JP2013130546A - Method for constructing shield structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for constructing a shield structure suitable for a storage space of wastes including radioactive material.SOLUTION: The method for constructing a shield structure 1 comprises the step of covering wastes 2 with a shield layer 3 formed of a shield material 12 so as to shield radiation emitted from the wastes 2 for reduction in the amount of radiation at a temporary storage space A of the wastes 2. Since the shield layer 3 is formed by spraying the shield material 12, the homogeneous shield layer 3 with a uniform thickness can be produced. As a result, a predetermined shield performance is reliably and rapidly obtained. The radiation dose to a worker B is thus reduced during construction.

Description

  The present invention relates to a method for constructing a shielding structure, and more particularly to a method for constructing a shielding structure in a temporary storage place for waste containing radioactive substances.

  Conventionally, as described in Patent Document 1 below, a cement solution is sprayed on the waste thrown into the final disposal site to form a coating layer that covers the waste, and then the waste is put on the coating layer. Waste landfill treatment methods that repeat this process are known. In this method, the formation of the coating layer makes it possible to efficiently perform further waste input work or to prevent the waste from being scattered around.

  In addition, as described in Patent Document 2 below, in a device for inspecting radioactive contamination of an object such as a floor surface, when the surface contamination of the object is measured by a radiation detector and a contaminated part is detected, An apparatus is known that sprays paint on the spot and visualizes the contaminated spot. In this apparatus, it is said that radioactive material can be prevented from scattering by spraying paint, and further, radioactive contamination can be removed by removing the coating film.

Japanese Patent No. 3668440 JP-A-4-58185

  By the way, for example, when a radioactive substance is released and diffused from a nuclear power plant or the like in an emergency, the radioactive substance may sink to the surrounding area and be deposited on soil or the like. In such areas, when topsoil is stripped or weeded or pruned for decontamination, waste containing radioactive materials is generated. The waste generated as a result of decontamination is temporarily stored (temporarily placed) on the ground for a certain period of time, then intermediately stored, and finally disposed.

  When storing waste generated by decontamination, an appropriate shielding structure should be installed around the waste to prevent radiation from being released into the atmosphere and to prevent leakage of radioactive materials into the ground. Need to build. Furthermore, since the waste is moved to the intermediate storage facility after the temporary storage period has elapsed, it is necessary to consider taking out the waste. However, since the above-described conventional technology is not premised on temporary storage of waste containing radioactive materials, it is difficult to cope with such a situation. Therefore, a construction method for an appropriate shielding structure in a temporary storage place for waste containing radioactive materials is desired.

  An object of this invention is to provide the construction method of the suitable shielding structure in the temporary storage place of the waste containing a radioactive substance.

  The construction method of the shielding structure that solves the above problems is a construction method of a shielding structure in a temporary storage place for waste containing radioactive substances, and has a radiation shielding function for waste placed on the ground. A shielding material that solidifies after spraying is sprayed, and a shielding layer formed by solidifying the shielding material is formed on the surface of the waste.

  According to this construction method, since the waste is covered with the shielding layer made of the shielding material, the radiation emitted from the waste is shielded, and the radiation dose in the temporary storage place of the waste can be reduced. Here, since the shielding layer is formed by spraying the shielding material, the shielding layer can be uniformly formed with a uniform thickness, and a predetermined shielding performance can be obtained reliably and quickly. Rapid construction is effective in reducing the amount of worker exposure during construction. Since this shielding layer can be made thinner than the shielding layer by the conventional embankment, the load on the waste is reduced. Furthermore, since the shielding material can be sprayed from the outside or the peripheral part of the temporary storage place to the waste placed in the central part of the temporary storage place, a heavy machine etc. is placed on the waste placed on the ground. There is no need to install, and the loading load during construction is also reduced. By reducing these loading loads, for example, when a waste is stored in a flexible container bag (hereinafter referred to as a container bag) or the like and temporarily stored, the container bag or the like can be prevented from being damaged. In addition, it is necessary to take out the waste after a certain period of time, but since the shielding layer by spraying can be made thinner than the shielding layer by embankment, it is easier to take out the waste, and when taking out the waste Less contaminated shielding material is generated, and the disposal amount of shielding material can be reduced. As described above, the shielding layer can be appropriately applied at the temporary storage place for waste.

