JP5997891B2 - Construction method for tubular structures - Google Patents

Description

  The present invention relates to a method for constructing a cylindrical structure having radiation shielding properties.

In a nuclear facility such as a nuclear power plant, there is a possibility that an accident that releases radiation to the outside may occur due to a great damage caused by a natural disaster such as a large-scale earthquake or tsunami or a terrorist attack. When such an accident occurs at a nuclear facility, workers can quickly perform recovery work under severe radiation conditions (for example, a meltdown state in a nuclear reactor or a critical state in a nuclear material facility). There is a need to do.
On the other hand, the time in which workers can work under such harsh radiation conditions is limited, and considering the time for reciprocating movement to the target point (for example, a meltdown reactor), safety can be improved. It is difficult to secure sufficient work time while ensuring.

  Therefore, for example, as shown in Patent Document 1 below, it is conceivable to use a shelter in which a chamber is formed surrounded by a wall portion having radiation shielding properties (made of a neutron shielding material). That is, a shelter is provided in or near the nuclear facility, and when an accident occurs, the worker reciprocates between the shelter and the destination point to ensure work time.

Utility Model Registration No. 3123960

  However, in the conventional shelter, it is difficult to transport materials necessary for restoration work through the shelter, and not only the destination point under severe radiation conditions but also between the destination point and the shelter. There is a possibility that workers may be exposed during the movement, and there is room for improvement in workability and safety.

  The present invention has been made in view of such circumstances, and has a cylindrical structure that can efficiently perform restoration work while ensuring the safety of workers even under severe radiation conditions. The purpose is to provide a construction method.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, in the construction method of the cylindrical structure according to the present invention, the peripheral wall of the cylindrical structure whose inside is a passage is directed toward the inside of the passage along the thickness direction of the peripheral wall according to the external radiation dose. The thickness is increased, and at least a layer containing water is provided on the peripheral wall, and water in the layer containing water is circulated .

  In order to work under radiation conditions using this cylindrical structure, the cylindrical structure is extended toward a destination point (for example, a meltdown reactor that emits a high radiation dose). At the same time, a passage is formed through which materials necessary for restoration work can be transported and workers can pass. Here, when the destination point is under severe radiation conditions, it is considered that the external radiation dose increases as the cylindrical structure approaches the destination point.

According to the construction method of the cylindrical structure of the present invention, the peripheral wall of the cylindrical structure is made thicker toward the inside of the passage along the thickness direction of the peripheral wall according to the external radiation dose. The following effects are achieved.
That is, an operator can increase the radiation shielding property of the peripheral wall by increasing the thickness of the peripheral wall of the cylindrical structure without going out from the inside of the passage of the installed cylindrical structure to the outside in the radiation state. Can do. Further, after securing the thickness of the peripheral wall according to the external radiation dose, the safety inside the passage is stably secured. Therefore, exposure of workers is prevented.
In addition, prevention in this specification is a concept including suppression, and the same applies hereinafter.

  In this way, at each location where the cylindrical structure is installed, according to the external radiation dose, by forming a peripheral wall with a thickness capable of shielding the radiation, the structure is not complicated more than necessary. The safety of workers in the passage can be ensured, and the cylindrical structure can be installed, for example, at a destination point under severe radiation conditions, so that restoration work can be performed efficiently and promptly.

Specifically, among the portion where the tubular structure is installed, for example, in the vicinity of the destination point in the harsh radiation conditions, as a circumferential wall of the tubular structure, radiation caries thia Alpha line, By laminating a layer containing water (preferably a layer containing light water, heavy water or boron water ) that can block almost all radiation such as beta rays, gamma rays, X-rays and neutron rays, Workers' exposure can be prevented and safety can be ensured .
Moreover, in the construction method of the cylindrical structure of the present invention, a pair of protective layers having radiation shielding properties and sandwiching the water-containing layer from both sides along the thickness direction may be provided on the peripheral wall. .
Moreover, in the construction method of the cylindrical structure of the present invention, the protective layer may be any one of a concrete layer, a metal layer, a graphite layer, and a polymer material layer.

  In order to extend the tubular structure in the ground, for example, a tunnel construction method such as a propulsion / traction method or an open-cut tunneling method can be used. In addition, the underground in this specification is a concept including not only the underground but also a semi-underground in which a part of the outer surface of the peripheral wall (the upper surface portion of the top wall portion, etc.) is exposed to the ground, and so on. It is.

  According to the construction method of the cylindrical structure of the present invention, recovery work can be performed efficiently while ensuring the safety of workers even under severe radiation conditions.

It is a top view which shows an example of the installation location of the cylindrical structure which concerns on one Embodiment of this invention, and the nuclear facility in which this cylindrical structure is installed. It is a front sectional view showing an example of a cylindrical body constituting the cylindrical structure according to the present embodiment. It is a front sectional view showing an example of a cylindrical body constituting the cylindrical structure according to the present embodiment. It is a sectional side view which shows an example of the cylindrical body which comprises the cylindrical structure which concerns on this embodiment. It is the figure which expands and shows (a) AA sectional drawing of FIG. 4, (b) BB sectional drawing, and (c) C section. It is a sectional side view explaining the connection procedure of the cylindrical body of the cylindrical structure which concerns on this embodiment, and cylindrical bodies. It is a figure which expands and shows the D section of FIG. It is a front sectional view showing an example of a cylindrical structure according to the present embodiment. It is a front sectional view showing an example of a cylindrical structure according to the present embodiment. It is a sectional side view which shows an example of the cylindrical structure which concerns on this embodiment.

Hereinafter, the cylindrical structure 1 which concerns on one Embodiment of this invention is demonstrated with reference to drawings.
As shown in FIG. 1, the cylindrical structure 1 of the present embodiment has been damaged greatly by natural disasters such as large-scale earthquakes and tsunamis and terrorist attacks. It is installed in a nuclear facility N such as a nuclear power plant that has occurred and is used for recovery work.

Specifically, the cylindrical structure 1 includes a work path, a work room, an operation room, and a facility (such as an atom) that releases damaged and dangerous high radioactivity (high radiation dose). It is a radiation protection culvert (radiation-resistant culvert) installed in the ground as a place (room) or the like that works close to the furnace building RB, the turbine building TB, etc., and is an underground installation type cylindrical shelter.
Note that the recovery work referred to in this specification includes not only emergency work immediately after the occurrence of the accident but also permanent work for decommissioning, for example. Moreover, the operation | work etc. for installing large machines, such as a crane unit used for taking out nuclear fuel melted down in the vicinity of a nuclear reactor, etc. are also included.

