JP2017111063A - Decontamination method of radioactive material and decontamination system thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a decontamination method of a radioactive material and a decontamination system thereof capable of not only decontaminating contaminated forests and hills (including copses) but continuously preventing the radioactive material from transferring from its area to residential areas and fields.SOLUTION: A decontamination method of the present invention has processes of: directly spraying inorganic particles adsorbing a radioactive material to at least any of forests and village vicinity mountains contaminated by the radioactive material; applying or spraying and infusing fluid dispersion or suspension containing the inorganic particles; providing a buffer zone containing a coagulant for agglutinating the inorganic particles on the boundary of at least any of the forests and village vicinity mountains and a residential area or fields; agglutinating the inorganic particles flown in the buffer zone by rainwater, or artificial flowing water and a fountain from at least any of the forests and the village vicinity mountains by the coagulant; and separating and recovering the agglutinated inorganic particles with the coagulant.SELECTED DRAWING: Figure 1

Description

  The present invention eliminates radioactive substances to prevent the residential areas and fields from being polluted by the migration of 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 thereof.

  It is expected that radioactive materials that leak inside the nuclear power generation related facility or for some reason from the nuclear power generation related facility or scatter will contaminate the surrounding environment and have a serious adverse effect on the human body. The accident at TEPCO's Fukushima Daiichi Nuclear Power Station that occurred in March 2011 led to a situation where the surrounding area was contaminated with radioactive cesium over a wide area. In order to quickly recover from this state, it is necessary to decontaminate a wide range of radioactive materials. First, decontamination work is proceeded preferentially in residential areas and fields that are deeply linked to the living environment of people. It was. As a result, decontamination of residential areas and fields is almost complete, but decontamination of forests and satoyama (including miscellaneous forests) is a vast area and decontamination work is Since it is more difficult than in plain fields such as fields, there are still areas where decontamination has not yet progressed.

  Some radioactive materials such as cesium have a half-life of several decades or more, and this damage will continue not only at the time of radioactive material scattering and leakage, but also after that. Therefore, there is a possibility that radioactive materials such as cesium will be transferred to residential areas and fields from forests and satoyama (including miscellaneous forests) that have not been decontaminated, and these living environment areas that have been decontaminated will be contaminated again. There is. Even in forests and satoyama (including miscellaneous forests) where decontamination work has already been completed, radioactive materials may not be completely removed due to the difficulty of decontamination work. Even in that case, there is a possibility that the living environment area may be recontaminated by radioactive materials remaining in forests and satoyama (mixed forests), and radioactive materials accumulated over time.

  In the case of a residential area or a farmland such as a field where the ground surface is exposed, the radioactive substance that has fallen with rain is adsorbed by the clay component. In that case, it is said that it is effective to decontaminate the surface soil by stripping the surface soil. (I) A method of scraping the surface using a large machine, (ii) High pressure 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 Documents 1 and 2 and Non-Patent Document 1, 2 to prevent gel-like precipitation in an aqueous solution containing both a polycation and a polyanion. A polyion complex containing ˜6 wt% salt (sodium chloride, potassium chloride, potassium sulfate, ammonium sulfate, etc.) is disclosed. And since the said patent document 1 cannot exhibit the adsorption fixation | immobilization capability of radioactive cesium only by use of the said polyion complex, in order to provide the capability, clay fine particle suspension and polyion complex (polyion complex) aqueous solution A decontamination method has been proposed in which the soil is spread on radioactive cesium-contaminated soil and the topsoil of the soil is peeled off. In this decontamination method, it is disclosed that bentonite is used as an example of clay fine particles.

  The salt of several wt% contained in the polyion complex aqueous solution disclosed in Patent Documents 1 and 2 and Non-Patent Document 1 is a component that inhibits the growth of plants. For this reason, the present inventors prevent the spread of radioactive substances that exfoliate and remove contaminated soil that has been immobilized using a dispersive polymer flocculant that does not produce a gel-like precipitate even if it does not contain 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 charge ratio is excessive.

  On the other hand, in the case of forests and satoyama (including miscellaneous forests), the ground surface is covered with fallen leaves and humus, and the fallen radioactive material is adsorbed on the humic substances (humic acid etc.) where fallen leaves and humus soil exist. It is thought that. For this reason, in the case of decontamination of forests and satoyama (including miscellaneous forests), it is judged that removal of fallen leaves and humus on the surface is effective as a decontamination method, and decontamination of nearly 90 percent is possible. As a decontamination method for forests and satoyama (miscellaneous 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. In addition, a radioactive substance decontamination method is disclosed in which a surface solution 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 Japanese Patent Laying-Open No. 2015-199057 JP2013-242161A

Naganawa Hirochika, Kumazawa Noriyuki, and 8 others, “Removal of radioactive cesium from soil surface using polyion complex as a fixing agent”, Japanese Atomic Energy Society Journal, 2011, Vol. 10, No. 4, p. 227-234

  Radioactive materials such as cesium move from forests and satoyama (including miscellaneous forests) where decontamination is not performed or insufficient, and these living environment areas that have been decontaminated are recontaminated. There is a need to establish a decontamination method for radioactive substances and to construct a decontamination system for them. That is, (1) Adsorb radioactive substances such as cesium remaining in or accumulated in contaminated forests and satoyama (including miscellaneous forests) such as deciduous and mulch soils efficiently and stably over the medium to long term. Use of adsorbents that can be retained, (2) Adsorbents of radioactive materials used for decontamination and soil treatment liquids shall not adversely affect the soil of forests and satoyama (miscellaneous forests) in terms of plant growth, etc. (3) In order to reduce the volume of pollutants caused by radioactive substances, the adsorbent that has adsorbed radioactive substances can be separated and collected from forests and satoyama (miscellaneous forests) without soil, and ( 4) Radioactive material decontamination methods that meet the requirements such as continuous suppression of radioactive material migration from forests and satoyama (including miscellaneous forests), and prevention of recontamination of residential areas and fields, etc. over the medium to long term In that pollution system . Furthermore, (5) labor saving of decontamination work and reduction of decontamination cost are also desired.

  However, since the decontamination methods described in Patent Documents 1 to 4 and Non-Patent Document 1 are for peeling off the topsoil, fallen leaves, and humus soil of contaminated soil sprayed or injected with a polyion complex aqueous solution, forests and satoyama Decontamination tends to be insufficient in (including miscellaneous forests). Furthermore, since contaminated soil and fallen leaves are stored as they are after separation and collection, or volume reduction processing is performed, management and processing of contaminants are required. In addition, radioactive materials are scattered from forests and satoyama (miscellaneous forests) that have not been decontaminated, and as a result, accumulation of radioactive materials starts in decontaminated places, and the concentration of radioactive materials increases with time. As a result, radioactive substances are transferred to residential areas and fields, and recontamination of those areas is likely to occur. In order to prevent recontamination, it is possible to decontaminate forests and satoyama (mixed 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 where people can live stably. In addition, a large increase in decontamination cost is inevitable because a wide range of decontamination operations are performed several times.

In addition, the decontamination methods described in Patent Documents 1 and 2 and Non-Patent Document 1 use a polyion complex solution to which salt such as sodium chloride is added in order to prevent gelation in a playground with an area of several hundred m ^2. The effect is confirmed by spraying and decontaminating after soil solidification. Small-scale soil fixation and pasture decontamination experiments are also being conducted in pastures and paddy fields. However, due to concerns about salt damage, it has not been applied to large forests and farmland. When applying the Chernobyl method to decontamination of large areas of forests and farmland, salt damage must be overcome. On the other hand, it is also conceivable to prevent salt damage by adding salts such as ammonium sulfate that do not affect plant growth. However, when nutrient salts such as ammonium sulfate are added to the forest, the forest may become over-nutrition and the forest ecosystem may be unbalanced. Furthermore, since a salt such as sodium chloride contained in the polyion complex aqueous solution may be transferred to a residential area, a field, or the like due to rain or the like, in that case, it is necessary to fully consider the adverse effects on the field. 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 to solve such a problem, and efficiently removes radioactive substances such as cesium remaining or accumulated in soil such as defoliation and humus soil present in contaminated forests and satoyama (including miscellaneous forests). In addition, it is not only easy to decontaminate a wide range of forests and satoyama (miscellaneous forests) that have been difficult to decontaminate by stably adsorbing and fixing over the medium and long term, but also forests and satoyama (miscellaneous forests) The purpose is to provide a decontamination method and a decontamination system for radioactive materials that can prevent recontamination of residential areas and fields, etc. by continuously suppressing the transfer of radioactive materials from the home to the residential area or fields. .

  The present inventor creates a safe space that can be continuously lived by decontaminating contaminated forests and wild mountains (including miscellaneous forests) and preventing the migration of radioactive materials to residential areas or fields, etc. In the process of spraying and injecting inorganic particles that adsorb radiation materials in forests and wild mountains (including miscellaneous forests), and in buffer zones provided at the boundaries between forests and wild mountains and residential areas or fields, the inflows from the forests and wild mountains By establishing a decontamination method having the steps of aggregating only the inorganic particles that have adsorbed the radiation material and the step of separating and collecting the agglomerated inorganic particles, and by constructing a decontamination system optimal for those methods, The present invention has been found out that the above problems can be solved.

