Cooling apparatus for reactor pressure vessel top cover and cooling method therefor

Abstract

To more efficiently cool a reactor pressure vessel top cover while considering a thermal stress load applied to the reactor pressure vessel top cover.SOLUTION: A cooling apparatus for a reactor pressure vessel top cover according to the present invention is the cooling apparatus for the reactor pressure vessel top cover that cools the reactor pressure vessel top cover that is installed on an upper part of a reactor pressure vessel accommodating at least a reactor core. In order to prevent heat from escaping from the reactor pressure vessel, a heat-insulating material is provided so as to cover a part of the outer peripheral portion of the reactor pressure vessel top cover with a predetermined gap from the reactor pressure vessel top cover. The cooling apparatus includes a cold air generator for generating cold air, and a cold air inlet side pipe whose one end is connected to the cold air generator and other end is connected to the gap formed between the reactor pressure vessel top cover and the heat-insulating material. The cold air generated by the cold air generator is supplied to the gap via the cold air inlet side pipe.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a cooling system and a cooling method for a reactor pressure vessel head. [Background technology]

[0002] In general, during periodic inspections or when the reactor is shut down in a nuclear power plant, it is necessary to cool the reactor pressure vessel and the reactor pressure vessel head in order to remove fuel and perform inspections.

[0003] The reactor pressure vessel can be cooled in a manner that follows the reactor water temperature by circulating and cooling the reactor water within the reactor pressure vessel.

[0004] On the other hand, since it is not easy to cool the top lid of the reactor pressure vessel using reactor water, the cooling process takes time, which is one of the reasons for delaying processes such as regular inspections.

[0005] Regarding cooling of the top lid of the reactor pressure vessel, there are a number of methods, including cooling by blowing air into the gap formed between the top lid of the reactor pressure vessel and the thermal insulation material using an air conditioning duct or local exhaust fan, and a method of attaching an element capable of supplying cooling water to the top lid of the reactor pressure vessel and cooling the top lid by flowing cooling water from the element.

[0006] For this reason, cooling the reactor pressure vessel head using a fluid such as air or cooling water is considered to be one of the effective methods for cooling the reactor pressure vessel head.

[0007] As a prior art document relating to cooling of such a reactor pressure vessel head, there can be mentioned the "Cooling device for reactor pressure vessel head" described in Patent Document 1.

[0008] Patent Document 1 describes a cooling device for a reactor pressure vessel top lid that is provided with a cooling device and that evenly cools the reactor pressure vessel top lid together with the reactor pressure vessel body with cooling water, thereby shortening periodic inspection intervals and improving worker safety. The cooling device is composed of a reactor pressure vessel top lid equipped with a cooling element and a cooling device that supplies a cooling medium to the cooling element. [Prior art documents] [Patent documents]

[0009] [Patent Document 1] Japanese Patent Application Publication No. 9-15368 Summary of the Invention [Problem to be solved by the invention]

[0010] However, the cooling device for the reactor pressure vessel head described in the above-mentioned Patent Document 1 uses cooling water for cooling, so the reactor pressure vessel head may be subject to metallic damage due to a sudden change in temperature. In addition, since cooling is performed by spraying cooling water from a cooling element, uneven cooling may occur between the vicinity of the spray nozzle and other areas.

[0011] The present invention has been made in consideration of the above-mentioned points, and an object of the present invention is to provide a cooling device and a cooling method for a reactor pressure vessel head which can cool the reactor pressure vessel head more efficiently, taking into account the thermal stress load on the reactor pressure vessel head. [Means for solving the problem]

[0012] In order to achieve the above object, the cooling device for a reactor pressure vessel head of the present invention is a cooling device for a reactor pressure vessel head that cools a reactor pressure vessel head that is installed on an upper portion of a reactor pressure vessel in which at least a reactor core is housed, comprising: a heat insulating material is installed so as to cover a part of the outer periphery of the reactor pressure vessel top lid with a predetermined gap between the reactor pressure vessel top lid and the heat insulating material so as to prevent heat from escaping from the reactor pressure vessel; a cold air generating device that generates cold air; and a cold air inlet side pipe having one end connected to the cold air generating device and the other end connected to the gap formed between the reactor pressure vessel top head and the thermal insulation material, The cold air generated by the cold air generating device is supplied to the gap via the cold air inlet side piping.

