JP6651113B2 - Radioactive substance decontamination method and decontamination system - Google Patents

Description

  The present invention provides a method for removing radioactive substances to prevent contamination of living quarters and fields due to migration of the radioactive substances from forests and satoyama where decontamination of radioactive substances such as cesium (Cs) has not progressed. The present invention relates to a dyeing method and a decontamination system.

  It is expected that radioactive materials leaking or scattered inside nuclear power generation facilities and from nuclear power generation facilities for some reason will pollute the surrounding environment and have a serious adverse effect on the human body. The accident at Tokyo Electric Power Company's Fukushima Daiichi Nuclear Power Station in March 2011 led to a situation where the surrounding area was widely contaminated with radioactive cesium. In order to promptly recover from this situation, it is necessary to decontaminate a wide range of radioactive materials.First of all, decontamination work on residential areas and fields that are deeply connected to human living environments has been promoted. Was done. As a result, decontamination of settlements and fields has been almost completely performed, but decontamination of forests and satoyama (including coppice forests) is large, Currently, there are areas where decontamination has not yet progressed because it is more difficult than in the case of flat land such as fields.

  Some radioactive materials such as cesium have half-lives of several decades or more, and this damage will not only occur when the radioactive materials are scattered or leaked, but will also continue throughout the years. For this reason, radioactive materials such as cesium may migrate from the forests and satoyama (including coppice forests) that have not been decontaminated to the settlements and fields, and these living environment areas that have been decontaminated may be contaminated again. There is. In addition, even in forests and satoyama (including mixed forests) where decontamination work has already been completed, radioactive materials may not be completely removed due to the difficulty of decontamination work. In such a case, there is a possibility that the living environment area will be re-contaminated by radioactive materials remaining in forests and satoyama (thick forests) and radioactive materials accumulated over time.

  Contamination of the surroundings by radioactive materials is that, in the case of a residential area or a farmland such as a field where the surface of the earth is exposed, the radioactive material that has fallen with rain is adsorbed by the clay component. In this case, it is considered effective to decontaminate the radioactive material by exfoliating the surface soil and decontaminating it. Conventionally, (i) a method of shaving the surface using a large-sized machine, (ii) a high-pressure method A method of washing with water using a washing machine, (iii) a method of solidifying and decontaminating soil using a polyion complex, and the like are known. As the decontamination method using the (iii) polyion complex, for example, in Patent Literatures 1 and 2 and Non-Patent Literature 1, 2 is used so that gel-like precipitation does not occur in an aqueous solution containing both a polycation and a polyanion. A polyion complex to which 〜6 wt% of a salt (sodium chloride, potassium chloride, potassium sulfate, ammonium sulfate, etc.) is added is disclosed. Patent Document 1 discloses that since the use of the polyion complex alone cannot exert the ability to adsorb and fix radioactive cesium, a clay fine particle suspension and a polyion complex (polyion complex) aqueous solution are used for the purpose of imparting the ability. A decontamination method has been proposed in which the soil is contaminated with radioactive cesium and the topsoil of the soil is peeled off. This decontamination method discloses that bentonite is used as an example of clay fine particles.

  Several wt% of the salt contained in the aqueous polyion complex solution disclosed in Patent Documents 1 and 2 and Non-patent Document 1 is a component that inhibits plant growth. Therefore, the present inventors have proposed to prevent the spread of radioactive substances by removing and removing contaminated soil that has been immobilized using a dispersible polymer flocculant that does not generate a gel-like precipitate even without containing salts such as sodium chloride. A method has been proposed (Patent Document 3). The dispersion-type polymer flocculant described in Patent Document 3 is a dispersion in which a cationic polymer and an anionic polymer are blended so that either one of the charge ratios becomes excessive.

  On the other hand, in the case of forests and satoyama (including coppice forests), the ground surface is covered with fallen leaves and humus, etc. It is thought that it is. Therefore, in the case of decontamination of forests and satoyama (including coppice forests), it is effective to remove the fallen leaves and mulch on the surface, and it is determined that decontamination can be performed by nearly 90%. As a method for decontaminating forests and satoyama (coppice forests), for example, in Patent Document 4, viscosity adjustment is performed so that an aqueous medium containing a biodegradable water-soluble or water-dispersible polymer can penetrate to the surface layer of forest soil. A radioactive substance decontamination method is disclosed in which the surface soil of contaminated soil is peeled off using a fixing solution containing an inorganic radioactive substance adsorbent such as bentonite.

JP 2013-185941 A JP 2014-6111 A JP-A-2005-199057 JP 2013-242161 A

Hirochika Naganawa, Noriyuki Kumazawa, and eight others, "Removal of radioactive cesium from soil surface using polyion complex as immobilizing agent", Journal of the Atomic Energy Society of Japan, 2011, Vol. 10, No. 4, p. 227-234

  Radioactive materials such as cesium migrate from the forests and satoyama (including coppice forests) where decontamination has not been performed or are insufficient to the settlements or fields, and these living environment areas that have been decontaminated are recontaminated. Therefore, it is required to establish a method for decontaminating radioactive substances and to construct a decontamination system for the radioactive substances. That is, (1) radioactive substances such as cesium remaining or accumulated in soil such as deciduous leaves and mulch present in contaminated forests and satoyama (including coppice forests) can be efficiently and stably adsorbed over a medium to long term. Use of adsorbents that can be retained, (2) Adsorbents of radioactive substances and soil treatment liquids used for decontamination do not adversely affect the soil of forests and satoyama (bushes) in terms of plant growth, etc. (3) In order to reduce the volume of contaminants caused by radioactive substances, it is possible to separate and collect the adsorbent, which has adsorbed radioactive substances, from forests and satoyama (thick forests) without containing soil, and ( 4) A method for decontamination of radioactive materials that satisfies that the control of the transfer of radioactive materials from forests and satoyama (including mixed forests) is continuously performed, and that re-contamination of residential areas and fields can be prevented in the medium to long term. The pollution system . Furthermore, (5) labor saving of decontamination work and reduction of decontamination cost are also desired.

  However, the decontamination methods described in Patent Documents 1 to 4 and Non-Patent Document 1 are intended to peel off topsoil, fallen leaves and mulch of contaminated soil sprayed or injected with a polyion complex aqueous solution. (Including coppice forests) tends to be insufficiently decontaminated. Furthermore, contaminated soil and fallen leaves are stored as they are after separation and collection, or are subjected to volume reduction treatment, so that management and treatment of contaminants are required. In addition, radioactive substances are scattered from forests and satoyama (thick forests) where decontamination has not been performed, and as a result, accumulation of radioactive substances starts in places where decontamination has been completed, and the concentration of radioactive substances increases over time. As a result, radioactive substances are transferred to the settlements and fields, and recontamination of those areas is likely to occur. In order to prevent re-contamination, it is possible to decontaminate forests and satoyama (coppice forests) again, but in that case, it is necessary to perform decontamination as many times as possible, so it is safe for residents in the medium to long term, In addition, it is not possible to provide a space in which people can stably live. In addition, a large increase in decontamination cost is inevitable due to performing a wide range of decontamination operations a plurality of times.

In addition, the decontamination methods described in Patent Documents 1 and 2 and Non-Patent Document 1 disclose a polyion complex solution to which a salt such as sodium chloride is added in a sports field having an area of several hundred m ² to prevent gelation. The effect is confirmed by decontamination by spraying and removing after solidifying the soil. Small-scale soil fixation in pastures and paddy fields and decontamination experiments of soil exfoliation are also being carried out. However, due to concerns about salt damage, application to large areas of forest and farmland has not been achieved. When applying the Chernobyl method to decontamination of large areas of forests and agricultural lands, it is necessary to overcome salt damage. On the other hand, a method of preventing salt damage by adding salts that do not affect the growth of plants, such as ammonium sulfate, may be considered. However, the addition of nutrients such as ammonium sulfate to forests can cause adverse effects such as overnutrition of forests and disruption of the balance of forest ecosystems. In addition, it is conceivable that salts such as sodium chloride contained in the aqueous solution of polyion complex may migrate to living quarters and fields due to rainfall or the like. In this case, it is necessary to sufficiently consider the adverse effects on the fields. Therefore, it is necessary to use a polyion complex that functions as a soil fixing agent at a low salt concentration.

  The present invention has been made in order to solve such a problem, and efficiently removes radioactive substances such as cesium remaining or accumulated in soil such as deciduous leaves and mulch present in contaminated forests and satoyama (including coppice forests). In addition to easily decontaminating a wide range of forests and satoyama (coppice forests) that have been difficult to decontaminate by stably adsorbing and immobilizing them over a medium to long term, forests and satoyama (coppice forests) It is intended to provide a decontamination method and a decontamination system for radioactive substances that can prevent re-contamination of living areas and fields, etc. by continuously suppressing the transfer of radioactive substances from homes to residential areas or fields. .

  The present inventor, in conjunction with decontamination of contaminated forests and wilderness forests (including coppice forests), to prevent the transfer of radioactive materials to settlements or fields, etc., to create a safe space where people can continue living, A step of spraying and injecting inorganic particles for adsorbing radioactive substances in forests and mountains (including coppice forests); and a buffer zone provided at the boundary between forests and mountains and settlements or fields. By establishing a decontamination method having a step of aggregating only the inorganic particles that have adsorbed radioactive substances and a step of separating and recovering the aggregated inorganic particles, by constructing an optimal decontamination system for those methods, The present inventors have found that the above problem can be solved, and have reached the present invention.

