JP2015117981A - Method for decontaminating fly ash containing radioactive cesium and decontamination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a novel method for decontaminating fly ash, specifically a simple method capable of sufficiently adsorbing radioactive cesium even from alkaline slurry containing the fly ash and separating an adsorbent from the slurry by magnetic force without using a superconducting magnet.SOLUTION: There is a provided a method for decontaminating fly ash containing radioactive cesium which comprises the steps: a preparation step of mixing fly ash containing radioactive cesium with water to prepare slurry in which the radioactive cesium is dissolved in the water; an adsorption step of mixing the slurry prepared in the preparation step with an adsorbent containing magnetic iron nanoparticles carrying a ferrocyanide compound in which other metals than iron are introduced to adsorb the radioactive cesium dissolved in the water; and a first separation step of separating the adsorbent which adsorbed the radioactive cesium in the adsorption step from the slurry by magnetic force.

Description

  The present invention relates to a decontamination method and decontamination apparatus for fly ash containing radioactive cesium.

  Due to the Great East Japan Earthquake that occurred on March 11, 2011, radioactive cesium was diffused widely from the Fukushima Daiichi Nuclear Power Station. Incineration residues are generated when combustibles contaminated with radioactive cesium are incinerated, but the concentration of radioactive cesium exceeds the designated waste standard of 8000 Bq / kg because radioactive cesium is concentrated especially in fly ash. In addition to Fukushima Prefecture, it occurs in neighboring Ibaraki, Tochigi and Miyagi prefectures.

According to the data from the Ministry of the Environment, incineration ash, which is designated as waste, has been stored in nearly 100,000 tons as of August 2013, and most of it is thought to be fly ash. The amount of combustibles within the decontamination removed substance generated with the decontamination in Fukushima prefecture, etc. is to range from several million m ³ to 10 million m ^3, 10 million in to 20 when incinerating them Ten thousand tons of fly ash is expected to be generated.

  Since most of the radioactive cesium contained in the fly ash exists as water-soluble cesium chloride, if the fly ash is stored in a disposal site or the like as it is, the radioactive cesium may be eluted into the environment.

  Therefore, a method using cement is known as a method for treating fly ash. Specifically, fly ash, moisture, and cement (or cement-based solidifying material) are mixed and granulated. By granulating fly ash and solidifying it, elution of water-soluble radioactive cesium can be prevented. However, since the volume of the processed material obtained by this method increases to about 1.4 times the initial fly ash volume, more storage space is required.

  As a method for decontaminating fly ash, a method using an adsorbent that adsorbs radioactive cesium (for example, Prussian blue) is also known. Specifically, fly ash is mixed with about 10 times as much water to prepare a slurry, and water-soluble radioactive cesium is dissolved in water. Next, the slurry is separated into fly ash and water, and the separated water is brought into contact with the adsorbent, whereby the radioactive cesium dissolved in water can be adsorbed onto the adsorbent. In this method, an adsorbent is mixed with water containing radioactive cesium, and the adsorbent adsorbed with radioactive cesium is separated again from water. The water containing radioactive cesium is passed through an adsorption tower packed with granulated adsorbent. It is necessary to carry out in the form of water, and a large-scale device is required. Moreover, although the slurry containing fly ash exhibits strong alkalinity, the adsorbent Prussian blue is decomposed under alkaline conditions, so the pH of the slurry needs to be adjusted to 7 or less.

  Furthermore, as a method for decontaminating fly ash, a method using a magnetized adsorbent (for example, one containing zeolite, ferrocyanide, etc.) is also known (Patent Document 1). Specifically, the magnetized adsorbent is put into water or slurry containing radioactive cesium, and the radioactive cesium is adsorbed on the magnetized adsorbent. Next, the magnetized adsorbent adsorbing radioactive cesium can be separated from water or slurry by using a magnetic separator. However, as described above, the slurry containing fly ash exhibits strong alkalinity, but since the ferrocyanide ferrocyanide of the magnetized adsorbent decomposes under alkaline conditions, it is necessary to adjust the pH of the slurry to 7 or less. Moreover, since the slurry containing fly ash contains a large amount of salts, if a magnetized adsorbent containing zeolite is used, the salts are adsorbed at the same time, and the radioactive cesium cannot be adsorbed sufficiently. Furthermore, in the method of Patent Document 1, since it is necessary to use a large and expensive superconducting magnet as the magnetic separation device, problems of installation space and cost arise. In addition, in order to make the superconducting magnet function effectively, there is a problem in terms of energy use, such as using a refrigerant such as helium, or requiring a refrigeration apparatus even without a refrigerant.

JP 2013-158671 A

  As described above, a plurality of methods for treating or decontaminating fly ash has already been reported, but there is still room for improvement. Therefore, the present invention is a new method for decontaminating fly ash, specifically, the radioactive cesium can be sufficiently adsorbed even if the slurry containing fly ash remains alkaline, and a superconducting magnet is used. It is an object of the present invention to provide a simple method capable of separating the adsorbent by magnetic force and a simple device for carrying out the method.

  As a result of intensive studies by the present inventors, the use of a ferrocyanide compound as a supplementary compound for radioactive cesium, in which the iron portion is replaced with a different metal, compared to a general ferrocyanide compound, Even if the slurry containing ash remains alkaline, radioactive cesium can be adsorbed sufficiently, and by using iron nanoparticles as a magnetic material, a large and expensive superconducting magnet should be used as a magnetic separation device. In addition, the present inventors have found that the adsorbent can be separated by a magnetic force (a magnetic force of a normal permanent magnet) from a small and inexpensive magnet that is widely used. In addition, copper, cobalt, nickel, etc. are applicable as a dissimilar metal used for a ferrocyanide compound.