  Further, in the construction method of the shielding structure, the step of measuring the radiation dose emitted from the waste through the shielding material at the time of spraying or after spraying the shielding material, and the updating of the shielding material according to the measured radiation dose. A step of determining whether or not spraying is necessary, and a step of further spraying the shielding material when it is determined that further spraying of the shielding material is necessary. According to this construction method, the radiation dose at the time when a shielding layer of a certain thickness is formed is measured, the necessity of further spraying of the shielding material is judged according to the measurement result, and further spraying is performed. If it is determined necessary, further shielding material is sprayed. Thereby, the shielding layer which satisfy | fills predetermined shielding performance can be formed with minimum thickness. As a result, the amount of shielding material used can be minimized, construction efficiency can be improved, and the exposure dose of workers can be further reduced. The ability to form the shielding layer with a minimum thickness is also effective in reducing the loading load and the disposal amount of the shielding material during removal. In addition, the spraying of the shielding material can be performed only on a portion where the radiation dose is locally high.

  Moreover, in the construction method of the said shielding structure, you may have the process of spraying a scattering prevention agent with respect to waste before spraying of shielding material. If the waste is placed in a state where it is not accommodated in a container bag or the like, or if it is accommodated but the container bag is damaged, the waste may be scattered during spraying. By scattering the anti-scattering agent before spraying the shielding material, it is possible to prevent the waste from being scattered.

  Moreover, in the construction method of the said shielding structure, you may have the process of covering waste with a net | network or a sheet | seat before spraying of shielding material. By covering the waste with a net or a sheet and spraying the shielding material thereon, the shielding layer can be easily removed when the waste is taken out.

  Moreover, in the construction method of the said shielding structure, you may have the process of forming the layer in which a waste is mounted containing a zeolite, before a waste is put. Zeolite has a function of adsorbing radioactive substances. According to this construction method, since the waste is placed on the layer containing zeolite, leakage of radioactive material into the ground can be prevented even when the container bag is damaged, for example.

  Moreover, in the construction method for the shielding structure, the shielding material may be sprayed in a wet manner. In this case, since the shielding material can be released further from the spray nozzle, spraying away from the waste can be easily performed. For example, even if the radiation level of the waste is high, the exposure dose of workers can be suppressed. In addition, since the material can be made more homogeneous, the shielding material can be satisfactorily adhered.

  Moreover, in the construction method of the said shielding structure, you may spray a shielding material by a dry type. In this case, blockage of the hose can be prevented, and continuous construction can be performed smoothly.

  ADVANTAGE OF THE INVENTION According to this invention, a shielding structure can be appropriately constructed in the temporary storage place of the waste containing a radioactive substance.

It is sectional drawing which shows one Embodiment of the shielding structure in the temporary storage place of a waste material. It is a flowchart which shows the construction method of the shielding structure in FIG. It is a schematic diagram of the construction system used for spraying of a shielding material. (A)-(c) is sectional drawing which shows the construction procedure of the shielding structure in FIG. (A)-(c) is sectional drawing which shows the construction procedure following FIG. (A)-(c) is sectional drawing which shows the construction procedure following FIG. It is typical sectional drawing which shows taking out of the waste material from the shielding structure of FIG. It is sectional drawing which shows the conventional shielding structure.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the shielding structure 1 is for shielding radiation emitted from the waste 2 in a temporary storage place (temporary storage place) A for the waste 2 containing radioactive substances. The waste 2 is accommodated in a plurality of container bags and placed on the ground G. The waste 2 is a removed material such as soil generated by decontamination in an area contaminated with radioactive substances. That is, the waste 2 is stripped top soil, bottom mud removed from lakes and the like, pruned branches and leaves, weeded grass, fallen leaves and incinerated ash.