FIG. 1 is a top view of a nuclear facility N, which is constructed facing the sea. The tubular structure 1 of this embodiment is extended in the ground from the port and the inland toward the reactor building RB and the turbine building TB of the nuclear facility N. In addition, the cylindrical structure 1 may be installed in the whole location shown by the thick solid line in FIG. 1, or selectively installed, for example, in a location with a high radiation dose among the locations shown by the thick solid line May be. Further, the end of the end of the tubular structure 1 in the direction in which the tubular structure 1 is extended (the target point on which the work is performed) is inserted into, for example, a reach shaft or a basement of a building, and various operations, materials, Used for equipment in / out and workers in and out.
In FIG. 1, a reference sign S1 indicates a ship loaded with fresh water (light water), a reference sign S2 indicates a pump ship, a reference sign S3 indicates a crane ship, and a reference sign S4 indicates a radioactive substance. A contaminated tank ship for storing contaminated water (hereinafter abbreviated as contaminated water), and a waste liquid tank for storing contaminated water is indicated by the symbol T.
The pump ship S2 is of, for example, a 1000t class equipped with a power source, a pump, and a water storage tank. The pump ship S2 is moored at a port, and the pump ship S2 receives fresh water (light water) from the ship S1 loaded with fresh water. Supplied. A power cable and a liquid (light water) mother pipe are connected from the pump ship S2 to the end of the tubular structure 1 on the base end side (the side opposite to the destination point where the work is performed).

This cylindrical structure 1 has a cylindrical shape with a passage inside and is installed in the ground, and its peripheral wall is a concrete layer along the thickness direction according to the external radiation dose, At least one of a water-containing layer, a metal layer, a graphite layer, and a polymer material layer is provided. That is, the peripheral wall of the cylindrical structure 1 has radiation shielding properties and is formed so as to prevent radiation from entering the passage through the peripheral wall.
And in the construction method of the cylindrical structure 1 of this embodiment, the thickness of the said peripheral wall according to the external radiation dose obtained by measuring the surrounding wall of this cylindrical structure 1 with a radiation dosimeter etc., for example. The thickness is increased toward the inside of the passage along the vertical direction.
The term “radiation” as used herein refers to various types of radiation including particle rays such as alpha rays, beta rays, and neutron rays, and electromagnetic waves such as gamma rays and X-rays. Of these, it means having at least one or more radiation shielding properties.
Moreover, the cylindrical structure 1 is set as the structure by which the several cylindrical body was connected in the extension direction of the channel | path.

  2 to 7 show cylinders installed in places where the external radiation dose is low (the radiation dose in the nuclear facility N is relatively low) in the cylindrical body constituting the cylindrical structure 1. FIG. 3 is a cross-sectional view (a diagram showing a cross section perpendicular to the extending direction of a passage) of the cylindrical body 10. Specifically, the cylindrical body 10 is installed at a location where the external radiation dose is a low / medium level dose equivalent (less than 200 mSv / h) among the installation locations of the cylindrical structure 1. It is.

In FIG. 2, the cylindrical body 10 has a cylindrical shape, and its peripheral wall 11 has a single steel layer (metal layer). Specifically, this cylindrical body 10 is formed using, for example, a large-diameter steel pipe. The thickness of the peripheral wall 11 of the cylindrical body 10 (the thickness of the steel layer) is set according to the external radiation dose.
The peripheral wall 11 of the cylindrical body 10 may be a metal layer such as an aluminum layer or a lead layer, a concrete layer, or a polymer material layer made of plastic or synthetic resin, instead of the steel layer. In this case, a large-diameter pipe material corresponding to each material described above can be used.

In order to install such a cylindrical tubular body 10 in the ground, for example, a propulsion / traction method can be used. That is, while digging in the horizontal direction from the start pit of the start shaft using the shield excavator, the cylindrical body 10 is sequentially pushed in by the main push jack so as to be connected to the rear side of the shield excavator.
The cylindrical body 10 is composed of a plurality of segments divided in the circumferential direction, and these segments are connected to each other in the circumferential direction and the extending direction of the passage (the axial direction of the cylindrical body 10). The cylindrical structure 1 may be configured (installation by a shield method).

  Although not particularly illustrated, a lifting means such as a removable eye plate for lifting the cylindrical body 10 with a crane or the like is provided on the outer peripheral surface of the cylindrical body 10. Moreover, moving means such as detachable wheels or rollers for horizontally moving the cylindrical body 10 on the ground may be disposed on the outer peripheral surface of the cylindrical body 10. These lifting means and moving means are preferably removed when the tubular body 10 is embedded in the ground. Note that these lifting means and moving means may not be disposed on the cylindrical body 10.

  Inside the cylindrical body 10, an illumination member 14 that secures illuminance in the passage, a fluid transfer member 15 that supplies or discharges at least one of gas and liquid into the passage, and an electric wiring member 16. Are disposed.

  Specifically, the illumination member 14 is, for example, a fluorescent lamp, and a plurality of illumination members 14 are provided on the top wall portion on the inner peripheral surface of the cylindrical body 10 with an interval in the extending direction of the passage. The fluid transfer member 15 is, for example, a gas transport pipe such as an air supply duct or an exhaust air duct, or a liquid transport pipe for transporting water and other liquids, and a side wall portion on the inner peripheral surface of the cylindrical body 10. Are provided depending on the application, and extend in the direction in which the passage extends. In the example shown in FIG. 2, for the gas transport pipe of the fluid transfer member 15, the air supply air duct (lower left portion in the figure) sends air toward the lower space in the passage, and the exhaust air duct ( The upper right portion in the figure is configured to suck air from the upper space in the passage. If a radioactive substance enters the passage, the radioactive substance easily floats in the upper space in the passage, and this configuration further enhances the safety in the passage. The electrical wiring member 16 is, for example, a power supply cable or an electrical signal cable, and a plurality of electrical wiring members 16 are provided depending on the application and extend in the direction in which the passage extends.

  In addition, a floor plate 17 on which a vehicle such as a cart and a worker P are placed and passed is disposed on the bottom wall portion on the inner peripheral surface of the cylindrical body 10, and the floor plate 17 includes the floor plate 17. An accommodation portion 18 is formed which is recessed from the upper surface and extends in the direction in which the passage extends, and can accommodate the electrical wiring member 16 and the like. Further, what is indicated by reference numeral 19 in FIG. 2 is a lid that covers the accommodating portion 18 so as to be opened and closed.

