JP6199643B2 - Radioactive contaminated water treatment apparatus and radioactive contaminated water treatment method - Google Patents

Description

  The present invention relates to a treatment apparatus for radioactively contaminated water and a method for treating radioactively contaminated water, which remove radioactive substances from water containing radioactive substances such as radioactive cesium (referred to as “radioactive contaminated water”).

  The Great East Japan Earthquake that struck Japan on March 11, 2011 was accompanied by the occurrence of a large tsunami, and it was an unprecedented disaster that caused devastating damage to municipalities on the coast of the Tohoku region. The damage caused by the tsunami also affected TEPCO's Fukushima Nuclear Power Station, causing the reactor cooling facility to stop functioning, fuel rod meltdown, steam explosions, etc. The alarming situation of the generation of radioactive material contaminated drainage was revealed. Therefore, removal of radioactive materials from radioactive material contaminated effluent is one of the issues that Japan must solve as quickly as possible.

  As main radionuclides released from radioactive material handling facilities such as nuclear power plants, iodine-131 (half-life 8.02 days) radioactive iodine produced by fission reaction of uranium-235 and cesium-134 (halved) And a radioactive cesium having a cesium-137 (half-life of 30.07 years).

Among these, radioactive iodine has a short half-life of about 8 days, so it was detected from purified water sludge immediately after the earthquake and became a problem. On the other hand, radioactive cesium has a long half-life and is widely diffused in the Tohoku and Kanto regions, so the treatment of soil, fallen leaves, rubble, sewage sludge and incinerated ash contaminated by radioactive cesium has become a major problem.
Among them, incinerated ash containing radioactive cesium, in particular incinerated fly ash, not only has volatilized radioactive cesium concentrated, but also exists in a form that is very easily dissolved in water as radioactive cesium becomes cesium chloride. Therefore, a large amount of radioactive cesium is dissolved in the cleaning wastewater discharged when such incinerated ash is cleaned. However, the technology for decontamination of radioactive cesium existing in a state dissolved in water has not been established yet, and there is an urgent need to establish a method for treating radioactive contamination water that removes radioactive substances from radioactive contamination water. .

  The technology to remove radioactive cesium uses the three-dimensional characteristics of ferrocyanic compounds (iron, copper, nickel salts, etc.) that can selectively incorporate cesium ions into the crystal lattice (see Figs. 1 and 2). Then, after adding and contacting the ferrocyanide powder to the radioactive cesium-containing wastewater, solid-liquid separation to reduce the radioactive cesium content and the arrangement of the SiO tetrahedral layer on the clay crystal lattice plane Utilizing the three-dimensional properties of montmorillonite clay minerals that can selectively incorporate cesium ions into a hexagonal structure with six oxygen atoms (see Fig. 3 and Fig. 4), radioactive montmorillonite clay mineral powders are radioactive. After adding and contacting cesium-containing wastewater, powder-like powder with cesium adsorption ability, such as technology to reduce the radioactive cesium content by solid-liquid separation The wear agent is contacted with radioactive cesium-containing waste water to adsorb and remove the cesium technique is known.

However, in the method of solid-liquid separation after bringing radioactive substance-containing wastewater into contact with a powdery adsorbent having radioactive substance adsorption capacity, it is difficult to separate water from the powdery adsorbent. There was a problem that a large amount of sludge (slurry) containing the substance was generated and the sludge volume reduction treatment was necessary.
As means for solving such a problem, a method using a granular adsorbent that is relatively easy to separate moisture, or a material having a radioactive substance adsorbing ability is attached to or supported on the surface or void of a porous material. The method of using the made radioactive substance removal substance can be mentioned.

  Regarding the former method, for example, in Patent Document 1 (Japanese Patent Laid-Open No. Sho 56-79999), an X-type zeolite having a diameter of 60 to 80 mesh is moistened, and then an aqueous copper sulfate solution is added to adsorb copper ions. Disclosed is an addition method for attaching a ferrocyanide metal compound by reacting with an aqueous potassium cyanide solution to form copper ferrocyanide in the voids and on each surface of the zeolite, and a treatment method using the adsorbed zeolite as an adsorbent. Has been.

  On the other hand, regarding the latter method, for example, in Patent Document 2 (Japanese Patent Laid-Open No. 9-173832), a porous resin is supported with a quaternary ammonium salt that is soluble in a low-boiling organic solvent and hardly soluble in water. After treatment with an aqueous solution containing hexacyanoferrate (II) (inventor's note: another name for ferrocyanide salt), the treated product is brought into contact with an aqueous solution containing copper salt to form hexacyanoiron (II) in the pores of the resin. A method for producing a hexacyanoferrate (II) -supported porous resin characterized by depositing copper acid and then extracting a quaternary ammonium salt in the resin with a low-boiling organic solvent is disclosed.

Further, Patent Document 3 (Japanese Patent Publication No. 62-43519) discloses a radioactive substance removing substance obtained by adding copper ferrocyanide to zeolite, and Patent Document 4 (Japanese Patent Laid-Open No. 9-173832). Discloses a radioactive substance removing substance obtained by supporting copper hexacyanoferrate (II) on a porous resin.
Furthermore, Patent Document 5 (Japanese Patent Publication No. 62-43519) discloses a radioactive substance removing substance obtained by adhering copper ferrocyanide to granular activated carbon.

JP-A-56-79999 Japanese Patent Laid-Open No. 9-173832 Japanese Examined Patent Publication No. 62-43519 Japanese Patent Laid-Open No. 9-173832 Japanese Examined Patent Publication No. 62-43519

  A ferrocyan compound has a very high cesium selective adsorption property to selectively adsorb radioactive cesium, and is a substance expected as an active ingredient of a radioactive cesium removing agent. However, when treated with a radioactive material adsorbent containing ferrocyan compounds, the cesium adsorptivity is too high, so the radioactive contamination level of the treated radioactive material adsorbent increases locally, and the radioactive material adsorbed after treatment Handling may be hindered at the stage of disposal.

  Therefore, the present invention relates to a method and apparatus for treating radioactive contaminated water using a radioactive material adsorbent containing a ferrocyan compound, and not only can efficiently remove radioactive cesium from radioactive contaminated water but also adsorb radioactive cesium. It is an object of the present invention to provide a new method and apparatus for removing radioactively contaminated water that can control the radioactive contamination level of the radioactive material adsorbent later.

The present invention includes a sparingly soluble ferrocyan compound that reduces the concentration of radioactivity by bringing into contact with water to be treated (radioactive contaminated water) containing a radioactive substance to adsorb and remove the radioactive substance in the water to be treated. A poorly soluble ferrocyan compound that adsorbs and removes a radioactive substance by bringing one radioactive substance adsorbing layer (1) into contact with the water to be treated having a reduced radioactivity concentration from the first radioactive substance adsorbing layer (1) And a second radioactive substance adsorption layer (2) having a higher content than the first radioactive substance adsorption layer (1) , wherein the first radioactive substance adsorption layer (1) In the path through which water passes, the ratio of the mass of the hardly soluble ferrocyan compound to the filling volume is 0.4 g / L or more and 11 g / L or less, and the second radioactive substance adsorption layer (2) is , Containing a poorly soluble ferrocyan compound to the filling volume The ratio of the mass is higher than 11g / L, and proposes a processing device of radioactive contaminated water, characterized in that it is 550 g / L or less.

The present invention also provides a radioactive substance having a ratio of the mass of the sparingly soluble ferrocyan compound to the filling volume of 0.4 g / L or more and 11 g / L or less of water to be treated (radioactive contaminated water) containing the radioactive substance. Water is passed through the adsorbing layer (1), and then the water is passed through the radioactive material adsorbing layer (2) having a ratio of the mass content of the poorly soluble ferrocyan compound to the filling volume higher than 11 g / L and 550 g / L or less. We propose a treatment method for radioactively contaminated water.

Furthermore, the present invention provides a method and apparatus for removing radioactively contaminated water, wherein the radioactive substance adsorbing layer 1 or the radioactive substance adsorbing layer 2 or both of them have a water-soluble ferrocyan compound-adsorbing action. Radioactive contaminated water containing a ferrous compound adsorbent or a CN adsorbing layer 3 containing a water-soluble ferrocyanide adsorbent as a layer different from the radioactive substance adsorbing layer 1 and the radioactive substance adsorbing layer 2 A cleaning method and a processing apparatus are proposed.

