JP5050155B1 - Radioactive material separation and removal method - Google Patents

Abstract

A method for separating and removing a radioactive substance from a substance contaminated with a radioactive substance such as cesium is provided.
The contaminated soil or sludge is put into a treatment tank filled with a cleaning fluid, and the fluid flows into a contact separation path including a plurality of contact separation pieces in an upward flow by a fluid such as air or liquid. As a result, the contaminated substance and the contact removal piece are brought into contact with each other by separating and sucking up the contaminated substance and separating the radioactive substance and ultrafine particles attached to it from the solid particles. The contact removal piece and the solid particles and ultrafine particles from the contact separation path are introduced into the separation tank at the upper part of the processing tank, and at least the contact removal piece is returned to the contact separation path while the contact removal piece is removed. Most of the solid particles and ultrafine particles are returned to the outside of the separation tank and the radioactive material is discharged out of the tank together with the suspended ultrafine particles, while the solid particles are induced to settle and settle. The so as to discharge from the vessel bottom to Sogai.
[Selection] Figure 2

Description

  The present invention relates to a method for separating and removing radioactive substances.

Regarding the Fukushima nuclear accident during the Great East Japan Earthquake, we are trying to collect it at the power plant where the accident occurred, but for radioactive materials represented by cesium released by the nuclear accident, the specific area of Fukushima Prefecture As a matter of fact, radioactive materials fall into the wilderness, dwellings, various facilities, etc., and cause damage that may occur, such as forests, fields, The contaminated soil in the school yard and the garden around the house is scraped, collected and stored. However, if the contaminated soil is stored as it is, the amount of storage will be enormous and the storage location will be limited, so a decontamination measure that separates and removes radioactive substances from the collected contaminated soil is required as an active measure. It has become.
Although the object is different, there is a technique disclosed in Patent Document 1 as an example of such decontamination countermeasures.

Japanese Patent Laid-Open No. 2002-233859

The technology according to Patent Document 1 relates to the purification of contaminated soil containing dioxins that are oily and difficult-to-decompose harmful substances. The purpose of this project is to reduce risks and reduce disposal costs. As a specific solution, the polluted soil containing slurried greasy harmful substances is used as a harmful substance. Mix and stir a permeable container containing an adsorbent that selectively adsorbs adsorbents to adsorb the harmful substances contained in the contaminated soil to the adsorbent, and then separate the container from the soil to be purified. To do. By this method, the treatment for the oil-based contaminants can be performed efficiently, and the remaining contaminated soil is contaminated at a sufficiently low concentration, so that the containment treatment can be carried out easily and safely even in a large amount. In this technology, the adsorbent that has adsorbed the harmful substance is either treated after adsorbing the harmful substance after it is separated from the soil to be contaminated or cleaned, or after being separated from the soil to be purified and washed. It will be used again.
However, since these adsorbents have an adsorption function, if a harmful substance is adsorbed to a certain level, it cannot be adsorbed any more, so it becomes a so-called saturated state, so it is necessary to shut down the apparatus and perform maintenance of the container Come out. Also, post-treatment of these adsorbents after adsorbing harmful substances seems to be simple, but in fact, disposal of adsorbents with adsorbed harmful substances requires a vast disposal site and removes harmful substances. Because it is adsorbed, a special storage method is required. Even if the adsorbent is washed again after cleaning the harmful substances from the adsorbent, once the adsorbed harmful substances are removed, the washing process and the post-treatment of the harmful substances removed by the washing take time. It is.

  The present invention is intended to solve the problems of such a conventional method, and the decontamination from substances contaminated with radioactive substances such as cesium can be performed efficiently and reliably and separated and removed. It is an object of the present invention to provide a method for separating and removing radioactive materials, which can be easily performed after the post-treatment of the radioactive materials is extremely reduced in volume.

