JP5921363B2 - Burial method - Google Patents

Description

  The present invention relates to an embedding treatment of a material containing a radioactive substance, for example, soil contaminated with a radioactive substance or debris of a building. More specifically, the present invention relates to an embedding treatment technique that can prevent adverse effects such as radiation exposure in the surrounding environment even when a material (including waste materials, debris, etc.) containing a radioactive substance is embedded.

For example, treatment of soil contaminated with radioactive substances, building debris, etc., that is, treatment of materials containing radioactive substances, has become a major social issue.
Here, when the embedding process normally performed in the treatment of soil, debris, etc. is applied to the treatment of materials containing radioactive substances, it will have an adverse effect on the surrounding environment of the embedding process such as radiation exposure. .

In addition, regarding the processing of materials containing radioactive substances, strict standards have been established for the radiation dose after treatment, and if the radiation dose after treatment is not lower than the standards, processing of materials containing radioactive substances It is not allowed.
And when the material containing a radioactive substance was processed by the conventional embedment method, it was very difficult for the radiation dose after embedment to be a level below the standard.

As another conventional technique, for example, it is conceivable to store a material containing a radioactive substance in a storage container dedicated to a radioactive substance (see Patent Document 1) and embed the container in the ground.
However, because the storage container dedicated to radioactive materials is expensive to manufacture and has a limited capacity, when processing such materials containing radioactive materials using such containers, the processing cost is low. It will be enormous.

JP 2009-109487 A

  The present invention has been proposed in view of the above-described problems of the prior art, and can process a material containing a radioactive substance without adversely affecting the surrounding environment such as radiation exposure, and is also a dedicated container. The purpose is to provide an embedding method that can be processed at a much lower cost compared to the case of using the above.

The embedding method of the present invention is
Forming a layer (4B) made of a barium compound (for example, barite) or an iron compound and / or a layer (5B) made of a material having a water barrier property at the bottom (3) of the recess (20);
Filling the granules (6) above the layer,
The granule (6) is formed by granulating a material containing a radioactive substance, and is covered with a barium compound or an iron compound that blocks radiation,
Forming a layer (4T) made of a barium compound or an iron compound in a region below the ground surface;
Forming a layer (5T) made of a material having a water-blocking property above a layer (4T) made of a barium compound or an iron compound formed below the ground surface;
It is characterized by having.

Here, the term “barium compound” is used to include barium alone (Ba). Further, the term “iron compound” is used to include iron simple substance (Fe).
In the present specification, the term “concave portion” is intended to include a space near an excavation hole (for example, a so-called “drilled hole”), a revetment wall, a retaining wall, and other structures. It is used.
In addition, in this specification, the term “bottom part of the recess” means that when a layer made of a material having a water-impervious property is formed at the bottom part, a region laminated directly on the layer (a layer made of a material having a water-impervious property). It is defined as a word that includes.

In the present invention, between the layer (4B) made of barium compound or iron compound formed on the bottom (3) of the recess (20) and the layer (4T) made of barium compound or iron compound formed near the ground surface. In the region, it is preferable to alternately laminate the layer (6) made of particles coated with a barium compound or an iron compound and the layer (4C) made of a barium compound or an iron compound.
Alternatively, the region between the barium compound layer (4B) formed on the bottom (3) of the recess (20) and the barium compound layer (4T) formed below the ground surface is covered with the barium compound. It is also preferable to form only the granular material (6).

  Further, in addition to forming a layer (4B) made of a barium compound or an iron compound on the bottom (3) of the recess (20), a water shielding material (for example, including the side and bottom surfaces of the recess) , Concrete, bentonite, water-impervious sheet, etc.).

  In the present invention, the recess (20) includes a drilling hole (for example, a hole excavated from the ground, a so-called “drilled hole”), a space near a revetment wall, and a space near a retaining wall. It is used.

According to the present invention having the above-described configuration, the granules (6) filled in the recesses (20) are covered with a barium compound or an iron compound that blocks radiation. Therefore, even if the granule (6) filled in the recess (20) is formed by granulating a material containing a radioactive substance, the radiation from the granule (6) is emitted from the granule (6). ) Is blocked by a barium compound or an iron compound.
Even if the radiation passed through the barium compound or iron compound covering the granules (6), the transmitted radiation was formed above the recess (20) and at the bottom (3) of the recess (20). It is completely blocked by the layers (4T, 4B) made of barium or iron compounds.
Therefore, a material containing a radioactive substance can be processed without adversely affecting the surrounding environment of the recess (20) such as radiation exposure.