That is, the present invention includes the following.
[1]
A preparation step in which fly ash containing radioactive cesium and water are mixed to prepare a slurry in which radioactive cesium is dissolved in water;
Adsorption that adsorbs radioactive cesium dissolved in water by mixing slurry prepared in the preparation process and adsorbent containing magnetic iron nanoparticles carrying ferrocyanide compound introduced with metal other than iron And a first separation step of separating the adsorbent adsorbing the radioactive cesium in the adsorption step from the slurry by magnetic force;
A method for decontaminating fly ash containing radioactive cesium.
[2]
The decontamination method according to [1], further including a dehydration step of dehydrating the treatment slurry obtained by separating the adsorbent obtained in the first separation step under reduced pressure.
[3]
The decontamination method according to [1] or [2], wherein the first separation step is performed using a magnet having a surface magnetic flux density of 2000 to 13000 gauss.
[4]
The decontamination method according to [1] or [2], wherein the first separation step is performed using a ferrite magnet or a neodymium magnet.
[5]
Before mixing the slurry and the adsorbent in the adsorption step, the method further includes a second separation step of separating the fly ash-derived magnetic substance (fly ash magnetized material) contained in the slurry from the slurry by magnetic force [1]. -Decontamination method in any one of [4].
[6]
The decontamination method according to [5], wherein the adsorbent separated in the first separation step is reused in the adsorption step.
[7]
The decontamination method according to any one of [1] to [6], wherein the magnetic iron nanoparticles contained in the adsorbent are magnetized before being mixed with the slurry in the adsorption step.
[8]
The decontamination method according to any one of [1] to [7], wherein the pH of the slurry mixed with the adsorbent in the adsorption step is adjusted to 8 to 10.
[9]
The decontamination method according to any one of [1] to [8], wherein the amount of adsorbent mixed in the adsorption step is 1% by weight or less of the weight of fly ash.
[10]
The decontamination method according to any one of [1] to [9], wherein the magnetic iron nanoparticles supporting the ferrocyanide compound form porous secondary particles having an average of 1 to 500 µm.
[11]
A fly ash decontamination device containing radioactive cesium,
Mixing fly ash containing radioactive cesium, water, and an adsorbent containing magnetic iron nanoparticles carrying ferrocyanide compounds introduced with metals other than iron, and using the radioactive cesium dissolved in water as the adsorbent A mixing tank for preparing the adsorbed slurry;
A magnetic separator for separating the adsorbent adsorbing radioactive cesium in the mixing tank from the slurry by magnetic force; and a vacuum dehydrator for dehydrating the treated slurry from which the adsorbent has been separated by the magnetic separator;
A decontamination apparatus.
[12]
The decontamination apparatus according to [11], wherein the magnetic separation apparatus includes a magnet having a surface magnetic flux density of 2000 to 13000 gauss.
[13]
The decontamination device according to [11], wherein the magnetic separation device has a ferrite magnet or a neodymium magnet.
[14]
A fly ash decontamination device containing radioactive cesium,
A first mixing tank in which fly ash containing radioactive cesium and water are mixed to prepare a slurry in which radioactive cesium is dissolved in water;
A first magnetic separation device that separates the fly ash-derived magnetic material contained in the slurry prepared in the first mixing tank from the slurry by magnetic force;
Mixing the pretreatment slurry from which the fly ash-derived magnetic material was separated by the first magnetic separation device and the adsorbent containing magnetic iron nanoparticles carrying the ferrocyanide compound introduced with a metal other than iron A second mixing tank for adsorbing radioactive cesium dissolved in water to the adsorbent; and a second magnetic separation device for separating the adsorbent adsorbing the radioactive cesium in the second mixing tank from the pretreatment slurry by magnetic force;
A decontamination apparatus.
[15]
The decontamination apparatus according to [14], further comprising a vacuum dehydrator that depressurizes and dehydrates the processing slurry from which the adsorbent has been separated by the second magnetic separator.
[16]
The decontamination apparatus according to [14] or [15], wherein the second magnetic separation apparatus includes a magnet having a surface magnetic flux density of 2000 to 13000 gauss.
[17]
The decontamination device according to [14] or [15], wherein the second magnetic separation device includes a ferrite magnet or a neodymium magnet.
[18]
The decontamination apparatus according to any one of [14] to [17], further comprising an adsorbent return line for returning the adsorbent separated by the second magnetic separation device to the second mixing tank.
[19]
Measuring means for measuring the amount of radioactive cesium adsorbed on the adsorbent separated by the second magnetic separation device;
Determining means for determining whether or not the amount of radioactive cesium measured by the measuring means has reached a predetermined amount; and when the determining means determines that the amount of radioactive cesium has not reached the predetermined amount, Return means for returning the adsorbent separated by the magnetic separation device of 2 to the second mixing tank via the adsorbent return line;
The decontamination apparatus according to [18], further comprising a control unit including:

  According to the present invention, the radioactive cesium can be sufficiently adsorbed even if the slurry containing fly ash remains alkaline, and the adsorbent can be removed by a general-purpose magnetic separator without using a magnetic separator including a superconducting magnet. Can be separated.

An example of the process of the decontamination method concerning this invention is shown. The process of the conventional decontamination method is shown. The outline of the decontamination apparatus of 1st Embodiment is shown. The outline of a magnetic separator is shown. The outline of the decontamination apparatus of 2nd Embodiment is shown. The outline of the decontamination apparatus of 3rd Embodiment is shown. The outline of the decontamination apparatus of 4th Embodiment is shown. The outline of the decontamination apparatus of 5th Embodiment is shown. The relationship between pH and elution of ferrocyanic ions (stirring time 60 minutes) is shown. The relationship between pH and elution of ferrocyanic ions is shown.

  Hereinafter, the present invention will be described in detail.

<Decontamination method of fly ash containing radioactive cesium>
The present invention relates to a method for decontaminating fly ash containing radioactive cesium, including a preparation step, an adsorption step, and a first separation step. The decontamination method according to the present invention may further include one or more processes selected from the group consisting of a dehydration process, a second separation process, and an aggregation process (for example, FIG. 1). Hereinafter, each step will be described.

[1. Preparation process]
The preparation step is a step of preparing a slurry in which radioactive cesium is dissolved in water by mixing fly ash containing radioactive cesium and water. Since most of the radioactive cesium contained in the fly ash is water-soluble, the water-soluble radioactive cesium contained in the fly ash can be dissolved in water by mixing the fly ash and water.

  Although the weight of the water mixed with fly ash is not specifically limited, For example, it can be 3-20 times, 4-15 times, 5-10 times, etc. of the weight of fly ash. By using such an amount of water, heat generation can be suppressed when the pH of the slurry is adjusted in the adsorption step described below.

[2. Adsorption process]
The adsorption step includes the slurry prepared in the preparation step and magnetic iron nanoparticles carrying a ferrocyanide compound into which a metal other than iron (heterogeneous metal) is introduced (hereinafter also simply referred to as “ferrocyanide compound”). This is a step of mixing the adsorbent and adsorbing the radioactive cesium dissolved in water to the adsorbent. Since the ferrocyanide compound contained in the adsorbent can adsorb radioactive cesium, the adsorbent can be adsorbed to the adsorbent by mixing the adsorbent with the slurry prepared in the preparation process. .

  Examples of ferrocyanide compounds include nickel ferrocyanide, copper ferrocyanide, cobalt ferrocyanide, and the like.

  Although the slurry prepared in the preparation step exhibits alkalinity, ferric ferrocyanide and the like conventionally used as an adsorbent are decomposed under alkaline conditions, and thus cannot sufficiently adsorb radioactive cesium. Further, there is a problem that harmful ferrocyan ions are generated due to decomposition of ferrocyanide and remain in the slurry.

  On the other hand, since the ferrocyanide compound used in the present invention is not easily decomposed even under alkaline conditions, it can be directly added to the slurry prepared in the preparation step. In addition, you may adjust pH of a slurry from a viewpoint of fully reducing the quantity of the ferrocyan ion produced by decomposition | disassembly of a ferrocyanide compound. For example, the pH of the slurry is preferably adjusted to 11 or less, more preferably 10 or less, and particularly preferably 9 or less. Although the minimum of pH of a slurry is not specifically limited, For example, it can be set as pH 7, pH 7.5, pH 8, etc.

