JP2023047744A - Method for decommissioning nuclear reactor - Google Patents

Abstract

To provide a method for decommissioning a nuclear reactor which can surely shield radiation for a long time while avoiding influence of change of severe environments and also is advantageous for reducing the burden of monitoring and maintenance.SOLUTION: A caisson body 10 for containing a nuclear reactor building 22 and a supporting foundation 24 is formed. A caisson shovel 20 digs the foundation in the lower part of the caisson body 10 so that weight of the nuclear reactor building 22, the supporting foundation 24, and the caisson body 10 makes the caisson body 10 sink. When the caisson body 10 is sunk, a space 28 in the lower part of the caisson body 10 and the inside of the caisson body 10 are filled with concrete C. After that, the nuclear reactor building 22, the supporting foundation 24, and the caisson body 10 are buried in the ground and the decommissioning work is finished.SELECTED DRAWING: Figure 10

Description

The present invention relates to a method for decommissioning a nuclear reactor.

In a nuclear power plant, a nuclear reactor decommissioning method has been disclosed in which a nuclear reactor in which a severe accident has occurred is shut down, sorted out to the extent that there is no danger, and abandoned in that state (see Patent Document 1).
In this decommissioning method, a water tank that houses the entire reactor building that houses the containment vessel is constructed, the containment vessel is submerged in the water tank, and radiation from the containment vessel is shielded with water. to be maintained.
That is, a water tank is used as the decommissioning structure, and the water tank consists of a bottom constructed under the ground immediately below the reactor building and the surrounding ground, and a submerged wall rising from the bottom and surrounding the reactor building and its surroundings. , and a ceiling that connects the upper end of the submerged wall above the reactor building.
Water is stored in the tank to submerge the reactor building.

JP 2020-176939 A

In the above conventional technology, the submerged wall and ceiling exposed from the ground in the aquarium are exposed to severe environmental changes such as wind and rain, direct sunlight, and temperature changes for a long period of time, which accelerates deterioration over time, resulting in cracks and damage. As a result, the water stored in the water tank may leak.
In addition, the ground that supports the reactor building in the water tank is immersed in water during an extremely long decommissioning period of, for example, 100 or 200 years or more, so the ground loosens in the water tank, causing the reactor building to tilt and collapse. Problems such as destroying the submerged wall may also occur.
Even if the spent fuel, etc., were completely removed from the reactor building and reactor containment vessel during decommissioning, high levels of radioactive materials would still remain in the reactor building and the supporting ground that supports this reactor building. Therefore, during an extremely long decommissioning period, the decommissioned structure must maintain its function of shielding radiation from the reactor building and supporting ground. function to shield the
Therefore, it is necessary to monitor the degree of deterioration of the water tank over a long period of time, and to repair cracks and damages as necessary. As such, some improvement is required.
The present invention has been made in view of the above points, and an object of the present invention is to reliably shield radiation for a long period of time while avoiding the effects of severe environmental changes, and to reduce the burden of monitoring and maintenance work. To provide a decommissioning method of a nuclear reactor which is advantageous in reducing the load.

In order to achieve the above-mentioned object, one embodiment of the present invention provides a caisson frame for housing the reactor building together with a support ground for supporting the reactor building, and excavates the ground below the caisson frame. By moving, the reactor building and the support ground are sunk into the ground together with the caisson frame, and after sinking, the space below the excavated caisson frame and the inside of the caisson frame are filled with concrete. It is characterized in that the reactor building and the supporting ground are buried in the ground together with the caisson frame.
In one embodiment of the present invention, the caisson frame includes a bottom wall that supports the support ground together with the reactor building and has a cutting edge protruding from the periphery of the lower surface of the bottom wall, and a bottom wall that is erected from the periphery of the bottom wall. and a side wall surrounding the supporting ground and the reactor building, and a ceiling wall connecting the upper ends of the side walls above the reactor building.
Moreover, one embodiment of the present invention is characterized in that the filling of the inside of the caisson frame with concrete is performed before the caisson frame is subsided.
Further, in one embodiment of the present invention, the caisson frame includes a bottom wall that supports the support ground together with the reactor building and has a cutting edge projecting from the periphery of the lower surface thereof; It has supporting ground and side walls surrounding the periphery of the reactor building, and after the subsidence, the space under the excavated caisson frame is filled with concrete, and the upper ends of the side walls are connected above the reactor building. A ceiling wall is provided, and the inside of the caisson frame is filled with concrete.
Further, in one embodiment of the present invention, a frame-shaped recess surrounding the reactor building and the supporting ground is excavated in the ground around the reactor building, and the bottom wall is constructed from the frame-shaped recess, The lower part of the side wall is constructed at a height from the periphery of the bottom wall to the ground surface.
In one embodiment of the present invention, after constructing the bottom wall and the lower part of the side wall, the ground inside the cutting edge is excavated to provide a space below the caisson frame inside the cutting edge. The ground below the caisson frame is excavated by an excavator brought into the space from the frame-shaped concave portion.
Moreover, one embodiment of the present invention is characterized in that the subsidence is performed until the upper surface of the ceiling wall is at least flush with the ground surface.
Moreover, one embodiment of the present invention is characterized in that compressed air corresponding to groundwater pressure is supplied to the space below the caisson frame when excavating the ground below the caisson frame.
Further, in one embodiment of the present invention, a material shaft extending in the vertical direction and penetrating through the support ground, the bottom wall and the ceiling wall of the caisson frame and having material blocks is provided, and the caisson frame is provided with a material shaft. When the ground below is excavated, excavated earth and sand is carried out by a bucket that moves up and down in the material shaft.
Moreover, one embodiment of the present invention is characterized in that a man shaft extending in the vertical direction and penetrating through the supporting ground, the bottom wall and the ceiling wall of the caisson frame and having a man block is provided. and
Further, in one embodiment of the present invention, a material shaft extending in the vertical direction and penetrating the support ground and the bottom wall of the caisson frame is provided and provided with a material block, and the ground below the caisson frame is excavated. When excavated earth and sand are carried out by a bucket that ascends and descends in the material shaft.
Moreover, one embodiment of the present invention is characterized in that a man shaft is provided which extends in the vertical direction, penetrates the support ground and the bottom wall of the caisson frame, and includes a man block.

