JP6563727B2 - Dust generation prevention device and dust generation prevention method - Google Patents

Description

  The present invention relates to a dust generation prevention device and a dust generation prevention method.

  Contaminated water containing radioactive pollutants such as radioactive cesium and radioactive strontium, for example, circulating water for core cooling and wastewater at nuclear power plants after the accident, reduce the radioactive pollutants below the standard value to prevent environmental destruction Otherwise, it is not allowed to discharge.

  For this reason, in the nuclear power plant after the accident, contaminated water obtained by collecting surplus reactor cooling water is stored in many 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 desirable to replace such a 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, the bolted tank cannot be easily disassembled without further decontamination treatment due to radioactive material adhering to the inner surface of the tank.

  Such a decontamination process on the inner surface of the tank may be carried out manually by using a deck brush or the like after the worker enters the tank after discharging the contaminated water in the tank. Here, since dust containing radioactive pollutants is scattered in the tank after discharging the contaminated water, the dust removal processing in the tank is performed before the decontamination processing of the tank inner surface. As this dust removal process, for example, ventilation for dust suction is performed until the radioactive substance concentration in the tank becomes a predetermined value or less.

On the other hand, the decontamination treatment of the tank inner surface is often performed immediately before the dismantling work. The dismantling work may be carried out within a relatively short time after the dust removal treatment is performed. For example, when the dismantling work is carried out several days after the dust removal treatment, radioactive dust is regenerated in the tank, This radioactive dust may be scattered during the decontamination treatment of the inner surface. Regarding this point, for example, ““ Status and Countermeasures for Contaminated Water at Fukushima Daiichi Nuclear Power Station ”, [online], December 2, 2014, Tokyo Electric Power Company, Inc. [searched on June 1, 2015] , The Internet (URL: http://www.tepco.co.jp/news/2014/images/141202b.pdf), p59 ”describes the following survey results. That is, after discharging the polluted water in the tank, ventilation for dust suction in the tank was performed until the radioactive substance concentration in the tank was sufficiently reduced to about 0.00002 Bq / cm ^3, and then the ventilation was stopped. Later changes in the concentration of radioactive material in the tank are being investigated. According to the results of the survey, the radioactive substance concentration did not increase until the third day after the ventilation was stopped, but then the radioactive substance concentration began to increase. After five days after the ventilation was stopped, the concentration of the radioactive substance was 0.00025 Bq. It has risen to near / cm ³ . The cause of this is not clear, but it is thought that the inner surface of the tank dries with the temperature change in the tank, and the radioactive material slightly remaining on the inner surface of the tank becomes dust. Here, after the dust removal process in the tank, it is often the case that the product is left for several days or more until the dismantling operation is performed. Therefore, it is important to prevent the generation of such radioactive dust.

  Generation of such radioactive dust can be prevented by removing radioactive material remaining on the inner surface of the tank. In order to remove such radioactive materials on the tank inner surface, for example, as a device for decontaminating the tank inner surface without entering the tank, the contamination adhered to the tank inner wall surface while moving along the tank inner wall surface An apparatus for removing a substance has been proposed (see Japanese Patent Laid-Open No. 10-2959).

  By using the decontamination apparatus proposed in the above publication, the radioactive material remaining on the inner wall surface of the tank can be removed, and as a result, generation of the radioactive dust can be prevented. However, this decontamination apparatus needs to supply cleaning water up to the maximum water level in the tank after discharging the polluted water when removing the pollutants on the inner wall surface of the tank. Here, since the contaminated water remains in the lower part of the tank after draining the contaminated water, when the cleaning water is supplied into the tank in this way, the cleaning water is mixed with the residual contaminated water, and as a result Large amount of contaminated water increases.

  Further, as a method other than using the decontamination apparatus proposed in the above publication, radioactive substances remaining on the inner surface of the tank can be removed by watering the inner surface of the tank for a long time, thereby preventing the generation of the radioactive dust. it can. However, also in this case, a large amount of cleaning water is mixed with residual contaminated water in the tank, and the amount of contaminated water increases.

Japanese Patent Laid-Open No. 10-2959 “About the situation and countermeasures for contaminated water at the Fukushima Daiichi Nuclear Power Station”, [online], December 2, 2014, Tokyo Electric Power Co., Inc. [searched on June 1, 2015], Internet (URL: http) //Www.tepco.co.jp/news/2014/images/141202b.pdf), p59

  The present invention has been made based on the above circumstances, and provides a dust generation prevention device and a dust generation prevention method capable of preventing the generation of radioactive dust during tank dismantling while suppressing an increase in contaminated water. Objective.

  The invention made in order to solve the above-mentioned problem is a dust generation prevention device at the time of dismantling of a tank storing radioactive polluted water, and is disposed in the tank by being inserted from the opening of the tank. A pump for sucking residual contaminated water from the bottom of the tank after discharging the contaminated water, and a water injection module which is disposed in the tank by being inserted through the opening of the tank, and injects contaminated water or cleaning water onto the inner surface of the side wall of the tank; A control unit that controls the pump and the water injection module, and the control unit sucks up the contaminated water by the pump, and causes the water injection module to inject the contaminated water onto the inner surface of the side wall. After the injection, control is performed to reinject the cleaning water by the water injection module so as to have a predetermined interval to at least a specific region on the inner surface of the side wall. A dust prevention device according to claim.

  In the dust generation preventing apparatus, the control unit causes the water injection module to inject the contaminated water into at least a specific region of the inner surface of the side wall of the tank, and then causes the cleaning water to be reinjected into the region so as to have a predetermined interval. I do. During this predetermined interval, radioactive contaminants such as radioactive strontium remaining on the inner surface of the side wall are dissolved in the contaminated water adhering to the inner surface of the side wall by the jetting, and the strontium and the like are dissolved by re-injecting cleaning water. Water is washed away. Accordingly, in the dust generation preventing device, the control unit performs the above-described control on the entire inner surface of the side wall of the tank, for example, so that the radioactive pollutant such as radioactive strontium remaining on the entire inner surface of the side wall of the tank is injected. Can be washed away with water. In this way, the dust generation prevention device injects the amount of contaminated water necessary for dissolving strontium and the amount of cleaning water necessary for washing away the contaminated water adhering to the inner surface of the side wall. In addition, radioactive strontium remaining on the inner surface of the side wall can be effectively removed while reducing the amount of cleaning water used. Therefore, the dust generation preventing device can prevent the generation of radioactive dust when the tank is dismantled while suppressing the amount of contaminated water that increases as the tank is cleaned.

  An adsorbent capable of purifying the contaminated water may be further provided in the contaminated water suction path by the pump, and the water jetting module may use water purified by the adsorbent as the cleaning water. In this way, the amount of external water that does not contain radioactive pollutants can be obtained by using the adsorbent capable of purifying contaminated water and using the water that has been purified with this adsorbent as the residual contaminated water in the tank. Can be reduced.