That is, the configuration of the present invention is as follows.
[1] The present invention is a decontamination method for decontaminating at least one of a forest and a satoyama contaminated with a radioactive substance, wherein the radioactive substance is adsorbed on at least one of the forest and the satoyama. A step of directly spraying the inorganic particles, or a step of applying or spraying and injecting a dispersion or suspension containing the inorganic particles, and at least one of the forests and satoyama and a boundary between the settlement or the field, In order to agglomerate the inorganic particles, a buffer zone containing a flocculant having a charge of the opposite polarity to the charge of the surface of the inorganic particles is provided, and from at least one of the forest and satoyama, rainwater or artificial water A step of aggregating the inorganic particles flowing into the buffer zone by running water or a fountain with the flocculant, and a step of separating and collecting the inorganic particles aggregated together with the flocculant; It provides a decontamination method of a radioactive substance having a.
[2] In the present invention, as a step before the step of coagulating the inorganic particles with the coagulant, the coagulant is used alone or with another material in a network or mesh filter container through which the inorganic particles can pass. A step of enclosing in a mixed form, and a step of installing the filtration container containing the coagulant in the buffer zone, wherein the coagulant is a post-process of coagulating the inorganic particles with the coagulant. The method for decontaminating a radioactive substance according to [1], further comprising the step of separating and collecting the filtration container containing the aggregated inorganic particles.
[3] In the present invention, the dispersion or suspension containing the inorganic particles adsorbing the radioactive substance further comprises an ionic polymer or a nonionic polymer having a charge having the same polarity as the charge of the surface of the inorganic particles. The method for decontaminating a radioactive substance according to the above [1] or [2], wherein the method comprises the steps of: (a) dissolving the ionic polymer or the nonionic polymer in a water-soluble or colloidal aqueous dispersion; I do.
[4] The present invention provides rainwater or artificial running water or a fountain in the buffer zone containing, as the coagulant, an ionic polymer (A) having a charge having a polarity opposite to that of the surface of the inorganic particles. The method for decontaminating a radioactive substance according to any one of the above [1] to [3], comprising a step of aggregating the inorganic particles that have flowed in by the ionic polymer (A).
[5] The present invention, said by the coagulant, have a cationic polymer and an anionic polymer, and the charge ratio of the cationic polymer and anionic polymer is formulated to deviate from 1 A polymer flocculant (C) having a charge of a polarity opposite to the charge of the surface of the inorganic particles , or a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and And an amphoteric polymer flocculant (D) having a charge of the opposite polarity to the charge of the surface of the inorganic particles by adjusting the charge ratio of the cation and anion to be outside of 1. C) or in the buffer zone containing the amphoteric polymer flocculant (D), the inorganic particles flowing in by rainwater or artificial running water or a fountain are mixed with the polymer flocculant (C) or the amphoteric polymer flocculant. It provides a decontamination method of radioactive material according to any one of [1] to [3], comprising the step of aggregating by (D).
[ 7 ] In the present invention, the aggregating agent includes an ionic polymer (A) having a charge of a polarity opposite to a charge of the surface of the inorganic particles, and the ionic polymer (A) and the ionic polymer By using a combination of the ionic polymer (B) having a charge of a polarity opposite to that of the polymer (A), the ionic polymer (A) is located on at least either side of a forest and a satoyama in the buffer zone. A) in the area containing), the step of aggregating the inorganic particles that have flowed in by rainwater or artificial running water or a fountain with the ionic polymer (A), and the ionic polymer (A) flowing out without agglomeration. The step [1] to [3], comprising a step of aggregating the ionic polymer (B) in a region containing the ionic polymer (B), which is located on the side of a field or a habitat in the buffer zone. What Either provide decontamination method of radioactive material according to an item.
[7] In the present invention, the aggregating agent comprises a cationic polymer and an anionic polymer blended so that the charge ratio between the two is out of 1, and a charge having a polarity opposite to that of the charge of the surface of the inorganic particles is provided. Excess polymer flocculant (C1), or having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and having a polarity opposite to that of the charge of the surface of the inorganic particles. includes both monomeric amphoteric polymer flocculant charge ratios were prepared as out of the 1 in 1 molecule of the structural unit (D1) so as to have a charge, the polymer flocculant (C1) or amphoteric polymer A flocculant (D1) , a polymer flocculant (C2) having an excess of a charge opposite in polarity to that of the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), or an amphoteric using a combination of polymeric flocculant (D2), wherein A region located on at least either side of a forest and a satoyama in an impact zone and containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), and is inflowed by rainwater or artificial running water or a fountain. Coagulating and solidifying the inorganic particles with the polymer coagulant (C1) or the amphoteric polymer coagulant (D1); and the polymer coagulant (C1) or the amphoteric polymer coagulant flowing out without coagulation. (D1) is located on the side of a field or a habitat in the buffer zone and contains the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) in the region containing the polymer flocculant (C2). ) Or a step of aggregating with the amphoteric polymer flocculant (D2). The method for decontaminating a radioactive substance according to any one of the above [1] to [3], comprising:
[8] The present invention provides the decontamination method according to any one of [1] to [ 7 ], wherein after decontaminating at least one of the forest and satoyama, at least one of the forest and satoyama is decontaminated. A step of exfoliating deciduous leaves and deciduous soil containing the deciduous leaves from the ground where the deciduous leaves are present, and adding the exfoliated deciduous and deciduous soil to agricultural land or wilderness for restoring ground strength And a method for decontaminating a radioactive substance comprising the steps of:
[9] The present invention, inorganic particles for adsorbing the radioactive material, bentonite, zeolite, layered silicate, ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, illite and kaolinite A method for decontaminating a radioactive substance according to any one of the above [1] to [8], which is one or more selected from the group.
[10] The present invention provides the method for decontaminating radioactive substances according to [9], wherein the inorganic particles that adsorb the radioactive substances are bentonite.
[11] The present invention is a decontamination system for decontaminating at least one of a forest and a satoyama contaminated with a radioactive substance, wherein the radioactive substance is adsorbed on at least one of the forest and the satoyama. Means for directly spraying the inorganic particles, or means for applying or spraying and injecting a dispersion or suspension containing the inorganic particles, and at least one of the forest, satoyama and deciduous leaves and a residential area or a field At the boundary with, to aggregate the inorganic particles, to provide a buffer zone containing a flocculant having a charge of a polarity opposite to the charge of the surface of the inorganic particles, from at least one of the forest and satoyama Means for aggregating the inorganic particles flowing into the buffer zone by rainwater or artificial running water or a fountain into the flocculant, and the inorganic particles agglomerated with the flocculant Provides a means of separating and recovering, the decontamination system of radioactive material having a.
[12] According to the present invention, a mesh-like or mesh-like filtration container through which the inorganic particles can pass is enclosed in the buffer zone in a state where the flocculant is enclosed alone or in the form of a mixture with another material. The system for decontaminating radioactive substances according to the above [11], which is characterized in that:
[13] The present invention provides the ionic polymer or the nonionic polymer, wherein the dispersion or suspension containing the inorganic particles that adsorb the radioactive substance further has a charge having the same polarity as the charge of the surface of the inorganic particles. Wherein the ionic polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion, and the system for decontaminating a radioactive substance according to the above [11] or [12] is provided. .
[14] The present invention is characterized in that the buffer zone contains , as the coagulant, an ionic polymer (A) having a charge of a polarity opposite to the charge of the surface of the inorganic particles. [11] A decontamination system for a radioactive substance according to any one of [13] to [13].
[15] The present invention, said by the buffer zone is to have a cationic polymer and an anionic polymer, and the charge ratio of the cationic polymer and anionic polymer is formulated to deviate from 1 A polymer flocculant (C) having a charge of a polarity opposite to the charge of the surface of the inorganic particles , or a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and By adjusting the charge ratio of the cation and the anion to be outside of 1, the amphoteric polymer flocculant (D) having a charge of the opposite polarity to the charge of the surface of the inorganic particles is contained as the flocculant. The radioactive substance decontamination system according to any one of the above [11] to [13] is provided.
[ 16 ] The present invention provides an ionic polymer having a charge of a polarity opposite to the charge of the surface of the inorganic particles, in the buffer zone, from at least one of a forest and a satoyama to a field or a residence. A) as a region containing the coagulant and a region containing an ionic polymer (B) having a charge having a polarity opposite to that of the ionic polymer (A) are separated in this order and connected in series. The radioactive material decontamination system according to any one of the above [11] to [13], which is provided in a specific manner.
[17] In the present invention, in the buffer zone, a cationic polymer and an anionic polymer are compounded from at least one of a forest and a satoyama toward a field or a residential area such that the charge ratio of the cationic polymer and the anionic polymer deviates from 1. A polymer flocculant (C1) having an excess of a charge opposite in polarity to the charge of the surface of the inorganic particles, or a cationic monomer structural unit and an anionic monomer structural unit in one molecule The amphoteric polymer flocculant (D1) having a charge ratio in one molecule of both monomer structural units so as to have a charge of the opposite polarity to the charge of the surface of the inorganic particles , The region to be contained as a flocculant and the charge ratio of the cationic polymer and the anionic polymer are blended so as to deviate from 1, and the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is excessively added. Opposite to the charge Polymer coagulant (C2) having an excess of anionic charge, or the polymer coagulant (C1) having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, An amphoteric polymer flocculant (D2) in which the charge ratio in one molecule of both monomer structural units is adjusted so that the charge opposite in polarity to the charge possessed by the amphoteric polymer flocculant (D1) becomes excessive. ) Are provided in series in this order separately from each other in this order, wherein the radioactive substance decontamination system according to any one of [11] to [13] is provided. provide.
[18] The present invention provides the decontamination system according to any one of [11] to [17], wherein after at least one of the forest and the satoyama is decontaminated, at least the forest and the satoyama are decontaminated. Means for peeling deciduous leaves and deciduous soil containing the deciduous leaves remaining in any state from the ground where the deciduous leaves are present, and removing the separated deciduous leaves and deciduous soil to agricultural lands and wilderness for the purpose of restoring the ground strength Means for decontaminating radioactive material.
[19] The present invention, inorganic particles for adsorbing the radioactive material, bentonite, zeolite, layered silicate, ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, illite and kaolinite The radioactive material decontamination system according to any one of the above [11] to [18], which is one or more selected from the group.
[20] The present invention provides the radioactive substance decontamination system according to [19], wherein the inorganic particles that adsorb the radioactive substance are bentonite.
[The invention's effect]

  According to the radioactive material decontamination method and decontamination system of the present invention, both decontamination of forests and satoyama (including coppice forests) and cesium from forests and satoyama (including coppice forests) where decontamination has not been performed or are insufficient. It is possible to suppress the transfer of radioactive substances such as to the residential area or the fields, and to prevent recontamination of these living environment areas that have already been decontaminated. At this time, since the transfer of the radioactive material is continuously suppressed, it is possible to prevent re-contamination of the residential area and the fields in the medium to long term. Also, soil such as deciduous leaves and mulch present in contaminated forests and satoyama (including coppice forests) does not need to be peeled off during decontamination work, and radioactive substances such as cesium remaining or accumulating at that location are removed by inorganic particles. Since the adsorbent, more preferably clay particles such as bentonite, can adsorb and immobilize efficiently and stably over a medium to long term, the decontamination work becomes easy.

  Furthermore, in the present invention, as a treatment liquid containing an aggregating agent for aggregating the inorganic particles, it is possible to use a treatment liquid that does not cause gelation or precipitation without adding an inorganic salt. The decontamination treatment can be carried out without adversely affecting plant growth in forests and satoyama (including coppice forests). On the other hand, in the present invention, a polyion complex aqueous solution to which an inorganic salt is added can be used as the treatment liquid containing the flocculant. In this case, however, the polyion complex is used in a buffer zone provided in a place different from forests and satoyama (including thick forests). Since the application or application of the complex aqueous solution is performed, it is possible to reduce the influence on the plant growth and the like of forests and satoyama (including coppice forests). Then, the inorganic particle adsorbent in the state of adsorbing and holding the radioactive substance is separated and collected from forests and satoyama in an aggregated state, so that the volume of contaminants can be reduced.

  As described above, the method and system for decontaminating radioactive materials according to the present invention can continuously prevent the transfer of radioactive materials to residential areas and fields, etc., while saving labor and costs for decontamination. It will contribute to providing a safe and secure living space in the future.

It is a figure which shows typically the decontamination method and decontamination system of the radioactive substance by this invention. It is a figure which shows the modification of the decontamination method and decontamination system of the radioactive substance by this invention typically. It is a figure which shows typically the decontamination method and decontamination system of this invention which coagulate inorganic particles using the coagulant containing the combination of two types of ionic polymers. It is a figure which shows typically an example of the aggregation form of the inorganic particle formed when one or two types of ionic polymers are used as a flocculant. It is a figure which shows typically an example of the aggregation form of the inorganic particle formed when using the dispersion type polymer which adjusted the cationic polymer excessively by the charge ratio as an aggregating agent. It is a figure which shows typically an example of the aggregation form of the inorganic particle formed when using an amphoteric polymer as a flocculant. It is a figure which shows typically the model experiment method of cesium (Cs) transfer. It is a figure which shows the measurement result of the radioactive Cs density | concentration (Bq / kg) measured in the cesium (Cs) transfer model experiment. It is a figure which shows typically the slope soil which divided the soil into four divisions for use in a forest demonstration test. It is a figure which shows the measurement result of the radioactive Cs density | concentration performed in each measurement point of a soil slope before performing a forest demonstration test. It is a figure which shows the outline of the setting conditions of a forest demonstration test. It is a figure which shows the measurement result of the radioactive Cs density | concentration performed in each measurement point of the soil slope in a forest demonstration test as a distribution of radioactive Cs density | concentration.

  FIG. 1 is a diagram schematically showing a radioactive substance decontamination method and a decontamination system according to the present invention. FIG. 1 shows both the forest 1 and the satoyama 2 as places where the present invention is applied, but the distinction between the forest 1 and the satoyama 2 is not clear, and at least one of the forest 1 and the satoyama 2 is included. It should be. At least any one of the forest 1 and the satoyama 2 is distinguished from a living place 3 or a field 4 which is a daily living space of a person, and a flat land, a playground, a road, and the like included in those areas. , Bushes, etc. are treated as being included in a part of Satoyama 2.

  As mentioned above, the decontamination of forest 1 and satoyama (including coppice forest) 2 is larger than in the case of a flat land such as a residential area 3 or a field 4 because of the large area and rich undulation. As decontamination work is difficult, there are areas where decontamination has not yet progressed. The method and system for decontaminating radioactive materials according to the present invention perform decontamination of at least one of the forest 1 and the satoyama (including the coppice forest) 2 in such a situation, and the contaminated forest 1 and the satoyama. The purpose of the present invention is to continuously suppress the transfer of radioactive substances from the (gross forest) 2 to the settlements 3 or the fields 4 and to reduce the volume of contaminants caused by radioactive substances. Therefore, as shown in FIG. 1, a buffer zone 5 is provided at a boundary between at least one of the forest 1 and the satoyama 2 and the settlement 3 or the field 4, and basically, the following three processes and those processes are performed. It is characterized by including means of (1). The buffer zone 5 is provided for performing decontamination of the contaminated forest 1 and satoyama 2 and coagulation and separation and recovery of contaminants by radioactive substances in separate processes, respectively. And a new decontamination method and decontamination system which have not been provided in the past can be provided in that the method has the effect of being able to continuously suppress the migration of the wastewater.

