portion of the reactor containment vessel 11, the reactor 15 is arranged in the space portion 16, and is suspended and supported by the structure 14 forming the inner wall portion of the space portion 16. A plurality of steam generators 17 are arranged around the reactor 15 in the reactor containment vessel 11. The plurality of steam generators 17 are supported by the structure 14. The reactor 15 and the plurality of steam generators 17 are connected by a cooling water pipe 18.

[0015] The reactor containment vessel 11 has a cavity 19 partitioned and formed below the reactor 15. The cavity 19 receives and cools the core melt that falls from the reactor 15. The reactor containment vessel 11 is provided with a cooling water pit 20 for storing cooling water in the base portion 12, and a cooling water injection device 21 is provided at the upper part of the containment vessel main body 13. The cooling water pit 20 is connected to the cooling water injection device 21 by a cooling water path 22, and a cooling water pump 23 is provided in the cooling water path 22.

[0016] The reactor 15 is configured by arranging a core 25 inside a reactor vessel 24. The reactor vessel 24 is configured by detachably providing a reactor vessel lid on the upper part of the reactor vessel main body. The reactor vessel 24 is provided with an inlet nozzle for supplying light water (coolant) as primary cooling water and an outlet nozzle for discharging the light water at the upper side portion. The reactor vessel 24 has cooling water pipes 18 from the steam generator 17 connected to the inlet nozzle and the outlet nozzle respectively. The core 25 arranged inside the reactor vessel 24 is composed of a plurality of fuel assemblies. The fuel assembly is configured by bundling a large number of fuel rods in a lattice shape by a support lattice. Note that the core 25 has a plurality of control rods for controlling the output of the reactor 15 arranged together with a large number of fuel rods.

[0017] In the reactor 15, neutrons are released when the nuclear fuel constituting the core 25 undergoes nuclear fission. The moderator and light water as primary cooling water reduce the kinetic energy of the released fast neutrons to thermal neutrons, making it easier for new nuclear fissions to occur, and at the same time, taking away the generated heat for cooling. At this time, by inserting control rods into the core 25, the number of neutrons generated in the core 25 is adjusted, thereby adjusting the output of the reactor 15.

[0018] The steam generator 17 is connected to a steam turbine provided outside the reactor containment vessel 11 via a steam pipe. The steam turbine is connected to a generator. The steam generator 17 generates steam by performing heat exchange between the high-temperature primary cooling water supplied from the reactor 15 and secondary cooling water. The generated steam is sent to the steam turbine to drive it, and power generation is performed by the generator. The steam that has driven the steam turbine is cooled and then returned to the steam generator 17.

[0019] <Cooling device for the core melt> FIG. 2 is a schematic diagram showing the cooling device for the core melt of the present embodiment.

[0020] As shown in FIGS. 1 and 2, the nuclear facility 10 includes a cooling device 30 for the core melt. The cooling device 30 for the core melt is configured such that the reactor 15 is supported by a structure 14 installed at the base portion 12 of the reactor containment vessel 11, and cools the core melt that falls from the lower portion of the reactor vessel 24 constituting the reactor 15. The cooling device 30 for the core melt includes a cavity 19, a water storage tank 31, a heat transfer member 32, and a spray nozzle 33.

[0021] The cavity 19 is provided in a hollow shape in the base portion 12 located below the reactor 15, and is disposed at a position horizontally displaced from the central portion of the reactor 15. The cavity 19 is a partitioned room and functions as a diffusion space portion where the core melt diffuses. The cavity 19 communicates with the lower space portion of the reactor vessel 24 through a transfer passage 34. That is, one end of the transfer passage 34 opens on the upper surface of the base portion 12, and the other end communicates with the side portion of the cavity 19. The transfer passage 34 has an L shape and includes a vertical passage 34a and a horizontal passage 34b. The upper end of the vertical passage 34a opens on the upper surface of the base portion 12, and the lower end communicates with one end of the horizontal passage 34b. The other end of the horizontal passage 34b communicates with the cavity 19. The transfer passage 34 is a through hole provided through the base portion 12, and it is preferable that a refractory material (for example, a metal pipe or the like) is disposed on the inner wall surface of the through hole.

[0022] The water storage tank 31 is provided in the cavity 19 and stores cooling water therein. The water storage tank 31 is a tank having a hollow interior and has a substantially sealed shape. The water storage tank 31 is provided in the lower half region of the cavity 19, and the upper half region of the cavity 19 serves as a diffusion space portion. The water storage tank 31 has an inlet portion 19a communicating with the transfer passage 34 located above the upper surface of the water storage tank 31. Although the water storage tank 31 is filled with cooling water inside, it is preferable that an air layer 31a is provided at the upper portion.