  The shielding structure 1 has a function of shielding radiation, preventing rainwater from entering the shielding structure 1, and further preventing leakage of radioactive substances into the ground. In the temporary storage place A, the waste 2 is stored until the waste 2 is transported to the intermediate storage facility (for example, about 3 years). The shielding structure 1 can be constructed by a quick and safe construction method. That is, in the construction of the shielding structure 1, the exposure dose of the worker is reduced to the minimum, and damage to the container bag of the waste 2 is prevented. The shielding structure 1 is constructed in consideration of not only safety during construction but also safety during transportation of the waste 2.

  The shielding structure 1 includes a water shielding sheet 4 laid on the ground G, an adsorption layer 6 formed on the water shielding sheet 4, a waste 2 loaded on the adsorption layer 6, and a surface of the waste 2 (Upper surface and side surface) and a shielding layer 3 covering the whole.

  The adsorption layer 6 is made of zeolite and has a function of adsorbing radioactive substances. That is, the adsorption layer 6 has a function of suppressing leakage of radioactive substances. The adsorption layer 6 may be formed only from zeolite, or may be formed by mixing zeolite and another substance such as a solidified material. The water shielding sheet 4 and the adsorption layer 6 constitute a shielding layer 7 below the waste 2.

The shielding layer 3 is made of a shielding material having a radiation shielding function. This shielding material preferably has a high density. As the shielding material, various materials can be adopted as long as the material has a radiation shielding function and solidifies and has a water shielding function. For example, ordinary concrete or heavy concrete can be used. When using concrete, the aggregate may contain iron. Further, the shielding material is not limited to concrete, and a mixture of magnesium or iron silicate mineral and magnesium oxide may be used. Alternatively, a material effective for shielding neutron beams may be used, and a substance containing a lot of hydrogen atoms, a substance containing a lot of hydrates, or a substance containing a lot of crystal water may be used. The density of the shielding material is preferably 2 kg / m ³ or more, and more preferably 2.5 kg / m ³ or more.

  Then, the construction method of the shielding structure 1 is demonstrated. FIG. 2 is a flowchart showing a construction method of the shielding structure 1, FIG. 3 is a schematic diagram of a construction system used for spraying the shielding material, and FIGS. 4 to 6 are sectional views showing a construction procedure of the shielding structure 1. .

  As shown in FIG. 3, the construction system 10 includes a compressor 11 that generates compressed air for spraying, a sprayer 13 that receives the shielding material 12 and sprays the shielding material 12, and a spray nozzle 14 at the tip. It has a material hose 16 provided. The compressor 11 and the sprayer 13 are connected by an air hose 17. The construction system 10 is a system that sprays the shielding material 12 in a wet manner. By adopting the wet spraying method, the spraying distance (distance from the spraying nozzle 14 to the spraying surface of the waste 2) can be increased, so the exposure dose of the worker B can be reduced, and the waste 2 This is particularly effective in terms of safety when the radiation level is high. Furthermore, the construction system 10 is compact and can be easily unitized and mounted on a vehicle. By using such a construction system 10, it is possible to efficiently work around the temporary storage places A scattered in the area.

  The construction system 10 may have a line for mixing the quick setting agent immediately before the spray nozzle 14. Moreover, in FIG. 3, although the case where the worker B has the material hose 16 is illustrated, when it is forced to approach the temporary storage place A (waste 2) to be sprayed, In consideration of safety, the material hose 16 and the spray nozzle 14 can be held by another heavy machine or the like.

  First, as shown in FIG. 2 and FIG. 4A, the water shielding sheet 4 is laid on the ground G (S1). Next, as shown in FIG. 4B, zeolite is spread over the entire surface of the water-impervious sheet 4 to form the adsorption layer 6 (S2). Here, the stacking height (thickness) of zeolite is about 5 cm. Further, the zeolite may be mixed with another substance so that the zeolite is solidified. By these steps S1 and S2, the lower shielding layer 7 is formed.

