Soil treatment device and soil treatment method

Abstract

A soil treatment device according to the present invention is a device that subjects soil containing mineral particles to which a radioactive substance is adsorbed to a treatment for separating the mineral particles from other particles. The soil treatment device comprises: a treatment unit having a flow path; a jetting unit that ejects a pressurized liquid from an upstream side toward a downstream side of the flow path; and a supply unit that is connected to the downstream side of the flow path relative to the jetting unit and supplies, toward the pressurized liquid ejected by the jetting unit, a slurry obtained by mixing a liquid with the soil. The jetting unit and the supply unit are configured to generate cavitation by generating a flow velocity difference at an interface between the pressurized liquid and the slurry.

Description

Soil treatment device and soil treatment method

[0001] The present invention relates to an apparatus and method for treating soil containing radioactive material.

[0002] Classification processing technology is known as one of the volume reduction technologies for removing radioactive materials from soil containing radioactive materials and reducing the volume of soil with high radioactive concentrations.

[0003] In classification processing technology, soil containing radioactive materials is classified into a group of small soil particles, such as clay and silt (hereinafter referred to as "fine particles"), and a group of larger soil particles, such as gravel and sand (hereinafter referred to as "coarse particles"). Radioactive materials such as radioactive cesium tend to adhere to relatively small particles (e.g., mineral particles such as mica), and are therefore found in large amounts in the fine particles after classification. Therefore, by separating and removing the fine particles from the soil, the concentration of radioactive materials can be reduced. The coarse particles remaining after the fine particles have been removed can be reused for construction purposes, etc.

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

[0005] JP 2013-140021 A

[0006] However, conventional classification techniques have room for improvement in terms of more reliably removing radioactive materials from soil.

[0007] SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and to provide a soil treatment device that can easily remove radioactive materials from soil.

[0008] In order to achieve the above-mentioned object, a soil treatment device according to one embodiment of the present invention is a device that performs a process on soil containing mineral particles to which radioactive substances have been adsorbed, separating the mineral particles from other particles, and is equipped with a treatment device having a flow path, an outlet unit that ejects pressurized liquid from the upstream side to the downstream side of the flow path, and a supply unit that is connected downstream of the outlet unit on the flow path and supplies a slurry mixed with liquid to the soil toward the pressurized liquid ejected by the outlet unit, and the outlet 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.

[0009] The soil treatment device according to the present invention can facilitate the removal of radioactive materials from soil.

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

[0011] (Findings on which the present invention is based) The present inventors have made extensive studies to make it easier to remove radioactive materials from soil, and have come to the following findings.

[0012] Conventional classification processing techniques have the following problems (1) and (2).

[0013] (1) It is known that radioactive substances such as radioactive cesium are easily adsorbed to particles of layered clay minerals. Examples of layered clay minerals include mica minerals (hereinafter simply referred to as "mica"), such as weathered biotite and its weathered product, vermiculite. Mineral particles such as mica may adhere to or be encapsulated in large sand particles or gravel particles. When mineral particles adhere to (or are encapsulated in) sand particles, even after classification, the mineral particles with adsorbed radioactive substances will be included in the coarse fraction after classification. Furthermore, when the mineral particles with adsorbed radioactive substances are large, they will be separated into the coarse fraction. This makes it difficult to reliably remove radioactive substances through classification. In response to this, it has been proposed to reduce the radioactive concentration by performing advanced classification and washing processes on the coarse fraction after classification (e.g., Patent Document 1). However, the method described in Patent Document 1 is considered to be difficult to reliably remove mineral particles that are attached to or encapsulated in sand particles. Details will be provided below.

[0014] Furthermore, recent research has reported that radioactive materials such as radioactive cesium are adsorbed to layered clay mineral particles and then trapped (immobilized) within them. The interlayer surfaces of layered clay mineral particles are negatively charged, making radioactive materials more likely to adsorb to these surfaces. When radioactive materials are adsorbed between the two layers that make up a layered clay mineral particle, the two layers sandwiching the radioactive material close over time. In this way, the radioactive materials are trapped within the layered clay mineral particle. When radioactive materials are immobilized within layered clay mineral particles, they are less likely to detach or elute from the particles. In particular, when radioactive materials are trapped in areas of large mica particles that have been altered by weathering, it becomes even more difficult to remove them using conventional classification techniques.

[0015] Therefore, it may be difficult to reduce the concentration of radioactive materials in the coarse particles and increase the decontamination rate.

[0016] (2) Furthermore, to more reliably remove radioactive materials from soil by classification, it is necessary to separate and remove soil particles in a particle size range that includes mineral particles, which are considered to be fine particles with high concentrations of radioactive materials. As mentioned above, if radioactive materials are trapped in mineral particles and are 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 whose radioactivity concentration is higher than a predetermined value (e.g., 8000 Bq / kg) and cannot be reused as is.

[0017] Therefore, after extensive research, the inventors of the present application discovered a method for generating cavitation by injecting a pressurized liquid into a slurry containing soil and creating a flow velocity difference at the interface between the pressurized liquid and the slurry. With this method, mineral particles with radioactive material adsorbed thereon can be separated from other particles by the impact force generated when bubbles generated by cavitation collapse. This makes it easier to remove the radioactive material from the soil. "Mineral particles with radioactive material adsorbed thereon" includes not only particles with radioactive material adsorbed on their surfaces, but also particles with radioactive material adsorbed between layers (trapped between layers).

[0018] According to the above method, the impact force generated when the bubbles collapse can separate mineral particles adhering to large soil particles, such as sand particles, from the soil particles. Alternatively, the impact force generated when the bubbles collapse can crush mineral particles to which radioactive material is adsorbed into smaller particles. As a result, the concentration of radioactive material in the coarse particles after classification can be reduced. Furthermore, by reducing the particle size of particles to which radioactive material is adsorbed, the volume of soil (fine particles) with a high concentration of radioactive material can be reduced. The inventors of the present invention have arrived at the present invention based on this novel finding.

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to these embodiments. For illustrative purposes, the dimensions of each element in the drawings may be exaggerated and are not necessarily drawn to scale. Furthermore, substantially identical elements in the drawings are designated by the same reference numerals.

[0020] For the sake of convenience, terms indicating directions such as "up," "down," "side," "left," and "right" are used below assuming a state of normal use, but are not intended to limit the state of use of the device according to the present invention. For reference, the drawings schematically show an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other. The Z-axis is, for example, the vertical direction. In the following description, when simply referring to the X-direction, the Y-direction, or the Z-direction, this refers to the respective axial direction and includes two opposite directions (for example, the -X-direction and the +X-direction).

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

[0022] [Soil Treatment Apparatus] Figures 1, 2A, and 2B are schematic diagrams illustrating the general structure and principle of a soil treatment apparatus according to a first embodiment. Figure 1 is a schematic side view of the soil treatment apparatus. 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 taken along line IIB-IIB in Figure 2A.

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

[0024] As shown in FIG. 1 , the soil treatment device 1 includes a treatment section 3, an outlet section 2 that injects pressurized liquid 20 into the treatment section 3, and a slurry supply section 4 that supplies a slurry 40 containing soil to the treatment section 3.

[0025] The processing unit 3 includes a flow path 30. The flow path 30 is configured, for example, by a pipe having a circular cross section. The flow path 30 extends, for example, in a horizontal direction perpendicular to the vertical direction. For ease of understanding, in FIG. 1 , 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 include, at its downstream end, an outlet 37 for discharging a mixture 70 containing the treated slurry 40 and the pressurized liquid 20 from the processing unit 3.

[0026] The ejection unit 2 is disposed so as to eject the pressurized liquid 20 in a direction (+X direction) from the upstream side to the downstream side of the flow path 30. The ejection unit 2 ejects the pressurized liquid 20 toward 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 a slurry 40, which is soil mixed with a liquid (e.g., water), to the flow path 30. The slurry supply unit 4 is connected to the flow path 30 downstream of the ejection unit 2. In the flow path 30, the slurry supply unit 4 supplies the slurry 40 toward the pressurized liquid 20 ejected by the ejection unit 2 in a direction intersecting the ejection direction of the pressurized liquid 20. In the example shown in FIG. 1 , the slurry supply unit 4 is configured to supply the slurry 40 in a direction (−Z direction) perpendicular to the ejection direction. The pressure of the liquid contained in the slurry 40 when supplied is, for example, approximately 1 atmosphere.

[0028] 2A and 2B, the ejection 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 by which cavitation is generated will be described below.

[0029] As shown in FIGS. 2A and 2B , the pressurized liquid 20 ejected from the ejection unit 2 is a high-speed fluid (e.g., pressure: 4 MPa, speed: approximately 50 m / s) moving 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 FIG. 2B , moves at high speed through the approximate center of the slurry 40. The slurry 40 is pulled by the flow of the pressurized liquid 20, forming a multiphase flow around the pressurized liquid 20 and flowing in the same direction as the pressurized liquid 20. The multiphase flow here refers to a flow containing at least the soil (solid phase) and liquid (liquid phase) contained in the slurry 40. A space 80 may exist above the slurry 40. Because the slurry 40 flows at a slower speed than the pressurized liquid 20, a flow velocity difference occurs at the interface 20s between the slurry 40 and the pressurized liquid 20. This results in cavitation. 2A , a shear force caused by the difference in flow velocity between the pressurized liquid 20 and the slurry 40 generates a vortex 82 in the slurry 40. Because the center of the vortex 82 is locally under low pressure, the liquid in the slurry 40 vaporizes, generating bubbles 81. The slurry 40 flows downstream, entraining the bubbles 81. As the slurry 40 flows downstream, the bubbles 81 are compressed by the surrounding liquid and collapse.

[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 contained within soil particles, such as sand particles, from the soil particles (hereinafter referred to as "disintegration"), but also crushing the mineral particles and dividing them into multiple smaller particles (hereinafter referred to as "crushing"). In this embodiment, the impact force generated when the bubbles 81 collapse causes disintegration, crushing, or both of the mineral particles.

[0031] The bubbles 81 caused by cavitation are generated one after another in the slurry 40 while the slurry 40 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 time the slurry 40 flows.