  The tank may further include a buffer tank for storing the contaminated water sucked up by the pump, and the water injection module may use the contaminated water stored in the buffer tank as the contaminated water for injection. . Thus, even if the capacity of the pump is low with respect to the amount of contaminated water injection required by the water injection module, the buffer tank for storing the contaminated water sucked up by the pump is provided in the tank. The contaminated water sucked up by the pump can be used. That is, by storing the contaminated water sucked up by the pump in the buffer tank, for example, the contaminated water stored in the buffer tank by another pump disposed outside the tank can be supplied to the water injection module. In addition, since the buffer tank is disposed in the tank, it is possible to simplify measures against leakage of contaminated water and reduce equipment costs.

  The water injection module may include a plurality of nozzles and a swing mechanism, and the swing mechanism includes a first axis parallel to an inflow direction of the contaminated water or the washing water and a direction perpendicular to the first axis. The nozzle may be continuously rotated around the second axis. As described above, the water ejection module has a plurality of nozzles and a swing mechanism, and the swing mechanism uses the one that continuously rotates the nozzle around the first axis and the second axis. Contaminated water and washing water can be efficiently sprayed on the entire inner surface of the side wall of the tank.

The ratio of the salinity of contaminated water injected by the water injection module to the salinity of seawater used for decontamination is A [%], the strontium concentration in seawater is B [mg / L], and adheres to the inner surface of the side wall. After that, the molecular weight of the strontium compound produced in the contaminated water is C, the solubility of the strontium compound is D [mg / L], and the average amount of contact of the cleaning water on the inner surface of the side wall by the injection of the water injection module is When it is set to E [cc / m < ² >], it is good for the said average contact amount E to satisfy | fill following formula (1).

In this way, strontium or the like remaining on the inner surface of the side wall is suppressed while increasing the amount of contaminated water by injecting the cleaning water so that the amount of contact of the cleaning water with the inner surface of the side wall satisfies the following formula (1). Since it becomes easy to melt | dissolve in contaminated water and it can wash away before the contaminated water adhering to the said side wall inner surface dries, the said radioactive strontium etc. can be removed more efficiently. Here, for example, when the salinity of contaminated water is equal to the salinity of seawater used for decontamination, the “salt concentration ratio A” is 100%. The “average amount of cleaning water in contact with the inner surface of the side wall” is a value obtained by dividing the total amount of cleaning water in contact with the inner surface of the side wall by jetting by the total area of the inner surface of the side wall.
E ≧ (A × B × C) / (87.6 × D) (1)

The contact amount of the contaminated water and the cleaning water to the inner surface of the side wall due to the injection of the water injection module is preferably 150 cc / m ² or more and 200 L / m ² or less on average. In this way, the radioactive contamination generated in the contaminated water adhering to the inner surface of the side wall by injecting the contaminated water or the cleaning water so that the contact amount of the contaminated water and the cleaning water to the inner surface of the side wall is within the above range. Even if the substance is not specified, strontium remaining on the inner surface of the side wall can be surely dissolved in the contaminated water, and the contaminated water adhering to the inner surface of the side wall can be washed away before drying. The radioactive strontium and the like can be removed.

  Another invention made in order to solve the above-mentioned problem is a method for preventing the generation of dust when dismantling a tank that has stored radioactive contaminated water, wherein the contaminated water is drained by a pump disposed in the tank. A step of sucking up residual contaminated water from the bottom of the subsequent tank, a step of injecting the contaminated water onto the inner surface of the side wall of the tank by a water injection module disposed in the tank, and a cleaning water on the inner surface of the side wall of the tank by the water injection module And at least a specific region of the inner surface of the side wall, wherein there is a predetermined interval between the injection by the injection step and the re-injection by the re-injection step. is there.

  In this way, the dust generation prevention method reinjects the cleaning water in the reinjection step so that at least a specific region on the inner surface of the side wall of the tank has a predetermined interval between the injection of the contaminated water in the injection step. I do. During this predetermined interval, radioactive contaminants such as strontium remaining on the inner surface of the side wall are dissolved in the contaminated water adhering to the inner surface of the side wall by the injection, and the strontium is re-injected by the re-injection of cleaning water in the re-injection step. The contaminated water in which etc. were dissolved is washed away. Therefore, by the dust generation prevention method, for example, by performing the injection step and the re-injection step on the entire inner surface of the side wall of the tank, the radioactive contaminants such as radioactive strontium remaining on the entire inner surface of the side wall of the tank are injected. Can be washed away with contaminated water. As described above, the dust generation prevention method injects the amount of contaminated water necessary for dissolving strontium and the amount of cleaning water necessary for washing away the contaminated water adhering to the inner surface of the side wall. In addition, radioactive strontium remaining on the inner surface of the side wall can be effectively removed while reducing the amount of cleaning water used. Therefore, the dust generation prevention method can prevent the generation of radioactive dust when the tank is dismantled while suppressing the amount of contaminated water that increases as the tank is cleaned.

  As described above, the dust generation preventing apparatus and the dust generation preventing method of the present invention can prevent the generation of radioactive dust during tank dismantling while suppressing an increase in contaminated water.

It is a mimetic diagram showing composition of a dust generation prevention device concerning one embodiment of the present invention. It is typical sectional drawing of the water-injection module of FIG. It is a typical front view of the water injection module of FIG.

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

[Dust generation prevention device]
The dust generation preventing device shown in FIG. 1 is a dust generation preventing device when the tank 1 storing radioactive contaminated water is dismantled. The dust generation prevention device is disposed in the tank 1 by insertion from the opening of the tank 1, a suction pump 2 that sucks residual contaminated water from the bottom of the tank 1 after discharging the contaminated water, and an opening from the opening of the tank 1. A water injection module 3 that is disposed in the tank 1 by insertion and injects cleaning water onto the inner surface of the side wall of the tank 1 and a controller 4 that controls the suction pump 2 and the water injection module 3 are mainly provided. The dust generation preventing device is disposed in the contaminated water suction path by the suction pump 2 and is disposed in the tank 1 and the adsorbent 5 capable of purifying the contaminated water, and is sucked up by the suction pump 2. And a buffer tank 6 for storing contaminated water. In addition, the dust generation prevention device supplies the contaminated water supply pipe 7 that supplies the contaminated water sucked up by the suction pump 2 to the buffer tank 6, and supplies the purified contaminated water in the buffer tank 6 to the water injection module 3. A purified water supply pipe 8 and a supply pump 9 that pumps purified water in the buffer tank 6 through the purified water supply pipe 8 are provided.

<Tank>
The tank 1 is not particularly limited. For example, the tank 1 is used for storing contaminated water such as circulating water for core cooling and waste water in a nuclear power plant after an accident, and bolts are provided between flanges arranged on the periphery of a plurality of plate members. A bolted tank formed by fastening is assumed.