  Next, as shown in FIG. 4C, the waste 2 is placed on the lower shielding layer 7 (S3). FIG. 4C shows a case where the waste 2 is stored in a plurality of container bags and stacked, but the waste 2 is not stored in the container bag and is stacked with the waste 2 exposed. You can also. In the present embodiment, the case where the shielding layer 7 is formed on the ground G will be described. However, for example, the ground G having a certain depth may be excavated, and the shielding layer 7 may be formed at the excavated position. In this case, by stacking the waste 2 from the excavated position to the ground, the amount of the waste 2 stored in the temporary storage place A having a limited area can be secured.

  Next, as shown in FIG. 5A, the anti-scattering agent 18 is sprayed on the surface (upper surface and side surface) of the stacked waste 2 (S4). The anti-scattering agent 18 is for preventing the waste 2 from being scattered by spraying the shielding material 12. Although the waste 2 is accommodated in the container bag, when the container bag is damaged and there is a possibility that the waste 2 may be scattered, the scattering of the anti-scattering agent 18 is effective. When the waste 2 is exposed without being accommodated in the container bag, the scattering of the anti-scattering agent 18 is particularly effective. The nozzle 19 for spraying the anti-scattering agent 18 may be prepared separately from the construction system 10 or the construction system 10 may be diverted. As the scattering preventing agent 18, a material mainly composed of a resin material or a material mainly composed of an inorganic material can be used. Note that the application of the anti-scattering agent 18 can be omitted.

  Next, as shown in FIG. 5B, the shielding material 12 is sprayed on the surface (upper surface and side surface) of the waste 2 (S5). In the spraying process, the procedure of charging the material and spraying is repeated. By continuously charging the material, it is possible to perform the material charging and spraying simultaneously in parallel. By spraying the shielding material 12, the shielding material 12 adheres to the uneven surface between the stacked wastes 2 and the side surfaces (vertical surfaces) of the wastes 2. In this spraying process, the shielding material 12 is sprayed so as to have a thickness of 5 cm over the entire surface. By this spraying, the first shielding layer 3a is formed. The spraying thickness of the first shielding layer 3 a can be appropriately set according to the radiation level of the waste 2. For example, the spraying thickness of the shielding layer 3a can be a minimum thickness that can shield the radiation from the waste 2. The spraying thickness of the shielding layer 3a is preferably 3 to 20 cm, more preferably 3 to 10 cm. In this spraying construction, the spraying thickness may be confirmed by dividing the spraying amount by the spraying area, or may be actually measured. When dividing the spray amount by the spray area, rebound of the shielding material 12 may be considered.

  Next, as shown in FIG. 5C, the radiation amount emitted from the waste 2 through the shielding layer 3a is measured by the radiation detector 20 (S6). Here, the radiation detector 20 may be disposed close to the shielding layer 3a, or may be disposed slightly apart from the shielding layer 3a. It is preferable to measure the surface dose at a plurality of locations by the radiation detector 20. In addition, although the material hose 16 and the spray nozzle 14 are not illustrated in FIG.5 (c), you may measure a radiation dose with the radiation detector 20, spraying the shielding material 12. FIG. The radiation detector 20 may be provided so as to extend from the tip of the spray nozzle 14.

  Next, it is determined whether further spraying of the shielding material 12 is necessary according to the radiation dose measured by the radiation detector 20 (S7). When it is determined that further spraying of the shielding material 12 is necessary, the shielding material 12 is further sprayed as shown in FIG. 6A (S5). Although the spraying thickness here can also be set suitably, it shall be 5 cm in thickness, for example. Thereby, the second shielding layer 3b is formed. The thickness of the shielding layer 3b is equal to the thickness of the shielding layer 3a. The spraying thickness of the shielding layer 3b is preferably 3 to 20 cm, more preferably 3 to 10 cm. In addition, the spraying of the shielding material 12 can also be performed only to the part where the radiation dose is locally high.