  According to the method and apparatus for removing radioactively contaminated water proposed by the present invention, in the first stage of treatment, the water to be treated is brought into contact with the radioactive substance adsorbing layer 1 having a low content of poorly soluble ferrocyan compound. After the radioactive material is adsorbed and removed evenly in the entire layer 1 to reduce the radioactive level of the contaminated water, the water to be treated is then brought into contact with the radioactive material adsorbing layer 2 having a high content of poorly soluble ferrocyan compound. Thus, radioactive substances can be adsorbed and removed to below the emission standard. Therefore, it is possible to prevent excessive adsorption at a portion in contact with highly concentrated contaminated water (for example, the inflow portion of the apparatus), and control so that the radioactive contamination level of the radioactive material adsorbent after the radioactive cesium adsorption does not become locally high. be able to.

Moreover, when a poorly soluble ferrocyan compound is added to radioactively contaminated water, the water-soluble ferrocyan compound may partially dissolve in the treated water. Although the ferrocyan compound itself is not toxic, it is not preferable because the total cyan amount specified by the environmental standards and wastewater standards increases. Therefore, in the method and apparatus for removing radioactively contaminated water, the water-soluble ferrocyan compound in which the radioactive substance adsorbing layer 1 or the radioactive substance adsorbing layer 2 or both have an action of adsorbing the water-soluble ferrocyan compound. A ferrocyan compound is treated by providing a CN adsorbing layer 3 containing a water-soluble ferrocyan compound adsorbent as a layer different from the radioactive material adsorbing layer 1 and the radioactive material adsorbing layer 2 containing the adsorbing agent. Dissolution in water can be suppressed, and the total cyan content of treated water can be suppressed.

It is the figure which showed typically the atomic arrangement of the crystal lattice of ferrocyanide. It is the figure which showed typically an example in the state where the cesium ion was taken in in the crystal lattice of ferrocyanide. It is the figure which showed typically the oxygen atom arrangement | sequence of the silicon oxide layer of a montmorillonite clay mineral. It is the figure which showed typically an example of the state by which the cesium ion was taken in in the hexagonal lattice of oxygen of the silicon oxide layer of a clay mineral. (A) It is the conceptual diagram which showed the processing apparatus using a cartridge-type reaction container as an example of the processing apparatus of this invention, (B) is the figure which showed the flow of the water in the apparatus. Similarly, it is the conceptual diagram which showed the other example of the processing apparatus of this invention. Similarly, it is the conceptual diagram which showed the other example of the processing apparatus of this invention. Similarly, it is the conceptual diagram which showed the other example of the processing apparatus of this invention. Similarly, it is the conceptual diagram which showed the other example of the processing apparatus of this invention. Similarly, it is the conceptual diagram which showed the other example of the processing apparatus of this invention. It is the conceptual diagram which showed an example of the processing flow in the case of operating the processing apparatus of this invention by a merry-go-round system. It is the conceptual diagram which showed the processing apparatus of the test 1.

  Next, the form for implementing this invention is demonstrated. However, the present invention is not limited to the embodiment described below.

<This cleaning method>
The method for treating radioactive contaminated water according to the present embodiment (referred to as “the present decontamination method”) is a radioactive radioactive water containing a radioactive substance and the following radioactive substance having a relatively low content of a hardly soluble ferrocyan compound. After passing through the adsorption layer 1 for treatment, it is treated by passing through the following radioactive substance adsorption layer 2 having a relatively high content of poorly soluble ferrocyan compound, and in some cases, further, a water-soluble ferrocyan compound adsorbent. This is a method for treating radioactively contaminated water, characterized in that it is treated by passing water through a CN adsorbing layer 3 containing water.

(Radioactive contaminated water)
The radioactively contaminated water as the water to be treated in the present decontamination method only needs to contain a radioactive substance, and is preferably radioactively contaminated water containing radioactive cesium.
The concentration of radioactive cesium in the radioactively contaminated water (treated water) is not particularly limited, and it is not prohibited to apply it to highly concentrated contaminated water, but the work at the time of disposal of radioactive waste after treatment Considering the human exposure risk, it is preferable that the radioactivity concentration by radioactive cesium is 10 to 5000 Bq / L.

Before passing the radioactively contaminated water (treated water) through the radioactive substance adsorbing layer 1, the pH of the radioactively contaminated water as the treated water may be adjusted to an acidic region.
At this time, if the pH of the water to be treated is low, the solubility of the poorly soluble ferrocyan compound in water can be lowered. On the other hand, if the pH of the water to be treated is too low, the cesium selective adsorption property of the poorly soluble ferrocyan compound is lowered. Therefore, it is preferable to adjust the radioactive contaminated water to pH 5 or lower. On the other hand, it has been found that when the pH of the water to be treated is lowered too much, the cesium selective adsorption property of the poorly soluble ferrocyan compound is lowered. Therefore, it is particularly preferable to adjust the pH of the water to be treated to 3 to 5.

  As means for adjusting the pH of the radioactively contaminated water, the means for adjusting the water to be treated to an acidic region, preferably pH 5 or lower, include hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, acetic acid, oxalic acid, etc. The method of adding an acid can be mentioned.

(Radioactive material adsorption layer 1)
The radioactive substance adsorbing layer 1 is a layer that plays a role of evenly adsorbing and removing most of the radioactive substance contained in the radioactively contaminated water as the water to be treated, particularly radioactive cesium, throughout the entire layer 1. It aims to reduce the level of radioactivity. Preferably, it is preferable to adsorb 60% or more, particularly 80% or more, particularly 90% or more of the radioactive substance contained in the radioactively contaminated water, particularly radioactive cesium.

The radioactive substance adsorption layer 1 is a layer made of adsorbent particles containing a hardly soluble ferrocyan compound and other raw materials.
Here, the “layer” of the radioactive substance adsorption layer 1 means a state in which adsorbent particles containing a hardly soluble ferrocyan compound and other raw materials are gathered densely, and in a part of the column, container, or tower. The case where the layers are densely gathered and the case where the cartridge is filled in a cartridge container are also included.

In the radioactive substance adsorbing layer 1, it is important that the ratio of the mass content of the poorly soluble ferrocyan compound to the filling volume of the layer 1 is 0.4 g / L or more and 11 g / L or less, especially 1.1 g / L. Above, and 5.5 g / L or less, Among these, it is especially preferable that they are 2.2 g / L or more and 5.5 g / L or less.
In the radioactive substance adsorbing layer 1, the ratio of the mass content of the hardly soluble ferrocyan compound to the filling volume of the layer 1 is 0.4 g / L or more and 11 g / L or less, and such a small amount of the hardly soluble ferrocyan compound is contained. It is preferably present in the layer 1 in a uniformly dispersed manner. If so, the radioactive substance, in particular, radioactive cesium does not concentrate on the inflow portion of the layer 1 and is adsorbed in a high amount of contamination, and can be dispersed and adsorbed and removed throughout the radioactive substance adsorbing layer 1.

  Examples of the poorly soluble ferrocyan compound include poorly soluble ferrocyan compounds such as Fe (III) salt, Fe (II) salt, Ni (II) salt, Cu (II) salt, Co (II) salt, Among these, Fe (III) salt (bituminous) is preferable in consideration of price and the like.

  The raw material other than the hardly soluble ferrocyan compound constituting the radioactive substance adsorbing layer 1, that is, “other raw material” is not particularly limited. For example, it may be a radioactive substance removing substance or its particle having the ability to adsorb a radioactive substance, or a water soluble ferrocyan compound adsorbent or its particle having the ability to adsorb a water soluble ferrocyan compound. Alternatively, it may be a substance or particles of which it is unclear whether or not it has the ability to adsorb both of the two.

  Examples of the radioactive substance removing substance include clay mineral and zeolite. As for the types of other radioactive substance removing substances, it is possible to select the radioactive substance removing substance contained according to the purpose and use it in combination as necessary, so it is also possible to remove multiple nuclides simultaneously It can be said that the versatility is extremely high.