  In addition, the tank 1 has a discharge port (not shown) for discharging the internal contaminated water before disassembly, but since there is a flange at the bottom, after the internal contaminated water is discharged from the discharge port, Inevitably remains. FIG. 1 shows the state of the tank 1 after the internal contaminated water is discharged from the discharge port.

  Although it does not specifically limit as a minimum of the average internal diameter of the tank 1, 3 m is preferable and 5 m is more preferable. On the other hand, the upper limit of the average inner diameter of the tank 1 is preferably 25 m, and more preferably 20 m. If the average inner diameter of the tank 1 is less than the lower limit, the tank capacity cannot be increased beyond a predetermined level, and the number of tanks 1 for storing contaminated water may increase. Conversely, if the average inner diameter of the tank 1 exceeds the above upper limit, it may not be easy to bring the cleaning water into contact with the inner surface of the side wall of the tank. 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 tank 1, 3 m is preferable and 5 m is more preferable. On the other hand, the upper limit of the average height of the tank 1 is preferably 25 m, and more preferably 20 m. If the average height of the tank 1 is less than the above lower limit, the installation area of the tank 1 increases with respect to the capacity capable of storing contaminated water, so that the storage efficiency with respect to the installation area may be reduced. Conversely, if the average height of the tank 1 exceeds the above upper limit, the water injection module 3 may not be disposed at an appropriate position in the tank 1 from the opening at the top of the tank 1.

  In addition, the contaminated water stored in the tank 1 may contain any contaminant as a substance for preventing dust generation according to the present invention, but is typically a radioactive substance, particularly radioactive strontium. It is considered as radioactive polluted water.

  Although it does not specifically limit as a pollutant density | concentration of the contaminated water stored in the tank 1, For example, it is 500 Bq / cc or more and 500,000 Bq / cc or less.

<Suction pump>
The suction pump 2 is disposed in the tank 1 by being inserted from an opening at the top of the tank 1. For example, the suction pump 2 is suspended by a wire or the like. As this suction pump 2, it is preferable to use a submersible pump. Among them, a known low water level drainage submersible pump that is disposed on the bottom of the tank 1 and sucks and sends out surrounding water from the lower part thereof is particularly preferably used. Thus, the amount of contaminated water inevitably remaining in the lower part of the tank 1 can be reduced by using the low-water level submersible pump.

  The lower limit of the width and depth of the suction pump 2 is preferably 40 cm, and more preferably 50 cm. On the other hand, the upper limit of the width and depth of the suction pump 2 is preferably 80 cm, and more preferably 70 cm. When the width or depth of the suction pump 2 is less than the lower limit, there is a possibility that the ability to transfer residual contaminated water in the lower part of the tank 1 to the buffer tank 6 through the opening in the upper part of the tank 1 may not be obtained. On the contrary, if the width or depth of the suction pump 2 exceeds the upper limit, the suction pump 2 may not be inserted from the opening at the top of the tank 1.

The lower limit of the wicking capability of the suction pump 2, preferably from 10 m ³ / time, 12m ³ / time is more preferable. On the other hand, the upper limit of the wicking ability, preferably 20 m ³ / time, 15 m ³ / time is more preferable. If the suction capacity is less than the lower limit, the time required for transferring contaminated water to the buffer tank 6 may be too long. On the contrary, if the suction capacity exceeds the upper limit, the suction pump 2 becomes too large, and there is a possibility that the suction pump 2 cannot be inserted from the opening at the top of the tank 1.

<Water injection module>
The water injection module 3 is fixed to the tip of the purified water supply pipe 8 to which the purified contaminated water is supplied, and a fixed portion 22 that defines the inflow path of the purified contaminated water, and the fixed portion 22 is purified. A trunk portion 23 supported rotatably about a first axis C ₁ parallel to the inflow direction of the contaminated water, and an inflow direction of the purified contaminated water to the torso portion 23 intersecting the first axis C _1. having and arm portion 24 which is rotatably supported around a second axis C ₂ perpendicular, is disposed in the arm portion 24, and two nozzles 25 for injecting clarified contaminated water.

Further, the water injection module 3 has a swing mechanism 26 that makes the direction of the nozzle variable. The swing mechanism 26 continuously rotates the arm part 24 with respect to the body part 23 and continuously rotates the body part 23 with respect to the fixed part 22 at a speed proportional to the rotational speed of the arm part 24. By doing so, the nozzle 25 is continuously rotated around the first axis C _{1 in} the inflow direction of the purified contaminated water to the water injection module 3 and the second axis C ₂ perpendicular to the inflow direction. Thereby, the water injection module 3 makes the jet of purified contaminated water contact the entire inner surface of the tank 1. That is, the purified contaminated water ejected by the water ejection module 3 contacts the entire inner surface of the top plate together with the inner surface of the side wall.

  Further, the water injection module 3 includes a speed adjusting mechanism 27 that restricts the rotation speed of the nozzle 25 by the swing mechanism 26 by restricting the rotation of the body part 23 relative to the fixed part 22.

  The lower limit of the water supply pressure to the water injection module 3 is preferably 0.3 MPa, and more preferably 0.5 MPa. On the other hand, the upper limit of the water supply pressure to the water injection module 3 is preferably 1.5 MPa, and more preferably 1.2 MPa. If the water supply pressure to the water injection module 3 is less than the above lower limit, the ejection speed of the purified contaminated water from the water injection module 3 becomes insufficient, and the purified contaminated water is placed far away from the inner surface of the side wall of the tank 1. There is a risk that it will not come into contact. Conversely, if the water supply pressure to the water injection module 3 exceeds the above upper limit, pressure resistance is required for the water injection module 3 and the piping to the water injection module 3, and the dust generation prevention device may become unnecessarily expensive. There is.

(Fixed part)
The fixed portion 22 has a flange 28 for connection to the purified water supply pipe 8, an inflow path 29 into which purified contaminated water flows, and the purified contaminated water that has passed through the inflow path 29 flows out radially outward. A plurality of outlets 30 to be provided.

(Torso)
Purified contaminated water flowing out from the outlet 30 in the radial direction flows through the body portion 23, and a second axis perpendicular to the inflow direction (first axis C ₁ ) of the purified contaminated water to the water injection module 3. It has an internal passage 31 extending along the C _2.

(Arm)
The arm portion 24 distributes the purified contaminated water after passing through the internal flow path 31 to the two nozzles 25.

(nozzle)
Nozzle 25, as shown in FIG. 3, eccentrically with respect to the arm portion 24 from the second axis C ₂ is arranged, it is arranged to rotate the arm portion 24 by reaction to injected clarified contaminated water Yes.

  These nozzles 25 are preferably ones that spray the purified contaminated water linearly without diffusing as much as possible. By ejecting the linearly purified contaminated water from the nozzle 25, the purified contaminated water sprayed on the inner surface of the side wall of the tank 1 forms a continuous water film along the inner surface of the side wall of the tank 1. Expands to form.