[0032] As shown in FIG. 1 , the region Rc in the flow path 30, which is configured to generate cavitation by the above mechanism, is referred to as the "cavitation generation region." The cavitation generation region Rc is located downstream of a 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, the slurry 40 flows around the pressurized liquid 20, as shown in FIGS. 2A and 2B . 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 an outlet 37 and sent to, for example, a classification device.

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

[0034] In this embodiment, the cavitation generated by the above mechanism is utilized, so that the separation of mineral particles (for example, sludge dissolution and crushing) can be performed more efficiently and more reliably.

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

[0036] In contrast, in this embodiment, cavitation is generated at the interface 20s between the flow of the soil-containing slurry 40 and the flow of the pressurized liquid 20, so that 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 path 30. Furthermore, because the slurry 40 entrains bubbles as it flows, the impact force caused by the collapse of the bubbles can be more reliably applied to the slurry 40. Furthermore, because the generation and collapse of bubbles is repeated while the slurry 40 and the pressurized liquid 20 are in contact with each other and flowing, high impact forces are repeatedly applied to the particles in the slurry 40. Therefore, separation of mineral particles can be further promoted downstream of the flow path 30.

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

[0038] [Soil Treatment Method] 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 generating step"). In the cavitation generating step, pressurized liquid is injected into a slurry in which soil is mixed with liquid, and a flow velocity difference is generated at the interface between the pressurized liquid and the slurry, thereby generating cavitation (see Figures 2A and 2B). The cavitation generating step can be performed using, for example, the soil treatment device 1 shown in Figure 1. Note that the device used in this step is not limited to the device shown in Figure 1, as long as it is configured to generate cavitation by utilizing the flow velocity difference between the slurry and the pressurized liquid.

[0039] 3A and 3B are schematic diagrams illustrating soil treatment methods I and II according to the first embodiment, respectively. As a reference example, a treatment method in which only classification treatment is performed is schematically shown in FIG.

[0040] 3A, 3B, and FIG. 12 of the Reference Example illustrate an example in which soil 10, which is the material to be treated, includes gravel particles (particle size: e.g., 2 mm or more) 11, sand particles (particle size: e.g., 74 μm or more and less than 2 mm) 12, and silt or clay particles (silt particle size: e.g., 5 μm or more and less than 74 μm, clay particle size: e.g., less than 5 μm) 13. These particles include mineral particles 15 to which radioactive materials such as radioactive cesium are 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. Examples of radioactive material-containing mineral particles 15 with various particle sizes, ranging from relatively small to 2 mm or more, are illustrated here. Some of the radioactive material-containing mineral particles 15 may be attached to or encapsulated in larger soil particles (e.g., gravel particles 11, sand particles 12, etc.).

[0041] For ease of understanding, the method of the reference example shown in FIG. 12 will be described first. In this reference example, the above-mentioned soil 10 is classified into a coarse fraction having a particle size of 75 μm or more and a fine fraction having a particle size of less than 75 μm. As a result, radioactive substance-containing mineral particles 15 having a particle size of 75 μm or more are classified as the coarse fraction. On the other hand, radioactive substance-containing mineral particles 15 having a particle size of less than 75 μm can be classified as the fine fraction. However, as shown in the figure, some of the radioactive substance-containing mineral particles 15 having a particle size of less than 75 μm may be classified as the coarse fraction together with sand particles 12 and gravel particles 11, etc., in a state of being attached to or encapsulated within these particles. As a result, it is difficult to sufficiently reduce the concentration of radioactive substances in the coarse fraction after classification.

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

[0043] <Soil Treatment Method I> As shown in Fig. 3A , in the cavitation generation step, in soil treatment method I, radioactive substance-containing mineral particles 15 are separated from other particles by the impact force generated when bubbles collapse. As a result, the radioactive substance-containing mineral particles 15 that have been attached to soil particles such as sand particles 12 and gravel particles 11 are separated from the soil particles (disintegration). In addition, the radioactive substance-containing mineral particles 15 and other mineral particles are crushed into smaller particles 14 (crushing). After crushing the radioactive substance-containing mineral particles 15, the radioactive substance may be adsorbed on the particles 14 or may be desorbed from the particles 14.

[0044] In the cavitation generating process, as shown in the figure, it is sufficient that at least the portions of the radioactive substance-containing mineral particles 15 to which the radioactive substance is adsorbed are crushed. For example, if the radioactive substance-containing mineral particles 15 are mica, the radioactive substance is mainly adsorbed or fixed to the portions of the mica particles that have been altered by weathering (weathered portions), so it is sufficient that at least the weathered portions are crushed. The weathered portions are located, for example, near the surfaces of the mica particles. The unweathered portions are harder than the weathered portions and are therefore less likely to be crushed, and can be discharged from the flow path while maintaining a certain size. Similarly, soil particles, which are harder than the weathered portions of mica, are also less likely to be crushed, so they are not crushed as small as the weathered portions and can be discharged from the flow path while maintaining a certain size.

[0045] After the cavitation generation step, the mixture of the treated slurry and the pressurized liquid is classified into a large particle group and a small particle group having a particle size smaller than that of the large particle group. In this processing method, the particle size of the large particle group is, for example, a particle group having a particle size equal to or larger than that of radioactive substance-containing mineral particles. The small particle group is, for example, a particle group having a particle size smaller than that of the radioactive substance-containing mineral particles. The small particle group includes particles 14 obtained after the radioactive substance-containing mineral particles 15 are crushed. The radioactive substance is included in the small particle group because it is adsorbed to or desorbed from the particles 14. Classification may be performed based on the particle size of the radioactive substance-containing mineral particles 15, which are relatively small (e.g., the particle size of silt or clay), thereby making the particle size at the classification point 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, radioactive material-containing mineral particles 15 are separated from larger soil particles by the cavitation generation process. Furthermore, the larger radioactive material-containing mineral particles 15 are crushed into smaller particles 14. Therefore, subsequent classification can more reliably separate the radioactive material into smaller particle groups. Therefore, the radioactive material concentration in the larger particle groups can be further reduced (i.e., the decontamination rate can be increased) compared to the method of the reference example ( FIG. 12 ). For example, soil with a radioactivity concentration of over 8000 Bq can be reduced to a concentration significantly below the reusable limit of 8000 Bq / kg (e.g., 1000 Bq / kg or less). Furthermore, since advanced classification, cleaning, and other processes are not required after this treatment, the equipment, costs, number of processes, and amount of water used for soil treatment can be reduced.

[0047] Furthermore, according to soil treatment method I, the radioactive substance-containing mineral particles 15 are crushed in the cavitation generation process, so that in the subsequent classification process, the particle size at the classification point can be made smaller, thereby making it possible to reduce the volume of soil with a high concentration of radioactive substances (small-diameter particle group) (i.e., to increase the volume reduction rate).

[0048] <Soil Treatment Method II> In the soil treatment method II, at least a thawing treatment is carried out by a cavitation generation step. As shown in Fig. 3B , in the cavitation generation step, the impact force generated when the bubbles collapse separates radioactive substance-containing mineral particles 15 that have been attached to (or contained within) soil particles such as sand particles 12 and gravel particles 11 from the soil particles (thawing).

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

[0050] In the soil treatment method II, the radioactive material-containing mineral particles 15 are separated from the larger soil particles by the cavitation generation process, and the radioactive material can be more reliably separated into small particle groups by the subsequent classification. Therefore, the concentration of radioactive material in the large particle groups can be further reduced (i.e., the decontamination rate can be increased) than in the method of the reference example (FIG. 12).

[0051] 1 to 2B, the soil treatment device 1 of this embodiment is configured such that the outlet unit 2 and the slurry supply unit 4 generate a flow velocity difference at the interface 20s between the pressurized liquid 20 and the slurry 40 in the flow path 30 of the treatment unit 3, thereby generating cavitation. With this configuration, the impact force generated when bubbles collapse due to cavitation can be used to perform processes such as sludge disintegration and crushing, which separate mineral particles from other particles. As a result, radioactive materials can be easily removed.

[0052] 2A and 2B, the above-described configuration allows the impact force caused by the collapse of bubbles to be applied to the mineral particles more efficiently than in conventional devices (such as the device described in Patent Document 1), thereby more reliably separating the mineral particles from other particles.

[0053] Furthermore, with the above configuration, the decomposition of mineral particles can be promoted while the soil-containing slurry 40 and the pressurized liquid 20 are flowing in the same direction, which allows for continuous treatment and allows for a large amount of soil to be treated per hour (for example, 12 tons / hour or more).

[0054] The emission section 2 and the slurry supply section 4 may be configured to perform a sludge breaker treatment in which radioactive material-containing mineral particles 15 attached to (or encapsulated within) soil particles such as sand particles 12 are separated from the soil particles by the impact force generated when bubbles generated by cavitation collapse, as shown in Fig. 3B. With this configuration, the amount of radioactive material contained in the large particle group after classification can be reduced in the subsequent classification treatment.

[0055] The discharge section 2 and the slurry supply section 4 may be configured to perform a crushing process in which the radioactive substance-containing mineral particles 15 are crushed into particles 14 having a particle size smaller than that of the radioactive substance-containing mineral particles 15 by the impact force generated when the bubbles generated by cavitation collapse, as shown in FIG. 3A . The soil treatment device 1 can repeatedly apply a strong impact force to the mineral particles, thereby having a high crushing capacity. With this configuration, the radioactive substance contained in the large particle group after classification can be further reduced in the subsequent classification process. Furthermore, radioactive substance can be removed even if the particle size at the classification point is reduced (for example, less than the particle size of the radioactive substance-containing mineral particles 15). Therefore, the volume of the small particle group having a high concentration of radioactive substance can be reduced.

[0056] The discharge unit 2 and the slurry supply unit 4 may be configured to separate the radioactive material-containing mineral particles from the soil particles by the impact force generated when the bubbles generated by cavitation collapse, and then crush the separated radioactive material-containing mineral particles. With this configuration, the sludge deflocculation process and the crushing process can be carried out simultaneously while the slurry 40 flows in contact with the pressurized liquid 20. Therefore, there is no need to prepare separate devices for sludge deflocculation and crushing, which further reduces the cost, number of steps, time, etc. required for the process.