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 satoyama contaminated with a radioactive substance, and adsorbs the radioactive substance on at least one of the forest and satoyama. The step of directly spraying inorganic particles, or the step of applying or spraying and injecting a dispersion or suspension containing the inorganic particles, and the boundary between at least one of the forest and satoyama and the residential area or the field, A buffer zone containing a flocculant for agglomerating inorganic particles is provided, and the agglomeration of the inorganic particles flowing into the buffer zone by rain water or artificial running water or fountain from at least one of the forest and satoyama There is provided a method for decontaminating a radioactive substance, comprising a step of aggregating with an agent and a step of separating and collecting the inorganic particles aggregated together with the aggregating agent.
[2] In the present invention, as a pre-step of the step of aggregating the inorganic particles with the aggregating agent, the aggregating agent is used alone or with another material in a mesh-like or mesh-like filtration container through which the inorganic particles can permeate. A step of enclosing in a mixed form and a step of installing the filtration container containing the flocculant in the buffer zone, and the flocculant as a subsequent step of aggregating the inorganic particles with the flocculant A method for decontaminating a radioactive substance according to the above [1], comprising the step of separating and collecting the filtration container containing the inorganic particles aggregated therewith.
[3] In the present invention, the dispersion or suspension containing inorganic particles that adsorb the radioactive substance further has an ionic polymer or nonionic high charge having the same polarity as the charge of the surface of the inorganic particles. The method for decontaminating radioactive materials according to [1] or [2] above, wherein the ionic polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion containing molecules. To do.
[4] In the buffer zone containing the ionic polymer (A) having a charge opposite to the charge on the surface of the inorganic particles as the flocculant, the present invention provides rainwater or artificial running water or fountain. The method for decontaminating a radioactive substance according to any one of [1] to [3], further comprising the step of aggregating the inorganic particles that have flowed in by the ionic polymer (A).
[5] In the present invention, the flocculant has an ionic polymer (A) having a charge opposite to the charge on the surface of the inorganic particles and a charge opposite to the ionic polymer (A). In an area containing at least one of a forest and a satoyama in the buffer zone and containing the ionic polymer (A). The step of aggregating the inorganic particles flowing in by running water or a fountain with the ionic polymer (A), and the ionic polymer (A) flowing out without agglomeration on the side of the field or residence in the buffer zone The radioactive substance according to any one of [1] to [3], further comprising a step of aggregating with the ionic polymer (B) in a region located and containing the ionic polymer (B). Decontamination method To provide.
[6] In the present invention, the flocculant is a polymer flocculant (C) having a cationic polymer and an anionic polymer, or a cationic monomer structural unit and an anionic monomer in one molecule. In the buffer zone containing the amphoteric polymer flocculant (D) having a body structural unit and containing the polymer flocculant (C) or the amphoteric polymer flocculant (D), rainwater or artificial running water or fountain The radioactive substance according to any one of [1] to [3], further comprising a step of aggregating the inorganic particles that have flowed in by the polymer flocculant (C) or the amphoteric polymer flocculant (D). Provide decontamination methods.
[7] In the present invention, the flocculant contains a cationic polymer and an anionic polymer so that the charge ratio of the two deviates from 1, and the charge of the opposite polarity to the charge of the surface of the inorganic particles is obtained. The polymer flocculant (C1) having an excess, or having a cationic monomer structural unit and an anionic monomer structural unit in one molecule and having a polarity opposite to the charge of the surface of the inorganic particles The amphoteric polymer flocculant (D1) prepared so that the charge ratio in one molecule of both monomer structural units deviates from 1 so as to have a charge, and the polymer flocculant (C1) or the amphoteric polymer A combination of a polymer flocculant (C2) having an excess charge opposite to the charge of the flocculant (D1) or an amphoteric polymer flocculant (D2); Located at least on either side of the front In the region containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), the inorganic particles introduced by rain water or artificial running water or fountain are converted into the polymer flocculant (C1) or the amphoteric polymer The step of aggregating and solidifying with a molecular flocculant (D1) and the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) flowing out without agglomeration are located on the side of a field or a residence in the buffer zone. And aggregating with the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) in a region containing the polymer flocculant (C2) or the amphoteric polymer flocculant (D2); The method for decontaminating a radioactive substance according to any one of [1] to [3], comprising:
[8] The present invention provides the decontamination method according to any one of [1] to [6], wherein after decontamination of at least one of the forest and satoyama, at least any of the forest and satoyama. The process of peeling off the fallen leaves and the humus containing the fallen leaves from the ground where the fallen leaves are present, and adding the peeled fallen leaves and the fallen leaves to the farmland or the wilderness for restoring the geological strength And a method for decontaminating a radioactive material.
[9] In the present invention, the inorganic particles that adsorb the radioactive substance are selected from the group consisting of bentonite, zeolite, layered silicate, ferrocyanide, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite, and kaolinite. The decontamination method for a radioactive substance according to any one of [1] to [8], which is one or more selected.
[10] The present invention provides the radioactive substance decontamination method according to [9], wherein the inorganic particles that adsorb the radioactive substance are bentonite.
[11] The present invention is a decontamination system for performing decontamination of at least one of a forest and satoyama contaminated with a radioactive substance, and adsorbs the radioactive substance to at least one of the forest and satoyama. Means for directly spraying 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 fallen leaves, and a residential area or a field A buffer zone containing a flocculant for agglomerating the inorganic particles is provided at the boundary with the water, and flows into the buffer zone by rain water or artificial running water or fountain from at least one of the forest and satoyama. A radioactive substance decontamination system comprising: means for aggregating the inorganic particles into the aggregating agent; and means for separating and collecting the inorganic particles agglomerated together with the aggregating agent. To provide.
[12] In the present invention, in the buffer zone, a net-like or mesh-like filtration container through which the inorganic particles can permeate is installed in a state where the flocculant is enclosed alone or in the form of a mixture with other materials. The radioactive substance decontamination system according to the above [11] is provided.
[13] The present invention provides an ionic polymer or nonionic polymer in which a dispersion or suspension containing inorganic particles that adsorb the radioactive substance further has a charge of the same polarity as the charge of the surface of the inorganic particles. And the ionic polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion, wherein the radioactive substance decontamination system according to [11] or [12] is provided. .
[14] The present invention is characterized in that a zone containing an ionic polymer (A) having a charge opposite in polarity to the charge of the inorganic particles is provided as the buffer zone. 11]-[13] The radioactive substance decontamination system according to any one of the above is provided.
[15] The present invention provides an ionic polymer having a charge opposite in polarity to the charge of the surface of the inorganic particles from at least one of forest and satoyama toward a field or a residential area in the buffer zone ( A region containing A) and a region containing an ionic polymer (B) having a charge opposite to that of the ionic polymer (A) are separated and provided in series in this order. The radioactive substance decontamination system according to any one of [11] to [13] is provided.
[16] In the present invention, the buffer zone is a polymer flocculant (C) having a cationic polymer and an anionic polymer, or a cationic monomer structural unit and an anionic monomer in one molecule. The radioactive substance decontamination system according to any one of [11] to [13] above, which contains an amphoteric polymer flocculant (D) having a body structural unit.
[17] In the buffer zone, the cationic polymer and the anionic polymer are blended so that a charge ratio of both of them deviates from 1 from at least one of the forest and the satoyama toward the field or the residential area. And a polymer flocculant (C1) having an excessive charge opposite in polarity to the charge of the inorganic particles, or a cationic monomer structural unit and an anionic monomer structural unit in one molecule. And an amphoteric polymer flocculant (D1) in which the charge ratio in one molecule of both monomer structural units is adjusted so as to have a charge opposite in polarity to the charge of the surface of the inorganic particles. The charge ratio of the region and the cationic polymer and the anionic polymer is mixed so as to deviate from 1, and the charge of the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is opposite. Excessive polar charge The polymer flocculant (C2), or the polymer flocculant (C1) or the amphoteric polymer flocculant having a cationic monomer structural unit and an anionic monomer structural unit in one molecule A region containing the amphoteric polymer flocculant (D2) in which the charge ratio in one molecule of both monomer structural units is adjusted so that the charge having the opposite polarity to the charge that (D1) has excessively becomes excessive; Are provided in series in this order, and the radioactive substance decontamination system according to any one of [11] to [13] is provided.
[18] The present invention provides the decontamination system according to any one of [11] to [17], wherein after decontamination of at least one of the forest and satoyama, at least the forest and satoyama Means for peeling the fallen leaves remaining in any state and the humus containing the fallen leaves from the ground where the fallen leaves are present, and the peeled fallen leaves and the humus soil to farmland and wilderness for restoring geological strength And a radiation material decontamination system.
[19] In the present invention, the inorganic particles that adsorb the radioactive substance are selected from the group consisting of bentonite, zeolite, layered silicate, ferric ferrocyanide, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite, and kaolinite. The radioactive substance decontamination system according to any one of [11] to [18], which is one or more selected.
[20] The present invention provides the radioactive substance decontamination system according to [19], wherein the inorganic particles that adsorb the radioactive substance are bentonite.

  According to the radioactive substance decontamination method and decontamination system according to the present invention, cesium from forests and satoyama (including miscellaneous forests) where decontamination has not been performed or is insufficient, as well as decontamination of forests and satoyama (including miscellaneous forests). It is possible to prevent the radioactive materials such as those from moving to residential areas or fields, and to prevent recontamination of these living environment areas that have already been decontaminated. At that time, since the migration of radioactive materials is continuously suppressed, recontamination of the residential area and the fields can be prevented in the medium to long term. In addition, soil such as deciduous leaves and humus soil present in contaminated forests and satoyama (including miscellaneous forests) does not need to be peeled off during decontamination work, and radioactive substances such as cesium remaining or accumulated in the place are removed from inorganic particles. Since the adsorbent, more preferably clay particles such as bentonite, can be efficiently adsorbed and immobilized over a medium to long term, the decontamination work is facilitated.

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

  As described above, the radioactive substance decontamination method and decontamination system according to the present invention can continuously prevent the migration of radioactive substances to residential areas and fields while reducing labor and cost of decontamination. We can 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 typically the modification of the decontamination method and decontamination system of the radioactive substance by this invention. It is a figure which shows typically the decontamination method and decontamination system of this invention which aggregate an inorganic particle using the coagulant containing the combination of 2 types of ionic polymers. It is a figure which shows typically an example of the aggregation form of the inorganic particle formed when 1 type or 2 types of ionic polymers are used as an aggregating agent. It is a figure which shows typically an example of the aggregation form of the inorganic particle formed when the dispersion type polymer which adjusted cationic polymer excessively with the charge ratio is used 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 a 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 4 divisions for using in a forest demonstration test. It is a figure which shows the measurement result of the radioactive Cs density | concentration performed at each measurement point of the soil slope before performing a forest verification test. It is a figure which shows the outline | summary 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 proof test as 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. Although FIG. 1 shows both forest 1 and satoyama 2 as places to which the present invention is applied, the distinction between forest 1 and satoyama 2 is not clear, and at least one of forest 1 and satoyama 2 is included. It only has to be done. At least one of the forest 1 and the satoyama 2 is distinguished from the residential area 3 or the field 4 which is a daily living space, and the flat land, playground and road included in those areas. , Miscellaneous forests, etc. are treated as part of Satoyama 2.

