Soil treatment equipment

Abstract

The present invention provides a soil treatment device that can make it easier to remove radioactive materials from soil. [Solution] The soil treatment apparatus is a device that performs a treatment on soil containing mineral particles on which radioactive materials have been adsorbed, separating the mineral particles from other particles, and comprises a processing unit having a flow channel and an ejection unit that ejects pressurized liquid from the upstream side to the downstream side of the flow channel, wherein the ejection unit is configured to eject pressurized liquid into a slurry obtained by mixing liquid with soil within the flow channel, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry, and the flow channel is configured to include a first part, a second part located downstream of the first part and having a smaller cross-sectional area than the first part that is perpendicular to the direction of extension of the flow channel, and a third part located downstream of the second part and having a larger cross-sectional area than the second part.

Description

Technical Field

[0001] A device for treating soil containing radioactive substances is concerned in the present invention.

Background Art

[0002] As one of the volume reduction technologies for removing radioactive substances from soil containing radioactive substances and reducing the volume of soil with a high radioactive concentration, a classification treatment technology is known.

[0003] In the classification treatment technology, soil containing radioactive substances is classified into, for example, a group of fine soil particles (hereinafter, "fine fraction") containing fine particles such as clay and silt, and a group of soil particles (hereinafter, "coarse fraction") containing gravel, sand, etc. and having a larger particle size than the fine fraction. Since radioactive substances such as radioactive cesium tend to adhere to particles with a relatively small particle size (for example, particles of minerals such as mica), they are contained in a large amount in the fine fraction after classification. Therefore, the concentration of radioactive substances can be reduced by separating and removing the fine fraction from the soil. The coarse fraction after the fine fraction is removed can be reused for construction or the like.

[0004] Patent Document 1 proposes washing the coarse fraction in order to further remove the radioactive substances contained in the coarse fraction after performing the above classification.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] However, in the conventional classification treatment technology, there is room for improvement from the viewpoint of more reliably removing radioactive substances from soil. <00,00033> The object of the present invention is to solve the above problem and to provide a soil treatment device that can easily remove radioactive materials from soil. [Means for solving the problem]

[0008] To achieve the above objective, a soil treatment apparatus according to one aspect of the present invention is a soil treatment apparatus that performs a process to separate mineral particles on which radioactive material has been adsorbed from other particles in soil, comprising: a processing unit having a flow channel; and an injection unit that injects a pressurized liquid from the upstream side to the downstream side of the flow channel, wherein the injection unit is configured to inject the pressurized liquid into a slurry obtained by mixing a liquid with the soil in the flow channel, thereby generating cavitation by creating a difference in flow velocity at the interface between the pressurized liquid and the slurry, and the flow channel is configured to include a first part; a second part located downstream of the first part and having a cross-sectional area perpendicular to the extending direction of the flow channel and smaller than that of the first part; and a third part located downstream of the second part and having a cross-sectional area larger than that of the second part. [Effects of the Invention]

[0009] According to the soil treatment apparatus of the present invention, it is possible to easily remove radioactive materials from soil. [Brief explanation of the drawing]

[0010] [Figure 1] This is a schematic side view of the soil treatment device according to the first embodiment. [Figure 2A] This is a schematic enlarged cross-sectional view of region A shown in Figure 1. [Figure 2B] Figure 2A is a schematic cross-sectional view along the IIB-IIB line. [Figure 3A] This is a schematic diagram illustrating a soil treatment method I according to the first embodiment. [Figure 3B] This is a schematic diagram illustrating another soil treatment method II according to the first embodiment. [Figure 4]It is a schematic cross-sectional view showing the soil treatment apparatus according to the second embodiment. [Figure 5A] It is a schematic enlarged cross-sectional view showing a part of the flow path of the treatment unit. [Figure 5B] It is a schematic enlarged cross-sectional view taken along the line VB-VB shown in FIG. 5A. [Figure 5C] It is a schematic enlarged cross-sectional view taken along the line VC-VC shown in FIG. 5A. [Figure 6] It is a schematic top view of the fringe used in the experiment. [Figure 7A] It is a schematic top perspective view showing the positional relationship between the conveying device and the hopper. [Figure 7B] It is a schematic cross-sectional view taken along the line VIIB-VIIB shown in FIG. 7A. [Figure 8A] It is a schematic perspective view showing a modified example of the liquid supply unit and the hopper. [Figure 8B] It is a top view of the liquid supply unit and the hopper shown in FIG. 8A. [Figure 9A] It is a schematic cross-sectional view showing a modified example of the flow path. [Figure 9B] It is a schematic cross-sectional view showing another modified example of the flow path. [Figure 9C] It is a schematic cross-sectional view showing still another modified example of the flow path. [Figure 10] It is a schematic side view showing the apparatus of the comparative example. [Figure 11A] It is a photograph showing the measurement sample after the crushing treatment of the example. [Figure 11B] It is a photograph showing the measurement sample of the comparative example. [Figure 11C] It is a diagram showing the particle size accumulation curves of the measurement samples of the example and the comparative example. [Figure 12] It is a schematic diagram showing the soil treatment method of the reference example.

Embodiments for Carrying Out the Invention

[0011] (Findings on which the present invention is based) The inventors of this invention conducted thorough research to facilitate the removal of radioactive materials from soil and obtained the following findings.

[0012] Conventional classification technologies have the following problems (1) and (2):

[0013] (1) Radioactive materials such as radioactive cesium are known to be easily adsorbed onto particles of layered clay minerals. Layered clay minerals include mica minerals such as weathered biotite and its weathered product, vermiculite (hereinafter simply referred to as "mica"). Particles of minerals such as mica may be attached to or embedded in larger grain sizes of sand particles, gravel particles, etc. If mineral particles are attached to (or embedded in) sand particles, etc., even if classification is performed, the coarse grain portion after classification will contain mineral particles with adsorbed radioactive materials. Furthermore, if the particle size of the mineral particles with adsorbed radioactive materials is large, those mineral particles will be separated into the coarse grain portion. For this reason, it is difficult to remove radioactive materials more reliably by classification. In response to this, it has been proposed to reduce the radioactive concentration by performing advanced classification and washing treatments on the coarse grain portion after classification (for example, Patent Document 1). However, it is considered difficult to more reliably detach mineral particles that are fixed to or embedded in sand particles, etc. using the method described in Patent Document 1. Further details will be provided later.

[0014] Furthermore, recent studies have reported that radioactive materials such as radioactive cesium can be adsorbed onto layered clay mineral particles and then trapped (fixed) within them. In layered clay mineral particles, the surfaces located between layers are negatively charged, making it easier for radioactive materials to be adsorbed onto these surfaces. When radioactive materials are adsorbed between two layers that make up a layered clay mineral particle, the two layers surrounding the radioactive material close over time. In this way, the radioactive material is trapped inside the layered clay mineral particle. When radioactive materials are fixed to layered clay mineral particles, they become difficult to detach or dissolve from those particles. In particular, in large-grained mica particles, if radioactive materials are trapped in parts altered by weathering, it becomes even more difficult to remove the radioactive materials using conventional classification techniques.

[0015] Therefore, it can be difficult to lower the concentration of radioactive material in the coarse particles and increase the decontamination rate.

[0016] (2) Furthermore, in order to more reliably remove radioactive materials from soil through classification, it is necessary to separate and remove soil particle groups within a particle size range that include mineral particles as fine particles with a high concentration of radioactive materials. As mentioned above, when radioactive materials are trapped in mineral particles and become difficult to dissolve or desorb, it becomes difficult to reduce the amount of fine particles to be separated and removed, and as a result, it may be difficult to increase the volume reduction rate. "Volume reduction" refers to reducing the volume of soil that has a radioactive concentration higher than a predetermined value (e.g., 8000 Bq / kg) and cannot be reused as is.

[0017] Therefore, the inventors of this application, after diligent study, have found a method to generate cavitation by injecting a pressurized liquid into a slurry containing soil, thereby creating a difference in flow velocity at the interface between the pressurized liquid and the slurry. According to this method, the impact force generated when the bubbles produced by cavitation collapse can separate mineral particles to which radioactive materials have been adsorbed from other particles. This makes it easier to remove radioactive materials from soil. "Mineral particles to which radioactive materials have been adsorbed" includes not only particles to which radioactive materials have been adsorbed on the surface, but also particles to which radioactive materials have been adsorbed (trapped) between layers.

[0018] According to the above method, the impact force during bubble collapse allows for the separation of mineral particles attached to larger soil particles, such as sand particles, from those soil particles. Alternatively, the impact force during bubble collapse can crush mineral particles to which radioactive materials have been adsorbed, resulting in smaller particles. As a result, the concentration of radioactive materials in the coarse-grained portion after classification can be further reduced. Furthermore, by reducing the particle size of the particles to which radioactive materials are attached, the volume of soil with a high concentration of radioactive materials (fine-grained portion) can be reduced. The inventors of this invention arrived at the present invention based on this novel finding.

[0019] Embodiments of the present invention will be described below with reference to the drawings. However, the present invention is not limited to these embodiments. For illustrative purposes, the dimensions of elements in the drawings may be exaggerated and may not necessarily be to scale. Also, substantially identical components in the drawings are denoted by the same reference numerals.

[0020] In the following explanation, for the sake of clarity, terms such as "up," "down," "side," "left," and "right" will be used to indicate directions, assuming the device is in its normal operating state. However, this does not mean that the usage state of the device according to the present invention is limited. For reference, the drawings schematically show mutually orthogonal X, Y, and Z axes. The Z axis is, for example, the vertical direction. In the following explanation, when simply referred to as the X direction, Y direction, or Z direction, it refers to the respective axis direction, including two opposite directions (for example, the -X direction and the +X direction).

[0021] 《First Embodiment》 A soil treatment apparatus and soil treatment method according to the first embodiment will be described.

[0022] [Soil treatment equipment] Figures 1, 2A, and 2B are schematic diagrams illustrating the general structure and principle of the soil treatment device according to the first embodiment. Figure 1 is a schematic side view of the soil treatment device. Figure 2A is a schematic enlarged cross-sectional view of region A shown in Figure 1, and Figure 2B is a schematic cross-sectional view along the line IIB-IIB in Figure 2A.

[0023] Soil treatment device 1 is a device for treating soil containing mineral particles on which radioactive materials have been adsorbed. In this embodiment, the soil to be treated contains mineral particles on which radioactive materials have been adsorbed and soil particles with a larger particle size than those mineral particles. The soil treated by soil treatment device 1 may be soil that has not undergone classification treatment, and may be soil with a broad particle size distribution including, for example, gravel particles (particle size: e.g., 2 mm or more), sand particles (particle size: e.g., 74 μm or more and less than 2 mm), silt particles (particle size: e.g., 5 μm or more and less than 74 μm), and clay particles (particle size: e.g., less than 5 μm).

[0024] As shown in Figure 1, the soil treatment apparatus 1 comprises a processing unit 3, an injection unit 2 that injects pressurized liquid 20 into the processing unit 3, and a slurry supply unit 4 that supplies a slurry 40 containing soil into the processing unit 3.

[0025] The processing unit 3 includes a flow path 30. The flow path 30 is composed of, for example, a pipe having a circular cross-section. The flow path 30 extends, for example, in a horizontal direction perpendicular to the vertical direction. In Figure 1, for clarity, the vertically upward direction is shown as the +Z direction, and the direction from the upstream side to the downstream side of the flow path 30 is shown as the +X direction. The flow path 30 may have an outlet 37 at its downstream end for discharging the mixture 70 containing the processed slurry 40 and pressurized liquid 20 from the processing unit 3.

[0026] The ejection unit 2 is positioned to eject the pressurized liquid 20 in the direction from the upstream side to the downstream side (+X direction) of the flow path 30. The ejection unit 2 ejects the pressurized liquid 20 into the slurry 40 in the flow path 30. The ejection unit 2 is, for example, a high-pressure ejector that ejects high-pressure water.

[0027] The slurry supply unit 4 supplies slurry 40, which is a mixture of soil and liquid (e.g., water), into the flow path 30. The slurry supply unit 4 is connected downstream of the discharge unit 2 in the flow path 30. In the flow path 30, the slurry supply unit 4 supplies slurry 40 toward the pressurized liquid 20 discharged by the discharge unit 2, in a direction intersecting the discharge direction of the pressurized liquid 20. In the example shown in Figure 1, the slurry supply unit 4 is configured to supply slurry 40 in a direction perpendicular to the discharge direction (-Z direction). The pressure of the liquid contained in the slurry 40 during supply is, for example, approximately 1 atmosphere.