  As shown in FIG. 6B, the radiation detector 20 measures the amount of radiation emitted from the waste 2 through the shielding layers 3a and 3b (S6), and further sprays the shielding material 12 in step S7. When it is determined that is unnecessary, the spraying construction is finished. Then, as shown in FIG. 6C, the shielding layer 3b solidifies and integrates the shielding layer 3a to form the shielding layer 3 (S8). The thickness of the shielding layer 3 formed by integrating the layers sprayed in a plurality of times is preferably 6 to 40 cm, and more preferably 6 to 20 cm. Through the above process, the shielding structure 1 for the waste 2 is completed.

  According to the construction method of the shielding structure 1 of the present embodiment, since the waste 2 is covered by the shielding layer 3 made of the shielding material 12, the radiation emitted from the waste 2 is shielded, and the temporary storage place of the waste 2 The radiation dose in A can be reduced. Here, since the shielding layer 3 is formed by spraying the shielding material 12, the shielding layer 3 can be formed with a uniform thickness and uniformity, and a predetermined shielding performance can be obtained reliably and quickly. Rapid construction is effective in reducing the amount of exposure of worker B during construction. Moreover, according to spray construction, since the shielding material 12 is compressed and adheres to the surface of the waste 2 with high density, the shielding layer 3 effective for shielding radiation can be formed. Since the shielding layer 3 can be made thinner than the shielding layer formed by conventional embankment, the load on the waste 2 is reduced. Furthermore, since the shielding material can be sprayed from the outside or the peripheral part of the temporary storage place A to the waste 2 placed in the central part of the temporary storage place A, the waste 2 placed on the ground G There is no need to install heavy machinery or the like on the top, and the overhead load during construction is also reduced. By reducing these loading loads, for example, when the waste 2 is stored in a container bag or the like and temporarily stored, the container bag or the like can be prevented from being damaged. Moreover, although it is necessary to take out the waste 2 after progress for a fixed period, since the shielding layer 3 by spraying can make the layer thickness thinner than the shielding layer by embankment as shown in FIG. Can be easily taken out, and the amount of the contaminated shielding material generated when the waste 2 is taken out is small, and the amount of the shielding material to be disposed can be reduced.

  As shown in FIG. 8, in the conventional shielding structure 100 using the embankment 25 and the cave 26, it was difficult to construct the embankment 25 uniformly by spreading and leveling, and the construction efficiency was low. For this reason, there has been a tendency for the dose of exposure to workers to increase. There is a possibility that the earth cutter 26 may deteriorate in the long term, and the function of preventing the scattering of the embankment 25 may be lost. Moreover, there is a possibility that the overload increases due to the heavy equipment getting on and the like, and the sandbag 26 and the container bag are damaged. Furthermore, in order to ensure the shielding performance, the embankment 25 has to be thick, and the disposal amount of the embankment 25 to be disposed at the time of taking out has increased. According to the shielding structure 1 of the present embodiment, the thin and uniform shielding layer 3 can be quickly applied, and the waste 2 can be appropriately applied at the temporary storage place A for the waste 2.

  Moreover, the radiation dose at the time of forming the shielding layer 3 having a certain thickness is measured, the necessity of further spraying of the shielding material 12 is determined according to the measurement result, and further spraying is necessary. When it is judged that the shielding material 12 is further sprayed. Thereby, the shielding layer 3 satisfying a predetermined shielding performance can be formed with a minimum thickness. As a result, the amount of the shielding material 12 used can be minimized, construction efficiency can be improved, and the exposure dose of the worker B can be further reduced. The ability to form the shielding layer 3 with a minimum thickness is also effective in reducing the loading load and the disposal amount of the shielding material during removal. For example, as shown in FIGS. 5B and 5C, when a predetermined shielding performance is exhibited in a state in which the shielding layer 3a is formed, the thin shielding layer 3 having only the shielding layer 3a is used. Can do.

  Moreover, the scattering of the waste 2 can be prevented by spraying the anti-scattering agent 18 before spraying the shielding material 12.