The clay mineral is not particularly limited as long as it has a three-dimensional structure with an oxygen sequence capable of selectively adsorbing cesium ions. Like the genus Montmorillonite, illite genus, vermiculite genus or kaolinite genus, it has a hexagonal structure with six oxygen atoms (Fig. 1) formed by the arrangement of SiO tetrahedral layers on the clay crystal lattice plane. The montmorillonite genus has a three-layer structure in which both sides of an ALO octahedral layer are sandwiched by SiO tetrahedral layers, or a two-layer structure composed of an ALO octahedral layer and an SiO tetrahedral layer. The kaolinite clay minerals are particularly suitable.
These clay minerals include bentonite, which is Na-type montmorillonite, acidic clay, which is H-type montmorillonite, activated clay that has been surface-treated by acid treatment to elute soluble cations, and kaolin. Can be mentioned.

  The zeolite may be either natural zeolite or synthetic zeolite. Since this type of zeolite has a high cation exchange capacity, radioactive cation nuclides can be removed. Therefore, radioactive strontium can be removed in addition to radioactive cesium. In particular, it is known that type 4A synthetic zeolite has high selective removal of strontium.

  As the water-soluble ferrocyan compound adsorbent, activated carbon, anion exchange resin, or the like can be used. However, the substance is not limited to these, and any substance having a function of adsorbing a water-soluble ferrocyan compound can be used.

As the activated carbon, all kinds of activated carbon powders such as coal-based, coconut shell-based, and wood-based can be used. Also, felt-like and cloth-like activated carbon fibers can be used.
The anion exchange resin may be in any form of granular, fibrous, liquid, or membrane as long as it is a strongly basic anion exchange resin. For example, a strongly basic anion exchange resin having a matrix made of a copolymer of styrene / divinylbenzene can be mentioned.

  Examples of the substance that is unclear whether or not it has the ability to adsorb radioactive substances and water-soluble ferrocyan compounds include foundry sand, coal ash, and filtered sand.

  As a suitable example of the radioactive substance adsorbing layer 1, particles made of a hardly soluble ferrocyan compound, and particles made of one or more non-ferrocyanic radioactive substance adsorbing materials selected from the group consisting of clay minerals and zeolites, Optionally containing particles composed of one or more water-soluble ferrocyan compound adsorbents selected from the group consisting of activated carbon and anion exchange resin, and a poorly soluble ferrocyan compound for the filling volume of layer 1 The example of the ratio of the containing mass of 0.4 g / L or more and 11 g / L or less can be given.

  The radioactive substance adsorbing layer 1 is a substance constituting the layer 1, that is, a hardly soluble ferrocyan compound and other raw materials, for example, particles containing each substance are formed, and the particles are placed in a container (reaction tower or column). It is also possible to form it by being filled in. At this time, as the solidification method of the particles, various solidification methods such as water glass solidification and cement solidification can be adopted, but the alginic acid solidification method described below is particularly preferable. As a preferred example produced by this alginic acid solidification method, the form of “radioactive material adsorbent A” described later can be mentioned.

The radioactive substance adsorption layer 1 may be one layer or two or more layers. That is, the radioactive polluted water may be treated by passing through one or more radioactive substance adsorbing layers 1 and then passing through the radioactive substance adsorbing layer 2 for treatment.
When the radioactive substance adsorption layer 1 is composed of two or more layers, the mass ratio of the hardly soluble ferrocyan compound in the two or more radioactive substance adsorption layers 1 may be the same or different. . For example, the content mass ratio of the hardly soluble ferrocyan compound can be adjusted so as to go downstream.
When the radioactive substance adsorbing layer 1 is composed of two or more layers, for example, two or more radioactive substance adsorbing layers 1 can be provided in the same column. Alternatively, the radioactive substance adsorbing layer 1 can be packed in separate columns or cartridges to form one layer of radioactive substance. The substance adsorption layer 1 can also be formed.

(Radioactive material adsorption layer 2)
The radioactive substance adsorbing layer 2 can adsorb radioactive substances, particularly radioactive cesium, which has not been adsorbed by the radioactive substance adsorbing layer 1, and can remove the amount of radioactive substances, particularly radioactive cesium, to below the emission standard, preferably treated. It is a layer that plays a role in removing radioactive materials in water, particularly radioactive cesium, to the extent that they are not contained or only slightly contained.

In addition, as the limit concentration in the public water area around the business site and the final disposal site, Cs134 is 60 Bq / L, Cs137 is 90 Bq / L, and the following formula is required.
Cs134 concentration (Bq / L) / 60 (Bq / L) + Cs137 concentration (Bq / L) / 90 (Bq / L)

The radioactive substance adsorption layer 2 is a layer containing a hardly soluble ferrocyan compound and, if necessary, other raw materials.
Here, the “layer” of the radioactive substance adsorbing layer 2 means a state in which particles made of a hardly soluble ferrocyan compound and other raw materials are gathered densely, and in a part of the column, vessel, or tower, The case where the layers are gathered to form a layer is also included, for example, when the cartridge container is filled.

In the radioactive substance adsorbing layer 2, it is important that the ratio of the mass content of the hardly soluble ferrocyan compound to the filling volume of the layer 2 is higher than 11 g / L and not higher than 550 g / L.
From the viewpoint of reliably adsorbing radioactive materials that have not been adsorbed by the radioactive material adsorption layer 1, particularly radioactive cesium, the ratio of the content of the hardly soluble ferrocyan compound in the radioactive material adsorption layer 2 is higher than 11 g / L and It is important that it is 550 g / L or less, and above all, it is preferably higher than 11 g / L and not more than 110 g / L, and particularly preferably higher than 11 g / L and not more than 55 g / L.

  The kind of the hardly soluble ferrocyan compound contained in the radioactive substance adsorbing layer 2 and the kind of the raw material (including the water soluble ferrocyan compound adsorbent) other than the hardly soluble ferrocyan compound are the same as those of the radioactive substance adsorbing layer 1.

  As a suitable example of the radioactive substance adsorbing layer 2, particles made of a hardly soluble ferrocyan compound, and particles made of one or more non-ferrocyanic radioactive substance adsorbing materials selected from the group consisting of clay minerals and zeolites, Optionally containing particles composed of one or more water-soluble ferrocyan compound adsorbents selected from the group consisting of activated carbon and anion exchange resin, and a poorly soluble ferrocyan compound with respect to the filling volume of the layer 2 An example in which the ratio of the contained mass is higher than 11 g / L and not higher than 550 g / L can be given.

  The radioactive substance adsorbing layer 2 is formed of particles constituting each of the substances constituting the layer 2, that is, the hardly soluble ferrocyan compound and other raw materials, for example, and the particles are contained in a container (reaction tower or column). It is also possible to form it by being filled in. As a preferred example, a form in which the radioactive substance adsorbing layer 2 is formed from “radioactive substance adsorbent A (described later)” in which the content of the hardly soluble ferrocyan compound is appropriately adjusted can be mentioned.

The radioactive substance adsorption layer 2 may be one layer or two or more layers. That is, the radioactively contaminated water may be treated by passing it through one or more radioactive material adsorbing layers 2.
When the radioactive substance adsorption layer 2 is composed of two or more layers, the mass ratio of the hardly soluble ferrocyan compound in the two or more radioactive substance adsorption layers 2 may be the same or different. . For example, the content mass ratio of the hardly soluble ferrocyan compound can be adjusted so as to go downstream.
When the radioactive substance adsorption layer 2 is composed of two or more layers, for example, two or more radioactive substance adsorption layers 2 can be provided in the same column, or one radioactive substance adsorption layer can be provided in separate columns or cartridges. 2 can also be provided.

(Ratio of radioactive substance adsorption layer 1 and radioactive substance adsorption layer 2)
The ratio of the total amount of radioactive material adsorbing layer 1 consisting of one or more layers to the total amount of radioactive material adsorbing layer 2 consisting of one or more layers is the radioactive contamination level of the waste adsorbent layer after treatment In addition, the ratio can be adjusted to an appropriate ratio in consideration of the replacement frequency of the adsorbent. For example, when the radioactive contamination level of the water to be treated is high, the ratio of the radioactive substance adsorbing layer 1 can be increased or the replacement frequency can be increased.