  First, as a first step, inorganic particles for adsorbing radioactive substances are directly sprayed on at least one of the forest 1 and the satoyama 2, or a dispersion or suspension containing the inorganic particles is applied or sprayed and injected. I do. In the deciduous leaves, mulch and topsoil contaminated by the radioactive material in the forest 1 and the satoyama 2, the radioactive material is transferred to the inorganic particles with the lapse of time by the adsorption action, and the radioactive material is decontaminated from the deciduous, humus and topsoil. At this time, radioactive substances are adsorbed from the contaminated litter, mulch and topsoil by allowing the inorganic particles to be sprayed or injected into the forest 1 or the satoyama 2 and allowed to stand. In this step, as will be described later, since inorganic particles having a porous and positive or negative charge are used, while the inorganic particles stay in the forest 1 or the satoyama 2 where the inorganic particles have been sprayed or injected. The radioactive substance adsorbed on the surface is hardly desorbed, and is stably adsorbed and retained for a long time.

  In the first step, the application or spraying and injection of the inorganic particles or the dispersion or suspension example containing the inorganic particles is performed by a spraying method depending on the location or area of the contaminated forest 1 or the satoyama 2. It is performed by a casting method or a brush coating method. In the case of performing a wide range of decontamination, a spraying method using a spray or the like is generally used. When spraying over a wider area, helicopter or the like may be used. After the viscosity of the dispersion or suspension containing the inorganic particles has been adjusted in advance, application or dispersion and injection are performed. In addition, a coating device or a spray device that can be heated at the time of coating or spraying can also be used.

  On the other hand, the buffer zone 5 provided at the boundary between at least one of the forest 1 and the satoyama 2 and the settlement 3 or the field 4 contains a coagulant for coagulating the inorganic particles. Then, by causing natural rainwater flowing in at least one of the forest 1 and the satoyama 2 or artificial flowing water or a fountain, the inorganic particles having adsorbed the radioactive substance flow into the buffer zone 5. The inorganic particles are agglomerated by the aggregating agent. In the present invention, this operation is performed as a second step.

  The buffer zone 5 shown in FIG. 1 is a zone provided to contain inorganic particles that adsorb radioactive substances, and if it is a boundary that can separate at least one of the forest 1 and the satoyama 2 from the settlement 3 or the field 4, The width (length and width) is not particularly limited. Among them, the length is determined according to the length of the boundary that is in contact with at least one of the forest and the satoyama, but the width does not need to be set extremely wide. Can be achieved. When there is no appropriate buffer zone at the boundary, the buffer zone 5 can be formed by simply creating a boundary portion in contact with the settlement 3 or the field 4 in at least one of the forest 1 and the satoyama 2. In addition, in the settlement 3 or the field 4, a suitable vacant space may be found at a boundary portion in contact with at least one of the forest 1 and the satoyama 2, and when the land needs to be developed, the land may be used as the buffer zone 5.

  When the inorganic particles are allowed to flow into the buffer zone 5 in the second step, it is practical to use naturally-occurring rainwater since decontamination can be easily performed. Although the generation of rainwater is irregular, even if the inorganic particles are left for a long period of time, the absorbed radioactive substance is stably adsorbed and retained, so that it hardly affects the decontamination effect. Do not give. The inorganic particles that have flowed out after the generation of rainwater can be re-sprayed or applied for replenishment and used for decontamination of new radioactive substances. In addition, when it is desired to periodically flow the inorganic particles into the buffer zone without depending on the occurrence of rainwater depending on the weather, for example, artificial water or a fountain is generated by installing a sprinkler or a pericopter or the like. You may.

  In the step of aggregating the inorganic particles, four cases are applied as a combination of the aggregating agents, and an aggregation method suitable for each combination is applied. The combination of the flocculants and the method of flocculating the inorganic particles to which the flocculants are applied will be described later in detail.

  Subsequently, as a third step, the inorganic particles aggregated together with the aggregating agent are separated and collected. The separation and recovery of the inorganic particles can be performed manually or by using a crane or the like for separating and collecting the inorganic particles alone or the soil containing the inorganic particles. The separated and recovered inorganic particles alone or the soil containing the inorganic particles are generally packed in storage bags or packs. In the case where the inorganic particles are separated and collected together with the soil, the soil is separated and removed using a crane having catching claws at the top and bottom, and then separated and collected by directly packing them in a storage bag or pack. Work can be speeded up and simplified. On the other hand, when separating and recovering the inorganic particles alone, it is preferable to use a net-like or mesh-like filtration container through which the inorganic particles can pass (see FIG. 2 described later).

  In the present invention, in addition to the first to third steps, after packing the separated and collected inorganic particles or the soil containing the inorganic particles in a storage bag or pack, the radioactive substance is scattered to the outside or It is also possible to adopt a process of transporting and collecting to a place where a treatment for preventing leakage has been performed, and then storing and preserving it. The storage and storage period of the inorganic particles are determined in advance according to the half-life period of the radioactive substance. That is, if the storage time up to a level that does not affect the human body is known, it is left in the state of storage / preservation for at least that long. In order to further enhance security, a longer storage / preservation time is set with a margin compared to the above-mentioned period. Finally, after being stored and preserved in a sealed state until the radiation dose is reduced to a level that does not affect the human body at all, it is discarded as ordinary industrial waste. In addition, as for the inorganic particles which are no longer affected by the radiation by the radioactive substance, those regenerated by the desorption operation can be reused. On the other hand, the inorganic particles, even during the storage and preservation period, if it becomes possible to regenerate by performing the desorption operation of the radioactive material under an environment where radiation is strictly controlled, reuse the recycled product You may.

  FIG. 1 shows an example of a decontamination method in which the inorganic particles that adsorb the radioactive substance aggregated together with the coagulant in the third step are separated or recovered alone or together with the soil containing the inorganic particles. In the present invention, in order to facilitate the separation and recovery of the inorganic particles, the radioactive substance may be decontaminated by a modification shown in FIG.

  In the decontamination method shown in FIG. 2, as a pre-process of the step of aggregating the inorganic particles with the aggregating agent, the aggregating agent is used alone or in a network- or mesh-shaped filtration container 6 through which the inorganic particles can pass. And a step of installing a filtration container 6 containing the coagulant in the buffer zone 5, wherein the step of encapsulating the inorganic particles with the coagulant comprises: A step of separating and collecting the filtration container 6 containing the inorganic particles aggregated together with the coagulant. As shown in FIG. 2, it is practical that the filtration container 6 installed in the buffer zone 5 is divided into small parts from the viewpoint of handling and transportability and used in a plurality of aggregates. Further, in the present invention, the flocculant may be used in a distinguished manner according to the flocculation mechanism. In this case, the filtration container 6 containing a suitable flocculant according to the function is classified according to the function. It can be installed in the area in the form of one or more aggregates.

  As the mesh-shaped or mesh-shaped filtration container 6, one having a hole or a hole having a diameter or size sufficient for the inorganic particles to pass through is used. As described later, the inorganic particles used in the present invention are clay or inorganic adsorbent having an average particle diameter of several μm or less, and thus the diameter or the size of the holes formed in the filtration container 6 is several μm or more. The inorganic particles have a particle size distribution, so that the particle size is practically 10 μm or more in consideration of the maximum particle size and the like. Further, in order to easily manufacture and obtain the filtration container 6, the thickness is more preferably 100 μm or more. On the other hand, since the filtration container 6 contains the coagulant, the upper limit of the diameter or size formed therein is preferably several cm or less. If the upper limit is more than 5 cm, not only is it necessary to take special measures to enclose the coagulant in the filtration container 6, but it is not practical in terms of the strength of the filtration container 6. As a material of the filtration container 6, for example, a fibrous cloth used for producing a flexible container pack or the like is practical because of its flexibility and excellent handleability. Metal.

  As the other material to be mixed with the coagulant, fine powder or fine particles that can be mixed with the inorganic particles can be used, and examples thereof include fir, wood chips, plastic pieces, and earth and sand. The inorganic particles may not only be uniformly mixed with other materials, but may also be locally unevenly distributed at the center, ends, or the like of the other materials. When the coagulant is included in the filtration container 6 alone, since the particle size of the coagulant is generally small, a water-soluble adhesive, a pressure-sensitive adhesive, a sizing agent, clay, or the like is used. It is practical to produce a lump having a large particle diameter and to include one or more in that form.

  In the present invention, when applying or spraying and injecting the inorganic particles that adsorb the radioactive substance in the form of a dispersion or suspension, the dispersion or suspension further comprises an average of the inorganic particles. It is preferable that the polymer contains an ionic polymer or a nonionic polymer having the same polarity as the electric charge, and the ionic polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion. Thereby, it is possible to prevent the non-particles from being scattered into the air, which is likely to be generated at the same time as or after coating or spraying and injecting the dispersion or suspension. The inorganic particles are fine particles, not only once applied or sprayed on the surface of fallen leaves or topsoil, but also cannot remain in a certain place due to scattering even after the process, so the decontamination effect of the radioactive material is sufficient May not be obtained. Since the ionic polymer or the nonionic polymer has a function of fixing the inorganic particles in a fixed place of soil such as fallen leaves and mulch, and leaving them to stand, the decontamination effect of radioactive substances is promoted. Further, in order to obtain a high decontamination effect, it is necessary to increase a contact area between the inorganic particles and soil such as fallen leaves and mulch, and it is essential that the inorganic particles are not aggregated. Therefore, an ionic polymer having a charge of the same polarity as the charge of the surface of the inorganic particles or a nonionic polymer having no charge is used.

  The ionic polymer having a charge of the same polarity as the average charge of the inorganic particles is a cationic polymer or a charge depending on whether the charge of the surface of the inorganic particles is positive (+) or negative (-), respectively. Anionic polymers can be used. The cationic polymer is, for example, at least one selected from cationized cellulose, cationized starch, a polymer having an amino group, and a polymer of a quaternary ammonium salt. Examples include at least one selected from methylcellulose, carboxymethylamylose, ligninsulfonic acid and its salts, polyacrylic acid and its salts, polysulfonic acid and its salts. These cationic polymers and anionic polymers are dissolved or dispersed by natural rainwater running water, or artificial running water or fountains, and the inorganic particles adsorbing the radioactive substance are as small particles as possible in the buffer zone. It is desirable to let it flow. Therefore, a water-soluble or water-dispersible polymer is preferable.

  The nonionic polymer means a polymer having no charge in the molecule. For example, (a) a natural polymer of a polysaccharide, (b) a water-soluble polymer such as a chemically synthesized polymer such as polyvinyl alcohol, or the like. From at least one of the group consisting of water-dispersible polymers, (c) natural polymers such as chitosan and casein, and (d) chemically synthesized polymers such as polylactic acid, polycaprolactan and polyaspartic acid. The following water-soluble or water-dispersible polymers can be used. Since these polymers have the characteristic of biodegradability, there is no need to perform a removal operation after application or spraying, which can contribute to labor saving in decontamination operation.

The polysaccharide is not particularly limited as long as it is substantially water-soluble and can be rigidified (hardened) by dehydration after plasticization (melting). Specific examples of the (a) polysaccharide natural polymer include the following polysaccharides, for example.
(A1) Unground starch such as corn starch and wheat starch,
(A2) unmodified starches such as tapioca and potato starch,
(A3) low-esterification, low-etherification, cross-linking, oxidation, acid treatment, dextrinization, and pregelatinized modified starch of each aboveground stem and rhizome starch;
(A4) Cellulose Carboxymethylcellulose (CMC), methylcellulose (MC), hydroxyethylcellulose, hydroxypropylcellulose, etc. (a5) Seaweed polysaccharide agar, alginic acid, carrageenan, etc. (a6) Microbial polysaccharide pullulan, dextran, xanthan gum, etc. (a7) Other vegetable polysaccharides such as mannan, gum arabic, guar gum, tragacanth gum, locust gum, tamarind and the like.

  After dispersing the above-mentioned starch in which the reactive hydroxyl group is ester-substituted (including an organic acid or an inorganic acid and further including a graft-substituted product) or ether-substituted (including a graft-substituted product) in water, a plasticizer is added. Emulsion water (emulsion water composed of water, a plasticizer and a dispersion stabilizer) may be added to form a water-dispersible polymer solution.

