JP6254064B2 - Powdered radioactive material adsorbent - Google Patents

Description

  The present invention relates to a technique for adsorbing a radioactive substance from a liquid contaminated with a radioactive substance (cesium, strontium, etc.) and purifying the contaminated liquid, and a technique for adsorbing and capturing the radioactive substance from the contaminated liquid. The present invention relates to a technique for solidifying highly granular zeolite into a shape that can be easily adsorbed and captured, and a form that can be easily adsorbed and captured and a form that is easy to install, exchange, transport, and discard.

  Radioactive materials released to the mountains, fields, and buildings in the nuclear reactor are attached to and deposited on various materials and washed with water to decontaminate them. In addition to flush water, it is washed out with rainwater, and the water in rivers, waterways and drainage channels contains radioactive substances. In addition, groundwater is in contact with the furnace and contains radioactive material. Furthermore, the reactor cooling water is also contaminated with radioactive materials, and the contaminated water is temporarily stored in a water storage tank.

Water contaminated with these radioactive substances is captured by a device that adsorbs, adheres to and removes the radioactive substances, and purified treated water with a low degree of pollution is released to the sea or the like. As a radioactive material adsorbent used in this apparatus, granular zeolite is widely used. However, the zeolite is arranged in a granular form so that it is confined so as not to flow down with water in the water passage or in a water passage container / equipment and is exposed to the liquid.
When the radioactive substance is sufficiently adsorbed, the granular zeolite is taken out and used in a form in which a new granular zeolite is filled in a constrained region or in a constrained container / equipment. This technique is known in Patent Documents 1 and 2.

  However, the removal of the zeolite adsorbed with the radioactive substance is a zeolite having a high radioactivity and is in the form of fluid particles, so that the removal treatment work becomes dangerous and requires careful work. In addition, since the container / equipment that contains the zeolite is also contaminated by the radioactive material, the disposal / decontamination work of the container / equipment remains. Furthermore, a post-treatment of the disposal of the zeolite itself that adsorbs a large amount of the recovered radioactive substance is required. This waste treatment is solidified with cement, glass, etc. and then buried in the secondary disposal site.

  As described above, post-treatment of radioactive material with granular zeolite is difficult or troublesome solidification work remains.

  In addition, the structure for using granular zeolite as a filter and allowing it to enter and exit requires a water-permeable restraining device such as a container / equipment, and the installation is complicated.

Furthermore, the formation of an adsorbing layer on the inner wall, ceiling, floor, etc. of a building has been difficult with granular zeolite in order to purify the air in a contaminated air atmosphere where radioactive materials are diffused in the air.
In addition, the applicant has developed a water purification and greening block by using alumina cement and activated silica to enclose charcoal and producing a coherent block. However, in this cited document 3, there was no disclosure or suggestion about the adsorption of radioactive substances and the use / purpose of zeolite (see cited document 3).

  In addition, it is conceivable that granular zeolite is mixed in the cement component of Portland cement and water is added to solidify it into a plate shape, a columnar shape, or a wall shape. When a large amount of components are required and the result is concrete, the water permeability is low, the zeolite is embedded in the concrete, there is no contact with the outside water and liquid, and the adsorptive power of radioactive materials is greatly increased. descend.

Japanese Patent No. 5314213 JP 2013-120097 A Japanese Patent No. 3748870

  The problem to be solved by the present invention is to solve these conventional problems, and by mixing a large amount of zeolite with a special cement-based solidifying material and adding water to knead, a large amount of zeolite with a small amount of solidifying material In addition, the solidified body can be solidified to a required shape and size, and the solidified body has high water permeability, so that the radioactive adsorptive power of the zeolite enclosed therein can be sufficiently exhibited. Furthermore, by solidifying it, it is possible to make it into a pipe shape, a plate shape, or a container shape, and easily form it into a form that is easily adsorbed or easy to use, so that loading and unloading can be easily performed. Moreover, it is to make it possible to use underground walls by forming underground walls.

  Furthermore, the adsorbent can be easily removed after adhering a high radioactive substance by using it as an adsorbent for radioactive substances, and it can be easily and quickly stored / moved in a safe place and buried deep in the ground. is there.

The configuration of the present invention that solves this problem is as follows.
1) As a powdered cementitious solidified material, a cemented solidified material in which 2 to 5 parts by weight of active silica and 1 to 3 parts by weight of powdered zirconia are mixed with 100 parts by weight of alumina cement is used. Powdered radioactive material adsorbent obtained by mixing powdered zeolite in a weight ratio of 1: 2 to 4 with respect to the solidified material
It is in.