  The adsorbent is a multilayer composite particle including magnetic iron nanoparticles, a coating layer that directly coats the magnetic iron nanoparticles, and a ferrocyanide compound bonded to the coating layer. When the adsorbent contains magnetic iron nanoparticles, the adsorbent can be separated from the slurry by magnetic force in the first separation step described below. The average particle size of the magnetic iron nanoparticles is not particularly limited as long as it is nano-order, but is preferably 1 to 1000 nm, more preferably 5 to 500 nm, and particularly preferably 100 to 200 nm. By using magnetic iron nanoparticles having such a particle size, the dispersion performance in the slurry, the adsorption performance of radioactive cesium, and the separation performance in the first separation step can be improved.

  From the viewpoint of magnetic separation performance and the like, it is more preferable that the magnetic iron nanoparticles supported by the ferrocyanide compound form a plurality of the particles to form porous secondary particles. The average particle size of the secondary particles is preferably 1 to 500 μm, more preferably 1 to 100 μm, and particularly preferably 6 to 20 μm. By being in the form of such secondary particles, the resistance to decomposition under alkaline conditions can be further improved, and the resistance to detachment of a physically complementary compound due to mechanical stirring, friction, or the like increases. Moreover, the speed | rate which adsorb | sucks radioactive cesium can be improved. Furthermore, the separation performance in the first separation step can be further improved. The adsorbent used in the present invention can be prepared based on, for example, the description of Japanese Patent No. 4932554.

  Since the adsorbent used in the present invention is excellent in the ability to adsorb radioactive cesium, it can sufficiently adsorb radioactive cesium dissolved in water in a small amount. Therefore, the mixing amount of the adsorbent can be set to, for example, 1% by weight or less, 0.5% by weight or less, 0.2% by weight or less of the weight of fly ash. The lower limit of the adsorbent mixing amount can be, for example, 0.01 wt%, 0.05 wt%, 0.1 wt%, and the like. By reducing the amount of adsorbent, it is possible to reduce the amount of used adsorbent that needs to be stored due to the adsorption of radioactive cesium.

  The magnetic iron nanoparticles contained in the adsorbent may be magnetized before mixing with the slurry. By preliminarily magnetizing, the adsorption rate of radioactive cesium can be improved. The method of magnetizing the magnetic iron nanoparticles is not particularly limited. For example, the method can be performed by bringing an adsorbent containing magnetic iron nanoparticles close to a magnet (for example, a neodymium magnet) for a certain period of time.

  The mixing time of the slurry and the adsorbent is appropriately changed depending on the properties of the fly ash to be decontaminated, the amount of adsorbent used, etc., for example, 5 minutes to 2 hours, 10 minutes to 1 hour, 15 minutes to 30 minutes. Etc.

[3. First separation step]
The first separation step is a step of separating the adsorbent that has adsorbed radioactive cesium in the adsorption step from the slurry by magnetic force. Since the adsorbent contains magnetic iron nanoparticles, the adsorbent can be separated from the slurry by magnetic force.

  By using iron nanoparticles as the magnetic material, the adsorbent can be separated by a magnetic separation apparatus including a small and inexpensive permanent magnet that is widely used without using a large and expensive superconducting magnet. Examples of the magnet used in the first separation step include a magnet having a surface magnetic flux density of 2000 to 13000 gauss, preferably 4000 gauss or more, more preferably 10,000 gauss or more. Specific examples include permanent magnets such as ferrite (isotropic and anisotropic) magnets, neodymium magnets, samarium cobalt magnets, alnico magnets, and ferrite magnets or neodymium magnets are particularly suitable.

  The adsorbent separated in the first separation step may be reused in the adsorption step. By adsorbing radioactive cesium to the adsorbent to the limit, the amount of used adsorbent that needs to be stored can be reduced.

[4. Dehydration process]
The decontamination method according to the present invention may further include a dehydration step. The dehydration step is a step of dehydrating the processing slurry obtained in the first separation step from which the adsorbent has been separated under reduced pressure. Since the used adsorbent that needs to be stored is separated in the first separation step, the treatment slurry in the dehydration step has already been decontaminated. Therefore, since it is not always necessary to strictly dehydrate the treated slurry, the dehydration process can be performed using a small and safe vacuum dehydrator.

  Treated fly ash and treated water are obtained by the dehydration process. The amount of the adsorbent-derived ferrocyan ion and the fly ash-derived heavy metal (cadmium, lead, etc.) contained in the treated water is sufficiently reduced along with the amount of radioactive cesium.

  The treated water may be reused in the preparation process. By reusing treated water, the amount of water in contact with radioactive cesium can be reduced.

[5. Second separation step]
The decontamination method according to the present invention may further include a second separation step. The second separation step is a step of separating the fly ash-derived magnetic substance (fly ash magnetized material) contained in the slurry from the slurry by magnetic force before mixing the slurry and the adsorbent in the adsorption step. Since the fly ash originally contains a magnetic material (fly ash magnetized material) that is slightly magnetized, the magnetic material can be separated by a magnetic force.

  When the slurry and adsorbent are mixed in the adsorption step without separating the fly ash-derived magnetic material, the fly ash-derived magnetic material (fly ash magnetized material) is separated into the adsorbent separated in the subsequent first separation step. ) Is mixed. As a result, the amount of radioactive cesium concentrate that needs to be stored increases. On the other hand, by separating in advance the magnetic material derived from fly ash in the second separation step, it is possible to reduce the amount of substances that need to be separated and separated in the first separation step.

  Examples of the magnet used in the second separation step include a magnet having a surface magnetic flux density of 2000 to 13000 gauss, preferably 4000 gauss or more, more preferably 10,000 gauss or more. Specific examples include permanent magnets such as ferrite (isotropic and anisotropic) magnets, neodymium magnets, samarium cobalt magnets, alnico magnets, and ferrite magnets or neodymium magnets are particularly suitable. The magnet used in the second separation step may be the same type as the magnet used in the first separation step, or may be a different type.

  It is preferable to reuse the adsorbent separated in the first separation step after separating the fly ash-derived magnetic material in the second separation step in the adsorption step. By separating the magnetic material derived from fly ash in advance, the purity of the adsorbent to be reused can be maintained high.

[6. Aggregation process]
The decontamination method according to the present invention may further include an aggregation step. The agglomeration step is a step of agglomerating and precipitating the fly ash contained in the processing slurry with a flocculant before the dehydration step.

  By passing through the agglomeration step, the amount of adsorbent-derived ferrocyanide and fly ash-derived heavy metals (cadmium, lead, etc.) contained in the treated water can be further reduced.

  The kind of the flocculant is not particularly limited, and those commonly used can be used. Examples of the flocculant include polyaluminum chloride (PAC), sulfate band, polyferric sulfate, and polymer flocculant (for example, anionic, cationic, and nonionic). These flocculants may be used alone or in combination of two or more.

  As described above, the decontamination method according to the present invention includes a preparation step, an adsorption step, and a first separation step, and optionally further includes a dehydration step, a second separation step, and an aggregation step. Note that the steps included in the decontamination method according to the present invention are not limited to those described above, and may include additional steps as necessary.