  The polyvinyl alcohol (PVA) used as one kind of the (b) chemically synthesized polymer preferably has a degree of polymerization of 1,000 to 5,000, more preferably 1,700 to 2,400. Further, the saponification degree of PVA is preferably from 85 to 99%, more preferably from 87 to 93%, since the solution is water-soluble.

  As the nonionic polymer, another (e) water-soluble or water-dispersible polymer may be used. (E) Examples of the water-soluble or water-dispersible polymer include water-soluble or water-soluble polymers such as polyvinyl acetate, polyvinyl alcohol, polyacrylamide, polyvinylpyrrolidone, polyacrylic acid and salts thereof, and polyacrylates containing hydroxyl groups. Synthetic polymer or one of water-dispersible synthetic polymers such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, styrene-acrylate copolymer, vinyl acetate-acrylate copolymer, etc. Alternatively, two or more kinds can be used.

  Among them, it is easy to form a continuous layer composed of the above-mentioned contaminated soil and polymer, and not only can the continuous layer exhibit strength and elasticity enough to withstand various peeling conditions, but also safety. Polyvinyl acetate or a polymer containing polyvinyl acetate as a main component is preferred from the viewpoints of ease of handling, reduction of environmental load during long-term storage, disposal, and low cost. In the present invention, the polymer containing polyvinyl acetate as a main component means a polymer containing 50% by mass or more, preferably 70% by mass or more of polyvinyl acetate. The preferred polyvinyl acetate preferably has a molecular weight of 2,000 to 50,000. If the molecular weight is less than 200, the strength of the polymer film becomes weak, and if it exceeds 50,000, the solubility in water is reduced, or the viscosity of the aqueous solution is increased, and the operability and workability as a soil fixing solution is reduced. Tend to.

  In the present invention, an ionic polymer having a charge of the same polarity as the average charge of the inorganic particles, or a nonionic polymer having no charge, in a state of being mixed with the inorganic particles, a dispersion or suspension. As a medium when used as an aqueous medium, an aqueous medium containing water as a main component is used. Here, the aqueous solvent is a medium in which water accounts for 80% by mass or more, preferably 90% by mass or more, and more preferably 95% by mass or more. Since the radioactive substance decontamination solution of the present invention is intended for decontamination of fallen leaves and soil, an aqueous medium containing water as a main component is used in consideration of ease of handling and workability and reduction of environmental load on the periphery. There is a need. In addition to water, for example, a small amount of a solvent such as water-soluble alcohols such as methyl alcohol, ethyl alcohol and 2-propanol, ethers such as diethyl ether and tetrahydrofuran, or ketones such as acetone, methyl ethyl ketone and cyclohexanone is used. You may. These solvents are used when it is necessary to adjust the viscosity of the radioactive substance decontamination solution of the present invention or to increase the solubility of the above various polymers as necessary. Among these solvents, ethyl alcohol is preferable in order to reduce the influence on the human body and the environmental load.

Next, the coagulant used in the decontamination method and the decontamination system of the present invention will be described. In the present invention, the following four combinations (i), (ii), (iii) and (iv) are applied, and an aggregation method suitable for each combination is applied.
(I) An ionic polymer having a charge of a polarity opposite to the charge of the surface of the inorganic particles As the coagulant, an ionic polymer having a charge of a polarity opposite to the charge of the surface of the inorganic particles (A) Use The ionic polymer (A) is contained in the buffer zone, and the inorganic particles flowing into the buffer zone by rainwater or artificial running water or a fountain are aggregated by the ionic polymer (A).

(Ii) Combination of Two Kinds of Ionic Polymer FIG. 3 shows a decontamination method of the present invention in which inorganic particles are aggregated using a flocculant containing a combination of two ionic polymers in the decontamination method of the present invention. It is a figure which shows the dyeing | staining method and the decontamination system typically. As the coagulant, an ionic polymer (A) 7 having a charge opposite to the charge of the surface of the inorganic particles and an ionic polymer having a charge opposite to the polarity of the ionic polymer (A) 7 (B) Use 8 combinations. As shown in FIG. 3, in the buffer zone, a region located adjacent to at least one of the forest 1 and the satoyama 2 and containing the ionic polymer (A) 7, rainwater or artificial running water or The inorganic particles that have flowed in by the fountain are aggregated by the ionic polymer (A) 7 having a charge of the opposite polarity. Thereafter, the ionic polymer (A) 7 flowing out without coagulation is placed in the buffer zone 5 adjacent to the residential area 3 or the field 4 in the region containing the ionic polymer (B) 8. Aggregation by the conductive polymer (B) 8.

  FIG. 4 is a diagram schematically showing an example of an aggregated form of inorganic particles formed when one or two kinds of ionic polymers are used in the methods (i) and (ii). . In FIG. 4, portions surrounded by a solid line and a dotted line correspond to the methods (i) and (ii), respectively. FIG. 4 shows an example of the inorganic particles having a negative (−) charge on the surface, wherein the cationic polymer and the anionic polymer are an ionic polymer (A) and an ionic polymer, respectively. Used as (B).

  As shown in the portion surrounded by the solid line in FIG. 4, in the method (i), after the inorganic particles 9 having a negative (−) charge on the surface flow in by rainwater or artificial running water or a fountain, a buffer is applied. Agglomerated by the cationic polymer 10 contained in the zone 5. Due to the aggregation, the movement of the inorganic particles is restricted and stays in the area of the buffer zone 5, so that the migration to the settlement 3 and the fields 4 can be suppressed. Excess cationic polymer 10 which does not participate in the aggregation of the inorganic particles 9 in the process remains in a non-aggregated state in a region adjacent to at least one of the forest 1 and the satoyama 2 in the buffer zone 5. .

  On the other hand, in the method (ii), the anionic polymer 11 is contained in the area adjacent to the settlement 3 or the satoyama 4 in the buffer zone 5 as shown below the portion surrounded by the dotted line in FIG. A new area is provided, and the cationic polymer 10 flowing into the area by natural rainwater or artificial running water or fountain is aggregated by the anionic polymer 11. The region containing the anionic polymer 11 is serially arranged downstream of the region containing the cationic polymer 10 for the main purpose of aggregating excess cationic polymer 10 with the anionic polymer 11. It is provided. In that region, the granulation effect that the inorganic particles 9 aggregated by the cationic polymer 10 are coarsened can be obtained at the same time (see the figure shown in the upper part of the portion surrounded by the dotted line in FIG. 4). This granulation effect contributes to the aggregation of the inorganic particles, and the cationic polymer 10 bonded or attached to the surface of the inorganic particles 9 coarsens the aggregated particles by ionic interaction with the anionic polymer 11. Is based on the action of

  In the above method (ii), an anionic polymer is used for aggregating the cationic polymer, but instead of the anionic polymer, an anion-rich amphoteric polymer having a high anion equivalent as described below is used. May be used.

  In this manner, the aggregate of the ionic polymer (A) and the inorganic particles and the aggregate of the ionic polymer (A) and the ionic polymer (B) gradually progress to granulation, and As a result, it is easy to be fixed to the buffer zone 5, so that the shift to the residential area 3 or the field 4 is suppressed. In addition, since these aggregates have a clear difference in size with respect to soil, they can be easily separated and collected. Therefore, in the next step, not only the inorganic particles aggregated by the ionic polymer (A) can be efficiently separated and recovered, but also by adopting the method (ii), the particles are coarsened by granulation. Separation and recovery of not only the aggregated inorganic particles but also the ionic polymer (A) and the ionic polymer (B) can be performed simultaneously. Thereby, the amount of the inorganic particles and the ionic polymers (A) and (B) remaining in the buffer zone is significantly reduced, and a large decontamination effect is obtained, and the load on the environment is significantly reduced. Can be.

<Ionic polymer flocculant>
The ionic polymer (A) used in the above methods (i) and (ii) may be any one having a charge of a polarity opposite to that of the surface of the inorganic particles, and the inorganic particles have Anionic or cationic polymers can be used depending on whether the average charge is positive (+) or negative (-), respectively. On the other hand, the ionic polymer (B) used in the method (ii) is an ionic polymer having a charge of a polarity opposite to that of the ionic polymer (A). For example, when the ionic polymer (A) has a positive (+) average charge, it has a negative (-) average charge.

  The anionic polymer is, for example, at least one selected from carboxymethylcellulose, carboxymethylamylose, ligninsulfonic acid and salts thereof, polyacrylic acid and salts thereof, polysulfonic acid and salts thereof, and a cationic polymer. Examples thereof include at least one selected from cationized cellulose, cationized starch, a polymer having an amino group, and a polymer of a quaternary ammonium salt. Either one of these anionic polymer and cationic polymer is selected according to the charge of the surface of the inorganic particles. If the charge of the surface of the inorganic particles is unknown, the inorganic particles used in advance are mixed with an anionic polymer or a cationic polymer, and the ionic polymer in which aggregation occurs is replaced with an ionic polymer. Apply as (A). The above-mentioned ionic polymer applied as the ionic polymer (A) is preferably a water-soluble or water-dispersible polymer in consideration of handleability, workability, and reduction of environmental load on the periphery.

(Iii) Polymer flocculant having cationic polymer and anionic polymer or amphoteric polymer flocculant As the flocculant, polymer flocculant (C) having cationic polymer and anionic polymer, or 1 An amphoteric polymer flocculant (D) having a cationic monomer structural unit and an anionic monomer structural unit in the molecule is used. In the decontamination method and the decontamination system shown in FIG. 1, after the polymer coagulant (C) or the amphoteric polymer coagulant (D) is contained in the buffer zone 5, natural rainwater or artificial running water or fountain is used. The inorganic particles that have flowed in are aggregated by the polymer flocculant (C) or the amphoteric polymer flocculant (D).

  As the polymer flocculant (C), a polymer obtained by blending the cationic polymer and the anionic polymer mentioned as examples in the above <ionic polymer> such that the charge ratio of both becomes approximately 1: 1. Either a flocculant or a polymer flocculant blended so that the charge ratio of both deviates from 1 can be used. Similarly, an amphoteric polymer aggregate having a cationic monomer structural unit and an anionic monomer structural unit in one molecule and prepared so that the charge ratio of both monomers is approximately 1: 1. Either the agent or a polymer flocculant prepared so that the charge ratio of the two deviates from 1 can be used.

<Polymer flocculant>
When a polymer flocculant containing a cationic polymer and an anionic polymer is used as the polymer flocculant (C) in the form of a dispersion aqueous solution or a suspension aqueous solution, the ionic polymer having different polarities in the aqueous solution is used. The precipitates tend to come close to each other and aggregate to cancel each other's charges. Therefore, the inorganic particles have little or no aggregation effect. However, if the polymer coagulant (C) can be applied or sprayed to the buffer zone without coagulation, the movement of each ionic polymer is restricted and locally on the surface and inside of the soil in the buffer zone. When the inorganic particles having the opposite polarity come close to each other, the particles can agglomerate. By utilizing this function, it is possible to promote aggregation with the inorganic particles that have adsorbed the radioactive substance.

  When using a polymer flocculant (C) blended so that the charge ratio of the cationic polymer and the anionic high component is approximately 1: 1, use a gel in the aqueous dispersion or suspension. Since a precipitate is generated due to the formation of a salt, it is usually necessary to newly add an inorganic salt such as sodium chloride in addition to the counter ion. However, since the application or application of the polymer flocculant (C) is performed in a buffer zone provided in a place different from forests and satoyama (including thick forests), adverse effects on plant growth and the like are limited only to the buffer zone. You. Therefore, adverse effects on forests and satoyama (including coppice forests) can be significantly reduced as compared with conventional decontamination methods.

  When a polymer flocculant compounded so that the charge ratio of the two deviates from 1 is used as the polymer flocculant (C), as described later, it is not necessary to newly add an inorganic salt such as sodium chloride. It was found that a colloidal solution without precipitates could be formed. Therefore, if the purpose is to minimize the effects on plant growth, etc., not only in forests and satoyama (including coppice forests) but also in other areas, cationic polymer as a polymer flocculant (C) It is preferable to use a polymer flocculant in which a charge ratio of an anionic polymer and an anionic polymer is out of 1.

<Polymer flocculant compounded so that the charge ratio of the cationic polymer and the anionic polymer deviates from 1>
The polymer coagulant used in the present invention, in which the charge ratio of the cationic polymer and the anionic polymer is out of 1, is an aqueous solution containing the cationic polymer and the anionic polymer. When the polymer is the first polymer and the other polymer is the second polymer, the first polymer is blended in excess of the charge ratio of the second polymer. The resulting dispersion type polymer flocculant. This dispersion type polymer flocculant forms a stable and uniform aqueous colloid in water for a long period of time without forming a precipitate, and finds that it has a large flocculation force when mixed with the inorganic particles. Applied.