  As described above, decontamination of forest 1 and satoyama (including miscellaneous forests) 2 is larger than the area of flat land such as residential area 3 or field 4 because of its large area and rich undulations. Because decontamination work is difficult, there are still areas where decontamination has not progressed. The radioactive substance decontamination method and decontamination system according to the present invention performs decontamination of at least one of forest 1 and satoyama (including miscellaneous forests) 2 under such circumstances, and contaminated forest 1 and satoyama. (Miscellaneous forest) The purpose is to continuously suppress the transfer of radioactive materials from 2 to residential areas 3 or fields 4 and to reduce the volume of contaminants due to radioactive materials. Therefore, as shown in FIG. 1, a buffer zone 5 is provided at the boundary between at least one of the forest 1 and the satoyama 2 and the residential area 3 or the field 4, and basically the following three steps and those steps are performed. It is the characteristic that the means of this is included. The buffer zone 5 is provided to perform decontamination of the contaminated forest 1 and satoyama 2 and the aggregation and separation / recovery of the pollutants by radioactive substances, respectively. It is possible to provide a new decontamination method and a decontamination system that have not been achieved in the past in that it has the effect of continuously suppressing the transition.

  First, as a first step, at least one of the forest 1 and the satoyama 2 is directly sprayed with inorganic particles that adsorb radioactive materials, or a dispersion or suspension containing the inorganic particles is applied or sprayed and injected. I do. In fallen leaves, humus soil and topsoil contaminated with radioactive substances in the forest 1 and satoyama 2, the radioactive substances are transferred to the inorganic particles as time passes by an adsorption action, and the radioactive substances are decontaminated from the fallen leaves, humus soil and topsoil. At this time, by leaving the inorganic particles dispersed or injected into the forest 1 or the satoyama 2, the radioactive material is adsorbed from the contaminated fallen leaves, humus and topsoil. In this step, since porous inorganic particles having a positive or negative charge are used as described later, the inorganic particles are dispersed or injected into the forest 1 or the satoyama 2 while remaining. The radioactive material adsorbed on the surface is hardly desorbed and is stably adsorbed and retained over a long period of time.

  In the first step, the application or dispersion and injection of the inorganic particles and the dispersion liquid or suspension containing the inorganic particles may be sprayed according to the location or area of the contaminated forest 1 or satoyama 2, It is performed by a pouring method or a brush coating method. Further, in the case of performing wide-area decontamination, a spraying method such as spray is generally used. When spraying over a wider area, a helicopter or the like may be used. The dispersion or suspension containing the inorganic particles is subjected to coating or spraying and injection after viscosity adjustment in advance. Further, 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 residential area 3 or the field 4 contains a flocculant for aggregating the inorganic particles. And after flowing the natural particle | grains flowing in at least one of the forest 1 and the satoyama 2, or the artificial particle | grain water or fountain, the inorganic particle which adsorb | sucked the said radioactive substance was made to flow in the buffer zone 5, The inorganic particles are aggregated by the aggregating agent. In the present invention, this operation is performed as the 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 and the residential area 3 or the field 4, Its width (length and width) is not particularly limited. Among them, the length is determined according to the length of the boundary that contacts at least one of the forest and the satoyama, but the width does not need to be set extremely wide, and a few meters is sufficient for the purpose of the present invention. Can be achieved. When there is no suitable buffer zone at the boundary, the boundary portion in contact with the residential area 3 or the field 4 in at least one of the forest 1 and the satoyama 2 can be made into the buffer zone 5 by simple creation. Further, in the residential area 3 or the field 4, an appropriate open space may be found at the boundary portion in contact with at least one of the forest 1 and the satoyama 2, and the creation area may be used as the buffer zone 5 when the creation is necessary.

  In the second step, when the inorganic particles are allowed to flow into the buffer zone 5, it is practical to use naturally occurring rainwater since decontamination work can be easily realized. Although the occurrence of rainwater is irregular, even if the inorganic particles are left standing for a long period of time, the adsorbed radioactive material is stably adsorbed and retained, so it has little effect on the decontamination effect. Not give. The inorganic particles that have flowed out after the occurrence of rainwater can be replenished by spraying or coating again and used for decontamination of new radioactive substances. In addition, when it is desired to periodically inject the inorganic particles into the buffer zone without depending on the occurrence of rainwater that depends on the weather, for example, artificial water or fountain is caused by installing a sprinkler or the like by a pericopter or the like. May be.

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

  Subsequently, as a third step, the inorganic particles aggregated together with the aggregating agent are separated and recovered. Separation and collection of the inorganic particles can be performed manually or using a crane for peeling and collecting the inorganic particles alone or the soil containing the inorganic particles. The separated inorganic particles alone or the soil containing the inorganic particles are generally packed in storage bags or packs. Among them, when separating and collecting the inorganic particles together with the soil, after separating and removing the soil using a crane having a collection claw up and down, it is separated and collected by packing it into a bag or pack for storage as it is. Work can be speeded up and simplified. On the other hand, when the inorganic particles are separated and recovered independently, it is preferable to use a mesh-like or mesh-like filtration container through which the inorganic particles can permeate (see FIG. 2 described later).

  In the present invention, in addition to the first to third steps described above, after the separated and recovered inorganic particles or the soil containing the inorganic particles are packed in a storage bag or pack, the radioactive material is scattered outside. You may employ | adopt the process preserve | saved and preserve | saved after conveying and collecting to the place where the treatment which does not leak is performed. The storage and storage period of the inorganic particles is determined in advance according to the half-life of the radioactive substance. That is, if the storage time up to a level at which there is no influence on the human body is known, the storage and storage state is left at least for that time. In order to further enhance safety, a longer storage / preservation time is set with a margin than the above-described period. Finally, after being stored and preserved in a sealed state until a period when radiation dose reduction is confirmed to a level that does not affect the human body at all, it is discarded as ordinary industrial waste. Moreover, the inorganic particle | grains from which the influence of the radiation by a radioactive substance was lose | eliminated can recycle what was reproduced | regenerated by the desorption operation. On the other hand, if the inorganic particles can be regenerated by performing the desorption operation of the radioactive material in an environment in which the radiation is strictly controlled even during storage and storage periods, the recycled product should be reused. May be.

  FIG. 1 shows an example of a decontamination method in which the inorganic particles that adsorb the radioactive substance aggregated together with the flocculant in the third step are separated or collected alone or together with the soil containing the inorganic particles. In the invention, in order to facilitate the separation and collection 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-step of the step of aggregating the inorganic particles with the aggregating agent, the aggregating agent may be used alone or in the net-like or mesh-like filtration container 6 through which the inorganic particles can permeate. And a step of encapsulating the material in a mixed form with the material, and a step of installing the filtration container 6 containing the flocculant in the buffer zone 5, and as a subsequent step of aggregating the inorganic particles with the flocculant, 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 a plurality of aggregates from the viewpoint of handleability and transportability. Further, in the present invention, the flocculant may be used depending on the flocculation mechanism. In that case, the filtration container 6 containing an appropriate flocculant is classified according to the function. Each area can be installed in the form of one or more aggregates.

  As the mesh-like or mesh-like filtration container 6, one having a hole or hole having a diameter or size sufficient for the inorganic particles to pass through is used. As will be described later, since the inorganic particles used in the present invention are clay or an inorganic adsorbent having an average particle size of several μm or less, the diameter of the hole formed in the filtration container 6 or the size of the hole is several μm or more. Since the inorganic particles have a particle size distribution, 10 μm or more is practical in consideration of the maximum particle size. Furthermore, in order to easily produce and obtain the filtration container 6, 100 μm or more is more preferable. On the other hand, since the filtration container 6 contains the flocculant, the upper limit of the diameter or size formed therein is preferably several cm or less. When the upper limit exceeds 5 cm, it is not only practical to devise special measures for encapsulating the flocculant in the filtration container 6, but also from the viewpoint of the strength of the filtration container 6. As the material of the filtration container 6, for example, a fibrous cloth used in the production of flexible container packs is practical because it is flexible and has excellent handleability. It may be made of metal.

  As the other material to be mixed with the flocculant, a fine powder or a fine piece that can be mixed with the inorganic particles can be used, and examples thereof include rice crackers, wood chips, plastic pieces, and earth and sand. The inorganic particles are not only uniformly mixed with other materials, but may be locally unevenly distributed at the center or end of other materials. Further, when the flocculant is encapsulated in the filtration container 6 alone, since the particle diameter of the flocculant is generally small, a water-soluble adhesive, adhesive, glue, clay or the like is used. It is practical to produce a lump having a large particle size and enclose one or more in that form.

