Method for dismantling nuclear facility and system for dismantling nuclear facility

Abstract

To dismantle a nuclear facility affected by a severe accident in an underwater environment by submerging the facility in water so that the water shields radiation from the nuclear facility.SOLUTION: The method for dismantling a nuclear facility includes: stopping water leakage at a leakage portion by using a particle dispersion liquid containing fine particles having a specific gravity greater than that of water, when dismantling a nuclear facility in which the water leakage portion has occurred due to a severe accident; and submerging at least a part of the nuclear facility. This makes it possible to submerge a reactor well and to perform dismantling work from above a reactor building.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] An embodiment of the present invention relates to a decommissioning technique for a nuclear reactor that has suffered a severe accident. [Background technology]

[0002] In the event of a severe accident, including a core meltdown, at a boiling water nuclear power plant, the reactor containment vessel and reactor pressure vessel are damaged, making dismantling operations extremely difficult in a flooded state. Furthermore, the high radiation levels inside the reactor building and the low water level make it difficult to identify the damaged areas and repair water leaks. In such cases, fuel debris must be removed and the reactor building dismantled in an air environment. However, much of the dismantling work must be performed remotely, and measures must be taken to prevent the leakage of radioactive dust generated during cutting work during dismantling. On the other hand, if the leaks can be sealed, the reactor well can be flooded, allowing dismantling operations to be carried out from above the reactor building. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6960170 [Patent Document 2] Patent No. 5757222 [Patent Document 3] Patent No. 6186980 [Patent Document 4] Patent No. 7070998 [Patent Document 5] Patent No. 7071003 [Patent Document 6] Utility Model Registration No. 3196318 Summary of the Invention [Problem to be solved by the invention]

[0004] Various technologies have been known in the past. For example, the fuel debris treatment method described in Patent Document 1 aims to settle ultra-high specific gravity muddy water containing barite, solidify the fuel debris, and store it. However, no consideration is given to methods for removing nuclear fuel material or radioactive material from areas where they remain, or methods for dismantling the reactor building.

[0005] Furthermore, the flooding methods for a containment vessel described in Patent Documents 2 and 3 assume that there is a damaged part in the containment vessel, but it is difficult to identify it, and so all the space is filled with concrete. Since a large amount of radioactive waste will be generated, a watertight structure is constructed upstream of the expected damaged part, and the containment vessel is then flooded. This flooding method has the problem that a lot of work must be done inside the reactor building, which is highly radioactive.

[0006] Furthermore, the reactor building flooding devices in Patent Documents 4 and 5 have a bottom constructed underground below the reactor building, and physically isolate the entire reactor building while flooding it. This is a very good concept as it reduces the risk of contaminated water leaking into the environment, but there are issues with this, such as the increased amount of work required, and in particular the need to construct an underground shield tunnel.

[0007] Furthermore, the nuclear reactor decommissioning support facility in Patent Document 6 constructs a pool that covers all of the multiple reactor buildings, and submerges the entire reactor buildings. However, there are issues such as the difficulty of constructing the bottom of the pool, the large scale of the pool, and the extremely large amount of water that the pool can hold.

[0008] An embodiment of the present invention has been made in consideration of these circumstances, and aims to submerge a nuclear facility that has suffered a severe accident, shield it from radiation with water, and dismantle the nuclear facility in an underwater environment. [Means for solving the problem]

[0009] In a nuclear facility dismantling method according to an embodiment of the present invention, when dismantling nuclear facility in which a water leak has occurred due to a severe accident, the leak site is sealed using a microparticle dispersion containing microparticles having a specific gravity greater than that of water, and at least a portion of the nuclear facility is submerged in water. [Effects of the Invention]

[0010] According to an embodiment of the present invention, a nuclear facility that has suffered a severe accident can be submerged, the water can be used to shield radiation, and the nuclear facility can be dismantled in an underwater environment. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 2 is a cross-sectional view showing the reactor building to be dismantled in the first embodiment. [Figure 2] FIG. 2 is a cross-sectional view showing the reactor building with the reactor well 9 submerged. [Figure 3] FIG. 10 is a cross-sectional view showing a reactor building to be dismantled in the second embodiment. [Figure 4] FIG. 11 is a cross-sectional view showing a reactor building to be dismantled in the third embodiment. [Figure 5] FIG. 2 is a cross-sectional view showing the configuration of drainage piping provided on the wall surface of a reactor building. [Figure 6] A cross-sectional view showing the drilling of drainage holes in the wall of the reactor building. [Figure 7] FIG. 2 is a cross-sectional view showing a state in which leaking water is circulated in the reactor building 1. [Figure 8] FIG. 1 is a cross-sectional view showing an example of a manner in which water remaining at the bottom of a reactor building is drained. [Figure 9] FIG. 10 is a cross-sectional view showing another example of a manner in which water remaining at the bottom of a reactor building is drained. [Figure 10] Cross-sectional view showing the dismantling and removal of the top lid of the reactor containment vessel. [Figure 11] Cross-sectional view showing the dismantling and removal of the top head of the reactor pressure vessel. [Figure 12] Cross-sectional view showing the dismantling and removal of the reactor pressure vessel structure. [Figure 13] FIG. 1 is a cross-sectional view showing the dismantling and removal of the main body of the reactor pressure vessel. [Figure 14] Cross-sectional view showing the dismantling and removal of the pedestal and fuel debris. [Figure 15] FIG. 10 is a cross-sectional view showing a reactor building to be dismantled in the fourth embodiment. [Figure 16] Cross-sectional view showing the dismantling and removal of the shield plug and the top lid of the reactor containment vessel. [Figure 17] Cross-sectional view showing the dismantling and removal of the top head of the reactor pressure vessel. [Figure 18] Cross-sectional view showing the dismantling and removal of the reactor pressure vessel structure. [Figure 19] A cross-sectional view showing the dismantling and removal of the upper concrete structure of the reactor building. [Figure 20] A cross-sectional view showing the dismantling and removal of the concrete body after the container transfer equipment has been moved. [Figure 21] Cross-sectional view showing the reactor building after the upper part has been dismantled and removed. [Figure 22] Cross-sectional view showing the state after removing the upper outer wall. [Figure 23] FIG. 10 is a cross-sectional view showing a state in which various devices have been rearranged. [Figure 24] Cross-sectional view showing the dismantling and removal of the reactor lower structure and fuel debris. [Figure 25] Cross-sectional view showing the dismantling and removal of the pedestal reactor containment vessel structure. [Figure 26] A cross-sectional view showing the dismantling and removal of temporary structures that interfere with the demolition work. [Figure 27] A cross-sectional view showing the demolition and removal of the reactor building floor and concrete frame. [Figure 28] FIG. 10 is a cross-sectional view showing the state after the water-stopping material accumulated on the upper part of the torus chamber has been removed. [Figure 29] FIG. 10 is a cross-sectional view showing the dismantling and removal of the lower structure of the pressure suppression chamber of the reactor containment vessel. [Figure 30] FIG. 1 is a cross-sectional view showing the dismantling and removal of the upper structure of the pressure suppression chamber of the reactor containment vessel. [Figure 31] FIG. 10 is a cross-sectional view showing the remaining vent pipe exposed. [Figure 32] Cross-sectional view showing the dismantling and removal of the vent pipe. [Figure 33]Cross-sectional view showing the dismantling and removal of the bottom of the reactor containment vessel. [Figure 34] A cross-sectional view showing the reactor building after dismantling is complete. DETAILED DESCRIPTION OF THE INVENTION

[0012] (First embodiment) Hereinafter, embodiments of a nuclear facility dismantling method and a nuclear facility dismantling system will be described in detail with reference to the drawings. Note that the scale of each component shown in the drawings may be changed as appropriate to facilitate understanding.

[0013] Reference numeral 1 in Fig. 1 denotes a nuclear reactor building. This reactor building 1 has suffered a severe accident, and decommissioning work is being carried out thereon. A nuclear facility dismantling system 100 according to the first embodiment dismantles this reactor building 1. A nuclear facility dismantling method is carried out using this nuclear facility dismantling system 100.

[0014] In the event of a severe accident, the fuel assemblies in the reactor melt due to overheating of the nuclear fuel, resulting in a so-called meltdown. The molten nuclear fuel leaks from the reactor pressure vessel 5 contained inside the reactor containment vessel 4. The reactor containment vessel 4 is also damaged by the increased pressure inside. Because the fuel debris 7 containing the molten nuclear fuel is highly radioactive, even remotely operated robots may malfunction due to the effects of radiation if the work of removing the fuel debris 7 is attempted using the partial submersion method. There is also a risk of workers being exposed to radiation.

[0015] If the inside of the reactor containment vessel 4 can be filled with water, the water can shield radiation. Furthermore, there are many other areas with high radiation levels besides the reactor containment vessel 4, and these need to be submerged. Therefore, the nuclear facility dismantling system 100 of the first embodiment submerges at least a portion of the reactor building 1, which is a nuclear facility.

[0016] FIG. 1 shows the overall configuration of a nuclear facility dismantling system 100 when leaking points in a reactor containment vessel 4 and a reactor well 9 formed above it are sealed with fine particles and the reactor containment vessel 4 and the reactor well 9 are flooded.

[0017] The structure of the reactor building 1 above the operation floor 2 has been dismantled and removed. The operation floor 2 of the reactor building 1 contains a reactor well 9, a spent fuel storage pool 10, an equipment storage pool 11, and a shield plug 12.

[0018] The reactor building 1 is a reinforced concrete structure. A reactor containment vessel 4 is provided inside the reactor building 1. The reactor containment vessel 4 is composed of a main body 4a, a pressure suppression chamber 4b, and a head 4c. The reactor containment vessel 4 also has a vent pipe 68. A reactor pressure vessel 5 is provided inside the reactor containment vessel 4. The reactor pressure vessel 5 is composed of a main body shell 5a, a head 5b, a reactor substructure 5c, and a head insulation material (not shown). The reactor pressure vessel 5 is supported on the bottom of the main body 4a of the reactor containment vessel 4 via a pedestal 6. Fuel debris 7 that falls from the reactor pressure vessel 5 due to a core meltdown is deposited on the bottom of the main body 4a of the reactor containment vessel 4. A boiling water reactor (BWR) is shown as an example here.