The cement-based solidified material of the present invention is a mixture of activated silica containing alumina cement as a main component. When kneaded with water, the pozzolanic reaction rate is large. Even if they are connected and contain a large amount of zeolite, the required strength can be exhibited. In addition, the solidified body has high water permeability and allows the inner zeolite to be in good contact with the outer liquid / water, and is expressed without inhibiting the radioactive substance adsorption power of the zeolite.
Moreover, when zirconia is mixed and solidified, zirconia has oxide ion conductivity and makes the function of zeolite effective, and further has high toughness due to phase transformation or microcracking mechanism.
Therefore, the solidified body of the present invention has high water permeability and radioactive substance adsorption power, and can obtain the required strength and toughness.
Moreover, by being solidified, it can be made into a shape that is easy to use, such as a pipe shape, a plate shape, a container shape, and the like, and its entry / exit and storage / transfer / disposal are also quick and easy.

  In particular, the granular zeolite, which is said to have a high adsorptive power for radioactive substances, is used for a granular cementitious solidified material in which 2 to 5 parts by weight of active silica and 1 to 3 parts by weight of zirconia are mixed in 100 parts by weight of alumina cement. A powdery radioactive material adsorbent in which powdery zeolite is mixed at a weight ratio of 1: 2 to 4, and a required amount of water is added to the mixture to knead to form a plate, pipe, or container. It can be solidified into solids of various shapes and sizes, so that it can be easily and quickly placed in contact with contaminated liquids, and can be easily and quickly replaced. Can be embedded easily.

  Moreover, the solidification by the cement-based solidified material can obtain a higher water permeability than the Portland cement solidified material, and can fully utilize the radioactive substance adsorbing power of the solidified zeolite.

In addition, the solidified shape can be cylindrical, pipe-shaped, plate-shaped, water storage container-shaped, wall-shaped, or layered, easy-to-use solid shape, and easy to install in waterways and water tanks.
In addition, it is easy to carry out, transport, store and embed the solidified material that absorbs a lot of radioactive material after use because it is a solid material. Therefore, post-treatment after adsorption of the radioactive material on the zeolite can be performed easily and quickly.

FIG. 1 is a longitudinal sectional view showing an example of using a bottomed cylindrical radioactive substance adsorbent as a filter cylinder for purification in a contaminated water storage tank of Example 1. FIG. FIG. 2 is a cross-sectional view of the first embodiment. FIG. 3 is an explanatory diagram showing an experiment of water permeability of the filter cylinder of Example 1. FIG. 4 is an explanatory view showing various embodiments of the present invention. FIG. 5 is an explanatory diagram of an embodiment of the underground wall of the building. FIG. 6 is an explanatory diagram showing the time-dependent change of Sr in the ICP-MS analysis result of the Sr adsorption test of each sample 1 and 2 of Formulation Examples 1 and 2. FIG. 7 is an explanatory diagram showing the change over time of Cs in the results of ICP-MS analysis of the Cs adsorption test of each sample 1 and 2 of Formulation Examples 1 and 2.

Here, the active silica used in the present invention is an amorphous material composed of spherical ultrafine particles having a specific surface area of about 100,000 to 300,000 cm ² / g and an average particle diameter of about 0.1 to 0.2 μm. Mainly silicon dioxide (generally 90% by weight or more), trace amounts of oxides (sodium oxide, aluminum oxide, potassium oxide, calcium oxide, titanium dioxide, iron dioxide, strontium oxide, zirconium oxide, niobium oxide, yttrium oxide, etc.) And can function as a pozzolana. Such activated silica is commercially available, for example, as a microsilica series from Elchem Japan Kogyo Co., Ltd.

In the granular cementitious solidified material of the present invention, the water permeability is poor when the active silica exceeds 2 to 5 parts by weight and the zirconia exceeds 1 to 3 parts by weight with respect to 100 parts by weight of the alumina cement. The inner structure was weak and lacked in strength, or the outer periphery of the zeolite was closed, which reduced the original function of the zeolite.
Moreover, it was good that zeolite was mixed at a weight ratio of 200 to 400 with respect to 100 parts by weight of the granular cementitious solidified material. If it is less than 200 parts by weight, the function of the zeolite is weakened, and if it exceeds 400 parts by weight, the strength as a solid material is weakened and easily broken.