  In the present invention, when the inorganic particles that adsorb the radioactive substance are applied or dispersed and injected in the form of a dispersion or suspension, the dispersion or suspension further contains an average of the inorganic particles. It is preferable that an ionic polymer or a nonionic polymer having a charge of the same polarity as the electric charge is included, and the ionic polymer or the nonionic polymer is a water-soluble or colloidal aqueous dispersion. Thereby, it is possible to prevent the particle-free scattering into the atmosphere that is likely to occur at the same time or after the application or dispersion and injection of the dispersion or suspension. The inorganic particles are fine particles, and not only when they are once applied or spread on the surface of fallen leaves or topsoil, but also after the process cannot stay in a certain place by scattering, so the decontamination effect of radioactive substances is sufficiently It may not be obtained. Since the ionic polymer or the nonionic polymer has a function of fixing the inorganic particles to a fixed place of soil such as fallen leaves or humus, and leaving it stationary, the decontamination effect of the radioactive substance is promoted. Further, in order to obtain a high decontamination effect, it is necessary to increase the contact area between the inorganic particles and soil such as fallen leaves and humus, and it is essential that the inorganic particles are not aggregated. Accordingly, an ionic polymer having a charge of the same polarity as that 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 has a cationic polymer or a charge depending on whether the surface of the inorganic particles has a positive (+) or negative (−), respectively. Anionic polymers can be used. Examples of the cationic polymer include at least one selected from cationized cellulose, cationized starch, a polymer having an amino group, or a polymer of a quaternary ammonium salt, and examples of the anionic polymer include carboxy Examples thereof include at least one selected from methyl cellulose, carboxymethyl amylose, lignin sulfonic acid and its salt, polyacrylic acid and its salt, and polysulfonic acid and its salt. These cationic polymers and anionic polymers are dissolved or dispersed by natural rainwater flow, artificial water flow or fountain, and inorganic particles adsorbing the radioactive substance are made 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 member selected from 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. A water-soluble or water-dispersible polymer can be used. Since these polymers have biodegradable characteristics, they do not need to be removed after coating or spraying, and can contribute to labor saving in decontamination work.

The polysaccharide is not particularly limited as long as it is substantially water-soluble and can be rigidized (cured) by dehydration after plasticization (melting). Specific examples of the natural polymer of (a) polysaccharide include the following polysaccharides.
(A1) Unmodified starch from ground stems such as corn starch and wheat starch,
(A2) Unmodified starch of rhizomes such as tapioca and potato starch,
(A3) Low-level esterification, low-level etherification, cross-linking, oxidation, acid treatment, dextrinization, and pregelatinized starch of each above-ground 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 plant polysaccharides such as mannan, gum arabic, guar gum, gum tragacanth, locust gum, tamarind, etc.

  Further, after the reactive hydroxyl group of the above starch is ester-substituted (including organic acids, inorganic acids, and further graft-substituted products) and ether-substituted (including graft-substituted products) are dispersed in water, then a plasticizer Emulsion water (emulsion water composed of water, plasticizer and dispersion stabilizer) may be added to form a water-dispersible polymer solution.

  The polyvinyl alcohol (PVA) used as one type of the (b) chemically synthesized polymer preferably has a degree of polymerization of 1000 to 5000, and more preferably 1700 to 2400. Furthermore, the saponification degree of PVA is preferably 85 to 99%, more preferably 87 to 93% because the solution is water-soluble.

  As the nonionic polymer, another (e) water-soluble or water-dispersible polymer may be used. (E) Examples of water-soluble or water-dispersible polymers include water-soluble polymers such as polyvinyl acetate, polyvinyl alcohol, polyacrylamide, polyvinyl pyrrolidone, polyacrylic acid and salts thereof, and polyacrylic acid esters containing hydroxyl groups. One kind of synthetic polymer or water-dispersible synthetic polymer such as ethylene-vinyl acetate copolymer, ethylene-vinyl alcohol copolymer, styrene-acrylic acid ester copolymer, vinyl acetate-acrylic acid ester copolymer Or 2 or more types can be used.

  Among them, it is easy to form a continuous layer composed of the contaminated soil and polymer, and the continuous layer can exhibit not only strength and elasticity that can sufficiently withstand various peeling conditions, but also safety. Polyvinyl acetate or a polymer containing polyvinyl acetate as a main component is preferable from the viewpoints of handleability, reduction of environmental burden during long-term storage, disposal property, and low price. In the present invention, the polymer mainly composed of polyvinyl acetate means a polymer containing 50% by mass or more, preferably 70% by weight or more of polyvinyl acetate. As a suitable polyvinyl acetate, it is preferable that molecular weight is 2000-50000. If the molecular weight is less than 200, the strength of the polymer film becomes weak, and if it exceeds 50000, the solubility in water decreases, or the viscosity of the aqueous solution increases and the operability and workability as a soil fixing solution decrease. 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 high component having no charge is mixed with the inorganic particles in 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 handling properties, workability, and reduction of the environmental load on the periphery. There is a need. In addition to water, for example, 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 are used in a small amount. May be. These solvents are used when it is necessary to adjust the viscosity with respect to the radioactive substance decontamination solution of the present invention or to enhance the solubility of the 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 flocculant used in the decontamination method and decontamination system of the present invention will be described. The present invention applies the four combinations shown in the following (i), (ii), (iii) and (iv), and applies an aggregation method suitable for each combination.
(I) Ionic polymer having a charge opposite to the charge on the surface of the inorganic particles As the aggregating agent, an ionic polymer having a charge opposite to the charge on the surface of the inorganic particles (A) Is used. The ionic polymer (A) is contained in the buffer zone, and the inorganic particles that have flowed into the buffer zone by rain water or artificial running water or fountain are aggregated by the ionic polymer (A).

(Ii) Combination of two types of ionic polymers FIG. 3 shows the removal of the present invention in which inorganic particles are aggregated using a flocculant containing a combination of two types of ionic polymers in the decontamination method of the present invention. It is a figure which shows typically the dyeing | staining method and a decontamination system. As the flocculant, the ionic polymer (A) 7 having a charge opposite in polarity to the charge of the inorganic particles and the ionic polymer having a charge opposite in polarity to the ionic polymer (A) 7 are used. (B) A combination of 8 is used. As shown in FIG. 3, in the buffer zone, located adjacent to at least one side of the forest 1 and the satoyama 2, in a region containing the ionic polymer (A) 7, rainwater or artificial running water or The inorganic particles that flowed in by the fountain are aggregated by the ionic polymer (A) 7 having a charge of opposite polarity. Thereafter, the ionic polymer (A) 7 that flows out without agglomeration is located in the buffer zone 5 adjacent to the residential area 3 or the field 4 side, and in the region containing the ionic polymer (B) 8, Is agglomerated 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 ionic polymers are used in the above methods (i) and (ii). . In FIG. 4, the portions surrounded by the solid line and the dotted line correspond to the methods (i) and (ii), respectively. FIG. 4 shows an example of inorganic particles having a negative (−) charge on the surface. The cationic polymer and the anionic polymer are the ionic polymer (A) and the ionic polymer, respectively. Used as (B).

  As shown in the part surrounded by a solid line in FIG. 4, in the method (i), after the inorganic particles 9 having a negative (−) charge flow into the surface by rain water or artificial running water or fountain, the buffering is performed. Aggregates by the cationic polymer 10 contained in the zone 5. Due to this aggregation, the movement of the inorganic particles is constrained and stays in the buffer zone 5, so that the transition to the residential area 3 and the field 4 can be suppressed. Excess cationic polymer 10 that does not participate in the aggregation of the inorganic particles 9 in the process remains in the buffer zone 5 in a region adjacent to at least one of the forest 1 and the satoyama 2 in an unaggregated state. .

  On the other hand, in the method (ii), the anionic polymer 11 is included in the buffer zone 5 in the region adjacent to the residential area 3 or the satoyama 4 side, as shown in the lower part of the portion surrounded by the dotted line in FIG. And a process of aggregating the cationic polymer 10 flowing out to the region by natural rain water or artificial running water or fountain by the anionic polymer 11 is adopted. The region containing the anionic polymer 11 is serially connected to the downstream side of the region containing the cationic polymer 10 mainly for the purpose of aggregating the excess cationic polymer 10 with the anionic polymer 11. It is provided. In this 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. It is based on the action of going.

  In the method (ii), an anionic polymer is used to agglomerate the cationic polymer. Instead of the anionic polymer, an anion-rich amphoteric polymer having a high anion equivalent is used as described below. May be used.

  In this way, the aggregates of the ionic polymer (A) and the inorganic particles and the aggregates of the ionic polymer (A) and the ionic polymer (B) are gradually granulated to form a large mass. Since it becomes easy to be fixed to the buffer zone 5, the transition to the residential area 3 and the field 4 is suppressed. Moreover, since these aggregates are clearly different in size from the soil, they can be easily separated and recovered. Therefore, not only can the inorganic particles agglomerated by the ionic polymer (A) be separated and recovered efficiently in the next step, but the method (ii) above was used to coarsen the particles by granulation. Not only the aggregated inorganic particles but also the ionic polymer (A) and the ionic polymer (B) can be separated and recovered at the same time. Thereby, the amount of the inorganic particles and the ionic polymers (A) and (B) remaining in the buffer zone is greatly reduced, a large decontamination effect is obtained, and the burden on the environment is greatly reduced. Can do.

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

  Examples of the anionic polymer include at least one selected from carboxymethyl cellulose, carboxymethyl amylose, lignin sulfonic acid and salts thereof, polyacrylic acid and salts thereof, polysulfonic acid and salts thereof, and cationic polymers. As such, at least one selected from cationized cellulose, cationized starch, a polymer having an amino group, or a polymer of a quaternary ammonium salt can be used. One of these anionic polymer and cationic polymer is selected according to the charge of the surface of the inorganic particles. If the charge on the surface of the inorganic particles is unknown, the inorganic particles used in advance and an anionic polymer or a cationic polymer are mixed, and the ionic polymer on which the aggregation has occurred is changed to the ionic polymer. Apply as (A). The ionic polymer applied as the ionic polymer (A) is preferably a water-soluble or water-dispersible polymer in consideration of handling properties, workability, and reduction of environmental load on the periphery.

(Iii) Polymer flocculant or amphoteric polymer flocculant having cationic polymer and anionic polymer 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 decontamination system shown in FIG. 1, after the polymer flocculant (C) or the amphoteric polymer flocculant (D) is contained in the buffer zone 5, natural rainwater or artificial running water or fountain The inorganic particles that have flowed in are aggregated with the polymer flocculant (C) or the amphoteric polymer flocculant (D).