[0019] The nuclear facility dismantling system 100 includes an injection device 13 that injects a microparticle dispersion 8 containing microparticles into nuclear facility. When dismantling nuclear facility where a water leak has occurred due to a severe accident, this nuclear facility dismantling system 100 seals the leak site with microparticles that have a specific gravity greater than that of water and floods at least a portion of the nuclear facility. The injection device 13 injects the microparticle dispersion 8 into the internal space of the nuclear facility where the leak site exists, and forms a microparticle deposition layer 8b in which the microparticles accumulate to a height higher than the leak site.

[0020] In a nuclear reactor where a severe accident has occurred, it may be difficult to identify the leak location. In such cases, the height of the leak location can be predicted from information such as the height of the water surface stored inside the reactor containment vessel 4. The injector 13 injects the microparticle dispersion 8 until it reaches this predicted height, forming a microparticle deposition layer 8b. It is sufficient that at least the height of the leak location can be predicted.

[0021] The microparticles contain at least barite as a weighting material, and optionally at least bentonite as a thickener. The microparticles are deposited without solidifying, and are a water-stopping material with fluidity. The blending ratio of materials such as barite and bentonite is adjusted in advance so that the microparticles have such properties. The deposited microparticles become fluid again when vibration is applied. In other words, even in a location where a microparticle deposition layer 8b has already formed, the microparticle deposition layer 8b can be washed away by applying vibration. Note that modes of applying vibration include modes of stirring.

[0022] The nuclear facility dismantling system 100 of the first embodiment first drills a hole in the top lid 4c of the reactor containment vessel 4 to form a drilled section 15. Next, the nuclear facility dismantling system 100 injects a microparticle dispersion 8 into the reactor containment vessel 4 through the drilled section 15 to form a microparticle deposition layer 8b in which microparticles are deposited between the reactor containment vessel 4 and the reactor pressure vessel 5. Furthermore, water is injected into the reactor containment vessel 4 to a height exceeding the reactor pressure vessel 5. Then, the reactor pressure vessel 5 is dismantled while being submerged in water.

[0023] During underwater dismantling, there is a possibility that sediments may be stirred up during the cutting work, and the cutting powder may become colloidal and cause the water to become cloudy. Therefore, the nuclear facility dismantling system 100 may drain the water near the dismantling work site and transfer it to a separate water purification facility to prevent the dispersion of colloidal particles containing radioactive materials into the water.

[0024] Furthermore, the nuclear facility dismantling system 100 drills the pressure suppression chamber 4b to form a drilled section 27. Next, the nuclear facility dismantling system 100 injects a microparticle dispersion 8 into the pressure suppression chamber 4b through the drilled section 27 to form a microparticle deposition layer 8b by depositing microparticles in the pressure suppression chamber 4b. Furthermore, the pressure suppression chamber 4b is filled with water, and water is injected into the reactor containment vessel 4 to a height exceeding the reactor pressure vessel 5. Then, the reactor pressure vessel 5 is dismantled while being submerged in water.

[0025] A specific description will be given below. For example, a frame 3 is arranged around the reactor building 1. The frame 3 is constructed on the ground near the reactor building 1 and extends over the reactor building 1. An injection device 13 is arranged on top of this frame 3.

[0026] The injector 13 has a function of injecting the microparticle dispersion 8 into the reactor well 9. This injector 13 includes a water injection pump. When the microparticle dispersion 8 is injected into the reactor well 9, the microparticles settle in the reactor well 9, forming a microparticle sediment layer 8b. For example, the microparticle sediment layer 8b is formed at the bottom of the reactor well 9, particularly around the periphery of the top lid 4c of the reactor containment vessel 4. This makes it possible to stop water leakage from the bottom of the reactor well 9. Furthermore, the injector 13 has a function of draining the supernatant 8a from the reactor well 9. That is, the injector 13 includes a discharge device 13a. This discharge device 13a is composed of, for example, a drainage pump, and discharges from the nuclear facility the supernatant water that is produced when the microparticles contained in the microparticle dispersion 8 injected into the nuclear facility settle.

[0027] The nuclear facility dismantling system 100 also includes a drilling device 70 that drills the top lid 4c of the reactor containment vessel 4 to form the drilled portion 15. The drilling device 70 includes devices such as a cutter, a drill, a laser, and a burner.

[0028] After the frame 3 is in place, the injection device 13 and the drilling device 70 are placed on top of the frame 3. The drilling device 70 then drills three upper and lower tiers of shield plugs 12 that are placed above the reactor well 9. When drilling the shield plugs 12, an anti-scattering agent is sprayed to suppress the generation of radioactive dust.

[0029] Furthermore, the drilling device 70 drills the top lid 4c of the reactor containment vessel 4 to form a drilled portion 15. Then, the injector 13 injects the microparticle dispersion 8 into the reactor containment vessel 4 through the drilled portion 15 in the top lid 4c.

[0030] A first tube bundle 14 consisting of a plurality of tubes for injecting or discharging the microparticle dispersion 8 is provided above the top lid 4c of the reactor containment vessel 4. A tightly fitting tube 16 that covers the perforated portion 15 and is in close contact with the top surface of the top lid 4c is also provided above the top lid 4c of the reactor containment vessel 4. A second tube bundle 18 consisting of a plurality of tubes for injecting or discharging the microparticle dispersion 8 is provided inside this tightly fitting tube 16.

[0031] To prevent dust generated during work on the reactor well 9 from leaking onto the operation floor 2, a ventilation and air conditioning system (not shown) that removes radioactive materials is connected to the injection pipe or drain pipe of the tight pipe 16. The gas (air bubbles) inside the tight pipe 16 can be guided to the ventilation and air conditioning system by switching a valve (not shown). The gas in the space between the reactor well 9 and the reactor containment vessel 4 is then purified by the ventilation and air conditioning system.

[0032] A tight fitting pipe 16 is connected so as to be in close contact with the outer surface of the top lid 4c of the reactor containment vessel 4. The drilling device 70 passes through the inside of this tight fitting pipe 16 and drills the shield plug 12 to form a perforated portion 15. Furthermore, the drilling device 70 drills the top lid insulation (not shown) of the reactor pressure vessel 5 and the top lid 5b of the reactor pressure vessel 5 to form a perforated portion 17. The injection device 13 injects the microparticle dispersion 8.

[0033] The second tube bundle 18 is inserted into the reactor containment vessel 4 through the perforated portion 15 in the top lid 4c of the reactor containment vessel 4. Furthermore, the second tube bundle 18 is inserted into the reactor pressure vessel 5 through the top lid insulation (not shown) of the reactor pressure vessel 5 and the perforated portion 17 in the top lid 5b.

[0034] A water intake section (not shown) is placed at the upper water level limit to prevent overflow onto the operation floor 2. A fourth pipe bundle 25, which bundles together multiple drainage pipes or exhaust pipes, is placed above this water intake section.

[0035] Furthermore, a hole is drilled in the side surface of the main body 4a of the reactor containment vessel 4 to form a drilled section 19. An isolation room 20 is arranged adjacent to this drilled section 19. An injection device 21 is arranged near the isolation room 20 and inside the frame 3.

[0036] The injector 21 has a function of injecting the microparticle dispersion 8 into the inside of the reactor containment vessel 4. The injector 21 injects the microparticle dispersion 8 into the inside of the pedestal 6 through the isolation room 20, the perforated portion 19, and the opening 28 of the pedestal 6. This injector 21 includes a water injection pump. The opening 28 of the pedestal 6 is, for example, an existing opening such as a delivery port (not shown) of a control rod drive mechanism. The injector 21 also has a function of draining the supernatant liquid 8a from inside the main body 4a of the reactor containment vessel 4. In other words, the injector 21 includes a discharge device 21a. This discharge device 21a is, for example, composed of a drainage pump.

[0037] Inside the main body 4a of the reactor containment vessel 4, a third tube bundle 22 consisting of a plurality of tubes into which the microparticle dispersion liquid 8 is injected is provided.

[0038] The nuclear facility dismantling system 100 includes a drilling device 71 that drills a hole in the pressure suppression chamber 4b to form the drilled portion 27.

[0039] The injection device 21 injects the microparticle dispersion 8 into the pressure suppression chamber 4b through the perforated portion 27 to form a microparticle deposition layer 8b inside the pressure suppression chamber 4b. The injection device 21 may also inject the microparticle dispersion 8 into the space outside the pressure suppression chamber 4b (torus chamber 32) to form the microparticle deposition layer 8b outside the pressure suppression chamber 4b.

[0040] Furthermore, an isolation pipe 26 is provided in a drilling section 29a in the floor surface 33 of the first floor of the reactor building 1 so as to be tightly attached to the outer surface of the pressure suppression chamber 4b with a rubber seal or by welding. The drilling device 71 drills a drilling section 27 in the pressure suppression chamber 4b of the reactor containment vessel 4. This drilling section 27 is disposed inside and isolated from the isolation pipe 26. In other words, gas or liquid flowing out from the inside of the pressure suppression chamber 4b is isolated by the isolation pipe 26.

[0041] A fifth tube bundle 30 consisting of a plurality of tubes for injecting the microparticle dispersion 8 through an isolation tube 26 arranged in the perforated portion 29a is arranged inside the pressure suppression chamber 4b of the containment vessel 4. The base end of the fifth tube bundle 30 is connected to the injection device 21 through the isolation tube 26.

[0042] In addition, a sixth tube bundle 31 consisting of a plurality of tubes for injecting the microparticle dispersion 8 into the torus chamber 32 is arranged through a perforated portion 29a in the floor surface 33 of the first floor of the reactor building 1. The base end of the sixth tube bundle 31 is connected to the injection device 21.

[0043] In addition, near the equipment storage pool 11, a container transfer facility 24 is installed to store the removed cut pieces (not shown) underwater in a waste container 23, close the lid, decontaminate, and transport the waste container.