(CN adsorption layer 3)
In addition to passing water through the radioactive substance adsorbing layer 1 and the radioactive substance adsorbing layer 2, if necessary, it may be further passed through the CN adsorbing layer 3 containing a water-soluble ferrocyan compound adsorbent for treatment.
Here, the “layer” of the CN adsorbing layer 3 means a state in which particles made of a water-soluble ferrocyan compound adsorbent are gathered densely, and a layer may be formed in a part of a column, container, or tower. For example, the case where it fills in the cartridge container is also included.

  When a poorly soluble ferrocyan compound is added to radioactively contaminated water, the water-soluble ferrocyan compound may partially dissolve in the treated water. Although there is no toxicity of the ferrocyan compound itself, it is not preferable because the total cyan amount specified by the environmental standards and the wastewater standards increases. Therefore, by passing water through the CN adsorbing layer 3 containing the water-soluble ferrocyan compound adsorbent, it is possible to remove the water-soluble ferrocyan compound that may partially elute from the hardly soluble ferrocyan compound. The total cyan content of water can be reduced.

The kind of the water-soluble ferrocyan compound adsorbent is as described above.
Further, as described above, when the radioactive substance adsorbing layer 1 and / or the radioactive substance adsorbing layer 2 contains a water-soluble ferrocyan compound adsorbent, the treatment can be performed without providing the CN adsorbing layer 3. It is possible to reduce the total cyan content of water. Therefore, in that case, it is preferable not to provide the CN adsorption layer 3.

(Other)
In this cleaning method, depending on the properties, purpose, and environment of the water to be treated, it is optional to pass the water through layers other than the radioactive substance adsorption layer 1, the radioactive substance adsorption layer 2, and the CN adsorption layer 3 for treatment. It is.

<This radioactive material adsorbent A>
As an example of a preferable radioactive substance adsorbent constituting the radioactive substance adsorbing layer 1 and the radioactive substance adsorbing layer 2, a porous granular material containing an alginate metal salt is used as a base particle, a poorly soluble ferrocyan compound, and other substances as required. (Hereinafter, the whole of the ferrocyan compound and other materials are referred to as “raw material”, but the sol-agent and the gelling agent are not included therein) scattered on the surface or inside of the base particles. There may be mentioned a radioactive material adsorbing material (hereinafter referred to as “the present radioactive substance adsorbing material A”) composed of a large number of particles (hereinafter referred to as “the present radioactive substance adsorbing material particles”).

Among them, together with a hardly soluble ferrocyan compound, one or more non-ferrocyan compounds selected from the group consisting of clay minerals, activated carbon, zeolite, and other radioactive substance adsorbents or other water-soluble ferrocyan adsorbents, or It is preferable that the other raw material is a radioactive material adsorbent composed of particles having a configuration in which the raw material is dispersed on the surface or inside of the base particles.
The raw material may be a substance having a radioactive substance removing action, a substance not having a radioactive substance removing action, or a substance having an unknown radioactive substance removing action.

If the radioactive material adsorbent particles are fine particles, it is difficult to separate the water from the radioactive material removal material even after solid-liquid separation after contacting the radioactive material-containing wastewater. A large amount of sludge will be generated. Therefore, it is preferable that the present radioactive substance adsorbent particles have a size that facilitates solid-liquid separation. From this viewpoint, the average particle diameter of the present radioactive substance adsorbent particles is preferably 1 mm or more. On the other hand, when the present radioactive substance adsorbent particles are too large, the surface area becomes small and the removal efficiency of the radioactive substance decreases, so that it is preferably 5 mm or less.
From this point of view, the average particle diameter of the present radioactive substance adsorbent particles is preferably 1 mm or more. In particular, considering contact efficiency and pressure loss, 1.5 mm or more or 5 mm or less, and especially 2 mm or more or 4 mm or less. Is particularly preferred.

The shape of the present radioactive substance adsorbent particles, in other words, the shape of the porous granular material (substrate) is arbitrary such as a spherical shape, an elliptical spherical shape, and a flat plate shape. Among them, the spherical shape is preferable in terms of dispersibility.
The radioactive material adsorbent particles are preferably a porous body containing a large number of voids leading from the particle surface to the inside in that the water to be treated can penetrate into the particles.

The metal alginate that constitutes the radioactive material adsorbent particles, when dropped into water containing divalent or higher metal ions such as barium ions or calcium ions, causes a gelation reaction instantly, It is known to make. For example, when a sodium alginate aqueous solution is dropped into a calcium chloride aqueous solution, sodium alginate and calcium chloride react to form a calcium alginate film on the surface of the sodium alginate aqueous solution, and the sodium alginate aqueous solution becomes spherical, so-called artificial seeds (Ikura) Is known to form.
Examples of the metal alginate that constitutes the present radioactive material adsorbent particles include sodium alginate, lithium alginate, potassium alginate, etc., among which sodium alginate, lithium alginate, and potassium alginate are preferable. Sodium alginate is particularly preferred.

(Raw material content)
From the viewpoint of the efficiency of removing radioactive substances, the present radioactive substance adsorbent particles preferably contain 60 w / w% or more of raw material in total as the total amount of raw materials on the surface and inside of the particle, and in particular, 70 w / w%. It is preferable to contain above.
What is necessary is just to adjust suitably the content rate of the ferrocyan compound in this radioactive substance adsorbent particle according to the content rate of the ferrocyan compound which the radioactive substance adsorption layer 1 or the radioactive substance adsorption layer 2 desires.
Further, in the present radioactive substance adsorbent particles, it is preferable that the raw material is dispersed at a uniform concentration on the surface and inside of the particles from the viewpoint of the radioactive substance removal efficiency.

(Method for producing the present radioactive substance adsorbent A)
The radioactive material adsorbent A includes a raw material sol preparation step of preparing a raw material sol solution by adding and dispersing a raw material to an aqueous solution of metal alginate, and dropping the raw material sol solution into an aqueous solution containing a gelling agent. To produce a calcium alginate gel, and a step of making the calcium alginate gel and a porous granulated product by drying the calcium alginate gel to release moisture (hereinafter referred to as “this production”). Method ").
However, the manufacturing method of this radioactive substance adsorbent A is not limited to this manufacturing method.

According to such a production method, it is possible to easily form a granular material at an arbitrary ratio easily by wrapping an arbitrary poorly water-soluble powdery raw material with a calcium alginate gel.
In addition, powder molding methods include rolling granulation molding, compaction molding, extrusion molding, etc., but all of these methods bring the compact into a compacted state. However, according to the present production method, the calcium alginate gel is dried to release moisture to remove voids in the particles. Therefore, it is possible to create a porous body containing many voids that lead from the particle surface to the inside, so that the water to be treated can easily enter the inside of the particle, so that the radioactive substance removing substance inside is also effective. Used.
Moreover, as will be described later, the particle size of the radioactive material adsorbent can be controlled by adjusting the concentration of the raw material to be added.

In the raw material sol preparation step, for example, a metal alginate as a solating agent is dissolved in water to prepare a viscous aqueous solution, and the raw material material is added to this aqueous solution and uniformly dispersed and mixed to form a raw material sol solution. Make it.
The metal alginate is soluble in water and becomes a viscous aqueous solution. The concentration of the aqueous solution of metal alginate is preferably 0.5 to 5 w / w%, particularly preferably v0.5 w / w% or more or 2 w / w% or less.
The amount of the raw material added to the aqueous solution of metal alginate is 5 w / w% or more, particularly 10 w / w% or more, or 20 w / w% or less with respect to the raw material sol solution, from the viewpoint of radioactive substance removal efficiency. preferable.

In the alginate gel preparation step, for example, a raw material sol solution containing a gelling agent such as calcium salt is prepared, and the raw material sol solution is dropped from a nozzle having an inner diameter of 2 mm to 3 mm into the gently stirred aqueous solution. By dripping, the calcium alginate gel which included the former raw material material uniformly is produced.
As the gelling agent, a metal salt having a valence of 2 or more can be used, and examples thereof include salts of barium, calcium, copper, iron, aluminum and the like. Specific examples include barium chloride, calcium chloride, copper sulfate, ferric chloride, polyaluminum chloride, and the like, among which calcium salts are particularly preferred for reasons such as price and safety in handling.
The calcium salt is not particularly limited as long as it is a water-soluble calcium salt such as a chloride salt, a bromide salt, or a nitrate. In view of price and the like, calcium chloride is preferable.
The concentration of the aqueous calcium salt solution is not particularly limited, but it is preferably 0.5 w / v% or more, particularly 1 w / v% or more from the viewpoint of gelation reactivity when an alginate sol is added. Or it is still more preferable that it is 5 w / v% or less.