Further, according to the present invention, it is not necessary to use a special container.
If a recess having a large volume is formed, even if a large amount of a material containing a radioactive substance exists, it can be sufficiently embedded.
Furthermore, the barium compound or the iron compound used for blocking radiation can be procured at a much lower cost than the cost of manufacturing a dedicated container.
Therefore, according to the embedding method of the present invention, it is possible to suitably embed a material containing a radioactive substance without increasing the processing cost.

In addition to this, according to the present invention, the layer (5T) made of a material having a water shielding property is formed above the layer (4T) made of barium compound or iron compound formed near the ground surface. Even if there is rainfall or snowfall at the treated site, there is no risk of contaminated water generating radiation entering the surrounding soil.
And unless a full-scale excavation work is performed with an excavating machine, the embedded material containing the radioactive substance will not be exposed to the atmosphere.

  Furthermore, in the present invention, a layer (5B) made of a material having a water shielding property is formed on the bottom (3) of the recess (20), and a water shielding material (for example, concrete, bentonite, water shielding sheet, etc.) is formed on the wall surface (2). Etc.), even if groundwater exists around the recess (20), a water shielding layer (5B) is formed on the bottom of the recess, and the walls of the recess (eg, inclined surfaces 2 and 2) are blocked. Since the water layer (5C) is formed, the groundwater does not come into contact with the pellets (6) filled in the recess, and the radioactive material is prevented from diffusing due to the flow of the groundwater.

It is a flowchart which shows the procedure which produces the pellet coat | covered with the barium compound. It is process drawing which shows the state which laid barite in the bottom part of a recessed part in 1st Embodiment. It is process drawing which shows the state which applied the water shielding material to the side wall of the recessed part in 1st Embodiment. It is explanatory drawing which shows the state which constructed 1st Embodiment. It is explanatory drawing which shows the state which constructed the modification of 1st Embodiment. It is explanatory drawing which shows the state which constructed the 2nd modification of 1st Embodiment. It is explanatory drawing which shows the state which constructed the 3rd modification of 1st Embodiment. In 2nd Embodiment, it is process drawing which shows the state which laid barite in the bottom part of a recessed part. FIG. 9 is a process diagram showing a state in which a pellet layer is formed above a layer on which barite is laid in FIG. 8 and further covered with barite in the second embodiment. It is explanatory drawing which shows the state which constructed 2nd Embodiment. It is explanatory drawing which shows the state which constructed the modification of 2nd Embodiment.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
First, with reference to FIG. 1, the procedure for producing pellets coated with a barium compound will be described.
In FIG. 1, in the first step S1, an object to be buried (for example, rubble) is incinerated in a dedicated incinerator. In the illustrated embodiment, the rubble that is an object to be buried is, for example, rubble that is contaminated with a radioactive substance.
In the second step S2, incineration ash generated after incineration is recovered from the incinerator. As described above, in the illustrated embodiment, rubble, which is an object to be buried, is contaminated with a radioactive substance, so that the incineration ash generated after the incineration contains a radioactive substance.

In the third step S3, the incinerated ash containing the radioactive substance is granulated.
In step S4, the pellet containing the radioactive substance is coated with a barium compound or an iron compound.
Here, the term “barium compound” is used to include barium alone (Ba). Further, the term “iron compound” is used to include iron simple substance (Fe).
Here, Ba or Fe has a large atomic number and a large number of electrons. Therefore, the radiation emitted from the radioactive substance is highly likely to collide with electrons and is difficult to transmit. There are many other substances with large atomic numbers, but barium compounds or iron compounds are most suitable in consideration of purchase costs, environmental effects, and the like.

Next, an embodiment of an embedding method for embedding pellets coated with a barium compound or an iron compound by the procedure described in FIG. 1 will be described.
Initially, with reference to FIGS. 2-4, 1st Embodiment of an embedment construction method is described.
In the process shown in FIG. 2, first, the recess 20 is formed in the ground 1. Here, the recessed part 20 has the inclined surfaces 2 and 2 and the horizontal bottom part 3 which oppose. Then, the coating layer 4 </ b> B is formed on the bottom 3 of the recess 20. The covering layer 4B is made of a barium compound (for example, “barite”) or an iron compound.