[0044] In the reactor well 9, the microparticle dispersion 8 is injected from the first tube bundle 14, and the precipitated microparticles form a microparticle sediment layer 8b. The microparticle sediment layer 8b seals off any gaps that have occurred between the main body 4a of the reactor containment vessel 4 and the top cover 4c of the reactor containment vessel 4. The microparticle sediment layer 8b also seals off any gaps that have occurred between the reactor containment vessel 4 and the reactor building 1 (reactor well 9, well platform 36). These gaps include, for example, openings in drain piping (not shown), system valves that remain open, and the like. These gaps are gaps (leakage points) that have occurred in connection with a severe accident.

[0045] Furthermore, in the reactor well 9 and the equipment storage pool 11, the supernatant liquid 8a, particles generated during work, and radioactive materials are transferred to a water storage container 43a through a transfer pump 40a and a transfer pipe 41b. In this way, the water levels in the reactor well 9 and the equipment storage pool 11 are controlled, and the turbidity and radiation dose at work locations in the reactor well 9 are improved.

[0046] The upper part of the sealed pipe 16 is connected to a ventilation and air conditioning system (not shown) that removes radioactive materials. When gas (gas phase) is present in the reactor containment vessel 4 and the reactor pressure vessel 5, this ventilation and air conditioning system purifies the gas inside the reactor containment vessel 4 and the reactor pressure vessel 5 through the sealed pipe 16.

[0047] In addition, when the perforated portion 15 of the reactor containment vessel 4 and the perforated portion 17 of the reactor pressure vessel 5 are formed in advance, an isolation device (not shown) is arranged to isolate each part. This isolation device may be provided with a ventilation and air conditioning system.

[0048] Next, an isolation room 20 is placed on the side of the containment vessel 4 so as to be in close contact with its main body 4a. Inside this isolation room 20, a drilling section 19 is drilled. To treat radioactive dust generated during this drilling work, the isolation room 20 is equipped with a ventilation and air conditioning system (not shown) that removes radioactive materials. This ventilation and air conditioning system purifies the gas inside the isolation room 20.

[0049] In addition, when the perforated portion 29 in the floor surface 33 of the first floor of the reactor building 1 and the opening 28 in the pedestal 6 are formed first, an isolation device (not shown) is arranged to isolate each part. This isolation device may be provided with a ventilation and air conditioning system (not shown).

[0050] Furthermore, an isolation tube 26 is placed through the perforated portion 29a so as to be in close contact with the pressure suppression chamber 4b of the reactor containment vessel 4. Then, the perforated portion 27 of the pressure suppression chamber 4b is perforated. Furthermore, a fifth tube bundle 30 for draining the supernatant liquid 8a of the microparticle dispersion 8 is placed through the isolation tube 26. This fifth tube bundle 30 can be positioned inside the pressure suppression chamber 4b.

[0051] The fifth pipe bundle 30 is connected to a ventilation and air conditioning system (not shown) that removes radioactive materials. This ventilation and air conditioning system purifies the gas inside the containment vessel 4. In addition, the isolation pipe 26 is connected to the ventilation and air conditioning system that removes radioactive materials in order to treat radioactive dust generated during the drilling work.

[0052] When the perforated portion 29a in the floor surface 33 of the first floor of the reactor building 1 and the perforated portion 27 in the pressure suppression chamber 4b are formed first, an isolation device (not shown) is installed to isolate the respective portions. This isolation device may be provided with a ventilation and air conditioning system (not shown).

[0053] Furthermore, the sixth tube bundle 31, which drains the supernatant liquid 8a, is disposed in the torus room 32 of the reactor building 1 through the perforated portion 29b. The sixth tube bundle 31 is positioned inside the torus room 32. The sixth tube bundle 31 is connected to a ventilation and air conditioning system (not shown) that removes radioactive materials. The ventilation and air conditioning system purifies the gas inside the torus room 32.

[0054] An injection device 21 is also disposed inside the frame 3. Furthermore, a third tube bundle 22 is disposed, which is composed of a plurality of tubes for injecting the microparticle dispersion liquid 8 and draining the supernatant liquid 8a. The third tube bundle 22 passes through an isolation room 20 and a perforated section 19, and extends from the perforated section 17 of the pedestal 6, which is the entrance for the control rod drive mechanism, into the interior of the pedestal 6.

[0055] When the microparticle dispersion 8 is injected from the third tube bundle 22, the microparticles, having a higher specific gravity than water, gradually settle and accumulate downward, forming a microparticle sediment layer 8b inside the containment vessel 4. When the height of the upper surface of this microparticle sediment layer 8b exceeds the height of the leak point and the leak point is covered with the microparticle sediment layer 8b, a watertight effect is achieved. Then, the water level inside the containment vessel 4 rises.

[0056] For example, if the leakage stops at the height of the floor 33 on the first floor of the reactor building 1 and a rise in the water level commensurate with the injection amount and space volume is observed, the injection device 21 will inject clean water instead of the microparticle dispersion liquid 8.

[0057] At this time, the reactor pressure vessel 5 has an opening (not shown) at its bottom through which the fuel debris 7 passed, and there is a possibility that the microparticle dispersion 8 or its supernatant liquid 8a may also spread from there. In addition, since the top lid 5b of the reactor pressure vessel 5 has a perforated portion 15, the gas inside the reactor pressure vessel 5 moves into the reactor containment vessel 4. This gas inside the reactor containment vessel 4 is discharged through a sealed pipe 16. Furthermore, this gas is purified by an air conditioning system (not shown).

[0058] 2 shows a state in which the leak point is watertight with a fine particle sediment layer 8b in the portion below the flange of the top lid 4c of the reactor containment vessel 4, and the reactor well 9 is submerged. In other words, a fine particle sediment layer 8b is formed in the region below the flange of the top lid 4c of the reactor containment vessel 4.

[0059] For example, suppose that the leak location is located at a position higher than the floor surface 33 of the first floor of the reactor building 1. In this case, the second tube bundle 18 is extended inside the top lid 4c of the reactor containment vessel 4 to a position approximately above the reactor pressure vessel top lid insulation (not shown). The microparticle dispersion 8 is then injected through this second tube bundle 18. Here, a manhole (not shown) opens in the well platform 36 of the reactor containment vessel 4 and the reactor pressure vessel 5. Therefore, the microparticle dispersion 8 is injected through this manhole (not shown) into the space between the reactor pressure vessel 5 and the reactor containment vessel 4. Here, a microparticle deposition layer 8b is formed between the reactor containment vessel 4 and the reactor pressure vessel 5.

[0060] As time passes, the amount of the fine particle sediment layer 8b increases. If a rising trend of the water level commensurate with the space volume is observed in relation to the injection amount, it is considered that the water has been stopped, and the injection device 13 injects clean water into the reactor well 9 instead of the fine particle dispersion liquid 8.

[0061] According to the first embodiment, a microparticle dispersion 8 containing microparticles with a specific gravity greater than that of water is injected into the reactor building 1, reactor containment vessel 4, and reactor pressure vessel 5, and the microparticles adhere to and deposit at the leak location, thereby sealing off the leak location. Furthermore, a microparticle deposition layer 8b can be formed by discharging the supernatant liquid 8a and allowing the microparticles to settle in the internal space of the nuclear facility. The height of the upper surface of the microparticle deposition layer 8b is set higher than the leak location. The leak location is then sealed off by this microparticle deposition layer 8b.

[0062] In addition, since the area can be submerged up to nearly the height of the operation floor 2, some shield plugs 12 remain partially submerged, and dismantling work can be carried out underwater on the remaining structures. Submersion also reduces the atmospheric dose, which also reduces exposure to radiation for workers and various equipment. The underwater cutting equipment can be a mechanical cutting device such as a cutter or drill, or a thermal cutting device such as a laser or burner.

[0063] It should be noted that the nuclear facility dismantling system 100 does not need to have a drainage function if the leaking point can be watertight by injecting the microparticle dispersion liquid 8 into the reactor containment vessel 4 only once. For example, even if water remains at the bottom of the main body 4a of the reactor containment vessel 4, microparticles will accumulate, and a microparticle accumulation layer 8b can be formed.

[0064] Furthermore, when the microparticle dispersion 8 is initially introduced, some water may remain in the containment vessel 4, diluting the microparticle dispersion 8. In this case, a drainage facility is added to the nuclear facility dismantling system 100. Then, the injection of the microparticle dispersion 8, settling, and discharge of the supernatant liquid 8a are repeated. This increases the amount of accumulated microparticles. By increasing the amount of accumulated microparticles, it is possible to stop water from leaking from multiple leak points lined up in the height direction of the containment vessel 4.

[0065] (Second embodiment) Next, a second embodiment will be described. Note that the same components as those shown in the above-described embodiment will be assigned the same reference numerals and redundant description will be omitted.

[0066] FIG. 3 shows a state in which the space between the well platform 36 and the top cover 4c of the containment vessel 4 is watertight with the particulate sediment layer 8b, and the reactor well 9 is submerged.

[0067] The nuclear facility dismantling system 100 of the second embodiment includes a water impermeable wall 35 that surrounds at least the periphery of the reactor well 9. The injection device 13 injects a microparticle dispersion 8 into the reactor well 9 to waterproof the leaking point at the bottom of the reactor well 9 with a microparticle deposition layer 8b.

[0068] In the second embodiment, first, a water impermeable wall 35 is constructed to surround the periphery of the reactor well 9. Next, the injection device 13 injects the microparticle dispersion 8 into the reactor well 9 to watertight the leaking point at the bottom of the reactor well 9 with a microparticle deposition layer 8b. Furthermore, the injection device 13 injects water into the reactor well 9 to a height exceeding the shield plug 12. Then, the shield plug 12 is dismantled while being submerged in water.

[0069] During underwater dismantling, there is a possibility that sediments may be stirred up during the cutting work, and the cutting powder may become colloidal and cause the water to become cloudy. Therefore, the nuclear facility dismantling system 100 may drain the water near the dismantling work site and transfer it to a separate water purification facility to prevent the dispersion of colloidal particles containing radioactive materials into the water.