[0028] In this embodiment, as shown in Figures 2A and 2B, the injection unit 2 and the slurry supply unit 4 are configured to generate cavitation by creating a flow velocity difference at the interface 20s between the pressurized liquid 20 and the slurry 40. The mechanism for generating cavitation will be described below.

[0029] As shown in Figures 2A and 2B, the pressurized liquid 20 ejected from the ejection unit 2 is a high-speed fluid (for example, pressure: 4 MPa, speed: approximately 50 m / s) traveling at high speed in the +X direction within the flow path 30. Within the flow path 30, the pressurized liquid 20 collides with the slurry 40 and, as shown in Figure 2B, travels at high speed through roughly the central part of the slurry 40. The slurry 40 is pulled by the flow of the pressurized liquid 20 and forms a multiphase flow that flows around the pressurized liquid 20 in the same direction as the pressurized liquid 20. This multiphase flow includes at least soil (solid phase) and liquid (liquid phase) contained in the slurry 40. A space 80 may exist above the slurry 40. Since the slurry 40 flows at a lower speed than the pressurized liquid 20, a velocity difference is created at the interface 20s between the slurry 40 and the pressurized liquid 20. This causes cavitation. Specifically, as shown in Figure 2A, vortices 82 are generated within the slurry 40 due to the shear force caused by the difference in flow velocity between the pressurized liquid 20 and the slurry 40. Because the center of the vortex 82 is locally low-pressure, the liquid in the slurry 40 vaporizes and bubbles 81 are generated. The slurry 40 flows downstream, entraining the bubbles 81. As the slurry 40 flows downstream, the bubbles 81 are compressed and collapse by the surrounding liquid.

[0030] When the bubbles 81 generated by cavitation collapse, a large impact force is generated. This impact force separates the mineral particles contained in the slurry 40 from other particles. In this specification, "separating mineral particles from other particles" includes not only separating mineral particles attached to or embedded in soil particles such as sand particles from those soil particles (hereinafter referred to as "separation"), but also crushing the mineral particles and dividing them into multiple smaller particles (hereinafter referred to as "crushing"). In this embodiment, the impact force when the bubbles 81 collapse causes sedimentation, crushing, or both of these processes to occur.

[0031] The bubbles 81 formed by cavitation are generated one after another in the slurry 40 as it flows in contact with the pressurized liquid 20, and then collapse. Therefore, the impact force caused by the collapse of the bubbles 81 can be applied to the particles in the slurry 40 throughout the flow of the slurry 40.

[0032] As shown in Figure 1, the region Rc in the flow path 30 configured to generate cavitation by the mechanism described above is called the "cavitation generation region". The cavitation generation region Rc is located downstream of the position P where the slurry 40 is supplied from the slurry supply unit 4 (hereinafter referred to as the "slurry supply position"). In the cavitation generation region Rc, as shown in Figures 2A and 2B, the slurry 40 flows around the pressurized liquid 20. The decomposition of mineral particles in the slurry 40 mainly occurs in the cavitation generation region Rc. Downstream of the cavitation generation region Rc, the slurry 40 and the pressurized liquid 20 are mixed to form a mixture 70. The mixture 70 is discharged from the outlet 37 and sent to, for example, a classification device.

[0033] In the example shown in Figure 1, no air inlet is provided upstream of the slurry supply position P in the flow path 30 to allow air to flow in from the outside. In this embodiment, the bubbles generated by cavitation are vaporized liquid in the slurry 40. Since cavitation is not generated by air introduced from the outside, it is not necessary to provide an air inlet in the flow path 30. However, an air inlet may be provided in the flow path 30 as long as it does not hinder the generation of cavitation due to the difference in flow velocity.

[0034] In this embodiment, since cavitation generated by the above mechanism is utilized, mineral particles can be separated more efficiently and reliably (e.g., sedimentation, crushing).

[0035] Patent Document 1 describes a method of cleaning soil using cavitation generated by a method different from that of the present invention. In Patent Document 1, pressurized fluid is ejected from a nozzle to generate bubbles, and soil is supplied to the region where bubbles exist near the nozzle. However, the inventors of the present invention have found that with such a configuration, it is difficult to reliably supply soil to the limited region where bubbles exist. Furthermore, the soil can only receive impact force in a limited region near the nozzle (the region where bubbles exist). For this reason, it is difficult to efficiently apply sufficient impact force to the soil to adequately separate radioactive materials or crush mineral particles.

[0036] In contrast, in this embodiment, cavitation is generated at the interface 20s between the flow of the slurry 40 containing soil and the flow of the pressurized liquid 20. Therefore, bubbles can be generated not only in the region near the outlet of the pressurized liquid 20, but also along the length of the flow channel 30. Furthermore, since the slurry 40 flows while entraining the bubbles, the impact force caused by the collapse of the bubbles can be more reliably applied to the slurry 40. Moreover, as the slurry 40 and the pressurized liquid 20 flow in contact, the generation and collapse of bubbles are repeated, so high impact forces are repeatedly applied to the particles in the slurry 40. Consequently, the separation of mineral particles can be further advanced toward the downstream side of the flow channel 30.

[0037] Furthermore, in the apparatus of Patent Document 1, the region where air bubbles exist is limited, and particles with relatively small particle sizes may not be easily affected by cavitation. In contrast, in the soil treatment apparatus 1 of this embodiment, the slurry 40 moves while entraining air bubbles, so the cavitation effect is more easily extended to the small particles contained in the slurry 40. In addition, in the soil treatment apparatus 1 of this embodiment, by reducing the amount of liquid relative to the soil in the slurry 40, the impact force when the air bubbles 81 collapse can be applied to the mineral particles more efficiently.

[0038] [Soil treatment methods] The soil treatment method of this embodiment includes a step of generating cavitation by the mechanism described above with reference to Figures 2A and 2B (hereinafter referred to as the "cavitation generation step"). In the cavitation generation step, a pressurized liquid is injected into a slurry obtained by mixing soil with a liquid, and cavitation is generated by creating a flow velocity difference at the interface between the pressurized liquid and the slurry (see Figures 2A and 2B). The cavitation generation step can be carried out, for example, using the soil treatment apparatus 1 shown in Figure 1. The apparatus used in this step is not limited to the apparatus shown in Figure 1, as it is configured to generate cavitation by utilizing the flow velocity difference between the slurry and the pressurized liquid.

[0039] Figures 3A and 3B are schematic diagrams illustrating soil treatment methods I and II according to the first embodiment, respectively. As a reference example, Figure 12 schematically shows a treatment method that performs only classification treatment.

[0040] Figures 3A, 3B, and the reference example Figure 12 illustrate a case where the soil 10 to be treated contains gravel particles (particle size: e.g., 2 mm or larger) 11, sand particles (particle size: e.g., 74 μm or larger and less than 2 mm) 12, and silt and clay particles (silt particle particle size: e.g., 5 μm or larger and less than 74 μm; clay particle particle size: e.g., less than 5 μm) 13. These particles include mineral particles 15 on which radioactive materials such as radioactive cesium have been adsorbed (hereinafter referred to as "radioactive material-containing mineral particles"). The particle size of the radioactive material-containing mineral particles 15 is not particularly limited. Here, examples of radioactive material-containing mineral particles 15 with various particle sizes, from relatively small to 2 mm or larger, are shown. Some of the radioactive material-containing mineral particles 15 may be attached to or embedded in soil particles with larger particle sizes (e.g., gravel particles 11, sand particles 12, etc.).

[0041] For clarity, let's first explain the method used in the example shown in Figure 12. In this example, the soil 10 described above is classified into, for example, coarse-grained material with a particle size of 75 μm or more and fine-grained material with a particle size of less than 75 μm. As a result, mineral particles 15 containing radioactive materials with a particle size of 75 μm or more are classified into the coarse-grained material. On the other hand, mineral particles 15 containing radioactive materials with a particle size of less than 75 μm can be separated into the fine-grained material. However, as shown in the figure, some of the mineral particles 15 containing radioactive materials with a particle size of less than 75 μm may be attached to or embedded in sand particles 12 or gravel particles 11, and may be classified into the coarse-grained material together with these particles 11, 12, etc. As a result, it is difficult to sufficiently reduce the concentration of radioactive materials in the coarse-grained material after classification.

[0042] In contrast, in soil treatment methods I and II of this embodiment, a cavitation generation process is performed before classification. This makes it possible to reduce the amount of radioactive material contained in the coarse particles after classification compared to the reference example method shown in Figure 12.

[0043] <Soil Treatment Method I> As shown in Figure 3A, in soil treatment method I, during the cavitation generation process, the impact force generated when bubbles collapse separates the radioactive material-containing mineral particles 15 from other particles. As a result, the radioactive material-containing mineral particles 15 that were attached to soil particles such as sand particles 12 and gravel particles 11 are separated from those soil particles (sludge removal). In addition, the radioactive material-containing mineral particles 15 and other mineral particles are crushed into smaller particles 14 (disintegration). After the disintegration of the radioactive material-containing mineral particles 15, the radioactive material may remain adsorbed on the particles 14 or may be detached from the particles 14.

[0044] In the cavitation generation process, as shown in the figure, it is sufficient that at least the portion of the radioactive material-containing mineral particles 15 to which the radioactive material is adsorbed is broken down. For example, if the radioactive material-containing mineral particles 15 are mica, the radioactive material is mainly adsorbed or fixed to the weathered portion (weathered portion) of the mica particle, so it is sufficient that at least the weathered portion is broken down. The weathered portion is located, for example, near the surface of the mica particle. The unweathered portion is harder than the weathered portion and is therefore less likely to be broken down, and can be discharged from the flow path while maintaining a certain size. Similarly, soil particles that are harder than the weathered portion of mica are also less likely to be broken down, and are not broken down as finely as the weathered portion, and can be discharged from the flow path while maintaining a certain size.

[0045] After the cavitation generation process, the mixture of the treated slurry and the pressurized liquid is classified into a large-diameter particle group and a small-diameter particle group with smaller particle sizes than the large-diameter particle group. In this processing method, the large-diameter particle group consists of particles with particle sizes greater than or equal to, for example, the radioactive material-containing mineral particles. The small-diameter particle group consists of particles with particle sizes smaller than, for example, the radioactive material-containing mineral particles. The small-diameter particle group includes particles 14 after the radioactive material-containing mineral particles 15 have been crushed. The radioactive material is included in the small-diameter particle group because it is either adsorbed onto the particles 14 or detached from the particles 14. Classification may also be performed based on the particle size of the relatively small radioactive material-containing mineral particles 15 (for example, the particle size of silt or clay), thereby making the particle size at the classification point even smaller. The particle size at the classification point may be less than 75 μm, for example, 20 μm or less.

[0046] According to soil treatment method I, the cavitation process separates radioactive material-containing mineral particles 15 from larger soil particles. Furthermore, the larger radioactive material-containing mineral particles 15 are broken down into smaller particles 14. Therefore, subsequent classification allows for more reliable separation of the radioactive material into the smaller particle group. Consequently, the concentration of radioactive material in the larger particle group can be further reduced (i.e., the decontamination rate can be increased) compared to the reference example method (Figure 12). For example, it becomes possible to reduce the radioactivity concentration of soil exceeding 8000 Bq to a concentration significantly below the 8000 Bq / kg threshold for reuse (e.g., 1000 Bq / kg or less). Additionally, since advanced classification and washing are not required after this treatment, the equipment, cost, number of steps, and water usage for soil treatment can be reduced.

[0047] Furthermore, according to soil treatment method I, the cavitation generation process breaks down the radioactive material-containing mineral particles 15, so in the subsequent classification process, the particle size at the classification point can be made smaller, thereby reducing the volume of soil with a high concentration of radioactive material (small-diameter particle group) (i.e., increasing the volume reduction rate).

[0048] <Soil Treatment Method II> In soil treatment method II, at least a demud treatment is performed by a cavitation generation process. As shown in Figure 3B, in the cavitation generation process, the impact force when bubbles collapse separates the radioactive material-containing mineral particles 15 that were attached to (or contained within) soil particles such as sand particles 12 and gravel particles 11 from the soil particles (demud removal).