  The lower limit of the ejection speed of purified contaminated water from the nozzle 25 is preferably 10 m / s, more preferably 20 m / s, and even more preferably 30 m / s. On the other hand, the upper limit of the ejection speed of the purified contaminated water from the nozzle 25 is preferably 100 m / s, more preferably 80 m / s, and even more preferably 60 m / s. If the ejection speed of the purified contaminated water from the nozzle 25 is less than the lower limit, the purified contaminated water after being ejected from the nozzle 25 may not reach every corner of the inner surface of the side wall of the tank 1. On the contrary, if the ejection speed of the purified contaminated water from the nozzle 25 exceeds the upper limit, the dust generation preventing device may be unnecessarily expensive.

The upper limit of the cross-sectional area expansion rate of the purified contaminated water sprayed from the nozzle 25 is preferably 2 times / m, more preferably 1.5 times / m, and further preferably 1.3 times / m. On the other hand, the lower limit of the cross-sectional area expansion rate of the purified contaminated water sprayed from the nozzle 25 is not particularly limited, but is theoretically 1 time / m is the minimum. When the cross-sectional area enlargement ratio of the purified contaminated water sprayed from the nozzle 25 exceeds the above upper limit, the purified contaminated water sprayed on the inner surface of the side wall of the tank 1 spreads discontinuously, and the side wall of the tank 1 It may not be easy to spread the entire inner surface. In addition, “the cross-sectional area enlargement ratio of the purified contaminated water” means that the water is jetted horizontally from the nozzle, and is in a plane perpendicular to the jet direction of the purified polluted water at a position where the horizontal distance from the nozzle tip is 10 m. The area of the region where the pressure measured when the contaminated water purified by the pressure sensor is 90% or more of the maximum value is S ₁ (mm ² ), and the opening area of the nozzle is S ₀ (mm ² ) , (S ₁ / S ₀ ) ^0.1 . The pressure sensor used here has a circular pressure receiving surface with a diameter of 3 mm.

  The lower limit of the equivalent circle diameter of the opening of the nozzle 25 is preferably 3 mm, more preferably 5 mm, and even more preferably 7 mm. On the other hand, the upper limit of the equivalent circle diameter of the opening of the nozzle 25 is preferably 15 mm, more preferably 12 mm, and even more preferably 10 mm. If the equivalent circle diameter of the opening of the nozzle 25 is less than the above lower limit, a sufficient amount of water may not be obtained. Conversely, if the equivalent circle diameter of the opening of the nozzle 25 exceeds the upper limit, there is a possibility that a sufficient ejection speed cannot be obtained. “Equivalent circle diameter” means the diameter of a perfect circle having the same area.

The lower limit of the amount of purified contaminated water ejected from the nozzle 25 is preferably 2 m ³ / h and more preferably 5 m ³ / h for each nozzle. On the other hand, the upper limit of the amount of purified contaminated water ejected from the nozzle 25 is preferably 30 m ³ / h and more preferably 15 m ³ / h for each nozzle. If the amount of purified water that has been purified from the nozzle 25 is less than the lower limit, the contaminated water that has been purified when sprayed onto the inner surface of the side wall of the tank 1 does not spread sufficiently along the inner surface of the side wall. There is a possibility that an area where the purified water does not adhere to the inner surface of the side wall is formed. On the other hand, when the amount of purified contaminated water ejected from the nozzle 25 exceeds the above upper limit, the amount of purified contaminated water used for dust prevention may increase.

(Swing mechanism)
The head swing mechanism 26 is driven by the water pressure of the purified contaminated water pumped to the water injection module 3 as a driving force and the first axis C ₁ parallel to the inflow direction of the purified contaminated water to the water injection module 3 and the inflow configured to continuously rotate the nozzle 25 about a direction perpendicular to the second axis C _2. In other words, the swing mechanism 26 uses the fact that the reaction of the water pressure acts in the rotational direction around the second axis C ₂ due to the eccentricity of the nozzle 25, so that the nozzle 25 moves the first axis C ₁ and the second axis C ₂ . Configured to rotate continuously around the center.

  As shown in FIG. 2, the swing mechanism 26 has a specific configuration such as a rolling bevel gear 32 disposed on the outer periphery of the arm portion 24 and an outer periphery of the fixed portion 22 so that the rolling bevel gear 32 is engaged. And a guide bevel gear 33 disposed on the surface.

With this configuration, the swing mechanism 26 is configured so that the arm portion supporting the nozzle 25 rotates about the second axis C ₂ by an angle corresponding to the gear ratio between the rolling bevel gear 32 and the guide bevel gear 33. rotate 24 around the first axis _{C 1.}

(Control mechanism)
The speed governing mechanism 27 includes a turbine 34 disposed coaxially in the inflow passage 29 of the fixed portion 22, a speed reducer 35 disposed within the body portion 23, which decelerates and outputs the rotation of the turbine 34, A driven gear 36 driven by the speed reducer 35 and a regulation gear 37 disposed on the outer periphery of the fixed portion 22 so that the driven gear 36 is engaged.

  The speed reducer 35 includes a first worm 38 that rotates coaxially and integrally with the turbine 34, a first worm wheel 39 that is supported in the body 23 so as to mesh with the first worm 38, and the first worm wheel 39. And a second worm wheel 41 which is supported in the body 23 so as to mesh with the second worm 40 and rotates integrally with the driven gear 36.

  The speed regulating mechanism 27 drives the driven gear 36 at a speed proportional to the rotational speed of the turbine 34 according to the flow rate of water in the inflow passage 29, thereby causing the body portion 23 at a speed corresponding to the amount of water jetted from the nozzle 25. Is rotated with respect to the fixed portion 22 to adjust the speed of the swing mechanism 26. More specifically, the speed adjusting mechanism 27 is added to the driven gear 36 by having the worm mechanism (38, 39, 40, 41) even if the swing mechanism 26 tries to rotate the driven gear 36 at a higher speed. Braking the rotational force generated.

  The water injection module 3 includes the swing mechanism 26 and the speed control mechanism 27 so that the purified contaminated water sprayed from the nozzle 25 is sequentially sprayed on the entire inner surface of the tank 1 to thereby remove the purified contamination. Water is brought into contact with the entire inner surface of the side wall of the tank 1.

  The lower limit of the average pitch of the central position of purified contaminated water that is jetted onto the inner wall of the tank 1 by the water jet module 3 is preferably 10 cm, and more preferably 20 cm. On the other hand, the upper limit of the average pitch is preferably 1.5 m and more preferably 1 m. If the average pitch is less than the lower limit, it may take longer than necessary to finish spraying purified water on the entire inner surface of the side wall of the tank 1. On the other hand, when the average pitch exceeds the upper limit, there may be a region where the purified water does not adhere to the inner surface of the side wall of the tank 1. The “average pitch” is the interval between adjacent parallel tracks of the central position of the purified contaminated water, and means the average value of the vertical distance from one point on the other track to the other track. . Further, “substantially parallel” means that the angle formed by both is 30 ° or less, preferably 15 ° or less.