In the porosification step, the granulated product can be made porous in the process of dehydrating the calcium alginate gel obtained as described above to dehydrate moisture from the granulated product.
Before the calcium alginate gel is dried, the calcium alginate gel may be washed with water or saline as necessary. Moreover, after freezing once at 0 degreeC--20 degreeC, you may add the process of performing the freezing and thawing | melting which makes this thaw. Excessive calcium ions can be removed by such washing, so that it can be expected to increase the removal rate of radioactive strontium similar to calcium, for example.

As the drying means, for example, known drying means such as natural drying, reduced pressure drying, and warm drying can be appropriately employed. Among these, heating drying is particularly preferable in terms of drying time.
The drying temperature is preferably 50 to 120 ° C., more preferably 50 ° C. or more or 100 ° C. or less, from the viewpoint of adjusting the size and ratio of voids inside the particles.

<This decontamination device>
The treatment apparatus for radioactive contaminated water according to the present embodiment (referred to as “the present decontamination treatment apparatus”) is an example of a treatment apparatus that can implement the present decontamination method.

The present decontamination treatment apparatus includes the radioactive substance adsorbing layer 1 and the radioactive substance adsorbing layer 2 in a path through which radioactively contaminated water (treated water) containing a radioactive substance is passed, and the radioactive substance adsorbing layer is provided. This is a radioactively contaminated water treatment apparatus having a configuration in which the radioactive substance adsorbing layer 1 is disposed upstream of the layer 2.
Here, the “path through which radioactively contaminated water (treated water) passes” includes tubes, towers, tanks, containers (including cartridge type), columns, and the like, and the form thereof is not particularly limited.

  As explained in the item of the present cleaning method, the substances constituting the radioactive substance adsorbing layers 1 and 2, that is, the hardly soluble ferrocyan compound and the other raw materials, for example, form particles containing the respective substances, The particles can also be formed by filling a container (including a reaction tower and a column). For example, the radioactive substance adsorbents 1 and 2 can be formed by filling the radioactive substance adsorbent A, in which the content of the hardly soluble ferrocyan compound is appropriately adjusted, into a container.

Moreover, the radioactive substance adsorption layers 1 and 2 may be one layer or two or more layers.
When the radioactive substance adsorbing layer 1 or 2 is composed of two or more layers, the mass ratio of the hardly soluble ferrocyan compound between the two or more radioactive substance adsorbing layers 1 or 2 may be the same or different. It may be a ratio. For example, it can also be formed so that the mass ratio of the hardly soluble ferrocyan compound increases as it goes downstream.

  In addition, when each of the radioactive substance adsorption layers 1 or 2 is composed of two or more layers, for example, two or more radioactive substance adsorption layers 1 and 2 can be provided in the same column, or in separate columns or cartridges. One radioactive substance adsorbing layer 1, 2 can also be provided.

  For example, in the reaction tank or reaction vessel, the radioactive substance adsorption layer 1 and the radioactive substance adsorption layer 2 and, if necessary, the CN adsorption layer 3 are formed in this order from the inlet, and flowed from the inlet of the reaction tank or reaction vessel. The present decontamination treatment apparatus is configured such that radioactive substance contaminated water (treated water) contacts the radioactive substance adsorption layer 1, the radioactive substance adsorption layer 2, and the CN adsorption layer 3 in this order, and the treated water is discharged from the discharge port. be able to.

  Moreover, the material which comprises the radioactive substance adsorption layer 1, the material which comprises the radioactive substance adsorption layer 2, and the material which comprises the CN adsorption layer 3 as needed are each filled in a separate reaction tank or reaction container, and radioactive. A substance adsorbing layer 1, a radioactive substance adsorbing layer 2 and a CN adsorbing layer 3 are formed, and first, radioactive substance contaminated water (treated water) is filled in a reaction vessel or reaction vessel filled with the material constituting the radioactive substance adsorbing layer 1. ) Through which the radioactive substance-contaminated water (treated water) drained from the drain of the reaction vessel or reaction vessel, and then the reaction vessel or reaction filled with the material constituting the radioactive substance adsorption layer 2 Water to be treated was passed through the container, and the radioactive substance contaminated water (treated water) drained from the reaction vessel or the drain of the reaction vessel was filled with the material constituting the CN adsorption layer 3. Pass the water to be treated into the reaction vessel or reaction vessel, and This removal washing apparatus configurations that can be obtained as a drained treated water from the drain outlet of 応槽 or reaction vessel may also be mentioned.

If the radioactive substance contaminated water (treated water) is treated using the present cleaning apparatus having the above-described configuration, the radioactive substance can be effectively removed from the treated water. In addition to the fact that a large facility such as a coagulation sedimentation treatment device is not required, you can enjoy the advantage of not generating sludge slurry as processing waste, and by combining various radioactive substance removal substances, you can combine multiple nuclides into one It can be removed simultaneously in the filling tank, and can be said to be a highly versatile treatment method.
In particular, considering the need for treatment of radioactive waste after treatment, there is no need to take out the packed tower, which has a high exposure risk for workers, and it is possible to dispose of the treated column as it is. A column method is more preferable.

  The radioactive substance adsorbing layer 1 and the radioactive substance adsorbing layer 2 are composed of a material constituting each layer, that is, particles made of a hardly soluble ferrocyan compound and particles made of other raw materials, with a predetermined ferrocyan compound content. Each layer may be formed by mixing so as to be, or formed from particles previously adjusted to have a predetermined ferrocyan compound content, for example, the present radioactive substance adsorbent (A). You may do it.

FIG. 5A is a view showing an example of a cartridge-type reaction container, that is, a detachable container, and FIG. 5B is a view showing the flow of water in the cartridge-type reaction container.
The main body of the reaction vessel can be formed from a synthetic resin such as FRP, a metal such as lead, aluminum or stainless steel, or other materials.
An inflow port and a drain port are provided at the upper part of the container body, and a water collecting pipe 4 extending to the bottom of the container through the inside of the container is connected to the drain port, and a water collecting part provided at the lower end of the water collecting pipe 4 4a is arrange | positioned at the bottom part in a container main body.
A radioactive substance adsorbing layer 1, a radioactive substance adsorbing layer 2, and a CN adsorbing layer 3 are formed in the container main body in order from the upper part to the lower part of the container main body, and the water collecting part is arranged in the CN adsorbing layer 3. It is installed.
And the said inflow port is connected with the to-be-processed water distribution pipe 5 so that attachment or detachment is possible, and the said drain outlet is connected with the to-be-treated water distribution pipe so that attachment or detachment is possible.

  As shown in FIG. 5 (B), radioactive substance contaminated water (treated water) flows into the container from the treated water circulation pipe 5 through the inlet and becomes a downward flow to adsorb the radioactive substance. The layer 1, the radioactive material adsorption layer 2, and the CN adsorption layer 3 are passed through in this order, and are treated while being in contact with each layer. The treated water thus treated is collected in the water collecting portion at the bottom of the container (in the CN adsorption layer 3). Water is collected into the water collection pipe 4 from 4a and discharged to the treated water distribution pipe 5 through the drain outlet at the upper end of the water collection pipe.

Next, a specific example in which the present cleaning apparatus is formed using a cartridge type reaction container will be described.
However, in addition to those described here, the radioactive concentration of the treated water, the allowable radioactive concentration of the treated water, the allowable radioactive concentration of the adsorbent after treatment, the allowable surface dose of the post-treatment column, and the allowable replacement frequency of the column In consideration of the above, it is possible to select various combinations of the adsorbent packing pattern in the column, the combination of the number of column stages to be connected, and the like and adopt various apparatus flow modes.