[0049] Next, similar to soil treatment method I, a classification step is performed to separate the mixture of slurry and pressurized liquid into a large-diameter particle group and a small-diameter particle group. The large-diameter particle group is, for example, a group of particles that include soil particles (in this example, sand particles 12 or gravel particles 11) to which radioactive material-containing mineral particles 15 were attached before silting. The small-diameter particle group is, for example, a group of particles that include radioactive material-containing mineral particles 15. The small-diameter particle group includes radioactive material-containing mineral particles 15 separated from the soil particles. The particle size at the classification point is, for example, 75 μm.

[0050] According to soil treatment method II, the cavitation generation process separates the radioactive material-containing mineral particles 15 from the larger soil particles, allowing for more reliable separation of the radioactive material into the smaller particle group through subsequent classification. Therefore, the concentration of radioactive material in the larger particle group can be further reduced (i.e., the decontamination rate can be increased) compared to the method in the reference example (Figure 12).

[0051] (effect) As shown in Figures 1 to 2B, the soil treatment apparatus 1 of this embodiment is configured such that the discharge unit 2 and the slurry supply unit 4 generate cavitation by creating a flow velocity difference at the interface 20s between the pressurized liquid 20 and the slurry 40 within the flow path 30 of the processing unit 3. With this configuration, the impact force when bubbles collapse due to cavitation can separate mineral particles from other particles, enabling processes such as demudging and crushing. As a result, radioactive materials can be easily removed.

[0052] Furthermore, as described above with reference to Figures 2A and 2B, the above configuration allows for more efficient application of impact force due to bubble collapse to the mineral particles compared to conventional devices (for example, the device described in Patent Document 1). Therefore, mineral particles can be separated from other particles more reliably.

[0053] Furthermore, with the above configuration, the decomposition of mineral particles can be promoted while the slurry 40 containing soil and the pressurized liquid 20 flow in the same direction. Therefore, continuous processing is possible, and the amount of soil processed per hour can be increased (for example, 12 tons / hour or more).

[0054] The ejection unit 2 and the slurry supply unit 4 may be configured to perform a demud removal process, as shown in Figure 3B, in which radioactive material-containing mineral particles 15 attached to (or embedded in) soil particles such as sand particles 12 are separated from the soil particles by the impact force when bubbles generated by cavitation collapse. With such a configuration, the amount of radioactive material contained in the large-diameter particle group after classification can be reduced in the subsequent classification process.

[0055] The discharge unit 2 and slurry supply unit 4 may be configured to perform a crushing process, as shown in Figure 3A, by crushing the radioactive material-containing mineral particles 15 into particles 14 smaller in diameter than the radioactive material-containing mineral particles 15, using the impact force when bubbles generated by cavitation collapse. The soil treatment device 1 can repeatedly apply strong impact forces to the mineral particles and therefore may have a high crushing capacity. With such a configuration, in the subsequent classification process, the amount of radioactive material contained in the large-diameter particle group after classification can be further reduced. Furthermore, even if the particle size at the classification point is reduced (for example, to less than the particle size of the radioactive material-containing mineral particles 15), it becomes possible to remove the radioactive material. Therefore, the volume of the small-diameter particle group with a high concentration of radioactive material can be reduced.

[0056] The discharge unit 2 and the slurry supply unit 4 may be configured to separate radioactive material-containing mineral particles from soil particles using the impact force generated when bubbles produced by cavitation collapse, and then to crush the separated radioactive material-containing mineral particles. With such a configuration, the demudging and crushing processes can be carried out simultaneously while the slurry 40 flows in contact with the pressurized liquid 20. Therefore, since it is not necessary to prepare separate devices for demudging and crushing, the cost, number of processes, and time required for processing can be further reduced.

[0057] This embodiment provides a soil treatment method that includes a cavitation generation step. In the cavitation generation step, a pressurized liquid is injected into a slurry obtained by mixing a liquid with soil, and cavitation is generated by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. As shown in Figures 3A and 3B, the impact force when the bubbles generated by cavitation collapse separates the mineral particles 15 on which radioactive material has been adsorbed from other particles. For example, the impact force causes disintegration, crushing, or both. This makes it easier to remove radioactive material, so that the decontamination rate and / or volume reduction rate can be increased.

[0058] The radioactive material adsorbed onto the mineral particles is, for example, radioactive cesium, and the mineral particles on which radioactive cesium is adsorbed may be, for example, mica particles. It has been reported that the majority of radioactive cesium is adsorbed or fixed onto mica. Therefore, by crushing and removing the mica particles on which radioactive cesium is adsorbed, radioactive cesium can be removed from the soil more effectively. As an example, it becomes possible to increase the decontamination rate, which was about 70% in conventional classification processes, to 80% or more, preferably about 90%.

[0059] For example, mica particles can be broken down by the impact force generated when bubbles produced by cavitation collapse. As an example, for instance, 50% or more, preferably 70% or more, of the mica particles (whether or not they contain radioactive material) in the slurry supplied to the processing unit 3 are broken down by the aforementioned impact force, becoming smaller particles than before they were introduced (see experimental results in Figures 11A and 11B described later).

[0060] In the soil treatment method of this embodiment, the ratio of the weight of the liquid used to the weight of the soil to be treated (hereinafter referred to as the "total solid-liquid ratio") is, for example, 5 to 15, preferably 10 or less. "Weight of soil" refers to the dry weight of the soil. "Weight of liquid used" is the total weight of the liquid used in the treatment, and includes the weight of the liquid contained in the slurry 40 (Figure 1) and the weight of the pressurized liquid 20 (Figure 1). By keeping the total solid-liquid ratio at 15 or less, the costs associated with soil treatment and the treatment of the liquid used can be reduced, and practicality can be improved.

[0061] The weight ratio of the pressurized liquid 20 (Figure 1) to the soil is 10 or less, preferably 6 or less. The weight ratio of the liquid contained in the slurry 40 to the soil (slurry solid-liquid ratio) is 5 or less, preferably 3 or less. By keeping the amount of liquid contained in the slurry 40 small, the impact force due to bubble collapse is more easily applied to the particles in the slurry 40, which allows for efficient separation of mineral particles.

[0062] Conventional processing methods, for example, involve performing a normal classification using a trommel, followed by advanced classification by applying mechanical impact force to the coarse particles. Such methods use a large amount of liquid, resulting in a total solid-liquid ratio exceeding, for example, 20. Since the liquid (water) used in the processing contains radioactive materials, its storage and disposal incur additional costs. In contrast, according to this embodiment, a cavitation generation process for demudging and crushing is performed on the entire soil before classification. In the subsequent classification process, the soil is classified after demudging, eliminating the need for advanced classification as in conventional methods. Therefore, the total solid-liquid ratio can be reduced compared to conventional methods.

[0063] For example, Waseda University News, Japan, Waseda University, June 4, 2019, https: / / www.waseda.jp / top / news / 65177 proposes adding water and a dispersant that lowers the zeta potential to the soil, performing high-pressure washing, and washing the soil containing the dispersant in turbulent water to disperse fine particles from granular soil into water (i.e., disintegrate granular soil). According to this method, the soil obtained after washing contains the dispersant, so it may not be able to be reused as is. Removing the dispersant from the soil after washing requires a large amount of water, which places a heavy burden on the environment. Moreover, this method is a treatment method that utilizes a dispersant, and as can be seen from the fact that the dispersant makes it difficult for air bubbles to collapse, it is not a soil treatment method that utilizes the impact force of air bubble collapse.

[0064] In contrast, according to this embodiment, the large impact force generated when bubbles collapse due to cavitation can be used to separate (disintegrate) aggregated soil particles. For this reason, it is not necessary to add chemicals such as dispersants that lower the zeta potential to the slurry for the purpose of disintegration treatment. In fact, in this embodiment, dispersants may reduce the disintegration or crushing effect. If a dispersant is added to the slurry, the bubbles generated by cavitation are stabilized by the action of the dispersant, so the collapse of the bubbles is suppressed. As a result, the impact force generated by the collapse of bubbles becomes less likely (or smaller), and the disintegration and crushing effect due to impact force may decrease. Also, if a dispersant (surfactant) is added to the slurry, the impact force when bubbles collapse is less likely to be applied to the soil particles. Furthermore, from the viewpoint of reusing the soil with low radioactivity concentration (large-diameter particle group) obtained by classifying the slurry after treatment, it is preferable that no dispersant is added to the slurry.

[0065] Furthermore, the slurry 40 supplied to the soil treatment device 1 of this embodiment may contain a small amount of a dispersant (for example, sodium hexametaphosphate). The amount of dispersant added may be, for example, less than 1% of the mass of soil in the slurry 40, or less than 0.5 mol / kg relative to the soil in the slurry 40. This makes it possible to suppress the re-aggregation of soil particles in the slurry 40 after treatment (before classification) while minimizing the influence of the dispersant on the demudging and crushing action using cavitation.

[0066] Figures 3A and 3B illustrate a method for treating soil 10 containing clay, silt, sand, and gravel. However, the soil treatment method of this embodiment can also be applied to treatments where only coarse-grained material (sand, gravel, etc.) or only fine-grained material (clay, silt) is to be treated after a normal classification process. Furthermore, the soil treatment method of this embodiment can also be applied to soil that has undergone prior sedimentation treatment to break down mineral particles.

[0067] Figures 3A and 3B show that the cavitation generation process causes the disintegration and crushing of mineral particles. However, due to the impact force caused by the collapse of bubbles, not only are mineral particles disintegrated, but lumps such as clay in the slurry may also be broken up. In addition, particles other than mineral particles may be crushed, or the edges of larger particles such as gravel particles may be rounded and polished. Changes that occur in mineral particles and other particles can be confirmed, for example, by observing the soil before and after the cavitation generation process or by comparing the particle size distribution.

[0068] 《Second Embodiment》 Figure 4 is a schematic cross-sectional view showing a soil treatment apparatus according to a second embodiment of the present invention. Below, we will mainly describe the differences from the soil treatment apparatus of the first embodiment, and redundant explanations will be omitted as appropriate.

[0069] The soil treatment apparatus 1a shown in Figure 4 comprises a processing unit 3 having a flow path 30, an injection unit 2 for injecting pressurized liquid 20, a slurry supply unit (sometimes called a "slurry supply device") 4 for supplying slurry 40, a classification unit 7, and a control unit 8. The slurry supply unit 4 comprises a liquid supply unit 5, a soil supply unit 6, and a mixing unit. The mixing unit is configured to mix the liquid 50 supplied from the liquid supply unit 5 with the soil 10 supplied from the soil supply unit 6. In this example, a hopper 41 functions as the mixing unit.

[0070] In the soil treatment apparatus 1a, the soil 10 to be treated is supplied to the hopper 41 by the soil supply unit 6. The liquid (water in this case) 50 to be mixed with the soil 10 is supplied to the hopper 41 by the liquid supply unit 5. The soil 10 and liquid 50, supplied separately to the hopper 41, are mixed on the inner wall of the hopper 41 to form a slurry 40, which is then supplied to the flow path 30 of the processing unit 3. In the flow path 30 of the processing unit 3, pressurized liquid 20 is injected into the slurry 40 from the discharge unit 2. Within the flow path 30, a process is performed to separate mineral particles in the slurry 40 from other particles using cavitation, similar to the previously described embodiment. The treated slurry 40 and pressurized liquid 20 are discharged from the discharge port 37 of the flow path 30 and sent to the classification unit 7.

[0071] The following describes the specific configuration of each component of the soil treatment device 1a. In the following description, the treatment conditions, size, and capacity of each component may be exemplified when treating soil 10 at a rate of 1 kg / min. However, the treatment conditions, size, and capacity of each component should be appropriately selected according to the type of soil, the amount of soil to be treated, etc., and are not limited to the values ​​exemplified.

[0072] (Ejection section) The ejection unit 2 comprises a high-pressure ejector equipped with a nozzle 22 having an ejection port at its tip, a high-speed jet pump 23 (capacity: e.g., 6.3 L / m × 5.5 MPa × 0.83 kW × 100 V) for example, a triple-plunger type, and piping 24 located upstream of the nozzle 22, which fluidly connects the high-speed jet pump 23 and the nozzle 22. The nozzle 22 is configured such that its cross-sectional area increases from the ejection port towards the piping 24.

[0073] The high-pressure ejector is configured to move at high speed, for example, along the portion of the flow path 30 that extends in the X direction. In this embodiment, the high-pressure ejector ejects a pressurized liquid (in this case, pressurized water) 20 at 4 MPa at a flow rate of 0.1 liters / second along the X direction. The velocity of the pressurized water is, for example, 50 m / s.