[0057] According to this embodiment, a soil treatment method is provided that includes a cavitation generation step. In the cavitation generation step, pressurized liquid is injected into a slurry prepared by mixing soil with a liquid, and a flow velocity difference is generated at the interface between the pressurized liquid and the slurry, thereby generating cavitation. As shown in Figures 3A and 3B, the impact force generated when bubbles generated by cavitation collapse separates mineral particles 15 that have adsorbed radioactive materials from other particles. For example, the impact force causes sludge disintegration, crushing, or both. This facilitates the removal of radioactive materials, thereby enabling a higher decontamination rate and / or volume reduction rate.

[0058] The radioactive material adsorbed to the mineral particles may be, for example, radioactive cesium, and the mineral particles to which the radioactive cesium is adsorbed may be, for example, mica particles. It has been reported that most of the radioactive cesium is adsorbed or fixed to mica. Therefore, by crushing and dissolving the mica particles to which the radioactive cesium is adsorbed, the radioactive cesium can be more effectively removed from the soil. As an example, it is 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 crushed by the impact force generated when bubbles generated by cavitation collapse. As an example, for example, 50% or more, preferably 70% or more of the mica particles (regardless of whether they contain radioactive materials) in the slurry supplied to the treatment section 3 are crushed by the impact force and become smaller particles than before they were introduced (see the experimental results in Figures 11A and 11B described below).

[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" refers to the total weight of the liquid used in the treatment, including the weight of the liquid contained in the slurry 40 (FIG. 1) and the weight of the pressurized liquid 20 (FIG. 1). By keeping the total solid-liquid ratio at 15 or less, costs associated with soil treatment and the disposal of the liquid used can be reduced, and practicality can be improved.

[0061] The weight ratio of pressurized liquid 20 (FIG. 1) to soil is not more than 10, preferably not more than 6. The weight ratio of liquid contained in slurry 40 to soil (slurry solid-liquid ratio) is not more than 5, preferably not more than 3. By keeping the amount of liquid contained in slurry 40 small, the impact force caused by bubble collapse is more easily applied to the particles in slurry 40, allowing for efficient separation of mineral particles.

[0062] In conventional treatment methods, for example, after normal classification using a trommel or the like, advanced classification is sometimes performed, in which coarse particles are subjected to mechanical impact force. In such methods, a large amount of liquid is used, and the total solid-liquid ratio exceeds, for example, 20. Since the liquid (water) used for treatment contains radioactive materials, its storage and disposal are additionally costly. In contrast, in this embodiment, before classification, a cavitation generation process is performed on the entire soil for thawing and crushing. In the subsequent classification process, the soil after thawing is classified, eliminating the need for advanced classification as in the past. Therefore, the total solid-liquid ratio can be made smaller than in the past.

[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 reduces the zeta potential to the soil, then performing high-pressure washing to wash the soil containing the dispersant in turbulent water, thereby dispersing fine particles from aggregated soil into water (i.e., de-sludging the aggregated soil). This method, however, leaves the soil after washing with dispersant, which may prevent it from being reused. Removing the dispersant from the washed soil requires a large amount of water, which places a significant burden on the environment. This method utilizes dispersants, but it does not rely on the impact force of bubble collapse, as evidenced by the fact that dispersants make bubbles less likely to collapse.

[0064] In contrast, according to this embodiment, the large impact force generated by the collapse of bubbles due to cavitation can be used to separate (disintegrate) aggregated soil particles. Therefore, there is no need to add chemicals, such as dispersants that reduce the zeta potential, to the slurry for the purpose of deflocculation. In this embodiment, dispersants may actually reduce the deflocculation or crushing effect. Adding a dispersant to the slurry stabilizes the bubbles generated by cavitation, thereby suppressing bubble collapse. This reduces (or reduces) the impact force generated by bubble collapse, potentially reducing the deflocculation and crushing effects due to the impact force. Furthermore, adding a dispersant (surfactant) to the slurry reduces the impact force exerted on the soil particles when the bubbles collapse. Furthermore, from the perspective of reusing the low-radioactive soil (large particle group) obtained by classifying the treated slurry, it is preferable not to add a dispersant to the slurry.

[0065] A small amount of dispersant (e.g., sodium hexametaphosphate) may be added to the slurry 40 supplied to the soil treatment apparatus 1 of this embodiment. The amount of dispersant added may be, for example, less than 1% of the mass of the soil in the slurry 40, or less than 0.5 mol / kg of the soil in the slurry 40. This minimizes the effect of the dispersant on the disintegration and crushing action using cavitation, while preventing re-agglomeration of soil particles in the slurry 40 after treatment (before classification).

[0066] 3A and 3B illustrate a method for treating soil 10 containing clay, silt, sand, and gravel, but the soil treatment method of this embodiment can also be applied to treating only coarse particles (sand, gravel, etc.) or only fine particles (clay, silt) after a normal classification process. The soil treatment method of this embodiment can also be applied to soil that has previously been subjected to a sludge treatment to break down mineral particles.

[0067] 3A and 3B show that the cavitation generation process results in the disintegration and crushing of mineral particles. However, the impact force caused by the collapse of the bubbles can not only disintegrate the mineral particles, but also loosen clumps of clay and other lumps in the slurry. Furthermore, particles other than mineral particles can be crushed, and large particles such as gravel particles can be rounded and polished. Changes in mineral particles and other particles can be confirmed, for example, by observing the soil before and after the cavitation generation process and comparing the particle size distribution.

[0068] Second Embodiment Fig. 4 is a schematic cross-sectional view showing a soil treatment device according to a second embodiment of the present invention. The following mainly describes the differences from the soil treatment device of the first embodiment, and redundant description will be omitted as appropriate.

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

[0070] In the soil treatment apparatus 1a, soil 10, which is the material to be treated, is supplied to a hopper 41 by a soil supply unit 6. Liquid (here, water) 50, to be mixed with the soil 10, is supplied to the hopper 41 by a liquid supply unit 5. The soil 10 and liquid 50, separately supplied to the hopper 41, are mixed on the inner wall of the hopper 41 to form a slurry 40, which is then supplied to a flow path 30 of a treatment unit 3. In the flow path 30 of the treatment unit 3, a pressurized liquid 20 is ejected from an ejection unit 2 onto the slurry 40. As in the previous embodiment, within the flow path 30, a process is performed in which mineral particles in the slurry 40 are separated from other particles using cavitation. The treated slurry 40 and pressurized liquid 20 are discharged from an outlet 37 of the flow path 30 and sent to a classification unit 7.

[0071] The specific configuration of each component of the soil treatment device 1a will be described below. In the following description, examples of the treatment conditions, size, capacity, etc. of each component when treating soil 10 at 1 kg / min may be given. Note that the treatment conditions, size, capacity, etc. of each component may be appropriately selected depending on the type of soil, the amount of soil to be treated, etc., and are not limited to the values ​​given as examples.

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

[0073] The high-pressure ejector is set to move at high speed along the portion of the flow path 30 extending in the X direction. In this embodiment, the high-pressure ejector ejects pressurized liquid 20 (here, pressurized water) of 4 MPa along the X direction at a flow rate of 0.1 liters / second. The speed of the pressurized water is, for example, 50 meters per second.

[0074] (Processing Section) The flow path 30 of the processing section 3 has a plurality of 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 extension direction of the flow path 30. In the example shown in Figure 4, a plurality of pipes with different diameters are connected to form the flow path 30, but these may also be formed integrally.

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

[0076] 4 , the flow path 30 includes a first portion 31, a second portion 32 located downstream (+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 downstream of the second portion 32 and having a larger cross-sectional area than the second portion 32. The slurry supply unit 4 is connected to the first portion 31. The downstream end of the second portion 32 and the upstream end of the third portion 33 form an enlarged portion 36 that enlarges the cross-sectional area of ​​the flow path 30.

[0077] 5A to 5C, the function of each part of the flow channel 30 will be specifically described. Fig. 5A is a schematic enlarged cross-sectional view showing a part of the flow channel 30. Figs. 5B and 5C are enlarged cross-sectional views taken along lines VB-VB and 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). The first portion 31 extends from the slurry supply position P to at least a portion of the third portion 33 in the ejection direction (X direction) of the pressurized liquid 20. In FIG. 4, the diameters of the first portion 31 to the third portion 33 are substantially constant; however, the diameters of the respective portions need not be substantially constant as long as they are set to have the functions described below.

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

[0080] <First Section> The first section 31 includes a region where the pressurized liquid 20 from the outlet 2 first collides with the slurry 40 at atmospheric pressure. After the collision, the pressurized liquid 20 passes through the slurry 40 and advances downstream (see FIG. 2B ). In the first section 31, the difference in flow velocity between the slurry 40 and the pressurized liquid 20 is large, so that vortices 82 are likely to be formed due to the difference in flow velocity, and a large amount of bubbles 81 is generated.

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

[0082] The length L1 of the first portion 31 along the X direction from the slurry supply position P to the tapered portion 34 may be smaller than the lengths L2 and L3 of the second portion 32 and the third portion 33 along the X direction (L1<L2, L3). The first portion 31 allows the slurry 40 to easily escape into the upper space 80, which tends to reduce the contact area between the slurry 40 and the pressurized liquid 20. By making the length L1 of the first portion 31 smaller than those of the second portion 32 and the third portion 33, the contact area (area of ​​the interface 20s) for generating cavitation can be increased more quickly.

[0083] <Second Portion> As shown in FIG. 5B , the second portion 32 is configured so that the slurry 40 flows to substantially fill the periphery of the pressurized liquid 20. The space 80 above the slurry 40 is narrower than the first portion 31. Because the space 80 is narrower, the slurry 40 is less likely to escape the impact force generated when the bubbles 81 collapse, and the impact force is more likely to act on the particles in the slurry 40. Furthermore, the slurry 40 can be more reliably brought into contact with the peripheral surface of the pressurized liquid 20. As a result, the area of ​​the interface 20s where the bubbles 81 are generated due to cavitation can be increased. Furthermore, because the radial thickness t of the slurry 40 is smaller than that of the first portion 31, the impact force generated when the bubbles 81 collapse is more likely to be transmitted throughout the entire thickness t of the slurry 40.

[0084] The cross-sectional area of ​​the second portion 32 may be set so that a flow of the slurry 40 is formed around the flow (jet flow) of the pressurized liquid 20. As shown in FIG. 5 , the diameter D2 of the second portion 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 equal to or larger than half the diameter D1. In this example, the diameter D2 of the second portion 32 is, for example, 21.6 mm.