  In addition, since the waste 2 is placed on the adsorption layer 6 containing zeolite, leakage of radioactive materials into the ground can be prevented even when the container bag is broken, for example.

  Further, since the shielding material 12 can be discharged further from the spray nozzle 14, spraying away from the waste 2 can be easily performed. For example, even when the radiation level of the waste 2 is high, the exposure dose of the worker B can be suppressed. Moreover, since the material can be made more homogeneous, the shielding material 12 can be adhered well.

  Furthermore, even when a crack or the like occurs in the shielding layer 3 due to some factor, the repair can be quickly repaired by spraying the cracked portion again by using the unitized construction system 10.

  As mentioned above, although embodiment of this invention was described, this invention is not limited to the said embodiment.

  For example, you may have the process of covering the waste 2 with a net | network or a sheet | seat before spraying of the shielding material 12. FIG. For example, the shielding layer 3 can be easily removed when the waste 2 is taken out by covering the waste 2 with a fine net or a waterproof sheet and spraying the shielding material 12 thereon. In this case, the net or the sheet functions as an edge cutting material between the waste 2 and the shielding layer 3. Even if the net or sheet is somewhat deteriorated over time, the shielding layer 3 can be easily removed.

  Furthermore, when spraying the shielding material 12 a plurality of times, the layer may be covered with a net or a sheet after each layer is sprayed. In other words, a net or sheet as an edge cutting material may be interposed between the first shielding layer 3a and the second shielding layer 3b. In this way, for example, the shielding layer 3a having a relatively high degree of contamination close to the waste 2 and the shielding layer 3b having a relatively low degree of contamination can be separated and removed, and the shielding material corresponding to the degree of contamination can be removed. Appropriate disposal becomes possible.

  Moreover, although the said embodiment demonstrated the case where the wet construction system 10 was used, you may spray the shielding material 12 by a dry type. In a wet construction system, a quick setting agent is mixed at the time of kneading and water is added just before the spray nozzle. In this case, blockage of the hose can be prevented, and continuous construction can be performed smoothly.

  Moreover, although the said embodiment demonstrated the case where spraying was performed in multiple times, measuring a radiation dose, the spraying thickness was set beforehand, spraying was performed only once, and it checked after that. The radiation dose may be measured for this purpose. The adsorption layer 6 below the waste 2 may be omitted.

  DESCRIPTION OF SYMBOLS 1 ... Shielding structure, 2 ... Waste, 3 ... Shielding layer, 6 ... Adsorption layer (layer containing zeolite), 7 ... Shielding layer, 12 ... Shielding material, 18 ... Antiscattering agent, A ... Temporary storage place.

Claims (7)

A method of constructing a shielding structure in a temporary storage place for waste containing radioactive materials,
The shielding material which has a radiation shielding function and solidifies after spraying is sprayed on the waste placed on the ground, and a shielding layer formed by solidifying the shielding material is formed on the surface of the waste. The construction method of the shielding structure characterized by doing. Measuring the amount of radiation emitted from the waste through the shielding material during or after spraying the shielding material;
Determining the necessity of further spraying of the shielding material according to the measured radiation dose; and
The method for constructing a shielding structure according to claim 1, further comprising a step of spraying the shielding material when it is determined that further spraying of the shielding material is necessary. The method for constructing a shielding structure according to claim 1 or 2, further comprising a step of spraying an anti-scattering agent on the waste before spraying the shielding material. The construction method for a shielding structure according to any one of claims 1 to 3, further comprising a step of covering the waste with a net or a sheet before spraying the shielding material. The construction of the shielding structure according to any one of claims 1 to 4, further comprising a step of forming a layer on which the waste is placed, including zeolite, before the waste is placed. Method.   6. The shielding structure construction method according to claim 1, wherein the shielding material is sprayed in a wet manner.   The said shielding material is sprayed by a dry type, The construction method of the shielding structure as described in any one of Claims 1-5 characterized by the above-mentioned.

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