[0074] (processing) The flow path 30 of the processing unit 3 has multiple sections 31 to 34 with different cross-sectional areas. The cross-sectional area of ​​the flow path 30 refers to the cross-sectional area perpendicular to the direction of extension of the flow path 30. In the example shown in Figure 4, multiple pipes of different diameters are connected to constitute the flow path 30, but these may be formed integrally.

[0075] In this embodiment, the flow path 30 has an enlarged section 36 with a larger cross-sectional area than its upstream and downstream sides. The enlarged section 36 is located downstream of the slurry supply position P to which the slurry supply unit 4 is connected in the flow path 30. Downstream of the enlarged section 36, the slurry 40 is at a lower pressure and the flow velocity difference between the slurry 40 and the pressurized liquid 20 is larger than upstream of the enlarged section 36, so the amount of bubbles generated by cavitation can be increased. Therefore, by providing the enlarged section 36, the cavitation generation region Rc in the flow path 30 can be made longer.

[0076] In the example shown in FIG. 4, the flow path 30 includes a first portion 31, a second portion 32 located on the downstream side (+X side) of the first portion 31 and having a smaller cross-sectional area than the first portion 31, and a third portion 33 located on the downstream side of the second portion 32 and having a larger cross-sectional area than the second portion 32. A slurry supply portion 4 is connected to the first portion 31. An enlarged portion 36 that enlarges the cross-sectional area of the flow path 30 is formed by the downstream end portion of the second portion 32 and the upstream end portion of the third portion 33.

[0077] Referring to FIGS. 5A to 5C, the functions of each part of the flow path 30 will be specifically described. FIG. 5A is a schematic enlarged cross-sectional view showing a part of the flow path 30. FIGS. 5B and 5C are enlarged cross-sectional views taken along line VB-VB and line VC-VC shown in FIG. 5A, respectively.

[0078] In the illustrated example, the cross-section of the flow path 30 is, for example, circular. In this case, the diameter D1 of the first portion 31 and the diameter D3 of the third portion 33 are larger than the diameter D2 of the second portion 32 (D2 < D1, D3). From the slurry supply position P of the first portion 31 to at least a part of the third portion 33, it extends in the ejection direction (X direction) of the pressurized liquid 20. In FIG. 4, the respective diameters of the first portion 31 to the third portion 33 are substantially constant, but the diameter of each portion may be set to have a function as described below and does not have to be substantially constant.

[0079] In the present embodiment, the cavitation generation region Rc includes a region that extends in the X direction from the slurry supply position P of the flow path 30 to at least a part of the third portion 33. In the illustrated example, the region from the slurry supply position P to the position where the pressurized liquid 20 collides with the inner wall of the pipe of the third portion 33 is the cavitation generation region Rc.

[0080] <First portion> The first part 31 includes a region where the pressurized liquid 20 from the ejection part 2 first collides with the slurry 40 at atmospheric pressure. After the collision, the pressurized liquid 20 travels downstream through the slurry 40 (see Fig. 2B). In the first part 31, since the flow velocity difference between the slurry 40 and the pressurized liquid 20 is large, vortices 82 are likely to be formed due to the flow velocity difference, and a large amount of bubbles 81 is generated.

[0081] The first part 31 has a sufficient cross-sectional area so that the pressurized liquid 20 can flow downstream through the slurry 40. As shown in Fig. 5A, the first part 31 may be configured to have a space 80 above the slurry 40 such that the slurry 40 collided by the pressurized liquid 20 can escape. In this example, the diameter (inner diameter) D1 of the first part 31 is, for example, 27.0 mm.

[0082] The length L1 along the X direction from the slurry supply position P to the tapered part 34 in the first part 31 may be smaller than the lengths L2 and L3 along the X direction of the second part 32 and the third part 33, respectively (L1 < L2, L3). In the first part 31, since the slurry 40 can easily escape into the upper space 80, the contact area between the slurry 40 and the pressurized liquid 20 is likely to be small. By keeping the length L1 of the first part 31 smaller than those of the second part 32 and the third part 33, the contact area (the area of the interface 20s) for generating cavitation can be increased more quickly.

[0083] <The second part> As shown in Figure 5B, the second section 32 is configured such that the slurry 40 flows so as to roughly fill the area around the pressurized liquid 20. The space 80 above the slurry 40 is narrower than that of the first section 31. Because the space 80 is narrower, the slurry 40 is less likely to escape from the impact force when the bubbles 81 collapse, and the impact force is more likely to act on the particles in the slurry 40. In addition, the slurry 40 can be made to contact the circumferential surface of the pressurized liquid 20 more reliably. As a result, the area of ​​the interface 20s where bubbles 81 are generated by cavitation can be increased. Furthermore, since the radial thickness t of the slurry 40 is kept smaller than that of the first section 31, the impact force when the bubbles 81 collapse is more easily transmitted over the entire thickness t of the slurry 40.

[0084] The cross-sectional area of ​​the second section 32 should be set so that a flow of slurry 40 is formed around the flow (jet flow) of the pressurized liquid 20. As shown in Figure 5, the diameter D2 of the second section 32 is set to be at least larger than the diameter Dj of the pressurized liquid 20 (jet flow). On the other hand, if the diameter D2 is too small, the flow rate of the slurry 40 may decrease or the slurry 40 may become clogged. To prevent this, the diameter (inner diameter) D2 may be at least half of the diameter D1. In this example, the diameter D2 of the second section 32 is, for example, 21.6 mm.

[0085] The cross-sectional area of ​​the second section 32 may be set to be larger than the cross-sectional area of ​​the piping 24 (Figure 4) of the discharge section 2. This makes it more certain that the cross-sectional area of ​​the second section 32 will be larger than the cross-sectional area of ​​the pressurized liquid 20. Therefore, as shown in Figure 5B, it is easier to form a flow of slurry 40 around the pressurized liquid 20.

[0086] When the flow rate of the slurry 40 is approximately constant, the cross-sectional area of ​​the slurry 40 decreases in the second section 32, causing the slurry 40 to accelerate. As a result, the velocity difference between the slurry 40 and the pressurized liquid 20 gradually decreases, making cavitation less likely to occur.

[0087] By providing the second section 32, the pressure of the slurry 40 is released in the third section 33, which promotes the generation of bubbles due to cavitation. The length L2 of the second section 32 may be smaller than, for example, the length L3 of the third section 33. This allows the slurry 40 to move faster in the third section 33, where the amount of bubbles generated increases.

[0088] <3rd part> In the third section 33, the cross-sectional area of ​​the flow channel 30 expands, causing the pressure in the slurry 40 to be rapidly released and generating bubbles 81. Also, as the flow velocity of the slurry 40 decreases, the velocity difference between the slurry 40 and the pressurized liquid 20 increases again, making it easier for vortices 82 to form and increasing the amount of bubbles 81. In the third section 33, the amount of bubbles 81 generated increases in this way, and the impact force when the bubbles 81 collapse can further dislodge and break down the soil in the slurry 40.

[0089] In the third part 33, the flow velocities of the pressurized liquid 20 and slurry 40 are reduced, making them more susceptible to the Coriolis force. As shown in Figure 5C, in the Northern Hemisphere, the flow of the pressurized liquid 20 is affected by the Coriolis force and curves to the right relative to the direction of travel (+X direction). Also, as shown in an enlarged view in Figure 5C, relatively heavier particles p1 in the slurry 40 are more susceptible to the Coriolis force and tend to accumulate on the right side of the direction of travel. Thus, relatively lighter particles p2 in the slurry 40 can flow separately from the relatively heavier particles p1, making it easier for the impact force from the collapse of bubbles 81 to act on the lighter particles p1 as well. Therefore, relatively light mineral particles such as mica can be broken down more efficiently. The mica that has been dissolved or broken down in the first part 31 and the second part 32 can be further broken down into smaller pieces in the third part 33. Alternatively, mica that is not sufficiently broken down in the first part 31 and the second part 32 due to the lack of cavitation effect can be broken down in the third part 33.

[0090] The diameter D3 of the third part 33 may be, for example, at most twice the diameter D2 of the second part 32 (D2 < D3 ≤ 2 × D2). Thereby, clogging is less likely to occur at the end on the downstream side of the second part 32. The diameter (inner diameter) D3 of the third part 33 is, for example, 41.6 mm.

[0091] A tapered portion whose diameter increases toward the third part 33 may be provided between the second part 32 and the third part 33. In this case, the diameter D3 of the third part 33 can be made even larger.

[0092] The length L3 of the third part 33 may be larger than each of the length L1 of the first part 31 and the length L2 of the second part 32. The length L3 may be larger than the length L4 from the slurry supply position P to the upstream end of the third part 33 (or the downstream end of the second part 32) in the flow path 30. By increasing the length L3 of the third part 33, deflocculation and disintegration (particularly disintegration) due to cavitation can be further advanced. In particular, efficient disintegration using the Coriolis force can be performed. Also, even when the soil contains relatively large (for example, particle size: 2 mm or more) mineral particles, the weathered portions of the particles can be sufficiently disintegrated.

[0093] In the third part 33, the portion located on the downstream side of the cavitation generation region Rc extends, for example, in the -Z direction and is connected to the classification part 7. In the example shown in FIG. 4, the pipe constituting the third part 33 is a bent pipe. After extending in the X direction, it bends downward. Instead, the bent pipe constituting the third part 33 may bend horizontally and extend to the classification part 7. Alternatively, the third part 33 may be constituted by a straight pipe extending in the X direction. In this case, a discharge port, for example, vertically downward, may be provided on the side surface of the third part 33.

[0094] Furthermore, a configuration in which a wall is provided to block the flow path of the third section, causing the pressurized liquid and slurry to collide with the wall, thereby disintegrating and crushing the mineral particles through collision, is also conceivable. However, according to the inventor's research, since the mineral particles are dispersed in the liquid, the impact force from the collision is not easily applied to the mineral particles themselves. For this reason, it is difficult to obtain sufficient effect (especially sufficient crushing ability). Rather, as described above, by increasing the length L3 of the third section 33 compared to the other sections and utilizing the Coriolis force along with the cavitation effect, the ability to crush the mineral particles can be more effectively enhanced.

[0095] The inventors of the present invention conducted a verification experiment to confirm the above-mentioned effect of the third part 33. In the verification experiment, a fringe was placed at position R shown in Figure 5C, and treatment was performed using the soil treatment device 1a. The surface condition of the fringe after treatment was observed. Figure 6 is a schematic top view of the fringe used in the experiment, showing the surface located on the flow channel side. As a result of the observation, it was confirmed that the central part 35c of the surface of the fringe 35 was worn. This is thought to be due to the impact of high-pressure water. In addition, rust was observed in the right part 352 located on the right side in the direction of travel of the pressurized liquid in the central part 35c, but no rust was observed in the left part 351 located on the left side. This is thought to be because irregularities were formed in the right part 352 due to collisions with relatively heavy particles. From these results, it was confirmed that in the third part of the flow channel, the slurry flows while heavy particles and light particles are separated by the Coriolis force.

[0096] <Tapered section> As shown in Figures 4 and 5A, the flow path 30 may further have a tapered portion 34 between the first portion 31 and the second portion 32, the tapered portion having a decreasing cross-sectional area from the first portion 31 to the second portion 32.

[0097] Large vortices 82, such as those in the first section 31, are less likely to form inside the tapered section 34. This allows the slurry 40 to flow more smoothly into the smaller diameter second section 32. By providing the tapered section 34, the slurry 40 or soil within the slurry 40 is less likely to clog the downstream end of the first section 31. Therefore, a decrease in processing speed due to clogging can be suppressed, especially when the soil contains small particles (such as clay and silt) or when the soil has a wide particle size distribution. The inclination angle α of the inner surface of the tapered section 34 is not particularly limited, but may be, for example, 45° or less. This allows for more effective suppression of clogging.

[0098] (Slurry Supply Department) As shown in Figure 4, the slurry supply unit 4 comprises a hopper 41, a liquid supply unit 5, and a soil supply unit 6.

[0099] <Hopper> The hopper 41 has an upper opening 411 and a lower opening 412. The hopper 41 has a tapered shape in which the inner diameter decreases from the upper opening 411 to the lower opening 412. The upper opening 411 is, for example, an opening that faces vertically upward. The lower opening 412 is fluidly connected to the first portion 31 of the flow path 30 of the processing unit 3. In this embodiment, the hopper 41 is frustoconical, but it may also be frustoconical.