  FIG. 6 shows a book consisting of a cartridge type reaction vessel 6 having a structure in which a radioactive substance adsorbing layer 1 and a radioactive substance adsorbing layer 2 are stacked and filled in the cartridge type reaction vessel in order from the upper part of the container main body downward. It is a decontamination processing device.

  Since the radioactive substance adsorption layer 1 contains a small amount of a poorly soluble ferrocyan compound dispersed therein, the radioactive cesium does not concentrate in the inflow portion and is adsorbed in a high amount of contamination, and the radioactive substance adsorption layer 1 It can be dispersed and adsorbed as a whole. Next, by passing water through the radioactive substance adsorbing layer 2, radioactive cesium can be removed to below the emission standard.

  In addition, since this cartridge type reaction vessel 6 does not include the CN adsorbing layer 3 as described above, the acidity of the water to be treated is adjusted to a pH (pH about 3 to 5) at which it is difficult to elute the water-soluble ferrocyan compound. In addition, it is preferable to pass water through the cartridge type reaction vessel.

  FIG. 7A includes a cartridge-type reaction vessel in which a radioactive substance adsorption layer 1, a radioactive substance adsorption layer 2, and a CN adsorption layer 3 are stacked and filled sequentially from the upper part of the container body toward the lower side. A decontamination apparatus comprising a cartridge type reaction vessel 7A is shown.

In this radioactive substance adsorbing layer 1, since a slightly soluble ferrocyan compound is present in a small amount and dispersed, the radioactive cesium is not concentrated in the inflow part and adsorbed in a high amount of contamination, and the radioactive substance adsorbing layer 1 can be dispersed and adsorbed and removed throughout.
Next, by passing water through the radioactive substance adsorbing layer 2, radioactive cesium can be removed to below the emission standard.
Furthermore, elution to the treated water of a water-soluble ferrocyan compound can be suppressed by passing water through the CN adsorption layer 3. In this case, it is not necessary to adjust the acidity of the water to be treated unlike the cartridge type reaction vessel 6.

FIG. 7B shows an apparatus having a configuration in which a cartridge type reaction vessel 7B formed with a radioactive substance adsorbing layer 1 formed therein is connected to the upstream side of the cartridge type reaction vessel 7A, that is, upstream. Yes.
By connecting the cartridge type reaction vessel 7B to the front stage of the cartridge type reaction vessel 7A, it is suitable when a longer-term treatment is required.

  Further, as shown in FIG. 7C, an apparatus having a configuration in which two or more cartridge-type reaction vessels 7B are connected to the upstream side, that is, the upstream side of the cartridge-type reaction vessel 7A can be used. In this way, by connecting a larger number of cartridge type reaction vessels 7B to the front stage of the cartridge type reaction vessel 7A, it is suitable when a longer period of processing is required.

FIG. 8A shows that a cartridge type reaction vessel 8A formed with the radioactive substance adsorbing layer 1 in the cartridge type reaction vessel is disposed on the most upstream side, and the container is provided at the drain port with the cartridge type reaction vessel. A dewashing treatment apparatus having a configuration in which a cartridge type reaction vessel 8B having a configuration in which a radioactive substance adsorption layer 2 and a CN adsorption layer 3 are stacked and filled in order from the upper part of the main body is connected is shown. Yes.
By comprising in this way, the elution to the treated water of a water-soluble ferrocyan compound can further be suppressed compared with the de-washing processing apparatus shown to FIG. 7 (A).

  FIG. 8B is an apparatus having a configuration in which a cartridge type reaction vessel 8A formed with a radioactive substance adsorbing layer 1 therein is further connected upstream of the cartridge type reaction vessel 8B, that is, upstream. . By connecting two cartridge-type reaction vessels 8A and 8A upstream of the cartridge-type reaction vessel 8B, it is suitable when a longer period of processing is required.

  Further, as shown in FIG. 8C, an apparatus having a configuration in which three or more cartridge-type reaction vessels 8A are connected to the upstream side of the cartridge-type reaction vessel 8B, that is, upstream. It is. In this way, by increasing the number of cartridge type reaction vessels 8A connected to the front stage of the cartridge type reaction vessel 8B, it is suitable when a longer period of processing is required.

  FIG. 9A shows a cartridge type reaction vessel 9A having a configuration in which a radioactive substance adsorbing layer 1 and a radioactive substance adsorbing layer 2 are stacked and filled in the cartridge type reaction vessel from the upper part of the container main body in the downward direction. A decontamination treatment apparatus having a configuration in which the cartridge type reaction vessel 9B having a configuration in which the CN adsorption layer 3 is formed in the cartridge type reaction vessel is connected to the drain port at the most upstream side. It is. The elution of the water-soluble ferrocyan compound into the treated water can be further suppressed as compared with the dewashing treatment apparatus shown in FIG.

FIG. 9B shows an apparatus having a configuration in which a cartridge type reaction container 9C having a radioactive substance adsorbing layer 1 formed therein is connected upstream of the cartridge type reaction container 9A. By connecting the cartridge type reaction container 9C to the front stage of the cartridge type reaction container 9A in this way, it is suitable when a longer-term treatment is required.
FIG. 9C shows an apparatus having a configuration in which two or more cartridge-type reaction vessels 9C are connected to the upstream side, that is, the upstream side of the cartridge-type reaction vessel 9A. By increasing the number of cartridge-type reaction vessels 9C connected to the preceding stage of the cartridge-type reaction vessel 9A in this way, it becomes possible to cope with longer-term processing.

  FIG. 10 (A) shows a cartridge type reaction vessel 10A provided with only the radioactive substance adsorption layer 1 in the upstream thereof, and a cartridge type provided only with the radioactive substance adsorption layer 2 at the drain thereof. This is a decontamination apparatus having a configuration in which a reaction vessel 10B is connected and a cartridge type reaction vessel 10C having only the CN adsorption layer 3 therein is connected to the drain port. It can cope with the treatment of water to be treated having a higher radioactivity concentration than the apparatus shown in FIGS.

FIG. 10B shows an apparatus having a configuration in which another (total of two) cartridge-type reaction vessels 10A are connected to the previous stage, that is, the upstream side of the cartridge-type reaction vessel 10B.
FIG. 10C shows an apparatus having a configuration in which another (a total of three) cartridge-type reaction vessels 10A are connected to the upstream side of the cartridge-type reaction vessel 10B, that is, the upstream side.
As described above, by increasing the number of cartridge-type reaction vessels 10A connected to the front stage of the cartridge-type reaction vessel 10B, it becomes possible to cope with longer-term processing.

In addition, in the cleaning treatment apparatus of each structure, the radioactive substance adsorption layer 1, the radioactive substance adsorption layer 2, or both of these layers may contain a water-soluble ferrocyan compound adsorbent.
If the radioactive substance adsorption layer 1 or the radioactive substance adsorption layer 2 or both layers contain a water-soluble ferrocyan compound adsorbent, the treatment of the water-soluble ferrocyan compound without adjusting the acidity of the water to be treated Elution into water can be suppressed. In addition, elution of the water-soluble ferrocyan compound from the waste can be suppressed even at the time of disposal of the waste after the treatment.

(Merry-go-round method)
When forming this decontamination treatment apparatus using a cartridge-type reaction vessel (also simply referred to as a “column”) as described above, the packed adsorbent can be used more effectively by adopting a water flow method called a merry-go-round method. can do.

  Hereinafter, as shown in FIG. 11, a merry-go-round process will be described based on an operation example of an apparatus in which the cartridge type reaction vessel 7A shown in FIG.

In the first round process shown on the left in FIG. 11, since water is passed in the order of the column 11A, the column 11B, and the column 11C from the treated water inflow side, the column 11A is first adsorbed among these columns. The substance concentration is high, and the saturated adsorption amount is first reached with respect to the concentration of the substance to be treated in the water to be treated. On the other hand, at this point, the columns 11B and 11C have not yet reached saturation adsorption.
Therefore, as shown in the center of FIG. 11, the column 11A that has reached saturation adsorption is removed as a used column, and a new column 11D is arranged on the most downstream side, and the column 11B, the column 11C, and the column 11D are connected in this order. .
Then, as shown on the right side of FIG. 11, the second round process is resumed, and the process is continued until the column 11B reaches saturation adsorption.
Similarly, the process after the third round of removing the column when the most upstream column reaches saturation adsorption and connecting the new column to the most downstream side may be repeated.