In order to achieve the above-mentioned object, the present invention according to claim 1, after introducing contaminated substances such as soil and sludge contaminated with radioactive substances into a treatment tank filled with a cleaning fluid, By introducing a fluid such as air or liquid, an upward flow can be generated. Inside the contact separation path including a plurality of contact separation pieces, the contaminated substance is sucked and raised with the fluid, and contacted with the contaminated substance is removed. The pieces are separated from each other by separating the radioactive material attached to the solid particles and the ultrafine particles from the solid particles. After the separation, the contact removal pieces from the contact separation path, the solid particles and the ultrafine particles are separated from the treatment tank. After introduction into the upper separation tank, at least the contact removal piece is refluxed into the contact separation path, while most of the solid particles and ultrafine particles excluding the contact removal piece are outside the separation tank. Back in Radioactive materials while solid particles to discharge process to the outside of the tank with ultrafine particles in suspension is to discharge the precipitate was derived precipitated from the tank bottom to Sogai Te.
The invention according to claim 2 is the method according to claim 1, wherein a plurality of parallel finely arranged vertical flow paths are discharged when the floating ultrafine particles are discharged out of the treatment tank together with the radioactive substance. It is made to induce discharge via.

  As described above, since the present invention is configured, the radioactive material such as cesium can be efficiently and reliably removed from the contaminated material, and it is contaminated by the collection of ultrafine particles including the separated and removed radioactive material. Therefore, it is possible to provide a method for separating and removing a radioactive material in which the volume of the material is extremely reduced so that the post-treatment including landfill can be dealt with in a smaller area.

  The longitudinal cross-sectional schematic diagram which shows one Embodiment of the radioactive substance isolation | separation removal method (apparatus) which is this invention as what follows the II line | wire of FIG.   II-II line schematic cross section of FIG.   The cross-sectional schematic diagram which shows other embodiment along the III-III line of FIG.   FIG. 4 is a schematic cross-sectional view taken along line IV-IV in FIG. 3.   The cross-sectional schematic diagram which shows other embodiment along the VV line of FIG.   VI-VI line schematic cross section of FIG.

  Hereinafter, an embodiment of the method of the present invention and the apparatus thereof will be described with reference to FIGS. In the following description, it is fundamental to use a metal material, particularly a stainless steel material, except for some contact removal pieces, but the invention is not limited to this.

  1 and 2, reference numeral 1 denotes a treatment tank, which is stably installed on a fixed base or a cargo handling platform of a vehicle such as a truck (including a trailer) or a railroad transport via a gantry (not shown). Transportation means include sea transportation means such as ships and floats. Here, in the processing tank 1, the left side of FIGS. 1 and 2 is the front side, and the right side is the rear side (the same applies hereinafter). The processing tank 1 has a rectangular cylinder shape such as a square at the top, and a large slope at the bottom so that one side is vertical and the other three adjacent surfaces are likely to sink (front is 45 degrees, left and right sides are around 60 degrees) With this, it is a downwardly narrowed cylindrical portion. The treatment tank 1 may have a round barrel shape as shown on the left side of FIG. The upper part of the treatment tank 1 is provided with a lid 2, and an inlet 3 into which contaminated soil (contaminated substance) is introduced as indicated by an arrow A is provided on the front side of the lid 2. The lid 2 may be appropriately opened and closed for maintenance and the like. An overflow port 4 is formed at the upper rear side of the treatment tank 1 and can overflow as indicated by an arrow X, whereby the water surface 5 is defined. Here, the pollutant refers to a radioactive substance, and the contaminated substance refers to a substance as a result of being contaminated with a radioactive substance.

  An upper water supply port 8 is provided in the middle of the front surface of the treatment tank 1 via an upper valve 7, and a lower water supply port 10 is provided near the lower end of the front surface via a lower valve 9. It is controlled so that water can be supplied as appropriate as in W2. A lower end outlet of the treatment tank 1 is formed with a lower end discharge opening 12, and the opening from the opening 12 is controlled to be opened and closed by a discharge valve 13 so as to be appropriately discharged as indicated by an arrow Z. Yes. Reference numeral 15 denotes a middle-stage discharge port, which opens at a position slightly higher than the upper water supply port 8 on the lower rear surface of the treatment tank 1. Reference numeral 16 denotes an intermediate valve, which can be controlled to be opened and closed so as to be discharged as indicated by an arrow Y.