[0100] The hopper 41 is configured to mix the liquid 50 and soil 10, which are supplied separately from the upper opening 411, on the inner wall of the hopper 41 to form a slurry 40, which is then discharged from the lower opening 412. The slurry 40 discharged from the lower opening 412 is supplied to the flow path 30 of the processing unit 3.

[0101] <Liquid supply section> The liquid supply unit 5 supplies liquid 50 from the upper opening 411 toward the inner wall of the hopper 41. The liquid 50 is, for example, water. The liquid supply unit 5 comprises a volute-type submersible pump (capacity: for example, 40 L / m × 4.2 m × 0.1 kW × 100 V) 53 and a liquid line 51 connected to the submersible pump 53. The liquid line 51 is provided with a liquid supply port for supplying liquid to the hopper 41. The liquid supply unit 5 is set to supply water to the hopper 41 at a flow rate of, for example, 0.05 liters / second.

[0102] The liquid line 51 has a portion that extends along at least a part of the periphery of the upper opening 411 of the hopper 41. In the example shown in Figure 4, the liquid line 51 has an annular portion 511 that extends in an annular shape along the periphery of the upper opening 411. The annular portion 511 is provided with a plurality of liquid supply ports for supplying the liquid 50 toward the inner wall of the hopper 41. The term "annular" is not limited to a circular annular shape, but also includes polygonal annular shapes such as rectangular annular shapes. The periphery of the upper opening 411 may be circular, and the annular portion 511 may be rectangular annular. In this example, the portion of the liquid line 51 that extends along the periphery of the upper opening 411 is annular, but it may be arc-shaped, linear, or otherwise.

[0103] During operation of the soil treatment device 1a, the liquid supply rate (in this case, water supply rate) from the liquid line 51 to the hopper 41 is, for example, 0.05 liters / second. The supply rate is not particularly limited and is set as appropriate based on the soil supply rate, the flow rate of the pressurized liquid, etc. It is also possible to change the liquid supply rate during operation via the control unit 8 depending on the operating status of the soil treatment device.

[0104] <Soil Supply Department> The soil supply unit 6 supplies soil 10 from the upper opening 411 toward the inner wall 41s of the hopper 41. In the example shown in Figure 4, the soil supply unit 6 includes a soil storage tank 61 for storing the soil 10 and a conveying device 62 for transporting the soil 10 supplied from the soil storage tank 61. The conveying device 62 is, for example, a belt conveyor. The soil 10 supplied to the conveying device 62 is transported to a predetermined input position Q above the hopper 41 and supplied from the input position Q to the hopper 41. The soil supply rate is, for example, 1 kg / min.

[0105] Figure 7A is a schematic top perspective view of the conveying device and hopper. Figure 7B is a schematic cross-sectional view along the VIIB-VIIB line shown in Figure 7A.

[0106] As shown in Figures 7A and 7B, the conveying device 62 includes a belt 621 above the hopper 41 that conveys the soil 10 to the input position Q. In a plan view, the input position Q is located inside the upper opening 411 of the hopper 41. The belt 621 is configured to move in one direction (in this case, the -X direction) to the input position Q, then make a U-turn downwards at the input position Q and move in the opposite direction (in this case, the +X direction). As a result, the soil 10 on the belt 621 is supplied from the input position Q toward the inner wall 41s of the hopper 41.

[0107] The position and conveying speed of the conveying device 62 are set so that the soil 10 is supplied, for example, to a region 410 of the inner wall 41s of the hopper 41 that is close to the upper end. Region 410 is a region whose height along the Z direction from the lower opening 412 of the hopper 41 is, for example, 1 / 2 or more of the height H of the hopper 41. This allows the soil 10 to travel a longer distance along the inner wall 41s together with the liquid 50, so that the soil 10 and the liquid 50 can be thoroughly mixed.

[0108] In this embodiment, as shown in Figure 7B, the inertial force generated by the transport can be used to cause heavier and lighter particles of the soil 10 to fall to different positions on the inner wall 41s. For example, if the soil 10 contains gravel particles 11, sand particles 12, and mineral particles 13 in order of heaviest to lightest, the heavier particles will fall further upstream (towards the +X side) relative to the transport direction. In this way, when the soil 10 is introduced, clumps of soil 10 can be broken up, making it easier to mix with the liquid 50. Therefore, a more uniform slurry 40 can be formed. In addition, it is possible to more effectively suppress the supply of soil clumps to the processing unit 3.

[0109] As shown in Figure 7A, the input position Q is offset from the center C of the lower opening 412 in a plan view. By offsetting the input position Q from the center C of the lower opening 412, the soil 10 can be supplied more reliably to the inner wall 41s of the hopper 41. Therefore, it is possible to prevent the particles of the input soil 10 from being sent directly from the lower opening 412 to the processing unit 3 without being mixed with the liquid 50.

[0110] The input position Q may be located downstream of the center C of the lower opening 412 in the transport direction of the transport device 62 (the -X direction in Figures 7A and 7B) in a plan view. With this configuration, particles in the soil 10 are propelled by inertial force from the input position Q towards the opposing portion of the inner wall 41s and are more likely to fall onto the inner wall 41s. Therefore, it is possible to suppress particles from falling into the lower opening 412 without contacting the inner wall 41s. In addition, even relatively heavy particles are more likely to fall into the region 410 near the upper end of the inner wall 41s, allowing them to be thoroughly mixed with the liquid 50.

[0111] The conveying device 62 may further include an adjustment member 622 upstream of the input position Q on the belt for adjusting the height of the soil 10. In a plan view, the adjustment member 622 extends across the width of the belt 621. The lower end of the adjustment member 622 is positioned at a predetermined distance t in the Z direction from the upper surface of the belt 621. By providing the adjustment member 622, the height of the soil 10 on the belt 621 can be kept below the distance t. This makes it possible to suppress clogging of the processing unit 3 due to an increase in the amount of soil 10 supplied. In addition, the amount of soil 10 supplied to the hopper 41 per unit time can be kept approximately constant.

[0112] <Classification Department> As shown in Figure 4, a mixture 70, which is a mixture of pressurized liquid 20 and slurry 40, is sent to the classification unit 7 from the discharge port 37 of the processing unit 3. The classification unit 7 classifies the mixture 70 into a group of large-diameter particles having a particle size above a predetermined classification point and a group of small-diameter particles having a particle size below the classification point and having a higher radioactive concentration than the large-diameter particle group. In this embodiment, classification is performed using a vibrating screen, but various known classification devices can be used, not limited to vibrating screens. Classification may be performed in multiple stages.

[0113] In the example shown in Figure 4, the classification unit 7 comprises a sieve 72 with a mesh size of 2 mm and a sieve 73 with a mesh size of 75 μm positioned downstream of sieve 72. This removes gravel particles 11 by sieve 72 and sand particles 12 by sieve 73. The mixture 70 that passes through sieve 72 is mud containing particles less than 75 μm in size, such as clay and silt, which also contain mineral particles 13. The majority of the radioactive material is contained in the mud. The mud may be further classified, for example, by a high-mesh separator.

[0114] In the cavitation generation region Rc, when a sedimentation treatment is performed to separate mineral particles on which radioactive material has been adsorbed from soil particles, the classification unit 7 may be configured to classify the mixture 70 into a group of large-diameter particles including soil particles (e.g., particle size 75 μm or larger) and a group of small-diameter particles including mineral particles (e.g., particle size less than 75 μm) (see Figure 3B).

[0115] Alternatively, if sediment removal and mineral particle crushing are performed in the cavitation generation region Rc, the classification unit 7 may be configured to classify the mixture 70 into a group of large-diameter particles having a particle size of 20 μm or larger than that of the mineral particles, and a group of small-diameter particles having a particle size smaller than that of the mineral particles (see Figure 3A).

[0116] (Control Unit) The control unit 8 is configured to control the operation of, for example, the discharge unit 2, the liquid supply unit 5, the soil supply unit 6, etc. This makes it possible to adjust, as appropriate, the mixing ratio of the soil 10 and liquid 50 contained in the slurry 40, the flow rate of the pressurized liquid 20, etc., depending on, for example, the type and condition of the soil 10 to be treated, the operating state of the soil treatment device 1a, etc.

[0117] (effect) In the soil treatment apparatus 1a of this embodiment, as illustrated in Figures 4 to 5C, the flow path 30 of the processing unit 3 has an enlarged section 36 downstream of the slurry supply position P that enlarges the cross-sectional area. The slurry supply unit 4 and the discharge unit 2 are configured such that the flow velocity difference between the slurry 40 and the pressurized liquid 20 is larger downstream of the enlarged section 36 than upstream of the enlarged section 36, and the amount of bubbles 81 generated by cavitation increases.

[0118] With this configuration, the pressure of the slurry 40 drops sharply downstream of the expansion section 36. Also, since the flow velocity of the slurry 40 decreases, the flow velocity ratio between the slurry 40 and the pressurized liquid 20 increases. As a result, the amount of bubbles 81 generated by cavitation can be increased downstream of the expansion section 36 compared to upstream of the expansion section 36. This further improves the separation of mineral particles in the slurry 40. Furthermore, the decrease in the flow velocity of the slurry 40 downstream of the expansion section 36 increases the effect of the Coriolis force. As a result, the particles in the slurry 40 separate as they flow, allowing the impact force during bubble collapse to be applied more efficiently to relatively lighter particles such as mineral particles.

[0119] Furthermore, the above configuration allows for a longer cavitation generation region Rc within the flow channel 30. Since cavitation can be continuously generated within the flow channel 30, the processing time for disintegrating and crushing mineral particles in the slurry 40 can be extended without increasing the amount of water used.

[0120] Furthermore, in the soil treatment apparatus 1a of this embodiment, the slurry supply unit 4 includes a hopper 41, a soil supply unit 6 that supplies soil 10 toward the inner wall 41s of the hopper 41, and a liquid supply unit 5 that supplies liquid 50 toward the inner wall 41s of the hopper 41. The soil supply unit 6 and the liquid supply unit 5 are configured such that the liquid 50 and the soil 10 are mixed on the inner wall 41s of the hopper 41 to form a slurry 40, which is then supplied from the lower opening 412 of the hopper 41 to the flow path 30 of the processing unit 3.

[0121] This configuration allows for more reliable mixing of the soil 10 and liquid 50 while keeping the amount of liquid 50 low. Therefore, it becomes possible to reduce the total solid-liquid ratio.

[0122] Furthermore, with the above configuration, slurry 40 having a substantially constant mixing ratio (mixing ratio of soil 10 to liquid 50) can be continuously supplied to the processing unit 3 at a substantially constant speed. In addition, the mixing ratio of liquid 50 to soil 10 can be easily adjusted. For example, the mixing ratio can be adjusted by the control unit 8 during operation.

[0123] Furthermore, with the above configuration, even if the soil 10 contains relatively small particles such as clay, the particles come into contact with the liquid 50 on the inner wall 41s of the hopper 41, making it less likely for them to adhere to the inner wall 41s. Therefore, the frequency of maintenance can be reduced.

[0124] Furthermore, with the above configuration, compared to the case where a pre-made slurry is transported and supplied to the processing unit, stirring operations, large mixing equipment, and slurry transport equipment are unnecessary, thereby reducing the cost required to form the slurry 40. Also, since the slurry does not need to be transported, there is no need to increase the amount of liquid to facilitate slurry transport.

[0125] Furthermore, with the above configuration, the liquid 50 can be mixed with the amount of soil 10 flowing through the hopper 41 without any stirring or other processes. This is advantageous because, if the soil 10 contains radioactive materials, dust containing radioactive materials is less likely to be stirred up.

[0126] In the soil treatment apparatus 1a of this embodiment, the liquid supply unit 5 includes a liquid line 51 that extends along at least a portion of the periphery of the upper opening 411 of the hopper 41 and transports liquid 50, and a plurality of liquid supply ports that are spaced apart from each other in the liquid line 51 and discharge liquid 50. With this configuration, it is easy to supply liquid 50 near the upper end of the inner wall 41s of the hopper 41. Also, because the liquid 50 tends to flow circumferentially along the inner wall 41s due to inertial force, the flow path of the liquid 50 can be lengthened. Therefore, the liquid 50 and the soil 10 can be mixed more reliably. Furthermore, by providing a plurality of liquid supply ports, the liquid 50 can flow over a wider area of ​​the inner wall 41s of the hopper 41. Therefore, the adhesion of soil particles to the inner wall 41s can be suppressed.