  In this way, since a plurality of columns are operated while being sequentially switched from the downstream side to the upstream side, this processing method is called a merry-go-round method. The advantage of this method is that the adsorbents of all the columns can be used effectively until reaching almost saturated adsorption, and a new column is always arranged in the most downstream, so that the quality of the treated water can always be kept good. .

  Although FIG. 11 shows an example in which columns are connected in three stages, the operation of the merry-go-round method is the same in both cases where the columns are connected in two stages and when the columns are connected in four or more stages. Is possible.

<Explanation of words>
In the present specification, when expressed as “X to Y” (X and Y are arbitrary numbers), unless otherwise specified, “X is preferably greater than X” or “preferably Y”. It also includes the meaning of “smaller”.
In addition, when expressed as “X or more” (X is an arbitrary number) or “Y or less” (Y is an arbitrary number), it is “preferably greater than X” or “preferably less than Y”. Includes intentions.

(Radioactive material adsorbent 2-1)
Iron ferrocyanide (III) is mixed in a 1 w / v% sodium alginate aqueous solution, and a raw material sol solution (alginate of iron (III) ferrocyanide 13 w / w% by weight composition ratio, 0.9 w / w% sodium alginate). Sodium sol) was prepared.
This raw material sol solution was dropped into a gelling agent composed of a 4 w / v% calcium chloride solution to obtain a spherical wet gel. And the obtained wet gel was dried at the drying temperature of 50 degreeC for 12 hours, and spherical porous body granulated material (radioactive substance adsorption material 2-1) was obtained.
The radioactive substance adsorbent 2-1 thus obtained has porous particles containing a metal alginate (calcium alginate) as base particles, and iron (III) ferrocyanide is scattered on the surface or inside of the base particles. The ratio of the content mass of ferric ferrocyanide to the filling volume of the radioactive substance adsorbing material 2-1 was 550 g / L.

(Radioactive material adsorbent 2-2, 1-1 to 1-4)
Ferrous ferrocyanide (III) and kaolin were mixed in a 1 w / v% sodium alginate aqueous solution to prepare a raw material sol solution (sodium alginate sol) having a weight composition ratio shown in Table 1.
This raw material sol solution was dropped into a gelling agent composed of a 4 w / v% calcium chloride solution to obtain a spherical wet gel. And the obtained wet gel was dried at the drying temperature of 50 degreeC for 12 hours, and spherical porous body granulated material (radioactive substance adsorption material 2-2, 1-1 to 1-4) was obtained.
The radioactive material adsorbent thus obtained has porous particles containing a metal alginate (calcium alginate) as base particles, and iron (III) ferrocyanide and kaolin are scattered on the surface or inside of the base particles. The ratio of the content of ferric ferrocyanide (III) to the filling volume of each radioactive material adsorbent is as shown in Table 1. there were.

(Radioactive material adsorbent 2-3, 1-5 to 1-8)
Ferrite iron (III) and powdered zeolite were mixed in a 1 w / v% sodium alginate aqueous solution to prepare a raw material sol solution (sodium alginate sol) having a weight composition ratio shown in Table 1.
This raw material sol solution was dropped into a gelling agent composed of a 4 w / v% calcium chloride solution to obtain a spherical wet gel. And the obtained wet gel was dried at the drying temperature of 50 degreeC for 12 hours, and spherical porous body granulated material (radioactive substance adsorption material 2-3, 1-5-1-8) was obtained.
The radioactive material adsorbent thus obtained has porous particles containing a metal alginate (calcium alginate) as base particles, and iron (III) ferrocyanide and zeolite are scattered on the surface or inside of the base particles. The ratio of the content of ferric ferrocyanide (III) to the filling volume of each radioactive material adsorbent is as shown in Table 1. there were.

(Radioactive material adsorbent 2-4, 1-9 to 1-12)
Ferrite iron (III) and activated carbon were mixed in a 1 w / v% sodium alginate aqueous solution to prepare a raw material sol solution (sodium alginate sol) having a weight composition ratio shown in Table 1.
This raw material sol solution was dropped into a gelling agent composed of a solution containing 3 w / w% calcium chloride and 1 w / v% polyaluminum chloride to obtain a spherical wet gel. And the obtained wet gel was dried at the drying temperature of 50 degreeC for 12 hours, and spherical porous body granulated material (radioactive substance adsorption material 2-4, 1-9 to 1-12) was obtained.
The radioactive material adsorbent thus obtained has porous particles containing alginate metal salt (calcium alginate and aluminum alginate) as base particles, and the poorly soluble ferrocyanide compound (iron ferrocyanide) and activated carbon are the base particles. Of iron (III) ferrocyanide with respect to the filling volume of each radioactive material adsorbent, consisting of particles with a structure dispersed on the surface or inside of the steel (average particle size of 2 to 3 mm) Was as shown in Table 1.

(Radioactive material adsorbent 2-5, 1-13 to 1-16)
Ferrite iron (III), powdered zeolite and activated carbon were mixed in a 1 w / v% sodium alginate aqueous solution to prepare a raw material sol solution (sodium alginate sol) having a weight composition ratio shown in Table 1.
This raw material sol solution was dropped into a gelling agent composed of a solution containing 3 w / v% calcium chloride and 1 w / v% polyaluminum chloride to obtain a spherical wet gel. And the obtained wet gel was dried at the drying temperature of 50 degreeC for 12 hours, and spherical porous body granulated material (radioactive substance adsorption material 2-5, 1-13 to 1-16) was obtained.
The thus obtained radioactive material adsorbent comprises porous particles containing metal alginate (calcium alginate and aluminum alginate) as base particles, and iron (III) ferrocyanide, powdered zeolite and activated carbon are the base particles. Of iron (III) ferrocyanide with respect to the filling volume of each radioactive material adsorbent, consisting of particles with a structure dispersed on the surface or inside of the steel (average particle size of 2 to 3 mm) Was as shown in Table 1.

<Test 1>
A radioactive substance adsorbent 2-1 was packed in 400 mL in a column having an inner diameter of 50 mm, and this column was connected in five stages as shown in FIG.
Seawater containing 100 Bq / L of radioactive cesium (pH 7.3, salt concentration 3.6 w / w%) was added to this treatment apparatus at a water passage speed of LV = 2 m / hour and a water passage magnification of 250 times (L / L). -Adsorbent).
Thereafter, the adsorbent was taken out from each column and mixed uniformly, and the radioactivity concentration of each adsorbent was measured.

  A similar water flow test was also performed for the radioactive material adsorbent 2-2. The results are shown in Table 2.

In the case of the radioactive substance adsorbent 2-1, in which the content of ferrous ferricyanide (III) with respect to the packed volume is 550 g / L, the radioactive concentration of each column packed adsorbent after treatment is the first and second stages. The third stage, the fourth stage, and the fifth stage were 179,000, 7,900, 1,000, 250, and 110 Bq / kg (all values in terms of dry matter, hereinafter the same). It was found that the adsorbent in the second and subsequent stages was hardly used effectively, while it was adsorbed intensively only in the first stage and reached an extremely high radioactivity level.
Further, in the case of the radioactive substance adsorbent 2-2 in which the content of ferrous ferrocyanide (III) with respect to the packed volume is 28 g / L, the radioactive concentration of each column packed adsorbent after the treatment is the first stage, The stage, the third stage, the fourth stage, and the fifth stage were 94,000, 39,000, 11,000, 6,000, and 3,800 Bq / kg, respectively. Although it is not as much as radioactive material adsorbent 2-1, the first and second stages on the inlet side are intensively adsorbed to a high radioactivity level, while the radioactivity levels after the third stage are compared. It turned out to be minor.
Such a tendency was the same for the radioactive substance adsorbents 2-3, 2-4, and 2-5 in which the content of ferric ferrocyanide (III) with respect to the filling volume was 28 g / L.

<Test 2>
Radioactive material adsorbent 1-1, 1-2 in which the content of iron (III) ferrocyanide with respect to the filling volume is 11, 3, 1, 0.4 g / L, respectively, in the same water flow test as in Test 1-1 , 1-3 and 1-4 were also carried out. Each result is shown in Table 3.