  In the conventional decontamination method, for example, as shown in FIG. 2, fly ash and water are mixed to prepare a slurry in which radioactive cesium is dissolved in water, and then the slurry is mixed before adsorbent is mixed. Separated into fly ash and water in which radioactive cesium is dissolved. At this time, it is necessary to perform separation using a large and expensive high-pressure filter press so that water containing radioactive cesium does not remain in the fly ash separated from the slurry. In addition, since ferric ferrocyanide and the like conventionally used as an adsorbent are decomposed under alkaline conditions, the adsorbent is introduced after adjusting the pH of water separated by a high pressure filter press or the like to 7 or less. There is a need. Furthermore, in order to separate the adsorbent adsorbing radioactive cesium, it is necessary to use a large and expensive superconducting magnet.

  On the other hand, in the decontamination method according to the present invention, for example, as shown in FIG. 1, the adsorbent can be directly charged into the slurry containing fly ash without necessarily adjusting the pH (adsorption process). Further, the adsorbent can be separated without using a superconducting magnet by a magnetic separation device using a small and inexpensive permanent magnet that is widely used (first separation step). Further, the treated slurry from which the adsorbent has been separated can be separated into treated fly ash and treated water by a small and safe vacuum dehydrator without using a high-pressure filter press (dehydration step). Therefore, fly ash containing radioactive cesium can be decontaminated in a narrow space with low cost and simple operation.

  Moreover, in the decontamination method according to the present invention, radioactive cesium is adsorbed and separated by the adsorbent at an early stage as compared with the conventional decontamination method (first separation step). Therefore, the radioactive contamination section is limited, and exposure management can be facilitated.

<Decontamination equipment for fly ash containing radioactive cesium>
An example of a decontamination apparatus according to the present invention for carrying out the above decontamination method will be described with reference to the drawings. In addition, the overlapping part is abbreviate | omitted suitably in description of each following embodiment.

[First Embodiment]
The 1st Embodiment of this invention is related with the decontamination apparatus provided with the mixing tank 101, the magnetic separation apparatus 102, and the pressure reduction dehydrator 103, as shown in FIG.

  The mixing tank 101 is a radioactive cesium-containing radioactive ash mixed with water and an adsorbent containing magnetic iron nanoparticles supported by a ferrocyanide compound introduced with a metal other than iron, and dissolved in water. A slurry in which cesium is adsorbed on an adsorbent is prepared. The mixing tank 101 has a stirrer 104 that mixes fly ash containing radioactive cesium, water, and an adsorbent, and a slurry sending line 105 that sends the slurry obtained by mixing to a magnetic separation device. Prepare. The outlet end of the slurry delivery line 105 is located above or inside the magnetic separator 102 so that the slurry can be introduced into the magnetic separator 102.

  The magnetic separation device 102 separates the adsorbent that has adsorbed radioactive cesium in the mixing tank 101 from the slurry by magnetic force. A processing slurry storage container 106 that stores the processing slurry from which the adsorbent has been separated by the magnetic separation device 102 is disposed below the magnetic separation device 102. The processing slurry container 106 includes a processing slurry delivery line 107 that delivers the processing slurry to the vacuum dehydrator 103. The outlet end of the processing slurry delivery line 107 is positioned above or inside the vacuum dehydrator 103 so that the processing slurry can be charged into the vacuum dehydrator 103.

  The processing slurry container 106 may further include a processing slurry return line 108 that returns the processing slurry to the mixing tank 101. The processing slurry return line 108 may be provided in the decontamination apparatus of the second embodiment.

  As the magnetic separation device, it is preferable to use a general-purpose simple maglet separator. For example, as shown in FIG. 4, the magnet separator includes a magnet core 901, an outer cylinder 902 that covers the outer periphery of the magnet core 901, a roller 903 that squeezes moisture from an adsorbent adhering to the outer cylinder 902, and a roller 903. And a scraper 904 that peels off the adsorbent squeezed from the outer cylinder 902.

  By using iron nanoparticles as the magnetic material contained in the adsorbent, the adsorbent can be separated by the magnetic force of a small and inexpensive magnet that is widely used without using a large and expensive superconducting magnet. . Therefore, a magnet having a surface magnetic flux density of, for example, 2000 to 13000 gauss, preferably 4000 gauss or more, more preferably 10,000 gauss or more can be used as the magnet core. Specifically, permanent magnets such as ferrite (isotropic and anisotropic) magnets, neodymium magnets, samarium cobalt magnets, and alnico magnets can be used as the magnet core.

  The vacuum dehydrator dehydrates the treated slurry from which the adsorbent has been separated by the magnetic separator. Since the used adsorbent that needs to be stored is separated by the magnetic separation device, the processing slurry that is put into the vacuum dehydrator has already been decontaminated. Therefore, since it is not always necessary to strictly dehydrate the treated slurry, a small and safe vacuum dehydrator can be used.

  In the decontamination apparatus according to the first embodiment configured as described above, fly ash containing radioactive cesium is mixed with water and an adsorbent in the mixing tank 101 to prepare a slurry. In the slurry, radioactive cesium is dissolved in water and adsorbed on the adsorbent. The slurry is sent to the magnetic separation device 102 via the slurry delivery line 105, and the adsorbent adsorbing the radioactive cesium is separated from the slurry by the magnetic force. The processing slurry from which the adsorbent has been separated is stored in the processing slurry storage container 106. The processing slurry stored in the processing slurry container 106 is sent to the vacuum dehydrator 103 via the processing slurry delivery line 107, dehydrated under reduced pressure, and separated into processed fly ash and treated water.

  When the processing slurry container 106 includes the processing slurry return line 108 and the radioactive cesium dissolved in the water remains in the processing slurry in excess of a predetermined amount, it is stored in the processing slurry container 106. The treated slurry is returned to the mixing tank 101 via the treated slurry return line 108.

  According to the decontamination apparatus of the first embodiment, fly ash containing radioactive cesium can be decontaminated safely in a narrow space at low cost.

[Second Embodiment]
As shown in FIG. 5, the second embodiment of the present invention relates to a decontamination apparatus including a mixing tank 201, a magnetic separation device 202, a vacuum dehydrator 203, an adsorbent return line 209, and a control unit 210.

  The second embodiment is different from the first embodiment in that an adsorbent return line 209 and a controller 210 are provided.

  The adsorbent return line 209 returns the adsorbent separated by the magnetic separation device 202 to the mixing tank 201.

  The control unit 210 includes a measurement unit 211 (hereinafter also referred to as “first measurement unit”), a determination unit 212 (hereinafter also referred to as “first determination unit”), and a return unit 213 (hereinafter referred to as “first return unit”). It is also referred to as “

  The measuring means 211 measures the amount of radioactive cesium adsorbed on the adsorbent separated by the magnetic separation device 202. Examples of the measuring means include a γ-ray measuring device, a Ge semiconductor detector, a NaI scintillation survey meter, a GM tube survey meter, and a measuring device using a large capacity CsI (TI) scintillator. Preferably, a measuring device using a large-capacity CsI (TI) scintillator capable of quick measurement in a time as short as 1 second is used.

  The determination unit 212 determines whether or not the amount of radioactive cesium measured by the measurement unit 211 has reached a predetermined amount. Examples of the determination means include a computer storing a reference value for determining whether or not to return the adsorbent to the mixing tank.