  FIG. 5 is a diagram schematically illustrating an example of an aggregated form of inorganic particles formed when a dispersion type polymer 12 in which a cationic polymer is excessively adjusted in charge ratio is used as an aggregating agent. The aggregation form shown in FIG. 5 is an example of what is observed in an aqueous solution when the inorganic particles 13 having a negative (−) charge on the surface are used.

  As shown in FIG. 5, the dispersion type polymer flocculant 12 used as the polymer flocculant (C) in the present invention is a cationic flocculant as exemplified in the combination of the two ionic polymers (i). The inclusion of both the polymer and the anionic polymer causes entanglement of the molecular chains, thereby forming a hydrophobic floc 14 serving as a nucleus for generating a large cohesive force. On the other hand, the formation of precipitates is suppressed by the presence of a hydrophilic molecular chain that has an increased affinity for water because either one of the cationic polymer or the anionic polymer is contained in excess, and the colloidal state in an aqueous solution And become evenly dispersed. As a result, the aqueous solution has an opaque or milky-white property, and has a great feature in that a uniform solution can be formed for a long period of time without forming a precipitate. When this dispersed polymer flocculant comes into contact with the inorganic particles after adsorbing the radioactive substance that has flowed in by rainwater or artificial running water or a fountain, flocculation occurs and is gradually converted into a large lump aggregate. As a result, it is possible to suppress the migration of the inorganic particles that have absorbed the radioactive substance to a place of residence or a field.

  The “opaque or milky white” of the dispersed polymer flocculant 12 is determined visually and by turbidity. For example, the turbidity of a colloidal solution of the polymer flocculant is measured at a wavelength of 660 nm using a spectrophotometer. When the turbidity was maintained at 85% or more even after 24 hours, it was concluded that the colloid was stably present without aggregation and precipitation. Further, in order to achieve the effects of the present invention, it is a necessary condition that the solution is a homogeneous solution in which no precipitate is observed even when left for 24 hours or more in summer and winter (temperature range: 5 to 30 ° C.).

  In the aqueous colloid solution used in the present invention, the amount of the cationic polymer and the anionic polymer is not made equal in charge ratio, but precipitates are formed by adding one of them in an excess in charge ratio. Therefore, it is not necessary to actively add a salt which is indispensable for obtaining a one-component polyion complex to the aqueous colloid solution as in the prior art. However, ionic polymers originally contain trace amounts of counter ions, and the colloidal aqueous solution used in the present invention may contain substantially trace amounts of salts. Has little effect on the generation of The salt for forming the counter ion varies depending on the type of the ionic polymer used, but generally, sodium chloride, potassium chloride, ammonium chloride, magnesium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, sulfate At least one kind of salt selected from magnesium, sodium nitrate, potassium nitrate and ammonium nitrate is used.

  In the cationic and anionic zwitterionic polymers contained in the dispersed polymer flocculant 12, the charge ratio of both ionic polymers is determined by the “ion equivalent mass” of the ionic polymer as follows. Is defined as

The molecular weight of one of the ionic polymers (A1) used in the present invention is defined as M ₁ , and the ionic equivalent mass is defined as EW ₁ . Ion equivalent weight of the ionic polymer _(A1) (EW 1), when the amount of the structural unit having the ion is 100 mole%, the same as the molecular weight of the structural unit having the ion (m _A). For example, when the proportion of constituent units having ions is 50 mol% and the proportion of constituent units having no ions is 50 mol%, the ion equivalent mass is determined by the molecular weight (m _A ) of the constituent units having ions and the proportion of ions. the sum _(m a + m _N) of the molecular weight of the structural unit which does not _{(m N).} Thus, the ion equivalent mass is determined by the molar ratio of the constituent unit having an ion to the constituent unit having no ion. In the case of other ionic polymer (B1), M ₂ the molecular weight of the ionic polymer _(B1), when the ion equivalent weight and EW _2, the ion equivalent weight is obtained in a similar manner.

The amount of one of the ionic polymer in the ionic polymer contained in the colloid solution (A1) of the present invention as a C _1, the other the amount of the ionic polymer (B1) C _Let it be ₂ . In that case, the colloid solution contains the ionic polymer (A1) at a concentration of (C ₁ / M ₁ ) mol and the ionic polymer (B1) at a concentration of (C ₂ / M ₂ ) mol. Therefore, in the colloid solution, the number of charges of each ion contained in the ionic polymer (A1) and the ionic polymer (B1) is P ₁ (equivalent) = (C ₁ / M ₁ ) × (M ₁ / EW ₁ ) and P ₂ (equivalent) = (C ₂ / M ₂ ) × (M ₂ / EW ₂ ).

If P ₁ = P ₂ (total charge is zero), then C ₁ / EW ₁ = C ₂ / EW ₂ . On the other hand, when the total charge of the aqueous colloid solution is not zero, P ₁ / P ₂ = (C ₁ / EW ₁ ) / (C 2 / EW ₂ )> 1 and (C ₁ / EW ₁ ) / (C ₂ / EW) ₂ ) The relationship of> 1 is satisfied. P ₁ and P ₂ are not specified as either an anionic polymer or a cationic polymer, and vice versa. Therefore, in the present invention, by blending an anionic polymer and a cationic polymer so as to satisfy the relationship of (C ₁ / EW ₁ ) / (C ₂ / EW ₂ )> 1, either one of the ions can be used. A colloidal aqueous solution in which a conductive polymer is excessively added at a charge ratio can be prepared.

<Amphoteric polymer flocculant>
The case where an amphoteric polymer is used as the polymer flocculant (C) will be described. An amphoteric polymer is a polymer having both positive (+) and negative (-) charges in the molecule, and has a binary structure having a cationic monomer structural unit and an anionic monomer structural unit. The polymer is synthesized as a ternary copolymer containing a nonionic monomer structural unit that functions as a hydrophobic unit as required. The polarity of the amphoteric polymer is adjusted so that the cation equivalent and the anion equivalent are almost the same and the charge ratio of both monomers is approximately 1: 1. It can also be prepared such that the charge ratio of the two deviates from 1 as in the case of an anion-rich amphoteric polymer having a high anion equivalent.

  The amphoteric polymer used as the polymer flocculant (C) is prepared by gelation in an aqueous dispersion or aqueous suspension, even if the amphoteric polymer is prepared so that the charge ratio of both monomers is approximately 1: 1. There is almost no occurrence of things. This is because a cationic monomer structural unit and an anionic monomer structural unit are separately arranged in one molecule, and in addition, both monomer structural units are determined by the presence of a counter ion and pH. This is because the units are adjusted so as not to be close to each other to suppress aggregation. Therefore, when an amphoteric polymer flocculant is used, the amphoteric polymer prepared so that the charge ratio of the monomers having the opposite polarities is approximately 1: 1 or the charge ratio of both is deviated from 1 Any of the prepared amphoteric polymers can be used without newly adding an inorganic salt such as sodium chloride to the aqueous dispersion or suspension.

  FIG. 6 is a diagram schematically illustrating an example of an aggregated form of inorganic particles formed when an amphoteric polymer is used as an aggregating agent. As shown in FIG. 6, the dispersion or suspension containing the amphoteric polymer flocculant 15 used as the polymer flocculant (C) in the present invention is a uniform solution that is stable for a long period without forming a precipitate. Because it can be formed, it can be applied or sprayed and injected into the buffer zone. The amphoteric polymer flocculant 15 flows in by rainwater or artificial running water or a fountain, and the inorganic particles (in FIG. 6, the inorganic particles 16 having a negative (1) charge on the surface in FIG. 6) after adsorbing the radioactive substance. Upon contact, agglomeration occurs, which is gradually converted to large lumps. As a result, it is possible to suppress the migration of the inorganic particles that have absorbed the radioactive substance to a place of residence or a field.

The amphoteric polymer flocculant used in the present invention generally contains the following monomer components.
(F) Cationic monomer Examples of the cationic monomer include monoallylamine, N-methylallylamine, N, N-dimethylallylamine, N-cyclohexylamine, N, N- (methyl) cyclohexylallylamine, N-dicyclohexylallylamine, diallylamine, N-methyldiallylamine, N-benzyldiallylamine and their addition salts, diallyldimethylammonium chloride, diallyldimethylammonium bromide, diallyldimethylammonium iodide, diallyldimethylammonium methylsulfate, diallylmethylammonium chloride, Diallylmethylammonium bromide, diallylmethylammonium iodide, diallylmethylammonium methylsulfate, diallyldibenzylammonium chloride, diallyldibenzylammonium bromide And diallylbenzyl ammonium iodide, diallylbenzylbenzyl methyl sulfate and the like.

(G) Anionic monomer Examples of the anionic monomer include (meth) acrylic acid and water-soluble salts such as a sodium salt, a potassium salt, and an ammonium salt thereof. In addition, an anionic monomer having two carboxyl groups can also be used, and examples thereof include maleic acid, fumaric acid, citraconic acid, and sodium, potassium, and ammonium salts thereof.

(H) Nonionic monomer Nonionic monomers include acrylamide and N-substituted products such as N-methyl, N, N-dimethyl, N, N-diethyl and N-hydroxymethylacrylamide. No.

  The amphoteric polymer used in the present invention is obtained by copolymerization of at least one or more of the above-mentioned cationic monomers and one or more of the above-mentioned anionic monomers. It may be a terpolymer containing one or more nonionic monomers. Copolymerization, such as a method of solution polymerization of an aqueous solution of the above-mentioned various monomer mixtures using a water-soluble initiator such as ammonium persulfate and potassium persulfate, or a method of photopolymerization using a photosensitizer, etc. It can be performed by a conventional method.

  When an amphoteric polymer is used as the polymer flocculant (C) in the present invention, the charge ratio of monomers having opposite polarities is changed according to the flocculated particle diameter and flocculation speed of the inorganic particles. An amphoteric polymer prepared so that the charge ratio of monomers having opposite polarities becomes approximately 1: 1; a cation-rich amphoteric polymer prepared such that the charge ratio of both deviates from 1; and an anion Not only one kind of rich amphoteric polymer but also two or more kinds may be used in combination.

(Iv) A polymer flocculant having two kinds of cationic polymer and anionic polymer or a combination of amphoteric polymer flocculant As the flocculant, a cationic polymer and an anionic polymer have a charge ratio of 1 And a polymer coagulant (C1) having an excess of a charge of the opposite polarity to the charge of the surface of the inorganic particles, or a cationic monomer structural unit and an anionic An amphoteric having a monomer structural unit and prepared such that the charge ratio in one molecule of both monomer structural units deviates from 1 so as to have a charge of the opposite polarity to the charge of the surface of the inorganic particle. A polymer flocculant (D1), a polymer flocculant (C2) having an excess of a charge having a polarity opposite to that of the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), Or an amphoteric polymer flocculant (D2) Use a combination with In the buffer zone of the decontamination method and the decontamination system shown in FIG. 3, the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is used instead of the ionic polymer (A) 7, Regions each containing the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) in place of the hydrophilic polymer (B) 8 are provided in series in this order. Here, the amphoteric polymer flocculant (D1) and the amphoteric polymer flocculant (D2) are each composed of a cation-rich amphoteric polymer having a high cation equivalent and a conversely an anion-rich amphoteric polymer having a high anion equivalent. Are used in such a manner that the electric charges of the combinations have the opposite polarities.

  In the buffer zone 5 shown in FIG. 3, a region located adjacent to at least one of the forest 1 and the satoyama 2 and containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1). The inorganic particles that have flowed in by rainwater, artificial flowing water or a fountain are aggregated by the polymer flocculant (C1) or the amphoteric polymer flocculant (D1). Thereafter, the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) flowing out without coagulation is positioned adjacent to the residential area 3 or the field 4 in the buffer zone, In the region containing the agent (C2) or the amphoteric polymer flocculant (D2), the polymer is coagulated by the polymer flocculant (C2) or the amphoteric polymer flocculant (D2).