1 and 2 show a first embodiment of a radioactive substance adsorption structure in a contaminated liquid storage tank.
The present invention will be described with reference to various embodiments shown in FIGS.
1 and 2, the reference numeral 1 is a reservoir tank for contaminated liquid containing radioactive substances of cesium and strontium, 11 is a contaminated liquid injection pipe with a valve, and 12 is a discharged discharged liquid with a valve. A tube, 13 is a tank lid, 2 is a filter cylinder which is a radioactive substance adsorbent solidified into a bottomed cylinder, and 21 is a stainless steel perforated with a large number of fine holes attached to the inner peripheral surface of the filter cylinder The inner cylinder, 22 is a suction pipe, 23 is a pump connected to the suction pipe, and 24 is a lid of the filter cylinder 2.

FIG. 3 is an explanatory view of the water permeability experiment of the present invention.
In FIG. 3, 3 is a water-resistant water container for water permeability experiments, 31 is a cement-based solidified material shown in Table 1, and zeolite and water are mixed and kneaded in the ratio of Formulation Example 1 in Table 3. The filter cylinder of the example produced in this way, 32 is a liquid containing an ash component, and 33 is permeated water in the filter cylinder.

FIG. 4 shows an example in which a radioactive substance adsorbing underground wall is formed on the ground inside the concrete wall that blocks contaminated groundwater containing radioactive substances.
In FIG. 4, 4 is a concrete wall facing the sea, 41 is a radioactive material adsorbing underground wall attached to the inner surface of the concrete wall prepared in Formulation Example 1 of Tables 1 and 3, and 42 contains a radioactive material. Contaminated water, 43 is the ground rock.

FIG. 5 is an explanatory view showing various embodiments of the radioactive substance adsorption structure of the application example of the present invention.
In FIG. 5 (a), 5 is a radioactivity building, 51 is a radioactive material adsorption layer formed by mixing and spraying a radioactive material adsorbent with water on the entire inner wall of the building 5 of the embodiment.
In FIG. 5B, 6 is a reactor building, 61 is a concrete underground wall provided on the outer periphery of the reactor building, 62 is a radioactive material adsorption underground wall of this embodiment, and is used as an inner wall of the concrete underground wall 61. Is formed.

In FIG. 5C, reference numeral 7 denotes a radioactive substance contaminated liquid feed pipe, and reference numeral 71 denotes a filter pipe which is the radioactive substance adsorbent of the embodiment disposed in the liquid feed pipe.
In FIG. 5 (d), 8 is a radioactive substance contaminated liquid feeding pipe, 81 is a radioactive substance adsorbing body of an embodiment that partitions the passage of the liquid feeding pipe, and 82 is a fine adhering to one surface of the radioactive substance adsorbing body. A perforated plate made of stainless steel having a large number of holes, 83 is a contaminated liquid passage, and 84 is a purified water passage for purified water that has passed through the radioactive substance adsorbent.

  In FIG. 5 (e), 9 is a contaminated liquid storage tank, 90 is a radioactive material adsorbent of an embodiment that divides the tank vertically, 91 is a stainless porous plate attached to the lower surface of the adsorbent, and 92 is a contaminated liquid , 93 is a contaminated water drain pipe, and 94 is a purified water drain pipe.

Example 1
Hereinafter, a description will be given of a first embodiment in which a plurality of filter cylinders solidified into a bottomed cylindrical body are disposed in the contaminated liquid storage tank of the present invention.

  Example 1 is a radioactive substance adsorbent (hereinafter referred to as a filter) according to claim 2 of the present invention, which is solidified into a bottomed cylindrical shape in a contaminated liquid storage tank 1 for temporarily storing a liquid contaminated with a radioactive substance. This is an example of the structure of the water storage tank 1 in which the cylinder 2 is provided vertically and the purified liquid in the filter cylinder 2 is discharged by the pump 23. A stainless steel porous inner cylinder 21 having a large number of fine holes is attached to the inner surface of the filter cylinder 2. This porous inner cylinder 21 is also a protective cylinder which prevents the collapse of the filter cylinder 2 of the radioactive substance adsorbent.

  The component blending ratios of the granular cement-based solidified material used in the filter barrel 2 of the cylindrical radioactive substance adsorbent in Example 1 are as shown in Table 1 below.

  Table 2 below shows the characteristics of the solid plate solidified by adding the required amount of water only with the above-mentioned powdered cementitious solidifying material. High compressive strength.

  In the examples, a granular radioactive material adsorbent was prepared by mixing zeolite in a weight ratio of 1: 3 as shown in Table 3 below with respect to the granular cement-based solidified material having the blending ratio shown in Table 1 above. Zeolite having a specific gravity of 1.0 and a particle size of 0.25 to 1.00 mm was used.