According to one embodiment of the present invention, a support ground for supporting the reactor building and a caisson frame for accommodating the reactor building are provided, and the ground below the caisson frame is excavated to obtain the reactor building and the supporting ground. The weight of the ground and the caisson frame will cause the caisson frame to sink into the ground, and the space below the excavated caisson frame and the inside of the caisson frame will be filled with concrete, and the caisson frame will be placed underground together with the reactor building and supporting ground. Buried.
Therefore, unlike the prior art, the caisson skeleton buried in the ground is not exposed to severe environmental changes such as wind and rain, direct sunlight, and temperature changes.
Therefore, for example, over a very long decommissioning period such as 100 years, 200 years or more, the concrete filled in the space below the caisson frame and the inside of the caisson frame is used to support the reactor building, the support ground that supports the reactor building, It is possible to continue to maintain a state of shielding radiation from the radioactive substances remaining in the reactor containment vessel.
In addition, since it is possible to continue shielding radiation from radioactive materials remaining in the reactor building and reactor containment vessel over an extremely long decommissioning period, monitoring work and maintenance during an extremely long decommissioning period will be possible. This is advantageous in significantly reducing the work load.
In addition, since the supporting ground contaminated with radioactive substances is stored in the caisson frame together with the reactor building and buried in the ground, a severe accident occurs and the fuel in the reactor remains as it is. It is suitable as
In addition, the ground below the caisson frame is excavated, and the weight of the reactor building, supporting ground, and caisson frame sinks the caisson frame into the ground. This is advantageous in terms of safety and certainty.
In addition, before installing the caisson frame, if a recess is excavated in the ground around the reactor building to surround the reactor building and the supporting ground, the bottom wall, cutting edge, and lower part of the side wall of the caisson frame can be easily constructed. In addition, in order to easily provide a space below the caisson frame, and in the space below the caisson frame, an excavator that excavates the ground below the caisson frame, lighting equipment, cameras, etc. It is advantageous for importing.
In addition, if the lower part of the side wall is constructed at the height from the circumference of the bottom wall to the ground surface, it will be necessary to set up the material shaft, man shaft, and compressed air supply pipe later, and to set up the side wall and ceiling wall. It is advantageous in facilitating the work of assembling the formwork.
In addition, if the caisson frame is submerged into the ground until the upper surface of the ceiling wall is at least flush with the ground surface, radiation from the radioactive materials remaining in the reactor building, supporting ground, and reactor containment vessel will be reduced. It is advantageous to keep the shielded state.
In addition, when groundwater springs up during excavation of the ground below the caisson frame, supplying compressed air corresponding to the groundwater pressure to the space below the caisson frame facilitates excavation of the ground by the excavator. be advantageous.
In addition, if groundwater springs up during excavation of the ground below the caisson frame, a material shaft with a material block attached to the upper end of the material shaft can be passed through the space below the caisson frame to carry out the excavated earth and sand. It is advantageous in efficiently performing
In addition, when groundwater springs up during excavation of the ground below the caisson frame, a man shaft with a man block connected to the upper end of the man shaft penetrates the space below the caisson frame. It is advantageous for smooth entry and exit of workers.