  As the polymer flocculant (C), a polymer in which the cationic polymer and the anionic polymer mentioned as examples in the above <ionic polymer> are blended so that the charge ratio between them is 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 the polymer flocculant prepared so that the charge ratio of both 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 suspension aqueous solution, the ionic polymers having different polarities in the aqueous solution They are close to each other, and agglomerated precipitates tend to be formed so as to cancel each other's electric charge. For this reason, an agglomeration effect is hardly obtained or very small for the inorganic particles. However, if the polymer flocculant (C) can be applied or dispersed in the buffer zone without agglomeration, the movement of each ionic polymer is constrained and locally on the surface and inside of the soil in the buffer zone. Aggregation can occur when inorganic particles having a charge of opposite polarity come close to each other. By utilizing this function, aggregation with inorganic particles adsorbed with a radioactive substance can be promoted.

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

  As a polymer flocculant (C), when using a polymer flocculant blended so that the charge ratio of the two deviates from 1, as described later, it is not necessary to newly add an inorganic salt such as sodium chloride. It was found that a colloidal solution that does not generate precipitates can be formed. Therefore, when aiming to minimize the impact on plant growth, etc. not only in forests and satoyama (including miscellaneous forests) but also in other regions, as a polymer flocculant (C), a cationic polymer It is preferable to use a polymer flocculant in which the charge ratio of the anionic polymer and the anionic polymer is different from 1.

<Polymer flocculant blended so that charge ratio of cationic polymer and anionic polymer deviates from 1>
The polymer flocculant blended so that the charge ratio of the cationic polymer and the anionic polymer deviates from 1 used in the present invention is either in the 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 excessively mixed with the charge ratio in comparison with the second polymer. The resulting dispersion type polymer flocculant. This dispersed polymer flocculant forms a uniform colloidal water solution that is stable for a long period of time without generating a precipitate, and has found that it has a large cohesive force when mixed with the inorganic particles. It has been applied.

  FIG. 5 is a diagram schematically showing an example of the aggregation form of inorganic particles formed when the dispersion polymer 12 in which the cationic polymer is excessively adjusted by the charge ratio is used as the 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 dispersive polymer flocculant 12 used as the polymer flocculant (C) in the present invention is cationic as exemplified in the combination of the two ionic polymers of (i). By including both the polymer and the anionic polymer, molecular chains are entangled, and a hydrophobic floc 14 serving as a nucleus for producing a large cohesive force is formed. On the other hand, since either one of the cationic polymer or anionic polymer is excessively contained, the formation of precipitates is suppressed by the presence of hydrophilic molecular chains with increased affinity with water. And uniformly dispersed. Accordingly, the aqueous solution has an opaque or milky white property, and has a great feature in that a uniform solution that is stable for a long period of time can be formed without forming a precipitate. When this dispersive polymer flocculant comes into contact with inorganic particles after adsorbing radioactive material that has flowed in by rainwater or artificial running water or fountain, agglomeration occurs and gradually converts to large agglomerates. Thereby, it can suppress that the inorganic particle which adsorb | sucked the radioactive substance transfers to a residence or a field.

  The “opaque or milky white” exhibited by the dispersive polymer flocculant 12 is determined visually and by turbidity. For example, the turbidity of the colloidal solution of the polymer flocculant is measured at a wavelength of 660 nm using a spectrophotometer. It was measured, and when the turbidity was maintained at 85% or more even after 24 hours, it was concluded that the colloid existed stably without aggregation and precipitation. In order to achieve the effect of the present invention, it is a necessary condition that the precipitate is not observed even if it is left for 24 hours or more in summer and winter (temperature range: 5 to 30 ° C.).

  The colloidal aqueous solution used in the present invention does not cause the addition amount of the cationic polymer and the anionic polymer to have an equal charge ratio, but adds either one so that the charge ratio is excessive. Therefore, it is not necessary to positively add a salt essential for obtaining a one-component polyion complex to the colloidal aqueous solution as in the prior art. However, the ionic polymer originally contains a trace amount of counter ions, and the aqueous colloidal solution used in the present invention may contain a trace amount of salt, but these counter ions are a precipitate of inorganic particles. Has little effect on the generation of. The salt for forming the counter ion differs depending on the type of ionic polymer used, but in general, sodium chloride, potassium chloride, ammonium chloride, magnesium chloride, sodium sulfate, potassium sulfate, ammonium sulfate, sulfuric acid At least one salt selected from magnesium, sodium nitrate, potassium nitrate, and ammonium nitrate is used.

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

The molecular weight of one of the ionic polymers (A1) used in the present invention is M ₁ , and the ion equivalent mass is EW ₁ . The ion equivalent mass (EW ₁ ) of the ionic polymer (A1) is the same as the molecular weight (m _A ) of the structural unit having an ion when the proportion of the structural unit having the ion is 100 mol%. For example, when the proportion of structural units having ions is 50 mol% and the proportion of structural units having no ions is 50 mol%, the ion equivalent mass has the molecular weight (m _A ) of the structural units having ions and ions. It becomes the sum (m _A + m _N ) with the molecular weight (m _N ) of the structural unit that does not. Thus, the ion equivalent mass is determined by the molar ratio between the structural unit having ions and the structural unit not having ions. In the case of the other ionic polymer (B1), when the molecular weight of the ionic polymer (B1) is M ₂ and the ion equivalent mass is EW ₂ , the ion equivalent mass is obtained in the same 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 ₂ . In that case, the ionic polymer (A1) is contained in the colloid solution at a concentration of (C ₁ / M ₁ ) mol, and the ionic polymer (B1) is contained at a concentration of (C ₂ / M ₂ ) mol. Therefore, in the colloid solution, the number of charges due to each ion contained in the ionic polymer (A1) and the ionic polymer (B1) is P ₁ (equivalent) = (C ₁ / M ₁ ) × (M ₁ ), respectively. / EW ₁ ) and P ₂ (equivalent) = (C ₂ / M ₂ ) × (M ₂ / EW ₂ ).

If P ₁ = P ₂ (total charge is zero), C ₁ / EW ₁ = C ₂ / EW ₂ . On the other hand, when the total charge of the colloidal aqueous 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 may be reversed. Therefore, in the present invention, by mixing the anionic polymer and the cationic polymer so as to satisfy the relationship of (C ₁ / EW ₁ ) / (C ₂ / EW ₂ )> 1, one of the ions It is possible to prepare an aqueous colloidal solution in which a functional polymer is excessively added at a charge ratio.

<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 is a binary copolymer 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 necessary. 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 about 1: 1, or the cation-rich amphoteric polymer having a high cation equivalent In contrast, like an anion-rich amphoteric polymer having a high anion equivalent, both can be prepared so that the charge ratio thereof deviates from 1.

  Even if the amphoteric polymer used as the polymer flocculant (C) is prepared so that the charge ratio of both monomers is approximately 1: 1, precipitation by gelation in a dispersed aqueous solution or a suspended aqueous solution There is almost no occurrence of things. This is because the cationic monomer structural unit and the anionic monomer structural unit are separately arranged in one molecule, and in addition, the monomer structure of both is determined by the presence of counter ions, pH, etc. This is because the units are adjusted so as not to be close to each other to suppress aggregation. Therefore, when the 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 the two deviates 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 aggregation form of inorganic particles formed when an amphoteric polymer is used as an aggregating agent. As shown in FIG. 6, the dispersion or suspension having 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 time without forming a precipitate. Since it can be formed, it can be applied or sprayed and injected into the buffer zone. The amphoteric polymer flocculant 15 flows in by rain water or artificial running water or fountain, and adsorbs the radioactive substance (in FIG. 6, inorganic particles 16 having a negative (1) charge on the surface) Aggregation occurs upon contact and gradually converts to large agglomerates. Thereby, it can suppress that the inorganic particle which adsorb | sucked the radioactive substance transfers to a 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, 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 Examples thereof include nium, diallyldibenzylammonium iodide, diallyldibenzylammonium methylsulfate and the like.

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

(H) Nonionic monomer Nonionic monomers include acrylic amides and N-substituted products such as N-methyl, N, N-dimethyl, N, N-diethyl, and N-hydroxymethylacrylamide. Can be mentioned.

  The amphoteric polymer used in the present invention is obtained by copolymerization of at least one or two or more of the above cationic monomers and one or more of the anionic monomers. It is good also as a ternary copolymer containing 1 type, or 2 or more types of a nonionic monomer. Copolymerization is a method in which an aqueous solution of the above-mentioned various monomer mixtures is solution-polymerized using a water-soluble initiator such as ammonium persulfate or potassium persulfate, or a photopolymerization method using a photosensitizer. It can be done by conventional methods.

  When the amphoteric polymer is used as the polymer flocculant (C) in the present invention, the charge ratio of the monomers having opposite polarities should be changed according to the aggregated particle diameter and aggregation rate of the inorganic particles. An amphoteric polymer prepared so that the charge ratio of monomers having opposite polarities is approximately 1: 1, and a cation-rich amphoteric polymer and anion prepared so that the charge ratio of both deviates from 1. You may use not only any 1 type of rich amphoteric polymer but 2 or more types together.

(Iv) Polymer flocculant having two kinds of cationic polymer and anionic polymer or a combination of amphoteric polymer flocculants As the flocculant, the charge ratio between the cationic polymer and the anionic polymer is 1 The polymer flocculant (C1) having an excess charge opposite to the charge on the surface of the inorganic particles, or a cationic monomer structural unit and anionic in one molecule Amphoteric having a monomer structural unit and having a charge ratio in one molecule of both monomer structural units deviating from 1 so as to have a charge opposite in polarity to the charge of the surface of the inorganic particles A polymer flocculant (D1), and a polymer flocculant (C2) having an excessive charge opposite in polarity to the charge excessively possessed by the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), Or amphoteric polymer flocculant (D2) Use a combination with. In the buffer zone of the decontamination method and 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, and ions A region containing the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) instead of the functional polymer (B) 8 is provided in series in this order. Here, the amphoteric polymer flocculant (D1) and the amphoteric polymer flocculant (D2) are either a cation-rich amphoteric polymer having a high cation equivalent or an anion-rich amphoteric polymer having a high anion equivalent, It is selected and used in such a combination that the electric charges of the opposite polarity are reversed.