  When the determination unit 212 determines that the amount of radioactive cesium has not reached a predetermined amount, the return unit 213 receives the adsorbent separated by the magnetic separation device 202 via the adsorbent return line 209. To be returned to. Examples of the return means include a blower that transports the adsorbent by suction.

  The control unit 210 is another measuring means (hereinafter referred to as “second measuring means”) (not shown) for measuring the amount of radioactive cesium remaining in the processing slurry from which the adsorbent has been separated by the magnetic separation device 202; Another determination means for determining whether or not the amount of radioactive cesium measured by the measurement means has reached a predetermined amount (hereinafter referred to as “second determination means”) (not shown); and second determination means When it is determined that the amount of radioactive cesium has reached a predetermined amount, another return means (hereinafter referred to as “second return means”) returns the processing slurry to the mixing tank 201 via the processing slurry return line 208. May be further included.

  Examples of the second measuring means include the same as the first measuring means.

Examples of the second determination unit include the same as the first determination unit. The second determination unit may be integrated with the first determination unit.
Examples of the second return means include a pump.

  In the decontamination apparatus of the second embodiment configured as described above, the adsorbent separated by the magnetic force separation apparatus 202 is measured for the amount of radioactive cesium adsorbed by the measuring means 211. Next, whether or not the adsorption amount of radioactive cesium has reached a predetermined amount is determined by the determination means 212, and if it is determined that the predetermined amount has not been reached, the return means 213 converts the adsorbent into the adsorbent. It is returned to the mixing tank 201 via the return line 209. On the other hand, when the determination unit 212 determines that the amount of radioactive cesium adsorbed has reached a predetermined amount, the adsorbent is stored in the mixing tank 201 without being returned.

  When the control unit 210 includes the second measurement unit, the second determination unit, and the second return unit, the amount of radioactive cesium in the treated slurry is measured by the second measurement unit. Next, it is determined whether or not the amount of radioactive cesium has reached a predetermined amount by the second determination means. If it is determined that the amount has reached the predetermined amount, the second return means will process the slurry. Is returned to the mixing tank 201 via the treated slurry return line 208. On the other hand, when it is determined by the second determination means that the amount of radioactive cesium has not reached the predetermined amount, the processing slurry is sent to the vacuum dehydrator 203 via the processing slurry delivery line 207.

  According to the decontamination apparatus of the second embodiment, fly ash containing radioactive cesium can be decontaminated safely in a narrow space at low cost. Further, by reusing the adsorbent, the amount of the used adsorbent that needs to be stored can be reduced.

[Third Embodiment]
As shown in FIG. 6, the third embodiment of the present invention includes a first mixing vessel 301, a first magnetic separation device 302, a second mixing vessel 303, a second magnetic separation device 304, and vacuum dehydration. The present invention relates to a decontamination apparatus including a machine 305.

  The 1st mixing tank 301 mixes the fly ash containing radioactive cesium and water, and prepares the slurry which radioactive cesium melt | dissolved in water. The first mixing tank 301 has a first stirrer 306 that mixes fly ash containing radioactive cesium and water, and sends the slurry obtained by mixing to the first magnetic separation device 302. A first slurry delivery line 307 is provided. The outlet end of the first slurry delivery line 307 is located above or inside the first magnetic separation device 302 so that the slurry can be introduced into the first magnetic separation device 302.

  The 1st magnetic separation apparatus 302 isolate | separates the magnetic body derived from fly ash contained in the slurry prepared in the 1st mixing tank 301 from a slurry with a magnetic force. A pretreatment slurry container 308 that contains the pretreatment slurry from which the fly ash-derived magnetic material has been separated by the first magnetic separation device 302 is disposed below the first magnetic separation device 302. The pretreatment slurry container 308 includes a pretreatment slurry delivery line 309 that delivers the pretreatment slurry to the second mixing tank 303. The outlet end of the pretreatment slurry delivery line 309 is located above or inside the second mixing tank 303 so that the pretreatment slurry can be charged into the second mixing tank 303.

  The second mixing tank 303 is composed of a pretreatment slurry from which fly ash-derived magnetic materials are separated by the first magnetic separation device 302, and magnetic iron nanoparticles supported by a ferrocyanide compound into which a metal other than iron is introduced. And adsorbent containing radioactive cesium dissolved in water. The second mixing tank 303 has a second stirrer 310 that mixes the pretreatment slurry and the adsorbent, and sends the slurry obtained by mixing to the second magnetic separation device 304. Two slurry delivery lines 311 are provided. The outlet end of the second slurry delivery line 311 is located above or inside the second magnetic separation device 304 so that the slurry can be introduced into the second magnetic separation device 304.

  The second magnetic separation device 304 separates the adsorbent that has adsorbed radioactive cesium in the second mixing tank 303 from the slurry by magnetic force. A processing slurry container 312 that stores the processing slurry from which the adsorbent has been separated by the second magnetic separation device 304 is disposed below the second magnetic separation device 304. The processing slurry container 312 includes a processing slurry delivery line 313 that delivers the processing slurry to the vacuum dehydrator 305. The outlet end of the processing slurry delivery line 313 is located above or inside the vacuum dehydrator 305 so that the processing slurry can be charged into the vacuum dehydrator 305.

  The processing slurry container 312 may further include a processing slurry return line 314 that returns the processing slurry to the second mixing tank 303. The processing slurry return line 314 may be provided in the decontamination apparatus of the fourth embodiment.

  Examples of the first and second magnetic separation devices include the same ones as the magnetic separation devices in the first embodiment.

  An example of the vacuum dehydrator is the same as the vacuum dehydrator in the first embodiment.

  In the decontamination apparatus of the third embodiment configured as described above, fly ash containing radioactive cesium is mixed with water in the mixing tank 301 to prepare a slurry. In the slurry, radioactive cesium is dissolved in water. The slurry is sent to the first magnetic separation device 302 via the first slurry delivery line 307, and the magnetic material derived from fly ash is separated from the slurry by the magnetic force. The pretreatment slurry from which the fly ash-derived magnetic material has been separated is stored in the pretreatment slurry container 308. The pretreatment slurry accommodated in the pretreatment slurry container 308 is sent to the second mixing tank 303 via the pretreatment slurry delivery line 309.

  The pretreatment slurry is mixed with the adsorbent in the second mixing vessel 303 to prepare further slurry. In the slurry, radioactive cesium dissolved in water is adsorbed by the adsorbent. The slurry is sent to the second magnetic separation device 304 via the second slurry delivery line 311, and the adsorbent adsorbing the radioactive cesium is separated from the slurry by the magnetic force. The processing slurry from which the adsorbent has been separated is stored in the processing slurry storage container 312. The processing slurry stored in the processing slurry container 312 is sent to the vacuum dehydrator 305 via the processing slurry delivery line 313, dehydrated under reduced pressure, and separated into processed fly ash and treated water.

  When the processing slurry container 312 includes the processing slurry return line 314 and the radioactive cesium dissolved in water remains in the processing slurry in excess of a predetermined amount, the processing slurry container 312 is stored in the processing slurry container 312. The treated slurry is returned to the second mixing tank 303 via the treated slurry return line 314.