[0085] The cross-sectional area of ​​the second portion 32 may be set to be larger than the cross-sectional area of ​​the pipe 24 (FIG. 4) of the emission unit 2. This makes it possible to more reliably make the cross-sectional area of ​​the second portion 32 larger than the cross-sectional area of ​​the pressurized liquid 20. Therefore, as shown in FIG. 5B , a flow of the slurry 40 is easily formed around the pressurized liquid 20.

[0086] When the flow rate of the slurry 40 is substantially constant, the cross-sectional area of ​​the slurry 40 decreases in the second portion 32, and the slurry 40 is accelerated. As a result, the difference in flow velocity between the slurry 40 and the pressurized liquid 20 gradually decreases, making it difficult for cavitation to occur.

[0087] By providing the second portion 32, the pressure of the slurry 40 is released in the subsequent third portion 33, thereby promoting the generation of bubbles by cavitation. The length L2 of the second portion 32 may be smaller than the length L3 of the third portion 33, for example. This allows the slurry 40 to move more quickly to the third portion 33, where the amount of bubbles generated increases.

[0088] <Third Section> In the third section 33, the cross-sectional area of ​​the flow path 30 expands, causing the pressure of the slurry 40 to be suddenly released, generating bubbles 81. Furthermore, the flow rate of the slurry 40 decreases, causing the flow rate difference between the slurry 40 and the pressurized liquid 20 to increase again, making it easier for vortices 82 to form, and increasing the number of bubbles 81. In this way, the number of bubbles 81 generated increases in the third section 33, and the impact force generated when the bubbles 81 collapse can further promote sludge dissolution and crushing of the soil in the slurry 40.

[0089] In the third portion 33, the flow velocities of the pressurized liquid 20 and the slurry 40 are reduced, making them more susceptible to the Coriolis force. As shown in FIG. 5C , in the Northern Hemisphere, the flow of the pressurized liquid 20 is affected by the Coriolis force and bends to the right relative to the direction of travel (+X direction). Furthermore, as shown enlarged in FIG. 5C , relatively heavy particles p1 in the slurry 40 are more susceptible to the Coriolis force and tend to accumulate to the right of the direction of travel. In this way, relatively light particles p2 in the slurry 40 can flow separately from the relatively heavy particles p1, making the impact force of the bubbles 81 more likely to act on the light particles p1. Therefore, relatively light mineral particles such as mica can be more efficiently crushed. The mica that has been thawed or crushed in the first portion 31 and the second portion 32 can be further crushed into smaller particles in the third portion 33. Alternatively, mica that is not sufficiently crushed in the first portion 31 and the second portion 32 due to the cavitation effect being difficult to reach can be crushed in the third portion 33 .

[0090] The diameter D3 of the third portion 33 may be, for example, two times or less the diameter D2 of the second portion 32 (D2<D3≦2×D2), which makes it less likely that clogging will occur at the downstream end of the second portion 32. The diameter (inner diameter) D3 of the third portion 33 is, for example, 41.6 mm.

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

[0092] The length L3 of the third portion 33 may be greater than the length L1 of the first portion 31 and the length L2 of the second portion 32. The length L3 may be greater than the length L4 of the flow path 30 from the slurry supply position P to the upstream end of the third portion 33 (or the downstream end of the second portion 32). Increasing the length L3 of the third portion 33 can further promote sludge disintegration and crushing (particularly crushing) by cavitation. In particular, efficient crushing can be achieved by utilizing the Coriolis force. Furthermore, even if the soil contains relatively large mineral particles (e.g., particle size: 2 mm or more), the weathered portions of the particles can be sufficiently crushed.

[0093] In the third portion 33, a portion located downstream of the cavitation generation region Rc extends, for example, in the −Z direction and is connected to the classifier 7. In the example shown in FIG. 4 , the piping that constitutes the third portion 33 is a bent piping that extends in the X direction and then bends downward. Alternatively, the bent piping that constitutes the third portion 33 may be bent horizontally and extend to the classifier 7. Alternatively, the third portion 33 may be formed using a straight piping that extends in the X direction. In this case, a discharge outlet that faces vertically downward, for example, may be provided on a side surface of the third portion 33.

[0094] Alternatively, a wall may be provided to block the flow path of the third section, allowing the pressurized liquid and slurry to collide against the wall, thereby disintegrating and crushing the mineral particles. However, according to the inventors' research, since the mineral particles are dispersed in the liquid, the impact force from the collision is unlikely to be applied to the mineral particles themselves. This makes it difficult to achieve sufficient effects (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 together with the cavitation effect, the crushing ability of the mineral particles can be more effectively improved.

[0095] The inventors conducted a confirmation experiment to verify the above-described effect of the third portion 33. In the confirmation experiment, a fringe was placed at position R shown in FIG. 5C , treatment was performed using the soil treatment device 1a, and the surface condition of the fringe after treatment was observed. FIG. 6 is a schematic top view of the fringe used in the experiment, showing the surface located on the flow path side. Observation revealed that the central portion 35c of the surface of the fringe 35 was worn. This is believed to be due to the impact of high-pressure water. Furthermore, rust was observed in the right-hand portion 352 of the central portion 35c, located to the right of the direction of flow of the pressurized liquid, but not in the left-hand portion 351. This is believed to be due to the formation of irregularities in the right-hand portion 352 due to the collision of relatively heavy particles. These results confirmed that, in the third portion of the flow path, the slurry flows while heavy and light particles are separated by the Coriolis force.

[0096] <Tapered portion> 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 cross-sectional area of ​​which decreases from the first portion 31 toward 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. The tapered section 34 makes it less likely for the slurry 40 or the soil contained in the slurry 40 to clog the downstream end of the first section 31. This makes it possible to prevent a decrease in treatment speed due to clogging, especially when the soil contains small particles (such as clay or 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 more effectively prevents clogging.

[0098] (Slurry Supply Unit) As shown in FIG. 4 , the slurry supply unit 4 includes 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 toward the lower opening 412. The upper opening 411 is, for example, an opening facing 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 has a truncated cone shape, but may also have a truncated polygonal pyramid shape.

[0100] The hopper 41 is configured to mix the liquid 50 and the soil 10, which are separately supplied 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 treatment section 3.

[0101] <Liquid Supply Unit> 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 includes a centrifugal submersible pump (capacity: for example, 40 L / m x 4.2 m x 0.1 kW x 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 that supplies the 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 portion of the periphery of the upper opening 411 of the hopper 41. In the example shown in FIG. 4 , the liquid line 51 has an annular portion 511 that extends annularly along the periphery of the upper opening 411. The annular portion 511 is provided with a plurality of liquid supply ports that supply 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 a polygonal annular shape such as a rectangular annular shape. The periphery of the upper opening 411 may be circular, and the annular portion 511 may be a rectangular annular shape. 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 also be arc-shaped, linear, or the like.

[0103] During operation of the soil treatment device 1a, the liquid supply rate (here, the 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 appropriately depending on the soil supply rate, the flow rate of the pressurized liquid, etc. It is also possible to change the liquid supply rate via the control unit 8 during operation depending on the operating state of the soil treatment device, etc.

[0104] <Soil Supply Unit> 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 Fig. 4, the soil supply unit 6 includes a soil storage tank 61 that stores the soil 10, and a conveying device 62 that conveys 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 conveyed to a predetermined input position Q above the hopper 41, and is supplied from the input position Q to the hopper 41. The soil supply rate is, for example, 1 kg / min.

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

[0106] 7A and 7B, the conveying device 62 includes a belt 621 above the hopper 41 that conveys the soil 10 to a loading position Q. In a plan view, the loading position Q is located inside the upper opening 411 of the hopper 41. The belt 621 is configured to move in one direction (here, the −X direction) to the loading position Q, then make a downward U-turn at the loading position Q and move in the opposite direction (here, the +X direction). In this way, the soil 10 on the belt 621 is supplied from the loading 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 near the upper end of the inner wall 41s of the hopper 41. The height of the region 410 in the Z direction from the lower opening 412 of the hopper 41 is, for example, equal to or greater than half the height H of the hopper 41. This increases the distance that the soil 10 flows along the inner wall 41s together with the liquid 50, allowing the soil 10 and the liquid 50 to be thoroughly mixed.

[0108] In this embodiment, as shown in FIG. 7B , the inertial force generated by the transport can be used to cause heavy and light 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 descending order of weight, the heavier particles will fall more upstream (+X side) in the transport direction. In this way, when the soil 10 is introduced, clumps of the soil 10 can be loosened, making it easier to mix with the liquid 50. This allows for the formation of a more uniform slurry 40. Furthermore, this more effectively prevents clumps of soil from remaining in the soil from being supplied to the treatment unit 3.

[0109] 7A , in a plan view, the input position Q is offset from the center C of the lower opening 412. By offsetting the input position Q from the center C of the lower opening 412, the soil 10 can be more reliably supplied to the inner wall 41s of the hopper 41. This prevents the input soil 10 particles from being sent directly from the lower opening 412 to the treatment section 3 without being mixed with the liquid 50.

[0110] In a plan view, the input position Q may be located downstream of the center C of the lower opening 412 in the conveying direction (-X direction in Figures 7A and 7B) of the conveying device 62. With this configuration, particles in the soil 10 are likely to fly out from the input position Q toward the opposing portion of the inner wall 41s due to inertial force and fall onto the inner wall 41s. This prevents particles from falling into the lower opening 412 without contacting the inner wall 41s. Furthermore, even relatively heavy particles are 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 for adjusting the height of the soil 10, located upstream of the input position Q on the belt. The adjustment member 622 extends across the width of the belt 621 in a plan view. The lower end of the adjustment member 622 is positioned 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 prevent clogging of the treatment section 3 due to an increase in the amount of soil 10 supplied. Furthermore, the amount of soil 10 supplied per unit time to the hopper 41 can be kept roughly constant.

[0112] <Classification Section> As shown in Fig. 4, a mixture 70 obtained by mixing the pressurized liquid 20 and the slurry 40 is sent to the classification section 7 from the outlet 37 of the treatment section 3. The classification section 7 classifies the mixture 70 into a large particle group having a particle size equal to or larger than a predetermined classification point, and a small particle group having a particle size less than the classification point and having a higher radioactive concentration than the large particle group. In this embodiment, classification is performed using a vibrating sieve, but this is not limited to a vibrating sieve, and various known classification devices can be used. Classification may be performed in multiple stages.