[0023] The heat transfer member 32 receives the core melt and transfers the heat of the core melt to the cooling water in the water storage tank 31. The heat transfer member 32 includes a plurality of heat transfer plates 41 and a plurality of heat transfer rods 42. The plurality of heat transfer plates 41 are arranged above the water storage tank 31. In this case, the plurality of heat transfer plates 41 may be arranged without gaps or may be arranged at a predetermined interval. The plurality of heat transfer rods 42 extend from the heat transfer plates 41 to the water storage tank 31. That is, the heat transfer rods 42 are arranged vertically inside the water storage tank 31, the upper end penetrates the upper surface of the water storage tank 31 and is connected to the lower surface of the heat transfer plate 41, and the lower part is connected to the bottom of the water storage tank 31. That is, the plurality of heat transfer plates 41 are supported by the water storage tank 31 by the plurality of heat transfer rods 42.

[0024] When the core melt is transferred onto the plurality of heat transfer plates 41, the heat transfer member 32 receives the core melt. Since the core melt is at a high temperature, the plurality of heat transfer plates 41 transfer the heat of the core melt to the cooling water in the water storage tank 31 via the plurality of heat transfer rods 42. Then, the cooling water in the water storage tank 31 is heated by the heat transferred from the heat transfer member 32.

[0025] The ejection nozzle 33 ejects the cooling water in the water storage tank 31 above the heat transfer member 32. Specifically, the ejection nozzle 33 ejects the cooling water in the water storage tank 31 toward the core melt received by the heat transfer member 32. One end of the ejection nozzle 33 communicates with the lower part of the water storage tank 31, and the other end is arranged above the heat transfer plate 41 of the heat transfer member 32. The ejection nozzle 33 includes a first vertical portion 51, a first horizontal portion 52, a second vertical portion 53, a second horizontal portion 54, and an ejection portion 55. One end of the first vertical portion 51 is connected to the lower part of the water storage tank 31, and the other end is connected to one end of the first horizontal portion 52. The other end of the first horizontal portion is connected to one end of the second vertical portion 53. The other end of the second vertical portion 53 is connected to one end of the second horizontal portion 54. The other end of the second horizontal portion 54 penetrates and is arranged in the cavity 19. That is, in the ejection nozzle 33, the ejection portion 55 provided at the other end of the second horizontal portion 54 is arranged above the heat transfer plate 41.

[0026] The injection nozzle 33 has an injection part 55 of the cooling water disposed on the side opposite to the inlet part 19a in the cavity 19. It is preferable to provide a plurality of injection nozzles 33 and injection parts 55. That is, by providing a plurality of injection nozzles 33 around the water storage tank 31 or by branching the tip of the injection nozzle 33 to provide a plurality of injection parts 55, it is preferable to inject the cooling water upward into the cavity 19 from a plurality of different locations. However, the injection nozzle 33 and the injection part 55 may be provided on the side of the inlet part 19a in the cavity 19.

[0027] The injection nozzle 33 has a release valve 56 provided in the middle part, that is, the second vertical part 53. The release valve 56 opens and closes according to the pressure of the cooling water in the water storage tank 31, and it is preferable to adopt a rupture disk. That is, when the pressure of the cooling water in the water storage tank 31 reaches a preset pressure, the release valve 56 is opened by the rupture of the rupture disk.

[0028] In addition, it is preferable that a sacrificial material concrete 61 is provided on the upper part of the heat transfer member 32 in the core melt cooling device 30. The sacrificial material concrete 61 is a sacrificial material that lowers the melting point of the core melt and reduces its viscosity, and is not limited to concrete.

[0029] Moreover, it is preferable that the core melt cooling device 30 is provided with a cooling water replenishing mechanism 62 for replenishing the cooling water to the water storage tank 31. That is, a replenishing tank 63 is arranged vertically above the water storage tank 31, the water storage tank 31 and the replenishing tank 63 are connected by a replenishing path 64, and an on-off valve 65 is provided in the replenishing path 64. In this case, it is preferable that the on-off valve 65 is a manual type. The cooling water replenishing mechanism 62 can replenish the cooling water in the replenishing tank 63 from the replenishing path 64 to the water storage tank 31 by free fall by opening the on-off valve 65. Note that the cooling water replenishing mechanism 62 is not limited to this configuration. For example, the cooling water replenishing mechanism 62 may have an electric on-off valve 66 and an electric pump 67 so that it can be remotely operated when the power supply is available or when the power supply is restored, and both may be provided together.

[0030] <Cooling Method for Core Melt> Figure 3 is a schematic diagram showing the operation of the cooling device for the core melt.