  According to the decontamination apparatus of the third embodiment, fly ash containing radioactive cesium can be decontaminated safely in a narrow space at low cost. Moreover, the quantity of the substance which needs to be stored can be reduced by separating the fly ash-derived magnetic material in advance.

[Fourth Embodiment]
As shown in FIG. 7, the fourth embodiment of the present invention includes a first mixing vessel 401, a first magnetic separation device 402, a second mixing vessel 403, a second magnetic separation device 404, and a vacuum dehydrator. 405, an adsorbent return line 415, and a controller 416.

  The fourth embodiment is different from the third embodiment in that an adsorbent return line 415 and a control unit 416 are provided.

  The adsorbent return line 415 returns the adsorbent separated by the second magnetic separation device 404 to the second mixing tank 403.

  The control unit 416 includes a measurement unit 417 (hereinafter also referred to as “first measurement unit”), a determination unit 418 (hereinafter also referred to as “first determination unit”), and a return unit 419 (hereinafter referred to as “first return unit”). It is also referred to as “

  The measuring means 417 measures the amount of radioactive cesium adsorbed on the adsorbent separated by the second magnetic separation device 404. Examples of the measuring means include a γ-ray measuring device, a Ge semiconductor detector, a NaI scintillation survey meter, a GM tube survey meter, and a measuring device using a large capacity CsI (TI) scintillator. Preferably, a measuring device using a large-capacity CsI (TI) scintillator capable of quick measurement in a time as short as 1 second is used.

  The determination unit 418 determines whether or not the amount of radioactive cesium measured by the measurement unit 417 has reached a predetermined amount. Examples of the determination means include a computer storing a reference value for determining whether or not to return the adsorbent to the second mixing tank.

  When the determination unit 418 determines that the amount of radioactive cesium has not reached the predetermined amount, the return unit 419 passes the adsorbent separated by the second magnetic separation device 404 via the adsorbent return line 415. It returns to the 2nd mixing tank 403. Examples of the return means include a blower that transports the adsorbent by suction.

  The controller 416 is another measuring means (hereinafter referred to as “second measuring means”) that measures the amount of radioactive cesium remaining in the processing slurry from which the adsorbent has been separated by the second magnetic separation device 404 (not shown). Another determination means for determining whether or not the amount of radioactive cesium measured by the second measurement means has reached a predetermined amount (hereinafter referred to as “second determination means”) (not shown); and second When the determination means determines that the amount of radioactive cesium has reached a predetermined amount, another return means for returning the processing slurry to the second mixing tank 403 via the processing slurry return line 414 (hereinafter “ (Referred to as “second return means”) (not shown).

  Examples of the second measuring means include the same as the first measuring means.

Examples of the second determination unit include the same as the first determination unit. The second determination unit may be integrated with the first determination unit.
Examples of the second return means include a pump.

  In the decontamination apparatus of the fourth embodiment configured as described above, the adsorbent separated by the second magnetic separation apparatus 404 is measured for the amount of radioactive cesium adsorbed by the measuring means 417. Next, it is determined whether or not the adsorption amount of radioactive cesium has reached a predetermined amount by the determination means 418. If it is determined that the predetermined amount has not been reached, the return means 419 converts the adsorbent into the adsorbent. It is returned to the second mixing tank 403 via the return line 415. On the other hand, when the determination unit 418 determines that the amount of radioactive cesium adsorption has reached a predetermined amount, the adsorbent is stored in the second mixing tank 403 without being returned.

  When the control unit 416 includes the second measurement unit, the second determination unit, and the second return unit, the amount of radioactive cesium in the treated slurry is measured by the second measurement unit. Next, it is determined whether or not the amount of radioactive cesium has reached a predetermined amount by the second determination means. If it is determined that the amount has reached the predetermined amount, the second return means will process the slurry. Is returned to the second mixing tank 403 via the processing slurry return line 414. On the other hand, when the second determination means determines that the amount of radioactive cesium has not reached the predetermined amount, the processing slurry is sent to the vacuum dehydrator 405 via the processing slurry delivery line 413.

  According to the decontamination apparatus of the fourth embodiment, fly ash containing radioactive cesium can be decontaminated safely in a narrow space at low cost. Further, by separating the fly ash-derived magnetic material in advance and reusing the adsorbent, the amount of substances that need to be stored can be further reduced.

[Fifth Embodiment]
As shown in FIG. 8, the fifth embodiment of the present invention relates to a decontamination apparatus including a mixing tank 501, a first magnetic separation device 502, a second magnetic separation device 503, and a vacuum dehydrator 504.

  In the fifth embodiment, as compared with the first embodiment, the first magnetic separation device 502 and the second magnetic separation device 503 are continuously arranged without providing the processing slurry return line 108. Is different.

  The 1st magnetic separation apparatus 502 isolate | separates the adsorbent which adsorb | sucked the radioactive cesium in the mixing tank 501 from a slurry with a magnetic force. A first processing slurry container 507 for storing the first processing slurry from which the adsorbent has been separated by the first magnetic separation device 502 is disposed below the first magnetic separation device 502. The first processing slurry container 507 includes a first processing slurry delivery line 508 that delivers the first processing slurry to the second magnetic separation device 503. The outlet end of the first treatment slurry delivery line 508 is located above or inside the second magnetic separation device 503 so that the first treatment slurry can be introduced into the second magnetic separation device 503.

  The second magnetic separation device 503 separates the adsorbent remaining in the first processing slurry from the first processing slurry by magnetic force. A second processing slurry container 509 that stores the second processing slurry from which the adsorbent has been further separated by the second magnetic separation device 503 is disposed below the second magnetic separation device 503. The second processing slurry container 509 includes a second processing slurry delivery line 510 that delivers the second processing slurry to the vacuum dehydrator 504. The outlet end of the second processing slurry delivery line 510 is located above or inside the vacuum dehydrator 504 so that the second processing slurry can be charged into the vacuum dehydrator 504.

  Examples of the first and second magnetic separation devices include the same ones as the magnetic separation devices in the first embodiment.

  In addition, you may arrange | position continuously so that the 2nd magnetic separation apparatus 503 may receive the 1st process slurry obtained with the 1st magnetic separation apparatus 502 directly.

  In the decontamination apparatus of the fifth embodiment configured as described above, fly ash containing radioactive cesium is mixed with water and an adsorbent in the mixing tank 501 to prepare a slurry. In the slurry, radioactive cesium is dissolved in water and adsorbed on the adsorbent. The slurry is sent to the first magnetic separation device 502 via the slurry delivery line 506, and the adsorbent adsorbing the radioactive cesium is separated from the slurry by the magnetic force. The first processing slurry from which the adsorbent has been separated is stored in the first processing slurry container 507. The first processing slurry stored in the first processing slurry container 507 is sent to the second magnetic separation device 503 via the first processing slurry delivery line 508, and the adsorbent remaining in the first processing slurry. Is separated from the first processing slurry by magnetic force. The second processing slurry from which the adsorbent is further separated is stored in the second processing slurry storage container 509. The second processing slurry stored in the second processing slurry storage container 509 is sent to the vacuum dehydrator 504 via the second processing slurry delivery line 510 and depressurized and dehydrated into the treated fly ash and the treated water. To be separated.