BRIEF DESCRIPTION OF THE DRAWINGS It is explanatory drawing of 1st Embodiment, (A) is a top view of the state which excavated the frame-shaped recessed part around the reactor building, (B) is the cross-sectional front view. FIG. 4 is a cross-sectional front view of a state in which the bottom wall of the caisson frame is built on the ground supporting the reactor building. Fig. 2 is a cross-sectional front view of a state in which a cutting edge having a cutting edge and a lower portion of a side wall are integrally constructed on a bottom wall of a caisson frame; (A) backfills the excavated earth and sand at the bottom of the frame-shaped recess so that the cutting edge touches the ground, provides a space below the caisson frame, backfills the earth and sand outside the cutting edge in the frame-shaped recess, and tops the bottom wall and a plan view of a state in which the supporting ground and the reactor building are supported inside the lower part of the side wall, and (B) is a cross-sectional front view of the same. (A) is a plan view of a state in which a material shaft, a man shaft, and a compressed air supply pipe are erected from the bottom wall through the supporting ground, and (B) is a cross-sectional front view of the same. (A) is a plan view of a state in which a caisson frame is constructed, a material block is provided on a material shaft, and a man block is provided on a man shaft, and (B) is a sectional front view of the same. FIG. 4 is a cross-sectional front view of a state in which the caisson frame sinks into the ground due to the weight of the reactor building, the weight of the supporting ground, and the weight of the caisson frame as the ground inside the cutting edge is excavated. Fig. 2 is a cross-sectional front view of a state in which the caisson frame is sunk into the ground until the upper surface of the ceiling wall and the ground surface are at the same height; It is the cross-sectional front view of a state in which the space under the caisson frame is filled with concrete. (A) is a plan view of a state in which the interior of the caisson frame is filled with concrete, various shafts and pipes protruding from the ceiling wall are removed, and the ceiling wall is closed, and (B) is a cross-sectional front view of the same. Explanatory diagram of the second embodiment, (A) is a plan view of a state in which the inside of the caisson frame is filled with concrete after building the caisson frame housing the reactor building and the supporting ground, (B) is It is the same cross-sectional front view. In the explanatory diagram of the third embodiment, (A) constructs a caisson frame that accommodates the reactor building and the supporting ground, erects a material shaft, a man shaft, and a compressed air supply pipe from the bottom wall A plan view of a state in which a material block is provided on a material shaft and a man block is provided on a man shaft, and (B) is a cross-sectional front view of the same. FIG. 4 is a cross-sectional front view of a state in which the caisson frame sinks into the ground due to the weight of the reactor building, the weight of the supporting ground, and the weight of the caisson frame as the ground inside the cutting edge is excavated. FIG. 10 is a cross-sectional front view of a state in which the upper end of the side wall sinks the caisson frame to a height located below the ground surface by the thickness of the ceiling wall. It is a cross-sectional front view of a state in which the space below the caisson frame is filled with concrete. (A) is a plan view of a side wall provided with a ceiling wall, and (B) is a cross-sectional front view of the same.

(First embodiment)
First, the first embodiment will be described with reference to FIGS. 1 to 10. FIG.
In the following embodiments, a severe accident occurs in a nuclear power plant, the reactor installed in the reactor building is in a state of core meltdown, and the melted fuel breaks through the bottom wall of the reactor building. The decommissioning method of the nuclear reactor when reaching the ground below and the ground is contaminated with radioactive substances will be described.
As shown in FIG. 1, a reactor building 22 is supported by support ground 24 that is contaminated with radioactive material.
As shown in FIG. 6, the caisson body 10 has a rectangular parallelepiped shape.
The caisson frame 10 includes a bottom wall 12 which is square in plan view and supports the reactor building 22 together with a support ground 24 of the reactor building 22, and a support ground 24 and the periphery of the reactor building 22 which rises from the four sides of the bottom wall 12. and a square ceiling wall 16 connecting the upper ends of the side walls 14 above the reactor building 22 to accommodate the supporting ground 24 and the reactor building 22 .
A cutting edge 1204 having a cutting edge 1204A at the lower end protrudes from four sides of the lower surface of the bottom wall 12 in a rectangular frame shape, and the caisson frame 10 housing the reactor building 22 and the supporting ground 24 is located inside the cutting edge 1204A. By excavating the ground, the weight of the reactor building 22, the weight of the supporting ground 24, and the weight of the caisson frame 10 sink into the ground.

In this embodiment, for example, the bottom wall 12 of the caisson frame 10 is a square with a side of about 50 m, the height of the caisson frame 10 is about 50 m, and the bottom wall 24 of the reactor building 22 is about 40 m on a side. , and the height of the reactor building 22 is about 40 m.
When the reactor building 22 has a cylindrical shape, the caisson frame 10 may have a rectangular parallelepiped shape, may have a cylindrical shape, or may have a shape other than a rectangular parallelepiped or a cylindrical shape. Various conventionally known structures can be adopted for the shape.
The depth of the support ground 24 accommodated in the caisson body 10 and the length of one side of the bottom wall 12 of the caisson body 10 are appropriately determined based on the degree of contamination of the support ground 24 with radioactive substances.