Although not particularly illustrated, the tubular body 10 of the tubular structure 1 includes moisture retaining means for retaining moisture in the ground outside the peripheral wall 11.
Specifically, as the moisture retaining means, for example, a liquid discharge pipe that discharges liquid from the inside of the passage toward the outside of the peripheral wall 11 is provided. The liquid discharge pipe penetrates the peripheral wall 11 in the thickness direction, and liquid such as liquid nitrogen or water glass (aqueous solution of alkali silicate glass) is circulated therein, and the liquid is grounded around the peripheral wall 11. Can be released.
Instead of using the liquid discharge pipe as the moisture retaining means, for example, a flow path is formed in the wall of the peripheral wall 11, and a part thereof is opened to the outside of the peripheral wall 11, or a pipe material is formed on the outer surface of the peripheral wall 11. And a plurality of openings may be opened at intervals in the extending direction of the passage.

  FIG. 3 shows another example of the cylindrical body 10 described above. The cylindrical body 10 in FIG. 3 has a rectangular tube shape with a polygonal cross section (in the illustrated example, a quadrangle), and the peripheral wall 11 has a single concrete layer. In addition, as the surrounding wall 11, it is good also as using the metal layer mentioned above, a polymeric material layer, etc. instead of a concrete layer.

  In order to install such a rectangular tubular body 10 in the ground, for example, an open-cut tunneling method can be used. That is, a retaining wall is created from the ground surface so that a groove is formed along the extending direction of the cylindrical structure 1 on the ground surface, and the ground is dug down to a predetermined depth while preventing the surrounding ground from collapsing with a retaining support. Then, the tubular body 10 is installed in the excavated groove by a lifting machine such as a crane and connected, and then backfilling is performed.

Further, in the cylindrical body 10 of FIG. 3, the floor plate 17, the accommodating portion 18, and the lid 19 described above are not provided, and the electric wiring member 16 is disposed on the side wall portion on the inner peripheral surface of the cylindrical body 10. ing.
As such a rectangular tube-shaped tubular body 10, a concrete box culvert having a desired radiation shielding property on the peripheral wall, a steel vessel container, or the like can be used. In this case, the manufacturing cost is reduced. Since it can do, it is preferable.

FIG. 4 shows a state in which a plurality of cylindrical bodies 10 described in FIG. 3 are connected in the extending direction of the passage, and shows a connection structure between adjacent cylindrical bodies 10.
As shown in FIG. 4, in the cylindrical structure 1, the cylindrical bodies 10 adjacent to each other in the extending direction of the passage are connected from either the inside or the outside of the passage. In the illustrated example, adjacent cylindrical bodies 10 are connected from the inside of the passage.

  4 and 5 (a) (c), the end of the tubular body 10 in the extending direction of the passage projects toward the inside of the passage, and the periphery of the opening periphery of the end. An annular flange portion 21 extending along the direction is formed. Further, a plurality of through holes penetrating in the extending direction are formed in the flange portion 21 at intervals in the circumferential direction.

  In FIG. 5C, the adjacent cylindrical bodies 10 are in a state in which a packing member 22 made of rubber, silicon packing, an O-ring or the like is disposed around the through hole between the flange portions 21 facing each other. Thus, the bolts and nuts inserted through the through holes are connected. In addition, a radiation leak preventing member 23 made of iron (steel), lead, concrete, or the like formed in a frame shape along the circumferential direction is disposed in contact with an end face facing the inside of the passage in the flange portion 21. The radiation leak preventing member 23 closes a gap between the opposing flanges 21 (a gap between opposite ends of the adjacent cylindrical bodies 10), and a radioactive substance enters the passage from this gap or emits radiation. Is prevented from entering.

  Moreover, the connection part of the cylindrical bodies 10 in the right end of FIG. 4 and what is shown by FIG.5 (b) are connection structures different from the connection structure mentioned above, In this example, the path | route of the cylindrical body 10 is shown. The flange portion 21 is not provided at the end portion in the extending direction, and instead, a plurality of tightening members 24 are provided at the end portion on the inner peripheral surface of the peripheral wall 11 at intervals in the circumferential direction. The fastening member 24 is formed with a through hole penetrating in the extending direction. The clamping members 24 that face each other at the end portions of the adjacent cylindrical bodies 10 are connected by bolts and nuts that are inserted through the through holes, thereby connecting the adjacent cylindrical bodies 10 to each other. In this example, end surfaces facing the extending direction are abutted on the peripheral wall 11 of the cylindrical body 10, and the radiation leak preventing member 23 is formed on the inner peripheral surface of the peripheral wall 11 so as to close the gap between the end surfaces. Abutment is arranged. The radiation leak preventing member 23 is preferably disposed after the gap between the end faces is sealed with a sealing material such as putty or silicon caulking.

  In FIG. 4, the fluid transfer members 15 of the cylindrical body 10 adjacent to each other in the extending direction of the passage are connected to each other via a connecting portion 25 such as a short pipe and a flange. Although not particularly shown, the electrical wiring members 16 of the adjacent cylindrical bodies 10 are connected to each other via a terminal block, a socket, a connector, and the like.

4 and 5, the connecting structure for connecting the adjacent cylindrical bodies 10 to each other from the inside of the passage has been described. However, for example, when the external radiation dose is low, the same configuration is used for the cylindrical body 10. It is good also as a connection structure which connects the cylindrical bodies 10 adjacent to each other from the outside of the passage. When connecting adjacent cylindrical bodies 10 from the exterior of a channel | path, airtightness and robustness can be ensured by using the connection structure of the flange part 21 mentioned above for the outer peripheral surface of the cylindrical body 10, and it is preferable. Further, in this case, it is desirable to connect the tubular bodies 10 to each other before performing the backfilling in the above-described open tunnel method.
Moreover, you may use the structure (sleeve joint structure, insertion joint structure) by which the edge parts of the adjacent cylindrical body 10 are fitted in the extension direction of a channel | path as another connection structure, for example.