  Reference numeral 20 denotes a contact separation path, which is formed inside a contact separation pipe 21 having a vertical long pipe portion, a horizontal short pipe portion at the upper end, and an elbow-shaped pipe portion therebetween, and a round pipe bent into an L shape. Yes. The horizontal short pipe portion is above the water surface 5. The contact separation pipe 21 is fixed vertically on the rear side in the treatment tank 1, and the lower end opening is opened between the upper water supply port 8 and the middle stage discharge port 15. In the contact separation pipe 21, a large number of contact removal pieces 22 having a spherical shape made of synthetic rubber having a diameter of about 2.5 mm and a specific gravity of about 1.02 are placed so as to be lifted by the addition of a floating force. A permeation mesh 23 having a bottom surface and a peripheral surface in the form of a fence with a constant interval is mounted around the lower end opening of the pipe 21 so that the contact removal piece 22 does not fall off from the lower end opening of the contact separation pipe 21. The diameter of the contact removal piece 22 is changed depending on the soil particle size (diameter) of the contaminated soil. The transmission mesh 23 can pass various particles that have settled as indicated by an arrow B1. Reference numeral 24 denotes an ascending promotion pipe, which is open upward and downward, and has an upper end attached to the center of the transmission mesh 23 and extends downward, and a lower air pipe 25 is connected to the middle so that air can be supplied as indicated by an arrow C1. ing. An upper air pipe 26 is connected near the lower portion of the contact separation pipe 21 so that compressed air can be supplied into the contact separation pipe 21 as indicated by an arrow C2.

  Reference numeral 28 denotes a separation tank, which is fixedly provided at approximately the upper center of the processing tank 1. The separation tank 28 has an upper part in which the three surfaces of the left and right side surfaces and the rear side surface are vertically formed and the front surface is open, and a lower part having four surfaces and narrowed downward. However, the middle height of the upper part is set to be close to the water surface 5. The lower part of the separation tank 28 and the contact separation pipe 21 are connected in a continuous manner by a reflux pipe 29. The lower end opening of the reflux pipe 29 is set higher than the opening of the upper air pipe 25 so that the contact removal piece 22 and the like that have been refluxed are raised again to be processed.

The separation mesh 30 is inserted into the front opening of the separation tank 28, and the separation mesh 30 is inserted through the slit 31 opened in the lid 2, and the lower end of the separation mesh 30 hits the front edge of the separation tank 28. The elastic packing 32 at the upper end is set so as to elastically contact the slit 31. This setting is ensured in a vertical manner via guides 33 provided on the left and right sides of the front end of the sorting tank 28. The separation mesh 30 functions to recirculate all of the contact removal pieces 22 into the original contact separation pipe 21 and allow the others to permeate and return to the treatment tank 1. As shown in FIG. 2, other than the contact removal piece 22 is also refluxed depending on the flow.
The separation mesh 30 is a net-like, fence-like or perforated plate shape. In this embodiment, the separation mesh 30 can be inserted and removed through a handle 34 provided at the upper end of the separation mesh 30.
Since the overflow port 4 corresponds to the rear side of the contact separation pipe 21, there is a possibility that the flow of the floating substance F may be obstructed. Therefore, as shown by the phantom line in FIG. It may be arranged at two or one place apart.
For example, the treatment tank 1 may be promoted to float through the air supply means 39 so as to be positioned at the lower left and right of the separation tank 28.
The input / sedimentation path of the contaminated soil was on the front side of the treatment tank 1, but as shown in phantom lines in FIG. You may make it settle independently. The sedimentation of the contaminated soil and the permeates T and F from the sorting mesh 30 do not cross each other.
Further, as shown in phantom lines in FIG. 1, instead of the overflow port 4, a circumferential trough 36 is provided on the outer periphery of the treatment tank 1 to overflow from the entire circumference of the treatment tank 1 and drain as shown in the right part of FIG. 2. You may make it discharge from the pipe 37. FIG. The circumferential trough 36 may be simplified to a partial trough 38 corresponding only to the rear side of the treatment tank 1 in which the floating substance flows in FIG. The partial trough 38 may be a plane U-shape 38 ′ extending to the rear side of the treatment tank 1 and the left and right side sides adjacent thereto.