Specifically, as shown in FIG. 1, before constructing the caisson frame 10, a square frame extending along the perimeter of the reactor building 22 is formed by excavating machines such as backhoes. The recess 28A is excavated.
The depth of the frame-shaped recess 28A to be excavated was determined based on the degree of radioactive contamination in order to install the formwork for constructing the cutting edge 1204 having the cutting edge 1204A. , the thickness of the bottom wall 12, and the dimension of the cutting edge 1204 from the lower surface of the bottom wall 12 to the cutting edge 1204A.
When the frame-shaped recess 28A is excavated, a prismatic ground having a substantially square cross section including the support ground 24 is provided from the bottom surface of the frame-shaped recess 28A to the lower surface of the reactor building 22. is injected to solidify the prismatic ground supporting the reactor building 22 to increase the strength of the prismatic ground.
Such ground improvement may be omitted, but if ground improvement is performed, the reactor building 22 can be restored to the reactor building 22 in the state shown in FIG. It is advantageous to firmly support the prismatic ground below 22 .
In addition, although not shown, by the underpinning method, a plurality of piles are driven into the ground outside the frame-shaped recess to the strong ground so as to surround the frame-shaped recess. You may make it suppress collapse of the wall surface of the outer side of a recessed part.

Next, as shown in FIG. 2, the bottom wall 12 of the caisson frame 10 is constructed on the prismatic ground located below the contaminated supporting ground 24 .
For constructing the bottom wall 12 of the caisson frame 10, various conventionally known construction methods such as a pipe roof construction method and a shield construction method can be employed.
For example, in the pipe roof construction method, a plurality of steel pipes are horizontally placed in a row of columns at equal intervals from the frame-shaped recess 28A into the ground located below the contaminated ground.
The cast adjacent steel pipes are integrally connected via joints, concrete is cast inside the steel pipes, and the bottom wall 12 of the caisson frame 10 is thereby formed over the entire ground surrounded by the frame-shaped recess 28A. is constructed.
In the shield construction method, a plurality of tunnels are horizontally constructed in parallel from the frame-shaped recess 28A by a shield machine in the ground located below the contaminated ground.
Next, after connecting the adjacent tunnels, concrete is placed in each tunnel to construct the reinforced concrete base 12 of the caisson frame 10 over the entire ground surrounded by the frame-shaped recess 28A.

Once the bottom wall 12 of the caisson body 10 has been constructed, as shown in FIG. Constructed integrally with wall 12 .
They are constructed by assembling a formwork in the frame-shaped recess 28A, arranging reinforcing bars and pouring concrete into the formwork, and forming a cutting edge 1204 made of reinforced concrete that has a cutting edge 1204A and is integrated with the bottom wall 12. Then, the bottom wall 12 and the lower part of the side wall 14 made of reinforced concrete with a height up to the ground surface G integrated with the cutting edge 1204 are constructed, and after construction, the formwork is removed.
Then, the bottom of the frame-shaped concave portion 28A is backfilled with excavated earth and sand so that the cutting edge 1204 touches the ground.

Next, as shown in FIG. 4 , a space 28 is provided below the bottom wall 12 of the caisson body 10 and inside the cutting edges 1204 , that is, below the caisson body 10 .
For example, when constructing the cutting edge 1204 , this space 28 is constructed by leaving a part of the cutting edge 1204 . A space 28 is provided by excavating the ground inside the cutting edge 1204 with an excavator such as a backhoe, or a portion of the cutting edge 1204 extending in a rectangular frame shape from the frame-shaped recess 28 is excavated below the cutting edge 1204. Various conventionally known methods such as excavating by excavating with .
Then, an excavator for excavating the ground below the caisson frame 10, a lighting device, a camera, etc. are carried into the space 28.例文帳に追加
In the present embodiment, the caisson excavator 20 and the rails 32 for traveling the caisson excavator 20 are carried into the space 28 because the caisson excavator 20 is used as an excavator for excavating the ground below the caisson skeleton 10 .
If the excavator used to form the space 28 is used as the excavator for excavating the ground below the caisson frame 10, the excavator may remain in the space 28, or the caisson excavator 20 and an excavator, the caisson excavator 20 and the rail 32 may be carried into the space 28 while the excavator remains.
After the excavator, lighting equipment, camera, etc. are carried into the space 28, as shown in FIG. Backfill.