[0113] In the example shown in Figure 4, the classification unit 7 includes a sieve 72 with a mesh size of 2 mm and a sieve 73 with a mesh size of 75 µm, which is disposed downstream of the sieve 72. As a result, gravel particles 11 are removed by the sieve 72, and sand particles 12 are removed by the sieve 73. The mixture 70 that has passed through the sieve 72 is muddy water containing particles with a particle size of less than 75 µm, such as clay and silt, including mineral particles 13. Most of the radioactive material is contained in the muddy water. The muddy water may be further classified, for example, by a high-mesh separator.

[0114] When a sludge thawing process is performed in the cavitation generation region Rc to separate mineral particles with adsorbed radioactive substances from soil particles, the classification unit 7 may be configured to classify the mixture 70 into a large particle group including soil particles (e.g., particle size 75 μm or more) and a small particle group including mineral particles (e.g., particle size less than 75 μm) (see Figure 3B).

[0115] Alternatively, when sludge thawing 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 particles having a particle size equal to or larger than the particle size of the mineral particles (e.g., 20 μm) and a group of small particles having a particle size smaller than the mineral particles (see Figure 3A).

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

[0117] 4 to 5C, in the soil treatment device 1a of this embodiment, the flow path 30 of the treatment unit 3 has an expansion section 36 that expands the cross-sectional area downstream of the slurry supply position P. The slurry supply unit 4 and the outlet unit 2 are configured so that the difference in flow velocity between the slurry 40 and the pressurized liquid 20 is greater downstream of the expansion section 36 than upstream of the expansion 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. Furthermore, because the flow velocity of the slurry 40 decreases, the flow velocity ratio between the slurry 40 and the pressurized liquid 20 increases. Therefore, 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. As a result, the mineral particles in the slurry 40 can be further separated. Furthermore, the decrease in the flow velocity of the slurry 40 downstream of the expansion section 36 increases the effect of the Coriolis force. Therefore, the particles in the slurry 40 flow while being separated by weight, so that the impact force at the collapse of the bubbles can be more efficiently applied to relatively light particles, such as mineral particles.

[0119] Furthermore, the above configuration can lengthen the cavitation generation region Rc within the flow path 30. Since it is possible to continue generating cavitation within the flow path 30, the processing time for thawing and crushing the mineral particles in the slurry 40 can be extended without increasing the amount of water used.

[0120] 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 so that the liquid 50 and the soil 10 are mixed on the inner wall 41s of the hopper 41 to form slurry 40, which is supplied from the lower opening 412 of the hopper 41 to the flow path 30 of the treatment unit 3.

[0121] With this configuration, the soil 10 and the liquid 50 can be mixed more reliably while keeping the amount of the liquid 50 small. Therefore, it is possible to reduce the overall solid-liquid ratio.

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

[0123] Furthermore, with the above configuration, even if the soil 10 contains relatively small particles such as clay, the particles are less likely to adhere to the inner wall 41s of the hopper 41 because they come into contact with the liquid 50 on the inner wall 41s. This reduces the frequency of maintenance.

[0124] Furthermore, compared to the case where a pre-prepared slurry is transported and supplied to the processing section, the above configuration eliminates the need for a stirring operation, a large mixing device, or a slurry transport device, thereby reducing the cost required to form the slurry 40. In addition, since there is no need to transport the slurry, there is no need to increase the amount of liquid to make it easier to transport the slurry.

[0125] Furthermore, with the above-described configuration, the liquid 50 can be mixed with the amount of soil 10 flowing down the hopper 41 without stirring, etc. This is advantageous when the soil 10 contains radioactive materials, as dust containing the radioactive materials is less likely to fly up.

[0126] In the soil treatment device 1a of this embodiment, the liquid supply unit 5 includes a liquid line 51 extending along at least a portion of the periphery of the upper opening 411 of the hopper 41 and transporting the liquid 50, and multiple liquid supply ports spaced apart from one another on the liquid line 51 and discharging the liquid 50. This configuration facilitates supplying the liquid 50 near the upper end of the inner wall 41s of the hopper 41. Furthermore, 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. This allows the liquid 50 and the soil 10 to be more reliably mixed. Furthermore, providing multiple liquid supply ports allows the liquid 50 to flow over a wider area of ​​the inner wall 41s of the hopper 41. This reduces soil particle adhesion to the inner wall 41s.

[0127] Furthermore, according to this embodiment, in a soil treatment method including a cavitation generation step, as shown in Figure 5A, it is 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 together with the slurry 40 in the ejection direction. In this method, in the cavitation generation step, the mineral particles in the slurry 40 can be thawed 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, thawing or crushing can be carried out more efficiently while reducing the amount of liquid used.

[0128] (Variation 1: Slurry Supply Unit) The slurry supply unit 4 may be configured so that the liquid 50 and the soil 10 flow downward while swirling on the inner wall 41s of the hopper 41, and are mixed during this process to form the slurry 40. With this configuration, the soil 10 and the liquid 50 can be mixed more reliably and more uniformly.

[0129] 8A and 8B are schematic perspective views showing modified examples of a liquid supply unit and a hopper, respectively, and a top view of the modified example shown in FIG. 8A.

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

[0131] With this configuration, the liquid 50 from the nozzle 52 tends to flow in a circumferential direction due to inertial force, and the liquid 50 tends to flow downward while swirling on 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 is longer, and the liquid 50 and the soil 10 can be mixed more reliably and more uniformly.

[0132] 8A and 8B, all of the nozzles 52 are inclined at the same angle θ with respect to the direction d, but the angles θ may be different from one another. Furthermore, if the nozzle 52 provided in at least one liquid supply port 512 is inclined with respect to the direction d, the effect of causing the liquid 50 to flow in a swirling manner can be obtained.

[0133] (Variation 2: Flow path of treatment unit) FIG. 9A is a schematic cross-sectional view showing a variation of the flow path. The flow path 30 shown in FIG. 9A has multiple expansion sections 36 downstream of the slurry supply position P. The multiple expansion sections 36 are arranged at a distance 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 the expansion 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 include alternating fourth and fifth portions 320 and 330 downstream of the third portion 33, thereby providing more expansions 36.

[0134] If each expansion section 36 is too long, it becomes difficult for vortices 84 (FIG. 9B) described below to be formed throughout the expansion section 36, and it may be difficult to obtain the effects of preventing soil particles from clogging and promoting the sludge disintegration and crushing action of the vortices 84. For this reason, the length of the expansion section 36 may be, for example, two times or less the length of the second section 32.

[0135] 9A , by providing multiple expansion sections 36 in the flow path 30, the cavitation generation region Rc can be further extended. Each expansion section 36 functions as a "treatment chamber" in which the processing of the soil in the slurry 40 progresses more intensively than in other sections. By providing such treatment chambers at intervals within the flow path 30, the processing intensity can be varied throughout the flow path 30, enabling more efficient thawing and crushing of the soil particles in the slurry 40. A configuration with multiple treatment chambers is particularly advantageous when, for example, the pressure of the pressurized liquid is increased (e.g., 8 MPa).

[0136] 9B is a schematic cross-sectional view showing another modified example of the flow channel, in which each of the first and third portions includes a plurality of portions with different cross-sectional areas.

[0137] 9B includes an upstream portion 311 and a downstream portion 312 located downstream of the upstream portion 311. A diameter D11 of the upstream portion 311, a diameter D12 of the downstream portion 312, and a diameter D2 of the second portion are set so that D11 > D12 > D2.

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

[0139] In this example, in the flow path 30, a tapered portion is disposed between every two portions having different cross-sectional areas (here, diameters) in order to prevent clogging by the slurry 40. The inclination angle of the tapered portion can be set appropriately. Depending on the difference in pipe diameter, there may be some portions where no tapered portion is disposed.

[0140] In this modification, as the slurry 40 flows from the upstream section 311 toward the downstream section 312, a portion of the slurry 40 comes into contact with a stepped portion of the piping (here, the inner surface of the tapered section 34), causing the slurry 40 to swirl back in the opposite direction (-X direction) to its traveling direction. The swirling flow then comes into contact with a stepped portion on the outlet side of the upstream section 311 and travels in the +X direction. As a result, in the upstream section 311, in addition to a localized vortex 82 (see FIG. 5A , not shown in FIG. 9B ) due to the flow velocity difference, 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 upstream and downstream ends of the stepped portion where the piping narrows. The vortex 83 can occur along the periphery of the cross-section of the slurry 40. The generation of vortices 83 prevents soil particles in the slurry 40 from stagnating at the stepped portions of the piping. Instead, they swirl and are pushed from the center of the piping toward the downstream section 312. This effectively prevents clogging of the slurry 40 and soil particles at the stepped portions. Even if relatively light soil particles float and adhere to the inner wall of the piping, they are removed from the inner wall by the swirling flow and sent to the downstream section 312. Furthermore, the slurry 40 returned by the vortices 83 again comes into contact with the high-pressure liquid and moves through the center of the flow cross section, further promoting soil disintegration and crushing using cavitation. Although not shown, a similar vortex may also occur between the downstream section 312 and the second section 32. It is preferable that the differences in diameter (differences in diameter) of the piping be adjusted so that the above-described clogging prevention effect of the vortices 83 can be achieved.

[0141] If the difference in cross-sectional area between the portion including the slurry supply position P and the second portion 32 is large, directly connecting the two portions would result in a large step, making the step more likely to become clogged with soil particles. In contrast, in this modification, the cross-sectional area (diameter) is gradually reduced from the portion including the slurry supply position P (here, the upstream portion 311) to the second portion 32, forming multiple step portions. This allows each step portion to be adjusted to a size that makes it less likely to become clogged with soil particles. Therefore, by setting the cross-sectional areas of the portion 311 including the slurry supply position P and the second portion 32 within a suitable range and adjusting the number and size of the step portions, clogging with the slurry 40 and soil particles can be suppressed.