For the experiment of water permeability of the filter cylinder 2 of the bottomed cylindrical radioactive material adsorbent prepared in the above-mentioned component ratios Tables 1 and 3, the bottomed cylindrical specimens shown in Table 3 above were prepared. A water permeability experiment was conducted.
As a specimen of Formulation Example 1 in Table 3, a bottomed cylindrical filter cylinder 31 having dimensions of a small outer diameter of 100 mm, an inner diameter of 75 mm, a height of 120 mm, and a bottom thickness of 20 mm was produced, and a water permeability experiment was performed. .

(Example of permeability test)
The filter cylinder 31 was placed vertically in cloudy water containing an ash component (cement component) in a water container 3 in which water was stored (state of FIG. 3A). The water level of the water container 3 at that time was 100 mm. The water in the water container 3 gradually permeated into the filter cylinder 31 and the water level in the filter cylinder 31 increased. Then, after 8 days, the water level in the filter cylinder 31 of the example became the same as the water level of the water container 3 and became 80 mm. This indicates that the filter cylinder 31 of the blending example 1 of the present invention has a considerably large water permeability as compared with a bottomed cylindrical body made of Portland cement concrete. Thus, it was found that the water permeability of the filter cylinder 31 of the example was considerably high. The water in the filter cylinder 31 was transparent with few ash components.

(Radioactive substance adsorption test)
Next, the radioactive substance adsorptive power test of Formulation Example 1 in Table 3 of the present invention was performed. Therefore, the two large and small filter samples (referred to as sample 1) of the formulation example 1 containing zeolite in Table 3 and the large and small filter sample (referred to simply as sample 2) of the blend example 2 not containing zeolite shown in Table 3 are prepared. These samples 1 and 2 were subjected to ICP-MS test analysis of Cs (cesium) and Sr (strontium). The results are shown in Tables 4 and 5 below. Moreover, it is shown as a graph in FIGS. As the standard solution used in this test, a standard solution of Sr was used at a concentration of 10.003 ppm, and a standard solution of 9992 ppm was used as a standard solution for Cs.

As can be seen from Table 4 and FIG. 6 above, with regard to the adsorption capacity of Sr, the sample 2 (large) and the sample 1 (large) having a larger surface area are larger than the sample 2 (small). Also showed high adsorption. The adsorption capacity of Sample 2 and Sample 1 of (Large) is slightly higher than that of Sample 1 (Example). Even in the case of (small), Sample 1 (Example) showed higher adsorption ability than Sample 2.
Adsorption of Sr was exhibited in a relatively short time, and (large) of samples 2 and 1 was almost below the lower limit of detection after the second day.

Further, as can be seen from Table 5 and FIG. 7, with respect to the Cs adsorption capacity, the sample 2 showed almost no Cs adsorption, whereas the sample 1 of the example showed Cs adsorption. It was. In sample 2 (large) and (small), (large) was considered to have slightly higher adsorption.
Sample 1 also showed the ability to adsorb Cs in a relatively short time as with Sr. In (large), it seemed that almost reached saturation on the fifth day.

  As described above, Sr of the filter cylinder 2, sample 1 prepared in the blending examples of Tables 1 and 3, the filter cylinder 31 of Example 1 below, and the other examples of the radioactive adsorbent of FIG. Cs adsorption force was judged to be large from the ICP-MS test analysis results.

  Next, in Example 1 of the contaminated water storage tank 1 shown in FIGS. 1 and 2, a filter cylinder 2 is produced using the radioactive substance adsorbent of Formulation Example 1 in Tables 1 and 3, and the inner surface is porous. A plurality of filter cylinders 2 with an upper lid having a structure with a cylinder 21 attached thereto are vertically arranged in a water storage tank 1 for radioactive liquid contamination, and are connected to a pump 23 in each filter cylinder 2. A suction tube 22 is arranged. The suction tube 22 can suck air or water from the outer periphery.

  Dirty water containing a radioactive substance is introduced into the water storage tank 1 to a predetermined water level. And if the pump 23 is operated and the inside of the filter cylinder 2 is made into a negative pressure, the contaminated liquid in the water storage tank 1 will permeate | transmit the filter cylinder 2 with the water head difference and air negative pressure. In the middle of the permeation, the radioactive substance comes into contact with the zeolite in the filter cylinder 2 and is adsorbed and trapped in the filter cylinder 2 and remains. And the water which adsorb | sucked and permeate | transmitted the radioactive substance with zeolite is stored in the filter cylinder 2, If the water level in the filter cylinder 2 rises, the water will be attracted | sucked in the suction pipe 22 and water will be sent outside. Is done. Since the water to be sent does not contain much radioactive material, it can be discharged as purified water to the secondary purification device or to the sea or the like if the degree of purification is high. Further, since the level of the contaminated liquid in the water storage tank 1 is lowered by the amount of purified water sent by the pump 23, the contaminated liquid can be further fed into the water storage tank 1. Therefore, the number of necessary water storage tanks 1 can be reduced.