[0070] A specific description will be given below. For example, the configuration of the reactor building 1 in the second embodiment is the same as that in the first embodiment. However, a water impermeable wall 35 is constructed to extend upward the pool lining walls of the reactor well 9, spent fuel storage pool 10, and equipment storage pool 11. In other words, the water impermeable wall 35 is constructed so as to surround the periphery of the reactor well 9, spent fuel storage pool 10, and equipment storage pool 11. When constructing this water impermeable wall 35, a drainage opening (not shown) above the pool lining wall is closed in advance. Note that the water impermeable wall 35 can be constructed by a connection method using welding or a mechanical fastening method using a sealing material such as a gasket.

[0071] The injection device 13 is disposed on the upper part of the frame 3. This injection device 13 may inject the microparticle dispersion liquid 8 into the torus chamber 32, the pressure suppression chamber 4b of the reactor containment vessel 4, and the main body 4a of the reactor containment vessel 4. In this way, when the reactor well 9 is flooded, even if water falls in, significant water leakage will not occur.

[0072] The shield plug 12 has a high radiation dose due to contamination with radioactive materials, and may also be displaced due to the effects of a severe accident. Therefore, by flooding the reactor well 9, the atmospheric dose can be reduced. The remotely operated heavy machinery 34 dismantles and removes the shield plug 12 from above underwater. Alternatively, the shield plug 12 may be dismantled and removed using general piloted heavy machinery (not shown).

[0073] Furthermore, after the shield plug 12 is removed, the reactor well 9 may be covered with a shielding lid (not shown) to mitigate the effects of radiation upward (skyshine) in case the water level in the reactor well 9 drops.

[0074] As in the first embodiment described above, a container transfer facility 24 is placed near the equipment storage pool 11. The container transfer facility 24 stores waste materials such as cut pieces of the shield plug 12 in a waste material container 23 underwater, closes the lid, decontaminates the waste material, and carries it out.

[0075] In this way, first, the microparticle dispersion 8 containing microparticles with a specific gravity heavier than water is injected into the torus chamber 32, the pressure suppression chamber 4b, and the main body 4a of the containment vessel 4. Then, the supernatant liquid 8a is drained and gradually precipitated and deposited, thereby increasing the microparticle deposition layer 8b.

[0076] Next, an opening (not shown) is formed through the shield plug 12 to the lowest level. Then, the microparticle dispersion 8 is injected below the shield plug 12. When the microparticle dispersion 8 is injected from above the top lid 4c of the reactor containment vessel 4, a microparticle sediment layer 8b is formed in the reactor well 9. This microparticle sediment layer 8b fills the gaps between the top lid 4c of the reactor containment vessel 4 and the well platform 36 and the lining of the reactor well 9. Then, the leaking point in the reactor well 9 is sealed off. At this time, no perforated portion 15 is present in the top lid 4c of the reactor containment vessel 4. However, if an opening already exists in the shield plug 12, it may be isolated by an openable / closable member such as a valve (not shown).

[0077] Next, the injection device 13 injects clean water into the reactor well 9. At this time, if a water impermeable wall 35 is present, the water level can be made higher than the operation floor 2, so the uppermost shield plug 12 can be submerged. The shield plug 12 is then cut and dismantled underwater. Here, remotely operated heavy machinery 34 or general piloted heavy machinery (not shown) crushes and cuts the shield plug 12 and stores it in a waste container 23 underwater. Then, the container transfer equipment 24 transfers the waste container 23 to the outside.

[0078] According to the second embodiment, the operation floor 2 can be submerged, which allows for underwater demolition work. Furthermore, submerging the operation floor 2 reduces the atmospheric dose, which leads to a reduction in worker exposure. Furthermore, the shield plug 12 can be removed underwater, which prevents dust from scattering. This increases work efficiency and reduces worker exposure when the top lid 4c of the reactor containment vessel 4 is subsequently removed. Furthermore, this also serves as a measure against overflow due to sloshing of water stored inside the reactor well 9 during an earthquake.

[0079] The drilling device 70 drills holes in the shield plug 12 in the vertical direction to form openings (not shown). After that, the injection device 13 injects the microparticle dispersion 8 into the reactor well 9. By measuring the water level, the amount of leakage due to hydraulic head pressure can be calculated. After the water level stops decreasing or becomes within an allowable range, clean water is injected to maintain the reactor well 9 at a predetermined water level. Furthermore, in areas where leakage is expected, such as gaps, obstacles may be placed to facilitate the settling and deposition of microparticles through the openings in the shield plug 12.

[0080] When removing the shield plug 12, if the surface dose and dust generation amount of the shield plug 12 are within the allowable range, the fragments or cut pieces thereof can be stored in the air. Alternatively, the waste container 23 can be placed inside the reactor well 9. The waste container 23 can be used to transport and store the fragments or cut pieces of the shield plug 12 underwater, and then the waste container 23 can be raised to the surface together with the water contained therein and closed with a lid. Alternatively, the lid of the waste container 23 can be closed underwater, and then the waste container 23 can be raised to the surface.

[0081] The shield plug 12 may be crushed or cut from above. Equipment used for this work includes, for example, remotely operated heavy machinery 34 or directly operated demolition equipment, a wire saw, or a disc saw. Also, before cutting the shield plug 12, a lifting wire may be fixed to the shield plug 12 with an anchor, and the shield plug 12 may be lifted up. Also, a transport device may be provided for scooping up crushed or cut pieces of the shield plug 12. Note that, during dismantling, water or a scattering prevention agent may be sprayed on the shield plug 12.

[0082] (Third embodiment) Next, a third embodiment will be described. Note that the same components as those shown in the above-described embodiments are denoted by the same reference numerals, and redundant description will be omitted.

[0083] 4 shows a state in which a pit 42 has been dug around the entire exterior of the reactor building 1 to construct an outer wall 37, and the leak point at the bottom of the reactor containment vessel 4 has been waterproofed with a fine particle sediment layer 8b. The outer wall 37 includes a lower outer wall 37a and an upper outer wall 37b. Here, the nuclear facility dismantling system 100 has a configuration in which the reactor well 9 is flooded with water, and water leaking from the reactor containment vessel 4 is circulated back into the reactor building 1.

[0084] The nuclear facility dismantling system 100 of the third embodiment includes a water storage container 43a and a transfer device 46. The water storage container 43a stores water discharged from the reactor building 1 (nuclear facility). The transfer device 46 is, for example, a pump. The transfer device 46 transfers the water stored in the water storage container 43a to the injection device 13. The injection device 13 mixes the water stored in the water storage container 43a with microparticles to form the microparticle dispersion 8 again.

[0085] The nuclear facility dismantling system 100 also forms a fine particle sediment layer 8b in the basement of the reactor building 1 and inside the reactor containment vessel 4. The nuclear facility dismantling system 100 further includes a water tank 80 that has an outer wall 37 surrounding the periphery of the reactor building 1, contains the entire reactor building 1, and holds water therein to submerge at least a portion of the reactor building 1. The injection device 21 injects the fine particle dispersion 8 into the water tank 80 to form a fine particle sediment layer 8b at the bottom of the water tank 80. As in the first embodiment, the reactor containment vessel 4 is submerged in water. Then, the reactor pressure vessel 5 is dismantled in a submerged state.

[0086] During underwater dismantling, there is a possibility that sediments may be stirred up during the cutting work, and the cutting powder may become colloidal and cause the water to become cloudy. Therefore, the nuclear facility dismantling system 100 may drain the water near the dismantling work site and transfer it to a separate water purification facility to prevent the dispersion of colloidal particles containing radioactive materials into the water.

[0087] A specific description will be given below. For example, the configuration of the reactor building 1 is almost the same as that of the first embodiment. Furthermore, a water impermeable wall 35 is provided, as in the second embodiment.

[0088] Even if the reactor well 9 can be flooded, there remains the possibility that the leakage from the reactor containment vessel 4 cannot be completely stopped. In addition, there remains the possibility that an external event such as a large-scale earthquake will occur, damaging the reactor well 9, which has deteriorated due to the severe accident, and the various components in contact with the water inside the reactor containment vessel 4, and increasing the amount of water leakage. Even in such cases, it is necessary to minimize the amount of water leakage into the environment outside the reactor building 1.

[0089] The nuclear equipment dismantling system 100 of the third embodiment prevents water leakage from the bottom of the water tank 80, drains the leaked water from the reactor building 1 into the water treatment equipment 43, purifies the drained water, and then floods the reactor well 9 by injecting water into the reactor well 9 again.

[0090] The outer wall 37 surrounds the reactor building 1 in case of overflow. A fine particle sediment layer 8b is formed at the bottom of the water tank 80. In other words, in a plan view of the reactor building 1, the area into which water leaking from the reactor well 9 and the containment vessel 4 flows out is surrounded by the fine particle sediment layer 8b. The water tank 80 is composed of the outer wall 37 and the fine particle sediment layer 8b at the bottom. The outer wall 37 supports the frame 3. In other words, the outer wall 37 constitutes a part of the frame 3.

[0091] Drainage outlets 44 are formed in the outer wall 37, for example, at two locations, one at the top and one at the bottom. Drainage pipes 45 are inserted into each of the drainage outlets 44. These drainage pipes 45 guide drainage water from the inside of the reactor building 1.

[0092] A water treatment facility 43 is provided on the outside of the frame 3 including the outer wall 37. The water treatment facility 43 is a controlled area facility that confines radioactive materials. A drainage pipe 45 is connected to the water treatment facility 43 via an on-off valve (not shown).

[0093] The water treatment equipment 43 purifies the stored water. This water treatment equipment 43 includes a water storage container 43a, transfer piping 41, a transfer device 46 (pump), particulate treatment equipment 46a, and a multi-nuclide removal device (not shown). The particulate treatment equipment 46a has a filter that removes solid components contained in the water. This particulate treatment equipment 46a removes solid components contained in the water. In addition, the multi-nuclide removal device (not shown) removes ions contained in the water. The transfer piping 41 transfers the purified clean water to the reactor well 9. The water treatment equipment 43 transfers the clean water to the reactor well 9 depending on the amount of water evaporation from the reactor well 9 and the amount of water leakage from the reactor well 9 and the containment vessel 4.