As shown in FIGS. 6 and 7, the tubular body 10 of the present embodiment has a removable protective wall 26 that covers both ends in the extending direction of the passage.
The protective wall 26 is made of, for example, an acrylic plate, a vinyl plate, an iron plate, or the like, and is formed in a shape corresponding to the cross-sectional shape of the peripheral wall 11 of the cylindrical body 10. In the illustrated example, the peripheral wall 11 of the cylindrical body 10 is formed in a quadrangular cross section, and the protective wall 26 is formed in a quadrangular plate shape correspondingly.

The outer peripheral edge portion of the protective wall 26 is folded back in the extending direction of the passage, and the folded portion is brought into contact with the inner circumferential surface of the peripheral wall 11 and screwed. Further, the inner peripheral surface portion of the corresponding peripheral wall 11 is covered from the end surface of the folded portion so as to close the gap between the folded portion of the protective wall 26 and the inner peripheral surface of the peripheral wall 11 so that the putty or the like is removable. A sealing member 27 is provided (applied).
Thus, in the present embodiment, both ends of the cylindrical body 10 in the extending direction are closed by the pair of protective walls 26. The protective wall 26 only needs to cover both ends of the cylindrical body 10. For example, the protective wall 26 is provided with a check valve structure, and the pressure in the cylindrical body 10 increases. In this case, the air in the passage may be allowed to escape to the outside through the check valve structure.

In order to connect the cylindrical body 10 provided with the protective wall 26 to another cylindrical body 10, as shown in FIG. 6, the end portions of the cylindrical bodies 10 to be connected are arranged close to each other. After the worker P connects the ends of the cylindrical body 10 (or before connecting), the screw and the sealing member 27 are removed, and the protective wall 26 is removed.
When the open-cut tunneling method is used, the right side in FIG. 6 is the front end side in the extending direction of the cylindrical structure 1, and the new cylindrical body 10 with the protective wall 26 attached is a cylindrical structure. It is connected to the end of the object 1 on the front end side. When the propulsion / traction method is used, the left side in FIG. 6 is the forward direction of the shield excavator, and the new cylindrical body 10 with the protective wall 26 attached is a cylindrical structure from the start shaft. 1 is connected to the end of the base end side (the right side in FIG. 6) of 1.

  Further, for the purpose of simplifying the work of removing the protective wall 26 and allowing the insides of the cylindrical bodies 10 to communicate with each other quickly, the protective wall 26 may be destroyed using, for example, a hammer. In addition, although not particularly illustrated, it is desirable that the worker P who performs the connecting operation of the cylindrical body 10 appropriately wears protective clothing or a mask having radiation shielding properties in consideration of the possibility of radioactive contamination. .

Further, for the purpose of preventing the radioactive substance from entering the existing cylindrical body 10, the end of the cylindrical body 10 (specifically, the cylindrical body 10 is newly formed in the extending direction of the passage). The protective wall 26 may be provided at the end facing the connecting direction), and the protective wall 26 may be removed after the new tubular body 10 is approached or abutted from this state.
In this embodiment, since the air conditioning unit is provided as the cylindrical body 10 as will be described later, in the connection work between the cylindrical bodies 10, the radioactive material may enter the passage and be radioactively contaminated. Even in such a case, it is possible to ensure the safety by performing decontamination and a leak test.

  8 to 10 are cross-sectional views of the cylindrical bodies 30 and 40 that are installed at locations where the external radiation dose is high among the cylindrical bodies constituting the cylindrical structure 1. In addition, in the cylindrical bodies 30 and 40, the same code | symbol is attached | subjected to the same member as the cylindrical body 10 mentioned above, and the description is abbreviate | omitted.

  Specifically, the cylindrical body 30 is installed at a location where the external radiation dose is a high level dose equivalent (about 10 to 500 mSv / h), for example, among the installation locations of the cylindrical structure 1. The peripheral wall 31 of the cylindrical body 30 is configured to protect the inside of the passage mainly from gamma rays. The cylindrical body 30 is used, for example, when the nuclear fuel is in a subcritical state and the dose of emitted neutron rays is relatively small.

  In addition, the cylindrical body 40 is installed, for example, in the installation location of the cylindrical structure 1, for example, the external radiation dose is a severe dose equivalent (200 millisievert / h or more) that is greatly affected by the neutron beam. The peripheral wall 41 of the cylindrical body 40 is configured to protect the inside of the passage mainly from neutron rays and gamma rays. The cylindrical body 40 is used, for example, when a large amount of neutron beams are emitted from a recritical nuclear fuel.

  The cylindrical body 30 (40) of the cylindrical structure 1 has a cylindrical shape with a passage inside, and its peripheral wall 31 (41) has a radiation shielding property with the layer 33 (43) containing water. And a pair of protective layers 32 (42) and 34 (44) sandwiching the water-containing layer 33 (43) from both sides along the thickness direction of the peripheral wall. In the following description, of the pair of protective layers 32 (42) and 34 (44), the protective layer disposed outside in the thickness direction with respect to the water-containing layer 33 (43) is referred to as the outer layer 32 (42). In other words, the protective layer disposed on the inner side in the thickness direction is referred to as an inner layer 34 (44).

  In the construction method of the cylindrical structure 1 of the present embodiment, the outer layer 32 (42) of the peripheral wall 31 (41) of the cylindrical structure 1 is used as a reference layer, and depending on the external radiation dose. The layer 33 (43) and the inner layer 34 (44) containing water are laminated toward the inside of the passage along the thickness direction with respect to the reference layer.

  In FIG. 8, the cylindrical body 30 has comprised the rectangular cylinder shape, and the outer layer 32 of the surrounding wall 31 is formed with the single concrete layer. As the outer layer 32, a metal layer such as a steel layer or an aluminum layer may be used instead of the concrete layer.

The inner layer 34 of the peripheral wall 31 includes a first inner layer 34a located on the outer side in the thickness direction and a second inner layer 34b located on the inner side in the thickness direction.
The first inner layer 34a is formed of a lead layer (metal layer), and the second inner layer 34b is formed of an iron (steel) layer (metal layer). As the first inner layer 34a, a graphite layer may be used instead of the lead layer. As such a first inner layer 34a, a block material or a plate material made of lead, graphite or the like can be used.