[0013] In order to achieve the above object, the present invention provides a method for cooling a reactor pressure vessel head, which cools a reactor pressure vessel head installed on an upper portion of a reactor pressure vessel in which at least a reactor core is housed, comprising the steps of: The cold air inlet piping has one end connected to a cold air generating device that generates cold air, and the other end connected to a gap formed between the reactor pressure vessel top lid and a thermal insulation material that is installed so as to cover a part of the outer periphery of the reactor pressure vessel top lid with a predetermined gap between the reactor pressure vessel top lid and a thermal insulation material to prevent heat from escaping from the reactor pressure vessel, and supplies the cold air generated by the cold air generating device to the gap via the cold air inlet piping. Effect of the Invention

[0014] According to the present invention, the reactor pressure vessel head can be cooled more efficiently by taking into consideration the thermal stress load on the reactor pressure vessel head. [Brief description of the drawings]

[0015] [Figure 1] 1 is a diagram showing a schematic structure of a boiling water nuclear power plant to which a cooling device and a cooling method for a reactor pressure vessel head of the present invention are applied; [Diagram 2] 1 is a diagram showing a first embodiment of a cooling device for a reactor pressure vessel head of the present invention. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0016] Hereinafter, a cooling system and a cooling method for a reactor pressure vessel head of the present invention will be described based on the illustrated embodiment. EXAMPLES

[0017] FIG. 1 shows a schematic structure of a boiling water nuclear power plant to which the cooling system and method for the reactor pressure vessel head of the present invention are applied.

[0018] As shown in the figure, the boiling water nuclear power plant in this embodiment includes a reactor and a reactor containment vessel 2. The reactor containment vessel 2 is installed in a reactor building 1, and a reactor containment vessel top lid 2A is attached to the upper end and sealed, and includes a dry well 9 formed therein and an annular suppression chamber 24 in which a suppression pool filled with cooling water 23 is formed.

[0019] One end of the vent passage connected to the dry well 9 is immersed in the cooling water 23 of the suppression pool in the pressure suppression chamber 24, and the pressure suppression chamber 24 is disposed in an annular torus chamber 26 formed in the reactor building 1.

[0020] The nuclear reactor includes a reactor pressure vessel 3 configured with a reactor pressure vessel top lid 3A attached, a core 27 loaded with a plurality of fuel assemblies containing nuclear fuel material, a steam separator (not shown), a steam dryer (not shown), etc. The core 27, the steam separator, and the steam dryer are disposed within the reactor pressure vessel 3, and each fuel assembly loaded within the core 27 has its lower end supported by a core support plate 28 and its upper end held by an upper lattice plate 29. The steam separator is disposed above the upper lattice plate 29, and the steam dryer is disposed above the steam separator.

[0021] A plurality of control rod guide tubes 30 are arranged below the core support plate 28, and a control rod (not shown) that is inserted and removed between the fuel assemblies in the core 27 to control the reactor power is arranged in each control rod guide tube 30.

[0022] In addition, a plurality of control rod drive mechanism housings 31 are attached to the bottom head of the reactor pressure vessel 3, and a control rod drive mechanism (not shown) is installed in each control rod drive mechanism housing 31 and connected to the control rod in the control rod guide tube 30.

[0023] The reactor pressure vessel 3 is installed on a cylindrical pedestal 5 provided on a concrete mat 32 provided at the bottom of the reactor containment vessel 2, and a cylindrical gamma ray shielding body 33 is installed at the upper end of the pedestal 5 and surrounds the reactor pressure vessel 3.

[0024] A pedestal opening 34 is formed in the pedestal 5, and communicates the dry well 9 in the reactor containment vessel 2 with an internal space 35 formed in the pedestal 5. A plurality of control rod drive mechanism housings 31 extend from the bottom head of the reactor pressure vessel 3 toward the internal space 35.

[0025] A cylindrical concrete biological shield 6, which is part of the reactor building 1, surrounds the reactor containment vessel 2. An access passage with an airlock door is provided so that workers can enter the reactor containment vessel 2 during maintenance and inspection carried out after the operation of the boiling water reactor nuclear power plant is shut down. This access passage penetrates the biological shield 6 and the reactor containment vessel 2.