[0094] Also provided is a particle treatment facility 47 equipped with an injection device 21. The particle treatment facility 47 is provided near the outside of the outer wall 37 and is a controlled area facility that confines radioactive materials. The particle treatment facility 47 includes a third tube bundle 22, a fifth tube bundle 30, and a sixth tube bundle 31. The injection device 21 has the function of injecting the particle dispersion liquid 8 and the function of draining water. The injection device 21 can inject water into the inside of the outer wall 37. The injection device 21 can also drain water from the inside of the outer wall 37.

[0095] The particulate treatment equipment 47 includes a seventh pipe bundle 47a consisting of multiple pipes, a purifier 47b, and a transfer pump 47c. The seventh pipe bundle 47a is connected to the transfer pump 47c through the purifier 47b. The transfer pump 47c is connected to the water storage container 43a of the water treatment equipment 43 via a transfer pipe 47d.

[0096] A predetermined injection pipe (not shown) may be connected to the seventh pipe bundle 47a. Then, the microparticle dispersion 8 and purified water purified by the water treatment equipment 43 may be injected into the torus chamber 32 through the predetermined injection pipe. Furthermore, purified water (flushing water) may be injected into the torus chamber 32 from another purified water source through the predetermined injection pipe. Also, a valve (not shown) for switching the water to be injected into the predetermined injection pipe may be provided.

[0097] A water washing nozzle (not shown) may be provided at the tip of the seventh tube bundle 47a. By spraying water from this water washing nozzle, suspended matter contained in the water in the torus chamber 32 is removed, and a flow path for the microparticle dispersion liquid 8 is secured.

[0098] A waste container 23 and container transfer equipment 24 are placed in the equipment storage pool 11. In addition, to enable underwater work in the reactor, lifting equipment 48 such as a crane is placed on top of the framework 3. On the operation floor 2, a remotely operated heavy machine 34 (Fig. 3), a submersible remotely operated heavy machine 49, and a floating remotely operated device 50 are placed.

[0099] The periphery of the reactor building 1 is surrounded by a pit 42, and the groundwater level 90 is lowered. For example, the periphery of the reactor building 1 is excavated and the pit 42 is constructed. Here, the basement structure of the reactor building 1 is exposed to the ground surface. Then, a foundation 38 for the exterior wall 37 is constructed, and the exterior wall 37 is constructed. Because the reactor building 1 is surrounded by the exterior wall 37, even if water overflows from the reactor building 1, the water will not leak outside the exterior wall 37.

[0100] The outer wall 37 is a structure such as a wall structure made of plate material designed only for water storage, a concrete structure with a metal lining, a double wall structure, a tank structure, a hull structure, etc. Furthermore, water leakage can be prevented by providing a predetermined member or water-stopping material between the outer wall 37 and the reactor building 1.

[0101] There is also a possibility that groundwater may flow into the bottom of the pit 42. For this reason, the water treatment facility 43 is equipped with a transfer pump 40 and transfer piping 41a for transferring the water in the pit 42. However, since there is a possibility that water may flow into the pit 42 from the reactor building 1, the concentration of radioactive materials contained in the water in the pit 42 is measured and monitored, and the water is then treated appropriately within the site, which is a radiation controlled area.

[0102] On the other hand, it is necessary to prepare for the possibility that the concentration of radioactive materials may exceed the water treatment standard on-site. For this reason, the water treatment facility 43 is equipped with a transfer pipe 41a and a transfer pump 40 for transferring the water from the pit 42 to the water treatment facility 43.

[0103] The reactor building 1 is provided with a drain outlet 44 that opens into its wall surface. The drain outlet 44 is provided mainly to transfer water that has flowed into the bottom of the torus room 32 to the outside of the reactor building 1. An end of a drain pipe 45 is connected to this drain outlet 44. The end of the drain pipe 45 is held in close contact with the wall surface of the reactor building 1 in a watertight and airtight manner.

[0104] The upper drainage pipe 45 is an overflow pipe that prevents the water level from exceeding the maximum water storage capacity assumed in the design, even in the unlikely event that a large-scale leak occurs from the reactor building 1 and the leaked water accumulates inside the outer wall 37. The two upper and lower drainage pipes 45 and drain outlets 44 have the same configuration. Therefore, in the following explanation, the lower drainage pipe 45 and drain outlet 44 are exemplified.

[0105] 5 shows the configuration of a drainage pipe 45 for draining water accumulating at the bottom of the reactor building 1 in the pit 42. The configuration of the portion where the drain outlet 44 and the drainage pipe 45 are connected is shown.

[0106] A platform 51 is provided at the bottom of the pit 42. An airtight facility 52 is placed on top of the platform 51. The airtight facility 52 is a facility for containing gas inside the reactor building 1. The airtight facility 52 is attached to the outer wall surface of the reactor building 1 so as to maintain airtightness and watertightness.

[0107] The airtight equipment 52 has an airtight door 53 and a door opening / closing mechanism 54 at the top. A drainage pipe 45 is arranged inside the airtight equipment 52. The drainage pipe 45 is installed so as to surround the drainage outlet 44 in the wall of the basement of the reactor building 1, and is in close contact with the wall surface of the reactor building 1 so as to maintain airtightness and watertightness.

[0108] A strainer 63 such as a mesh is attached to the end of the drain pipe 45. There is a possibility that the fine particle sediment layer 8b acting as a water-stopping material will flow into and accumulate inside the drain pipe 45. This may result in clogging of the strainer 63. Therefore, a flushing nozzle (not shown) for spraying clean water may be provided separately inside the drain pipe 45.

[0109] FIG. 6 shows the drilling of a drainage outlet 44 for draining water accumulating in the bottom of the reactor building 1 in the pit 42.

[0110] Before the drainage piping 45 is arranged, a hole drilling device 55 is arranged to open the drainage outlet 44 in the wall of the basement of the reactor building 1. The hole drilling device 55 includes, for example, a drill. The hole drilling device 55 is housed in an airtight container 56. The airtight container 56 includes, at its bottom, an airtight door 57 and a door opening / closing mechanism 58. The airtight door 57 of the airtight container 56 operates simultaneously with the airtight door 53 of the airtight equipment 52. The airtight container 56 can be connected to the airtight equipment 52 in an airtight state. The door opening / closing mechanism 58 opens and closes the airtight door 57 in an airtight state with the airtight equipment 52 maintained.

[0111] FIG. 7 shows a state in which a pit 42 has been dug in a part of the outside of the reactor building 1, and the pressure suppression chamber 4b of the torus room 32 has been buried in a fine particle sediment layer 8b, which is a water-stopping material. The pit 42 has been dug, and an outer wall 37 has been constructed around the entire periphery of the reactor building 1. The leaking point at the bottom of the reactor containment vessel 4 has been water-stopped by the fine particle sediment layer 8b, and the reactor well 9 has been flooded. Furthermore, the torus room 32 has been filled with the fine particle sediment layer 8b, limiting the range of the water leaking point. Water leaking from the reactor containment vessel 4 is sent to the reactor building 1, and this is a circulating mode.

[0112] It is necessary to reduce the load of excavating the pit 42 all around the reactor building 1. In this case, the area where the pit 42 is excavated is limited on the periphery of the reactor building 1, and only a part of the basement structure of the reactor building 1 is exposed above ground. Then, in preparation for overflow from the reactor building 1, the reactor building 1 is surrounded by an exterior wall 37. Because the range of the pit 42 around the reactor building 1 is limited, the foundation 38 of the exterior wall 37 can be constructed at first floor level. The exterior wall 37 is then constructed on this foundation 38.

[0113] 8 shows an example of how water accumulating at the bottom of the reactor building 1 is drained. Inside the torus room 32, a strainer structure 59 with a mesh is provided immediately above the vicinity of the drain outlet 44. Furthermore, a toy structure 60 is provided near the top of the strainer structure 59.

[0114] The fine particle sediment layer 8b is deposited up to the vicinity of the floor surface 33 of the first floor of the reactor building 1. By doing so, leakage water dropping from the first floor or above inside the reactor building 1 joins with the supernatant liquid 8a on the surface of the fine particle sediment layer 8b, passes through the toy structure 60, and falls into the strainer structure 59. Then, the water can be drained via the drain outlet 44.

[0115] An obstacle such as filler, stone, concrete, or grout may be provided at the bottom of the torus chamber 32 at a position lower than the bottom plate of the toy structure 60. The obstacle may be provided at the bottom of the torus chamber 32 to a height that prevents the microparticle dispersion 8 from flowing into the toy structure 60.

[0116] 9 shows another example in which the torus chamber 32 adjacent to the pit 42 is filled with a buffer material 61 and a fine particle deposition layer 8b, limiting the area of ​​water leakage and draining water accumulating at the bottom of the reactor building 1. In this example, the buffer material 61 is injected into the torus chamber 32 so as to cover the pressure suppression chamber 4b, and then the fine particle deposition layer 8b is deposited.

[0117] As shown in FIG. 7, before injecting the microparticle dispersion liquid 8 at the bottom of the torus chamber 32, the injection device 21 injects clean water (flushing water) into the torus chamber 32. For example, the clean water is injected through an injection pipe included in the sixth tube bundle 31. Then, by transferring the wastewater from the torus chamber 32 to a water treatment facility 43, radioactive materials present at the bottom of the torus chamber 32 can be removed or at least reduced. In other words, the torus chamber 32 is flushed with clean water. In this way, radioactive materials present at the bottom of the torus chamber 32 can be washed away.

[0118] Then, the microparticle dispersion 8 is injected into the torus chamber 32, and a microparticle sediment layer 8b is formed. Here, the microparticle dispersion 8 is injected up to below the floor surface 33 of the first floor of the reactor building 1. Note that the microparticle dispersion 8 may be injected up to below the floor surface 33 of the first floor of the reactor building 1 after the buffer material 61 (FIG. 9) is injected, cast, and placed.