Next, in the step shown in FIG. 3, a water shielding layer 5 </ b> C is formed on the inclined surfaces 2 and 2 that face each other.
The water shielding layer 5C is made of a water shielding material such as concrete, bentonite, and a water shielding sheet, for example. Then, by applying concrete or bentonite to the inclined surface 2, or by laying a water-impervious sheet on the inclined surface 2, the water-impervious layer 5C is formed.
Here, in this specification, laying a water shielding sheet on the inclined surface 2 is also expressed as “application of a water shielding material”.

In the step shown in FIG. 4, particles (hereinafter referred to as “pellets”) 6 are filled above the layer 4 </ b> B made of the barium compound or iron compound. Here, as described with reference to FIG. 1, the pellet 6 is composed of particles obtained by granulating a material containing radioactive material (incineration ash of rubble contaminated with radioactive material), barium compound or iron compound (radiation). A substance that exhibits a function of blocking the light).
When the pellet 6 is filled up to the vicinity of the upper edge of the concave portion 20, the upper surface thereof is covered with a barium compound (for example, barite) or iron compound layer 4T, and the upper portion thereof is covered with a water shielding layer 5T.
The water-impervious layer 5T is made of a water-impervious material (concrete, bentonite, water-impervious sheet) in the same manner as the water-impervious layer 5C.

According to the first embodiment shown in FIGS. 2 to 4, the layers 4 </ b> B and 4 </ b> T made of a barium compound or an iron compound are formed on the bottom 3 and the uppermost region of the recess 20, and the recess 20 is filled. The pellet 6 is coated with a barium compound or an iron compound that blocks radiation. Therefore, even if the pellet 6 filled in the recess 20 is formed by granulating a material containing a radioactive substance, the radiation from the granule is caused by the barium compound or iron compound covering the pellet 6. Blocked.
Even if the said radiation permeate | transmits the barium compound or iron compound which has coated the pellet 6, it will be interrupted | blocked completely by the water shielding layers 4B and 4T.
Therefore, a material containing a radioactive substance can be processed without adversely affecting the surrounding environment of the recess 20 such as radiation exposure.

  Further, even if groundwater exists around the recess 20, since the water shielding layer 5 </ b> C is formed on the inclined surfaces 2 and 2 of the recess 20, the groundwater is in contact with the pellet 6 filled in the recess 20. However, the situation where radioactive materials are diffused by the flow of groundwater is prevented.

Furthermore, it is not necessary to prepare a special container in the first embodiment.
And since the excavated recessed part 20 has a large volume, even if the material containing a radioactive substance exists in large quantities, it can be embedded enough.
Furthermore, the barium compound or the iron compound used for blocking radiation can be procured at a much lower cost than the cost of manufacturing a dedicated container.
Therefore, according to the first embodiment, it is possible to appropriately embed a material containing a radioactive substance without increasing the processing cost.

FIG. 5 shows a modification of the embedding method according to the first embodiment.
In the first embodiment shown in FIGS. 2 to 4, the barium compound or iron compound layer 4 </ b> T formed in the vicinity of the uppermost portion of the recess 20 from the barium compound or iron compound layer 4 </ b> B formed on the bottom 3 of the recess 20. Until now, only the pellet 6 which granulated the material containing a radioactive substance and coat | covered with the barium compound or the iron compound is included. In other words, the layer 4B to the layer 4T made of a barium compound or an iron compound are composed only of the pellet 6 layer (in a single layer).

  On the other hand, in the modification of the first embodiment shown in FIG. 5, the barium compound or iron formed in the vicinity of the uppermost portion of the recess 20 from the barium compound or iron compound layer 4B formed on the bottom 3 of the recess 20. In the region between the compound layers 4T, a plurality of pellet layers 6 (four layers in the example of FIG. 5) and a plurality of barium compound or iron compound layers 4C (three layers in the example of FIG. 5) are alternately arranged. Laminated.