The radioactive concentration of the first-stage, second-stage, third-stage, fourth-stage, and fifth-stage column-filled adsorbents after treatment is 61,000, 45 in the case of radioactive substance adsorbent 1-1, respectively. 000, 38,000, 26,000, 15,000 Bq / kg, in the case of radioactive material adsorbent 1-2, 42,000, 38,000, 32,000, 29,000, 21,000 Bq / kg, radioactive material In the case of the adsorbent 1-3, 33,000, 31,000, 30,000, 30,000, 26,000 Bq / kg, and in the case of the radioactive substance adsorbent 1-1, 31,000, 31,000, 30, 000, 30,000, 30,000 Bq / kg. It was found that the radioactivity level of the packed adsorbent after this treatment was almost uniform throughout.
Such a tendency is a combination of radioactive material adsorbents 1-5, 1-6, 1-7, 1-8, a combination of radioactive material adsorbents 1-9, 1-10, 1-11, 1-12, The same applies to the combinations of radioactive material adsorbents 1-13, 1-14, 1-15, and 1-16.

<Test 3>
50 L of radioactive material adsorbent 1-3, 1 L of radioactive material adsorbent 2-1 and 3 L of granular activated carbon as a water-soluble ferrocyan compound adsorbent are packed in this order into a cartridge-type column column with an inner volume of 54 L and a diameter of 260 mm. Then, as shown in FIG. 5, a cartridge type column (see FIG. 5) having three adsorbent layers in the container was produced.
Then, 10 m ^{3 of} seawater (pH 7.3, salt concentration 3.6 w / w%) containing a radioactive cesium concentration of 100 Bq / L was passed through this cartridge type column at 10 L / min.

As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L according to the ministerial ordinance (final revision: Ministry of the Environment Ordinance No. 15 on May 23, 2013) that establishes drainage standards.
Moreover, the radioactivity density | concentration of the upper layer of the layer filled with the radioactive substance adsorbent 1-3 after a process, and a lower layer is 32,000, 29,000 Bq / kg, respectively, and the radioactivity of the layer filled with the radioactive substance adsorbent 2-1. The concentration was 40,000 Bq / kg , and in particular, a site where the radioactivity concentration was extremely high locally was not observed.

<Test 4>
As a water-soluble ferrocyan compound adsorbent, a test similar to the above test was conducted except that an anion exchange resin (strongly basic anion exchange resin Evaion 500 manufactured by Mizuing Co., Ltd.) was used instead of granular activated carbon. The radioactive concentration of the treated water is less than 10 Bq / L, the total cyan concentration is less than 0.01 mg / L, and the layer filled with the radioactive substance adsorbent 1-3 after the treatment and the radioactive substance adsorbent 2-1 As for the layer filled with, the site where the radioactivity concentration was extremely high was not recognized.

<Test 5>
The radioactive substance adsorbent 1-11 is 50L, the radioactive substance adsorbent 2-4 is 4L, and the cartridge type column (see FIG. 6) having an inner volume of 54L, which is packed in this order from the upper layer to the lower layer, has a radioactive cesium concentration of 100Bq. The seawater containing / L was passed through 10 m ³ at 10 L / min.
As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L.
The radioactivity concentration of the radioactive material adsorbent 1-11 a packed bed was upper and lower activity concentrations, respectively 29,000,27,000Bq / kg, layer filled with radioactive material adsorbent 2- 4 after treatment Was 38,000 Bq / kg , and in particular, a site where the radioactivity concentration was extremely high locally was not observed.

<Test 6>
Radioactive substance adsorbent 3 produced under the same conditions as radioactive substance adsorbent 1-3 and radioactive substance adsorbent 2-1, except that ferrocyanide copper (II) was used instead of ferrocyanide (III) −3 and radioactive substance adsorbent 4-1 were replaced with radioactive substance adsorbent 1-3 and radioactive substance adsorbent 2-1, respectively, and test 5 was performed under the same conditions as in test 3.
As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L.
In addition, in the layer filled with the radioactive substance adsorbent 3-3 and the radioactive substance adsorbent 4-1 after the treatment, a site where the radioactivity concentration was extremely high was not recognized.

<Test 7>
The radioactive material adsorbent 5 produced under the same conditions as the radioactive material adsorbent 1-3 and the radioactive material adsorbent 2-1, except that nickel ferrocyanide (II) was used instead of the ferric iron ferricide (III). −3 and radioactive substance adsorbent 6-1 were replaced with radioactive substance adsorbent 1-3 and radioactive substance adsorbent 2-1, respectively, and test 7 was performed under the same conditions as in test 4.
As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L.
In addition, in the layer filled with the radioactive substance adsorbent 5-3 and the radioactive substance adsorbent 6-1 after the treatment, a site where the radioactivity concentration became extremely high locally was not recognized.

<Test 8>
Radioactive material adsorbent 7 produced under the same conditions as radioactive material adsorbent 1-3 and radioactive material adsorbent 2-1, except that cobalt ferrocyanide (II) was used in place of ferric ferrocyanide (III) −3 and radioactive substance adsorbent 8-1 were replaced with radioactive substance adsorbent 1-3 and radioactive substance adsorbent 2-1, respectively, and test 8 was performed under the same conditions as in test 5.
As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L.
In addition, in the layer filled with the radioactive substance adsorbent 7-3 and the radioactive substance adsorbent 8-1 after the treatment, a site where the radioactivity concentration was extremely high was not recognized.

<Test 9>
Radioactive material adsorbent 7 produced under the same conditions as radioactive material adsorbent 1-3 and radioactive material adsorbent 2-1, except that iron ferrocyanide (II) was used instead of ferric ferricide (III) −3 and radioactive substance adsorbent 8-1 were replaced with radioactive substance adsorbent 1-3 and radioactive substance adsorbent 2-1, respectively, and test 8 was performed under the same conditions as in test 5.
As a result, the radioactive concentration of the treated water was less than 10 Bq / L, and the total cyanide concentration was less than 1 mg / L.
In addition, in the layer filled with the radioactive substance adsorbent 7-3 and the radioactive substance adsorbent 8-1 after the treatment, a site where the radioactivity concentration was extremely high was not recognized.

Claims (4)

A first radioactive substance containing a poorly soluble ferrocyan compound that reduces the concentration of radioactivity by contacting the treated water (radioactive contaminated water) containing the radioactive substance to adsorb and remove the radioactive substance in the treated water An adsorption layer (1);
Activity concentration contacting the water to be treated is reduced for adsorbing and removing radioactive material from the first radioactive substance-adsorbing layer (1), radioactive substance-adsorbing content of the first insoluble ferrocyanide compound A second radioactive material adsorbing layer (2) higher than the layer (1) ,
In the first radioactive substance adsorbing layer (1), the ratio of the mass content of the hardly soluble ferrocyan compound to the filling volume is 0.4 g / L or more and 11 g / L in the path through which the water to be treated is passed. And
The second radioactive substance adsorbing layer (2) is characterized in that the ratio of the mass content of the hardly soluble ferrocyan compound to the filling volume is higher than 11 g / L and not higher than 550 g / L. Processing equipment. At least one of the first radioactive substance adsorbing layer (1) and the second radioactive substance adsorbing layer (2) contains a water-soluble ferrocyan compound adsorbent having an action of adsorbing a water-soluble ferrocyan compound. The apparatus for treating radioactive contaminated water according to claim 1. CN adsorption layer containing a water-soluble ferrocyan compound adsorbent for further passing the treated water that has passed through the first radioactive substance adsorption layer (1) and the second radioactive substance adsorption layer (2) (3) The radioactively contaminated water treatment apparatus according to claim 1 or 2, The first radioactive substance adsorbing layer in which the ratio of the mass content of the hardly soluble ferrocyan compound to the filling volume is 0.4 g / L or more and 11 g / L or less in the water to be treated (radioactive contaminated water) containing the radioactive substance Pass water to (1),
Thereafter, the ratio of the mass of the hardly soluble ferrocyan compound to the filling volume is higher than 11 g / L and the water is passed through the second radioactive substance adsorbing layer (2) having a capacity of 550 g / L or less . How to treat contaminated water.

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