[0026] In addition to the access passage, a control rod drive mechanism hatch 36 and an equipment hatch are provided penetrating the biological shield 6 and the reactor containment vessel 2. The control rod drive mechanism hatch 36 extends toward the side wall of the reactor building 1 facing the radioactive waste treatment building 37.

[0027] The above-mentioned access passage is provided by opening the airlock door, and the equipment hatch and the control rod drive mechanism hatch 36 are provided by opening each hatch, so that an area 38 outside the reactor containment vessel 2 in the reactor building 1 is connected to the dry well 9 in the reactor containment vessel 2. When the boiling water nuclear power plant is in operation, the airlock door and these hatches are closed.

[0028] An operation floor 39 is formed above the reactor containment vessel 2 in the reactor building 1, and a fuel storage pool 40 is formed surrounded by the operation floor 39, and cooling water is filled in the fuel storage pool 40. A plurality of spent fuel assemblies removed from the core 27 are stored in the cooling water in the fuel storage pool 40.

[0029] The reactor building 1 has a square cross section and four side walls. A radioactive waste treatment building 37 is located adjacent to the reactor building 1 and extends parallel to one side wall of the reactor building 1. A turbine building (not shown) is located adjacent to the other side wall of the reactor building 1, perpendicular to the side wall adjacent to the radioactive waste treatment building 37.

[0030] As shown in FIG. 2, the cooling device for the reactor pressure vessel top lid 3A in this embodiment cools the reactor pressure vessel top lid 3A by sending cold air generated by an air compressor 41 and a cold air generator 42 constituting a cold air generating device through a cold air inlet piping 43 into a gap 47 formed between the reactor pressure vessel top lid 3A and a thermal insulation material 44.

[0031] Specifically, the cooling device for the reactor pressure vessel top head 3A of this embodiment is provided with a thermal insulation material 44 that is installed to cover a part of the outer periphery of the reactor pressure vessel top head 3A with a specified gap 47 between the reactor pressure vessel top head 3A and the thermal insulation material 44 to prevent heat from escaping from the reactor pressure vessel 3, and is configured to include a cold air generating device consisting of an air compressor 41 that compresses air and a cold air generator 42 that generates cold air from the air compressed by the air compressor 41, and a cold air inlet side piping 43 whose one end is connected to the cold air generator 42, which is the cold air generating device, and whose other end is connected to the gap 47 formed between the reactor pressure vessel top head 3A and the thermal insulation material 44.

[0032] The cold air generated by a cold air generating device consisting of an air compressor 41 and a cold air generator 42 is supplied to the gap 47 via the cold air inlet piping 43 to cool the reactor pressure vessel top lid 3A.

[0033] That is, in the cooling method for the reactor pressure vessel top head in this embodiment, one end is connected to a cold air generating device that generates cold air and is composed of an air compressor 41 and a cold air generator 42, and the other end is connected to a gap 47 formed between the reactor pressure vessel top head 3A and a thermal insulation material 44 that is installed so as to cover a part of the outer periphery of the reactor pressure vessel top head 3A with a predetermined gap 47 between the reactor pressure vessel top head 3A and the thermal insulation material 44 to prevent heat from escaping from the reactor pressure vessel 3, and supplies cold air generated by the cold air generating device to the gap 47 via a cold air inlet side piping 43.

[0034] In addition, in this embodiment, a cold air outlet side pipe 45 for discharging cold air from within the gap 47 formed between the reactor pressure vessel top lid 3A and the thermal insulation material 44 is connected to the gap 47, and an orifice 46 is installed in this cold air outlet side pipe 45.

[0035] That is, an orifice 46 is installed in the cold air outlet side piping 45 which is connected to the gap 47 formed between the reactor pressure vessel top lid 3A and the thermal insulation material 44 and discharges the cold air from within the gap 47, and the cold air from within the gap 47 is discharged via the cold air outlet side piping 45 in which this orifice 46 is installed.

[0036] By installing the orifice 46 in the cold air outlet side piping 45 as described above, the orifice 46 makes the cold air outlet side piping 45 narrower than the cold air inlet side piping 43, so that cooling can be performed by maintaining the pressure in the gap 47 formed between the reactor pressure vessel top lid 3A and the thermal insulation material 44.