  According to the decontamination apparatus of the fifth embodiment, fly ash containing radioactive cesium can be decontaminated safely in a narrow space at low cost. Moreover, since it is not necessary to return processing slurry to a mixing tank, decontamination of fly ash can be performed rapidly.

  Although an example of the decontamination apparatus according to the present invention has been described with reference to the drawings, embodiments of the present invention are not limited to the above. In the range which does not deviate from the meaning of this invention, the apparatus which consists of a further structure is included by this invention. For example, the magnetic separation devices 102 and 202 in the first and second embodiments (second magnetic separation devices 304, 404, and 503 in the third, fourth, and fifth embodiments) and the vacuum dehydrator 103, Between 203,305,405,504, you may provide the coagulation tank (not shown) which mixes a process slurry and a coagulant | flocculant. Moreover, the supernatant water in the coagulation tank is returned to the mixing tanks 101, 201, and 501 in the first, second, and fifth embodiments (second mixing tanks 303 and 403 in the third and fourth embodiments). A supernatant water return line (not shown) may be provided. Furthermore, the treated water obtained by the vacuum dehydrators 103, 203, 305, 405, and 504 is mixed with the mixing tanks 101, 201, and 501 in the first, second, and fifth embodiments (third and fourth embodiments). The second mixing tank 303, 403) may be provided with a treated water return line (not shown).

  EXAMPLES Hereinafter, although this invention is demonstrated in detail using an Example, the technical scope of this invention is not limited to this.

<Example 1: Fly ash decontamination>
400 g of fly ash (initial concentration of radioactive cesium: 35000 Bq / kg) obtained from incineration of municipal waste obtained from a stalker furnace combustion incineration facility is mixed with 2 L of water (5 times the weight of fly ash) And a slurry was prepared. The pH of the slurry was adjusted to 10 or less. The concentration of radioactive cesium in the slurry was 6000 Bq / kg.

  In this example, 4 g of an adsorbent (1% by weight of the weight of fly ash) containing magnetic iron nanoparticles supported by a ferrocyanide compound using nickel as a different metal was added to the slurry, and the mixture was stirred at 200 rpm for 30 minutes. Stir. Thereafter, a cover was attached to the neodymium magnet, and the adsorbent was separated from the slurry using an instrument having a surface magnetic flux density measured on the cover surface of 5000 gauss. The concentration of radioactive cesium in the treated slurry from which the adsorbent was separated was 340 Bq / kg.

  The treated slurry was filtered (1 μm) to obtain treated fly ash and treated water. The concentrations of radioactive cesium in treated fly ash and treated water were 960 Bq / kg and 37 Bq / kg, respectively, which were below the designated waste standard of 8000 Bq / kg.

  The decontamination rate of radioactive cesium by the adsorbent in this example was about 94%. The concentration of radioactive cesium in the separated wet adsorbent was 650000 Bq / kg.

  In addition, the total cyanide concentration and heavy metal (cadmium, lead, etc.) concentration in the treated water also satisfied the wastewater standards. In addition, the drainage standard of total cyan concentration is less than 1 mg / L, the drainage standard of cadmium concentration is less than 0.1 mg / L, and the drainage standard of lead concentration is less than 0.1 mg / L.

<Example 2; pH dependence of ferrocyan ion elution>
Two types of porous secondary particles formed by assembling a plurality of magnetic iron nanoparticles supported by nickel ferrocyanide were prepared. The particle sizes of the two types of secondary particles were 6 μm (hereinafter referred to as “first adsorbent”) and 20 μm (hereinafter referred to as “second adsorbent”) on average.

  Sodium hydroxide was added to 1 L of water to adjust the pH to 8, 9, 10, and 11. 2 g of the first adsorbent and the second adsorbent were added to various waters adjusted in pH, respectively, and stirred at 200 rpm for a predetermined time to obtain a slurry. A part of the slurry (about 100 ml) was filtered through a membrane filter having a pore size of 1 μm, and the pH and total cyan concentration of the obtained filtrate were measured. The results are shown in Tables 1 and 2 and FIG.

  Similarly, using a slurry in which fly ash and water were mixed, the relationship between pH and elution of ferrocyan ion was examined. In this study, agglomeration operation using polyferric sulfate was also performed. The results are shown in FIG. In the figure, □ indicates the total cyan concentration measurement result in the supernatant obtained by the flocculation operation, and ◇ in the figure indicates the total cyan concentration measurement result in the filtrate dehydrated in the latter stage of the flocculation operation. The amount of water added to the fly ash is 5 to 10 times by weight, the amount of adsorbent added to the fly ash weight is 0.2% to 1%, and the stirring time is 30 minutes to 60 minutes. The relationship between the post-treatment pH and the total cyan density when carried out under conditions is shown.

  Although it is not always necessary to adjust the pH of the slurry, the elution of ferrocyanic ions can be further reduced by adjusting the pH below a certain value.

<Example 3: Pre-magnetization of adsorbent>
An adsorbent containing magnetic iron nanoparticles supported by nickel ferrocyanide was magnetized for several minutes close to a magnet bar containing a neodymium magnet. Specifically, an apparatus having a surface magnetic flux density of about 5000 Gauss with a cover attached to a neodymium magnet was magnetized by bringing it close to the adsorbent for about 3 minutes.

  A slurry was prepared by stirring 40 g of magnetized adsorbent, 20 kg of fly ash, and 100 kg of water for 60 minutes, and the adsorbent was separated from the slurry at a flow rate of 20 ml / min using a magnetic separator. The results are shown in Table 3. As a comparative control, the result of using an adsorbent which has not been magnetized in advance is also shown.

吸着剤をスラリーと混合する前に予め着磁することによって、放射性セシウムの除染率を向上させることができた。

By pre-magnetizing the adsorbent before mixing with the slurry, the decontamination rate of radioactive cesium could be improved.

<Example 4: Separation of fly ash-derived magnetic material (fly ash magnetized material)>
Two types of fly ash samples were prepared. 150 g of each fly ash sample and 750 g of water were mixed to prepare a slurry, and a magnetic body derived from fly ash was separated and recovered from the slurry using a magnet bar incorporating a neodymium magnet. The results are shown in Table 4.

  Further, the elemental composition of the separated and recovered magnetic material was subjected to fluorescent X-ray analysis. The results are shown in Table 5 (unit is% by weight). Aluminum (Al), silicon (Si), iron (Fe), etc. are increasing. Usually, aluminum is non-magnetic, but it is a complex oxide containing iron, aluminum, and silicon, and is considered to be slightly magnetic.

  About 2% of the weight of fly ash was magnetic.

  As an example, when the content of the magnetic substance contained in the fly ash is 1.7% by weight and the magnetic substance is not separated in advance, it is necessary to store it by adding 1 kg of adsorbent to 1 t of fly ash. The amount of the substance (mixture of adsorbent and fly ash-derived magnetic material) becomes 18 kg (1 kg + 17 kg) in terms of dry weight. Therefore, by removing the fly ash-derived magnetic material in advance, the amount of substances that need to be stored can be greatly reduced.

