JP6436842B2 - Tank dismantling method - Google Patents

Description

  The present invention relates to a tank dismantling method.

  Contaminated water containing radioactive pollutants such as radioactive cesium and radioactive strontium, for example, circulating water for core cooling and wastewater at the nuclear power plant after the accident, should be discharged if the radioactive pollutants are not removed to prevent environmental destruction. Is not allowed.

  For this reason, in the nuclear power plant after the accident, the contaminated water obtained by collecting the surplus reactor cooling water is stored in a large number of tanks. Many of these tanks are bolted tanks formed by joining a plurality of plate-like members on site by bolting. In such a bolt-clamped tank, leakage can occur due to deterioration of the packing or the like of the fastening portion between the members.

  Therefore, it is desired to replace the bolted tank with a welded tank that is formed by welding a plurality of plate-like members and has a longer life. However, even if polluted water is discharged from the bolted tank, there is a high possibility that radioactive pollutants are attached to the inner surface of the tank. If an attempt is made to dismantle a tank having such an inner surface contaminated with radioactive contaminants, the radioactive contaminant adhered to the inner wall surface of the tank may rise in the air and scatter.

  As a method of dismantling radioactive contamination facilities such as tanks, building a roof that covers the radioactive contamination facilities, and dismantling and decontaminating the facilities indoors, it is possible to remove radioactive contaminants to the outside. A method for preventing scattering has been proposed (see, for example, JP2013-181921A). However, the construction of a roof requires a large cost, and a large number of tanks are densely arranged in the nuclear power plant after the accident, so that the construction of the roof is extremely difficult technically.

JP2013-181921A

  In view of the above inconveniences, an object of the present invention is to provide a tank disassembly method capable of disassembling a tank while suppressing scattering of contaminants attached to the inner surface.

  The invention made in order to solve the above-mentioned problem is a method for disassembling a contaminated water tank in which radioactive substance-containing contaminated water has been stored, and is selectively used as a dust-induced region on the inner wall surface of the tank before the dismantling operation. It is a tank dismantling method characterized by including the process of spraying a sealing agent on.

  The tank dismantling method includes a step of selectively spraying a sealant on a dust-inducing region of the inner wall surface of the tank, so that the deposits containing contaminants on the inner surface of the tank side wall are scattered as dust when the tank is disassembled. The tank can be disassembled relatively safely while preventing the spread of contamination.

  It is preferable that the dust-inducing region includes a belt-like region including a water surface position of the contaminated water in the stored state on the inner surface of the side wall of the tank. In the inner surface of the tank side wall, the belt-like region including the position of the contaminated water in the stored state is deposited on the inner surface of the tank side wall while the solid content including the contaminated water is deposited during the contaminated water storage state. This is a region where there is a relatively high possibility that the inner wall surface of the tank is corroded or a corrosive substance containing a pollutant is generated. Therefore, by spraying the sealant on the area where there is a high possibility that precipitates and corrosive substances containing pollutants are formed during the storage of contaminated water, the deposits and corrosive substances containing pollutants are removed. Since it can fix to the inner wall face of a contaminated water tank, scattering of a pollutant can be suppressed efficiently.

  The dust raising area may include a lower band-like area on the inner surface of the side wall of the tank. The lower belt-like area of the inner wall of the tank indicates the possibility that solids containing pollutants are deposited from the contaminated water below the discharge limit remaining at the bottom of the tank after draining the contaminated water, and the inner wall surface of the tank. It is a region where there is a relatively high possibility that a corrosive substance containing a pollutant is generated due to corrosion. Therefore, by spraying the sealant on the area where there is a relatively high possibility that precipitates and corrosive substances containing pollutants are formed after draining the contaminated water, the deposits and corrosive substances containing pollutants are removed. Since it can fix to the inner wall face of a contaminated water tank, scattering of a pollutant can be suppressed efficiently.

  The dust raising area may include the bottom surface of the tank. As described above, since the dust-induced area includes the bottom surface of the tank, the contaminated water remaining at the bottom of the tank after draining the contaminated water or the residue obtained by drying the contaminated water is fixed by the sealant. Scattering is efficiently suppressed.