[0037] In this embodiment, cold air having a temperature lower than that of room temperature air can be sent into the gap 47 formed between the reactor pressure vessel top head 3A and the thermal insulation material 44, and by providing an orifice 46 in the cold air outlet piping 45, it becomes possible to effectively cool the reactor pressure vessel top head 3A.

[0038] Therefore, according to this embodiment, the reactor pressure vessel head 3A can be cooled more efficiently, taking into consideration the thermal stress load on the reactor pressure vessel head 3A.

[0039] The present invention is not limited to the above-described embodiments, and includes various modified examples. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and the present invention is not necessarily limited to those including all of the configurations described. In addition, it is possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace a part of the configuration of each embodiment with another configuration. [Explanation of symbols]

[0040] 1...reactor building, 2...reactor containment vessel, 2A...reactor containment vessel top lid, 3...reactor pressure vessel, 3A...reactor pressure vessel top lid, 5...pedestal, 6...biological shield, 9...dry well, 23...cooling water, 24...pressure suppression chamber, 26...torus room, 27...reactor core, 28...core support plate, 29...upper grid plate, 30...control rod guide tube, 31...control rod drive mechanism housing, 32...concrete mat, 33...gamma ray shield, 34...pedestal opening, 35...internal space, 36...control rod drive mechanism hatch, 37...radioactive waste treatment building, 38...area outside the reactor containment vessel, 39...operating floor, 40...fuel storage pool, 41...air compressor, 42...cold air generator, 43...cold air inlet piping, 44...thermal insulation, 45...cold air outlet piping, 46...orifice, 47...gap.

Claims

1. A reactor pressure vessel head cooling device that cools a reactor pressure vessel head installed at an upper portion of a reactor pressure vessel in which at least a reactor core is housed, comprising: a heat insulating material is installed so as to cover a part of the outer periphery of the reactor pressure vessel top lid with a predetermined gap between the reactor pressure vessel top lid and the heat insulating material so as to prevent heat from escaping from the reactor pressure vessel; a cold air generating device that generates cold air; and a cold air inlet side pipe having one end connected to the cold air generating device and the other end connected to the gap formed between the reactor pressure vessel top head and the thermal insulation material, 2. A cooling device for a reactor pressure vessel top head, comprising: a cooling device for supplying the cold air generated by the cold air generating device to the gap through the cold air inlet side piping.

2. 2. The cooling system for a reactor pressure vessel head according to claim 1, a cold air outlet side pipe for discharging the cold air in the gap is connected to the gap formed between the reactor pressure vessel top head and the thermal insulation material, 2. A cooling system for a reactor pressure vessel head, comprising: a cooling means for cooling the cool air from the cooling means;

3. The cooling device for a reactor pressure vessel head according to claim 1 or 2, 1. A cooling device for a reactor pressure vessel head, comprising: an air compressor for compressing air; and a cold air generator for generating the cold air from the air compressed by the air compressor.

4. A method for cooling a reactor pressure vessel head, which is installed at an upper portion of a reactor pressure vessel in which at least a reactor core is housed, comprising the steps of: A method for cooling a top lid of a reactor pressure vessel, characterized in that one end of the piping is connected to a cold air generating device that generates cold air, and the other end of the piping is connected to a gap formed between the top lid of the reactor pressure vessel and a thermal insulation material that is installed so as to cover a part of the outer periphery of the top lid of the reactor pressure vessel with a predetermined gap between the top lid of the reactor pressure vessel and the thermal insulation material to prevent heat from escaping from the reactor pressure vessel, and the cold air generated by the cold air generating device is supplied to the gap via a cold air inlet side piping that is connected to the gap formed between the top lid of the reactor pressure vessel and a thermal insulation material that is installed so as to cover a part of the outer periphery of the top lid of the reactor pressure vessel with a predetermined gap between the top lid of the reactor pressure vessel and the thermal insulation material to prevent heat from escaping from the reactor pressure vessel.

5. 5. A method for cooling a reactor pressure vessel head according to claim 4, comprising the steps of: a cooling method for a reactor pressure vessel top head, the cooling method comprising the steps of: providing an orifice in a cold air outlet piping that is connected to the gap formed between the reactor pressure vessel top head and the thermal insulation material and that discharges the cold air from within the gap; and discharging the cold air from within the gap through the cold air outlet piping in which the orifice is provided.

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