[0127] Furthermore, according to this embodiment, in a soil treatment method including a cavitation generation step, as shown in Figure 5A, it becomes possible to control the flow velocity difference between the pressurized liquid 20 and the slurry 40 so that the amount of bubbles generated by cavitation decreases and then increases again while the pressurized liquid 20 flows outward together with the slurry 40. In this method, in the cavitation generation step, mineral particles in the slurry 40 can be dissolved or crushed not only immediately after the pressurized liquid 20 collides with the slurry 40, but also after the amount of bubbles generated increases again. Therefore, the amount of liquid used can be reduced while dissolving or crushing can be carried out more efficiently.

[0128] (Modification 1: Slurry supply unit) The slurry supply unit 4 may be configured such that the liquid 50 and soil 10 flow downwards in a swirling motion along the inner wall 41s of the hopper 41, mixing together to form the slurry 40. With such a configuration, the soil 10 and liquid 50 can be mixed more reliably and uniformly.

[0129] Figure 8A is a schematic perspective view showing modified versions of the liquid supply unit and hopper, respectively. Figure 8B is a top view of the modified version shown in Figure 8A.

[0130] In the example shown in Figures 8A and 8B, the liquid line 51 includes an annular section 511 that extends in an annular shape along the periphery of the upper opening 411 of the hopper 41. Multiple liquid supply ports 512 are arranged in the annular section 511 at intervals from each other. A nozzle 52 extending downward is connected to each liquid supply port 512. As shown in Figure 8B, in a plan view along the height direction (Z direction) of the hopper 41, the direction in which the nozzle 52 extends is inclined by an angle θ (0° < θ < 90°) in the direction of flow of the liquid 50 flowing through the annular section 511, with respect to the direction d from the liquid supply port 512 toward the center C of the lower opening 412. The angle θ is, for example, 20° or more.

[0131] With this configuration, the liquid 50 from the nozzle 52 tends to flow circumferentially due to inertial force, so the liquid 50 tends to flow downward while swirling along the inner wall 41s of the hopper 41 together with the soil 10. Therefore, the path for mixing the liquid 50 and the soil 10 becomes longer, so the liquid 50 and the soil 10 can be mixed more reliably and more uniformly.

[0132] In the examples shown in Figures 8A and 8B, all of the nozzles 52 are inclined at the same angle θ with respect to direction d, but the angles θ may be different from each other. Also, if at least one nozzle 52 provided in the liquid supply port 512 is inclined with respect to direction d, the effect of swirling the liquid 50 can be obtained.

[0133] (Modification 2: Flow path of the processing unit) Figure 9A is a schematic cross-sectional view showing a modified example of the flow path. The flow path 30 shown in Figure 9A has a plurality of enlarged sections 36 downstream of the slurry supply position P. The plurality of enlarged sections 36 are spaced apart from each other. In this example, a fourth section 320, having a smaller cross-sectional area than the third section 33, is connected downstream of the third section 33, and a fifth section 330, having a larger cross-sectional area than the fourth section 320, is connected downstream of the fourth section 320 in this order. The fourth section 320 and the fifth section 330 form an enlarged section 36 that promotes the generation of cavitation. The cross-sectional area of ​​the fourth section 320 may be the same as or different from that of the second section 32. Similarly, the cross-sectional area of ​​the fifth section 330 may be the same as or different from that of the third section 33. The flow path 30 may have an alternating number of fourth sections 320 and fifth sections 330 downstream of the third section 33, thereby having more enlarged sections 36.

[0134] If each enlarged section 36 is too long, the vortex 84 (Figure 9B), described later, will not form easily across the enlarged section 36, and the effects of preventing soil particle clogging and promoting demud and crushing by the vortex 84 may not be obtained. For this reason, the length of the enlarged section 36 may be, for example, twice the length of the second section 32 or less.

[0135] According to the configuration shown in Figure 9A, the cavitation generation region Rc can be made even longer by providing multiple expansion sections 36 in the flow channel 30. Each expansion section 36 functions as a "treatment chamber" where the processing of soil in the slurry 40 proceeds more (more intensively) than in other parts. By forming such treatment chambers at intervals within the flow channel 30, the intensity of processing can be varied throughout the flow channel 30, making it possible to more efficiently dissolve and crush soil particles in the slurry 40. The configuration with multiple treatment chambers is particularly advantageous when, for example, the pressure of the pressurized liquid is increased (e.g., 8 MPa).

[0136] Figure 9B is a schematic cross-sectional view showing another modification of the flow path. In this modification, each of the first and third parts includes multiple sections with different cross-sectional areas.

[0137] The first portion 31 of the flow path 30 shown in Figure 9B includes an upstream portion 311 and a downstream portion 312 located downstream of the upstream portion 311. The diameters D11 of the upstream portion 311, D12 of the downstream portion 312, and D2 of the second portion are set such that D11 > D12 > D2.

[0138] The third part 33 includes an upstream part 331, a downstream part 332 located downstream of the upstream part 331, and an enlarged part 333 located between them. The diameters D31 of the upstream part 331, D32 of the downstream part 332, and D33 of the enlarged part are set such that D33 > D31 and D32 > D2. The diameter D33 of the enlarged part 333 may be the same as or approximately the same as the diameter D311 of the upstream part 311 of the first part 31. The diameters D31 and D32 may be the same as or approximately the same as the diameter D12 of the downstream part 312 of the first part 31. In this example, the diameters D31 and D32 are equal, but they may be different from each other.

[0139] In this example, in the flow path 30, tapered sections are placed between every two sections with different cross-sectional areas (in this case, diameter) to prevent clogging of the slurry 40. The angle of inclination of the tapered sections can be set as appropriate. Depending on the difference in pipe diameter, there may be places where tapered sections are not provided.

[0140] In this modified example, as the slurry 40 flowing through the first section 31 moves from the upstream section 311 to the downstream section 312, a portion of the slurry 40 comes into contact with the stepped section of the pipe (in this case, the inner surface of the tapered section 34), causing it to swirl back in the opposite direction of travel (-X direction). The swirling flow then comes into contact with the stepped section on the outlet side of the upstream section 311 and moves in the +X direction. As a result, in addition to the localized vortex 82 (see Figure 5A; not shown in Figure 9B) caused by the difference in flow velocity, a vortex 83 is generated along the length of the upstream section 311. The vortex 83 is the overall flow of the slurry 40 that occurs within the space defined by the stepped section where the pipe narrows, with its upstream and downstream ends defined. The vortex 83 can occur along the outer circumference of the flow cross-section of the slurry 40. The generation of vortices 83 prevents soil particles in the slurry 40 from accumulating at the stepped sections of the piping, causing them to swirl and be pushed from near the center of the piping towards the downstream section 312. Therefore, clogging of slurry 40 and soil particles at the stepped sections can be more effectively suppressed. Furthermore, even if relatively light soil particles float and adhere to the inner wall of the piping, the swirling flow detaches them from the inner wall and sends them to the downstream section 312. In addition, the slurry 40 returned by the vortices 83 travels through the center of the flow cross-section while again coming into contact with the high-pressure liquid, further promoting soil demudication and crushing using cavitation. Although not shown in the diagram, similar vortices can be generated between the downstream section 312 and the second section 32. It is preferable that each step (difference in diameter) of the piping be adjusted so that the clogging prevention effect of the vortices 83 described above can be obtained.

[0141] When the difference in cross-sectional area between the portion including the slurry supply position P and the second portion 32 is increased, directly connecting the two portions results in a step that is too large, making it easy for soil particles to clog. In contrast, in this modified example, the cross-sectional area (diameter) is gradually reduced from the portion including the slurry supply position P (in this case, the upstream portion 311) to the second portion 32, forming multiple stepped portions. This allows each stepped portion to be adjusted to a size that is less likely to cause clogging of soil particles. Therefore, by setting the cross-sectional areas of the portion including the slurry supply position P 311 and the second portion 32 to a suitable range, and by adjusting the number and size of the stepped portions, clogging of the slurry 40 and soil particles can be suppressed.

[0142] Furthermore, in this modified example, the slurry 40 flowing through the third section 3 generates more bubbles due to cavitation when it flows from the second section 32 to the upstream section 331, and when it flows from the upstream section 331 to the enlarged section 333. In this way, by gradually increasing the cross-sectional area (diameter) from the second section 32 to the enlarged section 333 with a larger cross-sectional area, the generation of bubbles can be promoted at multiple stepped sections. Therefore, the cavitation generation region can be made even longer.

[0143] Furthermore, in this modified example, by providing an enlarged portion 333 in the third portion 33, the slurry 40 comes into contact with the stepped portions of the upstream and downstream piping in the enlarged portion 333, generating vortices 84 along the length of the enlarged portion 333. This makes it possible to more effectively reduce clogging of slurry 40 and soil particles in the stepped portions, similar to the case of the vortices 83 described above. In addition to vortices caused by the difference in flow velocity, a swirling flow (vortex 84) is generated overall, which further promotes the disintegration of soil and mud in the slurry 40. In the third portion 33, the velocity of the pressurized liquid 20 is lower than in the first portion 31, so the length of the enlarged portion 333 may be smaller than the length of the upstream portion 311 (here, the length in the X direction of the portion sandwiched by piping with a diameter of less than D11, where vortices 83 are generated).

[0144] In the flow path 30 shown in Figure 9B, the upstream portion 311 of the first portion 31 and the enlarged portion 333 of the third portion 33 function as "processing chambers" where the slurry 40 is processed more effectively than in other portions. The length of the second portion (narrow portion) 32 connecting the first portion 31 and the third portion 33 is, for example, smaller than the length of the first portion 31 and the length of the third portion 33. This increases the proportion of the total length of the flow path 30 that is occupied by portions 31 and 33 where the sludge and crushing processes are greatly advanced, enabling more efficient processing.

[0145] As shown in Figure 9B, the slurry supply unit may include a hopper 41 and a tubular supply passage connecting the hopper 41 and the flow path 30. The supply passage includes an inclined supply passage 42 that slopes downward with respect to the horizontal. In a plan view, the inclined supply passage 42 and the flow path 30 may be perpendicular (or nearly perpendicular). The soil 10 and liquid 50 supplied separately to the hopper 41 are mixed as they flow through the inclined supply passage 42 to form slurry 40. The mixing time between the liquid 50 and the soil 10 and the supply rate of the slurry 40 can be adjusted by the inclination angle of the inclined supply passage 42.

[0146] Figure 9C is a schematic cross-sectional view showing another modification utilizing the vortices 83 and 84 described in Figure 9B. The flow path 30 shown in Figure 9C further comprises a sixth section 341 and a seventh section 342 downstream of the third section 33. The cross-sectional area of ​​the sixth section 341 is smaller than that of the third section 33. The seventh section 342 has a larger cross-sectional area than the sixth section 341. Here, the downstream side of the seventh section 342 extends downward to an outlet for discharging the mixture 70. In the flow path 30, tapered sections may be formed between two sections with different cross-sectional areas. In Figure 9C, the diameters of the first section 31, the third section 33, and the seventh section 342 are the same, but they may be different from each other. Also, the diameters and lengths of the second section 32 and the sixth section 341 may be the same or different from each other.

[0147] In the modified flow path 30, the third section 33 is an enlarged section 36 sandwiched between two narrow sections (the second section 32 and the sixth section 341). Vortices 84 are generated in the third section 33, similar to the enlarged section 333 in Figure 9B. Therefore, the first section 31 where vortices 83 are generated and the third section 33 where vortices 84 are generated function as processing chambers. Since the flow velocity of the pressurized liquid 20 in the third section 33 is smaller than that of the first section 31, the length of the third section 33 may be smaller than, for example, the length of the section in the first section 31 where vortices 83 are generated, in order to generate vortices 84 across the third section 33. Also, the third section 33 may be longer than the second section 32.

[0148] Furthermore, in this modified example, by increasing the cross-sectional area of ​​the seventh section 342 compared to the sixth section 341, it is possible to prevent the mixture 70 containing the slurry and pressurized liquid from coming into contact with the inner wall of the pipe (the inner wall extending vertically at the left end in this figure) and flowing back into the sixth section 641.

[0149] (Examples) To confirm the effectiveness of this embodiment, a mica crushing experiment was conducted using the soil treatment device 1a shown in Figure 4. The method and results of this experiment will be described below. Here, instead of actual soil, commercially available vermiculite mainly composed of dried mica was used as the material to be treated, and the particle size distribution after treatment was measured.