  The lower limit of the maximum interval of the central position of purified contaminated water that is jetted onto the inner wall of the tank 1 by the water jet module 3 is preferably 20 cm, and more preferably 30 cm. On the other hand, the upper limit of the maximum distance is preferably 2 m, and more preferably 1.5 m. If the maximum interval is less than the lower limit, it may take longer than necessary to finish spraying purified water on the entire inner surface of the tank 1. Conversely, if the maximum interval exceeds the upper limit, there may be a region where the purified water does not adhere to the inner surface of the side wall of the tank 1. The “maximum interval” means the maximum separation distance between all trajectories of the central position of the purified contaminated water, and the interval at the intersection between the trajectories is zero.

<Control unit>
The control unit 4 controls the suction pump 2 and the water injection module 3. Specifically, the control unit 4 performs control to suck up the contaminated water by the suction pump 2 and to inject the purified contaminated water onto the inner surface of the side wall of the tank 1 by the water injection module 3. Moreover, the control part 4 performs control which reinjects the contaminated water purified as washing water by the water injection module 3 so that it may have a predetermined interval to the at least specific area | region of the said side wall inner surface after this purified water injection. . The details of the operation of the dust generation preventing device under the control of the control unit 4 will be described later.

<Adsorbent>
The adsorbent 5 is disposed in the flow path of the contaminated water sucked up by the suction pump 2, and purifies residual contaminated water in the lower part of the tank 1 sucked up by the suction pump 2. Thereby, the contaminated water in which the radioactive pollutant concentration is reduced is transferred to the buffer tank 6 through the contaminated water supply pipe 7. Here, a part of the contaminated water supply pipe 7 through which the contaminated water sucked up by the suction pump 2 circulates is disposed so as to pass outside the tank 1 as will be described later. When contaminated water with a high concentration of radioactive pollutant flows through the section of the contaminated water supply pipe 7, it is necessary to take a strict countermeasure against leakage of contaminated water in the contaminated water supply pipe 7. Therefore, in order to prevent contaminated water having a high concentration of radioactive contaminants from flowing through the section of the contaminated water supply pipe 7 passing outside the tank 1, as shown in FIG. It is preferable to arrange the adsorbent 5 in the tank 1 therebetween. For example, the adsorbent 5 is disposed in the tank 1 by, for example, connecting an adsorbing tower for storing the adsorbent 5 to the upper part of the suction pump 2 in advance, and using a wire or the like from the opening of the upper part of the tank 1 together with the pump 2. This is done by hanging.

  Since the residual contaminated water in the lower part of the tank 1 mainly contains radioactive strontium as a radioactive pollutant, the adsorbent 5 is preferably an adsorbent that selectively adsorbs strontium. As an adsorbent that selectively adsorbs strontium, for example, a capsule adsorbent that has a film that does not permeate calcium and magnesium, selectively permeates strontium, and has an inorganic material that adsorbs strontium 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 lower limit of the width and depth of the adsorption tower that accommodates the adsorbent 5 is preferably 15 cm, and more preferably 20 cm. On the other hand, the upper limit of the width and depth of the adsorption tower is preferably 80 cm, and more preferably 70 cm. If the width or depth of the adsorption tower is less than the above lower limit, the volume of the adsorbent 5 cannot be increased beyond a predetermined level, and there is a possibility that the amount of contaminated water necessary for injection onto the inner surface of the tank 1 cannot be purified. Conversely, if the width or depth of the adsorption tower exceeds the above upper limit, the adsorbent tends to break through locally and the use efficiency of the adsorbent may decrease, or the adsorption tower becomes too large and the adsorption tower is placed above the tank 1. There is a possibility that it cannot be inserted from the opening.

<Buffer tank>
The buffer tank 6 is disposed in the tank 1 by being inserted from an opening at the top of the tank 1. The insertion from this opening is performed by suspending the buffer tank 6 with a wire or the like, for example. The buffer tank 6 stores the contaminated water purified by the adsorbent 5. Further, since the buffer tank 6 is disposed in the tank 1, it is possible to simplify the countermeasure against leakage of contaminated water. Therefore, for example, a foldable type can be used as the buffer tank 6.

  The suction pump 2 and the adsorbent 5 are limited in size because they are inserted from the opening at the top of the tank 1. Therefore, in many cases, the suction pump 2 having a suction capacity exceeding the amount of water supplied per unit time to the water injection module 3 and the adsorbent 5 having a purification capacity exceeding the above-mentioned supply water amount cannot be provided. Even when the suction pump 2 or the adsorbent 5 having such suction capacity or purification capacity lower than the above-mentioned supply water amount is used, the dust generation preventing device is provided with the buffer tank 6 for storing the contaminated water purified by the adsorbent 5 and the supply. Since the pump 9 is provided, the contaminated water whose amount of supplied water is purified can be supplied to the water injection module 3.

  The lower limit of the width and depth of the buffer tank 6 is preferably 50 cm, and more preferably 60 cm. On the other hand, the upper limit of the width and depth of the buffer tank 6 is preferably 80 cm, and more preferably 75 cm. If the width or depth of the buffer tank 6 is less than the above lower limit, there is a possibility that a sufficient amount of purified contaminated water for injection onto the inner surface of the tank 1 cannot be stored. Conversely, if the width or depth of the buffer tank 6 exceeds the above upper limit, the buffer tank 6 may not be inserted from the opening at the top of the tank 1.

The lower limit of the clarified volume of contaminated water can store buffer tank 6, preferably 3m ^3, 3.5 m ³ is more preferable. On the other hand, the upper limit of the capacity of the buffer tank 6 is preferably 5 m ^3, 4.5 m ³ is more preferable. If the capacity of the buffer tank 6 is less than the above lower limit, there is a possibility that the purified contaminated water in an amount contacting the entire inner surface of the side wall of the tank 1 cannot be stored in the buffer tank 6. On the contrary, if the capacity of the buffer tank 6 exceeds the above upper limit, the width or depth of the buffer tank 6 becomes too large, and there is a possibility that the buffer tank 6 cannot be inserted from the opening at the top of the tank 1.

<Contaminated water supply piping>
The contaminated water supply pipe 7 is a pipe for transferring residual contaminated water in the tank 1 that is sucked up by the pump 2 and purified by the adsorbent 5 to the buffer tank 6. The contaminated water supply pipe 7 is disposed through an opening in the upper part of the tank 1 so that an intermediate part passes through the outside of the tank 1.

<Purified water supply piping>
The purified water supply pipe 8 is a pipe for supplying the purified contaminated water stored in the buffer tank 6 to the water injection module 3. The purified water supply pipe 8 is disposed through an opening in the upper part of the tank 1 so that an intermediate part passes through the outside of the tank 1.

<Supply pump>
The supply pump 9 supplies the purified contaminated water to the water injection module 3 by pumping the purified contaminated water stored in the buffer tank 6 through the purified water supply pipe 8. The supply pump 9 is disposed outside the tank 1.