  The sealing agent may be a water-based paint. Thus, when the sealing agent is a water-based paint, even when contaminated water remains, the sealing agent is not repelled by the contaminated water, and a coating film can be formed on the inner surface of the tank. Out. For this reason, a pollutant can be more reliably fixed with a sealing agent, and scattering of a pollutant is suppressed more reliably.

  Here, the “reserved state” means a state in which water is intentionally stored in the tank and there is no intentional increase or decrease in the amount of water for one day or more. Does not include remaining water. The “water-based paint” means a paint defined in JIS-K5500 (2000), that is, a paint that can be diluted with water and that includes a water-soluble or water-dispersible film-forming element.

  As described above, the tank dismantling method of the present invention can dismantle the tank while suppressing the scattering of contaminants attached to the inner surface.

It is a typical section end view of a tank which shows a field which spreads sealant in a tank dismantling method of one embodiment of the present invention.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

[Tank dismantling method]
The tank disassembly method according to an embodiment of the present invention is a method for disassembling a contaminated water tank that has stored radioactive substance-containing contaminated water.

  The tank dismantling method includes a step of discharging the contaminated water stored in the contaminated water tank, a step of diluting the contaminated water remaining in the contaminated water tank after the contaminated water discharging step, and a low concentration contamination by diluting the contaminated water. A step of discharging water, a step of removing water remaining in the contaminated water tank, a step of selectively spraying a sealant on the dust-inducing area on the inner wall surface of the contaminated water tank, and a dismantling of the contaminated water tank And a step of performing.

<Contaminated water>
The pollutant contained in the contaminated water stored in the contaminated water tank dismantled by the tank dismantling method is a radioactive substance that is desired to prevent or suppress diffusion to the outside, and typically contains radioactive strontium. Radioactive contaminated water.

  The contaminated water containing such a radioactive substance is not particularly limited, and examples thereof include cooling water used for cooling the core in the nuclear power plant after the accident.

  Although it does not specifically limit as a pollutant density | concentration of the contaminated water stored in contaminated water, For example, you may be 500 Bq / cc or more and 500,000 Bq / cc or less.

<Contaminated water tank>
The contaminated water tank to be dismantled by the tank dismantling method is not particularly limited, but is used for storing contaminated water containing radioactive substances in the nuclear power plant after the accident, and between the flanges disposed on the periphery of a plurality of plate members. A bolted tank formed by fastening the bolts with bolts is assumed.

  In addition, the contaminated water tank dismantled by the tank dismantling method is formed of, for example, a general structural rolled steel material such as SS400 defined in JIS-G3101 (2010), and the inner surface is protected with, for example, tar epoxy resin. It can be set as the tank which gave rust painting. Such a tank may generate a corrosive material such as red rust containing a pollutant by causing a crack in the coating film of the anticorrosion coating to corrode.

  Although it does not specifically limit as a minimum of the average internal diameter of the contaminated water tank disassembled by the said tank dismantling method, 3 m is preferable and 5 m is more preferable. On the other hand, the upper limit of the average inner diameter of the contaminated water tank is preferably 25 m, and more preferably 20 m. When the average inner diameter of the contaminated water tank is less than the above lower limit, it is more efficient to move the contaminated water tank to prevent the scattering of contaminants, and there is a possibility that the merit of applying the tank dismantling method cannot be obtained. On the other hand, when the average inner diameter of the contaminated water tank exceeds the above upper limit, the contaminated water tank may not have a structure that can be easily disassembled, so that the effect of preventing the scattering of contaminants by the sealant may be insufficient. The “average inner diameter” means an average value of the minimum horizontal dimension inside the tank and the horizontal dimension orthogonal thereto.