A support member (not shown) is disposed between the outer peripheral surface of the first inner layer 34 a of the peripheral wall 31 and the inner peripheral surface of the outer layer 32, and the inner side of the outer layer 32 in the thickness direction is provided by the support member. The inner layer 34 is fixedly supported with a gap therebetween.
Then, the layer 33 containing water is applied to a porous member having a property of easily infiltrating water such as sponge and urethane disposed in the gap, and water (herein, water is, for example, fresh water (light water)). Covering with a vinyl material the one containing the property of shielding radiation (especially neutron beam) such as heavy water and boron water, including the water of the cylindrical body 40 described later) It is configured. In the layer 33 containing water, the vinyl material may not be disposed in the region that contacts the concrete layer of the outer layer 32. Further, as the layer 33 containing water, a gel member containing water may be used instead of using a porous member containing water.

  In addition, although not particularly illustrated, a portion corresponding to the water-containing layer 33 in the end surface of the peripheral wall 31 facing the passage extending direction is provided with a blocking portion that closes the water-containing layer 33 in a liquid-tight manner. ing. For example, a member having a property of not allowing water to pass between the outer layer 32 and the inner layer 34 at the end in the extending direction of the peripheral wall 31 is inserted in the closing portion, or the outer layer 32 (inner layer 34) The layer 33 containing water is provided by liquid-tightly closing the layer 33 containing water by folding the end portion in the extending direction toward the inside (outside) in the thickness direction. Further, the closing portion may be formed at the end of the peripheral wall 31 in the extending direction so as to cover the outer layer 32, the layer 33 containing water, and the inner layer 34 from the outside in the extending direction. Specifically, a closed portion made of, for example, a single concrete layer having the thickness of the peripheral wall 31 is formed at an end of the peripheral wall 31 in the extending direction, and the extending direction of the closed portion is Further, an outer layer 32, a layer 33 containing water, and an inner layer 34 may be provided on the inner side, and the layer 33 containing water may be liquid-tightly sealed by the closed portion.

The thickness of the peripheral wall 31 of the cylindrical body 30, and the thicknesses of the outer layer 32, the water-containing layer 33, and the inner layer 34 constituting the peripheral wall 31 are set according to the external radiation dose.
The outer layer 32 may have a configuration in which a plurality of layers are stacked in the thickness direction, like the inner layer 34. The cylindrical body 30 may be formed in a cylindrical shape.
Moreover, the connection structure similar to the cylindrical body 10 mentioned above can be used about the connection structure of the cylindrical bodies 30 adjacent to the extension direction of a channel | path.

  9 and 10, the cylindrical body 40 has a cylindrical shape, and the outer layer 42 and the inner layer 44 of the peripheral wall 41 are each formed of a single steel layer (metal layer). As the outer layer 42 and the inner layer 44, instead of a steel layer, a metal layer such as an aluminum layer or a lead layer, a concrete layer, a polymer material layer made of plastic or synthetic resin may be used.

Further, a plurality of support members 45 are disposed between the inner peripheral surface of the outer layer 42 of the peripheral wall 41 and the outer peripheral surface of the inner layer 44, and the support member 45 causes the outer layer 42 to move inward in the thickness direction. The inner layer 44 is fixedly supported with a gap. The cylindrical body 40 thus configured has a double tube structure.
A water-containing layer 43 is formed by filling the gap formed between the outer layer 42 and the inner layer 44 in a liquid-tight manner.
The thickness of the peripheral wall 41 of the cylindrical body 40 and the thicknesses of the outer layer 42, the water-containing layer 43 and the inner layer 44 constituting the peripheral wall 41 are set according to the external radiation dose.

In FIG. 9, what is indicated by reference numeral 46 is a water sealing port for supplying water to the gap between the outer layer 42 and the inner layer 44 after assembling the cylindrical body 40 into a double tubular shape. After filling and forming a layer 43 containing water, the water sealing port 46 is sealed. In the illustrated example, the water sealing port 46 is opened on the outer peripheral surface of the peripheral wall 41, but may be opened on the inner peripheral surface of the peripheral wall 41 (opening toward the inside of the passage).
Also, what is indicated by reference numeral 47 is a circulation pipe for taking out the water of the layer 43 containing water into the passage and then returning it to the layer 43 containing water again. That is, since the location where the cylindrical body 40 is installed in the cylindrical structure 1 is under severe radiation conditions, water is activated by the radiation that reaches the layer 43 containing water through the outer layer 42, and the radiation It is conceivable that the shielding performance deteriorates. Therefore, the cylindrical body 40 has a circulation structure that circulates the water of the layer 43 containing water, and the radiation shielding performance is stabilized by circulating such water and appropriately treating (exchange or clean). To ensure it.

  What is indicated by reference numeral 48 is an outflow pipe for extracting water from the water-containing layer 43 to the circulation pipe 47, and what is indicated by reference numeral 49 is an inflow for sending water from the circulation pipe 47 to the water-containing layer 43. It is a tube. What is indicated by reference numeral 50 is a protective cover.

As shown in FIG. 10, in order to connect the cylindrical bodies 40 adjacent in the extending direction of the passage, the inner layer 44 is inserted into the outer layer 42 from the extending direction. And in the edge part which the adjacent cylindrical body 40 opposes, the flange parts 51 formed in the outer layer 42 and the flange parts 52 formed in the inner layer 44 are connected. This process is sequentially repeated to increase the number of cylindrical bodies 40, and after assembly, water is sealed in the gap between the outer layer 42 and the inner layer 44. In the illustrated example, the flange portions 51 and 52 have an outer flange shape protruding outward in the radial direction. However, when using a propulsion / traction method, the flange portions 51 and 52 are radially inward. It is preferable that it is set as the inner flange shape which protrudes toward.
In each cylindrical body 40, both ends in the extending direction in the gap between the outer layer 42 and the inner layer 44 are sealed in advance, and the gap is configured to be liquid-tight, and the same as the cylindrical body 10 described above. A connecting structure may be used. In this case, the water sealing port 46, the outflow pipe 48, and the inflow pipe 49 are preferably provided in each cylindrical body 40.

Moreover, when the external radiation dose is not so high that the water of the layer 43 containing water is denatured, a configuration in which water is not circulated may be used. In this case, the circulation pipe 47, the outflow pipe 48, and the inflow pipe 49 may not be provided.
Further, in the cylindrical body 40, instead of the water-containing layer 43, a molten metal such as lead is injected into the gap between the outer layer 42 and the inner layer 44 and the metal is solidified to form a solid intermediate layer. May be. Also in this case, the circulation pipe 47, the outflow pipe 48, and the inflow pipe 49 are unnecessary.