Next, as shown in FIG. 5, material shafts 34A are erected at a pair of opposite corners of the bottom wall 12 inside the side wall 14 and around the reactor building 22, and the remaining pair of opposite corners are erected. In addition, a man shaft 36A is erected, a compressed air supply pipe 38 is erected inside them, and a cable insertion pipe (not shown) for inserting a power cable and a signal cable for supplying power to the lighting equipment to be established.
The material shaft 34A, the man shaft 36A, the compressed air supply pipe 38, and the lower part of the cable insertion pipe (not shown) pass through the support ground 24, penetrate the bottom wall 12, and reach the space 28, and the material shaft 34A. , the man shaft 36A, the compressed air supply pipe 38, and the upper ends of the cable insertion pipe (not shown) are positioned above the ceiling wall 16. As shown in FIG.

In the present embodiment, the caisson shovel 20 is the excavator that excavates the ground below the caisson frame 10, so the operator enters the space 28 from the manshaft 36A, and the plurality of rails 32 around the lower surface of the bottom wall 12. , and the caisson shovel 20 is drivably mounted on these rails 32 .
The caisson excavator 20 includes a traveling portion that travels along the rails 32, and a bendable arm that is rotatably provided on the traveling portion and has a bucket at its tip.
A plurality of lighting fixtures (not shown) are attached to the lower surface of the bottom wall 12, and a camera (not shown) is attached so as to be able to turn horizontally and swing up and down.

A ground remote control room (not shown) is provided on the ground away from the reactor building 22 for remote control of the caisson shovel 20 and cameras.
In the ground remote control room, there is an excavator operating device (not shown) for remotely operating the caisson excavator 20, and a display (not shown) that displays an image around the caisson excavator 20 based on image data supplied from a camera (not shown). equipment is installed.
The excavator operating device is connected to the caisson excavator 20 via a signal cable for supplying operating signals.
The display device is connected to the camera via a signal cable for transmitting image data. Hereinafter, these signal cables are collectively referred to as signal cables.

Next, a formwork for constructing the side wall 14 and the ceiling wall 16 is provided around the reactor building 22 and the supporting ground 24, and concrete is poured into this formwork. A side wall 14 and a ceiling wall 16 made of reinforced concrete, which are integrated under the constructed side wall 14, are constructed.
Side wall 14 surrounds reactor building 22 and supporting ground 24 , and ceiling wall 16 connects the upper end of side wall 14 above reactor building 22 and supporting ground 24 .
As a result, the bottom wall 12, the side walls 14, and the ceiling wall 16 are integrated to construct the caisson frame 10 in which the reactor building 22 and the supporting ground 24 are housed.
When constructing the ceiling wall 16, the material shaft 34A, the man shaft 36A, and the compressed air supply pipe 38 are protruded upward from the ceiling wall 16, and after constructing the ceiling wall 16, the material lock 34B is provided at the upper end of the material shaft 34A. , a man lock 36B is provided at the upper end of the man shaft 36A.

Once the caisson frame 10 housing the reactor building 22 and the supporting ground 24 is constructed in this way, the interior of the space 28 is illuminated with lighting fixtures, and while the excavation site is photographed with a camera, a ground remote control room is opened. 2, while monitoring the image around the caisson excavator 20 displayed on the display device, the caisson excavator 20 is remotely controlled by the excavator operating device to excavate the ground inside the cutting edge 1204A on the ground immediately below the caisson skeleton 10. continue.
By excavating the ground inside the cutting edge 1204A, the weight of the reactor building 22, the weight of the supporting ground 24, and the weight of the caisson frame 10 cause the caisson frame 10 to sink into the ground as shown in FIG. To go.
A bucket (not shown) is suspended from the material lock 34B and the material shaft 34A in the frame-shaped recess 28A by a wire. It rises in the material shaft 34 together with the bucket and is efficiently carried out to the outside of the caisson frame 10 from the material lock 34B.

Instead of the caisson excavator 20, an excavator such as a backhoe may excavate the ground below the caisson frame 10, or the caisson excavator 20 and an excavator such as a backhoe may be used together.
In this case, the excavation of the ground by the caisson shovel 20 or the backhoe is not limited to remote control, and may be optionally operated by a worker in the space 28 .
Excavation of the ground below the caisson shovel 20 is performed while monitoring the inclination of the caisson body 10 so that the caisson body 10 remains horizontal and sinks into the ground.

When the caisson body 10 subsides into the ground, if groundwater wells up in the space 28 below the caisson body 10, the compressed air supply pipe 38 is provided in this embodiment. Compressed air corresponding to ground water pressure is supplied from the feed pipe 38 to the space 28 below the caisson frame 10 .
That is, the present embodiment employs a pneumatic caisson construction method in which compressed air is supplied to the space 28 below the caisson frame 10 to excavate while preventing the inflow of groundwater, and the caisson frame 10 sinks. It goes without saying that the open caisson method may be adopted in the case of ground with little groundwater.
This prevents groundwater from seeping into the space 28 , which is advantageous for smooth excavation of the ground below the caisson frame 10 .
In this embodiment, since the material lock 34B and the material shaft 34A are provided, even when compressed air corresponding to the groundwater pressure is supplied to the space 28 below the caisson frame 10, excavated earth and sand can be removed. This is advantageous in carrying out the caisson frame 10 to the outside without any trouble.