  In the buffer zone 5 shown in FIG. 3, it is located adjacent to at least one side of the forest 1 and the satoyama 2, and is a region containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1). The inorganic particles that have flowed in by rain water, artificial running water or 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) that flows out without agglomeration is located adjacent to the residential area 3 or the field 4 side in the buffer zone, and the polymer agglomeration In the region containing the agent (C2) or the amphoteric polymer flocculant (D2), the particles are aggregated 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 the above-mentioned (ii) two kinds of ionic properties. The ionic polymer (A) and the ionic polymer (B) described in the section of polymer combination have the same functions. That is, the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is used to suppress migration to a residential area or a field by aggregating the inorganic particles adsorbed with 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) that flows out without agglomeration. It is used to agglomerate these (C1) or (D1) polymers for the purpose of preventing migration. Further, in the region containing the polymer flocculant (C2) or amphoteric polymer flocculant (D2), inorganic particles aggregated by the polymer flocculant (C1) or amphoteric polymer flocculant (D1) are produced. Since the effect of granulating is obtained, the aggregated particles can be coarsened. Thereby, the effect of suppressing and preventing the migration of the inorganic particles that have adsorbed the radioactive substance to the residential area 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). In addition, a polymer flocculant (C1) and an amphoteric polymer flocculant (D2), or a combination of the amphoteric polymer flocculant (D1) and the polymer flocculant (C2) may be used. This is because even in the combination of (C1) and (D2), or (D1) and (C2), there is basically no difference in the aggregation function between the inorganic particles and the polymer flocculant.

  Each flocculant used in the above four combinations (i), (ii), (iii) and (iv) is applied to or dispersed in the form of a dispersion aqueous solution or a colloidal solution. It is contained in the buffer zone 5 shown. In this case, the viscosity of the aqueous dispersion or colloidal aqueous solution is practically adjusted to a range of 2 to 4000 mPa · s in a temperature range of 4 to 30 ° C. from the viewpoint of work efficiency for coating or spreading. The viscosity is 2 mPa.s. If it is less than s, since the blending amount of each flocculant is small, the working efficiency for coating or spraying is greatly reduced. 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 coating or spraying becomes difficult.

  The dispersed aqueous solution or colloidal aqueous solution containing each of the above flocculants can be fixed by applying or spraying the buffer zone 5 by a spraying method, a pouring method, a brush coating method, or the like, and then drying. . Moreover, you may perform application | coating or dispersion | spreading by installation, such as a sprinkler, or a helicopter. The coating amount or dispersion amount of the aqueous dispersion or colloidal aqueous solution is determined based on the amount of each aggregating agent contained and the amount necessary for aggregating the inorganic particles and the polymer having a charge opposite to that of the inorganic particles. be able to.

  The configuration of the decontamination method and decontamination system according to the present invention is as described above. In the present invention, after decontamination of at least one of the forest and satoyama, at least one of the forest and satoyama is further performed. The process and means for peeling off the defoliation and the humus containing the defoliation from the ground where the defoliation exists, and the defoliated defoliation and defoliation to the farmland and the wilderness to restore the geological strength. It is preferable to have the process and means to add. The fallen leaves remaining in the state after decontamination and the humus containing the fallen leaves are used after performing radiation measurement and soil inspection, etc., and sufficiently confirming that there is no radiation effect due to radioactive substances.

  Conventionally, methods for adding new fertilizers and soils have been adopted to restore the geological strength of farmland and wilderness, but decontamination has already been completed by using the fallen leaves after decontamination and the humus containing the fallen leaves. Agricultural land and wilderness can be restored efficiently and safely. In particular, fallen leaves and mulch in the same area are compatible with farmland and wilderness from the viewpoint of climate and climate, so it is possible to increase the effect and speed of restoring geopower.

<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, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite and kaolinite can be used, and one or more selected from these groups can be used. . Since these inorganic particles are generally porous and have a positive (+) or negative (−) charge on the surface thereof, not only the adsorbability of radioactive substances but also each aggregating agent used in the present invention. It has a function of being aggregated by.

  The average particle diameter of the inorganic particles can be in the range of 0.01 to 20 μm, 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, the aggregation of inorganic particles is likely to occur, and the workability in the adjustment and application of the fixing solution becomes remarkable. In addition, 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 including the above-mentioned radiation substance-containing forest soil is greatly reduced, and peeling and removal becomes difficult. 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 standpoint of achievement as a radioactive substance adsorbent, handling properties, low cost, and the like. Bentonite is particularly useful because it has an effect of absorbing moisture in the surrounding soil (drying effect) by drying and is superior to other inorganic particles and promotes adsorption of radioactive substances such as Cs onto bentonite. Bentonite has exchangeable cations such as Na ⁺ , K +, Ca ²⁺ and Mg ²⁺ between layers, and has a function of adsorbing and holding Cs ⁺ which is a radioactive substance by ion exchange. And since Al3 ^{+ of} the alumina layer is substituted with Mg2 ⁺ or the like, the surface of bentonite has a negative charge. In addition, bentonite can be obtained at a low cost because it can be used as it is by adjusting the maximum particle size to 100 μm or less, preferably 50 μm or less, excluding coarse particles from the bentonite mine.

  The inorganic particle-based radioactive substance adsorbent can be dispersed in any amount in at least one of forest and satoyama. When the amount of the inorganic particles sprayed is small, it is impossible to adsorb all radioactive substances that contaminate forests and satoyama. Therefore, measure the radiation dose temporarily or periodically in forests and satoyama. Respond by increasing the spraying amount or spraying number based on the value. Even if the application amount is increased, the inorganic particles are almost harmless to the human body, so that even if left in a forest or satoyama, there is almost no problem. Furthermore, since the inorganic particles are swept into the buffer zone by the naturally occurring rainwater or running water or fountain by artificial sprinkling, the amount of the inorganic particles present in the forests and satoyama gradually decreases. The impact is reduced. When the decrease in the amount of the inorganic particles is remarkable and it is desired to maintain the decontamination continuously, the inorganic particles are sprayed again in the forest or 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 when the aqueous medium is 100 parts by mass. .5 to 5 parts by weight. When 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, the separation of the inorganic particles becomes remarkable, and it is not only difficult to perform uniform coating or spraying, but also the efficiency of the decontamination work is greatly reduced. To 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 ions The content of the functional 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 nonionic polymer is less than 0.2 parts by mass, the effect of preventing the particles from scattering into the atmosphere cannot be obtained, and when the content exceeds 60 parts by mass, a dispersion is obtained. Alternatively, the viscosity of the suspension is significantly increased, so that the efficiency of the decontamination work is greatly 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 basic configuration of the radioactive substance decontamination method and decontamination system according to the present invention described above, but the scope of the present invention is not limited to these examples.

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

  In this example, the polymer flocculant (C1) cation-excess polyion complex aqueous solution and the polymer flocculant (C2) anion-excess polyion complex aqueous solution are DADMAC and CMC in a mass ratio of DADMAC: CMC = 43: 3 and The coagulant | flocculant mix | blended by DADMAC: CMC = 1: 3 was adjusted and used for the aqueous solution which contains 1.5 mass%, respectively. Here, the DADMAC: CMC charge ratio of the aqueous cation excess polyion complex solution is 69: 1, while the DADMAC: CMC charge ratio of the aqueous anion excess polyion complex solution is 1: 3. Neither the cation-excess polyion complex aqueous solution nor the anion-excess polyion complex aqueous solution showed a precipitate, and exhibited a colloidal aqueous solution. The DADMAC: CMC charge ratio can be determined as follows.

The 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 represented by the formula (2) of CMC, the ion equivalent mass (EW ₁ ) can be calculated at 234 g / 0.9 equivalent. On the other hand, DADMAC has a molecular weight of 161.7 g per mol, high purity, and 1 equivalent of the charge per repeating structural unit represented by the above formula (1), so that the ion equivalent mass (EW ₂ ) is 161.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) is the basic configuration of the jig when performing the model experiment, and (b) is the conditions set when performing the model experiment.

  As shown in FIG. 7 (a), the jig for conducting the model experiment is basically a first layer container 17 containing 2 kg of humus, a second layer container 18 containing 4 kg of sand, and The container is composed of a third layer container 19, and a number of fine holes or holes are provided at the bottom of each container so that water sprayed or injected from the upper part of the first layer container 17 can pass therethrough. In the lowermost part, a water storage container 20 for receiving and accumulating water that has been sprayed or injected into the first-layer container 17 and passed through the second-layer and third-layer containers 18 and 19 is disposed.

  There are four conditions shown in FIG. 7B which are set when the model experiment is performed. In FIG. 7 (b), “humus and bentonite” indicate a layer in which a bentonite suspension is dispersed on the humus, and “PIC” is an abbreviation for polyion complex. For example, “sand and cation excess PIC” is a cation. The layer which spread | dispersed the excess polyion complex aqueous solution on sand is shown.

In FIG. 7 (b), when bentonite, which is inorganic particles, is mixed in the first layer container 17, 7L (liter) of water suspended in 10kg of humus is added and stirred and dried. 2kg of the thing was put. As bentonite, bentonite donmin (made by Volclay Japan Co., Ltd.) was used. Moreover, when spraying the said cation excess polyion complex aqueous solution to the container 18 of the 2nd layer in which sand was put, it sprayed on the conditions of 5 L (liter) / m < ² >. Similarly, when the anion-excess polyion complex aqueous solution was sprayed on the third layer container 19 containing sand, 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 radiation cesium concentration was measured using a CsI (TI) scintillation detector and expressed as a radiation dose per 1 kg of sand (becquerel (Bq) / kg).

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

  As shown in FIG. 8 (a), when bentonite is present in the first-layer container, the decrease in the radioactive Cs concentration after spraying or injecting water is greater than when no bentonite is present. I understand that The reason why the decrease in the concentration of radioactive Cs in the presence of bentonite is large is that the bentonite particles adsorbed by Cs in the humus 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 was increased when bentonite was present in the first layer. This increase in radioactive Cs concentration is because bentonite particles adsorbing the radioactive Cs concentration flow into the second layer by the water sprayed or injected from the upstream and are aggregated by the cation-excess polyion complex mixed in the second layer. Yes, resulting from the radiation dose supplemented with radioactive Cs.