  In FIG. 10, a reference numeral 53 indicates a boron water tank, a reference numeral 54 indicates a pump, a reference numeral 55 indicates an on-off valve, and a reference numeral 56 indicates a check valve. The reference numeral 57 indicates an end sealing lid, and the reference numeral 58 indicates an injection pipe joint. Specifically, the distal end of the cylindrical structure 1 (the end on the destination point where the work is performed) is arranged at a position approaching the front of a harsh radiation environment such as a nuclear reactor. Since further radiation-proof protection may be required, light water, boron water, or concrete can be injected and filled into the distal end portion of the tubular body 40 through the injection pipe joint 58. The reference numeral 59 indicates a removable lead cover, the reference numeral 60 indicates a rail, and the reference numeral 61 indicates an attachment. Specifically, the rail 60 provided at the upper portion of the distal end portion of the cylindrical body 40 is equipped with a self-propelled radiation-resistant camera, a radiation detector, or the like that can move forward and backward on the rail 60 as an attachment 61. The In addition, a work unit that can be remotely operated as an attachment 61 (a work unit here refers to an entire tubular body to be described later) on the surface (tip surface) facing the distal end side at the distal end portion of the tubular body 40. Including, but not limited to, working machines such as magic hands, shovels, rock drills, cranes (those for throwing in materials that shield radioactive materials or materials such as sand that subdues recriticality or fire) ) Is installed. In addition, since the rail 60 and the attachment 61 are provided on the outer peripheral surface and the front end surface of the cylindrical body 40, a space is formed on the outside (radially outer side and front end side portion) of the peripheral wall 41 of the cylindrical body 40. (For example, when the front-end | tip part of this cylindrical body 40 is inserted in the underground shaft or the basement of a building).

  Moreover, the cylindrical structure 1 of this embodiment is a cylindrical body 10, 30, 40 (henceforth abbreviated as a cylindrical body), a passage unit, a work unit, an operation unit, an isolation unit, a radiation dose monitoring unit, air At least one unit (module unit) is provided among the adjustment unit, the pump unit, the power supply unit, the decontamination unit, the carry-in unit, and the inlet / outlet unit.

Among each unit mentioned above, a passage unit is used for the purpose of the worker P and vehicles passing through an internal passage.
Work units include cranes, lifting machines such as cranes, magic hands, up and down excavators, rock drills, and other types of work machines. Workers P removes radioactive pollutants (contaminated water, etc.). In addition, it is used for the purpose of performing welding work, watering work, debris treatment work, and the like. The work unit is also used as a work place where the worker P works inside the passage and as a refuge when working outside the passage.
Here, when the work unit is provided with various work machines, for example, the tip of the cylindrical structure 1 is inserted into the reach shaft or the basement of the building, and the work by the machine is performed at the tip. Applicable when necessary. When using a lifting machine such as a crane, the column of the crane is extended upwardly through the top wall portion of the peripheral wall of the cylindrical body in an airtight manner.
The operation unit is used for the purpose of the operator P performing the operation from the inside of the passage when working with various work machines. In this case, the various work machines may be installed not only in the work unit but also outside the cylindrical structure 1.

The isolation unit is used for the purpose of isolating the inside of the cylindrical structure 1 from other units (cylindrical bodies) contaminated with radioactive substances. Specifically, the isolation unit includes, for example, a pair of units that are provided with airtight hatches at both ends in the extending direction of the passage and are connected to both ends in the extending direction with the isolation unit interposed therebetween. Of these, the radioactive substance can be prevented from flowing from one unit to another unit.
The radiation dose monitoring unit is used for the purpose of monitoring various radiation doses detected at least either outside or inside the cylindrical structure 1.

The air adjustment unit is used for the purpose of ventilating the air inside the cylindrical structure 1 or purifying the air with an air supply filter or an exhaust filter. In addition, it is more preferable that the air conditioning unit has a configuration in which the airtightness inside the passage can be confirmed (leak test) after connecting a plurality of cylindrical bodies. The air conditioning unit may be used as equipment for supplying ventilation (clean air) to the reactor building RB, turbine building TB, etc., or for circulating and purifying air in the building such as RB and TB. it can.
In addition, when the pump unit is provided with a layer containing water on the peripheral wall of the cylindrical structure 1, the liquid is supplied to the layer when water is supplied or drained, or when the liquid is used for recovery work. It is used in. The pump unit is also used for supplying a predetermined liquid to the liquid discharge pipe of the moisture holding means.
The power supply unit is used for the purpose of supplying electric power to the inside and outside of the cylindrical structure 1 and to machines and devices necessary for work.

The decontamination unit is used for the purpose of decontamination in advance so that the worker P entering and exiting the cylindrical structure 1 is contaminated with radioactive material or does not bring the radioactive material into the passage. is there.
The carry-in unit is used for the purpose of carrying in a small tubular body for extending the tubular structure 1 or carrying materials into the tubular structure 1. The carry-in port of the carry-in unit is provided, for example, at the top wall of the peripheral wall so that it can be opened and closed, and the cylindrical structure is semi-underground so that the shaft is dug from the ground surface toward the carry-in port or the carry-in port is exposed to the ground surface. It is possible to use the carry-in entrance by installing it in When the inside of the unit is required to be sealed, a hatch is attached to the carry-in entrance.
In this tubular structure 1, as a tubular body, one tubular body (a large tubular body such as the carry-in unit) and another tubular body (small tube) that can be accommodated in one tubular body. The cylindrical structure 1 is extended by feeding the other cylindrical body from the end portion (tip portion) in the extending direction of the passage of one cylindrical body. It has a set configuration. Such a small tubular body is used, for example, when the tubular body is extended in a space in the building after the distal end portion of the tubular structure 1 is inserted into the basement of the building.
In addition, the entrance / exit unit is used for the purpose of allowing the worker P to enter and exit the cylindrical structure 1 and to take materials in and out. Stairs, ladders, and the like are provided at the entrance / exit of the entrance / exit unit, and the entrance / exit is provided on the peripheral wall so as to be openable and closable, similarly to the entrance of the carry-in unit described above.
A plurality of functions of each unit described above may be provided for one cylindrical body.

  Further, as units other than the above-described units, a living room unit used for the purpose of carrying out office work, meetings, meals, breaks, etc. inside the tubular structure 1, an upper part of other units, The lower part is laminated so that the passages communicate with each other, and includes means for moving between upper and lower units such as stairs, and the passage of the layered (staircase) unit constituting the three-dimensional hierarchy and the tubular structure 1 is branched. When a branch unit used for the purpose and a flexible flexible joint unit that can easily connect cylindrical bodies having different passage directions are provided, recovery work can be performed more efficiently and safely. Therefore, it is preferable.