[0150] <Method of the crushing experiment> In this example, 1 kg of vermiculite was supplied together with liquid (water) 50 to the slurry supply unit 4 of the soil treatment device 1a shown in Figure 4, and passed through the flow path 30 of the treatment unit to perform a crushing treatment using cavitation. The treatment conditions, such as the supply speed of the material to be treated (vermiculite), the flow rate of the water mixed with the vermiculite, and the discharge conditions of the pressurized liquid (pressurized water), were set to be the same as the conditions exemplified in Figure 4.

[0151] Next, the mixture 70 discharged from the flow path 30 (a mixture of slurry containing treated vermiculite and pressurized water) was collected in a storage container and thoroughly stirred. After this, a certain amount of the mixture was taken from the bottom and top of the container, mixed, and used as a sample for measurement.

[0152] <Comparative Example> As a comparative example, the particle size distribution of vermiculite was measured after passing 1 kg of vermiculite through a comparative apparatus that does not have a pressurized water outlet. The comparative apparatus is a device for preparing a slurry and measuring the particle size distribution under the same conditions as in the example.

[0153] Figure 10 is a schematic side view of the comparative example apparatus. The comparative example apparatus 101 differs from the soil treatment apparatus 1a shown in Figure 4 in that it does not have a high-pressure ejector for discharging pressurized water, and the cross-sectional area of ​​the flow path 30 is substantially constant. The flow path 30 of apparatus 101 is inclined downward (-Z direction) with respect to the horizontal direction.

[0154] In the comparative example, 1 kg of vermiculite was supplied to the slurry supply section along with water and passed through the flow path 30. The supply rate of the material to be treated (vermiculite) and the flow rate of water mixed with the vermiculite were the same as in the example. Next, a sample for measurement was taken from the mixture 70 discharged from the flow path 30 in the same manner as in the example.

[0155] In the comparative example, the vermiculite is not subjected to impact forces from pressurized water collisions or cavitation. Therefore, the particle size distribution of the measurement sample obtained in the comparative example is approximately the same as the particle size distribution of the vermiculite supplied to the comparative example's apparatus. Accordingly, the particle size distribution measured in the comparative example can be considered to be approximately the same as the particle size distribution of the vermiculite before the crushing experiment in the example.

[0156] <Comparison of particle size distribution> Figures 11A and 11B are photographs showing the measurement samples for the example and comparative example, respectively. From these photographs, it can be confirmed that the particle size of the vermiculite after the crushing experiment in the example is clearly smaller than that of the vermiculite in the comparative example.

[0157] Next, in order to compare the particle size distribution in the small particle size range that is difficult to confirm visually, the particle size distribution of the measurement samples for the examples and comparative examples was measured. Here, the measurement samples for the examples and comparative examples were classified to remove the group of particles with a particle size of 0.212 mm or larger, and then the particle size distribution of the remaining group of particles was measured by laser diffraction.

[0158] Figure 11C shows the particle size volume curves obtained by laser diffraction for the Examples and Comparative Examples. In the results shown in Figure 11C, the proportion of particles with particle sizes between 0.02 mm and 0.04 mm is higher in the Examples than in the Comparative Examples. From this, it can be concluded that in the Examples, some of the vermiculite particles (for example, particles with a particle size of 0.2 mm or larger) were broken down to a particle size of, for example, around 0.02 mm.

[0159] As shown in Figures 11A to 11C, the results confirm that the soil treatment device 1a of this embodiment has sufficient crushing ability for mineral particles such as vermiculite. Furthermore, a comparison of Figure 11A and Figure 11B shows that more than 50% (more than 70% in this case) of the vermiculite introduced was crushed by the treatment of this device. In this case, vermiculite was used as the material to be treated, but it is thought that the device would also exhibit a certain level of crushing ability when using soil mixed with vermiculite and other soil particles.

[0160] (Other variations) The soil treatment apparatus and soil treatment method of the present invention are not limited to the apparatus and method illustrated in Figures 1 to 9B.

[0161] In Figures 1, 4, 8A, and 8B, the slurry supply unit 4 is equipped with a hopper 41, but it does not necessarily have to be equipped with a hopper. For example, pre-mixed slurry may be transported by piping, and this piping may be connected to the flow path of the processing unit. Also, in the example shown in Figure 4, soil and liquid are supplied to the hopper separately, but pre-mixed slurry may be supplied to the hopper.

[0162] Furthermore, it is also possible to treat soil using multiple soil treatment devices according to the first and second embodiments. In this case, the mixture discharged from the multiple soil treatment devices may be configured to be sent to a common classification unit or a common classification device. For example, the flow paths of the multiple soil treatment devices may be merged and sent to a common classification unit.

[0163] The apparatus and method having the configurations illustrated in Figures 1 to 9B can be widely applied to soil containing radioactive materials. For example, it can also be applied to soil containing organic components. Furthermore, it can be applied not only to soil containing radioactive materials, but also to the purification of soil containing impurities such as oil, and to soil sterilization. In addition, various powders and granules can be used as the material to be treated, not just soil. By applying this apparatus or method, it is possible to efficiently separate particles from each other, disperse particles, separate particles from impurities, and pulverize particles using cavitation.

[0164] Referring to Figures 4, 8A, and 8B, the slurry supply device (slurry supply unit) described above can be applied to various processing devices. The slurry supply device can be widely applied to devices for separating soil particles (including mineral particles) contained in soil from other particles and adhering substances by utilizing cavitation (see Figures 2A and 2B) generated by the difference in flow velocity between the slurry and the pressurized liquid. By applying the slurry supply device, the solid-liquid ratio in the slurry can be reduced, making it possible to separate soil particles more efficiently. In addition, since the amount of liquid contained in the slurry can be reduced, the cost of purifying the liquid after processing can be reduced. Furthermore, since operations such as stirring are not required during slurring, there is the advantage that radioactive materials are less likely to be dispersed. The slurry supply device can also be applied to devices for separating soil particles from radioactive materials by methods other than those described in the above embodiment.

[0165] The slurry supply device described above can also be applied to purification devices that separate soil particles from impurities such as oil, and to devices for sterilizing soil particles. Furthermore, it can also be applied to devices that disperse, mix, crush, and polish powders and granules other than soil. This makes it possible to obtain the same effects as in the above embodiment, such as reducing the amount of liquid mixed with soil or powders and granules.

[0166] This disclosure is not limited to the embodiments described above, and design modifications are possible without departing from the gist of this disclosure. Furthermore, by appropriately combining the configurations of any of the various embodiments (including modifications) described, the effects of each can be achieved.

[0167] This specification discloses soil treatment methods as described in the following sections. [Item 1] A method for treating soil containing mineral particles on which radioactive materials have been adsorbed, The process includes injecting a pressurized liquid into a slurry obtained by mixing a liquid with the soil, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. A soil treatment method wherein the mineral particles are separated from other particles by the impact force when the bubbles generated by the cavitation collapse. [Item 2] The soil further contains soil particles with a particle size larger than the mineral particles, The soil treatment method according to item 1, wherein the mineral particles attached to or embedded in the soil particles are separated from the soil particles by the impact force. [Item 3] The soil treatment method according to item 2, wherein the mineral particles separated from the soil particles are crushed by the impact force, resulting in particles with a smaller particle size than the mineral particles. [Item 4] The soil treatment method according to item 1, wherein the impact force causes the particles to become smaller in size than the mineral particles. [Item 5] The soil treatment method according to any one of items 1 to 4, wherein the radioactive material is radioactive cesium and the mineral is mica. [Item 6] The soil treatment method according to any one of items 1 to 5, wherein the ratio of the weight of the liquid used, including the liquid and the pressurized liquid, to the dry weight of the soil to be treated is 5 or more and 15 or less. [Item 7] The soil treatment method according to item 2 or 3, wherein the particle size of the soil particles is 0.075 mm or larger, and the particle size of the mineral particles is less than 0.075 mm. [Item 8] The soil treatment method according to item 2 or 3, further comprising, after generating the cavitation, classifying the mixture obtained by mixing the slurry and the pressurized liquid into a group of large-diameter particles containing soil particles and a group of small-diameter particles containing mineral particles. [Item 9] The soil treatment method according to item 4, further comprising, after generating the cavitation, classifying the mixture obtained by mixing the slurry and the pressurized liquid into a group of particles having a particle size greater than or equal to the particle size of the mineral particles and a group of particles having a particle size smaller than the mineral particles. [Item 10] A soil treatment method according to any one of items 1 to 9, wherein generating the cavitation involves controlling the flow velocity difference such that the amount of bubbles generated decreases and then increases as the pressurized liquid flows with the slurry in the outward direction.

[0168] This specification discloses soil treatment devices as described in the following sections. [Item 1] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, A soil treatment apparatus comprising an injection unit and a supply unit configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. [Item 2] The soil is a mixture of mineral particles and soil particles with a larger particle size than the mineral particles. The soil treatment apparatus according to item 1, wherein the discharge unit and the supply unit are configured to separate mineral particles attached to or embedded in the soil particles from the soil particles by the impact force when bubbles generated by cavitation collapse. [Item 3] The soil treatment apparatus according to item 2, wherein the discharge unit and the supply unit are configured to crush the mineral particles separated from the soil particles by the impact force to particles smaller in size than the mineral particles. Note that "configured to crush the mineral particles to particles smaller in size than the mineral particles" does not include cases where only a small portion of the mineral particles are crushed incidentally in the flow path. As an example, this includes cases where the discharge unit and the supply unit are configured to crush 50% or more of the mineral particles (such as mica particles) in the supplied slurry by the impact force of bubble collapse. [Item 4] The soil treatment apparatus according to item 1, wherein the discharge unit and the supply unit include a process of crushing the mineral particles by the impact force when the bubbles generated by cavitation collapse, thereby reducing them to particles smaller in size than the mineral particles. [Item 5] The flow path includes an enlarged portion downstream of the location to which the supply unit is connected, which enlarges the cross-sectional area perpendicular to the direction of extension of the flow path. The soil treatment apparatus according to any one of items 1 to 4, wherein the discharge unit and the supply unit are configured such that the flow velocity difference is greater downstream of the expansion unit than upstream of the expansion unit, thereby increasing the amount of bubbles generated by cavitation. [Item 6] The aforementioned supply unit is A hopper having a tapered shape in which the inner diameter decreases from the upper opening to the lower opening, A soil supply unit that supplies the soil from the upper opening toward the inner wall of the hopper, The hopper comprises a liquid supply unit that supplies the liquid from the upper opening toward the inner wall of the hopper, The soil supply unit and the liquid supply unit are configured such that the liquid and the soil are mixed on the inner wall of the hopper to form a slurry, which is then supplied to the flow path from the lower opening, as described in any one of items 1 to 5. [Item 7] The soil treatment apparatus according to item 2 or 3, further comprising a classification unit connected to the downstream side of the flow path, which classifies the mixture obtained by mixing the pressurized liquid and the slurry into a group of large-diameter particles containing soil particles and a group of small-diameter particles containing mineral particles. [Item 8] The soil treatment apparatus according to item 4, further comprising a classification unit connected to the downstream side of the flow path, which classifies the mixture obtained by mixing the pressurized liquid and the slurry into a group of particles having a particle size greater than or equal to the mineral particles and a group of particles having a particle size less than the mineral particles. [Item 9] The soil treatment apparatus according to any one of items 1 to 8, wherein the radioactive material is radioactive cesium and the mineral is mica.

[0169] This specification also discloses soil treatment devices as described in the following sections. [Item 1] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, The system includes an injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The injection unit is configured to inject the pressurized liquid into a slurry formed by mixing the liquid with the soil within the flow path, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. The aforementioned flow path is Part 1 and, A second portion located downstream of the first portion, having a cross-sectional area perpendicular to the direction of extension of the flow path that is smaller than that of the first portion, A soil treatment apparatus comprising a third portion located downstream of the second portion and having a larger cross-sectional area than the second portion. [Item 2] The soil treatment apparatus according to item 1, wherein the flow path is configured such that the amount of bubbles generated by cavitation in the third portion is greater than that in the second portion. [Item 3] The first part is connected to a supply unit that supplies the slurry, The soil treatment apparatus according to item 1 or 2, wherein the length of the third portion is greater than the length in the flow path from the location where the supply unit is connected to the upstream end of the third portion. [Item 4] The discharge unit comprises a nozzle section having a discharge port for discharging the pressurized liquid, and piping located upstream of the nozzle section and connected to the nozzle section, wherein the nozzle section is configured such that its cross-sectional area increases from the discharge port toward the piping side. The soil treatment apparatus according to any one of items 1 to 3, wherein the cross-sectional area of ​​the second part is greater than the cross-sectional area of ​​the piping of the discharge section. [Item 5] The aforementioned flow path is A fourth portion located downstream of the third portion and having a smaller cross-sectional area than the third portion, The soil treatment apparatus according to item 1 or 2, further comprising a fifth portion located downstream of the fourth portion and having a larger cross-sectional area than the fourth portion. [Item 6] The soil treatment apparatus according to any one of items 1 to 5, wherein the flow path further includes a tapered portion between the first portion and the second portion, wherein the cross-sectional area decreases as it moves from the first portion toward the second portion.