[0142] Furthermore, in this modification, the slurry 40 flowing through the third section 3 generates more bubbles due to cavitation when it flows from the second section 32 into the upstream section 331 and when it flows from the upstream section 331 into the expanded section 333. In this way, by gradually increasing the cross-sectional area (diameter) from the second section 32 to the expanded section 333 with a larger cross-sectional area, it is possible to promote bubble generation in multiple stepped sections. This makes it possible to further lengthen the cavitation generation region.

[0143] Furthermore, in this modification, the third section 33 includes an expanded section 333. In the expanded section 333, the slurry 40 comes into contact with the stepped portions of the upstream and downstream piping, generating a vortex 84 along the length of the expanded section 333. This, as with the vortex 83 described above, more effectively reduces clogging of the slurry 40 and soil particles in the stepped portions. Furthermore, in addition to the vortex caused by the flow velocity difference, an overall swirling flow (vortex 84) is generated, further promoting the disintegration and sludge dissolution of the soil in the slurry 40. Because the velocity of the pressurized liquid 20 is slower in the third section 33 than in the first section 31, the length of the expanded section 333 may be shorter than the length of the upstream section 311 (here, the length in the X direction of the portion sandwiched between piping with a diameter less than D11, where the vortex 83 occurs).

[0144] 9B , the upstream portion 311 of the first portion 31 and the enlarged portion 333 of the third portion 33 function as a "treatment chamber" that has a greater effect on treating the slurry 40 than the other portions. The length of the second portion (narrow portion) 32 that connects the first portion 31 and the third portion 33 is, for example, shorter than the lengths of the first portion 31 and the third portion 33. This allows the portions 31 and 33, where thawing and crushing processes progress significantly, to account for a greater proportion of the overall length of the flow path 30, enabling more efficient treatment.

[0145] As shown in FIG. 9B , the slurry supply unit may include a hopper 41 and a tubular supply channel connecting the hopper 41 and the flow path 30. The supply channel includes an inclined supply channel 42 that is inclined downward relative to the horizontal. In a plan view, the inclined supply channel 42 and the flow path 30 may be perpendicular (or approximately perpendicular). The soil 10 and liquid 50 separately supplied to the hopper 41 are mixed while flowing through the inclined supply channel 42 to form the slurry 40. The inclination angle of the inclined supply channel 42 makes it possible to adjust the mixing time of the liquid 50 and the soil 10 and the supply speed of the slurry 40.

[0146] FIG. 9C is a schematic cross-sectional view showing another modified example using the vortices 83 and 84 described in FIG. 9B . The flow path 30 shown in FIG. 9C further includes a sixth portion 341 and a seventh portion 342 downstream of the third portion 33. The cross-sectional area of ​​the sixth portion 341 is smaller than that of the third portion 33. The cross-sectional area of ​​the seventh portion 342 is larger than that of the sixth portion 341. Here, the downstream side of the seventh portion 342 extends downward to an outlet for discharging the mixture 70. A tapered portion may be formed between two portions of the flow path 30 having different cross-sectional areas. In FIG. 9C , the first portion 31, the third portion 33, and the seventh portion 342 have the same diameter, but these may be different from one another. The diameters and lengths of the second portion 32 and the sixth portion 341 may also be the same or different from one another.

[0147] In the flow path 30 of this modification, the third portion 33 is an expanded portion 36 sandwiched between two narrow portions (the second portion 32 and the sixth portion 341). Similar to the expanded portion 333 in FIG. 9B , a vortex 84 is generated in the third portion 33. Therefore, the first portion 31 where the vortex 83 is generated and the third portion 33 where the vortex 84 is generated function as a processing chamber. Because the flow velocity of the pressurized liquid 20 in the third portion 33 is slower than in the first portion 31, in order to generate the vortex 84 throughout the third portion 33, the length of the third portion 33 may be shorter than the length of the portion of the first portion 31 where the vortex 83 is generated. Furthermore, the third portion 33 may be longer than the second portion 32.

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

[0149] In order to confirm the effect of this embodiment, a mica crushing experiment was conducted using the soil treatment device 1a shown in Fig. 4, and the method and results thereof will be described. In this example, instead of actual soil, commercially available vermiculite containing only dried mica as the main component was used as the treated material, and the particle size distribution after treatment was measured.

[0150] <Method of 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 rate of the material to be treated (vermiculite), the flow rate of water to be mixed with the vermiculite, and the conditions for ejecting the pressurized liquid (pressurized water), were set to be the same as the conditions exemplified with reference to Figure 4.

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

[0152] <Comparative Example> As a comparative example, 1 kg of vermiculite was passed through a comparative apparatus not equipped with an outlet for pressurized water together with water, and the particle size distribution of the vermiculite was then measured. The comparative apparatus was an apparatus for producing a slurry under the same conditions as in the examples and measuring the particle size distribution.

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

[0154] In the comparative example, 1 kg of vermiculite was supplied to the slurry supply section together 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 measurement sample was collected 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 due to the collision of pressurized water or cavitation. Therefore, the particle size distribution of the measurement sample obtained in the comparative example is substantially the same as the particle size distribution of the vermiculite supplied to the apparatus in the comparative example. Therefore, the particle size distribution measured in the comparative example can be considered to be substantially the same as the particle size distribution of the vermiculite before the crushing experiment in the example.

[0156] 11A and 11B are photographs showing the measurement samples of the Example and Comparative Example, respectively. These photographs confirm that the particle size of the vermiculite after the crushing experiment of the Example is clearly smaller than the particle size of the vermiculite of the Comparative Example.

[0157] Next, in order to compare particle size distributions in a small particle size range that is difficult to visually confirm, particle size distribution measurements were performed on the measurement samples of the Examples and Comparative Examples. Here, the measurement samples of the Examples and Comparative Examples were classified to remove particles with particle sizes of 0.212 mm or more, and then the particle size distribution of the remaining particles was measured by laser diffraction.

[0158] 11C is a graph showing particle size accumulation curves obtained by laser diffraction in the Examples and Comparative Examples. The results shown in FIG. 11C show that the ratio of particles having particle diameters of 0.02 mm to 0.04 mm is higher in the Examples than in the Comparative Examples. This suggests that in the Examples, some of the vermiculite particles (e.g., particles having a diameter of 0.2 mm or more) were crushed to a diameter of, for example, around 0.02 mm.

[0159] 11A to 11C confirm that the soil treatment device 1a of this embodiment has sufficient crushing capabilities for mineral particles such as vermiculite. Furthermore, a comparison of FIGS. 11A and 11B reveals that more than 50% (more than 70% in this case) of the input vermiculite was crushed by the treatment with this device. While vermiculite was used as the treated material here, it is believed that a certain level of crushing capabilities will be exhibited even when soil containing a mixture of vermiculite and other soil particles is used.

[0160] (Other Modifications) The soil treatment device and soil treatment method of the present invention are not limited to the device and method exemplified in FIGS. 1 to 9B.

[0161] 1, 4, 8A, and 8B, the slurry supply unit 4 includes a hopper 41, but may not include a hopper. For example, a premixed slurry may be transported by a pipe, and this pipe may be connected to a flow path of the treatment unit. In the example shown in FIG. 4, the soil and liquid are separately supplied to the hopper, but a premixed slurry may be supplied to the hopper.

[0162] 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 sent to a common classifier or classifier. For example, the flow paths of the multiple soil treatment devices may be joined together and sent to a common classifier.

[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, they can also be applied to soil containing organic components. They are also applicable to the purification of soil containing impurities such as oil, soil sterilization, and other purposes, not limited to soil containing radioactive materials. Furthermore, various powders and granular materials can be used as the material to be treated, not limited to soil. By applying this apparatus or method, cavitation can be used to efficiently separate particles contained in a slurry, disperse particles, separate particles from impurities, and pulverize particles.

[0164] The slurry supply device (slurry supply unit) described above with reference to FIGS. 4, 8A, and 8B can be applied to various processing devices. The slurry supply device can be widely applied to devices for separating soil particles (including mineral particles) from other particles and deposits in soil by utilizing cavitation (see FIGS. 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, thereby enabling more efficient separation of soil particles. Furthermore, the amount of liquid contained in the slurry can be reduced, thereby reducing the cost of liquid purification after treatment. Furthermore, since operations such as stirring are not required during slurry formation, radioactive materials are less likely to disperse. 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 embodiments.

[0165] The above-described slurry supply device can also be applied to a purification device that separates soil particles from impurities such as oil, a device for sterilizing soil particles, etc. Furthermore, it can also be applied to devices that disperse, mix, crush, polish, etc. powder and granular materials other than soil. This can achieve the same effects as the above-described embodiment, such as reducing the amount of liquid to be mixed with soil or powder and granular materials.

[0166] The present disclosure is not limited to the above-described embodiments, and design modifications are possible within the scope of the present disclosure. Furthermore, by appropriately combining the configurations of any of the various exemplary embodiments (including modified examples), the effects of each embodiment can be achieved.

[0167] This specification discloses soil treatment methods described in the following items. [Item 1] A method for treating soil containing mineral particles having radioactive materials adsorbed thereon, comprising: injecting a pressurized liquid into a slurry prepared by mixing the soil with a liquid, thereby generating a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation; the mineral particles are separated from other particles by the impact force generated when bubbles generated by the cavitation collapse; [Item 2] The soil treatment method described in Item 1, wherein the soil further includes soil particles larger in size than the mineral particles, and the mineral particles attached to or encapsulated in the soil particles are separated from the soil particles by the impact force; [Item 3] The soil treatment method described in Item 2, wherein the mineral particles separated from the soil particles are crushed by the impact force to become particles smaller in size than the mineral particles; [Item 4] The soil treatment method described in Item 1, wherein the mineral particles are broken down into particles smaller in size than the mineral particles by the impact force. [Item 5] The soil treatment method of 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 of 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 to 15. [Item 7] The soil treatment method of Items 2 or 3, wherein the particle size of the soil particles is 0.075 mm or more and the particle size of the mineral particles is less than 0.075 mm. [Item 8] The soil treatment method of Items 2 or 3, further comprising, after generating the cavitation, classifying the mixture of the slurry and the pressurized liquid into a large particle group including the soil particles and a small particle group including the mineral particles. [Item 9] The soil treatment method according to Item 4, further comprising classifying the mixture of the slurry and the pressurized liquid after generating the cavitation into a group of particles having a particle size equal to or larger than the particle size of the mineral particles and a group of particles having a particle size smaller than the mineral particles.[Item 10] The soil treatment method according to any one of Items 1 to 9, wherein generating the cavitation includes controlling the flow velocity difference so that the amount of generated bubbles decreases and then increases while the pressurized liquid flows together with the slurry in the ejection direction.