  The dust generation preventing device uses purified contaminated water stored in the buffer tank 6 as contaminated water that is first jetted onto the inner surface of the tank 1. In addition, the dust generation preventing device uses purified contaminated water stored in the buffer tank 6 as cleaning water to be re-injected onto the inner surface of the tank 1. The operation of the dust generation preventing apparatus having the above configuration will be described below.

  In the dust prevention device, first, the control unit 4 sucks up the residual contaminated water in the lower part of the tank 1 by the suction pump 2, thereby purifying the contaminated water by the adsorbent 5 disposed in the suction path. The purified contaminated water is stored in the buffer tank 6. Next, the control unit 4 controls the supply pump 9 to supply the purified contaminated water in the buffer tank 6 to the water injection module 3 through the purified water supply pipe 8. When the purified contaminated water is supplied to the water injection module 3, the purified contaminated water is injected from the water injection module 3 so as to come into contact with the inner surface of the tank 1. The control unit 4 injects the contaminated water purified by the water injection module 3 in this way, and then controls the supply pump 9 after a predetermined time has elapsed to thereby again supply the purified water purified from the water injection module 3. It sprays on the tank 1 inner surface. Here, after the contact of the contaminated water purified by the first injection to a specific area on the inner surface of the side wall of the tank 1, the predetermined contaminated water is brought into contact with the area after a predetermined interval by the re-injection. Time is set. The control unit 4 controls injection and re-injection of the purified contaminated water by the water injection module 3 based on the set predetermined time.

  Since the control unit 4 controls the injection and re-injection of the purified contaminated water by the water injection module 3 in this way, the purified contaminated water contact by the first injection is performed in a specific region on the inner surface of the side wall of the tank 1. During the predetermined interval later, strontium remaining on the inner surface of the side wall dissolves in the purified contaminated water adhering to this region. After the strontium is dissolved in the purified contaminated water, the purified contaminated water is re-injected into this region, so that the purified contaminated water in which the strontium is dissolved is washed away by the purified contaminated water by the re-injection. The water injection module 3 makes the jet of contaminated water purified by the continuous rotation of the nozzle 25 abut on the entire inner surface of the tank 1, so that the control unit 4 controls the inner surface of the side wall of the tank 1 as described above. By controlling the injection and re-injection to the tank, the contaminated water purified by re-injection is applied after a predetermined interval on the entire inner surface of the side wall of the tank 1 after contact with the contaminated water purified by the first injection. Touch. Thereby, since the said dust generation | occurrence | production prevention apparatus can remove effectively the radioactive strontium which remains on the whole surface of the side wall inner surface of the tank 1, generation | occurrence | production of the radioactive dust at the time of tank 1 disassembly can be prevented.

  In addition, the dust generation preventing device injects an amount of purified contaminated water necessary for dissolving strontium, and an amount of purified purified water necessary to wash away the purified contaminated water adhering to the inner surface of the side wall of the tank 1. Therefore, the amount of contaminated water that increases with cleaning in the tank can be suppressed.

  The lower limit of the predetermined interval is preferably 10 minutes, and more preferably 15 minutes. On the other hand, the upper limit of the predetermined interval is preferably 30 minutes, and more preferably 20 minutes. If the predetermined interval is less than the lower limit, strontium remaining on the inner surface of the side wall is not sufficiently dissolved in the purified contaminated water adhering to the inner surface of the side wall by the first injection, and strontium on the inner surface of the side wall cannot be sufficiently removed. There is a fear. On the contrary, when the predetermined interval exceeds the upper limit, the purified contaminated water adhering to the inner surface of the side wall by the first injection starts to dry, and strontium dissolved in the purified contaminated water is deposited to deposit the side wall. May remain on the inner surface.

  Moreover, since the said dust generation | occurrence | production prevention apparatus uses the water which purified the residual contaminated water in the tank 1 as washing water sprayed to the tank 1 inner surface for preventing generation | occurrence | production of radioactive dust, it does not contain a radioactive pollutant. The amount of external water used can be reduced.

[Dust generation prevention method]
The dust generation prevention method is a dust generation prevention method performed using the dust generation prevention device of FIG. The dust generation preventing method is disposed in the tank 1 by sucking up the residual contaminated water from the lower part of the tank 1 after draining the polluted water by the suction pump 2 disposed in the tank 1, and in the tank 1. A step (injection process) of injecting purified water on the inner surface of the side wall of the tank 1 by the water injection module 3 and a reinjection of purified water as cleaning water on the inner surface of the side wall of the tank 1 by the water injection module 3 A process (re-injection process). The dust generation prevention method performs these steps so that a predetermined interval is formed between the injection by the injection step and the re-injection by the re-injection step in at least a specific region of the inner surface of the side wall.

<Suction process>
In the suction process, the control unit 4 controls the suction pump 2 to suck up the residual contaminated water in the tank 1 and purify the contaminated water flowing through the suction path by the adsorbent 5. The purified contaminated water is transferred to the buffer tank 6 through the contaminated water supply pipe 7 and stored in the buffer tank 6.

<Injection process>
In the injection step, the water injection module 3 injects contaminated water onto the inner surface of the side wall of the tank 1 after draining the contaminated water. In the injection step, purified contaminated water stored in the buffer tank 6 is used as the contaminated water injected onto the inner surface of the side wall of the tank 1. Specifically, in the injection process, the control unit 4 controls the supply pump 9 to suck up the purified contaminated water in the buffer tank 6 and pump it in the purified water supply pipe 8, thereby providing a water injection module. 3 is supplied. In addition, the control unit 4 causes the purified contaminated water to be injected onto the inner surface of the side wall of the tank 1 by the water injection module 3. Here, the control unit 4 continuously supplies the purified contaminated water so that the entire side wall inner surface of the tank 1 is wetted with the purified contaminated water by the contact and wetting and spreading of the purified contaminated water by the water injection module 3. Inject.

  In addition, as contaminated water injected in the said injection process, you may use as it is, without purifying the residual contaminated water in the tank 1, the contaminated water discharged | emitted from the other tank for storing contaminated water, etc., for example.

<Re-injection process>
In the re-injection step, cleaning water is injected onto the inner surface of the side wall of the tank 1 by the water injection module 3 after the injection step. In the re-injection step, purified contaminated water stored in the buffer tank 6 is used as the cleaning water that is injected onto the inner surface of the side wall of the tank 1. In the re-injection step, specifically, the control unit 4 causes the contaminated water purified by the water injection module 3 to be injected onto the inner surface of the side wall of the tank 1 by the same method as in the injection step. Here, the controller 4 reinjects the contaminated water purified by the water injection module 3 so as to have a predetermined interval to a specific area on the inner surface of the side wall of the tank 1 after the injection of the purified contaminated water in the injection process. Let spray.