  Moreover, as a minimum of the average height of the contaminated water tank disassembled by the said tank dismantling method, 3 m is preferable and 5 m is more preferable. On the other hand, the upper limit of the average height of the contaminated water tank is preferably 30 m, and more preferably 25 m. If the average height of the contaminated water tank is less than the lower limit, it is more efficient to move the contaminated water tank to prevent the scattering of pollutants, and there is a risk that the merit of applying the tank dismantling method cannot be obtained. . On the other hand, when the average height of the contaminated water tank exceeds the above upper limit, the contaminated water tank may not have a structure that can be easily disassembled, so that the effect of preventing the scattering of contaminants by the sealant may be insufficient.

[Contaminated water discharge process]
In the polluted water discharge process, the polluted water tank is discharged by general means such as outflow from a nozzle provided in the contaminated water tank, suction by a suction pump connected through a pipe inserted into the contaminated water tank, and the like. The polluted water stored in is discharged.

  This polluted water discharge step can be performed as a step of continuously supplying the polluted water discharged from the polluted water tank to the purification equipment to remove pollutants in the contaminated water, that is, a step for purifying the polluted water. is assumed.

[Contaminated water dilution process]
In the contaminated water dilution process, the contaminated water remaining after the contaminated water discharge process is diluted by supplying dilution water to the contaminated water tank.

  For example, most of the structures of contaminated water tanks used for storing contaminated water generated at the nuclear power plant after the accident are difficult to discharge the entire amount of stored contaminated water by general means. Therefore, by diluting the contaminated water remaining in the contaminated water tank in this contaminated water dilution step, the contaminant concentration is lowered to such an extent that an operator can work in the contaminated water tank.

  In the contaminated water dilution step, it is preferable to reduce the concentration of radioactive contaminants in the residual water in the contaminated water tank to 3,000 Bq / cc or less.

  In this contaminated water dilution step, it is preferable to introduce the diluted water so as to contact the entire inner surface of the side wall of the contaminated water tank, and it is more preferable to inject the diluted water so as to sequentially collide with the entire inner wall surface of the contaminated water tank. In this way, by bringing diluted water into contact with the inner wall surface of the contaminated water tank, the contaminants adhering to the inner surface of the sidewall of the contaminated water tank can be substantially washed away except for those contained in scale-like deposits. Can do.

  As a method of injecting the dilution water, it is preferable to use a three-dimensional cleaning nozzle that can inject while automatically changing the injection direction of the purified water by 360 ° according to the supply pressure of the purified water. As such a three-dimensional cleaning nozzle, a nozzle having a rotation mechanism for rotating the direction of the injection port about two axes orthogonal to each other is preferable.

<Dilution water>
The dilution water may be water having a low pollutant concentration, but purified water that has been supplied from the contaminated water tank to the purification facility in the contaminated water discharge step and from which the contaminant has been removed can be used. The contaminant concentration of the dilution water may be, for example, from the ND level (several Bq / cc) to 500 Bq / cc, depending on the capacity of the purification facility. Thus, by using the water which purified contaminated water as dilution water, the pollutant density | concentration of the stored water in a contaminated water tank can be reduced, without increasing the total amount of contaminated water.

(Purification equipment)
As purification equipment for obtaining purified water used as dilution water, it is preferable to use one provided with a filter unit, a primary adsorption tower, and a secondary adsorption tower.

  The filter unit filters out suspended matter and oil in the contaminated water. Thereby, the capability fall by the clogging of the adsorption agent of a primary adsorption tower and a secondary adsorption tower is suppressed, and adsorption capacity is fully exhibited.

  It is preferable that the plurality of filter units are connected in parallel so that a plurality of the filter units can selectively pass water, and are arranged so that the entire filter unit that is not allowed to pass water or a filter inside thereof can be replaced.

  As the filter disposed in the filter unit, for example, a membrane filter having an average opening diameter of about 0.2 μm is preferably used.

  Furthermore, the filter unit preferably has an activated carbon adsorbent layer on the downstream side of the membrane filter. When the filter unit has the activated carbon adsorbent layer, clogging of the adsorbent in the primary adsorption tower and the secondary adsorption tower can be more reliably prevented.

  The primary adsorption tower is filled with an adsorbent that selectively adsorbs strontium.