  As described above, the polymer flocculant (C1) and the polymer flocculant (C2), or the amphoteric polymer flocculant (D1) and the amphoteric polymer flocculant (D2) are (ii) two kinds of ionic It has the same function as the ionic polymer (A) and the ionic polymer (B) described in the section of the combination of polymers. That is, the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is used for suppressing migration to a place of residence or a field by aggregating the inorganic particles that have absorbed the radioactive substance. . In addition, the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) is used for the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) flowing out without flocculation to a place of residence or a field. It is used to agglomerate the polymers of (C1) or (D1) for the purpose of preventing migration. Further, in a region containing the polymer flocculant (C2) or the amphoteric polymer flocculant (D2), inorganic particles aggregated by the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) are formed. Since the effect of granulation is obtained, it is possible to increase the size of the aggregated particles. Thereby, the effect of suppressing and preventing the migration of the inorganic particles having adsorbed the radioactive substance to the habitat or the field becomes higher.

  The flocculant used in the method (iv) is replaced with the polymer flocculant (C1) and the polymer flocculant (C2), or the amphoteric polymer flocculant (D1) and the amphoteric polymer flocculant (D2). Alternatively, a combination of the polymer flocculant (C1) and the amphoteric polymer flocculant (D2), or a combination of the amphoteric polymer flocculant (D1) and the polymer flocculant (C2) may be used. This is because there is basically no difference in the aggregating function between the inorganic particles and the polymer aggregating agent even when the combination of (C1) and (D2) or the combination of (D1) and (C2).

  Each of the flocculants used in the above four combinations (i), (ii), (iii) and (iv) is applied or sprayed in the form of a dispersed aqueous solution or a colloidal solution to give It is contained in the buffer zone 5 shown. At this time, it is practical to adjust the viscosity of the aqueous dispersion or colloidal aqueous solution to a range of 2 to 4000 mPa · s in a temperature range of 4 to 30 ° C. from the viewpoint of working efficiency for coating or spraying. The viscosity is 2 mPa. If it is less than s, the working efficiency for application or spraying is greatly reduced because the amount of each coagulant is small. On the other hand, when the viscosity exceeds 4000 mPa · s, the viscosity of the aqueous dispersion or colloidal aqueous solution increases remarkably, so that application or spraying becomes difficult.

  The dispersion aqueous solution or the colloidal aqueous solution containing each of the above flocculants is applied or sprayed to the buffer zone 5 by a spraying method, a pouring method, a brush coating method, or the like, and then the flocculants can be fixed by drying. . Further, application or spraying may be performed by installing a sprinkler or the like, or using a helicopter or the like. The application amount or the application amount of the aqueous dispersion or colloidal aqueous solution is determined based on the amount of each coagulant contained and the amount necessary for aggregating the inorganic particles and the polymer having the opposite polarity charge with the inorganic particles. be able to.

  Although the configuration of the decontamination method and the decontamination system according to the present invention is as described above, in the present invention, after decontaminating at least one of the forest and the satoyama, at least one of the forest and the satoyama is further decontaminated. A step and means for peeling deciduous leaves and deciduous soil containing the deciduous leaves from the ground where the deciduous leaves are present, and removing the separated deciduous leaves and deciduous soil to agricultural lands and wilderness for restoring ground strength And adding means and means. Leaf litter that remains as it is after decontamination and mulch including the litter are used after performing radiation measurement, soil inspection, and the like to sufficiently confirm that the influence of radiation by the radioactive substance has disappeared.

  Conventionally, a method of adding a new fertilizer or soil has been adopted for restoring the fertility of agricultural lands and wilderness, but decontamination has already been completed by using leaf litter after decontamination and mulch containing the leaf litter. Regeneration of farmland and wilderness can be performed efficiently and safely. In particular, deciduous leaves and mulch in the same area have good compatibility with agricultural lands and wilderness in terms of climate and climate, so that it is possible to increase the effect and speed of restoring the fertility.

<Inorganic particles>
As the inorganic particle-based radioactive substance adsorbent used in the present invention, any inorganic particles having a radioactive substance adsorption function can be used. For example, bentonite, zeolite, layered silicate, ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, illite and kaolinite mentioned, the use of one or more selected from these groups Can be. Since these inorganic particles are generally porous and have a positive (+) or negative (-) charge on the surface, not only the ability to adsorb a radioactive substance but also each coagulant used in the present invention is used. Has a function of being aggregated by

  The average particle diameter of the inorganic particles may be in the range of 0.01 to 20 μm, but is preferably 1 to 2 μm. The maximum particle size of these inorganic particles is 100 μm or less, preferably 50 μm or less. When the average particle size is less than 0.01 μm, aggregation of the inorganic particles easily occurs, and the workability in adjusting the fixing solution, coating, and the like becomes remarkable. Further, when the average particle diameter exceeds 20 μm, inorganic particles having a large diameter come to be mixed, so that the mechanical strength of the fixed layer containing the above-mentioned radioactive substance-containing forest soil is greatly reduced, and it is difficult to remove and remove the fixed layer. For the same reason, the maximum particle size of these inorganic particles is 100 μm or less, preferably 50 μm or less.

In the present invention, among the above-mentioned inorganic particles, bentonite is preferred from the viewpoints of achievement as a radioactive substance adsorbent, handleability, low cost, and the like. Bentonite is particularly useful because it has a superior effect of absorbing moisture from surrounding soil and the like when dried (sanctation effect), and promotes the adsorption of radioactive substances such as Cs to bentonite. Bentonite has exchangeable cations such as Na ⁺ , K +, Ca ²⁺ , and Mg ²⁺ between layers, and has a function of adsorbing and retaining radioactive Cs ⁺ by ion exchange. Since Al ³⁺ in the alumina layer is replaced by Mg ²⁺ or the like, the surface of the bentonite has a negative charge. Bentonite can be obtained at a low cost because a mined bentonite mine can be used as it is with its maximum particle size adjusted to 100 μm or less, preferably 50 μm or less, excluding coarse particles.

  The inorganic particle-based radioactive material adsorbent can be sprayed in an arbitrary amount on at least one of a forest and a satoyama. If the application amount of the inorganic particles is small, it is not possible to adsorb all the radioactive materials contaminating the forest and satoyama, so that the radiation dose measurement is performed temporarily or periodically in the forest and satoyama, and the measurement is performed. It responds by increasing the amount of application or the number of applications based on the value. Even if the amount of application is large, the inorganic particles are almost harmless to the human body, so that there is almost no problem even if they are left in a forest or a satoyama. Further, the inorganic particles are washed away by a running water or a fountain due to naturally occurring rainwater or artificial watering, and the inorganic particles are washed away to the buffer zone, and the amount of the inorganic particles present in forests and satoyama gradually decreases. The effect is smaller. When the decrease in the amount of the inorganic particles is remarkable and it is desired to continuously maintain the decontamination, the inorganic particles are sprayed again on a forest or a satoyama.

  When applying or spraying and injecting the inorganic particles in the form of a dispersion or suspension, the amount is preferably 0.1 to 20 parts by mass, more preferably 0 to 20 parts by mass when the aqueous medium is 100 parts by mass. 0.5 to 5 parts by weight. If the content of the inorganic particles is less than 0.1 parts by mass, the amount of the dispersion or suspension applied or sprayed becomes large, and the efficiency of the decontamination work is greatly reduced. Further, when the content of the inorganic particles exceeds 20 parts by mass, separation of the inorganic particles becomes remarkable, and not only is it difficult to perform uniform application or spraying, but also the efficiency of decontamination work is significantly reduced. I do.

  When the dispersion or suspension containing the inorganic particles is further mixed with an ionic polymer having a charge of the same polarity as the average charge of the inorganic particles, or a nonionic polymer having no charge, the ion The content of the conductive polymer or the nonionic polymer is preferably 0.2 to 60 parts by mass, more preferably 0.5 to 5 parts by mass, when the aqueous medium is 100 parts by mass. When the content of the ionic polymer or the nonionic polymer is less than 0.2 parts by mass, the effect of preventing the particles from scattering into the air cannot be obtained. Alternatively, since the viscosity of the suspension is remarkably increased, the efficiency of the decontamination operation is significantly reduced. It is practical to adjust the viscosity of the dispersion or suspension to a range of 2 to 4000 mPa · s in a temperature range of 4 to 30 ° C.

  The present invention will be described by way of examples based on the above-described basic configuration of the radioactive substance decontamination method and the decontamination system according to the present invention, but the scope of the present invention is not limited to these examples.

[Example 1]
In this example, an experiment was conducted to confirm the migration of Cs, which is a radioactive substance, using bentonite having a negative (-) charge on the surface as inorganic particles. As described in the methods (iii) and (iv) above, a dispersion-type polymer flocculant having a cationic polymer and an anionic polymer was used as the polymer flocculant. As a cationic polymer, polydiallyldimethylammonium hydrochloride (or chloride) represented by the following formula (1) (Unisense FPA1001L, trade name of Senka Co., Ltd .: molecular weight of 100,000 to 500,000, hereinafter abbreviated as DADMAC); A sodium salt of carboxymethylcellulose represented by the following formula (2) (CMC Daicel 1220, trade name of Daicel Chemical Industries, Ltd .; molecular weight: 160,000 to 380,000; hereinafter abbreviated as CMC) is used as a molecule, and polycation excess (DADMAC) is used. An excess) and an aqueous solution of an excess of polyanion (excess of CMC) were prepared, respectively, and used as a polyion complex aqueous solution of a polymer flocculant (C1) and a polymer flocculant (C2), respectively.

  In this example, the aqueous solution of the polymer flocculant (C1) in excess of the cation-excess polyion complex and the aqueous solution of the polymer flocculant (C2) in the anion-excess polyion complex were DADMAC and CMC in a mass ratio of DADMAC: CMC = 43: 3 and The coagulants blended in a ratio of DADMAC: CMC = 1: 3 were used after adjusting to aqueous solutions containing 1.5% by mass each. Here, the charge ratio of DADMAC: CMC in the aqueous solution of the cation-excess polyion complex is 69: 1, while the charge ratio of DADMAC: CMC in the aqueous solution of the anion-excess polyion complex is 1: 3. Neither the cation-excessive polyion complex aqueous solution nor the anion-excessive polyion complex aqueous solution exhibited a colloidal aqueous solution in which no precipitate was formed. The charge ratio of DADMAC: CMC can be determined as follows.

CMC represented by the formula (2) has a degree of etherification of 0.8 to 1.0. Here, the degree of etherification, -R parts of CMC of -O-R is the number obtained by replacing the _-CH 2 COONa, employing 0.9 average as degree of etherification in the present embodiment. When the degree of etherification is 0 and 1, the molecular weight per mol is 162 g and 242 g, respectively. When the degree of etherification of CMC is 0.9, the apparent molecular weight can be calculated as 162 (g / mol) × 0.1 + 242 (g / mol) × 0.9 = 234 (g / mol). Since 0.9 equivalent of a negative charge is present per repeating structural unit of the CMC represented by the above formula (2), the ion equivalent mass (EW ₁ ) can be calculated as 234 g / 0.9 equivalent. On the other hand, DADMAC has a molecular weight of 161.7 g per 1 mol, is highly pure, and has one equivalent of a charge per repetitive structural unit represented by the above formula (1). Therefore, the ion equivalent mass (EW ₂ ) is 161.5 g. It can be calculated at 7 g / 1 equivalent, which is the same as the molecular weight of the repeating structural unit.

  The model experiment of Cs transfer was performed according to the method shown in FIG. In FIG. 7, (a) shows a basic configuration of a jig when performing a model experiment, and (b) shows conditions set when performing a model experiment.

  As shown in FIG. 7A, the jig for performing the model experiment basically includes a first layer container 17 containing 2 kg of humus, a second layer container 18 containing 4 kg of sand, and It is composed of a third-layer container 19 and provided at the bottom of each container with a large number of fine holes or holes capable of passing water sprayed or poured from the top of the first-layer container 17. At the lowermost part, a water storage container 20 for receiving or storing water that has been sprayed or injected into the first-layer container 17 and has passed through the second-layer and third-layer containers 18 and 19 is arranged.

  The conditions set when performing the model experiment are the four types shown in FIG. In FIG. 7B, “humus and bentonite” indicates a layer in which a bentonite suspension is sprayed on humus, and “PIC” is an abbreviation of a polyion complex. The layer which sprayed the excess polyion complex aqueous solution on the sand is shown.