[0119] The method of injecting the microparticle dispersion liquid 8 into the reactor containment vessel 4 is the same as in the previously described embodiment. Once the reactor well 9 is flooded, the shield plug 12 is dismantled and removed. Thereafter, as shown in FIG. 10, the top lid 4c of the reactor containment vessel 4 is dismantled and removed. For this dismantling and removal, any of or a combination of lifting equipment 48 such as a crane arranged on the framework 3, remotely operated heavy equipment 34 (FIG. 3) on the operation floor 2, underwater remotely operated heavy equipment 49, and floating remotely operated device 50 is used. The various cut pieces are stored in a waste container 23 and transported out of the framework 3 by container transfer equipment 24.

[0120] Additionally, the top lid 4c may be transported to either the spent fuel storage pool 10 or the equipment storage pool 11, shredded, and then stored in the waste container 23. Additionally, the top lid 4c may be shredded at the predetermined location where it was originally located and then transported to the waste container 23.

[0121] After the top head 4c of the reactor containment vessel 4 is removed, the top head 5b of the reactor pressure vessel 5 and the top head insulation material (not shown) are dismantled and removed, as shown in Fig. 11. Next, the internal and lower structures of the reactor pressure vessel 5 are dismantled and removed, as shown in Fig. 12.

[0122] The internal structures of the reactor pressure vessel 5 include, for example, a steam dryer, a steam separator, an upper grid plate, a core shroud, a fuel support bracket, and a core support plate.

[0123] The lower structures of the reactor pressure vessel 5 include, for example, a reactor bottom head, jet pumps, control rod drive mechanism guide tubes, control rod drive mechanism, in-core monitor, in-core monitor housing, control rod drive mechanism exchanger, fuel assemblies, fuel cladding tubes, and fuel debris 7.

[0124] Such structures related to the reactor pressure vessel 5 are evaluated for the possibility of fracture or falling off when lifted. This evaluation also includes how they will be handled during periodic inspections during their service life. Severely deformed or damaged structures are shredded, crushed, or cut inside the reactor pressure vessel 5 and then dismantled and removed.

[0125] Next, as shown in Fig. 13, the well platform 36 and the main body 5a of the reactor pressure vessel 5 are dismantled and removed. Next, as shown in Fig. 14, the pedestal 6, the internal pipes (not shown), valves (not shown), and biological shield wall (not shown) of the main body 4a of the reactor containment vessel 4 are dismantled and removed.

[0126] After the highly radioactive structures are removed first, the other structures inside the main body 4a of the reactor containment vessel 4 are dismantled and removed. Note that the policy for dismantling and removing structures other than the main body 4a of the reactor containment vessel 4 is determined according to the radiation dose. For example, in the case of low-radiation structures, there is no need to shield them from radiation with water, so they may be dismantled and removed after draining the water remaining in the reactor well 9, spent fuel storage pool 10, and equipment storage pool 11.

[0127] According to the third embodiment, the reactor well 9 can be submerged up to a position above the operation floor 2, making it possible to carry out dismantling work underwater. In addition, the water shielding effect of submersion reduces the atmospheric dose, which also leads to a reduction in exposure of workers and various equipment.

[0128] Furthermore, for structures below the top lid 4c of the containment vessel 4, bolts that were fastened to the equipment during its operation are cut off. Also, structures such as shrouds and jet pumps may remain in place without significant deformation. In such cases, the upper parts of these structures may be lifted and the lower parts cut off before removal. These structures are then transported to the spent fuel storage pool 10 or the equipment storage pool 11, where they are cut into pieces and stored in the waste container 23. This allows for parallel work, improving work efficiency.

[0129] Furthermore, by burying the torus chamber 32 in a water-stopping material or buffer material 61 (FIG. 9) containing the fine particle sediment layer 8b, water leaking from the reactor well 9 and the containment vessel 4 can be stably guided to the water treatment facility 43 outside the reactor building 1. This reduces the risk of contaminated water leaking into the external environment. Furthermore, by appropriately selecting the buffer material 61, the earthquake resistance of the pressure suppression chamber 4b can be improved.

[0130] After being lifted from inside the reactor containment vessel 4, a floor structure (not shown) may be provided in either the reactor well 9, the spent fuel storage pool 10, or the equipment storage pool 11 to temporarily store the removed structures.

[0131] Furthermore, by constructing the outer wall 37, even if the reactor well 9 is severely damaged by an earthquake, contaminated water will not leak into the surrounding environment. Even if the boundary of the water-storing portion inside the reactor building 1 is severely damaged and water falls, the falling water can be contained inside the outer wall 37. Furthermore, even if it is difficult to predict deterioration of the water boundary inside the reactor building 1, by providing the outer wall 37 to surround the periphery of the reactor building 1, it is possible to prepare for unpredictable circumstances.

[0132] (Fourth embodiment) Next, a fourth embodiment will be described. Note that the same components as those shown in the above-described embodiments are denoted by the same reference numerals, and redundant explanations will be omitted.

[0133] As shown in FIG. 15, in the fourth embodiment, the inside of an outer wall 37 surrounding the reactor building 1 is filled with water, and the entire reactor building 1 is submerged in water.

[0134] In the fourth embodiment, first, a water tank 80 is constructed to contain the entire reactor building 1 and to fill it with water, thereby submerging at least a portion of the reactor building 1. This water tank 80 has an outer wall 37 that surrounds the periphery of the reactor building 1. Next, a microparticle dispersion 8 is poured into the water tank 80, and a microparticle sediment layer 8b is formed by depositing microparticles at the bottom of the water tank 80. Furthermore, water is poured into the water tank 80 up to a height that exceeds at least the reactor containment vessel 4. Then, with at least the reactor containment vessel 4 submerged in water, the reactor containment vessel 4 and the reactor building 1 are dismantled.

[0135] During underwater dismantling, there is a possibility that sediments may be stirred up during the cutting work, and the cutting powder may become colloidal and cause the water to become cloudy. Therefore, the nuclear facility dismantling system 100 may drain the water near the dismantling work site and transfer it to a separate water purification facility to prevent the dispersion of colloidal particles containing radioactive materials into the water.

[0136] In this way, it is possible to ensure the depth of water necessary for radiation shielding when dismantling structures present at the height of the operation floor 2. It is also not necessary to construct the water shielding wall 35 (FIG. 4) of the third embodiment.

[0137] Even if the amount of water leakage from the containment vessel 4 and the reactor well 9 is reduced and the reactor well 9 is flooded by injecting the microparticle dispersion liquid 8 as in the above-described embodiment, there remains a possibility that water leakage from the surface of the containment vessel 4 cannot be completely stopped. In addition, there remains a possibility that an external event such as a large-scale earthquake will occur and damage will be caused to the reactor well 9 in the reactor building 1, which has deteriorated due to the severe accident, and the equipment in contact with the water stored in the containment vessel 4, thereby increasing the amount of water leakage to the outside of the containment vessel 4.

[0138] Furthermore, even if the water leaking outside the containment vessel 4 is circulated to the reactor well 9 via the water treatment equipment 43, deterioration and damage may occur due to the amount of water leakage exceeding the design assumption. Also, if the amount of water leakage is too large, the required capacity for drainage from the reactor building 1 and the capacity for water injection into the reactor well 9 may become excessive, and the circulation system design may not be viable. Furthermore, even if the circulation system design is viable, it is possible that a water flow that interferes with the demolition work may occur in the work area.

[0139] Even in such a case, the nuclear facility dismantling system 100 of the fourth embodiment can minimize the amount of water leakage into the external environment of the reactor building 1. By forming the fine particle deposition layer 8b in the basement of the reactor building 1 and inside the reactor containment vessel 4, water leakage from the bottom of the outer wall 37 is prevented, and the outer wall 37 allows the entire reactor building 1 to be submerged in water.

[0140] In the fourth embodiment, a fine particle sediment layer 8b is deposited on the bottom of the water tank 80, the bottom of the main body 4a of the reactor containment vessel 4, and the basement floor of the reactor building 1. A plurality of exterior wall drainage outlets 65 are formed in the exterior wall 37. Drainage pipes 66 extend from these exterior wall drainage outlets 65. The water treatment equipment 43 is disposed near the outside of the exterior wall 37. The water treatment equipment 43 is a controlled area facility that confines radioactive materials. The drainage pipes 66 are connected to the water treatment equipment 43 via an on-off valve (not shown).

[0141] In the third embodiment described above, a drain outlet 44 is arranged in the basement of the reactor building 1 to guide water leaking into the reactor building 1. In contrast, in the fourth embodiment, the entire reactor building 1 can be submerged in the water tank 80 by closing an on-off valve (not shown), which is different in that water can be stored inside the outer wall 37.

[0142] A fine particle sediment layer 8b is deposited on the bottom between the reactor building 1 and the containment vessel 4, and between the outer wall 37 and the reactor building 1. Furthermore, gaps that are leakage points may exist at the bottom of these areas, but the deposition of the fine particle sediment layer 8b makes it possible to minimize the need for waterproofing treatment in the gaps during work to connect the reactor building 1 to the containment vessel 4.

[0143] Measures to prevent overflow must be taken to prevent the entire reactor building 1 from being submerged. To prevent overflow, a lower drainage pipe 66a, an intermediate drainage pipe 66b, and an upper drainage pipe 66c are provided so that the maximum water storage capacity assumed in the design of the water tank 80 is not exceeded.

[0144] The water treatment equipment 43 purifies the water. In addition, a transfer pipe 41 and a transfer device 46 are provided to transfer the purified water from the water treatment equipment 43 to the reactor well 9. For example, the purified water is transferred depending on the amount of water evaporation from the reactor well 9 or the amount of water leakage from the reactor well 9 or the reactor containment vessel 4.