  In order to perform work under radiation conditions using the tubular structure 1 described above, the tubular structure is underground in the ground toward a destination point (for example, a meltdown reactor that emits a high radiation dose). The structure 1 is extended and a passage through which materials necessary for the restoration work can be transported and the worker P can pass is formed. Here, when the destination point is under severe radiation conditions, it is conceivable that the external radiation dose increases as the cylindrical structure 1 approaches the destination point.

According to the construction method of the cylindrical structure 1 of the present embodiment, the peripheral wall of the cylindrical structure 1 is thickened toward the inside of the passage along the thickness direction of the peripheral wall according to the external radiation dose. The following effects are achieved.
That is, the worker P increases the thickness of the peripheral wall of the cylindrical structure 1 without going out of the passage of the installed cylindrical structure 1 to the outside under the radiation condition, and the radiation shielding property of the peripheral wall is increased. Can be improved. Further, after securing the thickness of the peripheral wall according to the external radiation dose, the safety inside the passage is stably secured. Therefore, the exposure of the worker P is prevented.

  In this way, at each location in the ground where the cylindrical structure 1 is installed, the structure is unnecessarily complicated by forming a peripheral wall with a thickness capable of shielding radiation according to the external radiation dose. Therefore, it is possible to secure the safety of the worker P in the passage, and to install the cylindrical structure 1 up to, for example, immediately below the destination point under severe radiation conditions, so that the restoration work can be performed quickly and efficiently. be able to.

Further, the peripheral wall of the cylindrical structure 1 includes at least one layer of a concrete layer having radiation shielding properties along the thickness direction, a layer containing water, a metal layer, a graphite layer, and a polymer material layer. Therefore, the following effects are achieved.
That is, among the places where the cylindrical structure 1 is installed, for example, in the vicinity of a destination point under severe radiation conditions, as a peripheral wall of the cylindrical structure 1, alpha rays, beta rays, and gamma rays of radiation are included. By providing a concrete layer or a layer containing water (preferably a layer containing light water, heavy water, or boron water) that can shield almost all X-rays and neutron rays, etc., It can prevent and secure safety.

  On the other hand, at a location far from the destination point and where the radiation dose is relatively low, as a peripheral wall of the cylindrical structure 1, for example, a metal capable of shielding at least one of alpha rays, beta rays, gamma rays and X-rays of radiation By providing a layer (for example, a layer made of lead, steel, or aluminum), a graphite layer, or a polymer material layer (for example, a layer made of plastic or synthetic resin), the structure of the cylindrical structure 1 is not complicated. The exposure of the worker P in the passage can be prevented and safety can be ensured.

Furthermore, it is also possible to form the peripheral wall of the cylindrical structure 1 by appropriately combining (stacking) the layers made of the above-described materials in the thickness direction according to the external radiation dose. Safety will be improved.
In the construction method of the cylindrical structure 1 of the present embodiment, the peripheral wall includes a reference layer (outer layer) made of any one of a concrete layer, a metal layer, and a polymer material layer, and the reference is determined according to the external radiation dose. In order to laminate at least one of a concrete layer, a water-containing layer, a metal layer, a graphite layer, and a polymer material layer toward the inside of the passage along the thickness direction with respect to the layer (See, for example, FIGS. 8 to 10), the reference layer on the peripheral wall is laminated on the inner side of the passage of the reference layer according to the type of radiation and the radiation dose at the location where the cylindrical structure 1 is installed. By appropriately combining the layers to be made, safety inside the passage can be sufficiently secured.
In addition, what is necessary is just to form a new radiation shielding layer from the inside of a surrounding wall, when the radiation dose of the exterior of this cylindrical structure 1 increases after constructing the cylindrical structure 1. FIG.

Moreover, in the cylindrical structure 1 demonstrated using FIGS. 8-10, the surrounding wall has a layer containing water, and a pair which has radiation shielding property and sandwiches the layer containing water from the thickness direction of a surrounding wall. The protective layer is provided with the following effects. Of the pair of protective layers, the outer layer is the reference layer.
That is, since the peripheral wall includes a layer containing water (preferably, a layer containing light water, heavy water, or boron water), almost all of radiation such as alpha rays, beta rays, gamma rays, X rays, and neutron rays. Can be shielded. Further, since a pair of protective layers sandwiching the water-containing layer from the thickness direction is formed on the peripheral wall, as described above, the protective layer includes the water-containing layer with high radiation shielding properties. Since the protective layer itself has radiation shielding properties while maintaining the shape stably, the radiation shielding properties as a whole peripheral wall are sufficiently enhanced. Therefore, the exposure of the worker P in the passage can be prevented, and safety can be ensured.

Specifically, according to the structure of the peripheral wall 31 described with reference to FIG. 8, for example, a small amount of neutron radiation emitted from a nuclear fuel in a subcritical state is protected from the concrete layer while the water-containing layer 33 reliably protects the neutron beam. The protective layer 32 and the protective layer 34 made of a lead layer and an iron (steel) layer can reliably protect the gamma rays and prevent the worker P from being exposed in the passage.
Further, according to the structure of the peripheral wall 41 described with reference to FIGS. 9 and 10, for example, the water-containing layer 43 reliably protects neutron rays emitted from a nuclear fuel in a recritical state, while the water-containing layer 43 reliably protects the water. The layer 43 containing the steel and the protective layers 42 and 44 made of steel can reliably protect the gamma rays and prevent the worker P from being exposed in the passage.

  And since this cylindrical structure 1 is installed in the ground, the radiation radiated from the ground toward the cylindrical structure 1 is shielded and reduced by moisture in the ground, and the like. The effect of preventing the arrival of radiation to the water can be obtained more remarkably. In addition, since it is installed in the ground, the thickness of the peripheral wall is sufficiently secured in advance for the purpose of ensuring the strength against the weight of the soil, etc., so that the radiation shielding property of the peripheral wall is sufficiently ensured. The amount of increase in the thickness of the peripheral wall toward the inside of the passage can be reduced (for example, when the peripheral wall is made of a concrete layer, the thickness is at least 20 cm or more).