[0168] This specification discloses soil treatment devices described in the following items: [Item 1] A soil treatment device that performs a process on soil containing mineral particles having radioactive substances adsorbed thereon, separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and that supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, the outlet section and the supply section being configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation. [Item 2] The soil treatment device described in Item 1, wherein the soil is a mixture of the mineral particles and soil particles having a particle size larger than the mineral particles, and the outlet section and the supply section are configured to separate the mineral particles attached to or encapsulated in the soil particles from the soil particles by the impact force generated when bubbles generated by the cavitation collapse. [Item 3] The soil treatment device 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 into particles smaller in size than the mineral particles. Note that the phrase "configured to crush the mineral particles into particles smaller in size than the mineral particles" does not include cases where only a small portion of the mineral particles are crushed by chance within the flow path. For example, it includes cases where the discharge unit and the supply unit are configured to crush 50% or more of the mineral particles (e.g., mica particles) in the supplied slurry by the impact force of bubble collapse. [Item 4] The soil treatment device according to Item 1, wherein the discharge unit and the supply unit crush the mineral particles into particles smaller in size than the mineral particles by the impact force generated when the bubbles collapse due to the cavitation.[Item 5] The soil treatment device according to any one of Items 1 to 4, wherein the flow path includes an expansion section downstream of a position where the supply section is connected that expands a cross-sectional area perpendicular to the extension direction of the flow path, and the outlet section and the supply section are configured so that the flow velocity difference downstream of the expansion section is greater than that upstream of the expansion section, thereby increasing the amount of bubbles generated by the cavitation. [Item 6] The soil treatment device according to any one of Items 1 to 5, wherein the supply section includes: a hopper having a tapered shape whose inner diameter decreases from an upper opening toward a lower opening; a soil supply section that supplies the soil from the upper opening toward an inner wall of the hopper; and a liquid supply section that supplies the liquid from the upper opening toward the inner wall of the hopper, and the soil supply section and the liquid supply section are configured so that the liquid and the soil are mixed on the inner wall of the hopper to form the slurry, and the slurry is supplied to the flow path from the lower opening. [Item 7] The soil treatment device according to item 2 or 3, further comprising a classifier fluidly connected to the downstream side of the flow path and configured to classify the mixture of the pressurized liquid and the slurry into a large particle group containing the soil particles and a small particle group containing the mineral particles. [Item 8] The soil treatment device according to item 4, further comprising a classifier fluidly connected to the downstream side of the flow path and configured to classify the mixture of the pressurized liquid and the slurry into a particle group having a particle size equal to or larger than the mineral particles and a particle group having a particle size smaller than the mineral particles. [Item 9] The soil treatment device according to any one of items 1 to 8, wherein the radioactive substance is radioactive cesium and the mineral is mica.

[0169] This specification also discloses soil treatment devices described in the following items: [Item 1] A soil treatment device that performs a process on soil containing mineral particles having radioactive substances adsorbed thereon, separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; and an outlet section that outputs a pressurized liquid from the upstream side to the downstream side of the flow path, the outlet section being configured to output the pressurized liquid toward a slurry formed by mixing the soil with a liquid within the flow path, thereby generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry, the flow path being configured to include: a first section; a second section located downstream of the first section and having a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; and a third section located downstream of the second section and having a cross-sectional area larger than that of the second section. [Item 2] The soil treatment device described in Item 1, wherein the flow path is configured so that the amount of bubbles generated by the cavitation in the third section is greater than that in the second section. [Item 3] The soil treatment device according to item 1 or 2, further comprising a supply unit connected to the first portion and supplying the slurry, wherein the length of the third portion is greater than the length of the flow path from a position where the supply unit is connected to the upstream end of the third portion. [Item 4] The soil treatment device according to any one of items 1 to 3, wherein the outlet unit comprises a nozzle unit having an outlet for outletting the pressurized liquid and a pipe located upstream of the nozzle unit and connected to the nozzle unit, wherein the nozzle unit is configured so that its cross-sectional area increases from the outlet toward the pipe, and the cross-sectional area of ​​the second portion is greater than the cross-sectional area of ​​the pipe of the outlet unit. [Item 5] The soil treatment device according to item 1 or 2, wherein the flow path is further configured to include: a fourth portion located downstream of the third portion and having a cross-sectional area smaller than that of the third portion; and a fifth portion located downstream of the fourth portion and having a cross-sectional area larger than that of the fourth portion.[Item 6] The soil treatment device according to any one of Items 1 to 5, wherein the flow path further includes a tapered section between the first portion and the second portion, the cross-sectional area of ​​which decreases from the first portion toward the second portion.

[0170] This specification discloses the following slurry supplying devices: [Item 1] A slurry supplying device that supplies a slurry obtained by mixing soil with a liquid, comprising: a hopper having a tapered shape whose inner diameter decreases from an upper opening toward a lower opening; a soil supplying unit that supplies the soil from the upper opening toward an inner wall of the hopper; and a liquid supplying unit that supplies the liquid from the upper opening toward the inner wall, wherein the soil supplying unit and the liquid supplying unit are configured so that the liquid and the soil are mixed on the inner wall to form the slurry, which then flows out from the lower opening. [Item 2] The slurry supplying device according to Item 1, wherein the soil supplying unit and the liquid supplying unit are configured so that the liquid and the soil are mixed to form the slurry while flowing downward on the inner wall while swirling. [Item 3] The slurry supplying apparatus according to item 1 or 2, wherein the liquid supply unit is configured to include: a liquid line extending along at least a portion of the periphery of the upper opening and transporting the liquid; and a plurality of liquid supply ports arranged at intervals on the liquid line and supplying the liquid to the hopper. [Item 4] The slurry supplying apparatus according to item 3, wherein the plurality of liquid supply ports include a first liquid supply port, wherein the first liquid supply port is provided with a nozzle extending downward from the first liquid supply port, and wherein the extension direction of the nozzle is inclined with respect to the direction from the first liquid supply port toward the center of the lower opening in a plan view seen along the height direction of the hopper. [Item 5] The slurry supplying apparatus according to any one of items 1 to 4, wherein the soil supplying unit is configured to charge the soil toward the inner wall from a charging position offset from the center of the lower opening in a plan view seen along the height direction of the hopper. [Item 6] The slurry supplying apparatus according to item 5, wherein the soil supplying unit includes a conveying device that, in the plan view, conveys the soil from outside the upper opening to the loading position and drops the soil into the upper opening at the loading position. [Item 7] The slurry supplying apparatus according to item 6, wherein, in the plan view, the loading position is downstream of the center of the lower opening in the transport direction of the conveying device.[Item 8] The soil is soil containing a radioactive material. The slurry supplying device according to any one of Items 1 to 7. [Item 9] A soil treatment device that separates soil particles contained in soil from other particles or attached matter, comprising: a supply unit equipped with the slurry supplying device according to any one of Items 1 to 8; a flow path through which a slurry containing the soil is supplied from the supply unit; and an outlet unit that outputs a pressurized liquid from an upstream side to a downstream side of the flow path, wherein the outlet unit and the supply unit are configured to generate a flow velocity difference at an interface between the pressurized liquid and the slurry, thereby generating cavitation.

[0171] This specification discloses a soil treatment device and a soil treatment method as described in the following items: [Item 1] A soil treatment device that performs a process on soil containing mineral particles to which radioactive materials are adsorbed, separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side toward the downstream side of the flow path; and a supply section that is connected downstream of the outlet section on the flow path and that supplies a slurry, in which the soil is mixed with a liquid and to which no dispersant that reduces the zeta potential has been added, toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation. [Item 2] A soil treatment device that treats soil containing mineral particles having radioactive substances adsorbed thereon, by separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side toward the downstream side of the flow path; and a supply section that is connected to the flow path downstream of the outlet section and that supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein a dispersant of less than 0.5 mol / kg relative to the mass of the soil is added to the slurry that is supplied to the supply section, and the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation.[Item 3] A soil treatment device that treats soil containing mineral particles having radioactive substances adsorbed thereon, by separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and that supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation, and to crush the mineral particles into particles having a diameter smaller than that of the mineral particles by the impact force generated when bubbles generated by the cavitation collapse. [Item 4] The soil treatment device according to any one of Items 1 to 3, wherein the mineral particles are mica particles, and the outlet 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 an impact force generated when bubbles generated by the cavitation collapse, thereby breaking down the mica particles into particles having a particle size smaller than the mica particles. [Item 5] A soil treatment device that treats soil containing mineral particles having radioactive substances adsorbed thereon, by separating the mineral particles from other particles, the soil treatment device comprising: a treatment section having a flow path; an outlet section that discharges a pressurized liquid from the upstream side toward the downstream side of the flow path; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid discharged by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; and a third section that is located downstream of the second section and is longer than the second section and has a cross-sectional area larger than that of the second section.[Item 6] A soil treatment apparatus for treating soil containing mineral particles having radioactive substances adsorbed thereon, by separating the mineral particles from other particles, the soil treatment apparatus comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and that supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; and a third section that is located downstream of the second section and has a cross-sectional area larger than that of the second section and a length greater than the length from a position in the flow path where the supply section is connected to the downstream end of the second section. [Item 7] The soil treatment device according to Item 5 or 6, wherein the third portion includes an upstream portion, a downstream portion located downstream of the upstream portion, and an enlarged portion located between the upstream portion and the downstream portion and having a cross-sectional area larger than the upstream portion and the downstream portion.[Item 8] A soil treatment apparatus for treating soil containing mineral particles having radioactive substances adsorbed thereon, by separating the mineral particles from other particles, the apparatus comprising: a treatment section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; a third section that is located downstream of the second section and has a cross-sectional area larger than that of the second section; and a fourth section that is located downstream of the third section and has a cross-sectional area smaller than that of the third section. [Item 9] The soil treatment device according to any one of Items 1 to 8, wherein the supply unit comprises: a hopper having a tapered shape whose inner diameter decreases from the upper opening toward the lower opening; a soil supply unit that supplies the soil from the upper opening toward the inner wall of the hopper; and a liquid supply unit that supplies the liquid from the upper opening toward the inner wall of the hopper, wherein the soil supply unit and the liquid supply unit are configured to mix the liquid and the soil on the inner wall of the hopper to form the slurry, and supply the slurry to the flow path from the lower opening. [Item 10] The soil treatment device according to Item 9, wherein the soil supply unit and the liquid supply unit are configured to mix the liquid and the soil while flowing downward on the inner wall while swirling, to form the slurry. [Item 11] The soil treatment device according to Item 9 or 10, wherein the soil supply unit is configured to charge the soil toward the inner wall from a charge position offset from the center of the lower opening in a plan view seen along the height direction of the hopper.[Item 12] A method for treating soil containing mineral particles having radioactive substances adsorbed thereon, comprising: ejecting a pressurized liquid from an upstream side to a downstream side of a flow path for treating the soil; supplying a slurry, in which the soil has been mixed with a liquid and to which no dispersant that reduces the zeta potential has been added, toward the ejected pressurized liquid within the flow path; and generating a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation; and separating the mineral particles from other particles by the impact force generated when bubbles generated by the cavitation collapse. [Item 13] A method for treating soil containing mineral particles having radioactive materials adsorbed thereon, comprising: ejecting a pressurized liquid from an upstream side toward a downstream side of a flow path for treating the soil; supplying, within the flow path, a slurry prepared by mixing the soil with a liquid and adding a dispersant that reduces the zeta potential at a concentration of less than 0.5 mol / kg relative to the mass of the soil toward the ejected pressurized liquid; and generating a flow velocity difference at the interface between the pressurized liquid and the slurry to generate cavitation; wherein the mineral particles are separated from other particles by the impact force generated when bubbles generated by the cavitation collapse. [Item 14] A method for treating soil containing mineral particles having radioactive substances adsorbed thereon, the method comprising: injecting a pressurized liquid into a slurry prepared by mixing the soil with a liquid and not adding a dispersant that reduces the zeta potential; and generating cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry within a flow path extending in the direction of the pressurized liquid injection; and separating the mineral particles from other particles by the impact force generated when bubbles generated by the cavitation collapse.[Item 15] The soil treatment method according to any one of Items 12 to 14, further comprising: crushing the mineral particles into particles smaller in size than the mineral particles by the impact force; and, after generating the cavitation, transferring the mixture of the slurry and the pressurized liquid from the downstream side of the flow path to a classification section, and classifying the mixture in the classification section into a group of particles having a particle size equal to or larger than the particle size of the mineral particles and a group of particles having a particle size smaller than the mineral particles. [Item 16] The soil treatment method according to any one of Items 12 to 15, wherein a weight ratio of the liquid contained in the slurry to the soil is 5 or less.