In addition, since the manshaft 36A and the manlock 36B are provided, even when compressed air corresponding to the groundwater pressure is supplied to the space 28 below the caisson frame 10, the operator cannot reach the space 28. This is advantageous for smooth entry and exit.
Various conventionally known structures can be employed for the material lock 34B and the manlock 36B.
In addition, the side wall 14 of the caisson frame 10 may be provided with an entrance/exit for workers that can be opened and closed. In such a case, a pipe (not shown) that penetrates the ceiling wall 16 of the caisson body 10 is provided, and compressed air corresponding to the groundwater pressure is supplied to the inside of the caisson body 10 from the pipe (not shown). Intrusion of groundwater into the caisson frame 10 can be prevented by increasing the pressure inside the frame 10 .

As shown in FIG. 8, when the upper surface of the ceiling wall 16 of the caisson body 10 is lowered into the ground until the height of the caisson body 10 is substantially the same as the ground surface G, as shown in FIG. The space 28 below the caisson frame 10 where is located is filled with concrete C having good fluidity from a material lock 34B and a material shaft 34A to stabilize the caisson frame 10.例文帳に追加
Next, the material lock 34B is removed from the material shaft 34A, and the portion of the material shaft 34A protruding from the ceiling wall 16 is removed.
Also, the manlock 36B is removed from the manshaft 36A, the portion of the manshaft 36A projecting from the ceiling wall 16 is removed, and the portion of the compressed air supply pipe 38 projecting from the ceiling wall 16 is removed.

Then, for example, the portion of the material shaft 34 located in the ceiling wall 16 portion is removed, and from this removed portion, as shown in FIG. Alternatively, a hole for placing concrete is provided in advance in the ceiling wall 16, and the inside of the caisson frame 10 is filled with concrete C through this hole for placing concrete. Of course, the material shaft 34A, the man shaft 36A, and the compressed air supply pipe 38 are also filled with the concrete C.
After the caisson frame 10 is filled with concrete C, as shown in FIG. Close with C.
In this manner, the reactor building 22 and the support ground 24 are buried in the ground together with the caisson frame 10 to complete the decommissioning work.
It is optional, for example, to place concrete with a predetermined thickness on the ground surface G and the upper surface of the ceiling wall 16 .
When the caisson frame 10 is lowered into the ground until the upper surface of the ceiling wall 16 is almost at the same height as the ground surface G, the state of shielding radiation from the radioactive substances remaining in the reactor building 22 and the reactor containment vessel is maintained. However, the caisson frame 10 may be submerged into the ground until the upper surface of the ceiling wall 16 is at a position lower than the ground surface G. When concrete is placed on the upper surface of the ceiling wall 16 with a predetermined thickness, the subsidence of the caisson skeleton 10 into the ground may be stopped at a point where the upper surface of the ceiling wall 16 is higher than the ground surface G. .

According to the present embodiment, the caisson frame 10 housing the reactor building 22 and the supporting ground 24 is provided, and the reactor building 22 and the supporting ground 24 are separated by excavating the ground below the caisson frame 10. The accommodated caisson frame is lowered into the ground by the weight of the reactor building 22, the weight of the supporting ground 24, and the weight of the caisson frame 10, and after sinking into the ground, the space 28 below the excavated caisson frame 10. Then, the inside of the caisson body 10 is filled with concrete C, and the bottom wall 12 and side walls 14 of the caisson body 10 are buried in the ground together with the reactor building 22 and the support ground 24.例文帳に追加
Therefore, the bottom wall 12 and side walls 14 of the caisson body 10, the space 28 below the excavated caisson body 10, and the concrete C filled inside the caisson body 10 are exposed to severe environmental changes such as wind and rain, direct sunlight, and temperature changes. Without being exposed to, for example, over a very long decommissioning period such as 100 years, 200 years or more, the reactor building 22 , the reactor containment vessel, and the support ground 24 can continue to be shielded from radiation.
In addition, over an extremely long decommissioning period, it is possible to continue to shield the radiation from the radioactive materials remaining in the reactor building 22, the reactor containment vessel, and the support ground 24, so the extremely long decommissioning period This is advantageous in significantly reducing the burden of monitoring work and maintenance work in the system.