  As described above, when bentonite is added to humus, the radioactive Cs in the mulch is transferred to bentonite by an ion exchange reaction, and the bentonite particles moved by water spraying or injection 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 containing an ionic polymer or a nonionic polymer having the same negative (−) charge as the bentonite surface in the suspension having bentonite. Even if it is used, it is easily guessed that the measurement results of the radioactive Cs concentration in the first layer and the second layer show the same tendency as shown in FIG. For example, using a suspension of bentonite in which biodegradable water-soluble starch (corn starch) is dissolved [water: bentrite: starch = 100: 30: 5 (mass ratio)], the first layer It was found that a starch layer can be formed near the surface of the mulch when applied to the mulch in a container. This starch layer can keep bentonite inside the humus for a long period of time, so that sufficient contact between the bentonite and the radioactive Cs contained in the humus can be ensured, and the adsorption of radioactive Cs is promoted. Has the effect of And since starch flows out with water when water is sprayed or poured into the container of the 1st layer, even if it contains starch, it has little influence on movement of bentonite. Thus, the addition of an ionic polymer or a nonionic polymer is considered to make it possible to further enhance the decontamination effect by bentonite.

[Example 2]
Based on the results of the model experiment of Cs transition, the soil that was actually left in the forest in the state of rain was used, and the soil mounting test was conducted by dividing the soil 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 compartment was performed by placing a long plastic bag containing black soil to prevent the inflow of soil between the compartments. The humus soil contaminated with radioactive Cs on the surface of the forest was collected and moved to the top of the soil slope for placement. Thus, the humus moved to the top of the soil slope can be regarded as corresponding to the humus present in at least one of the forest and satoyama in the present invention. Moreover, the measurement point (●) shown in FIG. 9 means a location where the radioactive Cs concentration was actually measured. The measurement of the radioactive Cs concentration was carried out at three points, upper, middle and lower, using a CsI (TI) scintillation detector.

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

Next, using the soil for forest demonstration test shown in FIG. 9, changes in radioactive Cs concentration due to the presence or absence of bentonite and the presence or absence of cation-excess polyion complex and anionic polyion complex were examined at each measurement point of radioactive Cs concentration. FIG. 11 is a diagram illustrating an outline of conditions set when the forest demonstration test is performed. In FIG. 11, the left two rows of soil disperse suspended aqueous solution containing 1% by mass of bentonite at 5 L / m ^{2 on} the collected humus, whereas the right two rows of soil disperse bentonite. Did not do. In addition, in the left two rows of soil slopes where the vent inner cylinders were sprayed, the cation-excess polyion complex (polyion complex is abbreviated as PIC) solution from the middle to the soil located on the left side. An anionic PIC aqueous solution was applied under the condition of 5 L / m ^{2 over} the lower part. On the other hand, the soil located on the right side in the left two rows of soils was not coated with the aqueous solution of both polyion complexes. Similarly, in the right two rows of soils that were not sprayed with bentonite, the cation excess PIC aqueous solution from the top to the middle point and the anion excess PIC aqueous solution from the middle point to the bottom were respectively 5 L / s. 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 where 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 reforming the test soil under these conditions, the soil was informed for one month, the surface soil was collected, and the radioactive Cs concentration was measured at three measurement points, upper, middle and lower. .

  In the four rows of soil shown in FIG. 11, the measurement results of the radioactive Cs concentration carried out at each of the upper, middle and lower measurement points are combined with the measurement results immediately after the humus soil recovery, and the distribution of the radioactive Cs concentration is 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 total of the radioactive Cs concentration performed 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 with the average value of the measured value of (1)-(4) shown in FIG.

  As shown in FIG. 12, the slope soil after being left for one month has a slight distribution of radioactive Cs concentration measured by the presence or absence of bentonite and the presence or absence of a cation-excess polyion complex and an anionic polyion complex, as compared with immediately after humus recovery. Different. However, except for the case where bentonite and cation-excess polyion complex are present (the leftmost side of FIG. 12), in the other three cases, the tendency that the ratio of radioactive Cs concentration in the middle and lower parts is higher than the upper part is almost the same. The same. On the other hand, when bentonite and cation-excess polyion complex are present (the leftmost side in FIG. 12), the ratio of the radioactive Cs concentration at the top of the soil slope is high. From this, the radioactive Cs was adsorbed in the humic soil. It can be seen that bentonite particles are agglomerated by the cation-rich polyion complex and are supplemented with radioactive Cs in the upper part of the soil slope. Therefore, it was confirmed in the forest demonstration test that the cation-excess polyion complex has an effect of aggregating bentonite particles adsorbing radioactive Cs and suppressing downward migration of slope soil.

  Furthermore, when bentonite particles and cation-rich polyion complex are present, the ratio of radioactive Cs concentration is low in the middle of the soil slope by spraying the anion-rich polyion complex from the middle to the bottom of the slope soil. In the lower part, the height was high, and a marked difference was observed between the middle and lower part of the slope soil compared to the other three cases shown in FIG. Although it is considered that the inorganic particles aggregated by the cation-excess polyion complex are granulated by the excess anionic polyion complex and the aggregated particles are coarsened, the details are unknown. Originally, the anion-rich polyion complex contained in the middle to the lower part of the soil slope is used to aggregate the cation-rich polyion complex contained in the middle from the upper part of the soil slope. It is conceivable to have an effect of promoting coarsening by granulation of inorganic particles aggregated by excess polyion complex.

  In this way, the inorganic particles aggregated with the cation-excess polyion complex above the slope soil are separated with the soil containing the aggregated inorganic particles, and then the inorganic particles are used with a sieve having a diameter of a predetermined size or more. In a form in which only the aggregates are separated and collected, or the soil containing the aggregated inorganic particles is packed as it is in a storage bag or pack. Thereafter, the radioactive material is transported to a place where it is treated so that it does not scatter or leak to the outside, and is collected and stored. Agglomerates of inorganic particles granulated by cation-rich polyion complex and agglomerates of cation-rich polyion complex and anion-rich polyion complex in the middle and below the slope soil can be stored in the same way. After being packed into a pack or the like, it is stored and preserved in a predetermined place.

  In addition, when the aggregate of inorganic particles adsorbing radioactive Cs is stored and stored separately from soil, as shown in FIG. 2, a net-like or mesh-like filtration container 6 through which the inorganic particles can be used is used. It is preferable to do this. The filtration container 6 is placed in the upper part of the buffer zone 5 after enclosing the cation-rich polyion complex alone or mixed with other materials. And after the said inorganic particle aggregates with a cation excess polyion complex, only the filtration container 6 containing the said inorganic particle aggregated with the cation excess polyion complex is isolate | separated from the buffer zone 5, and is collect | recovered. When inorganic particles adsorbed with radioactive Cs are included with other materials, only the aggregates of inorganic particles are separated by a sieve or the like, or the aggregated inorganic particles are packed together with other materials in a storage bag or pack. After collection, store and save in a predetermined place. This eliminates the need to separate and collect the inorganic particles agglomerated by the cation-excess polyion complex together with the topsoil of the buffer zone 5, thereby greatly reducing the labor of the separation and recovery process. In addition, the method shown in FIG. 2 is advantageous in that the decontamination work is facilitated because the inorganic particles adsorbing the radioactive Cs can be prevented from scattering to the outside even when the filtration container 6 is left standing for a long period of time. Have

  Further, FIG. 2 shows a method in which the flocculant of the anion-excess polyion complex is sprayed on the soil in the lower part of the buffer zone 5, but instead of the spraying method, the anion-excess polyion complex can be used alone or in other ways. You may use the filtration container enclosed with the form mixed with these materials. As described above, in the method shown in FIG. 2, the buffer zone 5 is roughly divided into two zones according to the function of the flocculant, and each flocculant is included in the form of one or a plurality of aggregates in each zone. A filtration container can be installed.

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

  As the cationic polymer, for example, polydiallyldimethylammonium hydrochloride (or chloride) represented by the above formula (1) (Senka Co., Ltd., trade name: Unisense FPA1001L: molecular weight: 100,000 to 500,000, hereinafter abbreviated as DADMAC) is used. As the anionic polymer, for example, a sodium salt of carboxymethyl cellulose represented by the above formula (2) (Daicel Chemical Industries, Ltd., trade name CMC Daicel 1220: molecular weight 160,000 to 380,000, hereinafter abbreviated as CMC) is used. In this case, the Cs migration model experiment and the forest demonstration test can be performed in the same manner as in Examples 1 and 2, except that the types of the flocculants and the combinations thereof are different. DADMA and CCMC are bentonites that adsorb radioactive Cs by basically the same ionic interaction as the dispersion polymer flocculant having the cationic polymer and the anionic polymer used in the methods (iii) and (iv). And a function of aggregating an ionic polymer having a charge of opposite polarity. Therefore, it can be easily guessed that the same decontamination effects as those shown in FIGS. 8 and 12 can be obtained by the methods (i) and (ii).

  Further, in the present invention, it is preferable to use bentonite as inorganic particles that adsorb radioactive Cs, but it is not limited to bentonite. As inorganic particles, for example, zeolite, layered silicate, ferrocyanide, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite or kaolinite are used depending on the availability, handling and price. May be. By checking the charge of the surface of these inorganic particles in advance, or mixing these inorganic particles with ionic polymer, dispersive polymer or amphoteric polymer and checking for the occurrence of aggregation in advance, The type and combination of molecular flocculants can be selected.