Specifically, when the peripheral wall of the cylindrical structure 1 is buried underground without being exposed to the ground surface, the above-described effects are easily obtained with certainty. In addition, for example, in the case where it is installed in the semi-basement so that only the top wall portion of the peripheral wall is exposed to the ground surface, and if it is configured to have an entrance / exit entrance that can be opened and closed on the top wall portion, enter the passage It is possible to efficiently move the worker P in and out, and carry in and out the materials and equipment while preventing the radiation from reaching.
In addition, for the purpose of preventing radioactive contamination of the groundwater of the nuclear facility N, a groundwater flow path may be formed in the passage of the cylindrical structure 1.

  Moreover, in the construction method of the cylindrical structure 1 of this embodiment, since moisture was held in the ground outside the peripheral wall, the following effects are produced.

Specifically, the cylindrical structure 1 of the present embodiment is provided with a moisture retaining means for retaining moisture in the ground outside the peripheral wall.
That is, by the water retaining means, for example, liquid nitrogen is released to the outside of the peripheral wall to freeze the water in the ground, or water glass is discharged to hold the water in the ground, thereby The radiation shielding property in the ground can be improved. Thereby, not only the radiation shielding property of the surrounding wall of the cylindrical structure 1 but also the radiation shielding property in the ground outside the surrounding wall can be secured stably, and the safety in the passage is further improved.
Further, in this case, since the flow of underground fluid outside the peripheral wall is restricted, for example, contaminated groundwater is prevented from reaching the peripheral wall of the cylindrical structure 1.
In addition, when using liquid nitrogen, by discharging liquid nitrogen not only around the peripheral wall of the cylindrical structure 1 but also into the ground on the tip side in the extending direction, the soil and the bedrock are frozen, Drilling can be performed more efficiently and safely.

  In addition, since the cylindrical structure 1 is configured by connecting a plurality of cylindrical bodies, the structure of the peripheral walls of these cylindrical bodies is changed to external radiation at locations in the ground where the respective cylindrical bodies are installed. Each can be set according to the amount. Therefore, the effects described above can be obtained easily and reliably.

Moreover, since the cylindrical bodies adjacent in the extending direction of the passage are connected from either the inside or the outside of the passage, the following effects can be obtained.
That is, for example, when the external radiation dose at the location where the cylindrical body is installed is high, or when it is desired to ensure the safety of the worker P, by connecting the cylindrical bodies from the inside of the passage, It is possible to prevent the worker P performing this connection work from being exposed. Moreover, when the external radiation dose in the location which installs a cylindrical body is low, a connection operation | work can be performed more rapidly by connecting a cylindrical body from the exterior of a channel | path. In addition, when connecting cylindrical bodies from the exterior of a channel | path, it is preferable to use an open-cut tunnel method.

  In addition, since the protective walls 26 are provided at both ends of the tubular body in the extending direction of the passage, work when transporting the tubular body or connecting the tubular body to another tubular body. Sometimes, radioactive material can be prevented from entering the inside of the cylindrical body, and radioactive contamination in the passage can be prevented. In addition, since the protective wall 26 can be removed after completion | finish of a connection operation | work, a channel | path can be used effectively, ensuring the safety | security in a channel | path.

Moreover, the cylindrical body of the cylindrical structure 1 has one cylindrical body and another cylindrical body that can be accommodated in the one cylindrical body, and the other cylindrical body is When it is the structure extended by being sent out from the edge part of the extension direction of the channel | path of one cylindrical body, there exist the following effects.
That is, in this case, when the cylindrical structure 1 is extended, the other cylindrical body is sent out from the end portion in the extending direction of the passage of the one cylindrical body through the inside of the passage of the one cylindrical body. Therefore, the cylindrical body can be extended without the worker P appearing outside the passage with a high radiation dose. In addition, according to this configuration, for example, the tubular body can be extended toward the destination while securing safety even in a building or the like where a crane or other lifting machine cannot be provided.

In addition, as a cylindrical body of the cylindrical structure 1, a passage unit, a work unit, an operation unit, an isolation unit, a radiation dose monitoring unit, an air conditioning unit, a pump unit, a power supply unit, a decontamination unit, a carry-in unit, and an entrance / exit unit Since at least one or more units are provided, the following effects are obtained.
That is, the recovery operation can be performed more efficiently and safely by appropriately using, as the cylindrical body, a unit having a function corresponding to the installation location and application.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above-described embodiment, the cylindrical structure 1 is installed in the ground. However, the present invention is not limited to this, and the cylindrical structure 1 may be installed on the ground. In this case, the extension toward the destination point and the construction of each unit are simple, the installation of the cylindrical structure 1 is simple, and the formation of the passage is easy.

  Moreover, in above-mentioned embodiment, in FIGS. 8-10, the outer layer 32 (42) is made into the reference | standard layer among the surrounding walls 31 (41) of the cylindrical structure 1, According to the external radiation dose, The peripheral wall 31 (41) is thickened by laminating the layer 33 (43) and the inner layer 34 (44) containing water toward the inside of the passage along the thickness direction with respect to the reference layer. However, the present invention is not limited to this. That is, for example, with respect to the peripheral wall 11 shown in FIGS. 2 and 3, the same material as the peripheral wall 11 is attached to the inner peripheral surface and solidified to increase the thickness toward the inside of the passage. It doesn't matter.

  Moreover, you may combine suitably the component demonstrated by the above-mentioned embodiment of this invention. In addition, the above-described components can be replaced with well-known components without departing from the spirit of the present invention.

1 cylindrical structure 11, 31, 41 peripheral wall 32, 42 outer layer (reference layer)
33, 43 Water-containing layers (layers stacked on the reference layer)
34, 44 Inner layer (layer to be laminated on the reference layer)

Claims (3)

According to the external radiation dose, the peripheral wall of the cylindrical structure whose inside is a passage is thickened toward the inside of the passage along the thickness direction of the peripheral wall,
A construction method for a cylindrical structure , wherein at least a layer containing water is provided on the peripheral wall, and the water in the layer containing water is circulated .   It is a construction method of the cylindrical structure according to claim 1,
  A construction method for a cylindrical structure, wherein a pair of protective layers having radiation shielding properties and sandwiching the water-containing layer from both sides along the thickness direction are provided on the peripheral wall.   It is a construction method of the cylindrical structure according to claim 2,
  The method for constructing a cylindrical structure, wherein the protective layer is any one of a concrete layer, a metal layer, a graphite layer, and a polymer material layer.

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