In addition, by excavating the ground below the caisson frame 10, the caisson frame housing the reactor building 22 and the support ground 24 is obtained by increasing the weight of the reactor building 22, the weight of the support ground 24, and the weight of the caisson frame 10. Since the caisson body 10 is submerged in the ground, the subsidence of the caisson frame 10 can be reliably performed, which is advantageous in safely and reliably performing the decommissioning work.
It should be noted that the present embodiment is of course applied to the decommissioning method of the nuclear reactor when the fuel in the nuclear reactor is properly removed from the reactor building 22, but in the present invention, the fuel contaminated with radioactive substances is also applied. Since the supporting ground 24 is housed in the caisson frame 10 together with the reactor building 22 and buried in the ground, it is suitable as a decommissioning method of a nuclear reactor in which a severe accident occurs and the fuel in the reactor remains as it is. .

(Second embodiment)
Next, a second embodiment will be described with reference to FIG.
In the following description of the embodiment, the same parts and members as those of the first embodiment are denoted by the same reference numerals and the description thereof is omitted, and the different parts are mainly described.
In the second embodiment, as shown in FIG. 11(A), the ceiling wall 16 is provided with concrete filling holes 1620 .
Then, as shown in FIG. 11(B), if the caisson frame 10 accommodating the reactor building 22 and the support ground 24 is constructed, unlike the first embodiment, from the concrete filling hole 1620 The inside of the caisson frame 10 is filled with concrete C, and the concrete filling hole 1620 is closed with the concrete C.

After filling the inside of the caisson frame 10 with the concrete C, as in the first embodiment, the excavated area is illuminated with lighting fixtures and the excavated area is photographed with a camera as shown in FIGS. The ground below the reactor building 22 is excavated by the caisson excavator 20, and the excavated earth and sand is carried out of the caisson frame 10 by a bucket that moves up and down in the material shaft 34, and the caisson frame 10 sinks into the ground. A lot of work is done.
After the caisson body 10 sinks into the ground, as shown in FIG. 9, the space 28 below the caisson body 10 is filled with concrete C from the material shaft 34, and as shown in FIG. , the man shaft 36A and the hole in the ceiling wall 16 through which the compressed air supply pipe 38 was inserted are closed with concrete C, and the decommissioning work is completed.

The second embodiment differs from the first embodiment in that the work of filling the inside of the caisson body 10 with concrete C is performed before the caisson body 10 is lowered.
According to the second embodiment, when the caisson frame 10 sinks into the ground, the weight of the reactor building 22, the weight of the support ground 24, and the weight of the caisson frame 10 are added to the inside of the caisson frame 10. Since the weight of the filled concrete C is added, the subsidence of the caisson frame 10 into the ground can be performed more reliably, which is advantageous for safer and more reliable decommissioning work.

(Third Embodiment)
Next, a third embodiment will be described with reference to FIGS. 12 to 16. FIG.
The third embodiment differs from the first and second embodiments in that the caisson body 10 does not have the ceiling wall 16 and the ceiling wall 16 is provided after the caisson body 10 sinks down.
As shown in FIG. 12, the caisson body 10 includes a square bottom wall 12 and side walls 14 erected from four sides of the bottom wall 12. The caisson body 10 of the first embodiment shown in FIG. Since it does not have the ceiling wall 16 as compared with , the inside of the side wall 14 is open above the reactor building 22 and the supporting ground 24 .

Once the caisson frame 10 housing the reactor building 22 and the supporting ground 24 has been constructed, the excavation site is illuminated with lighting fixtures and the excavation site is photographed with a camera. In the remote control room, while monitoring the image around the caisson excavator 20 displayed on the display device, by remotely operating the caisson excavator 20 with the excavator operation device, the inside of the cutting edge 1204A can be detected on the ground immediately below the caisson skeleton 10. Excavate the ground.
By excavating the ground inside the cutting edge 1204A, the weight of the reactor building 22, the weight of the support ground 24, and the weight of the caisson frame 10 cause the caisson frame 10 to sink into the ground as shown in FIG. To go.
A bucket (not shown) is suspended from the material lock 34B and the material shaft 34A in the frame-shaped recess 28A by a wire. It rises in the material shaft 34 together with the bucket and is efficiently carried out to the outside of the caisson frame 10 from the material lock 34B.
In the third embodiment, similarly to the first embodiment, compressed air is supplied to the space 28 below the caisson frame 10 to prevent the inflow of groundwater while excavating, thereby sinking the caisson frame 10. Although the matic caisson construction method is adopted, it goes without saying that the open caisson method may be adopted in the case of ground with little groundwater.