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

[0173] DESCRIPTION OF SYMBOLS 1, 1a Soil treatment device 2 Emission section 3 Treatment section 4 Slurry supply section 5 Liquid supply section 6 Soil supply section 7 Classification section 8 Control section 10 Soil 11 Gravel particles 12 Sand particles 13 Mineral particles 15 Radioactive material-containing mineral particles 20 Pressurized liquid 20s Interface 22 Nozzle 23 High-speed jet pump 24 Piping 30 Flow path 31 First section 32 Second section 33 Third section 34 Tapered section 35 Fringe 35c Central section 36 Expanded section 37 Discharge outlet 40 Slurry 41 Hopper 41s Inner wall 50 Liquid 51 Liquid line 52 Nozzle 53 Submersible pump 61 Soil storage tank 62 Conveyor device 70 Mixture 72, 73 Sieve 80 Space 81 Air bubbles 82 Vortex 320 Fourth portion 330 Fifth portion 351 Left portion 352 Right portion 411 Upper opening 412 Lower opening 511 Annular portion 512 Liquid supply port 621 Belt 622 Adjusting member C Center d Direction P Slurry supply position Q Input position Rc Cavitation generation region

Claims

1. A soil treatment device that treats soil containing mineral particles to which radioactive substances have been adsorbed, by separating the mineral particles from other particles, comprising: a treatment section having a flow path; an outlet section that discharges a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected downstream of the flow path from the outlet section and supplies a slurry, in which the soil has been mixed with a liquid and to which no dispersant that reduces the zeta potential has been added, toward the pressurized liquid discharged by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation.

2. A soil treatment device that treats soil containing mineral particles to which radioactive substances have been adsorbed, by separating the mineral particles from other particles, the device comprising: a processing section having a flow path; an outlet section that ejects a pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry obtained by mixing a liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein a dispersant of less than 0.5 mol / kg relative to the mass of the soil is added to the slurry that is supplied to the supply section, and the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation.

3. A soil treatment device that treats soil containing mineral particles to which radioactive substances have been adsorbed, by separating the mineral particles from other particles, the soil treatment device comprising: a processing section having a flow path; an outlet section that ejects pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry mixed with liquid to the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate a flow velocity difference at the interface between the pressurized liquid and the slurry, thereby generating cavitation, and the impact force generated when bubbles generated by the cavitation collapse, crushing the mineral particles into particles smaller in diameter than the mineral particles.

4. A soil treatment device as described in any one of claims 1 to 3, wherein the mineral particles are mica particles, and the outlet section and the supply section are configured to crush 50% or more of the mica particles contained in the slurry supplied from the supply section to the treatment section by the impact force generated when the bubbles generated by the cavitation collapse, into particles having a smaller particle size than the mica particles.

5. A soil treatment device that processes soil containing mineral particles having radioactive substances adsorbed thereon to separate the mineral particles from other particles, comprising: a treatment section having a flow path; an outlet section that ejects pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry obtained by mixing liquid with the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; and a third section that is located downstream of the second section and is longer than the second section and has a cross-sectional area that is larger than that of the second section.

6. A soil treatment device that treats soil containing mineral particles having radioactive substances adsorbed thereon by separating the mineral particles from other particles, the soil treatment device comprising: a processing section having a flow path; an outlet section that ejects pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies a slurry mixed with liquid to the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; and a third section that is located downstream of the second section and has a cross-sectional area larger than that of the second section and a length greater than the length from the position in the flow path where the supply section is connected to the downstream end of the second section.

7. A soil treatment device as described in claim 5 or 6, wherein the third portion includes an upstream portion, a downstream portion located downstream of the upstream portion, and an enlarged portion located between the upstream portion and the downstream portion and having a cross-sectional area larger than the upstream portion and the downstream portion.

8. A soil treatment device that processes soil containing mineral particles having radioactive substances adsorbed thereon to separate the mineral particles from other particles, comprising: a treatment section having a flow path; an outlet section that ejects pressurized liquid from the upstream side of the flow path toward the downstream side; and a supply section that is connected to the flow path downstream of the outlet section and supplies slurry mixed with liquid to the soil toward the pressurized liquid ejected by the outlet section, wherein the outlet section and the supply section are configured to generate cavitation by creating a flow velocity difference at the interface between the pressurized liquid and the slurry, and the flow path is configured to include: a first section; a second section that is located downstream of the first section and has a cross-sectional area perpendicular to the extension direction of the flow path that is smaller than that of the first section; a third section that is located downstream of the second section and has a cross-sectional area larger than that of the second section; and a fourth section that is located downstream of the third section and has a cross-sectional area smaller than that of the third section.

9. A soil treatment device as described in any one of claims 1 to 8, wherein the supply unit comprises: a hopper having a tapered shape whose 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; and a liquid supply unit that supplies the liquid from the upper opening toward the inner wall of the hopper, wherein the soil supply unit and the liquid supply unit are configured so that the liquid and the soil are mixed on the inner wall of the hopper to form the slurry, which is then supplied to the flow path from the lower opening.

10. The soil treatment device according to claim 9, wherein the soil supply section and the liquid supply section are configured so that the liquid and the soil are mixed to form the slurry while flowing downward on the inner wall in a swirling manner.

11. A soil treatment device as described in claim 9 or 10, wherein the soil supply unit is configured to inject the soil toward the inner wall from an injecting position offset from the center of the lower opening when viewed in a plan view along the height direction of the hopper.

12. A method for treating soil containing mineral particles having radioactive substances adsorbed thereon, comprising: ejecting a pressurized liquid from the upstream side to the downstream side of a flow path for treating the soil; supplying a slurry, in which the soil has been mixed with a liquid and no dispersant that reduces the zeta potential has been added, toward the ejected pressurized liquid within the flow path; and generating a flow velocity difference at the interface between the pressurized liquid and the slurry to generate cavitation; wherein the mineral particles are separated from other particles by the impact force generated when bubbles generated by the cavitation collapse.

13. A method for treating soil containing mineral particles having radioactive substances adsorbed thereon, comprising: ejecting a pressurized liquid from the upstream side to the downstream side of a flow path for treating the soil; supplying, within the flow path, toward the ejected pressurized liquid, a slurry prepared by mixing the soil with a liquid and adding a dispersant that reduces the zeta potential at less than 0.5 mol / kg relative to the mass of the soil; and generating a flow rate difference at the interface between the pressurized liquid and the slurry to generate cavitation; wherein the mineral particles are separated from other particles by the impact force generated when bubbles generated by the cavitation collapse.

14. A method for treating soil containing mineral particles having radioactive substances adsorbed thereon, comprising: injecting a pressurized liquid into a slurry prepared by mixing the soil with a liquid and not adding a dispersant that reduces the zeta potential; and generating cavitation by creating a flow rate difference at the interface between the pressurized liquid and the slurry within a flow path extending in the direction of the pressurized liquid injection; wherein the impact force generated when bubbles generated by the cavitation collapse causes the mineral particles to be separated from other particles.

15. A soil treatment method according to any one of claims 12 to 14, further comprising: causing the impact force to crush the mineral particles into particles smaller in diameter than the mineral particles; and after generating the cavitation, transferring the mixture of the slurry and the pressurized liquid from the downstream side of the flow path to a classification section; and classifying the mixture in the classification section into a group of particles having a diameter equal to or larger than the diameter of the mineral particles and a group of particles having a diameter smaller than the mineral particles.

16. The soil treatment method according to any one of claims 12 to 15, wherein the weight ratio of the liquid contained in the slurry to the soil is 5 or less.

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