When mixing the bentonite which is an inorganic particle into the container 17 of the first layer in FIG. 7 (b), 7 L (liter) of water in which 500 g is suspended in 10 kg of mulch was added, stirred and dried. 2kg of things were put. As bentonite, bentonite donmin (manufactured by Volclay Japan, Inc.) was used. When the aqueous solution of the cation-excess polyion complex was sprayed on the second layer container 18 containing sand, the solution was sprayed under the condition of 5 L (liter) / m ² . Similarly, when the aqueous solution of anion-excess polyion complex was sprayed on the third-layer container 19 containing sand, the spraying was performed under the condition of 5 L (liter) / m ² . Here, the anion-excess polyion complex mixed in the third layer plays a role of suppressing the cation-excess polyion complex mixed in the second layer from flowing out to the lower water storage container 20. The amount of water sprayed or injected from the upper part of the first layer container 17 is 24 L (liter) corresponding to an average rainfall of 150 m for one month in Japan. The radiocesium concentration was measured using a CsI (TI) scintillation detector, and expressed as a radiation dose per 1 kg of sand (Becquerel (Bq) / kg).

  FIG. 8 shows the measurement results of the radioactive Cs concentration (Bq / kg) measured in the Cs transfer model experiment. In FIG. 8, (a) and (b) are the measurement results of the first layer and the second layer, respectively. The difference in the radioactive Cs concentration with and without the bentonite and the difference in the radioactive Cs concentration with and without the cation-excess polyion complex, respectively, are shown. (A) and (b) can be compared.

  As shown in FIG. 8A, in the case where bentonite is present in the first layer container, the decrease in the radioactive Cs concentration after spraying or injecting water is larger than in the case where there is no bandonite. You can see that it is. The reason why the decrease in the radioactive Cs concentration was large in the presence of bentonite is that the bentonite particles to which Cs in the humus was adsorbed were washed away with water.

  As for the difference in the radioactive Cs concentration depending on the presence or absence of the cation-excess polyion complex, as shown in FIG. 8B, the radioactive Cs concentration increased when bentonite was present in the first layer. This increase in the radioactive Cs concentration is due to the bentonite particles adsorbing the radioactive Cs concentration flowing into the second layer due to the water sprayed or injected from the upstream and being aggregated by the cation-excess polyion complex mixed in the second layer. And consequently due to the radiation dose supplemented with radioactive Cs.

  As described above, when bentonite is added to humus, radioactive Cs in humus shifts to bentonite by ion exchange reaction, and further, bentonite particles moved by spraying or injecting water are aggregated by the cation-excess polyion complex, It was confirmed that it was captured in the sand.

  In the model experiment shown in FIG. 7, an aqueous solution or suspension simultaneously containing an ionic polymer or a nonionic polymer having the same negative (−) charge as the charge on the surface of bentonite was added to the suspension having bentonite. Even if it is used, it is easily presumed that the measurement results of the radioactive Cs concentration in the first and second layers show the same tendency as that shown in FIG. For example, the first layer is formed by using a solution in which biodegradable water-soluble starch (corn starch) is dissolved in a suspension having bentonite [water: bentolite: starch = 100: 30: 5 (mass ratio)]. It was found that a starch layer could be formed near the surface of the mulch when applied to the mulch placed in the container. This starch layer allows bentonite to be left inside the humus for a medium to long term, so that the contact between the bentonite and the radioactive Cs contained in the humus can be sufficiently ensured, and the adsorption of radioactive Cs is promoted. It has the effect of doing. Then, when water is sprayed or poured into the container of the first layer, the starch flows out together with the water, so that even if starch is included at the same time, the movement of bentonite is hardly affected. Thus, it is considered that the addition of the ionic polymer or the nonionic polymer makes it possible to further enhance the decontamination effect by bentonite.

[Example 2]
Based on the model experiment results of the Cs migration described above, the soil actually encountered rainfall while being left in the forest was used, and the soil was divided into four sections as schematically shown in FIG. went. The shape and area of each soil divided into four sections are as shown in FIG. The partitioning of each section was performed by arranging black plastic in a slender plastic bag to prevent inflow of soil between the sections. The humus contaminated with radioactive Cs at the forest surface was collected and moved to the top of the soil slope and placed. The humus moved to the uppermost part of the soil slope in this way can be regarded as the humus existing in at least one of the forest and the satoyama in the present invention. Further, the measurement points (●) shown in FIG. 9 mean the points where the radioactive Cs concentration was actually measured. The measurement of the radioactive Cs concentration was performed using an CsI (TI) scintillation detector at three points: upper, middle, and lower, respectively.

  Before conducting the forest demonstration test, first, the radioactive Cs concentration was measured at three points, that is, upper, middle and lower parts shown in FIG. FIG. 10 shows the measurement results. As shown in FIG. 10, the radioactive Cs concentration is higher in the lower humus than in the upper side, and it can be seen that the radioactive Cs moves from the upper side to the lower side by rainfall.

Next, using the soil for the forest demonstration test shown in FIG. 9, at each measurement point of the radioactive Cs concentration, the change in the radioactive Cs concentration due to the presence or absence of bentonite and the presence or absence of the cation-excess polyion complex and the anionic polyion complex was examined. FIG. 11 is a diagram illustrating an outline of conditions set when the forest demonstration test is performed. In FIG. 11, the soil in the left two rows is sprayed with a suspended aqueous solution containing 1% by mass of bentonite at 5 L / m ^{2 on} the collected humus, whereas the soil in the right two rows is sprayed with bentonite. Did not do. In addition, in the soil on the left side of the soil slopes in the left two rows where the vent inner cylinder was sprayed, the cation-excess polyion complex (polyion complex is abbreviated as PIC) aqueous solution was applied from the top to the middle point on the soil located on the left side. An aqueous solution of anionic PIC was applied to the lower part under the condition of 5 L / m ² . On the other hand, the soil located on the right side of the soil in the left two rows was not coated with both polyion complex aqueous solutions. Similarly, for the soil on the left side where no bentonite was sprayed, the soil located on the left side was filled with a cation-excess PIC aqueous solution from the top to the middle point and an anion-rich PIC aqueous solution from the middle point to the bottom at 5 L / each. while was applied under the condition of m ^2, soil located on the right side was not applied in both the polyion complex solution. Here, the zone to which the cation-excess PIC aqueous solution and the anionic PIC aqueous solution are applied can be regarded as a buffer zone provided in the present invention. After the test soil was modified under these conditions and the soil was notified for one month, the soil on the surface was collected, and the radioactive Cs concentration was measured at three measurement points: upper, middle and lower. .

  FIG. 12 shows the distribution of the radioactive Cs concentration in the four rows of soil shown in FIG. Show. The distribution of the radioactive Cs concentration shown in FIG. 12 means the ratio of the radioactive Cs concentration at each measurement point when the sum of the radioactive Cs concentrations measured at each of the upper, middle, and lower measurement points is 100%. . In addition, the measurement result immediately after humus collection shown in FIG. 12 was represented by the average value of the measurement values (1) to (4) shown in FIG.

  As shown in FIG. 12, the distribution of the radioactive Cs concentration of the slope soil after one month of storage was slightly different from that immediately after the collection of humus soil, as measured by the presence or absence of bentonite and the presence or absence of the cation-excess polyion complex and the anionic polyion complex. different. However, except for the presence of bentonite and a cation-excess polyion complex (leftmost in FIG. 12), in the other three cases, the tendency that the ratio of the radioactive Cs concentration in the middle and lower parts is higher than that in the upper part is almost the same. Is the same. On the other hand, when bentonite and a cation-excess polyion complex were present (the leftmost part in FIG. 12), the ratio of the radioactive Cs concentration in the upper part of the soil slope was high. Therefore, radioactive Cs was adsorbed in the mulch. It can be seen that the bentonite particles were agglomerated by the cation-excess polyion complex, and radioactive Cs was captured at the upper part of the soil slope. Therefore, also in the forest demonstration test, it was confirmed that the cation-excess polyion complex had an effect of aggregating bentonite particles to which radioactive Cs had been adsorbed and suppressing migration of slope soil downward.

  Further, in the presence of bentonite particles and a cation-excess polyion complex, by spreading the anion-excess polyion complex from the middle to the lower part of the slope soil, the ratio of the radioactive Cs concentration is lower in the middle of the soil slope. , In the lower part, and a remarkable difference was observed between the middle part and the lower part of the slope soil as compared with the other three cases shown in FIG. This may be because inorganic particles aggregated by the cation-excess polyion complex were granulated by the excess anionic polyion complex to increase the size of the aggregated particles, but the details are unknown. Originally, the anion-rich polyion complex contained from the middle to the lower part of the soil slope was used to aggregate the cation-rich polyion complex contained from the upper part to the middle of the soil slope. It is conceivable that the excess polyion complex has the effect of promoting the coarsening of the inorganic particles aggregated by granulation.

  In this way, the inorganic particles aggregated with the cation-excess polyion complex above the sloped soil are separated together with the soil containing the aggregated inorganic particles, and then the inorganic particles are sieved using a sieve or the like having a diameter equal to or more than a predetermined size. In a form in which only the aggregates are separated and collected, or in a form as it is, the soil containing the aggregated inorganic particles is packed in a storage bag or pack. Thereafter, the radioactive material is transported to a place where treatment has been performed so as not to be scattered or leaked to the outside, collected, and stored and preserved. Aggregates of inorganic particles granulated by the cationic excess polyion complex, and aggregates of the cationic excess polyion complex and the anion excess polyion complex in the middle and below the slope soil are also stored in a bag for storage by the same treatment. After stuffing in a pack or the like, it is stored and stored in a predetermined place.

  When the aggregate of the inorganic particles adsorbing the radioactive Cs is stored and stored separately from the soil, as shown in FIG. 2, a mesh or mesh filter container 6 through which the inorganic particles can pass is used. Is preferred. After the filtration container 6 is filled with the cation-excess polyion complex alone or in a form mixed with another material, the filtration container 6 is placed in a portion above the buffer zone 5. After the inorganic particles are aggregated by the cation-excess polyion complex, only the filtration container 6 containing the inorganic particles aggregated together with the cation-excess polyion complex is separated from the buffer zone 5 and collected. When the inorganic particles adsorbing the radioactive Cs are contained together with other materials, only the aggregates of the inorganic particles are separated by a sieve or the like, or the aggregated inorganic particles are packed together with other materials into a storage bag or pack. After collection, store and store in a predetermined place. This eliminates the need to separate and collect the inorganic particles aggregated by the cation-excess polyion complex together with the topsoil of the buffer zone 5, thereby greatly reducing the separation and collection process. In addition, the method shown in FIG. 2 has an advantage that the decontamination work is facilitated even when the filtration container 6 is left for a long period of time because scattering of the inorganic particles adsorbing the radioactive Cs to the outside can be suppressed. Having.

  FIG. 2 shows a method in which the flocculant of the anion-excess polyion complex is sprayed on the soil below the buffer zone 5, but instead of the method of spraying, the anion-excess polyion complex is used alone or in another form. A filtration container sealed in a form mixed with the above materials may be used. As described above, in the method shown in FIG. 2, the buffer zone 5 is roughly divided into two areas according to the function of the coagulant, and each area includes each coagulant in the form of one or a plurality of aggregates. A filtration vessel can be installed.

  In the above Examples 1 and 2, the effect of the present invention was described using the dispersion type polymer flocculant having the cationic polymer and the anionic polymer described in the above methods (iii) and (iv). Even when the cationic polymer or anionic polymer described in the above methods (i) and (ii) is used, similar effects can be obtained in a model experiment of Cs migration and a forest demonstration test.

  As the cationic polymer, for example, polydiallyldimethylammonium hydrochloride (or chloride) represented by the above formula (1) (Unisense FPA1001L, trade name of Senka Corporation: molecular weight of 100,000 to 500,000, hereinafter abbreviated as DADMAC) is used. As the anionic polymer, for example, a sodium salt of carboxymethylcellulose represented by the above formula (2) (CMC Daicel 1220, trade name of Daicel Chemical Industries, Ltd .; molecular weight 160,000 to 380,000, hereinafter abbreviated as CMC) is used. In this case, a model experiment and a forest demonstration test of Cs migration can be performed in the same manner as in Examples 1 and 2, except for the type of coagulant and the combination thereof. DADMA and CCMC are bentonite that adsorbs radioactive Cs by the same ionic interaction as the dispersion type polymer flocculant having a cationic polymer and an anionic polymer used in the methods (iii) and (iv). And a function of aggregating an ionic polymer having a charge of the opposite polarity. Therefore, it can be easily inferred that the methods (i) and (ii) can provide substantially the same decontamination effect as the results shown in FIGS. 8 and 12.