  The filter cylinder 2 in which the radioactive substance of Example 1 is adsorbed until saturation is lifted from the contaminated liquid storage tank 1 with a crane or the like, sealed in a special sealed container, and transported / stored or buried underground. Because of this, post-treatment after radioactive material adsorption is safe and quick.

The embodiment shown in FIGS. 4 and 5 is another application example / adsorption structure example in which the particulate radioactive material adsorbent of the present invention is solidified .
FIG. 4 shows the excavation of many continuous underground holes inside the concrete wall 4 in the building where contaminated water is stored, and water is added to the particulate radioactive material adsorbents of the present invention shown in Tables 1 and 3. In this example, the radioactive material adsorbing underground wall 41 is formed by kneading, pouring into the underground hole and solidifying in the ground inside the concrete wall 4. In this example, the contaminated water is isolated and stored inside the concrete wall 4, but when the concrete wall 4 flows out or leaks from the crack / gap of the concrete wall 4, the radioactive material adsorption underground wall 41 inside the concrete wall 4 is contaminated. By adsorbing radioactive substances in the water, the liquid that flows out and leaks from the concrete wall 4 is purified and flows out into the sea, so that the pollution of the sea can be reduced.
FIG. 5A shows a radioactive substance adsorbing layer 51 obtained by kneading water into the granular radioactive substance adsorbent of the present invention on the ceiling, floor, and inner walls of the radioactivity-preventing building 5 and spraying them on the walls, ceiling, and floor. This is an example for forming indoor air. This is an example of purifying the air by adsorbing radioactive materials in the contaminated air in the building. FIG. 5B shows a case where a recess is excavated inside the concrete underground wall 61 surrounding the ground of the reactor building 6, and necessary water is added to the granular radioactive material adsorbent of the present invention in this recess. The radioactive material adsorption underground wall 62 is formed by mixing and pouring. In this example, only the purified water from the contaminated water under the building can be discharged to the outside. FIG. 5 (c) shows that the filter pipe 71 according to the embodiment of the present invention is disposed in the contaminated water supply pipe 7, and only the water purified by removing the contaminating radioactive substances in the liquid path is supplied to the liquid path. It is extracted from the water, and the purified water in the liquid passage is separated and processed. In FIG. 5 (d), the liquid supply pipe 8 is partitioned by a plate-shaped radioactive substance adsorbent 81 using the present invention , purified from the contaminated liquid and discharged through another path, and the purified water is discharged to the sea or the like. This is an example of enabling release. FIG. 5 (e) shows an example in which a plate-like radioactive substance adsorbing body 90 using the present invention is provided inside the polluted liquid storage tank 9 and is divided into upper and lower parts. This is an example in which the body 90 is permeated to purify the water so that the purified water can be discharged from the drain pipe 94.

  The present invention can also be used for materials and products of adsorption filters for other elements other than radioactive material adsorption filters.

DESCRIPTION OF SYMBOLS 1 Water storage tank 11 Contaminated liquid injection pipe 12 Contaminated liquid discharge pipe 13 Tank lid 2 Filter cylinder 21 Stainless steel porous inner cylinder 22 Suction pipe 23 Pump 24 Lid 3 Water container 31 Filter cylinder 32 Liquid 33 Permeated water 4 Concrete wall body 41 Radioactive material adsorption underground wall 42 Contaminated water 43 Rock 5 Radioactivity building 51 Radioactive material adsorption layer 6 Reactor building 61 Concrete underground wall 62 Radioactive material adsorption underground wall 7 Liquid feed pipe 71 Filter pipe 8 Liquid feed pipe 81 Radioactive Substance adsorbent 82 Perforated plate 83 Contaminated liquid passage 84 Purified water passage 9 Contaminated liquid storage tank 90 Radioactive material adsorbent 91 Perforated plate 92 Conduit pipe 93 Contaminated water discharge pipe 94 Purified water drain pipe

Claims (1)

As the granular cement-based solidified material, a cement-based solidified material in which 2 to 5 parts by weight of active silica and 1 to 3 parts by weight of granular zirconia are mixed with 100 parts by weight of alumina cement is used. On the other hand, a granular radioactive substance adsorbent in which granular zeolite is mixed at a weight ratio of 1: 2-4 .

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