In the modification of FIG. 5, the region between the barium compound or iron compound layer 4 </ b> B formed on the bottom 3 of the recess 20 and the barium compound or iron compound layer 4 </ b> T formed near the top of the recess 20. The first embodiment shown in FIGS. 2 to 4 is formed by forming a layer 4C made of a plurality of barium compounds or iron compounds between the barium compound or iron compound layers 4T formed above (opening side) 20. The radiation is blocked better than the form, and the influence of the radiation on the ground side is further reduced.
About the structure except the above in the modification shown in FIG. 5, and an effect, it is the same as that of 1st Embodiment of FIGS.

FIG. 6 shows a second modification of the first embodiment.
2 to 5, the barium compound or iron compound layer 4 </ b> B is formed on the bottom 3 of the recess 20, whereas in the second modification of FIG. 6, the bottom 3 of the recess 20 is not water-tight. A layer 5B made of a material having the same is formed. Therefore, even if the bottom surface and the side surface of the recess 20 are surrounded by the layers 5B and 5C made of a material having water shielding properties, even if groundwater exists around the recess 20, the water shielding layer 5B on the bottom surface of the recess 20 and the inclined surfaces 2, 2 The water-impervious layer 5 </ b> C prevents the groundwater from contacting the pellet 6. Therefore, the radioactive material is prevented from diffusing due to the flow of groundwater.
The water shielding layer 5B is also made of a water shielding material (concrete, bentonite, water shielding sheet) in the same manner as the water shielding layers 5C and 5T.
The other configurations and operational effects of the second modification of FIG. 6 are the same as those of FIGS.

FIG. 7 shows a third modification of the first embodiment.
In FIG. 7, a layer 5 </ b> B made of a water-impervious material is formed on the bottom 3 of the recess 20, and a barium compound or iron compound layer 4 </ b> B is formed immediately above the layer 5 </ b> B. Therefore, in addition to preventing the ground water and the pellet 6 from coming into contact, even if radiation is transmitted through the barium compound or iron compound covering the pellet 6 and emitted downward, the barium compound or iron compound Is completely blocked by the layer 4B.
The other configurations and operational effects of the third modified example of FIG. 7 are the same as those of FIGS.

In FIGS. 1-7, after forming the water shielding layer 5C over the entire inclined surface 2 of the recess 20 (see FIG. 3), the water shielding layer 5B, the barium compound or iron compound layer 4B, and the pellet 6 are laminated. Yes. On the other hand, although illustration is abbreviate | omitted, it is also possible to form 5 C of water shielding layers in the inclined surface 2 intermittently.
That is, if the water shielding layer 5C is formed on a part of the inclined surface 2, and then any of the water shielding layer 5B, the barium compound or iron compound layer 4B, and the pellet 6 are laminated to the level of the water shielding layer 5B. For example, it is possible to form the water shielding layer 5C on the inclined surface 2 by repeating the process of forming the water shielding layer 5C further upward.

Next, a second embodiment of the burying method will be described with reference to FIGS.
In the second embodiment shown in FIGS. 8 to 10, for example, a material containing a radioactive substance is embedded in a region near the revetment.
In FIG. 8, the revetment wall 7 is built on the ground 1 facing the ocean 8, and the reclamation groove 20L is excavated on the side separated from the revetment wall 7 (left side in FIGS. 8 to 10). Here, the reclamation groove 20L includes the slope 72 on the surface opposite to the ocean 8 side of the revetment wall 7 (the left surface in FIGS. 6 to 10), the slope 2 on the side separated from the revetment wall 7 and the bottom. It is surrounded by 3.
The code | symbol 9 in FIGS. 8-10 shows the revetment block (for example, tetrapod) installed in the coast.

As shown in FIG. 8, a water shielding layer 5C is formed on the bottom 3 and the slope 2 in the landfill groove 20L. The water-impervious layer 5C is also made of a water-impervious material (concrete, bentonite, water-impervious sheet), similar to the water-impervious layer 5C in the first embodiment.
Then, a barium compound (for example, barite) or iron compound layer 4 is formed immediately above the water shielding layer 5 </ b> C formed on the bottom 3.

9, a layer of pellets 6 is stacked above the barium compound or iron compound layer 4 formed in the step of FIG. 8. As in the first embodiment, the pellet 6 is also coated with a barium compound or an iron compound by granulating a material containing a radioactive substance.
As shown in FIG. 9, a barium compound or iron compound layer 4 is further laminated on the layer filled with pellets 6. And the layer of the pellet 6 and the layer 4 of a barium compound or an iron compound are laminated | stacked alternately.