[0170] This specification discloses slurry supply devices as described in the following sections. [Item 1] A slurry supply device that supplies a slurry of liquid mixed with soil, A hopper having a tapered shape in which the inner diameter decreases from the upper opening to the lower opening, A soil supply unit that supplies the soil from the upper opening toward the inner wall of the hopper, It comprises a liquid supply unit that supplies the liquid from the upper opening toward the inner wall, A slurry supply device wherein the soil supply unit and the liquid supply unit are configured such that the liquid and the soil are mixed on the inner wall to form a slurry, which flows out from the lower opening. [Item 2] The slurry supply device according to item 1, wherein the soil supply unit and the liquid supply unit are configured such that the liquid and the soil are mixed as they flow downward in a swirling motion along the inner wall to form the slurry. [Item 3] The aforementioned liquid supply unit is A liquid line extending along at least a portion of the periphery of the upper opening and conveying the liquid, A slurry supply device according to item 1 or 2, comprising a plurality of liquid supply ports arranged at intervals from each other in the liquid line for supplying the liquid to the hopper. [Item 4] The plurality of liquid supply ports include the first liquid supply port, The first liquid supply port is provided with a nozzle that extends downward from the first liquid supply port. The slurry supply device according to item 3, wherein, in a plan view along the height direction of the hopper, the extending direction of the nozzle is inclined with respect to the direction from the first liquid supply port toward the center of the lower opening. [Item 5] The slurry supply device according to any one of items 1 to 4, wherein the soil supply unit is configured to supply the soil toward the inner wall from an input position offset from the center of the lower opening in a plan view along the height direction of the hopper. [Item 6] The slurry supply device according to item 5, wherein the soil supply unit includes a conveying device that, in a plan view, conveys the soil from outside the upper opening to the input position and drops the soil into the upper opening at the input position. [Item 7] The slurry supply device according to item 6, wherein the input position is located downstream of the center of the lower opening in the conveying direction of the conveying device in the plan view. [Item 8] The slurry supply device according to any one of items 1 to 7, wherein the soil is soil containing radioactive material. [Item 9] A soil treatment apparatus that performs a process to separate soil particles contained in soil from other particles or attached substances, A supply unit equipped with a slurry supply device described in any one of items 1 to 8, A channel through which the slurry containing the soil is supplied from the supply unit, The system includes an injection unit that ejects pressurized liquid from the upstream side to the downstream side of the flow path, A soil treatment apparatus comprising an injection unit and a supply unit configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry.

[0171] This specification discloses soil treatment equipment and soil treatment methods as described in the following sections. [Item 1] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry, in which the soil is mixed with liquid and no dispersant to lower the zeta potential is added, toward the pressurized liquid discharged by the discharge unit, A soil treatment apparatus comprising an injection unit and a supply unit configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. [Item 2] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, The slurry supplied to the supply unit is given a dispersant at a concentration of less than 0.5 mol / kg relative to the mass of the soil. A soil treatment apparatus comprising an injection unit and a supply unit configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. [Item 3] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, The soil treatment apparatus is configured such that the discharge unit and the supply unit generate cavitation by creating a difference in flow velocity at the interface between the pressurized liquid and the slurry, and the impact force generated when the bubbles produced by the cavitation collapse crushes the mineral particles into particles smaller than the mineral particles. [Item 4] The aforementioned mineral particles are mica particles, The soil treatment apparatus according to any one of items 1 to 3, wherein the discharge unit and the supply unit are configured to crush 50% or more of the mica particles contained in the slurry supplied from the supply unit to the treatment unit by the impact force when bubbles generated by cavitation collapse, thereby reducing them to particles smaller in size than the mica particles. [Item 5] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, The injection unit and the supply unit are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. The aforementioned flow path is Part 1 and, A second portion located downstream of the first portion, having a cross-sectional area perpendicular to the direction of extension of the flow path that is smaller than that of the first portion, A soil treatment apparatus comprising a third portion located downstream of the second portion, longer than the second portion, and having a larger cross-sectional area than the second portion. [Item 6] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, The injection unit and the supply unit are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. The aforementioned flow path is Part 1 and, A second portion located downstream of the first portion, having a cross-sectional area perpendicular to the direction of extension of the flow path that is smaller than that of the first portion, A soil treatment apparatus comprising a third portion located downstream of the second portion, having a larger cross-sectional area than the second portion, and having a length greater than the length from the position in the flow path to the downstream end of the second portion. [Item 7] The third part is, An upstream portion, and a downstream portion located downstream of the aforementioned upstream portion, The soil treatment apparatus according to item 5 or 6, comprising an enlarged portion located between the upstream portion and the downstream portion, and having a larger cross-sectional area than the upstream portion and the downstream portion. [Item 8] A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, An injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The system includes a supply unit connected downstream of the discharge unit in the flow path, which supplies a slurry of soil mixed with liquid to the pressurized liquid discharged by the discharge unit, The injection unit and the supply unit are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. The aforementioned flow path is Part 1 and, A second portion located downstream of the first portion, having a cross-sectional area perpendicular to the direction of extension of the flow path that is smaller than that of the first portion, A third portion located downstream of the second portion and having a larger cross-sectional area than the second portion, A soil treatment apparatus comprising a fourth portion located downstream of the third portion and having a smaller cross-sectional area than the third portion. [Item 9] The aforementioned supply unit is A hopper having a tapered shape in which the inner diameter decreases from the upper opening to the lower opening, A soil supply unit that supplies the soil from the upper opening toward the inner wall of the hopper, The hopper comprises a liquid supply unit that supplies the liquid from the upper opening toward the inner wall of the hopper, The soil supply unit and the liquid supply unit are configured such that the liquid and the soil are mixed on the inner wall of the hopper to form a slurry, which is then supplied to the flow path from the lower opening, according to any one of items 1 to 8. [Item 10] The soil supply unit and the liquid supply unit are configured such that the liquid and the soil are mixed as they flow downward in a swirling motion along the inner wall to form the slurry, as described in item 9. [Item 11] The soil supply unit is configured to supply the soil toward the inner wall from an input position offset from the center of the lower opening in a plan view along the height direction of the hopper, as described in item 9 or 10. [Item 12] A method for treating soil containing mineral particles on which radioactive materials have been adsorbed, The process includes injecting a pressurized liquid from the upstream to the downstream side of a flow channel for treating the soil, supplying a slurry containing the soil mixed with liquid and without a dispersant that lowers the zeta potential, to the injected pressurized liquid within the flow channel, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. A soil treatment method wherein the mineral particles are separated from other particles by the impact force when the bubbles generated by the cavitation collapse. [Item 13] A method for treating soil containing mineral particles on which radioactive materials have been adsorbed, The process involves injecting a pressurized liquid from the upstream to the downstream side of a flow channel for treating the soil, supplying a slurry to the injected pressurized liquid, which is a mixture of the soil and a liquid, with a dispersant that lowers the zeta potential added at a rate of less than 0.5 mol / kg relative to the mass of the soil, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. A soil treatment method wherein the mineral particles are separated from other particles by the impact force when the bubbles generated by the cavitation collapse. [Item 14] A method for treating soil containing mineral particles on which radioactive materials have been adsorbed, The process involves discharging a pressurized liquid into a slurry obtained by mixing a liquid with the soil, without adding a dispersant that lowers the zeta potential, and generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry in a channel extending in the direction of discharge of the pressurized liquid. A soil treatment method wherein the mineral particles are separated from other particles by the impact force when the bubbles generated by the cavitation collapse. [Item 15] The impact force causes the mineral particles to break down into particles with a smaller particle size than the mineral particles. A soil treatment method according to any one of items 12 to 14, further comprising: generating the cavitation; transferring the mixture obtained by mixing the slurry and the pressurized liquid from the downstream side of the flow path to a classification section; and further classifying the mixture in the classification section into a group of particles having a particle size greater than or equal to the particle size of the mineral particles and a group of particles having a particle size smaller than the particle size of the mineral particles. [Item 16] The soil treatment method according to any one of items 12 to 15, wherein the weight ratio of the liquid contained in the slurry to the soil is 5 or less. [Industrial applicability]

[0172] The soil treatment method according to the present invention can easily remove radioactive materials from the soil, and is therefore useful for decontamination and volume reduction of contaminated soil. [Explanation of symbols]

[0173] 1, 1a Soil treatment device 2. Ejection section 3 Processing Unit 4. Slurry supply section 5 Liquid supply section 6. Soil Supply Department 7 Classification Department 8 Control Unit 10 soil 11. Gravel particles 12 sand particles 13 Mineral particles 15 Mineral particles containing radioactive materials 20 Pressurized liquid 20s interface 22 nozzles 23 High-speed jet pump 24 Piping 30 flow channels 31 Part 1 32 Part 2 33 Part 3 34 Tapered section 35 Fringe 35c central part 36 Enlarged section 37 Outlet 40 Slurry 41 Hoppa 41s interior wall 50 liquid 51 Liquid Line 52 nozzles 53 Submersible pump 61 Soil storage tank 62 Conveying device 70 mixture 72, 73 sieve 80 space 81 bubbles 82 Vortex 320 Part 4 330 Part 5 351 Left side part 352 Right side part 411 Upper opening 412 Lower opening 511 Ring section 512 Liquid supply port 621 Belt 622 Adjustment Member C center d direction P Slurry supply position Q input position Rc cavitation generation area

Claims

1. A soil treatment apparatus that performs a process to separate mineral particles from other particles in soil containing mineral particles on which radioactive materials have been adsorbed, A processing unit having a flow channel, The system includes an injection unit that ejects pressurized liquid from the upstream side to the downstream side of the aforementioned flow path, The injection unit is configured to inject the pressurized liquid into a slurry obtained by mixing the liquid with the soil within the flow path, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry. The aforementioned flow path is Part 1 and, A second portion located downstream of the first portion, having a cross-sectional area perpendicular to the direction of extension of the flow path that is smaller than that of the first portion, A soil treatment apparatus comprising a third portion located downstream of the second portion and having a larger cross-sectional area than the second portion.

2. The soil treatment apparatus according to claim 1, wherein the flow path is configured such that the amount of bubbles generated by cavitation in the third portion is greater than that in the second portion.

3. The first part is connected to a supply unit that supplies the slurry, The soil treatment apparatus according to claim 1 or 2, wherein the length of the third portion is greater than the length of the flow path from the position where the supply unit is connected to the upstream end of the third portion.

4. The discharge unit comprises a nozzle section having a discharge port for discharging the pressurized liquid, and piping located upstream of the nozzle section and connected to the nozzle section, wherein the nozzle section is configured such that its cross-sectional area increases from the discharge port towards the piping side. The soil treatment apparatus according to claim 1 or 2, wherein the cross-sectional area of ​​the second portion is larger than the cross-sectional area of ​​the piping of the discharge portion.

5. The aforementioned flow path is A fourth portion located downstream of the third portion and having a smaller cross-sectional area than the third portion, The soil treatment apparatus according to claim 1 or 2, further comprising a fifth portion located downstream of the fourth portion and having a larger cross-sectional area than the fourth portion.

6. The soil treatment apparatus according to claim 1 or 2, wherein the flow path further includes a tapered portion between the first portion and the second portion, the tapered portion having a decreasing cross-sectional area from the first portion toward the second portion.

7. The soil treatment apparatus according to claim 1 or 2, wherein the third portion is longer than the second portion.

8. The third part is, An upstream portion, and a downstream portion located downstream of the aforementioned upstream portion, The soil treatment apparatus according to claim 1 or 2, comprising an enlarged portion located between the upstream portion and the downstream portion, and having a larger cross-sectional area than the upstream portion and the downstream portion.

9. The soil treatment apparatus according to claim 1 or 2, wherein the flow path is configured to further include a fourth portion located downstream of the third portion and having a smaller cross-sectional area than the third portion.

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