[0145] A particle treatment facility 47 is disposed near the outside of the outer wall 37 as a controlled area facility for confining radioactive materials. The particle treatment facility 47 includes an injection device 21. The injection device 21 injects water into the inside of the outer wall 37.

[0146] The injection device 21 includes a third tube bundle 22, a fifth tube bundle 30, and a sixth tube bundle 31. The injection device 21 has a drainage function and a function of injecting the microparticle dispersion 8. The seventh tube bundle 47a is connected to a transfer pump 47c through a purifier 47b. A transfer pipe 47d extending from the transfer pump 47c is connected to a water storage container 43a of the water treatment facility 43.

[0147] As dismantling equipment, waste containers 23 and container transfer equipment 24 are placed in the equipment storage pool 11. Also, to enable underwater work, lifting equipment 48 such as a crane is placed on top of the framework 3. Furthermore, remotely operated heavy machinery 34 (Fig. 3), underwater remotely operated heavy machinery 49, and floating remotely operated device 50 are placed on the operation floor 2.

[0148] In the fourth embodiment, the configuration of the outer wall 37 may be either the configuration in the third embodiment shown in Fig. 4 or the configuration in Fig. 7. In the fourth embodiment, the configuration in Fig. 7 is exemplified.

[0149] As shown in Figure 15, a pit 42 is formed around the periphery of the reactor building 1, and the basement structure of the reactor building 1 is exposed to the ground. Then, a foundation 38 for the exterior wall 37 is constructed, and the exterior wall 37 is constructed to surround the reactor building 1. The exterior wall 37 is a structure such as a wall structure made of plate material that is designed only for water storage, a concrete structure with a metal lining, a double-wall structure, a tank structure, or a hull structure.

[0150] Furthermore, water leakage can be prevented by placing a predetermined member or water-stopping material between the outer wall 37 and the reactor building 1. Furthermore, since there is a possibility that groundwater may flow into the bottom of the pit 42, a transfer pump 40 and transfer piping 41 are provided to transfer the water stored in the pit 42 to water treatment equipment 43. However, since there is a possibility that water may also flow into the pit 42 from the reactor building 1, the concentration of radioactive materials contained in the water in the pit 42 is measured and monitored, and the water is then treated appropriately within the site, which is a radiation controlled area.

[0151] The outer wall 37 can be constructed in two stages, a lower outer wall 37a and an upper outer wall 37b. The outer wall 37 may also be constructed in multiple stages, with two or more stages.

[0152] When the upper part of the reactor building 1 is dismantled and removed, it becomes possible to shallow the water depth by the amount of the dismantling. For example, after the container transfer equipment 24 and the upper part of the frame 3 are removed, the water level inside the outer wall 37 is lowered below the position of the outer wall drain outlet 65 at the top of the lower outer wall 37a. Then, the upper outer wall 37b is removed and removed. Then, the container transfer equipment 24 and the upper part of the frame 3 are repositioned so that the overall height of the outer wall 37 is lowered. In this way, the distance to the structures below the reactor building 1 is shortened, which improves the efficiency of removing the dismantled parts and reduces the amount of contaminated water stored.

[0153] A specific description will be given below. As shown in Fig. 15, after the various devices described above are arranged, before the microparticle dispersion liquid 8 is injected into the bottom of the torus chamber 32, the injection device 21 uses its water injection function to flush the torus chamber 32. For example, clean water is injected into the torus chamber 32 from a predetermined injection pipe (not shown) of the sixth tube bundle 31. Then, the wastewater from the torus chamber 32 is transferred to the water treatment facility 43. In this way, radioactive materials present at the bottom of the torus chamber 32 can be removed or at least reduced.

[0154] Next, the injector 21 injects the microparticle dispersion 8 to a position below the floor surface 33 of the first floor of the reactor building 1. Note that the injector 21 may inject the microparticle dispersion 8 after injecting, placing, and arranging a buffer material 61 (FIG. 9) inside the reactor building 1. The method of injecting the microparticle dispersion 8 into the reactor containment vessel 4 is the same as in the above-described embodiment.

[0155] When the inside of the outer wall 37 is flooded to the extent that the operation floor 2 and the reactor well 9 are submerged, the shield plug 12 is dismantled and removed. After that, as shown in Figure 16, the top lid 4c of the reactor containment vessel 4 is dismantled and removed.

[0156] If the operation floor 2 has a high radiation level, the concrete floor structure of the operation floor 2 may be dismantled and removed before or after the shield plug 12 is removed.

[0157] Next, as shown in FIG. 17, the top head insulation material (not shown) of the reactor pressure vessel 5 and the top head 5b are dismantled and removed. Then, as shown in FIG. 18, the internal structures of the reactor pressure vessel 5 are dismantled and removed. Furthermore, as shown in Figure 19, the well platform 36, the main body 5a of the reactor pressure vessel 5, and the upper part of the main body 4a of the reactor containment vessel 4 will be shredded, crushed, cut, and dismantled and removed. Note that dismantling and removal will be carried out after evaluating the possibility of each component breaking or falling off when lifted. Then, the metal liner and reinforced concrete framework that make up the operation floor 2 and spent fuel storage pool 10 above the reactor building 1 will be dismantled and removed.

[0158] Next, as shown in FIG. 20, the container transfer equipment 24 is moved to another location. After that, the concrete body of the equipment storage pool 11 is dismantled and removed. Then, taking into consideration the radiation dose of the remaining materials inside the reactor building 1, the upper outer wall 37b is removed and the frame 3 is lowered. Note that even if the water level drops, the water depth required for radiation shielding is ensured. Then, as shown in FIG. 21, the reactor building 1 is dismantled and removed to a position lower than the removal target height position 67 of the upper part of the reactor building 1.

[0159] 22, the water level inside the water tank 80 is lowered, and then the container transfer equipment 24, the lifting equipment 48, the underwater remotely operated heavy machine 49, and the floating remotely operated device 50 are temporarily removed. Here, the water level is lowered while ensuring the water depth necessary to shield the remaining materials at the bottom of the reactor building 1 from radiation, in order to prevent water from overflowing from the lower outer wall 37a.

[0160] The entire water surface of the water tank 80 is covered with a cover hood (not shown), which collects gases such as bubbles that are generated in the water. This gas is sent to a ventilation and air conditioning system (not shown) for ventilation and purification. The upper part of the frame 3 is removed, and the upper outer wall 37b and upper drainage piping 66c are also removed. After that, the upper part of the frame 3 is reassembled on top of the lower outer wall 37a, and the cover hood that covers the water surface is removed.

[0161] Next, as shown in Figure 23, the container transfer equipment 24, lifting equipment 48, underwater remotely operated heavy equipment 49 (Figure 15), and floating remotely operated device 50 are placed inside the water tank 80. Then, as shown in Figure 24, the reactor lower structure 5c and fuel debris 7 are dismantled and removed. Furthermore, as shown in Figure 25, the pedestal 6, the pipes (not shown), valves (not shown) inside the main body 4a of the reactor containment vessel 4, and the biological shield wall (not shown) are dismantled and removed.

[0162] After the highly radioactive structures are removed, the dismantling and removal policy for the remaining structures will be determined according to their radiation levels. If the radiation levels are low, the reactor well 9, spent fuel storage pool 10, and equipment storage pool 11 in the reactor building 1 can be drained before dismantling and removal.

[0163] If the structures remaining inside the reactor building 1 have a high radiation dose, the demolition work will continue with the inside of the lower outer wall 37a submerged in water. The procedure for dismantling and removing the structures by underwater work will be described below. Note that, among the work procedures described below, if it is expected that the radiation dose in the atmosphere is high enough to allow demolition work in air, the water may be drained and the demolition work may be carried out in air.

[0164] First, as shown in Figure 26, temporary structures such as the isolation room 20, the third pipe bundle 22, the fifth pipe bundle 30, and the isolation pipe 26 that interfere with the demolition work are dismantled and removed. Next, as shown in Figure 27, the reinforced concrete structure above the floor surface 33 on the first floor of the reactor building 1 is dismantled and removed.

[0165] Furthermore, as shown in FIG. 28, the particulate sediment layer 8b filled in the torus chamber 32 is returned to a liquid state by pouring water and stirring. Then, the particulate sediment layer 8b that has been returned to a liquid state is removed by slurry transfer using suction or by scooping. Here, the particulate sediment layer 8b is replaced with clean water. At this time, if a buffer material 61 (FIG. 9) is present in addition to the particulate sediment layer 8b, it is removed by scooping and replaced with clean water.

[0166] Next, as shown in Fig. 29, the upper part of the pressure suppression chamber 4b of the reactor containment vessel 4 is dismantled and removed. Then, as shown in Fig. 30, the lower part of the pressure suppression chamber 4b of the reactor containment vessel 4 is dismantled and removed. At this time, if buffer material 61 (Fig. 9) exists in addition to the fine particle deposition layer 8b, it is removed by scooping and replaced with clean water.

[0167] Next, as shown in Figure 31, the structures above the vent pipe 68 remaining at the bottom of the main body 4a of the reactor containment vessel 4 are dismantled and removed together with the concrete skeleton. At this point, the remaining vent pipe 68 is exposed. Then, as shown in Figure 32, the vent pipe 68 is dismantled and removed. Furthermore, as shown in Figure 33, the bottom of the main body 4a of the reactor containment vessel 4 and the concrete skeleton supporting it are dismantled and removed.

[0168] Finally, as shown in Figure 34, the fine particle sediment layer 8b at the bottom of the reactor building 1 is removed, the water is drained, and the bottom of the reactor building 1 is exposed to the air. Then, remaining objects are removed, completing all dismantling and removal.

[0169] According to the fourth embodiment, it is expected that radiation exposure can be reduced and work efficiency can be improved in the overall dismantling work of the reactor building 1. If the structures outside the reactor containment vessel 4 are highly radioactive, highly radioactive materials such as fuel debris 7 may remain inside and outside the system. Even in such cases, underwater work can be performed by flooding.