The lower limit of the average contact amount of clarified contaminated water to the inner surface of the side wall due to the injection of water jetting module 3 in the injection step and re-injection process is preferably 150 cc / m ^2, respectively, 200 cc / m ² Gayori preferable. In contrast, the upper limit of the average contact amount of the clarified contaminated water, preferably 200L / ^{m 2} respectively, more preferably ^{100L / m 2, 50L / m} 2 is more preferred. If the average contact amount of purified contaminated water in the injection process is less than the lower limit, strontium remaining on the inner surface of the side wall of the tank 1 may not be sufficiently dissolved in the purified contaminated water adhering to the inner surface of the side wall. is there. Further, if the average contact amount of the purified contaminated water in the re-injection process is less than the lower limit, the purified contaminated water adhering to the inner wall of the side wall in which strontium is dissolved may not be sufficiently washed away. Therefore, by injecting the purified contaminated water in such an amount that the average contact amount of the purified contaminated water is equal to or more than the above lower limit, the injection process and the re-injection process are repeated after the injection process without repeating a plurality of times. By performing the re-injection process once, radioactive strontium remaining on the inner surface of the side wall of the tank 1 can be effectively removed. That is, radioactive strontium remaining on the inner surface of the side wall of the tank 1 can be obtained by injecting the purified contaminated water in such an amount that the average contact amount is equal to or greater than the lower limit, and performing the injection step and the re-injection step only once. Can be removed sufficiently. On the other hand, if the average contact amount of the purified contaminated water exceeds the upper limit, the amount of purified contaminated water sprayed on the inner surface of the tank 1 may be excessive, or the time required for injection may be excessively long. .

When the radioactive pollutant produced | generated in the purified contaminated water adhering to the side wall inner surface of the tank 1 in the said injection process can be specified, the water injection module 3 in a reinjection process is made to satisfy | fill following formula (1). It is possible to further reduce the average contact amount of the purified contaminated water on the inner surface of the side wall by the injection of, and further suppress the injection amount of the purified contaminated water. That is, the ratio of the salinity of contaminated water injected by the water injection module 3 to the salinity of seawater used for decontamination treatment is A [%], the strontium concentration in seawater is B [mg / L], and the side wall After adhering to the inner surface, the molecular weight of the strontium compound produced in the purified contaminated water is C, the solubility of the strontium compound is D [mg / L], and the above-mentioned by the injection of the water injection module 3 in the re-injection step When the average contact amount of purified contaminated water on the inner surface of the side wall is E [cc / m ² ], the average contact amount E may satisfy the following formula (1). Here, the average film thickness of the purified contaminated water adhered to the inner surface of the side wall of the tank 1 in the injection process is set to 0.1 mm. The numerical value “87.6” in the following formula (1) is the molecular weight of strontium.
E ≧ (A × B × C) / (87.6 × D) (1)

For example, when it can be specified that SrCO ₃ is generated in the purified contaminated water adhering to the inner surface of the side wall of the tank 1 in the injection process, if this contaminated water is all contaminated water using seawater for decontamination, that is, A value Is 100%, the molecular weight of SrCO ₃ is 147.6, the solubility is 11 mg / L, and the strontium concentration B in seawater is assumed to be 8 mg / L. The average contact amount E of the contaminated water is calculated as 123 cc / m ² . For example, when it can be specified that SrSO ₄ is generated in the purified contaminated water adhering to the inner wall of the tank 1 in the injection step, the molecular weight of SrSO ₄ is 183.7 and the solubility is 114 mg / L. From (1), the average contact amount E of purified contaminated water in the re-injection process is calculated as 15 cc / m ² . In this way, after the contaminated water purified in the injection process adheres to the inner surface of the side wall of the tank 1, when the radioactive pollutant generated in the contaminated contaminated water can be identified, the water injection in the re-injection process By making the injection amount by the module 3 such that the average contact amount becomes the minimum average contact amount E calculated from the above formula (1), the injection amount of purified contaminated water in the re-injection step Can be greatly reduced.

  As described above, the dust generation preventing method is performed between the injection of the purified contaminated water in the injection process and the injection of the purified contaminated water in the re-injection process in a specific region on the inner surface of the side wall of the tank 1. These steps are performed so that a predetermined interval can be made. For example, the injection direction at the start of injection in the injection process is the same as the injection direction at the start of injection in the reinjection process, and the injection in the reinjection process is performed after the predetermined interval has elapsed since the injection start time in the injection process. Control to start. Thereby, the said dust generation | occurrence | production prevention method can ensure the said predetermined interval between the injection in an injection process, and the injection in a reinjection process in the specific area | region of the side wall inner surface of the tank 1. FIG. Here, the water injection module 3 makes the jet of contaminated water purified by the continuous rotation of the nozzle 25 contact the entire inner surface of the tank 1, so that the water injection module 3 is in contact with the inner surface of the side wall of the tank 1 as described above. By performing the injection process and the re-injection process, after the purified contaminated water is injected over the entire inner surface of the side wall of the tank 1, the purified contaminated water by the re-injection comes into contact after a predetermined interval. Specifically, in the above control, first, the water injection module 3 performs the injection in the injection process, and the injection is stopped when the purified contaminated water adheres to the entire inner surface of the side wall of the tank 1. Then, the said control starts the injection of the reinjection process by the water injection module 3 at the time when the said interval has passed from the injection start time in the injection process.

  As described above, the dust generation prevention method is configured to perform a predetermined interval between the injection in the injection process and the injection in the re-injection process in at least a specific region of the inner surface of the side wall of the tank 1. Do. Thereby, since the said dust generation | occurrence | production prevention method can remove effectively the radioactive strontium which remains on the said side wall inner surface, generation | occurrence | production of the radioactive dust at the time of tank 1 disassembly can be prevented.

  The injection step and the re-injection step can be easily controlled by rotating the nozzle 25 of the water injection module 3 so that the injection interval to at least a specific region on the inner surface of the side wall of the tank 1 is not less than the predetermined interval. can do. Since the water injection module 3 has the above-described structure, the cleaning water can be injected over the entire inner surface of the tank 1 by the rotation of the nozzle 25 during the injection interval. Therefore, in this case, the re-injection process can be performed following the above-described injection process only by simple control of rotating the nozzle 25 of the water injection module 3 for a predetermined time. The “injection interval to a specific area” means that the contaminated water purified to a specific area is sprayed to the specific area from the point of time when the purified water is injected to the specific area by the continuously rotating nozzle. Means the period up to

  In order to efficiently remove strontium on the inner surface of the side wall of the tank 1, it is preferable that the radioactive strontium concentration of the purified contaminated water injected in the reinjection step is lower. For this reason, as a specific upper limit of the radioactive strontium density | concentration of the purified contaminated water, 100 Bq / cc which can be purified by circulating the adsorbent 5 is preferable, and 50 Bq / cc is more preferable.