In the present invention, it is preferable to use bentonite as the inorganic particles for adsorbing radioactive Cs, but it is not limited to bentonite. The inorganic particles, easy availability, depending on the handling and cost, for example, zeolites, sheet silicates, ferric ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, illite or kaolinite May be used. By examining in advance the charge of the surface of these inorganic particles, or by mixing these inorganic particles with an ionic polymer, dispersing polymer or amphoteric polymer and checking in advance for the occurrence of aggregation, The type and combination of molecular coagulants can be selected.

  As described above, according to the radioactive material decontamination method and the decontamination system according to the present invention, in the decontamination of forests and satoyama (including coppice forests), forests and satoyama (coppice forests) where decontamination has not been performed or is insufficient. ), The migration of radioactive materials such as cesium to living quarters and fields can be suppressed, and recontamination of these living environment areas that have already been decontaminated can be prevented. At that time, since the transfer of the radioactive material is continuously suppressed, it is possible to prevent re-contamination of the settlement or the field in the medium to long term. Also, soil such as deciduous leaves and mulch present in contaminated forests and satoyama (including coppice forests) does not need to be peeled off during decontamination work, and radioactive substances such as cesium remaining or accumulating at that location are removed by inorganic particles. Since the adsorbent can efficiently and stably adsorb and fix the medium over a medium to long term, the decontamination work is facilitated. Furthermore, since the inorganic particle adsorbent in which the radioactive substance is adsorbed and immobilized is separated and collected from forests and satoyama in an aggregated state, the volume of contaminants can be reduced.

  Therefore, the method and system for decontaminating radioactive materials according to the present invention can continuously prevent the transfer of radioactive materials to living quarters and fields while reducing labor and cost for decontamination. In the future, it will be possible to provide a safe and secure living space in the future, and its technical utility is extremely high.

DESCRIPTION OF SYMBOLS 1 ... forest, 2 ... satoyama, 3 ... residence, 4 ... field, 5 ... buffer zone, 6 ... filtration container, 7 ... ionic polymer (A) , 8 ... ionic polymer (B), 9 ... inorganic particles having negative (-) charge on the surface, 10 ... cationic polymer, 11 ... anionic polymer, 12 ... Dispersion type polymer flocculant, 13 ... inorganic particles having a negative (-) charge on the surface, 14 ... hydrophobic clock, 15 ... amphoteric polymer flocculant, 16 ... negative on the surface (-) Inorganic particles having electric charge, 17: first layer container, 18: second layer container, 19: third layer container, 20: water storage container.

Claims (20)

A decontamination method for decontaminating at least one of forest and satoyama contaminated with radioactive materials,
At least one of the forest and satoyama, a step of directly spraying the inorganic particles that adsorb the radioactive material, or a step of applying or spraying and injecting a dispersion or suspension containing the inorganic particles,
A buffer zone containing a coagulant having a charge of a polarity opposite to the charge of the surface of the inorganic particles, in order to agglomerate the inorganic particles, at the boundary between at least one of the forest and satoyama and the settlement or the field. Provided, from at least one of the forest and satoyama, a step of aggregating the inorganic particles flowing into the buffer zone by rainwater or artificial running water or fountain, by the coagulant,
A step of separating and collecting the inorganic particles aggregated together with the flocculant,
A method for decontaminating a radioactive substance having: As a step before the step of aggregating the inorganic particles by the aggregating agent,
A step of enclosing the flocculant alone or in a form mixed with another material in a mesh-like or mesh-like filter vessel through which the inorganic particles can pass, and installing the filter vessel containing the flocculant in the buffer zone And a step of
As a step after the step of coagulating the inorganic particles with the coagulant,
The method for decontaminating a radioactive substance according to claim 1, further comprising a step of separating and collecting the filtration container containing the inorganic particles aggregated together with the flocculant.   The dispersion or suspension containing the inorganic particles that adsorb the radioactive substance further includes an ionic polymer or a nonionic polymer having a charge of the same polarity as the charge of the surface of the inorganic particles, 3. The method according to claim 1, wherein the polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion.   In the buffer zone containing the ionic polymer (A) having a charge of a polarity opposite to the charge of the surface of the inorganic particles as the coagulant, the inorganic particles that have flowed in by rainwater or artificial running water or a fountain are The method for decontaminating a radioactive substance according to any one of claims 1 to 3, further comprising a step of aggregating with the ionic polymer (A). The coagulant, have a cationic polymer and an anionic polymer, and, charges the charge ratio of the cationic polymer and an anionic polymer having the surface of the inorganic particles by incorporating into and out from 1 Polymer coagulant (C) having a charge of opposite polarity to the above , or a charge ratio of a cation and an anion having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and Comprises an amphoteric polymer flocculant (D) having a charge of the opposite polarity to the charge of the surface of the inorganic particles by adjusting so as to deviate from 1 .
In the buffer zone containing the polymer flocculant (C) or the amphoteric polymer flocculant (D), the inorganic particles that have flowed in by rainwater or artificial running water or a fountain are mixed with the polymer flocculant (C) or The method for decontaminating a radioactive substance according to any one of claims 1 to 3, further comprising a step of coagulating with the amphoteric polymer coagulant (D). The aggregating agent includes an ionic polymer (A) having a charge of a polarity opposite to the charge of the surface of the inorganic particles, and the ionic polymer (A) and the ionic polymer (A) Using a combination of ionic polymers (B) having charges of opposite polarity,
In the buffer zone, located in at least one of the forest and the satoyama, and containing the ionic polymer (A), the inorganic particles that have flowed in by rainwater or artificial flowing water or a fountain are collected by the ionic polymer. A step of aggregating with the molecule (A), and wherein the ionic polymer (A) flowing out without aggregating is located on the side of a field or a residence in the buffer zone, and contains the ionic polymer (B). The method of decontaminating a radioactive substance according to any one of claims 1 to 3, further comprising a step of causing the ionic polymer (B) to aggregate in a region. The coagulant, a cationic polymer and an anionic polymer are blended so that the charge ratio between the two deviates from 1, and a polymer coagulant having an excess of a charge opposite in polarity to the charge of the surface of the inorganic particles (C1) or a molecule having both a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and having a polarity opposite to that of the surface of the inorganic particles. An amphoteric polymer flocculant (D1) prepared such that the charge ratio in one molecule of the monomer structural unit deviates from 1 ;
The polymer flocculant (C1) or the amphoteric polymer flocculant (D1 ) and a charge having a polarity opposite to the charge of the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) in excess. excess with polymer flocculant (C2), or using a combination of amphoteric polymer flocculant and (D2),
In the buffer zone, located on at least either side of forest and satoyama and containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), rainwater or artificial running water or fountain Coagulating and solidifying the flowed inorganic particles with the polymer flocculant (C1) or the amphoteric polymer flocculant (D1);
The polymer flocculant (C1) or the amphoteric polymer flocculant (D1) flowing out without flocculation is located on the side of a field or a residential area in the buffer zone, and the polymer flocculant (C2) or the amphoteric polymer flocculant (C2) A step of coagulating with the polymer coagulant (C2) or the amphoteric polymer coagulant (D2) in a region containing the polymer coagulant (D2);
The method for decontaminating a radioactive substance according to any one of claims 1 to 3, comprising: In the decontamination method according to any one of claims 1 to 7,
After decontaminating at least one of the forest and satoyama,
A step of exfoliating deciduous leaves and humus containing the deciduous leaves remaining in at least one of the forest and satoyama from the ground where the deciduous leaves are present,
Adding the exfoliated litter and mulch to farmland or wilderness for the purpose of restoring fertility,
A method for decontaminating a radioactive substance having: Inorganic particles to adsorb the radioactive material, bentonite, zeolite, layered silicate, ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, at least one selected from the group of illite and kaolinite The method for decontaminating a radioactive substance according to any one of claims 1 to 8.   The method for decontaminating a radioactive substance according to claim 9, wherein the inorganic particles that adsorb the radioactive substance are bentonite. A decontamination system for decontaminating at least one of forest and satoyama contaminated with radioactive materials,
Means for directly spraying the inorganic particles that adsorb the radioactive material, or means for applying or spraying and injecting a dispersion or suspension containing the inorganic particles to at least one of the forest and the satoyama ,
In order to aggregate the inorganic particles at the boundary between the forest, the satoyama and the defoliation and the place of residence or the field, a buffer containing a coagulant having a charge of a polarity opposite to the charge of the surface of the inorganic particles. Providing a zone, from at least one of the forest and satoyama, means for aggregating the inorganic particles that have flowed into the buffer zone by rainwater or artificial running water or a fountain into the coagulant,
Means for separating and collecting the inorganic particles aggregated together with the flocculant,
Radioactive material decontamination system having   In the buffer zone, a mesh-shaped or mesh-shaped filtration container through which the inorganic particles can pass is installed in a state where the coagulant is enclosed alone or in the form of a mixture with other materials. The radioactive substance decontamination system according to claim 11.   The dispersion or suspension containing the inorganic particles that adsorb the radioactive substance further contains an ionic polymer or a nonionic polymer having a charge of the same polarity as the charge of the surface of the inorganic particles, 13. The radioactive substance decontamination system according to claim 11, wherein the molecule or the nonionic polymer is a water-soluble or colloidal aqueous dispersion. The buffer zone according to any one of claims 11 to 13 , wherein the ionic polymer (A) having a charge having a polarity opposite to the charge of the surface of the inorganic particles is contained as the coagulant. A radioactive substance decontamination system according to Item. The buffer zone is to have a cationic polymer and an anionic polymer, and, charges the charge ratio of the cationic polymer and an anionic polymer having the surface of the inorganic particles by incorporating into and out from 1 Polymer coagulant (C) having a charge of opposite polarity to the above , or a charge ratio of a cation and an anion having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and 12. An amphoteric polymer coagulant (D) having a charge having a polarity opposite to that of the charge of the surface of the inorganic particles by adjusting the particle size to deviate from 1 as the coagulant. The radioactive substance decontamination system according to any one of claims 13 to 13. In the buffer zone, from at least one of a forest and a satoyama toward a field or a residential area,
A region containing , as the coagulant, an ionic polymer (A) having a charge of a polarity opposite to the charge of the surface of the inorganic particles, and a charge of a polarity opposite to that of the ionic polymer (A) The region containing the ionic polymer (B) is
The radioactive substance decontamination system according to any one of claims 11 to 13, wherein the radioactive substance decontamination system is provided separately in series in this order. In the buffer zone,
From at least one of the forest and satoyama to the fields and residential areas,
A cationic polymer and an anionic polymer are blended so that the charge ratio between the two is out of 1, and a polymer flocculant (C1) or 1 having an excess of a charge having an opposite polarity to the charge of the surface of the inorganic particles It has a cationic monomer structural unit and an anionic monomer structural unit in the molecule, and has a charge of the opposite polarity to the charge of the surface of the inorganic particles. A region containing the amphoteric polymer flocculant (D1) whose charge ratio in one molecule is adjusted as the flocculant ,
The charge ratio of the cationic polymer and the anionic polymer is deviated from 1 and the charge has a polarity opposite to the charge of the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) in excess. A polymer flocculant (C2) having an excess of the above, or a polymer flocculant (C1) or an amphoteric compound having a cationic monomer structural unit and an anionic monomer structural unit in one molecule. Contains an amphoteric polymer flocculant (D2) in which the charge ratio in one molecule of both monomer structural units is adjusted so that the charge of the opposite polarity to the excess charge of the molecular flocculant (D1) becomes excessive. The area to be
The radioactive substance decontamination system according to any one of claims 11 to 13, wherein the radioactive substance decontamination system is provided separately in series in this order. In the decontamination system according to any one of claims 11 to 17,
After decontaminating at least one of the forest and satoyama,
Means for exfoliating deciduous leaves and mulch including the deciduous leaves remaining in at least one of the forest and satoyama from the ground where the deciduous leaves are present,
Means for adding the exfoliated deciduous and mulch soils to agricultural land or wilderness for restoring fertility,
Radiation material decontamination system having Inorganic particles to adsorb the radioactive material, bentonite, zeolite, layered silicate, ferrocyanide, crystal Shirikochitaneto, mica, vermicular light, smectite Mont montmorillonite, at least one selected from the group of illite and kaolinite The radioactive material decontamination system according to any one of claims 11 to 18.   20. The radioactive substance decontamination system according to claim 19, wherein the inorganic particles that adsorb the radioactive substance are bentonite.

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