[0170] Furthermore, the outer wall 37 is configured to be stacked or separately removable. Therefore, after a predetermined height range of the reactor building 1 is removed, the water level inside the outer wall 37 is lowered, and the outer wall 37 is dismantled and removed from above. Furthermore, the reactor building 1 is 30 meters or more high, and the lower the building, the deeper the demolition work becomes, making it inefficient. However, according to the fourth embodiment, the work scaffolding can be lowered in stages, making the dismantling and removal work easier. Furthermore, since underwater work continues, dust scattering can be prevented. Furthermore, since the seismic strength decreases during the demolition process, the demolition equipment itself can be lowered, improving seismic resistance and work efficiency.

[0171] The present invention has been described above based on the first to fourth embodiments, but the configuration applied in any of the embodiments may be applied to other embodiments, and the configurations applied in each embodiment may be combined.

[0172] In the above-described embodiment, the nuclear facility includes various devices installed in a nuclear power plant, such as the reactor building 1, the reactor well 9, the shield plug 12, the reactor containment vessel 4, the reactor pressure vessel 5, the pressure suppression chamber 4b, the pedestal 6, the vent pipe 68, the control rod drive mechanism, and the reactor core. The nuclear facility may also be part of the nuclear facility dismantling system 100. For example, the nuclear facility includes the outer wall 37.

[0173] In the above-described embodiment, the manner in which a microparticle deposition layer 8b is formed to stop water from leaking from a leaking location includes not only the manner in which a microparticle deposition layer 8b is formed inside a room in which the leak is located to stop water from leaking, but also the manner in which a microparticle deposition layer 8b is formed outside a room in which the leak is located to stop water from leaking.

[0174] In the above-described embodiment, "submerging" includes submerging the equipment to be dismantled. "Submerging" also includes filling the interior of the equipment to be dismantled with water. "Submerging" also includes submerging the highly radioactive parts of the equipment to be dismantled to a depth at which the radiation level is sufficiently attenuated.

[0175] Although the above-described embodiment exemplifies a form applied to the decommissioning of a boiling water reactor (BWR), other forms are also possible. For example, the above-described embodiment may be applied to the decommissioning of an advanced boiling water reactor (ABWR), a pressurized water reactor (PWR), or a graphite-moderated boiling water pressure tube reactor (RBMK).

[0176] According to at least one of the embodiments described above, the leak point is sealed using the microparticle dispersion 8 containing microparticles with a specific gravity greater than that of water. This allows a nuclear facility that has suffered a severe accident to be submerged in water, shielding it from radiation with water, and dismantling the nuclear facility in an underwater environment.

[0177] Although several embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the invention. These embodiments can be implemented in various other forms, and various omissions, substitutions, modifications, and combinations can be made without departing from the spirit of the invention. These embodiments and modifications thereof are intended to be included within the scope and spirit of the invention, as well as within the scope of the invention described in the claims and their equivalents. [Explanation of symbols]

[0178] 1... reactor building, 2... operation floor, 3... frame, 4... reactor containment vessel, 4a... main body, 4b... pressure suppression chamber, 4c... head, 5... reactor pressure vessel, 5a... main body shell, 5b... head, 5c... reactor lower structure, 6... pedestal, 7... fuel debris, 8... particulate dispersion, 8a... supernatant, 8b... particulate sediment layer, 9... reactor well, 10... spent fuel storage pool, 11... equipment storage pool, 12... shield plug, 13... injection device, 13a... exhaust device, 14... first tube bundle, 15 ...Perforation part, 16...Tight tube, 17...Perforation part, 18...Second tube bundle, 19...Perforation part, 20...Isolation room, 21...Injection device, 21a...Ejection device, 22...Third tube bundle, 23...Waste container, 24...Container transfer equipment, 25...Fourth tube bundle, 26...Isolation tube, 2 7...perforation part, 28...opening part, 29...perforation part, 29a...perforation part, 29b...perforation part, 30...5th tube bundle, 31...6th tube bundle, 32...torus room, 33...floor surface, 34...remote control heavy equipment, 35...water-shielding wall, 36...well platform, 37...outside Wall, 37a...lower exterior wall, 37b...upper exterior wall, 38...foundation, 40, 40a...transfer pump, 41...transfer piping, 41a, 41b...transfer piping, 42...pit, 43...water treatment equipment, 43a...water storage container, 44...drain outlet, 45...drainage piping, 46...transfer device, 46a...particle treatment equipment, 47...particle treatment equipment, 47a...seventh pipe bundle, 47b...purification device, 47c...transfer pump, 47d...transfer piping, 48...lifting equipment, 49...underwater remotely operated heavy equipment, 50...floating remotely operated equipment, 51... Frame, 52...airtight equipment, 53...airtight door, 54...door opening and closing mechanism, 55...hole drilling device, 56...airtight container, 57...airtight door, 58...door opening and closing mechanism, 59...strainer structure, 60...toy structure, 61...buffer material, 63...strainer, 65...exterior wall drain outlet, 66...drainage piping, 66a...lower drainage piping, 66b...intermediate drainage piping, 66c...upper drainage piping, 67...removal target height position, 68...vent pipe, 70, 71...drilling device, 80...water tank, 90...groundwater level, 100...nuclear equipment dismantling system.

Claims

1. When dismantling a nuclear facility where a water leak has occurred due to a severe accident, the leak location is sealed off using a microparticle dispersion containing at least microparticles having a specific gravity greater than that of water, and at least a portion of the nuclear facility is submerged in water. Nuclear equipment dismantling method.

2. The microparticles include at least barite as a weighting material and at least bentonite as a thickening agent. The method for dismantling nuclear facility according to claim 1.

3. forming a particulate deposition layer in an internal space of the nuclear facility where the leak location exists, by depositing the particulates until the particulates reach a height higher than the leak location; The method for dismantling nuclear facility according to claim 1 or 2.

4. constructing a water impermeable wall surrounding a reactor well formed above a reactor containment vessel included in the nuclear facility; Injecting the microparticle dispersion into the reactor well to seal the leaking portion at the bottom of the reactor well with the microparticles; injecting the water into the reactor well to a height above a shield plug disposed above the reactor well; dismantling the shield plug while the shield plug is submerged in water; The method for dismantling nuclear facility according to claim 1 or 2.

5. a perforated portion is formed by perforating an upper cover of a reactor containment vessel included in the nuclear facility; injecting the particulate dispersion into the reactor containment vessel through the perforated portion to form a particulate deposition layer in which the particulates are deposited between the reactor containment vessel and a reactor pressure vessel contained inside the reactor containment vessel; injecting the water into the reactor containment vessel to a height exceeding the reactor pressure vessel; dismantling the reactor pressure vessel while the reactor pressure vessel is submerged in water; The method for dismantling nuclear facility according to claim 1 or 2.

6. a pressure suppression chamber of a reactor containment vessel included in the nuclear facility is drilled to form a drilled portion; the microparticle dispersion is injected into the pressure suppression chamber through the perforated portion to form a microparticle deposition layer in which the microparticles are deposited in the pressure suppression chamber; filling the pressure suppression chamber with the water and injecting the water into the reactor containment vessel to a height exceeding a reactor pressure vessel contained within the reactor containment vessel; dismantling the reactor pressure vessel while the reactor pressure vessel is submerged in water; The method for dismantling nuclear facility according to claim 1 or 2.

7. constructing a water tank having an outer wall surrounding a reactor building included in the nuclear facility, the water tank containing the entire reactor building, and the water tank storing the water therein to submerge at least a portion of the reactor building; pouring the microparticle dispersion into the water tank to deposit the microparticles on the bottom of the water tank to form a microparticle deposition layer; injecting the water into the water tank to a height that exceeds at least a reactor containment vessel provided inside the reactor building; dismantling the reactor containment vessel and the reactor building while at least the reactor containment vessel is submerged in water; The method for dismantling nuclear facility according to claim 1 or 2.

8. When dismantling a nuclear facility where a water leakage site has occurred due to a severe accident, an injection device is provided that injects a microparticle dispersion containing the microparticles into the nuclear facility in order to watertightly seal the leakage site with the microparticles having a specific gravity greater than that of water and to flood at least a portion of the nuclear facility. Nuclear facility dismantling system.

9. a discharge device that discharges, from the nuclear facility, the supernatant water that is generated when the microparticles contained in the microparticle dispersion that has been injected into the nuclear facility settle; The nuclear facility dismantling system according to claim 8.

10. a water storage container for storing the water discharged from the nuclear facility; a transfer device that transfers the water stored in the water storage container to the injection device so that the water stored in the water storage container is mixed with the fine particles to form the fine particle dispersion again; Equipped with The nuclear facility dismantling system according to claim 8 or 9.

11. a water impermeable wall surrounding a reactor well formed above a reactor containment vessel included in the nuclear facility; the injection device injects the microparticle dispersion into the reactor well to seal the leaking portion at the bottom of the reactor well with the microparticles; The nuclear facility dismantling system according to claim 8 or 9.

12. the injection device injects the microparticle dispersion into the internal space of the nuclear facility where the leak location exists, and forms a microparticle deposition layer by depositing the microparticles until the height is higher than the leak location. The nuclear facility dismantling system according to claim 8 or 9.

13. a drilling device for drilling an upper cover of a reactor containment vessel included in the nuclear facility to form a drilled portion, the injection device injects the particulate dispersion into the reactor containment vessel through the perforated portion to form the particulate deposition layer between the reactor containment vessel and a reactor pressure vessel contained inside the reactor containment vessel. The nuclear facility dismantling system according to claim 12.

14. a drilling device for drilling a pressure suppression chamber of a reactor containment vessel included in the nuclear facility to form a drilled portion, the injection device injects the microparticle dispersion into the pressure suppression chamber through the perforated portion to form the microparticle deposition layer in the pressure suppression chamber. The nuclear facility dismantling system according to claim 12.

15. a water tank having an outer wall surrounding a reactor building included in the nuclear facility, containing the entire reactor building, and storing the water therein to submerge at least a portion of the reactor building; the injection device injects the microparticle dispersion into the water tank to form the microparticle deposition layer on the bottom of the water tank; The nuclear facility dismantling system according to claim 12.

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