  It is preferable that a plurality of primary adsorption towers are provided. All of the primary adsorption towers are connected in series so that water can pass through all but excluding any one, and the separated primary adsorption towers are replaced with new ones. The new primary adsorption tower after replacement may be piped so that it can be connected to the most downstream side. Thereby, it is possible to purify continuously by sequentially replacing the primary adsorption tower with breakthrough, that is, the adsorption capacity being saturated, with a new one.

  As an adsorbent that selectively adsorbs strontium packed in the primary adsorption tower 14, for example, it has a film that does not transmit calcium and magnesium but selectively transmits strontium, and adsorbs strontium. A capsule-like adsorbent having an inorganic material inside can be used.

  Examples of the membrane that selectively permeates strontium include a calcium alginate membrane. Examples of the inorganic material that adsorbs strontium include A-type zeolite and X-type zeolite. Such an adsorbent for strontium is preferably supported on a porous body that also functions as a filter medium for filtering out suspended substances and oil. Examples of such a carrier include activated carbon and zeolite.

  The secondary adsorption tower is filled with an adsorbent that adsorbs a radioactive substance other than strontium.

  It is preferable that a plurality of secondary adsorption towers are provided. All of the secondary adsorption towers are connected in series so that water can pass through all but excluding any one, and the separated secondary adsorption towers are replaced with new ones. The new secondary adsorption tower after replacement may be piped so that it can be connected to the most downstream side. Thereby, it is possible to purify continuously by sequentially replacing the secondary adsorption tower with breakthrough, that is, the adsorption capacity being saturated, with a new one.

  Examples of the adsorbent packed in the secondary adsorption tower include an adsorbent composed of titanium oxide carrying cobalt ferrocyanide or iron ferrocyanide, an adsorbent composed of inorganic carbon and alumina (removal target: many Element), an adsorbent composed of a cesium oxide-based inorganic material (removal object: Sb, Se, Te, iodic acid), an adsorbent composed of activated carbon supporting iodine (removal object: iodine), and tannin. Adsorbent composed of activated carbon (removal object: transuranium element (U, np, Pu, Am, Cm)), adsorbent composed of activated carbon carrying reduced iron (removal object: Sb, Se, Te, many Element), adsorbent composed of aluminum-containing inorganic carbon material (removal object: Sb, Se, Te, Tc), various chelating agents (eg, DDTC, oxine, DTPA, cuperon, etc.) That the absorbent consists of activated carbon (removal target: transuranium (U, np, Pu, Am, Cm)) include those containing, and the like. Here, the removal target is “multi-element”: Ag, Cd, Eu, Mn, Co, Y, Ru, Ce, Te, ni, Zn, Rh, nd, Sn, Sb, Tc, Pr, Sm, Gd, It means that part or all of V and transuranium elements (U, np, Pu, Am, Cm) are to be removed.

[Residual water removal process]
In the residual water removal step, the water remaining in the contaminated water tank is removed by, for example, suction using a low water level submersible pump. This residual water removal process removes residual water that could interfere with the dismantling of the contaminated water tank or leak to the surroundings due to dismantling, allowing workers to dismantle in the contaminated water tank .

  The low water level submersible pump used in the residual water removal process is, for example, a well-known low water level drainage pump widely used in civil engineering work sites, that is, it is placed on the bottom of a contaminated water tank, and is placed from the bottom to the surroundings. Mention may be made of pumps capable of sucking and delivering water.

  In the residual water removal step, the amount of contaminated water remaining in the contaminated water tank may be further reduced by combining a step of absorbing the contaminated water with, for example, a waste cloth.

[Sealing agent spraying process]
In the sealant spraying process, by selectively spraying the sealant on the dust-inducing area on the inner wall surface of the contaminated water tank, dust generation including contaminants is prevented from occurring in the contaminated water tank dismantling process described later. Further, it is possible to suppress the deposits containing the pollutant on the inner wall surface of the contaminated water tank from being detached from the inner wall surface of the contaminated water tank and flying up into the air.