[0031] As shown in Figure 1, in the nuclear facility 10, for example, it is assumed that a severe accident occurs and a core damage accident due to core melting occurs. At this time, as shown in Figures 1 and 3, the lower part of the reactor vessel 24 of the nuclear reactor 15 is damaged, and the core melt 25A in which the core 25 has melted flows out. The core melt 25A flowing out from the lower part of the reactor vessel 24 falls into the vertical passage 34a of the transfer passage 34 provided below the reactor vessel 24. Then, the core melt 25A flows from the vertical passage 34a of the transfer passage 34 through the horizontal passage 34b and reaches the cavity 19 from the inlet 19a.

[0032] The core melt 25A flowing into the cavity 19 is received by the heat transfer member 32. The heat transfer member 32 has a plurality of heat transfer plates 41 receiving the core melt 25A, and the heat of the core melt 25A is transferred to the cooling water in the water storage tank 31 by a plurality of heat transfer rods 42. The cooling water in the water storage tank 31 is heated by the heat of the core melt 25A transferred by the heat transfer member 32. The cooling water in the water storage tank 31 is heated and expands, and applies pressure to the rupture disc 56 via the ejection nozzle 33. When the pressure of the cooling water in the water storage tank 31 reaches a predetermined pressure, the rupture disc (rupture disc) 56 ruptures and opens.

[0033] Then, the cooling water in the water storage tank 31 reaches the ejection part 55 through the ejection nozzle 33 and the rupture disc 56, and the ejection part 55 ejects the cooling water toward the core melt 25A received by the heat transfer member 32. And the core melt 25A is cooled by the cooling water ejected from the ejection part 55.

[0034] In addition, when the sacrificial material concrete 61 is provided on the upper part of the heat transfer member 32, the core melt 25A flowing into the cavity 19 contacts the sacrificial material concrete 61 and melts and mixes, so that the melting point is further lowered and the viscosity is reduced.

[0035] In addition, since the core melt 25A is at several thousand degrees Celsius, the cooling water that cools the core melt 25A on the heat transfer member 32 vaporizes, reducing the cooling water in the water storage tank 31. At this time, an operator or a detector detects the decrease in the cooling water in the water storage tank 31 and activates the cooling water replenishment mechanism 62 to replenish the water storage tank 31 with cooling water.

[0036] [Operational Effects of the Present Embodiment] The core melt cooling device according to the first aspect is a core melt cooling device 30 that supports the nuclear reactor 15 by a structure 14 installed at the base portion 12 of the nuclear reactor containment vessel 11 and cools the core melt 25A that falls from the lower part of the nuclear reactor vessel 24. In the core melt cooling device 30, a cavity 19 provided in a hollow shape in the base portion 12, a water storage tank 31 provided in the cavity 19 for storing cooling water, a heat transfer member 32 that receives the core melt 25A and transfers the heat of the core melt 25A to the cooling water in the water storage tank 31, and a spray nozzle 33 that sprays the cooling water in the water storage tank 31 above the heat transfer member 32 are provided.

[0037] According to the core melt cooling device according to the first aspect, when the lower part of the nuclear reactor vessel 24 is damaged and the core melt 25A in which the core 25 has melted falls, the core melt 25A is transferred to the cavity 19. The core melt 25A transferred to the cavity 19 is received by the heat transfer member 32, and the heat of the core melt 25A is transferred to the cooling water in the water storage tank 31. Then, the cooling water in the water storage tank 31 is heated and expanded by the heat of the core melt 25A transferred from the heat transfer member 32 and is ejected toward the core melt 25A on the heat transfer member 32 through the spray nozzle 33, and the core melt 25A is cooled by the cooling water. As a result, even when the power supply in the nuclear power facility 10 is lost, the core melt 25A flowing out of the nuclear reactor vessel 24 can be cooled early.

[0038] Also, according to the core melt cooling device, by ejecting cooling water from the ejection nozzle 33 to cool the core melt 25A transferred to the cavity 19, the occurrence of a steam explosion due to the contact between the core melt 25A and a large amount of cooling water can be suppressed. Furthermore, by simply providing the water storage tank 31, the heat transfer member 32, and the ejection nozzle 33 in the cavity 19, the complication of the structure can be suppressed and an increase in the manufacturing cost can be suppressed.

[0039] The core melt cooling device according to the second aspect is the core melt cooling device according to the first aspect, and further, the heat transfer member 32 includes a heat transfer plate 41 disposed above the water storage tank 31 and a heat transfer rod 42 extending from the heat transfer plate 41 to the water storage tank 31. Thereby, the core melt 25A can be received by the heat transfer plate 41, and the heat of the core melt 25A can be appropriately transferred to the cooling water in the water storage tank 31 by the heat transfer rod 42.