In the process shown in FIG. 10, the water shielding layer 5 </ b> T is formed further above the barium compound or iron compound layer 4 located at the uppermost position. Similarly to the water shielding layer 5C, the water shielding layer 5T is also made of a water shielding material (concrete, bentonite, water shielding sheet).
8 to 10, the upper surface 71 of the revetment wall 7 and the ground surface (ground surface) 1f are flush with each other (same level), but the level of the upper surface 71 of the revetment wall 7 is set to the ground surface (ground surface) 1f. Can be set high. In FIGS. 6 to 10, the water shielding layer 5 </ b> T and the ground surface (ground surface) 1 f are flush with each other (at the same level), but the water shielding layer 5 </ b> T (or a region embedded in the second embodiment) is present. It can also be formed so as to be higher (projected) than the surrounding ground surface (ground surface) 1f.
In the second embodiment of FIGS. 8 to 10, the pellet 6 made of a material containing a radioactive substance is not only covered with a barium compound or an iron compound, but each layer filled with the pellet 6 is made of a barium compound or an iron compound. It is covered with a layer 4 and further covered with a water shielding layer 5T. This prevents radiation from leaking outside. Therefore, although not clearly shown, it is possible to build a building above the water-impervious layer 5T and make a person resident.

According to 2nd Embodiment of FIGS. 8-10, it is possible to excavate the reclamation groove | channel 20L as a recessed part in the side which is not in contact with the water of the revetment wall 7, and to reclaim the material containing a radioactive substance.
Other configurations and operational effects in the second embodiment of FIGS. 8 to 10 are the same as those of the first embodiment and its modifications shown in FIGS.

FIG. 11 shows a modification of the second embodiment.
In FIGS. 8 to 10, a plurality of barium compound or iron compound 4C and a plurality of pellet 6 layers are alternately stacked in a space between the bottom 3 and the uppermost water shielding layer 5T. doing.
In contrast, in the modification of FIG. 11, the region between the barium compound or iron compound layer 4 formed on the bottom 3 and the barium compound or iron compound layer 4 in the vicinity of the top is filled with pellets 6. It consists of a single layer.

According to the modification of 2nd Embodiment of FIG. 11, a landfill operation | work is simplified, it is possible to reduce work labor and cost, and to shorten a construction period.
Other configurations and operational effects in the modification of the second embodiment of FIG. 11 are the same as those of the second embodiment of FIGS.

In the second embodiment (including the modification) of FIGS. 8 to 11, the reclamation groove 20 </ b> L is excavated in a region adjacent to the revetment wall 7, but the construction is not limited to the vicinity of the revetment wall 7. Absent.
Although not shown in the drawings, a material that includes a radioactive substance in the concave portion between the retaining wall and the slope by constructing a retaining wall or a retaining wall (not shown) on the slope of the slope. It is also possible to fill. Here, the earth retaining wall is smaller in thickness than the revetment wall and may have poor water impermeability, so the wall of the earth retaining wall is also made of a water impervious material (concrete, bentonite, water impervious sheet). It is preferable to form a water shielding layer.

  It should be noted that the illustrated embodiment is merely an example, and is not a description to limit the technical scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Ground 2 ... Inclined surface 3 ... Bottom part 4, 4B, 4C, 4T ... Layer 5C which consists of barium compound or iron compound, 5T ... Water shielding layer 6 ... Granule / Pellet 7 ... Revetment wall 8 ... Ocean 10 ... Building

Claims (3)

Forming a layer made of a barium compound or an iron compound and / or a layer made of a material having a water barrier property at the bottom of the recess;
Filling the particles above the layer,
The granule is formed by granulating a material containing a radioactive substance, and is covered with a barium compound or an iron compound that blocks radiation,
Forming a layer made of a barium compound or an iron compound in a region below the ground surface;
Forming a layer made of a material having a water barrier property above a layer made of a barium compound or an iron compound formed below the ground surface;
A buried construction method characterized by comprising: The region between the barium compound or iron compound layer formed at the bottom of the recess and the barium compound or iron compound layer formed below the ground surface is composed of particles coated with barium compound or iron compound. The embedding method according to claim 1, wherein the layers and the layers made of a barium compound or an iron compound are alternately laminated. The embedding method according to any one of claims 1 and 2, wherein the concave surface is covered with a water shielding material.

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