  As described above, according to the radioactive substance decontamination method and decontamination system according to the present invention, forests and satoyama (miscellaneous forests) in which decontamination has not been performed or are insufficient, as well as decontamination of forests and satoyama (including miscellaneous forests). In addition, radioactive substances such as cesium can be prevented from moving to residential areas and fields, and recontamination of these living environment areas that have already been decontaminated can be prevented. At that time, since the migration of the radioactive material is continuously suppressed, recontamination of a residential area or a field can be prevented in the medium to long term. In addition, soil such as deciduous leaves and humus soil present in contaminated forests and satoyama (including miscellaneous forests) does not need to be peeled off during decontamination work, and radioactive substances such as cesium remaining or accumulated in the place are removed from inorganic particles. Since the adsorbent can be adsorbed and fixed efficiently and stably over the medium to long term, decontamination work is facilitated. Furthermore, since the inorganic particle adsorbent in a state in which the radioactive substance is adsorbed and immobilized is separated and collected from the forest or satoyama in an aggregated state, the volume of contaminants can be reduced.

  Therefore, the radioactive substance decontamination method and decontamination system according to the present invention can continuously prevent radioactive substances from migrating to residential areas and fields while reducing labor and cost of decontamination. In the future, it will be possible to provide a safe and secure living space, and its technical usefulness is extremely high.

DESCRIPTION OF SYMBOLS 1 ... Forest, 2 ... Satoyama, 3 ... Residence, 4 ... Tabata, 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 ... Dispersive polymer flocculant, 13 ... inorganic particles having negative (-) charge on the surface, 14 ... hydrophobic clock, 15 ... amphoteric polymer flocculant, 16 ... negative on the surface (-) Inorganic particles having a charge, 17 ... first layer container, 18 ... second layer container, 19 ... third layer container, 20 ... water storage container.

Claims (20)

A decontamination method for decontamination of at least one of forest and satoyama contaminated with radioactive substances,
Directly spraying inorganic particles that adsorb radioactive materials on at least one of the forest and satoyama, or applying or spraying and injecting a dispersion or suspension containing the inorganic particles; and
A buffer zone containing a flocculant for agglomerating the inorganic particles is provided at the boundary between at least one of the forest and satoyama and the place of residence or field, and from at least one of the forest and satoyama, rainwater or Agglomerating the inorganic particles that have flowed into the buffer zone by artificial water or fountain with the flocculant;
Separating and collecting the inorganic particles aggregated together with the flocculant;
A method for decontaminating radioactive materials. As a pre-process of the process of aggregating the inorganic particles with the aggregating agent,
A step of enclosing the flocculant alone or mixed with another material in a net-like or mesh-like filtration container through which the inorganic particles can be permeable, and the filtration container containing the flocculant is installed in the buffer zone And a step of
As a subsequent step of aggregating the inorganic particles with the aggregating agent,
2. The radioactive substance decontamination method according to claim 1, further comprising a step of separating and collecting the filtration container containing inorganic particles aggregated together with the aggregating agent.   The dispersion or suspension containing the inorganic particles that adsorb the radioactive substance further contains an ionic polymer or a nonionic polymer having the same polarity as the charge of the surface of the inorganic particles, and the ionic property 3. The radioactive substance decontamination 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 opposite to the charge on the surface of the inorganic particles as the aggregating agent, the inorganic particles that have flowed in by rainwater, artificial running water or fountain The decontamination method of the radioactive substance as described in any one of Claims 1-3 which has the process aggregated with the said ionic polymer (A). The flocculating agent has an ionic polymer (A) having a charge opposite to the charge on the surface of the inorganic particles and an ionic polymer having a charge opposite to the ionic polymer (A) ( Including the combination of B),
In the buffer zone, located on at least one side of the forest and satoyama, in the region containing the ionic polymer (A), the inorganic particles introduced by rain water or artificial running water or fountain are treated with the ionic high A step of aggregating with a molecule (A), and the ionic polymer (A) flowing out without agglomeration is located on the side of a field or a residence in the buffer zone, and contains the ionic polymer (B) The decontamination method of the radioactive substance as described in any one of Claims 1-3 which has the process aggregated by the said ionic polymer (B) in a area | region. The flocculant is a polymer flocculant (C) having a cationic polymer and an anionic polymer, or an amphoteric polymer having a cationic monomer structural unit and an anionic monomer structural unit in one molecule. Including a molecular flocculant (D),
In the buffer zone containing the polymer flocculant (C) or the amphoteric polymer flocculant (D), the inorganic particles introduced by rainwater or artificial running water or fountain are used as the polymer flocculant (C) or The decontamination method of the radioactive substance as described in any one of Claims 1-3 which has the process aggregated with the said amphoteric polymer flocculent (D). The flocculant is a polymer flocculant that contains a cationic polymer and an anionic polymer so that the charge ratio of the two deviates from 1, and has an excessive charge opposite in polarity to the charge on the surface of the inorganic particles. (C1), or having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and having both the charge of the opposite polarity to the charge of the surface of the inorganic particles The amphoteric polymer flocculant (D1) prepared so that the charge ratio in one molecule of the monomer structural unit deviates from 1, and the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) is excessive. Including a combination of a polymer flocculant (C2) having an excess charge opposite to that of the charge in the amphoteric polymer flocculant (D2),
In the buffer zone, located on at least one side of forest and satoyama, in the region containing the polymer flocculant (C1) or the amphoteric polymer flocculant (D1), by rain water or artificial running water or fountain A step of agglomerating and solidifying the inflowing inorganic particles with the polymer flocculant (C1) or the amphoteric polymer flocculant (D1);
The polymer flocculant (C1) or the amphoteric polymer flocculant (D1) that flows out without being agglomerated is located on the side of the field or residence in the buffer zone, and the polymer flocculant (C2) or the amphoteric A step of aggregating with the polymer flocculant (C2) or the amphoteric polymer flocculant (D2) in a region containing the polymer flocculant (D2);
The decontamination method of the radioactive substance as described in any one of Claims 1-3 which has these. In the decontamination method as described in any one of Claims 1-7,
After decontaminating at least one of the forest and satoyama,
Detaching the defoliation remaining in at least one of the forest and satoyama and the humus containing the defoliation from the ground where the defoliation exists; and
Adding the peeled defoliation and humus to farmland or wilderness for restoring geological power;
A method for decontamination of radioactive material having   The inorganic particles that adsorb the radioactive substance are at least one selected from the group consisting of bentonite, zeolite, layered silicate, ferric ferrocyanide, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite and kaolinite. Item 9. The radioactive substance decontamination method according to any one of Items 1 to 8.   The method for decontaminating a radioactive substance according to claim 9, wherein the inorganic particles adsorbing the radioactive substance are bentonite. A decontamination system for decontaminating at least one of forests and satoyama contaminated with radioactive substances,
Means for directly spraying inorganic particles that adsorb radioactive materials on at least one of the forest and satoyama, or means for applying or spraying and injecting a dispersion or suspension containing the inorganic particles; ,
A buffer zone containing a flocculant for aggregating the inorganic particles is provided at the boundary between at least one of the forest, satoyama, and defoliation and a residential area or a field, and from at least one of the forest and satoyama, Means for aggregating the inorganic particles that have flowed into the buffer zone by rain water or artificial running water or fountain into the aggregating agent;
Means for separating and collecting the inorganic particles aggregated together with the flocculant;
A radioactive material decontamination system.   A net-like or mesh-like filtration container through which the inorganic particles can pass is installed in the buffer zone in a state in which the flocculant 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 inorganic particles that adsorb the radioactive substance further contains an ionic polymer or nonionic polymer having the same polarity as the charge of the surface of the inorganic particles, and the ionic high 13. The radioactive substance decontamination system according to claim 11 or 12, wherein the molecule or the nonionic polymer is a water-soluble or colloidal aqueous dispersion.   14. The zone containing the ionic polymer (A) having a charge opposite in polarity to the charge of the inorganic particles is provided as the buffer zone. The radioactive substance decontamination system as described in the paragraph. In the buffer zone, from at least one of the forest and satoyama toward the field or residence,
A region containing an ionic polymer (A) having a charge opposite in polarity to the charge of the inorganic particles, and an ionic polymer having a charge opposite in polarity to the ionic polymer (A) ( The region containing B) is
The radioactive substance decontamination system according to any one of claims 11 to 13, wherein the system is separated in this order and provided in series.   The buffer zone is a polymer flocculant (C) having a cationic polymer and an anionic polymer, or an amphoteric polymer having a cationic monomer structural unit and an anionic monomer structural unit in one molecule. The radioactive substance decontamination system according to any one of claims 11 to 13, further comprising a molecular flocculant (D). In the buffer zone,
From at least one of the forest and satoyama toward the field or residence,
A polymer flocculant (C1) having a charge opposite to the charge on the surface of the inorganic particles, and a cationic flocculant and an anionic polymer mixed so that the charge ratio of the two deviates from 1; or Both monomer structural units have a cationic monomer structural unit and an anionic monomer structural unit in one molecule, and have a charge opposite in polarity to the charge of the surface of the inorganic particles. A region containing an amphoteric polymer flocculant (D1) having a charge ratio of one molecule of
Charges that are mixed so that the charge ratio of the cationic polymer and the anionic polymer deviates from 1, and the charge that is opposite to the charge that the polymer flocculant (C1) or the amphoteric polymer flocculant (D1) has in excess A polymer flocculant (C2) having an excess of cation, or having a cationic monomer structural unit and an anionic monomer structural unit in one molecule, the polymer flocculant (C1) or the amphoteric polymer Contains amphoteric polymer flocculant (D2) in which the charge ratio in one molecule of both monomer structural units is adjusted so that the charge of polarity opposite to that of the molecular flocculant (D1) is 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 peeling off the defoliation remaining in at least one of the forest and satoyama and the humus containing the defoliation from the ground where the defoliation exists;
Means for adding the exfoliated defoliation and mulch to farmland or wilderness for restoring geological power;
A radiation material decontamination system.   The inorganic particles that adsorb the radioactive substance are at least one selected from the group consisting of bentonite, zeolite, layered silicate, ferric ferrocyanide, crystalline silicotitanate, mica, vermiculite, smectite montmorillonite, illite and kaolinite. Item 19. The radioactive substance decontamination system according to any one of Items 11 to 18.   20. The radioactive substance decontamination system according to claim 19, wherein the inorganic particles adsorbing the radioactive substance are bentonite.

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