[0040] The core melt cooling device according to the third aspect is the core melt cooling device according to the first aspect or the second aspect, and further, one end of the ejection nozzle 33 communicates with the water storage tank 31, the other end is disposed above the heat transfer member 32, and an opening valve 56 that opens according to the pressure of the cooling water in the water storage tank 31 is provided in the middle portion. Thereby, until the pressure of the cooling water in the water storage tank 31 reaches a predetermined pressure, the core melt 25A can be diffused on the heat transfer member 32, and by ejecting the cooling water at the predetermined pressure, the cooling water can be ejected over a wide range to appropriately cool the core melt 25A.

[0041] The core melt cooling device according to the fourth aspect is the core melt cooling device according to the third aspect, and further, the opening valve 56 has a rupture disk. Thereby, the simplification of the structure of the opening valve 56 can be achieved.

[0042] The core melt cooling device according to the fifth aspect is the core melt cooling device according to any one of the first to fourth aspects, and further, in the ejection nozzle 33, the cooling water ejection part 55 is arranged on the side opposite to the inlet part 19a of the core melt 25A in the cavity 19. Thereby, the cooling water is ejected toward the downstream part of the core melt 25A spread on the heat transfer member 32, and the core melt 25A can be appropriately cooled.

[0043] The core melt cooling device according to the sixth aspect is the core melt cooling device according to any one of the first to fifth aspects, and further, a sacrificial material concrete (sacrificial material) 61 is arranged on the upper part of the heat transfer plate 41. Thereby, the core melt 25A transferred to the cavity 19 is received by the sacrificial material concrete 61 and melted and mixed, so that the melting point is lowered and the viscosity is reduced, and it can be cooled early.

[0044] The core melt cooling device according to the seventh aspect is the core melt cooling device according to any one of the first to sixth aspects, and further, a cooling water replenishing mechanism 62 for replenishing cooling water to the water storage tank 31 is provided. Thereby, cooling water can always be ensured in the water storage tank 31, and the core melt 25A can be appropriately cooled over a predetermined period.

[0045] The nuclear power facility according to the eighth aspect includes a reactor containment vessel 11, a reactor 15 arranged inside the reactor containment vessel 11, and a core melt cooling device 30. Thereby, even when the power supply is lost in the nuclear power facility 10, the core melt 25A flowing out from the reactor vessel 24 can be cooled early, and the safety can be improved.

Explanation of symbols

[0046] 10 Nuclear power facility 11 Reactor containment vessel 12 Foundation part 13 Containment vessel main body 14 Structure 15 Reactor 16 Space section 17 Steam generator 18 Cooling water pipe 19 Cavity 20 Cooling water pit 21 Cooling water injection device 22 Cooling water path 23 Cooling water pump 24 Reactor vessel 25 Core 25A Core melt 30 Core melt cooling device 31 Water storage tank 32 Heat transfer member 33 Ejection nozzle 34 Transfer passage 41 Heat transfer plate 42 Heat transfer rod 51 First vertical part 52 First horizontal part 53 Second vertical part 54 Second horizontal part 55 Ejection part 56 Open valve 61 Sacrificial material concrete 62 Cooling water replenishment mechanism 63 Replenishment tank 64 Replenishment path 65 On-off valve 66 Electric on-off valve 67 Electric pump

Claims

1. In a core melt cooling device that supports a nuclear reactor by a structure installed at the base of a nuclear reactor containment vessel and cools a core melt that falls from the lower part of the nuclear reactor vessel, a cavity provided in the base part in a hollow shape, a water storage tank provided in the cavity for storing cooling water, a heat transfer member that receives the core melt and transfers the heat of the core melt to the cooling water in the water storage tank, a spray nozzle that sprays the cooling water in the water storage tank above the heat transfer member, and a core melt cooling device comprising the above.

2. The heat transfer member has a heat transfer plate disposed above the water storage tank and a heat transfer rod extending from the heat transfer plate to the water storage tank. The core melt cooling device according to Claim 1.

3. One end of the spray nozzle communicates with the water storage tank, the other end is disposed above the heat transfer member, and a release valve that opens according to the pressure of the cooling water in the water storage tank is provided in the middle part. The core melt cooling device according to Claim 1 or Claim 2.

4. The release valve has a rupture disk. The core melt cooling device according to Claim 3.

5. The spray nozzle is arranged such that the cooling water ejection part is on the side opposite to the inlet part of the core melt in the cavity. The core melt cooling device according to Claim 1.

6. A sacrificial material is disposed on the upper part of the heat transfer plate. The core melt cooling device according to Claim 2.

7. A cooling water replenishing mechanism for replenishing cooling water to the water storage tank is provided. The core melt cooling device according to Claim 1.

8. A reactor containment vessel, a reactor disposed inside the reactor containment vessel, a core melt cooling device according to claim 1, and a nuclear power facility including the same.

Images