  Moreover, you may use other water whose radioactive strontium density | concentration is below the said upper limit other than the water which purified the contaminated water in the tank 1 as washing water reinjected in the said reinjection process. For example, external water that does not contain radioactive pollutants, rainwater, seawater, groundwater, or the like can be used as the washing water. By using rainwater, seawater, groundwater or the like as the washing water, the amount of external water that does not contain radioactive pollutants can be reduced. In addition, when using rainwater, seawater, ground water, etc., it is preferable to remove impurities by filtration. In addition, when rainwater collected on the top plate of the tank 1 is used as the washing water, it is not necessary to approve the handling of the hose around the tank 1, so that the installation period of equipment for preventing dust generation can be shortened. Therefore, it is particularly preferable to filter and use rainwater collected on the top plate of the tank 1 as the cleaning water to be reinjected in the reinjection step.

  In addition, in the case of using water other than the purified water in the tank 1 for both the contaminated water injected in the injection process and the washing water injected in the re-injection process, The adsorbent 5 can be omitted.

[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.

  For example, in the above-described embodiment, the buffer tank and the supply pump are provided. If the suction capacity of the suction pump and the purification capacity of the adsorbent exceed the amount of water supplied per unit time to the water injection module, the suction pump Since the contaminated water purified by the pump can be directly supplied to the water injection module, the buffer tank and the supply pump can be omitted. Further, even when the suction capacity of one suction pump and the purification capacity of one adsorbent are lower than the amount of water supplied per unit time to the water injection module, the total suction capacity and the plurality of adsorption capacity of the plurality of suction pumps. When the total purification capacity of the agent satisfies the above supply water amount, the buffer tank and the supply pump can be omitted by arranging a plurality of suction pumps and a plurality of adsorbents. Specifically, a plurality of suction pumps and a plurality of adsorbents are arranged in the contaminated water storage tank by inserting from a plurality of openings above the tank that stores radioactive contaminated water (hereinafter referred to as a contaminated water storage tank). The contaminated water purified by the plurality of suction pumps and the plurality of adsorbents may be simultaneously supplied to the water injection module.

  Moreover, although the said embodiment demonstrated the structure which arrange | positions one buffer tank in a contaminated water storage tank, you may arrange | position a some buffer tank in a contaminated water storage tank. In this case, for example, a plurality of buffer tanks are inserted into the contaminated water storage tank from a plurality of openings above the contaminated water storage tank. By doing so, a buffer tank having a smaller outer size can be used, and the buffer tank can be easily inserted into the contaminated water storage tank.

  In the above embodiment, a three-dimensional nozzle type cleaning module having a plurality of nozzles and a swing mechanism is used as the water injection module, but the cleaning water can be injected onto the inner surface of the side wall of the contaminated water storage tank. If so, other cleaning modules may be used. For example, a two-dimensional nozzle type cleaning module that uses a rotating spray ball or a one-dimensional nozzle type cleaning module that sprays in the horizontal direction may be used as the water injection module. When the one-dimensional nozzle type cleaning module is used, for example, the nozzle is moved in the vertical direction while spraying the cleaning water in the horizontal direction, so that the contaminated water or the cleaning water is applied to the entire inner surface of the side wall of the contaminated water storage tank. Can be injected.

  Moreover, although the said embodiment demonstrated the structure which injects contaminated water and washing | cleaning water on the whole side wall inner surface with a water injection module, contaminated water and washing | cleaning water are injected only to the one part area | region of side wall inner surface with a water injection module. A configuration may be adopted. In this way, even when contaminated water and cleaning water are sprayed to only a part of the inner surface of the side wall, the radioactive material remaining on the inner surface of the tank in that region can be removed, so the amount of radioactive dust generated when the tank is disassembled can be reduced. .

  The dust generation prevention device and dust generation prevention method of the present invention can prevent the generation of radioactive dust at the time of dismantling of the tank while suppressing the increase of the contaminated water, so that the contaminated water generated particularly in the nuclear power plant after the accident is stored. It can be suitably used when dismantling the contaminated water tank.

DESCRIPTION OF SYMBOLS 1 Tank 2 Suction pump 3 Water injection module 4 Control part 5 Adsorbent 6 Buffer tank 7 Contaminated water supply piping 8 Purified water supply piping 9 Supply pump 22 Fixed part 23 Trunk part 24 Arm part 25 Nozzle 26 Swing mechanism 27 Speed control Mechanism 28 Flange 29 Inflow path 30 Outlet 31 Internal flow path 32 Rolling bevel gear 33 Guide bevel gear 34 Turbine 35 Reduction gear 36 Driven gear 37 Restriction gear 38 First worm 39 First worm wheel 40 Second worm 41 Second worm wheel C ₁ , C ₂ axis

Claims (6)

A device for preventing the generation of dust when dismantling a tank that has stored radioactively contaminated water,
A pump that is disposed in the tank by insertion from the opening of the tank, and sucks up the residual contaminated water from the bottom of the tank after discharging the contaminated water;
A water injection module which is disposed in the tank by insertion from the opening of the tank, and injects contaminated water or washing water to the inner surface of the side wall of the tank;
A control unit for controlling the pump and the water injection module,
The control unit sucks up the contaminated water by the pump, injects the contaminated water onto the inner surface of the side wall by the water injection module, and after the injection of the contaminated water, gives a predetermined interval to at least a specific region of the inner surface of the side wall. An apparatus for preventing dust generation, wherein control is performed to re-inject cleaning water by the water injection module. Further equipped with an adsorbent capable of purifying contaminated water in the contaminated water suction route by the pump,
The dust generation preventing apparatus according to claim 1, wherein the water injection module uses water purified by the adsorbent as the cleaning water. The tank further includes a buffer tank for storing contaminated water sucked up by the pump,
The dust generation preventing device according to claim 1 or 2, wherein the water injection module uses contaminated water stored in the buffer tank as the contaminated water for injection. The water injection module has a plurality of nozzles and a swing mechanism,
The said swing mechanism rotates the said nozzle continuously centering on the 1st axis | shaft parallel to the inflow direction of the said contaminated water or washing water, and the 2nd axis | shaft perpendicular | vertical to this 1st axis | shaft. The dust generation prevention apparatus of Claim 2 or Claim 3. Contact of contaminated water and cleaning water into the inner surface of the side wall due to the injection of the water jetting module is from claim 1 to claim 4, is The average 150 cc / m ² or more 200L / m ² or less The dust generation prevention apparatus as described. A method for preventing the generation of dust at the time of dismantling a tank that stored radioactively contaminated water,
A process of sucking up residual contaminated water from the bottom of the tank after draining contaminated water by a pump disposed in the tank;
A step of injecting the contaminated water onto the inner surface of the side wall of the tank by a water injection module disposed in the tank;
Re-injecting cleaning water onto the inner surface of the side wall of the tank by the water injection module,
A dust generation prevention method, wherein a predetermined interval exists between the injection by the injection step and the re-injection by the re-injection step in at least a specific region of the inner surface of the side wall.

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