  <First Operation Method> Into the treatment tank 1, cleaning water (cleaning fluid) 6 is introduced through the lower water supply port 10 as indicated by an arrow W <b> 2 in FIG. 2, and the water level has reached the level of the water surface 5 due to the overflow X. At the time (may be before the level of the water surface 5), contaminated soil (or sludge, etc.) contaminated with radioactive material (cesium) is introduced through the inlet 3 as indicated by arrow A in FIG. As described above, air is continuously supplied into the ascending promotion pipe 24 and the contact separation path 20. The cleaning water and air supply are continued. In addition, there are cases where a certain amount of contaminated soil is introduced at a time or sequentially.

The input contaminated soil settles in the washing water 6. Since the inside of the contact separation path 20 is in a state where an upward flow L is generated in the contact separation path 20 by the supply of air of the arrows C1 and C2 and a suction force is generated from the lower end, the sedimented contaminated soil is indicated by the arrow B1. And it sucks like B2 and ascends in the contact separation path 20 as shown by an arrow L.
The rising contaminated soil rises while repeating contact with a large number of contact removal pieces 22 in the supplied rising air and washing water, so that silt and clay (0. (Up to 002 mm and fine particles of airborne particles smaller than that) are separated, and even radioactive materials are separated. These separated substances are introduced into the separation tank 28 together with the washing water and the contact removal piece 22, and the contact removal piece 22 is returned to the original contact separation path 20 through the reflux pipe 29 by the permeation restriction by the separation mesh 30. It is. Here, the slightly separated unseparated material is also refluxed as shown in FIG. 2 and is again subjected to the separation action by the contact removal piece 22.

  On the other hand, the solid particles, silt, clay, and radioactive substance in the separation tank 28 pass through the holes of the separation mesh 30 and are returned to the treatment tank 1. The returned solid particles / silt and the clay content of 0.002 mm or more settle in the processing tank 1 as indicated by an arrow B and settle in the bottom of the processing tank 1 or partly as indicated by arrows B1 and B2. Some of them are guided into the contact separation path 20 and again undergo the contact separation action. The sediments may be discharged periodically as indicated by arrow Z by opening the discharge valve 13 during continuous operation, or may be discharged together after continuous operation for a fixed time.

  Ultrafine particles finer than 0.002 mm out of the clay content tend to float and float in the wash water 6 as indicated by arrows F in FIGS. 1 and 2 together with radioactive substances. Since the water supply W2 is continuously performed, it is automatically discharged sequentially from the overflow port 4, and the discharged product is subjected to post-processing such as coagulation sedimentation, dehydration or drying, and hermetically packing. The result is a reduced volume.

When such separation processing is made constant, the water supply W2 and the air supply C1, C2 from the lower water supply port 10 are stopped, and thereby the continuous operation is stopped. In the stop state, what floats in the processing tank 1 is divided into those that settle like sand gravel and silt and those that float like clay, and the sediment is, for example, level H in FIG. After sedimentation, it is discharged in the direction of arrow Z. On the other hand, clay floating on the upper side other than the sediment is discharged as indicated by arrow Y by opening the middle stage valve 16.
The continuous operation may be repeated, and it is also possible to arrange a plurality of devices and operate them simultaneously or with mutual time adjustment to perform parallel processing.