<Dust-induced area>
The dust-inducing area will be described with reference to FIG. 1. Of the inner surface of the side wall of the contaminated water tank X, the upper belt-like area A1 including the water surface position of the stored contaminated water, and the inner surface of the side wall of the contaminated water tank X Of these, it is preferable to use a lower region, that is, a region including at least one of the lower band region A2 near the bottom surface and the bottom surface A3 of the contaminated water tank X. More preferably, the region includes the belt-like region A2 and the bottom surface A3 and does not include other portions.

(Upper strip area)
The upper belt-like region A1 is a region including a portion of the inner surface of the side wall of the contaminated water tank X that may be in contact with both contaminated water and air during the contaminated water storage state. Therefore, the upper belt-like region A1 has a possibility that the solid content containing the pollutant in the contaminated water is deposited and adhered in a scale shape, or a scale-like corrosive material generated by corroding the inner wall surface of the contaminated water tank X. This is a region where there is a relatively high possibility of the presence of. Therefore, the generation of dust containing contaminants can be efficiently suppressed by selectively spraying the sealant on the upper strip region A1.

  The lower limit of the average width in the vertical direction of the upper strip region A1 is preferably 0.3 m, and more preferably 0.5 m. On the other hand, the upper limit of the average width of the upper belt-like region A1 is preferably 2 m, and more preferably 1.5 m. When the average width of the upper belt-like region A1 is less than the lower limit, it is not possible to cover a range where there are many deposits containing contaminants, and there is a possibility that scattering of contaminants cannot be sufficiently suppressed. On the contrary, when the average width of the upper belt-like region A1 exceeds the upper limit, the amount of the sealant used may increase and the cost may increase, or the sealant may exist at the division position of the contaminated water tank X. The dismantling workability of the contaminated water tank X may be reduced.

  Moreover, it is preferable to make the vertical center of upper strip | belt-shaped area | region A1 correspond with the position where the water surface existed in the contaminated water storage state. The lower limit of the tolerance between the center of the upper belt-like region A1 and the position where the water surface is present, that is, the specific accuracy of the position where the water surface is present is preferably 5 cm, and more preferably 10 cm. On the other hand, the upper limit of the allowable error between the center of the upper belt-like region A1 and the position where the water surface is located is preferably 50 cm, and more preferably 30 cm. When the allowable error between the center of the upper belt-like region A1 and the position where the water surface is located is less than the lower limit, the identification of the upper belt-like region A1 becomes complicated, and the cost for spraying the sealant may increase unnecessarily. There is. Conversely, if the tolerance between the center of the upper belt-like region A1 and the position where the water surface is located exceeds the above upper limit, it is not possible to cover a range where there are many contaminants containing contaminants, and the scattering of contaminants is sufficient. There is a possibility that it cannot be suppressed. Further, the allowable error between the center of the upper belt-like region A1 and the position where the water surface is located is a value obtained by subtracting the maximum vertical width of the region where contaminants can adhere from the average vertical width of the upper belt-like region A1. Needs to be a small value.

(Lower band)
The lower belt-like region A2 is a region corresponding to the surface of the contaminated water remaining after draining the contaminated water, unlike the upper belt-like region A1, of the inner wall of the contaminated water tank X. However, in the lower belt-like region A2, similarly to the upper belt-like region A1, the solid content containing the pollutant in the contaminated water may be deposited and adhered in a scale shape, or the inner wall surface of the contaminated water tank X is corroded. This is a region where the possibility of the presence of scale-like corrosion products is relatively high. Therefore, by selectively spraying the sealant on the lower strip region A2, the generation of dust containing contaminants can be efficiently suppressed.

  The lower limit of the average width in the vertical direction of the lower strip region A2 is preferably 0.3 m, and more preferably 0.5 m. On the other hand, the upper limit of the average width of the lower belt-like region A2 is preferably 2 m, and more preferably 1.5 m. When the average width of the lower belt-like region A2 is less than the lower limit, it is not possible to cover a range where there are many deposits containing contaminants, and there is a possibility that the scattering of contaminants cannot be sufficiently suppressed. On the contrary, when the average width of the lower belt-like region A2 exceeds the above upper limit, the amount of the sealant used may increase and the cost may increase, or the sealant may exist at the division position of the contaminated water tank X. The dismantling workability of the contaminated water tank X may be reduced.