101 ・ ・ Mixing tank 102 ・ ・ Magnetic separator 103 ・ ・ Dehydrator 104 ・ ・ Agitator 105 ・ ・ Slurry delivery line 106 ・ ・ Processed slurry container 107 ・ ・ Processed slurry delivery line 108 ・ ・ Processed slurry return line 901・ ・ Magnet core 902 ・ ・ Outer cylinder 903 ・ ・ Roller 904 ・ ・ Scraper 201 ・ ・ Mixing tank 202 ・ ・ Magnetic separation device 203 ・ ・ Dehydrator 204 ・ ・ Stirrer 205 ・ ・ Slurry delivery line 206 ・ Processed slurry Container 207 ··· Processed slurry delivery line 208 ··· Processed slurry return line 209 ·· Adsorbent return line 210 · · Control unit 211 · · Measuring means 212 · · Determination means 213 · · Return means 301 · · First mixing Tank 302 ··· First magnetic separation device 303 · · Second mixing vessel 304 · · Second magnetic separation device 05 .. Decompression dehydrator 306 .. First stirrer 307 .. First slurry delivery line 308 .. Pretreatment slurry container 309 .. Pretreatment slurry delivery line 310 .. Second agitator 311. Second slurry delivery line 312 ... Processed slurry container 313 ... Processed slurry delivery line 314 ... Processed slurry return line 401 ... First mixing tank 402 ... First magnetic separation device 403 ... Mixing tank 404 ··· second magnetic separation device 405 · · vacuum dehydrator 406 · · first stirrer 407 · · first slurry delivery line 408 · · pretreatment slurry container 409 · · pretreatment slurry delivery line 410 ·· Second stirrer 411 ·· Second slurry delivery line 412 ·· Processed slurry container 413 ·· Processed slurry delivery line 414 ·· Process Rally return line 415 .. Adsorbent return line 416 .. Control part 417 ..Measurement means 418 ..Determination means 419 ..Return means 501 ..Mixing tank 502 .. First magnetic separation device 503. Magnetic separation device 504 .. Vacuum dehydrator 505 .. Stirrer 506 .. Slurry delivery line 507 .. First treatment slurry container 508 .. First treatment slurry delivery line 509 .. Second treatment slurry container 510 .. Second treatment slurry delivery line

Claims (19)

A preparation step in which fly ash containing radioactive cesium and water are mixed to prepare a slurry in which radioactive cesium is dissolved in water;
Adsorption that adsorbs radioactive cesium dissolved in water by mixing slurry prepared in the preparation process and adsorbent containing magnetic iron nanoparticles carrying ferrocyanide compound introduced with metal other than iron And a first separation step of separating the adsorbent adsorbing the radioactive cesium in the adsorption step from the slurry by magnetic force;
A method for decontaminating fly ash containing radioactive cesium.   The decontamination method according to claim 1, further comprising a dehydration step of dehydrating the treated slurry obtained by separating the adsorbent obtained in the first separation step under reduced pressure.   The decontamination method according to claim 1 or 2, wherein the first separation step is performed using a magnet having a surface magnetic flux density of 2000 to 13000 gauss.   The decontamination method according to claim 1 or 2, wherein the first separation step is performed using a ferrite magnet or a neodymium magnet.   5. The method according to claim 1, further comprising a second separation step of separating magnetic material derived from fly ash contained in the slurry from the slurry by magnetic force before mixing the slurry and the adsorbent in the adsorption step. Decontamination method as described.   The decontamination method according to claim 5, wherein the adsorbent separated in the first separation step is reused in the adsorption step.   The decontamination method according to claim 1, wherein the magnetic iron nanoparticles contained in the adsorbent are magnetized before being mixed with the slurry in the adsorption step.   The decontamination method according to any one of claims 1 to 7, wherein the pH of the slurry mixed with the adsorbent in the adsorption step is adjusted to 8 to 10.   The decontamination method according to any one of claims 1 to 8, wherein the amount of adsorbent mixed in the adsorption step is 1% by weight or less of the weight of fly ash.   The decontamination method according to any one of claims 1 to 9, wherein the magnetic iron nanoparticles carrying the ferrocyanide compound form porous secondary particles having an average of 1 to 500 µm. A fly ash decontamination device containing radioactive cesium,
Mixing fly ash containing radioactive cesium, water, and an adsorbent containing magnetic iron nanoparticles carrying ferrocyanide compounds introduced with metals other than iron, and using the radioactive cesium dissolved in water as the adsorbent A mixing tank for preparing the adsorbed slurry;
A magnetic separator for separating the adsorbent adsorbing radioactive cesium in the mixing tank from the slurry by magnetic force; and a vacuum dehydrator for dehydrating the treated slurry from which the adsorbent has been separated by the magnetic separator;
A decontamination apparatus.   The decontamination device according to claim 11, wherein the magnetic separation device has a magnet having a surface magnetic flux density of 2000 to 13000 gauss.   The decontamination apparatus according to claim 11, wherein the magnetic separation device includes a ferrite magnet or a neodymium magnet. A fly ash decontamination device containing radioactive cesium,
A first mixing tank in which fly ash containing radioactive cesium and water are mixed to prepare a slurry in which radioactive cesium is dissolved in water;
A first magnetic separation device that separates the fly ash-derived magnetic material contained in the slurry prepared in the first mixing tank from the slurry by magnetic force;
Mixing the pretreatment slurry from which the fly ash-derived magnetic material was separated by the first magnetic separation device and the adsorbent containing magnetic iron nanoparticles carrying the ferrocyanide compound introduced with a metal other than iron A second mixing tank for adsorbing radioactive cesium dissolved in water to the adsorbent; and a second magnetic separation device for separating the adsorbent adsorbing the radioactive cesium in the second mixing tank from the pretreatment slurry by magnetic force;
A decontamination apparatus.   The decontamination apparatus according to claim 14, further comprising a vacuum dehydrator for dehydrating the processing slurry from which the adsorbent has been separated by the second magnetic separation apparatus.   The decontamination apparatus according to claim 14 or 15, wherein the second magnetic separation apparatus has a magnet having a surface magnetic flux density of 2000 to 13000 gauss.   The decontamination device according to claim 14 or 15, wherein the second magnetic separation device has a ferrite magnet or a neodymium magnet.   The decontamination apparatus according to any one of claims 14 to 17, further comprising an adsorbent return line for returning the adsorbent separated by the second magnetic separation device to the second mixing tank. Measuring means for measuring the amount of radioactive cesium adsorbed on the adsorbent separated by the second magnetic separation device;
Determining means for determining whether or not the amount of radioactive cesium measured by the measuring means has reached a predetermined amount; and when the determining means determines that the amount of radioactive cesium has not reached the predetermined amount, Return means for returning the adsorbent separated by the magnetic separation device of 2 to the second mixing tank via the adsorbent return line;
The decontamination apparatus according to claim 18, further comprising: a control unit including:

Images