  <Second operation method> This operation method is operated in the same manner as the continuous operation, and after a predetermined time, the water supply W2 and the air supply C1, C2 are stopped. Due to this stop, solid particles such as sand and gravel settle, the sediment is accumulated up to the H level, and there is a state where floating clay is present thereon. After that, overflow X is performed by supplying water W1, and ultrafine particles and radioactive substances are discharged. On the other hand, suspended clay is extracted as shown by arrow Y, and the precipitate is shown by arrow Z. Discharged. In the emptied treatment tank 1, the water supply W2 is made again, and when the water is full, the contaminated soil is introduced as shown in A, and the separation and circulation by the water supply W2 and the air supply C1, C2 is performed as in the continuous operation. The action is performed and the overflow X is performed to discharge the ultrafine particles and the radioactive substance. After that, the water supply W2 and the air supply C1, C2 are stopped and the sediment is accumulated up to the H level, and there is a state in which floating clay is present thereon. Thereafter, as described above, the overflow X and the discharge Y, Z is made. Such intermittent operation is repeated.

<Third Operation Method>... After the inside of the treatment tank 1 is filled with water, the air supply C1 and C2 is performed while the water supply is stopped, and the separation and circulation action is repeatedly performed in the contact separation path 20. After the operation for a certain period of time, the air supply C1 and C2 is stopped, so that solid particles such as gravel and silt settle to level H. Thereafter, by supplying water W1 and W2, ultrafine particles and radioactive substances are discharged by overflow X, while solid particles such as gravel and sediments such as silt are discharged as indicated by arrow Z. . The floating clay remaining on the sediment is discharged as indicated by arrow Y.
These operation methods, the first, second and third operation methods are, for example, the first (continuous) operation method and the second (intermittent) operation method, the first (continuous) operation method and the third (and It is also possible to drive in combination like driving in combination.

  3 and 4 show another embodiment. In this embodiment, in the stage before overflowing the ultrafine particles floating together with the radioactive substance to the outside of the processing tank 1, they are guided to discharge through the plurality of parallel arrangement type levitation promoting paths 40 as vertical flow paths. Thus, the directivity of flying is imparted to the ultrafine particles and the radioactive substance so that the overflow can be performed more reliably. Reference numeral 41 denotes a floating promotion body, which is a three-dimensional lattice having a square unit, and is made of a thin plate and is fixedly disposed on both the left and right sides of the separation tank 28 from the side to the rear side wall in the treatment tank 1. The upper end is set to be lower by about h1 than the overflow port 4, and the lower end is set to be higher by about h2 than the middle discharge port 15. The reason why it is lower by about h1 is to let it flow in the lower basin than the water surface 5, and the reason why it is made higher by about h2 is to prevent the levitation promoting body 41 from interfering with the flow of drainage from the middle stage outlet 15. Because. If the levitation air pipe 43 is provided so that the jet outlet 42 corresponds to the levitation promotion path 40, the levitation object can be captured more actively and the levitation can be guided.

Since the overflow port 4 corresponds to the rear side of the contact separation pipe 21, there is a possibility that the flow of the floating substance F may be obstructed. Therefore, as shown by a virtual line in FIG. It may be arranged at two or one place apart.
As shown in phantom lines in FIG. 3, instead of the overflow port 4, a circumferential trough 36 is provided on the outer periphery of the processing tank 1 to cause overflow from the entire periphery of the processing tank 1, as shown in the right part of FIG. 4. You may make it discharge more. The circumferential trough 36 may be simplified to a partial trough 38 corresponding only to the rear side of the treatment tank 1 from which the floating substance flows in FIG. The partial trough 38 may be a plane U-shape 38 ′ extending to the rear side of the treatment tank 1 and the left and right side sides adjacent thereto.
If the upper surface portion of the levitation promoting body 41 is formed so as to descend stepwise toward the overflow port 4, as shown in the upper left of FIG. As shown in the lower left of FIG. 4, if the lower surface portion of the levitation promoting body 41 has a shape that rises stepwise toward the front side of the treatment tank 1, the levitation substance can be captured more reliably.