  Moreover, it is preferable that the vertical center of the lower belt-like region A2 coincides with the position where the surface of the contaminated water remaining after discharging the contaminated water was present. The lower limit of the allowable error between the center of the lower belt-like region A2 and the position where the water surface is located is preferably 5 cm, and more preferably 10 cm. On the other hand, the upper limit of the allowable error between the center of the lower belt-like region A2 and the position where the water surface is located is preferably 50 cm, and more preferably 30 cm. If the tolerance between the center of the lower belt-like region A2 and the position where the water surface is located is less than the lower limit, the specification of the lower belt-like region A2 becomes complicated, and the cost for spraying the sealant may increase unnecessarily. There is. On the contrary, when the tolerance between the center of the lower belt-like region A2 and the position where the water surface is present exceeds the above upper limit, it is not possible to cover the area where there are many contaminants including contaminants, and the scattering of contaminants is sufficient. There is a possibility that it cannot be suppressed. In addition, the allowable error between the center of the lower belt-like region A2 and the position where the water surface is located is a value obtained by subtracting the maximum width in the vertical direction of the region where contaminants can adhere from the average width in the vertical direction of the lower belt-like region A2. Needs to be a small value.

(Bottom)
The bottom surface A3 is a region where there is a high possibility that a precipitate containing contaminants from the contaminated water in the contaminated water tank X exists. Therefore, by selectively spraying the sealant on the bottom surface A3, generation of dust containing contaminants can be efficiently suppressed.

  When the contaminated water tank X is a bolted tank, the bottom surface A3 preferably includes the outer surface of the flange for bolt connection, but excludes a region near the bolt so as not to hinder the operation of removing the bolt. May be.

<Sealant>
The sealing agent should just be what can form a layer with high adhesiveness on the inner wall surface of the contaminated water tank X by spraying. Examples of such sealants include water-based paints, solvent-type paints, and gelling agents. Among them, as a sealant, even when water adheres to the inner wall surface of the contaminated water tank X, it is difficult to prevent layer formation, and workers in the contaminated water tank X due to release of volatile organic compounds, etc. A water-based paint is preferable because it is difficult to cause a decrease in workability.

(Water-based paint)
Examples of the water-based paint include siliceous paints, metal silicate paints, acrylic resin acrylic emulsion paints, and the like.

  As such a water-based coating material, for example, those commercially available as an asbestos scattering inhibitor can be used.

(Solvent paint)
Examples of the solvent-type paint include a two-component resin paint containing an organic compound and its curing agent in an organic solvent, and moisture that cures when the organic compound contained in the organic solvent reacts with moisture in the air. Examples thereof include curable resin paints.

  Examples of the two-component resin paint include urethane resin paint and epoxy resin paint.

  Examples of the moisture curable resin coating include acrylic silicon resin paints.

(Gelling agent)
The gelling agent is used in a state where contaminated water is attached to the inner wall surface of the contaminated water tank X. That is, the gelling agent gels by absorbing the water adhering to the inner wall surface of the contaminated water tank X, and suppresses the scattering of the contaminated water and contaminants in the contaminated water.

  Examples of the gelling agent include polymer-absorbing polymers.

  The gelling agent is particularly effective as a sealant sprayed on the bottom surface A3 when the contaminated water remaining on the bottom of the contaminated water tank X is not completely removed in the residual water removing step.

  In addition, when a gelling agent is used as the sealant, water remaining at the bottom of the contaminated water tank X is fixed together with radioactive pollutants contained in the contaminated water or sediment, and is emitted from the contaminants by this water. The effect of shielding radiation can be obtained, and the risk of exposure to workers can be reduced.

  Examples of the method for spraying the sealant include spraying by pressurizing the sealant and spraying from the spray tip, spraying by dispersing the sealant in a jet of gas such as compressed air, and the like. Moreover, you may carry out about the bottom face A3 by spreading the spraying agent by gravity fall.