As shown in FIG. 14, if the upper end of the side wall 14 is lowered into the ground from the ground surface G by the thickness of the ceiling wall 16, as shown in FIG. Concrete C is placed and filled from the lock 34B and the material shaft 34A to stabilize the caisson frame 10. - 特許庁
Next, as shown in FIG. 16, a formwork is assembled above the reactor building 22, concrete is poured into the formwork, and a ceiling wall 16 connecting the upper ends of the side walls 14 is provided.
Next, as in the first embodiment, as shown in FIG. 10, the material lock 34B, the portion of the material shaft 34A projecting from the ceiling wall 16, the manlock 36B, and the manshaft 36A projecting from the ceiling wall 16 parts etc. are removed, the part of the compressed air supply pipe 38 protruding from the ceiling wall 16 is removed, the inside of the caisson frame 10 is filled with concrete C, the material shaft insertion hole 1210, the man shaft insertion hole 1212, and the compressed air supply The pipe insertion hole 1214 is closed with concrete C, and the decommissioning work is completed.

According to the third embodiment, when the caisson structure 26 subsides, the space inside the side wall 14 is always open upward, so that workers can enter and exit the caisson frame 10 and various It is advantageous for working.

10 Caisson frame 12 Bottom wall 1204 Cutting edge 1204A Cutting edge 14 Side wall 16 Ceiling wall 1620 Concrete filling hole 20 Caisson excavator 22 Reactor building 24 Support ground 28A Frame-shaped recess 28 Space 32 Rail 34A Material shaft 34B Material lock 36A Man shaft 36B Man Lock 38 Compressed air supply pipe G Ground surface C Concrete

Claims (12)

A caisson frame housing the reactor building is provided together with a supporting ground for supporting the reactor building,
By excavating the ground below the caisson frame, the reactor building and the support ground are sunk into the ground together with the caisson frame,
After subsidence, the space below the excavated caisson frame and the inside of the caisson frame are filled with concrete, and the reactor building and the support ground are buried in the ground together with the caisson frame.
A method for decommissioning a nuclear reactor, characterized by: The caisson frame includes a bottom wall that supports the support ground together with the reactor building and has a cutting edge projecting from the periphery of the lower surface thereof, and a periphery of the support ground and the reactor building that is erected from the periphery of the bottom wall. and a ceiling wall connecting the upper ends of the side walls above the reactor building,
The method for decommissioning a nuclear reactor according to claim 1, characterized in that: Filling the inside of the caisson frame with concrete is performed before sinking the caisson frame,
3. The method of decommissioning a nuclear reactor according to claim 1 or 2, characterized in that: The caisson frame includes a bottom wall that supports the supporting ground together with the reactor building and has a cutting edge protruding from the periphery of the lower surface thereof, and a bottom wall that is erected from the bottom wall and surrounds the supporting ground and the reactor building. a side wall;
After the subsidence, the space below the excavated caisson frame is filled with concrete, a ceiling wall is provided above the reactor building to connect the upper ends of the side walls, and the inside of the caisson frame is filled with concrete.
The method for decommissioning a nuclear reactor according to claim 1, characterized in that: Excavating a frame-shaped recess surrounding the reactor building and the supporting ground in the ground around the reactor building,
constructing the bottom wall from the frame-shaped recess and constructing a lower portion of the side wall at a height from the circumference of the bottom wall to the ground surface;
The method for decommissioning a nuclear reactor according to any one of claims 1 to 4, characterized in that: After constructing the bottom wall and the lower part of the side wall, the ground inside the cutting edge is excavated to provide a space below the caisson frame inside the cutting edge,
Excavation of the ground below the caisson frame is performed by an excavator brought into the space from the frame-shaped recess,
The decommissioning method of the nuclear reactor according to claim 5, which is characterized by the following. The subsidence is performed until the upper surface of the ceiling wall is at least flush with the ground surface.
The method for decommissioning a nuclear reactor according to any one of claims 2 to 4, or claim 5 or claim 6, which is a citation of any one of claims 2 to 4, characterized in that: When excavating the ground below the caisson frame, compressed air corresponding to groundwater pressure is supplied to the space below the caisson frame,
The method for decommissioning a nuclear reactor according to any one of claims 1 to 7, characterized in that: a material shaft extending in the vertical direction and penetrating through the supporting ground, the bottom wall and the ceiling wall of the caisson frame and having a material block;
When excavating the ground below the caisson frame, excavated soil is carried out by a bucket that moves up and down in the material shaft,
The method of decommissioning a nuclear reactor according to claim 8 quoting claim 2 or 3, characterized in that: A man shaft extending in the vertical direction and penetrating through the supporting ground, the bottom wall and the ceiling wall of the caisson frame and having a man block is provided,
10. The method of decommissioning a nuclear reactor according to claim 9, characterized in that: a material shaft extending vertically through the support ground and the bottom wall of the caisson frame and having a material block;
When excavating the ground below the caisson frame, excavated soil is carried out by a bucket that moves up and down in the material shaft,
The method for decommissioning a nuclear reactor according to claim 8 quoting claim 4, characterized in that: a man shaft extending vertically and penetrating through the support ground and the bottom wall of the caisson frame and having a man block;
12. The method for decommissioning a nuclear reactor according to claim 11, wherein:

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