In another embodiment shown in FIGS. 5 and 6, the levitation promoting body 41 is formed by an assembly of round pipes (or square pipes), and a levitation promoting path 40 is formed in each pipe and between the pipes. Yes. As a result, the flying directivity is imparted to the ultrafine particles and the radioactive substance so that the overflow can be performed more reliably. The levitation promoting body 41 is fixedly disposed on both the left and right sides from the side of the separation tank 28 to the rear side wall, and the height is lower by about h1 than the overflow port 4 and the lower end is lower than the middle discharge port 15. It is set so as to be higher than h2. The reason why it is lower by about h1 is to let it flow in the lower basin than the water surface 5, and the reason why it is about higher by h2 is to prevent the levitation promoting body 41 from interfering with the flow of drainage from the middle stage outlet 15. Because. If the levitation air pipe 43 is provided so that the jet outlet 42 corresponds to the levitation promotion path 40, the levitation object can be captured more actively and the levitation can be guided. 36 is a circumferential trough and 38 'is a partial trough. A step system can also be applied to the levitation promoting body 41 as shown on the left side of FIG.
As shown in the upper right column of FIG. 5, the round pipes of the levitation promoting body 41 may be arranged vertically and horizontally so as to be separated from each other, or may be arranged in a staggered manner as shown in the lower right column. . Furthermore, as shown in the upper part of the lower left column of FIG. 6, the levitation promoting body 41 has a unit shape in which pipes are brought together, its axis is inclined with respect to the water surface 5, and the levitation substance from the upper end opening is on the right side. You may make it easy to flow into an overflow port, and as shown in the lower stage, you may make the pipe the same height, but the direction which faces diagonally inclined shape.

In all the above embodiments, the upper end outlet of the contact separation pipe 21 is higher than the water surface 5, but it may be set below the water surface.
Although the single contact separation pipe 21 is provided in one processing tank 1, a plurality of contact separation pipes 21 may be provided. In this case, it is possible to simplify the separation tank 28 with a single separation tank 28 for the plurality of contact separation pipes 21.
The ascending promotion pipe 24 and the lower air pipe 25 may be omitted.
The polluted substances that are input include soil, earth and sand (river sand, sea sand, etc.), sludge, rice, vegetables, fruits, waste trees, rubble, and various other objects. If necessary, pulverize and pulverize and add finely.

  DESCRIPTION OF SYMBOLS 1 ... Processing tank 3 ... Input port 4 ... Overflow port 5 ... Water surface 6 ... Washing water 8, 10 ... Water supply port 12, 15 ... Discharge port 20 ... Contact separation path 21 ... Contact separation pipe 22 ... Contact removal piece 28 ... Separation tank 29 ... Return pipe 30 ... Separation mesh 40 ... Levitation promotion path 41 ... Levitation promotion body.

Claims (2)

  After introducing contaminated substances such as soil and sludge contaminated with radioactive materials into a treatment tank filled with cleaning fluid, an upward flow can be generated by introducing fluid such as air or liquid, and contact separation inside In the contact separation path including a plurality of pieces, the contaminated substance with the fluid is sucked and raised to bring the contaminated substance and the contact removal piece into contact with each other, so that the radioactive substance attached to the solid particle and the ultrafine substance are attached to it. After separating the particles, the contact removal piece from the contact separation path and the solid particles and ultrafine particles are introduced into the separation tank at the top of the treatment tank, and at least the contact removal piece is in the contact separation path. While returning to the inside, most of the solid particles and ultrafine particles excluding the contact removal piece are returned to the inside of the treatment tank, which is the outer area of the separation tank, and the radioactive material is discharged out of the tank together with the suspended ultrafine particles. While solid particles are radioactive separated off method so as to discharge the Sogai The precipitate from vessel bottom by inducing precipitation of. The invention according to claim 2 is the method according to claim 1, wherein a plurality of parallel finely arranged vertical flow paths are discharged when the floating ultrafine particles are discharged out of the treatment tank together with the radioactive substance. A method for separating and removing radioactive substances that is induced to discharge via

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