[Contaminated water tank dismantling process]
In the contaminated water tank dismantling process, the wall of the contaminated water tank X is divided into a plurality of plate pieces to facilitate carrying out from the contaminated water tank installation location.

  As the method of dividing the wall of the contaminated water tank, when the contaminated water tank X is a bolted tank, the bolt is removed, and when the contaminated water tank X is a welded tank, cutting using, for example, a band saw is performed. The method by is mentioned.

  It is preferable to divide the wall of the contaminated water tank X at a position other than the dust-inducing region in which the sealant is dispersed, that is, the upper strip region A1, the lower strip region A2, and the bottom surface A3 of the contaminated water tank X. Conversely, if the contaminated water tank X is a bolted tank, the upper belt-like region is set so as not to include the bolted flange position, that is, the water surface height in the contaminated water storage state is set in the horizontal direction. It is preferable to set between the flanges.

  Further, when dividing the wall of the contaminated water tank X, particularly when dividing the wall in the dust-inducing region where the sealant is sprayed, the air in the vicinity of the divided portion where the work is performed is sucked, for example, Air may be released after dust is removed by a filter or the like. As a result, the scattering of contaminants can be prevented more reliably.

<Advantages>
As described above, the tank dismantling method can dismantle the contaminated water tank X while suppressing the scattering of pollutants adhering to the inner surface, so that it is possible to prevent the diffusion of the contamination and also to the health hazard of the worker who performs the dismantling work. Can be prevented.

[Other Embodiments]
The said embodiment does not limit the structure of this invention. Therefore, in the above-described embodiment, the components of each part of the above-described embodiment can be omitted, replaced, or added based on the description and common general knowledge of the present specification, and they are all interpreted as belonging to the scope of the present invention. Should.

  In the tank dismantling method, the contaminated water discharging step is not essential, and the method of applying the sealant spraying step and the contaminated water tank disassembling step to the tank from which the contaminated water has been discharged in advance is also a tank dismantling method according to the present invention. It is understood as an aspect.

  In the tank dismantling method, the contaminated water dilution step may be omitted when the pollutant concentration of the stored contaminated water is not high.

  In the tank dismantling method, the residual water removing step may be omitted when the remaining contaminated water does not hinder the operation of the sealing agent spraying step and the contaminated water tank disassembling step.

  The tank disassembly method may further include another process. As an example, the tank disassembling method may include a step of reducing deposits on the inner wall surface of the contaminated water tank by, for example, spraying or blasting of cleaning water after the contaminated water discharging step and before the sealing agent spraying step. .

  The tank dismantling method according to the present invention is widely applicable for disassembling a contaminated water tank, but in particular dismantles a contaminated water tank disposed for the purpose of storing contaminated water generated at the nuclear power plant after the accident. Therefore, it can be suitably used.

A1 Upper strip region A2 Lower strip region A3 Bottom X Contaminated water tank

Claims (4)

A method for dismantling a contaminated water tank that had stored radioactive material-containing contaminated water,
Before dismantling work, a step of selectively spraying a sealant on the dust-induced region of the inner wall surface of the tank ,
The dust-induced region includes a band-shaped region including the water surface position of the contaminated water in the stored state among the side wall inner surface of the tank,
The average width in the vertical direction of the belt-like region is 0.3 m or more and 2 m or less,
Vertical central and tolerances between the water surface position in the storage state of the contaminated water, the tank demolition method according to claim der Rukoto least 50cm below 5cm above band region. A method for dismantling a contaminated water tank that had stored radioactive material-containing contaminated water,
Before dismantling work, a step of selectively spraying a sealant on the dust-inducing area of the inner wall surface of the tank
With
A tank dismantling method in which the dust-inducing region includes a lower band-like region of the inner side wall of the tank. A method for dismantling a contaminated water tank that had stored radioactive material-containing contaminated water,
Before dismantling work, a step of selectively spraying a sealant on the dust-inducing area of the inner wall surface of the tank
With
A tank disassembly method in which the dust-inducing region includes a bottom surface of the tank. The tank disassembly method according to any one of claims 1 to 3 , wherein the sealant is a water-based paint.

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